[Characteristics of Chemical Components in PM₂.₅ from the Coal Dust of Power Plants].

PubMed

Wang, Yu-xiu; Peng, Lin; Wang, Yan; Zhang, Teng; Liu, Hai-li; Mu, Ling

2016-01-15

The ashes under dust catcher of typical power plants in Yangquan was collected and the contents of elements, irons, EC (elemental carbon) and OC (organic carbon) were measured in PM₂. The characteristics of its chemical composition was studied and the degree of similarity of coal dust's source profiles of PM₂.₅ between Yangquan and other cities were compared using the coefficient of divergence method. The result indicated that the main chemical components of PM₂.₅ from the coal dust were SO₄²⁻,Ca, NO₃⁻, OC, EC, Al, Si, Na, Fe, Mg and Cl⁻, accounting for 57.22% of the total mass. The enrichment factor of Pb in PM₂.₅ of coal dust was the largest with a significant enrichment condition, reaching 10.66-15.91. The coefficient of divergence of source profiles of PM₂.₅ between blind coal and fault coal was 0.072, so it was believed that they must be similar. Compared with other cities, the chemical composition of coal dust in Yangquan had specificity, in particular, the content of Ca was obviously higher than those in other domestic cities.

Aerosol transport over the western Mediterranean basin: Evidence of the contribution of fine particles to desert dust plumes over Alborán Island

NASA Astrophysics Data System (ADS)

Valenzuela, A.; Olmo, F. J.; Lyamani, H.; Granados-Muñoz, M. J.; Antón, M.; Guerrero-Rascado, J. L.; Quirantes, A.; Toledano, C.; Perez-Ramírez, D.; Alados-Arboledas, L.

2014-12-01

Eight months (June 2011 to January 2012) of aerosol property data were obtained at the remote site of Alborán Island (35.95°N, 3.03°W) in the western Mediterranean basin. The aim of this work is to assess the aerosol properties according to air mass origin and transport over this remote station with a special focus on air mass transport from North Africa. For air masses coming from North Africa, different aerosol properties showed strong contributions from mineral dust lifted from desert areas. Nevertheless, during these desert dust intrusions, some atmospheric aerosol properties are clearly different from pure mineral dust particles. Thus, Angström exponent α(440-870) presents larger values than those reported for pure desert dust measured close to dust source regions. These results combine with α(440, 670) - α(670, 870) ≥ 0.1 and low single scattering albedo (ω(λ)) values, especially at the largest wavelengths. Most of the desert dust intrusions over Alborán can be described as a mixture of dust and anthropogenic particles. The analyses support that our results apply to North Africa desert dust air masses transported from different source areas. Therefore, our results indicate a significant contribution of fine absorbing particles during desert dust intrusions over Alborán arriving from different source regions. The aerosol optical depth data retrieved from Sun photometer measurements have been used to check Moderate Resolution Imaging Spectroradiometer retrievals, and they show reasonable agreement, especially for North African air masses.

New directions: Mineral dust and ozone - Heterogeneous chemistry

NASA Astrophysics Data System (ADS)

Ramachandran, S.

2015-04-01

Aerosols, the tiny solid or liquid particles suspended in air and produced from natural sources and anthropogenic activities, continue to contribute the largest uncertainty to radiative forcing (IPCC, 2013). Aerosol particles give rise to radiative forcing directly through scattering and absorption of solar and infrared radiation in the atmosphere. Aerosols also give rise to indirect radiative forcing by modifying the cloud optical properties and lifetimes. Among the aerosol species mineral dust and black carbon cause a warming (positive forcing) while sulphate and sea salt cause a cooling (negative forcing) of the Earth-atmosphere system. In tropics and sub-tropics mineral dust is a major contributor to aerosol loading and optical thickness. The global source strength of dust aerosol varies significantly on spatial and temporal scales. The source regions of dust are mainly deserts, dry lake beds, and semi-arid regions, in addition to drier regions where vegetation has been reduced or soil surfaces that are disturbed by man made activities. Anthropogenic activities mainly related to agriculture such as harvesting, ploughing, overgrazing, and cement production and transport also produce mineral dust. An estimated 2500 terragram (Tg, 1012 g) of mineral dust is emitted into the atmosphere per year, and dominates the aerosol mass over continental regions in south Asia and China accounting for ∼35% of the total aerosol mass (IPCC, 2013). In India, dust is prevalent throughout the north and western India during the year and peaks during premonsoon season.

Characterization of alluvial dust sources and their temporal development - a multi-sensor approach for the Aïr Massif, Niger

NASA Astrophysics Data System (ADS)

Feuerstein, Stefanie; Schepanski, Kerstin

2017-04-01

One of the world's largest sources of atmospheric dust is the Sahara. It is said that 55% of the total global dust emission can be linked to the desert in northern Africa. Thus, understanding the Saharan dust sources is of great importance to estimate the total global dust load and its variability. Especially one type of dust sources has gained attention in dust research in recent years: The emission of dust from sediments formed by hydrologic processes, so called alluvial dust sources. These sediments were either formed in the past under the influences of a more humid paleoclimate or are deposited recently, e.g. during strong precipitation events when surficial runoff leads to the activation of wadi systems or to the occurrence of flash floods. Especially the latter phenomenon is able to deliver a huge amount of potentially erodible sediments. The research presented here focuses on the characterization of these alluvial dust sources with special attention on their temporal variability in relation to wet and dry phases. A study area covering the Aïr Massif in Niger is analysed over a four years time span from January 2013 to December 2016. The whole cycle from sediment formation to dust emission is illustrated by using data of various satellite sensors that are able to capture the processes taking place at the land surface as well as in the atmosphere: (1) The rainfall distribution for the study area is shown by time series of the TRMM precipitation estimates. A catchment analysis of the area helps to estimate the amount of surficial runoff and to detect areas of potential sediment accumulation. (2) Changes in the sediment structure of the land surface are analysed using atmospherically corrected time series of NASA's Landsat-8 OLI satellite. A land cover classification shows the distribution of alluvial sediments over the area; fresh layers of alluvial deposits are detected. Furthermore, the evolution of the vegetation cover, which inhibits dust emission, is analysed by calculating NDVI time series from the Landsat data. (3) The MSG Dust Product is used to determine the frequency of dust emission from the investigation area. Furthermore, the product allows the precise localization of the sources. Therefore the alluvial sediments can directly be connected to dust emission. By combining the findings of these different satellite sensors, a profound analysis of alluvial dust sources on different levels is possible. The connection between the amount of precipitation and the supply of potentially erodible sediments is shown, which leads to a better understanding of the temporal evolution and importance of this source type.

Iceland Polar Vortex 2016 campaign: Winter and high-altitude dust size distributions with the balloon-borne Light Optical Aerosol Counter (LOAC)

NASA Astrophysics Data System (ADS)

Renard, Jean-Baptiste; Dagsson-Waldhauserova, Pavla; Olafsson, Haraldur; Arnalds, Olafur; Vignelles, Damien; Verdier, Nicolas

2017-04-01

Iceland has the largest area of volcaniclastic sandy desert on Earth where dust is originating from volcanic, but also glaciogenic sediments. Total Icelandic desert areas cover 44,000 km2 which makes Iceland the largest Arctic as well as European desert. The mean frequency of days with dust suspension was to 135 dust days annually in 1949-2011. The annual dust deposition was calculated as 31 - 40.1 million tons yr-1 affecting the area of > 500,000 km2. About 50% of the suspended PM10 are submicron particles. Icelandic dust is of volcanic origin; it is very dark in colour and contains sharp-tipped shards with bubbles. Such properties allow even large particles to be easily transported long distances as revealed on the satellite MODIS images with dust plumes traveling over 1000 km at times. There is a need to understand better the vertical distribution of such aerosols as well as their residence time in the atmosphere, especially during occasions such as polar vortex. Four LOAC flights were performed under meteorological balloons in Iceland in January 9-13 2016 when stratospheric polar vortex occurred above Iceland. LOAC is an optical aerosol counter that uses a new optical design to retrieve the size concentrations in 19 size classes between 0.2 and 100 micrometers, and to provide an estimate of the main nature of aerosols. Vertical profile of aerosol size distribution showed the presence of volcanic dust particles up to altitudes of 8 km for two of the flights (9-10 January). The MODIS satellite images confirmed a dust plume present above the southern coast from the deposits of September 2015 glacial outburst flood (jökulhlaup) while the rest of the country was covered by snow. These deposits had been actively suspended in November and December 2015. The ground PM10 mass concentration measurements in Reykjavik showed elevated PM measurements over 100 micrograms.m-3, confirming the particle presence 250 km far from the source. The number concentration exceeded 200 particles cm-3 at altitude of 1 km and 60 particles cm-3 at altitude of 5 km, which is at least 5 times higher than during background conditions. The particles were < 3 micrometers in size at altitudes >1 km while largest particles, up to 20 micrometers, were detected close to the ground. Such high number concentrations in several km height were captured by LOAC during a typical Saharan dust plume. On the other hand, aircraft measurements of winter dust storm in 2007 with an aerosol spectrometer (0.1-3 micrometers) detected only 30-50 particles per cm3 in altitude 1900 m. Our results show that fine volcanic glacially reworked dust can reach high altitudes relatively close to the dust source and reside in terms of days under winter atmospheric conditions. The remaining question is the further transport of these high altitude particles outside Iceland.

Transport of Alaskan Dust into the Gulf of Alaska and Comparison with Similar High-Latitude Dust Environments

NASA Technical Reports Server (NTRS)

Crusium, John; Levy, Rob; Wang, Jun; Campbell, Rob; Schroth, Andrew W.

2012-01-01

Transport of Alaskan dust into the Gulf of Alaska and comparison with similar high-latitude dust environments. An airborne flux of the micronutrient iron, derived from dust originating from coastal regions may be an important contributor of iron to the Gulf of Alaska's (GoA) oligotrophic waters. Dust blowing off glacier termini and dry riverbeds is a recurring phenomenon in Alaska, usually occurring in the autumn. Since previous studies assumed that dust originating in the deserts of Asia was the largest source of . airborne iron to the GoA, the budget of aeolian deposition of iron needs to be reassessed. Since late 20 I 0, our group has been monitoring dust activity using satellites over the Copper River Delta (CRD) where the most vigorous dust plumes have been observed. Since 2011, sample aerosol concentration and their composition are being collected at Middleton Island (100km off shore of CRD). This presentation will show a summary of the ongoing dust observations and compare with other similar environments (Patagonia, Iceland) by showing case studies. Common features will be highlighted

Large Salt Dust Storms Follow a 30-Year Rainfall Cycle in the Mar Chiquita Lake (Córdoba, Argentina)

PubMed Central

Stein, Ariel F.

2016-01-01

Starting in 2006, a new source of intense salt dust storms developed in Mar Chiquita (Córdoba, Argentina), the largest saline lake in South America. Storms originate from vast mudflats left by a 30-year expansion-retreat cycle of the lake due to changes in the regional rainfall regime. The annual frequency of salt dust storms correlated with the size of the salt mudflats. Events were restricted to the coldest months, and reached up to 800 km from the source. Occurrence of dust storms was associated with specific surface colors and textures easily identifiable in satellite images. High-emission surfaces were characterized by the presence of sodium sulfate hydrous/anhydrous crystals (mirabilite and thenardite), and a superficial and variable water table, which may result in the periodic development of a characteristic “fluffy” surface derived from salt precipitation-dissolution processes. HYSPLIT model simulation estimates a deposition maximum near the sources (of about 2.5 kg/ha/yr), and a decreasing trend from the emission area outwards, except for the relative secondary maximum modeled over the mountain ranges in southern Bolivia and northern Argentina due to an orographic effect. The 2009 total deposition of salt dust generated in Mar Chiquita was estimated at 6.5 million tons. PMID:27258088

Large Salt Dust Storms Follow a 30-Year Rainfall Cycle in the Mar Chiquita Lake (Córdoba, Argentina).

PubMed

Bucher, Enrique H; Stein, Ariel F

2016-01-01

Starting in 2006, a new source of intense salt dust storms developed in Mar Chiquita (Córdoba, Argentina), the largest saline lake in South America. Storms originate from vast mudflats left by a 30-year expansion-retreat cycle of the lake due to changes in the regional rainfall regime. The annual frequency of salt dust storms correlated with the size of the salt mudflats. Events were restricted to the coldest months, and reached up to 800 km from the source. Occurrence of dust storms was associated with specific surface colors and textures easily identifiable in satellite images. High-emission surfaces were characterized by the presence of sodium sulfate hydrous/anhydrous crystals (mirabilite and thenardite), and a superficial and variable water table, which may result in the periodic development of a characteristic "fluffy" surface derived from salt precipitation-dissolution processes. HYSPLIT model simulation estimates a deposition maximum near the sources (of about 2.5 kg/ha/yr), and a decreasing trend from the emission area outwards, except for the relative secondary maximum modeled over the mountain ranges in southern Bolivia and northern Argentina due to an orographic effect. The 2009 total deposition of salt dust generated in Mar Chiquita was estimated at 6.5 million tons.

Polycyclic Aromatic Hydrocarbons in Residential Dust: Sources of Variability

PubMed Central

Metayer, Catherine; Petreas, Myrto; Does, Monique; Buffler, Patricia A.; Rappaport, Stephen M.

2013-01-01

Background: There is interest in using residential dust to estimate human exposure to environmental contaminants. Objectives: We aimed to characterize the sources of variability for polycyclic aromatic hydrocarbons (PAHs) in residential dust and provide guidance for investigators who plan to use residential dust to assess exposure to PAHs. Methods: We collected repeat dust samples from 293 households in the Northern California Childhood Leukemia Study during two sampling rounds (from 2001 through 2007 and during 2010) using household vacuum cleaners, and measured 12 PAHs using gas chromatography–mass spectrometry. We used a random- and a mixed-effects model for each PAH to apportion observed variance into four components and to identify sources of variability. Results: Median concentrations for individual PAHs ranged from 10 to 190 ng/g of dust. For each PAH, total variance was apportioned into regional variability (1–9%), intraregional between-household variability (24–48%), within-household variability over time (41–57%), and within-sample analytical variability (2–33%). Regional differences in PAH dust levels were associated with estimated ambient air concentrations of PAH. Intraregional differences between households were associated with the residential construction date and the smoking habits of residents. For some PAHs, a decreasing time trend explained a modest fraction of the within-household variability; however, most of the within-household variability was unaccounted for by our mixed-effects models. Within-household differences between sampling rounds were largest when the interval between dust sample collections was at least 6 years in duration. Conclusions: Our findings indicate that it may be feasible to use residential dust for retrospective assessment of PAH exposures in studies of health effects. PMID:23461863

Aerosol Sources, Absorption, and Intercontinental Transport: Synergies among Models, Remote Sensing, and Atmospheric Measurements

NASA Technical Reports Server (NTRS)

Chin, Mian; Ginoux, Paul; Dubovik, Oleg; Holben, Brent; Kaufman, Yoram; chu, Allen; Anderson, Tad; Quinn, Patricia

2003-01-01

Aerosol climate forcing is one of the largest uncertainties in assessing the anthropogenic impact on the global climate system. This uncertainty arises from the poorly quantified aerosol sources, especially black carbon emissions, our limited knowledge of aerosol mixing state and optical properties, and the consequences of intercontinental transport of aerosols and their precursors. Here we use a global model GOCART to simulate atmospheric aerosols, including sulfate, black carbon, organic carbon, dust, and sea salt, from anthropogenic, biomass burning, and natural sources. We compare the model calculated aerosol extinction and absorption with those quantities from the ground-based sun photometer measurements from AERONET at several different wavelengths and the field observations from ACE-Asia, and model calculated total aerosol optical depth and fine mode fractions with the MODIS satellite retrieval. We will also estimate the intercontinental transport of pollution and dust aerosols from their source regions to other areas in different seasons.

Aerosol Sources, Absorption, and Intercontinental Transport: Synergies Among Models, Remote Sensing, and Atmospheric Measurements

NASA Technical Reports Server (NTRS)

Chin, Mian; Chu, Allen; Levy, Robert; Remer, Lorraine; Kaufman, Yoram; Dubovik, Oleg; Holben, Brent; Eck, Tom; Anderson, Tad; Quinn, Patricia

2004-01-01

Aerosol climate forcing is one of the largest uncertainties in assessing the anthropogenic impact on the global climate system. This uncertainty arises from the poorly quantified aerosol sources, especially black carbon emissions, our limited knowledge of aerosol mixing state and optical properties, and the consequences of intercontinental transport of aerosols and their precursors. Here we use a global model GOCART to simulate atmospheric aerosols, including sulfate, black carbon, organic carbon, dust, and sea salt, from anthropogenic, .biomass burning, and natural sources. We compare the model calculated aerosol extinction and absorption with those quantities from the ground-based sun photometer measurements from AERON" at several different wavelengths and the field observations from ACE-Asia, and model calculated total aerosol optical depth and fine mode fractions with the MODIS satellite retrieval. We will also estimate the intercontinental transport of pollution and dust aerosols from their source regions to other areas in different seasons.

High Proportions of Sub-micron Particulate Matter in Icelandic Dust Storms in 2015

NASA Astrophysics Data System (ADS)

Dagsson Waldhauserova, Pavla; Arnalds, Olafur; Olafsson, Haraldur; Magnusdottir, Agnes

2017-04-01

Iceland is extremely active dust region and desert areas of over 44,000 km2 acknowledge Iceland as the largest Arctic and European desert. Frequent dust events, up to 135 dust days annually, transport dust particles far distances towards the Arctic and Europe. Satellite MODIS pictures have revealed dust plumes exceeding 1,000 km. The annual dust deposition was calculated as 40.1 million tons yr-1. Two dust storms were measured in transverse horizontal profile about 90 km far from different dust sources in southwestern Iceland in the summer of 2015. Aerosol monitor DustTrak DRX 8533EP was used to measure PM mass concentrations corresponding to PM1, PM2.5, PM4, PM10 and the total PM15 at several places within the dust plume. Images from camera network operated by the Icelandic Road and Coastal Administration were used to estimate the visibility and spatial extent of measured dust events. A numerical simulation of surface winds was carried out with the numerical model HIRLAM with horizontal resolution of 5 km and used to calculate the total dust flux from the sources. The in situ measurements inside the dust plumes showed that aeolian dust can be very fine. The study highlights that suspended volcanic dust in Iceland causes air pollution with extremely high PM1 concentrations comparable to the polluted urban stations in Europe or Asia rather than reported dust event observations from around the world. The PM1/PM2.5 ratios are generally low during dust storms outside of Iceland, much lower than > 0.9 and PM1/PM10 ratios of 0.34-0.63 found in our study. It shows that Icelandic volcanic dust consists of higher proportion of submicron particles compared to crustal dust. The submicron particles are predicted to travel long distances. Moreover, such submicron particles pose considerable health risk because of high potential for entering the lungs. Icelandic volcanic glass has often fine pipe-vesicular structures known from asbestos and high content of heavy metals. Previous in situ measurements at the dust source in 2013 revealed extremely high number concentrations of submicron particles, specifically in the size range 0.3-0.337 μm. The PM2.5/PM10 ratios of mass concentrations seem to be lower at the dust sources that in some distance from the sources as measured in 2015. Common dust storms in Iceland are of several hundred thousand tons of magnitude from relatively well defined main dust sources. Numerical simulations were used calculate the total dust flux from the sources as 180,000 - 280,000 tons in this study. The mean PM1 (PM10) concentrations inside of the dust plumes varied from 97 to 241 µg m-3 (PM10 = 158 to 583 µg m-3). The extent of moderate dust events was calculated as 2.450 km2 to 4.220 km2 of the land area suggesting the regional scale of the events. Dust plumes reported here passed the most densely inhabited areas of Iceland, health risk warnings for the general public were, however, not issued. The data provided stresses the need for such warning system and is an important step towards its development.

Relative Impact of Emissions Controls and Meteorology on Air Pollution Mitigation Associated with the Asia-Pacific Economic Cooperation (APEC) Conference in Beijing, China

NASA Astrophysics Data System (ADS)

Zhang, Y.; Wang, Y.; Schauer, J. J.; de Foy, B.

2016-12-01

The Beijing government and its surrounding provinces implemented a series of measures to ensure haze-free skies during the 22nd Asia-Pacific Economic Cooperation (APEC) conference (November 10th - 11th, 2014). These measures included restrictions on traffic, construction, and industrial activity. Twelve hour measurements of the concentration and composition of ambient fine particulate matter (PM2.5) were performed for 5 consecutive months near the APEC conference site before (September 11th - November 2nd, 2014), during (November 3rd - 12th, 2014) and after (November 13th, 2014 - January 31st, 2015). The measurements are used in a positive matrix factorization model to determine the contributions from seven sources of PM2.5: secondary aerosols, mobile source, industrial emission, road dust, soil dust, biomass burning and residual oil combustion. The source apportionment results are integrated with backward trajectory analysis using Weather Research and Forecast (WRF) meteorological simulations, which determine the relative influence of new regulation and meteorology upon improved air quality during the APEC conference. Data show that controls are very effective, but meteorology must be taken into account to determine the actual influence of the controls on pollution reduction. The Industry source control is the most effective for reducing concentrations, follows by secondary aerosol and biomass controls, while the least effective control is for the residual oil combustion source. The largest reductions in concentrations occur when air mass transport is from the west-northwest (Ulanqab). Secondary aerosol and mobile source reductions are most significant for air mass transport from the north-northwest (Xilingele League) origin, and least significant for northeast transport (Chifeng via Tangshan conditions). The largest reductions of soil dust, biomass burning, and industrial source are distinctly seen for Ulanqab conditions and least distinct for Xilingele League.

Remote-sensing-based analysis of landscape change in the desiccated seabed of the Aral Sea--a potential tool for assessing the hazard degree of dust and salt storms.

PubMed

Löw, F; Navratil, P; Kotte, K; Schöler, H F; Bubenzer, O

2013-10-01

With the recession of the Aral Sea in Central Asia, once the world's fourth largest lake, a huge new saline desert emerged which is nowadays called the Aralkum. Saline soils in the Aralkum are a major source for dust and salt storms in the region. The aim of this study was to analyze the spatio-temporal land cover change dynamics in the Aralkum and discuss potential implications for the recent and future dust and salt storm activity in the region. MODIS satellite time series were classified from 2000-2008 and change of land cover was quantified. The Aral Sea desiccation accelerated between 2004 and 2008. The area of sandy surfaces and salt soils, which bear the greatest dust and salt storm generation potential increased by more than 36 %. In parts of the Aralkum desalinization of soils was found to take place within 4-8 years. The implication of the ongoing regression of the Aral Sea is that the expansion of saline surfaces will continue. Knowing the spatio-temporal dynamics of both the location and the surface characteristics of the source areas for dust and salt storms allows drawing conclusions about the potential hazard degree of the dust load. The remote-sensing-based land cover assessment presented in this study could be coupled with existing knowledge on the location of source areas for an early estimation of trends in shifting dust composition. Opportunities, limits, and requirements of satellite-based land cover classification and change detection in the Aralkum are discussed.

Laboratory estimate of the regional shortwave refractive index and single scattering albedo of mineral dust from major sources worldwide

NASA Astrophysics Data System (ADS)

Di Biagio, C.; Formenti, P.; Caponi, L.; Cazaunau, M.; Pangui, E.; Journet, E.; Nowak, S.; Caquineau, S.; Andreae, M. O.; Kandler, K.; Saeed, T.; Piketh, S.; Seibert, D.; Williams, E.; Balkanski, Y.; Doussin, J. F.

2017-12-01

Mineral dust is one of the most abundant aerosol species in the atmosphere and strongly contributes to the global and regional direct radiative effect. Still large uncertainties persist on the magnitude and overall sign of the dust direct effect, where indeed one of the main unknowns is how much mineral dust absorbs light in the shortwave (SW) spectral range. Aerosol absorption is represented both by the imaginary part (k) of the complex refractive index or the single scattering albedo (SSA, i.e. the ratio of the scattering to extinction coefficient). In this study we present a new dataset of SW complex refractive indices and SSA for mineral dust aerosols obtained from in situ measurements in the 4.2 m3 CESAM simulation chamber at LISA (Laboratoire Interuniversitaire des Systemes Atmospheriques) in Créteil, France. Investigated dust aerosol samples were issued from major desert sources worldwide, including the African Sahara and Sahel, Eastern Asia, the Middle East, Southern Africa, Australia, and the Americas, with differing iron oxides content. Results from the present study provide a regional mapping of the SW absorption by dust and show that the imaginary part of the refractive index largely varies (by up to a factor 6, 0.003-0.02 at 370 nm and 0.001-0.003 at 950 nm) for the different source areas due to the change in the particle iron oxide content. The SSA for dust varies between 0.75-0.90 at 370 nm and 0.95-0.99 at 950 nm, with the largest absorption observed for Sahelian and Australian dust aerosols. Our range of variability for k and SSA is well bracketed by already published literature estimates, but suggests that regional‒dependent values should be used in models. The possible relationship between k and the dust iron oxides content is investigated with the aim of providing a parameterization of the regional‒dependent dust absorption to include in climate models.

Modeling carbonaceous particle formation in an argon graphite cathode dc discharge

NASA Astrophysics Data System (ADS)

Michau, A.; Lombardi, G.; Colina Delacqua, L.; Redolfi, M.; Arnas, C.; Bonnin, X.; Hassouni, K.

2010-12-01

We develop a model for the nucleation, growth and transport of carbonaceous dust particles in a non-reactive gas dc discharge where the carbon source is provided by cathode sputtering. We consider only the initial phase of the discharge when the dust charge density remains small with respect to the electron density. We find that an electric field reversal at the entrance of the negative glow region promotes trapping of negatively charged clusters and dust particles, confining them for long times in the plasma and favoring molecular growth. An essential ingredient for this process is electron attachment, which negatively charges the initially neutral clusters. We perform sensitivity studies on several number parameters: size of the largest molecular edifice, sticking coefficient, etc.

Trans-Pacific transport of dust aerosols from East Asia: Insights gained from multiple observations and modeling.

PubMed

Guo, Jianping; Lou, Mengyun; Miao, Yucong; Wang, Yuan; Zeng, Zhaoliang; Liu, Huan; He, Jing; Xu, Hui; Wang, Fu; Min, Min; Zhai, Panmao

2017-11-01

East Asia is one of the world's largest sources of dust and anthropogenic pollution. Dust particles originating from East Asia have been recognized to travel across the Pacific to North America and beyond, thereby affecting the radiation incident on the surface as well as clouds aloft in the atmosphere. In this study, integrated analyses are performed focusing on one trans-Pacific dust episode during 12-22 March 2015, based on space-borne, ground-based observations, reanalysis data combined with Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT), and the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem). From the perspective of synoptic patterns, the location and strength of Aleutian low pressure system largely determined the eastward transport of dust plumes towards western North America. Multi-sensor satellite observations reveal that dust aerosols in this episode originated from the Taklimakan and Gobi Deserts. Moreover, the satellite observations suggest that the dust particles can be transformed to polluted particles over the East Asian regions after encountering high concentration of anthropogenic pollutants. In terms of the vertical distribution of polluted dust particles, at the very beginning, they were mainly located in the altitudes ranging from 1 km to 7 km over the source region, then ascended to 2 km-9 km over the Pacific Ocean. The simulations confirm that these elevated dust particles in the lower free troposphere were largely transported along the prevailing westerly jet stream. Overall, observations and modeling demonstrate how a typical springtime dust episode develops and how the dust particles travel over the North Pacific Ocean all the way to North America. Copyright © 2017 Elsevier Ltd. All rights reserved.

Potentials and problems of building detailed dust records using peat archives: An example from Store Mosse (the "Great Bog"), Sweden

NASA Astrophysics Data System (ADS)

Kylander, Malin E.; Martínez-Cortizas, Antonio; Bindler, Richard; Greenwood, Sarah L.; Mörth, Carl-Magnus; Rauch, Sebastien

2016-10-01

Mineral dust deposition is a process often overlooked in northern mid-latitudes, despite its potential effects on ecosystems. These areas are often peat-rich, providing ample material for the reconstruction of past changes in atmospheric deposition. The highly organic (up to 99% in some cases) matrix of atmospherically fed mires, however, makes studying the actual dust particles (grain size, mineralogy) challenging. Here we explore some of the potentials and problems of using geochemical data from conservative, lithogenic elements (Al, Ga, Rb, Sc, Y, Zr, Th, Ti and REE) to build detailed dust records by using an example from the 8900-yr peat sequence from Store Mosse (the ;Great Bog;), which is the largest mire complex in the boreo-nemoral region of southern Sweden. The four dust events recorded at this site were elementally distinct, suggesting different dominant mineral hosts. The oldest and longest event (6385-5300 cal yr BP) sees a clear signal of clay input but with increasing contributions of mica, feldspar and middle-REE-rich phosphate minerals over time. These clays are likely transported from a long-distance source (<100 km). While dust deposition was reduced during the second event (5300-4370 cal yr BP), this is the most distinct in terms of its source character with [Eu/Eu∗]UCC revealing the input of plagioclase feldspar from a local source, possibly active during this stormier period. The third (2380-2200 cal yr BP) and fourth (1275-1080 cal yr BP) events are much shorter in duration and the presence of clays and heavy minerals is inferred. Elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element. The broad changes in major mineral hosts, grain size, source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern Europe. The two most recent dust events are much shorter in duration, which in combination with evidence of their local and regional character, may explain why they have not been seen elsewhere.

Source Apportionment of Particulate Matter Collected Upwind and Downwind of a Steel Facility in Granite City, IL (USA)

NASA Astrophysics Data System (ADS)

Duvall, R. M.; Norris, G. A.; Willis, R. D.; Turner, J. R.; Kaleel, R.; Sweitzer, T.; Preston, B.; Hays, M. D.

2009-04-01

St. Louis is currently in nonattainment of the annual PM2.5 National Ambient Air Quality Standard (NAAQS). Granite City Steel Works (GSCW), located in Granite City, IL is considered to be a significant source impacting the St. Louis area and the largest PM2.5 point source contributor. Twelve grab samples were collected in and around the steel facility including the basic oxygen furnace, steel and iron slag crushing, coal pulverizing, baghouse dust, paved road dust, and unpaved road dust. The bulk samples were resuspended in a resuspension chamber using a PM2.5 cutpoint and collected on Teflon, quartz and polycarbonate filters. Fine particulate matter (PM) samples (12-hr and 24-hr) were collected upwind and downwind of GSCW from October 13 to December 13, 2007 to identify sources contributing to nonattainment in St. Louis. The samples were analyzed for trace metals (X-Ray Fluorescence), ions (Ion Chromatography), elemental and organic carbon (thermal optical analysis), and organic species (solvent extraction Gas Chromatography/Mass Spectrometry). Source apportionment was conducted using the EPA Chemical Mass Balance (CMB) Model (v 8.2). Major sources impacting the 12-hr samples included the blast oxygen furnace, secondary sulfate, and road dust. Higher excess steel and coke works contributions were associated with higher wind speeds (greater than 5 mph) and more variability in source impacts was observed. Major sources impacting the 24-hr samples included secondary sulfate and motor vehicles (diesel and gasoline). Contributions were similar between the coke and steel works sources. Disclaimer: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Emissions from vehicles, tailpipe and vehicle re-entrained road dust

NASA Astrophysics Data System (ADS)

Zhu, Dongzi

Emissions from transportation are some of the largest sources of urban air pollution. Transportation emissions originate from both the engine-through combustion processes and non-tailpipe re-suspended road dust emissions induced by vehicle travel on unpaved and paved roads. Gaseous and particulate emissions from transportation sources have negative impacts on human health, visibility and may influence the global radiation balance. Fugitive dust emissions originating from vehicle travel on paved and unpaved roads constitute a significant fraction of the PM10 in many areas of the western US impacting their attainment status of National Ambient Air Quality Standards. The research used three novel instrument platforms developed at the Desert Research Institute. The In-Plume Emissions Test Stand (IPETS) was designed to provide characterization of exhaust emissions from in-use individual vehicles or engines by analyzing air as close as 1 m from the exhaust port. Real-world emission factors can be quantified by in-plume measurements and provide more realistic measures for emission inventories, source modeling, and receptor modeling than certification measurements. The Testing Re-entrained Aerosol Kinetic Emissions from Roads (TRAKER) provides an effective alternate approach to the EPA AP-42 road dust emissions estimation techniques by sampling 1000s of km of roads versus isolated 3 m sections. The Portable Deposition Monitoring Platform (PDMP incorporates PM and meteorological instruments to characterize the downwind change in particle concentrations to define depositional losses in different environments. The research outcome provides important knowledge for understanding diesel engine emissions, road dust emissions and aerosol deposition process near road sources.

The impact of seasonal varied human activity on characteristics and sources of heavy metals in metropolitan road dusts.

PubMed

Men, Cong; Liu, Ruimin; Wang, Qingrui; Guo, Lijia; Shen, Zhenyao

2018-10-01

Due to significant human activity, road dust is becoming contaminated by heavy metals in many cities. To comprehensively investigate the variation of contamination level and sources of heavy metals in road dust, 10 heavy metals in road dust samples from Beijing, China, in both summer and winter, were evaluated by spatial analysis using geographic information system (GIS) mapping technology and the positive matrix factorization (PMF) Model. Although the concentrations of some heavy metals between summer and winter had similarities, the differences of others and spatial distributions of heavy metals between summer and winter were considerable. The mean concentrations of As, Cd, Cr, Cu, and Fe were lower in winter, while those of Hg, Mn, Ni, Pb, and Zn were higher. According to the values of the Pollution Index (PI) and Nemerow Integrated Pollution Index (NIPI), there were no obvious differences between summer and winter, but the range between different sites in winter was nearly twice that of summer. Based on the PMF model, four sources of heavy metals in the dust samples were identified. Although the types of sources were consistent, the relative contributions of each source differed between summer and winter. Non-exhaust vehicle emissions was the most important source in summer (34.47 wt%), while fuel combustion contributed the largest proportion to the total heavy metals in winter (32.40 wt%). The impact of each source also showed spatial variation different trends in summer and winter. With the alteration of seasons, intensity of human activities also changed, such as the number of tourists, energy needs for building temperature regulation, construction, and the amount of pesticides and fertilizer. That might be the reason for the variation of heavy metal concentrations and relative contribution of their sources between summer and winter. Copyright © 2018 Elsevier B.V. All rights reserved.

Relative impact of emissions controls and meteorology on air pollution mitigation associated with the Asia-Pacific Economic Cooperation (APEC) conference in Beijing, China.

PubMed

Wang, Yuqin; Zhang, Yang; Schauer, James Jay; de Foy, Benjamin; Guo, Bo; Zhang, Yuanxun

2016-11-15

The Beijing government and its surrounding provinces implemented a series of measures to ensure haze-free skies during the 22(nd) Asia-Pacific Economic Cooperation (APEC) conference (November 10(th)-11(th), 2014). These measures included restrictions on traffic, construction, and industrial activity. Twelve hour measurements of the concentration and composition of ambient fine particulate matter (PM2.5) were performed for 5 consecutive months near the APEC conference site before (September 11(th)-November 2(nd), 2014), during (November 3(rd)-12(th), 2014) and after (November 13(th), 2014-January 31(st), 2015). The measurements are used in a positive matrix factorization model to determine the contributions from seven sources of PM2.5: secondary aerosols, traffic exhaust, industrial emission, road dust, soil dust, biomass burning and residual oil combustion. The source apportionment results are integrated with backward trajectory analysis using Weather Research and Forecast (WRF) meteorological simulations, which determine the relative influence of new regulation and meteorology upon improved air quality during the APEC conference. Data show that controls are very effective, but meteorology must be taken into account to determine the actual influence of the controls on pollution reduction. The industry source control is the most effective for reducing concentrations, followed by secondary aerosol and biomass controls, while the least effective control is for the residual oil combustion source. The largest reductions in concentrations occur when air mass transport is from the west-northwest (Ulanqab). Secondary aerosol and traffic exhaust reductions are most significant for air mass transport from the north-northwest (Xilingele League) origin, and least significant for northeast transport (Chifeng via Tangshan conditions). The largest reductions of soil dust, biomass burning, and industrial source are distinctly seen for Ulanqab conditions and least distinct for Xilingele League. Copyright © 2016 Elsevier B.V. All rights reserved.

Source apportionment of fine particles and its chemical components over the Yangtze River Delta, China during a heavy haze pollution episode

NASA Astrophysics Data System (ADS)

Li, L.; An, J. Y.; Zhou, M.; Yan, R. S.; Huang, C.; Lu, Q.; Lin, L.; Wang, Y. J.; Tao, S. K.; Qiao, L. P.; Zhu, S. H.; Chen, C. H.

2015-12-01

An extremely high PM2.5 pollution episode occurred over the eastern China in January 2013. In this paper, the particulate matter source apportionment technology (PSAT) method coupled within the Comprehensive air quality model with extensions (CAMx) is applied to study the source contributions to PM2.5 and its major components at six receptors (Urban Shanghai, Chongming, Dianshan Lake, Urban Suzhou, Hangzhou and Zhoushan) in the Yangtze River Delta (YRD) region. Contributions from 4 source areas (including Shanghai, South Jiangsu, North Zhejiang and Super-region) and 9 emission sectors (including power plants, industrial boilers and kilns, industrial processing, mobile source, residential, volatile emissions, dust, agriculture and biogenic emissions) to PM2.5 and its major components (sulfate, nitrate, ammonia, organic carbon and elemental carbon) at the six receptors in the YRD region are quantified. Results show that accumulation of local pollution was the largest contributor during this air pollution episode in urban Shanghai (55%) and Suzhou (46%), followed by long-range transport (37% contribution to Shanghai and 44% to Suzhou). Super-regional emissions play an important role in PM2.5 formation at Hangzhou (48%) and Zhoushan site (68%). Among the emission sectors contributing to the high pollution episode, the major source categories include industrial processing (with contributions ranging between 12.7 and 38.7% at different receptors), combustion source (21.7-37.3%), mobile source (7.5-17.7%) and fugitive dust (8.4-27.3%). Agricultural contribution is also very significant at Zhoushan site (24.5%). In terms of the PM2.5 major components, it is found that industrial boilers and kilns are the major source contributor to sulfate and nitrate. Volatile emission source and agriculture are the major contributors to ammonia; transport is the largest contributor to elemental carbon. Industrial processing, volatile emissions and mobile source are the most significant contributors to organic carbon. Results show that the Yangtze River Delta region should focus on the joint pollution control of industrial processing, combustion emissions, mobile source emissions, and fugitive dust. Regional transport of air pollution among the cities are prominent, and the implementation of regional joint prevention and control of air pollution will help to alleviate fine particulate matter concentrations under heavy pollution case significantly.

Seasonal and Elevational Variations of Black Carbon and Dust in Snow and Ice in the Solu-Khumbu, Nepal and Estimated Radiative Forcings

NASA Astrophysics Data System (ADS)

Kaspari, S.; Painter, T. H.; Gysel, M.; Skiles, M.; Schwikowski, M.

2014-12-01

Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snowpits at elevations between 5400 and 6400 m asl from Mera glacier located in the Solu-Khumbu region of Nepal. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). BC and Fe concentrations are substantially higher at elevations < 6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations < 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass-balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter-spring snow/ice horizons are sufficient to reduce albedo by 6-10% relative to clean snow, corresponding to localized instantaneous radiative forcings of 75-120 W m-2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40-42% relative to clean snow and give localized instantaneous radiative forcings of 488 to 525 W m-2. Adding the BC absorption to the other impurities results in additional radiative forcings of 3 W m-2. While these results suggest that the snow albedo and radiative forcing effect of dust is considerably greater than BC, there are several sources of uncertainty.

Knudsen cell: Investigations about the uptake of important traces gases on ambient airborne mineral dust

NASA Astrophysics Data System (ADS)

Horn, Sabrina; Herrmann, Hartmut

2013-04-01

Mineral dust constitutes one of the largest mass fractions of natural aerosol. Its emission is estimated between 800 - 2000 Tg/a]. The dust is emitted through sand and dust storms in the arid regions of our planet, in particular by the great desserts such as the Sahara. The complex chemical composition of mineral dust is similar to crust material, because the dust is produced by soil erosion. The main components of mineral dust are SiO2 and Al2O3, whereas the active oxides (Fe2O3, TiO2) show some variety in content due to the dust source region. Mineral dust particles can be transported over several 1000 km and during its transport the surface can be changed by the uptake of water vapor and trace gases. On such modified surfaces homo- and heterogeneous reactions can occur. Trace gas uptakes play an important role in atmospheric chemistry as sinks or sources for several gaseous species. Hence, it is necessary to study these reactions. Among several experimental setups, the Knudsen cell is one of the promising tools to study reactive uptakes from the gas phase and the release of products formed by dust surface-mediated reactions. The Knudsen cell, implemented by Golden et al. in 1975, is a high vacuum flow reactor operating under molecular flow conditions, i.e., gas-wall collisions are highly preferred over gas-gas collisions. Despite several Knudsen cell studies examining the reaction between different traces gases and model dust surfaces constituted of not more than a few components, no measurements utilizing collected ambient mineral dust are done so far. For a better understanding of the chemistry on mineral dust surfaces gas uptake measurements will be done with a Knudsen cell. The first measurements are done with isopropanol on TiO2. Afterwards there are studies with different substrates like, Al2O3 (α- and γ-phase), FeO2, Arizona test dust, air collected mineral dust from the Cap Verde islands. In the beginning SO2, NO2 and HNO3 will be used.

Dust storms and the risk of asthma admissions to hospitals in Kuwait.

PubMed

Thalib, Lukman; Al-Taiar, Abdullah

2012-09-01

Arid areas in the Arabian Peninsula are one of the largest sources of global dust, yet there is no data on the impact of this on human health. This study aimed to investigate the impact of dust storms on hospital admissions due to asthma and all respiratory diseases over a period of 5 years in Kuwait. A population-based retrospective time series study of daily emergency asthma admissions and admissions due to respiratory causes in public hospitals in Kuwait was analyzed in relation to dust storm events. Dust storm days were defined as the mean daily PM(10)>200 μg/m(3) based on measurements obtained from all six monitoring sites in the country. During the five-year study period, 569 (33.6%) days had dust storm events and they were significantly associated with an increased risk of same-day asthma and respiratory admission, adjusted relative risk of 1.07 (95% CI: 1.02-1.12) and 1.06 (95% CI: 1.04-1.08), respectively. This was particularly evident among children. Dust storms have a significant impact on respiratory and asthma admissions. Evidence is more convincing and robust compared to that from other geographical settings which highlights the importance of public health measures to protect people's health during dust storms and reduce the burden on health services due to dust events. Copyright © 2012 Elsevier B.V. All rights reserved.

Operational prediction of air quality for the United States: applications of satellite observations

NASA Astrophysics Data System (ADS)

Stajner, Ivanka; Lee, Pius; Tong, Daniel; Pan, Li; McQueen, Jeff; Huang, Jianping; Huang, Ho-Chun; Draxler, Roland; Kondragunta, Shobha; Upadhayay, Sikchya

2015-04-01

Operational predictions of ozone and wildfire smoke over United States (U.S.) and predictions of airborne dust over the contiguous 48 states are provided by NOAA at http://airquality.weather.gov/. North American Mesoscale (NAM) weather predictions with inventory based emissions estimates from the U.S. Environmental Protection Agency (EPA) and chemical processes within the Community Multiscale Air Quality (CMAQ) model are combined together to produce ozone predictions. Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is used to predict wildfire smoke and dust storm predictions. Routine verification of ozone predictions relies on AIRNow compilation of observations from surface monitors. Retrievals of smoke column integrals from GOES satellites and dust column integrals from MODIS satellite instruments are used for verification of smoke and dust predictions. Recent updates of NOAA's operational air quality predictions have focused on mobile emissions using the projections of mobile sources for 2012. Since emission inventories are complex and take years to assemble and evaluate causing a lag of information, we recently began combing inventory information with projections of mobile sources. In order to evaluate this emission update, these changes in projected NOx emissions from 2005-2012 were compared with observed changes in Ozone Monitoring Instrument (OMI) NO2 observations and NOx measured by surface monitors over large U.S. cities over the same period. Comparisons indicate that projected decreases in NOx emissions from 2005 to 2012 are similar, but not as strong as the decreases in the observed NOx concentrations and in OMI NO2 retrievals. Nevertheless, the use of projected mobile NOx emissions in the predictions reduced biases in predicted NOx concentrations, with the largest improvement in the urban areas. Ozone biases are reduced as well, with the largest improvement seen in rural areas. Recent testing of PM2.5 predictions is relying on emissions inventories augmented by real time sources from wildfires and dust storms. The evaluation of these test predictions relies on surface monitor data, but efforts are in progress to include comparisons with satellite observed aerosol optical depth (AOD) products. Testing of PM2.5 predictions continues to exhibit seasonal biases: overprediction in the winter and underprediction in the summer. The current efforts focus on bias correction and development of linkages with global atmospheric composition predictions.

Legal immigrants: invasion of alien microbial communities during winter occurring desert dust storms.

PubMed

Weil, Tobias; De Filippo, Carlotta; Albanese, Davide; Donati, Claudio; Pindo, Massimo; Pavarini, Lorenzo; Carotenuto, Federico; Pasqui, Massimiliano; Poto, Luisa; Gabrieli, Jacopo; Barbante, Carlo; Sattler, Birgit; Cavalieri, Duccio; Miglietta, Franco

2017-03-10

A critical aspect regarding the global dispersion of pathogenic microorganisms is associated with atmospheric movement of soil particles. Especially, desert dust storms can transport alien microorganisms over continental scales and can deposit them in sensitive sink habitats. In winter 2014, the largest ever recorded Saharan dust event in Italy was efficiently deposited on the Dolomite Alps and was sealed between dust-free snow. This provided us the unique opportunity to overcome difficulties in separating dust associated from "domestic" microbes and thus, to determine with high precision microorganisms transported exclusively by desert dust. Our metagenomic analysis revealed that sandstorms can move not only fractions but rather large parts of entire microbial communities far away from their area of origin and that this microbiota contains several of the most stress-resistant organisms on Earth, including highly destructive fungal and bacterial pathogens. In particular, we provide first evidence that winter-occurring dust depositions can favor a rapid microbial contamination of sensitive sink habitats after snowmelt. Airborne microbial depositions accompanying extreme meteorological events represent a realistic threat for ecosystem and public health. Therefore, monitoring the spread and persistence of storm-travelling alien microbes is a priority while considering future trajectories of climatic anomalies as well as anthropogenically driven changes in land use in the source regions.

The effect of mineral dust transport on PM10 concentrations and physical properties in Istanbul during 2007-2014

NASA Astrophysics Data System (ADS)

Flores, Rosa M.; Kaya, Nefel; Eşer, Övgü; Saltan, Şehnaz

2017-11-01

Mineral dust is the most significant source of natural particulate matter. In urban regions, where > 50% of the world population is currently living, local emissions of particulate matter are further aggravated by mineral dust loadings from deserts. The megacity of Istanbul is located in an area sensitive to local pollution due to transportation (i.e., private cars, public transportation, aircrafts, ships, heavy diesel trucks, etc.), industrial emissions, residential heating, and long-range transport from Europe, Asia, and deserts. In this work, the effect of desert dust transport on PM10 concentrations and physical properties was investigated for the period of 2007-2014 in the touristic area of Aksaray, Istanbul. The Dust Regional Atmospheric Model (DREAM8b) was used to predict dust loading in Istanbul during dust transport events. Variations on surface PM10 concentrations were investigated according to seasons and during dust transport events. Cluster analysis of air mass backward trajectories was useful to understand frequency analysis and air mass trajectory dependence of PM10 concentrations on dust loadings. The effect of desert dust transport on aerosol optical depths was also investigated. It was observed that PM10 concentrations exceeded the air quality standard of 50 μg m- 3 50% of the time during the study period. The largest number of exceedances in air quality standard occurred during the spring and winter seasons. Approximately 40-60% of the dust loading occurs during the spring. Desert dust and non-desert dust sources contribute to 22-72% and 48-81% of the ground-level PM10 concentrations in Aksaray, Istanbul during the study period. Averaged AOD observed during dust transport events in spring and summer ranged 0.35-0.55. Cluster analysis resolved over 82% the variability of individual air mass backward trajectories into 5 clusters. Overall, air masses arriving to Istanbul at 500 m are equally distributed into northern (52%) and southern (48%). Frequency analysis of PM10 concentrations with mean air mass backward trajectories showed that PM10 from local anthropogenic sources may be enhanced by long-range transport from the African Desert, Asian Desert, Arabian Peninsula, Russia, and Ukraine. The work presented here provides the first integrated assessment for evaluation of occurrence and quantification of the effect of dust transport to ground-level PM10 concentrations in Istanbul, which is helpful for human health prevention and implementation of air quality control measures.

Source apportionment of airborne particulate matter using organic compounds as tracers

NASA Astrophysics Data System (ADS)

Schauer, James J.; Rogge, Wolfgang F.; Hildemann, Lynn M.; Mazurek, Monica A.; Cass, Glen R.; Simoneit, Bernd R. T.

A chemical mass balance receptor model based on organic compounds has been developed that relates source contributions to airborne fine particle mass concentrations. Source contributions to the concentrations of specific organic compounds are revealed as well. The model is applied to four air quality monitoring sites in southern California using atmospheric organic compound concentration data and source test data collected specifically for the purpose of testing this model. The contributions of up to nine primary particle source types can be separately identified in ambient samples based on this method, and approximately 85% of the organic fine aerosol is assigned to primary sources on an annual average basis. The model provides information on source contributions to fine mass concentrations, fine organic aerosol concentrations and individual organic compound concentrations. The largest primary source contributors to fine particle mass concentrations in Los Angeles are found to include diesel engine exhaust, paved road dust, gasoline-powered vehicle exhaust, plus emissions from food cooking and wood smoke, with smaller contribution from tire dust, plant fragments, natural gas combustion aerosol, and cigarette smoke. Once these primary aerosol source contributions are added to the secondary sulfates, nitrates and organics present, virtually all of the annual average fine particle mass at Los Angeles area monitoring sites can be assigned to its source.

Source apportionment of airborne particulate matter using organic compounds as tracers

NASA Astrophysics Data System (ADS)

Schauer, James J.; Rogge, Wolfgang F.; Hildemann, Lynn M.; Mazurek, Monica A.; Cass, Glen R.; Simoneit, Bernd R. T.

A chemical mass balance receptor model based on organic compounds has been developed that relates sours; contributions to airborne fine particle mass concentrations. Source contributions to the concentrations of specific organic compounds are revealed as well. The model is applied to four air quality monitoring sites in southern California using atmospheric organic compound concentration data and source test data collected specifically for the purpose of testing this model. The contributions of up to nine primary particle source types can be separately identified in ambient samples based on this method, and approximately 85% of the organic fine aerosol is assigned to primary sources on an annual average basis. The model provides information on source contributions to fine mass concentrations, fine organic aerosol concentrations and individual organic compound concentrations. The largest primary source contributors to fine particle mass concentrations in Los Angeles are found to include diesel engine exhaust, paved road dust, gasoline-powered vehicle exhaust, plus emissions from food cooking and wood smoke, with smaller contribution:; from tire dust, plant fragments, natural gas combustion aerosol, and cigarette smoke. Once these primary aerosol source contributions are added to the secondary sulfates, nitrates and organics present, virtually all of the annual average fine particle mass at Los Angeles area monitoring sites can be assigned to its source.

Effect of soil texture and chemical properties on laboratory-generated dust emissions from SW North America

NASA Astrophysics Data System (ADS)

Mockford, T.; Zobeck, T. M.; Lee, J. A.; Gill, T. E.; Dominguez, M. A.; Peinado, P.

2012-12-01

Understanding the controls of mineral dust emissions and their particle size distributions during wind-erosion events is critical as dust particles play a significant impact in shaping the earth's climate. It has been suggested that emission rates and particle size distributions are independent of soil chemistry and soil texture. In this study, 45 samples of wind-erodible surface soils from the Southern High Plains and Chihuahuan Desert regions of Texas, New Mexico, Colorado and Chihuahua were analyzed by the Lubbock Dust Generation, Analysis and Sampling System (LDGASS) and a Beckman-Coulter particle multisizer. The LDGASS created dust emissions in a controlled laboratory setting using a rotating arm which allows particle collisions. The emitted dust was transferred to a chamber where particulate matter concentration was recorded using a DataRam and MiniVol filter and dust particle size distribution was recorded using a GRIMM particle analyzer. Particle size analysis was also determined from samples deposited on the Mini-Vol filters using a Beckman-Coulter particle multisizer. Soil textures of source samples ranged from sands and sandy loams to clays and silts. Initial results suggest that total dust emissions increased with increasing soil clay and silt content and decreased with increasing sand content. Particle size distribution analysis showed a similar relationship; soils with high silt content produced the widest range of dust particle sizes and the smallest dust particles. Sand grains seem to produce the largest dust particles. Chemical control of dust emissions by calcium carbonate content will also be discussed.

A Sleeping Giant Awakened: Reignition of AGN Activity, Reborn Star Formation, and a Multiphase Outflow in one of the Largest Radio Galaxies Known

NASA Astrophysics Data System (ADS)

Tremblay, Grant; O'Dea, Christopher; Labiano, Alvaro; Baum, Stefi; McDermid, Richard; Combes, Francoise; Garcia-Burillo, Santiago; Davis, Timothy

2014-08-01

3C 236 is the second largest known radio galaxy and one of the largest objects in the known Universe. Its central AGN has recently reignited after a 10 Myr dormancy period, giving rise to a very young and compact radio source and a 1000 km/sec outflow of warm ionized and atomic HI gas. We propose GMOS-N IFU observations to resolve this outflow, determine its driver, and estimate the relative coupling efficiencies between the warm ionized, atomic, and cold molecular gas phases. We will assemble a much-needed spatially resolved Balmer decrement (extinction map) across the dramatic double dust lanes of this source, enabling high spatial resolution star formation rate, efficiency, and gas excitation and velocity maps. These will address several mysteries related to the very high star formation efficiency and the unique nature of the multiphase outflow in this source. 3C 236 is such a remarkable galaxy that whatever the results of the proposed observations, they will have wide-ranging implications for the triggering of star formation and AGN activity, their possibly coupled co-evolution, and the feedback effects of the latter on the former.

Emissions inventory of PM2.5 trace elements across the United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adam Reff; Prakash V. Bhave; Heather Simon

2009-08-15

This paper presents the first National Emissions Inventory (NEI) of fine particulate matter (PM2.5) that includes the full suite of PM2.5 trace elements (atomic number >10) measured at ambient monitoring sites across the U.S. PM2.5 emissions in the NEI were organized and aggregated into a set of 84 source categories for which chemical speciation profiles are available (e.g., Unpaved Road Dust, Agricultural Soil, Wildfires). Emission estimates for ten metals classified as Hazardous Air Pollutants (HAP) were refined using data from a recent HAP NEI. All emissions were spatially gridded, and U.S. emissions maps for dozens of trace elements (e.g., Fe,more » Ti) are presented for the first time. Nationally, the trace elements emitted in the highest quantities are silicon (3.8 x 10{sup 5} ton/yr), aluminium (1.4 x 10{sup 5} ton/yr), and calcium (1.3 x 10{sup 5} ton/yr). Our chemical characterization of the PM2.5 inventory shows that most of the previously unspeciated emissions are comprised of crustal elements, potassium, sodium, chlorine, and metal-bound oxygen. Coal combustion is the largest source of S, Se, Sr, Hg and primary sulfates. This work also reveals that the largest PM2.5 sources lacking specific speciation data are off-road diesel-powered mobile equipment, road construction dust, marine vessels, gasoline-powered boats, and railroad locomotives. 28 refs., 4 figs.« less

Gravitational lensing reveals extreme dust-obscured star formation in quasar host galaxies

NASA Astrophysics Data System (ADS)

Stacey, H. R.; McKean, J. P.; Robertson, N. C.; Ivison, R. J.; Isaak, K. G.; Schleicher, D. R. G.; van der Werf, P. P.; Baan, W. A.; Berciano Alba, A.; Garrett, M. A.; Loenen, A. F.

2018-06-01

We have observed 104 gravitationally lensed quasars at z ˜ 1-4 with Herschel/SPIRE, the largest such sample ever studied. By targeting gravitational lenses, we probe intrinsic far-infrared (FIR) luminosities and star formation rates (SFRs) more typical of the population than the extremely luminous sources that are otherwise accessible. We detect 72 objects with Herschel/SPIRE and find 66 per cent (69 sources) of the sample have spectral energy distributions (SEDs) characteristic of dust emission. For 53 objects with sufficiently constrained SEDs, we find a median effective dust temperature of 38^{+12}_{-5} K. By applying the radio-infrared correlation, we find no evidence for an FIR excess that is consistent with star-formation-heated dust. We derive a median magnification-corrected FIR luminosity of 3.6^{+4.8}_{-2.4} × 10^{11} L_{⊙} and median SFR of 120^{+160}_{-80} M_{⊙} yr^{-1}} for 94 quasars with redshifts. We find ˜10 per cent of our sample have FIR properties similar to typical dusty star-forming galaxies at z ˜ 2-3 and a range of SFRs <20-10 000 M⊙ yr-1 for our sample as a whole. These results are in line with current models of quasar evolution and suggests a coexistence of dust-obscured star formation and AGN activity is typical of most quasars. We do not find a statistically significant difference in the FIR luminosities of quasars in our sample with a radio excess relative to the radio-infrared correlation. Synchrotron emission is found to dominate at FIR wavelengths for <15 per cent of those sources classified as powerful radio galaxies.

Dust emission and transport over Iraq associated with the summer Shamal winds

NASA Astrophysics Data System (ADS)

Karam Francis, Diana Bou; Flamant, Cyrille; Chaboureau, Jean-Pierre; Banks, Jamie

2016-04-01

In this study, we investigate the diurnal evolution of the summer Shamal wind (a quasi-permanent low-level northwesterly wind feature) and its role in dust emission and transport over Iraq, using ground-based and space-borne observations together with a numerical simulation performed with the mesoscale model Meso-NH. A 6-year dataset from the synoptic stations over Iraq allows establishing the prominence of the link between strong near surface winds and reduced visibility in the summer. The detailed processes at play during Shamal events are explored on the basis of a Meso-NH simulation for a given, representative case study (25 June-3 July 2010). The Shamal exhibits an out-of-phase relationship between the surface wind and winds in the lower troposphere (typically 500 m above ground level), the maximum surface wind speeds being observed during the day while in altitude the maximum wind speeds are observed at night. The daytime near surface winds, at the origin of dust emission, are associated with the downward transfer of momentum from the nocturnal low-level jet to the surface due to turbulent mixing after solar heating commences each day. For the first time, an estimate of the dust load associated with summer Shamal events over Iraq has been made using aerosol optical depths derived from the Spinning Enhanced Visible and Infrared Imager, the Moderate Resolution Imaging Spectroradiometer, and the simulation. The dust load exhibits a large diurnal variability, with a daily minimum value of 1 Tg around 0600 UTC and a daily peak of 2.5 Tg or more around 1500 UTC, and is driven by the diurnal cycle of the near surface wind speed. The daily dust load peak associated with the summer Shamal over Iraq is in the same order of magnitude as those derived from simulations downstream of the Bodélé depression in Chad, known to be the world's largest dust source. Keywords: Dust, Low Level Jet, Shamal winds, Middle East, dust sources.

Growth impacts of Saharan dust, mineral nutrients, and CO2 on a planktonic herbivore in southern Mediterranean lakes.

PubMed

Villar-Argaiz, Manuel; Cabrerizo, Marco J; González-Olalla, Juan Manuel; Valiñas, Macarena S; Rajic, Sanja; Carrillo, Presentación

2018-05-17

Rising levels of CO 2 can boost plant biomass but reduce its quality as a food source for herbivores. However, significant uncertainties remain as to the degree to which the effect is modulated by other environmental factors and the underlying processes causing these responses in nature. To address these questions, we carried out CO 2 -manipulation experiments using natural seston from three lakes under nutrient-enriched conditions (mimicking eutrophication and atmospheric dust-input processes) as a food source for the planktonic Daphnia pulicaria. Contrary to expectations, there were no single effects of rising CO 2 on herbivorous growth. Instead, synergistic CO 2  × nutrient interactions indicated that CO 2 did not support higher zooplankton growth rates unless supplemented with dust or inorganic nutrients (nitrogen, N; phosphorus, P) in two of three studied lakes. The overall positive correlation between zooplankton growth and seston carbon (C), but not seston C:P, suggested that this was a food quantity-mediated response. In addition, we found that this correlation improved when the data were grouped according to the nutrient treatments, and that the response was largest for dust. The synergistic CO 2  × nutrient effects reported here imply that the effects of rising CO 2 levels on herbivorous growth may be strongly influenced by eutrophication processes and the increase in dust deposition predicted for the Mediterranean region. Copyright © 2018 Elsevier B.V. All rights reserved.

Simulating the Regional Impact of Dust on the Middle East Climate and the Red Sea

NASA Astrophysics Data System (ADS)

Osipov, Sergey; Stenchikov, Georgiy

2018-02-01

The Red Sea is located between North Africa and the Arabian Peninsula, the largest sources of dust in the world. Satellite retrievals show very high aerosol optical depth in the region, which increases during the summer season, especially over the southern Red Sea. Previously estimated and validated radiative effect from dust is expected to have a profound thermal and dynamic impact on the Red Sea, but that impact has not yet been studied or evaluated. Due to the strong dust radiative effect at the sea surface, uncoupled ocean modeling approaches with prescribed atmospheric boundary conditions result in an unrealistic ocean response. Therefore, to study the impact of dust on the regional climate of the Middle East and the Red Sea, we employed the Regional Ocean Modeling System fully coupled with the Weather Research and Forecasting model. We modified the atmospheric model to account for the radiative effect of dust. The simulations show that, in the equilibrium response, dust cools the Red Sea, reduces the surface wind speed, and weakens both the exchange at the Bab-el-Mandeb strait and the overturning circulation. The salinity distribution, freshwater, and heat budgets are significantly altered. A validation of the simulations against satellite products indicates that accounting for radiative effect from dust almost completely removes the bias and reduces errors in the top of the atmosphere fluxes and sea surface temperature. Our results suggest that dust plays an important role in the energy balance, thermal, and circulation regimes in the Red Sea.

Impact and monitoring of dust storms in Taklimakan desert

NASA Astrophysics Data System (ADS)

Feng, G. G.; Li, X.; Zheng, Z.

2012-12-01

The Taklimakan is China's largest, driest, and warmest desert in total area of 338000km^2 with perimeter of 436 km, it is also known as one of the world's largest shifting-sand deserts. Fully 85 percent of the total area consists of mobile, crescent-shaped sand dunes and are virtually devoid of vegetation. The abundant sand provides material for frequent intense dust storms. The Taklimakan desert fills the expansive Tarim Basin between the Kunlun Mountains and the Tibet Plateau to the south and the Tian Shan Mountains to the north. The Tarim River flows across the basin from west-to-east. In these places, the oases created by fresh surface water support agriculture. Studies outside Xinjiang indicated that 80% dust source of storms was from farmland. Dust storms in the Tarim Basin occur for 20 to 59 days, mainly in spring every year. However, little effort was taken to investigate soil wind erosion and dust emission around the desert. Quantitative understanding of individual dust events in the arid Taklimakan desert, for example, the dust emission rates and the long-range transport, are still incomplete. Therefore, the dust events were observed through routine satellite sensors, lidar instruments, airborne samplers, and surface-based aerosol monitors. Soil wind erosion and suspended particulates emission of four major dust storms from the desert and the typical oasis farmlands at the north rim of the desert were measured using creep sampler, BSNE and TSP at eight heights in 2012. In addition, Aqua satellite AOD data, the NAAPS Global Aeosol model, the CALIPSO satellite products, EPA's AirNow AQI of PM2.5 and HYSPLIT Back Trajectory model were applied to analyze dust transport across the Pacific. Four significant dust storms were observed at the north rim of Taklimakan desert in the spring, 2012. During those events, predominant wind direction ranged from 296 to 334°, wind speed over 7 m/s at 2 m lasted for 471-1074 min, gust wind speed ranged from 11-18m/s. It was determined that the horizontal dust flux was 0.6 to 4.3 kg/m. Dust clouds are formed when the friction from high surface wind speeds (>6 m/s) lifts loose dust particles into the atmospheric boundary layer or above. Analysis shows that a dust storm in the Taklimakan desert on April 23th produced a huge atmospheric dust cloud, it was transported across the Pacific Ocean to reach the West Coast of North America 12 days later, corresponding to 6 m/s average transport speed. The observations in the Pacific Coast indicated that aerosol concentrations were elevated which resulted in Air Quality Index (AQI) to the yellow moderate category.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

NASA Technical Reports Server (NTRS)

Perlwitz, Jan P.; Fridlind, Ann M.; Knopf, Daniel A.; Miller, Ron L.; García-Pando, Carlos Perez

2017-01-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 24 micrometer contributes the largest INP number.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Fridlind, A. M.; Knopf, D. A.; Miller, R. L.; Pérez García-Pando, C.

2017-12-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 2-4 μm contributes the largest INP number.

Dust grains from the heart of supernovae

NASA Astrophysics Data System (ADS)

Bocchio, M.; Marassi, S.; Schneider, R.; Bianchi, S.; Limongi, M.; Chieffi, A.

2016-03-01

Dust grains are classically thought to form in the winds of asymptotic giant branch (AGB) stars. However, there is increasing evidence today for dust formation in supernovae (SNe). To establish the relative importance of these two classes of stellar sources of dust, it is important to know the fraction of freshly formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the interstellar medium. With this aim, we have developed a new code, GRASH_Rev, that allows following the dynamics of dust grains in the shocked SN ejecta and computing the time evolution of the mass, composition, and size distribution of the grains. We considered four well-studied SNe in the Milky Way and Large Magellanic Cloud: SN 1987A, CasA, the Crab nebula, and N49. These sources have been observed with both Spitzer and Herschel, and the multiwavelength data allow a better assessment the mass of warm and cold dust associated with the ejecta. For each SN, we first identified the best explosion model, using the mass and metallicity of the progenitor star, the mass of 56Ni, the explosion energy, and the circumstellar medium density inferred from the data. We then ran a recently developed dust formation model to compute the properties of freshly formed dust. Starting from these input models, GRASH_Rev self-consistently follows the dynamics of the grains, considering the effects of the forward and reverse shock, and allows predicting the time evolution of the dust mass, composition, and size distribution in the shocked and unshocked regions of the ejecta. All the simulated models aagree well with observations. Our study suggests that SN 1987A is too young for the reverse shock to have affected the dust mass. Hence the observed dust mass of 0.7-0.9 M⊙ in this source can be safely considered as indicative of the mass of freshly formed dust in SN ejecta. Conversely, in the other three SNe, the reverse shock has already destroyed between 10-40% of the initial dust mass. However, the largest dust mass destruction is predicted to occur between 103 and 105 yr after the explosions. Since the oldest SN in the sample has an estimated age of 4800 yr, current observations can only provide an upper limit to the mass of SN dust that will enrich the interstellar medium, the so-called effective dust yields. We find that only between 1-8% of the currently observed mass will survive, resulting in an average SN effective dust yield of (1.55 ± 1.48) × 10-2M⊙. This agrees well with the values adopted in chemical evolution models that consider the effect of the SN reverse shock. We discuss the astrophysical implications of our results for dust enrichment in local galaxies and at high redshift.

Impacts of Saharan Dust on the Atmospheric Radiative Balance in the Caribbean during SALTRACE 2013

NASA Astrophysics Data System (ADS)

Sauer, D. N.; Weinzierl, B.; Gross, S.; Minikin, A.; Freudenthaler, V.; Gasteiger, J.; Mayer, B. C.

2013-12-01

Direct and indirect aerosol radiative effects represent one of the largest uncertainties in the modeling of the climate system. To better quantify the effects of aerosols on the Earth's radiative balance and understand important physical effects on small scales such as the influence of aerosols on clouds, detailed measurements of aerosol properties are needed to build a globally representative data set. Mineral dust is among the most abundant aerosols and the Sahara Desert constitutes its largest source. During frequent dust outbreaks thick elevated aerosol layers are formed and transported over large distances -often across the Atlantic Ocean into the Caribbean. The Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in June/July 2013 continues the SAMUM field experiments conducted in 2006 and 2008. It aims to study the long-range transport of Saharan mineral dust, the properties of aged mineral dust aerosol, and its impact on radiative quantities and cloud processes. The experiment led to an extensive data set on dust layers from Senegal to the Caribbean using airborne in-situ and remote sensing measurements, complemented with ground-based remote sensing and in-situ measurements on sites in Barbados and Puerto Rico as well as satellite remote sensing data. The airborne data were obtained with an extensive aerosol payload aboard the DLR-operated Falcon 20E research aircraft. The measurements cover the entire size range of atmospheric aerosol with a combination of cabin-operated and wing-mounted instruments. In addition, particle properties such as absorption coefficients and volatility are measured. A nadir-looking 2-μm Doppler-lidar system aboard the aircraft was used for wind measurements and served as a path finder for the selection of representative aerosol in-situ levels. In the Caribbean the dust usually arrives in several layers with distinct properties: the mostly undisturbed pure dust layer in altitudes up to 4-5 km, a transition layer where mixing and cloud processing has occurred, and a lower layer with a significant contribution from marine boundary layer aerosol. Here we present a case study of the direct radiative effects of Saharan dust layers found over Barbados using airborne in-situ and ground-based lidar observations. Using the radiative transfer package libRadtran we estimate the direct radiative forcing and radiative heating rate profiles inside the tropospheric column over Barbados. To deduce aerosol optical properties for the radiative transfer model, particle size distributions, aerosol refractive indices, and shape distributions are obtained from in-situ data. Coinciding lidar observations are used to deduce the vertical extent and structure of the different aerosol layers. To study the effect of aerosol aging on the radiative balance we compare the model results from in-situ data obtained in Barbados with results based on data from Senegal and the Cape Verde region and from the SAMUM field experiments, which characterized the dust properties near the source.

Trends and sources vs air mass origins in a major city in South-western Europe: Implications for air quality management.

PubMed

Fernández-Camacho, R; de la Rosa, J D; Sánchez de la Campa, A M

2016-05-15

This study presents a 17-years air quality database comprised of different parameters corresponding to the largest city in the south of Spain (Seville) where atmospheric pollution is frequently attributed to traffic emissions and is directly affected by Saharan dust outbreaks. We identify the PM10 contributions from both natural and anthropogenic sources in this area associated to different air mass origins. Hourly, daily and seasonal variation of PM10 and gaseous pollutant concentrations (CO, NO2 and SO2), all of them showing negative trends during the study period, point to the traffic as one of the main sources of air pollution in Seville. Mineral dust, secondary inorganic compounds (SIC) and trace elements showed higher concentrations under North African (NAF) air mass origins than under Atlantic. We observe a decreasing trend in all chemical components of PM10 under both types of air masses, NAF and Atlantic. Principal component analysis using more frequent air masses in the area allows the identification of five PM10 sources: crustal, regional, marine, traffic and industrial. Natural sources play a more relevant role during NAF events (20.6 μg · m(-3)) than in Atlantic episodes (13.8 μg · m(-3)). The contribution of the anthropogenic sources under NAF doubles the one under Atlantic conditions (33.6 μg · m(-3) and 15.8 μg · m(-3), respectively). During Saharan dust outbreaks the frequent accumulation of local anthropogenic pollutants in the lower atmosphere results in poor air quality and an increased risk of mortality. The results are relevant when analysing the impact of anthropogenic emissions on the exposed population in large cities. The increase in potentially toxic elements during Saharan dust outbreaks should also be taken into account when discounting the number of exceedances attributable to non-anthropogenic or natural origins. Copyright © 2016 Elsevier B.V. All rights reserved.

Sources of particulate matter components in the Athabasca oil sands region: investigation through a comparison of trace element measurement methodologies

NASA Astrophysics Data System (ADS)

Phillips-Smith, Catherine; Jeong, Cheol-Heon; Healy, Robert M.; Dabek-Zlotorzynska, Ewa; Celo, Valbona; Brook, Jeffrey R.; Evans, Greg

2017-08-01

The province of Alberta, Canada, is home to three oil sands regions which, combined, contain the third largest deposit of oil in the world. Of these, the Athabasca oil sands region is the largest. As part of Environment and Climate Change Canada's program in support of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring program, concentrations of trace elements in PM2. 5 (particulate matter smaller than 2.5 µm in diameter) were measured through two campaigns that involved different methodologies: a long-term filter campaign and a short-term intensive campaign. In the long-term campaign, 24 h filter samples were collected once every 6 days over a 2-year period (December 2010-November 2012) at three air monitoring stations in the regional municipality of Wood Buffalo. For the intensive campaign (August 2013), hourly measurements were made with an online instrument at one air monitoring station; daily filter samples were also collected. The hourly and 24 h filter data were analyzed individually using positive matrix factorization. Seven emission sources of PM2. 5 trace elements were thereby identified: two types of upgrader emissions, soil, haul road dust, biomass burning, and two sources of mixed origin. The upgrader emissions, soil, and haul road dust sources were identified through both the methodologies and both methodologies identified a mixed source, but these exhibited more differences than similarities. The second upgrader emissions and biomass burning sources were only resolved by the hourly and filter methodologies, respectively. The similarity of the receptor modeling results from the two methodologies provided reassurance as to the identity of the sources. Overall, much of the PM2. 5-related trace elements were found to be anthropogenic, or at least to be aerosolized through anthropogenic activities. These emissions may in part explain the previously reported higher levels of trace elements in snow, water, and biota samples collected near the oil sands operations.

iss012e21250

NASA Image and Video Library

2006-03-21

ISS012-E-21250 (2 March 2006) --- Dust and smog in northeast China are featured in this image photographed by an Expedition 12 crewmember on the International Space Station. Much of the land surface is obscured in this oblique image of the North China Plain and parts of Inner Mongolia. In the center of the view a mass of gray smog—mainly industrial pollution and smoke from domestic burning—obscures Beijing and surrounding cities. Numerous plumes with their source points appear within the mass. Beijing suffers some of the worst air pollution in the world from these chronic sources, and the characteristic colors and textures of the smog can be easily seen through windows of the International Space Station. The coastline of Bo Hai Bay, 300 kilometers east of Beijing, is visible at left. The light brown material in Bo Hai Bay is sediment from the Yellow and other rivers. Separated from the smog mass by a band of puffy, white cumulus clouds is a light brown plume of dust. The line of white cloud has developed along the escarpment that separates the heavily populated North China Plain – location of the largest population agglomeration on Earth – and the sparsely populated semi-desert plains of Inner Mongolia. Observers saw a number of dust events in most Northern Hemisphere deserts in the spring of 2006, and the Gobi and the Takla Makan deserts of western China were no exception. Dust plumes originating in these deserts typically extend eastward hundreds of kilometers, regularly depositing dust on Beijing, the Korean peninsula and Japan. Some plumes even extend over the Pacific Ocean. In extreme cases, visible masses of Gobi-derived dust have reached North America.

Source appointment of fine particle number and volume concentration during severe haze pollution in Beijing in January 2013.

PubMed

Liu, Zirui; Wang, Yuesi; Hu, Bo; Ji, Dongsheng; Zhang, Junke; Wu, Fangkun; Wan, Xin; Wang, Yonghong

2016-04-01

Extreme haze episodes repeatedly shrouded Beijing during the winter of 2012-2013, causing major environmental and health problems. To better understand these extreme events, particle number size distribution (PNSD) and particle chemical composition (PCC) data collected in an intensive winter campaign in an urban site of Beijing were used to investigate the sources of ambient fine particles. Positive matrix factorization (PMF) analysis resolved a total of eight factors: two traffic factors, combustion factors, secondary aerosol, two accumulation mode aerosol factors, road dust, and long-range transported (LRT) dust. Traffic emissions (54%) and combustion aerosol (27%) were found to be the most important sources for particle number concentration, whereas combustion aerosol (33%) and accumulation mode aerosol (37%) dominated particle volume concentrations. Chemical compositions and sources of fine particles changed dynamically in the haze episodes. An enhanced role of secondary inorganic species was observed in the formation of haze pollution. Regional transport played an important role for high particles, contribution of which was on average up to 24-49% during the haze episodes. Secondary aerosols from urban background presented the largest contributions (45%) for the rapid increase of fine particles in the severest haze episode. In addition, the invasion of LRT dust aerosols further elevated the fine particles during the extreme haze episode. Our results showed a clear impact of regional transport on the local air pollution, suggesting the importance of regional-scale emission control measures in the local air quality management of Beijing.

A Combined Observational and Modeling Approach to Study Modern Dust Transport from the Patagonia Desert to East Antarctica

NASA Technical Reports Server (NTRS)

Gasso, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.

2010-01-01

The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS ,POLDER, OMI,), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (approx.54deg S) and from the shores of the Colihue Huapi lake in Central Patagonia (approx.46deg S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6-7 and 9-10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant de- position over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and approx.800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the presence of dust at approx.1500 km SW of South Africa five days after, the limited capabilities of existing satellite platforms to differentiate between aerosol types do not permit a definitive conclusion. In addition, the model simulations show dust lifting to the free troposphere as it travels south but it could not be confirmed by the satellite observations due to cloudiness. This work demonstrates that complementary information from existing transport models, satellite and surface data can yield a consistent picture of the dust transport from the Patagonia desert to Antarctica. It also illustrates the limitation of using any of these approaches individually to characterize the transport of dust in a heavily cloudy area.

Role of Surface Wind and Vegetation Cover in Multi-decadal Variations of Dust Emission in the Sahara and Sahel

NASA Technical Reports Server (NTRS)

Kim, Dong; Chin, Mian; Remer, Lorraine A.; Diehl, Thomas L.; Bian, Huisheng; Yu, Hongbin; Brown, Molly E.; Stockwell, William R.

2016-01-01

North Africa, the world's largest dust source, is non-uniform, consisting of a permanently arid region (Sahara), a semi-arid region (Sahel), and a relatively moist vegetated region (Savanna), each with very different rainfall patterns and surface conditions. This study aims to better understand the controlling factors that determine the variation of dust emission in North Africa over a 27-year period from 1982 to 2008, using observational data and model simulations. The results show that the model-derived Saharan dust emission is only correlated with the 10-m winds (W10m) obtained from reanalysis data, but the model-derived Sahel dust emission is correlated with both W10m and the Normalized Difference Vegetation Index (NDVI) that is obtained from satellite. While the Saharan dust accounts for 82 of the continental North Africa dust emission (1340-1570 Tg year(exp -1) in the 27-year average, the Sahel accounts for 17 with a larger seasonal and inter-annual variation (230-380 Tg year(exp -1), contributing about a quarter of the transatlantic dust transported to the northern part of South America. The decreasing dust emission trend over the 27-year period is highly correlated with W10m over the Sahara (R equals 0.92). Over the Sahel, the dust emission is correlated with W10m (R 0.69) but is also anti-correlated with the trend of NDVI (R equals 0.65). W10m is decreasing over both the Sahara and the Sahel between 1982 and 2008, and the trends are correlated (R equals 0.53), suggesting that Saharan Sahelian surface winds are a coupled system, driving the inter-annual variation of dust emission.

Contribution of PAHs from coal-tar pavement sealcoat and other sources to 40 U.S. lakes

USGS Publications Warehouse

Van Metre, Peter C.; Mahler, Barbara J.

2010-01-01

Contamination of urban lakes and streams by polycyclic aromatic hydrocarbons (PAHs) has increased in the United States during the past 40 years. We evaluated sources of PAHs in post-1990 sediments in cores from 40 lakes in urban areas across the United States using a contaminant mass-balance receptor model and including as a potential source coal-tar-based (CT) sealcoat, a recently recognized source of urban PAH. Other PAH sources considered included several coal- and vehicle-related sources, wood combustion, and fuel-oil combustion. The four best modeling scenarios all indicate CT sealcoat is the largest PAH source when averaged across all 40 lakes, contributing about one-half of PAH in sediment, followed by vehicle-related sources and coal combustion. PAH concentrations in the lakes were highly correlated with PAH loading from CT sealcoat (Spearman's rho=0.98), and the mean proportional PAH profile for the 40 lakes was highly correlated with the PAH profile for dust from CT-sealed pavement (r=0.95). PAH concentrations and mass and fractional loading from CT sealcoat were significantly greater in the central and eastern United States than in the western United States, reflecting regional differences in use of different sealcoat product types. The model was used to calculate temporal trends in PAH source contributions during the last 40 to 100 years to eight of the 40 lakes. In seven of the lakes, CT sealcoat has been the largest source of PAHs since the 1960s, and in six of those lakes PAH trends are upward. Traffic is the largest source to the eighth lake, located in southern California where use of CT sealcoat is rare.

The Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments

NASA Astrophysics Data System (ADS)

Kemper, Ciska; Andersen, Anja; Baes, Maarten; Gomez, Haley; Watson, Darach

This meeting addresses the life cycle of dust in the Universe, which covers the formation, evolution and destruction of dust in a range of environments, ranging from the smallest to the largest scales. Bringing together observational and theoretical astrophysicists as well as meteoriticists and experimentalists allows for a cross-disciplinary dialogue. The meeting follows a successful tradition of astrophysical dust meetings, starting in Albany in 1972, with the latest edition "Cosmic Dust: Near and Far" organized by Th. Henning taking place in Heidelberg in 2008. Since that meeting, the field of dust astrophysics has made major leaps forward with the host of data arriving from such missions as the infrared space telescopes Spitzer and Herschel, and the sample return mission, Stardust, which took dust samples from comet Wild-2. The largest telescope on Earth, ALMA, has also recently come online, allowing for investigations into the origin of dust in the Universe, making this is excellent time to review the status of the field of dust astrophysics. The meeting aims to create an environment in which all aspects of the life cycle of dust are discussed, from an astrophysical, chemical and mineralogical perspective, and its effect on a range of environments. Observational insights, theoretical models and experimental approaches all contribute to our view of the life cycle of dust, and the meeting addresses new developments and future projects in all these areas.

Identification of dust source regions and dust emission trends across North Africa and the Middle East using MISR satellite observations

NASA Astrophysics Data System (ADS)

Yu, Y.; Kalashnikova, O. V.; Garay, M. J.; Notaro, M.

2017-12-01

Global arid and semi-arid regions supply 1100 to 5000 Tg of Aeolian dust to the atmosphere each year, primarily from North Africa and secondarily from the Middle East. Previous dust source identification methods, based on either remotely-sensed aerosol optical depth (AOD) or dust activity, yield distinct dust source maps, largely due to the limitations in each method and remote-sensing product. Here we apply a novel motion-based method for dust source identification. Dust plume thickness and motion vectors from Multi-angle Imaging SpectroRadiometer (MISR) Cloud Motion Vector Product (CMVP) are examined to identify the regions with high frequency of fast moving-dust plumes, by season. According to MISR CMVP, Bodele depression is the most important dust source across North Africa, consistent with previous studies. Seasonal variability of dust emission across the North Africa is largely driven by climatology of wind and precipitation, featuring the influence of Sharav Cyclone and western African monsoon. In the Middle East, Iraq, Kuwait, and eastern Saudi Arabia are identified as dust source regions, especially during summer months, when the Middle Eastern Shamal wind is active. Furthermore, dust emission trend at each dust source are diagnosed from the motion-based dust source dataset. Increase in dust emission from the Fertile Crescent, Sahel, and eastern African dust sources are identified from MISR CMVP, implying potential contribution from these dust sources to the upward trend in AOD and dust AOD over the Middle East in the 21st century. By comparing with various dust source identification studies, we conclude that the motion-based identification of dust sources is an encouraging alternative and compliment to the AOD-only source identification method.

Spatial and temporal patterns of dust emissions (2004-2012) in semi-arid landscapes, southeastern Utah, USA

USGS Publications Warehouse

Flagg, Cody B.; Neff, Jason C.; Reynolds, Richard L.; Belnap, Jayne

2013-01-01

Aeolian dust can influence nutrient availability, soil fertility, plant interactions, and water-holding capacity in both source and downwind environments. A network of 85 passive collectors for aeolian sediment spanning numerous plant communities, soil types, and land-use histories covering approximately 4000 square kilometers across southeastern Utah was used to sample horizontal emissions of aeolian sediment. The sample archive dates to 2004 and is currently the largest known record of field-scale dust emissions for the southwestern United States. Sediment flux peaked during the spring months in all plant communities (mean: 38.1 g m−2 d−1), related to higher, sustained wind speeds that begin in the early spring. Dust flux was lowest during the winter period (mean: 5 g m−2 d−1) when surface wind speeds are typically low. Sites dominated by blackbrush and sagebrush shrubs had higher sediment flux (mean: 19.4 g m−2 d−1) compared to grasslands (mean: 11.2 g m−2 d−1), saltbush shrublands (mean: 10.3 g m−2 d−1), and woodlands (mean: 8.1 g m−2 d−1). Contrary to other studies on dust emissions, antecedent precipitation during one, two, and three seasons prior to sample collection did not significantly influence emission rates. Physical site-scale factors controlling dust emissions were complex and varied from one vegetation type to another.

Evaluating Ice Nucleating Particle Concentrations From Prognostic Dust Minerals in an Earth System Model

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Knopf, D. A.; Fridlind, A. M.; Miller, R. L.; Pérez García-Pando, C.; DeMott, P. J.

2016-12-01

The effect of aerosol particles on the radiative properties of clouds, the so-called, indirect effect of aerosols, is recognized as one of the largest sources of uncertainty in climate prediction. The distribution of water vapor, precipitation, and ice cloud formation are influenced by the atmospheric ice formation, thereby modulating cloud albedo and thus climate. It is well known that different particle types possess different ice formation propensities with mineral dust being a superior ice nucleating particle (INP) compared to soot particles. Furthermore, some dust mineral types are more proficient INP than others, depending on temperature and relative humidity.In recent work, we have presented an improved dust aerosol module in the NASA GISS Earth System ModelE2 with prognostic mineral composition of the dust aerosols. Thus, there are regional variations in dust composition. We evaluated the predicted mineral fractions of dust aerosols by comparing them to measurements from a compilation of about 60 published literature references. Additionally, the capability of the model to reproduce the elemental composition of the simulated dusthas been tested at Izana Observatory at Tenerife, Canary Islands, which is located off-shore of Africa and where frequent dust events are observed. We have been able to show that the new approach delivers a robust improvement of the predicted mineral fractions and elemental composition of dust.In the current study, we use three-dimensional dust mineral fields and thermodynamic conditions, which are simulated using GISS ModelE, to calculate offline the INP concentrations derived using different ice nucleation parameterizations that are currently discussed. We evaluate the calculated INP concentrations from the different parameterizations by comparing them to INP concentrations from field measurements.

Long-term trends of chemical characteristics and sources of fine particle in Foshan City, Pearl River Delta: 2008-2014.

PubMed

Tan, Jihua; Duan, Jingchun; Ma, Yongliang; He, Kebin; Cheng, Yuan; Deng, Si-Xin; Huang, Yan-Ling; Si-Tu, Shu-Ping

2016-09-15

Foshan is a major international ceramic center and the most polluted city in the Pearl River Delta (PRD). Here we present the results of the first long-term PM2.5 (particles <2.5μm) sampling and chemical characterization study of the city. A total of 2774 samples were collected at six sites from 2008 to 2014, and analyzed for water soluble species, elements and carbonaceous species. The major constituents of PM2.5 were sulfate, OC (Organic Carbon), nitrate, ammonium and EC (Elemental Carbon), which accounted for 50%-88% of PM2.5. PM2.5 and the most abundant chemical species decreased from 2008 to 2011, but rebounded in 2012-2013. After 2008, the chemical composition of PM2.5 changed dramatically due to the implementation of pollution control measures. From 2008 to 2011, SO4(2-) and NO3(-) were the two largest components; subsequently, however, OC was the largest component. The respective contributions of SO4(2-), NO3(-) and OC to the sum of water soluble species and carbonaceous species were 30.5%, 22.9% and 19.9% in 2008; and 20.2%, 16.5% and 30.2% in 2014. Distinct differences in nitrate and sulfate, and in mass ratio [NO3(-)]/[SO4(2-)] imply that mobile sources tended to more important in Foshan during 2012-2014. The results indicate that pollution control measures implemented during 2008-2014 had a large effect on anthropogenic elements (Pb, As, Cd, Zn and Cu) and water soluble species, but little influence on crustal elements (V, Mn, Ti, Ba and Fe) and carbonaceous species. The PMF method was used for source apportionment of PM2.5. Industry (including the ceramic industry and coal combustion), vehicles and dust were the three most important sources and comprised 39.2%, 20.0% and 18.4% of PM2.5 in 2008, respectively. However, secondary aerosols, vehicles and industry were the three most important sources and comprised 29.5%, 22.4% and 20.4% of PM2.5 in 2014, respectively. During the seven year study interval, the contributions of primary sources (industry and dust) decreased significantly, but secondary sources increased dramatically. Industry, dust and vehicles contributed 36.6μgm(-3), 13.9μgm(-3), and 9.2μgm(-3) to the reduction of PM2.5, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Sensitivity of spectral climate signals to the emissions of atmospheric dust

NASA Astrophysics Data System (ADS)

Xu, X.; Wang, J.; Wang, Y.; Henze, D. K.; Zhang, L.

2015-12-01

Mineral dust particles profoundly influence the Earth climate due to their varied affects on the radiation and cloud physics. The knowledge of dust emissions from daily to seasonal scales is thus important for interpreting the past and predicting the future climate changes. Satellite measured radiances in the shortwave and thermal infrared are sensitive to the amount and properties of mineral dust present in the atmosphere. Therefore, the climate (i.e., monthly averages) of these reflectance spectra could contain valuable information on the change of dust emissions. In this work, we investigate the feasibility of using the climate of spectral radiances for recovering dust emissions. An observation simulation system (OSS) that incorporates the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) with forward and adjoint global chemistry transport models (GEOS-Chem and FIM-Chem) has been applied to generate synthetic hyperspectral climate data in the shortwave and thermal infrared (TIR) for summer 2008. Along with the calculation of radiances at the top of the atmosphere (TOA), the OSS also computes their Jacobians of these synthetic data to dust optical depth, plume height, and effective radius, as well as the adjoint gradients of spectral radiances to dust emissions. We found that the brightness temperature (BT) in the TIR spectra at TOA is sensitive to both of the dust plume height and particle size. For the same relative changes of these parameters, BT shows largest change with respect to particle size at the wavenumber of 890-1200 cm-1. This demonstrates the potential for retrieving three-dimensional dust information along with the particle size from hyperspectral TIR measurements. We also assess the information content of monthly versus instantaneous radiances for constraining dust emissionsthe from the calculated adjoint gradients. Our analysis may guide new applications of long-term spectral radiance measurements (such as those from GOME, AIRS, IASI, and CrIS instruments) to constrain dust sources, and thus reduce uncertainty in our broader understanding of the impacts of mineral dust on climate.

Identification of Dust Source Regions at High-Resolution and Dynamics of Dust Source Mask over Southwest United States Using Remote Sensing Data

NASA Astrophysics Data System (ADS)

Sprigg, W. A.; Sahoo, S.; Prasad, A. K.; Venkatesh, A. S.; Vukovic, A.; Nickovic, S.

2015-12-01

Identification and evaluation of sources of aeolian mineral dust is a critical task in the simulation of dust. Recently, time series of space based multi-sensor satellite images have been used to identify and monitor changes in the land surface characteristics. Modeling of windblown dust requires precise delineation of mineral dust source and its strength that varies over a region as well as seasonal and inter-annual variability due to changes in land use and land cover. Southwest USA is one of the major dust emission prone zone in North American continent where dust is generated from low lying dried-up areas with bare ground surface and they may be scattered or appear as point sources on high resolution satellite images. In the current research, various satellite derived variables have been integrated to produce a high-resolution dust source mask, at grid size of 250 m, using data such as digital elevation model, surface reflectance, vegetation cover, land cover class, and surface wetness. Previous dust source models have been adopted to produce a multi-parameter dust source mask using data from satellites such as Terra (Moderate Resolution Imaging Spectroradiometer - MODIS), and Landsat. The dust source mask model captures the topographically low regions with bare soil surface, dried-up river plains, and lakes which form important source of dust in southwest USA. The study region is also one of the hottest regions of USA where surface dryness, land use (agricultural use), and vegetation cover changes significantly leading to major changes in the areal coverage of potential dust source regions. A dynamic high resolution dust source mask have been produced to address intra-annual change in the aerial extent of bare dry surfaces. Time series of satellite derived data have been used to create dynamic dust source masks. A new dust source mask at 16 day interval allows enhanced detection of potential dust source regions that can be employed in the dust emission and transport pathways models for better estimation of emission of dust during dust storms, particulate air pollution, public health risk assessment tools and decision support systems.

Transported African Dust to the Amazon: Physiochemical Properties and Associated Nutrients

NASA Astrophysics Data System (ADS)

Barkley, A.; Blackwelder, P. L.; Prospero, J. M.; Gaston, C.

2017-12-01

African dust plays an essential role in fertilizing both oceanic and terrestrial ecosystems by supplying vital biological nutrients such as iron and phosphorus. During Boreal winter, large quantities of African dust are transported across the Atlantic Ocean to the Amazon Basin. It is thought that the Bodélé Depression, part of Paleolake Mega Chad, serves as a major source of this dust, although its importance is debated. The soil in this topographical depression contains a distinctive blend of fluvial and diatomaceous sediments that are thought to supply the Amazon with the nutrients necessary to maintain soil fertility. However, the composition and physical properties of dust transported to the Amazon remain under-explored. Here we present measurements of the size, morphology, and chemical composition of transported dust collected in Cayenne, French Guiana and soil samples collected from the Bodélé Depression using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Inductively coupled plasma mass spectrometry and soluble phosphorus measurements were also performed to investigate the nutrient profiles of filters collected during different air mass transport conditions. In addition to mineral dust, SEM revealed the presence of whole and fragmented freshwater diatoms transported from the Bodélé Depression, or other ephemeral African paleolakes, that were mixed with dust containing iron oxides and micronutrient-rich authigenic clays. Interestingly, transported diatoms were found to the be the largest transported particles with diameters well above 10 μm (up to 70 μm). The low density and high surface-to-volume ratios of diatoms could allow a longer range transport than dust of a comparable size. Therefore, the diatoms could act as a vehicle by which higher micronutrient fluxes could be transported to the Amazon.

Identifying sources of aeolian mineral dust: Present and past

USGS Publications Warehouse

Muhs, Daniel R; Prospero, Joseph M; Baddock, Matthew C; Gill, Thomas E

2014-01-01

Aeolian mineral dust is an important component of the Earth’s environmental systems, playing roles in the planetary radiation balance, as a source of fertilizer for biota in both terrestrial and marine realms and as an archive for understanding atmospheric circulation and paleoclimate in the geologic past. Crucial to understanding all of these roles of dust is the identification of dust sources. Here we review the methods used to identify dust sources active at present and in the past. Contemporary dust sources, produced by both glaciogenic and non-glaciogenic processes, can be readily identified by the use of Earth-orbiting satellites. These data show that present dust sources are concentrated in a global dust belt that encompasses large topographic basins in low-latitude arid and semiarid regions. Geomorphic studies indicate that specific point sources for dust in this zone include dry or ephemeral lakes, intermittent stream courses, dune fields, and some bedrock surfaces. Back-trajectory analyses are also used to identify dust sources, through modeling of wind fields and the movement of air parcels over periods of several days. Identification of dust sources from the past requires novel approaches that are part of the geologic toolbox of provenance studies. Identification of most dust sources of the past requires the use of physical, mineralogical, geochemical, and isotopic analyses of dust deposits. Physical properties include systematic spatial changes in dust deposit thickness and particle size away from a source. Mineralogy and geochemistry can pinpoint dust sources by clay mineral ratios and Sc-Th-La abundances, respectively. The most commonly used isotopic methods utilize isotopes of Nd, Sr, and Pb and have been applied extensively in dust archives of deep-sea cores, ice cores, and loess. All these methods have shown that dust sources have changed over time, with far more abundant dust supplies existing during glacial periods. Greater dust supplies in glacial periods are likely due to greater production of glaciogenic dust particles from expanded ice sheets and mountain glaciers, but could also include dust inputs from exposed continental and insular shelves now submerged. Future dust sources are difficult to assess, but will likely differ from those of the present because of global warming. Global warming could bring about shifts in dust sources by changes in degree or type of vegetation cover, changes in wind strength, and increases or decreases in the size of water bodies. A major uncertainty in assessing dust sources of the future is related to changes inhuman land use, which could affect land surface cover, particularly due to increased agricultural endeavors and water usage.

Source apportionment of fine particulate matter in China in 2013 using a source-oriented chemical transport model.

PubMed

Shi, Zhihao; Li, Jingyi; Huang, Lin; Wang, Peng; Wu, Li; Ying, Qi; Zhang, Hongliang; Lu, Li; Liu, Xuejun; Liao, Hong; Hu, Jianlin

2017-12-01

China has been suffering high levels of fine particulate matter (PM 2.5 ). Designing effective PM 2.5 control strategies requires information about the contributions of different sources. In this study, a source-oriented Community Multiscale Air Quality (CMAQ) model was applied to quantitatively estimate the contributions of different source sectors to PM 2.5 in China. Emissions of primary PM 2.5 and gas pollutants of SO 2 , NO x , and NH 3 , which are precursors of particulate sulfate, nitrate, and ammonium (SNA, major PM 2.5 components in China), from eight source categories (power plants, residential sources, industries, transportation, open burning, sea salt, windblown dust and agriculture) were separately tracked to determine their contributions to PM 2.5 in 2013. Industrial sector is the largest source of SNA in Beijing, Xi'an and Chongqing, followed by agriculture and power plants. Residential emissions are also important sources of SNA, especially in winter when severe pollution events often occur. Nationally, the contributions of different source sectors to annual total PM 2.5 from high to low are industries, residential sources, agriculture, power plants, transportation, windblown dust, open burning and sea salt. Provincially, residential sources and industries are the major anthropogenic sources of primary PM 2.5 , while industries, agriculture, power plants and transportation are important for SNA in most provinces. For total PM 2.5 , residential and industrial emissions are the top two sources, with a combined contribution of 40-50% in most provinces. The contributions of power plants and agriculture to total PM 2.5 are about 10%, respectively. Secondary organic aerosol accounts for about 10% of annual PM 2.5 in most provinces, with higher contributions in southern provinces such as Yunnan (26%), Hainan (25%) and Taiwan (21%). Windblown dust is an important source in western provinces such as Xizang (55% of total PM 2.5 ), Qinghai (74%), Xinjiang (59%). The large variation in sources of PM 2.5 across China suggests that PM 2.5 mitigation programs should be designed separately for different regions/provinces. Copyright © 2017 Elsevier B.V. All rights reserved.

Recently Deglaciated High-Altitude Soils of the Himalaya: Diverse Environments, Heterogenous Bacterial Communities and Long-Range Dust Inputs from the Upper Troposphere

PubMed Central

Stres, Blaz; Sul, Woo Jun; Murovec, Bostjan; Tiedje, James M.

2013-01-01

Background The Himalaya with its altitude and geographical position forms a barrier to atmospheric transport, which produces much aqueous-particle monsoon precipitation and makes it the largest continuous ice-covered area outside polar regions. There is a paucity of data on high-altitude microbial communities, their native environments and responses to environmental-spatial variables relative to seasonal and deglaciation events. Methodology/Principal Findings Soils were sampled along altitude transects from 5000 m to 6000 m to determine environmental, spatial and seasonal factors structuring bacterial communities characterized by 16 S rRNA gene deep sequencing. Dust traps and fresh-snow samples were used to assess dust abundance and viability, community structure and abundance of dust associated microbial communities. Significantly different habitats among the altitude-transect samples corresponded to both phylogenetically distant and closely-related communities at distances as short as 50 m showing high community spatial divergence. High within-group variability that was related to an order of magnitude higher dust deposition obscured seasonal and temporal rearrangements in microbial communities. Although dust particle and associated cell deposition rates were highly correlated, seasonal dust communities of bacteria were distinct and differed significantly from recipient soil communities. Analysis of closest relatives to dust OTUs, HYSPLIT back-calculation of airmass trajectories and small dust particle size (4–12 µm) suggested that the deposited dust and microbes came from distant continental, lacustrine and marine sources, e.g. Sahara, India, Caspian Sea and Tibetan plateau. Cyanobacteria represented less than 0.5% of microbial communities suggesting that the microbial communities benefitted from (co)deposited carbon which was reflected in the psychrotolerant nature of dust-particle associated bacteria. Conclusions/Significance The spatial, environmental and temporal complexity of the high-altitude soils of the Himalaya generates ongoing disturbance and colonization events that subject heterogeneous microniches to stochastic colonization by far away dust associated microbes and result in the observed spatially divergent bacterial communities. PMID:24086740

Chemical composition and sources of particle pollution in affluent and poor neighborhoods of Accra, Ghana

NASA Astrophysics Data System (ADS)

Zhou, Zheng; Dionisio, Kathie L.; Verissimo, Thiago G.; Kerr, Americo S.; Coull, Brent; Arku, Raphael E.; Koutrakis, Petros; Spengler, John D.; Hughes, Allison F.; Vallarino, Jose; Agyei-Mensah, Samuel; Ezzati, Majid

2013-12-01

The highest levels of air pollution in the world now occur in developing country cities, where air pollution sources differ from high-income countries. We analyzed particulate matter (PM) chemical composition and estimated the contributions of various sources to particle pollution in poor and affluent neighborhoods of Accra, Ghana. Elements from earth’s crust were most abundant during the seasonal Harmattan period between late December and late January when Saharan dust is carried to coastal West Africa. During Harmattan, crustal particles accounted for 55 μg m-3 (37%) of fine particle (PM2.5) mass and 128 μg m-3 (42%) of PM10 mass. Outside Harmattan, biomass combustion, which was associated with higher black carbon, potassium, and sulfur, accounted for between 10.6 and 21.3 μg m-3 of fine particle mass in different neighborhoods, with its contribution largest in the poorest neighborhood. Other sources were sea salt, vehicle emissions, tire and brake wear, road dust, and solid waste burning. Reducing air pollution in African cities requires policies related to energy, transportation and urban planning, and forestry and agriculture, with explicit attention to impacts of each strategy in poor communities. Such cross-sectoral integration requires emphasis on urban environment and urban poverty in the post-2015 Development Agenda.

The role of deep convection and nocturnal low-level jets for dust emission in summertime West Africa: Estimates from convection-permitting simulations

PubMed Central

Heinold, B; Knippertz, P; Marsham, JH; Fiedler, S; Dixon, NS; Schepanski, K; Laurent, B; Tegen, I

2013-01-01

[1] Convective cold pools and the breakdown of nocturnal low-level jets (NLLJs) are key meteorological drivers of dust emission over summertime West Africa, the world’s largest dust source. This study is the first to quantify their relative contributions and physical interrelations using objective detection algorithms and an off-line dust emission model applied to convection-permitting simulations from the Met Office Unified Model. The study period covers 25 July to 02 September 2006. All estimates may therefore vary on an interannual basis. The main conclusions are as follows: (a) approximately 40% of the dust emissions are from NLLJs, 40% from cold pools, and 20% from unidentified processes (dry convection, land-sea and mountain circulations); (b) more than half of the cold-pool emissions are linked to a newly identified mechanism where aged cold pools form a jet above the nocturnal stable layer; (c) 50% of the dust emissions occur from 1500 to 0200 LT with a minimum around sunrise and after midday, and 60% of the morning-to-noon emissions occur under clear skies, but only 10% of the afternoon-to-nighttime emissions, suggesting large biases in satellite retrievals; (d) considering precipitation and soil moisture effects, cold-pool emissions are reduced by 15%; and (e) models with parameterized convection show substantially less cold-pool emissions but have larger NLLJ contributions. The results are much more sensitive to whether convection is parameterized or explicit than to the choice of the land-surface characterization, which generally is a large source of uncertainty. This study demonstrates the need of realistically representing moist convection and stable nighttime conditions for dust modeling. Citation: Heinold, B., P. Knippertz, J. H. Marsham, S. Fiedler, N. S. Dixon, K. Schepanski, B. Laurent, and I. Tegen (2013), The role of deep convection and nocturnal low-level jets for dust emission in summertime West Africa: Estimates from convection-permitting simulations, J. Geophys. Res. Atmos., 118, 4385–4400, doi:10.1002/jgrd.50402. PMID:25893153

A review of semi-volatile organic compounds (SVOCs) in the indoor environment: occurrence in consumer products, indoor air and dust.

PubMed

Lucattini, Luisa; Poma, Giulia; Covaci, Adrian; de Boer, Jacob; Lamoree, Marja H; Leonards, Pim E G

2018-06-01

As many people spend a large part of their life indoors, the quality of the indoor environment is important. Data on contaminants such as flame retardants, pesticides and plasticizers are available for indoor air and dust but are scarce for consumer products such as computers, televisions, furniture, carpets, etc. This review presents information on semi-volatile organic compounds (SVOCs) in consumer products in an attempt to link the information available for chemicals in indoor air and dust with their indoor sources. A number of 256 papers were selected and divided among SVOCs found in consumer products (n = 57), indoor dust (n = 104) and air (n = 95). Concentrations of SVOCs in consumer products, indoor dust and air are reported (e.g. PFASs max: 13.9 μg/g in textiles, 5.8 μg/kg in building materials, 121 ng/g in house dust and 6.4 ng/m 3 in indoor air). Most of the studies show common aims, such as human exposure and risk assessment. The main micro-environments investigated (houses, offices and schools) reflect the relevance of indoor air quality. Most of the studies show a lack of data on concentrations of chemicals in consumer goods and often only the presence of chemicals is reported. At the moment this is the largest obstacle linking chemicals in products to chemicals detected in indoor air and dust. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Development of High-Resolution Dynamic Dust Source Function - A Case Study with a Strong Dust Storm in a Regional Model

NASA Technical Reports Server (NTRS)

Kim, Dongchul; Chin, Mian; Kemp, Eric M.; Tao, Zhining; Peters-Lidard, Christa D.; Ginoux, Paul

2017-01-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 0203 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events.

Development of High-Resolution Dynamic Dust Source Function -A Case Study with a Strong Dust Storm in a Regional Model

PubMed Central

Kim, Dongchul; Chin, Mian; Kemp, Eric M.; Tao, Zhining; Peters-Lidard, Christa D.; Ginoux, Paul

2018-01-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 02-03 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events. PMID:29632432

Development of High-Resolution Dynamic Dust Source Function -A Case Study with a Strong Dust Storm in a Regional Model.

PubMed

Kim, Dongchul; Chin, Mian; Kemp, Eric M; Tao, Zhining; Peters-Lidard, Christa D; Ginoux, Paul

2017-06-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 02-03 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events.

Millennial-scale fluctuations in Saharan dust supply across the decline of the African Humid Period

NASA Astrophysics Data System (ADS)

Zielhofer, Christoph; von Suchodoletz, Hans; Fletcher, William J.; Schneider, Birgit; Dietze, Elisabeth; Schlegel, Michael; Schepanski, Kerstin; Weninger, Bernhard; Mischke, Steffen; Mikdad, Abdeslam

2017-09-01

The Sahara is the world's largest dust source with significant impacts on trans-Atlantic terrestrial and large-scale marine ecosystems. Contested views about a gradual or abrupt onset of Saharan aridity at the end of the African Humid Period dominate the current scientific debate about the Holocene Saharan desiccation. In this study, we present a 19.63 m sediment core sequence from Lake Sidi Ali (Middle Atlas, Morocco) at the North African desert margin. We reconstruct the interaction between Saharan dust supply and Western Mediterranean hydro-climatic variability during the last 12,000 yr based on analyses of lithogenic grain-sizes, XRF geochemistry and stable isotopes of ostracod shells. A robust chronological model based on AMS 14C dated pollen concentrates supports our multi-proxy study. At orbital-scale there is an overall increase in southern dust supply from the Early Holocene to the Late Holocene, but our Northern Saharan dust record indicates that a gradual Saharan desiccation was interrupted by multiple abrupt dust increases before the 'southern dust mode' was finally established at 4.7 cal ka BP. The Sidi Ali record features millennial peaks in Saharan dust increase at about 11.1, 10.2, 9.4, 8.2, 7.3, 6.6, 6.0, and 5.0 cal ka BP. Early Holocene Saharan dust peaks coincide with Western Mediterranean winter rain minima and North Atlantic cooling events. In contrast, Late Holocene dust peaks correspond mostly with prevailing positive phases of the North Atlantic Oscillation. By comparing with other North African records, we suggest that increases in Northern Saharan dust supply do not solely indicate sub-regional to regional aridity in Mediterranean Northwest Africa but might reflect aridity at a trans-Saharan scale. In particular, our findings support major bimillennial phases of trans-Saharan aridity at 10.2, 8.2, 6.0 and 4.2 cal ka BP. These phases coincide with North Atlantic cooling and a weak African monsoon.

Seasonal provenance changes in present-day Saharan dust collected in and off Mauritania

NASA Astrophysics Data System (ADS)

Friese, Carmen A.; van Hateren, Johannes A.; Vogt, Christoph; Fischer, Gerhard; Stuut, Jan-Berend W.

2017-08-01

Saharan dust has a crucial influence on the earth climate system and its emission, transport and deposition are intimately related to, e.g., wind speed, precipitation, temperature and vegetation cover. The alteration in the physical and chemical properties of Saharan dust due to environmental changes is often used to reconstruct the climate of the past. However, to better interpret possible climate changes the dust source regions need to be known. By analysing the mineralogical composition of transported or deposited dust, potential dust source areas can be inferred. Summer dust transport off northwest Africa occurs in the Saharan air layer (SAL). In continental dust source areas, dust is also transported in the SAL; however, the predominant dust input occurs from nearby dust sources with the low-level trade winds. Hence, the source regions and related mineralogical tracers differ with season and sampling location. To test this, dust collected in traps onshore and in oceanic sediment traps off Mauritania during 2013 to 2015 was analysed. Meteorological data, particle-size distributions, back-trajectory and mineralogical analyses were compared to derive the dust provenance and dispersal. For the onshore dust samples, the source regions varied according to the seasonal changes in trade-wind direction. Gibbsite and dolomite indicated a Western Saharan and local source during summer, while chlorite, serpentine and rutile indicated a source in Mauritania and Mali during winter. In contrast, for the samples that were collected offshore, dust sources varied according to the seasonal change in the dust transporting air layer. In summer, dust was transported in the SAL from Mauritania, Mali and Libya as indicated by ferroglaucophane and zeolite. In winter, dust was transported with the trades from Western Sahara as indicated by, e.g., fluellite.

The Use of Principal Component Analysis for Source Identification of PM2.5 from Selected Urban and Regional Background Sites in Poland

NASA Astrophysics Data System (ADS)

Błaszczak, Barbara

2018-01-01

The paper reports the results of the measurements of water-soluble ions and carbonaceous matter content in the fine particulate matter (PM2.5), as well as the contributions of major sources in PM2.5. Daily PM2.5 samples were collected during heating and non-heating season of the year 2013 in three different locations in Poland: Szczecin (urban background), Trzebinia (urban background) and Złoty Potok (regional background). The concentrations of PM2.5, and its related components, exhibited clear spatiotemporal variability with higher levels during the heating period. The share of the total carbon (TC) in PM2.5 exceeded 40% and was primarily determined by fluctuations in the share of OC. Sulfates (SO42-), nitrates (NO3-) and ammonium (NH4+) dominated in the ionic composition of PM2.5 and accounted together 34% (Szczecin), 30% (Trzebinia) and 18% (Złoty Potok) of PM2.5 mass. Source apportionment analysis, performed by PCA-MLRA model (Principal Component Analysis - Multilinear Regression Analysis), revealed that secondary aerosol, whose presence is related to oxidation of gaseous precursors emitted from fuel combustion and biomass burning, had the largest contribution in observed PM2.5 concentrations. In addition, the contribution of traffic sources together with road dust resuspension, was observed. The share of natural sources (sea spray, crustal dust) was generally lower.

Global dust sources detection using MODIS Deep Blue Collection 6 aerosol products

NASA Astrophysics Data System (ADS)

Pérez García-Pando, C.; Ginoux, P. A.

2015-12-01

Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Remote sensing sensors are the most useful tool to locate dust sources. These sensors include microwaves, visible channels, and lidar. On the global scale, major dust source regions have been identified using polar orbiting satellite instruments. The MODIS Deep Blue algorithm has been particularly useful to detect small-scale sources such as floodplains, alluvial fans, rivers, and wadis , as well as to identify anthropogenic sources from agriculture. The recent release of Collection 6 MODIS aerosol products allows to extend dust source detection to the entire land surfaces, which is quite useful to identify mid to high latitude dust sources and detect not only dust from agriculture but fugitive dust from transport and industrial activities. This presentation will overview the advantages and drawbacks of using MODIS Deep Blue for dust detection, compare to other instruments (polar orbiting and geostationary). The results of Collection 6 with a new dust screening will be compared against AERONET. Applications to long range transport of anthropogenic dust will be presented.

Spatial and temporal source apportionment of PM2.5 in Georgia, 2002 to 2013

NASA Astrophysics Data System (ADS)

Zhai, Xinxin; Mulholland, James A.; Russell, Armistead G.; Holmes, Heather A.

2017-07-01

The Chemical Mass Balance (CMB) receptor model was applied to estimate PM2.5 source impacts over Georgia from 2002 to 2013 using ambient PM2.5 species concentration data from 13 sites. Measurements of 19 PM2.5 species were used as inputs along with measurement-based source profiles to estimate the impacts of nine sources, including both primary components (from heavy duty diesel vehicle, light duty gasoline vehicle, biomass burning, coal combustion, and suspended dust sources) and secondary pollutants (ammonium sulfate, ammonium bisulfate, ammonium nitrate, and secondary organic carbon). From 2002 to 2013, PM2.5 total mass decreased from 13.8 μg/m3 to 9.2 μg/m3 averaged across all sites, a 33% decrease. Largest decreases were observed for secondary sulfate and nitrate species (58% and 44%, respectively). The amount of neutralization by ammonium did not change substantially over the time period in spite of substantial decreases in sulfate and nitrate concentrations. Total mobile source impacts decreased more at urban sites (39%) than rural sites (23%), whereas biomass burning decreased more at rural sites (34%) than urban sites (27%). The estimated central-site source impacts are found to spatially represent large areas for secondary pollutants, smaller areas for biomass burning and dust, and very local areas for mobile sources and coal combustion. Trends from the National Emissions Inventory were compared with the annual trends of mobile source impacts, coal combustion impacts, and sulfate concentrations, resulting in statistically significant positive trends with Pearson R2 of 0.80, 0.64, and 0.79, respectively. Results presented here suggest that PM2.5 reductions in Georgia and the Southeast have been achieved by control of both stationary and mobile sources, and that PM2.5 is comprised of increasing fractions of biomass burning emissions and suspended dust. The temporal trends of source impacts at each site adds information about source changes beyond the every-three-year emission inventories for evaluation of emission-based model results.

Dust deposition in southern Nevada and California, 1984-1989: Relations to climate, source area, and source lithology

NASA Astrophysics Data System (ADS)

Reheis, Marith C.; Kihl, Rolf

1995-05-01

Dust samples collected annually for 5 years from 55 sites in southern Nevada and California provide the first regional source of information on modern rates of dust deposition, grain size, and mineralogical and chemical composition relative to climate and to type and lithology of dust source. The average silt and clay flux (rate of deposition) in southern Nevada and southeastern California ranges from 4.3 to 15.7 g/m2/yr, but in southwestern California the average silt and clay flux is as high as 30 g/m2/yr. The climatic factors that affect dust flux interact with each other and with the factors of source type (playas versus alluvium), source lithology, geographic area, and human disturbance. Average dust flux increases with mean annual temperature but is not correlated to decreases in mean annual precipitation because the regional winds bring dust to relatively wet areas. In contrast, annual dust flux mostly reflects changes in annual precipitation (relative drought) rather than temperature. Although playa and alluvial sources produce about the same amount of dust per unit area, the total volume of dust from the more extensive alluvial sources is much larger. In addition, playa and alluvial sources respond differently to annual changes in precipitation. Most playas produce dust that is richer in soluble salts and carbonate than that from alluvial sources (except carbonate-rich alluvium). Gypsum dust may be produced by the interaction of carbonate dust and anthropogenic or marine sulfates. The dust flux in an arid urbanizing area may be as much as twice that before disturbance but decreases when construction stops. The mineralogic and major-oxide composition of the dust samples indicates that sand and some silt is locally derived and deposited, whereas clay and some silt from different sources can be far-traveled. Dust deposited in the Transverse Ranges of California by the Santa Ana winds appears to be mainly derived from sources to the north and east.

Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

NASA Astrophysics Data System (ADS)

Wittmann, Monika; Dorothea Groot Zwaaftink, Christine; Steffensen Schmidt, Louise; Guðmundsson, Sverrir; Pálsson, Finnur; Arnalds, Olafur; Björnsson, Helgi; Thorsteinsson, Throstur; Stohl, Andreas

2017-03-01

Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ˜ 1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m-2. At the station located higher on the glacier ( ˜ 1525 m a.s.l.), the model produced nine dust events, with one single event causing ˜ 5 g m-2 of dust deposition and a total deposition of ˜ 10 g m-2 yr-1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of the 1.6 m w.e. melt in total) at the station located further upglacier. Our findings show that dust has a strong influence on the mass balance of glaciers in Iceland.

Forest fires and PM10 pollution: the March 2012 case in Northern Spain

NASA Astrophysics Data System (ADS)

Rasilla Álvarez, Domingo; García Codron, Juan Carlos; Carracedo Martín, Virginia

2016-04-01

Forest fires are one of the largest sources of particulate matter, carbon monoxide, volatile organic compounds and other pollutants at regional scale. They significantly impact on local air quality and human health, even far from their original sources. March 2012 was one of the largest fire activity late winter and early spring seasons across northern Spain and Portugal. Official statistics from the Spanish and Portuguese authorities show that, during that month, approximately 35.000 ha were burned, representing the top March season in Cantabria (N. Spain) and the northern distritos of Portugal since 1981, most of them occurring in the mountainous areas, as depicted from the FIRMS database (https://firms.modaps.eosdis.nasa.gov/). At the same time, an analysis of the pollution data (Airbase dataset; http://www.eea.europa.eu/) show an increase in PM10 average values and exceedences of the limit values across the same area simultaneously or immediately after the main fire activity episodes. A comprehensive analysis of this fire and pollution event was undertaken to analyze the possible contribution of forest fires and other sources of PM10 to the high levels of this pollutant at ground level. Besides statistics of fire activity, satellite "hot spots" and ground level pollution data, we have included in our analysis meteorological records (synoptic stations, upper air soundings), backtrajectories (http://ready.arl.noaa.gov/HYSPLIT.php) and dust forecast models (https://www.bsc.es/earth-sciences/mineral-dust/catalogo-datos-dust). The results show a good agreement between the spatial and temporal variability of the levels of PM10 and the direction of the pollution plumes downwind the forest fires. The activity was mostly concentrated during 3 events, the first one between February 25th to March 3rd; the second spanning from 10th to 17th, and the last one, the most severe of the three, at the end of March. The climatological background was favourable, because most of the Iberian Peninsula recorded severe moisture deficits at the end of the winter, as shown by the drought indices. At synoptic time scale, the episodes of generalized burning coincided with warmer and drier than usual conditions, although wind speed was low, in agreement with the prevailing stable atmosphere. Saharian dust advections seem to have an indirect contribution to the high levels of PM10, probably by resuspension of old air masses. Moreover, the possible advection of old polluted layers from Eastern Europe, through a European blocking circulation (cut off high), is also considered.

Disintegration of Dust Aggregates in Interstellar Shocks and the Lifetime of Dust Grains in the ISM

NASA Technical Reports Server (NTRS)

Dominik, C.; Jones, A. P.; Tielens, A. G. G. M.; Cuzzi, Jeff (Technical Monitor)

1994-01-01

Interstellar grains are destroyed by shock waves moving through the ISM. In fact, the destruction of grains may be so effective that it is difficult to explain the observed abundance of dust in the ISM as a steady state between input of grains from stellar sources and destruction of grains in shocks. This is especially a problem for the larger grains. Therefore, the dust grains must be protected in some way. Jones et al. have already considered coatings and the increased post-shock drag effects for low density grains. In molecular clouds and dense clouds, coagulation of grains is an important process, and the largest interstellar grains may indeed be aggregates of smaller grains rather than homogeneous particles. This may provide a means to protect the larger grains, in that, in moderate velocity grain-grain collisions in a shock the aggregates may disintegrate rather than be vaporized. The released small particles are more resilient to shock destruction (except in fast shocks) and may reform larger grains later, recovering the observed size distribution. We have developed a model for the binding forces in grain aggregates and apply this model to the collisions between an aggregate and fast small grains. We discuss the results in the light of statistical collision probabilities and grain life times.

[Preliminary study of source apportionment of PM10 and PM2.5 in three cities of China during spring].

PubMed

Gao, Shen; Pan, Xiao-chuan; Madaniyazi, Li-na; Xie, Juan; He, Ya-hui

2013-09-01

To study source apportionment of atmospheric PM10 (particle matter ≤ 10 µm in aerodynamic diameter) and PM2.5 (particle matter ≤ 2.5 µm in aerodynamic diameter) in Beijing,Urumqi and Qingdao, China. The atmospheric particle samples of PM10 and PM2.5 collected from Beijing between May 17th and June 18th, 2005, from Urumqi between April 20th and June 1st, 2006 and from Qingdao between April 4th and May 15th, 2005, were detected to trace the source apportionment by factor analysis and enrichment factor methods. In Beijing, the source apportionment results derived from factor analysis model for PM10 were construction dust and soil sand dust (contributing rate of variance at 45.35%), industry dust, coal-combusted smoke and vehicle emissions (contributing rate at 31.83%), and biomass burning dust (13.57%). The main pollution element was Pb, while the content (median (minimum value-maximum value)was 0.216 (0.040-0.795) µg/m(3)) . As for PM2.5, the sources were construction dust and soil sand dust (38.86%), industry dust, coal-combusted smoke and vehicle emissions (25.73%), biomass burning dust (13.10%) and burning oil dust (11.92%). The main pollution element was Zn (0.365(0.126-0.808) µg/m(3)).In Urumqi, source apportionment results for PM10 were soil sand dust and coal-combusted dust(49.75%), industry dust, vehicle emissions and secondary particles dust (30.65%). The main characteristic pollution element was Cd (0.463(0.033-1.351) ng/m(3)). As for PM2.5, the sources were soil sand dust and coal-combusted dust (43.26%), secondary particles dust (22.29%), industry dust and vehicle emissions (20.50%). The main characteristic pollution element was As (14.599 (1.696-36.741) µg/m(3)).In Qingdao, source apportionment results for PM10 were construction dust (30.91%), vehicle emissions and industry dust (29.65%) and secondary particles dust (28.99%). The main characteristic pollution element was Pb (64.071 (5.846-346.831) µg/m(3)). As for PM2.5, the sources were secondary particles dust, industry dust and vehicle emissions (49.82%) and construction dust (33.71%). The main characteristic pollution element was Pb(57.340 (5.004-241.559) µg/m(3)).Enrichment factors of Zn, Pb, As and Cd in PM2.5 were higher than those in PM10 both in Beijing and Urumqi. The major sources of the atmospheric particles PM10 and PM2.5 in Beijing were cement dust from construction sites and sand dust from soil; while the major sources of those in Urumqi were pollution by smoke and sand dust from burning coal. The major sources of the atmospheric particles PM10 in Qingdao were cement dust from construction sites; however, the major sources of PM2.5 there were secondary particles dust, industry dust and vehicle emissions. According to our study, the heavy metal elements were likely to gather in PM2.5.

Geochemical evidence for diversity of dust sources in the southwestern United States

USGS Publications Warehouse

Reheis, M.C.; Budahn, J.R.; Lamothe, P.J.

2002-01-01

Several potential dust sources, including generic sources of sparsely vegetated alluvium, playa deposits, and anthropogenic emissions, as well as the area around Owens Lake, California, affect the composition of modern dust in the southwestern United States. A comparison of geochemical analyses of modern and old (a few thousand years) dust with samples of potential local sources suggests that dusts reflect four primary sources: (1) alluvial sediments (represented by Hf, K, Rb, Zr, and rare-earth elements, (2) playas, most of which produce calcareous dust (Sr, associated with Ca), (3) the area of Owens (dry) Lake, a human-induced playa (As, Ba, Li, Pb, Sb, and Sr), and (4) anthropogenic and/or volcanic emissions (As, Cr, Ni, and Sb). A comparison of dust and source samples with previous analyses shows that Owens (dry) Lake and mining wastes from the adjacent Cerro Gordo mining district are the primary sources of As, Ba, Li, and Pb in dusts from Owens Valley. Decreases in dust contents of As, Ba, and Sb with distance from Owens Valley suggest that dust from southern Owens Valley is being transported at least 400 km to the east. Samples of old dust that accumulated before European settlement are distinctly lower in As, Ba, and Sb abundances relative to modern dust, likely due to modern transport of dust from Owens Valley. Thus, southern Owens Valley appears to be an important, geochemically distinct, point source for regional dust in the southwestern United States. Copyright ?? 2002 Elsevier Science Ltd.

Mineral dust transport in the Arctic modelled with FLEXPART

NASA Astrophysics Data System (ADS)

Groot Zwaaftink, Christine; Grythe, Henrik; Stohl, Andreas

2016-04-01

Aeolian transport of mineral dust is suggested to play an important role in many processes. For instance, mineral aerosols affect the radiation balance of the atmosphere, and mineral deposits influence ice sheet mass balances and terrestrial and ocean ecosystems. While many efforts have been done to model global dust transport, relatively little attention has been given to mineral dust in the Arctic. Even though this region is more remote from the world's major dust sources and dust concentrations may be lower than elsewhere, effects of mineral dust on for instance the radiation balance can be highly relevant. Furthermore, there are substantial local sources of dust in or close to the Arctic (e.g., in Iceland), whose impact on Arctic dust concentrations has not been studied in detail. We therefore aim to estimate contributions of different source regions to mineral dust in the Arctic. We have developed a dust mobilization routine in combination with the Lagrangian dispersion model FLEXPART to make such estimates. The lack of details on soil properties in many areas requires a simple routine for global simulations. However, we have paid special attention to the dust sources on Iceland. The mobilization routine does account for topography, snow cover and soil moisture effects, in addition to meteorological parameters. FLEXPART, driven with operational meteorological data from European Centre for Medium-Range Weather Forecasts, was used to do a three-year global dust simulation for the years 2010 to 2012. We assess the model performance in terms of surface concentration and deposition at several locations spread over the globe. We will discuss how deposition and dust load patterns in the Arctic change throughout seasons based on the source of the dust. Important source regions for mineral dust found in the Arctic are not only the major desert areas, such as the Sahara, but also local bare-soil regions. From our model results, it appears that total dust load in the Arctic atmosphere is dominated by dust from Africa and Asia. However, in the lower atmosphere, local sources also contribute strongly to dust concentrations. Especially from Iceland, significant amounts of dust are mobilized. These local sources with relatively shallow transport of dust also affect the spatial distribution of dust deposition. For instance, model estimates show that in autumn and winter most of the deposited dust in Greenland originates from sources north of 60 degrees latitude.

Atmospherically transported elements and deposition in the Southeastern United States: Local or transoceanic?

USGS Publications Warehouse

Holmes, C.W.; Miller, R.

2004-01-01

Saharan dust is persistently transported and deposited in ecosystems of the western Atlantic Ocean. This dust is an aggregate of clay and quartz particles cemented with Fe oxides. Samples collected and analyzed from Mali (central Africa), the Azores, the Caribbean and the Eastern United States document the levels of minor and trace metals in the dust. Metal loadings, particularly the toxic elements - Hg and As, are significantly higher than average crustal rocks. Over the past decade, the focus has been to understand the cycling of Hg in south Florida, but As has received very little attention. Arsenic in the sediment deposited in the past decade in south Florida averages 14 mg/kg and appears to be correlated with Al, a proxy for dust. The largest available aerosol data set containing As is the IMPROVE (Interagency Monitoring of Protected Visual Environments) data set. The average concentrations in aerosols collected during this program range from 17 mg/kg in the Virgin Islands to 79 mg/kg at Chassahowitzka, Florida. At Chassahowitzka, most of the As appears to be associated with organic C. If it is assumed that the concentrations in Mali dust and in the aerosols in the Virgin Islands are indicative of soil dust, then the higher values at Chassahowitzka may be derived from local or regional sources. A simple calculation indicates that African dust supplies about 25% of the As deposited from aerosols in the southeastern United States. Comparison of the average yearly As concentrations measured in the Virgin Islands and Everglades shows a negative relationship with the North Atlantic Oscillation (NAO). This relationship demonstrates the influence of climate on the transport and deposition of aerosols to the southeastern United States.

Temporal variation of PM10 concentration and properties in Istanbul 2007-2015

NASA Astrophysics Data System (ADS)

Flores, Rosa M.; Kaya, Nefel; Eşer, Övgü; Saltan, Şehnaz

2017-04-01

The study of temporal variation of atmospheric aerosols is essential for a better understanding of sources, transport, and accumulation in the atmosphere. In addition, the study of aerosol properties is important for the understanding of their formation and potential impacts on ecosystems and climate change. Istanbul is a Megacity that often shows exceedance in particulate matter (PM) standard values, especially during the winter season. In this work, temporal variations of hourly ground-level PM10 concentrations, aerosol optical depth (AOD), aerosol index (AI), vertical distribution, and mineral dust loadings were investigated according to air mass trajectory clusters in Istanbul during 2007-2015. Aerosol properties (i.e., AOD, AI, and vertical distribution) and mineral dust loadings were retrieved from satellite observations and the BSC-DREAM8b model, respectively. Air mass backward trajectories and clustering were supplied by NOAA-HYSPLIT model. Mineral dust transport events were characterized according to the exceedance of a dust loading threshold value. The total number of mineral dust transport events ranged from 115 to 183 during the study period. The largest number of mineral dust transport events were observed in 2008 and 2014. However, the highest ground-level PM10 measurements were observed in 2012-2013 with approximately 70% of the daily average concentrations exceeding the air quality standard of 50 µg m-3. Overall, 5-6 air mass trajectory clusters were able to resolve over 85% of the total spatial variance. These trajectories vary in frequency and direction throughout the years, however, the main trajectories favor aerosol transport from N, NE, NNE, and S, and SE. Evaluation of mineral dust loading and PM10 concentrations is helpful for successful development and implementation of air quality management strategies on local levels.

Controlling dust from concrete saw cutting.

PubMed

Shepherd, Susan; Woskie, Susan

2013-01-01

Cutting concrete with gas-powered saws is ubiquitous in the construction industry and a source of exposure to respirable crystalline silica. Volunteers from the New England Laborers Training Center were recruited to participate in a field experiment examining dust reductions through the use of water, from a hose and from a sprayer, as a dust control. In four series of tests, reinforced concrete pipe was cut under both "dry" and "wet" control conditions. Overall, the geometric mean respirable dust concentration for "dry" cutting (14.396 mg/m³) exceeded both types of water-based controls by more than tenfold. Wet cutting reduced the respirable dust concentration by 85% compared with dry cutting when comparing tests paired by person and saw blade (n = 79 pairs). Using a respirable cyclone, a total of 178 samples were taken. Due to the high variability in dust exposure found in this and other studies of saw cutting, the data were examined for potential exposure determinants that contribute to that variability. Using mixed models, three fixed effects were statistically significant: control condition, worker experience, and location. A random effect for subject was included in the model to account for repeated measures. When each of the significant fixed effects was included with the random effect, it was apparent that inclusion of worker experience or location reduced the between-worker component of exposure variability, while inclusion of control condition (wet vs. dry) explained a large portion of the within-subject variability. Overall, the fixed effect variable for control condition explained the largest fraction of the total exposure variability.

Test chamber investigation of the volatilization from source materials of brominated flame retardants and their subsequent deposition to indoor dust.

PubMed

Rauert, C; Harrad, S; Stranger, M; Lazarov, B

2015-08-01

Numerous studies have reported elevated concentrations of brominated flame retardants (BFRs) in dust from indoor micro-environments. Limited information is available, however, on the pathways via which BFRs in source materials transfer to indoor dust. The most likely hypothesized pathways are (a) volatilization from the source with subsequent partitioning to dust, (b) abrasion of the treated product, transferring microscopic fibers or particles to the dust (c) direct uptake to dust via contact between source and dust. This study reports the development and application of an in-house test chamber for investigating BFR volatilization from source materials and subsequent partitioning to dust. The performance of the chamber was evaluated against that of a commercially available chamber, and inherent issues with such chambers were investigated, such as loss due to sorption of BFRs to chamber surfaces (so-called sink effects). The partitioning of polybrominated diphenyl ethers to dust, post-volatilization from an artificial source was demonstrated, while analysis in the test chamber of a fabric curtain treated with the hexabromocyclododecane formulation, resulted in dust concentrations exceeding substantially those detected in the dust pre-experiment. These results provide the first experimental evidence of BFR volatilization followed by deposition to dust. Brominated flame retardants (BFRs) are ubiquitous in indoor air and dust, leading to human exposure and resultant concerns about their adverse impact on health. Indoor dust has been demonstrated to constitute an important vector of human exposure to BFRs, especially for toddlers. Despite the greater importance of dust contamination in the context of human exposure to BFRs, the mechanisms via which BFRs transfer from source materials to dust have hitherto been subject to only limited research. In this study, a test chamber is utilized to simulate the migration of BFRs to dust via volatilization from source materials and subsequent deposition to dust. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Relative Contributions of the Saharan and Sahelian Sources to the Atmospheric Dust Load Over the North Atlantic

NASA Technical Reports Server (NTRS)

Ginoux, Paul; Chin, M.; Torres, O.; Prospero, J.; Dubovik, O.; Holben, B.; Einaudi, Franco (Technical Monitor)

2000-01-01

It has long been recognized that Saharan desert is the major source for long range transport of mineral dust over the Atlantic. The contribution from other natural sources to the dust load over the Atlantic has generally been ignored in previous model studies or been replaced by anthropogenically disturbed soil emissions. Recently, Prospero et.at. have identified the major dust sources over the Earth using TOMS aerosol index. They showed that these sources correspond to dry lakes with layers of sediment deposed in the late Holocene or Pleistocene. One of the most active of these sources seem to be the Bodele depression. Chiapello et al. have analyzed the mineralogical composition of dust on the West coast of Africa. They found that Sahelian dust events are the most intense but are less frequent than Saharan plumes. This suggests that the Bodele depression could contribute significantly to the dust load over the Atlantic. The relative contribution of the Sahel and Sahara dust sources is of importance for marine biogeochemistry or atmospheric radiation, because each source has a distinct mineralogical composition. We present here a model study of the relative contributions of Sahara and Sahel sources to the atmospheric dust aerosols over the North Atlantic. The Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model is used to simulate dust distribution in 1996-1997. Dust particles are labeled depending on their sources. In this presentation, we will present the comparison between the model results and observations from ground based measurements (dust concentration, optical thickness and size distribution) and satellite data (TOMS aerosol index). The relative contribution of each source will then be analyzed spatially and temporally.

Harmattan, Saharan heat low, and West African monsoon circulation: modulations on the Saharan dust outflow towards the North Atlantic

NASA Astrophysics Data System (ADS)

Schepanski, Kerstin; Heinold, Bernd; Tegen, Ina

2017-09-01

The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the Sahel, is characterized by three major circulation regimes: (1) the harmattan (trade winds), (2) the Saharan heat low (SHL), and (3) the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes.This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August), during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment) field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) flying on board the geostationary Meteosat Second Generation (MSG) satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs) allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the Sahel regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the Sahel are predominantly activated during the second half of the day, when downdrafts associated with deep moist convection are the major atmospheric driver. Complementary to the satellite-based analysis on dust source activations and implications from their diurnal cycle, simulations on atmosphere and dust life cycle were performed using the mesoscale atmosphere-dust model system COSMO-MUSCAT (COSMO: COnsortium for Small-scale MOdelling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model). Fields from this simulation were analysed regarding the variability of the harmattan, the Saharan heat low, and the monsoon circulation as well as their impact on the variability of the Saharan dust outflow towards the North Atlantic. This study illustrates the complexity of the interaction among the three major circulation regimes and their modulation of the North African dust outflow. Enhanced westward dust fluxes frequently appear following a phase characterized by a deep SHL. Ultimately, findings from this study contribute to the quantification of the interannual variability of the atmospheric dust burden.

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

USGS Publications Warehouse

Reynolds, R.L.; Reheis, M.C.; Neff, J.C.; Goldstein, H.; Yount, J.

2006-01-01

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3-4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12-15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.

Investigations of Wind/WAVES Dust Impacts

NASA Astrophysics Data System (ADS)

St Cyr, O. C.; Wilson, L. B., III; Rockcliffe, K.; Mills, A.; Nieves-Chinchilla, T.; Adrian, M. L.; Malaspina, D.

2017-12-01

The Wind spacecraft launched in November 1994 with a primary goal to observe and understand the interaction between the solar wind and Earth's magnetosphere. The waveform capture detector, TDS, of the radio and plasma wave investigation, WAVES [Bougeret et al., 1995], onboard Wind incidentally detected micron-sized dust as electric field pulses from the recollection of the impact plasma clouds (an unintended objective). TDS has detected over 100,000 dust impacts spanning almost two solar cycles; a dataset of these impacts has been created and was described in Malaspina & Wilson [2016]. The spacecraft continues to collect data about plasma, energetic particles, and interplanetary dust impacts. Here we report on two investigations recently conducted on the Wind/WAVES TDS database of dust impacts. One possible source of dust particles is the annually-recurring meteor showers. Using the nine major showers defined by the American Meteor Society, we compared dust count rates before, during, and after the peak of the showers using averaging windows of varying duration. However, we found no statistically significant change in the dust count rates due to major meteor showers. This appears to be an expected result since smaller grains, like the micron particles that Wind is sensitive to, are affected by electromagnetic interactions and Poynting-Robertson drag, and so are scattered away from their initial orbits. Larger grains tend to be more gravitationally dominated and stay on the initial trajectory of the parent body so that only the largest dust grains (those that create streaks as they burn up in the atmosphere) are left in the orbit of the parent body. Ragot and Kahler [2003] predicted that coronal mass ejections (CMEs) near the Sun could effectively scatter dust grains of comparable size to those observed by Wind. Thus, we examined the dust count rates immediately before, during, and after the passage of the 350 interplanetary CMEs observed by Wind over its 20+ year lifetime. We found a statistically significant and consistent trend of count rate deficits during the ICMEs compared to the periods immediately before and after the ICMEs. These preliminary results suggest that ICMEs may scatter micron-sized dust, or that they may exclude it during their initiation.

Aerosol contamination survey during dust storm process in Northwestern China using ground, satellite observations and atmospheric modeling data

NASA Astrophysics Data System (ADS)

Filonchyk, Mikalai; Yan, Haowen; Shareef, Tawheed Mohammed Elhessin; Yang, Shuwen

2018-01-01

The present survey addresses the comprehensive description of geographic locations, transport ways, size, and vertical aerosol distribution during four large dust events which occurred in the Northwest China. Based on the data from 35 ground-based air quality monitoring stations and the satellite data, emission flows for dust events within the period of 2014 to 2017 have been estimated. The data show that maximum peak daily average PM10 and PM2.5 concentrations exceeded 380 and 150 μg/m3, respectively, and the PM2.5/PM10 ratio was ranging within 0.12-0.66. Both satellite data and simulation data of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) coincide with location and extension of a dust cloud. The Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) found dust at 0 to 10 km altitude which remained at this level during the most part of its trajectory. The vertical aerosol distribution at a wave of 532 nm total attenuated backscatter coefficient range of 0.0025-0.003 km-1 × sr-1. Moderate Resolution Imaging Spectroradiometer (MODIS) (Terra) Collection 6 Level-3 aerosol products data show that aerosol optical depth (AOD) at pollution epicenters exceeds 1. A comprehensive data survey thus demonstrated that the main sources of high aerosol pollutions in the territory were deserted areas of North and Northwest China as well as the most part of the Republic of Mongolia, where one of the largest deserts, Gobi, extends.

Evaluation of an improved prototype mini-baghouse to control the release of respirable crystalline silica from sand movers.

PubMed

Alexander, Barbara M; Esswein, Eric J; Gressel, Michael G; Kratzer, Jerry L; Feng, H Amy; Miller, Arthur L; Cauda, Emanuele; Heil, Graeham

2018-01-01

The OSHA final rule on respirable crystalline silica (RCS) will require hydraulic fracturing companies to implement engineering controls to limit workers' exposure to RCS. RCS is generated by pneumatic transfer of quartz-containing sand during hydraulic fracturing operations. Chronic inhalation of RCS can lead to serious disease, including silicosis and lung cancer. NIOSH research identified at least seven sources where RCS aerosols were generated at hydraulic fracturing sites. NIOSH researchers developed an engineering control to address one of the largest sources of RCS aerosol generation, RCS escaping from thief hatches on the top of sand movers. The control, the NIOSH Mini-Baghouse Retrofit Assembly (NMBRA), mounts on the thief hatches. Unlike most commercially available engineering controls, the NMBRA has no moving parts and requires no power source. This article details the results of an evaluation of generation 3 of the NMBRA at a sand mine in Arkansas from May 19-21, 2015. During the evaluation, 168 area air samples were collected at 12 locations on and around a sand mover with and without the NMBRA installed. Analytical results for respirable dust and RCS indicated the use of the NMBRA effectively reduced concentrations of both respirable dust and RCS downwind of the thief hatches. Reductions of airborne respirable dust were estimated at 99+%; reductions in airborne RCS ranged from 98-99%. Analysis of bulk samples of the dust showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS. Use of an improved filter fabric and a larger area of filter cloth led to substantial improvements in filtration and pressures during these trials, as compared to the generation 2 NMBRA. Planned future design enhancements, including a weather cover, will increase the performance and durability of the NMBRA. Future trials are planned to evaluate the long-term operability of the technology.

Attic Dust Analysis Approach for Evaluation of Heavy Metal Deposition on the El Paso Del Norte Region

NASA Astrophysics Data System (ADS)

Shekhter, E. G.; van Pelt, S.; Pannell, K.; Gill, T. E.; Barnes, M. A.

2010-12-01

The El Paso del Norte region in the United States is a region of complex topography that is the home to more than 2 million people who share the same air. A large non-ferrous smelter (primary lead-copper smelter),owned by the American Smelting and Refining Company (ASARCO), was functioning in the Rio Grande River valley on the west side of the Franklin Mountains that divide the city of El Paso and across the river from Juarez, Mexico’s largest city on the United States border. During the more than 100 years of operation, beginning in 1887, the ASARCO smelter emissions considerably deteriorated the already complex environmental condition on the US-Mexican border. In order to identify the sources and patterns of heavy metal dispersion, we used an attic dust analyses approach which has not been previously been applied in this area. Undisturbed attic dust can provide an integrated history of atmospheric loading of particulates emanating from geological, biological and anthropogenic sources and can help to reconstruct the air pollution history on a local scale. We sampled attic dust and dust from undisturbed surfaces in 15 buildings of varying ages from three neighborhoods in the cities of El Paso and Juarez. The dust samples and samples of unpolluted buried soil horizons in the area were extracted with aqua regia and analyzed by ICP-AES and ICP-MS. Enrichment ratios (ER) were calculated by dividing the concentration of a trace metal in the attic dust by the mean concentration of the same element in the buried soil horizons. Mean ER for Pb were 263.3, 95.4, and 70.2 for dust collected in a neighborhood near the smelter, downtown Juarez, and an El Paso neighborhood on the other side of the Franklin Mountains from the smelter. Greater ER for As, Cd, Zn, Sb, and Cu followed the same trends, by neighborhood, noted for Pb. In addition, dust collected from attics surfaces (pipes, ducts, storage containers) post-dating smelter disclosure had lower ER for the trace metals than samples collected on adjacent surfaces that were present during the period of smelter operation. Based on the evidence provided by dust chemistry, we conclude that heavy metal contamination was predominantly from smelter stack emissions, was preferentially deposited on the near field, and generally followed the lower path provided by Rio Grande valley rather than mixing to heights that could result in movement over the Franklin Mountains and deposition on the east side of El Paso.

A new dust source map of Central Asia derived from MODIS Terra/Aqua data using dust enhancement techniques

NASA Astrophysics Data System (ADS)

Nobakht, Mohamad; Shahgedanova, Maria; White, Kevin

2017-04-01

Central Asian deserts are a significant source of dust in the middle latitudes, where economic activity and health of millions of people are affected by dust storms. Detailed knowledge of sources of dust, controls over their activity, seasonality and atmospheric pathways are of crucial importance but to date, these data are limited. This paper presents a detailed database of sources of dust emissions in Central Asia, from western China to the Caspian Sea, obtained from the analysis of the Moderate Resolution Imaging Spectroradiometer (MODIS) data between 2003 and 2012. A dust enhancement algorithm was employed to obtain two composite images per day at 1 km resolution from MODIS Terra/Aqua acquisitions, from which dust point sources (DPS) were detected by visual analysis and recorded in a database together with meteorological variables at each DPS location. Spatial analysis of DPS has revealed several active source regions, including some which were not widely discussed in literature before (e.g. Northern Afghanistan sources, Betpak-Dala region in western Kazakhstan). Investigation of land surface characteristics and meteorological conditions at each source region revealed mechanisms for the formation of dust sources, including post-fire wind erosion (e.g. Lake Balkhash basin) and rapid desertification (e.g. the Aral Sea). Different seasonal patterns of dust emissions were observed as well as inter-annual trends. The most notable feature was an increase in dust activity in the Aral Kum.

Inter-annual variability of wintertime PM2.5 chemical composition in Xi'an, China: Evidences of changing source emissions.

PubMed

Xu, Hongmei; Cao, Junji; Chow, Judith C; Huang, R-J; Shen, Zhenxing; Chen, L W Antony; Ho, Kin Fai; Watson, John G

2016-03-01

Chemical characteristics of PM2.5 in Xi'an in wintertime of 2006, 2008, and 2010 were investigated. Markers of OC2, EC1, and NO3(-)/SO4(2-) ratio were calculated to investigate the changes in PM2.5 emission sources over the 5-year period. Positive matrix factorization (PMF) model was used to identify and quantify the main sources of PM2.5 and their contributions. The results showed that coal combustion, motor vehicular emissions, fugitive dust, and secondary inorganic aerosol accounted for more than 80% of PM2.5 mass. The importance of these major sources to the PM2.5 mass varied yearly: coal combustion was the largest contributor (31.2% ± 5.2%), followed by secondary inorganic aerosol (20.9% ± 5.2%) and motor vehicular emissions (19.3% ± 4.8%) in 2006; the order was still coal combustion emissions (27.6% ± 3.4%), secondary inorganic aerosol (23.2% ± 6.9%), and motor vehicular emissions (20.9% ± 4.6%) in 2008; while coal combustion emission further decreased (24.1% ± 3.1%) with fugitive dust (19.4% ± 5.5%) increasing in 2010. The changes in PM2.5 chemical compositions and source contributions can be attributed to the social and economic developments in Xi'an, China, including energy structure adjustment, energy consumption, the expansion of civil vehicles, and the increase of urban construction activities. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of Atmospheric Processes on the Solubility and Composition of Iron in Saharan Dust

NASA Astrophysics Data System (ADS)

Ingall, E. D.; Longo, A.; Feng, Y.; Lai, B.; Landing, W. M.; Shelley, R.; Nenes, A.; Mihalopoulos, N.; Violaki, K.

2016-12-01

Iron is a key micronutrient that is vital for all organisms. The supply of bioavailable, soluble iron controls primary productivity in approximately 30% of the world's oceans. The significant contribution of atmospheric aerosols to the bioavailable iron budget in vast ocean regions, underscores the need to understand the controls and transformations of aerosol iron solubility during atmospheric transport. The Sahara Desert contains the largest and most active sources of aerosol dust globally and can be a key source of nutrients to the Mediterranean Sea, much of the North Atlantic Ocean, and even as far as the Gulf of Mexico. Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated aerosol iron in Mediterranean samples. In Atlantic samples, iron(II & III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation state became more reduced, and aerosol acidity increased. Atmospheric processing, including acidic reactions and photo-reduction, likely influence the form of iron minerals and the oxidation state in Saharan dust aerosols and contribute to increases in aerosol iron solubility. Overall, these findings suggest that a combination of factors affects aerosol iron solubility during long-distance atmospheric transport and emphasize the need to consider reductive mechanisms as well as proton-induced solubilization of aerosol iron in modeling studies.

Source influence on emission pathways and ambient PM2.5 pollution over India (2015-2050)

NASA Astrophysics Data System (ADS)

Venkataraman, Chandra; Brauer, Michael; Tibrewal, Kushal; Sadavarte, Pankaj; Ma, Qiao; Cohen, Aaron; Chaliyakunnel, Sreelekha; Frostad, Joseph; Klimont, Zbigniew; Martin, Randall V.; Millet, Dylan B.; Philip, Sajeev; Walker, Katherine; Wang, Shuxiao

2018-06-01

India is currently experiencing degraded air quality, and future economic development will lead to challenges for air quality management. Scenarios of sectoral emissions of fine particulate matter and its precursors were developed and evaluated for 2015-2050, under specific pathways of diffusion of cleaner and more energy-efficient technologies. The impacts of individual source sectors on PM2.5 concentrations were assessed through systematic simulations of spatially and temporally resolved particulate matter concentrations, using the GEOS-Chem model, followed by population-weighted aggregation to national and state levels. We find that PM2.5 pollution is a pan-India problem, with a regional character, and is not limited to urban areas or megacities. Under present-day emissions, levels in most states exceeded the national PM2.5 annual standard (40 µg m-3). Sources related to human activities were responsible for the largest proportion of the present-day population exposure to PM2.5 in India. About 60 % of India's mean population-weighted PM2.5 concentrations come from anthropogenic source sectors, while the remainder are from other sources, windblown dust and extra-regional sources. Leading contributors are residential biomass combustion, power plant and industrial coal combustion and anthropogenic dust (including coal fly ash, fugitive road dust and waste burning). Transportation, brick production and distributed diesel were other contributors to PM2.5. Future evolution of emissions under regulations set at current levels and promulgated levels caused further deterioration of air quality in 2030 and 2050. Under an ambitious prospective policy scenario, promoting very large shifts away from traditional biomass technologies and coal-based electricity generation, significant reductions in PM2.5 levels are achievable in 2030 and 2050. Effective mitigation of future air pollution in India requires adoption of aggressive prospective regulation, currently not formulated, for a three-pronged switch away from (i) biomass-fuelled traditional technologies, (ii) industrial coal-burning and (iii) open burning of agricultural residue. Future air pollution is dominated by industrial process emissions, reflecting larger expansion in industrial, rather than residential energy demand. However, even under the most active reductions envisioned, the 2050 mean exposure, excluding any impact from windblown mineral dust, is estimated to be nearly 3 times higher than the WHO Air Quality Guideline.

[Geochemical characteristics and sources of atmospheric particulates in Shanghai during dust storm event].

PubMed

Qian, Peng; Zheng, Xiang-min; Zhou, Li-min

2013-05-01

Atmospheric particulates were sampled from three sampling sites of Putuo, Minhang and Qingpu Districts in Shanghai between Oct. , 2009 and Oct. , 2010. In addition, particulate samples were also collected from Nantong, Zhengzhou, Xi'an, and Beijing city where dust storm dust transported along during spring. Element compositions of atmospheric particulates were determined by XRF and ICP-MS. The concentrations of major and trace elements in atmospheric particulates from Putuo, Minhang and Qingpu Districts were similar, indicating their common source. The UCC standardization distribution map showed that the major element composition of dust storm samples was similar to that of loess in northwestern China, indicating that the dust storm dust was mainly derived from Western desert and partly from local area. The REE partition patterns of dust storm dusts among different cities along dust transport route were similar to each other, as well as to those of northern loess, which indicates that the dust storm samples may have the same material source as loess, which mainly comes from crust material. However, the REE partition patterns of non-dust storm particulates were different among the studied cities, and different from those of loess, which suggests that the non-dust storm samples may be mixed with non-crust source material, which is different from dust storm dust and loess. The major element composition and REE partition pattern are effective indicators for source tracing of dust storm dust.

Temporal variation of fine and coarse particulate matter sources in Jeddah, Saudi Arabia

PubMed Central

Lim, Chris C.; Thurston, George D.; Shamy, Magdy; Alghamdi, Mansour; Khoder, Mamdouh; Mohorjy, Abdullah M.; Alkhalaf, Abdulrahman K.; Brocato, Jason; Chen, Lung Chi; Costa, Max

2017-01-01

This study provides the first comprehensive analysis of the seasonal variations and weekday/weekend differences in fine (PM2.5) and coarse (PM2.5–10) particulate matter mass concentrations, elemental constituents, and potential source origins in Jeddah, Saudi Arabia. Air quality samples were collected over one year, from June 2011 to May 2012 at a frequency of three times per week, and analyzed. The average mass concentrations of PM2.5 (21.9 µg/m3) and PM10 (107.8 µg/m3) during the sampling period exceeded the recommended annual average levels by the World Health Organization (WHO) for PM2.5 (10 µg/m3) and PM10 (20 µg/m3), respectively. Similar to other Middle Eastern locales, PM2.5–10 is the prevailing mass component of atmospheric particulate matter at Jeddah, accounting for approximately 80% of the PM10 mass. Considerations of enrichment factors, absolute principal component analysis (APCA), concentration roses, and backward trajectories identified the following source categories for both PM2.5 and PM2.5–10: 1) soil/road dust; 2) incineration; and 3) traffic; and for PM2.5 only, 4) residual oil burning. Soil/road dust accounted for a major portion of both the PM2.5 (27%) and PM2.5–10 (77%) mass, and the largest source contributor for PM2.5 was from residual oil burning (63%). Temporal variations of PM2.5–10 and PM2.5 were observed, with the elevated concentration levels observed for mass during the spring (due to increased dust storm frequency), and on weekdays (due to increased traffic). The predominant role of windblown soil and road dust in both the PM2.5 and PM2.5–10 masses in this city may have implications regarding the toxicity of these particles versus those in the western world where most PM health assessments have been made in the past. These results support the need for region-specific epidemiological investigations to be conducted and considered in future PM standard setting. PMID:28635552

Dusty Lyman-alpha Emitters As Seen By Spitzer

NASA Astrophysics Data System (ADS)

Dolan, Kyle; Scarlata, C.; Colbert, J. W.; Teplitz, H. I.; Hayes, M.

2013-01-01

We have used the IRAC and MIPS Spitzer archive to derive the full mid-IR SED for the largest sample of local Lyman-alpha emitters, probing the internal activities of these sources as well as analyzing the role that dust properties play in the Lyman-alpha escape fraction. We utilized all available IRAC and MIPS data for a sample of about 100 local Lyman-alpha emitters at redshift 0.2≤z≤0.4 , originally discovered by Deharveng et al. (2008) and Cowie et al. (2011), to quantify the level of star formation (SF) and AGN activity in these sources, probing into dust-enshrouded regions that block UV and optical photons from escaping. In order to derive the total bolometric IR luminosity from 8μm to 1000μm, we fit the IR data to the template SEDs derived by Chary and Elbaz (2001). Using this information, we quantified the total star formation rate (SFR) of these galaxies and how much SF is missed by optical and UV surveys. We also identified any AGN activity and produced new estimates for AGN contamination within the population of Lyman-alpha emitters. This work has been supported by NASA's Astrophysics Data Analysis Program, Award # NNX11AH84G.

Global Scale Attribution of Anthropogenic and Natural Dust Sources and their Emission Rates Based on MODIS Deep Blue Aerosol Products

NASA Technical Reports Server (NTRS)

Ginoux, Paul; Prospero, Joseph M.; Gill, Thomas E.; Hsu, N. Christina; Zhao, Ming

2012-01-01

Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1 deg) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.

Aeolian Environments of Iceland

NASA Astrophysics Data System (ADS)

Arnalds, Olafur; Olafsson, Haraldur; Dagsson Waldhauserová, Pavla

2017-04-01

Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland's location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since the time of the settlement of Iceland in the late ninth century. There are about 135 dust events per annum, ranging from minor storms to >300,000 t of dust emitted in single storms. Dust can be generated from all the major sandy areas of Iceland; however the amount of finer particles that become dust varies with the surfaces. There are areas that produce more dust by far compared to the general sandy deserts; they have therefore been termed "dust plume areas" or "dust hot-spots". They are characterized by repeated charging of fine sediments with a relatively high proportion of finer (silty) materials which, upon repeated wind erosion become sorted downwind from the sources with loss of silt (dust) and an increasing saltation component (sand). Dust production is on the order of 30-40 million tons annually, some travelling over 1000 km and deposited on land and sea. Dust deposited on deserts tends to be re-suspended during subsequent storms. High PM10 concentrations occur during major dust storms. They are more frequent in the wake of volcanic eruptions, such as after the Eyjafjallajökull 2010 eruption. Airborne dust affects human health, with negative effects enhanced by the tubular morphology of the grains, and the basaltic composition with its high metal content. Dust deposition on snow and glaciers intensifies melting. Moreover, the dust production probably also influences atmospheric conditions and parameters that affect climate change.

Analysis of Aerosol Optical and Physical Properties and Their Impact on Surface Radiative Energy Budget and Atmospheric Thermodynamics during Aerose Campaigns

NASA Astrophysics Data System (ADS)

Flores, A.; Joseph, E.; Nalli, N. R.; Morris, V.; Aerose Team

2010-12-01

Western Africa is one of the largest sources of mineral dust aerosol in the world. With uncertainty of how dust impacts on weather and climate, the trans-Atlantic Aerosols and Ocean Science Expeditions (AEROSE) are good opportunities to address this issue. Recent studies have suggested that the Saharan air layer (SAL) can alter the dynamics, microphysics and thermodynamics of tropical systems (e.g., Dunion and Velden 2004), cools the sea surface temperature (e.g., Lau and Kim 2007), suppress deep convection (e.g., Mapes and Zuidema 1996; Wong and Dessler 2005), and alter the radiation balance of the atmosphere (e.g., Slingo et al. 2006). AEROSE constitutes a comprehensive approach, in terms of both measurements and modeling, for gaining understanding of the impacts of long-range transport of mineral dust in the tropical Atlantic (Morris et al. 2006; Nalli et al. 2010). Sounding data from AEROSE shows a well-maintained and static stability of the SAL well across the Atlantic (Nalli et al. 2005). Results of the current study may shed light on the role of dust on the thermodynamics of the SAL and its impact on sea surface temperature. This work will involve using radiative transfer models for calculating total heating rates during heavy dusty days encountered during AEROSE campaigns and analysis of the physical properties of the aerosols.

The Development and Testing of a Prototype Mini-Baghouse to Control the Release of Respirable Crystalline Silica from Sand Movers

PubMed Central

Alexander, Barbara M.; Esswein, Eric J.; Gressel, Michael G.; Kratzer, Jerry L.; Feng, H. Amy; King, Bradley; Miller, Arthur L.; Cauda, Emanuele

2016-01-01

Inhalation of respirable crystalline silica (RCS) is a significant risk to worker health during well completions operations (which include hydraulic fracturing) at conventional and unconventional oil and gas extraction sites. RCS is generated by pneumatic transfer of quartz-containing sand during hydraulic fracturing operations. National Institute for Occupational Safety and Health (NIOSH) researchers identified concentrations of RCS at hydraulic fracturing sites that exceed 10 times the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and up to 50 times the NIOSH Recommended Exposure Limit (REL). NIOSH research identified at least seven point sources of dust release at contemporary oil and gas extraction sites where RCS aerosols were generated. NIOSH researchers recommend the use of engineering controls wherever they can be implemented to limit the RCS released. A control developed to address one of the largest sources of RCS aerosol generation is the NIOSH mini-baghouse assembly, mounted on the thief hatches on top of the sand mover. This manuscript details the results of a trial of the NIOSH mini-baghouse at a sand mine in Arkansas, November 18 – 21, 2013. During the trial, area air samples were collected at 12 locations on and around a sand mover with and without the mini-baghouse control installed. Analytical results for respirable dust and RCS indicate the use of the mini-baghouse effectively reduced both respirable dust and RCS downwind of the thief hatches. Reduction of airborne respirable dust ranged from 85% to 98%; reductions in airborne RCS ranged from 79% to 99%. A bulk sample of dust collected by the baghouse assembly showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS. Planned future design enhancements will increase the performance and durability of the mini-baghouse, including an improved bag clamp mechanism and upgraded filter fabric with a modified air-to-cloth ratio. Future trials are planned to determine additional respirable dust and RCS concentration reductions achieved through these design changes. PMID:27003622

Investigation of dust storms entering Western Iran using remotely sensed data and synoptic analysis.

PubMed

Boloorani, Ali D; Nabavi, Seyed O; Bahrami, Hosain A; Mirzapour, Fardin; Kavosi, Musa; Abasi, Esmail; Azizi, Rasoul

2014-01-01

One of the natural phenomena which have had considerable impacts on various regions of the world, including Iran, is "dust storm". In recent years, this phenomenon has taken on new dimensions in Iran and has changed from a local problem to a national issue. This study is an attempt to investigate the formation of the dust storms crossing the Western Iran. To find the sources of the dust storms entering Iran, first we examine three determined dust paths in the region and their temporal activities, using MODIS satellite images. Then, four regions were identified as dust sources through soil, land cover and wind data. Finally, atmospheric analyses are implemented to find synoptic patterns inducing dust storms. Source 1 has covered the region between the eastern banks of Euphrates and western banks of Tigris. Source 2 is in desert area of western and south-western Iraq. Finally source 3 is bounded in eastern and south-eastern deserts of Saudi Arabia called Rub-Al-Khali desert, or Empty Quarter. Moreover, south-eastern part of Iraq (source 4) was also determined as a secondary source which thickens the dust masses originating from the above mentioned sources. The study of synoptic circulations suggests that the dust storms originating from source 1 are formed due to the intense pressure gradient between the low-pressure system of Zagros and a high-pressure cell formed on Mediterranean Sea. The dust events in sources 2 and 3 are outcomes of the atmospheric circulations dominant in the cold period of the year in mid-latitudes.

Characterization, heavy metal content and health risk assessment of urban road dusts from the historic center of the city of Thessaloniki, Greece.

PubMed

Bourliva, Anna; Christophoridis, Christophoros; Papadopoulou, Lambrini; Giouri, Katerina; Papadopoulos, Argyrios; Mitsika, Elena; Fytianos, Konstantinos

2017-06-01

In the present study, an investigation of the mineralogy and morphology, the heavy metal content and the health risk of urban road dusts from the second largest city of Greece was conducted. For this reason road dust samples from selected sites within the city core area were collected. No differences were observed in the mineralogy of road dusts coming from different sampling sites, and they were mainly consisted of quartz and calcite, while an elevated amorphous content was detected. Morphologically road dusts presented Ca-rich, Fe-rich and silicates particles with various shapes and sizes. The mean concentrations of Cd, Cr, Cu, Mn, Ni, Pb and Zn in road dust were 1.76, 104.9, 662.3, 336.4, 89.43, 209 and 452.8 μg g -1 , respectively. A series of spatial distribution patterns revealed that the hotspot areas were tended to associate with major road junctions and regions with high traffic. Combination of pollution indexes and statistical analyses (correlation analysis, cluster analysis and principal component analysis) revealed that road dusts have a severe influence by anthropogenic activities. In attempt to identify the source of metals through geostatistical and multivariate statistical analyses, it was concluded as follows: Cr, Cu, Fe and Zn mainly originated from tire/break wear and vehicle abrasions, while Cd, Mn and Pb were mainly related to fuel/oil leakage from automobiles along with oil lubricants and vehicle abrasion. Hazard quotient values for children based on total metal concentrations for the road dust ingestion route were lower than safe level (=1). However, the fact that the Hazard Index value for Pb (0.459) which is a particularly toxic metal, was close to safe level, renders essential further investigation in order to provide more reliable characterizations of potential health risks.

Transoceanic transport of metals and deposition in the Southeastern United States

NASA Astrophysics Data System (ADS)

Holmes, C. W.

2003-12-01

Saharan dust is persistently being transported and deposited in ecosystems of the western Atlantic Ocean. Satellite photos reveal that this dust is transported in tropospheric low-pressure waves that cross the central Atlantic Ocean. This dust is an aggregate of clay and quartz particles cemented with iron oxides. Analysis of dust samples collected from Mali (central Africa), the Azores, the Caribbean and the Eastern United States show that metal concentrations are significantly higher than average crustal rocks. Over the past decade, there has been a significant effort to understand the cycling of mercury in south Florida, but other metals has received very little attention. Trace metal measurements on the ombrogeneous sediment formed during the last decade in south Florida indicates that metals can be correlated with aluminum, which is considered a proxy for dust. The largest available aerosol data set is provided by the IMPROVE (Interagency Monitoring of Protected Visual Environments) program. Focusing on arsenic as an example, the average concentration in aerosols collected during this program range from 17 mg/kg in the Virgin Islands to 79 mg/kg at Chassahowitzka, Florida. At Chassahowitzka, most of the arsenic appears to be associated with organic carbon. If it is assumed that the concentrations in Mali dust and in the aerosols in the Virgin Islands are indicative of soil dust, then the higher values at Chassahowitzka are most likely derived from local or regional sources. A simple calculation indicates that African dust supplies about 25 % of the arsenic deposited from aerosols in the southeastern United States. Comparison of the average yearly arsenic concentrations measured in the Virgin Islands and Everglades shows a negative relationship with the North Atlantic Oscillation Index (NAO). This relationship demonstrates the influence of climate on the transport and deposition of aerosols with associated metals to the southeastern United States.

Geochemical characterization of critical dust source regions in the American West

NASA Astrophysics Data System (ADS)

Aarons, Sarah M.; Blakowski, Molly A.; Aciego, Sarah M.; Stevenson, Emily I.; Sims, Kenneth W. W.; Scott, Sean R.; Aarons, Charles

2017-10-01

The generation, transport, and deposition of mineral dust are detectable in paleoclimate records from land, ocean, and ice, providing valuable insight into earth surface conditions and cycles on a range of timescales. Dust deposited in marine and terrestrial ecosystems can provide critical nutrients to nutrient-limited ecosystems, and variations in dust provenance can indicate changes in dust production, sources and transport pathways as a function of climate variability and land use change. Thus, temporal changes in locations of dust source areas and transport pathways have implications for understanding interactions between mineral dust, global climate, and biogeochemical cycles. This work characterizes dust from areas in the American West known for dust events and/or affected by increasing human settlement and livestock grazing during the last 150 years. Dust generation and uplift from these dust source areas depends on climate and land use practices, and the relative contribution of dust has likely changed since the expansion of industrialization and agriculture into the western United States. We present elemental and isotopic analysis of 28 potential dust source area samples analyzed using Thermal Ionization Mass Spectrometry (TIMS) for 87Sr/86Sr and 143Nd/144Nd composition and Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) for 176Hf/177Hf composition, and ICPMS for major and trace element concentrations. We find significant variability in the Sr, Nd, and Hf isotope compositions of potential source areas of dust throughout western North America, ranging from 87Sr/86Sr = 0.703699 to 0.740236, εNd = -26.6 to 2.4, and εHf = -21.7 to -0.1. We also report differences in the trace metal and phosphorus concentrations in the geologic provinces sampled. This research provides an important resource for the geochemical tracing of dust sources and sinks in western North America, and will aid in modeling the biogeochemical impacts of increased dust generation and deposition caused by higher drought frequency and human activity.

Earth Observations taken by the Expedition 17 Crew

NASA Image and Video Library

2008-10-16

ISS017-E-019616 (16 Oct. 2008) --- A dust storm in Turkmenistan, Central Asia is featured in this image photographed by an Expedition 17 crewmember on the International Space Station. This west-looking view, taken with a short focal length lens from the station, shows a wide swath of central Asia--from Afghanistan, along the length of Turkmenistan to the Caspian Sea. Winds blowing down the largest river valley in the region, the Amudarya, were strong enough to raise a large dust storm. Dust appears as a light brown mass extending into the center of the image from the lower right. Diffuse dust from prior windy weather appears over much of the area making a regional haze that clouds much of the landscape detail. The haze partly obscures the irrigated agriculture in Turkmenistan and entirely obscures the Caspian Sea. Numerous rivers rise in the Hindu Kush mountain complex (lower left). The Band-i Amir River is a major tributary of the main regional river, the Amudarya, which it reaches via a deep canyon. The Amudarya River was the major historical contributor of water to the Aral Sea, but today extensive diversion of river water for agricultural purposes has lead to extensive exposure and desiccation of the sea bed. The exposed sea bed is a major source of saline dusts contaminated with agricultural chemicals that pose a significant environmental hazard to central Asia. To a lesser extent, dusts are also mobilized from sediments along the Amudarya river channel. The Paropamisus Range and the Amudarya (also known as the Oxus River) are mentioned in histories of Alexander the Great's famous military expedition from Greece to India. His horsemen made a fast side excursion from near the Caspian Sea (top right) as far as the Amudarya (lower right).

Collection and analysis of samples for polycyclic aromatic hydrocarbons in dust and other solids related to sealed and unsealed pavement from 10 cities across the United States, 2005-07

USGS Publications Warehouse

Van Metre, Peter C.; Mahler, Barbara J.; Wilson, Jennifer T.; Burbank, Teresa L.

2008-01-01

Parking lots and driveways are dominant features of the modern urban landscape, and in the United States, sealcoat is widely used on these surfaces. One of the most widely used types of sealcoat contains refined coal tar; coal-tar-based sealcoat products have a mean polycyclic aromatic hydrocarbon (PAH) concentration of about 5 percent. A previous study reported that parking lots in Austin, Texas, treated with coal-tar sealcoat were a major source of PAH compounds in streams. This report presents methods for and data from the analysis of concentrations of PAH compounds in dust from sealed and unsealed pavement from nine U.S. cities, and concentrations of PAH compounds in other related solid materials (sealcoat surface scrapings, nearby street dust, and nearby soil) from three of those same cities and a 10th city. Dust samples were collected by sweeping dust from areas of several square meters with a soft nylon brush into a dustpan. Some samples were from individual lots or driveways, and some samples consisted of approximately equal amounts of material from three lots. Samples were sieved to remove coarse sand and gravel and analyzed by gas chromatography/mass spectrometry. Concentrations of PAHs vary greatly among samples with total PAH (sigmaPAH), the sum of 12 unsubstituted parent PAHs, ranging from nondetection for all 12 PAHs (several samples from Portland, Oregon, and Seattle, Washington; sigmaPAH of less than 36,000 micrograms per kilogram) to 19,000,000 micrograms per kilogram for a sealcoat scraping sample (Milwaukee, Wisconsin). The largest PAH concentrations in dust are from a driveway sample from suburban Chicago, Illinois (sigmaPAH of 9,600,000 micrograms per kilogram).

Interactive Soil Dust Aerosol Model in the GISS GCM. Part 1; Sensitivity of the Soil Dust Cycle to Radiative Properties of Soil Dust Aerosols

NASA Technical Reports Server (NTRS)

Perlwitz, Jan; Tegen, Ina; Miller, Ron L.

2000-01-01

The sensitivity of the soil dust aerosol cycle to the radiative forcing by soil dust aerosols is studied. Four experiments with the NASA/GISS atmospheric general circulation model, which includes a soil dust aerosol model, are compared, all using a prescribed climatological sea surface temperature as lower boundary condition. In one experiment, dust is included as dynamic tracer only (without interacting with radiation), whereas dust interacts with radiation in the other simulations. Although the single scattering albedo of dust particles is prescribed to be globally uniform in the experiments with radiatively active dust, a different single scattering albedo is used in those experiments to estimate whether regional variations in dust optical properties, corresponding to variations in mineralogical composition among different source regions, are important for the soil dust cycle and the climate state. On a global scale, the radiative forcing by dust generally causes a reduction in the atmospheric dust load corresponding to a decreased dust source flux. That is, there is a negative feedback in the climate system due to the radiative effect of dust. The dust source flux and its changes were analyzed in more detail for the main dust source regions. This analysis shows that the reduction varies both with the season and with the single scattering albedo of the dust particles. By examining the correlation with the surface wind, it was found that the dust emission from the Saharan/Sahelian source region and from the Arabian peninsula, along with the sensitivity of the emission to the single scattering albedo of dust particles, are related to large scale circulation patterns, in particular to the trade winds during Northern Hemisphere winter and to the Indian monsoon circulation during summer. In the other regions, such relations to the large scale circulation were not found. There, the dependence of dust deflation to radiative forcing by dust particles is probably dominated by physical processes with short time scales. The experiments show that dust radiative forcing can lead to significant changes both in the soil dust cycle and in the climate state. To estimate dust concentration and radiative forcing by dust more accurately, dust size distributions and dust single scattering albedo in the model should be a function of the source region, because dust concentration and climate response to dust radiative forcing are sensitive to dust radiative parameters.

How Early Holocene Greening of the Afro-Asian Dust Belt Changed Sources of Mineral Dust in West Asia

NASA Astrophysics Data System (ADS)

Pourmand, A.; Sharifi, A.; Goes, L. M.; Clement, A. C.; Canuel, E. A.; Naderi Beni, A.; Ahmady-Birgani, H.

2016-12-01

Production, transport and deposition of mineral dust have significant temporal and spatial impacts on different components of the Earth systems. In modern times, dust plumes can be associated with their source origin(s) using satellite and land-based measurements and back-trajectory reconstruction of air masses. Reconstructing past changes in the sources of mineral dust as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleo-dust, and their potential source origins. In this contribution, we present a 13,000-year record of variations in radiogenic Sr-Nd-Hf isotopes and Rare Earth Element (REE) anomalies from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in sources of dust over West Asia. The geochemical fingerprint of dust particles deposited during the low-flux, early Holocene period (11,700-6,000 yr BP) is distinctly different from times of high dust fluxes during the Younger Dryas, and that of the mid-late Holocene. This indicates that the composition of mineral dust deposited at the receptor site changed as a function of prevailing atmospheric circulation regimes and land exposure. Simulations of atmospheric circulation over the region show the Northern Hemisphere Westerly Jet (NHWJ) was displaced poleward across the study area during the early Holocene when solar insolation was higher. This shift, coupled with lower dust emissions simulated based on greening of the Afro-Asian Dust Belt during the early Holocene likely led to potential sources in Central Asia to dominate dust export to West Asia during this period, in contrast to the dominant western and southwest Asian and Eastern African sources that prevail during the modern period.

The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

NASA Astrophysics Data System (ADS)

Wiacek, A.; Peter, T.; Lohmann, U.

2010-09-01

This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons, without explicitly modelling dust emission and deposition processes. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high ice clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Downstream of the investigated dust sources, practically none of the simulated air parcels reached conditions of homogeneous ice nucleation (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through atmospheric regions supersaturated with respect to ice but subsaturated with respect to water, where so-called "warm ice clouds" (T≳-40 °C) theoretically may form prior to supercooled water or mixed-phase clouds. The importance of "warm ice clouds" and the general influence of dust in the mixed-phase cloud region are highly uncertain due to both a considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work, and due to uncertainties in sub-grid scale vertical transport processes unresolved by the present trajectory analysis. For "classical" cirrus-forming temperatures (T≲-40 °C), our results show that only mineral dust ice nuclei that underwent mixed-phase cloud-processing, most likely acquiring coatings of organic or inorganic material, are likely to be relevant. While the potential paucity of deposition ice nuclei shown in this work dimishes the possibility of deposition nucleation, the absence of liquid water droplets at T≲-40 °C makes the less explored contact freezing mechanism (involving droplet collisions with bare ice nuclei) highly inefficient. These factors together indicate the necessity of further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.

Simulating Dust Regional Impact on the Middle East Climate and the Red Sea

NASA Astrophysics Data System (ADS)

Osipov, Sergey; Stenchikov, Georgiy

2017-04-01

Dust is one of the most abundant aerosols, however, currently only a few regional climate downscalings account for dust. This study focuses on the Middle East and the Red Sea regional climate response to the dust aerosol radiative forcing. The Red Sea is located between North Africa and Arabian Peninsula, which are first and third largest source regions of dust, respectively. MODIS and SEVIRI satellite observations show extremely high dust optical depths in the region, especially over the southern Red Sea during the summer season. The significant north-to-south gradient of the dust optical depth over the Red Sea persists throughout the entire year. Modeled atmospheric radiative forcing at the surface, top of the atmosphere and absorption in the atmospheric column indicate that dust significantly perturbs radiative balance. Top of the atmosphere modeled forcing is validated against independently derived GERB satellite product. Due to strong radiative forcing at the sea surface (daily mean forcing during summer reaches -32 Wm-2 and 10 Wm-2 in SW and LW, respectively), using uncoupled ocean model with prescribed atmospheric boundary conditions would result in an unrealistic ocean response. Therefore, here we employ the Regional Ocean Modeling system (ROMS) fully coupled with the Weather Research and Forecasting (WRF) model to study the impact of dust on the Red Sea thermal regime and circulation. The WRF was modified to interactively account for the radiative effect of dust. Daily spectral optical properties of dust are computed using Mie, T-matrix, and geometric optics approaches, and are based on the SEVIRI climatological optical depth. The WRF model parent and nested domains are configured over the Middle East and North Africa (MENA) region and over the Red Sea with 30 and 10 km resolution, respectively. The ROMS model over the Red Sea has 2 km grid spacing. The simulations show that, in the equilibrium response, dust causes 0.3-0.5 K cooling of the Red Sea surface waters, and weakens the overturning circulation in the Red Sea. The salinity distribution, freshwater, and heat budgets are significantly perturbed. This indicates that dust plays an important role in the formation of the Red Sea energy balance and circulation regimes, and has to be thoroughly accounted for in future modeling studies.

Sensitivity of WRF-chem predictions to dust source function specification in West Asia

NASA Astrophysics Data System (ADS)

Nabavi, Seyed Omid; Haimberger, Leopold; Samimi, Cyrus

2017-02-01

Dust storms tend to form in sparsely populated areas covered by only few observations. Dust source maps, known as source functions, are used in dust models to allocate a certain potential of dust release to each place. Recent research showed that the well known Ginoux source function (GSF), currently used in Weather Research and Forecasting Model coupled with Chemistry (WRF-chem), exhibits large errors over some regions in West Asia, particularly near the IRAQ/Syrian border. This study aims to improve the specification of this critical part of dust forecasts. A new source function based on multi-year analysis of satellite observations, called West Asia source function (WASF), is therefore proposed to raise the quality of WRF-chem predictions in the region. WASF has been implemented in three dust schemes of WRF-chem. Remotely sensed and ground-based observations have been used to verify the horizontal and vertical extent and location of simulated dust clouds. Results indicate that WRF-chem performance is significantly improved in many areas after the implementation of WASF. The modified runs (long term simulations over the summers 2008-2012, using nudging) have yielded an average increase of Spearman correlation between observed and forecast aerosol optical thickness by 12-16 percent points compared to control runs with standard source functions. They even outperform MACC and DREAM dust simulations over many dust source regions. However, the quality of the forecasts decreased with distance from sources, probably due to deficiencies in the transport and deposition characteristics of the forecast model in these areas.

Scavenging of pollutant acid substances by Asian mineral dust particles - article no. L07816

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsumoto, J.; Takahashi, K.; Matsumi, Y.

2006-04-13

Uptakes of sulfate and nitrate onto Asian dust particles during transport from the Asian continent to the Pacific Ocean were analyzed by using a single-particle time-of-flight mass spectrometer. Observation was conducted at Tsukuba in Japan in the springtime of 2004. Sulfate-rich dust particles made their largest contribution during the 'dust event' in the middle of April 2004. As a result of detailed analysis including backward trajectory calculations, it was confirmed that sulfate components originating from coal combustion in the continent were internally mixed with dust particles. Even in the downstream of the outflow far from the continental coastline, significant contributionmore » of Asian dust to sulfate was observed. Asian dust plays critical roles as the carrier of sulfate over the Pacific Ocean.« less

Probing the Interstellar Dust towards the Galactic Centre using X-ray Dust Scattering Halos

NASA Astrophysics Data System (ADS)

Jin, C.; Ponti, G.; Haberl, F.; Smith, R.

2017-10-01

Dust scattering creates an X-ray halo that contains abundant information about the interstellar dust along the source's line-of-sight (LOS), and is most prominent when the LOS nH is high. In this talk, I will present results from our latest study of a bright dust scattering halo around an eclipsing X-ray binary at 1.45 arcmin away from Sgr A*, namely AX J1745.6-2901. This study is based on a large set of XMM-Newton and Chandra observations, and is so-far the best dust scattering halo study of a X-ray transient in the Galactic centre (GC). I will show that the foreground dust of AX J1745.6-2901 can be decomposed into two major thick dust layers. One layer contains (66-81)% of the total LOS dust and is several kpc away from the source, and so is most likely to reside in the Galactic disc. The other layer is local to the source. I will also show that the dust scattering halo can cause the source spectrum to severely depend on the source extraction region. Such spectral bias can be corrected by our new Xspec model, which is likely to be applicable to Sgr A* and other GC sources as well.

Modern dust aerosol availability in northwestern China.

PubMed

Wang, Xunming; Cheng, Hong; Che, Huizheng; Sun, Jimin; Lu, Huayu; Qiang, Mingrui; Hua, Ting; Zhu, Bingqi; Li, Hui; Ma, Wenyong; Lang, Lili; Jiao, Linlin; Li, Danfeng

2017-08-18

The sources of modern dust aerosols and their emission magnitudes are fundamental for linking dust with climate and environment. Using field sample data, wind tunnel experiments and statistical analysis, we determined the contributions of wadis, gobi (stony desert), lakebeds, riverbeds, and interdunes to modern dust aerosol availability in the three important potential dust sources including the Tarim Basin, Qaidam Basin, and Ala Shan Plateau of China. The results show that riverbeds are the dominant landscape for modern dust aerosol availabilities in the Qaidam Basin, while wadis, gobi, and interdunes are the main landscapes over the Ala Shan Plateau and Tarim Basin. The Ala Shan Plateau and Tarim Basin are potential dust sources in northwestern China, while the Qaidam Basin is not a major source of the modern dust aerosols nowadays, and it is not acting in a significant way to the Loess Plateau presently. Moreover, most of modern dust aerosol emissions from China originated from aeolian processes with low intensities rather than from major dust events.

Desert Dust and Health: A Central Asian Review and Steppe Case Study.

PubMed

Sternberg, Troy; Edwards, Mona

2017-11-03

In Asian deserts environmental and anthropomorphic dust is a significant health risk to rural populations. Natural sources in dry landscapes are exacerbated by human activities that increase the vulnerability to dust and dust-borne disease vectors. Today in Central and Inner Asian drylands, agriculture, mining, and rapid development contribute to dust generation and community exposure. Thorough review of limited dust investigation in the region implies but does not quantify health risks. Anthropogenic sources, such as the drying of the Aral Sea, highlight the shifting dust dynamics across the Central EurAsian steppe. In the Gobi Desert, our case study in Khanbogd, Mongolia addressed large-scale mining's potential dust risk to the health of the local population. Dust traps showed variable exposure to particulates among herder households and town residents; dust density distribution indicated that sources beyond the mine need to be considered when identifying particulate sources. Research suggests that atmospheric dust from multiple causes may enhance human particulate exposure. Greater awareness of dust in greater Central Asia reflects community concern about related health implications. Future human well-being in the region will require more thorough information on dust emissions in the changing environment.

Desert Dust and Health: A Central Asian Review and Steppe Case Study

PubMed Central

Sternberg, Troy; Edwards, Mona

2017-01-01

In Asian deserts environmental and anthropomorphic dust is a significant health risk to rural populations. Natural sources in dry landscapes are exacerbated by human activities that increase the vulnerability to dust and dust-borne disease vectors. Today in Central and Inner Asian drylands, agriculture, mining, and rapid development contribute to dust generation and community exposure. Thorough review of limited dust investigation in the region implies but does not quantify health risks. Anthropogenic sources, such as the drying of the Aral Sea, highlight the shifting dust dynamics across the Central EurAsian steppe. In the Gobi Desert, our case study in Khanbogd, Mongolia addressed large-scale mining’s potential dust risk to the health of the local population. Dust traps showed variable exposure to particulates among herder households and town residents; dust density distribution indicated that sources beyond the mine need to be considered when identifying particulate sources. Research suggests that atmospheric dust from multiple causes may enhance human particulate exposure. Greater awareness of dust in greater Central Asia reflects community concern about related health implications. Future human well-being in the region will require more thorough information on dust emissions in the changing environment. PMID:29099792

Improved Dust Forecast Products for Southwest Asia Forecasters through Dust Source Database Advancements

NASA Astrophysics Data System (ADS)

Brooks, G. R.

2011-12-01

Dust storm forecasting is a critical part of military theater operations in Afghanistan and Iraq as well as other strategic areas of the globe. The Air Force Weather Agency (AFWA) has been using the Dust Transport Application (DTA) as a forecasting tool since 2001. Initially developed by The Johns Hopkins University Applied Physics Laboratory (JHUAPL), output products include dust concentration and reduction of visibility due to dust. The performance of the products depends on several factors including the underlying dust source database, treatment of soil moisture, parameterization of dust processes, and validity of the input atmospheric model data. Over many years of analysis, seasonal dust forecast biases of the DTA have been observed and documented. As these products are unique and indispensible for U.S. and NATO forces, amendments were required to provide the best forecasts possible. One of the quickest ways to scientifically address the dust concentration biases noted over time was to analyze the weaknesses in, and adjust the dust source database. Dust source database strengths and weaknesses, the satellite analysis and adjustment process, and tests which confirmed the resulting improvements in the final dust concentration and visibility products will be shown.

Laboratory study of PCB transport from primary sources to settled dust.

PubMed

Liu, Xiaoyu; Guo, Zhishi; Krebs, Kenneth A; Greenwell, Dale J; Roache, Nancy F; Stinson, Rayford A; Nardin, Joshua A; Pope, Robert H

2016-04-01

Dust is an important sink for indoor air pollutants, such as polychlorinated biphenyls (PCBs) that were used in building materials and products. In this study, two types of dust, house dust and Arizona Test Dust, were tested in a 30-m(3) stainless steel chamber with two types of panels. The PCB-containing panels were aluminum sheets coated with a PCB-spiked primer or caulk. The PCB-free panels were coated with the same materials but without PCBs. The dust evenly spread on each panel was collected at different times to determine its PCB content. The data from the PCB panels were used to evaluate the PCB migration from the source to the dust through direct contact, and the data from the PCB-free panels were used to evaluate the sorption of PCBs through the dust/air partition. Settled dust can adsorb PCBs from air. The sorption concentration was dependent on the congener concentration in the air and favored less volatile congeners. When the house dust was in direct contact with the PCB-containing panel, PCBs migrated into the dust at a much faster rate than the PCB transfer rate due to the dust/air partition. The dust/source partition was not significantly affected by the congener's volatility. For a given congener, the ratio between its concentration in the dust and in the source was used to estimate the dust/source partition coefficient. The estimated values ranged from 0.04 to 0.16. These values are indicative of the sink strength of the tested house dust being in the middle or lower-middle range. Published by Elsevier Ltd.

Identification of dust storm source areas in West Asia using multiple environmental datasets.

PubMed

Cao, Hui; Amiraslani, Farshad; Liu, Jian; Zhou, Na

2015-01-01

Sand and Dust storms are common phenomena in arid and semi-arid areas. West Asia Region, especially Tigris-Euphrates alluvial plain, has been recognized as one of the most important dust source areas in the world. In this paper, a method is applied to extract SDS (Sand and Dust Storms) sources in West Asia region using thematic maps, climate and geography, HYSPLIT model and satellite images. Out of 50 dust storms happened during 2000-2013 and collected in form of MODIS images, 27 events were incorporated as demonstrations of the simulated trajectories by HYSPLIT model. Besides, a dataset of the newly released Landsat images was used as base-map for the interpretation of SDS source regions. As a result, six main clusters were recognized as dust source areas. Of which, 3 clusters situated in Tigris-Euphrates plain were identified as severe SDS sources (including 70% dust storms in this research). Another cluster in Sistan plain is also a potential source area. This approach also confirmed six main paths causing dust storms. These paths are driven by the climate system including Siberian and Polar anticyclones, monsoon from Indian Subcontinent and depression from north of Africa. The identification of SDS source areas and paths will improve our understandings on the mechanisms and impacts of dust storms on socio-economy and environment of the region. Copyright © 2014 Elsevier B.V. All rights reserved.

Atmosphere aerosol/dust composition over central Asia and western Siberia derived from snow/ice core records and calibrated with NASA remote sensing data

NASA Astrophysics Data System (ADS)

Aizen, V. B.; Aizen, E. M.; Joswiak, D. R.; Surazakov, A. B.; Takeuchi, N.

2007-12-01

The vast arid and semi-arid regions of central Asia, Mongolia, and Northern China are the world's second largest source of atmospheric mineral dust. In recent years, severe dust storms in Asia have intensified in frequency, duration, and areal coverage. However, limited spatial and temporal extent of aerosol measurements precludes definitive statements to be made regarding relationship between the Asian aerosol generation and climate. It has been well known that glaciers are the natural archives of environmental records related to past climate and aerosol generation. In our research, we utilized central Asian and western Siberia shallow ice-core records recovered from Altai, Tien Shan and Pamir mountain glaciers. Despite the fact that ice-core data may extend climate/aerosol records back in time, their sparse coverage is inadequate to document aerosol spatial distribution. The NASA products from Aura, Terra and Aqua satellite missions address this gap identifying aerosol sources, transport pathways, and area of deposition. The main objective of our research is to evaluate an affect of climate variability on dynamics of Asian aerosol loading to atmosphere and changes in aerosol transport pathways. Dust particle, major and rare earth element analysis from dust aerosols deposited and accumulated in Altai, Tien Shan and Pamir glaciers suggests that loess from Tajikistan, Afghanistan and north-western China are main sources of aerosol loading into the upper troposphere over the central Asia and western Siberia. At the same time, the soluble ionic component of the ice-cores, related to aerosol generated from evaporate deposits, demonstrated both anthropogenic and natural impacts on atmospheric chemistry over these regions. Large perturbations of Ca2+ derived from CaCO3- rich dust transported from Goby Desert to Altai and Tien Shan. Origin and pathway of the ice-core aerosol depositions for the last 10-years were identified through calibrating ice-core records with dust storm land surface records and remote sensing aerosol data at the monthly/seasonal/annual to event/daily scale. For instance, in southwestern Asia, severe drought developed from 1998 to 2002 has intensified the frequency, duration, and spatial coverage of large dust storms originated in Iran, Afghanistan, Tajikistan, Taklimakan and Goby Deserts. The Pamir and Tien Shan ice-core records revealed, that concentration of major and REE elements during summer is about two times greater in period of 1998-2002 than at the following years. Our qualitative analysis based on ice-core records, the MODIS and SeaWiFS images and determined the origin of dust, transport pathways and aerosol spatial distribution over central Asia and western Siberia in summer 2000, 2001 and 2002. The transport pathways were reconstructed on the basis of visibility observations and NCAR MM5-predicted winds with further validation against of satellite data and isotope- geochemical ice-core data analysis.

X-ray shout echoing through space

NASA Astrophysics Data System (ADS)

2004-01-01

a flash of X-rays hi-res Size hi-res: 3991 Kb Credits: ESA, S. Vaughan (University of Leicester) EPIC camera shows the expanding rings caused by a flash of X-rays XMM-Newton's X-ray EPIC camera shows the expanding rings caused by a flash of X-rays scattered by dust in our Galaxy. The X-rays were produced by a powerful gamma-ray burst that took place on 3 December 2003. The slowly fading afterglow of the gamma-ray burst is at the centre of the expanding rings. Other, unrelated, X-ray sources can also be seen. The time since the gamma-ray explosion is shown in each panel in hours. At their largest size, the rings would appear in the sky about five times smaller than the full moon. a flash of X-rays hi-res Size hi-res: 2153 Kb Credits: ESA, S. Vaughan (University of Leicester) EPIC camera shows the expanding rings caused by a flash of X-rays (Please choose "hi-res" version for animation) XMM-Newton's X-ray EPIC camera shows the expanding rings caused by a flash of X-rays scattered by dust in our Galaxy. The X-rays were produced by a powerful gamma-ray burst that took place on 3 December 2003. The slowly fading afterglow of the gamma-ray burst is at the centre of the expanding rings. Other, unrelated, X-ray sources can also be seen. The time since the gamma-ray explosion is shown in each panel in seconds. At their largest size, the rings would appear in the sky about five times smaller than the full moon. This echo forms when the powerful radiation of a gamma-ray burst, coming from far away, crosses a slab of dust in our Galaxy and is scattered by it, like the beam of a lighthouse in clouds. Using the expanding rings to precisely pin-point the location of this dust, astronomers can identify places where new stars and planets are likely to form. On 3 December 2003 ESA's observatory, Integral, detected a burst of gamma rays, lasting about 30 seconds, from the direction of a distant galaxy. Within minutes of the detection, thanks to a sophisticated alert network, many observatories around the world were pointing their instruments at this mysterious source in the sky, named GRB 031203, in the attempt to decipher its nature. Also ESA's X-ray observatory, XMM-Newton, joined the hunt and observed the source in detail, using its on-board European Photon Imaging Camera (EPIC). The fading X-ray emission from GRB 031203 - called the `afterglow' - is clearly seen in XMM-Newton's images. But much more stunning are the two rings, centred on the afterglow, which appear to expand thousand times faster than the speed of light. Dr. Simon Vaughan, of the University of Leicester, United Kingdom, leads an international team of scientists studying GRB 031203. He explains that these rings are what astronomers call an `echo'. They form when the X-rays from the distant gamma-ray burst shine on a layer of dust in our own Galaxy. "The dust scatters some of the X-rays, causing XMM-Newton to observe these rings, much in the same way as fog scatters the light from a car's headlights," said Vaughan. Although the afterglow is the brightest feature seen in XMM-Newton's images, the expanding echo is much more spectacular. "It is like a shout in a cathedral," Vaughan said. "The shout of the gamma-ray burst is louder, but the Galactic reverberation, seen as the rings, is much more beautiful." The rings seem to expand because the X-rays scattered by dust farther from the direction of GRB 031203 take longer to reach us than those hitting the dust closer to the line of sight. However, nothing can move faster than light. "This is precisely what we expect because of the finite speed of light," said Vaughan. "The rate of expansion that we see is just a visual effect." He and his colleagues explain that we see two rings because there are two thin sheets of dust between the source of the gamma-ray burst and Earth, one closer to us creating the wider ring and one further away where the smaller ring is formed. Since they know precisely at what speed the X-ray light travels in space, the team in Leicester have determined accurately the distance to the dust sheets by measuring the size of the expanding rings. The nearest dust sheet is located 2900 light years away and is probably part of the Gum nebula, a bubble of hot gas resulting from many supernova explosions. The other dust layer is about 4500 light years away. Understanding how dust is distributed in our Galaxy is important because dust favours the collapse of cool gas clouds, which can then form stars and planets. Knowing where dust is located helps astronomers to determine where star and planet formation is likely to occur. Expanding X-ray dust scattering rings, such as those around GRB 031203, have never been seen before. Slower-moving rings, caused by a similar effect, have been seen in visible light around a very few exploding stars, mostly supernovae. The expanding rings also provide much needed information on the gamma-ray burst itself. Gamma-ray bursts are the most powerful explosive events in the Universe, but astronomers are still trying to understand the mystery that surrounds their origin. Some occur with the supernova explosion of a massive star when it has used up all of its fuel, although only stars which have lost their outer layers and which collapse to make a black hole seem able to make a gamma-ray burst. The delayed X-rays from the echo of GRB 031203 are very useful because they tell astronomers how bright the burst was in the X-ray spectrum when it went off on 3 December. The only direct data available from that moment are those obtained by ESA's Integral observatory in the gamma-ray range. "XMM-Newton's measurements are thus crucial to better understand the nature of the burst," said Dr. Fred Jansen, XMM-Newton's project scientist. "The more details we gather of the burst, the more we can learn on how black holes are made." Today, ESA's Integral and XMM-Newton observatories provide astronomers with their most powerful facilities for studying gamma-ray bursts. In 2004 a new gamma-ray satellite, called `Swift', will be launched as part of a collaboration between the USA, United Kingdom and Italy. Swift will add to the flotilla of satellites providing fast and accurate locations of gamma-ray bursts on the sky, which can then be followed with XMM-Newton. This will provide even more opportunities for new discoveries in this cutting-edge field. Notes to editors A scientific paper describing this discovery by Dr. Simon Vaughan and his collaborators has been accepted for publication in ``The Astrophysical Journal'' (see http://arxiv.org/abs/astro-ph/0312603). The other members in Vaughan's team are R. Willingale, P. O'Brien, J. Osborne, A. Levan, M. Watson and J. Tedds from the University of Leicester, United Kingdom; J. Reeves from NASA's Goddard Space Flight Center in Greenbelt, USA; D. Watson from the Neils Bohr Institute for Astronomy in Copenhagen, Denmark; M. Santos-Lleo, P. Rodriguez-Pascual and N. Schartel from ESA's XMM-Newton Science Operations Centre in Villafranca, Spain. Figure caption XMM-Newton's X-ray EPIC camera shows the expanding rings caused by a flash of X-rays scattered by dust in our Galaxy. The X-rays were produced by a powerful gamma-ray burst that took place on 3 December 2003. The slowly fading afterglow of the gamma-ray burst is at the centre of the expanding rings. Other, unrelated, X-ray sources can also be seen. The time since the gamma-ray explosion is shown in each panel in hours. At their largest size, the rings would appear in the sky about five times smaller than the full moon. Credit: ESA, S. Vaughan (University of Leicester) Video caption XMM-Newton's X-ray EPIC camera shows the expanding rings caused by a flash of X-rays scattered by dust in our Galaxy. The X-rays were produced by a powerful gamma-ray burst that took place on 3 December 2003. The slowly fading afterglow of the gamma-ray burst is at the centre of the expanding rings. Other, unrelated, X-ray sources can also be seen. The time since the gamma-ray explosion is shown in each panel in seconds. At their largest size, the rings would appear in the sky about five times smaller than the full moon. Credit: ESA, S. Vaughan (University of Leicester) More about XMM-Newton XMM-Newton can detect more X-ray sources than any previous satellite and is helping to solve many cosmic mysteries of the violent Universe, from black holes to the formation of galaxies. It was launched on 10 December 1999, using an Ariane-5 rocket from French Guiana. It is expected to return data for a decade. XMM-Newton's high-tech design uses over 170 wafer-thin cylindrical mirrors spread over three telescopes. Its orbit takes it almost a third of the way to the Moon, so that astronomers can enjoy long, uninterrupted views of celestial objects.

Effects of phosphate-solubilizing bacteria, native microorganisms, and rock dust on Jatropha curcas L. growth.

PubMed

Santana, E B; Marques, E L S; Dias, J C T

2016-10-05

Microorganisms with the ability to release nutrients to the soil from insoluble sources may be useful for plant cultivation. We evaluated the growth-promoting effect on Jatropha curcas L. of phosphate-solubilizing bacteria (PSB) and the native microbiota in soil with or without rock dust. J. curcas L. is important for biodiesel production. The experiments were performed in a greenhouse under a random-statistical design with 14 replicates. The soil received increasing dosages of rock dust. The presence of resident microorganisms and PSB inoculum was correlated with plant height, biomass production, and phosphorus content in plants for 120 days. Native soil microorganisms were detected and identified using denaturing gradient gel electrophoresis and DNA sequence analysis. Several bacterial populations belonged to the genus Bacillus. Populations associated with the phyla Chytridiomycota and Ascomycota were detected among the fungi. The best results for the variable plant height were correlated with the presence of resident microbiota and rock dust until the end of the experiment. The largest biomass production and the highest content of phosphorus occurred in the presence of soil-resident microbiota only up to 120 days. No significant effects were observed for biomass production with the use of PSB combined with rock dust. J. curcas L. under the influence of only resident microbiota showed the best plant growth results. Future research will focus on the specificity of resident microbiota activity in plant growth promotion and the isolation of these microorganisms to produce a new inoculum to be tested in various plants.

Aeolian system dynamics derived from thermal infrared data

NASA Astrophysics Data System (ADS)

Scheidt, Stephen Paul

Thermal infrared (TIR) remote-sensing and field-based observations were used to study aeolian systems, specifically sand transport pathways, dust emission sources and Saharan atmospheric dust. A method was developed for generating seamless and radiometrically accurate mosaics of thermal infrared data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. Using a combination of high resolution thermal emission spectroscopy results of sand samples and mosaic satellite data, surface emissivity was derived to map surface composition, which led to improvement in the understanding of sand accumulation in the Gran Desierto of northern Sonora, Mexico. These methods were also used to map sand transport pathways in the Sahara Desert, where the interaction between sand saltation and dust emission sources was explored. The characteristics and dynamics of dust sources were studied at White Sands, NM and in the Sahara Desert. At White Sands, an application was developed for studying the response of dust sources to surface soil moisture based on the relationship between soil moisture, apparent thermal inertia and the erosion potential of dust sources. The dynamics of dust sources and the interaction with sand transport pathways were also studied, focusing on the Bodele Depression of Chad and large dust sources in Mali and Mauritania. A dust detection algorithm was developed using ASTER data, and the spectral emissivity of observed atmospheric dust was related to the dust source area in the Sahara. At the Atmospheric Observatory (IZO) in Tenerife, Spain where direct measurement of the Saharan Air Layer could be made, the cycle of dust events occurring in July 2009 were examined. From the observation tower at the IZO, measurements of emitted longwave atmospheric radiance in the TIR wavelength region were made using a Forward Looking Infrared Radiometer (FLIR) handheld camera. The use of the FLIR to study atmospheric dust from the Saharan is a new application. Supporting data from AERONET and other orbital data enabled study of net radiative forcing.

Export of microplastics from land to sea. A modelling approach.

PubMed

Siegfried, Max; Koelmans, Albert A; Besseling, Ellen; Kroeze, Carolien

2017-12-15

Quantifying the transport of plastic debris from river to sea is crucial for assessing the risks of plastic debris to human health and the environment. We present a global modelling approach to analyse the composition and quantity of point-source microplastic fluxes from European rivers to the sea. The model accounts for different types and sources of microplastics entering river systems via point sources. We combine information on these sources with information on sewage management and plastic retention during river transport for the largest European rivers. Sources of microplastics include personal care products, laundry, household dust and tyre and road wear particles (TRWP). Most of the modelled microplastics exported by rivers to seas are synthetic polymers from TRWP (42%) and plastic-based textiles abraded during laundry (29%). Smaller sources are synthetic polymers and plastic fibres in household dust (19%) and microbeads in personal care products (10%). Microplastic export differs largely among European rivers, as a result of differences in socio-economic development and technological status of sewage treatment facilities. About two-thirds of the microplastics modelled in this study flow into the Mediterranean and Black Sea. This can be explained by the relatively low microplastic removal efficiency of sewage treatment plants in the river basins draining into these two seas. Sewage treatment is generally more efficient in river basins draining into the North Sea, the Baltic Sea and the Atlantic Ocean. We use our model to explore future trends up to the year 2050. Our scenarios indicate that in the future river export of microplastics may increase in some river basins, but decrease in others. Remarkably, for many basins we calculate a reduction in river export of microplastics from point-sources, mainly due to an anticipated improvement in sewage treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oxidative potential and inflammatory impacts of source apportioned ambient air pollution in Beijing.

PubMed

Liu, Qingyang; Baumgartner, Jill; Zhang, Yuanxun; Liu, Yanju; Sun, Yongjun; Zhang, Meigen

2014-11-04

Air pollution exposure is associated with a range of adverse health impacts. Knowledge of the chemical components and sources of air pollution most responsible for these health effects could lead to an improved understanding of the mechanisms of such effects and more targeted risk reduction strategies. We measured daily ambient fine particulate matter (<2.5 μm in aerodynamic diameter; PM2.5) for 2 months in peri-urban and central Beijing, and assessed the contribution of its chemical components to the oxidative potential of ambient air pollution using the dithiothreitol (DTT) assay. The composition data were applied to a multivariate source apportionment model to determine the PM contributions of six sources or factors: a zinc factor, an aluminum factor, a lead point factor, a secondary source (e.g., SO4(2-), NO3(2-)), an iron source, and a soil dust source. Finally, we assessed the relationship between reactive oxygen species (ROS) activity-related PM sources and inflammatory responses in human bronchial epithelial cells. In peri-urban Beijing, the soil dust source accounted for the largest fraction (47%) of measured ROS variability. In central Beijing, a secondary source explained the greatest fraction (29%) of measured ROS variability. The ROS activities of PM collected in central Beijing were exponentially associated with in vivo inflammatory responses in epithelial cells (R2=0.65-0.89). We also observed a high correlation between three ROS-related PM sources (a lead point factor, a zinc factor, and a secondary source) and expression of an inflammatory marker (r=0.45-0.80). Our results suggest large differences in the contribution of different PM sources to ROS variability at the central versus peri-urban study sites in Beijing and that secondary sources may play an important role in PM2.5-related oxidative potential and inflammatory health impacts.

CV-Dust: Atmospheric aerosol in the Cape Verde region: carbon and soluble fractions of PM10

NASA Astrophysics Data System (ADS)

Pio, C.; Nunes, T.; Cardoso, J.; Caseiro, A.; Custódio, D.; Cerqueira, M.; Patoilo, D.; Almeida, S. M.; Freitas, M. C.

2012-04-01

Every year, billions of tons of eroded mineral soils from the Saharan Desert and the Sahel region, the largest dust source in the world, cross Mediterranean towards Europe, western Asia and the tropical North Atlantic Ocean as far as the Caribbean and South America. Many aspects of the direct and indirect effects of dust on climate are not well understood and the bulk and surface chemistry of the mineral dust particles determines interactions with gaseous and other particle species. The quantification of the magnitude of warming or cooling remains open because of the strong variability of the atmospheric dust burden and the lack of representative data for the spatial and temporal distribution of the dust composition. CV-Dust is a project that aims at provide a detailed data on the size distribution and the size-resolved chemical and mineralogical composition of dust emitted from North Africa using a natural laboratory like Cape Verde. This archipelago is located in an area of massive dust transport from land to ocean, and is thus ideal to set up sampling devices that are able to characterize and quantify dust transported from Africa. Moreover, Cape Verde's future economic prospects depend heavily on the encouragement of tourism, therefore it is essential to elucidate the role of Saharan dust may play in the degradation of Cape Verde air quality. The main objectives of CV-Dust project are: 1) to characterize the chemical and mineralogical composition of dust transported from Africa by setting up an orchestra of aerosol sampling devices in the strategic archipelago of Cape Verde; 2) to identify the sources of particles in Cape Verde by using receptor models; 3) to elucidate the role Saharan dust may play in the degradation of Cape Verde air quality; 4) to model processes governing dust production, transport, interaction with the radiation field and removal from the atmosphere. Here we present part of the data obtained throughout the last year, involving a set of more than 100 PM10 samples, addressing mainly their mass concentrations and the chemical composition of water soluble ions and carbon species (carbonates and organic and elemental carbon). Different PM10 samplers worked simultaneously in order to collect enough mass to make the aerosol characterization through the different methodologies and to collect aerosols in different filter matrixes, which have to be appropriated to the chemical and mineralogical analysis. The sampling site was located at Santiago Island, in the surroundings of Praia City (14° 55' N e 23° 29' W, 98 m at sea level). High concentrations, up to more than 400 μg m-3, are connected to north-east and north-northeast winds, and it was identified several dust events characteristic of "bruma seca", whose duration is on average of two to four days. Backward trajectories analysis confirms that the high concentrations in Cape Verde are associated with air masses passing over the Sahara. During dust events the percentage of inorganic water soluble ions for the total PM10 mass concentration decreased significantly to values lower than 10% in comparison with remainder data that range around 45±10%. Acknowledgement: This work was funded by the Portuguese Science Foundation (FCT) through the project PTDD/AAC-CLI/100331/2008 and FCOMP-01-0124-FEDER-008646 (CV-Dust). J. Cardoso acknowledges the PhD grant SFRH-BD-6105-2009 from FCT.

The effects of dust on Colorado mountain snow cover albedo and compositional links to dust-source areas

NASA Astrophysics Data System (ADS)

Goldstein, H. L.; Reynolds, R. L.; Landry, C.; Derry, J. E.; Kokaly, R. F.; Breit, G. N.

2016-12-01

Dust deposited on mountain snow cover (DOS) changes snow albedo, enhances absorption of solar radiation, and effectively increases rates of snow melt, leading to earlier-than-normal runoff and overall smaller late-season water supplies for tens of millions of people and industries in the American West. Visible-spectrum reflectance of DOS samples is on the order of 0.2 (80% absorption), in stark contrast to the high reflectivity of pure snow which approaches 1.0. Samples of DOS were collected from 12 high-elevation Colorado mountain sites near the end of spring from 2013 through 2016 prior to complete snow melt, when most dust layers had merged into one layer. These samples were analyzed to measure dust properties that affect snow albedo and to link DOS to dust-source areas. Dust mass loadings to snow during water year 2014 varied from 5 to 30 g/m2. Median particle sizes centered around 20 micrometers with more than 80% of the dust <63 micrometers. Dark minerals, carbonaceous matter, and iron oxides, including nano-sized hematite and goethite, together diminished reflectance according to their variable concentrations. Documenting variations in dust-particle masses, sizes, and compositions helps determine their influences on snow-melt and may be useful for modeling snow-melt effects from future dust. Furthermore, variations in dust components and particle sizes lead to new ways to recognize sources of dust by comparison with properties of fine-grained sediments in dust-source areas. Much of the DOS in the San Juan Mountains, Colorado can be linked to southern Colorado Plateau source areas by compositional similarities and satellite imagery. Understanding dust properties that affect snow albedo and recognizing the sources of dust deposited on snow cover may guide mitigation of dust emission that affects water resources of the Colorado River basin.

How the Assumed Size Distribution of Dust Minerals Affects the Predicted Ice Forming Nuclei

NASA Technical Reports Server (NTRS)

Perlwitz, Jan P.; Fridlind, Ann M.; Garcia-Pando, Carlos Perez; Miller, Ron L.; Knopf, Daniel A.

2015-01-01

The formation of ice in clouds depends on the availability of ice forming nuclei (IFN). Dust aerosol particles are considered the most important source of IFN at a global scale. Recent laboratory studies have demonstrated that the mineral feldspar provides the most efficient dust IFN for immersion freezing and together with kaolinite for deposition ice nucleation, and that the phyllosilicates illite and montmorillonite (a member of the smectite group) are of secondary importance.A few studies have applied global models that simulate mineral specific dust to predict the number and geographical distribution of IFN. These studies have been based on the simple assumption that the mineral composition of soil as provided in data sets from the literature translates directly into the mineral composition of the dust aerosols. However, these tables are based on measurements of wet-sieved soil where dust aggregates are destroyed to a large degree. In consequence, the size distribution of dust is shifted to smaller sizes, and phyllosilicates like illite, kaolinite, and smectite are only found in the size range 2 m. In contrast, in measurements of the mineral composition of dust aerosols, the largest mass fraction of these phyllosilicates is found in the size range 2 m as part of dust aggregates. Conversely, the mass fraction of feldspar is smaller in this size range, varying with the geographical location. This may have a significant effect on the predicted IFN number and its geographical distribution.An improved mineral specific dust aerosol module has been recently implemented in the NASA GISS Earth System ModelE2. The dust module takes into consideration the disaggregated state of wet-sieved soil, on which the tables of soil mineral fractions are based. To simulate the atmospheric cycle of the minerals, the mass size distribution of each mineral in aggregates that are emitted from undispersed parent soil is reconstructed. In the current study, we test the null-hypothesis that simulating the presence of a large mass fraction of phyllosilicates in dust aerosols in the size range 2 m, in comparison to a simple model assumption where this is neglected, does not yield a significant effect on the magnitude and geographical distribution of the predicted IFN number. Results from sensitivity experiments are presented as well.

Conditions and Dynamics Within a Regional Mars Dust Storm

NASA Astrophysics Data System (ADS)

Rafkin, S. C.; Pla-García, J.; Leung, C. W. S.

2017-12-01

There have never been in situ observations at or near the active lifting center of a regional dust storm on Mars. In the absence of in situ data, it is common to employ numerical models to provide guidance on the physical processes and conditions operating in an unobserved location or weather system. Consequently, the Mars Regional Atmospheric Modeling System (MRAMS) is employed to study the structure and dynamics of a simulated large regional storm using a fully interactive dust cycle. The simulations provide the first ever glimpse of the conditions that might occur inside one of these storms. The simulated storm shows extremely complex structure, highly heterogeneous lifting centers, and a variety of deep dust transport circulations. The active lifting centers show broader organization into a mesoscale system in much the same way that thunderstorms on Earth can organize into mesoscale convective structures. In many of the active dust plumes, the mixing ratio of dust peaks near the surface and drops off with height. The surface mixing ratio maximum is partly due to the surface being the source of dust, with entrainment of less dusty air as the plume rises. However, it is also because the mixing ratio can be dominated by a few large dust aerosol, since the mass is proportional to the cubed of the radius. Once lifted, the largest dust tends to sediment out while the smaller dust continues to be advected upward by the plume. This size-sorting process tends to drive the mixing ratio profile to a maximum near the surface. In dusty plumes near the surface, the air temperature is as much as 20K colder than nearby areas. This is due to solar absorption higher in the dust column limiting direct heating deeper into the atmosphere. Overall, within the plume, there is an inversion, and although the top of the plume is warmer than below, it is near neutral buoyancy compared to the less dusty air on either side. Apparently, adiabatic cooling nearly offsets the expected positive heating perturbation at the top of the dusty plume. A very strong low level just forms in the vicinity of the storm, accompanied by system-wide negative pressure deficits and circulation patterns strongly suggestive of the wind-enhanced interaction of radiation and dust (WEIRD) feedback mechanism.

The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

NASA Astrophysics Data System (ADS)

Wiacek, A.; Peter, T.; Lohmann, U.

2010-02-01

This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Without explicitly modelling dust emission and deposition processes, dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Practically none of the simulated air parcels reached regions where homogeneous ice nucleation can take place (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through regions supersaturated with respect to ice but subsaturated with respect to water, where "warm" (T≳-40 °C) ice clouds may form prior to supercooled water or mixed-phase clouds. The importance of "warm" ice clouds and the general influence of dust in the mixed-phase cloud region are highly uncertain due to considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work. For "classical" cirrus-forming temperatures, our results show that only mineral dust IN that underwent mixed-phase cloud-processing previously are likely to be relevant, and, therefore, we recommend further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.

Using dust, gas and stellar mass-selected samples to probe dust sources and sinks in low-metallicity galaxies

NASA Astrophysics Data System (ADS)

De Vis, P.; Gomez, H. L.; Schofield, S. P.; Maddox, S.; Dunne, L.; Baes, M.; Cigan, P.; Clark, C. J. R.; Gomez, E. L.; Lara-López, M.; Owers, M.

2017-10-01

We combine samples of nearby galaxies with Herschel photometry selected on their dust, metal, H I and stellar mass content, and compare these to chemical evolution models in order to discriminate between different dust sources. In a companion paper, we used an H I-selected sample of nearby galaxies to reveal a subsample of very gas-rich (gas fraction >80 per cent) sources with dust masses significantly below predictions from simple chemical evolution models, and well below Md/M* and Md/Mgas scaling relations seen in dust and stellar-selected samples of local galaxies. We use a chemical evolution model to explain these dust-poor, but gas-rich, sources as well as the observed star formation rates (SFRs) and dust-to-gas ratios. We find that (I) a delayed star formation history is required to model the observed SFRs; (II) inflows and outflows are required to model the observed metallicities at low gas fractions; (III) a reduced contribution of dust from supernovae (SNe) is needed to explain the dust-poor sources with high gas fractions. These dust-poor, low stellar mass galaxies require a typical core-collapse SN to produce 0.01-0.16 M⊙ of dust. To match the observed dust masses at lower gas fractions, significant grain growth is required to counteract the reduced contribution from dust in SNe and dust destruction from SN shocks. These findings are statistically robust, though due to intrinsic scatter it is not always possible to find one single model that successfully describes all the data. We also show that the dust-to-metal ratio decreases towards lower metallicity.

Urban dust in the Guanzhong Basin of China, part I: A regional distribution of dust sources retrieved using satellite data.

PubMed

Long, Xin; Li, Nan; Tie, Xuexi; Cao, Junji; Zhao, Shuyu; Huang, Rujin; Zhao, Mudan; Li, Guohui; Feng, Tian

2016-01-15

Urban dust pollution has been becoming an outstanding environmental problem due to rapid urbanization in China. However, it is very difficult to construct an urban dust inventory, owing to its small horizontal scale and strong temporal/spatial variability. With the analysis of visual interpretation, maximum likelihood classification, extrapolation and spatial overlaying, we quantified dust source distributions of urban constructions, barrens and croplands in the Guanzhong Basin using various satellite data, including VHR (0.5m), Lansat-8 OLI (30 m) and MCD12Q1 (500 m). The croplands were the dominant dust sources, accounting for 40% (17,913 km(2)) of the study area in summer and 36% (17,913 km(2)) in winter, followed by barrens, accounting for 5% in summer and 10% in winter. Moreover, the total constructions were 126 km(2), including 84% of active and 16% inactive. In addition, 59% of the constructions aggregated on the only megacity of the study area, Xi'an. With high accuracy exceeding 88%, the proposed satellite-data based method is feasible and valuable to quantify distributions of dust sources. This study provides a new perspective to evaluate regional urban dust, which is seldom quantified and reported. In a companied paper (Part-2 of the study), the detailed distribution of the urban dust sources is applied in a dynamical/aerosol model (WRF-Dust) to assess the effect of dust sources on aerosol pollution. Copyright © 2015 Elsevier B.V. All rights reserved.

Change in atmospheric mineral aerosols in response to climate: Last glacial period, preindustrial, modern, and doubled carbon dioxide climates

USGS Publications Warehouse

Mahowald, N.M.; Muhs, D.R.; Levis, S.; Rasch, P.J.; Yoshioka, M.; Zender, C.S.; Luo, C.

2006-01-01

Desert dust simulations generated by the National Center for Atmospheric Research's Community Climate System Model for the current climate are shown to be consistent with present day satellite and deposition data. The response of the dust cycle to last glacial maximum, preindustrial, modern, and doubled-carbon dioxide climates is analyzed. Only natural (non-land use related) dust sources are included in this simulation. Similar to some previous studies, dust production mainly responds to changes in the source areas from vegetation changes, not from winds or soil moisture changes alone. This model simulates a +92%, +33%, and -60% change in dust loading for the last glacial maximum, preindustrial, and doubled-carbon dioxide climate, respectively, when impacts of carbon dioxide fertilization on vegetation are included in the model. Terrestrial sediment records from the last glacial maximum compiled here indicate a large underestimate of deposition in continental regions, probably due to the lack of simulation of glaciogenic dust sources. In order to include the glaciogenic dust sources as a first approximation, we designate the location of these sources, and infer the size of the sources using an inversion method that best matches the available data. The inclusion of these inferred glaciogenic dust sources increases our dust flux in the last glacial maximum from 2.1 to 3.3 times current deposition. Copyright 2006 by the American Geophysical Union.

Advances in Mineral Dust Source Composition Measurement with Imaging Spectroscopy at the Salton Sea, CA

NASA Astrophysics Data System (ADS)

Green, R. O.; Realmuto, V. J.; Thompson, D. R.; Mahowald, N. M.; Pérez García-Pando, C.; Miller, R. L.; Clark, R. N.; Swayze, G. A.; Okin, G. S.

2015-12-01

Mineral dust emitted from the Earth's surface is a principal contributor to direct radiative forcing over the arid regions, where shifts in climate have a significant impact on agriculture, precipitation, and desert encroachment around the globe. Dust particles contribute to both positive and negative forcing, depending on the composition of the particles. Particle composition is a function of the surface mineralogy of dust source regions, but poor knowledge of surface mineralogy on regional to global scales limits the skill of Earth System models to predict shifts in regional climate around the globe. Earth System models include the source, emission, transport and deposition phases of the dust cycle. In addition to direct radiative forcing contributions, mineral dust impacts include indirect radiative forcing, modification of the albedo and melting rates of snow and ice, kinetics of tropospheric photochemistry, formation and deposition of acidic aerosols, supply of nutrients to aquatic and terrestrial ecosystems, and impact on human health and safety. We demonstrate the ability to map mineral dust source composition in the Salton Sea dust source region with imaging spectroscopy measurements acquired as part of the NASA HyspIRI preparatory airborne campaign. These new spectroscopically derived compositional measurements provide a six orders of magnitude improvement over current atlases for this dust source region and provide a pathfinder example for a remote measurement approach to address this critical dust composition gap for global Earth System models.

Biogeochemistry Science and Education Part One: Using Non-Traditional Stable Isotopes as Environmental Tracers Part Two: Identifying and Measuring Undergraduate Misconceptions in Biogeochemistry

NASA Astrophysics Data System (ADS)

Mead, Chris

This dissertation is presented in two sections. First, I explore two methods of using stable isotope analysis to trace environmental and biogeochemical processes. Second, I present two related studies investigating student understanding of the biogeochemical concepts that underlie part one. Fe and Hg are each biogeochemically important elements in their own way. Fe is a critical nutrient for phytoplankton, while Hg is detrimental to nearly all forms of life. Fe is often a limiting factor in marine phytoplankton growth. The largest source, by mass, of Fe to the open ocean is windblown mineral dust, but other more soluble sources are more bioavailable. To look for evidence of these non-soil dust sources of Fe to the open ocean, I measured the isotopic composition of aerosol samples collected on Bermuda. I found clear evidence in the fine size fraction of a non-soil dust Fe source, which I conclude is most likely from biomass burning. Widespread adoption of compact fluorescent lamps (CFL) has increased their importance as a source of environmental Hg. Isotope analysis would be a useful tool in quantifying this impact if the isotopic composition of Hg from CFL were known. My measurements show that CFL-Hg is isotopically fractionated, in a unique pattern, during normal operation. This fractionation is large and has a distinctive, mass-independent signature, such that CFL Hg can be uniquely identified from other sources. Misconceptions research in geology has been a very active area of research, but student thinking regarding the related field of biogeochemistry has not yet been studied in detail. From interviews with 40 undergraduates, I identified over 150 specific misconceptions. I also designed a multiple-choice survey (concept inventory) to measure understanding of these same biogeochemistry concepts. I present statistical evidence, based on the Rasch model, for the reliability and validity of this instrument. This instrument will allow teachers and researchers to easily quantify learning outcomes in biogeochemistry and will complement existing concept inventories in geology, chemistry, and biology.

Compositional trends in aeolian dust along a transect across the southwestern United States

USGS Publications Warehouse

Goldstein, H.L.; Reynolds, R.L.; Reheis, M.C.; Yount, J.C.; Neff, J.C.

2008-01-01

Aeolian dust strongly influences ecology and landscape geochemistry over large areas that span several desert ecosystems of the southwestern United States. This study evaluates spatial and temporal variations and trends of the physical and chemical properties of dust in the southwestern United States by examining dust deposited in natural depressions on high isolated surfaces along a transect from the Mojave Desert to the central Colorado Plateau. Aeolian dust is recognized in these depressions on the basis of textural, chemical, isotopic, and mineralogical characteristics and comparisons of those characteristics to the underlying bedrock units. Spatial and temporal trends suggest that although local dust sources are important to the accumulated material in these depressions, Mojave Desert dust sources may also contribute. Depth trends in the depressions suggest that Mojave sources may have contributed more dust to the Colorado Plateau recently than in the past. These interpretations point to the important roles of far-traveled aeolian dust for landscape geochemistry and imply future changes to soil geochemistry under changing conditions in far-distant dust source areas. Copyright 2008 by the American Geophysical Union.

Dust emission and transport over Iraq associated with the summer Shamal winds

NASA Astrophysics Data System (ADS)

Bou Karam Francis, D.; Flamant, C.; Chaboureau, J.-P.; Banks, J.; Cuesta, J.; Brindley, H.; Oolman, L.

2017-02-01

In this study, we investigate the diurnal evolution of the summer Shamal wind (a quasi-permanent low-level northwesterly wind feature) and its role in dust emission and transport over Iraq, using ground-based and space-borne observations together with a numerical simulation performed with the mesoscale model meso-NH. A 6-year dataset from the synoptic stations over Iraq allows establishing the prominence of the link between strong near surface winds and reduced visibility in the summer. The detailed processes at play during Shamal events are explored on the basis of a meso-NH simulation for a given, representative case study (25 June-3 July 2010). The Shamal exhibits an out-of-phase relationship between the surface wind and winds in the lower troposphere (typically 500 m above ground level), the maximum surface wind speeds being observed during the day while in altitude the maximum wind speeds are observed at night. The daytime near surface winds, at the origin of dust emission, are associated with the downward transfer of momentum from the nocturnal low-level jet to the surface due to turbulent mixing after solar heating commences each day. For the first time, an estimate of the dust load associated with summer Shamal events over Iraq has been made using aerosol optical depths derived from the Spinning Enhanced Visible and Infrared Imager, the Moderate Resolution Imaging Spectroradiometer, and the simulation. The dust load exhibits a large diurnal variability, with a daily minimum value of 1 Tg around 0600 UTC and a daily peak of 2.5 Tg or more around 1500 UTC, and is driven by the diurnal cycle of the near surface wind speed. The daily dust load peak associated with the summer Shamal over Iraq is in the same order of magnitude as those derived from simulations downstream of the Bodélé depression in Chad, known to be the world's largest dust source.

Enhancing weak transient signals in SEVIRI false colour imagery: application to dust source detection in southern Africa

NASA Astrophysics Data System (ADS)

Murray, Jon E.; Brindley, Helen E.; Bryant, Robert G.; Russell, Jacqui E.; Jenkins, Katherine F.

2013-04-01

Understanding the processes governing the availability and entrainment of mineral dust into the atmosphere requires dust sources to be identified and the evolution of dust events to be monitored. To achieve this aim a wide range of approaches have been developed utilising observations from a variety of different satellite sensors. Global maps of source regions and their relative strengths have been derived from instruments in low Earth orbit (e.g. Total Ozone Monitoring Spectrometer (TOMS) (Prospero et al., 2002), MODerate resolution Imaging Spectrometer (MODIS) (Ginoux et al., 2012)). Instruments such as MODIS can also be used to improve precise source location (Baddock et al., 2009) but the information available is restricted to the satellite overpass times which may not be coincident with active dust emission from the source. Hence, at a regional scale, some of the more successful approaches used to characterise the activity of different sources use high temporal resolution data available from instruments in geostationary orbit. For example, the widely used red-green-blue (RGB) dust scheme developed by Lensky and Rosenfeld (2008) (hereafter LR2008) makes use of observations from selected thermal channels of the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) in a false colour rendering scheme in which dust appears pink. This scheme has provided the basis for numerous studies of north African dust sources and factors governing their activation (e.g. Schepanski et al., 2007, 2009, 2012). However, the LR2008 imagery can fail to identify dust events due to the effects of atmospheric moisture, variations in dust layer height and optical properties, and surface conditions (Brindley et al., 2012). Here we introduce a new method designed to circumvent some of these issues and enhance the signature of dust events using observations from SEVIRI. The approach involves the derivation of a composite clear-sky signal for selected channels on an individual time-step and pixel basis. These composite signals are subtracted from each observation in the relevant channels to enhance weak transient signals associated with low levels of dust emission. Different channel combinations are then rendered in false colour imagery to better identify dust source locations and activity. We have applied this new clear-sky difference (CSD) algorithm over three key source regions in southern Africa: the Makgadikgadi Basin, Etosha Pan, and the Namibian and western South African coast. Case studies indicate that advantages associated with the CSD approach include an improved ability to detect dust and distinguish multiple sources, the observation of source activation earlier in the diurnal cycle, and an improved ability to pinpoint dust source locations. These advantages are confirmed by a survey of four-years of data, comparing the results obtained using the CSD technique with those derived from LR2008 dust imagery. On average the new algorithm more than doubles the number of dust events identified, with the greatest improvement for the Makgadigkadi Basin and coastal regions. We anticipate exploiting this new activation record derived using the CSD approach to better understand the surface and meteorological conditions controlling dust uplift and subsequent atmospheric transport.

Regional and Global Aspects of Aerosols in Western Africa: From Air Quality to Climate

NASA Technical Reports Server (NTRS)

Chin, Mian; Diehl, Thomas; Kucsera, Tom; Spinhime, Jim; Palm, Stephen; Holben, Brent; Ginoux, Paul

2006-01-01

Western Africa is one of the most important aerosol source regions in the world. Major aerosol sources include dust from the world's largest desert Sahara, biomass burning from the Sahel, pollution aerosols from local sources and long-range transport from Europe, and biogenic sources from vegetation. Because these sources have large seasonal variations, the aerosol composition over the western Africa changes significantly with time. These aerosols exert large influences on local air quality and regional climate. In this study, we use the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model to analyze satellite lidar data from the GLAS instrument on the ICESat and the sunphotometer data from the ground-based network AERONET taken in both the wet (September - October 2003) and dry (February - March 2004) seasons over western Africa. We will quantify the seasonal variations of aerosol sources and compositions and aerosol spatial (horizontal and vertical) distributions over western Africa. We will also assess the climate impact of western African aerosols. Such studies will be applied to support the international project, Africa Monsoon Multidisciplinary Analysis (AMMA) and to analyze the AMMA data.

Sr-Nd-Hf isotopic fingerprinting of transatlantic dust derived from North Africa

NASA Astrophysics Data System (ADS)

Zhao, Wancang; Balsam, William; Williams, Earle; Long, Xiaoyong; Ji, Junfeng

2018-03-01

Long-range transport of African dust plays an important role in understanding dust-climate relationships including dust source areas, dust pathways and associated atmospheric and/or oceanic processes. Clay-sized Sr-Nd-Hf isotopic compositions can be used as geochemical fingerprints to constrain dust provenance and the pathways of long-range transported mineral dust. We investigated the clay-sized Sr-Nd-Hf isotopic composition of surface samples along four transects bordering the Sahara Desert. The transects are from Mali, Niger/Benin/Togo, Egypt and Morocco. Our results show that the Mali transect on the West African Craton (WAC) produces lower εNd (εNd-mean = -16.38) and εHf (εHf-mean = -9.59) values than the other three transects. The Egyptian transect exhibits the lowest 87Sr/86Sr ratios (87Sr/86Srmean = 0.709842), the highest εHf (εHf-mean = -0.34) and εNd values of the four transects. Comparison of the clay-sized Sr-Nd-Hf isotopic values from our North African samples to transatlantic African dust collected in Barbados demonstrates that the dust's provenance is primarily the western Sahel and Sahara as well as the central Sahel. Summer emission dust is derived mainly from the western Sahel and Sahara regions. The source of transatlantic dust in spring and autumn is more varied than in the summer and includes dust not only from western areas, but also south central areas. Comparison of the Sr-Nd-Hf isotopic fingerprints between the source and sink of transatlantic dust also suggests that a northwestward shift in dust source occurs from the winter, through the spring and into the summer. The isotopic data we develop here provide another tool for discriminating changes in dust archives resulting from paleoenvironmental evolution of source regions.

Case study of dust event sources from the Gobi and Taklamakan deserts: An investigation of the horizontal evolution and topographical effect using numerical modeling and remote sensing.

PubMed

Fan, Jin; Yue, Xiaoying; Sun, Qinghua; Wang, Shigong

2017-06-01

A severe dust event occurred from April 23 to April 27, 2014, in East Asia. A state-of-the-art online atmospheric chemistry model, WRF/Chem, was combined with a dust model, GOCART, to better understand the entire process of this event. The natural color images and aerosol optical depth (AOD) over the dust source region are derived from datasets of moderate resolution imaging spectroradiometer (MODIS) loaded on a NASA Aqua satellite to trace the dust variation and to verify the model results. Several meteorological conditions, such as pressure, temperature, wind vectors and relative humidity, are used to analyze meteorological dynamic. The results suggest that the dust emission occurred only on April 23 and 24, although this event lasted for 5days. The Gobi Desert was the main source for this event, and the Taklamakan Desert played no important role. This study also suggested that the landform of the source region could remarkably interfere with a dust event. The Tarim Basin has a topographical effect as a "dust reservoir" and can store unsettled dust, which can be released again as a second source, making a dust event longer and heavier. Copyright © 2016. Published by Elsevier B.V.

Regional variability in dust-on-snow processes and impacts in the Upper Colorado River Basin

USGS Publications Warehouse

Skiles, S. McKenzie; Painter, Thomas H.; Belnap, Jayne; Holland, Lacey; Reynolds, Richard L.; Goldstein, Harland L.; Lin, J.

2015-01-01

Dust deposition onto mountain snow cover in the Upper Colorado River Basin frequently occurs in the spring when wind speeds and dust emission peaks on the nearby Colorado Plateau. Dust loading has increased since the intensive settlement in the western USA in the mid 1880s. The effects of dust-on-snow have been well studied at Senator Beck Basin Study Area (SBBSA) in the San Juan Mountains, CO, the first high-altitude area of contact for predominantly southwesterly winds transporting dust from the southern Colorado Plateau. To capture variability in dust transport from the broader Colorado Plateau and dust deposition across a larger area of the Colorado River water sources, an additional study plot was established in 2009 on Grand Mesa, 150 km to the north of SBBSA in west central, CO. Here, we compare the 4-year (2010–2013) dust source, deposition, and radiative forcing records at Grand Mesa Study Plot (GMSP) and Swamp Angel Study Plot (SASP), SBBSA's subalpine study plot. The study plots have similar site elevations/environments and differ mainly in the amount of dust deposited and ensuing impacts. At SASP, end of year dust concentrations ranged from 0.83 mg g−1 to 4.80 mg g−1, and daily mean spring dust radiative forcing ranged from 50–65 W m−2, advancing melt by 24–49 days. At GMSP, which received 1.0 mg g−1 less dust per season on average, spring radiative forcings of 32–50 W m−2 advanced melt by 15–30 days. Remote sensing imagery showed that observed dust events were frequently associated with dust emission from the southern Colorado Plateau. Dust from these sources generally passed south of GMSP, and back trajectory footprints modelled for observed dust events were commonly more westerly and northerly for GMSP relative to SASP. These factors suggest that although the southern Colorado Plateau contains important dust sources, dust contributions from other dust sources contribute to dust loading in this region, and likely account for the majority of dust loading at GMSP.

Early-Holocene greening of the Afro-Asian dust belt changed sources of mineral dust in West Asia

NASA Astrophysics Data System (ADS)

Sharifi, Arash; Murphy, Lisa N.; Pourmand, Ali; Clement, Amy C.; Canuel, Elizabeth A.; Naderi Beni, Abdolmajid; Lahijani, Hamid A. K.; Delanghe, Doriane; Ahmady-Birgani, Hesam

2018-01-01

Production, transport and deposition of mineral dust have significant impacts on different components of the Earth systems through time and space. In modern times, dust plumes are associated with their source region(s) using satellite and land-based measurements and trajectory analysis of air masses through time. Reconstruction of past changes in the sources of mineral dust as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleo-dust, and that of their potential source origins. In this contribution, we present a 13,000-yr record of variations in radiogenic Sr-Nd-Hf isotopes and Rare Earth Element (REE) anomalies as well as dust grain size from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in the sources of dust over the interior of West Asia. Our data shows that although the grain size of dust varies in a narrow range through the entire record, the geochemical fingerprint of dust particles deposited during the low-flux, early Holocene period (11,700-6,000 yr BP) is distinctly different from aerosols deposited during high dust flux periods of the Younger Dryas and the mid-late Holocene (6,000-present). Our findings indicate that the composition of mineral dust deposited at the study site changed as a function of prevailing atmospheric circulation regimes and land exposure throughout the last deglacial period and the Holocene. Simulations of atmospheric circulation over the region show the Northern Hemisphere Summer Westerly Jet was displaced poleward across the study area during the early Holocene when Northern Hemisphere insolation was higher due to the Earth's orbital configuration. This shift, coupled with lower dust emissions simulated based on greening of the Afro-Asian Dust Belt during the early Holocene likely led to potential sources in Central Asia dominating dust export to West Asia during this period. In contrast, the dominant western and southwest Asian and Eastern African sources have prevailed during the mid-Holocene to modern times.

Evaluations of bit sleeve and twisted-body bit designs for controlling roof bolter dust

PubMed Central

Beck, T.W.

2015-01-01

Drilling into coal mine roof strata to install roof bolts has the potential to release substantial quantities of respirable dust. Due to the proximity of drill holes to the breathing zone of roof bolting personnel, dust escaping the holes and avoiding capture by the dust collection system pose a potential respiratory health risk. Controls are available to complement the typical dry vacuum collection system and minimize harmful exposures during the initial phase of drilling. This paper examines the use of a bit sleeve in combination with a dust-hog-type bit to improve dust extraction during the critical initial phase of drilling. A twisted-body drill bit is also evaluated to determine the quantity of dust liberated in comparison with the dust-hog-type bit. Based on the results of our laboratory tests, the bit sleeve may reduce dust emissions by one-half during the initial phase of drilling before the drill bit is fully enclosed by the drill hole. Because collaring is responsible for the largest dust liberations, overall dust emission can also be substantially reduced. The use of a twisted-body bit has minimal improvement on dust capture compared with the commonly used dust-hog-type bit. PMID:26257435

Dust Deposition Events on Mt. Elbrus, Caucasus Mountains in the 21st Century Reconstructed from the Shallow Firn and Ice Cores (Invited)

NASA Astrophysics Data System (ADS)

Shahgedanova, M.; Kutuzov, S.; Mikhalenko, V.; Ginot, P.; Lavrentiev, I.

2013-12-01

This paper presents and discusses a record of dust deposition events reconstructed from the shallow firn and ice cores extracted on the Western Plateau, Mt. Elbrus, Caucasus Mountains, Russia. A combination of SEVIRI imagery, HYSPLIT trajectory model, meteorological and atmospheric optical depth data were used to establish timing of deposition events and source regions of dust with very high temporal (hours) and spatial (c. 50-100 km) resolution. The source regions of the desert dust transported to Mt. Elbrus were primarily located in the Middle East, in particular in eastern Syria and in the Syrian Desert at the border between Saudi Arabia, Iraq and Jordan. Northern Sahara, the foothills of the Djebel Akhdar Mountains in eastern Libya and the border region between Libya and Algeria were other important sources of desert dust. Dust sources in the Sahara were natural (e.g. palaeolakes and alluvial deposits in the foothills) while in the Middle East, dust entrainment occurred from both natural (e.g. dry river beds) and anthropogenic (e.g. agricultural fields) sources. The overall majority of dust deposition events occurred between March and June and, less frequently, dust deposition events occurred in February and October. In all cases, dust deposition was associated with depressions causing strong surface wind and dust uplift in the source areas, transportation of dust to the Caucasus with a strong south-westerly flow from the Sahara or southerly flow from the Middle East, merging of the dust clouds with precipitation-bearing weather fronts and precipitation over the Caucasus region. The Saharan depressions were vigorous and associated with stronger daily wind speeds of 20-30 m/s at the 700 hPa level; depressions forming over the Middle East and the associated wind speeds were weaker at 12-15 m/s. The Saharan depressions were less frequent than those carrying dust from the Middle East but higher dust loads were associated with the Saharan depressions. A higher frequency of dust deposition events on Mt. Elbrus was registered in 2007-2010 due to the prolonged drought in the Middle East resulting in a more frequent activation of dust sources, including agricultural fields abandoned because of the draught.

AzTEC 1.1 mm OBSERVATIONS OF THE MBM12 MOLECULAR CLOUD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, M. J.; Kim, S.; Youn, S.

2012-02-10

We present 1.1 mm observations of the dust continuum emission from the MBM12 high-latitude molecular cloud observed with the Astronomical Thermal Emission Camera (AzTEC) mounted on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. We surveyed 6.34 deg{sup 2} centered on MBM12, making this the largest area that has ever been surveyed in this region with submillimeter and millimeter telescopes. Eight secure individual sources were detected with a signal-to-noise ratio of over 4.4. These eight AzTEC sources can be considered to be real astronomical objects compared to the other candidates based on calculations of the false detection rate. Themore » distribution of the detected 1.1 mm sources or compact 1.1 mm peaks is spatially anti-correlated with that of the 100 {mu}m emission and the {sup 12}CO emission. We detected the 1.1 mm dust continuum emitting sources associated with two classical T Tauri stars, LkH{alpha}262 and LkH{alpha}264. Observations of spectral energy distributions (SEDs) indicate that LkH{alpha}262 is likely to be Class II (pre-main-sequence star), but there are also indications that it could be a late Class I (protostar). A flared disk and a bipolar cavity in the models of Class I sources lead to more complicated SEDs. From the present AzTEC observations of the MBM12 region, it appears that other sources detected with AzTEC are likely to be extragalactic and located behind MBM12. Some of these have radio counterparts and their star formation rates are derived from a fit of the SEDs to the photometric evolution of galaxies in which the effects of a dusty interstellar medium have been included.« less

Temporal variations of fine and coarse particulate matter sources in Jeddah, Saudi Arabia.

PubMed

Lim, Chris C; Thurston, George D; Shamy, Magdy; Alghamdi, Mansour; Khoder, Mamdouh; Mohorjy, Abdullah M; Alkhalaf, Abdulrahman K; Brocato, Jason; Chen, Lung Chi; Costa, Max

2018-02-01

This study provides the first comprehensive analysis of the seasonal variations and weekday/weekend differences in fine (aerodynamic diameter <2.5 μm; PM 2.5 ) and coarse (aerodynamic diameter 2.5-10 μm; PM 2.5-10 ) particulate matter mass concentrations, elemental constituents, and potential source origins in Jeddah, Saudi Arabia. Air quality samples were collected over 1 yr, from June 2011 to May 2012 at a frequency of three times per week, and analyzed. The average mass concentrations of PM 2.5 (21.9 μg/m 3 ) and PM 10 (107.8 μg/m 3 ) during the sampling period exceeded the recommended annual average levels by the World Health Organization (WHO) for PM 2.5 (10 μg/m 3 ) and PM 10 (20 μg/m 3 ), respectively. Similar to other Middle Eastern locales, PM 2.5-10 is the prevailing mass component of atmospheric particulate matter at Jeddah, accounting for approximately 80% of the PM 10 mass. Considerations of enrichment factors, absolute principal component analysis (APCA), concentration roses, and backward trajectories identified the following source categories for both PM 2.5 and PM 2.5-10 : (1) soil/road dust, (2) incineration, and (3) traffic; and for PM 2.5 only, (4) residual oil burning. Soil/road dust accounted for a major portion of both the PM 2.5 (27%) and PM 2.5-10 (77%) mass, and the largest source contributor for PM 2.5 was from residual oil burning (63%). Temporal variations of PM 2.5-10 and PM 2.5 were observed, with the elevated concentration levels observed for mass during the spring (due to increased dust storm frequency) and on weekdays (due to increased traffic). The predominant role of windblown soil and road dust in both the PM 2.5 and PM 2.5-10 masses in this city may have implications regarding the toxicity of these particles versus those in the Western world where most PM health assessments have been made in the past. These results support the need for region-specific epidemiological investigations to be conducted and considered in future PM standard setting. Temporal variations of fine and coarse PM mass, elemental constituents, and sources were examined in Jeddah, Saudi Arabia, for the first time. The main source of PM 2.5-10 is natural windblown soil and road dust, whereas the predominant source of PM 2.5 is residual oil burning, generated from the port and oil refinery located west of the air sampler, suggesting that targeted emission controls could significantly improve the air quality in the city. The compositional differences point to a need for health effect studies to be conducted in this region, so as to directly assess the applicability of the existing guidelines to the Middle East air pollution.

Dust emission mechanisms in the central Sahara: new insights from remote field observations

NASA Astrophysics Data System (ADS)

Allen, C.; Washington, R.; Engelstaedter, S.

2013-12-01

North Africa is the world's largest source of mineral aerosol (dust). The Fennec Project, an international consortium led by the University of Oxford, is the first project to systematically instrument the remote central Sahara Desert. These observations have, among others, provided new insights into the atmospheric mechanisms of dust emission. Bordj Badji Mokhtar, in south-west Algeria, is within kilometres of the centre of the global mean summer dust maximum. The site, operated by Fennec partners ONM Algerie, has been heavily instrumented since summer 2011. During the Intensive Observation Period (IOP) in June 2011, four main emission mechanisms were observed and documented: cold pool outflows, low level jets (LLJs), monsoon surges and dry convective plumes. Establishing the relative importance of dust emission mechanisms has been a long-standing research goal. A detailed partitioning exercise of dust events during the IOP shows that 45% of the dust over BBM was generated by local emission in cold pool outflows, 14% by LLJs and only 2% by dry convective plumes. 27% of the dust was advected to the site rather than locally emitted and 12% of the dust was residual or ';background' dust. The work shows the primacy of cold pool outflows for dust emission in the region and also the important contribution of dust advection. In accordance with long-held ideas, the cube of wind speed is strongly correlated with dust emission. Surprisingly however, particles in long-range advection (>500km) were found to be larger than locally emitted dust. Although a clear LLJ wind structure is evident in the mean diurnal cycle during the IOP (12m/s peak winds at 935hPa between 04-05h), LLJs are only responsible for a relatively small amount of dust emission. There is significant daily variability in LLJ strength; the strongest winds are produced by a relatively small number of events. The position and strength of the Saharan Heat Low is strongly associated with the development (or otherwise) of LLJs. However, the presence of a LLJ is not a guarantee of dust emission. Momentum calculations show that dust emission always occurs if momentum mixes down to the surface, but mix-down does not always happen - particularly if the surface temperature inversion is strong or ground heating is weak. Fennec findings are not only providing new insights into dust emission processes, they are also an excellent test-bed for models and satellite algorithms in a region where high-quality ';ground-truthing' measurements have been scarce. Conditions of (relatively) high water vapour appear to be a common cause of error. In one model, wind speeds in the core of monsoon LLJs are underestimated by 8.5m/s compared to observations.

Large-scale Desert Dust Deposition on the Himalayan Snow Cover: A Climatological Perspective from Satellite Observations

NASA Astrophysics Data System (ADS)

Gautam, R.; Hsu, N. C.; Lau, W. K.

2013-12-01

The Himalaya-Tibetan Plateau (HTP) has a profound influence on the Asian climate. The HTP are also among the largest snow/ice-covered regions on the Earth and provide major freshwater resource to the downstream densely-populated regions of Asia. Recent studies indicate climate warming over the HTP amplified by atmospheric heating and deposition of absorbing aerosols (e.g. dust and soot) over the HTP snowpack and glaciers. Recently, greater attention has focused on the effects of soot deposition on accelerated snowmelt and glacier retreat in the HTP, associated with increasing anthropogenic emissions in Asia. On the other hand, the role of transported dust affecting snow albedo/melt is not well understood over the HTP, in spite of the large annual cycle of mineral dust loading, particularly over the northern parts of south Asia during pre-monsoon season. This study addresses the large-scale effects of dust deposition on snow albedo in the elevated HTP from a satellite observational perspective. Dust aerosol transport, from southwest Asian arid regions, is observed in satellite imagery as darkening of the Himalayan snowpack. Additionally, multi-year spaceborne lidar observations, from CALIPSO, also show dust advected to elevated altitudes (~5km) over the Himalayan foothills, and episodically reaching the top of the western Himalaya. Spectral surface reflectance analysis of dust-laden snow cover (from MODIS) indicates enhanced absorption in the shorter visible wavelengths, yielding a significant gradient in the visible-nearIR reflectance spectrum. While soot in snow is difficult to distinguish from remote sensing, our spectral reflectance analysis of dust detection in the snowpack is consistent with theoretical simulations of snow darkening due to dust impurity. We find that the western HTP, in general, is influenced by enhanced dust deposition due to its proximity to major dust sources (and prevailing dust transport pathways), compared to the eastern HTP. Coinciding with the snowmelt period, dust deposition appears to further cause snow reflectance reduction, i.e. snow darkening, from spring to summer months. Among the entire HTP, we show that the western Himalaya and the Hindu-Kush snowpack are subjected to greater dust deposition and snow albedo reduction. Thus, our satellite-based observational study addresses the spatial variability of large-scale dust deposition on snow cover in the extensive HTP. A climatological and inter-annual perspective of the spatial variability of dust-induced snow darkening over the HTP will be presented, using ~10 years of MODIS spectral reflectance data (at high spatial resolution of ~1km). Results from this study provide insight into the particular role of desert dust towards accelerated seasonal snowmelt in the HTP.

SMART-COMMIT Observations and Deep-Blue Retrievals of Saharan Dust Properties during NAMMA

NASA Technical Reports Server (NTRS)

Tsay, Si-Chee; Hsu, N. Christina; Ji, Qiang; Jeong, Myeong-Jae

2007-01-01

Monsoon rainfalls sustain the livelihood of more than half of the world's population. The interaction between natural/anthropogenic aerosols, clouds, and precipitation is a critical mechanism that drives the water cycle and fresh water distribution. Analyses of the longterm trend of July-August precipitation anomaly for the last 50 years in the 20" century depict that the largest regional precipitation deficit occurs over the Sahel, where the monsoon water cycle plays an important role. Thus, it is of paramount importance to study how dust aerosols, as well as air pollution and smoke, influence monsoon variability. The NASA African Monsoon Multidisciplinary Activities (NAMMA) was conducted during the international AMMA Special Observation Period (SOP-3) of September 2006 to better comprehend the key attributes of the Saharan Air Layer (SAL) and how they evolve from the source regions to the Atlantic Ocean. The SAL occurs during the late spring through early fall and originates as a result of low-level convergence induced by heat lows over the Sahara that lifts hot, dry, dust laden air aloft into a well mixed layer that extends up to 500mb. This is crucial for understanding the impact of SAL on the key atmospheric processes that determine precipitation over West Africa and tropical cyclogenesis. Results obtained from the synergy of satellite (Deep- Blue) and surface (SMART-COMMIT) observations will be presented and discussed how the physical, optical and radiative properties of the dust in the SAL evolve from the continental to the marine environment.

Sensitivity of desert dust emission modelling to horizontal resolution: the example of the Bodélé Depression

NASA Astrophysics Data System (ADS)

Bouet, Christel; Cautenet, Guy; Marticorena, Béatrice; Bergametti, Gilles; Minvielle, Fanny; Schmechtig, Catherine; Laurent, Benoit

2010-05-01

Atmospheric aerosols are known to play an important role in the Earth's climate system. However, the quantification of aerosol radiative impact on the Earth's radiative budget is very complex because of the high variability in space and time of aerosol mass and particle number concentrations, and optical properties as well. In many regions, like in desert regions, dust is the largest contribution to aerosol optical thickness [Tegen et al., 1997]. Consequently, it appears fundamental to well represent mineral dust emissions to reduce uncertainties concerning aerosol radiative impact on the Earth's radiative budget. Recently, several studies (e.g. Prospero et al. [2002]) underlined that the Bodélé depression, in northern Chad, is probably the most important source of mineral dust in the world. However many models fail in simulating these large dust emissions. Indeed, dust emission is a threshold phenomenon mainly driven by the intensity of surface wind velocity. Realistic estimates of dust emissions then rely on the quality and accuracy of the surface wind fields. Koren and Kaufman [2004] showed that the reanalysis data (NCEP), which can be used as input data in numerical models, underestimates surface wind velocity in the Bodélé Depression by up to 50%. Such an uncertainty on surface wind velocity cannot allow an accurate simulation of the dust emission. In mesoscale meteorological models, global reanalysis datasets are used to initialize and laterally nudge the models that compute meteorological parameters (like wind velocity) with a finer spatial and temporal resolutions. The question arises concerning the precision of the wind speeds calculated by these models. Using the Regional Atmospheric Modeling System (RAMS, Cotton et al. [2003]) coupled online with the dust production model developed by Marticorena and Bergametti [1995] and recently improved by Laurent et al. [2008] for Africa, the influence of the horizontal resolution of the mesoscale meteorological model on the simulation of dust emission in the Bodélé Depression is investigated. A one year simulation is run in order to test the capability of the model to represent the pronounced seasonal cycle of dust emission in this region. Routine measurements from meteorological stations as well as satellite imagery are used to evaluate the accuracy of the simulations.

A multidisciplinary approach to trace Asian dust storms from source to sink

NASA Astrophysics Data System (ADS)

Yan, Yan; Sun, Youbin; Ma, Long; Long, Xin

2015-03-01

Tracing the source of dust storm (DS) in mega-cities of northern China currently suffers ambiguities from different approaches including source-sink proxy comparison, air mass back trajectory modeling, and satellite image monitoring. By integrating advantages of all three methods, we present a multidisciplinary approach to trace the provenance of dust fall in Xi'an during the spring season (March to May) of 2012. We collected daily dust fall to calculate dust flux variation, and detected eight DS events with remarkable high flux values based on meteorological comparison and extreme detection algorithm. By combining MODIS images and accompanying real-time air mass back trajectories, we attribute four of them as natural DS events and the other four as anthropogenic DS events, suggesting the importance of natural and anthropogenic processes in supplying long-range transported dust. The primary sources of these DS events were constrained to three possible areas, including the northern Chinese deserts, Taklimakan desert, and Gurbantunggut desert. Proxy comparisons based upon the quartz crystallinity index and oxygen isotope further confirmed the source-to-sink linkage between the natural DS events in Xi'an and the dust emissions from the northern Chinese deserts. The integration of geochemical and meteorological tracing approaches favors the dominant contribution of short-distance transportation of modern dust fall on the Chinese Loess Plateau. Our study shows that the multidisciplinary approach could permit a better source identification of modern dust and should be applied properly for tracing the provenance fluctuations of geological dust deposits.

Regional Modeling of Dust Mass Balance and Radiative Forcing over East Asia using WRF-Chem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Siyu; Zhao, Chun; Qian, Yun

The Weather Research and Forecasting model with Chemistry (WRF-Chem) is used to investigate the seasonal and annual variations of mineral dust over East Asia during 2007-2011, with a focus on the dust mass balance and radiative forcing. A variety of measurements from in-stu and satellite observations have been used to evaluate simulation results. Generally, WRF-Chem reproduces not only the column variability but also the vertical profile and size distribution of mineral dust over and near the dust source regions of East Asia. We investigate the dust lifecycle and the factors that control the seasonal and spatial variations of dust massmore » balance and radiative forcing over the seven sub-regions of East Asia, i.e. source regions, the Tibetan Plateau, Northern China, Southern China, the ocean outflow region, and Korea-Japan regions. Results show that, over the source regions, transport and dry deposition are the two dominant sinks. Transport contributes to ~30% of the dust sink over the source regions. Dust results in a surface cooling of up to -14 and -10 W m-2, atmospheric warming of up to 20 and 15 W m-2, and TOA cooling of -5 and -8 W m-2 over the two major dust source regions of East Asia, respectively. Over the Tibetan Plateau, transport is the dominant source with a peak in summer. Over identified outflow regions, maximum dust mass loading in spring is contributed by the transport. Dry and wet depositions are the comparably dominant sinks, but wet deposition is larger than dry deposition over the Korea-Japan region, particularly in spring (70% versus 30%). The WRF-Chem simulations can generally capture the measured features of dust aerosols and its radaitve properties and dust mass balance over East Asia, which provides confidence for use in further investigation of dust impact on climate over East Asia.« less

Laboratory study of PCB transport from primary sources to ...

EPA Pesticide Factsheets

Transport of house dust and Arizona Test Dust on polychlorinated biphenyl (PCB)-containing panels and PCB-free panels was investigated in a 30-m3 stainless steel chamber. The PCB-containing panels were aluminum sheets coated with a PCB-spiked, oil-based primer or two-part polysulfide caulk. The PCB-free panels were coated with the same materials but they were not spiked with PCBs. The dust was weighed and spread on the panels as evenly as possible. The dust on each panel was collected at different times to determine its PCB content. The dust data collected from the PCB panels were used to evaluate the PCB migration from the source to the dust through direct contact, and the data from the PCB-free panels were used to evaluate the sorption of PCBs through the dust/air partition. Settled dust can adsorb PCBs from air. The sorption concentration was dependent on the congener concentration in the air and favored less volatile congeners. When the house dust was in direct contact with a primary source, PCBs migrated into the dust at a much faster rate than the PCB transfer rate due to the dust/air partition. Unlike the dust/air partition, the dust/source partition was not significantly affected by the volatility of the congener. This research is important to decision makers, environmental engineers, and researchers who are concerned with risk assessment and risk management for PCB contamination.

High Latitude Dust Sources, Transport Pathways and Impacts

NASA Astrophysics Data System (ADS)

Bullard, J. E.; Baddock, M. C.; Darlington, E.; Mockford, T.; Van-Soest, M.

2017-12-01

Estimates from field studies, remote sensing and modelling all suggest around 5% of global dust emissions originate in the high latitudes (≥50°N and ≥40°S), a similar proportion to that from the USA (excluding Alaska) or Australia. This paper identifies contemporary sources of dust within the high latitudes and their role within local, regional and hemispherical environmental systems. Field data and remote sensing analyses are used to identify the environmental and climatic conditions that characterize high latitude dust sources in both hemispheres. Examples from Arctic and sub-Arctic dust sources are used to demonstrate and explain the different regional relationships among dust emissions, glacio-fluvial dynamics and snow cover. The relative timing of dust input to high latitude terrestrial, cryospheric and marine systems determines its short to medium term environmental impact. This is highlighted through quantifying the importance of locally-redistributed dust as a nutrient input to high latitude soils and lakes in West Greenland.

Regional and climatic controls on seasonal dust deposition in the southwestern U.S.

USGS Publications Warehouse

Reheis, M.C.; Urban, F.E.

2011-01-01

Vertical dust deposition rates (dust flux) are a complex response to the interaction of seasonal precipitation, wind, changes in plant cover and land use, dust source type, and local vs. distant dust emission in the southwestern U.S. Seasonal dust flux in the Mojave-southern Great Basin (MSGB) deserts, measured from 1999 to 2008, is similar in summer-fall and winter-spring, and antecedent precipitation tends to suppress dust flux in winter-spring. In contrast, dust flux in the eastern Colorado Plateau (ECP) region is much larger in summer-fall than in winter-spring, and twice as large as in the MSGB. ECP dust is related to wind speed, and in the winter-spring to antecedent moisture. Higher summer dust flux in the ECP is likely due to gustier winds and runoff during monsoonal storms when temperature is also higher. Source types in the MSGB and land use in the ECP have important effects on seasonal dust flux. In the MSGB, wet playas produce salt-rich dust during wetter seasons, whereas antecedent and current moisture suppress dust emission from alluvial and dry-playa sources during winter-spring. In the ECP under drought conditions, dust flux at a grazed-and-plowed site increased greatly, and also increased at three annualized, previously grazed sites. Dust fluxes remained relatively consistent at ungrazed and currently grazed sites that have maintained perennial vegetation cover. Under predicted scenarios of future climate change, these results suggest that an increase in summer storms may increase dust flux in both areas, but resultant effects will depend on source type, land use, and vegetation cover. ?? 2011.

Chemical characterization and source identification of PM2.5 at multiple sites in the Beijing-Tianjin-Hebei region, China

NASA Astrophysics Data System (ADS)

Huang, Xiaojuan; Liu, Zirui; Liu, Jingyun; Hu, Bo; Wen, Tianxue; Tang, Guiqian; Zhang, Junke; Wu, Fangkun; Ji, Dongsheng; Wang, Lili; Wang, Yuesi

2017-11-01

The simultaneous observation and analysis of atmospheric fine particles (PM2.5) on a regional scale is an important approach to develop control strategies for haze pollution. In this study, samples of filtered PM2.5 were collected simultaneously at three urban sites (Beijing, Tianjin, and Shijiazhuang) and at a regional background site (Xinglong) in the Beijing-Tianjin-Hebei (BTH) region from June 2014 to April 2015. The PM2.5 at the four sites was mainly comprised of organic matter, secondary inorganic ions, and mineral dust. Positive matrix factorization (PMF) demonstrated that, on an annual basis, secondary inorganic aerosol was the largest PM2.5 source in this region, accounting for 29.2-40.5 % of the PM2.5 mass at the urban sites; the second-largest PM2.5 source was motor vehicle exhaust, particularly in Beijing (24.9 %), whereas coal combustion was also a large source in Tianjin (12.4 %) and Shijiazhuang (15.5 %), with particular dominance in winter. Secondary inorganic aerosol plays a vital role in the haze process, with the exception of the spring haze in Shijiazhuang and Tianjin, for which the dust source was crucial. In addition to secondary transformations, local direct emissions (coal combustion and motor vehicle exhaust) significantly contribute to the winter haze at the urban sites. Moreover, with the aggravation of haze pollution, the OC / EC mass ratio of PM2.5 decreased considerably and the nitrate-rich secondary aerosol increased during all four seasons in Beijing, both of which indicate that local motor vehicle emissions significantly contribute to the severe haze episodes in Beijing. To assess the impacts of regional transport on haze pollution, the PMF results were further processed with backward-trajectory cluster analysis, revealing that haze pollution usually occurred when air masses originating from polluted industrial regions in the south prevailed and is characterized by high PM2.5 loadings with considerable contributions from secondary aerosols. This study suggests that control strategies to mitigate haze pollution in the BTH region should focus on the reduction of gaseous precursor emissions from fossil fuel combustion (motor vehicle emissions in Beijing and coal combustion in Tianjin, Hebei, and nearby provinces).

ON INFRARED EXCESSES ASSOCIATED WITH Li-RICH K GIANTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rebull, Luisa M.; Carlberg, Joleen K.; Gibbs, John C.

2015-10-15

Infrared (IR) excesses around K-type red giants (RGs) have previously been discovered using Infrared Astronomy Satellite (IRAS) data, and past studies have suggested a link between RGs with overabundant Li and IR excesses, implying the ejection of circumstellar shells or disks. We revisit the question of IR excesses around RGs using higher spatial resolution IR data, primarily from the Wide-field Infrared Survey Explorer. Our goal was to elucidate the link between three unusual RG properties: fast rotation, enriched Li, and IR excess. Our sample of RGs includes those with previous IR detections, a sample with well-defined rotation and Li abundancemore » measurements with no previous IR measurements, and a large sample of RGs asserted to be Li-rich in the literature; we have 316 targets thought to be K giants, about 40% of which we take to be Li-rich. In 24 cases with previous detections of IR excess at low spatial resolution, we believe that source confusion is playing a role, in that either (a) the source that is bright in the optical is not responsible for the IR flux, or (b) there is more than one source responsible for the IR flux as measured in IRAS. We looked for IR excesses in the remaining sources, identifying 28 that have significant IR excesses by ∼20 μm (with possible excesses for 2 additional sources). There appears to be an intriguing correlation in that the largest IR excesses are all in Li-rich K giants, though very few Li-rich K giants have IR excesses (large or small). These largest IR excesses also tend to be found in the fastest rotators. There is no correlation of IR excess with the carbon isotopic ratio, {sup 12}C/{sup 13}C. IR excesses by 20 μm, though relatively rare, are at least twice as common among our sample of Li-rich K giants. If dust shell production is a common by-product of Li enrichment mechanisms, these observations suggest that the IR excess stage is very short-lived, which is supported by theoretical calculations. Conversely, the Li-enrichment mechanism may only occasionally produce dust, and an additional parameter (e.g., rotation) may control whether or not a shell is ejected.« less

On Infrared Excesses Associated with Li-Rich K Giants

NASA Technical Reports Server (NTRS)

Rebull, Luisa M.; Carlberg, Joleen K.; Gibbs, John C.; Deeb, J. Elin; Larsen, Estefania; Black, David V.; Altepeter, Shailyn; Bucksbee, Ethan; Cashen, Sarah; Clarke, Matthew;

Petrogenic organic carbon and PAHs in snow deposited on Athabasca oil sands region lakes

NASA Astrophysics Data System (ADS)

Ahad, J. M.; Pakdel, H.; Gammon, P. R.; Savard, M. M.

2017-12-01

Fugitive dust associated with surface mining activities is one of the principal vectors for transport of airborne contaminants in Canada's Athabasca oil sands (AOS) region. The two main sources for mining-related dust - unprocessed oil sand and petroleum coke (petcoke) - contain high levels of bitumen-derived organic contaminants such as polycyclic aromatic hydrocarbons (PAHs). Here, we report the radiocarbon (14C) contents of solvent-extractable organics in snow particulates deposited during the winter of 2016-17 on fourteen lakes across the AOS region to quantify the contribution of anthropogenic dust transported directly to these ecosystems. Concentrations of parent and alkylated PAHs were determined in both dissolved and particulate fractions of snow. Radiocarbon isotope ratios (Δ14C) ranged from -805 to -177‰, indicating a significant contribution of petrogenic or fossil (i.e., Δ14C = -1000‰) carbon in snowpack dust at some sites. More negative Δ14C values were generally found in samples containing higher levels of particulate matter and at lakes closer to the geographic center of AOS mining operations. Concentrations of PAHs > 2 rings were significantly higher in the particulate phase and in samples with the largest petrogenic carbon components. Relatively high levels of PAHs at some distal sites associated with less negative Δ14C values pointed to an important modern carbon contribution, potentially ash originating from the 1.5 million acre 2016 Fort McMurray wildfire. As demonstrated here, fugitive dust in snow covering AOS region lakes can contain significant petrogenic organic carbon and high levels of PAHs, particularly in areas close (i.e., < 25 km) to the center of AOS mining operations. The spring snowmelt thus provides a direct pathway for mining-related contaminants to lake sediments.

Composition and Source Identification of Chemical Species in Dust from Selected Indoor Environments in Ile-Ife, Nigeria

NASA Astrophysics Data System (ADS)

Ogundele, Lasun T.; Olasinde, Roseline T.; Owoade, Oyediran K.; Olise, Felix S.

2018-05-01

This study presents the elemental compositions and concentrations of indoor dust and identifies the major sources in some selected indoor environments in Ile-Ife, Nigeria. The dust samples were collected from 16 indoor environments comprising offices, churches, residential and staff quarters using a cyclonic high power vacuum cleaner. The dust samples were analyzed for elemental concentrations using x-ray fluorescences. The data sets were analyzed for the possible sources and their contributions using Principal Component Factor Analysis (PCFA). The result showed that dust samples contained several elements: K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Ga, As, Rb, Sr, Se, Zr, V, and Sc. The PCFA identified three factors with the percentage variance of 92, 77, 71 and 68%, for the office, church, residential, and staff quarters, respectively, for the combined elemental data of each of the site classes. The identified sources were track-in-soil, road and windblown soil dust, paint debris, household dust from personal care materials, cooking, and cleaning activities. The unintentional track-in-soil due to mobility of the occupants, structural materials, and outdoor air was the major sources contributing to the indoor dust.

Surface Properties Associated With Dust Storm Plume's Point-Source Locations In The Border Region Of The US And Mexico

NASA Astrophysics Data System (ADS)

Bleiweiss, M. P.; DuBois, D. W.; Flores, M. I.

2013-12-01

Dust storms in the border region of the Southwest US and Northern Mexico are a serious problem for air quality (PM10 exceedances), health (Valley Fever is pandemic in the region) and transportation (road closures and deadly traffic accidents). In order to better understand the phenomena, we are attempting to identify critical characteristics of dust storm sources so that, possibly, one can perform more accurate predictions of events and, thus, mitigate some of the deleterious effects. Besides the emission mechanisms for dust storm production that are tied to atmospheric dynamics, one must know those locations whose source characteristics can be tied to dust production and, therefore, identify locations where a dust storm is eminent under favorable atmospheric dynamics. During the past 13 years, we have observed, on satellite imagery, more than 500 dust events in the region and are in the process of identifying the source regions for the dust plumes that make up an event. Where satellite imagery exists with high spatial resolution (less than or equal to 250m), dust 'plumes' appear to be made up of individual and merged plumes that are emitted from a 'point source' (smaller than the resolution of the imagery). In particular, we have observed events from the ASTER sensor whose spatial resolution is 15m as well as Landsat whose spatial resolution is 30m. Tying these source locations to surface properties such as NDVI, albedo, and soil properties (percent sand, silt, clay, and gravel; soil moisture; etc.) will identify regions with enhanced capability to produce a dust storm. This, along with atmospheric dynamics, will allow the forecast of dust events. The analysis of 10 events from the period 2004-2013, for which we have identified 1124 individual plumes, will be presented.

A large source of dust missing in particulate matter emission inventories? Wind erosion of post-fire landscapes

Treesearch

N. S. Wagenbrenner; S. H. Chung; B. K. Lamb

2017-01-01

Wind erosion of soils burned by wildfire contributes substantial particulate matter (PM) in the form of dust to the atmosphere, but the magnitude of this dust source is largely unknown. It is important to accurately quantify dust emissions because they can impact human health, degrade visibility, exacerbate dust-on-snow issues (including snowmelt timing, snow chemistry...

Mapping erodibility in dust source regions based on geomorphology, meteorology, and remote sensing

NASA Astrophysics Data System (ADS)

Parajuli, Sagar Prasad; Yang, Zong-Liang; Kocurek, Gary

2014-09-01

Mineral dust in the atmosphere has implications for Earth's radiation budget, biogeochemical cycles, hydrological cycles, human health, and visibility. Currently, the simulated vertical mass flux of dust differs greatly among the existing dust models. While most of the models utilize an erodibility factor to characterize dust sources, this factor is assumed to be static, without sufficient characterization of the highly heterogeneous and dynamic nature of dust source regions. We present a high-resolution land cover map of the Middle East and North Africa (MENA) in which the terrain is classified by visually examining satellite images obtained from Google Earth Professional and Environmental Systems Research Institute Basemap. We show that the correlation between surface wind speed and Moderate Resolution Imaging Spectroradiometer deep blue aerosol optical depth (AOD) can be used as a proxy for erodibility, which satisfactorily represents the spatiotemporal distribution of soil-derived dust sources. This method also identifies agricultural dust sources and eliminates the satellite-observed dust component that arises from long-range transport, pollution, and biomass burning. The erodible land cover of the MENA region is grouped into nine categories: (1) bedrock: with sediment, (2) sand deposit, (3) sand deposit: on bedrock, (4) sand deposit: stabilized, (5) agricultural and urban area, (6) fluvial system, (7) stony surface, (8) playa/sabkha, and (9) savanna/grassland. Our results indicate that erodibility is linked to the land cover type and has regional variation. An improved land cover map, which explicitly accounts for sediment supply, availability, and transport capacity, may be necessary to represent the highly dynamic nature of dust sources in climate models.

Reconciling PM10 analyses by different sampling methods for Iron King Mine tailings dust.

PubMed

Li, Xu; Félix, Omar I; Gonzales, Patricia; Sáez, Avelino Eduardo; Ela, Wendell P

2016-03-01

The overall project objective at the Iron King Mine Superfund site is to determine the level and potential risk associated with heavy metal exposure of the proximate population emanating from the site's tailings pile. To provide sufficient size-fractioned dust for multi-discipline research studies, a dust generator was built and is now being used to generate size-fractioned dust samples for toxicity investigations using in vitro cell culture and animal exposure experiments as well as studies on geochemical characterization and bioassay solubilization with simulated lung and gastric fluid extractants. The objective of this study is to provide a robust method for source identification by comparing the tailing sample produced by dust generator and that collected by MOUDI sampler. As and Pb concentrations of the PM10 fraction in the MOUDI sample were much lower than in tailing samples produced by the dust generator, indicating a dilution of Iron King tailing dust by dust from other sources. For source apportionment purposes, single element concentration method was used based on the assumption that the PM10 fraction comes from a background source plus the Iron King tailing source. The method's conclusion that nearly all arsenic and lead in the PM10 dust fraction originated from the tailings substantiates our previous Pb and Sr isotope study conclusion. As and Pb showed a similar mass fraction from Iron King for all sites suggesting that As and Pb have the same major emission source. Further validation of this simple source apportionment method is needed based on other elements and sites.

Approaches to Children’s Exposure Assessment: Case Study with Diethylhexylphthalate (DEHP)

PubMed Central

Ginsberg, Gary; Ginsberg, Justine; Foos, Brenda

2016-01-01

Children’s exposure assessment is a key input into epidemiology studies, risk assessment and source apportionment. The goals of this article are to describe a methodology for children’s exposure assessment that can be used for these purposes and to apply the methodology to source apportionment for the case study chemical, diethylhexylphthalate (DEHP). A key feature is the comparison of total (aggregate) exposure calculated via a pathways approach to that derived from a biomonitoring approach. The 4-step methodology and its results for DEHP are: (1) Prioritization of life stages and exposure pathways, with pregnancy, breast-fed infants, and toddlers the focus of the case study and pathways selected that are relevant to these groups; (2) Estimation of pathway-specific exposures by life stage wherein diet was found to be the largest contributor for pregnant women, breast milk and mouthing behavior for the nursing infant and diet, house dust, and mouthing for toddlers; (3) Comparison of aggregate exposure by pathways vs biomonitoring-based approaches wherein good concordance was found for toddlers and pregnant women providing confidence in the exposure assessment; (4) Source apportionment in which DEHP presence in foods, children’s products, consumer products and the built environment are discussed with respect to early life mouthing, house dust and dietary exposure. A potential fifth step of the method involves the calculation of exposure doses for risk assessment which is described but outside the scope for the current case study. In summary, the methodology has been used to synthesize the available information to identify key sources of early life exposure to DEHP. PMID:27376320

A simulation of Asian dust events observed from 20 to 29 December 2009 in Korea by using ADAM2

NASA Astrophysics Data System (ADS)

Park, Soon-Ung; Choe, Anna; Park, Moon-Soo

2013-01-01

The Asian dust Aerosol Model 2 (ADAM2) with the MM5 meteorological model has been employed to study long-range transport process of Asian dust and to estimate dust emission, deposition (wet and dry) and concentration over the Asian dust source region and the downwind regions for dust events observed in Korea during the period of 20-29 December 2009, which is one of the dust events chosen by the 3rd Meeting of Working Group for Joint Research on Dust Sand Storm among Mongolia, China, Japan and Korea to study intensively for the development of an early warning system in Asia. It is found that the model simulates quite well the starting and ending times of dust events and the peak dust concentrations with their occurrence times both in the source region and downwind regions. The dust emission in the dust source region is found to be associated with a developing synoptic weather system accompanied with strong surface winds over the source region that usually travels east to southeastward across the source region and then turns to move northeastward toward the north western Pacific Ocean. The dust emitted in the source region is found to be split into two parts: one is transported southeastward to the East China Sea in front of the surface high pressure system and experiencing enhanced deposition due to the sinking motion induced by the southeastward traveling the surface high pressure system whereas, the other moves northeastward toward the surface low pressure system and then lifted upward to form a upper-level high dust concentration layer that results in a favorable condition for the long-range transport of dust. It is also found that the maximum ten-day total dust emission of about 23 t km-2 occurs in the domain Northwestern China (NWC). However, the maximum ten-day total dust deposition of 21 t km-2 with the maximum mean surface concentration of 555 μg m-3 and the column integrated mean concentration of 2.9 g m-2 occurs in the domain Central-northern China (CNC). The column-integrated PM10 concentration is found to increase toward northeastward especially in the domain North northeastern China (NNEC) due to the upper-level transported high PM10 concentration. The ten-day total dust deposition, mean surface PM10 and column integrated PM10 concentrations in the downwind domains are found to decrease away from the source region from 2.44 t km-2, 112 μg m-3 and 1.68 g m-2, respectively in the domain YES to 0.06 t km-2, 2.1 μg m-3 and 0.4 g m-2, respectively in the domain Northwestern Pacific 1 (NWP1). Much of the total dust deposition is largely contributed by wet deposition in the far downwind region of the seas while that is contributed by dry deposition in the source region.

Compositions of modern dust and surface sediments in the Desert Southwest, United States

USGS Publications Warehouse

Reheis, M.C.; Budahn, J.R.; Lamothe, P.J.; Reynolds, R.L.

2009-01-01

Modern dusts across southwestern United States deserts are compositionally similar to dust-rich Av soil horizons (depths of 0-0.5 cm and 1-4 cm at 35 sites) for common crustal elements but distinctly different for some trace elements. Chemical compositions and magnetic properties of the soil samples are similar among sites relative to dust sources, geographic areas, and lithologic substrates. Exceptions are Li, U, and W, enriched in Owens Valley, California, and Mg and Sr, enriched in soils formed on calcareous fan gravel in southeast Nevada. The Av horizons are dominated by dust and reflect limited mixing with substrate sediments. Modern dust samples are also similar across the region, except that Owens Valley dusts are higher in Mg, Ba, and Li and dusts both there and at sites to the north on volcanic substrates are higher in Sb and W. Thus, dust and Av horizons consist of contributions from many different sources that are well mixed before deposition. Modern dusts contain significantly greater amounts of As, Cd, Cr, Cu, Ni, Pb, and Sb than do Av horizons, which record dust additions over hundreds to thousands of years. These results suggest that modern dust compositions are influenced by anthropogenic sources and emissions from Owens (dry) Lake after its artificial desiccation in 1926. Both modern dusts and Av horizons are enriched in As, Ba, Cu, Li, Sb, Th, U, and W relative to average crustal composition, which we interpret to indicate that the geologic sources of dust in the southwestern United States are geochemically distinctive.

Dust loading of the normal atmosphere

NASA Astrophysics Data System (ADS)

Hall, F. F., Jr.

1983-01-01

Soil dust can contribute to atmospheric turbidity over most of the globe. The major sources of this dust are in the world's arid regions, where loadings of over 1000 micrograms/cu m can occur during strong winds. Saharan dust transported across the Atlantic can produce loadings up to 100 micrograms/cu m in the Western Hemisphere. Asian sources yield springtime loadings of 5-10 micrograms/cu m at Midway Island. Other important sources of dust are agricultural plowing and vehicular traffic on graded roads. The U.S. air quality standard of 75 micrograms/cu m is often exceeded in rural areas.

Using 87Sr/86Sr Ratios of Carbonate Minerals in Dust to Quantify Contributions from Desert Playas to the Urban Wasatch Front, Utah, USA

NASA Astrophysics Data System (ADS)

Goodman, M.; Carling, G. T.; Fernandez, D. P.; Rey, K.; Hale, C. A.; Nelson, S.; Hahnenberger, M.

2017-12-01

Desert playas are important dust sources globally, with potential harmful health impacts for nearby urban areas. The Wasatch Front (population >2 million) in western Utah, USA, is located directly downwind of several playas that contribute to poor air quality on dust event days. Additionally, the exposed lakebed of nearby Great Salt Lake is a growing dust source as water levels drop in response to drought and river diversions. To investigate contributions of playa dust to the Wasatch Front, we sampled dust emissions from the exposed lakebed of Great Salt Lake and seven playas in western Utah, including Sevier Dry Lake, and dust deposition at four locations stretching 160 km from south to north along the Wasatch Front, including Provo, Salt Lake City, Ogden, and Logan. The samples were analyzed for mineralogy, bulk chemistry, and 87Sr/86Sr ratios for source apportionment. The mineralogy of playa dust and Wasatch Front dust samples was dominated by quartz, feldspar, chlorite and calcite. Bulk geochemical composition was similar for all playa dust sources, with higher anthropogenic metal concentrations in the Wasatch Front. Strontium isotope (87Sr/86Sr) ratios in the carbonate fraction of the dust samples were variable in the playa dust sources, ranging from 0.7105 in Sevier Dry Lake to 0.7150 in Great Salt Lake, providing a powerful tool for apportioning dust. Based on 87Sr/86Sr mixing models, Great Salt Lake contributed 0% of the dust flux at Provo, 20% of the dust flux at Salt Lake City, and 40% of the dust flux at Ogden and Logan during Fall 2015. Contrastingly, Great Salt Lake dust was less important in Spring of 2016, contributing 0% of the dust flux at Provo and <10% of the dust flux to Salt Lake City and Logan. Two major dust events that occurred on 3 November 2015 and 23 April 2016 had similar wind and climate conditions as understood by HYSPLIT backward trajectories, meaning that seasonal variability in dust emissions is due to playa surface conditions rather than meteorologic conditions. Further sampling and analysis are needed to understand and quantify patterns in seasonal changes in dust emissions and deposition. These findings suggest that 87Sr/86Sr ratios of the carbonate fraction in dust may be useful for evaluating dust emissions from carbonate-rich playas around the world.

Dust Production and Particle Acceleration in Supernova 1987A Revealed with ALMA

NASA Technical Reports Server (NTRS)

Indebetouw, R.; Matsuura, M.; Dwek, E.; Zanardo, G.; Barlow, M. J.; Baes, M.; Bouchet, P.; Burrows, D. N.; Chevalier, R.; Clayton, G. C.;

A new false color composite technique for dust enhancement and point source determination in Middle East

NASA Astrophysics Data System (ADS)

Karimi, Khadijeh; Taheri Shahraiyni, Hamid; Habibi Nokhandan, Majid; Hafezi Moghaddas, Naser; Sanaeifar, Melika

2011-11-01

The dust storm happens in the Middle East with very high frequency. According to the dust storm effects, it is vital to study on the dust storms in the Middle East. The first step toward the study on dust storm is the enhancement of dust storms and determination of the point sources. In this paper, a new false color composite (FCC) map for the dust storm enhancement and point sources determination in the Middle East has been developed. The 28 Terra-MODIS images in 2008 and 2009 were utilized in this study. We tried to replace the Red, Green and Blue bands in RGB maps with the bands or maps that enhance the dust storms. Hence, famous indices for dust storm detection (NDDI, D and BTD) were generated using the different bands of MODIS images. These indices with some bands of MODIS were utilized for FCC map generation with different combinations. Among the different combinations, four better FCC maps were selected and these four FCC are compared using visual interpretation. The results of visual interpretations showed that the best FCC map for enhancement of dust storm in the middle east is an especial combination of the three indices (Red: D, Green: BTD and Blue: NDDI). Therefore, we utilized of this new FCC method for the enhancement of dust storms and determination of point sources in Middle East.

Insight to forcing of late Quaternary climate change from aeolian dust archives in eastern Australia

NASA Astrophysics Data System (ADS)

McGowan, H. A.; Marx, S.; Soderholm, J.; Denholm, J.; Petherick, L.

2010-12-01

The Australian continent is the largest source of dust in the Southern Hemisphere. Historical dust emissions records display inter-annual variability in response to the El Niño Southern Oscillation (ENSO) phenomenon and inter-decadal variability which has been linked to the Pacific Decadal Oscillation (PDO). These reflect change in hydrometeorology of the continents two major dust source regions, the Murray-Darling Basin and the Lake Eyre Basin. The historical records do not allow longer term variability of ENSO and the PDO and their influence on Australia to be quantified. Importantly, sub-Milankovitch centennial to multi-millennial scale climate cycles and their impacts are not represented in the historical records. In this paper we present summary results from the analysis of two aeolain dust records spanning 7 ka and 45 ka. These were developed from ombrotrophic mire and lacustrine sediment cores collected from the Australian Alps and southeast Queensland. Both sites are located in the southeast Australian dust transport pathway and provide rare insight to forcings of climate variability and its impacts on eastern Australia through the late Quaternary. Age controls for the cores were established using 14C and 210Pb dating [McGowan et al. 2008, 2010]. The cores were sliced into 2 to 5 mm segments with a sub-sample of each segment combusted at 450°C for 12 hrs to destroy organic material and allow recovery of mineral dust. Geochemical fingerprinting of the < 90 µm fraction of the dust was used to determine provenance and to account for contamination by fluvial and/or colluvial sediments [Marx et al. 2005]. Analysis of the dust records, proxy for hydrometeorology, identified tropical ocean teleconnections, variability of solar irradiance and change in ocean deep water circulation as the principal causes of inter-decadal to centennial scale climate cycles and change. Predictions of future climate must consider these forcings so that in water scarce regions of Australia the effect on the hydroclimate is incorporated into the design of water allocation policy and infrastructure, and the management of environmental systems. Comparison with ice core records from Greenland and Antarctica indicate both synchronicity of global climate variability and the impact of forcings originating from the North Hemisphere. These results highlight the potential for adverse impacts on the climate of Australia by disturbance to North Atlantic Ocean circulation. References Marx, S. K., et al. 2005: Provenance of long travelled dust determined with ultra trace element composition: A pilot study with samples from New Zealand glaciers. Earth Surf. Processes Landforms, 30, 699-716. McGowan, H.A., et al. 2008: An ultra-high resolution record of aeolian sedimentation during the late Quaternary from eastern Australia. Palaeogeogr. Palaeoclimatol. Palaeoecol., 265(3-4), 171-181. McGowan, H. A., et al. 2010: Evidence of solar and tropical ocean forcing of hydroclimate cycles in southeastern Australia for the past 6500 years. Geophys. Res. Lett., 37, L10705, doi:10.1029/2010GL042918.

Large-Scale Structure of the Carina Nebula.

PubMed

Smith; Egan; Carey; Price; Morse; Price

2000-04-01

Observations obtained with the Midcourse Space Experiment (MSX) satellite reveal for the first time the complex mid-infrared morphology of the entire Carina Nebula (NGC 3372). On the largest size scale of approximately 100 pc, the thermal infrared emission from the giant H ii region delineates one coherent structure: a (somewhat distorted) bipolar nebula with the major axis perpendicular to the Galactic plane. The Carina Nebula is usually described as an evolved H ii region that is no longer actively forming stars, clearing away the last vestiges of its natal molecular cloud. However, the MSX observations presented here reveal numerous embedded infrared sources that are good candidates for sites of current star formation. Several compact infrared sources are located at the heads of dust pillars or in dark globules behind ionization fronts. Because their morphology suggests a strong interaction with the peculiar collection of massive stars in the nebula, we speculate that these new infrared sources may be sites of triggered star formation in NGC 3372.

Using thermal infrared (TIR) data to characterize dust sources, dust fall and the linkage to climate in the Middle East

NASA Astrophysics Data System (ADS)

Mohammad, R.; Ramsey, M.; Scheidt, S. P.

2010-12-01

Prior to mineral dust deposition affecting albedo, aerosols can have direct and indirect effects on local to regional scale climate by changing both the shortwave and longwave radiative forcing. In addition, mineral dust causes health hazards, such as respiratory-related illnesses and deaths, loss of agricultural soil, and safety hazards to aviation and motorists due to reduced visibility. Previous work utilized satellite and ground-based TIR data to describe the direct longwave radiative effect of the Saharan Air Layer (SAL) over the Atlantic Ocean originating from dust storms in the Western Sahara. TIR emission spectroscopy was used to identify the spectral absorption features of that dust. The current research focuses on Kuwait and utilizes a comprehensive set of spatial, analytical and geological tools to characterize dust emissions and its radiative effects. Surface mineral composition maps for the Kuwait region were created using ASTER images and GIS datasets in order to identify the possible sources of wind-blown dust. Backward trajectory analysis using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model suggests the dust source areas were located in Iraq, Syria, Jordan and Saudi Arabia. Samples collected from two dust storms (May and July 2010) were analyzed for their mineral composition and to validate the dust source areas identified by the modeling and remote sensing analysis. These air fall dust samples were collected in glass containers on a 13 meter high rooftop in the suburb of Rumaithiya in Kuwait. Additional samples will be collected to expand the analysis and their chemical compositions will be characterized by a combination of laboratory X-ray fluorescence (XRF), Scanning Electron Microscopy (SEM) and TIR emission spectroscopy. The overarching objective of this ongoing research is to both characterize the effects of mineral dust on climate as well as establish a predictive tool that can identify dust storm sources and potentially aid in establishing a more accurate prediction and warning system in the Middle East region.

Environmental determinants of different blood lead levels in children: a quantile analysis from a nationwide survey.

PubMed

Etchevers, Anne; Le Tertre, Alain; Lucas, Jean-Paul; Bretin, Philippe; Oulhote, Youssef; Le Bot, Barbara; Glorennec, Philippe

2015-01-01

Blood lead levels (BLLs) have substantially decreased in recent decades in children in France. However, further reducing exposure is a public health goal because there is no clear toxicological threshold. The identification of the environmental determinants of BLLs as well as risk factors associated with high BLLs is important to update prevention strategies. We aimed to estimate the contribution of environmental sources of lead to different BLLs in children in France. We enrolled 484 children aged from 6months to 6years, in a nationwide cross-sectional survey in 2008-2009. We measured lead concentrations in blood and environmental samples (water, soils, household settled dusts, paints, cosmetics and traditional cookware). We performed two models: a multivariate generalized additive model on the geometric mean (GM), and a quantile regression model on the 10th, 25th, 50th, 75th and 90th quantile of BLLs. The GM of BLLs was 13.8μg/L (=1.38μg/dL) (95% confidence intervals (CI): 12.7-14.9) and the 90th quantile was 25.7μg/L (CI: 24.2-29.5). Household and common area dust, tap water, interior paint, ceramic cookware, traditional cosmetics, playground soil and dust, and environmental tobacco smoke were associated with the GM of BLLs. Household dust and tap water made the largest contributions to both the GM and the 90th quantile of BLLs. The concentration of lead in dust was positively correlated with all quantiles of BLLs even at low concentrations. Lead concentrations in tap water above 5μg/L were also positively correlated with the GM, 75th and 90th quantiles of BLLs in children drinking tap water. Preventative actions must target household settled dust and tap water to reduce the BLLs of children in France. The use of traditional cosmetics should be avoided whereas ceramic cookware should be limited to decorative purposes. Copyright © 2014 Elsevier Ltd. All rights reserved.

IRAS observations of a large circumstellar dust shell around W Hydrae

NASA Technical Reports Server (NTRS)

Hawkins, G. W.

1990-01-01

IRAS observations at 60 and 100 microns reveal a large 30-40-arcmin (about 1-pc) diameter dust shell centered on the oxygen-rich red giant W Hya. Except for SNRs, this is the largest mass-loss envelope, in apparent diameter, known around any evolved star, including PN. W Hya's radiation field, stronger than the interstellar radiation field in the outer envelope, is sufficient to heat dust grains with IR emissivity proportional to lambda exp -1.2 to temperatures of about 40 K implied by the ratio of intensities at 60 and 100 microns.

Online Characterisation of Mineral Dust Aerosol by Single Particle Mass Spectrometry: Mineralogical Signatures of Potential Source Areas in North Africa.

NASA Astrophysics Data System (ADS)

Marsden, N. A.; Allan, J. D.; Flynn, M.; Ullrich, R.; Moehler, O.; Coe, H.

2017-12-01

The mineralogy of individual dust particles is important for atmospheric processes because mineralogy influences optical properties, their potential to act as ice nucleating particles (INP) and geochemical cycling of elements to the ocean. Bulk mineralogy of transported mineral dust has been shown to be a reflection of the source area and size fractionation during transport. Online characterisation of single particle mineralogy is highly desirable as the composition of individual particles can be reported at a temporal resolution that is relevant to atmospheric processes. Single particle mass spectrometry (SPMS) has indentified and characterised the composition of ambient dust particles but is hampered by matrix effects that result in a non-quantatative measurement of composition. The work presented describes a comparison of mass spectral characteristics of sub 2.5μm particle fractions generated from; i) nominally pure samples from the clay mineral society (CMS), ii) soil samples collected from potential source areas in North Africa and iii) ambient measurement of transported African dust made at the Cape Verde Islands. Using a novel approach to analyse the mass spectra, the distinct characteristics of the various dust samples are obtained from the online measurements. Using this technique it was observed that dust generated from sources on the North West Margin of the Sahara Desert have distinct characteristics of illite in contrast to the kaolinitic characteristics of dust generated from sources in the Sahel. These methods offer great potential for describing the hourly variation in the source and mineralogy of transported mineral dust and the online differentiation of mineral phase in multi-mineralic dust samples.

Satellite Reveals How Much Saharan Dust Feeds Amazon's Plants

NASA Image and Video Library

2015-02-24

What connects Earth's largest, hottest desert to its largest tropical rainforest? The Sahara Desert is a near-uninterrupted brown band of sand and scrub across the northern third of Africa. The Amazon rainforest is a dense green mass of humid jungle that covers northeast South America. But after strong winds sweep across the Sahara, a tan cloud rises in the air, stretches between the continents, and ties together the desert and the jungle. It’s dust. And lots of it. For the first time, a NASA satellite has quantified in three dimensions how much dust makes this trans-Atlantic journey. Scientists have not only measured the volume of dust, they have also calculated how much phosphorus – a natural plant fertilizer present in Saharan sands from part of the desert’s past as a lake bed – gets carried across the ocean from one of the planet’s most desolate places to one of its most fertile. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Migration of Matter from the Edgeworth-Kuiper and Main Asteroid Belts to the Earth

NASA Technical Reports Server (NTRS)

Ipatov. S. I.; Oegerle, William (Technical Monitor)

2002-01-01

The main asteroid belt (MAB), the Edgeworth-Kuiper belt (EKB), and comets belong to the main sources of dust in the Solar System. Most of Jupiter-family comets came from the EKB. Comets can be distracted due to close encounters with planets and the Sun, collisions with small bodies, a nd internal forces. We support the Eneev's idea that the largest objects in the ELB and MAB could be formed directly by the compression of rarefied dust condensations of the protoplanetary cloud but not by the accretion of small (for example, 1-km) planetesimals. The total mass of planetesimals that entered the EKB from the feeding zone of the giant planets during their accumulation could exceed tens of Earth's masses. These planetesimals increased eccentricities of 'local' trans-Neptunian objects (TNOs) and swept most of these TNOs. A small portion of such planetesimals could left beyond Neptune's orbit in highly eccentric orbits. The results of previous investigations of migration and collisional evolution of minor bodies were summarized. Mainly our recent results are presented.

Effects of microwave radiation on house dust mites, Dermatophagoides pteronyssinus and Dermatophagoides farinae (Astigmata: Pyroglyphidae).

PubMed

Ernieenor, F C L; Ho, T M

2010-11-01

Dermatophagoides pteronyssinus and Dermatophagoides farinae mites are commonly found in house dust, and are important sources of allergens affecting humans. Various approaches to killing the mites have been examined. This study investigated the mortalities of adult mites exposed to 2,450 MHz microwave radiation produced by 3 ovens at various exposure times and power settings. The ovens all had 3 power settings. The average maximum water temperatures generated at high, medium and low power settings were 99.4 +/- 0.2, 84.1 +/- 0.4 and 44.8 +/- 0.9 degrees C, respectively. At high and medium settings, there was 100.0% mortality in both species when exposed for 300 seconds. The mean mortality rates at low power were 10.8 +/- 0.7% for D. pteronyssinus and 9.7 +/- 2.6% for D. farinae. When mites were exposed in the presence of culture media, the mortality rates decreased with increasing weight of media. The mean mortality with the largest amount of media tested at high power setting was 61.4%.

Analysis of land surface and synoptic conditions during dust storm events in the Middle East via a new high resolution inventory of mineral dust derived from SEVIRI.

NASA Astrophysics Data System (ADS)

Hennen, Mark

2017-04-01

This paper provides the most up-to-date dust climatology for the Middle East, presenting a new high resolution inventory of over 27,000 dust emission events observed over the Middle East in 2006 - 2013. The inventory was derived from the dust RGB product of the Spinning Enhanced Visual and InfraRed Imager (SEVIRI) on-board Meteosat's second generation satellite (MSG). Mineral dust emissions were derived from visual inspection of the SEVIRI scenes which have 4-5 km2 spatial and 15-minute temporal resolution. The location of every emission event was recorded in a database, along with time and trajectory of dust movement. This is an improvement on previous studies, which derive dust source areas from the daily observations of Aerosol Optical Depth whose maxima do not necessarily coincide with sources of emissions and produces more accurate information on the location of the key dust sources in the region. Results showed that dust sources are constrained to relatively small areas, with 21% of dust emission generated from just 0.9% of total surface area of the Middle East, mainly from eight source regions including the Tigris-Euphrates flood plains of Iraq and Syria, Western and Northern Saudi Arabia and the Sistan Basin in Eastern Iran. The Tigris-Euphrates flood plain was the most active dust region, producing 41% of all dust events with a peak activity in 2009. The southern areas of the Arabian Peninsula recorded very few dust emission observations, in contrast to many previous studies which do not use such high temporal resolution data. The activation and frequency of dust emissions are characterised by strong seasonality developing in response to specific synoptic conditions. To characterise synoptic conditions conducive to the development of dust storms, dust days' emission thresholds, based on number of dust emission events per day / per region and specific to each of the eight main dust emitting regions, were determined. ERA Interim reanalysis data were used to characterise synoptic conditions on the identified dust days. With vegetation cover dictating the ability for surface areas to deflate, Normalised Difference Vegetation Index (NDVI) data was acquired from the Moderate Resolution Imaging Spectrodiometer (MODIS) (MOD13A2) 1km database and correlated with dust emission frequency data in the region of greatest dust activity, the Tigris and Euphrates flood plain in Iraq and Syria.

Trans boundary transport of pollutants by atmospheric mineral dust.

PubMed

Erel, Yigal; Dayan, Uri; Rabi, Reut; Rudich, Yinon; Stein, Mordechai

2006-05-01

The transport of anthropogenic pollution by desert dust in the Eastern Mediterranean region was studied by analyzing major and trace element composition, organic species, and Pb isotope ratios in suspended dust samples collected in Jerusalem, Israel. Dust storms in this region are associated with four distinct synoptic conditions (Red Sea Trough (RS), Eastern High (EH), Sharav Cyclone (SC), and Cold Depression (Cyprus low, CD)) that carry dust mostly from North African (SC, CD, EH) and Arabian and Syrian (RS, EH) deserts. Substantial contamination of dust particles by Pb, Cu, Zn, and Ni is observed, while other elements (Na, Ca, Mg, Mn, Sr, Rb, REE, U, and Th) display natural concentrations. Sequential extraction of the abovementioned elements from the dust samples shows that the carbonate and sorbed fractions contain most of the pollution, yet the Al-silicate fraction is also contaminated, implying that soils and sediments in the source terrains of the dust are already polluted. We identified the pollutant sources by using Pb isotopes. It appears that before the beginning of the dust storm, the pollutants in the collected samples are dominated by local sources but with the arrival of dust from North Africa, the proportion of foreign pollutants increases. Organic pollutants exhibit behavior similar and complementary to that of the inorganic tracers, attesting to the importance of anthropogenic-pollutant addition en route of the dust from its remote sources. Pollution of suspended dust is observed under all synoptic conditions, yet it appears that easterly winds carry higher proportions of local pollution and westerly winds carry pollution emitted in the Cairo basin. Therefore, pollution transport by mineral dust should be accounted for in environmental models and in assessing the health-related effects of mineral dust.

Dust Storm Hits Canary Islands

NASA Technical Reports Server (NTRS)

2002-01-01

A thick pall of sand and dust blew out from the Sahara Desert over the Atlantic Ocean yesterday (January 6, 2002), engulfing the Canary Islands in what has become one of the worst sand storms ever recorded there. In this scene, notice how the dust appears particularly thick in the downwind wake of Tenerife, the largest of the Canary Islands. Perhaps the turbulence generated by the air currents flowing past the island's volcanic peaks is churning the dust back up into the atmosphere, rather than allowing it to settle toward the surface. This true-color image was captured by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite, on January 7, 2002. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

Enhancing weak transient signals in SEVIRI false color imagery: Application to dust source detection in southern Africa

NASA Astrophysics Data System (ADS)

Murray, J. E.; Brindley, H. E.; Bryant, R. G.; Russell, J. E.; Jenkins, K. F.; Washington, R.

2016-09-01

A method is described to significantly enhance the signature of dust events using observations from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI). The approach involves the derivation of a composite clear-sky signal for selected channels on an individual time step and pixel basis. These composite signals are subtracted from each observation in the relevant channels to enhance weak transient signals associated with either (a) low levels of dust emission or (b) dust emissions with high salt or low quartz content. Different channel combinations, of the differenced data from the steps above, are then rendered in false color imagery for the purpose of improved identification of dust source locations and activity. We have applied this clear-sky difference (CSD) algorithm over three (globally significant) source regions in southern Africa: the Makgadikgadi Basin, Etosha Pan, and the Namibian and western South African coast. Case study analyses indicate three notable advantages associated with the CSD approach over established image rendering methods: (i) an improved ability to detect dust plumes, (ii) the observation of source activation earlier in the diurnal cycle, and (iii) an improved ability to resolve and pinpoint dust plume source locations.

Constant Chinese Loess Plateau dust source since the Late Miocene

NASA Astrophysics Data System (ADS)

Bird, Anna; Millar, Ian; Stevens, Thomas; Rodenburg, Tanja; Rittner, Martin; Vermeesch, Pieter; Lu, Huayu

2017-04-01

The dramatic deepening of northern hemisphere glaciation at the Pliocene-Pleistocene boundary is accompanied by major changes in global climate. The role of the global atmospheric dust cycle in this event is not clear; in particular, whether, changes in the dust cycle influenced climates change, or resulted from it. Miocene and Quaternary wind-blown Chinese loess records past dust-cycle history, influences of aridification and monsoon circulation. Previous work on the vast Chinese Loess Plateau is in conflict over whether changes in dust source occur at the Pliocene-Pleistocene boundary (2.59 Ma), or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics (Sun 2005; Nie et al. 2014a). Here we present Sr, Nd and Hf isotopic data from multiple sites and show that the dust source remains the same across these boundaries. The use of isotope tracers from multiple sites allows us to demonstrate that shifts in sediment geochemistry can be explained by grain-size and weathering changes. Nd and Hf isotopes show that the dust was dominantly sourced from the Tibetan Plateau, with some input from bedrock underlying the Badain Jaran/Tengger deserts. This shows that a major established and constant dust source on the northern Tibetan Plateau has been active and unchanged since the late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are therefore a function of climate change in the Tibetan Plateau source regions rather than due to expanding source areas controlled by aridification over a widening area over the Pliocene and Quaternary.

Multi-Decadal Aerosol Variations from 1980 to 2009: A Perspective from Observations and a Global Model

NASA Technical Reports Server (NTRS)

Chin, Mian; Diehl, T.; Tan, Q.; Prospero, J. M.; Kahn, R. A.; Remer, L. A.; Yu, H.; Sayer, A. M.; Bian, H.; Geogdzhayev, I. V.;

High-Resolution Submillimeter and Near-Infrared Studies of the Transition Disk around Sz 91

NASA Technical Reports Server (NTRS)

Tsukagoshi, Takashi; Momose, Munetake; Hashimoto, Jun; Kudo, Tomoyuki; Andrews, Sean; Saito, Masao; Kitamura, Yoshimi; Ohashi, Nagayoshi; Wilner, David; Kawabe, Ryohei;

Type II supernovae as a significant source of interstellar dust.

PubMed

Dunne, Loretta; Eales, Stephen; Ivison, Rob; Morgan, Haley; Edmunds, Mike

2003-07-17

Large amounts of dust (>10(8)M(o)) have recently been discovered in high-redshift quasars and galaxies corresponding to a time when the Universe was less than one-tenth of its present age. The stellar winds produced by stars in the late stages of their evolution (on the asymptotic giant branch of the Hertzsprung-Russell diagram) are thought to be the main source of dust in galaxies, but they cannot produce that dust on a short enough timescale (&<1 Gyr) to explain the results in the high-redshift galaxies. Supernova explosions of massive stars (type II) are also a potential source, with models predicting 0.2-4M(o) of dust. As massive stars evolve rapidly, on timescales of a few Myr, these supernovae could be responsible for the high-redshift dust. Observations of supernova remnants in the Milky Way, however, have hitherto revealed only 10(-7)-10(-3)M(o) each, which is insufficient to explain the high-redshift data. Here we report the detection of approximately 2-4M(o) of cold dust in the youngest known Galactic supernova remnant, Cassiopeia A. This observation implies that supernovae are at least as important as stellar winds in producing dust in our Galaxy and would have been the dominant source of dust at high redshifts.

Influence of the Latitudinal Temperature Gradient on Soil Dust Concentration and Deposition in Greenland

NASA Technical Reports Server (NTRS)

Tegen, Ina; Rind, David

2000-01-01

To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the Goddard Institute for Space Studies General Circulation Model (GISS GCM) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.

High-latitude dust in the Earth system

USGS Publications Warehouse

Bullard, Joanna E; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; NcKenna Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

2016-01-01

Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 km2 and contribute at least 80–100 Tg yr−1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

High Latitude Dust in the Earth System

NASA Technical Reports Server (NTRS)

Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert;

X-Ray Dust Tomography: Mapping the Galaxy one X-ray Transient at a Time

NASA Astrophysics Data System (ADS)

Heinz, Sebastian; Corrales, Lia

2018-01-01

Tomography using X-ray light echoes from dust scattering by interstellar clouds is an accurate tool to study the line-of-sight distribution of dust. It can be used to measure distances to molecular clouds and X-ray sources, it can map Galactic structure in dust, and it can be used for precision measurements of dust composition and grain size distribution. Necessary conditions for observing echoes include a suitable X-ray lightcurve and sufficient dust column density to the source. I will discuss a tool set for studying dust echoes and show results obtained for some of the brightest echoes detected to date.

Pacific patterns of dust deposition, iron supply and export production

NASA Astrophysics Data System (ADS)

Winckler, G.; Anderson, R. F.; Park, J.; Schwartz, R.; Pahnke, K.; Struve, T.; Lamy, F.; Gersonde, R.

2015-12-01

The scarcity of iron limits marine export production and carbon uptake in about a quarter of the global ocean where the surface concentration of nitrate and phosphate is high, as biological utilization of these macronutrients is incomplete. Of these high nutrient low chlorophyll (HNLC) regions, the Southern Ocean is the region where variations in iron availability can have the largest effect on Earth's carbon cycle through its fertilizing effect on marine ecosystems, both in the modern and in the past. Recent work in the Subantarctic South Atlantic (Martínez-Garcia et al., 2009, 2014, Anderson et al., 2014) suggests that dust-driven iron fertilization lowered atmospheric CO2 by up to 40 ppm in the latter half of each glacial cycle of the late Pleistocene, with the increase in Subantarctic productivity consuming a greater fraction of the surface nutrients and thus driving more storage of carbon in the ocean interior. The other sectors of the Southern Ocean remain poorly constrained, including the Pacific Sector, that accounts for the largest surface area of the Subantarctic Southern Ocean. Here we report records of dust deposition, iron supply and export production from a set of cores from the Subantarctic Pacific (PS75, Lamy et al 2014) and initial results about the origin of dust transported to the Subantarctic Pacific Ocean from radiogenic isotopes and rare earth elements. We test how tightly dust and biological productivity are coupled over glacial/interglacial and millennial timescales in the Subantarctic Pacific and place the region in a context of global patterns of biological productivity, nutrient utilization and iron fertilization by dust, including comparisons to the other Pacific HNLC regions, the Subarctic North Pacific and equatorial Pacific.

Low latitude ice core evidence for dust deposition on high altitude glaciers

NASA Astrophysics Data System (ADS)

Gabrielli, P.; Thompson, L. G.

2017-12-01

Polar ice cores from Antarctica and Greenland have provided a wealth of information on dust emission, transport and deposition over glacial to interglacial timescales. These ice cores mainly entrap dust transported long distances from source areas such as Asia for Greenland and South America for Antarctica. Thus, these dust records provide paleo-information about the environmental conditions at the source and the strength/pathways of atmospheric circulation at continental scales. Ice cores have also been extracted from high altitude glaciers in the mid- and low-latitudes and provide dust records generally extending back several centuries and in a few cases back to the last glacial period. For these glaciers the potential sources of dust emission include areas that are close or adjacent to the drilling site which facilitates the potential for a strong imprinting of local dust in the records. In addition, only a few high altitude glaciers allow the reconstruction of past snow accumulation and hence the expression of the dust records in terms of fluxes. Due to their extreme elevation, a few of these high altitude ice cores offer dust histories with the potential to record environmental conditions at remote sources. Dust records (in terms of dust concentration/size, crustal trace elements and terrigenous cations) from Africa, the European Alps, South America and the Himalayas are examined over the last millennium. The interplay of the seasonal atmospheric circulation (e.g. westerlies, monsoons and vertical convection) is shown to play a major role in determining the intensity and origin of dust fallout to the high altitude glaciers around the world.

Ground truth of (sub-)micrometre cometary dust - Results of MIDAS onboard Rosetta

NASA Astrophysics Data System (ADS)

Mannel, Thurid; Bentley, Mark; Schmied, Roland; Torkar, Klaus; Jeszenszky, Harald; Romsted, Jens; Levasseur-Regourd, A.; Weber, Iris; Jessberger, Elmar K.; Ehrenfreund, Pascale; Köberl, Christian; Havnes, Ove

2016-10-01

The investigation of comet 67P by Rosetta has allowed the comprehensive characterisation of pristine cometary dust particles ejected from the nucleus. Flying alongside the comet at distances as small as a few kilometres, and with a relative velocity of only centimetres per second, the Rosetta payload sampled almost unaltered dust. A key instrument to study this dust was MIDAS (the Micro-Imaging Dust Analysis System), a dedicated atomic force microscope that scanned the surfaces of hundreds of (sub-)micrometre sized particles in 3D with resolutions down to nanometres. This offers the unique opportunity to explore the morphology of smallest cometary dust and expand our current knowledge about cometary material.Here we give an overview of dust collected and analysed by MIDAS and highlight its most important features. These include the ubiquitous agglomerate nature of the dust, which is found at all size scales from the largest (>10 µm) through to the smallest (<1 µm) dust particles. The sub-units show characteristic sizes and shapes that are compared with model predictions for interstellar dust.Our findings constrain key parameters of the evolution of the early Solar System. We will discuss which dust growth model is favoured by the observed morphology and how the results restrict cometary formation. Finally, dust particles detected by MIDAS resemble primitive interplanetary dust which is a strong argument for a common cometary origin.

Source diagnostics of polycyclic aromatic hydrocarbons in urban road runoff, dust, rain and canopy throughfall.

PubMed

Zhang, Wei; Zhang, Shucai; Wan, Chao; Yue, Dapan; Ye, Youbin; Wang, Xuejun

2008-06-01

Diagnostic ratios and multivariate analysis were utilized to apportion polycyclic aromatic hydrocarbon (PAH) sources for road runoff, road dust, rain and canopy throughfall based on samples collected in an urban area of Beijing, China. Three sampling sites representing vehicle lane, bicycle lane and branch road were selected. For road runoff and road dust, vehicular emission and coal combustion were identified as major sources, and the source contributions varied among the sampling sites. For rain, three principal components were apportioned representing coal/oil combustion (54%), vehicular emission (34%) and coking (12%). For canopy throughfall, vehicular emission (56%), coal combustion (30%) and oil combustion (14%) were identified as major sources. Overall, the PAH's source for road runoff mainly reflected that for road dust. Despite site-specific sources, the findings at the study area provided a general picture of PAHs sources for the road runoff system in urban area of Beijing.

Working Group on Circumstellar/Interstellar Relationships

NASA Technical Reports Server (NTRS)

Glassgold, A. E.

1986-01-01

Stars of various types are believed to be the main source of interstellar (IS) dust grans. The most important confirmed source is evolved giant and supergiant stars. Supernovae also contribute to the mass loss. The differences between circumstellar (CS) and IS dust were reviewed using the following topics: alteration of CS dust grains, size distribution, space observation of CS and IS dust, comparison of infrared spectra, isotopic signatures, Magellanic clouds and nearby galaxies, life cycles of dust grains, and physical and chemical data.

Singlet Oxygen Production by Illuminated Road Dust and Winter Street Sweepings

NASA Astrophysics Data System (ADS)

Schneider, S.; Gan, L.; Gao, S.; Hoy, K. S.; Kwasny, J. R.; Styler, S. A.

2017-12-01

Road dust is an important urban source of primary particulate matter, especially in cities where sand and other traction materials are applied to roadways in winter. Although the composition and detrimental health effects of road dust are reasonably well characterized, little is currently known regarding its chemical behaviour. Motivated by our previous work, in which we showed that road dust is a photochemical source of singlet oxygen (1O2), we investigated 1O2 production by bulk winter street sweepings and by road dust collected in a variety of urban, industrial, and suburban locations in both autumn and spring. In all cases, the production of 1O2 by road dust was greater than that by Arizona test dust and desert-sourced dust, which highlights the unique photochemical environment afforded by this substrate. Mechanistically, we observed correlations between 1O2 production and the UV absorbance properties of dust extracts, which suggests the involvement of chromophoric dissolved organic matter in the observed photochemistry. Taken together, this work provides evidence that road dust-mediated photochemistry may influence the environmental lifetime of pollutants that react via 1O2-mediated pathways, including polycyclic aromatic hydrocarbons.

Infrared analysis of LMC superbubbles

NASA Technical Reports Server (NTRS)

Verter, Fran; Dwek, Eli

1990-01-01

Researchers are analyzing three superbubbles in the Large Magellanic Cloud (LMC), cataloged by Meaburn (1980) as LMC-1, LMC-4 (a.k.a. Shapley Constellation III), and LMC-5. Superbubbles are the largest infrared sources in the disks of external galaxies. Their expansion requires multiple supernovae from successive generations of star formation. In LMC superbubbles, the grains swept up by shocks and winds represent an interstellar medium (ISM) whose abundances are quite different from the Galaxy. By applying the Dwek (1986) grain model, we can derive the composition and size spectrum of the grains. The inputs to this model are the dust emission in the four Infrared Astronomy Satellite (IRAS) bands and the interstellar radiation field (ISRF) that provides the heating. The first step in the project is to derive the ISRF for star-forming regions on the periphery of superbubbles. Researchers are doing this by combining observations at several wavelengths to determine the energy budget of the region. They will use a UV image to trace the ionizing stellar radiation that escapes, an H alpha image to trace the ionizing stellar radiation that is absorbed by gas, and the four IRAS images to trace the stellar radiation, both ionizing and non-ionizing, that is absorbed by dust. This multi-wavelength approach has the advantages that we do not have to assume the shape of the IMF or the extinction of the source.

Eolian Dust and the Origin of Sedimentary Chert

USGS Publications Warehouse

Cecil, C. Blaine

2004-01-01

This paper proposes an alternative model for the primary source of silica contained in bedded sedimentary chert. The proposed model is derived from three principal observations as follows: (1) eolian processes in warm-arid climates produce copious amounts of highly reactive fine-grained quartz particles (dust), (2) eolian processes in warm-arid climates export enormous quantities of quartzose dust to marine environments, and (3) bedded sedimentary cherts generally occur in marine strata that were deposited in warm-arid paleoclimates where dust was a potential source of silica. An empirical integration of these observations suggests that eolian dust best explains both the primary and predominant source of silica for most bedded sedimentary cherts.

Sources and Levels of PCBs in Indoor Environments

EPA Science Inventory

Source assessment• Primary sources – caulk and light ballasts (6 schools)• Secondary sources – paint, tile, furnishings, etc. (3 schools)• Emission rate estimation Environmental levels (6 schools except dust)• Air, surface, dust, soil PCB c...

Detection of anthropogenic dust using CALIPSO lidar measurements

NASA Astrophysics Data System (ADS)

Huang, J.; Liu, J.; Chen, B.; Nasiri, S. L.

2015-04-01

Anthropogenic dusts are those produced by human activities on disturbed soils, which are mainly cropland, pasture, and urbanized regions and are a subset of the total dust load which includes natural sources from desert regions. Our knowledge of anthropogenic dusts is still very limited due to a lack of data on source distribution and magnitude, and on their effect on radiative forcing which may be comparable to other anthropogenic aerosols. To understand the contribution of anthropogenic dust to the total global dust load and its effect on radiative transfer and climate, it is important to identify them from total dust. In this study, a new technique for distinguishing anthropogenic dust from natural dust is proposed by using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) dust and planetary boundary layer (PBL) height retrievals along with a land use dataset. Using this technique, the global distribution of dust is analyzed and the relative contribution of anthropogenic and natural dust sources to regional and global emissions are estimated. Results reveal that local anthropogenic dust aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25% of the global continental dust load. Of these anthropogenic dust aerosols, more than 53% come from semi-arid and semi-wet regions. Annual mean anthropogenic dust column burden (DCB) values range from 0.42 g m-2 with a maximum in India to 0.12 g m-2 with a minimum in North America. A better understanding of anthropogenic dust emission will enable us to focus on human activities in these critical regions and with such knowledge we will be better able to improve global dust models and to explore the effects of anthropogenic emission on radiative forcing, climate change and air quality in the future.

Profiling of Saharan dust from the Caribbean to western Africa - Part 2: Shipborne lidar measurements versus forecasts

NASA Astrophysics Data System (ADS)

Ansmann, Albert; Rittmeister, Franziska; Engelmann, Ronny; Basart, Sara; Jorba, Oriol; Spyrou, Christos; Remy, Samuel; Skupin, Annett; Baars, Holger; Seifert, Patric; Senf, Fabian; Kanitz, Thomas

2017-12-01

A unique 4-week ship cruise from Guadeloupe to Cabo Verde in April-May 2013 see part 1, Rittmeister et al. (2017) is used for an in-depth comparison of dust profiles observed with a polarization/Raman lidar aboard the German research vessel Meteor over the remote tropical Atlantic and respective dust forecasts of a regional (SKIRON) and two global atmospheric (dust) transport models (NMMB/BSC-Dust, MACC/CAMS). New options of model-observation comparisons are presented. We analyze how well the modeled fine dust (submicrometer particles) and coarse dust contributions to light extinction and mass concentration match respective lidar observations, and to what extent models, adjusted to aerosol optical thickness observations, are able to reproduce the observed layering and mixing of dust and non-dust (mostly marine) aerosol components over the remote tropical Atlantic. Based on the coherent set of dust profiles at well-defined distances from Africa (without any disturbance by anthropogenic aerosol sources over the ocean), we investigate how accurately the models handle dust removal at distances of 1500 km to more than 5000 km west of the Saharan dust source regions. It was found that (a) dust predictions are of acceptable quality for the first several days after dust emission up to 2000 km west of the African continent, (b) the removal of dust from the atmosphere is too strong for large transport paths in the global models, and (c) the simulated fine-to-coarse dust ratio (in terms of mass concentration and light extinction) is too high in the models compared to the observations. This deviation occurs initially close to the dust sources and then increases with distance from Africa and thus points to an overestimation of fine dust emission in the models.

Sensitivity of surface characteristics on the simulation of wind-blown-dust source in North America

NASA Astrophysics Data System (ADS)

Park, S. H.; Gong, S. L.; Gong, W.; Makar, P. A.; Moran, M. D.; Stroud, C. A.; Zhang, J.

Recently, a wind-blown-dust-emission module has been built based on a state-of-the-art wind erosion theory and evaluated in a regional air-quality model to simulate a North American dust storm episode in April 2001 (see Park, S.H., Gong, S.L., Zhao, T.L., Vet, R.J., Bouchet, V.S., Gong, W., Makar, P.A., Moran, M.D., Stroud, C., Zhang, J. 2007. Simulation of entrainment and transport of dust particles within North America in April 2001 ("Red Dust episode"). J. Geophys. Res. 112, D20209, doi:10.1029/2007JD008443). A satisfactorily detailed assessment of that module, however, was not possible because of a lack of information on some module inputs, especially soil moisture content. In this paper, the wind-blown-dust emission was evaluated for two additional dust storms using improved soil moisture inputs. The surface characteristics of the wind-blown-dust source areas in southwestern North America were also investigated, focusing on their implications for wind-blown-dust emissions. The improved soil moisture inputs enabled the sensitivity of other important surface characteristics, the soil grain size distribution and the land-cover, to dust emission to be investigated with more confidence. Simulations of the two 2003 dust storm episodes suggested that wind-blown-dust emissions from the desert areas in southwestern North America are dominated by emissions from dry playas covered with accumulated alluvial deposits whose particle size is much smaller than usual desert sands. As well, the source areas in the northwestern Texas region were indicated to be not desert but rather agricultural lands that were "activated" as a wind-blown-dust sources after harvest. This finding calls for revisions to the current wind-blown-dust-emission module, in which "desert" is designated to be the only land-cover category that can emit wind-blown dust.

A survey of spatially distributed exterior dust lead loadings in New York City

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caravanos, Jack; Weiss, Arlene L.; School of Medicine, New York University, NY 10016

This work documents ambient lead dust deposition values (lead loading) for the boroughs of New York City in 2003-2004. Currently, no regulatory standards exist for exterior concentrations of lead in settled dust. This is in contrast to the clearance and risk assessment standards that exist for interior residential dust. The reported potential for neurobehavioral toxicity and adverse cognitive development in children due to lead exposure prompts public health concerns about undocumented lead sources. Such sources may include settled dust of outdoor origin. Dust sampling throughout the five boroughs of NYC was done from the top horizontal portion of pedestrian trafficmore » control signals (PTCS) at selected street intersections along main thoroughfares. The data (n=214 samples) show that lead in dust varies within each borough with Brooklyn having the highest median concentration (730{mu}g/ft{sup 2}), followed in descending order by Staten Island (452{mu}g/ft{sup 2}), the Bronx (382{mu}g/ft{sup 2}), Queens (198{mu}g/ft{sup 2}) and finally, Manhattan (175{mu}g/ft{sup 2}). When compared to the HUD/EPA indoor lead in dust standard of 40{mu}g/ft{sup 2}, our data show that this value is exceeded in 86% of the samples taken. An effort was made to determine the source of the lead in the dust atop of the PTCS. The lead in the dust and the yellow signage paint (which contains lead) were compared using isotopic ratio analysis. Results showed that the lead-based paint chip samples from intact signage did not isotopically match the dust wipe samples taken from the same surface. We know that exterior dust containing lead contributes to interior dust lead loading. Therefore, settled leaded dust in the outdoor environment poses a risk for lead exposure to children living in urban areas, namely, areas with elevated childhood blood lead levels and background lead dust levels from a variety of unidentified sources.« less

Integrated spatiotemporal characterization of dust sources and outbreaks in Central and East Asia

NASA Astrophysics Data System (ADS)

Darmenova, Kremena T.

The potential of atmospheric dust aerosols to modify the Earth's environment and climate has been recognized for some time. However, predicting the diverse impact of dust has several significant challenges. One is to quantify the complex spatial and temporal variability of dust burden in the atmosphere. Another is to quantify the fraction of dust originating from human-made sources. This thesis focuses on the spatiotemporal characterization of sources and dust outbreaks in Central and East Asia by integrating ground-based data, satellite multisensor observations, and modeling. A new regional dust modeling system capable of operating over a span of scales was developed. The modeling system consists of a dust module DuMo, which incorporates several dust emission schemes of different complexity, and the PSU/NCAR mesoscale model MM5, which offers a variety of physical parameterizations and flexible nesting capability. The modeling system was used to perform for the first time a comprehensive study of the timing, duration, and intensity of individual dust events in Central and East Asia. Determining the uncertainties caused by the choice of model physics, especially the boundary layer parameterization, and the dust production scheme was the focus of our study. Implications to assessments of the anthropogenic dust fraction in these regions were also addressed. Focusing on Spring 2001, an analysis of routine surface meteorological observations and satellite multi-sensor data was carried out in conjunction with modeling to determine the extent to which integrated data set can be used to characterize the spatiotemporal distribution of dust plumes at a range of temporal scales, addressing the active dust sources in China and Mongolia, mid-range transport and trans-Pacific, long-range transport of dust outbreaks on a case-by-case basis. This work demonstrates that adequate and consistent characterization of individual dust events is central to establishing a reliable climatology, ultimately leading to improved assessments of dust impacts on the environment and climate. This will also help to identify the appropriate temporal and spatial scales for adequate intercomparison between model results and observational data as well as for developing an integrated analysis methodology for dust studies.

Numerical simulations of Asian dust storms using a coupled climate-aerosol microphysical model

NASA Astrophysics Data System (ADS)

Su, Lin; Toon, Owen B.

2009-07-01

We have developed a three-dimensional coupled microphysical/climate model based on the National Center for Atmospheric Research Community Atmospheres Model and the University of Colorado/NASA Community Aerosol and Radiation Model for Atmospheres. We have used the model to investigate the sources, removal processes, transport, and optical properties of Asian dust aerosol and its impact on downwind regions. The model simulations are conducted primarily during the time frame of the Aerosol Characterization Experiment-Asia field experiment (March-May 2001) since considerable in situ data are available at that time. Our dust source function follows Ginoux et al. (2001). We modified the dust source function by using the friction velocity instead of the 10-m wind based on wind erosion theory, by adding a size-dependent threshold friction velocity following Marticorena and Bergametti (1995) and by adding a soil moisture correction. A Weibull distribution is implemented to estimate the subgrid-scale wind speed variability. We use eight size bins for mineral dust ranging from 0.1 to 10 μm radius. Generally, the model reproduced the aerosol optical depth retrieved by the ground-based Aerosol Robotic Network (AERONET) Sun photometers at six study sites ranging in location from near the Asian dust sources to the Eastern Pacific region. By constraining the dust complex refractive index from AERONET retrievals near the dust source, we also find the single-scattering albedo to be consistent with AERONET retrievals. However, large regional variations are observed due to local pollution. The timing of dust events is comparable to the National Institute for Environmental Studies (NIES) lidar data in Beijing and Nagasaki. However, the simulated dust aerosols are at higher altitudes than those observed by the NIES lidar.

HONO and Inorganic Fine Particle Composition in Typical Monsoon Region with Intensive Anthropogenic Emission: In-situ Observations and Source Identification.

NASA Astrophysics Data System (ADS)

Xie, Y.; Nie, W.; Ding, A.; Huang, X.

2015-12-01

Yangtze River Delta (YRD) is one of the most typical monsoon area with probably the most largest population intensity in the world. With sharply economic development and the large anthropogenic emissions, fine particle pollution have been one of the major air quality problem and may further have impact on the climate system. Though a lot of control policy (sulfur emission have been decreasing from 2007) have been conducted in the region, studies showed the sulfate in fine particles still take major fraction as the nitrate from nitrogen oxides increased significantly. In this study, the role of inorganic chemical compositions in fine particles was investigated with two years in-situ observation. Sulfate and Nitrate contribute to fine particle mass equally in general, but sulfate contributes more during summer and nitrate played more important role in winter. Using lagrangian dispersion backward modeling and source contribution clustering method, the impact of airmass coming from different source region (industrial, dust, biogenic emissions, etc) on fine particle inorganic compositions were discussed. Furthermore, we found two unique cases showing in-situ implications for sulfate formation by nitrogen dioxide oxidation mechanisms. It was showed that the mixing of anthropogenic pollutants with long-range transported mineral dust and biomass burning plume would enhance the sulfate formation by different chemistry mechanisms. This study focus on the complex aspects of fine particle formation in airmasses from different source regions: . It highlights the effect of NOx in enhancing the atmospheric oxidization capacity and indicates a potentially very important impact of increasing NOx on air pollution formation and regional climate change in East Asia.

Estimation of micrometeorites and satellite dust flux surrounding Mars in the light of MAVEN results

NASA Astrophysics Data System (ADS)

Pabari, J. P.; Bhalodi, P. J.

2017-05-01

Recently, MAVEN observed dust around Mars from ∼150 km to ∼1000 km and it is a puzzling question to the space scientists about the presence of dust at orbital altitudes and about its source. A continuous supply of dust from various sources could cause existence of dust around Mars and it is expected that the dust could mainly be from either the interplanetary source or the Phobos/Deimos. We have studied incident projectiles or micrometeorites at Mars using the existing model, in this article. Comparison of results with the MAVEN results gives a new value of the population index S, which is reported here. The index S has been referred in a power law model used to describe the number of impacting particles on Mars. In addition, the secondary ejecta from natural satellites of Mars can cause a dust ring or torus around Mars and remain present for its lifetime. The dust particles whose paths are altered by the solar wind over its lifetime, could present a second plausible source of dust around Mars. We have investigated escaping particles from natural satellites of Mars and compared with the interplanetary dust flux estimation. It has been found that flux rate at Mars is dominated (∼2 orders of magnitude higher) by interplanetary particles in comparison with the satellite originated dust. It is inferred that the dust at high altitudes of Mars could be interplanetary in nature and our expectation is in agreement with the MAVEN observation. As a corollary, the mass loss from Martian natural satellites is computed based on the surface erosion by incident projectiles.

High particulate iron(II) content in glacially sourced dusts enhances productivity of a model diatom

PubMed Central

Shoenfelt, Elizabeth M.; Sun, Jing; Winckler, Gisela; Kaplan, Michael R.; Borunda, Alejandra L.; Farrell, Kayla R.; Moreno, Patricio I.; Gaiero, Diego M.; Recasens, Cristina; Sambrotto, Raymond N.; Bostick, Benjamin C.

2017-01-01

Little is known about the bioavailability of iron (Fe) in natural dusts and the impact of dust mineralogy on Fe utilization by photosynthetic organisms. Variation in the supply of bioavailable Fe to the ocean has the potential to influence the global carbon cycle by modulating primary production in the Southern Ocean. Much of the dust deposited across the Southern Ocean is sourced from South America, particularly Patagonia, where the waxing and waning of past and present glaciers generate fresh glaciogenic material that contrasts with aged and chemically weathered nonglaciogenic sediments. We show that these two potential sources of modern-day dust are mineralogically distinct, where glaciogenic dust sources contain mostly Fe(II)-rich primary silicate minerals, and nearby nonglaciogenic dust sources contain mostly Fe(III)-rich oxyhydroxide and Fe(III) silicate weathering products. In laboratory culture experiments, Phaeodactylum tricornutum, a well-studied coastal model diatom, grows more rapidly, and with higher photosynthetic efficiency, with input of glaciogenic particulates compared to that of nonglaciogenic particulates due to these differences in Fe mineralogy. Monod nutrient accessibility models fit to our data suggest that particulate Fe(II) content, rather than abiotic solubility, controls the Fe bioavailability in our Fe fertilization experiments. Thus, it is possible for this diatom to access particulate Fe in dusts by another mechanism besides uptake of unchelated Fe (Fe′) dissolved from particles into the bulk solution. If this capability is widespread in the Southern Ocean, then dusts deposited to the Southern Ocean in cold glacial periods are likely more bioavailable than those deposited in warm interglacial periods. PMID:28691098

Trace-metal concentrations in African dust: effects of long-distance transport and implications for human health

USGS Publications Warehouse

Garrison, Virginia; Lamothe, Paul; Morman, Suzette; Plumlee, Geoffrey S.; Gilkes, Robert; Prakongkep, Nattaporn

2010-01-01

The Sahara and Sahel lose billions of tons of eroded mineral soils annually to the Americas and Caribbean, Europe and Asia via atmospheric transport. African dust was collected from a dust source region (Mali, West Africa) and from downwind sites in the Caribbean [Trinidad-Tobago (TT) and U.S. Virgin Islands (VI)] and analysed for 32 trace-elements. Elemental composition of African dust samples was similar to that of average upper continental crust (UCC), with some enrichment or depletion of specific trace-elements. Pb enrichment was observed only in dust and dry deposition samples from the source region and was most likely from local use of leaded gasoline. Dust particles transported long-distances (VI and TT) exhibited increased enrichment of Mo and minor depletion of other elements relative to source region samples. This suggests that processes occurring during long-distance transport of dust produce enrichment/depletion of specific elements. Bioaccessibility of trace-metals in samples was tested in simulated human fluids (gastric and lung) and was found to be greater in downwind than source region samples, for some metals (e.g., As). The large surface to volume ratio of the dust particles (<2.5 µm) at downwind sites may be a factor.

AIRUSE-LIFE+: a harmonized PM speciation and source apportionment in 5 Southern European cities

NASA Astrophysics Data System (ADS)

Amato, F.; Alastuey, A.; Karanasiou, A.; Lucarelli, F.; Nava, S.; Calzolai, G.; Severi, M.; Becagli, S.; Gianelle, V. L.; Colombi, C.; Alves, C.; Custódio, D.; Nunes, T.; Cerqueira, M.; Pio, C.; Eleftheriadis, K.; Diapouli, E.; Reche, C.; Minguillón, M. C.; Manousakas, M.; Maggos, T.; Vratolis, S.; Harrison, R. M.; Querol, X.

2015-09-01

The AIRUSE-LIFE+ project aims at characterising similarities and heterogeneities in PM sources and contributions in urban areas from the Southern Europe. Once the main PMx sources are identified, AIRUSE aims at developing and testing the efficiency of specific and non-specific measures to improve urban air quality. This article reports the results of the source apportionment of PM10 and PM2.5 conducted at three urban background sites (Barcelona, Florence and Milan, BCN-UB, FI-UB, MLN-UB) one sub-urban background site (Athens, ATH-SUB) and one traffic site (Porto, POR-TR). After collecting 1047 PM10 and 1116 PM2.5 24 h samples from January 2013 to February 2014 simultaneously at the 5 cities, these were analysed for the contents of OC, EC, anions, cations, major and trace elements and levoglucosan. The USEPA PMF5 receptor model was applied to these datasets in a harmonised way for each city. The sum of vehicle exhaust and non-exhaust contributes within 3.9-10.8 μg m-3 (16-32 %) to PM10 and 2.3-9.4 μg m-3 (15-36 %) to PM2.5, although a fraction of secondary nitrate is also traffic-related but could not be estimated. Important contributions arise from secondary particles (nitrate, sulphate and organics) in PM2.5 (37-82 %) but also in PM10 (40-71 %) mostly at background sites, revealing the importance of abating gaseous precursors in designing air quality plans. Biomass burning (BB) contributions vary widely, from 14-24 % of PM10 in POR-TR, MLN-UB and FI-UB, 7 % in ATH-SUB to < 2 % in BCN-UB. In PM2.5, BB is the second most important source in MLN-UB (21 %) and in POR-TR (18 %), the third one in FI-UB (21 %) and ATH-SUB (11 %), but again negligible (< 2 %) in BCN-UB. This large variability among cities is mostly due to the degree of penetration of biomass for residential heating. In Barcelona natural gas is very well supplied across the city and used as fuel in 96 % of homes, while, in other cities, PM levels increase on an annual basis by 1-9 μg m-3 due to this source. Other significant sources are: - Local dust, 7-12 % of PM10 at SUB and UB sites and 19 % at the TR site, revealing a contribution from road dust resuspension. In PM2.5 percentages decrease to 2-7 % at SUB-UB sites and 15 % at the TR site. - Industries, mainly metallurgy, contributing 4-11 % of PM10 (5-12 % in PM2.5), but only at BCN-UB, POR-TR and MLN-UB. No clear impact of industrial emissions was found in FI-UB and ATH-SUB. - Natural contributions from sea salt (13 % of PM10 in POR-TR but only 2-7 % in the other cities) and Saharan dust (14 % in ATH-SUB), but less than 4 % in the other cities. During high pollution days, the largest specific source (i.e. excluding SSO and SNI) of PM10 and PM2.5 are: VEX+NEX in BCN-UB (27-22 %) and POR-TR (31-33 %), BB in FI-UB (30-33 %) and MLN-UB (35-26 %) and Saharan dust in ATH-SUB (52-45 %) During those days, there are also quite important Industrial contributions in BCN-UB (17-18 %) and Local dust in POR-TR (28-20 %).

Urban dust in the Guanzhong basin of China, part II: A case study of urban dust pollution using the WRF-Dust model.

PubMed

Li, Nan; Long, Xin; Tie, Xuexi; Cao, Junji; Huang, Rujin; Zhang, Rong; Feng, Tian; Liu, Suixin; Li, Guohui

2016-01-15

We developed a regional dust dynamical model (WRF-Dust) to simulate surface dust concentrations in the Guanzhong (GZ) basin of China during two typical dust cases (19th Aug. and 26th Nov., 2013), and compared model results with the surface measurements at 17 urban and rural sites. The important improvement of the model is to employ multiple high-resolution (0.5-500 m) remote sensing data to construct dust sources. The new data include the geographic information of constructions, croplands, and barrens over the GZ basin in summer and winter of 2013. For the first time, detailed construction dust emissions have been introduced in a regional dust model in large cities of China. Our results show that by including the detailed dust sources, model performance at simulating dust pollutions in the GZ basin is significantly improved. For example, the simulated dust concentration average for the 17 sites increases from 28 μg m(-3) to 59 μg m(-3), closing to the measured concentration of 66 μg m(-3). In addition, the correlation coefficient (r) between the calculated and measured dust concentrations is also improved from 0.17 to 0.57, suggesting that our model better presents the spatial variation. Further analysis shows that urban construction activities are the crucial source in controlling urban dust pollutions. It should be considered by policy makers for mitigating particulate air pollution in many Chinese cities. Copyright © 2015 Elsevier B.V. All rights reserved.

African dust outbreaks over the Mediterranean Basin during 2001-2011: concentrations, phenomenology and trends

NASA Astrophysics Data System (ADS)

Pey, Jorge; Querol, Xavier; Alastuey, Andres; Forastiere, Franceso; Stafoggia, Massimo

2013-04-01

Concentrations, phenomenology and trends of African dust outbreaks over the whole Mediterranean Basin werestudied on an 11-year period (2001-2011). This work has been performed in the context of the MED-PARTICLES (LIFE programme, EU) project, devoted to quantify short-term health effects of particulate matter over the Mediterranean region by distinguishing different particle sizes, chemical components and sources, with emphasis in the effects of African dust. In order to evaluate conduct this investigation, PM10 data from 19 regional and suburban background sites West to East in the Mediterranean area were compiled. After identifying the daily occurrence of African dust outbreaks, a methodology for estimating natural dust contributions on daily PM10 concentrations was applied. Our findings point out that African dust outbreaks are sensibly more frequent in southern sitesacross the Mediterranean, from 30 to 37 % of the annual days, whereas they occur less than 20% of the annual days in northern sites. The central Mediterranean emerges as a transitional area, with slightly higher frequency of dust episodes in its lower extreme when compared to similar latitudinal positions in western and eastern sides of the Basin. A decreasing south to north gradient of African dust contribution to PM10, driven by the latitudinal position of the monitoring sites at least 25°E westwards across the Basin,is patent across the Mediterranean. From 25°E eastwards, higher annual dust contributions are encountered due to the elevated annual occurrence of severe episodesof dust but also because of inputs from Middle Eastern deserts. Concerning seasonality patterns and intensity characteristics, a clear summer prevalence is observed in the western part, with low occurrence of severe episodes (daily dust averages over 100 µg m-3 in PM10); no seasonal trend is detected in the central region, with moderate-intensity episodes; and significantly higher contributions are common in autumn-spring in the eastern side, with occurrence of various severe episodes throughout the year. Overall, African dust emerges as the largest PM10 source in regional background southern sites of the Mediterranean (35-50% of PM10), with seasonal peak contributions to PM10 up to 80% of the total mass in the eastern side. The multi-year study of African dust episodes and their contributions to PM10 concentrations displaysa consistent decreasing trend in the period 2006/2007 to 2011 in 4 of the 17 studied regions, all of them located in the NW of the Mediterranean. Such decrease is almost parallel to that of NAO (North Atlantic Oscillation) index for the summer period, being progressively more negative since 2006. As a consequence, a sharp change in the atmospheric circulation over the last 5 years (a similar negative NAO period occurred in the 1950 decade) have affected the number of African dust episodes and consequently the annual dust inputs to PM10observed in the NW part of the Mediterranean. By investigating mean temperatures and geopotential height maps at 850hPa it is evident a displacement of warm air masses accomplishing African dust towards the central Mediterranean in the 2007-2008 period, and towards the NW African coast and the Canary Islands in the 2009-2011 period. Acknowledgements This study has been founded by the LIFE programme of the European Commission under the Grant Agreement LIFE10 ENV/IT/327. Partial founding was received from the Autonomous Government of Catalonia and the Spanish Ministry of Agriculture, Food and Environment. PM10 data were obtained from EMEP, Airbase and ACTRIS databases. Most of the interpretations were performed thanks to the support of HYSPLIT model, SKIRON, BSC-DREAM and NRL-NAAPS aerosol maps, NCEP/NCAR meteorological database, and image products from MODIS and SeaWiFs NASA satellites.

Natural dust and acid rain

Treesearch

Erhard M. Winkler

1976-01-01

Atmospheric dust originates from three sources, terrestrial airborn matter, volcanic, and cosmic. Terrestrial natural dust makes up the main bulk reflecting the soil composition to 150 miles away. Soil erosion from flood plains, plowed fields and construction sites are the main source. Quartz, feldspar, the carbonates calcite and dolomite, and clay minerals are the...

Performance evaluation of CESM in simulating the dust cycle

NASA Astrophysics Data System (ADS)

Parajuli, S. P.; Yang, Z. L.; Kocurek, G.; Lawrence, D. M.

2014-12-01

Mineral dust in the atmosphere has implications for Earth's radiation budget, biogeochemical cycles, hydrological cycles, human health and visibility. Mineral dust is injected into the atmosphere during dust storms when the surface winds are sufficiently strong and the land surface conditions are favorable. Dust storms are very common in specific regions of the world including the Middle East and North Africa (MENA) region, which contains more than 50% of the global dust sources. In this work, we present simulation of the dust cycle under the framework of CESM1.2.2 and evaluate how well the model captures the spatio-temporal characteristics of dust sources, transport and deposition at global scale, especially in dust source regions. We conducted our simulations using two existing erodibility maps (geomorphic and topographic) and a new erodibility map, which is based on the correlation between observed wind and dust. We compare the simulated results with MODIS satellite data, MACC reanalysis data, and AERONET station data. Comparison with MODIS satellite data and MACC reanalysis data shows that all three erodibility maps generally reproduce the spatio-temporal characteristics of dust optical depth globally. However, comparison with AERONET station data shows that the simulated dust optical depth is generally overestimated for all erodibility maps. Results vary greatly by region and scale of observational data. Our results also show that the simulations forced by reanalysis meteorology capture the overall dust cycle more realistically compared to the simulations done using online meteorology.

Applying geochemical signatures of atmospheric dust to distinguish current mine emissions from legacy sources

NASA Astrophysics Data System (ADS)

Dong, Chenyin; Taylor, Mark Patrick

2017-07-01

Resolving the source of environmental contamination is the critical first step in remediation and exposure prevention. Australia's oldest silver-zinc-lead mine at Broken Hill (>130 years old) has generated a legacy of contamination and is associated with persistent elevated childhood blood lead (Pb) levels. However, the source of environmental Pb remains in dispute: current mine emissions; remobilized mine-legacy lead in soils and dusts; and natural lead from geological weathering of the gossan ore body. Multiple lines of evidence used to resolve this conundrum at Broken Hill include spatial and temporal variations in dust Pb concentrations and bioaccessibility, Pb isotopic compositions, particle morphology and mineralogy. Total dust Pb loading (mean 255 μg/m2/day) and its bioaccessibility (mean 75% of total Pb) is greatest adjacent to the active mining operations. Unweathered galena (PbS) found in contemporary dust deposits contrast markedly to Pb-bearing particles from mine-tailings and weathered gossan samples. Contemporary dust particles were more angular, had higher sulfur content and had little or no iron and manganese. Dust adjacent to the mine has Pb isotopic compositions (208Pb/207Pb: 2.3197; 206Pb/207Pb: 1.0406) that are a close match (99%) to the ore body with values slightly lower (94%) at the edge of the city. The weight of evidence supports the conclusion that contemporary dust Pb contamination in Broken Hill is sourced primarily from current mining activities and not from weathering or legacy sources.

Modelling absorbing aerosol with ECHAM-HAM: Insights from regional studies

NASA Astrophysics Data System (ADS)

Tegen, Ina; Heinold, Bernd; Schepanski, Kerstin; Banks, Jamie; Kubin, Anne; Schacht, Jacob

2017-04-01

Quantifying distributions and properties of absorbing aerosol is a basis for investigations of interactions of aerosol particles with radiation and climate. While evaluations of aerosol models by field measurements can be particularly successful at the regional scale, such results need to be put into a global context for climate studies. We present an overview over studies performed at the Leibniz Institute for Tropospheric Research aiming at constraining the properties of mineral dust and soot aerosol in the global aerosol model ECHAM6-HAM2 based on different regional studies. An example is the impact of different sources for dust transported to central Asia, which is influenced, by far-range transport of dust from Arabia and the Sahara together with dust from local sources. Dust types from these different source regions were investigated in the context of the CADEX project and are expected to have different optical properties. For Saharan dust, satellite retrievals from MSG SEVIRI are used to constrain Saharan dust sources and optical properties. In the Arctic region, on one hand dust aerosol is simulated in the framework of the PalMod project. On the other hand aerosol measurements that will be taken during the DFG-funded (AC)3 field campaigns will be used to evaluate the simulated transport pathways of soot aerosol from European, North American and Asian sources, as well as the parameterization of soot ageing processes in ECHAM6-HAM2. Ultimately, results from these studies will improve the representation of aerosol absorption in the global model.

Anthropogenic fugitive, combustion and industrial dust is a significant, underrepresented fine particulate matter source in global atmospheric models

NASA Astrophysics Data System (ADS)

Philip, Sajeev; Martin, Randall V.; Snider, Graydon; Weagle, Crystal L.; van Donkelaar, Aaron; Brauer, Michael; Henze, Daven K.; Klimont, Zbigniew; Venkataraman, Chandra; Guttikunda, Sarath K.; Zhang, Qiang

2017-04-01

Global measurements of the elemental composition of fine particulate matter across several urban locations by the Surface Particulate Matter Network reveal an enhanced fraction of anthropogenic dust compared to natural dust sources, especially over Asia. We develop a global simulation of anthropogenic fugitive, combustion, and industrial dust which, to our knowledge, is partially missing or strongly underrepresented in global models. We estimate 2-16 μg m-3 increase in fine particulate mass concentration across East and South Asia by including anthropogenic fugitive, combustion, and industrial dust emissions. A simulation including anthropogenic fugitive, combustion, and industrial dust emissions increases the correlation from 0.06 to 0.66 of simulated fine dust in comparison with Surface Particulate Matter Network measurements at 13 globally dispersed locations, and reduces the low bias by 10% in total fine particulate mass in comparison with global in situ observations. Global population-weighted PM2.5 increases by 2.9 μg m-3 (10%). Our assessment ascertains the urgent need of including this underrepresented fine anthropogenic dust source into global bottom-up emission inventories and global models.

Metal sources and exposures in the homes of young children living near a mining-impacted Superfund site.

PubMed

Zota, Ami R; Schaider, Laurel A; Ettinger, Adrienne S; Wright, Robert O; Shine, James P; Spengler, John D

2011-01-01

Children living near hazardous waste sites may be exposed to environmental contaminants, yet few studies have conducted multi-media exposure assessments, including residential environments where children spend most of their time. We sampled yard soil, house dust, and particulate matter with aerodynamic diameter <2.5 in 59 homes of young children near an abandoned mining area and analyzed samples for lead (Pb), zinc (Zn), cadmium (Cd), arsenic (As), and manganese (Mn). In over half of the homes, dust concentrations of Pb, Zn, Cd, and As were higher than those in soil. Proximity to mine waste (chat) piles and the presence of chat in the driveway significantly predicted dust metals levels. Homes with both chat sources had Pb, Zn, Cd, and As dust levels two to three times higher than homes with no known chat sources after controlling for other sources. In contrast, Mn concentrations in dust were consistently lower than in soil and were not associated with chat sources. Mn dust concentrations were predicted by soil concentrations and occupant density. These findings suggest that nearby outdoor sources of metal contaminants from mine waste may migrate indoors. Populations farther away from the mining site may also be exposed if secondary uses of chat are in close proximity to the home.

Characterization of aerosolized bacteria and fungi from desert dust events in Mali, West Africa

USGS Publications Warehouse

Kellogg, C.A.; Griffin, Dale W.; Garrison, V.H.; Peak, K.K.; Royall, N.; Smith, R.R.; Shinn, E.A.

2004-01-01

Millions of metric tons of African desert dust blow across the Atlantic Ocean each year, blanketing the Caribbean and southeastern United States. Previous work in the Caribbean has shown that atmospheric samples collected during dust events contain living microbes, including plant and opportunistic human pathogens. To better understand the potential downwind public health and ecosystem effects of the dust microbes, it is important to characterize the source population. We describe 19 genera of bacteria and 3 genera of fungi isolated from air samples collected in Mali, a known source region for dust storms, and over which large dust storms travel.

Reassessing the penultimate interglacial analog for current climate change, evidence from Antarctic dust

NASA Astrophysics Data System (ADS)

Aarons, S. M.; Aciego, S.; McConnell, J.

2017-12-01

Dust emissions and transport are linked to spatial and temporal climate variability, with dust provenance providing clues to past climate and climate impacts. The penultimate interglacial period (MIS 5e) has been suggested as an analog to Holocene climate change. We present the first evaluation of the MIS 5e ice archive developed at Taylor Glacier, East Antarctica and provide a record of dust transported to Taylor Glacier during MIS 5e. Our record shows significant differences between MIS 5e, Holocene, and pre-industrial dust transported to East Antarctica. The MIS 5e dust is sourced from New Zealand and southern South America (SSA), while the Holocene dust is sourced from local Antarctic, SSA, and potentially Australian sources. This profound change in composition suggests a variation in atmospheric transport pathways and/or paleo-environmental conditions between the interglacial periods, and indicates that MIS 5e should be reassessed as an analog for climate change and associated impacts.

Characteristics and transport of organochlorine pesticides in urban environment: air, dust, rain, canopy throughfall, and runoff.

PubMed

Zhang, Wei; Ye, Youbin; Hu, Dan; Ou, Langbo; Wang, Xuejun

2010-11-01

Characteristics and transport of organochlorine pesticides (OCPs) in urban multiple environments, including air, dust, rain, canopy throughfall, and runoff water, are explored in this study. Hexachlorocyclohexanes (HCHs) dominated in both air and rain water, and dichlorodiphenyltrichloroethane (DDT) related substances showed a higher affinity to dust. Relatively high concentrations of DDT and dichlorodiphenyldichloroethylene (DDE) in air, rain and dust imply that technical DDT in the environment has been degrading, and there may be unknown local or regional emission sources that contain DDTs in the study area. Source identification showed that DDTs in Beijing urban environments with a fresh signature may originate from the atmospheric transport from remote areas. The ratio of α-/γ-HCH in dust, rain, canopy throughfall and runoff were close to 1, indicating the possible use of lindane. OCPs in runoff were transported from various sources including rain, dust, and canopy throughfall. In runoff, DDTs and hexachlorobenzene (HCB) were mainly transported from dust, and HCHs were mainly from rain and canopy throughfall.

Emerging ecological datasets with application for modeling North American dust emissions

NASA Astrophysics Data System (ADS)

McCord, S.; Stauffer, N. G.; Garman, S.; Webb, N.

2017-12-01

In 2011 the US Bureau of Land Management (BLM) established the Assessment, Inventory and Monitoring (AIM) program to monitor the condition of BLM land and to provide data to support evidence-based management of multi-use public lands. The monitoring program shares core data collection methods with the Natural Resources Conservation Service's (NRCS) National Resources Inventory (NRI), implemented on private lands nationally. Combined, the two programs have sampled >30,000 locations since 2003 to provide vegetation composition, vegetation canopy height, the size distribution of inter-canopy gaps, soil texture and crusting information on rangelands and pasture lands across North America. The BLM implements AIM on more than 247.3 million acres of land across the western US, encompassing major dust source regions of the Chihuahuan, Sonoran, Mojave and Great Basin deserts, the Colorado Plateau, and potential high-latitude dust sources in Alaska. The AIM data are publicly available and can be used to support modeling of land surface and boundary-layer processes, including dust emission. While understanding US dust source regions and emission processes has been of national interest since the 1930s Dust Bowl, most attention has been directed to the croplands of the Great Plains and emission hot spots like Owens Lake, California. The magnitude, spatial extent and temporal dynamics of dust emissions from western dust source areas remain highly uncertain. Here, we use ensemble modeling with empirical and physically-based dust emission schemes applied to AIM monitoring data to assess regional-scale patterns of aeolian sediment mass fluxes and dust emissions. The analysis enables connections to be made between dust emission rates at source and other indicators of ecosystem function at the landscape scale. Emerging ecological datasets like AIM provide new opportunities to evaluate aeolian sediment transport responses to land surface conditions, potential interactions with disturbances (e.g., fire) and ecological change (e.g., invasive species), and the impacts of anthropogenic land use and land cover change.

An assessment of SEVIRI imagery at different temporal resolutions and the effect on accurate dust emission mapping

NASA Astrophysics Data System (ADS)

Hennen, Mark; White, Kevin; Shahgedanova, Maria

2017-04-01

This paper compares Dust RGB products derived from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) data at 15 minute, 30 minute and hourly temporal resolutions. From January 2006 to December 2006, observations of dust emission point sources were observed at each temporal resolution across the entire Middle East region (38.50N; 30.00E - 10.00N; 65.50E). Previous work has demonstrated that 15-minute resolution SEVIRI data can be used to map dust sources across the Sahara by observing dust storms back through sequential images to the point of first emission (Schepanski et al., 2007; 2009; 2012). These observations have improved upon lower resolution maps, based on daily retrievals of aerosol optical depth (AOD), whose maxima can be biased by prevalent transport routes, not necessarily coinciding with sources of emissions. Based on the thermal contrast of atmospheric dust to the surface, brightness temperature differences (BTD's) in the thermal infrared (TIR) wavelengths (8.7, 10.8 and 12.0 µm) highlight dust in the scene irrespective of solar illumination, giving both increased accuracy of dust source areas and a greater understanding of diurnal emission behaviour. However, the highest temporal resolution available (15-minute repeat capture) produces 96 images per day, resulting in significantly higher data storage demands than 30 minute or hourly data. To aid future research planning, this paper investigates what effect lowering the temporal resolution has on the number and spatial distribution of the observed dust sources. The results show a reduction in number of dust emission events observed with each step decrease in temporal resolution, reducing by 17% for 30-minute resolution and 50% for hourly. These differences change seasonally, with the highest reduction observed in summer (34% and 64% reduction respectively). Each resolution shows a similar spatial distribution, with the biggest difference seen near the coastlines, where near-shore convective cloud patterns obscure atmospheric dust soon after emission, restricting the opportunity to be observed at hourly resolution.

A parameterization of dust emission (PM10) fluxes of dust events observed at Naiman in Inner Mongolia using the monitored tower data

NASA Astrophysics Data System (ADS)

Park, Soon-Ung; Ju, Jae-Won; Lee, In-Hye; Joo, Seung Jin

2016-09-01

The optimal regression equations for the dust emission flux parameterized with the friction velocity (u*) only, the friction velocity with the threshold friction velocity (u*t) and the friction velocity together with the flux Richardson number (Rf) in the dust source region are derived using the sonic anemometer measured momentum and kinematic heat fluxes at 8 m height and the two-level (3 m and 15 m height) measured PM10 concentrations from a 20-m monitoring tower located at Naiman in the Asian dust source region in China for the period from March 2013 to November 2014. The analysis period is divided into three sub-periods based on the Normalized Difference Vegetation Index (NDVI) to eliminate the effect of vegetation on the dust emission flux. The dust event is identified as a peak half hourly mean dust concentration (PM10) at 3 m height exceeding the sub-period mean dust concentration plus one standard deviation of the sub-period. The total of 317 dust events is identified with the highest number of dust event of 18.8 times a month in summer. The optimal regression equations of the dust emission flux (Fc) for dust events parameterized with u* and Rf are found to simulate quite well the dust emission flux estimated by the observed data at the site for all periods especially for the unstable stratification, suggesting the potential usefulness of these equations parameterized by u* with Rf rather than those by u* only and u* together with u*t for the estimation of the dust emission flux in the Asian dust source region.

Characterisation of mineral dust emission in the Middle EAST using the Spinning Enhanced Visible and Infrared Imager (SEVIRI)

NASA Astrophysics Data System (ADS)

Hennen, M.; Shahgedanova, M.; White, K.

2015-12-01

Using the Spinning Enhanced Visual and InfraRed Imager (SEVIRI) on-board Meteosat's second generation satellite (MSG), mineral dust emissions from the Middle East were observed at a high temporal and spatial resolution between the years 2006 and 2013. This research provides a subjective derivation of mineral dust source locations in the Middle East using the thermal infrared Dust RGB product. Focusing on the brightness temperature difference around 10.8 µm channel and their spectral contrast with clear sky conditions, the Dust RGB product has been recognised as a major asset in detecting dust. While the product has already been used to map dust emissions in Sahara and south Africa, this research is the first to map dust emissions in the Middle East using SEVIRI, one of the dustiest regions in the world second only to the Sahara Desert. For every dust storm activation within the Middle East, the point of first emission is derived from visual inspection of each 15 minute image, these points were then recorded in a dust source climatology (DSC) database, along with time and direction of dust movement. To take account of potential errors inherent in this subjective detection method, a degree of confidence is associated with each data point with relevance to time of day (which has a strong effect on ability to detect dust in these products) and weather conditions, in particular presence of clouds. These results are compared with an automated retrieval using Aerosol Optical Depth (AOD) measurements form the Moderate Resolution Image Spectrometer (MODIS); which, due to its sun-synchronous orbit allows a measurement of dust in the atmosphere once a day. Differences in the spatial distribution of SEVIRI dust sources and MODIS inferred dust source regions can be explained by inherent transport bias in the latter's low sampling rate and prevailing wind conditions. This database will provide an important tool in further understanding dust emission processes in the region, laying the foundations for future studies relating to climatic conditions, especially droughts, and changes in land cover.

Mining cosmic dust from the blue ice lakes of Greenland

NASA Technical Reports Server (NTRS)

Maurette, M.; Brownlee, D. E.; Fehrenback, L.; Hammer, C.; Jehano, C.; Thomsen, H. H.

1985-01-01

Extraterrestrial material, most of which invisible settles to Earth's surface as dust particles smaller than a millimeter in size were investigated. Particles of 1/10 millimeter size fall at a rate of one/sq m/yr collection of extraterrestrial dust is important because the recovered cosmic dust particles can provide important information about comets. Comets are the most important source of dust in the solar system and they are probably the major source of extraterrestrial dust that is collectable at the Earth's surface. A new collection site for cosmic dust, in an environment where degradation by weathering is minimal is reported. It is found that the blue ice lakes on the Greenland ice cap provide an ideal location for collection of extraterrestrial dust particles larger than 0.1 mm in size. It is found that the lakes contain large amounts of cosmic dust which is much better preserved than similar particles recovered from the ocean floor.

Geochemical and microbiological fingerprinting of airborne dust that fell in Canberra, Australia, in October 2002

NASA Astrophysics Data System (ADS)

de Deckker, Patrick; Abed, Raeid M. M.; de Beer, Dirk; Hinrichs, Kai-Uwe; O'Loingsigh, Tadhg; Schefuß, Enno; Stuut, Jan-Berend W.; Tapper, Nigel J.; van der Kaars, Sander

2008-12-01

During the night of 22-23 October 2002, a large amount of airborne dust fell with rain over Canberra, located some 200 km from Australia's east coast, and at an average altitude of 650 m. It is estimated that during that night about 6 g m-2 of aeolian dust fell. We have conducted a vast number of analyses to "fingerprint" some of the dust and used the following techniques: grain size analysis; scanning electron microscope imagery; major, trace, and rare earth elemental, plus Sr and Nd isotopic analyses; organic compound analyses with respective compound-specific isotope analyses; pollen extraction to identify the vegetation sources; and molecular cloning of 16S rRNA genes in order to identify dust bacterial composition. DNA analyses show that most obtained 16S rRNA sequences belong mainly to three groups: Proteobacteria (25%), Bacteriodetes (23%), and gram-positive bacteria (23%). In addition, we investigated the meteorological conditions that led to the dust mobilization and transport using model and satellite data. Grain sizes of the mineral dust show a bimodal distribution typical of proximal dust, rather than what is found over oceans, and the bimodal aspect of size distribution confirms wet deposition by rain droplets. The inorganic geochemistry points to a source along/near the Darling River in NW New South Wales, a region that is characteristically semiarid, and both the organic chemistry and palynoflora of the dust confirm the location of this source area. Meteorological reconstructions of the event again clearly identify the area near Bourke-Cobar as being the source of the dust. This study paves the way for determining the export of Australian airborne dust both in the oceans and other continents.

Assessments of the contribution of land use change to the dust emission in Central Asia

NASA Astrophysics Data System (ADS)

Xi, X.; Sokolik, I. N.

2015-12-01

While the dust emission from arid and semi-arid regions is known as a natural process induced by wind erosion, human may affect the dust emission directly through land use disturbances and indirectly by climate change. There has been much debate on the relative importance of climate change and land use to the global dust budget, as past estimates on the proportion of dust contributed by land use, in particular agricultural practices, remains very uncertain. This to the large extent stems from the way how human-made dust sources are identified and how they are treated in models. This study attempts to assess the land use contribution to the dust emission in Central Asia during 2000-2014 by conducting multiple experiments on the total emission in the WRF-Chem-DuMo model, and applying two methods to separate the natural and anthropogenic sources. The model experiments include realistic treatments of agriculture (e.g., expansion and abandonment) and water body changes (e.g., Aral Sea desiccation) in the land cover map of WRF-Chem-DuMo, but impose no arbitrary labeling of dust source type or adjustment to the erosion threshold. Intercomparison of the model experiments will be focused on the magnitude, interannual variability, and climate sensitivity of dust fluxes resulting from the selections of surface input data and dust flux parameterizations. Based on annual land use intensity maps, the sensitivity of the anthropogenic dust proportion to selection of the threshold value will be evaluated. In conjunction with the empirical method, satellite-derived annual land classifications will be used to track the land cover dynamics, and separate potential human-made source areas.

Linking Barbados Mineral Dust Aerosols to North African Sources Using Elemental Composition and Radiogenic Sr, Nd, and Pb Isotope Signatures

NASA Astrophysics Data System (ADS)

Bozlaker, Ayse; Prospero, Joseph M.; Price, Jim; Chellam, Shankararaman

2018-01-01

Large quantities of African dust are carried across the Atlantic to the Caribbean Basin and southern United States where it plays an important role in the biogeochemistry of soils and waters and in air quality. Dusts' elemental and isotopic composition was comprehensively characterized in Barbados during the summers of 2013 and 2014, the season of maximum dust transport. Although total suspended insoluble particulate matter (TSIP) mass concentrations varied significantly daily and between the two summers, the abundances (μg element/g TSIP) of 50 elements during "high-dust days" (HDD) were similar. Aerosols were regularly enriched in Na, Cu, Zn, As, Se, Mo, Cd, Sn, Sb, and W relative to the upper continental crust. Enrichment of these elements, many of which are anthropogenically emitted, was significantly reduced during HDD, attributed to mixing and dilution with desert dust over source regions. Generally, Ti/Al, Si/Al, Ca/Al, Ti/Fe, Si/Fe, and Ca/Fe ratios during HDD differed from their respective values in hypothesized North African source regions. Nd isotope composition was relatively invariant for "low-dust days" (LDD) and HDD. In contrast, HDD-aerosols were more radiogenic exhibiting higher 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios compared to LDD. Generally, Barbados aerosols' composition ranged within narrow limits and was much more homogeneous than that of hypothesized African source soils. Our results suggest that summertime Barbados aerosols are dominated by a mixture of particles originating from sources in the Sahara-Sahel regions. The Bodélé Depression, long suspected as a major source, appears to be an insignificant contributor of summertime western Atlantic dust.

Application of Synchrotron Microprobe Methods to Solid-Phase Speciation of Metals and Metalloids in House Dust

DOE Office of Scientific and Technical Information (OSTI.GOV)

S Walker; H Jamieson; P Rasmussen

2011-12-31

Determination of the source and form of metals in house dust is important to those working to understand human and particularly childhood exposure to metals in residential environments. We report the development of a synchrotron microprobe technique for characterization of multiple metal hosts in house dust. We have applied X-ray fluorescence for chemical characterization and X-ray diffraction for crystal structure identification using microfocused synchrotron X-rays at a less than 10 {micro}m spot size. The technique has been evaluated by application to archived house dust samples containing elevated concentrations of Pb, Zn, and Ba in bedroom dust, and Pb and Asmore » in living room dust. The technique was also applied to a sample of soil from the corresponding garden to identify linkages between indoor and outdoor sources of metals. Paint pigments including white lead (hydrocerussite) and lithopone (wurtzite and barite) are the primary source of Pb, Zn, and Ba in bedroom dust, probably related to renovation activity in the home at the time of sampling. The much lower Pb content in the living room dust shows a relationship to the exterior soil and no specific evidence of Pb and Zn from the bedroom paint pigments. The technique was also successful at confirming the presence of chromated copper arsenate treated wood as a source of As in the living room dust. The results of the study have confirmed the utility of this approach in identifying specific metal forms within the dust.« less

Atmospheric Ice-Nucleating Particles in the Dusty Tropical Atlantic

NASA Astrophysics Data System (ADS)

Price, H. C.; Baustian, K. J.; McQuaid, J. B.; Blyth, A.; Bower, K. N.; Choularton, T.; Cotton, R. J.; Cui, Z.; Field, P. R.; Gallagher, M.; Hawker, R.; Merrington, A.; Miltenberger, A.; Neely, R. R., III; Parker, S. T.; Rosenberg, P. D.; Taylor, J. W.; Trembath, J.; Vergara-Temprado, J.; Whale, T. F.; Wilson, T. W.; Young, G.; Murray, B. J.

2018-02-01

Desert dust is one of the most important atmospheric ice-nucleating aerosol species around the globe. However, there have been very few measurements of ice-nucleating particle (INP) concentrations in dusty air close to desert sources. In this study we report the concentration of INPs in dust laden air over the tropical Atlantic within a few days' transport of one of the world's most important atmospheric sources of desert dust, the Sahara. These measurements were performed as part of the Ice in Clouds Experiment-Dust campaign based in Cape Verde, during August 2015. INP concentrations active in the immersion mode, determined using a droplet-on-filter technique, ranged from around 102 m-3 at -12°C to around 105 m-3 at -23°C. There is about 2 orders of magnitude variability in INP concentration for a particular temperature, which is determined largely by the variability in atmospheric dust loading. These measurements were made at altitudes from 30 to 3,500 m in air containing a range of dust loadings. The ice active site density (ns) for desert dust dominated aerosol derived from our measurements agrees with several laboratory-based parameterizations for ice nucleation by desert dust within 1 to 2 orders of magnitude. The small variability in ns values determined from our measurements (within about 1 order of magnitude) is striking given that the back trajectory analysis suggests that the sources of dust were geographically diverse. This is consistent with previous work, which indicates that desert dust's ice-nucleating activity is only weakly dependent on source.

Modeling of intercontinental Saharan dust transport: What consequences on atmospheric concentrations and deposition fluxes in the Caribbean?

NASA Astrophysics Data System (ADS)

Laurent, Benoit; Formenti, Paola; Desboeufs, Karine; Vincent, Julie; Denjean, Cyrielle; Siour, Guillaume; Mayol-Bracero, Olga L.

2015-04-01

The Dust Aging and Transport from Africa to the Caribbean (Dust-AttaCk) project aims todocument the physical and optical properties of long-range transported African dust to the Caribbean. A comprehensive field campaign was conducted in Cape San Juan, Puerto Rico (18.38°N 65.62°W) during June-July 2012, offering the opportunity to constrain the way Saharan dust are transported from North Africa to the Caribbean by 3D models. Our main objectives are: (i) to discuss the ability of the CHIMERE Eulerian off-line chemistry-transport model to simulate atmospheric Saharan dust loads observed in the Caribbean during the Dust-AttaCk campaign, as well as the altitude of the dust plumes transport over the North Atlantic Ocean up to the Caribbean, (ii) to study the main Saharan dust emission source areas contributing to the dust loads in the Caribbean, (iii) to estimate the Saharan dust deposition in the Caribbean for deposition events observed during the Dust-AttaCk campaign. The dust model outputs are hourly dust concentration fields in µg m-3 for 12 aerosol size bins up to 30 µm and for each of the 15 sigma pressure vertical levels, column integrated dustaerosol optical depth (AOD), and dry and wet deposition fluxes.The simulations performed for the Dust-AttaCk campaign period as well as satellite observations (MODIS AOD, SEVIRI AOD) are used to identify the Saharan emission source regions activated and to study the evolution of the dust plumes tothe Cape San Juan station. In complement, the vertical transport of dust plumes transported from Saharan dust sources and over the North Atlantic Ocean is investigated combining model simulations and CALIOP observations. Aerosol surface concentrations and AOD simulated with CHIMERE are compared with sin-situ observations at Cape San Juan and AERONET stations. Wet deposition measurements performed allow us to constrain dust deposition flux simulated in the Caribbean after long-range transport.

The brightest high-latitude 12-micron IRAS sources

NASA Technical Reports Server (NTRS)

Hacking, P.; Beichman, C.; Chester, T.; Neugebauer, G.; Emerson, J.

1985-01-01

The Infrared Astronomical Satellite (IRAS) Point Source catalog was searched for sources brighter than 28 Jy (0 mag) at 12 microns with absolute galactic latitude greater than 30 deg excluding the Large Magellanic Cloud. The search resulted in 269 sources, two of which are the galaxies NGC 1068 and M82. The remaining 267 sources are identified with, or have infrared color indices consistent with late-type stars some of which show evidence of circumstellar dust shells. Seven sources are previously uncataloged stars. K and M stars without circumstellar dust shells, M stars with circumstellar dust shells, and carbon stars occupy well-defined regions of infrared color-color diagrams.

New Observational Evidence of Active Asteroid P/2010 A2: Slow Rotation of the Largest Fragment

NASA Astrophysics Data System (ADS)

Kim, Yoonyoung; Ishiguro, Masateru; Lee, Myung Gyoon

2017-06-01

We report new observations of the active asteroid P/2010 A2 taken when it made its closest approach to Earth (1.06 au in 2017 January) after its first discovery in 2010. Despite a crucial role of the rotational period in clarifying its ejection mechanism, the rotational property of P/2010 A2 has not yet been studied due to the extreme faintness of this tiny object (∼120 m in diameter). Taking advantage of the best observing geometry since the discovery, we succeed in obtaining the rotational light curve of the largest fragment with Gemini/GMOS-N. We find that (1) the largest fragment has a double-peaked period of 11.36 ± 0.02 hr spinning much slower than its critical spin period; (2) the largest fragment is a highly elongated object (a/b ≥ 1.94) with an effective radius of {61.9}-9.2+16.8 m; (3) the size distribution of the ejecta follows a broken power law (the power indices of the cumulative size distributions of the dust and fragments are 2.5 ± 0.1 and 5.2 ± 0.1, respectively); (4) the mass ratio of the largest fragment to the total ejecta is around 0.8; and (5) the dust cloud morphology is in agreement with the anisotropic ejection model in Kim et al. These new characteristics of the ejecta obtained in this work are favorable to the impact shattering hypothesis.

Dust sources and atmospheric circulation in concert controlling Saharan dust emission and transport towards the Western Mediterranean Basin

NASA Astrophysics Data System (ADS)

Schepanski, Kerstin; Mallet, Marc; Heinold, Bernd; Ulrich, Max

2017-04-01

Dust transported from north African source regions towards Europe is a ubiquitous phenomenon in the Mediterranean region, a geographic region that is in part densely populated. Besides its impacts on the atmospheric radiation budget, dust suspended in the atmosphere results in reduced air quality, which is generally sensed as a reduction in quality of life. Furthermore, the exposure to dust aerosols enhances the prevalence of respiratory diseases, which reduces the general human wellbeing, and ultimately results in an increased loss of working hours due to illness and hospitalization rates. Characteristics of the atmospheric dust life cycle that determine dust transport will be presented with focus on the ChArMEx special observation period in June and July 2013 using the atmosphere-dust model COSMO-MUSCAT (COSMO: Consortium for Small-scale MOdeling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model). Modes of atmospheric circulation were identified from empirical orthogonal function (EOF) analysis of the geopotential height at 850 hPa for summer 2013 and compared to EOFs calculated from 1979-2015 ERA-Interim reanalysis. Generally, two different phases were identified. They are related to the eastward propagation of the subtropical ridge into the Mediterranean basin, the position of the Saharan heat low, and the predominant Iberian heat low. The relation of these centres of action illustrates a dipole pattern for enhanced (reduced) dust emission fluxes, stronger (weaker) meridional dust transport, and consequent increase (decrease) atmospheric dust concentrations and deposition fluxes. In concert, the results from this study aim at illustrating the relevance of knowing the dust source locations in concert with the atmospheric circulation. Ultimately, this study addresses the question of what is finally transported towards the Mediterranean basin and Europe from which source regions - and fostered by which atmospheric circulation pattern. Outcomes from this study contribute to the understanding of varying atmospheric mineral dust contributions to the aerosol burden affecting populated areas around Europe.

East Asian origin of central Greenland last glacial dust: just one possible scenario?

NASA Astrophysics Data System (ADS)

Újvári, Gábor; Stevens, Thomas; Svensson, Anders; Klötzli, Urs Stephan; Manning, Christina; Németh, Tibor; Kovács, János

2016-04-01

Dust in Greenland ice cores is used to reconstruct the activity of dust emitting regions and atmospheric circulation for the last glacial period. However, the source dust material to Greenland over this period is the subject of considerable uncertainty. Here we use new clay mineral and Sr-Nd isotopic data from eleven loess samples collected around the Northern Hemisphere and compare the 87Sr/86Sr and 143Nd/144Nd isotopic signatures of fine (<10 μm) separates to existing Greenland ice core dust data (GISP2, GRIP; [1]; [2]). Smectite contents and kaolinite/chlorite (K/C) ratios allow exclusion of continental US dust emitting regions as potential sources, because of the very high (>3.6) K/C ratios and extremely high (>~70%) smectite contents. At the same time, Sr-Nd isotopic compositions demonstrate that ice core dust isotopic compositions can be explained by East Asian (Chinese loess) and/or Central/East Central European dust contributions. Central/East Central European loess Sr-Nd isotopic compositions overlap most with ice core dust, while the Sr isotopic signature of Chinese loess is slightly more radiogenic. Nevertheless, an admixture of 90‒10 % from Chinese loess and circum-Pacific volcanic material would also account for the Sr‒Nd isotopic ratios of central Greenland LGM dust. At the same time, sourcing of ice core dust from Alaska, continental US and NE Siberia seems less likely based on Sr and Nd isotopic signatures. The data demonstrate that currently no unique source discrimination for Greenland dust is possible using both published and our new data [3]. Thus, there is a need to identify more diagnostic tracers. Based on initial Hf isotope analyses of fine separates of three loess samples (continental US, Central Europe, China), an apparent dependence of Hf isotopic signatures on the relative proportions of radiogenic clay minerals (primarily illite) was found, as these fine dust fractions are apparently zircon-free. The observed difference between major potential source regions in 176Hf/177Hf that reach several ɛHf units and the first order clay mineralogy dependence of Hf isotopic signatures means there is strong potential for distinguishing between the two hypothesized Greenland dust sources using Hf isotopes [3]. [1] Biscaye P.E., Grousset F.E., Revel M., Van der Gaast S., Zielinski G.A., Vaars A., Kukla G. (1997). Asian provenance of glacial dust (stage 2) in the Greenland Ice Sheet Project 2 Ice Core, Summit, Greenland. Journal of Geophysical Research 102, 26765-26781. [2] Svensson A., Biscaye P.E., Grousset F.E. (2000) Characterization of late glacial continental dust in the Greenland Ice Core Project ice core. Journal of Geophysical Research 105, 4637-4656. [3] Újvári G., Stevens T., Svensson A., Klötzli U.S., Manning, C., Németh T., Kovács J., Sweeney M.R., Gocke M., Wiesenberg G.L.B., Markovic S.B., Zech M. (in press). Two possible source regions for Central Greenland last glacial dust. Geophysical Research Letters, doi: 10.1002/2015GL066153.

Field-testing a new directional passive air sampler for fugitive dust in a complex industrial source environment.

PubMed

Ferranti, E J S; Fryer, M; Sweetman, A J; Garcia, M A Solera; Timmis, R J

2014-01-01

Quantifying the sources of fugitive dusts on complex industrial sites is essential for regulation and effective dust management. This study applied two recently-patented Directional Passive Air Samplers (DPAS) to measure the fugitive dust contribution from a Metal Recovery Plant (MRP) located on the periphery of a major steelworks site. The DPAS can collect separate samples for winds from different directions (12 × 30° sectors), and the collected dust may be quantified using several different measurement methods. The DPASs were located up and down-prevailing-wind of the MRP processing area to (i) identify and measure the contribution made by the MRP processing operation; (ii) monitor this contribution during the processing of a particularly dusty material; and (iii) detect any changes to this contribution following new dust-control measures. Sampling took place over a 12-month period and the amount of dust was quantified using photographic, magnetic and mass-loading measurement methods. The DPASs are able to effectively resolve the incoming dust signal from the wider steelworks complex, and also different sources of fugitive dust from the MRP processing area. There was no confirmable increase in the dust contribution from the MRP during the processing of a particularly dusty material, but dust levels significantly reduced following the introduction of new dust-control measures. This research was undertaken in a regulatory context, and the results provide a unique evidence-base for current and future operational or regulatory decisions.

Interactions Between Mineral Dust, Climate, and Ocean Ecosystems

NASA Technical Reports Server (NTRS)

Gasso, Santiago; Grassian, Vicki H.; Miller, Ron L.

2010-01-01

Over the past decade, technological improvements in the chemical and physical characterization of dust have provided insights into a number of phenomena that were previously unknown or poorly understood. In addition, models are now incorporating a wider range of physical processes, which will allow us to better quantify the climatic and ecological impacts of dust. For example, some models include the effect of dust on oceanic photosynthesis and thus on atmospheric CO 2 (Friedlingstein et al. 2006). The impact of long-range dust transport, with its multiple forcings and feedbacks, is a relatively new and complex area of research, where input from several disciplines is needed. So far, many of these effects have only been parameterized in models in very simple terms. For example, the representation of dust sources remains a major uncertainty in dust modeling and estimates of the global mass of airborne dust. This is a problem where Earth scientists could make an important contribution, by working with climate scientists to determine the type of environments in which easily erodible soil particles might have accumulated over time. Geologists could also help to identify the predominant mineralogical composition of dust sources, which is crucial for calculating the radiative and chemical effects of dust but is currently known for only a few regions. Understanding how climate and geological processes control source extent and characterizing the mineral content of airborne dust are two of the fascinating challenges in future dust research.

Climatology of dust distribution over West Asia from homogenized remote sensing data

NASA Astrophysics Data System (ADS)

Nabavi, Seyed Omid; Haimberger, Leopold; Samimi, Cyrus

2016-06-01

In the past decade, West Asia has witnessed more frequent and intensified dust storms affecting Iran and Persian Gulf countries. Employing a varying threshold that takes into account systematic differences between TOMS and OMI data, TOMS-OMI Aerosol Index data are used to identify long-term changes in the horizontal distribution of dust storms in West Asia from 1980 to present. The northwest of Iraq and east of Syria are identified as emerging dusty areas, whereas east of Saudi Arabia and southeast of Iraq are identified as permanent dusty areas, including both dust sources and affected areas. Whereas the frequency of dust events increased slightly in the permanent dusty areas, it increased markedly in the emerging dusty areas. As expected, the frequency of dust events is highest in June and July. The dust source areas are identified as the Iraq-Saudi Arabia boundary region and (recently) the northwest of Iraq, using MODIS deep blue aerosol optical depth data. Subsequently, a lagged correlation was implemented between identified dust sources and whole West Asia to determine the main paths and receptors of intense dust storms. Accordingly, southwest of Iran and Persian Gulf countries were determined as main receptors of summertime dust storms in West Asia. During spring, dust storms mostly hit the northern half of the region and reach to the Caspian Sea. Analyzing atmospheric patterns, Shamal and Frontal patterns were found as dominant atmospheric circulations simultaneous with summertime and springtime dust storms, respectively.

The Detectability of Exo-Earths and Super-Earths via Resonant Signatures in Exozodiacal Clouds

NASA Technical Reports Server (NTRS)

Stark, Christopher C.; Kuchner, Marc

2008-01-01

Directly imaging extrasolar terrestrial planets necessarily means contending with the astrophysical noise of exozodiacal dust and the resonant structures created by these planets in exozodiacal clouds. Using a custom tailored hybrid symplectic integrator we have constructed 120 models of resonant structures created by exo-Earths and super-Earths on circular orbits interacting with collisionless steady-state dust clouds around a Sun-like star. Our models include enough particles to overcome the limitations of previous simulations that were often dominated by a handful of long-lived particles, allowing us to quantitatively study the contrast of the resulting ring structures. We found that in the case of a planet on a circular orbit, for a given star and dust source distribution, the morphology and contrast of the resonant structures depend on only two parameters: planet mass and (square root)ap/Beta, where ap is the planet's semi-major axis and Beta is the ratio of radiation pressure force to gravitational force on a grain. We constructed multiple-grain-size models of 25,000 particles each and showed that in a collisionless cloud, a Dohnanyi crushing law yields a resonant ring whose optical depth is dominated by the largest grains in the distribution, not the smallest. We used these models to estimate the mass of the lowest-mass planet that can be detected through observations of a resonant ring for a variety of assumptions about the dust cloud and the planet's orbit. Our simulations suggest that planets with mass as small as a few times Mars' mass may produce detectable signatures in debris disks at ap greater than or approximately equal to 10 AU.

High-Resolution Submillimeter and Near-Infrared Studies of the Transition Disk Around Sz 91

NASA Technical Reports Server (NTRS)

Tsukagoshi, Takashi; Momose, Munetake; Abe, Lyu; Akiyama, Eiji; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Currie, Thayne; Egner, Sebastian E.; Goto, Miwa;

Inside the Belly of a Mars Dust Storm

NASA Astrophysics Data System (ADS)

Rafkin, Scot; Pla-Garcia, Jorge

2017-04-01

There have never been in situ observations at or near the active lifting center of a regional dust storm on Mars. Landed meteorological packages have recorded the atmospheric environment during large and global dust storms, but only at a distance from the presumed active areas. In the absence of in situ data, it is common to employ numerical models to provide guidance on the physical processes and conditions operating in an unobserved location or weather system. This is a reasonable approach assuming the model has been adequately validated at other locations. Consequently, the Mars Regional Atmospheric Modeling System (MRAMS) is employed to study the structure and dynamics of a simulated large regional storm in the Isidis Basin area, and to provide the first ever glimpse of the conditions that might occur inside one of these storms. The simulation has five grids, and dust lifting is permitted only on grids three through five. Limiting the dust lifting to the three highest resolution grids forces the model to produce a dust storm no larger than the size of the third grid domain. The simulation is run for a total of five sols with the simulations starting at 0500 (local time). Dust lifting is activated at 0500 local on the second sol, and continues through sol 3. Lifting is deactivated on sol 4 in order to force dust storm decay. The simulated storm shows extremely complex structure, highly heterogenous lifting centers, and a variety of deep dust transport circulations. The active lifting centers show broader organization into a mesoscale system in much the same way that thunderstorms on Earth can organize into mesoscale convective structures. In many of the active dust plumes, the mixing ratio of dust peaks near the surface and drops off with height. The surface mixing ratio maximum is partly due to the surface being the source of dust, with entrainment of less dusty air as the plume rises. However, it is also because the mixing ratio can be dominated by a few large dust aerosol, since the mass is proportional to the cubed of the radius. Once lifted, the largest dust tends to sediment out while the smaller dust continues to be advected upward by the plume. This size-sorting process tends to drive the mixing ratio profile to a maximum near the surface. In dusty plumes near the surface, the air temperature is as much as 20K colder than nearby areas. This is due to solar absorption higher in the dust column limiting direct heating deeper into the atmosphere. Overall, within the plume, there is an inversion, and although the top of the plume is warmer than below, it is near neutral buoyancy compared to the less dusty air on either side. Apparently, adiabatic cooling nearly offsets the expected positive heating perturbation at the top of the dusty plume. A very strong low level jet forms in the vicinity of the storm, accompanied by system-wide negative pressure deficits and circulation patterns strongly suggestive of the wind-enhanced interaction of radiation and dust (WEIRD) feedback mechanism.

EXTRAGALACTIC MILLIMETER-WAVE SOURCES IN SOUTH POLE TELESCOPE SURVEY DATA: SOURCE COUNTS, CATALOG, AND STATISTICS FOR AN 87 SQUARE-DEGREE FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vieira, J. D.; Crawford, T. M.; Switzer, E. R.

2010-08-10

We report the results of an 87 deg{sup 2} point-source survey centered at R.A. 5{sup h}30{sup m}, decl. -55{sup 0} taken with the South Pole Telescope at 1.4 and 2.0 mm wavelengths with arcminute resolution and milli-Jansky depth. Based on the ratio of flux in the two bands, we separate the detected sources into two populations, one consistent with synchrotron emission from active galactic nuclei and the other consistent with thermal emission from dust. We present source counts for each population from 11 to 640 mJy at 1.4 mm and from 4.4 to 800 mJy at 2.0 mm. The 2.0more » mm counts are dominated by synchrotron-dominated sources across our reported flux range; the 1.4 mm counts are dominated by synchrotron-dominated sources above {approx}15 mJy and by dust-dominated sources below that flux level. We detect 141 synchrotron-dominated sources and 47 dust-dominated sources at signal-to-noise ratio S/N >4.5 in at least one band. All of the most significantly detected members of the synchrotron-dominated population are associated with sources in previously published radio catalogs. Some of the dust-dominated sources are associated with nearby (z << 1) galaxies whose dust emission is also detected by the Infrared Astronomy Satellite. However, most of the bright, dust-dominated sources have no counterparts in any existing catalogs. We argue that these sources represent the rarest and brightest members of the population commonly referred to as submillimeter galaxies (SMGs). Because these sources are selected at longer wavelengths than in typical SMG surveys, they are expected to have a higher mean redshift distribution and may provide a new window on galaxy formation in the early universe.« less

Origin of Bermuda's clay-rich Quaternary paleosols and their paleoclimatic significance

USGS Publications Warehouse

Herwitz, S.R.; Muhs, D.R.; Prospero, J.M.; Mahan, S.; Vaughn, B.

1996-01-01

Red clayey paleosols that are chiefly the product of aerosolic dust deposition are interbedded in the Quaternary carbonate formations of the Bermuda oceanic island system. These paleosols provide a basis for reconstructing Quaternary atmospheric circulation patterns in the northwestern Atlantic. Geochemical analyses were performed on representative paleosol samples to identify their parent dust source. Fine-grained fractions were analyzed by energy-dispersive X ray fluorescence to determine trace element (Zr, Y, La, Ti, and Nb) concentrations and to derive geochemical signatures based on immobile element ratios. These ratios were compared with geochemical signatures determined for three possible sources of airborne dust: (1) Great Plains loess, (2) Mississippi River Valley loess, and (3) Saharan dust. The Zr/Y and Zr/La ratios provided the clearest distinction between the hypothesized dust sources. The low ratios in the paleosol B horizons most closely resemble Saharan dust in the <2-??m size class fraction. Contributions from the two North American loessial source areas could not be clearly detected. Thus Bermuda paleosols have a predominantly Saharan aerosolic dust signature. Saharan dust deposition on Bermuda during successive Quaternary glacial periods is consistent with patterns of general circulation models, which indicate that during glacial maxima the northeast summer trade winds were stronger than at present and reached latitudes higher than 30 ?? N despite lower-than-present sea surface temperatures in the North Atlantic.

On The Origins Of Cosmic Dust And The Evolution Of Nearby Galaxies With The Herschel Space Observatory

NASA Astrophysics Data System (ADS)

Clark, Christopher Jonathan Redfern

2015-04-01

Using multiwavelength observations, centred around the unique far-infrared and submillimetre window provided by the Herschel Space Observatory, this thesis investigates the origins and evolution of cosmic dust in the local Universe - by examining individual sources of dust in our own galaxy, and by studying dust in nearby galaxies. I search Herschel observations of the remnants of Kepler’s (SN1604) and Tycho’s (SN1572) supernovæ, both Type-Ia explosions, for evidence of dust creation by these events. Being the only Type-Ia supernovæ known to have occurred in our Galaxy within the past 1,000 years, these remnants are the only ones both close enough to resolve, and young enough that they are dominated by their ejecta dynamics. There is no indication of any recently manufactured dust associated with either supernova remnant. It therefore appears that Type-Ia supernovæ do not contribute significantly to the dust budgets of galaxies. The Crab Nebula, the result of a Type-II supernova (SN1054), is also investigated using Herschel and multiwavelength data. After accounting for other sources of emission, a temperature of Td = 63.1 K and mass of Md = 0.21 M⊙ is derived for the Crab Nebula’s dust component. I create a map of the distribution of dust in the Crab Nebula, the first of its kind, by means of a resolved component separation, revealing that the dust is located in the dense filamentary ejecta. We can be confident that this dust will survive in the long term, and be injected into the galactic dust budget. This is the first detection of manufactured supernova dust for which this can be said. Next I use the Herschel-ATLAS to assemble HAPLESS: the Herschel- ATLAS Phase-1 Limited Extent Spatial Sample - a blind, volume-limited, dust- selected sample of nearby galaxies. The majority of this sample is made up of curious very blue galaxies. Often irregular and/or flocculent in morphology, with extremely blue UV-NIR colours, these galaxies appear to be prominent in the local dusty universe. In the absence of reliable photometry for the HAPLESS galaxies, I describe the function and testing of a purpose-built photometric pipeline - CAAPR: Chris’ Adequate Aperture Photometry Routine. The photometry conducted with CAAPR exhibits flux greater by factors of, on average, 1.6 in the FUV and 1.4 in r-band, relative to the previously-available photometry. In comparison to other surveys of dust in local galaxies, the HAPLESS systems show a strong propensity towards very late morphological types and extremely blue FUV-Ks colours. The dust in the HAPLESS galaxies appears to be very cold, with a median temperature of 14.6 K. They are also exceptionally dust rich, with a median dust mass of 5.3 × 106 M(_{\\odot}) , and a median Md/M(_{\\star}) of 4.4×10-3 - greater by a factor of 1.8-3.7 than that seen in other local surveys. The curious very blue HAPLESS galaxies, whilst accounting for only 6% of the stellar mass in our sample, contain over 35% of the dust mass. I show that the more dust-rich a galaxy (as defined by Md/M(_{\\star})), the smaller the fraction of its UV luminosity that suffers dust absorption - this effect is observed to be particularly dramatic in the case of the curious very blue objects. Either the emissivity or geometry of the dust in these systems must be highly unusual. HAPLESS suggests a dust mass volume density of the local universe of (3.7 ± 0.7) × 105 M(_{\\odot}) Mpc-3; the largest value reported to date. The HAPLESS 250 μm luminosity function is in good agreement with surveys of far larger volumes, suggesting that we do not sample an over-dense region of space. The HAPLESS galaxies are extraordinarily gas rich; the median HAPLESS gas fraction is 0.52, and 19% of the sample have gas fractions >0.8. The median HAPLESS gas-to-dust ratio is ≍260, 2-3 times larger than in other local surveys. The very blue galaxies of the sample are found to be particularly gas rich; a chemical and dust evolution model indicates that they are at an early stage of converting their gas into stars. A dust-selected survey such as H-ATLAS is a particularly efficient way of identifying young systems of this kind, which should therefore provide valuable insights into the chemical evolution of young galaxies.

Persistence of deeply sourced iron in the Pacific Ocean

PubMed Central

Horner, Tristan J.; Williams, Helen M.; Hein, James R.; Saito, Mak A.; Burton, Kevin W.; Halliday, Alex N.; Nielsen, Sune G.

2015-01-01

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe−Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface. PMID:25605900

Persistence of deeply sourced iron in the Pacific Ocean.

PubMed

Horner, Tristan J; Williams, Helen M; Hein, James R; Saito, Mak A; Burton, Kevin W; Halliday, Alex N; Nielsen, Sune G

2015-02-03

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.

AIRUSE-LIFE+: a harmonized PM speciation and source apportionment in five southern European cities

NASA Astrophysics Data System (ADS)

Amato, Fulvio; Alastuey, Andrés; Karanasiou, Angeliki; Lucarelli, Franco; Nava, Silvia; Calzolai, Giulia; Severi, Mirko; Becagli, Silvia; Gianelle, Vorne L.; Colombi, Cristina; Alves, Celia; Custódio, Danilo; Nunes, Teresa; Cerqueira, Mario; Pio, Casimiro; Eleftheriadis, Konstantinos; Diapouli, Evangelia; Reche, Cristina; Cruz Minguillón, María; Manousakas, Manousos-Ioannis; Maggos, Thomas; Vratolis, Stergios; Harrison, Roy M.; Querol, Xavier

2016-03-01

The AIRUSE-LIFE+ project aims at characterizing similarities and heterogeneities in particulate matter (PM) sources and contributions in urban areas from southern Europe. Once the main PMx sources are identified, AIRUSE aims at developing and testing the efficiency of specific and non-specific measures to improve urban air quality. This article reports the results of the source apportionment of PM10 and PM2.5 conducted at three urban background sites (Barcelona, Florence and Milan, BCN-UB, FI-UB and MLN-UB), one suburban background site (Athens, ATH-SUB) and one traffic site (Porto, POR-TR). After collecting 1047 PM10 and 1116 PM2.5 24 h samples during 12 months (from January 2013 on) simultaneously at the five cities, these were analysed for the contents of OC, EC, anions, cations, major and trace elements and levoglucosan. The USEPA PMF5 receptor model was applied to these data sets in a harmonized way for each city. The sum of vehicle exhaust (VEX) and non-exhaust (NEX) contributes between 3.9 and 10.8 µg m-3 (16-32 %) to PM10 and 2.3 and 9.4 µg m-3 (15-36 %) to PM2.5, although a fraction of secondary nitrate is also traffic-related but could not be estimated. Important contributions arise from secondary particles (nitrate, sulfate and organics) in PM2.5 (37-82 %) but also in PM10 (40-71 %), mostly at background sites, revealing the importance of abating gaseous precursors in designing air quality plans. Biomass burning (BB) contributions vary widely, from 14-24 % of PM10 in POR-TR, MLN-UB and FI-UB, 7 % in ATH-SUB, to < 2 % in BCN-UB. In PM2.5, BB is the second most important source in MLN-UB (21 %) and in POR-TR (18 %), the third one in FI-UB (21 %) and ATH-SUB (11 %), but is again negligible (< 2 %) in BCN-UB. This large variability among cities is mostly due to the degree of penetration of biomass for residential heating. In Barcelona natural gas is very well supplied across the city and is used as fuel in 96 % of homes, while in other cities, PM levels increase on an annual basis by 1-9 µg m-3 due to biomass burning influence. Other significant sources are the following. - Local dust, 7-12 % of PM10 at SUB and UB sites and 19 % at the TR site, revealing a contribution from road dust resuspension. In PM2.5 percentages decrease to 2-7 % at SUB-UB sites and 15 % at the TR site. - Industry, mainly metallurgy, contributing 4-11 % of PM10 (5-12 % in PM2.5), but only at BCN-UB, POR-TR and MLN-UB. No clear impact of industrial emissions was found in FI-UB and ATH-SUB. - Natural contributions from sea salt (13 % of PM10 in POR-TR, but only 2-7 % in the other cities) and Saharan dust (14 % in ATH-SUB, but less than 4 % in the other cities). During high pollution days, the largest sources (i.e. excluding secondary aerosol factors) of PM10 and PM2.5 are VEX + NEX in BCN-UB (27-22 %) and POR-TR (31-33 %), BB in FI-UB (30-33 %) and MLN-UB (35-26 %) and Saharan dust in ATH-SUB (52-45 %). During those days, there are also quite important industrial contributions in BCN-UB (17-18 %) and local dust in POR-TR (28-20 %).

Source analysis of radiocesium in river waters using road dust tracers.

PubMed

Murakami, Michio; Saha, Mahua; Iwasaki, Yuichi; Yamashita, Rei; Koibuchi, Yukio; Tsukada, Hirofumi; Takada, Hideshige; Sueki, Keisuke; Yasutaka, Tetsuo

2017-11-01

Following the Fukushima Dai-ichi Nuclear Power Station accident, regional road dust, heavily contaminated with radiocesium, now represents a potential source of radiocesium pollution in river water. To promote effective countermeasures for reducing the risk from radiocesium pollution, it is important to understand its sources. This study evaluated the utility of metals, including Al, Fe, and Zn as road dust tracers, and applied them to analyze sources of 137 Cs in rivers around Fukushima during wet weather. Concentrations of Zn in road dust were higher than agricultural and forest soils, whereas concentrations of Fe and Al were the opposite. Concentrations of Zn were weakly but significantly correlated with benzothiazole, a molecular marker of tires, indicating Zn represents an effective tracer of road dust. Al, Fe, and Zn were frequently detected in suspended solids in river water during wet weather. Distribution coefficients of these metals and 137 Cs exceeded 10 4 , suggesting sorptive behavior in water. Although concentrations of Al, Fe, Zn, and 137 Cs were higher in fine fractions of road dust and soils than in coarse fractions, use of ratios of 137 Cs to Al, Fe, or Zn showed smaller differences among size fractions. The results demonstrate that combinations of these metals and 137 Cs are useful for analyzing sources of radiocesium in water. These ratios in river water during wet weather were found to be comparable with or lower than during dry weather and were closer to soils than road dust, suggesting a limited contribution from road dust to radiocesium pollution in river water. Copyright © 2017 Elsevier Ltd. All rights reserved.

PM₁₀ and PM₂.₅ sources at an insular location in the western Mediterranean by using source apportionment techniques.

PubMed

Pey, Jorge; Alastuey, Andrés; Querol, Xavier

2013-07-01

PM₁₀ and PM₂.₅ chemical composition has been determined at a suburban insular site in the Balearic Islands (Spain) during almost one and a half year. As a result, 200 samples with more than 50 chemical parameters analyzed have been obtained. The whole database has been analyzed by two receptor modelling techniques (Principal Component Analysis and Positive Matrix Factorisation) in order to identify the main PM sources. After that, regression analyses with respect to the PM mass concentrations were conducted to quantify the daily contributions of each source. Four common sources were identified by both receptor models: secondary nitrate coupled with vehicular emissions, secondary sulphate influenced by fuel-oil combustion, aged marine aerosols and mineral dust. In addition, PCA isolated harbour emissions and a mixed anthropogenic factor containing industrial emissions; whereas PMF isolated an additional mineral factor interpreted as road dust+harbour emissions, and a vehicular abrasion products factor. The use of both methodologies appeared complementary. Nevertheless, PMF sources by themselves were better differentiated. Besides these receptor models, a specific methodology to quantify African dust was also applied. The combination of these three source apportionment tools allowed the identification of 8 sources, being 4 of them mineral (African, regional, urban and harbour dusts). As a summary, 29% of PM₁₀ was attributed to natural sources (African dust, regional dust and sea spray), whereas the proportion diminished to 11% in PM₂.₅. Furthermore, the secondary sulphate source, which accounted for about 22 and 32% of PM₁₀ and PM₂.₅, is strongly linked to the aged polluted air masses residing over the western Mediterranean in the warm period. Copyright © 2013 Elsevier B.V. All rights reserved.

Global Distributions of Mineral Dust Properties from SeaWiFS and MODIS: From Sources to Sinks

NASA Technical Reports Server (NTRS)

Hsu, N. Christina; Bettenhausen, C.; Sayer, A.

2011-01-01

The impact of natural and anthropogenic sources of mineral dust has gained increasing attention from scientific communities in recent years. Indeed, these airborne dust particles, once lifted over the source regions, can be transported out of the boundary layer into the free troposphere and can travel thousands of kilometers across the oceans resulting in important biogeochemical impacts on the ecosystem. Due to the relatively short lifetime (a few hours to about a week), the distributions of these mineral dust particles vary extensively in both space and time. Consequently, satellite observations are needed over both source and sink regions for continuous temporal and spatial sampling of aerosol properties. With the launch of SeaWiFS in 1997, Terra/MODIS in 1999, and Aqua/MODIS in 2002, high quality comprehensive aerosol climatology is becoming feasible for the first time. As a result of these unprecedented satellite data records, studies of the radiative and biogeochemical effects due to dust aerosols are now possible. In this study, we will show the comparisons of satellite retrieved aerosol optical thickness using Deep Blue algorithm with data from AERONET sunphotometers over desert and semi-desert regions as well as vegetated areas. Our results indicate reasonable agreements between these two. These new satellite products will allow scientists to determine quantitatively the aerosol properties near sources using high spatial resolution measurements from Sea WiFS and MODIS-like instruments. The multiyear satellite measurements since 1997 from Sea WiFS will be compared with those retrieved from MODIS and MISR, and will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with the dust outbreaks over the entire globe. Finally, the trends observed over the last decade based upon the SeaWiFS time series in the amounts of tropospheric aerosols due to natural and anthropogenic sources (such as changes in the frequency of dust storms) will be discussed.

Dust Storm over the Middle East: Retrieval Approach, Source Identification, and Trend Analysis

NASA Astrophysics Data System (ADS)

Moridnejad, A.; Karimi, N.; Ariya, P. A.

2014-12-01

The Middle East region has been considered to be responsible for approximately 25% of the Earth's global emissions of dust particles. By developing Middle East Dust Index (MEDI) and applying to 70 dust storms characterized on MODIS images and occurred during the period between 2001 and 2012, we herein present a new high resolution mapping of major atmospheric dust source points participating in this region. To assist environmental managers and decision maker in taking proper and prioritized measures, we then categorize identified sources in terms of intensity based on extracted indices for Deep Blue algorithm and also utilize frequency of occurrence approach to find the sensitive sources. In next step, by implementing the spectral mixture analysis on the Landsat TM images (1984 and 2012), a novel desertification map will be presented. The aim is to understand how human perturbations and land-use change have influenced the dust storm points in the region. Preliminary results of this study indicate for the first time that c.a., 39 % of all detected source points are located in this newly anthropogenically desertified area. A large number of low frequency sources are located within or close to the newly desertified areas. These severely desertified regions require immediate concern at a global scale. During next 6 months, further research will be performed to confirm these preliminary results.

[Chemical Compositions and Sources Apportionment of Re-suspended Dust in Jincheng].

PubMed

Wang, Yan; Peng, Lin; Li, Li-juan; Zhang, Teng; Liu, Hai-li; Mu, Ling

2016-01-15

In order to make effective plan to provide the scientific basis for prevention and control of re-suspended dust (RD), samples of particulate sources including RD and other pollution sources of Jincheng were collected. Elements, ions and carbon in particulate sources were analyzed. Enrichment factor, potential ecological risk assessment, and chemical mass balance model were used to analyze the chemical composition and the source of RD. The result indicated that the main components in RD of Jingeheng were Si, TC, Ca, OC, Al, Mg, Na, Fe, K and SO4(2-), contributing 61.14% of total mass of RD. The most abundant content of RD was crustal elements, and the ions were enriched in the fine particles. The mass fraction of OC in PM2. was higher, whereas the mass fraction of EC in PM10 was higher, indicating that secondary organic pollutants were mainly dominated in the fine particles. The dust PM2.5 and PM10 potential ecological risk indexes were extremely strong, and PM2.5 had higher ecological harm than PM10. Pb had the highest enrichment factor of 196.97 in PM2.5, which was followed by As, Cr, Ni, V, Zn and Cu, the enrichment factors of which were all greater than 10, indicating that they were apparently enriched and affected by human activities. Soil dust, construction dust, vehicle exhaust, and coal dust were the main sources of RD.

Characterization of Asian Dust Properties Near Source Region During ACE-Asia

NASA Technical Reports Server (NTRS)

Tsay, Si-Chee; Hsu, N. Christina; King, Michael D.; Kaufman, Yoram J.; Herman, Jay R.

2004-01-01

Asian dust typically originates in desert areas far from polluted urban regions. During transport, dust layers can interact with anthropogenic sulfate and soot aerosols from heavily polluted urban areas. Added to the complex effects of clouds and natural marine aerosols, dust particles reaching the marine environment can have drastically different properties than those from the source. Thus, understanding the unique temporal and spatial variations of Asian aerosols is of special importance in regional-to-global climate issues such as radiative forcing, the hydrological cycle, and primary biological productivity in the mid-Pacific Ocean. During ACE-Asia campaign, we have acquired ground- based (temporal) and satellite (spatial) measurements to infer aerosol physical/optical/radiative properties, column precipitable water amount, and surface reflectivity over this region. The inclusion of flux measurements permits the determination of aerosol radiative flux in addition to measurements of loading and optical depth. At the time of the Terra/MODIS, SeaWiFS, TOMS and other satellite overpasses, these ground-based observations can provide valuable data to compare with satellite retrievals over land. In this paper, we will demonstrate new capability of the Deep Blue algorithm to track the evolution of the Asian dust storm from sources to sinks. Although there are large areas often covered by clouds in the dust season in East Asia, this algorithm is able to distinguish heavy dust from clouds over the entire regions. Examination of the retrieved daily maps of dust plumes over East Asia clearly identifies the sources contributing to the dust loading in the atmosphe. We have compared the satellite retrieved aerosol optical thickness to the ground-based measurements and obtained a reasonable agreement between these two. Our results also indicate that there is a large difference in the retrieved value of spectral single scattering albedo of windblown dust between different sources in East Asia.

Source reconciliation of atmospheric dust causing visibility impairment in Class I areas of the western United States

NASA Astrophysics Data System (ADS)

Kavouras, Ilias G.; Etyemezian, Vicken; Dubois, David W.; Xu, Jin; Pitchford, Marc

2009-01-01

Aerosol data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, air mass backward trajectories, land use maps, soil characteristics maps, diagnostic ratios of elemental composition, and multivariate linear regression were utilized as part of a semiquantitative analysis. The purpose of the analysis was to determine the types of dust-causing events that contribute to low visibility at a given site when the sum of extinction from coarse mass (CM) and fine soil (FS) was larger than any other aerosol component and the reconstructed aerosol extinction coefficient was among the 20% highest (calculated on a calendar year basis) for that site. For these "worst dust days," the above tools were used to ascribe the cause of low visibility to one of the following types of events: (1) transcontinental transport of dust originating from Asia; (2) windblown dust events from sources located nearby the site and; (3) transport of windblown dust from sources upwind of the site. Depending on the weight of evidence, a low or high level of confidence was associated with the assignment of one of these three events. Absence of convincing evidence resulted in ascribing the worst dust day to "undetermined events." Of the 610 worst dust days over the 2001-2003 period, 51% were associated with one of the three event types with high confidence and an additional 30% were accounted for with low confidence. Of the 496 worst dust days associated with an event (either low or high confidence), Asian dust was the assigned event on 55 days (for 2001-2002), locally generated windblown dust on 201 days, and transport from upwind source areas susceptible to wind erosion on 240 days. Events associated with windblown episodes from source areas in the United States and Mexico exhibited the highest dust concentrations. Asian dust events were associated with lower dust concentrations and a larger FS-to-CM ratio. Some variations between Asian dust and continental North American dust were observed in organic matter (OMC), black carbon (LAC), and nitrate (NO3-) content. None of the tools used in this study was adequate for identifying events associated with mechanically released dust by anthropogenic activities including, agriculture, construction and motor vehicle travel on paved and unpaved roads. Some of the worst dust days may have been caused by these types of activities, especially in central Arizona and northern and Southern California, where the fraction of undetermined events was higher than in other regions within the western United States. All in all, the methods and results of this study can help improve the performance of large-scale dust emission models and provide insight into the distribution of the types of events that cause dust resultant haze in relatively remote areas of the western United States.

The role of airborne mineral dusts in human disease

USGS Publications Warehouse

Morman, Suzette A.; Plumlee, Geoffrey S.

2013-01-01

Exposure to fine particulate matter (PM) is generally acknowledged to increase risk for human morbidity and mortality. However, particulate matter (PM) research has generally examined anthropogenic (industry and combustion by-products) sources with few studies considering contributions from geogenic PM (produced from the Earth by natural processes, e.g., volcanic ash, windborne ash from wildfires, and mineral dusts) or geoanthropogenic PM (produced from natural sources by processes that are modified or enhanced by human activities, e.g., dusts from lakebeds dried by human removal of water, dusts produced from areas that have undergone desertification as a result of human practices). Globally, public health concerns are mounting, related to potential increases in dust emission from climate related changes such as desertification and the associated long range as well as local health effects. Recent epidemiological studies have identified associations between far-traveled dusts from primary sources and increased morbidity and mortality in Europe and Asia. This paper provides an outline of public health research and history as it relates to naturally occurring inorganic mineral dusts. We summarize results of current public health research and describe some of the many challenges related to understanding health effects from exposures to dust aerosols.

Onset of frequent dust storms in northern China at ~AD 1100.

PubMed

He, Yuxin; Zhao, Cheng; Song, Mu; Liu, Weiguo; Chen, Fahu; Zhang, Dian; Liu, Zhonghui

2015-11-26

Dust storms in northern China strongly affect the living and health of people there and the dusts could travel a full circle of the globe in a short time. Historically, more frequent dust storms occurred during cool periods, particularly the Little Ice Age (LIA), generally attributed to the strengthened Siberian High. However, limited by chronological uncertainties in proxy records, this mechanism may not fully reveal the causes of dust storm frequency changes. Here we present a late Holocene dust record from the Qaidam Basin, where hydrological changes were previously reconstructed, and examine dust records from northern China, including the ones from historical documents. The records, being broadly consistent, indicate the onset of frequent dust storms at ~AD 1100. Further, peaked dust storm events occurred at episodes of high total solar irradiance or warm-dry conditions in source regions, superimposed on the high background of frequent dust storms within the cool LIA period. We thus suggest that besides strong wind activities, the centennial-scale dust storm events over the last 1000 years appear to be linked to the increased availability of dust source. With the anticipated global warming and deteriorating vegetation coverage, frequent occurrence of dust storms in northern China would be expected to persist.

Organic marker compounds in surface soils of crop fields from the San Joaquin Valley fugitive dust characterization study

NASA Astrophysics Data System (ADS)

Rogge, Wolfgang F.; Medeiros, Patricia M.; Simoneit, Bernd R. T.

Fugitive dust from the erosion of arid and fallow land, after harvest and during agricultural activities, can at times be the dominant source of airborne particulate matter. In order to assess the source contributions to a given site, chemical mass balance (CMB) modeling is typically used together with source-specific profiles for organic and inorganic constituents. Yet, the mass balance closure can be achieved only if emission profiles for all major sources are considered. While a higher degree of mass balance closure has been achieved by adding individual organic marker compounds to elements, ions, EC, and organic carbon (OC), major source profiles for fugitive dust are not available. Consequently, neither the exposure of the population living near fugitive dust sources from farm land, nor its chemical composition is known. Surface soils from crop fields are enriched in plant detritus from both above and below ground plant parts; therefore, surface soil dust contains natural organic compounds from the crops and soil microbiota. Here, surface soils derived from fields growing cotton, safflower, tomato, almonds, and grapes have been analyzed for more than 180 organic compounds, including natural lipids, saccharides, pesticides, herbicides, and polycyclic aromatic hydrocarbon (PAH). The major result of this study is that selective biogenically derived organic compounds are suitable markers of fugitive dust from major agricultural crop fields in the San Joaquin Valley. Aliphatic homologs exhibit the typical biogenic signatures of epicuticular plant waxes and are therefore indicative of fugitive dust emissions and mechanical abrasion of wax protrusions from leaf surfaces. Saccharides, among which α- and β-glucose, sucrose, and mycose show the highest concentrations in surface soils, have been proposed to be generic markers for fugitive dust from cultivated land. Similarly, steroids are strongly indicative of fugitive dust. Yet, triterpenoids reveal the most pronounced distribution differences for all types of cultivated soils examined here and are by themselves powerful markers for fugitive dust that allow differentiation between the types of crops cultivated. PAHs are also found in some surface soils, as well as persistent pesticides, e.g., DDE, Fosfall, and others.

Hf-Nd isotopic variability in mineral dust from Chinese and Mongolian deserts: implications for sources and dispersal

PubMed Central

Zhao, Wancang; Sun, Youbin; Balsam, William; Lu, Huayu; Liu, Lianwen; Chen, Jun; Ji, Junfeng

2014-01-01

Mineral dust provenances are closely related to the orogenic processes which may have distinct Hf-Nd isotopic signatures. Here we report the clay-sized (<2 μm) Hf-Nd isotope data from Asian dust sources to better constrain the source and transport dynamics of dust deposition in the North Pacific. Our results show that there is a more positive radiogenic Hf isotopic composition with clay-sized fractions than the corresponding bulk sample and a decoupling of the Hf-Nd couplets in the clay formation during the weathering process. The clay-sized Hf-Nd isotopic compositions of the desert samples from the Sino-Korean-Tarim Craton (SKTC) are different from those of the Gobi and deserts from the Central Asian Orogeny Belt (CAOB) due to varying tectonic and weathering controls. The Hf-Nd isotopic compositions of dust in the North Pacific central province (NPC) match closely with those from the Taklimakan, Badain Jaran and adjacent Tengger deserts, implying that the NPC dust was mainly transported from these potential sources by the westerly jet. Our study indicates that dusts from the CAOB Gobi deserts either didn't arrive in NPC or were quantitatively insignificant, but they were likely transported to the North Pacific margin province (NPM) by East Asian winter monsoon. PMID:25060781

Hf-Nd isotopic variability in mineral dust from Chinese and Mongolian deserts: implications for sources and dispersal.

PubMed

Zhao, Wancang; Sun, Youbin; Balsam, William; Lu, Huayu; Liu, Lianwen; Chen, Jun; Ji, Junfeng

2014-07-25

Mineral dust provenances are closely related to the orogenic processes which may have distinct Hf-Nd isotopic signatures. Here we report the clay-sized (<2 μm) Hf-Nd isotope data from Asian dust sources to better constrain the source and transport dynamics of dust deposition in the North Pacific. Our results show that there is a more positive radiogenic Hf isotopic composition with clay-sized fractions than the corresponding bulk sample and a decoupling of the Hf-Nd couplets in the clay formation during the weathering process. The clay-sized Hf-Nd isotopic compositions of the desert samples from the Sino-Korean-Tarim Craton (SKTC) are different from those of the Gobi and deserts from the Central Asian Orogeny Belt (CAOB) due to varying tectonic and weathering controls. The Hf-Nd isotopic compositions of dust in the North Pacific central province (NPC) match closely with those from the Taklimakan, Badain Jaran and adjacent Tengger deserts, implying that the NPC dust was mainly transported from these potential sources by the westerly jet. Our study indicates that dusts from the CAOB Gobi deserts either didn't arrive in NPC or were quantitatively insignificant, but they were likely transported to the North Pacific margin province (NPM) by East Asian winter monsoon.

Heavy metals and polycyclic aromatic hydrocarbons: pollution and ecological risk assessment in street dust of Tehran.

PubMed

Saeedi, Mohsen; Li, Loretta Y; Salmanzadeh, Mahdiyeh

2012-08-15

50 street dust samples from four major streets in eastern and southern Tehran, the capital of Iran, were analyzed for metal pollution (Cu, Cr, Pb, Ni, Cd, Zn, Fe, Mn and Li). Hakanson's method was used to determine the Risk Index (RI) and ecological risks. Amongst these samples, 21 were also analyzed for polycyclic aromatic hydrocarbons (PAHs). Correlation, cluster and principal component analyses identified probable natural and anthropogenic sources of contaminants. The dust had elevated concentrations of Pb, Cd, Cu, Cr, Ni, Zn, Fe and PAHs. Enrichment factors of Cu, Pb, Cd and Zn showed that the dust is extremely enriched in these metals. Multivariate statistical analyses revealed that Cu, Pb, Zn, Fe and PAHs and, to a lesser extent, Cr and Ni have common anthropogenic sources. While Mn and Li were identified to have natural sources, Cd may have different anthropogenic origins. All samples demonstrated high ecological risk. Traffic and related activities, petrogenic and pyrogenic sources are likely to be the main anthropogenic sources of heavy metals and PAHs in Tehran dust. Copyright © 2012 Elsevier B.V. All rights reserved.

Dust-Metal Sources in an Urbanized Arid Zone: Implications for Health-Risk Assessments.

PubMed

García-Rico, Leticia; Meza-Figueroa, Diana; Gandolfi, A Jay; Del Río-Salas, Rafael; Romero, Francisco M; Meza-Montenegro, Maria Mercedes

2016-04-01

The available information concerning metal pollution in different dust sources and the health effects in children remains limited in Mexico. This study focuses on Hermosillo, which is an urbanized area located in the Sonoran Desert in which soil resuspension and dust emission processes are common. The metal content of arsenic (As), chromium (Cr), manganese (Mn), and lead (Pb) were determined in three dust sources (playgrounds, roofs, and roads), each representing different exposure media (EM) for these elements. The metal levels in dust were found in the order of Mn > Cr > Pb > As with the highest metal content found in road dust. Despite the similar average metal distributions, principal component analysis shows a clear separation of the three EM with playground dust related to Cr and Mn and road dust to As and Pb. However, the geoaccumulation index results indicate that dust samples are uncontaminated to moderately polluted, except for Pb in road dust, which is considerably high. In addition, the enrichment factor suggests an anthropogenic origin for all of the studied metals except for Mn. In this context, the hazard index (HI) for noncarcinogenic risk is >1 in this population and thus represents a potential health risk. The spatial distribution for each metal on EM and the HI related to the marginality index could represent a more accurate decision-making tool in risk assessment studies.

Saharan Dust Deposition May Affect Phytoplankton Growth in the Mediterranean Sea at Ecological Time Scales

PubMed Central

Gallisai, Rachele; Peters, Francesc; Volpe, Gianluca; Basart, Sara; Baldasano, José Maria

2014-01-01

The surface waters of the Mediterranean Sea are extremely poor in the nutrients necessary for plankton growth. At the same time, the Mediterranean Sea borders with the largest and most active desert areas in the world and the atmosphere over the basin is subject to frequent injections of mineral dust particles. We describe statistical correlations between dust deposition over the Mediterranean Sea and surface chlorophyll concentrations at ecological time scales. Aerosol deposition of Saharan origin may explain 1 to 10% (average 5%) of seasonally detrended chlorophyll variability in the low nutrient-low chlorophyll Mediterranean. Most of the statistically significant correlations are positive with main effects in spring over the Eastern and Central Mediterranean, conforming to a view of dust events fueling needed nutrients to the planktonic community. Some areas show negative effects of dust deposition on chlorophyll, coinciding with regions under a large influence of aerosols from European origin. The influence of dust deposition on chlorophyll dynamics may become larger in future scenarios of increased aridity and shallowing of the mixed layer. PMID:25333783

Atmospheric effects on the mapping of Martian thermal inertia and thermally derived albedo

NASA Technical Reports Server (NTRS)

Hayashi, Joan N.; Jakosky, Bruce M.; Haberle, Robert M.

1995-01-01

We examine the effects of a dusty C02 atmosphere on the thermal inertia and thermally derived albedo of Mars and we present a new map of thermal inertias. This new map was produced using a coupled surface atmosphere (CSA) model, dust opacities from Viking infrared thermal mapper (IRTM) data, and C02 columns based on topography. The CSA model thermal inertias are smaller than the 2% model thermal inertias, with the difference largest at large thermal inertia. Although the difference between the thermal inertias obtained with the two models is moderate for much of the region studied, it is largest in regions of either high dust opacity or of topographic lows, including the Viking Lander 1 site and some geologically interesting regions. The CSA model thermally derived albedos do not accurately predict the IRTM measured albedos and are very similar to the thermally derived albedos obtained with models making the 2% assumption.

Atmospheric effects on the mapping of Martian thermal inertia and thermally derived albedo

NASA Technical Reports Server (NTRS)

Hayashi, Joan N.; Jakosky, Bruce M.; Haberle, Robert M.

1995-01-01

We examine the effects of a dusty CO2 atmosphere on the thermal inertia and thermally derived albedo of Mars and we present a new map of thermal inertias. This new map was produced using a coupled surface atmosphere (CSA) model, dust opacities from Viking infrared thermal mapper (IRTM) data, and CO2 columns based on topography. The CSA model thermal inertias are smaller than the 2% model thermal inertias, with the difference largest at large thermal inertia. Although the difference between the thermal inertias obtained with the two models is moderate for much of the region studied, it is largest in regions of either high dust opacity or of topographic lows, including the Viking Lander 1 site and some geologically interesting regions. The CSA model thermally derived albedos do not acurately predict the IRTM measured albedos and are very similar to the thermally derived albedos obtained with models making the 2% assumption.

Assessment of State-of-the-Art Dust Emission Scheme in GEOS

NASA Technical Reports Server (NTRS)

Darmenov, Anton; Liu, Xiaohong; Prigent, Catherine

2017-01-01

The GEOS modeling system has been extended with state of the art parameterization of dust emissions based on the vertical flux formulation described in Kok et al 2014. The new dust scheme was coupled with the GOCART and MAM aerosol models. In the present study we compare dust emissions, aerosol optical depth (AOD) and radiative fluxes from GEOS experiments with the standard and new dust emissions. AOD from the model experiments are also compared with AERONET and satellite based data. Based on this comparative analysis we concluded that the new parameterization improves the GEOS capability to model dust aerosols originating from African sources, however it lead to overestimation of dust emissions from Asian and Arabian sources. Further regional tuning of key parameters controlling the threshold friction velocity may be required in order to achieve more definitive and uniform improvement in the dust modeling skill.

The geologic records of dust in the Quaternary

USGS Publications Warehouse

Muhs, Daniel R.

2013-01-01

Study of geologic records of dust composition, sources and deposition rates is important for understanding the role of dust in the overall planetary radiation balance, fertilization of organisms in the world’s oceans, nutrient additions to the terrestrial biosphere and soils, and for paleoclimatic reconstructions. Both glacial and non-glacial processes produce fine-grained particles that can be transported by the wind. Geologic records of dust flux occur in a number of depositional archives for sediments: (1) loess deposits; (2) lake sediments; (3) soils; (4) deep-ocean basins; and (5) ice sheets and smaller glaciers. These archives have several characteristics that make them highly suitable for understanding the dynamics of dust entrainment, transport, and deposition. First, they are often distributed over wide geographic areas, which permits reconstruction of spatial variation of dust flux. Second, a number of dating methods can be applied to sediment archives, which allows identification of specific periods of greater or lesser dust flux. Third, aeolian sediment particle size and composition can be determined so that dust source areas can be ascertained and dust transport pathways can be reconstructed. Over much of the Earth’s surface, dust deposition rates were greater during the last glacial period than during the present interglacial period. A dustier Earth during glacial periods is likely due to increased source areas, greater aridity, less vegetation, lower soil moisture, possibly stronger winds, a decreased intensity of the hydrologic cycle, and greater production of dust-sized particles from expanded ice sheets and glaciers.

Can Transport of Saharan Dust Explain Extensive Clay Deposits in the Amazon Basin? A Test Using Radiogenic Isotopes

NASA Astrophysics Data System (ADS)

Andreae, M. O.; Abouchami, W.; Näthe, K.; Kumar, A.; Galer, S. J.; Jochum, K. P.; Williams, E.; Horbe, A. M.; Rosa, J. W.; Adams, D. K.; Balsam, W. R.

2012-12-01

The Bodélé Depression, located in the Southern Sahara, is a huge source of atmospheric dust and thus an important element in biogeochemical cycles and the radiative budget of Earth's atmosphere. Previous studies have shown that Saharan dust transport across the Atlantic acts as an important source of mineral nutrients to the Amazon rainforest. The Belterra Clay, which outcrops extensively across the Amazon Basin in Brazil, has been proposed to result from dry deposition of African dusts. We have investigated this hypothesis by measuring the radiogenic isotopic composition (Sr, Nd and Pb) of a suite of samples from the Belterra Clay, the Bodélé Depression, dusts deposits collected at various locations along the airmass transport trajectory, as well as loess from the Cape Verde Islands. Radiogenic isotope systems are powerful tracers of provenance and can be used to fingerprint dust sources and atmospheric transport patterns. Our results identify distinct isotopic signatures in the Belterra Clay samples and the African sources. The Belterra Clay display radiogenic Sr and Pb isotope ratios associated with non-radiogenic Nd isotope signatures. In contrast, Bodélé samples and dusts deposits show lower Pb isotope ratios, variable 87Sr/86Sr, and relatively homogeneous Nd isotopic compositions, albeit more radiogenic than those of the Belterra Clay. Our data show unambiguously that the Belterra Clay is not derived from African dust deposition, nor from the Andean chain, as originally suggested by W. Sombroek. Rather, isotopic compositions and Nd model ages are consistent with simple mixing of Archean and younger Proterozoic terranes within the Amazon Basin as a result of weathering and erosion under humid tropical conditions. Whether Saharan dusts contribute to the fertilization in the Amazon Basin cannot be ruled out, however, since the African dust isotopic signature is expected to be entirely overprinted by local sources. Radiogenic isotope data obtained on aerosol filters collected in the US Virgin Islands and Tobago are similar to those of aerosols from Mali, demonstrating that the African dust isotope signal is detectable and transported as far as Central and South America. Thus, while it appears undeniable that Saharan dust reaches the Amazon Basin, its importance for overall soil fertility requires a careful assessment of the dust budget versus bedrock weathering rates for key nutrient elements.

Impact of Radiatively Interactive Dust Aerosols on Dust Transport and Mobilization in the NASA Goddard Earth Observing System (GEOS-5) Earth Model

NASA Astrophysics Data System (ADS)

Colarco, P. R.; Rocha Lima, A.; Darmenov, A.; Bloecker, C.

2017-12-01

Mineral dust aerosols scatter and absorb solar and infrared radiation, impacting the energy budget of the Earth system which in turns feeds back on the dynamical processes responsible for mobilization of dust in the first place. In previous work with radiatively interactive aerosols in the NASA Goddard Earth Observing System global model (GEOS-5) we found a positive feedback between dust absorption and emissions. Emissions were the largest for the highest shortwave absorption considered, which additionally produced simulated dust transport in the best agreement with observations. The positive feedback found was in contrast to other modeling studies which instead found a negative feedback, where the impact of dust absorption was to stabilize the surface levels of the atmosphere and so reduce wind speeds. A key difference between our model and other models was that in GEOS-5 we simulated generally larger dust particles, with correspondingly larger infrared absorption that led to a pronounced difference in the diurnal cycle of dust emissions versus simulations where these long wave effects were not considered. In this paper we seek to resolve discrepancies between our previous simulations and those of other modeling groups. We revisit the question of dust radiative feedback on emissions with a recent version of the GEOS-5 system running at a higher spatial resolution and including updates to the parameterizations for dust mobilization, initial dust particle size distribution, loss processes, and radiative transfer, and identify key uncertainties that remain based on dust optical property assumptions.

High-throughput sequencing analysis of the bacteria in the dust storm which passed over Canberra, Australia on 22-23 September 2009

NASA Astrophysics Data System (ADS)

Munday, Chris; De Deckker, Patrick; Tapper, Nigel; Allison, Gwen

2014-05-01

Following a prolonged drought in Australia in the first decade of the 21st century, several dust storms affected the heavily populated East coast of Australia. The largest such storm occurred on 22-23 September 2009 and had a front of an estimated 3000km. A 24hr average PM10 concentration of over 2,000μg/m3 was recorded in several locations and an hourly peak of over 15,000μg/m3 was recorded (Leys et al. 2011). Over two time periods duplicate aerosol samples were collected on 47mm diameter cellulose nitrate membranes at a location removed from anthropogenic influences. One set of samples was collected in the afternoon the dust event started and another was collected overnight. Additionally, overnight rainfall was collected in a sterile bottle.DNA was directly extracted one membrane from each time point for molecular cloning and high throughput sequencing, while the other was cultivated on Tryptic Soy Agar (TSA). High throughput sequencing was performed using the 454 Titanium platform. From the three samples, 19,945 curated sequences were obtained representing 942 OTUS, with the three samples approximately equal in number. Unclassified Rhizobiales and Stenotrophomonas were the most abundant groups which could be attributed names. A total of 942 OTUs were identified (cutoff = 0.03), and despite the temporal relation of the samples, only eleven were found in all three samples, indicating that the dust storm evolved in composition as it passed over the region. Approximately 800 and 500 CFU/m3 were found in the two cultivated samples, tenfold more than was collected from previous dust events (Lim et al, 2011). Identification of cultivars revealed a dominance of the gram positive Firmicutes phylum, while the clone library showed a more even distribution of taxa, with Actinobacteria the most common and Firmicutes comprising less than 10% of sequences. Collectively, the analyses indicate that the concentration of cultivable organisms during the dust storm dramatically relative to calm conditions. A diverse and variable population of microorganisms were present reflecting the vast source and dynamic nature of the storm.

Dust: a metric for use in residential and building exposure assessment and source characterization.

PubMed Central

Lioy, Paul J; Freeman, Natalie C G; Millette, James R

2002-01-01

In this review, we examine house dust and residential soil and their use for identifying sources and the quantifying levels of toxicants for the estimation of exposure. We answer critical questions that focus on the selection of samples or sampling strategies for collection and discuss areas of uncertainty and gaps in knowledge. We discuss the evolution of dust sampling with a special emphasis on work conducted after the publication of the 1992 review by McArthur [Appl Occup Environ Hyg 7(9):599-606 (1992)]. The approaches to sampling dust examined include surface wipe sampling, vacuum sampling, and other sampling approaches, including attic sampling. The metrics of presentation of results for toxicants in dust surface loading (micrograms per square centimeter) or surface concentration (micrograms per gram) are discussed. We evaluate these metrics in terms of how the information can be used in source characterization and in exposure characterization. We discuss the types of companion information on source use and household or personal activity patterns required to assess the significance of the dust exposure. The status and needs for wipe samplers, surface samplers, and vacuum samplers are summarized with some discussion on the strengths and weaknesses of each type of sampler. We also discuss needs for research and development and the current status of standardization. Case studies are provided to illustrate the use of house dust and residential soil in source characterization, forensic analyses, or human exposure assessment. PMID:12361921

Dust: a metric for use in residential and building exposure assessment and source characterization.

PubMed

Lioy, Paul J; Freeman, Natalie C G; Millette, James R

2002-10-01

In this review, we examine house dust and residential soil and their use for identifying sources and the quantifying levels of toxicants for the estimation of exposure. We answer critical questions that focus on the selection of samples or sampling strategies for collection and discuss areas of uncertainty and gaps in knowledge. We discuss the evolution of dust sampling with a special emphasis on work conducted after the publication of the 1992 review by McArthur [Appl Occup Environ Hyg 7(9):599-606 (1992)]. The approaches to sampling dust examined include surface wipe sampling, vacuum sampling, and other sampling approaches, including attic sampling. The metrics of presentation of results for toxicants in dust surface loading (micrograms per square centimeter) or surface concentration (micrograms per gram) are discussed. We evaluate these metrics in terms of how the information can be used in source characterization and in exposure characterization. We discuss the types of companion information on source use and household or personal activity patterns required to assess the significance of the dust exposure. The status and needs for wipe samplers, surface samplers, and vacuum samplers are summarized with some discussion on the strengths and weaknesses of each type of sampler. We also discuss needs for research and development and the current status of standardization. Case studies are provided to illustrate the use of house dust and residential soil in source characterization, forensic analyses, or human exposure assessment.

An Israeli haboob: Sea breeze activating local anthropogenic dust sources in the Negev loess

NASA Astrophysics Data System (ADS)

Crouvi, Onn; Dayan, Uri; Amit, Rivka; Enzel, Yehouda

2017-02-01

Meso-scale weather systems, such as convective haboobs, are considered to be an important dust generation mechanism. In Israel, however, rather than of meso-scale weather systems, most dust storms are generated by synoptic-scale systems, originating from Sahara and Arabia. Consequently, only distal sources of suspended and deposited dust in Israel are currently reported. Here we report the first detailed study on the merging of synoptic- and meso-scale weather systems leading to a prominent dust outbreak over the Negev, Israel. During the afternoon of May 2nd, 2007, a massive dust storm covered the northern Negev, forming a one kilometer high wall of dust. The haboob was associated with PM10 concentrations of 1000-1500 μg m-3 that advanced at a speed of 10-15 m s-1 and caused temporary closure of local airports. In contrast to most reported haboobs, this one was generated by a sea breeze front acting as a weak cold front enhanced by a cold core cyclone positioned over Libya and Egypt. The sea breeze that brought cold and moist marine air acted as a gravity current with strong surface winds. The sources for the haboob were the loessial soils of the northwestern Negev, especially agricultural fields that were highly disturbed in late spring to early summer. Such surface disturbance is caused by agricultural and/or intensive grazing practices. Our study emphasizes the importance of local dust sources in the Negev and stresses loess recycling as an important process in contemporary dust storms over Israel.

Synchrotron X-ray fluorescence analyses of stratospheric cosmic dust - New results for chondritic and low-nickel particles

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Sutton, S. R.

1990-01-01

Trace element abundance determinations were performed using synchrotron X-ray fluorescence on nine particles collected from the stratosphere and classified as cosmic. Improvements to the Synchrotron Light Source allowed the detection of all elements between Cr and Mo, with the exceptions of Co and As, in our largest particle. The minor and trace element abundance patterns of three Ni-depleted particles were remarkably similar to those of extraterrestrial igneous rocks. Fe/Ni and Fe/Mn ratios suggest that one of these may be of lunar origin. All nine particles exhibited an enrichment in Br, ranging from 1.3 to 38 times the C1 concentration. Br concentrations were uncorrelated with particle size, as would be expected for a surface correlated component acquires from the stratosphere.

Content of Heavy Metal in the Dust of Leisure Squares and Its Health Risk Assessment-A Case Study of Yanta District in Xi'an.

PubMed

Shao, Tianjie; Pan, Lihuan; Chen, Zhiqing; Wang, Ruiyuan; Li, Wenjing; Qin, Qing; He, Yuran

2018-02-25

Taking Yanta District in Xi'an as the research object, the present study measures the contents of Cadmium (Cd), Lead (Pb), Copper (Cu), Nickel (Ni), and Chromium (Cr) in dust samples and further assesses the health risk of heavy metals intake through dust based on the assessment method of human exposure risk proposed by U.S. EPA, with an aim to investigate the content of heavy metal in the dust of leisure squares and its exposure risk. As the results indicate, the average contents of five heavy metals are obviously higher than the soil background value in Shaanxi Province. Therefore, Cd, Ni, Cu, Pb, and Cr are obviously enriched in urban surface dust in Shaanxi Province, due to the influence of human activities. In addition, it can also be found that the non-carcinogen exposure risk in children is significantly higher than that in adults with the risk values of these five heavy metals all one order of magnitude higher than those of adults. Irrespective of whether addressing the results for children or adults, the non-carcinogen exposure doses of five heavy metals are sorted as Cr > Pb > Cu > Ni > Cd. According to the present situation, for a child, the total non-carcinogenic risk values of five heavy metals have exceeded the safety limit in 11 of the 20 leisure squares in Yanta District of Xi'an. That means the leisure squares are no longer suitable for physical and recreational activities. For the five heavy metals, the average non-carcinogenic risk value of Cr is largest, and causes the largest threat to health in Yanta District, Xi'an. The carcinogenic exposure doses of the heavy metals Cr, Cd, and Ni are very low in respiratory pathways and there is no carcinogenic health risk. In general, the Cr content in dust in domestic cities is higher than that of foreign cities; however, the Pb content is much lower.

Multiple sources supply eolian mineral dust to the Atlantic sector of coastal Antarctica: Evidence from recent snow layers at the top of Berkner Island ice sheet

NASA Astrophysics Data System (ADS)

Bory, Aloys; Wolff, Eric; Mulvaney, Robert; Jagoutz, Emil; Wegner, Anna; Ruth, Urs; Elderfield, Harry

2010-03-01

The Sr and Nd isotopic composition of dust extracted from recent snow layers at the top of Berkner Island ice sheet (located within the Filchner-Ronne Ice Shelf at the southern end of the Weddell Sea) enables us, for the first time, to document dust provenance in Antarctica outside the East Antarctic Plateau (EAP) where all previous studies based on isotopic fingerprinting were carried out. Berkner dust displays an overall crust-like isotopic signature, characterized by more radiogenic 87Sr/ 86Sr and much less radiogenic 143Nd/ 144Nd compared to dust deposited on the EAP during glacial periods. Differences with EAP interglacial dust are not as marked but still significant, indicating that present-day Berkner dust provenance is distinct, at least to some extent, from that of the dust reaching the EAP. The fourteen snow-pit sub-seasonal samples that were obtained span a two-year period (2002-2003) and their dust Sr and Nd isotopic composition reveals that multiple sources are at play over a yearly time period. Southern South America, Patagonia in particular, likely accounts for part of the observed spring/summer dust deposition maxima, when isotopic composition is shifted towards "younger" isotopic signatures. In the spring, possible additional inputs from Australian sources would also be supported by the data. Most of the year, however, the measured isotopic signatures would be best explained by a sustained background supply from putative local sources in East Antarctica, which carry old-crust-like isotopic fingerprints. Whether the restricted East Antarctic ice-free areas produce sufficient eolian material has yet to be substantiated however. The fact that large (> 5 μm) particles represent a significant fraction of the samples throughout the entire time-series supports scenarios that involve contributions from proximal sources, either in Patagonia and/or Antarctica (possibly including snow-free areas in the Antarctic Peninsula and other areas as well). This also indicates that additional dust transport, which does not reach the EAP, must occur at low-tropospheric levels to this coastal sector of Antarctica.

A method of evaluating effects of antecedent precipitation on duststorms and its application to Yuma, Arizona, 1981-1988

USGS Publications Warehouse

MacKinnon, D.J.; Elder, D.F.; Helm, P.J.; Tuesink, M.F.; Nist, C.A.

1990-01-01

Precipitation causes several short- and long-term effects on wind-induced surface erodibility and subsequent dust emission. Among the principal effects considered by this paper are soil moisture, soil crusts, and vegetation. A quantitative method is developed to assess these effects using differences between the potential and the actual amounts of dust emitted from dust sources as inferred from surface meteorological measurements obtained downwind from those sources. The results of this assessment must be interpreted with caution, however, when the size and location of dust sources are unknown. Using meteorological data recorded near Yuma, Arizona at the Yuma Marine Corps Air Station (YMCAS), the method is applied to calculate the potential and actual amounts of dust emitted from upwind dust sources during the spring and fall/winter seasons between January 1, 1981 and May 31, 1988. (Spring is considered to be the period between February 1 and May 31; fall/winter, between October 1 and January 31.) Because summer precipitation is intermittent and wind patterns are localized, summer meteorological data are not used to evaluate regional correlations between precipitation and dust storms. For the period between 1981 and 1988, a correlation of -0.60 was found between fall/winter precipitation and the actual amount of dust emitted from sources upwind of YMCAS during the following spring. A particularly strong reduction in dust emission was noted during the springs of 1983 and 1984 following the start of an 'El Nino event' in fall/winter 1982. Photographs taken at a geological and meteorological data-collection (Geomet) site, located in the natural desert 25 km southeast of YMCAS, show a correspondence between increased antecedent precipitation recorded at the site and increased vegetation. Whereas the annual precipitation totals at YMCAS and the Geomet site from the beginning of 1982 through 1984 are high, their seasonal totals, especially during the fall/winter seasons, are disparate. This fall/winter precipitation disparity may account for evidence suggesting that significant vegetation growth occurred at dust sources upwind of YMCAS by spring 1983, but that such growth did not occur at the Geomet site until fall/ winter of 1983. Spatial inhomogeneity in fall/winter precipitation probably contributed to the relatively low correlation (-0.60) between fall/winter precipitation recorded at YMCAS and the actual amount of dust emitted from upwind sources during the following spring. ?? 1990 Kluwer Academic Publishers.

Soil organic carbon dust emission: an omitted global source of atmospheric CO2.

PubMed

Chappell, Adrian; Webb, Nicholas P; Butler, Harry J; Strong, Craig L; McTainsh, Grant H; Leys, John F; Viscarra Rossel, Raphael A

2013-10-01

Soil erosion redistributes soil organic carbon (SOC) within terrestrial ecosystems, to the atmosphere and oceans. Dust export is an essential component of the carbon (C) and carbon dioxide (CO(2)) budget because wind erosion contributes to the C cycle by removing selectively SOC from vast areas and transporting C dust quickly offshore; augmenting the net loss of C from terrestrial systems. However, the contribution of wind erosion to rates of C release and sequestration is poorly understood. Here, we describe how SOC dust emission is omitted from national C accounting, is an underestimated source of CO(2) and may accelerate SOC decomposition. Similarly, long dust residence times in the unshielded atmospheric environment may considerably increase CO(2) emission. We developed a first approximation to SOC enrichment for a well-established dust emission model and quantified SOC dust emission for Australia (5.83 Tg CO(2)-e yr(-1)) and Australian agricultural soils (0.4 Tg CO(2)-e yr(-1)). These amount to underestimates for CO(2) emissions of ≈10% from combined C pools in Australia (year = 2000), ≈5% from Australian Rangelands and ≈3% of Australian Agricultural Soils by Kyoto Accounting. Northern hemisphere countries with greater dust emission than Australia are also likely to have much larger SOC dust emission. Therefore, omission of SOC dust emission likely represents a considerable underestimate from those nations' C accounts. We suggest that the omission of SOC dust emission from C cycling and C accounting is a significant global source of uncertainty. Tracing the fate of wind-eroded SOC in the dust cycle is therefore essential to quantify the release of CO(2) from SOC dust to the atmosphere and the contribution of SOC deposition to downwind C sinks. © 2013 John Wiley & Sons Ltd.

Meteorological Situations Favouring the Development of Dust Plumes over Iceland

NASA Astrophysics Data System (ADS)

Schepanski, K.; Szodry, K.

2017-12-01

The knowledge on mineral dust emitted at high latitudes is limited, but its impact on the polar environments is divers. Within a warming climate, dust emitted from regions in cold climates is expected to increase due to the retreat of the ice sheet and increasing melting rates. Therefore, and for its extensive impacts on different aspects of the climate system, a better understanding of the atmospheric dust life-cycle at high latitudes/cold climates in general, and the spatio-temporal distribution of dust sources in particular, are essential. At high-latitudes, glacio-fluvial sediments as found on river flood plains e.g. supplied by glaciers are prone to wind erosion when dry and bare. In case of the occurrence of strong winds, sediments are blown out and dust plumes develop. As dust uplift is controlled by soil surface characteristics, the availability of suitable sediments, and atmospheric conditions, an interannual variability in dust source activity is expected. We investigated atmospheric circulation patterns that favour the development of dust plumes over Iceland, which presents a well-known dust source at high latitudes. Using the atmosphere model COSMO (COnsortium for Small-scale MOdeling), we analysed the wind speed distribution over the Iceland region for identified and documented dust cases. As one outcome of the study, the position of the Icelandic low, the anticyclones located over Northern Europe, and the resulting pressure gradients are of particular relevance. The interaction of the synoptic-scale winds with the Icelandic orography may locally enhance the wind speeds and thus foster local dust emission. Results from this study suggest that the atmospheric circulation determined by the pressure pattern is of particular relevance for the formation of dust plumes entering the North Atlantic.

IRAS images of nearby dark clouds

NASA Technical Reports Server (NTRS)

Wood, Douglas O. S.; Myers, Philip C.; Daugherty, Debra A.

1994-01-01

We have investigated approximately 100 nearby molecular clouds using the extensive, all-sky database of IRAS. The clouds in this study cover a wide range of physical properties including visual extinction, size, mass, degree of isolation, homogeneity and morphology. IRAS 100 and 60 micron co-added images were used to calculate the 100 micron optical depth of dust in the clouds. These images of dust optical depth compare very well with (12)CO and (13)CO observations, and can be related to H2 column density. From the optical depth images we locate the edges of dark clouds and the dense cores inside them. We have identified a total of 43 `IRAS clouds' (regions with A(sub v) greater than 2) which contain a total of 255 `IRAS cores' (regions with A(sub v) greater than 4) and we catalog their physical properties. We find that the clouds are remarkably filamentary, and that the cores within the clouds are often distributed along the filaments. The largest cores are usually connected to other large cores by filaments. We have developed selection criteria to search the IRAS Point Source Catalog for stars that are likely to be associated with the clouds and we catalog the IRAS sources in each cloud or core. Optically visible stars associated with the clouds have been identified from the Herbig and Bell catalog. From these data we characterize the physical properties of the clouds including their star-formation efficiency.

The delivery of organic matter from asteroids and comets to the early surface of Mars

NASA Technical Reports Server (NTRS)

Flynn, G. J.

1996-01-01

Carbon delivered to the Earth by interplanetary dust particles may have been an important source of pre-biotic organic matter (Anders, 1989). Interplanetary dust is shown to deliver an order-of-magnitude higher surface concentration of carbon onto Mars than onto Earth, suggesting interplanetary dust may be an important source of carbon on Mars as well.

Evaluation of coral pathogen growth rates after exposure to atmospheric African dust samples

USGS Publications Warehouse

Lisle, John T.; Garrison, Virginia H.; Gray, Michael A.

2014-01-01

Laboratory experiments were conducted to assess if exposure to atmospheric African dust stimulates or inhibits the growth of four putative bacterial coral pathogens. Atmospheric dust was collected from a dust-source region (Mali, West Africa) and from Saharan Air Layer masses over downwind sites in the Caribbean [Trinidad and Tobago and St. Croix, U.S. Virgin Islands (USVI)]. Extracts of dust samples were used to dose laboratory-grown cultures of four putative coral pathogens: Aurantimonas coralicida (white plague type II), Serratia marcescens (white pox), Vibrio coralliilyticus, and V. shiloi (bacteria-induced bleaching). Growth of A. coralicida and V. shiloi was slightly stimulated by dust extracts from Mali and USVI, respectively, but unaffected by extracts from the other dust sources. Lag time to the start of log-growth phase was significantly shortened for A. coralicida when dosed with dust extracts from Mali and USVI. Growth of S. marcescens and V. coralliilyticus was neither stimulated nor inhibited by any of the dust extracts. This study demonstrates that constituents from atmospheric dust can alter growth of recognized coral disease pathogens under laboratory conditions.

Present and Past Impact of Glacially Sourced Dust on Iron Fertilization of the Southern Ocean

NASA Astrophysics Data System (ADS)

Shoenfelt, E. M.; Winckler, G.; Kaplan, M. R.; Sambrotto, R.; Bostick, B. C.

2016-12-01

An increase in iron-containing dust flux and a more efficient biological pump in the Southern Ocean have been associated with the CO2 drawdown and global cooling of the Last Glacial Maximum (LGM). While iron (Fe) mineralogy is known to affect Fe bioavailability through its impact on Fe solubility, there are limited studies investigating the importance of Fe mineralogy in dust fluxes to the Southern Ocean, and no previous studies investigating interactions between eukaryotic phytoplankton and particulate-phase Fe in natural dusts applicable to Southern Ocean environments. Since physically weathered bedrock becomes less soluble as it becomes weathered and oxidized, we hypothesized that glacially sourced dusts would contain more Fe(II)-rich primary minerals and would be more bioavailable than dusts from areas not impacted by glaciers. We used a series of natural dusts from Patagonia as the sole Fe source in incubation experiments with the model diatom Phaeodactylum tricornutum, and evaluated Fe bioavailability using culture growth rates, cell density, and variable fluorescence. Monod curves were also used to evaluate the efficiency of the different particulates as sources of nutrient Fe. Using these Monod curves fit to growth rates plotted against particulate Fe concentrations, we observed that 1) Fe(II)-rich primary silicates were significantly more effective as an Fe source to diatoms than Fe(III)-rich oxides, that 2) Fe(II) content itself was responsible for the difference in Fe bioavailability/efficiency of the Fe nutrient source, and that 3) surface interactions with the particulates were important. In an effort to explore the possibility that Fe mineralogy impacted Fe bioavailability in past oceans, we will present our hypotheses regarding productivity and Fe mineralogy/bioavailability through the last glacial cycle.

Composition and sources of atmospheric dusts in snow at 3200 meters in the St. Elias Range, southeastern Alaska, USA

USGS Publications Warehouse

Hinkley, T.K.

1994-01-01

Dusts in snow from the accumulation zone in the St. Elias Range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition. These dusts, with respect to their composition and to the moderate degree of variation that occurs through a depositional year, are similar those deposited in Greenland. The high portion of the St. Elias Range is isolated from dominance by any local dust source terranes, because of altitude and the extent of the surrounding glacierized and snow-covered region. In Greenland the altitude is typically lower, but local sources are even less likely to dominate the character of the dusts deposited into the ice record there. The similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial-period conditions are uniform and representative of a broad regional or even hemispheric background dust. The dusts in the snow were measured by means of a suite of major, minor, and trace rock-forming metals chosen to give information about rock types, their constituent minerals, degree of degradation (weathering), and energies of atmospheric uptake from source. The variations in amounts of rock dust through the year in the St. Elias Range snowpack have no time-stratigraphic correspondence to the also large variations in concentrations of other species that are not constituents of rock-derived dusts, such the anions chloride, sulfate, and nitrate; the highs and lows of the two types of materials are apparently completely independent. The structure revealed by the moderately fine-scale sampling of the present study (??? 10 increments/y) serves as a background for the interpretation of analysis of ice core samples, in which annual layers may be too compressed to permit analysis of sub-annual samples. ?? 1994.

Composition and sources of atmospheric dusts in snow at 3200 meters in the St. Elias Range, southeastern Alaska, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinkley, T.K.

1994-08-01

Dusts in snow from the accumulation zone in the St. Elias Range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition. These dusts, with respect to their composition and to the moderate degree of variation that occurs through a depositional year, are similar to those deposited in Greenland. The high portion of the St. Elias Range is isolated from dominance by any local dust source terranes, because of altitude and the extent of the surrounding glacierized and snow-covered region. In Greenland the altitude is typically lower, but local sources are even less likely tomore » dominate the character of the dusts deposited into the ice record there. The similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial-period conditions are uniform and representative of a broad regional or even hemispheric background dust. The dusts in the snow were measured by means of a suite of major, minor, and track rock-forming metals chosen to give information about rock types, their constituent minerals, degree of degradation (weathering), and energies of atmospheric uptake from source. The variations in amounts of rock dust through the year in the St. Elias Range snowpack have no time-stratigraphic correspondence to the also-large variations in concentrations of other species that are not constituents of rock-derived dusts, such the anions chloride, sulfate, and nitrate; the highs and lows of the two types of materials are apparently completely independent. The structure revealed by the moderately fine-scale sampling of the present study ([approximately]10 increments/y) serves as a background for the interpretation of analysis of ice core samples, in which annual layers may be too compressed to permit analysis of sub-annual samples.« less

Sensitization to house dust mites in Reykjavik, Iceland, in the absence of domestic exposure to mites.

PubMed

Hallas, T E; Gislason, D; Björnsdottir, U S; Jörundsdottir, K B; Janson, C; Luczynska, C M; Gislason, T

2004-05-01

House dust mites are common sources of indoor allergens. In Reykjavik, Iceland, 9% of the young adult population had serum-specific IgE to Dermatophagoides pteronyssinus. Sensitization to mites is usually assumed to be due to exposure to house dust mites in the indoor environment. This investigation was carried out to measure the concentrations of house dust mite allergens and to investigate which species of mites were present in beds in Iceland. A total of 197 randomly selected adults were visited at home using the European Community Respiratory Health Survey (ECRHS) II Indoor protocol. Dust samples were collected from mattresses for measurement of house dust mite allergen concentrations and to estimate the number and type of house dust mites. Additional samples from mattresses and floors were collected from the homes of 10 patients with positive skin prick tests (SPT) to D. pteronyssinus. House dust mite allergen concentrations were measured using ELISA and examination of mite species was carried out using microscopy. Climatic parameters were assessed using psychrometer readings in the bedrooms and outdoors. We found two single mite specimens, both D. pteronyssinus, in two dust samples. Mite allergen analyses indicated that two other dust samples had Der f 1 results close to the cut-off of 0.1 microg/g of dust. No samples were positive for Der p 1. In an additional collection of dust from the homes of 10 SPT-positive patients no Dermatophagoides spp. were found. Reykjavik citizens are exposed to extremely low amounts of house dust mite allergens in their homes. Possible alternative sources for sensitization are discussed, such as bird nests, exposure from travelling abroad, or other mites or invertebrates that cross-react with house dust mite allergens. Our findings suggest that exposures other than to house dust mites indoors are possible sources of mite allergen exposure.

Kuiper Belt Dust Grains as a Source of Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Liou, Jer-Chyi; Zook, Herbert A.; Dermott, Stanley F.

1996-01-01

The recent discovery of the so-called Kuiper belt objects has prompted the idea that these objects produce dust grains that may contribute significantly to the interplanetary dust population. In this paper, the orbital evolution of dust grains, of diameters 1 to 9 microns, that originate in the region of the Kuiper belt is studied by means of direct numerical integration. Gravitational forces of the Sun and planets, solar radiation pressure, as well as Poynting-Robertson drag and solar wind drag are included. The interactions between charged dust grains and solar magnetic field are not considered in the model. Because of the effects of drag forces, small dust grains will spiral toward the Sun once they are released from their large parent bodies. This motion leads dust grains to pass by planets as well as encounter numerous mean motion resonances associated with planets. Our results show that about 80% of the Kuiper belt grains are ejected from the Solar System by the giant planets, while the remaining 20% of the grains evolve all the way to the Sun. Surprisingly, the latter dust grains have small orbital eccentricities and inclinations when they cross the orbit of the Earth. This makes them behave more like asteroidal than cometary-type dust particles. This also enhances their chances of being captured by the Earth and makes them a possible source of the collected interplanetary dust particles; in particular, they represent a possible source that brings primitive/organic materials from the outer Solar System to the Earth. When collisions with interstellar dust grains are considered, however, Kuiper belt dust grains around 9 microns appear likely to be collisionally shattered before they can evolve toward the inner part of the Solar System. The collision destruction can be applied to Kuiper belt grains up to about 50 microns. Therefore, Kuiper belt dust grains within this range may not be a significant part of the interplanetary dust complex in the inner Solar System.

The Continuous Monitoring of Desert Dust using an Infrared-based Dust Detection and Retrieval Method

NASA Technical Reports Server (NTRS)

Duda, David P.; Minnis, Patrick; Trepte, Qing; Sun-Mack, Sunny

2006-01-01

Airborne dust and sand are significant aerosol sources that can impact the atmospheric and surface radiation budgets. Because airborne dust affects visibility and air quality, it is desirable to monitor the location and concentrations of this aerosol for transportation and public health. Although aerosol retrievals have been derived for many years using visible and near-infrared reflectance measurements from satellites, the detection and quantification of dust from these channels is problematic over bright surfaces, or when dust concentrations are large. In addition, aerosol retrievals from polar orbiting satellites lack the ability to monitor the progression and sources of dust storms. As a complement to current aerosol dust retrieval algorithms, multi-spectral thermal infrared (8-12 micron) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Meteosat-8 Spinning Enhanced Visible and Infrared Imager (SEVIRI) are used in the development of a prototype dust detection method and dust property retrieval that can monitor the progress of Saharan dust fields continuously, both night and day. The dust detection method is incorporated into the processing of CERES (Clouds and the Earth s Radiant Energy System) aerosol retrievals to produce dust property retrievals. Both MODIS (from Terra and Aqua) and SEVERI data are used to develop the method.

Origin-Dependent Variations in the Atmospheric Microbiome in Eastern Mediterranean Dust Storms

NASA Astrophysics Data System (ADS)

Rudich, Y.; Gat, D.

2017-12-01

Microorganisms carried by dust storms are transported through the atmosphere and may affect human health and the functionality of microbial communities in various environments. Characterizing the dust-borne microbiome in dust storms of different origins, or that followed different trajectories, provides valuable data to improve our understanding of global health and environmental impacts. We present a comparative study on the diversity of dust- borne bacterial communities in dust storms from three distinct origins—North Africa, Syria and Saudi Arabia—and compare them with local bacterial communities sampled on clear days, all collected at a single location, in Israel. Storms from different dust origins exhibited distinct bacterial communities, with signature bacterial taxa for each source. Dust storms were characterized by a lower abundance of selected antibiotic resistance genes (ARGs) compared with ambient dust, asserting that the origin of these genes is local, possibly anthropogenic. With the progression of the storm, the storm-borne bacterial community showed increasing resemblance to ambient dust, suggesting mixing with local dust. We will also discuss how exposure to dust containing biological components affect lung epithelial cells. These results show, for the first time, that dust storms from different sources display distinct bacterial communities, suggesting possible distinct effects on the environment and public health.

Aerosols and water vapor dynamics over the Kingdom of Saudi Arabia

NASA Astrophysics Data System (ADS)

Farahat, Ashraf; El-Askary, Hesham; Al-Shaibani, Abdulaziz; Dogan, Umran

2014-05-01

The Kingdom of Saudi Arabia contains a vast desert area and the home of some of the largest deserts worldwide. This nature subjects the area to numerous dust storms. This is in addition to local emissions transported from industrial activities. The Arabian Peninsula dust storms have a major impact on air quality and affects dust cycle around the world. The nature of dust also affects air, ground traffics, and human health. Aerosols play a pivotal role in global climate change through their effects on the hydrological cycle and solar energy budget. Recently there have been some trials to study the nature of dust over the kingdom using satellite remote sensing and modeling to investigate the impact of aerosols of natural and anthropogenic origins from both local emissions and long-range transport on the air quality and atmospheric composition, yet a lot more needs to be done. In this study, data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board of Terra and Aqua satellites are used to analyze aerosols properties over the thirteen provinces of the Kingdom of Saudi Arabia from April 2003 to January 2012. This analysis will help to characterize aerosol and cloud properties, and the seasonal hydrological factors to establish the relative contributions of aerosols derived from different regions to the different Saudi provinces and their impacts on local atmospheric composition and air quality. During this period, we have examined possible nature and anthropogenic/natural aerosols/dust sources. The analysis is based on important parameters including the aerosol optical depth (AOD), fine mode fraction (FMF), cloud properties including cloud top temperature (CTT), cloud top pressure (CTP) and the water vapor column. Correlation between water vapor and AOD was observed over three provinces which could be a result of pollution aerosols rather than dust and is, hence, acting as cloud condensation nuclei (CCN). Increasing anomalous aerosols pattern over 2010-2012 is also observed. Acknowledgement The authors would like to acknowledge the support provided by the King Abdel Aziz City for Science & Technology (KACST) for funding this work under grant No. (MT-110-010). The support provided by the Deanship of Research at King Fahd University of Petroleum & Minerals (KFUPM) is gratefully acknowledged.

PM10 and PM2.5 chemical source profiles with optical attenuation and health risk indicators of paved and unpaved road dust in Bhopal, India.

PubMed

Samiksha, Shilpi; Sunder Raman, Ramya; Nirmalkar, Jayant; Kumar, Samresh; Sirvaiya, Rohit

2017-03-01

Size classified (PM 10 and PM 2.5 ) paved and unpaved road dust chemical source profiles, optical attenuation and potential health risk from exposure to these sources are reported in this study. A total of 45 samples from 9 paved road and 6 unpaved road sites located in and around Bhopal were re-suspended in the laboratory, collected onto filter substrates and subjected to a variety of chemical analyses. In general, road dust was enriched (compared to upper continental crustal abundance) in anthropogenic pollutants including Sb, Cu, Zn, Co, and Pb. Organic and elemental carbon (OC/EC) in PM 10 and PM 2.5 size fractions were 50-75% higher in paved road dust compared to their counterparts in unpaved road dust. Further, the results suggest that when it is not possible to include carbon fractions in source profiles, the inclusion of optical attenuation is likely to enhance the source resolution of receptor models. Additionally, profiles obtained in this study were not very similar to the US EPA SPECIATE composite profiles for PM 10 and PM 2.5 , for both sources. Specifically, the mass fractions of Si, Fe, OC, and EC were most different between SPECIATE composite profiles and Bhopal composite profiles. An estimate of health indicators for Bhopal road dust revealed that although Cr was only marginally enriched, its inhalation may pose a health risk. The estimates of potential lifetime incremental cancer risk induced by the inhalation of Cr in paved and unpaved road dust (PM 10 and PM 2.5 ) for both adults and children were higher than the baseline values of acceptable risk. These results suggest that road dust Cr induced carcinogenic risk should be further investigated. Copyright © 2016 Elsevier Ltd. All rights reserved.

Physical and Chemical Characteristics of Desert Dust Deposited on Mt. Elbrus, Caucasus as Documented in Snow Pit and Shallow Core Records

NASA Astrophysics Data System (ADS)

Kutuzov, S.; Shahgedanova, M.; Mikhalenko, V.; Ginot, P.; Lavrentiev, I.; Popov, G.

2013-12-01

We present a study of dust deposition events and its physical and chemical characteristics in Caucasus Mountains as documented by snow and firn pack at Mt Elbrus. Dust samples were collected from the shallow ice cores and snow pits in 2009-2013 at the western Elbrus plateau (5150 m a.s.l.). Particle size distribution and chemical analysis (major ions, trace elements) were completed for each sample using Coulter Counter Multisizer III, scanning electron microscopy (SEM), IC and ICPMS analysis. It was shown that desert dust deposition occurred in Caucasus 4-8 times a year and originates from the Northern Sahara and the deserts of the Middle East. Analysis of volumetric particle size distributions showed that the modal values ranged between 2 μm and 4 μm although most samples were characterised by modal values of 2.0-2.8 μm with an average of 2.6 μm. These values are lower than those obtained from the ice cores in central and southern Asia following the deposition of long-travelled dust and are closer to those reported for the European Alps and the polar ice cores. All samples containing dust have a single mode which is usually interpreted as a single source region. They do not reveal any significant differences between the Saharan and the Middle Eastern sources. The annual average dust mass concentrations were 10-15 mg kg-1 which is higher than the average concentrations reported for other mountain regions and this was strongly affected by dust deposition events. The deposition of dust resulted in elevated concentrations of most ions, especially Ca2+, Mg2+, K+, and sulphates. Dust originated from multiple sources in the Middle East including Mesopotamia or passing over the Middle East was characterised by the elevated concentrations of nitrates and ammonia which is related to a high atmospheric loads of ammonium emitted by agricultural sources and high concentrations of ammonium in dust originating from this region. By contrast, samples of the Saharan dust showed low concentrations consistent with the low ammonium loads in the source region. . The research leading to these results has received funding from the European Union Seventh Framework Programme FP7-PEOPLE-2010-IIF under grant agreement PIIF-GA-2010-275071 Russian Foundation for Basic Research (grants 11-05-00304 and 13-05-10069).

A novel integrated approach for the hazardous radioactive dust source terms estimation in future nuclear fusion power plants.

PubMed

Poggi, L A; Malizia, A; Ciparisse, J F; Gaudio, P

2016-10-01

An open issue still under investigation by several international entities working on the safety and security field for the foreseen nuclear fusion reactors is the estimation of source terms that are a hazard for the operators and public, and for the machine itself in terms of efficiency and integrity in case of severe accident scenarios. Source term estimation is a crucial key safety issue to be addressed in the future reactors safety assessments, and the estimates available at the time are not sufficiently satisfactory. The lack of neutronic data along with the insufficiently accurate methodologies used until now, calls for an integrated methodology for source term estimation that can provide predictions with an adequate accuracy. This work proposes a complete methodology to estimate dust source terms starting from a broad information gathering. The wide number of parameters that can influence dust source term production is reduced with statistical tools using a combination of screening, sensitivity analysis, and uncertainty analysis. Finally, a preliminary and simplified methodology for dust source term production prediction for future devices is presented.

Herschel-ATLAS: Dust Temperature and Redshift Distribution of SPIRE and PACS Detected Sources Using Submillimetre Colours

NASA Technical Reports Server (NTRS)

Amblard, A.; Cooray, Asantha; Serra, P.; Temi, P.; Barton, E.; Negrello, M.; Auld, R.; Baes, M.; Baldry, I. K.; Bamford, S.;

Glacial/interglacial changes of Southern Hemisphere wind circulation from the geochemistry of South American dust

NASA Astrophysics Data System (ADS)

Gili, Stefania; Gaiero, Diego M.; Goldstein, Steven L.; Chemale, Farid; Jweda, Jason; Kaplan, Michael R.; Becchio, Raúl A.; Koester, Edinei

2017-07-01

The latitudinal displacement of the southern westerlies and associated climate systems is a key parameter for understanding the variations of Southern Hemisphere atmospheric circulation during the Late Quaternary Period. To increase understanding of past atmospheric circulation and of the paleo-environmental conditions associated with continental dust sources, we dig deeper into dust provenance in paleo-archives of the Southern Hemisphere. We present here a Sr-Nd isotopic and rare earth element study of surface sediments collected along a ∼4000 km latitudinal band from arid and semi-arid terrains in southern South America. Findings from terrains that served as paleo-dust suppliers are compared with modern dust collected from monitoring stations along the same latitudinal band, which affords a test on how actual present-day aeolian compositions compare to those of the past potential source areas. Moreover, the comparison between past and present-day datasets is useful for understanding present-day atmospheric circulation. Armed with a new comprehensive dataset, we revise previous interpretations of the provenance of dust trapped in the Antarctic ice and sediments deposited in the South Atlantic sector of the Southern Ocean. These comparisons support multiple source regions in southern South America that changed with climates. The findings reveal that, although Patagonia plays an important role in contributing dust to the higher latitudes, central Western Argentina and (to a lesser extent) the southern Puna region also emerge as potentially important dust sources during glacial times. The southern Altiplano appears to be a major contributor during interglacial periods as well. We rely in part on an understanding of modern wind-dust activities to conclude that the possible presence of southern South America source regions - other than Patagonia - in East Antarctic ice is consistent with an overall equatorward displacement during glacial times of both the mid-latitude westerlies and the subtropical jet stream.

Identifying Dust Sources by Positive Matrix Factorization (PMF)

NASA Astrophysics Data System (ADS)

Engelbrecht, Johann P.

2010-05-01

This presentation is on the source attribution by Positive Matrix Factorization (PMF) of aerosol samples collected in Iraq, a major source of mineral dust in the Middle East. Globally transported mineral dust from North Africa, the Middle East, China, and elsewhere are routinely being sampled at high elevation monitoring sites such as those on the Canary Islands and Hawaii, and many ambient monitoring sites worldwide. Chemical results of these filter samples reflect differences in sources impacting at each site, further complicated by the regional geomorphology and meteorology. Trace elements, isotopes, elemental ratios, and mineralogy are generally being used to pinpoint geological source regions of natural and anthropogenic dusts. A receptor site is seldom impacted by only one source at a time. Dust palls are continually being modified by added dust from soils across which they migrate, also by particle segregation in the dust plume, and precipitation of the coarser particles. The result is that dust is a mixture, with contributions from different sources, each with a different chemical and mineralogical signature. PMF is a non-negative factorization procedure that produces only positive factor scores and loadings, in contrast to classical factor analysis (FA) and Principal Components Analysis (PCA). PMF enables us to resolve factors (chemical signatures) for source types contributing to the ambient chemical data set, and also models the source-type contributions to individual ambient samples. The latter can often be related to specific source regions. PMF was applied separately to two ambient data sets collected in Iraq in 2006, the one on Teflon membrane filters and the other on quartz fiber. Each of the filter types were previously analyzed for different chemical species: Teflon membrane for elements, by XRF and ICP-MS, while quartz fiber filters were analyzed for ions and carbon. [Engelbrecht et al. 2009] A set of 392 Teflon filter samples analyzed for 25 elemental species was modeled by PMF. A five factor solution identified three soil factors, a silicate soil, limestone soil, and a gypsum soil, as well as a salt factor and an anthropogenic metal factor. Similarly, a set of 362 quartz filter samples analyzed for 10 selected chemical species was modeled by PMF. A five factor solution provided a limestone-gypsum soil, diesel combustion, secondary ammonium sulfate, salt and agricultural-burnpit combustion source type. Examples of time series plots of PMF factor contributions for each of six sampling sites (Balad, Baghdad, Tallil, Tikrit, Taji, and Al Asad) will be discussed. Engelbrecht , J. P., McDonald, E. V., Gillies, J. A., Jayanty, R. K. M., Casuccio, G., and Gertler, A. W., 2009, Characterizing mineral dusts and other aerosols from the Middle East - Part 1: Ambient sampling: Inhalation Toxicology, v. 21, p. 297-326.

Chemistry and mineralogy of Martian dust: An explorer's primer

NASA Technical Reports Server (NTRS)

Gooding, James L.

1991-01-01

A summary of chemical and mineralogical properties of Martian surface dust is offered for the benefit of engineers or mission planners who are designing hardware or strategies for Mars surface exploration. For technical details and specialized explanations, references should be made to literature cited. Four sources used for information about Martian dust composition: (1) Experiments performed on the Mars surface by the Viking Landers 1 and 2 and Earth-based lab experiments attempting to duplicate these results; (2) Infrared spectrophotometry remotely performed from Mars orbit, mostly by Mariner 9; (3) Visible and infrared spectrophotometry remotely performed from Earth; and (4) Lab studies of the shergottite nakhlite chassignite (SNC) clan of meteorites, for which compelling evidence suggests origin on Mars. Source 1 is limited to fine grained sediments at the surface whereas 2 and 3 contain mixed information about surface dust (and associated rock) and atmospheric dust. Source 4 has provided surprisingly detailed information but investigations are still incomplete.

Quantifying road dust resuspension in urban environment by Multilinear Engine: A comparison with PMF2

NASA Astrophysics Data System (ADS)

Amato, F.; Pandolfi, M.; Escrig, A.; Querol, X.; Alastuey, A.; Pey, J.; Perez, N.; Hopke, P. K.

Atmospheric PM pollution from traffic comprises not only direct emissions but also non-exhaust emissions because resuspension of road dust that can produce high human exposure to heavy metals, metalloids, and mineral matter. A key task for establishing mitigation or preventive measures is estimating the contribution of road dust resuspension to the atmospheric PM mixture. Several source apportionment studies, applying receptor modeling at urban background sites, have shown the difficulty in identifying a road dust source separately from other mineral sources or vehicular exhausts. The Multilinear Engine (ME-2) is a computer program that can solve the Positive Matrix Factorization (PMF) problem. ME-2 uses a programming language permitting the solution to be guided toward some possible targets that can be derived from a priori knowledge of sources (chemical profile, ratios, etc.). This feature makes it especially suitable for source apportionment studies where partial knowledge of the sources is available. In the present study ME-2 was applied to data from an urban background site of Barcelona (Spain) to quantify the contribution of road dust resuspension to PM 10 and PM 2.5 concentrations. Given that recently the emission profile of local resuspended road dust was obtained (Amato, F., Pandolfi, M., Viana, M., Querol, X., Alastuey, A., Moreno, T., 2009. Spatial and chemical patterns of PM 10 in road dust deposited in urban environment. Atmospheric Environment 43 (9), 1650-1659), such a priori information was introduced in the model as auxiliary terms of the object function to be minimized by the implementation of the so-called "pulling equations". ME-2 permitted to enhance the basic PMF solution (obtained by PMF2) identifying, beside the seven sources of PMF2, the road dust source which accounted for 6.9 μg m -3 (17%) in PM 10, 2.2 μg m -3 (8%) of PM 2.5 and 0.3 μg m -3 (2%) of PM 1. This reveals that resuspension was responsible of the 37%, 15% and 3% of total traffic emissions respectively in PM 10, PM 2.5 and PM 1. Therefore the overall traffic contribution resulted in 18 μg m -3 (46%) in PM 10, 14 μg m -3 (51%) in PM 2.5 and 8 μg m -3 (48%) in PM 1. In PMF2 this mass explained by road dust resuspension was redistributed among the rest of sources, increasing mostly the mineral, secondary nitrate and aged sea salt contributions.

The Origin and Evolution of Interstellar Dust in the Local and High-redshift Universe

NASA Technical Reports Server (NTRS)

Dwek, Eliahu

2012-01-01

In this talk I will begin by reviewing our current state of knowledge regarding the origin and evolution of dust in the local solar neighborhood. using chemical evolution models, I will discuss their many different input parameters and their uncertainties. An important consequence of these models is the delayed injection of dust from AGB stars, compared to supernova-condensed dust, into the interstellar medium. I will show that these stellar evolutionary effects on dust composition are manifested in the infrared spectra of local galaxies. The delayed production of dust in AGB stars has also important consequences for the origin of the large amount of dust detected in high-redshift galaxies, when the universe was less that approx. 1 Gyr old. Supernovae may have been the only viable dust sources in those galaxies. Recent observations of sN1987a show a significant mass of dust in the ejecta of this SN. Is that production rate high enough to account for the observed dust mass in these galaxies? If not, what are the alternative viable sources of dust, and how do they depend on the nature of the galaxy (starburst or AGN) and its star formation history .

The Origin and Evolution of Interstellar Dust in the Local and High-Redshift Universe

NASA Technical Reports Server (NTRS)

Dwek, Eliahu

2011-01-01

In this talk I will begin by reviewing our current state of knowledge regarding the origin and evolution of dust in the local solar neighborhood. Using chemical evolution models, I will discuss their many different input parameters and their uncertainties. An important consequence of these models is the delayed injection of dust from AGB stars, compared to supernova-condensed dust, into the interstellar medium. I will show that these stellar evolutionary effects on dust composition are manifested in the infrared spectra of local galaxies. The delayed production of dust in AGB stars has also important consequences for the origin of the large amount of dust detected in high-redshift galaxies, when the universe was less that - 1 Gyr old. Supernovae may have been the only viable dust sources in those galaxies. Recent observations of SN1987a show a significant mass of dust in the ejecta of this SN. Is that production rate high enough to account for the observed dust mass in these galaxies? If not, what are the alternative viable sources of dust, and how do they depend on the nature of the galaxy (starburst or AGN) and its star formation history.

Late-glacial elevated dust deposition linked to westerly wind shifts in southern South America

PubMed Central

Vanneste, Heleen; De Vleeschouwer, François; Martínez-Cortizas, Antonio; von Scheffer, Clemens; Piotrowska, Natalia; Coronato, Andrea; Le Roux, Gaël

2015-01-01

Atmospheric dust loadings play a crucial role in the global climate system. Southern South America is a key dust source, however, dust deposition rates remain poorly quantified since the last glacial termination (~17 kyr ago), an important timeframe to anticipate future climate changes. Here we use isotope and element geochemistry in a peat archive from Tierra del Fuego, to reconstruct atmospheric dust fluxes and associated environmental and westerly wind changes for the past 16.2 kyr. Dust depositions were elevated during the Antarctic Cold Reversal (ACR) and second half of the Younger Dryas (YD) stadial, originating from the glacial Beagle Channel valley. This increase was most probably associated with a strengthening of the westerlies during both periods as dust source areas were already available before the onset of the dust peaks and remained present throughout. Congruent with glacier advances across Patagonia, this dust record indicates an overall strengthening of the wind belt during the ACR. On the other hand, we argue that the YD dust peak is linked to strong and poleward shifted westerlies. The close interplay between dust fluxes and climatic changes demonstrates that atmospheric circulation was essential in generating and sustaining present-day interglacial conditions. PMID:26126739

Development of electro-optic systems for self cleaning concentrated solar reflectors

NASA Astrophysics Data System (ADS)

Stark, Jeremy W.

The current demand for energy usage in the world is increasing at a rapid pace; in China alone, the electricity usage has increased by 12% per year from 2006-2010, where more than 75% of electrical power is produced by coal burning facilities. Numerous studies have shown the effects of carbon dioxide emissions on global climate change, and even showing the permanence of high carbon dioxide levels after emissions cease. Current trends away from carbon emitting power facilities are pushing solar energy into a position for many new solar power plants to be constructed. Terrestrial solar energy at AM1.5 is generally given at 1kW/m2, which is a vast free source of energy that can be be harvested to meet the global demand for electricity. Aside from some areas receiving intermittent levels of solar insolation, one of the largest hindrances to large scale solar power production is obscuration of sunlight on solar collectors caused by dust deposition. In areas with the highest average solar insolation, dust deposition is a major problem for maintaining a constant maximum power output. The southern Negev desert in Israel receives on average 17g/m2 per month in dust deposition on solar installations, which in turn causes losses of a third of the total power output of the installation. In these areas, water is a scarce commodity, which can only be used to clean solar installations at a prohibitive cost. To resolve this problem, a cost effective solution would be the application of electrodynamic screens (EDS), which can be implemented by embedding a set of parallel electrodes into the sun facing surface of solar collectors, including concentrating mirrors or photovoltaic (PV) modules, and applying a low frequency pulsed voltage to these electrodes. Three major contributions made in the course of this research in advancing (EDS) for self-cleaning solar mirrors are: (1) development of non-contact specular reflectometer for solar mirrors that allows measurement of reflectance loss as a function of dust deposition, (2) development of a dust deposition analyzer capable of measuring size distribution of deposited dust and provides mass concentration of dust on the surface of the mirror, and (3) optimization of electrode geometry of EDS film for minimizing optical reflection losses caused by the lamination of the film on the mirror surface while maintaining high reflection efficiency with high dust removal efficiency. The non-contact specular reflectometer and the dust deposition analyzer allowed experimental investigation of reflection losses as functions of surface mass concentration of dust on mirrors for validation of the optical model presented in this study.

Status, sources, and human health risk assessment of PAHs via foliar dust from different functional areas in Nanjing, China.

PubMed

Zha, Yan; Zhang, Yin L; Tang, Jie; Sun, Kai

2018-05-12

The present study was carried out to assess and understand the potential health risk, level of contamination, composition pattern, and sources of urban foliar dust in Nanjing City with respect to polycyclic aromatic hydrocarbons (PAHs). Five urban functional areas of foliar dust were analysed and the contents of 16 priority PAHs were determined. Total PAH concentrations in foliar dust ranged from 1.77 to 19.02 μg·g -1 , with an average value of 6.98 μg·g -1 . The PAH pattern was dominated by four and five-ring PAHs (contributing > 38% of total PAHs) in all of the five functional areas. The results indicated that the combustion of fossil fuel, coal, and biomass, as well as vehicle traffic emissions were the major sources of PAHs. The estimated incremental lifetime cancer risk due to PAHs in foliar dust were 8.19 × 10 -6 , 6.63 × 10 -6 , and 9.65 × 10 -6 for childhood, adolescence and adulthood, respectively, indicating a high risk of cancer from exposure to foliar dust in Nanjing. Our results indicated that foliar dust might be a useful indicator of atmospheric PAH pollution.

THE NEOWISE-DISCOVERED COMET POPULATION AND THE CO + CO{sub 2} PRODUCTION RATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, James M.; Stevenson, Rachel; Kramer, Emily

2015-12-01

The 163 comets observed during the WISE/NEOWISE prime mission represent the largest infrared survey to date of comets, providing constraints on dust, nucleus size, and CO + CO{sub 2} production. We present detailed analyses of the WISE/NEOWISE comet discoveries, and discuss observations of the active comets showing 4.6 μm band excess. We find a possible relation between dust and CO + CO{sub 2} production, as well as possible differences in the sizes of long and short period comet nuclei.

Use of Combined A-Train Observations to Validate GEOS Model Simulated Dust Distributions During NAMMA

NASA Technical Reports Server (NTRS)

Nowottnick, E.

2007-01-01

During August 2006, the NASA African Multidisciplinary Analyses Mission (NAMMA) field experiment was conducted to characterize the structure of African Easterly Waves and their evolution into tropical storms. Mineral dust aerosols affect tropical storm development, although their exact role remains to be understood. To better understand the role of dust on tropical cyclogenesis, we have implemented a dust source, transport, and optical model in the NASA Goddard Earth Observing System (GEOS) atmospheric general circulation model and data assimilation system. Our dust source scheme is more physically based scheme than previous incarnations of the model, and we introduce improved dust optical and microphysical processes through inclusion of a detailed microphysical scheme. Here we use A-Train observations from MODIS, OMI, and CALIPSO with NAMMA DC-8 flight data to evaluate the simulated dust distributions and microphysical properties. Our goal is to synthesize the multi-spectral observations from the A-Train sensors to arrive at a consistent set of optical properties for the dust aerosols suitable for direct forcing calculations.

PERSPECTIVE: Dust, fertilization and sources

NASA Astrophysics Data System (ADS)

Remer, Lorraine A.

2006-11-01

Aerosols, tiny suspended particles in the atmosphere, play an important role in modifying the Earth's energy balance and are essential for the formation of cloud droplets. Suspended dust particles lifted from the world's arid regions by strong winds contain essential minerals that can be transported great distances and deposited into the ocean or on other continents where productivity is limited by lack of usable minerals [1]. Dust can transport pathogens as well as minerals great distance, contributing to the spread of human and agricultural diseases, and a portion of dust can be attributed to human activity suggesting that dust radiative effects should be included in estimates of anthropogenic climate forcing. The greenish and brownish tints in figure 1 show the wide extent of monthly mean mineral dust transport, as viewed by the MODerate resolution Imaging Spectroradiometer (MODIS) satellite sensor. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite Figure 1. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite. The brighter the color, the greater the aerosol loading. Red and reddish tints indicate aerosol dominated by small particles created primarily from combustion processes. Green and brownish tints indicate larger particles created from wind-driven processes, usually transported desert dust. Note the bright green band at the southern edge of the Saharan desert, the reddish band it must cross if transported to the southwest and the long brownish transport path as it crosses the Atlantic to South America. Image courtesy of the NASA Earth Observatory (http://earthobservatory.nasa.gov). Even though qualitatively we recognize the extent and importance of dust transport and the role that it plays in fertilizing nutrient-limited regions, there is much that is still unknown. We are just now beginning to quantify the amount of dust that exits one continental region and the fraction that arrives at another continent [2]. At the deposition end of the chain, it is still unclear how the limited minerals in the dust such as iron are released for uptake by organisms either on land or in the ocean. Not all dust deposited into oceans results in a phytoplankton bloom. The process requires a chemical pathway that mobilizes a fraction of the iron into soluble form. Meskhidze et al [3] show that phytoplankton blooms following dust transport from the Gobi desert in Asia into the Pacific ocean result in a phytoplankton bloom only if the dust is accompanied by high initial SO2-to-dust ratios, suggesting that sulfuric acid coatings on the dust particle mobilize the embedded iron in the dust for phytoplankton uptake. Quantifying transport, deposition and nutrient availability are the latter ends of a puzzle that must begin by identifying and quantifying dust emission at the sources. The emission process is complex at the microscale requiring the right conditions for saltation and bombardment, which makes identification and inclusion of sources in global transport models very difficult. The result is that estimates of annual global dust emissions range from 1000 to 3000 Tg per year [4]. Even as global estimates of dust emissions are uncertain, localizing the sources brings even greater uncertainty. It has been recognized for several years that dust sources are not uniformly distributed over the arid regions of the Earth, but are regulated to topographic lows associated with dried lake deposits [5]. Using aerosol information from satellites, a comprehensive map of the world's source regions shows sources localized to specific areas of the Earth's arid regions [6]. Still these maps suggest broad emission sources covering several degrees of latitude and longitude. In the paper by Koren and co-authors [7] appearing in this issue, one particular dust source, the Bodélé depression in Chad, is analyzed in detail. They find that the specific topography of the depression combined with the prevailing wind direction in the winter provides perfect conditions for aerosol saltation, uplift and transport. The winter Bodélé dust is carried over the populated regions of west Africa where it can be affected by smoke and urban pollution before it continues transport over the Atlantic and towards Amazonia. Although Koren et al do not speculate on the chemical possibilities in their paper, the interaction between the dust and the pollutants provides opportunity for acids to coat the dust particles and to mobilize the iron compounds, creating a highly efficient fertilizing agent for ocean phytoplankton and the biota of the Amazon forest. Koren et al do quantify the dust emission of the Bodélé depression, estimating that this small area produces approximately 50% of the Saharan dust deposited in the Amazon. The findings of Koren and his co-authors suggest that dust emission sources may be highly localized spots in the Earth's deserts that can be mapped precisely by satellites of moderate to fine resolution. Like fire hot spots that localize smoke emission, desert dust hot spots can be identified with great detail. This can provide aerosol transport models with better source emission information and improve estimates that will help in making estimates concerning biogeochemical processes and also estimates of climate forcing and response. References [1] Swap R et al 1992 Saharan dust in the Amazon basin Tellus B 44 133-49 (doi:10.1034/j.1600-0889.1992.t01-1-00005.x) [2] Kaufman Y J, Koren I, Remer L A, Tanré D, Ginoux P and Fan S 2005 Dust transport and deposition observed from the Terra-MODIS space observations J. Geophys. Res. 110 D10S12 (doi:10.1029/2003JD004436) [3] Meskhidze N, Chameides W L and Nenes A 2005 Dust and pollution: a recipe for enhanced ocean fertizilation? J. Geophys. Res. 110 (D3) D03301 (doi:10.1029/2004JD005082) [4] Cakur R V et al 2006 Constraining the magnitude of the global dust cycle by minimizing the difference between a model and observations J. Geophys. Res. 111 D06207 (doi:10.1029/2005JD005791) [5] Ginoux P et al 2001 Sources and distribution of dust aerosol simulated with the GOCART model J. Geophys. Res. 106 20255-74 (doi:10.1029/2000JD000053) [6] Prospero J M, Ginoux P, Torres O, Nicholson S E and Gill T E 2002 Environmental characterization of global sources of atmospheric soil dust identified with the NIMBUS 7 total Ozone Mapping Spectrometer (TOMS) absorbing aerosol product Rev. Geophys. 40 (1) 1002 (doi:10.1029/2000RG000095) [7] Koren I, Kaufman Y J, Washington R, Todd M C, Rudich Y, Martins J V and Rosenfeld D 2006 The Bodélé depression: a single spot in the Sahara that provides most of the mineral dust to the Amazon forest Environ. Res Lett. 1 014005 (doi:10.1088/1748-9326/1/1/014005) Photo of Lorraine A Remer Lorraine A Remer received a BS degree in atmospheric science from the University of California, Davis, in 1980, an MS degree in oceanography from the Scripps Institution of Oceanography, University of California, San Diego, in 1983, and a PhD degree, also in atmospheric science from the University of California, Davis, in 1991. She became involved with the MODIS retrievals of atmospheric aerosols in 1991, first as a Research Scientist with Science Systems and Applications, Inc., and subsequently with the National Aeronautics and Space Administration, which she joined in 1998. She is an Associate Member of the MODIS Science Team and a Member of the Global Aerosol Climatology Project Science Team.

Impact of Asian Dust on Climate and Air Quality

NASA Technical Reports Server (NTRS)

Chin, Mian; Tan, Qian; Diehl, Thomas; Yu, Hongbin

2010-01-01

Dust generated from Asian permanent desert and desertification areas can be efficiently transported around the globe, making significant radiative impact through their absorbing and scattering solar radiation and through their deposition on snow and ice to modify the surface albedo. Asian dust is also a major concern of surface air quality not only in the source and immediate downwind regions but also areas thousands of miles away across the Pacific. We present here a global model, GOCART, analysis of data from satellite remote sensing instrument (MODIS, MISR, CALIPSO, OMI) and other observations on Asian dust sources, transport, and deposition, and use the model to assess the Asian dust impact on global climate and air quality.

The dusty ballerina skirt of Jupiter

NASA Astrophysics Data System (ADS)

Horanyi, M.; Morfill, G.; Gruen, E.

1993-12-01

We suggest a model to explain the unexpected recurrent dust events that were observed during the Jupiter encounter by the dust detector on board the Ulysses spacecraft. This model is based dust-magnetosphere interactions. Dust particles inside the Jovian magnetosphere collect electrostatic charges and their interaction with the magnetic and electric fields can lead to energization and subsequent ejection. We discuss the dusty regions (ring/halo, `gossamer' ring) and also Io as potential sources for the Ulysses events. This model favors Io as a source. The mass and velocity range of the escaping particles are compatible with the observations, and we also suggest internal periodicities to explain the recurrent nature of the Ulysses dust events.

Using Nd and Sr isotopes to trace dust and volcanic inputs to soils on French Guadeloupe Island

NASA Astrophysics Data System (ADS)

Guo, J.; Pereyra, Y.; Ma, L.; Gaillardet, J.; Sak, P. B.; Bouchez, J.

2017-12-01

Soil is at the central part of the Critical Zone for its important roles in sustaining ecosystems and agriculture. At French Guadeloupe, a tropical humid volcanic island, previous studies have shown that the mineral nutrient elements such as K, Na, Ca, and Mg are highly depleted in the surface soil. And mineral nutrients introduced by dusts are an important mineral nutrient source for vegetation growth in this area. It is important to understand and quantify the sources of the mineral dust added to surface soils. Nd isotope ratios, due to their distinct signatures between two unique end-members in soils for this area: the young volcanic areas like Guadeloupe and the dust source region from the old continental shields like Sahara Desert, can be a robust tracer to understand this critical process. Nevertheless, Sr isotope ratios can trace the inputs of marine aerosols. Here we present a new Nd isotope study on Guadeloupe soil depth profiles, combined with previous Sr isotope data, to fingerprint the sources of dust and volcanic inputs into soils. Soil samples from three surface profiles (0 - 1000cm deep) at different locations of the Guadeloupe Island were systematically analyzed. The results show distinct depth variations for Nd isotope signature along profiles. For all profiles, deep soils are relatively consisted with bedrock value (ɛNd: 5.05). But in surface soils (0-600cm), unlike Sr isotope ratios that are significantly modified by marine aerosol input, Nd isotope ratios show similar decrease (to ɛNd:-10) and frequent fluctuations toward the surface, suggesting dust is the dominant source of Nd in these soils. This conclusion is further supported by REE and other trace element data. Thus, with a simplified two end-member model, Sahara dust contributes the Nd percentages in soils varying from 10.7% at the deepest profiles to 69.5% on surface, showing a significant amount of Nd on the surface soil came from dust source. The deep soil profiles are also characterized by the presence of Nd isotope spikes with negative values, suggesting dust signatures at depth. Such a feature could be related to the presence of a paleo-soil surface at the spike depth that was buried by later volcanic eruption. Both Nd and Sr isotopes hence show dust and volcanic inputs are important factors for soil developments on French Guadeloupe Island.

Probing the interstellar dust towards the Galactic Centre: dust-scattering halo around AX J1745.6-2901

NASA Astrophysics Data System (ADS)

Jin, Chichuan; Ponti, Gabriele; Haberl, Frank; Smith, Randall

2017-07-01

AX J1745.6-2901 is an X-ray binary located at only 1.45 arcmin from Sgr A⋆, showcasing a strong X-ray dust-scattering halo. We combine Chandra and XMM-Newton observations to study the halo around this X-ray binary. Our study shows two major thick dust layers along the line of sight (LOS) towards AX J1745.6-2901. The LOS position and NH of these two layers depend on the dust grain models with different grain size distributions and abundances. But for all the 19 dust grain models considered, dust layer-1 is consistently found to be within a fractional distance of 0.11 (mean value: 0.05) to AX J1745.6-2901 and contains only (19-34) per cent (mean value: 26 per cent) of the total LOS dust. The remaining dust is contained in layer-2, which is distributed from the Earth up to a mean fractional distance of 0.64. A significant separation between the two layers is found for all the dust grain models, with a mean fractional distance of 0.31. Besides, an extended wing component is discovered in the halo, which implies a higher fraction of dust grains with typical sizes ≲590 Å than considered in current dust grain models. Assuming AX J1745.6-2901 is 8 kpc away, dust layer-2 would be located in the Galactic disc several kpc away from the Galactic Centre (GC). The dust scattering halo biases the observed spectrum of AX J1745.6-2901 severely in both spectral shape and flux, and also introduces a strong dependence on the size of the instrumental point spread function and the source extraction region. We build xspec models to account for this spectral bias, which allow us to recover the intrinsic spectrum of AX J1745.6-2901 free from dust-scattering opacity. If dust layer-2 also intervenes along the LOS to Sgr A⋆ and other nearby GC sources, a significant spectral correction for the dust-scattering opacity would be necessary for all these GC sources.

Fertilisation of the Southern Atlantic: Ephemeral River Valleys as a replenishing source of nutrient-enriched mineral aerosols

NASA Astrophysics Data System (ADS)

Dansie, Andrew; Wiggs, Giles; Thomas, David

2016-04-01

Oceanic dust deposition provides biologically important iron and macronutrients (Phosphorus (P) and Nitrogen-based (N) compounds) that contribute to phytoplankton growth, marine productivity and oceanic atmospheric CO2 uptake. Research on dust emission sources to date has largely focused on the northern hemisphere and on ephemeral lakes and pans. Our work considers the ephemeral river valleys of the west coast of Namibia as an important yet overlooked source of ocean-fertilizing dust. Dust plumes are frequently emitted from the river valleys by strong easterly winds during the Southern Hemisphere winter, when the upwelling of the Benguela Current is at its weakest. We present field data from dust emission source areas along the main river channels near the coastal termini of the Huab, Kuiseb and Tsauchab river valleys. Collected data include erodible surface sediment, wind-blown flux, and associated meteorological data. Extensive surface sediment sampling was also undertaken throughout the combined 34,250 km2 extent of each river valley catchment with samples collected from within the main river channels, the main branches of each river system, selected tributaries, and into the upper watersheds. Geochemical data show valley sediment and wind-blown flux material have high concentrations of bioavailable Fe, P and N, exceeding that measured at the major dry lake basin dust sources in southern Africa. The contribution of fertilising deposition material is enhanced by both the spatial proximity of the source areas to the ocean and enrichment of source material by ephemeral fluvial accumulation and desiccation. Results show that geographical factors within each watershed play a key role in the nutrient composition of the emitting fluvial deposits in the river valleys. Analysis explores potential relationships between land use, geology, climate and precipitation in the upper watersheds and their influence on bioavailability of Fe, P and N compounds in wind-erodible valley sediments. MODIS data for dust plume identification and chlorophyll concentration in the southern Atlantic is utilised to investigate associations between recorded dust emission events and phytoplankton growth in the ocean surface waters.

Abrupt Late Holocene Shift in Atmospheric Circulation Recorded by Mineral Dust in the Siple Dome Ice Core, Antarctica

NASA Astrophysics Data System (ADS)

Koffman, B. G.; Goldstein, S. L.; Kaplan, M. R.; Winckler, G.; Bory, A. J. M.; Biscaye, P.

2015-12-01

Atmospheric dust directly influences Earth's climate by altering the radiative balance and by depositing micronutrients in the surface ocean, affecting global biogeochemical cycling. In addition, mineral dust particles provide observational evidence constraining past atmospheric circulation patterns. Because dust can originate from both local and distant terrestrial sources, knowledge of dust provenance can substantially inform our understanding of past climate history, atmospheric transport pathways, and differences in aerosol characteristics between glacial and interglacial climate states. Dust provenance information from Antarctic ice cores has until now been limited to sites in East Antarctica. Here we present some of the first provenance data from West Antarctica. We use Sr-Nd isotopes to characterize dust extracted from late Holocene ice (~1000-1800 C.E.) from the Siple Dome ice core. The data form a tight array in Sr-Nd isotope space, with 87Sr/86Sr ranging between ~0.7087 and 0.7102, and ɛNd ranging between ~ -7 and -16. This combination is unique for Antarctica, with low Nd and low Sr isotope ratios compared to high-elevation East Antarctic sites, requiring a dust source from ancient (Archean to early Proterozoic) and unweathered continental crust, which mixes with young volcanic material. Both components are likely sourced from Antarctica. We also observe significant, systematic variability in Sr and Nd isotopic signatures through time, reflecting changes in the mixing ratio of these sources, and hypothesize that these changes are driven by shifts in circulation patterns. A large change occurs over about 10 years at ca. 1125 C.E. (ΔɛNd = +3 and Δ87Sr/86Sr = -0.0014). This shift coincides with changes in climate proxies in Southern Hemisphere paleoclimate records reflecting variability in the Westerlies. We therefore interpret the shift in dust provenance at Siple Dome to be related to larger-scale circulation changes. In general, the observed shifts in the particle source signatures indicate that dust transport pathways to and around the West Antarctic Ice Sheet are highly responsive to perturbations in atmospheric circulation, and can record rapid shifts in provenance.

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

USGS Publications Warehouse

Moskowitz, Bruce M; Reynolds, Richard L.; Goldstein, Harland L.; Beroquo, Thelma; Kokaly, Raymond F.; Bristow, Charlie S

2016-01-01

Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth’s most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002–0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM < 0.1 μm. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4% in magnetite, and 65% in ferric silicates. Structural iron in clay minerals may account for much of the iron in the ferric silicates. We estimate that the mean ferric oxides flux exported from the Bodélé Depression is 0.9 Tg/yr with greater than 50% exported as ferric oxide nanoparticles (<0.1 μm). The high surface-to-volume ratios of ferric oxide nanoparticles once entrained into dust plumes may facilitate increased atmospheric chemical and physical processing and affect iron solubility and bioavailability to marine and terrestrial ecosystems.

Bioaccessibility and Speciation of Potential Toxicants in Some Geogenic Sources of Atmospheric Particulate Matter

NASA Astrophysics Data System (ADS)

Morman, S. A.; Wolf, R. E.; Plumlee, G.; Reynolds, R. L.

2008-12-01

The correlation of exposure to particulate matter (PM) and increased morbidity and mortality was established in the 1970's. Research focused on elucidating mechanisms of action (i.e. particle size, composition, and biodurability), has generally examined anthropogenic sources such as solid or liquid combustion byproducts of fossil fuels, byproducts from the smelting of metal ores, and commercial/industrial mineral dusts (asbestos, crystalline silica. metal dusts). While many studies exist on agricultural exposures to inorganic dust, far fewer have examined health issues related to particulate matter contributions from rural, non-agricultural dusts or other geogenic sources. Geogenic PM (produced by natural processes such as volcanic ash, volcanic fog (vog), dusts from dry lakes or glacial deposits, smoke and windborne ash from wildfires, and dusts containing various soil pathogens) and geoanthropogenic PM (produced from natural sources by processes that are modified or enhanced by human activities such as dusts from lakebeds dried by human removal of water, dusts produced from areas that have undergone desertification as a result of human practices etc.) are increasingly recognized as potential agents of toxicity and disease, via both environmental and occupational exposures. Surface sediment on some dry lake beds may contribute significant amounts of mineral dusts to the atmospheric load. For example, Owens Lake (a dry lake in southern California) has been a major source of PM10 (particulate matter less than 10 micrometers) dust in the United States. Dusts from dry and drying saline lakes may contain high concentrations of metals, such as arsenic, with known human health toxicity. Wildfires, consuming over nine million acres in 2007, also contribute significant amounts of particulate matter in addition to their other hazards. Designed to estimate the bioaccessibility of metals in soils, dusts and other environmental materials by measuring the reactivity of the materials in simulated body fluids (SBFs), physiologically based extraction tests (PBETs) are an inexpensive, acellular in vitro test. Bioaccessibility, defined as the fraction of a potential toxicant that becomes soluble in the SBF (e.g. gastric, intestinal, lung or lysosomal fluid), is an indication of the amounts of a potential toxicant that may be available for absorption through ingestion or inhalation. PBETs were conducted on artificially generated dust samples from playas in the Mojave Desert and soil and ash samples from recent California wildfires. Speciation, an important factor in assessing toxicity, was evaluated using high performance liquid chromatography (HPLC) separation with ICP-MS detection for arsenic and chromium.

Detection of anthropogenic dust using CALIPSO lidar measurements

NASA Astrophysics Data System (ADS)

Huang, J. P.; Liu, J. J.; Chen, B.; Nasiri, S. L.

2015-10-01

Anthropogenic dusts are those produced by human activities on disturbed soils, which are mainly cropland, pastureland, and urbanized regions, and are a subset of the total dust load which includes natural sources from desert regions. Our knowledge of anthropogenic dusts is still very limited due to a lack of data. To understand the contribution of anthropogenic dust to the total global dust load, it is important to identify it apart from total dust. In this study, a new technique for distinguishing anthropogenic dust from natural dust is proposed by using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) dust and planetary boundary layer (PBL) height retrievals along with a land use data set. Using this technique, the global distribution of dust is analyzed and the relative contribution of anthropogenic and natural dust sources to regional and global emissions are estimated. Results reveal that local anthropogenic dust aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25 % of the global continental dust load. Of these anthropogenic dust aerosols, more than 53 % come from semi-arid and semi-wet regions. Annual mean anthropogenic dust column burden (DCB) values range from 0.42 g m-2, with a maximum in India, to 0.12 g m-2, with a minimum in North America. A better understanding of anthropogenic dust emission will enable us to focus on human activities in these critical regions and with such knowledge we will be more able to improve global dust models and to explore the effects of anthropogenic emission on radiative forcing, climate change, and air quality in the future.

A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

NASA Astrophysics Data System (ADS)

Kumar, A.; Abouchami, W.; Galer, S. J. G.; Garrison, V. H.; Williams, E.; Andreae, M. O.

2014-01-01

Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers - Sr, Nd and Pb - to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and atmospheric transport.

Size- and density-distributions and sources of polycyclic aromatic hydrocarbons in urban road dust.

PubMed

Murakami, Michio; Nakajima, Fumiyuki; Furumai, Hiroaki

2005-11-01

Polycyclic aromatic hydrocarbons (PAHs) present in size- and density-fractionated road dust were measured to identify the important fractions in urban runoff and to analyse their sources. Road dust was collected from a residential area (Shakujii) and a heavy traffic area (Hongo Street). The sampling of road dust from the residential area was conducted twice in different seasons (autumn and winter). The collected road dust was separated into three or four size-fractions and further fractionated into light (<1.7 g/cm3) and heavy (>1.7 g/cm3) fractions by using cesium chloride solution. Light particles constituted only 4.0+/-1.4%, 0.69+/-0.03% and 3.4+/-1.0% of the road dust by weight for Shakujii (November), Shakujii (February) and Hongo Street, respectively but contained 28+/-10%, 33+/-3% and 44+/-8% of the total PAHs, respectively. The PAH contents in the light fractions were 1-2 orders of magnitude higher than those in the heavy fractions. In the light fractions, the 12PAH contents in February were significantly higher than the 12PAH contents in November (P<0.01), whereas in the heavy fractions, no significant difference was found (P>0.05). Cluster analysis revealed that there was a significant difference in the PAH profiles between locations rather than between size-fractions, density-fractions and sampling times. Multiple regression analysis indicated that asphalt/pavement was the major source of Shakujii road dust, and that tyre and diesel vehicle exhaust were the major sources of finer and coarser fractions collected from Hongo Street road dust, respectively.

Persistent organic contaminants in Saharan dust air masses in West Africa, Cape Verde and the eastern Caribbean

USGS Publications Warehouse

Garrison, Virginia H.; Majewski, Michael S.; Foreman, William T.; Genualdi, Susan A.; Mohammed, Azad; Massey Simonich, Stacy L.

2014-01-01

Anthropogenic semivolatile organic compounds (SOCs) that persist in the environment, bioaccumulate, are toxic at low concentrations, and undergo long-range atmospheric transport (LRT) were identified and quantified in the atmosphere of a Saharan dust source region (Mali) and during Saharan dust incursions at downwind sites in the eastern Caribbean (U.S. Virgin Islands, Trinidad and Tobago) and Cape Verde. More organochlorine and organophosphate pesticides (OCPPs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyl (PCB) congeners were detected in the Saharan dust region than at downwind sites. Seven of the 13 OCPPs detected occurred at all sites: chlordanes, chlorpyrifos, dacthal, dieldrin, endosulfans, hexachlorobenzene (HCB), and trifluralin. Total SOCs ranged from 1.9–126 ng/m3 (mean = 25 ± 34) at source and 0.05–0.71 ng/m3 (mean = 0.24 ± 0.18) at downwind sites during dust conditions. Most SOC concentrations were 1–3 orders of magnitude higher in source than downwind sites. A Saharan source was confirmed for sampled air masses at downwind sites based on dust particle elemental composition and rare earth ratios, atmospheric back trajectory models, and field observations. SOC concentrations were considerably below existing occupational and/or regulatory limits; however, few regulatory limits exist for these persistent organic compounds. Long-term effects of chronic exposure to low concentrations of SOCs are unknown, as are possible additive or synergistic effects of mixtures of SOCs, biologically active trace metals, and mineral dust particles transported together in Saharan dust air masses.

Dust composition changes from Taylor Glacier (East Antarctica) during the last glacial-interglacial transition: A multi-proxy approach

NASA Astrophysics Data System (ADS)

Aarons, Sarah M.; Aciego, Sarah M.; Arendt, Carli A.; Blakowski, Molly A.; Steigmeyer, August; Gabrielli, Paolo; Sierra-Hernández, M. Roxana; Beaudon, Emilie; Delmonte, Barbara; Baccolo, Giovanni; May, Nathaniel W.; Pratt, Kerri A.

2017-04-01

Mineral dust is transported in the atmosphere and deposited in oceans, ice sheets and the terrestrial biosphere. Temporal changes in locations of dust source areas and transport pathways have implications for global climate and biogeochemical cycles. The chemical and physical characterization of the dust record preserved in ice cores is useful for identifying of dust source regions, dust transport, dominant wind direction and storm trajectories. Here, we present a 50,000-year geochemical characterization of mineral dust entrapped in a horizontal ice core from the Taylor Glacier in East Antarctica. Strontium (Sr) and neodymium (Nd) isotopes, grain size distribution, trace and rare earth element (REE) concentrations, and inorganic ion (Cl- and Na+) concentrations were measured in 38 samples, corresponding to a time interval from 46 kyr before present (BP) to present. The Sr and Nd isotope compositions of insoluble dust in the Taylor Glacier ice shows distinct changes between the Last Glacial Period (LGP in this study ranging from ∼46.7-15.3 kyr BP) the early Holocene (in this study ranging from ∼14.5-8.7 kyr BP), and zero-age samples. The 87Sr/86Sr isotopic composition of dust in the Taylor Glacier ice ranged from 0.708 to 0.711 during the LGP, while the variability during the early Holocene is higher ranging from 0.707 to 0.714. The εNd composition ranges from 0.1 to -3.9 during the LGP, and is more variable from 1.9 to -8.2 during the early Holocene. The increased isotopic variability during the early Holocene suggests a shift in dust provenance coinciding with the major climate transition from the LGP to the Holocene. The isotopic composition and multiple physical and chemical constraints support previous work attributing Southern South America (SSA) as the main dust source to East Antarctica during the LGP, and a combination of both local Ross Sea Sector dust sources and SSA after the transition into the Holocene. This study provides the first high time resolution data showing variations in dust provenance to East Antarctic ice during a major climate regime shift, and we provide evidence of changes in the atmospheric transport pathways of dust following the last deglaciation.

Characterizing Mineral Dust from the Arabian Coast of the Red Sea

NASA Astrophysics Data System (ADS)

Puthan Purakkal, J.; Stenchikov, G. L.; Engelbrecht, J. P.

2014-12-01

The Arabian Peninsula is one of the Earth's major sources of atmospheric dust. Along with profound negative effects on human activity and natural processes in this region, dust is an important nutrient source for the oligothrophic northern Red Sea. From preliminary observations it is estimated that some 18-20 major dust storms per year deposit about 6 Mt of mineral dust into the Red Sea. To better understand the optical properties, health, and ecological impacts of dust, we study the mineralogical, chemical and morphological properties of surface soil samples collected at prevbiously identified potential dust sources along the Arabian coast of the Red Sea. Many of these dust sources lie within a narrow coastal region and because of their proximity to the Red Sea, are important contributors to the dust/nutrient balance, during both dusty and fair weather conditions. Bulk samples were collected from the top 10 mm of soils from three sites along the Arabian coast of the Red Sea. The soil samples were sieved to separate the < 38μm particle fractions for chemical and mineralogical analysis. X-ray diffractometry (XRD) was applied to measure the mineral content of the dust. The chemical composition of individual particles was analyzed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). From the XRD analysis of the sieved samples from An Masayat (23.3322 N, 38.9481 E), Buthna (23.2960 N, 38.9384 E) and Rabugh pipeline Road (23.292 N, 38.91 E), it was found that the dust was composed largely of hematite, goethite, calcite, dolomite, quartz, chlorite, muscovite, amphibole, epidote and plagioclase. Our results are being compared to, and show similarities to those of Engelbrecht et al. , collected at 15 Middle East sites. Both the mineralogical content and chemical composition of samples bear the signatures of the regional geology. Engelbrecht, J. P., McDonald, E. V., Gillies, J. A., Jayanty, R. K. M., Casuccio, G., and Gertler, A. W., 2009, Characterizing mineral dusts and other aerosols from the Middle East - Part 2: Grab samples and re-suspensions: Inhalation Toxicology, v. 21, p. 327-336.

Could gradual changes in Holocene Saharan landscape have caused the observed abrupt shift in North Atlantic dust deposition?

NASA Astrophysics Data System (ADS)

Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

2017-09-01

The abrupt change in North Atlantic dust deposition found in sediment records has been associated with a rapid large scale transition of Holocene Saharan landscape. We hypothesize that gradual changes in the landscape may have caused this abrupt shift in dust deposition either because of the non-linearity in dust activation or because of the heterogeneous distribution of major dust sources. To test this hypothesis, we investigate the response of North Atlantic dust deposition to a prescribed 1) gradual and spatially homogeneous decrease and 2) gradual southward retreat of North African vegetation and lakes during the Holocene using the aerosol-climate model ECHAM-HAM. In our simulations, we do not find evidence of an abrupt increase in dust deposition as observed in marine sediment records along the Northwest African margin. We conclude that such gradual changes in landscape are not sufficient to explain the observed abrupt changes in dust accumulation in marine sediment records. Instead, our results point to a rapid large-scale retreat of vegetation and lakes in the area of significant dust sources.

Characteristics of Dust Deposition at High Elevation Sites in Caucasus Over the Past 190 years Recorded in Ice Cores.

NASA Astrophysics Data System (ADS)

Kutuzov, Stanislav; Ginot, Patrick; Mikhaenko, Vladimir; Krupskaya, Victoria; Legrand, Michel; Preunkert, Suzanne; Polukhov, Alexey; Khairedinova, Alexandra

2017-04-01

The nature and extent of both radiative and geochemical impacts of mineral dust on snow pack and glaciers depend on physical and chemical properties of dust particles and its deposition rates. Ice cores can provide information about amount of dust particles in the atmosphere and its characteristic and also give insights on strengths of the dust sources and its changes in the past. A series of shallow ice cores have been obtained in Caucasus mountains, Russia in 2004 - 2015. A 182 meter ice core has been recovered at the Western Plateau of Mt. Elbrus (5115 m a.s.l.) in 2009. The ice cores have been dated using stable isotopes, NH4+ and succinic acid data with the seasonal resolution. Samples were analysed for chemistry, concentrations of dust and black carbon, and particle size distributions. Dust mineralogy was assessed by XRD. Individual dust particles were analysed using SEM. Dust particle number concentration was measured using the Markus Klotz GmbH (Abakus) implemented into the CFA system. Abakus data were calibrated with Coulter Counter multisizer 4. Back trajectory cluster analysis was used to assess main dust source areas. It was shown that Caucasus region experiencing influx of mineral dust from the Sahara and deserts of the Middle East. Mineralogy of dust particles of desert origin was significantly different from the local debris material and contained large proportion of calcite and clay minerals (kaolinite, illite, palygorskite) associated with material of desert origin. Annual dust flux in the Caucasus Mountains was estimated as 300 µg/cm2 a-1. Particle size distribution depends on individual characteristics of dust deposition event and also on the elevation of the drilling site. The contribution of desert dust deposition was estimated as 35-40 % of the total dust flux. Average annual Ca2+ concentration over the period from 1824 to 2013 was of 150 ppb while some of the strong dust deposition events led to the Ca2+ concentrations reaching 4400 ppb. An increase of dust and Ca2+ concentration was registered since the beginning of XX century. The ice core record depicts also a prominent increase of dust concentration in 1980's which may be related to the increase of dust sources strength in North Africa.

THE IMPACT OF ACCURATE EXTINCTION MEASUREMENTS FOR X-RAY SPECTRAL MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Randall K.; Valencic, Lynne A.; Corrales, Lia, E-mail: lynne.a.valencic@nasa.gov

Interstellar extinction includes both absorption and scattering of photons from interstellar gas and dust grains, and it has the effect of altering a source's spectrum and its total observed intensity. However, while multiple absorption models exist, there are no useful scattering models in standard X-ray spectrum fitting tools, such as XSPEC. Nonetheless, X-ray halos, created by scattering from dust grains, are detected around even moderately absorbed sources, and the impact on an observed source spectrum can be significant, if modest, compared to direct absorption. By convolving the scattering cross section with dust models, we have created a spectral model asmore » a function of energy, type of dust, and extraction region that can be used with models of direct absorption. This will ensure that the extinction model is consistent and enable direct connections to be made between a source's X-ray spectral fits and its UV/optical extinction.« less

NHEXAS PHASE I REGION 5 STUDY--METALS IN DUST ANALYTICAL RESULTS

EPA Science Inventory

This data set includes analytical results for measurements of metals in 1,906 dust samples. Dust samples were collected to assess potential residential sources of dermal and inhalation exposures and to examine relationships between analyte levels in dust and in personal and bioma...

Geochemical fingerprint of desert surface sediments and aeolian dust exported from southern South America

NASA Astrophysics Data System (ADS)

Gili, S.; Gaiero, D. M.; Jweda, J.; Koestner, E.; Chemale, F.; Kaplan, M. R.; Goldstein, S. L.

2012-12-01

Wind-transported dust is a tracer of atmospheric circulation and also provides important information about the climatic conditions prevailing in dust source areas. Understanding the origin of mineral dust deposited in different environments (e.g., continent, ocean, polar ice sheet) and the variability of its concentration and composition, can be used as a proxy for the interpretation of the wind systems characteristics and probable changes in the atmospheric circulation patterns. In order to improve the atmospheric circulation models developed for the Southern Hemisphere, it is necessary to increase the understanding of the characteristics of the South American dust sources. Prospero et al., (2002), showed the existence of three present-day persist dust sources in South America: Patagonia (39°-52°S), central-western Argentina (26°-33°S), and the Puna-Altiplano plateau (19°-26°S). An important question to be addressed is whether these dust sources were also important during the last glacial-interglacial cycles. In most cases, researchers working in the reconstruction of paleo-environments in the Southern Hemisphere have employed sparse geochemical and isotopic data from southern South American samples. As a consequence, there are no regional or systematic studies that define their geochemical "fingerprints" of likely sources. The main goal of this work is to identify the "fingerprints" of materials exported from these areas by means of rare earth elements (REEs) and Sr-Nd-Pb-isotopes measured in surface sediments (topsoils) and mineral dust samples. Samples (n=86) were taken across the "arid diagonal" of southern South America in a N-S transect from Uyuni (20°39'S, 68°11'W, Bolivia) to Bahia Blanca (38°43'S, 62°15'W, Argentina) representing different geomorphologic environments: e.g., ephemeral lakes, lowland areas, edges of salt flats, alluvial fans, dunes, etc. Preliminary data indicate the existence of a heterogeneous chemical/isotopic signature along the "arid diagonal": a) the Altiplano and Puna have chemical and isotopic compositions inherited from the large volume of Cenozoic ignimbrites and from the Late Paleozoic granitoids (south of 21°S), respectively, b) the potential dust source in central-western Argentina appears to show a separate geochemical fingerprint explained basically by the mixing of metamorphic rocks from Eastern Sierras Pampeanas, Central Argentina and, c) dust from Patagonia with clear chemical/isotopic signatures characteristic of the Quaternary volcanism (Gaiero et al., 2004; 2007). These results are promising, as they would enable the identification of the main dust source regions in provenance studies of different paleoclimatic records (Pampean loess, Antarctic ice cores, Atlantic and Southern oceans, etc).

The X-ray Halo of GX5-1

NASA Technical Reports Server (NTRS)

Smith, Randall K.; Dame, T. M.; Costantini, Elisa; Predehl, Peter

2006-01-01

Using Chandra observations we have measured the energy-resolved dust-scattered X-ray halo around the low-mass X-ray binary GX5-1, detecting for the first time multiply scattered X-rays from interstellar dust. % e compared the observed X-ray halo at various energies to predictions from a range of dust models. These fits used both smoothly-distributed dust as well as dust in clumped clouds, with CO and 21 cm observations helping to determine the position of the clouds along the line of sight. We found that the BARE-GR-B model of Zubko, Dwek & Arendt (2004) generally led to the best results, although inadequacies in both the overall model and the data limit our conclusions. We did find that the composite dust models of Zubko, Dwek & Arendt (2004), especially the "no carbon" models, gave uniformly poor results. Although models using cloud positions and densities derived naively from CO and 21 cm data gave generally poor results, plausible adjustments to the distance of the largest cloud and the mass of a cloud in the expanding 3 kpc Arm lead to significantly improved fits. We suggest that combining X-ray halo, CO, and 21 cm observations will be a fruitful method to improve our understanding of both the gas and dust phases of the interstellar medium.

MISR Decadal Observations of Mineral Dust: Property Characterization and Climate Applications

NASA Technical Reports Server (NTRS)

Kalashnikova, Olga V.; Garay, Michael J.; Sokolik, Irina; Kahn, Ralph A.; Lyapustin, A.; Diner, David J.; Lee, Jae N.; Torres, Omar; Leptoukh, Gregory G.; Sabbah, Ismail

2012-01-01

The Multi-angle Imaging SpectroRadiometer (MISR) provides a unique, independent source of data for studying dust emission and transport. MISR's multiple view angles allow the retrieval of aerosol properties over bright surfaces, and such retrievals have been shown to be sensitive to the non-sphericity of dust aerosols over both land and water. MISR stereographic views of thick aerosol plumes allow height and instantaneous wind derivations at spatial resolutions of better than 1.1 km horizontally and 200m vertically. We will discuss the radiometric and stereo-retrieval capabilities of MISR specifically for dust, and demonstrate the use of MISR data in conjunction with other available satellite observations for dust property characterization and climate studies.First, we will discuss MISR non-spherical (dust) fraction product over the global oceans. We will show that over the Atlantic Ocean, changes in the MISR-derived non-spherical AOD fraction illustrate the evolution of dust during transport. Next, we will present a MISR satellite perspective on dust climatology in major dust source regions with a particular emphasis on the West Africa and Middle East and discuss MISR's unique strengths as well as current product biases. Finally, we will discuss MISR dust plume product and climatological applications.

Eastern Equatorial Pacific Dust Provenance on Deglacial Timescales

NASA Astrophysics Data System (ADS)

Xie, R.; Marcantonio, F.

2008-12-01

Changing patterns of eolian dust deposition preserved in deep-sea sediments have the potential to provide us with a better understanding of changes in past atmospheric circulation. One way in which to determine the provenance of dust in deep-sea sediments is to use radiogenic isotopic tracers which can fingerprint potential dust sources. Models (e.g., [1]) suggest that sources of dust to the Eastern Equatorial Pacific (EEP) are from areas as diverse as Asia, North, Central, and South America, and, perhaps, even Africa. Here, we investigate spatial and temporal changes in the provenance of the eolian component in the EEP by measuring Pb, Sr, and Nd isotope ratios in dust extracted from sediments along a transect at 110oW from 7oN to 3oS (ODP sites 853 - 848). In this region, although fluxes of dust were higher during the last glacial maximum (LGM) than those in the Holocene by up to 100%, the glacial flux of dust displayed a shallower meridional gradient [2]. However, it is unclear whether this shallower gradient is due to a mean southerly displacement of the Intertropical Convergence Zone (ITCZ). Most of the dust trying to pass through the ITCZ will be scavenged and rained out at the ITCZ. Along the meridional gradient, therefore, temporal variations in the Pb, Sr, and Nd isotopic fingerprints of the distinct dust sources will determine the extent to which the position of the ITCZ changes on deglacial timescales. [1] Mahowald et al., 2005, Global Biogeochemical Cycles 19, GB4025. [2] McGee et al., 2007, EPSL 257, 215-230.

Using Si depletion in aerosol to identify the sources of crustal dust in two Chinese megacities

NASA Astrophysics Data System (ADS)

Zhao, Qing; He, Kebin; Rahn, Kenneth A.; Ma, Yongliang; Yang, Fumo; Duan, Fengkui

2010-07-01

Depletion of Si in transported dust has been recognized for many years. It can be used to distinguish between transported and local dust in cities, although it rarely has been. Here we use the variations of the Si/Al ratio in 15 months of continuous PM 2.5 samples at Beijing (northern China) and Chongqing (southwestern China) to reveal the seasonal patterns of their dust sources. For both cities, peaks of concentration for Si and Al in PM 2.5 corresponded with minima of Si/Al, and could often be linked to pulsed air flow from deserts to the northwest. With significant depletion (up to 80%) and homogeneous distribution at urban and rural sites, Si/Al showed a clear seasonal evolution, which decreased from spring to summer, increased from fall to winter, and collapsed during Chinese Spring Festival, indicating the dominance of transported dust, local fugitive dust and firework influence, respectively. The low ratios implied that desert dust is a common source during spring at Chongqing, whereas its presence during cold season at Beijing was also more frequent than expected. Failing to recognize the depletion of Si may lead to an overestimate of desert dust by 15%-65% when using the average abundance of Al in crust (6%-8%), as in previous studies. The difference in Si/Al ratio between local and transported dust implies that >60% of the dust at Beijing came from outside the city during the springs of 2004-2006. This result can help resolve the contradictory findings on this topic that have been presented earlier.

Gas Inside the 97 AU Cavity around the Transition Disk Sz 91

NASA Astrophysics Data System (ADS)

Canovas, H.; Schreiber, M. R.; Cáceres, C.; Ménard, F.; Pinte, C.; Mathews, G. S.; Cieza, L.; Casassus, S.; Hales, A.; Williams, J. P.; Román, P.; Hardy, A.

2015-05-01

We present ALMA (Cycle 0) band 6 and band 3 observations of the transition disk Sz 91. The disk inclination and position angle are determined to be i = 49.°5 ± 3.°5°and PA = 18.°2 ± 3.°5 and the dusty and gaseous disk are detected up to ˜220 and ˜400 AU from the star, respectively. Most importantly, our continuum observations indicate that the cavity size in the millimeter-sized dust distribution must be ˜97 AU in radius, the largest cavity observed around a T Tauri star. Our data clearly confirm the presence of 12CO (2-1) well inside the dust cavity. Based on these observational constraints we developed a disk model that simultaneously accounts for the 12CO and continuum observations (i.e., gaseous and dusty disk). According to our model, most of the millimeter emission comes from a ring located between 97 and 140 AU. We also find that the dust cavity is divided into an innermost region largely depleted of dust particles ranging from the dust sublimation radius up to 85 AU, and a second, moderately dust-depleted region, extending from 85 to 97 AU. The extremely large size of the dust cavity, the presence of gas and small dust particles within the cavity, and the accretion rate of Sz 91 are consistent with the formation of multiple (giant) planets.

Alpine lakes preserve mineral dust signatures: Implications for long-range mineral dust transport and Last Glacial Maximum (LGM) tornado frequency in the United States

NASA Astrophysics Data System (ADS)

Bhattacharya, A.; Lora, J. M.; Pollen, A.; Vollmer, T.; Thomas, M.; Leithold, E. L.; Mitchell, J.; Tripati, A.

2016-12-01

The net amount of mineral dust accumulation in arid and semi-arid regions might not be entirely sourced locally or even regionally; in fact, new evidence suggests that there could be significant contributions from distal sources. The contribution from the distal sources needs to be identified, and accounted for, in order to accurately understand the meteorological and climatologic factors, both regional and global, that control mineral dust accumulation in arid and semi-arid regions. Most importantly, if identified, the two components of mineral dust accumulation- fine fraction (typically <4 microns) and coarse fraction (typically >25 microns)- could provide critical information about regional as well as global climate. There are large-scale climatological controls on the finer fraction of mineral dust, while the coarser fraction is related to intense invents (i.e., the occurrence of cyclones). However, studies attempting to separate these two size fractions in terrestrial archives have been limited. Here we separate the two size fractions using grain size analysis, and use trace element analysis in each size fraction to identify contributing source regions. We apply this technique to well-dated cores collected from three lakes that are distributed across the western, southwestern and Great Plains in the United States: Pear Lake in the Sierra Nevada Mountains (CA), Senator Beck Lake in the San Juan Mountains (CO), and North Lake (WY). These lakes are uniquely situated to monitor dust fluxes; previous studies have demonstrated that sedimentation in these lakes are dominated by mineral dust accumulation; there is also evidence of remotely and locally sourced dust in these lakes, and of textural differences between the two types of dust fractions. We compare our results with previously published data on dust from loess deposits in the United States, and isotopic modeling (LMDZ). We find evidence that the finer-grain size fraction in alpine lake cores could be of remote origin; work is underway to quantify this contribution. Most importantly, we find that during the Last Glacial Maximum (LGM) the Great Plains may not have witnessed an increase in the incidence of tornado frequency. Acknowledgements: James Sigman, Jacob Ashford, Jason Neff and Amato Evan

Variability in the Correlation between Asian Dust Storms and Chlorophyll a Concentration from the North to Equatorial Pacific

PubMed Central

Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

2013-01-01

A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997–2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54–0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32–0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas. PMID:23460892

Variability in the correlation between Asian dust storms and chlorophyll a concentration from the North to Equatorial Pacific.

PubMed

Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

2013-01-01

A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997-2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54-0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32-0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas.

Atmospheric Movement of Microorganisms in Clouds of Desert Dust and Implications for Human Health

PubMed Central

Griffin, Dale W.

2007-01-01

Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources. PMID:17630335

Atmospheric movement of microorganisms in clouds of desert dust and implications for human health

USGS Publications Warehouse

Griffin, Dale W.

2007-01-01

Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

Atmospheric movement of microorganisms in clouds of desert dust and implications for human health.

PubMed

Griffin, Dale W

2007-07-01

Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

Monitoring An Intensive Dust Event over Northern China Using Multi-satellite Observation

NASA Astrophysics Data System (ADS)

She, L.; Xue, Y.; Guang, J.; Mei, L.; Che, Y.; Fan, C.; Xie, Y.

2017-12-01

The deserts in western/northern China are one of the major mineral dust source regions of the world. Large amount of dust are emitted and blown east and southeast, especially in spring. An intensive dust event occurred over Northern China during May 3 - 8, 2017. The dust storms came from deserts in China and Mongolia. Due to the long-distance transport, more than ten provinces were affected by this dust event, several provinces occurred strong dust storm. In this study, multi-satellite data were employed to analyse the spatial-temporal evolution and dynamic transport behaviour of the dust plume, especially the geostationary satellite data - Himawari8 Advanced Himawari Imager (AHI) data. AHI data was used to estimate hourly Aerosol Optical Depth (AOD) to monitoring the aerosol distribution as well as the dust plume movements, as the dust storms often characterized by high AOD. A simple dust index was also calculated based on AHI VIS and TIR data to estimate the dust intensity. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data and the Ozone Monitoring Instrument (OMI) Aerosol Index were used as additional data sources to monitor the dust vertical distribution and provide independent information of dust presence. MODIS aerosol product and AERONET aerosol measurements were compared with the AHI retrieved AODs, the comparisons show a good agreement. The dust index was compared with the ground measurements as well as the corresponding RGB image. Simulations from HYSPLIT back-trajectory analysis shows similar temporal variation with the calculated AOD and dust index of the dust plume. Those comparisons with other satellite products and ground measurements suggested both the calculated AOD and dust index well depicted the dust events compared.

Prototype detector development for measurement of high altitude Martian dust using a future orbiter platform

NASA Astrophysics Data System (ADS)

Pabari, Jayesh; Patel, Darshil; Chokhawala, Vimmi; Bogavelly, Anvesh

2016-07-01

Dust devils mostly occur during the mid of Southern hemisphere summer on Mars and play a key role in the background dust opacity. Due to continuous bombardment of micrometeorites, secondary ejecta come out from the Moons of the Mars and can easily escape. This phenomenon can contribute dust around the Moons and therefore, also around the Mars. Similar to the Moons of the Earth, the surfaces of the Martian Moons get charged and cause the dust levitation to occur, adding to the possible dust source. Also, interplanetary dust particles may be able to reach the Mars and contribute further. It is hypothesized that the high altitude Martian dust could be in the form of a ring or tori around the Mars. However, no such rings have been detected to the present day. Typically, width and height of the dust torus is ~5 Mars radii wide (~16950 km) in both the planes as reported in the literature. Recently, very high altitude dust at about 1000 km has been found by MAVEN mission and it is expected that the dust may be concentrated at about 150 to 500 km. However, a langmuir probe cannot explain the source of such dust particles. It is a puzzling question to the space scientist how dust has reached to such high altitudes. A dedicated dust instrument on future Mars orbiter may be helpful to address such issues. To study origin, abundance, distribution and seasonal variation of Martian dust, a Mars Orbit Dust Experiment (MODEX) is proposed. In order to measure the Martian dust from a future orbiter, design of a prototype of an impact ionization dust detector has been initiated at PRL. This paper presents developmental aspects of the prototype dust detector and initial results. The further work is underway.

African Dust Aerosols as Atmospheric Ice Nuclei

NASA Technical Reports Server (NTRS)

DeMott, Paul J.; Brooks, Sarah D.; Prenni, Anthony J.; Kreidenweis, Sonia M.; Sassen, Kenneth; Poellot, Michael; Rogers, David C.; Baumgardner, Darrel

2003-01-01

Measurements of the ice nucleating ability of aerosol particles in air masses over Florida having sources from North Africa support the potential importance of dust aerosols for indirectly affecting cloud properties and climate. The concentrations of ice nuclei within dust layers at particle sizes below 1 pn exceeded 1/cu cm; the highest ever reported with our device at temperatures warmer than homogeneous freezing conditions. These measurements add to previous direct and indirect evidence of the ice nucleation efficiency of desert dust aerosols, but also confirm their contribution to ice nuclei populations at great distances from source regions.

The Dynamics and Characteristics of Aeolian Dust in Dryland Central Asia: Possible Impacts on Respiratory Health in the Aral Sea Basin

NASA Astrophysics Data System (ADS)

Wiggs, G. F.; O'Hara, S.; Wegerdt, J.; van der Meer, J.; Small, I.; Hubbard, R.

2003-12-01

Over the last 40 years over 36,000 km2 of the former Aral Sea bed have been exposed creating a potentially significant aeolian dust source. It is widely believed, but little researched, that increased dust storm activity in the region has had a major impact on human health. In this paper we report the findings of a study into the link between dust exposure and respiratory health amongst children in the Autonomous Republic of Karakalpakstan, located on the southern shore of the Aral Sea. Data were collected over a 12 month period at 16 sites located within a broad transect running north to south through Karakalpakstan. At each site monthly measurements of dust deposition were undertaken linked with daily meteorological data at 6 stations. At 3 sites weekly measurements of PM10 were also carried out. Approximately 100 children (aged 7-10 years) were randomly selected within 5 km of each dust trap site and data were collected on their respiratory health and environmental exposures. Lung function data were also collected using a handheld spirometer. A linear regression model was used to predict lung function for the children incorporating variables for Forced Expiratory Volume in one second (FEV1), age, gender, height and weight and we estimated the impact of dust deposition rates on the odds of having abnormal lung function using logistic regression. The findings indicate that dust deposition rates across the region are high with sites located near the former shore of the sea being the worst affected. For these northerly regions the former Aral Sea bed is the most likely source of dust. The situation for the rest of the country seems to be far more complex. In these regions it appears that local sources (agricultural fields, abandoned irrigation grounds, overgrazed dunes, and unpaved roads) and more distant sources to the south and south-west represent significant sediment providers, particularly in the early summer when agricultural fields are ploughed. We found some evidence of a dose-related impact of dust levels on lung function. These associations were statistically significant for all measures of dust exposure but were most marked for levels of winter dust exposure and level of PM2.5 exposure. The results from this study suggest that aeolian dust dynamics in the region are spatially and temporally highly variable and, counter to local and regional perceptions, the former bed of the Aral Sea does not appear to be the only significant source. Nevertheless, there is also evidence of a dose-related impact of airborne dust on the risk of having abnormally low lung function in children living in the Aral Sea Area.

Ice Nucleating Particle Properties in the Saharan Air Layer Close to the Dust Source

NASA Astrophysics Data System (ADS)

Boose, Y.; Garcia, I. M.; Rodríguez, S.; Linke, C.; Schnaiter, M.; Nickovic, S.; Lohmann, U.; Kanji, Z. A.; Sierau, B.

2015-12-01

In August 2013 and 2014 measurements of ice nucleating particle (INP) concentrations, aerosol particle size distributions, chemistry and fluorescence were conducted at the Izaña Atmospheric Observatory located at 2373 m asl on Tenerife, west off the African shore. During summer, the observatory is frequently within the Saharan Air Layer and thus often exposed to dust. Absolute INP concentrations and activated fractions at T=-40 to -15°C and RHi=100-150 % were measured. In this study, we discuss the in-situ measured INP properties with respect to changes in the chemical composition, the biological content, the source regions as well as transport pathways and thus aging processes of the dust aerosol. For the first time, ice crystal residues were also analyzed with regard to biological content by means of their autofluorescence signal close to a major dust source region. Airborne dust samples were collected with a cyclone for additional offline analysis in the laboratory under similar conditions as in the field. Both, in-situ and offline dust samples were chemically characterized using single-particle mass spectrometry. The DREAM8 dust model extended with dust mineral fractions was run to simulate meteorological and dust aerosol conditions for ice nucleation. Results show that the background aerosol at Izaña was dominated by carbonaceous particles, which were hardly ice-active under the investigated conditions. When Saharan dust was present, INP concentrations increased by up to two orders of magnitude even at water subsaturated conditions at T≤-25°C. Differences in the ice-activated fraction were found between different dust periods which seem to be linked to variations in the aerosol chemical composition (dust mixed with changing fractions of sea salt and differences in the dust aerosol itself). Furthermore, two biomass burning events in 2014 were identified which led to very low INP concentrations under the investigated temperature and relative humidity conditions.

Cytotoxicity, oxidative stress and expression of adhesion molecules in human umbilical vein endothelial cells exposed to dust from paints with or without nanoparticles.

PubMed

Mikkelsen, Lone; Jensen, Keld A; Koponen, Ismo K; Saber, Anne T; Wallin, Håkan; Loft, Steffen; Vogel, Ulla; Møller, Peter

2013-03-01

Nanoparticles in primary form and nanoproducts might elicit different toxicological responses. We compared paint-related nanoparticles with respect to effects on endothelial oxidative stress, cytotoxicity and cell adhesion molecule expression. Primary human umbilical vein endothelial cells were exposed to primary nanoparticles (fine, photocatalytic or nanosized TiO(2), aluminium silicate, carbon black, nano-silicasol or axilate) and dust from sanding reference- or nanoparticle-containing paints. Most of the samples increased cell surface expressions of vascular cell adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 (ICAM-1), but paint sanding dust samples generally generated less response than primary particles of TiO(2) and carbon black. We found no relationship between the expression of adhesion molecules, cytotoxicity and production of reactive oxygen species. In conclusion, sanding dust from nanoparticle-containing paint did not generate more oxidative stress or expression of cell adhesion molecules than sanding dust from paint without nanoparticles, whereas the primary particles had the largest effect on mass basis.

Spatial and Temporal Dust Source Variability in Northern China Identified Using Advanced Remote Sensing Analysis

NASA Technical Reports Server (NTRS)

Taramelli, A.; Pasqui, M.; Barbour, J.; Kirschbaum, D.; Bottai, L.; Busillo, C.; Calastrini, F.; Guarnieri, F.; Small, C.

2013-01-01

The aim of this research is to provide a detailed characterization of spatial patterns and temporal trends in the regional and local dust source areas within the desert of the Alashan Prefecture (Inner Mongolia, China). This problem was approached through multi-scale remote sensing analysis of vegetation changes. The primary requirements for this regional analysis are high spatial and spectral resolution data, accurate spectral calibration and good temporal resolution with a suitable temporal baseline. Landsat analysis and field validation along with the low spatial resolution classifications from MODIS and AVHRR are combined to provide a reliable characterization of the different potential dust-producing sources. The representation of intra-annual and inter-annual Normalized Difference Vegetation Index (NDVI) trend to assess land cover discrimination for mapping potential dust source using MODIS and AVHRR at larger scale is enhanced by Landsat Spectral Mixing Analysis (SMA). The combined methodology is to determine the extent to which Landsat can distinguish important soils types in order to better understand how soil reflectance behaves at seasonal and inter-annual timescales. As a final result mapping soil surface properties using SMA is representative of responses of different land and soil cover previously identified by NDVI trend. The results could be used in dust emission models even if they are not reflecting aggregate formation, soil stability or particle coatings showing to be critical for accurately represent dust source over different regional and local emitting areas.

Submillimeter Observations of CLASH 2882 and the Evolution of Dust in this Galaxy

NASA Technical Reports Server (NTRS)

Dwek, Eli; Staguhn, Johannes; Arendt, Richard G; Kovacs, Attila; Decarli, Roberto; Egami, Eiichi; Michalowski, Michal J.; Rawle, Timothy D.; Toft, Sune; Walter, Fabian

2015-01-01

Two millimeter observations of the MACS J1149.6+2223 cluster have detected a source that was consistent with the location of the lensed MACS 1149-JD galaxy at z = 9.6. A positive identification would have rendered this galaxy as the youngest dust forming galaxy in the universe. Follow up observation with the AzTEC 1.1 mm camera and the IRAM NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm have not confirmed this association. In this paper we show that the NOEMA observations associate the 2 mm source with [PCB2012] 2882,12 source number 2882 in the Cluster Lensing And Supernova survey with Hubble (CLASH) catalog of MACS J1149.6 +2223. This source, hereafter referred to as CLASH 2882, is a gravitationally lensed spiral galaxy at z = 0.99. We combine the Goddard IRAM Superconducting 2-Millimeter Observer (GISMO) 2 mm and NOEMA 1.3 mm fluxes with other (rest frame) UV to far-IR observations to construct the full spectral energy distribution of this galaxy, and derive its star formation history, and stellar and interstellar dust content. The current star formation rate of the galaxy is 54/mu/Solar Mass/yr, and its dust mass is about 5 × 10(exp 7)/mu Solar Mass, where mu is the lensing magnification factor for this source, which has a mean value of 2.7. The inferred dust mass is higher than the maximum dust mass that can be produced by core collapse supernovae and evolved AGB stars. As with many other star forming galaxies, most of the dust mass in CLASH 2882 must have been accreted in the dense phases of the interstellar medium.

WMO SDS-WAS NAMEE Regional Center: Towards continuous evaluation of dust models in Northern Africa

NASA Astrophysics Data System (ADS)

Basart, Sara; García-Castillo, Gerardo; Cuevas, Emilio; Terradellas, Enric

2016-04-01

One of the most important activities of the Regional Center for Northern Africa, Middle East and Europe of the World Meteorological Organization's Sand and Dust Storm Warning Advisory and Assessment System (WMO SDS-WAS, http://sds-was.aemet.es) is the dust model intercomparison and forecast evaluation, which is deemed an indispensable service to the users and an invaluable tool to assess model skills. Currently, the Regional Center collects daily dust forecasts from models run by nine partners (BSC, ECMWF, NASA, NCEP, SEEVCCC, EMA, CNR-ISAC, NOA and UK Met Office). A multi-model ensemble has also been set up in an effort to provide added-value products to the users. The first problem to address the dust model evaluation is the scarcity of suitable routine observations near the Sahara, the world's largest source of mineral dust. The present contribution presents preliminary results of dust model evaluation using new observational datasets. The current routine evaluation of dust predictions is focused on total-column dust optical depth (DOD) and uses remote-sensing retrievals from sun-photometric (AERONET) and satellite (MODIS) measurements. However, most users of dust forecasts are interested in the concentration near the surface (in the air we breathe) rather than in the total column content. Therefore, evaluation of the predicted surface concentration is also necessary. In this context, the initiative of the African Monsoon Interdisciplinary Analysis (AMMA) International Program to establish permanent measuring stations in the Sahel is extremely important. Tapered Element Oscillating Microbalance (TEOM) monitors continuously record PM10 in M'Bour (Senegal); Cinzana (Mali) and Banizoumbou (Niger). This surface model evaluation is complemented with the PM10 observation from the Air Quality Control and Monitoring Network (AQCMN) of the Canary Islands (Spain). The region, located in the sub-tropical Eastern Atlantic (roughly 100 km west of the Moroccan coast), is frequently affected by intrusions of Saharan dust. Regional Node are evaluated during two years (2013-2014) with observations recorded in the Sahelian region and Canary Islands. Additionally, since the data sets of weather records have an excellent spatial and temporal coverage, observations of horizontal visibility included in meteorological reports are used as an alternative way to monitor dust events in near-real-time (NRT). Recently, a new visibility product that includes more than 1,500 METAR stations has implemented in the SDS-WAS NAMEE Regional Center. The present contribution also will demonstrate how the visibility can complement the information provided by other observing systems (air quality monitoring stations, sun photometers, vertical profilers or satellite products) and numerical simulations presenting its application in tracking several dust episodes. Otherwise, the vertical distribution of aerosol also influences the radiative effect at the top of the atmosphere, especially when aerosols have strong absorption of shortwave radiation. The free troposphere contribution to aerosol optical depth (AOD) and the altitude of lofted layers are provided thanks to the vertical profiling capability of the lidar/ceilomenter technique. Currently, a lidar located in Dakar (Senegal) and a ceilometer in Santa Cruz de Tenerife (Canary Islands, Spain) provide near-real-time (NRT) vertical profiles of aerosols, which are compared with those simulated by models.

Styles and Timing of Volatile-driven Activity in the Eastern Hellas Region of Mars

NASA Technical Reports Server (NTRS)

Crown, David A.; Bleamaster, Leslie F., III; Mest, Scott C.; Teneva, Lida T.

2005-01-01

Hellas basin, the largest well-preserved impact structure on the Martian surface, is Mars deepest depositional sink and has long been recognized as a source for global dust storms. The basin and surrounding highlands span a wide range in latitude and elevation, exhibit landforms shaped by a diversity of geologic processes, and preserve exposures of Noachian, Hesperian, and Amazonian units. Geologically contemporaneous volcanism and volatile-driven activity in the circum-Hellas highlands provide resources for potential Martian life. Hellas is a geologically significant region for evaluating volatile abundance, distribution and cycling and changes in surface conditions on Mars. Current work integrates geologic studies of the basin floor and east rim using Viking Orbiter, Mars Global Surveyor, and Mars Odyssey datasets to provide a synthesis of the history of volatiles in the region.

Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport.

PubMed

Shahan, M R; Seaman, C E; Beck, T W; Colinet, J F; Mischler, S E

2017-09-01

Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. If deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coal dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float coal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float coal dust to respirable dust ranged from 10.3 to 13.8. The ratios measured on the longwall face were between 18.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8.

Modeling the biogeochemical impact of atmospheric phosphate deposition from desert dust and combustion sources to the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Richon, Camille; Dutay, Jean-Claude; Dulac, François; Wang, Rong; Balkanski, Yves

2018-04-01

Daily modeled fields of phosphate deposition to the Mediterranean from natural dust, anthropogenic combustion and wildfires were used to assess the effect of this external nutrient on marine biogeochemistry. The ocean model used is a high-resolution (1/12°) regional coupled dynamical-biogeochemical model of the Mediterranean Sea (NEMO-MED12/PISCES). The input fields of phosphorus are for 2005, which are the only available daily resolved deposition fields from the global atmospheric chemical transport model LMDz-INCA. Traditionally, dust has been suggested to be the main atmospheric source of phosphorus, but the LMDz-INCA model suggests that combustion is dominant over natural dust as an atmospheric source of phosphate (PO4, the bioavailable form of phosphorus in seawater) for the Mediterranean Sea. According to the atmospheric transport model, phosphate deposition from combustion (Pcomb) brings on average 40.5×10-6 mol PO4 m-2 yr-1 over the entire Mediterranean Sea for the year 2005 and is the primary source over the northern part (e.g., 101×10-6 mol PO4 m-2 yr-1 from combustion deposited in 2005 over the north Adriatic against 12.4×10-6 from dust). Lithogenic dust brings 17.2×10-6 mol PO4 m-2 yr-1 on average over the Mediterranean Sea in 2005 and is the primary source of atmospheric phosphate to the southern Mediterranean Basin in our simulations (e.g., 31.8×10-6 mol PO4 m-2 yr-1 from dust deposited in 2005 on average over the south Ionian basin against 12.4×10-6 from combustion). The evaluation of monthly averaged deposition flux variability of Pdust and Pcomb for the 1997-2012 period indicates that these conclusions may hold true for different years. We examine separately the two atmospheric phosphate sources and their respective flux variability and evaluate their impacts on marine surface biogeochemistry (phosphate concentration, chlorophyll a, primary production). The impacts of the different phosphate deposition sources on the biogeochemistry of the Mediterranean are found localized, seasonally varying and small, but yet statistically significant. Differences in the geographical deposition patterns between phosphate from dust and from combustion will cause contrasted and significant changes in the biogeochemistry of the basin. We contrast the effects of combustion in the northern basin (Pcomb deposition effects are found to be 10 times more important in the northern Adriatic, close to the main source region) to the effects of dust in the southern basin. These different phosphorus sources should therefore be accounted for in modeling studies.

Metal contamination in campus dust of Xi'an, China: a study based on multivariate statistics and spatial distribution.

PubMed

Chen, Hao; Lu, Xinwei; Li, Loretta Y; Gao, Tianning; Chang, Yuyu

2014-06-15

The concentrations of As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V and Zn in campus dust from kindergartens, elementary schools, middle schools and universities of Xi'an, China were determined by X-ray fluorescence spectrometry. Correlation coefficient analysis, principal component analysis (PCA) and cluster analysis (CA) were used to analyze the data and to identify possible sources of these metals in the dust. The spatial distributions of metals in urban dust of Xi'an were analyzed based on the metal concentrations in campus dusts using the geostatistics method. The results indicate that dust samples from campuses have elevated metal concentrations, especially for Pb, Zn, Co, Cu, Cr and Ba, with the mean values of 7.1, 5.6, 3.7, 2.9, 2.5 and 1.9 times the background values for Shaanxi soil, respectively. The enrichment factor results indicate that Mn, Ni, V, As and Ba in the campus dust were deficiently to minimally enriched, mainly affected by nature and partly by anthropogenic sources, while Co, Cr, Cu, Pb and Zn in the campus dust and especially Pb and Zn were mostly affected by human activities. As and Cu, Mn and Ni, Ba and V, and Pb and Zn had similar distribution patterns. The southwest high-tech industrial area and south commercial and residential areas have relatively high levels of most metals. Three main sources were identified based on correlation coefficient analysis, PCA, CA, as well as spatial distribution characteristics. As, Ni, Cu, Mn, Pb, Zn and Cr have mixed sources - nature, traffic, as well as fossil fuel combustion and weathering of materials. Ba and V are mainly derived from nature, but partly also from industrial emissions, as well as construction sources, while Co principally originates from construction. Copyright © 2014 Elsevier B.V. All rights reserved.

Probing the Spatial Distribution of the Interstellar Dust Medium by High Angular Resolution X-ray Halos of Point Sources

NASA Astrophysics Data System (ADS)

Xiang, Jingen

X-rays are absorbed and scattered by dust grains when they travel through the interstellar medium. The scattering within small angles results in an X-ray ``halo''. The halo properties are significantly affected by the energy of radiation, the optical depth of the scattering, the grain size distributions and compositions, and the spatial distribution of dust along the line of sight (LOS). Therefore analyzing the X-ray halo properties is an important tool to study the size distribution and spatial distribution of interstellar grains, which plays a central role in the astrophysical study of the interstellar medium, such as the thermodynamics and chemistry of the gas and the dynamics of star formation. With excellent angular resolution, good energy resolution and broad energy band, the Chandra ACIS is so far the best instrument for studying the X-ray halos. But the direct images of bright sources obtained with ACIS usually suffer from severe pileup which prevents us from obtaining the halos in small angles. We first improve the method proposed by Yao et al to resolve the X-ray dust scattering halos of point sources from the zeroth order data in CC-mode or the first order data in TE mode with Chandra HETG/ACIS. Using this method we re-analyze the Cygnus X-1 data observed with Chandra. Then we studied the X-ray dust scattering halos around 17 bright X-ray point sources using Chandra data. All sources were observed with the HETG/ACIS in CC-mode or TE-mode. Using the interstellar grain models of WD01 model and MRN model to fit the halo profiles, we get the hydrogen column densities and the spatial distributions of the scattering dust grains along the line of sights (LOS) to these sources. We find there is a good linear correlation not only between the scattering hydrogen column density from WD01 model and the one from MRN model, but also between N_{H} derived from spectral fits and the one derived from the grain models WD01 and MRN (except for GX 301-2 and Vela X-1): N_{H,WD01} = (0.720±0.009) × N_{H,abs} + (0.051±0.013) and N_{H, MRN} = (1.156±0.016) × N_{H,abs} + (0.062±0.024) in the units 10^{22} cm^{-2}. Then the correlation between FHI and N_{H} is obtained. Both WD01 model and MRN model fits show that the scattering dust density very close to these sources is much higher than the normal interstellar medium and we consider it is the evidence of molecular clouds around these X-ray binaries. We also find that there is the linear correlation between the effective distance through the galactic dust layer and hydrogen scattering olumn density N_{H} excluding the one in x=0.99-1.0 but the correlation does not exist between he effective distance and the N_{H} in x=0.99-1.0. It shows that the dust nearby the X-ray sources is not the dust from galactic disk. Then we estimate the structure and density of the stellar wind around the special X-ray pulsars Vela X-1 and GX 301-2. Finally we discuss the possibility of probing the three dimensional structure of the interstellar using the X-ray halos of the transient sources, probing the spatial distributions of interstellar dust medium nearby the point sources, even the structure of the stellar winds using higher angular resolution X-ray dust scattering halos and testing the model that the black hole can be formed from the direct collapse of a massive star without supernova using the statistical distribution of the dust density nearby the X-ray binaries.

Properties of transported African mineral dust aerosols in the Mediterranean region

NASA Astrophysics Data System (ADS)

Denjean, Cyrielle; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Triquet, Sylvain; Zapf, Pascal; Loisil, Rodrigue; Bourrianne, Thierry; Freney, Evelyn; Dupuy, Regis; Sellegri, Karine; Schwarzenbock, Alfons; Torres, Benjamin; Mallet, Marc; Cassola, Federico; Prati, Paolo; Formenti, Paola

2015-04-01

The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), one intensive airborne campaign (ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) has been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.

Anthropogenic- and natural sources of dust in peatland during the Anthropocene

NASA Astrophysics Data System (ADS)

Fiałkiewicz-Kozieł, B.; Smieja-Król, B.; Frontasyeva, M.; Słowiński, M.; Marcisz, K.; Lapshina, E.; Gilbert, D.; Buttler, A.; Jassey, V. E. J.; Kaliszan, K.; Laggoun-Défarge, F.; Kołaczek, P.; Lamentowicz, M.

2016-12-01

As human impact have been increasing strongly over the last decades, it is crucial to distinguish human-induced dust sources from natural ones in order to define the boundary of a newly proposed epoch - the Anthropocene. Here, we track anthropogenic signatures and natural geochemical anomalies in the Mukhrino peatland, Western Siberia. Human activity was recorded there from cal AD 1958 (±6). Anthropogenic spheroidal aluminosilicates clearly identify the beginning of industrial development and are proposed as a new indicator of the Anthropocene. In cal AD 1963 (±5), greatly elevated dust deposition and an increase in REE serve to show that the geochemistry of elements in the peat can be evidence of nuclear weapon testing; such constituted an enormous force blowing soil dust into the atmosphere. Among the natural dust sources, minor signals of dryness and of the Tunguska cosmic body (TCB) impact were noted. The TCB impact was indirectly confirmed by an unusual occurrence of mullite in the peat.

Anthropogenic- and natural sources of dust in peatland during the Anthropocene

PubMed Central

Fiałkiewicz-Kozieł, B.; Smieja-Król, B.; Frontasyeva, M.; Słowiński, M.; Marcisz, K.; Lapshina, E.; Gilbert, D.; Buttler, A.; Jassey, V. E. J.; Kaliszan, K.; Laggoun-Défarge, F.; Kołaczek, P.; Lamentowicz, M.

2016-01-01

As human impact have been increasing strongly over the last decades, it is crucial to distinguish human-induced dust sources from natural ones in order to define the boundary of a newly proposed epoch - the Anthropocene. Here, we track anthropogenic signatures and natural geochemical anomalies in the Mukhrino peatland, Western Siberia. Human activity was recorded there from cal AD 1958 (±6). Anthropogenic spheroidal aluminosilicates clearly identify the beginning of industrial development and are proposed as a new indicator of the Anthropocene. In cal AD 1963 (±5), greatly elevated dust deposition and an increase in REE serve to show that the geochemistry of elements in the peat can be evidence of nuclear weapon testing; such constituted an enormous force blowing soil dust into the atmosphere. Among the natural dust sources, minor signals of dryness and of the Tunguska cosmic body (TCB) impact were noted. The TCB impact was indirectly confirmed by an unusual occurrence of mullite in the peat. PMID:27995953

The role of forest in mitigating the impact of atmospheric dust pollution in a mixed landscape.

PubMed

Santos, Artur; Pinho, Pedro; Munzi, Silvana; Botelho, Maria João; Palma-Oliveira, José Manuel; Branquinho, Cristina

2017-05-01

Atmospheric dust pollution, especially particulate matter below 2.5 μm, causes 3.3 million premature deaths per year worldwide. Although pollution sources are increasingly well known, the role of ecosystems in mitigating their impact is still poorly known. Our objective was to investigate the role of forests located in the surrounding of industrial and urban areas in reducing atmospheric dust pollution. This was tested using lichen transplants as biomonitors in a Mediterranean regional area with high levels of dry deposition. After a multivariate analysis, we have modeled the maximum pollution load expected for each site taking into consideration nearby pollutant sources. The difference between maximum expected pollution load and the observed values was explained by the deposition in nearby forests. Both the dust pollution and the ameliorating effect of forested areas were then mapped. The results showed that forest located nearby pollution sources plays an important role in reducing atmospheric dust pollution, highlighting their importance in the provision of the ecosystem service of air purification.

Magnetic characteristics of industrial dust from different sources of emission: A case study of Poland

NASA Astrophysics Data System (ADS)

Szuszkiewicz, Marcin; Magiera, Tadeusz; Kapička, Aleš; Petrovský, Eduard; Grison, Hanna; Gołuchowska, Beata

2015-05-01

Dust emission and deposition in topsoil have negative effect on individual components of the ecosystem. In addition to routine geochemical analyses, magnetic measurements may provide useful complementary information related to the type, concentration and grain-size distribution of the technogenic magnetic particles (TMPs) and thus the degree of contamination of the environment. The aim of this contribution is to use magnetic parameters in distinguishing dust from a wide range of sources of air pollution (power industry, cement, coke, ceramic industries and biomass combustion). We measured magnetic susceptibility, hysteresis parameters and thermomagnetic curves. Our results suggest that predominant component in tested samples is magnetite, only dust from coking plant and the combustion of lignite contained also maghemite and/or hematite. Mixture of sizes, ranging from fine single-domain to coarse multi-domain grains, was detected. Our results indicate that industrial dusts from various sources of emissions have different specific magnetic properties and magnetic measurements may provide very helpful information.

Anthropogenic- and natural sources of dust in peatland during the Anthropocene.

PubMed

Fiałkiewicz-Kozieł, B; Smieja-Król, B; Frontasyeva, M; Słowiński, M; Marcisz, K; Lapshina, E; Gilbert, D; Buttler, A; Jassey, V E J; Kaliszan, K; Laggoun-Défarge, F; Kołaczek, P; Lamentowicz, M

2016-12-20

As human impact have been increasing strongly over the last decades, it is crucial to distinguish human-induced dust sources from natural ones in order to define the boundary of a newly proposed epoch - the Anthropocene. Here, we track anthropogenic signatures and natural geochemical anomalies in the Mukhrino peatland, Western Siberia. Human activity was recorded there from cal AD 1958 (±6). Anthropogenic spheroidal aluminosilicates clearly identify the beginning of industrial development and are proposed as a new indicator of the Anthropocene. In cal AD 1963 (±5), greatly elevated dust deposition and an increase in REE serve to show that the geochemistry of elements in the peat can be evidence of nuclear weapon testing; such constituted an enormous force blowing soil dust into the atmosphere. Among the natural dust sources, minor signals of dryness and of the Tunguska cosmic body (TCB) impact were noted. The TCB impact was indirectly confirmed by an unusual occurrence of mullite in the peat.

LADEE Search for a Dust Exosphere: A Historical Perspective

NASA Technical Reports Server (NTRS)

Glenar, D. A.; Stubbs, T. J.; Elphic, R.

2014-01-01

The LADEE search for exospheric dust is strongly motivated by putative detections of forward-scattered sunlight from exospheric dust grains which were observed during the Apollo era. This dust population, if it exists, has been associated with charging and transport of dust near the terminators. It is likely that the concentration of these dust grains is governed by a saltation mechanism originated by micrometeoroid impacts, which are the source of the more tenuous ejecta cloud.

Sources of halogenated brominated retardants in house dust in an industrial city in southern China and associated human exposure.

PubMed

Chen, She-Jun; Ding, Nan; Zhu, Zhi-Cheng; Tian, Mi; Luo, Xiao-Jun; Mai, Bi-Xian

2014-11-01

Halogenated flame retardants (HFRs) are a class of ubiquitous pollutants in the environment and attract increasing attention. In the present study, HFR concentrations were measured in indoor and outdoor dust in an important industrial city (Dongguan) in southern China, in which their presence and associated human exposure are unknown. The HFRs were dominated by polybrominated diphenyl ethers (PBDEs) and decabromodiphenyl ethane (DBDPE), with mean concentrations of 2365 and 2441 ng/g in the indoor dust, respectively, which were 2-3 order of magnitude higher the concentrations of other HFRs. However elevated tri- to hepta-BDE concentrations (869 ng/g) were found in Houjie Town, a furniture manufacturing center. The mean indoor/outdoor (I/O) ratios of HFR concentrations in the dust were all larger than one (1.55-16.4), suggesting the importance of indoors sources for HFRs in indoor dust in this industrial city. Principal component analysis (PCA) showed that the correlations among the HFRs in the indoor dust probably revealed differences in their commercial applications, while most HFRs in the outdoor dust have similar sources except for phased-out BDE47 and 99. The compositions of lower brominated PBDEs varied among the towns, probably due to their different sources or influence of photo-degradation. Nevertheless, the similar composition of highly brominated congeners indicated little photo-degradation encountered in the ambient environment. The non-cancer risk associated with indoor dust ingestion is low for the general population in Dongguan, but some children in the furniture manufacturing center have significantly high risk of exposure to banned PBDEs. Copyright © 2014 Elsevier Inc. All rights reserved.

Tracing geogenic and anthropogenic sources in urban dusts: Insights from lead isotopes

NASA Astrophysics Data System (ADS)

Del Rio-Salas, R.; Ruiz, J.; De la O-Villanueva, M.; Valencia-Moreno, M.; Moreno-Rodríguez, V.; Gómez-Alvarez, A.; Grijalva, T.; Mendivil, H.; Paz-Moreno, F.; Meza-Figueroa, D.

2012-12-01

Tracing the source of metals in the environment is critical to understanding their pollution level and fate. Geologic materials are an important source of airborne particulate matter, but the contribution of contaminated soil to concentrations of Pb in airborne dust is not yet widely documented. To examine the potential significance of this mechanism, surface soil samples were collected, as well as wind-transported dust trapped at 1 and 2 m height at seven different locations including residential, industrial, high-traffic and rural sites. Samples of dust deposited on roofs from 24 schools were also obtained and analyzed for Pb isotope ratios. Spatial distribution of Pb of airborne and sedimented dust suggests a process dominated by re-suspension/sedimentation, which was controlled by erosion, traffic and topography of the urban area. Anthropogenic lead input in the city grades outward the urban zone toward geogenic values. Our results shows that Pb-isotopic signatures of leaded gasoline are imprinted in dust sedimented on roofs. Considering that leaded-gasoline has not been in use in Mexico since two decades ago, this signature shows not only a Pb-legacy in soil, but also a re-suspension process affecting air column below 3 m in height. The combination of the 207Pb/206Pb data of the surrounding rocks and urban dust, reveal three well-defined zones with remarkable anthropogenic influence, which correspond to the oldest urban sectors. This work highlights the importance of spatial characterization of metals in particles suspended below a height of 3 m of the airborne column, a fact that should be considered to identify exposure paths to humans and the potential risks. Lead isotope signatures allowed the identification of geogenic and anthropogenic emission sources for dust, a matter that deserves consideration in the efforts to control airborne metal emissions.

A 16-year record of eolian dust in Southern Nevada and California, USA: Controls on dust generation and accumulation

USGS Publications Warehouse

Reheis, M.C.

2006-01-01

An ongoing project monitors modern dust accumulation in the arid southwestern United States to (1) determine the rate and composition of dust inputs to soils and (2) relate dust accumulation to weather patterns to help predict the effects of climate change on dust production and accumulation. The 16-year records of 35 dust-trap sites in the eastern Mojave Desert and southern Great Basin reveal how generation and accumulation of dust, including the silt-clay, carbonate, and soluble-salt fractions, is affected by the amount and seasonal distribution of rainfall and the behavior of different source types (alluvium, dry playas, and wet playas). Accumulation rates (fluxes) of the silt-clay fraction of dust, including carbonates, range from about 2-20 g/m2/yr. Average rates are higher in the southern part of the study area (south of latitude 36.5??N) and annually fluctuate over a larger range than rates in the northern part of the area. Sites throughout the study area show peaks in dust flux in the 1984-1985 sampling period and again in 1997-1999; northern sites also show increased flux in 1987-1988 and southern sites in 1989-1991. These peaks of dust flux correspond with both La Nina (dry) conditions and with strong El Nino (wet) periods. The accumulation rates of different components of mineral dusts fluctuate differently. For example, soluble-salt flux increases in 1987-1988, coincident with a moderate El Nino event, and increases very strongly in 1997-1999, overlapping with a strong El Nino event. Both of these high-rainfall winters were preceded and accompanied by strong summer rains. In contrast, little or no change in soluble-salt flux occurred during other periods of high winter rainfall but little summer rain, e.g. 1992-1995. The differences between northern vs. southern sites and between sites with playa dust sources vs. alluvial dust sources indicate that regional differences in the response of precipitation and vegetation growth to ENSO influence and differences in the response of source types control dust production and accumulation. A major factor is the hydrologic condition of surface sediments. The silt-clay and soluble-salt fluxes increased during the El Nino events of 1987-1988 and 1997-1998 at sites close to "wet" playas with shallow depths to groundwater (<10 m), consistent with the concept that active evaporative concentration of salts disrupts surface crusts and increases the susceptibility of surface sediment to deflation. The silt-clay flux also increased during drought periods (1989-1991, 1995-1997) at sites downwind of alluvial sources and "dry" playas with deeper groundwater (<10 m). These increases are probably related to the die-off of drought-stressed vegetation on alluvial sediments, and in some cases to local runoff events that deliver fresh sediment to playa margins and distal portions of alluvial fans. ?? 2006 Elsevier Ltd. All rights reserved.

Atmospheric dust events in Central Asia: Relationship to wind, soil type, and land use

USDA-ARS?s Scientific Manuscript database

Xinjiang Province is one of the most important source regions of atmospheric dust in China. Spatial-temporal characteristics of dust events in the region were investigated by time series analysis of annual dust event frequency and meteorological data collected at 101 stations in Xinjiang Province fr...

Thorium-derived dust fluxes to the tropical Pacific Ocean, 58 Ma

NASA Astrophysics Data System (ADS)

Woodard, Stella C.; Thomas, Deborah J.; Marcantonio, Franco

2012-06-01

Eolian dust in pelagic deep sea sediments can be used to reconstruct ancient wind patterns and paleoenvironmental response to climate change. Traditional methods to determine dust accumulation involve isolating the non-dissolvable aluminosilicate minerals from deep sea sediments through a series of chemical leaches, but cannot differentiate between minerals from eolian, authigenic and volcanogenic sources. Other geochemical proxies, such as sedimentary 232Th and crustal 4He content, have been used to construct high-resolution records of atmospheric dust fluxes to the deep sea during the Quaternary. Here we use sedimentary Th content as a proxy for terrigenous material (eolian dust) in ˜58 Myr-old sediments from the Shatsky Rise (ODP Site 1209) and compare our results with previous dust estimates generated using the traditional chemical extraction method and sedimentary 4Hecrustal concentrations. We find excellent agreement between Th-based dust estimates and those generated using the traditional method. In addition our results show a correlation between sedimentary Th and 4Hecrustal content, which suggests a source older than present day Asian loess supplied dust to the central subtropical Pacific Ocean during the early Paleogene.

Studying Dust Scattering Halos with Galactic X-ray Binaries

NASA Astrophysics Data System (ADS)

Beeler, Doreen; Corrales, Lia; Heinz, Sebastian

2018-01-01

Dust is an important part of the interstellar medium (ISM) and contributes to the formation of stars and planets. Since the advent of modern X-ray telescopes, Galactic X-ray point sources have permitted a closer look at all phases of the ISM. Interstellar metals from oxygen to iron — in both gas and dust form — are responsible for absorption and scattering of X-ray light. Dust scatters the light in a forward direction and creates a diffuse halo image surrounding many bright Galactic X-ray binaries. We use all the bright X-ray point sources available in the Chandra HETG archive to study dust scattering halos from the local ISM. We have described a data analysis pipeline using a combination of the data reduction software CIAO and Python. We compare our results from Chandra HETG and ACIS-I observations of a well studied dust scattering halo around GX 13+1, in order to characterize any systematic errors associated with the HETG data set. We describe how our data products will be used to measure ISM scaling relations for X-ray extinction, dust abundance, and dust-to-metal ratios.

Featured Image: Making Dust in the Lab

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

This remarkable photograph (which spans only 10 m across; click for a full view) reveals what happens when you form dust grains in a laboratory under conditions similar to those of interstellar space. The cosmic life cycle of dust grains is not well understood we know that in the interstellar medium (ISM), dust is destroyed at a higher rate than it is produced by stellar sources. Since the amount of dust in the ISM stays constant, however, there must be additional sources of dust production besides stars. A team of scientists led by Daniele Fulvio (Pontifical Catholic University of Rio de Janeiro and the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena) have now studied formation mechanisms of dust grains in the lab by mimicking low-temperature ISM conditions and exploring how, under these conditions, carbonaceous materials condense from gas phase to form dust grains. To read more about their results and see additional images, check out the paper below.CitationDaniele Fulvio et al 2017 ApJS 233 14. doi:10.3847/1538-4365/aa9224

Do Sahara dunes make dust? Some dunes do and some dunes don't

NASA Astrophysics Data System (ADS)

Bristow, Charlie

2017-04-01

The Sahara desert is responsible for producing around half of the atmospheric mineral dust on Earth. While most of the Sahara has the potential to produce dust some areas have been identified using remote sensing as especially prolific dust sources such as the Bodélé Depression in Chad which is described as the dustiest place on Earth. Geomorphological analysis indicates that these areas are usually topographic lows, such as the Bodélé, as well as regions on the flanks of topographic highs. This view was challenged by Crouvi et al. (2012) who suggest that active sand dunes are the most frequent dust sources. In this paper we use an experimental dust chamber to generate dust from dune sediments collected from the crest of active sand dunes across the Sahara including samples from the Bodélé depression, as well as dune sands from Algeria, Egypt, Libya, Morocco and Tunisia. The experiments produced a wide range of results indicating that some dune sands, including those from the Bodélé produce much more dust than others.

In-depth survey report: control technology for manual transfer of chemical powders at the B. F. Goodrich Company, Marietta, Ohio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gressel, M.G.; Heitbrink, W.A.; McGlothlin, J.D.

1985-12-01

A field study was conducted in the B.F. Goodrich Industrial Plastics Division facility, Marietta, Ohio to evaluate sources of worker dust exposure at a ventilated booth used for the weigh out and transfer of powdered materials from large drums to small bags. The sources of dust exposure evaluated were: depth of scooping, clothing, worker anthropometry, work practices, biomechanics, and specific items in the job cycle. Dust exposure for workers wearing clean clothing was not significantly different from exposure for workers wearing dirty clothing. Depth of scooping from the drum significantly affected dust exposure. There appeared also to be a relationshipmore » between the size of the worker and dust exposure when scooping from the bottom of the drum. Work practices may also play a part. The authors conclude that, while the results showed abnormally high dust levels, all three workers studied wore respirable dust respirators during the experiment to protect them from these high levels. Air flow patterns at the booth suggest that the ventillation provided may even contributed to dust exposure.« less

Changing sources of strontium to soils and ecosystems across the Hawaiian Islands

USGS Publications Warehouse

Chadwick, O.A.; Derry, L.A.; Bern, C.R.; Vitousek, P.M.

2009-01-01

Strontium isotope ratios assist ecosystem scientists in constraining the sources of alkaline earth elements, but their interpretation can be difficult because of complexities in mineral weathering and in the geographical and environmental controls on elemental additions and losses. Hawaii is a "natural laboratory" where a number of important biogeochemical variables have either limited ranges or vary in systematic ways, providing a unique opportunity to understand the impact of time, climate, and atmospheric inputs on the evolution of base cation sources to ecosystems. There are three major sources of strontium (Sr) to these ecosystems, each with distinct isotopic compositions: basalt lava, Asian dust, and rainfall. We present Sr isotope and concentration data on both bulk soil digests and NH4Ac extracts from soil profiles covering a wide range of environments and substrate ages. Bulk soil material from dry climates and/or young substrate ages with > 80????g g- 1 Sr retain basalt-like Sr isotopic signatures, whereas those with Sr concentrations < 80????g g- 1 can have isotope signatures that range from basalt-like values to the more radiogenic values associated with continental dust. Although both dust accumulation and lava weathering are time- and rainfall-dependent, the overall concentration of Sr drops with increasing leaching even as quartz and mica derived from continental dust sources increase to > 40% by mass. At elevated dust levels, lava-derived Sr is low and dust-derived Sr is the dominant control of 87Sr/86Sr in bulk soils; however, 87Sr/86Sr of NH4Ac-extractable Sr largely reflects atmospheric deposition of marine aerosol in these situations. Overall, whole-soil Sr isotope values are controlled by complex interactions between Sr provided by lava weathering but partially lost by leaching, and Sr provided by dust but held in more resistant minerals. The isotopic composition of NH4Ac-extractable Sr and of the biota is controlled by lava weathering and rainfall contribution of Sr with only minor contributions from radiogenic dust sources. ?? 2009 Elsevier B.V.

Background PM2.5 source apportionment in the remote Northwestern United States

NASA Astrophysics Data System (ADS)

Hadley, Odelle L.

2017-10-01

This study used the Environmental Protection Agency's positive matrix factorization model (EPA PMF5.0) to identify five primary source factors contributing to the ambient PM2.5 concentrations at Cheeka Peak Atmospheric Observatory (CPO), Neah Bay WA between January 2011 and December 2014. CPO is home to both an IMPROVE (Interagency Monitoring for Protected Visual Environments) and a NCore multi-pollutant monitoring site. Chemically resolved particulate data from the IMPROVE site was the input data to EPA PMF5.0 and the resulting source factors were derived solely from these data. Solutions from the model were analyzed in context with trace gas and meteorological data collected at the NCore site located roughly 10 m away. Seasonal and long-term trends were analyzed for all five factors and provide the first complete source apportionment analysis of PM2.5 at this remote location. The first factor, identified as marine-traffic residual fuel oil (RFO), was the highest contributor to PM2.5 during late summer. Over the 4-year analysis, the RFO percent contribution to total PM2.5 declined. This is consistent with previous studies and may be attributed to regulations restricting the sulfur content of ship fuel. Biomass combustion emissions (BMC) and sea salt were the largest PM2.5 sources observed at CPO in winter, accounting for over 80% of the fine particulate. BMC accounted for a large percent of the fine particulate pollution when winds were easterly, or continental. Sea salt was the dominant winter factor when winds blew from the west. Measured trace carbon monoxide (CO) and reactive nitrogen species (NOy) were most strongly correlated with the BMC factor and continental winds. The fourth factor was identified as aged crustal material, or dust. In all three years, dust peaked in the spring and was associated exclusively with north-easterly winds. The last factor was identified as aged sea salt mixed with nitrate, sulfate, and other components common to RFO and BMC source factors. It did not exhibit a strong seasonal cycle or dependence on wind direction.

An Isotopic Map of Dust Source Areas in the McMurdo Sound Sector of Antarctica

NASA Astrophysics Data System (ADS)

Blakowski, M. A.; Aciego, S.; Delmonte, B.; Baroni, C.; Salvatore, M. C.

2014-12-01

The McMurdo Sound sector of Antarctica features a unique, polar desert ecosystem characterized by low temperatures, hyper-aridity, and high-speed winds. These climatic conditions result in limited water sources, sparse vegetation, underdeveloped soils, and abundant unconsolidated sediment easily influenced by wind-driven transport. Radiogenic isotopes (87Sr/86Sr, 143Nd/144Nd) provide constant signatures of dust from source- to sink-areas. Accordingly, aeolian dust derived from arid regions has been recognized in many studies as an important tracer of atmospheric circulation, as well as a tool for deciphering past climatic conditions in dust source regions. However, while major global dust sources (e.g. from South America, Africa, and Asia) are well studied and easily identifiable via distinct isotopic signatures when encountered in different depositional environments (e.g. Antarctic ice cores), local material from sources in and around the ice-free Dry Valleys and surrounding areas have remained in need of further documentation. We analyzed 40 samples of silt, sand, glacial drift, and weathered regolith material in both fine (<5μm) and coarse fractions collected from Victoria Land and the McMurdo Sound sector, including Cape Royds, Cape Bird, and the McMurdo Ice Shelf. Here we present an ArcGIS-generated, high-precision geochemical map of Antarctic PSAs synthesized from our data and combined with geomorphological and stratigraphic information on the studied sites. We believe that our expanded isotopic catalogue and map can be used to enhance and/or prompt regional studies in a variety of disciplines, such as by providing greater constraints on models of regional dust variability and transport pathways and of the melting history of the Antarctic ice sheet, and by determining the provenance of dust archived in ice cores, lake sediment, soil records, and impurities in Antarctic sea-ice.

Accumulation degree and source apportionment of trace metals in smaller than 63 μm road dust from the areas with different land uses: A case study of Xi'an, China.

PubMed

Shi, Dongqi; Lu, Xinwei

2018-09-15

Finer urban dusts have more serious environmental detriment and health risk than coarser urban dusts. The trace metals Pb, Cu, Zn, Cr, Co, Ba, Mn, Ni, V, Y, Rb, Ga, Hf, and Zr were analyzed using X-ray fluorescence spectrometry in smaller than 63 μm road dust collected from the areas with different land use types and human activities in Xi'an city. The purposes of this study were to reveal the impact of human activities on the environment through element enrichment factor, and to determine the sources of trace metals measured by multivariate statistical analysis and multiple liner regression of absolute principal component scores. The results indicated that the smaller than 63 μm road dust in Xi'an, in comparison to the element background value of local soil, had higher Cu, Pb, Zn, Cr, Y, Hf and Zr concentrations. Trace metals had different variations in the dusts, while the anthropogenic trace metals had no significant difference in the four areas owing to the wide existing of human activities. The accumulation level of Pb was the highest, followed by Cr, Cu and Zn, and then was Hf and Zr, while the other trace metals were deficient or deficient to minimal enrichment in the finer road dust. Source analysis results indicated that Co, Ga, Mn, Ni, V, Rb and Y mainly originated from natural source, which accounted about 57%-87% for these metals' concentration. Ba, Cr, Pb, Cu and Zn primarily derived from traffic source, which contributed approximately 59%-79% to these metals' content. Hf and Zr were mainly from construction source, which contributed 74.6% to Hf concentration and 78.2% to Zr concentration. The study indicated that traffic and construction activities had a predominant influence on local environment. Copyright © 2018 Elsevier B.V. All rights reserved.

[Groups and sources of yeasts in house dust].

PubMed

Glushakova, A M; Zheltikova, T M; Chernov, I Iu

2004-01-01

House dust contains bacteria, mycelial fungi, microarthropods, and yeasts. The house dust samples collected in 25 apartments in Moscow and the Moscow region were found to contain yeasts belonging to the genera Candida, Cryptococcus, Debaryomyces, Rhodotorula, Sporobolomyces, and Trichosporon. The most frequently encountered microorganisms were typical epiphytic yeasts, such as Cryptococcus diffluens and Rhodotorula mucilaginosa, which are capable of long-term preservation in an inactive state. The direct source of epiphytic yeasts occurring in the house dust might be the indoor plants, which were contaminated with these yeasts, albeit to a lesser degree than outdoor plants. Along with the typical epiphytic yeasts, the house dust contained the opportunistic yeast pathogens Candida catenulata, C. guillermondii, C. haemulonii, C. rugosa, and C. tropicalis, which are known as the causal agents of candidiasis. We failed to reveal any correlation between the abundance of particular yeast species in the house dust, residential characteristics, and the atopic dermatitis of the inhabitants.

Saturn's largest ring.

PubMed

Verbiscer, Anne J; Skrutskie, Michael F; Hamilton, Douglas P

2009-10-22

Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter's gossamer rings and Saturn's E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128R(S) to 207R(S) (Saturn's radius R(S) is 60,330 km). The ring's vertical thickness of 40R(S) matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring's normal optical depth of approximately 2 x 10(-8) is comparable to that of Jupiter's faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward and many of them ultimately strike the dark leading face of Iapetus.

Sources and perceptions of indoor and ambient air pollution in rural Alaska.

PubMed

Ware, Desirae; Lewis, Johnnye; Hopkins, Scarlett; Boyer, Bert; Noonan, Curtis; Ward, Tony

2013-08-01

Even though Alaska is the largest state in the United States, much of the population resides in rural and underserved areas with documented disparities in respiratory health. This is especially true in the Yukon-Kuskokwim (southwest) and Ahtna (southcentral) Regions of Alaska. In working with community members, the goal of this study was to identify the air pollution issues (both indoors and outdoors) of concern within these two regions. Over a two-year period, 328 air quality surveys were disseminated within seven communities in rural Alaska. The surveys focused on understanding the demographics, home heating practices, indoor activities, community/outdoor activities, and air quality perceptions within each community. Results from these surveys showed that there is elevated potential for PM10/PM2.5 exposures in rural Alaska communities. Top indoor air quality concerns included mold, lack of ventilation or fresh air, and dust. Top outdoor air pollution concerns identified were open burning/smoke, road dust, and vehicle exhaust (e.g., snow machines, ATVs, etc.). These data can now be used to seek additional funding for interventions, implementing long-term, sustainable solutions to the identified problems. Further research is needed to assess exposures to PM10/PM2.5 and the associated impacts on respiratory health, particularly among susceptible populations such as young children.

Quantifying global dust devil occurrence from meteorological analyses

PubMed Central

Jemmett-Smith, Bradley C; Marsham, John H; Knippertz, Peter; Gilkeson, Carl A

2015-01-01

Dust devils and nonrotating dusty plumes are effective uplift mechanisms for fine particles, but their contribution to the global dust budget is uncertain. By applying known bulk thermodynamic criteria to European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses, we provide the first global hourly climatology of potential dust devil and dusty plume (PDDP) occurrence. In agreement with observations, activity is highest from late morning into the afternoon. Combining PDDP frequencies with dust source maps and typical emission values gives the best estimate of global contributions of 3.4% (uncertainty 0.9–31%), 1 order of magnitude lower than the only estimate previously published. Total global hours of dust uplift by dry convection are ∼0.002% of the dust-lifting winds resolved by ECMWF, consistent with dry convection making a small contribution to global uplift. Reducing uncertainty requires better knowledge of factors controlling PDDP occurrence, source regions, and dust fluxes induced by dry convection. Key Points Global potential dust devil occurrence quantified from meteorological analyses Climatology shows realistic diurnal cycle and geographical distribution Best estimate of global contribution of 3.4% is 10 times smaller than the previous estimate PMID:26681815

Effective and Accurate Morphology Models for Asian and Saharan Mineral Dust Scattering Properties

NASA Astrophysics Data System (ADS)

Stegmann, P.; Yang, P.

2017-12-01

It is well known that mineral dust particles from desert sources can have a significant influence on the planetary radiation balance. In order to determine the sign and magnitude of the dust radiative forcing effect, complex models have been and continue to be developed. Key factors which influence the single-scattering properties of mineral dust are dust source regions and thus mineralogical composition, and its mixture with water, sea salt, and products of human activity, such as soot. The ensemble of mineral dust scattering particles may then be modeled either as a simple placeholder shape, often ellipsoidal, through the utilization of an appropriate effective medium refractive index scheme. On the other hand, the scattering particles may be represented in a more rigorous manner, such as Voronoi-tessellated aggregates including fractal soot chains. The consequences and differences of either choice are investigated in the project at hand. It will be shown that the effective medium model indicates a drastic dependence of the mineral dust particle composition on the particle size. Thus the refractive index of a dust particle is in fact a function of its size, amongst other factors. Regional differences between African and Asian mineral dust are also of significance.

Estimation of Dust Emission from the Western Coastal Plains of Arabian Peninsula

NASA Astrophysics Data System (ADS)

Anisimov, Anatolii; Stenchikov, Georgiy

2016-04-01

This study is aimed at quantifying local-scale dust emission from the coastal areas of western Arabian Peninsula. The dust emitted from these areas is frequently deposited directly to the Red Sea, acting as an important component of the nutrient balance of marine ecosystems. Most chemicals including iron, phosphorus, and nitrogen are introduced to the Red Sea with airborne dust. This process is especially significant for the oligotrophic northern Red Sea, where nutrients from the Indian Ocean cannot reach and the nutrient supply from land river discharge is negligible. The dust deposition to the Red Sea associated with major dust storms was recently estimated to be about 6 Tg/yr, but this estimate does not account for local, small-scale dust outbreaks occurring during fair weather conditions or moderate winds. The seasonality and the magnitude of this nutrient supply are largely unknown. In the present study, we quantify dust emissions using the fine-scale off-line version-4 of the Community Land Model (CLM4) with the high-resolution datasets as input parameters. We examine the model sensitivity to the spatial resolution of input land cover and vegetation data, and compare the results with weather station observations and reanalysis to choose the best model configuration. The model results are shown to be in reasonable agreement with station visibility measurements and the frequency of dust event reports. To improve the spatial characteristics of dust emission, we apply two state-of-the-art dust source functions. We found that the source function based on measurements from SEVIRI satellite substantially improves the simulation results, being in good agreement with both reanalysis data and station measurements. We identify the major dust source hot-spot areas over the coastal plain and analyze the seasonal and diurnal variability of dust emissions. The annual dust generation from the 145000 km2 coastal area reaches 6 Tg/yr. Roughly half of emitted dust could be deposited to the Red Sea, which is comparable to the deposition from major dust events. A substantial part of this dust is generated in the northern coastal plain and is predominantly deposited to the northern Red Sea, providing essentially the sole supply of nutrients to the oceanic ecosystems.

Measuring Dust Emission from the Mojave Desert (USA) by Daily Remote-Camera Observations and Wind-Erosion Measurements: Bearing on "Unseen" Sources and Global Dust Abundance

NASA Astrophysics Data System (ADS)

Reynolds, R. L.; Urban, F.; Goldstein, H. L.; Fulton, R.

2017-12-01

A large gap in understanding the effects of atmospheric dust at all spatial scales is uncertainty about how much and whence dust is emitted annually. Digital recording of dust emission at high spatial and temporal resolution would, together with periodic flux measurements, support improved estimates of local-scale dust flux where infrastructure could support remote internet enabled cameras. Such recording would also elucidate wind-erosion dynamics when combined with meteorological data. Remote camera recording of dust-emitting settings on and around Soda Lake (Mojave Desert) was conducted every 15 minutes during daylight between 10 Nov. 2010 and 31 Dec. 2016 and images uploaded to a web server. Examination of 135,000 images revealed frequent dust events, termed "dust days" when plumes obscured mountains beyond source areas. Such days averaged 68 (sd=10) per year (2011 through 2016). We examined satellite retrievals (MODIS, GOES) for dust events during six cloudless days of highest and longest duration dust emission but none were observed. From Apr. 2000 through May 2013, aeolian sediments collected at three sites were sampled and weighed. Estimates of the emitted mass of silt- and clay-size fractions were made on the basis of measured horizontal mass flux, particle sizes of sediment in collectors, and roughly determined areas of dust generation. Over this period, nearly 4 Tg yr-1 of dust (as particulate matter <63 micrometers) were emitted across the study area. Much higher rates (about 7 Tg yr-1) were estimated for a subset period from Jan. 2011 through May 2013 following a major Mojave River flood in the basin in late Dec. 2010 that deposited flood sediment across the lake basin. Increased emission was likely related to the availability of fresh, unanchored flood sediment. Within the Mojave and Great Basin deserts of North America, many settings akin to those at Soda Lake similarly emit dust that is rarely detected in satellite retrievals. These findings strongly imply that local and regional dust emissions from western North America are far underestimated and that, by extension to relatively small dust-source areas across all drylands, global dust emissions may also be underestimated.

Mars Dust and LETKF Data Assimilation of TES Observations

NASA Astrophysics Data System (ADS)

Greybush, S. J.; Hoffman, R. N.; Wilson, R.; Kang, J.; Zhao, Y.; Hoffman, M. J.; Kalnay, E.; Miyoshi, T.

2012-12-01

Simulation and prediction of dust storms remains one of the greatest challenges in Martian meteorology. Large-scale dust storms impact all Mars operations including spacecraft observations. What makes the difference between a regional event and a planet-encircling event? What are the predictability characteristics of these events and of the transition from regional to global? We examine the meteorology, including dustiness, in the Mars reanalysis created with the GFDL Mars Global Climate Model (MGCM) Local Ensemble Transform Kalman Filter (LETKF) data assimilation system (DAS). Characterizing the distribution and temporal evolution of dust in the Martian atmosphere is a considerable challenge. Spacecraft observations are sparse and have limitations in vertical coverage, dust physical properties are not well known, and model parameterizations of surface lifting have limited success in reproducing observed variability. Methods for generating a dust reanalysis begin with satellite inferred dust information in the form of column opacities, dust profile retrievals, or the original radiances. Opacities may be estimated from a formal retrieval of the satellite data or inferred through surface brightness temperatures. The opacities have been ingested via ad hoc adjustments to model tracer fields (Conrath vertical distributions, changes to the boundary layer dust only, etc.), but could also be assimilated by the LETKF or other advanced DAS. We will present dust distributions in the most recent version of the MGCM-LETKF Mars reanalysis. Current results are from two DASs, one assuming a fixed dust distribution and one using TES opacities and updating the boundary layer dust only. In these reanalyses, a full year of Thermal Emission Spectrometer (TES) temperature profiles have been assimilated. Since an accurate characterization of the sources and sinks of dust would greatly improve our understanding of the Martian dust cycle and its representation in numerical weather prediction models, we will examine two advanced DAS techniques that have been demonstrated in terrestrial DASs and could be applied to the problem -- surface dust flux estimation and estimating the surface parameters that control the source of dust (roughness, inventories). The surface dust flux method requires no a priori information about the fluxes, and uses only atmospheric observations. For the terrestrial CO2 problem, surface sources and sinks of CO2 have been estimated using only time-dependent measurements of atmospheric CO2, temperatures, and winds, and without a priori information on the surface fluxes. This scenario is very analogous to the case of Mars. On Mars we have only information on temperature and dust opacities at spacecraft overpass locations. Results for terrestrial CO2 and plans for Mars dust will be presented. However, to improve model parameterizations of dust lifting, we need to understand not only the planetary distribution of dust but also the evolution of its sources and sinks and their relation to meteorology. The surface parameters method assumes the physical properties have a persistence or damped persistence evolution equation. These are then treated as part of the model state vector in the LETKF. This approach is then analogous to the bias correction method used in LETKF to improve the atmospheric state estimation.

Mice housed on coal dust-contaminated sand: A model to evaluate the impacts of coal mining on health.

PubMed

Caballero-Gallardo, Karina; Olivero-Verbel, Jesus

2016-03-01

Coal dust is the most important air pollutant in coal mining in regards to producing deleterious health effects. It permeates the surrounding environment threatening public health. The aim of this study was to evaluate the toxic effects associated with exposure to sand contaminated with coal dust particles below 38 μm in diameter, obtained from a mineral sample collected in the largest coal mine in South America, La Loma, Cesar, Colombia. Sterilized sand was spiked with coal dust to obtain concentrations ranging from zero to 4% coal dust. To model natural exposure, mice were housed for eight weeks in boxes containing this mixture as bedding after which, they were euthanized and blood and tissue samples were collected. Real time PCR analysis revealed an increase in Cyp1A1 mRNA for living on sand with coal dust concentrations greater than 2% compared to mice living on sand without coal dust. Unexpectedly, for mice on coal dust-polluted sand, Sod1, Scd1 and Nqo1 hepatic mRNA were downregulated. The Comet assay in peripheral blood cells and the micronucleus test in blood smears, showed a significant potential genotoxic effect only at the highest coal dust concentration. Histopathological analysis revealed vascular congestion and peribronchial inflammation in the lungs. A dose-response relationship for the presence of hepatic steatosis, vacuolization and nuclei enlargements was observed in the exposed animals. The data suggest living on a soil polluted with coal dust induces molecular, cellular and histopathological changes in mice. Accordingly, the proposed model can be used to identify deleterious effects of exposure to coal dust deposited in soils that may pose health risks for surrounding wildlife populations. Copyright © 2016 Elsevier Inc. All rights reserved.

Tracing Sources and Contamination Assessments of Heavy Metals in Road and Foliar Dusts in a Typical Mining City, China

PubMed Central

Yang, Jie; Teng, Yanguo; Song, Liuting; Zuo, Rui

2016-01-01

Road and foliar dust samples from four land-use districts of Panzhihua City, a famous V-Ti magnetite production area of China, were collected to investigate the sources and distribution characteristics of 9 heavy metals (V, Pb, Cd, Cu, Zn, Ni, Cr, Fe, and Mn). The results suggest that foliar samples had smaller particle size and higher heavy metal contents than road dusts. The contamination assessments of heavy metals were as follows: Pb and V (significant enrichment) > Zn, Ni, Cr, Fe, and Mn (moderate enrichment) > Cd and Ni (minimal enrichment). Statistical analyses showed Pb, as the primary pollution element, originated from waste incineration and lead-fuel combustion. The sources of Zn, Ni, Cr, Fe, V, and Mn were fugitive dust and traffic activities. Potential origins of Cu were corrosion of alloys used in vehicle components, vehicle covers, or other metallic surfaces and materials. The sources of Cd were different from any other heavy metals. Traffic and industrial activities were the main anthropogenic origins of heavy metals in dusts of Panzhihua, and more attention should be paid to heavy metal pollution in agricultural area. PMID:27992518

Tracing Sources and Contamination Assessments of Heavy Metals in Road and Foliar Dusts in a Typical Mining City, China.

PubMed

Yang, Jie; Teng, Yanguo; Song, Liuting; Zuo, Rui

2016-01-01

Road and foliar dust samples from four land-use districts of Panzhihua City, a famous V-Ti magnetite production area of China, were collected to investigate the sources and distribution characteristics of 9 heavy metals (V, Pb, Cd, Cu, Zn, Ni, Cr, Fe, and Mn). The results suggest that foliar samples had smaller particle size and higher heavy metal contents than road dusts. The contamination assessments of heavy metals were as follows: Pb and V (significant enrichment) > Zn, Ni, Cr, Fe, and Mn (moderate enrichment) > Cd and Ni (minimal enrichment). Statistical analyses showed Pb, as the primary pollution element, originated from waste incineration and lead-fuel combustion. The sources of Zn, Ni, Cr, Fe, V, and Mn were fugitive dust and traffic activities. Potential origins of Cu were corrosion of alloys used in vehicle components, vehicle covers, or other metallic surfaces and materials. The sources of Cd were different from any other heavy metals. Traffic and industrial activities were the main anthropogenic origins of heavy metals in dusts of Panzhihua, and more attention should be paid to heavy metal pollution in agricultural area.

A study of impact of Asian dusts and their transport pathways to Hong Kong using multiple AERONET data, trajectory, and in-situ measurements

NASA Astrophysics Data System (ADS)

Wong, Man Sing; Nichol, Janet Elizabeth; Lee, Kwon Ho

2010-10-01

Hong Kong, a commercial and financial city located in south-east China has suffered serious air pollution for the last decade due largely to rapid urban and industrial expansion of the cities of mainland China. However, the potential sources and pathways of aerosols transported to Hong Kong have not been well researched due to the lack of air quality monitoring stations in southern China. Here, an integrated method combining the AErosol RObotic NETwork (AERONET) data, trajectory and Potential Source Contribution Function (PSCF) modeling is used to identify the potential transport pathways and contribution of sources from four characteristic aerosol types. Four characteristic aerosol types were defined using a total of 730 AERONET data measurements between 2005 and 2008. They are coastal urban, polluted urban, dust (likely to be long distance desert dust), and heavy pollution. Results show that the sources of polluted urban and heavy pollution are associated with industrial emissions in southern China, whereas coastal urban aerosols have been affected both from natural marine aerosol and emissions. The PSCF map of dust shows a wide range of pathways followed by east- and south-eastwards trajectories from northwest China to Hong Kong. Although the contribution from dust sources is small compared to the anthropogenic aerosols, a serious recent dust outbreak has been observed in Hong Kong with an elevation of the Air Pollution Index to 500, compared with 50-100 on normal days. Therefore, the combined use of clustered AERONET data, trajectory and the PSCF models can help to resolve the longstanding issue about source regions and characteristics of pollutants carried to Hong Kong.

West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad

PubMed Central

Armitage, Simon J.; Bristow, Charlie S.; Drake, Nick A.

2015-01-01

From the deglacial period to the mid-Holocene, North Africa was characterized by much wetter conditions than today. The broad timing of this period, termed the African Humid Period, is well known. However, the rapidity of the onset and termination of the African Humid Period are contested, with strong evidence for both abrupt and gradual change. We use optically stimulated luminescence dating of dunes, shorelines, and fluviolacustrine deposits to reconstruct the fluctuations of Lake Mega-Chad, which was the largest pluvial lake in Africa. Humid conditions first occur at ∼15 ka, and by 11.5 ka, Lake Mega-Chad had reached a highstand, which persisted until 5.0 ka. Lake levels fell rapidly at ∼5 ka, indicating abrupt aridification across the entire Lake Mega-Chad Basin. This record provides strong terrestrial evidence that the African Humid Period ended abruptly, supporting the hypothesis that the African monsoon responds to insolation forcing in a markedly nonlinear manner. In addition, Lake Mega-Chad exerts strong control on global biogeochemical cycles because the northern (Bodélé) basin is currently the world’s greatest single dust source and possibly an important source of limiting nutrients for both the Amazon Basin and equatorial Atlantic. However, we demonstrate that the final desiccation of the Bodélé Basin occurred around 1 ka. Consequently, the present-day mode and scale of dust production from the Bodélé Basin cannot have occurred before 1 ka, suggesting that its role in fertilizing marine and terrestrial ecosystems is either overstated or geologically recent. PMID:26124133

Source Identification Of Airborne Antimony On The Basis Of The Field Monitoring And The Source Profiling

NASA Astrophysics Data System (ADS)

Iijima, A.; Sato, K.; Fujitani, Y.; Fujimori, E.; Tanabe, K.; Ohara, T.; Shimoda, M.; Kozawa, K.; Furuta, N.

2008-12-01

The results of the long-term monitoring of airborne particulate matter (APM) in Tokyo indicated that APM have been extremely enriched with antimony (Sb) compared to crustal composition. This observation suggests that the airborne Sb is distinctly derived from human activities. According to the material flow analysis, automotive brake abrasion dust and fly ash from waste incinerator were suspected as the significant Sb sources. To clarify the emission sources of the airborne Sb, elemental composition, particle size distribution, and morphological profiles of dust particles collected from two possible emission sources were characterized and compared to the field observation data. Brake abrasion dust samples were generated by using a brake dynamometer. During the abrasion test, particle size distribution was measured by an aerodynamic particle sizer spectrometer. Concurrently, size- classified dust particles were collected by an Andersen type air sampler. Fly ash samples were collected from several municipal waste incinerators, and the bulk ash samples were re-dispersed into an enclosed chamber. The measurement of particle size distribution and the collection of size-classified ash particles were conducted by the same methodologies as described previously. Field observations of APM were performed at a roadside site and a residential site by using an Andersen type air sampler. Chemical analyses of metallic elements were performed by an inductively coupled plasma atomic emission spectrometry and an inductively coupled plasma mass spectrometr. Morphological profiling of the individual particle was conducted by a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. High concentration of Sb was detected from both of two possible sources. Particularly, Sb concentrations in a brake abrasion dust were extremely high compared to that in an ambient APM, suggesting that airborne Sb observed at the roadside might have been largely derived from mechanical abrasion of automotive brake pads. The peak of the mass-based particle size distribution of brake abrasion dust was found in a diameter of 2-3 μm. From the morphological viewpoints, shape of brake abrasion dust particle was typically edge- shaped, and high concentrated Sb and sulfur were simultaneously detected in a brake abrasion dust particle because Sb2S3 is used as a solid lubricant for automotive brake pad. Indeed, at the roadside site, total concentration of airborne Sb was twice as much as that observed at residential site. Moreover, the most concentrated Sb was found in a diameter of 2.1-3.6 μm for the roadside APM. Furthermore, in the collected particles with this size range, we found a number of particles of which morphological profiles were similar to those of the brake abrasion dust. Consequently, an automotive brake abrasion dust is expected as the predominant source of airborne Sb in the roadside atmosphere.

Characteristics and sensitivity analysis of multiple-time-resolved source patterns of PM2.5 with real time data using Multilinear Engine 2

NASA Astrophysics Data System (ADS)

Peng, Xing; Shi, Guo-Liang; Gao, Jian; Liu, Jia-Yuan; HuangFu, Yan-Qi; Ma, Tong; Wang, Hai-Ting; Zhang, Yue-Chong; Wang, Han; Li, Hui; Ivey, Cesunica E.; Feng, Yin-Chang

2016-08-01

With real time resolved data of Particulate matter (PM) and chemical species, understanding the source patterns and chemical characteristics is critical to establish controlling of PM. In this work, PM2.5 and chemical species were measured by corresponding online instruments with 1-h time resolution in Beijing. Multilinear Engine 2 (ME2) model was applied to explore the sources, and four sources (vehicle emission, crustal dust, secondary formation and coal combustion) were identified. To investigate the sensitivity of time resolution on the source contributions and chemical characteristics, ME2 was conducted with four time resolution runs (1-h, 2-h, 4-h, and 8-h). Crustal dust and coal combustion display large variation in the four time resolutions runs, with their contributions ranging from 6.7 to 10.4 μg m-3 and from 6.4 to 12.2 μg m-3, respectively. The contributions of vehicle emission and secondary formation range from 7.5 to 10.5 and from 14.7 to 16.7 μg m-3, respectively. The sensitivity analyses were conducted by principal component analysis-plot (PCA-plot), coefficient of divergence (CD), average absolute error (AAE) and correlation coefficients. For the four time resolution runs, the source contributions and profiles of crustal dust and coal combustion were more unstable than other source categories, possibly due to the lack of key markers of crustal dust and coal combustion (e.g. Si, Al). On the other hand, vehicle emission and crustal dust were more sensitive to time series of source contributions at different time resolutions. Findings in this study can improve our knowledge of source contributions and chemical characteristics at different time solutions.

Modeling of mineral dust in the atmosphere: Sources, transport, and optical thickness

NASA Technical Reports Server (NTRS)

Tegen, Ina; Fung, Inez

1994-01-01

A global three-dimensional model of the atmospheric mineral dust cycle is developed for the study of its impact on the radiative balance of the atmosphere. The model includes four size classes of minearl dust, whose source distributions are based on the distributions of vegetation, soil texture and soil moisture. Uplift and deposition are parameterized using analyzed winds and rainfall statistics that resolve high-frequency events. Dust transport in the atmosphere is simulated with the tracer transport model of the Goddard Institute for Space Studies. The simulated seasonal variations of dust concentrations show general reasonable agreement with the observed distributions, as do the size distributions at several observing sites. The discrepancies between the simulated and the observed dust concentrations point to regions of significant land surface modification. Monthly distribution of aerosol optical depths are calculated from the distribution of dust particle sizes. The maximum optical depth due to dust is 0.4-0.5 in the seasonal mean. The main uncertainties, about a factor of 3-5, in calculating optical thicknesses arise from the crude resolution of soil particle sizes, from insufficient constraint by the total dust loading in the atmosphere, and from our ignorance about adhesion, agglomeration, uplift, and size distributions of fine dust particles (less than 1 micrometer).

Northern hemisphere dust storms on Mars

NASA Technical Reports Server (NTRS)

James, P. B.

1993-01-01

Dust storms in the northern hemisphere of Mars appear to be less common than the more familiar southern hemisphere storms, and essentially, no activity north of about 30 latittude has been documented. The data are, however, subject to an observational bias because Mars is near aphelion during oppositions, which occur during the most likely seasons for dust activity in the north. The amount of dust activity in the northern hemisphere is clearly very relevant to the role of atmospheric transport in the dust cycle. The classic global storms that occur during spring in the southern hemisphere are observed to transport dust from sources in the southern hemisphere to sinks or temporary depositories in the north. The question of whether atmospheric transport can close the dust cycle, i.e., return the dust to the southern hemisphere sources on some timescale, is clearly relevant to the solution of the puzzle of how the dust storm cycle is modulated, i.e., why storms occur in some years but not in others. There are data that suggest that the spring/early summer season in the northern hemisphere of Mars during the year following the major 1977 storms observed by Viking was very dusty. A number of observations of the vicinity of the receding north polar cap showed clear evidence of substantial dust activity in the sub-Arctic region.

Chemical characterization of atmospheric dust from a weekly time series in the north Red Sea between 2006 and 2010

NASA Astrophysics Data System (ADS)

Torfstein, Adi; Teutsch, Nadya; Tirosh, Ofir; Shaked, Yeala; Rivlin, Tanya; Zipori, Assaf; Stein, Mordechai; Lazar, Boaz; Erel, Yigal

2017-08-01

Atmospheric dust loads and chemical compositions serve as a key link between global climate patterns and marine biogeochemical cycles. The primary source of atmospheric dust in the world today is the Sahara-Arabian desert belt. Although this source was also active during the Quaternary, the interpretation of paleo-dust records and their effects on marine ecosystems is complicated by the scarcely reported atmospheric load patterns of bioavailable phases (i.e., water and acid leachable phases) and present-day contamination of anthropogenic components. This study reports a multi-annual time series of atmospheric dust loads (2006-2016) and their chemical compositions (2006-2010) collected in the north Gulf of Aqaba (north Red Sea) at a weekly to bi-weekly resolution. Major and trace element abundances in each sample are reported for three fractions: water-soluble salts, carbonates and oxides (weak acid leach), and Al-silicates. Dust loads vary seasonally from low values in late summer (∼20-30 μg m-3) to higher values in the fall, and highest values in late winter and early spring (∼150-250 μg m-3). Major and trace element abundances allow to distinguish between the sources and chemical compositions that dominate high and low dust loads in each season. The water leachable fraction (L0) is relatively enriched in Na, Ca, K and Mg, the acid-leachable fraction (L1) is enriched in Ca as well as Na, Al, Mg, Zn, Cd and Pb, and the silicate residue (L2) in Al and Fe. High dust loads occurring mainly during winter and spring months are characterized by low Mg/Ca (L1, L2), low K/Al and Na/Al (L1) and high Ca/Al (L1), high Mg/Al (L2) and relatively un-weathered (L2) contents. High dust load intervals during winter months are characterized by low passing air masses originating from the Sahara, while the ambient winter dust (low dust load) is associated with proximal source regions from the East Sahara and Arabian Peninsula. During late winter and spring months, high dust loads originate from central and west Sahara and to a lesser extent from north Sahara. Low dust loads characterize the summer with limited compositional variability relative to winter-spring months. Summer dust is generally characterized by high K/Al (L1) ratios relative to late winter and spring. It is also relatively high in anthropogenic trace elements in the L0 and L1 fractions (e.g., Zn/Al, Pb/Al, Cr/Al, Ni/Al and V/Al), whereby back trajectories indicate the source of these components is primarily from south and east Europe. The total load (ng m-3) of anthropogenic trace elements however, remains higher during winter and spring, stemming from the overall significantly higher dust loads characterizing this time window. The temporal load patterns of important micronutrients such as Fe, Cd, Zn, Cu, Ni and others in the bio-available phases (L0, L1) are not correlated with major nutrients or Chlorophyll-a sea surface concentrations, suggesting that the atmospheric dust plays a limited role in driving primary productivity in the oligotrophic surface waters of the Gulf of Aqaba. On a wider scale, the results provide unique chemical fingerprinting of Sahara-Arabian dust that can be applied to reconstruct past trends in dust loads recorded in deep-sea cores and other geological archives from this and other regions.

The ALMA-PILS survey: 3D modeling of the envelope, disks and dust filament of IRAS 16293-2422

NASA Astrophysics Data System (ADS)

Jacobsen, S. K.; Jørgensen, J. K.; van der Wiel, M. H. D.; Calcutt, H.; Bourke, T. L.; Brinch, C.; Coutens, A.; Drozdovskaya, M. N.; Kristensen, L. E.; Müller, H. S. P.; Wampfler, S. F.

2018-04-01

Context. The Class 0 protostellar binary IRAS 16293-2422 is an interesting target for (sub)millimeter observations due to, both, the rich chemistry toward the two main components of the binary and its complex morphology. Its proximity to Earth allows the study of its physical and chemical structure on solar system scales using high angular resolution observations. Such data reveal a complex morphology that cannot be accounted for in traditional, spherical 1D models of the envelope. Aims: The purpose of this paper is to study the environment of the two components of the binary through 3D radiative transfer modeling and to compare with data from the Atacama Large Millimeter/submillimeter Array. Such comparisons can be used to constrain the protoplanetary disk structures, the luminosities of the two components of the binary and the chemistry of simple species. Methods: We present 13CO, C17O and C18O J = 3-2 observations from the ALMA Protostellar Interferometric Line Survey (PILS), together with a qualitative study of the dust and gas density distribution of IRAS 16293-2422. A 3D dust and gas model including disks and a dust filament between the two protostars is constructed which qualitatively reproduces the dust continuum and gas line emission. Results: Radiative transfer modeling in our sampled parameter space suggests that, while the disk around source A could not be constrained, the disk around source B has to be vertically extended. This puffed-up structure can be obtained with both a protoplanetary disk model with an unexpectedly high scale-height and with the density solution from an infalling, rotating collapse. Combined constraints on our 3D model, from observed dust continuum and CO isotopologue emission between the sources, corroborate that source A should be at least six times more luminous than source B. We also demonstrate that the volume of high-temperature regions where complex organic molecules arise is sensitive to whether or not the total luminosity is in a single radiation source or distributed into two sources, affecting the interpretation of earlier chemical modeling efforts of the IRAS 16293-2422 hot corino which used a single-source approximation. Conclusions: Radiative transfer modeling of source A and B, with the density solution of an infalling, rotating collapse or a protoplanetary disk model, can match the constraints for the disk-like emission around source A and B from the observed dust continuum and CO isotopologue gas emission. If a protoplanetary disk model is used around source B, it has to have an unusually high scale-height in order to reach the dust continuum peak emission value, while fulfilling the other observational constraints. Our 3D model requires source A to be much more luminous than source B; LA 18 L⊙ and LB 3 L⊙.

Iron Mineralogy and Speciation in Clay-Sized Fractions of Chinese Desert Sediments

NASA Astrophysics Data System (ADS)

Lu, Wanyi; Zhao, Wancang; Balsam, William; Lu, Huayu; Liu, Pan; Lu, Zunli; Ji, Junfeng

2017-12-01

Iron released from Asian desert dust may be an important source of bioavailable iron for the North Pacific Ocean and thereby may stimulate primary productivity. However, the Fe species of the fine dusts from this source region are poorly characterized. Here we investigate iron species and mineralogy in the clay-sized fractions (<2 μm), the size fraction most prone to long-distance transport as dust. Samples were analyzed by sequential chemical extraction, X-ray diffraction, and diffuse reflectance spectrometry. Our results show that Fe dissolved from easily reducible iron phases (ferrihydrite and lepidocrocite) and reducible iron oxides (dominated by goethite) are 0.81 wt % and 2.39 wt %, respectively, and Fe dissolved from phyllosilicates extracted by boiling HCl (dominated by chlorite) is 3.15 wt %. Dusts originating from deserts in northwestern China, particularly the Taklimakan desert, are relatively enriched in easily reducible Fe phases, probably due to abundant Fe contained in fresh weathering products resulting from the rapid erosion associated with active uplift of mountains to the west. Data about Fe speciation and mineralogy in Asian dust sources will be useful for improving the quantification of soluble Fe supplied to the oceans, especially in dust models.

An exterior and interior leaded dust deposition survey in New York City: results of a 2-year study.

PubMed

Caravanos, Jack; Weiss, Arlene L; Jaeger, Rudolph J

2006-02-01

Environmental concentrations of leaded dust were monitored by weekly sample collection of interior and exterior settled dust that had accumulated due to atmospheric deposition. The weekly deposition amounts were measured and the cumulative rates of lead in dust that deposited on a weekly basis over 2 year's time were determined. The sampling analysis revealed that the median values of leaded dust for the interior plate (adjacent to the open window), unsheltered exterior plate, and the sheltered exterior plate were 4.8, 14.2, and 32.3 microg/feet2/week, respectively. The data supports the existence of a continuous source of deposited leaded dust in interior and exterior locations within New York City. Additional data from a control plate (interior plate with the window closed) demonstrate that the source of the interior lead deposition was from exterior (environmental) sources. Because of the ubiquitous nature of lead in our environment and the toxic threat of lead to the cognitive health of children, this data provides a framework for the understanding of environmental exposure to lead and its potential for continuing accumulation within an urban environment.

The Origin of Dust in the Early Universe

NASA Technical Reports Server (NTRS)

Dwek, Eli

2011-01-01

In this talk I will describe the origin of dust in the early universe. I will be presenting observations of the spectral energy distribution of the galaxy J1148+5251, and present estimates of the dust mass in this high redshift (z=6.4) object. I will then discuss the origin of this dust, and the role of SN and AGB stars as dust sources, and the effect of SNRs on the destruction of dust in the interstellar medium of this galaxy.

The Origin of Dust in the Early Universe

NASA Technical Reports Server (NTRS)

Dwek, Eliahu

2010-01-01

In this talk I will describe the origin of dust in the early universe. I will be presenting observations of the spectral energy distribution of the galaxy J1148+5251, and present estimates of the dust mass in this high redshift (z=6.4) object. I will then discuss the origin of this dust, and the role of SN and AGB stars as dust sources, and the effect of SNRs on the destruction of dust in the interstellar medium of this galaxy.

Comet or asteroid shower in the late Eocene?

PubMed

Tagle, Roald; Claeys, Philippe

2004-07-23

The passage of a comet shower approximately 35 million years ago is generally advocated to explain the coincidence during Earth's late Eocene of an unusually high flux of interplanetary dust particles and the formation of the two largest craters in the Cenozoic, Popigai and the Chesapeake Bay. However, new platinum-group element analyses indicate that Popigai was formed by the impact of an L-chondrite meteorite. Such an asteroidal projectile is difficult to reconcile with a cometary origin. Perhaps instead the higher delivery rate of extraterrestrial matter, dust, and large objects was caused by a major collision in the asteroid belt.

Insights from Synthetic Star-forming Regions. II. Verifying Dust Surface Density, Dust Temperature, and Gas Mass Measurements With Modified Blackbody Fitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koepferl, Christine M.; Robitaille, Thomas P.; Dale, James E., E-mail: koepferl@usm.lmu.de

We use a large data set of realistic synthetic observations (produced in Paper I of this series) to assess how observational techniques affect the measurement physical properties of star-forming regions. In this part of the series (Paper II), we explore the reliability of the measured total gas mass, dust surface density and dust temperature maps derived from modified blackbody fitting of synthetic Herschel observations. We find from our pixel-by-pixel analysis of the measured dust surface density and dust temperature a worrisome error spread especially close to star formation sites and low-density regions, where for those “contaminated” pixels the surface densitiesmore » can be under/overestimated by up to three orders of magnitude. In light of this, we recommend to treat the pixel-based results from this technique with caution in regions with active star formation. In regions of high background typical in the inner Galactic plane, we are not able to recover reliable surface density maps of individual synthetic regions, since low-mass regions are lost in the far-infrared background. When measuring the total gas mass of regions in moderate background, we find that modified blackbody fitting works well (absolute error: + 9%; −13%) up to 10 kpc distance (errors increase with distance). Commonly, the initial images are convolved to the largest common beam-size, which smears contaminated pixels over large areas. The resulting information loss makes this commonly used technique less verifiable as now χ {sup 2} values cannot be used as a quality indicator of a fitted pixel. Our control measurements of the total gas mass (without the step of convolution to the largest common beam size) produce similar results (absolute error: +20%; −7%) while having much lower median errors especially for the high-mass stellar feedback phase. In upcoming papers (Paper III; Paper IV) of this series we test the reliability of measured star formation rate with direct and indirect techniques.« less

Long-term aerosol measurements in Gran Canaria, Canary Islands: Particle concentration, sources and elemental composition

NASA Astrophysics Data System (ADS)

Gelado-Caballero, MaríA. D.; López-GarcíA, Patricia; Prieto, Sandra; Patey, Matthew D.; Collado, Cayetano; HéRnáNdez-Brito, José J.

2012-02-01

There are very few sets of long-term measurements of aerosol concentrations over the North Atlantic Ocean, yet such data is invaluable in quantifying atmospheric dust inputs to this ocean region. We present an 8-year record of total suspended particles (TSP) collected at three stations on Gran Canaria Island, Spain (Taliarte at sea level, Tafira 269 m above sea level (a.s.l.) and Pico de la Gorra 1930 m a.s.l.). Using wet and dry deposition measurements, the mean dust flux was calculated at 42.3 mg m-2 d-1. Air mass back trajectories (HYSPLIT, NOAA) suggested that the Sahara desert is the major source of African dust (dominant during 32-50% of days), while the Sahel desert was the major source only 2-10% of the time (maximum in summer). Elemental composition ratios of African samples indicate that, despite the homogeneity of the dust in collected samples, some signatures of the bedrocks can still be detected. Differences were found for the Sahel, Central Sahara and North of Sahara regions in Ti/Al, Mg/Al and Ca/Al ratios, respectively. Elements often associated with pollution (Pb, Cd, Ni, Zn) appeared to share a common origin, while Cu may have a predominantly local source, as suggested by a decrease in the enrichment factor (EF) of Cu during dust events. The inter-annual variability of dust concentrations is investigated in this work. During winter, African dust concentration measurements at the Pico de la Gorra station were found to correlate with the North Atlantic Oscillation (NAO) index.

Understanding the dust cycle at high latitudes: integrating models and observations

NASA Astrophysics Data System (ADS)

Albani, S.; Mahowald, N. M.; Maggi, V.; Delmonte, B.; Winckler, G.; Potenza, M. A. C.; Baccolo, G.; Balkanski, Y.

2017-12-01

Changing climate conditions affect dust emissions and the global dust cycle, which in turn affects climate and biogeochemistry. Paleodust archives from land, ocean, and ice sheets preserve the history of dust deposition for a range of spatial scales from close to the major hemispheric sources to remote sinks such as the polar ice sheets. In each hemisphere common features on the glacial-interglacial time scale mark the baseline evolution of the dust cycle, and inspired the hypothesis that increased dust deposition to ocean stimulated the glacial biological pump contributing to the reduction of atmospheric carbon dioxide levels. On the other hand finer geographical and temporal scales features are superposed to these glacial-interglacial trends, providing the chance of a more sophisticated understanding of the dust cycle, for instance allowing distinctions in terms of source availability or transport patterns as recorded by different records. As such paleodust archives can prove invaluable sources of information, especially when characterized by a quantitative estimation of the mass accumulation rates, and interpreted in connection with climate models. We review our past work and present ongoing research showing how climate models can help in the interpretation of paleodust records, as well as the potential of the same observations for constraining the representation of the global dust cycle embedded in Earth System Models, both in terms of magnitude and physical parameters related to particle sizes and optical properties. Finally we show the impacts on climate, based on this kind of observationally constrained model simulations.

Iron fertilization of the Subantarctic Ocean during the last ice age

NASA Astrophysics Data System (ADS)

Martinez-Garcia, A.

2015-12-01

Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean. The scarcity of iron limits marine productivity and carbon uptake in one-quarter of the world ocean where the concentration of major nutrients (phosphorus and nitrogen) is perennially high. The Southern Ocean is the region where variations in iron availability can have the largest effect on Earth's carbon cycle through its fertilizing effect on marine ecosystems. Paleoceanographic records from the Subantarctic Atlantic have revealed a remarkable correlation between phytoplankton productivity and aeolian iron flux during glacial periods supporting the iron fertilization hypothesis. In addition, a recent study has shown that peak glacial times and millennial cold events were nearly universally associated not only with increases in dust flux and export production, but also with an increase in nutrient consumption (the last indicated by higher foraminifera-bound δ15N) (Martinez-Garcia et al. 2014). This combination of changes is uniquely consistent with ice age iron fertilization of the Subantarctic Atlantic. The strengthening of the biological pump associated with the observed increase in Subantarctic nutrient consumption during the high-dust intervals of the last two ice ages can explain up to ~40 ppm of the CO2 decrease that characterizes the transitions from mid-climate states to full ice age conditions. However, the impact of iron fertilization in other sectors of the Southern Ocean characterized by lower ice age dust fluxes than the Atlantic remains unclear. A series of recently published records from the Subantarctic Pacific indicate that dust deposition and marine export production were three times higher during glacial periods than during interglacials (Lamy et al. 2014). Here we present new measurements of foraminifera-bound nitrogen isotopes in a sediment core located in the Subantarctic Pacific (PS75/56-1), which allow us to evaluate the impact of iron fertilization on major nutrient consumption in the largest Southern Ocean sector.

A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

USGS Publications Warehouse

Kumar, A.; Abouchami, W.; Galer, S.J.G.; Garrison, V.H.; Williams, E.; Andreae, M.O.

2014-01-01

Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and atmospheric transport.

Anthropogenic Environments

USDA-ARS?s Scientific Manuscript database

Aerosols or airborne dust can originate from sources unrelated to anthropogenic activity but may also be initiated or exacerbated by anthropogenic actions. Anthropogenic dust refers to dust activity (emission and suppression) that is present due to human activity. Wind erosion in the U.S. is a sign...

Emergency hospital visits in association with volcanic ash, dust storms and other sources of ambient particles: a time-series study in Reykjavík, Iceland.

PubMed

Carlsen, Hanne Krage; Gislason, Thorarinn; Forsberg, Bertil; Meister, Kadri; Thorsteinsson, Throstur; Jóhannsson, Thorsteinn; Finnbjornsdottir, Ragnhildur; Oudin, Anna

2015-04-13

Volcanic ash contributed significantly to particulate matter (PM) in Iceland following the eruptions in Eyjafjallajökull 2010 and Grímsvötn 2011. This study aimed to investigate the association between different PM sources and emergency hospital visits for cardiorespiratory causes from 2007 to 2012. Indicators of PM10 sources; "volcanic ash", "dust storms", or "other sources" (traffic, fireworks, and re-suspension) on days when PM10 exceeded the daily air quality guideline value of 50 µg/m3 were entered into generalized additive models, adjusted for weather, time trend and co-pollutants. The average number of daily emergency hospital visits was 10.5. PM10 exceeded the air quality guideline value 115 out of 2191 days; 20 days due to volcanic ash, 14 due to dust storms (two days had both dust storm and ash contribution) and 83 due to other sources. High PM10 levels from volcanic ash tended to be significantly associated with the emergency hospital visits; estimates ranged from 4.8% (95% Confidence Interval (CI): 0.6, 9.2%) per day of exposure in unadjusted models to 7.3% (95% CI: -0.4, 15.5%) in adjusted models. Dust storms were not consistently associated with daily emergency hospital visits and other sources tended to show a negative association. We found some evidence indicating that volcanic ash particles were more harmful than particles from other sources, but the results were inconclusive and should be interpreted with caution.

Reconstructing transport pathways for late Quaternary dust from eastern Australia using the composition of trace elements of long traveled dusts

NASA Astrophysics Data System (ADS)

Petherick, Lynda M.; McGowan, Hamish A.; Kamber, Balz S.

2009-04-01

The southeast Australian dust transport corridor is the principal pathway through which continental emissions of dust from central and eastern Australia are carried to the oceans by the prevailing mid-latitude westerly circulation. The analysis of trace elements of aeolian dust, preserved in lake sediment on North Stradbroke Island, southeast Queensland, is used to reconstruct variation in the intensity and position of dust transport to the island over the past 25,000 yrs. Separation of local and long traveled dust content of lake sediments is achieved using a unique, four-element (Ga, Ni, Tl and Sc) separation method. The local and continental chronologies of aeolian deposition developed by this study show markedly different records, and indicate varied responses to climate variability on North Stradbroke Island (local aeolian sediment component) and in eastern and central Australia (long traveled dust component). The provenance of the continental component of the record to sub-geologic catchment scales was accomplished using a ternary mixing model in which the chemical identification of dusts extracted, from the lake sediments, was compared to potential chemical characteristics of surface dust from the source areas using 16 trace elements. The results indicate that the position and intensity of dust transport pathways during the late Quaternary varied considerably in response to changing atmospheric circulation patterns as well as to variations in sediment supply to dust source areas, which include the large anabranching river systems of the Lake Eyre and Murray-Darling Basins.

Removal of floating dust in glow discharge using plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ticos, C. M.; Jepu, I.; Lungu, C. P.

2010-07-05

Dust can be an inconvenient source of impurities in plasma processing reactors and in many cases it can cause damage to the plasma-treated surfaces. A technique for dust expulsion out of the trapping region in plasma is presented here, based on the wind force exerted on dust particles by a pulsed plasma jet. Its applicability is demonstrated by removing floating dust in the sheath of parallel-plate capacitive radio-frequency plasma.

Cosmic dust

NASA Technical Reports Server (NTRS)

Brownlee, Donald E.; Sandford, Scott A.

1992-01-01

Dust is a ubiquitous component of our galaxy and the solar system. The collection and analysis of extraterrestrial dust particles is important to exobiology because it provides information about the sources of biogenically significant elements and compounds that accumulated in distant regions of the solar nebula and that were later accreted on the planets. The topics discussed include the following: general properties of interplanetary dust; the carbonaceous component of interplanetary dust particles; and the presence of an interstellar component.

High concentrations of regional dust from deserts to plains across the central Rocky Mountains, USA

NASA Astrophysics Data System (ADS)

Reynolds, R. L.; Munson, S. M.; Fernandez, D. P.; Neff, J. C.

2015-12-01

Regional mineral dust in the American Southwest affects snow-melt rates, biogeochemical cycling, visibility, and public health. We measured total suspended particulates (TSP) across a 500-km-long sampling network of five remote sites in Utah and Colorado, USA, forming a gradient in distance from major dust emitting areas. The two westernmost sites on the Colorado Plateau desert had similar TSP concentrations (2008-2012, daily average=126 μg m-3; max. daily average over a two-week period=700 μg m-3 at Canyonlands National Park, Utah), while the easternmost High Plains site, close to cropped and grazed areas in northeastern Colorado, had an average concentration of 143 μg m-3 in 2011-2012 (max. daily average=656 μg m-3). Such concentrations rank comparably with those of TSP in several African and Asian cities in the paths of frequent dust storms. Dust loadings at the two intervening montane sites decreased from the western slope of the Rocky Mountains (Telluride, daily average=68 μg m-3) to an eastern site (Niwot Ridge, daily average=58 μg m-3). Back-trajectory analyses and satellite retrievals indicated that the three westernmost sites received most dust from large desert-source regions as far as 300 km to their southwest. These sources also sometimes sent dust to the two easternmost sites, which additionally captured dust from sources north and northwest of the central Rocky Mountains as well as locally at the Plains site. The PM10 fraction accounted for <15% of TSP, but most TSP is only slightly larger (typical median size, 15-20 μm) after about 100-800 km transport distances. Correlations between TSP and PM10 values indicate increases in both fractions during regional wind storms, especially related to Pacific frontal systems during late winter to late spring. These measurements and observations indicate that most dust deposition and associated air-quality problems in the interior American West are connected to regional dust sources and not to those in Asia.

Spectral Remote Sensing of Dust Sources on the U.S. Great Plains from 1930s Panchromatic Aerial Phtography

NASA Astrophysics Data System (ADS)

Bolles, K.; Forman, S. L.

2017-12-01

Understanding the spatiotemporal dynamics of dust sources is essential to accurately quantify the various impacts of dust on the Earth system; however, a persistent deficiency in modeling dust emission is detailed knowledge of surface texture, geomorphology, and location of dust emissive surfaces, which strongly influence the effects of wind erosion. Particle emission is closely linked to both climatic and physical surface factors - interdependent variables that respond to climate nonlinearly and are mitigated by variability in land use or management practice. Recent efforts have focused on development of a preferential dust source (PDS) identification scheme to improve global dust-cycle models, which posits certain surfaces are more likely to emit dust than others, dependent upon associated sediment texture and geomorphological limitations which constrain sediment supply and availability. In this study, we outline an approach to identify and verify the physical properties and distribution of dust emissive surfaces in the U.S. Great Plains from historical aerial imagery in order to establish baseline records of dust sources, associated erodibility, and spatiotemporal variability, prior to the satellite era. We employ a multi-criteria, spatially-explicit model to identify counties that are "representative" of the broader landscape on the Great Plains during the 1930s. Parameters include: percentage of county cultivated and uncultivated per the 1935 Agricultural Census, average soil sand content, mean annual Palmer Drought Severity Index (PDSI), maximum annual temperature and percent difference to the 30-year normal maximum temperature, and annual precipitation and percent difference to the 30-year normal precipitation level. Within these areas we generate random points to select areas for photo reproduction. Selected frames are photogrammetrically scanned at 1200 dpi, radiometrically corrected, mosaicked and georectified to create an IKONOS-equivalent image. Gray-level co-occurrence matrices are calculated in a 3x3 moving window to determine textural properties of the mosaic and delineate bare surfaces of different sedimentological properties. Field stratigraphic assessments and spatially-referenced historical data are integrated within ArcGIS to ground-truth imagery.

Exploring the dust content of galactic winds with Herschel - II. Nearby dwarf galaxies

NASA Astrophysics Data System (ADS)

McCormick, Alexander; Veilleux, Sylvain; Meléndez, Marcio; Martin, Crystal L.; Bland-Hawthorn, Joss; Cecil, Gerald; Heitsch, Fabian; Müller, Thomas; Rupke, David S. N.; Engelbracht, Chad

2018-06-01

We present the results from an analysis of deep Herschel Space Observatory observations of six nearby dwarf galaxies known to host galactic-scale winds. The superior far-infrared sensitivity and angular resolution of Herschel have allowed detection of cold circumgalactic dust features beyond the stellar components of the host galaxies traced by Spitzer 4.5 μm images. Comparisons of these cold dust features with ancillary data reveal an imperfect spatial correlation with the ionized gas and warm dust wind components. We find that typically ˜10-20 per cent of the total dust mass in these galaxies resides outside of their stellar discs, but this fraction reaches ˜60 per cent in the case of NGC 1569. This galaxy also has the largest metallicity (O/H) deficit in our sample for its stellar mass. Overall, the small number of objects in our sample precludes drawing strong conclusions on the origin of the circumgalactic dust. We detect no statistically significant trends with star formation properties of the host galaxies, as might be expected if the dust were lifted above the disc by energy inputs from ongoing star formation activity. Although a case for dust entrained in a galactic wind is seen in NGC 1569, in all cases, we cannot rule out the possibility that some of the circumgalactic dust might be associated instead with gas accreted or removed from the disc by recent galaxy interaction events, or that it is part of the outer gas-rich portion of the disc that lies below the sensitivity limit of the Spitzer 4.5 μm data.

Aeolian controls of soil geochemistry and weathering fluxes in high-elevation ecosystems of the Rocky Mountains, Colorado

USGS Publications Warehouse

Lawrence, Corey R.; Reynolds, Richard L.; Kettterer, Michael E.; Neff, Jason C.

2013-01-01

When dust inputs are large or have persisted for long periods of time, the signature of dust additions are often apparent in soils. The of dust will be greatest where the geochemical composition of dust is distinct from local sources of soil parent material. In this study the influence of dust accretion on soil geochemistry is quantified for two different soils from the San Juan Mountains of southwestern Colorado, USA. At both study sites, dust is enriched in several trace elements relative to local rock, especially Cd, Cu, Pb, and Zn. Mass-balance calculations that do not explicitly account for dust inputs indicate the accumulation of some elements in soil beyond what can be explained by weathering of local rock. Most observed elemental enrichments are explained by accounting for the long-term accretion of dust, based on modern isotopic and geochemical estimates. One notable exception is Pb, which based on mass-balance calculations and isotopic measurements may have an additional source at one of the study sites. These results suggest that dust is a major factor influencing the development of soil in these settings and is also an important control of soil weathering fluxes. After accounting for dust inputs in mass-balance calculations, Si weathering fluxes from San Juan Mountain soils are within the range observed for other temperate systems. Comparing dust inputs with mass-balanced based flux estimates suggests dust could account for as much as 50–80% of total long-term chemical weathering fluxes. These results support the notion that dust inputs may sustain chemical weathering fluxes even in relatively young continental settings. Given the widespread input of far-traveled dust, the weathering of dust is likely and important and underappreciated aspect of the global weathering engine.

Aeolian controls of soil geochemistry and weathering fluxes in high-elevation ecosystems of the Rocky Mountains, Colorado

NASA Astrophysics Data System (ADS)

Lawrence, Corey R.; Reynolds, Richard L.; Ketterer, Michael E.; Neff, Jason C.

2013-04-01

When dust inputs are large or have persisted for long periods of time, the signature of dust additions are often apparent in soils. The of dust will be greatest where the geochemical composition of dust is distinct from local sources of soil parent material. In this study the influence of dust accretion on soil geochemistry is quantified for two different soils from the San Juan Mountains of southwestern Colorado, USA. At both study sites, dust is enriched in several trace elements relative to local rock, especially Cd, Cu, Pb, and Zn. Mass-balance calculations that do not explicitly account for dust inputs indicate the accumulation of some elements in soil beyond what can be explained by weathering of local rock. Most observed elemental enrichments are explained by accounting for the long-term accretion of dust, based on modern isotopic and geochemical estimates. One notable exception is Pb, which based on mass-balance calculations and isotopic measurements may have an additional source at one of the study sites. These results suggest that dust is a major factor influencing the development of soil in these settings and is also an important control of soil weathering fluxes. After accounting for dust inputs in mass-balance calculations, Si weathering fluxes from San Juan Mountain soils are within the range observed for other temperate systems. Comparing dust inputs with mass-balanced based flux estimates suggests dust could account for as much as 50-80% of total long-term chemical weathering fluxes. These results support the notion that dust inputs may sustain chemical weathering fluxes even in relatively young continental settings. Given the widespread input of far-traveled dust, the weathering of dust is likely and important and underappreciated aspect of the global weathering engine.

Diagnostic evaluation of the Community Earth System Model in simulating mineral dust emission with insight into large-scale dust storm mobilization in the Middle East and North Africa (MENA)

NASA Astrophysics Data System (ADS)

Parajuli, Sagar Prasad; Yang, Zong-Liang; Lawrence, David M.

2016-06-01

Large amounts of mineral dust are injected into the atmosphere during dust storms, which are common in the Middle East and North Africa (MENA) where most of the global dust hotspots are located. In this work, we present simulations of dust emission using the Community Earth System Model Version 1.2.2 (CESM 1.2.2) and evaluate how well it captures the spatio-temporal characteristics of dust emission in the MENA region with a focus on large-scale dust storm mobilization. We explicitly focus our analysis on the model's two major input parameters that affect the vertical mass flux of dust-surface winds and the soil erodibility factor. We analyze dust emissions in simulations with both prognostic CESM winds and with CESM winds that are nudged towards ERA-Interim reanalysis values. Simulations with three existing erodibility maps and a new observation-based erodibility map are also conducted. We compare the simulated results with MODIS satellite data, MACC reanalysis data, AERONET station data, and CALIPSO 3-d aerosol profile data. The dust emission simulated by CESM, when driven by nudged reanalysis winds, compares reasonably well with observations on daily to monthly time scales despite CESM being a global General Circulation Model. However, considerable bias exists around known high dust source locations in northwest/northeast Africa and over the Arabian Peninsula where recurring large-scale dust storms are common. The new observation-based erodibility map, which can represent anthropogenic dust sources that are not directly represented by existing erodibility maps, shows improved performance in terms of the simulated dust optical depth (DOD) and aerosol optical depth (AOD) compared to existing erodibility maps although the performance of different erodibility maps varies by region.

Environmental tobacco smoke as a source of polycyclic aromatic hydrocarbons in settled household dust.

PubMed

Hoh, Eunha; Hunt, Richard N; Quintana, Penelope J E; Zakarian, Joy M; Chatfield, Dale A; Wittry, Beth C; Rodriguez, Edgar; Matt, Georg E

2012-04-03

Environmental tobacco smoke is a major contributor to indoor air pollution. Dust and surfaces may remain contaminated long after active smoking has ceased (called 'thirdhand' smoke). Polycyclic aromatic hydrocarbons (PAHs) are known carcinogenic components of tobacco smoke found in settled house dust (SHD). We investigated whether tobacco smoke is a source of PAHs in SHD. House dust was collected from 132 homes in urban areas of Southern California. Total PAHs were significantly higher in smoker homes than nonsmoker homes (by concentration: 990 ng/g vs 756 ng/g, p = 0.025; by loading: 1650 ng/m(2) vs 796 ng/m(2), p = 0.012). We also found significant linear correlations between nicotine and total PAH levels in SHD (concentration, R(2) = 0.105; loading, R(2) = 0.385). Dust collected per square meter (g/m(2)) was significantly greater in smoker homes and might dilute PAH concentration in SHD inconsistently. Therefore, dust PAH loading (ng PAH/m(2)) is a better indicator of PAH content in SHD. House dust PAH loadings in the bedroom and living room in the same home were significantly correlated (R(2) = 0.468, p < 0.001) suggesting PAHs are distributed by tobacco smoke throughout a home. In conclusion, tobacco smoke is a source of PAHs in SHD, and tobacco smoke generated PAHs are a component of thirdhand smoke.

Global potential of dust devil occurrence

NASA Astrophysics Data System (ADS)

Jemmett-Smith, Bradley; Marsham, John; Knippertz, Peter; Gilkeson, Carl

2014-05-01

Mineral dust is a key constituent in the climate system. Airborne mineral dust forms the largest component of the global aerosol budget by mass and subsequently affects climate, weather and biogeochemical processes. There remains large uncertainty in the quantitative estimates of the dust cycle. Dry boundary-layer convection serves as an effective mechanism for dust uplift, typically through a combination of rotating dust devils and non-rotating larger and longer-lived convective plumes. These microscale dry-convective processes occur over length scales of several hundred metres or less. They are difficult to observe and model, and therefore their contribution to the global dust budget is highly uncertain. Using an analytical approach to extrapolate limited observations, Koch and Renno (2006) suggest that dust devils and plumes could contribute as much as 35%. Here, we use a new method for quantifying the potential of dust devil occurrence to provide an alternative perspective on this estimate. Observations have shown that dust devil and convective plume occurrence is favoured in hot arid regions under relatively weak background winds, large ground-to-air temperature gradients and deep dry convection. By applying such known constraints to operational analyses from the European Centre for Medium Range Weather Forecasts (ECMWF), we provide, to the best of the authors' knowledge, the first hourly estimates of dust devil occurrence including an analysis of sensitivity to chosen threshold uplift. The results show the expected diurnal variation and allow an examination of the seasonal cycle and day-to-day variations in the conditions required for dust devil formation. They confirm that desert regions are expected to have by far the highest frequency of dry convective vortices, with winds capable of dust uplift. This approach is used to test the findings of Koch and Renno (2006). Koch J., Renno N. (2006). The role of convective plumes and vortices on the global aerosol budget. Geophys. Res. Lett., L18806.

Estimating occupational exposure to carcinogens in Quebec.

PubMed

Labrèche, France; Duguay, Patrice; Ostiguy, Claude; Boucher, Alexandre; Roberge, Brigitte; Peters, Cheryl E; Demers, Paul A

2013-09-01

We estimated the extent of exposure to occupational carcinogens in Quebec, Canada, to help raise awareness of occupational cancers. Proportions of workers exposed to 21 recognized and 17 probable carcinogens (according to Quebec occupational health regulation and the International Agency for Research on Cancer [IARC] classification) were extracted from various sources: workplace monitoring data, research projects, a population survey, radiation protection data, exposure estimates from the Carcinogen Exposure Canada (CAREX Canada) Project database, and published exposure data. These proportions were applied to Quebec labor force data. Among the 38 studied, carcinogens with the largest proportions of exposed workers were solar radiation (6.6% of workers), night shift work/rotating shift work including nights (6.0%), diesel exhaust fumes (4.4%), wood dust (2.9%) and polycyclic aromatic hydrocarbons (2.0%). More than 15 carcinogens were identified in several industrial sectors, and up to 100,000 young workers are employed in these sectors. Although crude, estimates obtained with different data sources allow identification of research and intervention priorities for cancer in Quebec. Copyright © 2013 Wiley Periodicals, Inc.

Heavy metals in the atmosphere coming from a copper smelter in Chile

NASA Astrophysics Data System (ADS)

Romo-Kröger, C. M.; Morales, J. R.; Dinator, M. I.; Llona, F.; Eaton, L. C.

The Chilean mine El Teniente is the world's largest underground copper mine. It operates a giant smelter at Caletones (34° 7' S, 70° 27' W) and we have found it is the major source of air contamination in the region. In August 1991 a special circumstance occurred due to a labor strike, with total cessation of activities. A time series analysis of airborne particles collected at a site about 13 km from the smelter was performed in a period including the strike. The PIXE method and other techniques were used to analyse fine (<2.5 μm) and coarse (2.5-15 μm) particles on Nuclepore filters. S, Cu, Zn and As were quite enriched in normal working periods relative to the strike period. Elemental characterization of soil samples by radioactive source analysis demonstrated that this group of elements did not come from airborne soil dust. Cluster analyses of the interelement correlation matrices, resulting from PIXE data, showed one group (Si, K, Ca, Fe) with main origin in soil and another group (S, Cu, Zn, As) coming from the copper smelter.

Dust Episodes in Hong Kong (South China) and their Relationship with the Sharav and Mongolian Cyclones and Jet Streams

NASA Technical Reports Server (NTRS)

Lee, Y. C.; Wenig, Mark; Zhang, Zhenxi; Sugimoto, Nobuo; Larko, Dave; Diehl, Thomas

2012-01-01

The study presented in this paper analyses two dust episodes in Hong Kong, one occurring in March 2006 and the other on 22 March 2010. The latter is the worst dust episode on Hong Kong record. The focus is on the relationship between the dust episodes and the Sharav/Mongolian cyclones and jet streams. The 16 March 2006 episode is traceable to a continental-scale Saharan dust outbreak of 5-9 March 2006 caused by the cold front of an East Mediterranean Sharav cyclone arriving at north-west Africa on 5 March 2006. The eastward movement of the cyclone along the North African coast is clearly illustrated in the geopotential height contours. Simulations by the chemistry transport model GOCART provide a visible evidence of the transport as well as an estimate of contributions from the Sahara to the aerosol concentration levels in Hong Kong. The transport simulations suggest that the dust is injected to the polar jet north of the Caspian Sea, while it is transported eastward simultaneously by the more southerly subtropical jet. The major source of dust for Hong Kong is usually the Gobi desert. Despite the effect of remote sources, the 16 March 2006 dust episode was still mainly under the influence of the Mongolian cyclone cold fronts. In the recent episode of 22 March 2010, the influence of the Mongolian cyclone predominated as well. It appears that the concurrent influence of the Sharav and Mongolian cyclones on Hong Kong and East Asia is not a common occurrence. Besides transporting dusts from non-East Asian sources to Hong Kong and East Asia, the strong subtropical jet on 21 March 2010 (i.e. 1 day prior to the major dust episode) is believed to have strengthened an easterly monsoon surge to South China causing the transport of voluminous dusts to Taiwan and Hong Kong the following day.

Oil refinery dusts: morphological and size analysis by TEM.

PubMed

Sielicki, Przemysław; Janik, Helena; Guzman, Agnieszka; Broniszewski, Mieczysław; Namieśnik, Jacek

2011-03-01

The objectives of this work were to develop a means of sampling atmospheric dusts on the premises of an oil refinery for electron microscopic study to carry out preliminary morphological analyses and to compare these dusts with those collected at sites beyond the refinery limits. Carbon and collodion membranes were used as a support for collection of dust particles straight on transmission electron microscopy (TEM) grids. Micrographs of the dust particles were taken at magnifications from ×4,000 to ×80,000 with a Tesla BS500 transmission electron microscope. Four parameters were defined on the basis of the micrographs: surface area, Feret diameter, circumference, and shape coefficient. The micrographs and literature data were used to classify the atmospheric dusts into six groups: particles with an irregular shape and rounded edges; particles with an irregular shape and sharp edges; soot and its aggregates; spherical particles; singly occurring, ultrafine dust particles; and particles not allocated to any of the previous five groups. The types of dusts found in all the samples were similar, although differences did exist between the various morphological parameters. Dust particles with the largest Feret diameter were present in sample 3 (mean, 0.739 μm)-these were collected near the refinery's effluent treatment plant. The particles with the smallest diameter were found in the sample that had been intended to be a reference sample for the remaining results (mean, 0.326 μm). The dust particles collected in the refinery had larger mean Feret diameters, even 100% larger, than those collected beyond it. Particles with diameters from 0.1 to 0.2 μm made up the most numerous group in all the samples collected in the refinery.

Intra-annual variations in atmospheric dust and tritium in the North Pacific region detected from an ice core from Mount Wrangell, Alaska

NASA Astrophysics Data System (ADS)

Yasunari, Teppei J.; Shiraiwa, Takayuki; Kanamori, Syosaku; Fujii, Yoshiyuki; Igarashi, Makoto; Yamazaki, Koji; Benson, Carl S.; Hondoh, Takeo

2007-05-01

The North Pacific is subject to various seasonal climate phenomena and material circulations. Therefore intra-annual ice core data are necessary for an assessment of the climate variations. To assess past variations, a 50-m ice core was drilled at the summit of Mount Wrangell Volcano, Alaska. The dust number, tritium concentrations, and stable hydrogen isotope were analyzed. The period covered was from 1992 to 2002. We found that the concentrations of both fine dust (0.52-1.00 μm), an indicator of long-range transport, and coarse dust (1.00-8.00 μm) increased together every spring. Moreover, their concentrations increased drastically after 2000, corresponding to the recent increase in Asian dust outbreaks in spring. Additionally, an increase in the spring of 2001 corresponded to the largest dust storm recorded in east Asia since 1979. Therefore our findings imply that Asian dust strongly polluted Mount Wrangell every spring. The stratospheric tracer, tritium, had late spring maxima almost every year, and we found this useful for ice core dating to identify late spring in the North Pacific region. We also found that a high positive annual correlation existed between the calculated tritium and fine dust fluxes from late spring to summer. We propose that an annual relationship between the stratosphere-troposphere exchange and Asian dust storm are most closely connected in late spring because their activities are weak in summer. The Mount Wrangell ice core is important and useful for assessing the dust and tritium circulation in the distant past around the North Pacific with probable intra-annual timescale information.

Characterization of synoptic patterns causing dust outbreaks that affect the Arabian Peninsula

NASA Astrophysics Data System (ADS)

Hermida, L.; Merino, A.; Sánchez, J. L.; Fernández-González, S.; García-Ortega, E.; López, L.

2018-01-01

Dust storms pose serious weather hazards in arid and semiarid regions of the earth. Understanding the main synoptic conditions that give rise to dust outbreaks is important for issuing forecasts and warnings to the public in cases of severe storms. The aim of the present study is to determine synoptic patterns that are associated with or even favor dust outbreaks over the Arabian Peninsula. In this respect, red-green-blue dust composite images from the Meteosat Second Generation (MSG) satellite are used to detect dust outbreaks affecting the Arabian Peninsula, with possible influences in southwestern Asia and northeastern Africa, between 2005 and 2013. The Meteosat imagery yielded a sample of 95 dust storm days. Meteorological fields from NCEP/NCAR reanalysis data of wind fields at 10 m and 250 hPa, mean sea level pressure, and geopotential heights at 850 and 500 hPa were obtained for the dust storm days. Using principal component analysis in T-mode and non-hierarchical k-means clustering, we obtained four major atmospheric circulation patterns associated with dust outbreaks during the study days. Cluster 4 had the largest number of days with dust events, which were constrained to summer, and cluster 3 had the fewest. In clusters 1, 2 and 3, the jet stream favored the entry of a low-pressure area or trough that varied in location between the three clusters. Their most northerly location was found in cluster 4, along with an extensive low-pressure area supporting strong winds over the Arabian Peninsula. The spatial distribution of aerosol optical depth for each cluster obtained was characterized using the Moderate Resolution Imaging Spectroradiometer data. Then, using METAR stations, clusters were also characterized in terms of frequency and visibility.

Dust Composition in Climate Models: Current Status and Prospects

NASA Astrophysics Data System (ADS)

Pérez García-Pando, C.; Miller, R. L.; Perlwitz, J. P.; Kok, J. F.; Scanza, R.; Mahowald, N. M.

2015-12-01

Mineral dust created by wind erosion of soil particles is the dominant aerosol by mass in the atmosphere. It exerts significant effects on radiative fluxes, clouds, ocean biogeochemistry, and human health. Models that predict the lifecycle of mineral dust aerosols generally assume a globally uniform mineral composition. However, this simplification limits our understanding of the role of dust in the Earth system, since the effects of dust strongly depend on the particles' physical and chemical properties, which vary with their mineral composition. Hence, not only a detailed understanding of the processes determining the dust emission flux is needed, but also information about its size dependent mineral composition. Determining the mineral composition of dust aerosols is complicated. The largest uncertainty derives from the current atlases of soil mineral composition. These atlases provide global estimates of soil mineral fractions, but they are based upon massive extrapolation of a limited number of soil samples assuming that mineral composition is related to soil type. This disregards the potentially large variability of soil properties within each defined soil type. In addition, the analysis of these soil samples is based on wet sieving, a technique that breaks the aggregates found in the undisturbed parent soil. During wind erosion, these aggregates are subject to partial fragmentation, which generates differences on the size distribution and composition between the undisturbed parent soil and the emitted dust aerosols. We review recent progress on the representation of the mineral and chemical composition of dust in climate models. We discuss extensions of brittle fragmentation theory to prescribe the emitted size-resolved dust composition, and we identify key processes and uncertainties based upon model simulations and an unprecedented compilation of observations.

Directional Unfolded Source Term (DUST) for Compton Cameras.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, Dean J.; Horne, Steven M.; O'Brien, Sean

2018-03-01

A Directional Unfolded Source Term (DUST) algorithm was developed to enable improved spectral analysis capabilities using data collected by Compton cameras. Achieving this objective required modification of the detector response function in the Gamma Detector Response and Analysis Software (GADRAS). Experimental data that were collected in support of this work include measurements of calibration sources at a range of separation distances and cylindrical depleted uranium castings.

Fugitive Dust Emissions: Development of a Real-time Monitor

DTIC Science & Technology

2011-10-01

the mechanical disturbance of soils which injects particles into the air. Common sources of FD include vehicles driving on unpaved roads...agricultural tilling, and heavy construction operations. For these sources the dust-generation process is caused by two basic physical phenomena...visibility, source apportionment , etc. The PM10 standard set by the U.S. Environmental Protection Agency in 1987 is an example of size-selective

Ecological Restoration Programs Induced Amelioration of the Dust Pollution in North China Plain

NASA Astrophysics Data System (ADS)

Long, X.; Tie, X.; Li, G.; Junji, C.

2017-12-01

With Moderate Resolution Imaging Spectroradiometer (MODIS) land cover product (MCD12Q1), we quantitatively evaluate the ecological restoration programs (ERP) induced land cover change in China by calculating gridded the land use fraction (LUF). We clearly capture two obvious vegetation (grass and forest) protective barriers arise between the dust source region DSR and North China Plain NCP from 2011 to 2013. The WRF-DUST model is applied to investigate the impact of ERPs on dust pollution from 2 to 8 March 2016, corresponding to a national dust storm event over China. Despite some model biases, the WRF-DUST model reasonably reproduced the temporal variations of dust storm event, involving IOA of 0.96 and NMB of 2% for DSR, with IOA of 0.83 and NMB of -15% for downwind area of NCP. Generally, the WRF-DUST model well capture the spatial variations and evolutions of dust storm events with episode-average [PMC] correlation coefficient (R) of 0.77, especially the dust storm outbreak and transport evolution, involving daily average [PMC] R of 0.9 and 0.73 on 4-5 March, respectively. It is found that the ERPs generally reduce the dust pollution in NCP, especially for BTH, involving upper dust pollution control benefits of -15.3% (-21.0 μg m-3) for BTH, and -6.2% (-9.3 μg m-3) for NCP. We are the first to conduct model sensitivity studies to quantitatively evaluate the impacts of the ERPs on the dust pollution in NCP. And our narrative is independently based on first-hand sources, whereas government statistics.

Lead in Chinese villager house dust: Geographical variation and influencing factors.

PubMed

Bi, Xiangyang; Liu, Jinling; Han, Zhixuan; Yang, Wenlin

2015-12-01

House dust has been recognized as an important contributor to Pb exposure of children. Here we conducted a comprehensive study to investigate geographical variation of Pb in Chinese villager house dust. The influences of outdoor soil Pb concentrations, dates of construction, house decoration materials, heating types, and site specific pollution on Pb concentrations in house dust were evaluated. The concentrations of Pb in 477 house dust samples collected from twenty eight areas throughout China varied from 12 to 2510 mg/kg, with a median concentration of 42 mg/kg. The median Pb concentrations in different geographical areas ranged from 16 (Zhangjiakou, Hebei) to 195 mg/kg (Loudi, Hunan). No correlations were found between the house dust Pb concentrations and the age of houses, as well as house decoration materials. Whereas outdoor soil, coal combustion, and site specific pollution may be potential Pb sources. Principal component analysis (PCA) confirmed that elemental compositions of the house dust were controlled by both anthropogenic and geogenic sources. Using scanning electron microscopy (SEM), the Pb bearing particles in the house dust were also studied. Copyright © 2015 Elsevier Ltd. All rights reserved.

40 CFR 63.1544 - Standards for fugitive dust sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... according to, a standard operating procedures manual that describes in detail the measures that will be put... (c) of this section, the standard operating procedures manual shall be submitted to the Administrator... 40 Protection of Environment 12 2011-07-01 2009-07-01 true Standards for fugitive dust sources. 63...

40 CFR 63.1544 - Standards for fugitive dust sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... according to, a standard operating procedures manual that describes in detail the measures that will be put... (c) of this section, the standard operating procedures manual shall be submitted to the Administrator... 40 Protection of Environment 12 2010-07-01 2010-07-01 true Standards for fugitive dust sources. 63...

Aerosol optical, microphysical and radiative forcing properties during variable intensity African dust events in the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Fernández, A. J.; Molero, F.; Salvador, P.; Revuelta, A.; Becerril-Valle, M.; Gómez-Moreno, F. J.; Artíñano, B.; Pujadas, M.

2017-11-01

Aerosol measurements at two AERONET (AErosol RObotic NETwork) sites of the Iberian Peninsula: Madrid (40°.45N, 3.72W) and La Coruña (43°.36N, 8°.42W) have been analyzed for the period 2012-2015 to assess aerosol optical properties (intensive and extensive) throughout the atmospheric column and their radiative forcing (RF) and radiative forcing efficiency (RFeff) estimates at the Bottom and Top Of Atmosphere (BOA and TOA respectively). Specific conditions as dust-free and African dust have been considered for the study. Unprecedented, this work uses the quantification of the African dust aerosol at ground level which allows us to study such AERONET products at different intensity levels of African events: Low (L), High (H) and very high (VH). The statistical difference between dust-free and African dust conditions on the aforementioned parameters, quantified by means of the non-parametric Kolmogorov-Smirnov test, is quite clear in Madrid, however it is not in La Coruña. Scattering Angstrom Exponent (SAE) and Absorption Angstrom Exponent (AAE) were found to be 1.64 ± 0.29 and 1.14 ± 0.23 respectively in Madrid for dust-free conditions because typical aerosol sources are traffic emissions and residential heating, and black carbon is an important compound in this aerosol kind. On the other hand, SAE and AAE were 0.96 ± 0.60 and 1.44 ± 0.51 for African dust conditions in this location. RF (at shortwave radiation) seems to decrease as the African dust contribution at ground level is larger which indicates the cooling effect of African dust aerosol in Madrid. We have also proved the potential of a 2D-cluster analysis based on AAE and SAE to differentiate both situations in Madrid. Conversely, it is suggested that aerosols observed in La Coruña under dust-free conditions might come from different sources. Then, SAE and AAE are not good enough indicators to distinguish between dust-free and African dust conditions. Besides, as La Coruña is at a further distance than Madrid from the African dust source it is believed that aerosol optical properties might significantly change due to some deposition and aging/coating process and therefore the cooling effect (RF decreases as the African dust contribution at ground level is larger) is not observed.

Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport

PubMed Central

Shahan, M.R.; Seaman, C.E.; Beck, T.W.; Colinet, J.F.; Mischler, S.E.

2017-01-01

Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. If deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coal dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float coal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float coal dust to respirable dust ranged from 10.3 to 13.8. The ratios measured on the longwall face were between 18.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8. PMID:28936001

Directional analysis and filtering for dust storm detection in NOAA-AVHRR imagery

NASA Astrophysics Data System (ADS)

Janugani, S.; Jayaram, V.; Cabrera, S. D.; Rosiles, J. G.; Gill, T. E.; Rivera Rivera, N.

2009-05-01

In this paper, we propose spatio-spectral processing techniques for the detection of dust storms and automatically finding its transport direction in 5-band NOAA-AVHRR imagery. Previous methods that use simple band math analysis have produced promising results but have drawbacks in producing consistent results when low signal to noise ratio (SNR) images are used. Moreover, in seeking to automate the dust storm detection, the presence of clouds in the vicinity of the dust storm creates a challenge in being able to distinguish these two types of image texture. This paper not only addresses the detection of the dust storm in the imagery, it also attempts to find the transport direction and the location of the sources of the dust storm. We propose a spatio-spectral processing approach with two components: visualization and automation. Both approaches are based on digital image processing techniques including directional analysis and filtering. The visualization technique is intended to enhance the image in order to locate the dust sources. The automation technique is proposed to detect the transport direction of the dust storm. These techniques can be used in a system to provide timely warnings of dust storms or hazard assessments for transportation, aviation, environmental safety, and public health.

Constraining the Dust Opacity Law in Three Small and Isolated Molecular Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, K. A.; Thanjavur, K.; Di Francesco, J.

Density profiles of isolated cores derived from thermal dust continuum emission rely on models of dust properties, such as mass opacity, that are poorly constrained. With complementary measures from near-infrared extinction maps, we can assess the reliability of commonly used dust models. In this work, we compare Herschel -derived maps of the optical depth with equivalent maps derived from CFHT WIRCAM near-infrared observations for three isolated cores: CB 68, L 429, and L 1552. We assess the dust opacities provided from four models: OH1a, OH5a, Orm1, and Orm4. Although the consistency of the models differs between the three sources, themore » results suggest that the optical properties of dust in the envelopes of the cores are best described by either silicate and bare graphite grains (e.g., Orm1) or carbonaceous grains with some coagulation and either thin or no ice mantles (e.g., OH5a). None of the models, however, individually produced the most consistent optical depth maps for every source. The results suggest that either the dust in the cores is not well-described by any one dust property model, the application of the dust models cannot be extended beyond the very center of the cores, or more complex SED fitting functions are necessary.« less

Aeolian transport of Icelandic dust: a look from Space

NASA Astrophysics Data System (ADS)

Smejda, Ladislav; Dagsson Waldhauserova, Pavla; Hejcman, Michal

2017-04-01

Iceland represents a unique type of Arctic environment where glaciers capture the precipitation, consequently forming large deserts on the leeward side. Deserts are subject to strong winds and dust is reported to be suspended at least 135 days a year. Icelandic dust has seven major dust sources in extensive deserts, consisting mainly of volcanic glass. In this paper, we address a new approach to the question of the island's contribution to atmospheric dust transport in the North Atlantic and Arctic Oceans. We explore the strengths and limitations of satellite imagery for the study of high altitude dust storm phenomenon, and more specifically the potential of freely available set of tools for remote sensing and spatial data analysis, the Earth Engine provided by Google. This cloud-based geospatial processing platform requires only a web browser on the side of a user, and it allows writing powerful and versatile algorithms for scientific analysis of spatial data. We demonstrate how this approach can be applied to mapping of Icelandic dust sources and studying the wind erosion and transport of particles in the atmosphere in high latitudes.

SIGNATURES OF RECENT ASTEROID DISRUPTIONS IN THE FORMATION AND EVOLUTION OF SOLAR SYSTEM DUST BANDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kehoe, A. J. Espy; Colwell, J. E.; Kehoe, T. J. J.

We have performed detailed dynamical modeling of the structure of a faint dust band observed in coadded InfraRed Astronomical Satellite data at an ecliptic latitude of 17° that convincingly demonstrates that it is the result of a relatively recent (significantly less than 1 Ma) disruption of an asteroid and is still in the process of forming. We show here that young dust bands retain information on the size distribution and cross-sectional area of dust released in the original asteroid disruption, before it is lost to orbital and collisional decay. We find that the Emilkowalski cluster is the source of thismore » partial band and that the dust released in the disruption would correspond to a regolith layer ∼3 m deep on the ∼10 km diameter source body's surface. The dust in this band is described by a cumulative size-distribution inverse power-law index with a lower bound of 2.1 (implying domination of cross-sectional area by small particles) for dust particles with diameters ranging from a few μm up to a few cm. The coadded observations show that the thermal emission of the dust band structure is dominated by large (mm–cm size) particles. We find that dust particle ejection velocities need to be a few times the escape velocity of the Emilkowalski cluster source body to provide a good fit to the inclination dispersion of the observations. We discuss the implications that such a significant release of material during a disruption has for the temporal evolution of the structure, composition, and magnitude of the zodiacal cloud.« less

Optical, physical and chemical properties of transported African mineral dust aerosols in the Mediterranean region

NASA Astrophysics Data System (ADS)

Denjean, Cyrielle; Di Biagio, Claudia; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Loisil, Rodrigue; Triquet, Sylvain; Zapf, Pascal; Roberts, Greg; Bourrianne, Thierry; Torres, Benjamin; Blarel, Luc; Sellegri, Karine; Freney, Evelyn; Schwarzenbock, Alfons; Ravetta, François; Laurent, Benoit; Mallet, Marc; Formenti, Paola

2014-05-01

The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), two intensive airborne campaigns (TRAQA, TRansport and Air QuAlity, 18 June - 11 July 2012, and ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) have been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.

Lead Exposure Assessment among Pregnant Women, Newborns, and Children: Case Study from Karachi, Pakistan.

PubMed

Fatmi, Zafar; Sahito, Ambreen; Ikegami, Akihiko; Mizuno, Atsuko; Cui, Xiaoyi; Mise, Nathan; Takagi, Mai; Kobayashi, Yayoi; Kayama, Fujio

2017-04-13

Lead (Pb) in petrol has been banned in developed countries. Despite the control of Pb in petrol since 2001, high levels were reported in the blood of pregnant women and children in Pakistan. However, the identification of sources of Pb has been elusive due to its pervasiveness. In this study, we assessed the lead intake of pregnant women and one- to three-year-old children from food, water, house dust, respirable dust, and soil. In addition, we completed the fingerprinting of the Pb isotopic ratios (LIR) of petrol and secondary sources (food, house-dust, respirable dust, soil, surma (eye cosmetics)) of exposure within the blood of pregnant women, newborns, and children. Eight families, with high (~50 μg/dL), medium (~20 μg/dL), and low blood levels (~10 μg/dL), were selected from 60 families. The main sources of exposure to lead for children were food and house-dust, and those for pregnant women were soil, respirable dust, and food. LIR was determined by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) with a two sigma uncertainty of ±0.03%. The LIR of mothers and newborns was similar. In contrast, surma , and to a larger extent petrol, exhibited a negligible contribution to both the child's and mother's blood Pb. Household wet-mopping could be effective in reducing Pb exposure. This intake assessment could be replicated for other developing countries to identify sources of lead and the burden of lead exposure in the population.

Climate change and climate systems influence and control the atmospheric dispersion of desert dust: implications for human health

USGS Publications Warehouse

Griffin, Dale W.; Ragaini, Richard C.

2010-01-01

The global dispersion of desert dust through Earth’s atmosphere is greatly influenced by temperature. Temporal analyses of ice core data have demonstrated that enhanced dust dispersion occurs during glacial events. This is due to an increase in ice cover, which results in an increase in drier terrestrial cover. A shorter temporal analysis of dust dispersion data over the last 40 years has demonstrated an increase in dust transport. Climate systems or events such as the North Atlantic Oscillation, the Indian Ocean subtropical High, Pacific Decadal Oscillation, and El Nino-Sothern Oscillation are known to influence global short-term dust dispersion occurrence and transport routes. Anthropogenic influences on dust transport include deforestation, harmful use of topsoil for agriculture as observed during the American Dust Bowl period, and the creation of dry seas (Aral Sea) and lakes (Lake Owens in California and Lake Chad in North Africa) through the diversion of source waters (for irrigation and drinking water supplies). Constituents of desert dust both from source regions (pathogenic microorganisms, organic and inorganic toxins) and those scavenged through atmospheric transport (i.e., industrial and agricultural emissions) are known to directly impact human and ecosystem health. This presentation will present a review of global scale dust storms and how these events can be both a detriment and benefit to various organisms in downwind environments.

Top-down estimate of dust emissions through integration of MODIS and MISR aerosol retrievals with the GEOS-Chem adjoint model

NASA Astrophysics Data System (ADS)

Wang, Jun; Xu, Xiaoguang; Henze, Daven K.; Zeng, Jing; Ji, Qiang; Tsay, Si-Chee; Huang, Jianping

2012-04-01

Predicting the influences of dust on atmospheric composition, climate, and human health requires accurate knowledge of dust emissions, but large uncertainties persist in quantifying mineral sources. This study presents a new method for combined use of satellite-measured radiances and inverse modeling to spatially constrain the amount and location of dust emissions. The technique is illustrated with a case study in May 2008; the dust emissions in Taklimakan and Gobi deserts are spatially optimized using the GEOS-Chem chemical transport model and its adjoint constrained by aerosol optical depth (AOD) that are derived over the downwind dark-surface region in China from MODIS (Moderate Resolution Imaging Spectroradiometer) reflectance with the aerosol single scattering properties consistent with GEOS-chem. The adjoint inverse modeling yields an overall 51% decrease in prior dust emissions estimated by GEOS-Chem over the Taklimakan-Gobi area, with more significant reductions south of the Gobi Desert. The model simulation with optimized dust emissions shows much better agreement with independent observations from MISR (Multi-angle Imaging SpectroRadiometer) AOD and MODIS Deep Blue AOD over the dust source region and surface PM10 concentrations. The technique of this study can be applied to global multi-sensor remote sensing data for constraining dust emissions at various temporal and spatial scales, and hence improving the quantification of dust effects on climate, air quality, and human health.

Top-down Estimate of Dust Emissions Through Integration of MODIS and MISR Aerosol Retrievals With the Geos-chem Adjoint Model

NASA Technical Reports Server (NTRS)

Wang, Jun; Xu, Xiaoguang; Henze, Daven K.; Zeng, Jing; Ji, Qiang; Tsay, Si-Chee; Huang, Jianping

2012-01-01

Predicting the influences of dust on atmospheric composition, climate, and human health requires accurate knowledge of dust emissions, but large uncertainties persist in quantifying mineral sources. This study presents a new method for combined use of satellite-measured radiances and inverse modeling to spatially constrain the amount and location of dust emissions. The technique is illustrated with a case study in May 2008; the dust emissions in Taklimakan and Gobi deserts are spatially optimized using the GEOSChem chemical transport model and its adjoint constrained by aerosol optical depth (AOD) that are derived over the downwind dark-surface region in China from MODIS (Moderate Resolution Imaging Spectroradiometer) reflectance with the aerosol single scattering properties consistent with GEOS-chem. The adjoint inverse modeling yields an overall 51% decrease in prior dust emissions estimated by GEOS-Chem over the Taklimakan-Gobi area, with more significant reductions south of the Gobi Desert. The model simulation with optimized dust emissions shows much better agreement with independent observations from MISR (Multi-angle Imaging SpectroRadiometer) AOD and MODIS Deep Blue AOD over the dust source region and surface PM10 concentrations. The technique of this study can be applied to global multi-sensor remote sensing data for constraining dust emissions at various temporal and spatial scales, and hence improving the quantification of dust effects on climate, air quality, and human health.

The role of seasonality of mineral dust concentration and size on glacial/interglacial dust changes in the EPICA Dronning Maud Land ice core

NASA Astrophysics Data System (ADS)

Wegner, Anna; Fischer, Hubertus; Delmonte, Barbara; Petit, Jean-Robert; Erhardt, Tobias; Ruth, Urs; Svensson, Anders; Vinther, Bo; Miller, Heinrich

2015-10-01

We present a record of particulate dust concentration and size distribution in subannual resolution measured on the European Project for Ice Coring in Antarctica (EPICA) Dronning Maud Land (EDML) ice core drilled in the Atlantic sector of the East Antarctic plateau. The record reaches from present day back to the penultimate glacial until 145,000 years B.P. with subannual resolution from 60,000 years B.P. to the present. Mean dust concentrations are a factor of 46 higher during the glacial (~850-4600 ng/mL) compared to the Holocene (~16-112 ng/mL) with slightly smaller dust particles during the glacial compared to the Holocene and with an absolute minimum in the dust size at 16,000 years B.P. The changes in dust concentration are mainly attributed to changes in source conditions in southern South America. An increase in the modal value of the dust size suggests that at 16,000 years B.P. a major change in atmospheric circulation apparently allowed more direct transport of dust particles to the EDML drill site. We find a clear in-phase relation of the seasonal variation in dust mass concentration and dust size during the glacial (r(conc,size) = 0.8) but no clear phase relationship during the Holocene (0 < r(conc,size) < 0.4). With a simple conceptual 1-D model describing the transport of the dust to the ice sheet using the size as an indicator for transport intensity, we find that the effect of the changes in the seasonality of the source emission strength and the transport intensity on the dust decrease over Transition 1 can significantly contribute to the large decrease of dust concentration from the glacial to the Holocene.

THEMIS Observations of Mars Aerosol Optical Depth from 2002-2008

NASA Technical Reports Server (NTRS)

Smith, Michael D.

2009-01-01

We use infrared images obtained by the Thermal Emission Imaging System (THEMIS) instrument on-board Mars Odyssey to retrieve the optical depth of dust and water ice aerosols over more than 3.5 martian years between February 2002 (MY 25, Ls=330 ) and December 2008 (MY 29, Ls=183). These data provide an important bridge between earlier TES observations and recent observations from Mars Express and Mars Reconnaissance Orbiter. An improvement to our earlier retrieval to include atmospheric temperature information from THEMIS Band 10 observations leads to much improved retrievals during the largest dust storms. The new retrievals show moderate dust storm activity during Mars Years 26 and 27, although details of the strength and timing of dust storms is different from year to year. A planet-encircling dust storm event was observed during Mars Year 28 near Southern Hemisphere Summer solstice. A belt of low-latitude water ice clouds was observed during the aphelion season during each year, Mars Years 26 through 29. The optical depth of water ice clouds is somewhat higher in the THEMIS retrievals at approximately 5:00 PM local time than in the TES retrievals at approximately 2:00 PM, suggestive of possible local time variation of clouds.

Long-range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the western Mediterranean basin

NASA Astrophysics Data System (ADS)

Ancellet, Gerard; Pelon, Jacques; Totems, Julien; Chazette, Patrick; Bazureau, Ariane; Sicard, Michaël; Di Iorio, Tatiana; Dulac, Francois; Mallet, Marc

2016-04-01

Long-range transport of biomass burning (BB) aerosols between North America and the Mediterranean region took place in June 2013. A large number of ground-based and airborne lidar measurements were deployed in the western Mediterranean during the Chemistry-AeRosol Mediterranean EXperiment (ChArMEx) intensive observation period. A detailed analysis of the potential North American aerosol sources is conducted including the assessment of their transport to Europe using forward simulations of the FLEXPART Lagrangian particle dispersion model initialized using satellite observations by MODIS and CALIOP. The three-dimensional structure of the aerosol distribution in the ChArMEx domain observed by the ground-based lidars (Minorca, Barcelona and Lampedusa), a Falcon-20 aircraft flight and three CALIOP tracks, agrees very well with the model simulation of the three major sources considered in this work: Canadian and Colorado fires, a dust storm from western US and the contribution of Saharan dust streamers advected from the North Atlantic trade wind region into the westerlies region. Four aerosol types were identified using the optical properties of the observed aerosol layers (aerosol depolarization ratio, lidar ratio) and the transport model analysis of the contribution of each aerosol source: (i) pure BB layer, (ii) weakly dusty BB, (iii) significant mixture of BB and dust transported from the trade wind region, and (iv) the outflow of Saharan dust by the subtropical jet and not mixed with BB aerosol. The contribution of the Canadian fires is the major aerosol source during this episode while mixing of dust and BB is only significant at an altitude above 5 km. The mixing corresponds to a 20-30 % dust contribution in the total aerosol backscatter. The comparison with the MODIS aerosol optical depth horizontal distribution during this episode over the western Mediterranean Sea shows that the Canadian fire contributions were as large as the direct northward dust outflow from Sahara.

Long range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the Western Mediterranean basin

NASA Astrophysics Data System (ADS)

Ancellet, G.; Pelon, J.; Totems, J.; Chazette, P.; Bazureau, A.; Sicard, M.; Di Iorio, T.; Dulac, F.; Mallet, M.

2015-11-01

Long range transport of biomass burning (BB) aerosols between North America and the Mediterranean region took place in June 2013. A large number of ground based and airborne lidar measurements were deployed in the Western Mediterranean during the Chemistry-AeRosol Mediterranean EXperiment (ChArMEx) intensive observation period. A detailed analysis of the potential North American aerosol sources is conducted including the assessment of their transport to Europe using forward simulations of the FLEXPART Lagrangian particle dispersion model initialized using satellite observations by MODIS and CALIOP. The three dimensional structure of the aerosol distribution in the ChArMEx domain observed by the ground-based lidars (Menorca, Barcelona and Lampedusa), a Falcon-20 aircraft flight and three CALIOP tracks, agree very well with the model simulation of the three major sources considered in this work: Canadian and Colorado fires, a dust storm from Western US and the contribution of Saharan dust streamers advected from the North Atlantic trade wind region into the Westerlies region. Four aerosol types were identified using the optical properties of the observed aerosol layers (aerosol depolarization ratio, lidar ratio) and the transport model analysis of the contribution of each aerosol source: (I) pure BB layer, (II) weakly dusty BB, (III) significant mixture of BB and dust transported from the trade wind region (IV) the outflow of Saharan dust by the subtropical jet and not mixed with BB aerosol. The contribution of the Canadian fires is the major aerosol source during this episode while mixing of dust and BB is only significant at altitude above 5 km. The mixing corresponds to a 20-30 % dust contribution in the total aerosol backscatter. The comparison with the MODIS AOD horizontal distribution during this episode over the Western Mediterranean sea shows that the Canadian fires contribution were as large as the direct northward dust outflow from Sahara.

The paleo-ocean characteristics of the Taklimakan dust aerosol: high sulfate from primary sources and implication for climate modeling

NASA Astrophysics Data System (ADS)

Huang, K.; Zhuang, G.; Fu, J. S.; Dong, X.

2017-12-01

Multi-year monitoring of dust aerosol from the Taklimakan Desert has been conducted at one site in the hinterland of the desert, Tazhong and another site at the southern edge of the desert, Hotan. Compared to the other two important desert source regions of China, i.e. Gobi and Loess Plateau, the Taklimakan Desert is characterized of high calcium with a Ca/Al elemental ratio of around 1.50. The unique feature of the Taklimakan dust aerosol is its abundant sulfate. For instance, the mean concentration of sulfate over Tazhong reached as high as 34.7 and 48.8 ug/m3 during the spring of 2007 and 2008, respectively. During the dust storm events, the daily concentration of sulfate frequently exceeded 100 ug/m3. Sulfate showed strong correlations with the primary aerosol species such as Ca2+, Mg2+, Na+, Cl-, Al, Fe, Ti, etc. but weakly correlated with the secondary aerosol species such as NO3- and NH4+. The mass ratio of sulfate in the total suspended particles showed a relatively stable percentage of around 2.5% regardless of the intensity of the dust events. In addition, individual particle analysis using the scanning electron microscope (SEM) technique found that gypsum (CaSO4) particles could account for 11.1% of total number of particles as well as abundant Na2SO4 and NaCl particles. All the evidences above suggested the high sulfate observed in the Taklimakan Desert were largely attributed to primary sources but not formed via the traditional gas-to-particle formation pathway. As the Taklimakan Desert was speculated to be ocean 5-7 million years, the dried sea salts from the paleo-ocean should be the major source of the dust aerosol. Also, the dried salt lakes in the northwestern China may contribute to the high sulfate. Based on two different methods, the contribution of primary sources to sulfate over the Taklimakan Desert is estimated to be around 43% - 82%. This study implied that the cooling effect of the Taklimakan dust aerosol could be underestimated if the explicit dust chemical composition is not considered for modeling.

Dust temperature distributions in star-forming condensations

NASA Technical Reports Server (NTRS)

Xie, Taoling; Goldsmith, Paul F.; Snell, Ronald L.; Zhou, Weimin

1993-01-01

The FIR spectra of the central IR condensations in the dense cores of molecular clouds AFGL 2591. B335, L1551, Mon R2, and Sgr B2 are reanalyzed here in terms of the distribution of dust mass as a function of temperature. FIR spectra of these objects can be characterized reasonably well by a given functional form. The general shapes of the dust temperature distributions of these objects are similar and closely resemble the theoretical computations of de Muizon and Rouan (1985) for a sample of 'hot centered' clouds with active star formation. Specifically, the model yields a 'cutoff' temperature below which essentially no dust is needed to interpret the dust emission spectra, and most of the dust mass is distributed in a broad temperature range of a few tens of degrees above the cutoff temperature. Mass, luminosity, average temperature, and column density are obtained, and it is found that the physical quantities differ considerably from source to source in a meaningful way.

Geochemical and mineralogical evidence for Sahara and Sahel dust additions to Quaternary soils on Lanzarote, eastern Canary Islands, Spain

USGS Publications Warehouse

Muhs, D.R.; Budahn, J.; Skipp, G.; Prospero, J.M.; Patterson, D.; Bettis, E. Arthur

2010-01-01

Africa is the most important source of dust in the world today, and dust storms are frequent on the nearby Canary Islands. Previous workers have inferred that the Sahara is the most important source of dust to Canary Islands soils, with little contribution from the Sahel region. Soils overlying a late Quaternary basalt flow on Lanzarote, Canary Islands, contain, in addition to volcanic minerals, quartz and mica, exotic to the island's bedrock. Kaolinite in the soils also likely has an exotic origin. Trace-element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and African dust. Major-element geochemistry, clay mineralogy and interpretation of satellite imagery suggest that dust additions to the Canary Islands come not only from the Sahara Desert, but also from the Sahel region. ?? Published 2010. This article is a US Government work and is in the public domain in the USA.

On the Effect of Dust Particles on Global Cloud Condensation Nuclei and Cloud Droplet Number

NASA Technical Reports Server (NTRS)

Karydis, V. A.; Kumar, P.; Barahona, D.; Sokolik, I. N.; Nenes, A.

2011-01-01

Aerosol-cloud interaction studies to date consider aerosol with a substantial fraction of soluble material as the sole source of cloud condensation nuclei (CCN). Emerging evidence suggests that mineral dust can act as good CCN through water adsorption onto the surface of particles. This study provides a first assessment of the contribution of insoluble dust to global CCN and cloud droplet number concentration (CDNC). Simulations are carried out with the NASA Global Modeling Initiative chemical transport model with an online aerosol simulation, considering emissions from fossil fuel, biomass burning, marine, and dust sources. CDNC is calculated online and explicitly considers the competition of soluble and insoluble CCN for water vapor. The predicted annual average contribution of insoluble mineral dust to CCN and CDNC in cloud-forming areas is up to 40 and 23.8%, respectively. Sensitivity tests suggest that uncertainties in dust size distribution and water adsorption parameters modulate the contribution of mineral dust to CDNC by 23 and 56%, respectively. Coating of dust by hygroscopic salts during the atmospheric aging causes a twofold enhancement of the dust contribution to CCN; the aged dust, however, can substantially deplete in-cloud supersaturation during the initial stages of cloud formation and can eventually reduce CDNC. Considering the hydrophilicity from adsorption and hygroscopicity from solute is required to comprehensively capture the dust-warm cloud interactions. The framework presented here addresses this need and can be easily integrated in atmospheric models.

MECA Workshop on Dust on Mars 3

NASA Technical Reports Server (NTRS)

Lee, Steven (Editor)

1989-01-01

Articles and abstracts of articles presented at this workshop are given. It was the goal of the workshop to stimulate cooperative research on, and discussion of, dust related processes on Mars, and to provide background information and help in planning of the Mars Observer mission. These topics are considered: How is dust ejected from the Martian surface into the atmosphere; How does the global atmospheric circulation affect the redistribution of dust on Mars; Are there sources and sinks of dust on Mars, if so, where are they and how do they vary in time; and How many components of dust are there on Mars, and what are their properties. There were four primary discussion sessions: (1) Dust in the atmosphere; (2) Dust on the surface; (3) Dust properties; and (4) Dust observations from future spacecraft missions.

Impact of Radiatively Interactive Dust Aerosols in the NASA GEOS-5 Climate Model: Sensitivity to Dust Particle Shape and Refractive Index

NASA Technical Reports Server (NTRS)

Colarco, Peter R.; Nowottnick, Edward Paul; Randles, Cynthia A.; Yi, Bingqi; Yang, Ping; Kim, Kyu-Myong; Smith, Jamison A.; Bardeen, Charles D.

2013-01-01

We investigate the radiative effects of dust aerosols in the NASA GEOS-5 atmospheric general circulation model. GEOS-5 is improved with the inclusion of a sectional aerosol and cloud microphysics module, the Community Aerosol and Radiation Model for Atmospheres (CARMA). Into CARMA we introduce treatment of the dust and sea salt aerosol lifecycle, including sources, transport evolution, and sinks. The aerosols are radiatively coupled to GEOS-5, and we perform a series of multi-decade AMIP-style simulations in which dust optical properties (spectral refractive index and particle shape distribution) are varied. Optical properties assuming spherical dust particles are from Mie theory, while those for non-spherical shape distributions are drawn from a recently available database for tri-axial ellipsoids. The climatologies of the various simulations generally compare well to data from the MODIS, MISR, and CALIOP space-based sensors, the ground-based AERONET, and surface measurements of dust deposition and concentration. Focusing on the summertime Saharan dust cycle we show significant variability in our simulations resulting from different choices of dust optical properties. Atmospheric heating due to dust enhances surface winds over important Saharan dust sources, and we find a positive feedback where increased dust absorption leads to increased dust emissions. We further find that increased dust absorption leads to a strengthening of the summertime Hadley cell circulation, increasing dust lofting to higher altitudes and strengthening the African Easterly Jet. This leads to a longer atmospheric residence time, higher altitude, and generally more northward transport of dust in simulations with the most absorbing dust optical properties. We find that particle shape, although important for radiance simulations, is a minor effect compared to choices of refractive index, although total atmospheric forcing is enhanced by greater than 10 percent for simulations incorporating a spheroidal shape distribution versus ellipsoidal or spherical shapes.

Dust Deposition and Migration of the ITCZ through the Last Glacial Cycle in the Central Equatorial Pacific (Line Islands).

NASA Astrophysics Data System (ADS)

Reimi Sipala, M. A.; Marcantonio, F.

2014-12-01

Atmospheric dust can be used to record climate change in addition to itself playing a role in several key climate processes, such as affecting Earth's albedo, fomenting rain coalescence, encouraging biological productivity, and enhancing carbon export though particle sinks. Using deep sea sediments, it is possible to quantify and locate the sources and sinks of atmospheric dust. A key area of research is the shift in the inter-tropical converge zone (ITCZ), a thermally influenced area that shifts according to the northern and southern hemisphere temperature gradient. This ongoing project focuses on the changes of the ITCZ over the Central Equatorial Pacific (CEP) over the past ~25000 years. The research focuses on two cores taken from the Line Islands Ridge at 0° 29' N (ML1208-18GC), and 4° 41' N (ML1208-31BB). The main aim is to quantify the magnitude and provenance of windblown dust deposited in the CEP, and to address questions regarding the nature of the variations of dust through ice-age climate transitions. Radiogenic isotopes (Sr, Nd, Pb) have been successfully used to distinguish between different potential dust sources in the aluminosilicates fractions of Pacific Sediments. Our preliminary Pb isotope ratios suggest that, for modern deposition, the northern core's (31BB) detrital sediment fraction is likely sourced from Asian Loess (average ratios are 206Pb/204Pb = 18.88, 207Pb/204Pb = 15.69, 208Pb/204Pb = 39.06). The equatorial core's (18GC) detrital fraction has a less radiogenic Pb signature, which is consistent with South American dust sourcing (206Pb/204Pb = 18.62, 207Pb/204Pb = 15.63, 208Pb/204Pb = 38.62). This is indicative of a strong modern ITCZ that acts as an effective barrier for inter-hemispheric dust transport. Prior to Holocene time, the changes in Pb isotope ratios in both cores appear to be in anti-phase; the northern core becomes less radiogenic up to the LGM, while the southern core becomes more radiogenic. This is potentially due to a weakening of the ITCZ during glacial times. Future work on Nd isotope will shed additional light on subtle differences in dust isotopic composition within the source regions of interest, including the different volcanic zones of South America.

Mineral dust emission from the Bodélé Depression, northern Chad, during BoDEx 2005

NASA Astrophysics Data System (ADS)

Todd, Martin C.; Washington, Richard; Martins, José Vanderlei; Dubovik, Oleg; Lizcano, Gil; M'bainayel, Samuel; Engelstaedter, Sebastian

2007-03-01

Mineral dust in the atmosphere is an important component of the climate system but is poorly quantified. The Bodélé Depression of northern Chad stands out as the world's greatest source region of mineral dust into the atmosphere. Frequent dust plumes are a distinguishing feature of the region's climate. There is a need for more detailed information on processes of dust emission/transport and dust optical properties to inform model simulations of this source. During the Bodélé Dust Experiment (BoDEx) in 2005, instrumentation was deployed to measure dust properties and boundary layer meteorology. Observations indicate that dust emission events are triggered when near-surface wind speeds exceed 10 ms-1, associated with synoptic-scale variability in the large-scale atmospheric circulation. Dust emission pulses in phase with the diurnal cycle of near-surface winds. Analysis of dust samples shows that the dust consists predominantly of fragments of diatomite sediment. The particle size distribution of this diatomite dust estimated from sun photometer data, using a modified Aeronet retrieval algorithm, indicates a dominant coarse mode (radius centered on 1-2 μm) similar to other Saharan dust observations. Single-scattering albedo values are high, broadly in line with other Saharan dust even though the diatomite composition of dust from the Bodélé is likely to be unusual. The radiative impact of high dust loadings results in a reduction in surface daytime maximum temperature of around 7°C in the Bodélé region. Using optical and physical properties of dust obtained in the field, we estimate the total dust flux emitted from the Bodélé to be 1.18 ± 0.45 Tg per day during a substantial dust event. We speculate that the Bodélé Depression (˜10,800 km2) may be responsible for between 6-18% of global dust emissions, although the uncertainty in both the Bodélé and global estimates remains high.

From Cores to Envelopes to Disks: A Multi-scale View of Magnetized Star Formation

NASA Astrophysics Data System (ADS)

Hull, Charles L. H.

2014-12-01

Observations of polarization in star forming regions have been made across many wavelengths, many size scales, and many stages of stellar evolution. One of the overarching goals of these observations has been to determine the importance of magnetic fields -- which are the cause of the polarization -- in the star formation process. We begin by describing the commissioning and the calibration of the 1.3 mm dual-polarization receiver system we built for CARMA (the Combined Array for Research in Millimeter-wave Astronomy), a radio telescope in the eastern Sierra region of California. One of the primary science drivers behind the polarization system is to observe polarized thermal emission from dust grains in the dense clumps of dust and gas where the youngest, Class 0 protostars are forming. We go on to describe the CARMA TADPOL survey -- the largest high-resolution (~1000 AU scale) survey to date of dust polarization in low-mass protostellar cores -- and discuss our main findings: (1) Magnetic fields (B-fields) on scales of ~1000 AU are not tightly aligned with protostellar outflows. Rather, the data are consistent both with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular) and where they are randomly aligned. (2) Sources with high CARMA polarization fractions have consistent B-field orientations on large scales (~20'', measured using single-dish submillimeter telescopes) and small scales (~2.5'', measured by CARMA). We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the ~1000 AU scales of protostellar envelopes. Finally, (3) While on the whole outflows appear to be randomly aligned with B-fields, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. This work shows that the ~1000 AU protostellar envelope may be a turning point: at larger scales B-fields may still retain the memory of the global B-field drawn in from the ambient medium; but at smaller scales the B-fields may be affected by the dynamics of both envelope and disk rotation. This sets the stage for ALMA (the Atacama Large Millimeter/submillimeter Array), which will soon reveal the morphology of B-fields in circumstellar disks themselves.

An extreme dust storm over the Arabian Peninsula in Spring 2015: the role of convective mixing and vortex stretching

NASA Astrophysics Data System (ADS)

Hauser, Seraphine; Pante, Gregor; Pantillon, Florian; Knippertz, Peter

2017-04-01

The Arabian Peninsula is one of the World's largest dust sources. Severe dust storms occur throughout the year dominated by synoptic-scale driven frontal systems in winter and spring and convective systems during summer and autumn. Dust storm frequency peaks in spring, when extra-tropical upper-level troughs associated with near-surface cold fronts regularly penetrate into the peninsula. In this study we investigate the dynamics of an extreme springtime dust event, which covered the entire Arabian Peninsula and the adjacent Indian Ocean in early April 2015. In addition to the more common trough/frontal characteristics, EUMETSAT's false-colour dust product shows a striking vortex-like structure during the initial state of the storm. Several SYNOP stations on the Arabian Peninsula report severe dust storms, rapid temperature drop, strong increase in wind speed up to 40 kn and zero visibility for several hours on 01 and 02 April. Remarkably also, 61 mm of rainfall are observed on 01 April at the station Arar in northern Saudi Arabia (annual average 52 mm), clearly indicating a convective contribution to this event. Some evidence for significant precipitation is also found in satellite products. Operational analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF) show a distinct short-wave upper-level trough swiftly propagating across the region during this period, accompanied by high relative vorticity values of up to 10 times the planetary vorticity. This vorticity is associated with the trough's curvature, but also with the large cyclonic shear at the northern side of the subtropical jet. The passage of the upper-level disturbance is well timed to overpass the region of the Arabian Peninsula heat low around midday, where vorticity is thermally generated. Most likely the deep boundary layer facilitated the triggering of convection by the upper-level forcing. Ultimately, downward mixing of the high vorticity by convection plus vortex stretching cause exceptionally high vorticity near the surface, which initiated this extreme and unusual dust storm. Short-range ECMWF forecasts produce precipitation but not as extreme as measured at Arar. The model also generates strong near-surface winds, which are generally in good agreement with the SYNOP observations. Interestingly, however, the 10 m wind direction falls short to reflect the extreme cyclonic curvature evident in station observations, pointing to an underestimation of the vortex in the model. We hypothesise that the ECMWF model with its parameterised convection is unable to realistically represent the vertical mixing and vortex stretching. Numerical simulations on the convection permitting scale might improve forecasts of such events, but this is yet to be tested.

Hourly elemental concentrations in PM2.5 aerosols sampled simultaneously at urban background and road site

NASA Astrophysics Data System (ADS)

Dall'Osto, M.; Querol, X.; Amato, F.; Karanasiou, A.; Lucarelli, F.; Nava, S.; Calzolai, G.; Chiari, M.

2012-08-01

Hourly-resolved aerosol chemical speciation data can be a highly powerful tool to determine the source origin of atmospheric pollutants in urban Environments. Aerosol mass concentrations of seventeen elements (Na, Mg, Al, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr and Pb) were obtained by time (1 h) and size (PM2.5 particulate matter <2.5 μm) resolved Particle Induced X-ray Emission (PIXE) measurements. In the Marie Curie FP7-EU framework of SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies), the unique approach used is the simultaneous PIXE measurements at two monitoring sites: urban background (UB) and a street canyon traffic road site (RS). Elements related to primary non exhaust traffic emission (Fe, Cu), dust resuspension (Ca) and anthropogenic Cl were found enhanced at the RS, whereas industrial related trace metals (Zn, Pb, Mn) were found at higher concentrations at the more ventilated UB site. When receptor modelling was performed with positive matrix factorization (PMF), nine different aerosol sources were identified at both sites: three types of regional aerosols (secondary sulphate (S) - 27%, biomass burning (K) - 5%, sea salt (Na-Mg) - 17%), three types of dust aerosols (soil dust (Al-Ti) - 17%, urban crustal dust (Ca) - 6%, and primary traffic non exhaust brake dust (Fe-Cu) - 7%), and three types industrial aerosol plumes-like events (shipping oil combustion (V-Ni) - 17%, industrial smelters (Zn-Mn) - 3%, and industrial combustion (Pb-Cl) - 5%). The validity of the PMF solution of the PIXE data is supported by strong correlations with external single particle mass spectrometry measurements. Beside apportioning the aerosol sources, some important air quality related conclusions can be drawn about the PM2.5 fraction simultaneously measured at the UB and RS sites: (1) the regional aerosol sources impact both monitoring sites at similar concentrations regardless their different ventilation conditions; (2) by contrast, local industrial aerosol plumes associated with shipping oil combustion and smelters activities have a higher impact on the more ventilated UB site; (3) a unique source of Pb-Cl (associated with industrial combustion emissions) is found a to be the major (82%) source of Cl in the urban agglomerate; (4) PM2.5 traffic brake dust (Fe-Cu) is mainly primarily emitted and not resuspended, whereas PM2.5 urban crustal dust (Ca) is found mainly resuspended by both traffic vortex and sea breeze; (5) urban dust (Ca) is found the aerosol source most affected by land wetness, reduced by a factor of eight during rainy days and suggesting that wet roads may be a solution for reducing dust concentrations in road sites, far more effective than street sweeping activities.

Scientists Detect Radio Emission from Rapidly Rotating Cosmic Dust Grains

NASA Astrophysics Data System (ADS)

2001-11-01

Astronomers have made the first tentative observations of a long-speculated, but never before detected, source of natural radio waves in interstellar space. Data from the National Science Foundation's 140 Foot Radio Telescope at the National Radio Astronomy Observatory in Green Bank, W.Va., show the faint, tell-tale signals of what appear to be dust grains spinning billions of times each second. This discovery eventually could yield a powerful new tool for understanding the interstellar medium - the immense clouds of gas and dust that populate interstellar space. The NRAO 140 Foot Radio Telescope The NRAO 140-Foot Radio Telescope "What we believe we have found," said Douglas P. Finkbeiner of Princeton University's Department of Astrophysics, "is the first hard evidence for electric dipole emission from rapidly rotating dust grains. If our studies are confirmed, it will be the first new source of continuum emission to be conclusively identified in the interstellar medium in nearly the past 20 years." Finkbeiner believes that these emissions have the potential in the future of revealing new and exciting information about the interstellar medium; they also may help to refine future studies of the Cosmic Microwave Background Radiation. The results from this study, which took place in spring 1999, were accepted for publication in Astrophysical Journal. Other contributors to this paper include David J. Schlegel, department of astrophysics, Princeton University; Curtis Frank, department of astronomy, University of Maryland; and Carl Heiles, department of astronomy, University of California at Berkeley. "The idea of dust grains emitting radiation by rotating is not new," comments Finkbeiner, "but to date it has been somewhat speculative." Scientists first proposed in 1957 that dust grains could emit radio signals, if they were caused to rotate rapidly enough. It was believed, however, that these radio emissions would be negligibly small - too weak to be of any impact to current radio astronomy research, and the idea was largely forgotten. In the 1990s this perception began to change when scientists and engineers designed sensitive instruments to detect the faint afterglow of the Big Bang, which is seen in the Universe as the Cosmic Microwave Background Radiation. While making detailed maps of this faint and cold radiation, scientists also detected signals at approximately the same wavelength and intensity as the background radiation, but clearly emanating from within the Milky Way's galactic plane. The researchers expected to detect some emission from the Milky Way, but what they encountered was much brighter than anticipated. This discovery caused some concern among researchers because of the need to have a very clear "window" on the Universe to study the background radiation in great detail. If there were a source of radio emission in our own galactic "back yard," then studies of the microwave background radiation would need to recognize these emissions and correct for them. "We want to be clear, however, that nothing we have found invalidates the current interpretation of the Cosmic Microwave Background Radiation," assured Finkbeiner. "Nobody has done anything wrong in neglecting these signals - so far." Scientists considered several plausible mechanisms for this anomalous emission, but these theories failed to explain the observed spatial distribution of this emission across the sky. This predicament prompted theorists to rethink the spinning dust idea, leading to a 1998 model by Bruce Draine (Princeton University) and Alex Lazarian (University of Wisconsin), which proposed rotational dust-grain emission as an important mechanism. Draine and Lazarian assumed that small dust grains, perhaps having no more than 100 atoms each, would populate many interstellar dust clouds in the Galaxy. Each grain would have a small electric dipole and would therefore react to the charged ions that race through the clouds at tremendous speeds. As an ion either strikes or passes near a dust grains, the grain would "spin up," reaching speeds of up to one trillion revolutions per minute, causing it to radiate. The rate of rotation of these dust grains directly correlates to the frequencies at which they radiate. For example, a dust grain rotating 10 billion times each second would emit radio waves at 10 gigahertz (GHz). In looking for this elusive signal, the researchers narrowed their search to 10 dust clouds within the Milky Way Galaxy. These specific clouds were selected because their location and properties would help to eliminate other possibilities for these emissions. "Our goal was to find those areas within the Milky Way Galaxy that would help us rule out other sources of emission," said Finkbeiner. "By selected these specific targets, we believe that the signals we received are very indicative of rapidly rotating dust grains." The researchers emphasize, however, that additional observations will be required to confirm their results, and other potential emission mechanisms have not been ruled out. Particularly, it is possible that a portion of this radiation is due to the presence of ferro-magnetic minerals within the dust grains. Additional studies with more sensitive equipment will be necessary to confirm these results conclusively. "What we think is the most intriguing, however," said Finkbeiner, "is that with further advances in radio astronomy, the faint emissions from rotating dust grains may reveal previously unknown details about the dynamics of the interstellar medium. By detecting and understanding this emission we also hope to give astronomers a tool to greatly refine future studies of the Cosmic Microwave Background Radiation." The NSF's 140 Foot Radio Telescope now is decommissioned after a long and highly productive career. Research will continue on the newly commissioned Robert C. Byrd Green Bank Telescope, which is the world's largest fully steerable radio telescope. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Fugitive Dust Emission Factors for Puff and Mobile Military Sources Measured by Micro-pulse Lidar - A Summary of Results

NASA Astrophysics Data System (ADS)

Yuen, W.; Du, K.; Rood, M. J.; Kemme, M. R.; Kim, B.; Hashmonay, R. A.

2010-12-01

A summary of the development of a novel optical remote sensing (ORS) method that determined fugitive dust emission factors for unique military activities is described for puff and mobile sources. Four field campaigns characterized artillery back blasts as puff sources (M549A1 and M107), and movement of military vehicles (M1A1, M113, Bradley Fighting Vehicle (BFV), M88, M270, M577, and HEMTT) and an airborne helicopter (Bell 210) as mobile sources. The ORS method includes a Micro-Pulse Lidar (MPL) and a reflective target that determines one-dimensional (1-D) light extinction coefficient profiles. The MPL was mounted on a positioner that allows the MPL to automatically scan vertically, which allowed 1-D extinction coefficient profiles to be measured at select angles from horizontal. Two-dimensional (2-D) light extinction coefficient profiles were then determined by interpolating the 1-D extinction profiles measured at select angles. Dust property, in the form of the mass extinction efficiency (MEE), was measured using Open Path- Fourier Transform Infrared Spectrometry (OP-FTIR) and Open Path- Laser Transmissometry (OP-LT) in the first three field campaigns and an OP-LT and DustTrak™ in the fourth field campaign. MEE was used to convert the 2-D light extinction coefficient profiles to 2-D dust mass concentration profiles. Emission factors were determined by integrating the 2-D mass concentration profiles with measured wind vectors. Results from these field campaigns show that: 1) artillery with stronger recoiling forces generates more fugitive dust; 2) the dust emission factors for tracked vehicles are correlated with vehicle momentum; 3) emission factor decreases with increasing speed for airborne helicopters; and 4) wheeled vehicles (HEMTT) generate more fugitive dust than tracked vehicles (M88, M270, M577).

Seasonal Variation and Exposure Risks of Perchlorate in Soil, Indoor Dust, and Outdoor Dust in China.

PubMed

Li, Yiwen; Liao, Ruoying; Gan, Zhiwei; Qu, Bing; Wang, Rong; Chen, Mengqin; Ding, Sanglan; Su, Shijun

2018-04-25

A total of 97 paired soil, outdoor dust, and indoor dust samples were collected in the national scale of China in summer, and the perchlorate levels were compared with those in soil and outdoor dust samples collected in winter in our previous study. The median perchlorate concentrations in the outdoor dust, indoor dust, and soil samples were 8.10, 11.4, and 0.05 mg/kg, respectively, which were significantly lower than those in the winter samples due to the natural factors and human activities. No significant differences in perchlorate concentrations were found between Northern and Southern China in the dust samples, whereas the difference was obtained in the soil samples. In the terms of possible source, the perchlorate levels in the outdoor dust exhibited strong correlation with SO 4 2- (r 2  = 0.458**) and NO 3 - (r 2  = 0.389**), indicating part of perchlorate in outdoor environment was likely from atmospheric oxidative process in summer. The perchlorate, SO 4 2- , and Cl - levels in the indoor dust were significantly related to those in the outdoor dust, suggesting that outdoor contaminants might be an important source for indoor environment. Furthermore, the human exposure to perchlorate was under relatively safe state in China except for special sites or periods with high perchlorate levels. Dust made an unexpected contribution of 41.3% to the total daily perchlorate intake for children, whereas 2.46% for adults in China based on biomonitoring, which deserves more attention.

Understanding the Transport of Patagonian Dust and Its Influence on Marine Biological Activity in the South Atlantic Ocean

NASA Technical Reports Server (NTRS)

Johnson, Matthew; Meskhidze, Nicholas; Kiliyanpilakkil, Praju; Gasso, Santiago

2010-01-01

Modeling and remote sensing techniques were applied to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of soluble-iron- laden mineral dust deposition on marine primary productivity in the South Atlantic Ocean (SAO) surface waters. The global chemistry transport model GEOS-Chem, implemented with an iron dissolution scheme, was applied to evaluate the atmospheric transport and deposition of mineral dust and bioavailable iron during two dust outbreaks originating in the source regions of Patagonia. In addition to this "rapidly released" iron, offline calculations were also carried out to estimate the amount of bioavailable iron leached during the residence time of dust in the ocean mixed layer. Model simulations showed that the horizontal and vertical transport pathways of Patagonian dust plumes were largely influenced by the synoptic meteorological patterns of high and low pressure systems. Model-predicted horizontal and vertical transport pathways of Patagonian dust over the SAO were in reasonable agreement with remotely-sensed data. Comparison between remotely-sensed and offline calculated ocean surface chlorophyll-a concentrations indicated that, for the two dust outbreaks examined in this study, the deposition of bioavailable iron in the SAO through atmospheric pathways was insignificant. As the two dust transport episodes examined here represent typical outflows of mineral dust from South American sources, our study suggests that the atmospheric deposition of mineral dust is unlikely to induce large scale marine primary productivity and carbon sequestration in the South Atlantic sector of the Southern Ocean.

The effect of radiation pressure on spatial distribution of dust inside H II regions

NASA Astrophysics Data System (ADS)

Ishiki, Shohei; Okamoto, Takashi; Inoue, Akio K.

2018-02-01

We investigate the impact of radiation pressure on spatial dust distribution inside H II regions using one-dimensional radiation hydrodynamic simulations, which include absorption and re-emission of photons by dust. In order to investigate grain-size effects as well, we introduce two additional fluid components describing large and small dust grains in the simulations. Relative velocity between dust and gas strongly depends on the drag force. We include collisional drag force and coulomb drag force. We find that, in a compact H II region, a dust cavity region is formed by radiation pressure. Resulting dust cavity sizes (˜0.2 pc) agree with observational estimates reasonably well. Since dust inside an H II region is strongly charged, relative velocity between dust and gas is mainly determined by the coulomb drag force. Strength of the coulomb drag force is about 2 order of magnitude larger than that of the collisional drag force. In addition, in a cloud of mass 105 M⊙, we find that the radiation pressure changes the grain-size distribution inside H II regions. Since large (0.1 μm) dust grains are accelerated more efficiently than small (0.01 μm) grains, the large-to-small grain mass ratio becomes smaller by an order of magnitude compared with the initial one. Resulting dust-size distributions depend on the luminosity of the radiation source. The large and small grain segregation becomes weaker when we assume stronger radiation source, since dust grain charges become larger under stronger radiation and hence coulomb drag force becomes stronger.

Infrared Luminosities and Dust Properties of z ≈ 2 Dust-obscured Galaxies

NASA Astrophysics Data System (ADS)

Bussmann, R. S.; Dey, Arjun; Borys, C.; Desai, V.; Jannuzi, B. T.; Le Floc'h, E.; Melbourne, J.; Sheth, K.; Soifer, B. T.

2009-11-01

We present SHARC-II 350 μm imaging of twelve 24 μm bright (F 24 μm > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Boötes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 μm imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 μm flux density. The 350 μm upper limits for the 8 non-detected DOGs are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: T dust > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of ≈3 × 108 M sun. In comparison to other dusty z ~ 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 × 1013 L sun versus 6 × 1012 L sun for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus ~30 K) and lower inferred dust masses (3 × 108 M sun versus 3 × 109 M sun). Wide-field Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 μm bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive galaxies at z ~ 2 involves a submillimeter bright, cold-dust, and star-formation-dominated phase followed by a 24 μm bright, warm-dust and AGN-dominated phase.

Surface dust wipes are the best predictors of blood leads in young children with elevated blood lead levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gulson, Brian, E-mail: brian.gulson@mq.edu.au; CSIRO Earth Science and Resource Engineering, North Ryde NSW 2113; Anderson, Phil

Background: As part of the only national survey of lead in Australian children, which was undertaken in 1996, lead isotopic and lead concentration measurements were obtained from children from 24 dwellings whose blood lead levels were ≥15 µg/dL in an attempt to determine the source(s) of their elevated blood lead. Comparisons were made with data for six children with lower blood lead levels (<10 µg/dL). Methods: Thermal ionisation and isotope dilution mass spectrometry were used to determine high precision lead isotopic ratios ({sup 208}Pb/{sup 206}Pb, {sup 207}Pb/{sup 206}Pb and {sup 206}Pb/{sup 204}Pb) and lead concentrations in blood, dust from floormore » wipes, soil, drinking water and paint (where available). Evaluation of associations between blood and the environmental samples was based on the analysis of individual cases, and Pearson correlations and multiple regression analyses based on the whole dataset. Results and discussion: The correlations showed an association for isotopic ratios in blood and wipes (r=0.52, 95% CI 0.19–0.74), blood and soil (r=0.33, 95% CI −0.05–0.62), and blood and paint (r=0.56, 95% CI 0.09–0.83). The regression analyses indicated that the only statistically significant relationship for blood isotopic ratios was with dust wipes (B=0.65, 95% CI 0.35–0.95); there were no significant associations for lead concentrations in blood and environmental samples. There is a strong isotopic correlation of soils and house dust (r=0.53, 95% CI 0.20–0.75) indicative of a common source(s) for lead in soil and house dust. In contrast, as with the regression analyses, no such association is present for bulk lead concentrations (r=−0.003, 95% CI −0.37–0.36), the most common approach employed in source investigations. In evaluation of the isotopic results on a case by case basis, the strongest associations were for dust wipes and blood. -- Highlights: • Children with elevated blood lead ≥15 µg/dL compared with a group with <10 µg/dL. • High precision lead isotopic ratios in blood, house dust wipes, soil, water, paint. • Associations for isotopic measures of blood and dust, blood and soil, blood and paint. • Regressions gave significance for isotopic measures of blood/dust and dust/soil.« less

Emergency Hospital Visits in Association with Volcanic Ash, Dust Storms and Other Sources of Ambient Particles: A Time-Series Study in Reykjavík, Iceland

PubMed Central

Carlsen, Hanne Krage; Gislason, Thorarinn; Forsberg, Bertil; Meister, Kadri; Thorsteinsson, Throstur; Jóhannsson, Thorsteinn; Finnbjornsdottir, Ragnhildur; Oudin, Anna

2015-01-01

Volcanic ash contributed significantly to particulate matter (PM) in Iceland following the eruptions in Eyjafjallajökull 2010 and Grímsvötn 2011. This study aimed to investigate the association between different PM sources and emergency hospital visits for cardiorespiratory causes from 2007 to 2012. Indicators of PM10 sources; “volcanic ash”, “dust storms”, or “other sources” (traffic, fireworks, and re-suspension) on days when PM10 exceeded the daily air quality guideline value of 50 µg/m3 were entered into generalized additive models, adjusted for weather, time trend and co-pollutants. The average number of daily emergency hospital visits was 10.5. PM10 exceeded the air quality guideline value 115 out of 2191 days; 20 days due to volcanic ash, 14 due to dust storms (two days had both dust storm and ash contribution) and 83 due to other sources. High PM10 levels from volcanic ash tended to be significantly associated with the emergency hospital visits; estimates ranged from 4.8% (95% Confidence Interval (CI): 0.6, 9.2%) per day of exposure in unadjusted models to 7.3% (95% CI: −0.4, 15.5%) in adjusted models. Dust storms were not consistently associated with daily emergency hospital visits and other sources tended to show a negative association. We found some evidence indicating that volcanic ash particles were more harmful than particles from other sources, but the results were inconclusive and should be interpreted with caution. PMID:25872017

BIOAVAILABILITY OF PBDES IN MALE RATS FROM ORALLY ADMINISTERED HOUSEHOLD DUST

EPA Science Inventory

Recently, household dust has been implicated as a major source of polybrominated diphenyl ether (PBDE) exposure in humans. This finding has very important implications especially for young children, who are thought to ingest more dust than adults, and may be more susceptible t...

76 FR 17028 - Approval and Promulgation of Gila River Indian Community's Tribal Implementation Plan

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-28

... and judicial review in Tribal court, requirements for area sources of fugitive dust and fugitive... administrative appeals and judicial review in Tribal court, requirements for area sources of fugitive dust and... Risks and Safety Risks'' (62 FR 19885, April 23, 1997), because it is not economically significant. In...

Source apportionment of particulate matter in a South Asian Mega City: A case study of Karachi

NASA Astrophysics Data System (ADS)

Shahid, imran

2016-04-01

Pakistan is facing unabated air pollution as a major issue and its cities are more vulnerable as compared to urban centers in the developed world. During the last few decades, there has been a rapid increase in population, urbanization, industrialization, transportation and other human activities. In year June 2015 heat wave in largest South Asian mega city Karachi more than 1500 people died in one week. Unfortunately no air quality monitoring system is operation in any city of Pakistan. There is a sharp increase in both the variety and quantity of air pollutants and their corresponding sources. In this study contributions of different sources to particulate matter concentration has estimated in urban area of Karachi. Carbonaceous species (elemental carbon, organic carbon, carbonate carbon), soluble ions (Ca++, Mg++, Na+, K+, NH4+, Cl-, NO3-, SO4--), saccharides (levoglucosan, galactosan, mannosan, sucrose, fructose, glucose, arabitol and mannitol) were measured in atmospheric fine (PM2.5) and coarse (PM10) particles collected under pre-monsoon conditions (March - April 2009) at an urban site in Karachi (Pakistan). Average concentrations of PM2.5 were 75μg/m3 and of PM10 437μg/m3. The large difference between PM10 and PM2.5 originated predominantly from mineral dust. "Calcareous dust" and „siliceous dust" were the overall dominating material in PM, with 46% contribution to PM2.5 and 78% to PM10-2.5. 20 Combustion particles and secondary organics (EC+OM) comprised 23% of PM2.5 and 6% of PM10-2.5. EC, as well as OC ambient levels were higher (59% and 56%) in PM10-2.5 than in 22 PM2.5. Biomass burning contributed about 3% to PM2.5, and had a share of about 13% of "EC+OM" in PM2.5. The impact of bioaerosol (fungal spores) was minor and had a share of 1 and 2% of the OC in the PM2.5 and PM10-2.5 size fractions. Of secondary inorganic constituents (NH4)2SO4 contributes 4.4% to PM2.5 and no detectable quantity to PM10-2.5. The sea salt contribution is about 2% both to PM2.5 and PM10-2.5. In order to make air quality better and risk free in South Asian cities a comprehensive and integrated regional effort is required that include continuous air quality monitoring, source apportionment and implementation of regional air quality policies.

Trace Metals in Saharan Dust: The Use of in Vitro Bioaccessibility Extractions To Assess Potential Health Risks in a Dustier World: Chapter 3

USGS Publications Warehouse

Morman, Suzette A.; Garrison, Virginia H.; Plumlee, Geoffrey S.

2013-01-01

Exposure to fine particulate matter (PM) is acknowledged as a risk factor for human morbidity and mortality. Epidemiology and toxicology studies have focused on anthropogenic sources of PM and few consider contributions produced by natural processes (geogenic), or PM produced from natural sources as a result of human activities (geoanthropogenic PM). The focus of this study was to elucidate relationships between human/ecosystem health and dusts produced by a system transitioning from a dominantly natural to a geoanthropogenic PM source. As part of a larger study investigating the relationship between atmospheric transportation of African dust, human health, and coral reef declines, we examined dust samples sourced in Mali, Africa, collected using high-volume samplers from three sites (Mali, Tobago and U.S. Virgin Islands). Inhalation and ingestion exposure pathways were explored by filter extractions using simulated lung and gastric fluids. Bioaccessibility varied by metal and extraction fluid. Although too few samples were analyzed for robust statistics, concentrations for several metals decreased slightly while bioaccessibility increased at downwind sites.

High-resolution submillimeter and near-infrared studies of the transition disk around Sz 91

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsukagoshi, Takashi; Momose, Munetake; Hashimoto, Jun

2014-03-10

To reveal the structures of a transition disk around a young stellar object in Lupus, Sz 91 , we have performed aperture synthesis 345 GHz continuum and CO(3-2) observations with the Submillimeter Array (∼1''-3'' resolution) and high-resolution imaging of polarized intensity at the K{sub s} -band using the HiCIAO instrument on the Subaru Telescope (0.''25 resolution). Our observations successfully resolved the inner and outer radii of the dust disk to be 65 and 170 AU, respectively, which indicates that Sz 91 is a transition disk source with one of the largest known inner holes. The model fitting analysis of themore » spectral energy distribution reveals an H{sub 2} mass of 2.4 × 10{sup –3} M {sub ☉} in the cold (T < 30 K) outer part at 65 AU 3 × 10{sup –9} M {sub ☉}) of hot (T ∼ 180 K) dust possibly remains inside the inner hole of the disk. The structure of the hot component could be interpreted as either an unresolved self-luminous companion body (not directly detected in our observations) or a narrow ring inside the inner hole. Significant CO(3-2) emission with a velocity gradient along the major axis of the dust disk is concentrated on the Sz 91 position, suggesting a rotating gas disk with a radius of 420 AU. The Sz 91 disk is possibly a rare disk in an evolutionary stage immediately after the formation of protoplanets because of the large inner hole and the lower disk mass than other transition disks studied thus far.« less

Aerosol Chemical Composition in Asian Continental Outflow during the TRACE-P Campaign: Comparison with PEM-West B

NASA Technical Reports Server (NTRS)

Dibb, Jack E.; Talbot, Robert W.; Scheuer, Eric M.; Seid, Garry; Avery, Melody A.; Singh, Hanwant B.

2003-01-01

Aerosol associated soluble ions and the radionuclide tracers (7)Be and (210)Pb were quantified in 414 filter samples collected in spring 2001 from the DC-8 during the Transport and Chemical Evolution over the Pacific (TRACE-P) campaign. Binning the data into near Asia (flights from Hong Kong and Japan) and remote Pacific (all other flights) revealed large enhancements of NO3(-), SO4(-), C2O4(-), NH4(+), K(+), Mg2(+), and Ca2(+) near Asia. The boundary layer and lower troposphere were most strongly influenced by continental outflow, and the largest enhancements were seen in Ca2(+) (a dust tracer) and NO3(-) (reflecting uptake of HNO3 onto the dust). Comparing the TRACE P near Asia bin with earlier results from the same region during PEM-West B (in 1994) shows at least twofold enhancements during TRACE P in most of the ions listed above. Calcium and NO3(-) were most enhanced in this comparison as well (more than sevenfold higher in the boundary layer and threefold higher in the lower troposphere). Independent estimation of Asian emissions of gaseous precursors of the aerosol-associated ions suggest only small changes between the two missions, and precipitation fields do not suggest any significant difference in the efficiency of the primary sink, precipitation scavenging. It thus appears that with the possible exception of dust, the enhancements of aerosol-associated species during TRACE P cannot be explained by stronger sources or weaker sinks. We argue that the enhancements largely reflect the fact that TRACE P focused on characterizing Asian outflow, and thus the DC-8 was more frequently flown into regions that were influenced by well-organized flow off the continent.

Kent in space: Cosmic dust to space debris

NASA Astrophysics Data System (ADS)

McDonnell, J. A. M.

1994-10-01

The dusty heritage of the University of Kent's Space Group commenced at Jodrell Bank, Cheshire, U.K., the home of the largest steerable radio telescope. While Professor Bernard Lovell's 250 ft. diameter telescope was used to command the U.S. deep space Pioneer spacecraft, Professor Tony McDonnell, as a research student in 1960, was developing a space dust detector for the US-UK Ariel program. It was successful. With a Ph.D. safely under the belt, it seemed an inevitable step to go for the next higher degree, a B.T.A.] Two years with NASA at Goddard Space Flight Center, Greenbelt, provided excellent qualifications for such a graduation ('Been to America'). A spirited return to the University of Kent at Canterbury followed, to one of the green field UK University sites springing from the Robbins Report on Higher Education. Swimming against the current of the brain drain, and taking a very considerable reduction in salary, it was with some disappointment that he found that the UK Premier Harold Wilson's 'white-hot technological revolution' never quite seemed to materialize in terms of research funding] Research expertise, centered initially on cosmic dust, enlarged to encompass planetology during the Apollo program, and rightly acquired international acclaim, notching up a history of space missions over 25 years. The group now comprises 38 people supported by four sources: the government's Research Councils, the University, the Space Agencies and Industry. This paper describes the thrust of the group's Research Plan in Space Science and Planetology; not so much based on existing international space missions, but more helping to shape the direction and selection of space missions ahead.

Hourly elemental concentrations in PM2.5 aerosols sampled simultaneously at urban background and road site during SAPUSS - diurnal variations and PMF receptor modelling

NASA Astrophysics Data System (ADS)

Dall'Osto, M.; Querol, X.; Amato, F.; Karanasiou, A.; Lucarelli, F.; Nava, S.; Calzolai, G.; Chiari, M.

2013-04-01

Hourly-resolved aerosol chemical speciation data can be a highly powerful tool to determine the source origin of atmospheric pollutants in urban environments. Aerosol mass concentrations of seventeen elements (Na, Mg, Al, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr and Pb) were obtained by time (1 h) and size (PM2.5 particulate matter < 2.5 μm) resolved aerosol samples analysed by Particle Induced X-ray Emission (PIXE) measurements. In the Marie Curie European Union framework of SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies), the approach used is the simultaneous sampling at two monitoring sites in Barcelona (Spain) during September-October 2010: an urban background site (UB) and a street canyon traffic road site (RS). Elements related to primary non-exhaust traffic emission (Fe, Cu), dust resuspension (Ca) and anthropogenic Cl were found enhanced at the RS, whereas industrial related trace metals (Zn, Pb, Mn) were found at higher concentrations at the more ventilated UB site. When receptor modelling was performed with positive matrix factorization (PMF), nine different aerosol sources were identified at both sites: three types of regional aerosols (regional sulphate (S) - 27%, biomass burning (K) - 5%, sea salt (Na-Mg) - 17%), three types of dust aerosols (soil dust (Al-Ti) - 17%, urban crustal dust (Ca) - 6%, and primary traffic non-exhaust brake dust (Fe-Cu) - 7%), and three types of industrial aerosol plumes-like events (shipping oil combustion (V-Ni) - 17%, industrial smelters (Zn-Mn) - 3%, and industrial combustion (Pb-Cl) - 5%, percentages presented are average source contributions to the total elemental mass measured). The validity of the PMF solution of the PIXE data is supported by very good correlations with external single particle mass spectrometry measurements. Some important conclusions can be drawn about the PM2.5 mass fraction simultaneously measured at the UB and RS sites: (1) the regional aerosol sources impact both monitoring sites at similar concentrations regardless their different ventilation conditions; (2) by contrast, local industrial aerosol plumes associated with shipping oil combustion and smelters activities have a higher impact on the more ventilated UB site; (3) a unique source of Pb-Cl (associated with combustion emissions) is found to be the major (82%) source of fine Cl in the urban agglomerate; (4) the mean diurnal variation of PM2.5 primary traffic non-exhaust brake dust (Fe-Cu) suggests that this source is mainly emitted and not resuspended, whereas PM2.5 urban dust (Ca) is found mainly resuspended by both traffic vortex and sea breeze; (5) urban dust (Ca) is found the aerosol source most affected by land wetness, reduced by a factor of eight during rainy days and suggesting that wet roads may be a solution for reducing urban dust concentrations.

Giant Exoplanet and Debris Disk (Artist's Concept)

NASA Image and Video Library

2017-10-11

This artist's rendering shows a giant exoplanet causing small bodies to collide in a disk of dust. A study in The Astronomical Journal finds that giant exoplanets with long-period orbits are more likely to be found around young stars that have a disk of dust and debris than those without disks. The study focused on planets more than five times the mass of Jupiter. The astronomers are conducting the largest survey to date of stars with dusty debris disks, and finding the best evidence yet that giant planets are responsible for keeping that material in check. https://photojournal.jpl.nasa.gov/catalog/PIA22082

Estimating Children's Soil/Dust Ingestion Rates through Retrospective Analyses of Blood Lead Biomonitoring from the Bunker Hill Superfund Site in Idaho.

PubMed

von Lindern, Ian; Spalinger, Susan; Stifelman, Marc L; Stanek, Lindsay Wichers; Bartrem, Casey

2016-09-01

Soil/dust ingestion rates are important variables in assessing children's health risks in contaminated environments. Current estimates are based largely on soil tracer methodology, which is limited by analytical uncertainty, small sample size, and short study duration. The objective was to estimate site-specific soil/dust ingestion rates through reevaluation of the lead absorption dose-response relationship using new bioavailability data from the Bunker Hill Mining and Metallurgical Complex Superfund Site (BHSS) in Idaho, USA. The U.S. Environmental Protection Agency (EPA) in vitro bioavailability methodology was applied to archived BHSS soil and dust samples. Using age-specific biokinetic slope factors, we related bioavailable lead from these sources to children's blood lead levels (BLLs) monitored during cleanup from 1988 through 2002. Quantitative regression analyses and exposure assessment guidance were used to develop candidate soil/dust source partition scenarios estimating lead intake, allowing estimation of age-specific soil/dust ingestion rates. These ingestion rate and bioavailability estimates were simultaneously applied to the U.S. EPA Integrated Exposure Uptake Biokinetic Model for Lead in Children to determine those combinations best approximating observed BLLs. Absolute soil and house dust bioavailability averaged 33% (SD ± 4%) and 28% (SD ± 6%), respectively. Estimated BHSS age-specific soil/dust ingestion rates are 86-94 mg/day for 6-month- to 2-year-old children and 51-67 mg/day for 2- to 9-year-old children. Soil/dust ingestion rate estimates for 1- to 9-year-old children at the BHSS are lower than those commonly used in human health risk assessment. A substantial component of children's exposure comes from sources beyond the immediate home environment. von Lindern I, Spalinger S, Stifelman ML, Stanek LW, Bartrem C. 2016. Estimating children's soil/dust ingestion rates through retrospective analyses of blood lead biomonitoring from the Bunker Hill Superfund Site in Idaho. Environ Health Perspect 124:1462-1470; http://dx.doi.org/10.1289/ehp.1510144.

Effects of interstellar dust scattering on the X-ray eclipses of the LMXB AX J1745.6-2901 in the Galactic Centre

NASA Astrophysics Data System (ADS)

Jin, Chichuan; Ponti, Gabriele; Haberl, Frank; Smith, Randall; Valencic, Lynne

2018-07-01

AX J1745.6-2901 is an eclipsing low-mass X-ray binary in the Galactic Centre (GC). It shows significant X-ray excess emission during the eclipse phase, and its eclipse light curve shows an asymmetric shape. We use archival XMM-Newton and Chandra observations to study the origin of these peculiar X-ray eclipsing phenomena. We find that the shape of the observed X-ray eclipse light curves depends on both photon energy and the shape of the source extraction region, and also shows differences between the two instruments. By performing detailed simulations for the time-dependent X-ray dust-scattering halo, as well as directly modelling the observed eclipse and non-eclipse halo profiles of AX J1745.6-2901, we obtained solid evidence that its peculiar eclipse phenomena are indeed caused by the X-ray dust scattering in multiple foreground dust layers along the line of sight (LOS). The apparent dependence on the instruments is caused by different instrumental point spread functions. Our results can be used to assess the influence of dust-scattering in other eclipsing X-ray sources, and raise the importance of considering the timing effects of dust-scattering halo when studying the variability of other X-ray sources in the GC, such as Sgr A⋆. Moreover, our study of halo eclipse reinforces the existence of a dust layer local to AX J1745.6-2901 as reported by Jin et al. (2017), as well as identifying another dust layer within a few hundred parsecs to the Earth, containing up to several tens of percent LOS dust, which is likely to be associated with the molecular clouds in the Solar neighbourhood. The remaining LOS dust is likely to be associated with the molecular clouds located in the Galactic disc in-between.

Polybrominated diphenyl ethers (PBDEs) and heavy metals in road dusts from a plastic waste recycling area in north China: implications for human health.

PubMed

Tang, Zhenwu; Huang, Qifei; Yang, Yufei; Nie, Zhiqiang; Cheng, Jiali; Yang, Jun; Wang, Yuwen; Chai, Miao

2016-01-01

Road dusts were collected from an area where intense mechanical recycling of plastic wastes occurs in Wen'an, north China. These dusts were investigated for polybrominated diphenyl ethers (PBDEs) and heavy metals contamination to assess the health risk related to these components. Decabromodiphenyl ether (BDE-209) and Σ21PBDE concentrations in these dusts ranged from 2.67 to 10,424 ng g(-1) and from 3.23 to 10,640 ng g(-1), respectively. These PBDE concentrations were comparable to those observed in road dust from e-waste recycling areas but were 1-2 orders of magnitude higher than concentrations in outdoor or road dusts from other areas. This indicates that road dusts in the study area have high levels of PBDE pollution. BDE-209 was the predominant congener, accounting for 86.3% of the total PBDE content in dusts. Thus, commercial deca-BDE products were the dominant source. The average concentrations of As, Cd, Cr, Cu, Hg, Pb, Sb, and Zn in these same dust samples were 10.1, 0.495, 112, 54.7, 0.150, 71.8, 10.6, and 186 mg kg(-1), respectively. The geoaccumulation index suggests that road dusts in this area are moderately to heavily polluted with Cd, Hg, and Sb. This study shows that plastic waste processing is a major source of toxic pollutants in road dusts in this area. Although the health risk from exposure to dust PBDEs was low, levels of some heavy metals in this dust exceeded acceptable risk levels for children and are of great concern.

Determining the Influence of Dust on Post-Glacial Lacustrine Sedimentation in Bald Lake, Uinta Mountains, Utah

NASA Astrophysics Data System (ADS)

O'Keefe, S. S.; McElroy, R.; Munroe, J. S.

2016-12-01

Dust is increasingly recognized as an important component of biogeochemical cycling and ecosystem function in mountain environments. Previous work has shown that delivery of dust to the Uinta Mountains of northeastern Utah has influenced pedogenesis, soil nutrient status, and surface water chemistry. An array of passive and active samplers in the alpine zone of the Uintas provides detailed information about contemporary dust fluxes, along with physical and geochemical properties of modern dust. Reconstruction of changes in the dust system over time, however, requires continuous sedimentary archives sensitive to dust inputs. A radiocarbon-dated 3.5-m core (spanning 12.7 kyr) collected from subalpine Bald Lake may provide such a record. Passive dust collectors in the vicinity of the lake constrain the geochemical properties of modern dust, whereas samples of regolith constrain properties of the local surficial material within the watershed. Together, these represent two end member sources of clastic sediment to Bald Lake basin: allochthonous dust and autochthonous regolith. Ba and Eu are found in higher abundances in the dust than in the watershed regolith. Zr and Th are found to be lower in the dust than in the watershed. Geochemical analysis of the sediment core allows the relative contribution of exotic and local material to the lake to be considered as a time series covering the post-glacial interval when indicator elements are plotted. Findings suggest Bald Lake's dust record tracks regional aridity and corresponds to low-stands of large lakes in the southwestern United States. Spatial variability of elemental abundances in the watershed suggests there are more than two input sources contributing to the lake over time.

Development of Atmospheric Chemistry-Aerosol Transport Model for Bioavailable Iron From Dust and Combustion Source

NASA Astrophysics Data System (ADS)

Ito, A.; Feng, Y.

2009-12-01

An accurate prediction of bioavailable iron fraction for ocean biota is hampered by uncertainties in modeling soluble iron fractions in atmospheric aerosols. It has been proposed that atmospheric processing of mineral aerosols by anthropogenic pollutants may be a key pathway to transform insoluble iron into soluble forms. The dissolution of dust minerals strongly depends on solution pH, which is sensitive to the heterogeneous uptake of soluble gases by the dust particle. Due to the complexity, previous model assessments generally use a common assumption in thermodynamical equilibrium between gas and aerosol phases. Here, we compiled an emission inventory of iron from combustion and dust source, and incorporated a dust iron dissolution scheme in a global chemistry-aerosol transport model (IMPACT). We will examine and discuss the uncertainties in estimation of dissolved iron as well as comparisons of the model results with available observations.

Use of dust storm observations on satellite images to identify areas vulnerable to severe wind erosion

USGS Publications Warehouse

Breed, C.S.; McCauley, J.F.

1986-01-01

Blowing dust is symptomatic of severe wind erosion and deterioration of soils in areas undergoing dessication and/or devegetation. Dust plumes on satellite images can commonly be traced to sources in marginally arable semiarid areas where protective lag gravels or vegetation have been removed and soils are dry, as demonstrated for the Portales Valley, New Mexico. Images from Landsat and manned orbiters such as Skylab and the Space Shuttle are useful for illustrating the regional relations of airborne dust plumes to source areas. Geostationary satellites such as GOES are useful in tracking the time-histories of episodic dust storms. These events sometimes go unrecognized by weather observers and are the precursors of long-term land degradation trends. In areas where soil maps and meteorological data are inadequate, satellite images provide a means for identifying problem areas where measures are needed to control or mitigate wind erosion. ?? 1986 D. Reidel Publishing Company.

Lead concentrations and isotope ratios in street dust determined by electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

PubMed

Nageotte, S M; Day, J P

1998-01-01

A major source of environmental lead, particularly in urban areas, has been from the combustion of leaded petrol. Street dust has previously been used to assess urban lead contamination, and the dust itself can also be a potential source of lead ingestion, particularly to children. The progressive reduction of lead in petrol, in recent years, would be expected to have been reflected in a reduction of lead in urban dust. We have tested this hypothesis by repeating an earlier survey of Manchester street dust and carrying out a comparable survey in Paris. Samples were collected from streets and parks, lead was extracted by digestion with concentrated nitric acid and determined by electrothermal atomic absorption spectrometry. Lead isotope ratios were measured by inductively coupled plasma mass spectrometry. Results for Manchester show that lead concentrations have fallen by about 40% (street dust averages, 941 micrograms g-1 (ppm) in 1975 down to 569 ppm in 1997). In Paris, the lead levels in street dust are much higher and significant differences were observed between types of street (not seen in Manchester). Additionally, lead levels in parks were much lower than in Manchester. Samples collected under the Eiffel Tower had very high concentrations and lead isotope ratios showed that this was unlikely to be fallout from motor vehicles but could be due to the paint used on the tower. Isotope ratios measurements also revealed that lead additives used in France and the UK come from different sources.

Geochemical variations in aeolian mineral particles from the Sahara-Sahel Dust Corridor.

PubMed

Moreno, Teresa; Querol, Xavier; Castillo, Sonia; Alastuey, Andrés; Cuevas, Emilio; Herrmann, Ludger; Mounkaila, Mohammed; Elvira, Josep; Gibbons, Wes

2006-10-01

The Sahara-Sahel Dust Corridor runs from Chad to Mauritania and expels huge amounts of mineral aerosols into the Atlantic Ocean. Data on samples collected from Algeria, Chad, Niger, and Western Sahara illustrate how corridor dust mineralogy and chemistry relate to geological source and weathering/transport history. Dusts sourced directly from igneous and metamorphic massifs are geochemically immature, retaining soluble cations (e.g., K, Na, Rb, Sr) and accessory minerals containing HFSE (e.g., Zr, Hf, U, Th) and REE. In contrast, silicate dust chemistry in desert basins (e.g., Bodélé Depression) is influenced by a longer history of transport, physical winnowing (e.g., loss of Zr, Hf, Th), chemical leaching (e.g., loss of Na, K, Rb), and mixing with intrabasinal materials such as diatoms and evaporitic salts. Mineral aerosols blown along the corridor by the winter Harmattan winds mix these basinal and basement materials. Dusts blown into the corridor from sub-Saharan Africa during the summer monsoon source from deeply chemically weathered terrains and are therefore likely to be more kaolinitic and stripped of mobile elements (e.g., Na, K, Mg, Ca, LILE), but retain immobile and resistant elements (e.g., Zr, Hf, REE). Finally, dusts blown southwestwards into the corridor from along the Atlantic Coastal Basin will be enriched in carbonate from Mesozoic-Cenozoic marine limestones, depleted in Th, Nb, and Ta, and locally contaminated by uranium-bearing phosphate deposits.