Photochemical organonitrate formation in wet aerosols

NASA Astrophysics Data System (ADS)

Lim, Yong Bin; Kim, Hwajin; Kim, Jin Young; Turpin, Barbara J.

2016-10-01

Water is the most abundant component of atmospheric fine aerosol. However, despite rapid progress, multiphase chemistry involving wet aerosols is still poorly understood. In this work, we report results from smog chamber photooxidation of glyoxal- and OH-containing ammonium sulfate or sulfuric acid particles in the presence of NOx and O3 at high and low relative humidity. Particles were analyzed using ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). During the 3 h irradiation, OH oxidation products of glyoxal that are also produced in dilute aqueous solutions (e.g., oxalic acids and tartaric acids) were formed in both ammonium sulfate (AS) aerosols and sulfuric acid (SA) aerosols. However, the major products were organonitrogens (CHNO), organosulfates (CHOS), and organonitrogen sulfates (CHNOS). These were also the dominant products formed in the dark chamber, indicating non-radical formation. In the humid chamber (> 70 % relative humidity, RH), two main products for both AS and SA aerosols were organonitrates, which appeared at m / z- 147 and 226. They were formed in the aqueous phase via non-radical reactions of glyoxal and nitric acid, and their formation was enhanced by photochemistry because of the photochemical formation of nitric acid via reactions of peroxy radicals, NOx and OH during the irradiation.

Mercury Wet Scavenging and Deposition Differences by Precipitation Type.

PubMed

Kaulfus, Aaron S; Nair, Udaysankar; Holmes, Christopher D; Landing, William M

2017-03-07

We analyze the effect of precipitation type on mercury wet deposition using a new database of individual rain events spanning the contiguous United States. Measurements from the Mercury Deposition Network (MDN) containing single rainfall events were identified and classified into six precipitation types. Mercury concentrations in surface precipitation follow a power law of precipitation depth that is modulated by precipitation system morphology. After controlling for precipitation depth, the highest mercury deposition occurs in supercell thunderstorms, with decreasing deposition in disorganized thunderstorms, quasi-linear convective systems (QLCS), extratropical cyclones, light rain, and land-falling tropical cyclones. Convective morphologies (supercells, disorganized, and QLCS) enhance wet deposition by a factor of at least 1.6 relative to nonconvective morphologies. Mercury wet deposition also varies by geographic region and season. After controlling for other factors, we find that mercury wet deposition is greater over high-elevation sites, seasonally during summer, and in convective precipitation.

Aerosol Production from Charbroiled and Wet-Fried Meats

NASA Astrophysics Data System (ADS)

Niedziela, R. F.; Blanc, L. E.

2012-12-01

Previous work in our laboratory focused on the chemical and optical characterization of aerosols produced during the dry-frying of different meat samples. This method yielded a complex ensemble of particles composed of water and long-chain fatty acids with the latter dominated by oleic, stearic, and palmitic acids. The present study examines how wet-frying and charbroiling cooking methods affect the physical and chemical properties of their derived aerosols. Samples of ground beef, salmon, chicken, and pork were subject to both cooking methods in the laboratory, with their respective aerosols swept into a laminar flow cell where they were optically analyzed in the mid-infrared and collected through a gas chromatography probe for chemical characterization. This presentation will compare and contrast the nature of the aerosols generated in each cooking method, particularly those produced during charbroiling which exposes the samples, and their drippings, to significantly higher temperatures. Characterization of such cooking-related aerosols is important because of the potential impact of these particles on air quality, particularly in urban areas.

Aerosol Deposition in Health and Disease

PubMed Central

2012-01-01

Abstract The success of inhalation therapy is not only dependent upon the pharmacology of the drugs being inhaled but also upon the site and extent of deposition in the respiratory tract. This article reviews the main mechanisms affecting the transport and deposition of inhaled aerosol in the human lung. Aerosol deposition in both the healthy and diseased lung is described mainly based on the results of human studies using nonimaging techniques. This is followed by a discussion of the effect of flow regime on aerosol deposition. Finally, the link between therapeutic effects of inhaled drugs and their deposition pattern is briefly addressed. Data show that total lung deposition is a poor predictor of clinical outcome, and that regional deposition needs to be assessed to predict therapeutic effectiveness. Indeed, spatial distribution of deposited particles and, as a consequence, drug efficiency is strongly affected by particle size. Large particles (>6 μm) tend to mainly deposit in the upper airway, limiting the amount of drugs that can be delivered to the lung. Small particles (<2 μm) deposit mainly in the alveolar region and are probably the most apt to act systemically, whereas the particle in the size range 2–6 μm are be best suited to treat the central and small airways. PMID:22686623

Characterisation of nutrients wet deposition under influence of Saharan dust at Puerto-Rico in Caribbean Sea

NASA Astrophysics Data System (ADS)

Desboeufs, Karine; Formenti, Paola; Triquet, Sylvain; Laurent, Benoit; Denjean, Cyrielle; Gutteriez-Moreno, Ian E.; Mayol-Bracero, Olga L.

2015-04-01

Large quantities of African dust are carried across the North Atlantic toward the Caribbean every summer by Trade Winds. Atmospheric deposition of dust aerosols, and in particular wet deposition, is widely acknowledged to be the major delivery pathway for nutrients to ocean ecosystems, as iron, phosphorus and various nitrogen species. The deposition of this dustis so known to have an important impact on biogeochemical processes in the Tropical and Western Atlantic Ocean and Caribbean including Puerto-Rico. However, very few data exists on the chemical composition in nutrients in dusty rain in this region. In the framework of the Dust-ATTAcK project, rainwater was collected at the natural reserve of Cape San Juan (CSJ) (18.38°N, 65.62°W) in Puerto-Ricobetween 20 June 2012 and 12 July 2012 during thedusty period. A total of 7 rainwater events were sampled during various dust plumes. Complementary chemical analyses on aerosols in suspension was also determined during the campaign. The results on dust composition showed that no mixing with anthropogenic material was observed, confirming dust aerosols were the major particles incorporated in rain samples. The partitioning between soluble and particulate nutrients in rain samples showed that phosphorous solubility ranged from 30 and 80%. The average Fe solubility was around 0.5%, in agreement with Fe solubility observed in rains collected in Niger during African monsoon. That means that the high solubility measurements previously observed in Caribbean was probably due to an anthropogenic influence. Atmospheric wet deposition fluxes of soluble and total nutrients (N, P, Si, Fe, Co, Cu, Mn, Ni, Zn) to Caribbean Sea were determined. Atmospheric P and N inputs were strongly depleted relative to the stoichiometry of phytoplankton Fe, N, P and Si requirements.The nitrogen speciation was also determined and showed the predominance of ammonium form. 3-D modeling was used to estimate the spatial extend of these fluxes over the

Formation and deposition of volcanic sulfate aerosols on Mars

NASA Technical Reports Server (NTRS)

Settle, M.

1979-01-01

The paper considers the formation and deposition of volcanic sulfate aerosols on Mars. The rate limiting step in sulfate aerosol formation on Mars is the gas phase oxidation of SO2 by chemical reactions with O, OH, and HO2; submicron aerosol particles would circuit Mars and then be removed from the atmosphere by gravitational forces, globally dispersed, and deposited over a range of equatorial and mid-latitudes. Volcanic sulfate aerosols on Mars consist of liquid droplets and slurries containing sulfuric acid; aerosol deposition on a global or hemispheric scale could account for the similar concentrations of sulfur within surficial soils at the two Viking lander sites.

Modeling investigation of light-absorbing aerosols in the Amazon Basin during the wet season

NASA Astrophysics Data System (ADS)

Wang, Qiaoqiao; Saturno, Jorge; Chi, Xuguang; Walter, David; Lavric, Jost; Moran-Zuloaga, Daniel; Ditas, Florian; Pöhlker, Christopher; Brito, Joel; Carbone, Samara; Artaxo, Paulo; Andreae, Meinrat

2017-04-01

We use a global chemical transport model (GEOS-Chem) to interpret observed light-absorbing aerosols in Amazonia during the wet season. Observed aerosol properties, including black carbon (BC) concentration and light absorption, at the Amazon Tall Tower Observatory (ATTO) site in the central Amazon have relatively low background levels but frequently show high peaks during the study period of January-April 2014. With daily temporal resolution for open fire emissions and modified aerosol optical properties, our model successfully captures the observed variation in fine/coarse aerosol and BC concentrations as well as aerosol light absorption and its wavelength dependence over the Amazon Basin. The source attribution in the model indicates the important influence of open fire on the observed variances of aerosol concentrations and absorption, mainly from regional sources (northern South America) and from northern Africa. The contribution of open fires from these two regions is comparable, with the latter becoming more important in the late wet season. The analysis of correlation and enhancement ratios of BC versus CO suggests transport times of < 3 days for regional fires and 11 days for African plumes arriving at ATTO during the wet season. The model performance of long-range transport of African plumes is also evaluated with observations from AERONET, MODIS, and CALIOP. Simulated absorption aerosol optical depth (AAOD) averaged over the wet season is lower than 0.0015 over the central Amazon, including the ATTO site. We find that more than 50% of total absorption at 550 nm is from BC, except for the northeastern Amazon and the Guianas, where the influence of dust becomes significant (up to 35 %). The brown carbon contribution is generally between 20 and 30 %. The distribution of absorption Ångström exponents (AAE) suggests more influence from fossil fuel combustion in the southern part of the basin (AAE 1) but more open fire and dust influence in the northern part

Characteristics of Wet Deposition in Japan

NASA Astrophysics Data System (ADS)

Iwasaki, A.; Arakaki, T.

2017-12-01

Acid deposition survey in Japan has started since 1991 by Japan Environmental Laboratories Association (JELA). The JELA has about 60 monitoring sites for wet deposition including remote, rural and urban area. The measured constituents of wet deposition are; precipitation, pH, electric conductivity, major Anions, and major Cations. From those data, we analyze spatial and temporal variations of wet deposition components in Japan. Among the 60 monitoring sites, 39 sampling sites were selected in this study, which have kept sampling continuously between 2003JFY and 2014JFY. All samples were collected by wet-only samplers. To analyze area characteristics, all the areas were divided into 6 regions; Northern part of Japan (NJ), Facing the Japan Sea (JS), Eastern part of Japan (EJ), Central part of Japan (CJ), Western part of Japan (WJ) and Southern West Islands (SW). NO3- and non-sea-salt-SO42- (nss-SO42-) are major components of rain acidification. Especially, between December and February (winter) the air mass from west affected the temporal variations of those acid components and the concentrations were higher in JS and WJ regions than those in other regions. Japanese ministry of the Environment reported that mixing ratio of NO2 in Japan has been less than 0.04ppm since 1976, and that of SO2 has been less than 0.02ppm since 1978. Their concentrations in Japan have remained flat or slowly decreased recently. However the temporal variations of NO3-/nss-SO42- ratio in winter in JS region were significantly increased on average at 2.2% y-1 from 2003JFY to 2014JFY. The results suggest that long-range transboundary air pollutants increased NO3- concentrations and NO3-/nss-SO42- ratio.

Dispersion of aerosol particles in the atmosphere: Fukushima

NASA Astrophysics Data System (ADS)

Haszpra, Tímea; Lagzi, István; Tél, Tamás

2013-04-01

Investigation of dispersion and deposition of aerosol particles in the atmosphere is an essential issue, because they have an effect on the biosphere and atmosphere. Moreover, aerosol particles have different transport properties and chemical and physical transformations in the atmosphere compared to gas phase air pollutants. The motion of a particle is described by a set of ordinary differential equations. The large-scale dynamics in the horizontal direction can be described by the equations of passive scalar advection, but in the vertical direction a well-defined terminal velocity should be taken into account as a term added to the vertical wind component. In the planetary boundary layer turbulent diffusion has an important role in the particle dispersion, which is taken into account by adding stochastic terms to the deterministic equations above. Wet deposition is also an essential process in the lower levels of the atmosphere, however, its precise parameterization is a challenge. For the simulations the wind field and other necessary data were taken from the ECMWF ERA-Interim database. In the case of the Fukushima Daiichi nuclear disaster (March-April 2011) radioactive aerosol particles were also released in the planetary boundary layer. Simulations (included the continuous and varying emission from the nuclear power plant) will be presented for the period of 14-23 March. Results show that wet deposition also has to be taken into consideration in the lower levels of the atmosphere. Furthermore, dynamical system characteristics are evaluated for the aerosol particle dynamics. The escape rate of particles was estimated both with and without turbulent diffusion, and in both cases when there was no wet deposition and also when wet deposition was taken into consideration.

A numerical study of the effects of aerosol hygroscopic properties to dry deposition on a broad-leaved forest

NASA Astrophysics Data System (ADS)

Katata, Genki; Kajino, Mizuo; Matsuda, Kazuhide; Takahashi, Akira; Nakaya, Ko

2014-11-01

To investigate the impact of hygroscopic growth on dry deposition onto forest canopies, numerical simulations of PM2.5 sulfate deposition using a multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) ware performed. The scheme of particle dry deposition in SOLVEG was extended for application to a broad-leaved forest. An aerosol hygroscopic model based on the widely used κ-Köhler theory was incorporated into the model to calculate water uptake by the aerosols. The model accurately reproduced essential turbulent exchange fluxes (momentum, heat, and water vapor) over the canopies and the soil temperature and moisture for a deciduous broad-leaved forest in central Japan. Temporal variations in the measured PM2.5 sulfate deposition velocity were generally reproduced by the model. By considering an increase in particle diameter due to hygroscopic growth, the prediction accuracy of the modeled deposition velocity under humid conditions was improved. Numerical experiments for varying aerosol size distributions and hygroscopic properties showed that the geometric mean diameter and hygroscopicity of particles have a large influence on hygroscopic growth levels. The results also suggested that the deposition velocity of wet particles increased due to hygroscopic growth when the relative humidity (RH) was approximately 50%, and that the velocity reached five times greater than that under dry conditions when RH exceeded 95%.

METHODS OF CALCULATINAG LUNG DELIVERY AND DEPOSITION OF AEROSOL PARTICLES

EPA Science Inventory

Lung deposition of aerosol is measured by a variety of methods. Total lung deposition can be measured by monitoring inhaled and exhaled aerosols in situ by laser photometry or by collecting the aerosols on filters. The measurements can be performed accurately for stable monod...

Changes in wet nitrogen deposition in the United States between 1985 and 2012

NASA Astrophysics Data System (ADS)

Du, Enzai; de Vries, Wim; Galloway, James N.; Hu, Xueyang; Fang, Jingyun

2014-09-01

The United States (US) is among the global hotspots of nitrogen (N) deposition and assessing the temporal trends of wet N deposition is relevant to quantify the effectiveness of existing N regulation policies and its consequent environmental effects. This study analyzed changes in observed wet deposition of dissolved inorganic N (DIN = ammonium + nitrate) in the US between 1985 and 2012 by applying a Mann-Kendall test and Regional Kendall test. Current wet DIN deposition (2011-2012) data were used to gain insight in the current pattern of N deposition. Wet DIN deposition generally decreased going from Midwest > Northeast > South > West region with a national mean rate of 3.5 kg N ha-1 yr-1. Ammonium dominated wet DIN deposition in the Midwest, South and West regions, whereas nitrate and ammonium both contributed a half in the Northeast region. Wet DIN deposition showed no significant change at the national scale between 1985 and 2012, but profound changes occurred in its components. Wet ammonium deposition showed a significant increasing trend at national scale (0.013 kg N ha-1 yr-2), with the highest increase in the Midwest and eastern part of the South region. Inversely, wet nitrate deposition decreased significantly at national scale (-0.014 kg N ha-1 yr-2), with the largest reduction in the Northeast region. Overall, ratios of ammonium versus nitrate in wet deposition showed a significant increase in all the four regions, resulting in a transition of the dominant N species from nitrate to ammonium. Distinct magnitudes, trends and patterns of wet ammonium and nitrate deposition suggest the needs to control N emissions by species and regions to avoid negative effects of N deposition on ecosystem health and function in the US.

Research of transport and deposition of aerosol in human airway replica

NASA Astrophysics Data System (ADS)

Lizal, Frantisek; Jedelsky, Jan; Elcner, Jakub; Durdina, Lukas; Halasova, Tereza; Mravec, Filip; Jicha, Miroslav

2012-04-01

Growing concern about knowledge of aerosol transport in human lungs is caused by great potential of use of inhaled pharmaceuticals. Second substantial motive for the research is an effort to minimize adverse effects of particular matter emitted by traffic and industry on human health. We created model geometry of human lungs to 7th generation of branching. This model geometry was used for fabrication of two physical models. The first one is made from thin walled transparent silicone and it allows a measurement of velocity and size of aerosol particles by Phase Doppler Anemometry (PDA). The second one is fabricated by stereolithographic method and it is designed for aerosol deposition measurements. We provided a series of measurements of aerosol transport in the transparent model and we ascertained remarkable phenomena linked with lung flow. The results are presented in brief. To gather how this phenomena affects aerosol deposition in human lungs we used the second model and we developed a technique for deposition fraction and deposition efficiency assessment. The results confirmed that non-symmetric and complicated shape of human airways essentially affects transport and deposition of aerosol. The research will now focus on deeper insight in aerosol deposition.

Multicomponent aerosol particle deposition in a realistic cast of the human upper respiratory tract.

PubMed

Nordlund, Markus; Belka, Miloslav; Kuczaj, Arkadiusz K; Lizal, Frantisek; Jedelsky, Jan; Elcner, Jakub; Jicha, Miroslav; Sauser, Youri; Le Bouhellec, Soazig; Cosandey, Stephane; Majeed, Shoaib; Vuillaume, Grégory; Peitsch, Manuel C; Hoeng, Julia

2017-02-01

Inhalation of aerosols generated by electronic cigarettes leads to deposition of multiple chemical compounds in the human airways. In this work, an experimental method to determine regional deposition of multicomponent aerosols in an in vitro segmented, realistic human lung geometry was developed and applied to two aerosols, i.e. a monodisperse glycerol aerosol and a multicomponent aerosol. The method comprised the following steps: (1) lung cast model preparation, (2) aerosol generation and exposure, (3) extraction of deposited mass, (4) chemical quantification and (5) data processing. The method showed good agreement with literature data for the deposition efficiency when using a monodisperse glycerol aerosol, with a mass median aerodynamic diameter (MMAD) of 2.3 μm and a constant flow rate of 15 L/min. The highest deposition surface density rate was observed in the bifurcation segments, indicating inertial impaction deposition. The experimental method was also applied to the deposition of a nebulized multicomponent aerosol with a MMAD of 0.50 μm and a constant flow rate of 15 L/min. The deposited amounts of glycerol, propylene glycol and nicotine were quantified. The three analyzed compounds showed similar deposition patterns and fractions as for the monodisperse glycerol aerosol, indicating that the compounds most likely deposited as parts of the same droplets. The developed method can be used to determine regional deposition for multicomponent aerosols, provided that the compounds are of low volatility. The generated data can be used to validate aerosol deposition simulations and to gain insight in deposition of electronic cigarette aerosols in human airways.

Wet deposition of mercury at Lhasa, the capital city of Tibet.

PubMed

Huang, Jie; Kang, Shichang; Wang, Shuxiao; Wang, Long; Zhang, Qianggong; Guo, Junming; Wang, Kang; Zhang, Guoshuai; Tripathee, Lekhendra

2013-03-01

Quantifying the contribution of mercury (Hg) in wet deposition is important for understanding Hg biogeochemical cycling and anthropogenic sources, and verifying atmospheric models. Mercury in wet deposition was measured over the year 2010, in Lhasa the capital and largest city in Tibet. Precipitation samples were analyzed for total Hg (HgT), particulate-bound Hg (HgP), and reactive Hg (HgR). The volume-weighted mean (VWM) concentrations and wet deposition fluxes of HgT, HgP and HgR in precipitation were 24.8 ng L-1 and 8.2 μg m-2 yr-1, 19.9 ng L-1 and 7.1 μg m-2 yr-1, and 0.5 ng L-1 and 0.19 μg m-2 yr-1, respectively. Concentrations of HgT and HgP were statistically higher during the non-monsoon season than during the monsoon season, while HgR concentrations were statistically higher during the monsoon season than during the non-monsoon season. Most HgT, HgP and HgR wet deposition occurred during the monsoon season. Concentrations of HgP and HgR were 77% and 5% of the HgT on average (VWM), respectively. Concentrations of HgT and HgP were weakly negatively correlated with precipitation amount (r2 = 0.09 and 0.10; p < 0.05), indicating that below-cloud scavenging of Hg from the local atmosphere was an important mechanism contributing Hg to precipitation. High HgP%, as well as a significant positive correlation between HgT and HgP, confirms that Hg wet deposition at Lhasa was primarily occurring in the form of atmospheric HgP below-cloud scavenging. Moreover, the HgT concentration, rather than the precipitation amount, was found to be the governing factor affecting HgT wet deposition flux. A comparison among modeled wet and dry deposition fluxes, and measurements suggested that estimates of both wet and dry Hg deposition fluxes by the GEOS-Chem model were 2 to 3 times higher than the measured annual wet flux. Copyright © 2013 Elsevier B.V. All rights reserved.

Relative contributions of gaseous oxidized mercury and fine and coarse particle-bound mercury to mercury wet deposition at nine monitoring sites in North America

NASA Astrophysics Data System (ADS)

Cheng, Irene; Zhang, Leiming; Mao, Huiting

2015-08-01

Relative contributions to mercury wet deposition by gaseous oxidized mercury (%GOM) and fine and coarse particle-bound mercury (%FPBM and %CPBM) were estimated making use of monitored FPBM air concentration and mercury wet deposition at nine North American locations. Scavenging ratios of particulate inorganic ions (K+ and Ca2+, Mg2+ and Na+) were used as a surrogate for those of FPBM and CPBM, respectively. FPBM and CPBM were estimated to contribute 8-36% and 5-27%, respectively, depending on the location, to total wet deposition. The rest of the 39-87% was attributed to the contribution of GOM. The average %GOM, %FPBM and %CPBM among all locations were 65%, 17%, and 18%, respectively. The relative distributions of %GOM, %FPBM, and %CPBM were influenced by Hg(II) gas-particle partitioning, urban site characteristics, and precipitation type. At the regional scale, %GOM dominated over %FPBM and %CPBM. However, the sum of FPBM and CPBM contributed to nearly half of the total Hg wet deposition in urban areas, which was greater than other site categories and is attributed to higher FPBM air concentrations. At four locations, %FPBM exceeded %GOM during winter in contrast to summer, suggesting the efficient snow scavenging of aerosols. The results from this study are useful in improving mercury transport models since most of these models do not estimate CPBM, but frequently use monitored mercury wet deposition data for model evaluation.

Chamber for Aerosol Deposition of Bioparticles

NASA Technical Reports Server (NTRS)

Kern, Roger; Kirschner, Larry

2008-01-01

Laboratory apparatus is depicted that is a chamber for aerosol deposition of bioparticles on surfaces of test coupons. It is designed for primary use in inoculating both flat and three-dimensional objects with approximately reproducible, uniform dispersions of bacterial spores of the genus Bacillus so that the objects could be used as standards for removal of the spores by quantitative surface sampling and/or cleaning processes. The apparatus is also designed for deposition of particles other than bacterial spores, including fungal spores, viruses, bacteriophages, and standard micron-sized beads. The novelty of the apparatus lies in the combination of a controllable nebulization system with a settling chamber large enough to contain a significant number of test coupons. Several companies market other nebulizer systems, but none are known to include chambers for deposition of bioparticles to mimic the natural fallout of bioparticles. The nebulization system is an expanded and improved version of commercially available aerosol generators that include nebulizers and drying columns. In comparison with a typical commercial aerosol generator, this system includes additional, higher-resolution flowmeters and an additional pressure regulator. Also, unlike a typical commercial aerosol generator, it includes stopcocks for separately controlling flows of gases to the nebulizer and drying column. To maximize the degree of uniformity of dispersion of bioaerosol, the chamber is shaped as an axisymmetrical cylinder and the aerosol generator is positioned centrally within the chamber and aimed upward like a fountain. In order to minimize electric charge associated with the aerosol particles, the drying column is made of aluminum, the drying column is in direct contact with an aluminum base plate, and three equally spaced Po-210 antistatic strips are located at the exit end of the drying column. The sides and top of the chamber are made of an acrylic polymer; to prevent

Validating CFD Predictions of Pharmaceutical Aerosol Deposition with In Vivo Data.

PubMed

Tian, Geng; Hindle, Michael; Lee, Sau; Longest, P Worth

2015-10-01

CFD provides a powerful approach to evaluate the deposition of pharmaceutical aerosols; however, previous studies have not compared CFD results of deposition throughout the lungs with in vivo data. The in vivo datasets selected for comparison with CFD predictions included fast and slow clearance of monodisperse aerosols as well as 2D gamma scintigraphy measurements for a dry powder inhaler (DPI) and softmist inhaler (SMI). The CFD model included the inhaler, a characteristic model of the mouth-throat (MT) and upper tracheobronchial (TB) airways, stochastic individual pathways (SIPs) representing the remaining TB region, and recent CFD-based correlations to predict pharmaceutical aerosol deposition in the alveolar airways. For the monodisperse aerosol, CFD predictions of total lung deposition agreed with in vivo data providing a percent relative error of 6% averaged across aerosol sizes of 1-7 μm. With the DPI and SMI, deposition was evaluated in the MT, central airways (bifurcations B1-B7), and intermediate plus peripheral airways (B8 through alveoli). Across these regions, CFD predictions produced an average relative error <10% for each inhaler. CFD simulations with the SIP modeling approach were shown to accurately predict regional deposition throughout the lungs for multiple aerosol types and different in vivo assessment methods.

Validating CFD Predictions of Pharmaceutical Aerosol Deposition with In Vivo Data

PubMed Central

Tian, Geng; Hindle, Michael; Lee, Sau; Longest, P. Worth

2015-01-01

Purpose CFD provides a powerful approach to evaluate the deposition of pharmaceutical aerosols; however, previous studies have not compared CFD results of deposition throughout the lungs with in vivo data. Methods The in vivo datasets selected for comparison with CFD predictions included fast and slow clearance of monodisperse aerosols as well as 2D gamma scintigraphy measurements for a dry powder inhaler (DPI) and softmist inhaler (SMI). The CFD model included the inhaler, a characteristic model of the mouth-throat (MT) and upper tracheobronchial (TB) airways, stochastic individual pathways (SIPs) representing the remaining TB region, and recent CFD-based correlations to predict pharmaceutical aerosol deposition in the alveolar airways. Results For the monodisperse aerosol, CFD predictions of total lung deposition agreed with in vivo data providing a percent relative error of 6% averaged across aerosol sizes of 1-7μm. With the DPI and SMI, deposition was evaluated in the MT, central airways (bifurcations B1-B7), and intermediate plus peripheral airways (B8 through alveoli). Across these regions, CFD predictions produced an average relative error <10% for each inhaler. Conclusions CFD simulations with the SIP modeling approach were shown to accurately predict regional deposition throughout the lungs for multiple aerosol types and different in vivo assessment methods. PMID:25944585

The role of anisotropic expansion for pulmonary acinar aerosol deposition

PubMed Central

Hofemeier, Philipp; Sznitman, Josué

2016-01-01

Lung deformations at the local pulmonary acinar scale are intrinsically anisotropic. Despite progress in imaging modalities, the true heterogeneous nature of acinar expansion during breathing remains controversial, where our understanding of inhaled aerosol deposition still widely emanates from studies under self-similar, isotropic wall motions. Building on recent 3D models of multi-generation acinar networks, we explore in numerical simulations how different hypothesized scenarios of anisotropic expansion influence deposition outcomes of inhaled aerosols in the acinar depths. While the broader range of particles acknowledged to reach the acinar region (dp = 0.005–5.0 μm) are largely unaffected by the details of anisotropic expansion under tidal breathing, our results suggest nevertheless that anisotropy modulates the deposition sites and fractions for a narrow band of sub-micron particles (dp ~ 0.5–0.75 μm), where the fate of aerosols is greatly intertwined with local convective flows. Our findings underscore how intrinsic aerosol motion (i.e. diffusion, sedimentation) undermines the role of anisotropic wall expansion that is often attributed in determining aerosol mixing and acinar deposition. PMID:27614613

COMPARISONS OF SPATIAL PATTERNS OF WET DEPOSITION TO MODEL PREDICTIONS

EPA Science Inventory

The Community Multiscale Air Quality model, (CMAQ), is a "one-atmosphere" model, in that it uses a consistent set of chemical reactions and physical principles to predict concentrations of primary pollutants, photochemical smog, and fine aerosols, as well as wet and dry depositi...

Aerosol characteristics and sources for the Amazon basin during the wet season

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

Artaxo, P.; Maenhaut, W.; Storms, H.

1990-09-20

Fine (< 2.0 {mu}m) and coarse (2.0 - 15 {mu}m) aerosol fractions were collected using stacked filter units, at three sites under the forest canopy and at three levels of a tower inside the jungle. Particle-induced x-ray emission (PIXE) was used to measure concentrations Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr, and Pb. Morphological and trace element measurements of individual particles were carried out by automated electron probe x-ray microanalysis. Gravimetric analysis was performed to obtain the fine and coarse aerosol mass concentration. The concentrations ofmore » soil dust related elements (Al, Si, Ti, Fe, Mn) were 5 times larger in the wet season compared to the 1985 ABLE 2A dry season experiment. Biogenic aerosol related elements in the fine fraction showed lower concentrations in the wet season. Fine aerosol mass concentration averaged only 2.1 {plus minus} 0.7 {mu}g m{sup {minus}3}, while the average coarse mass concentration was 6.1 {plus minus} 1.8 {mu}g m{sup {minus}3}. Sulfur concentrations averaged 76 {plus minus} 14 ng m{sup {minus}3} in the fine fraction and 37 {plus minus} 9 ng m{sup {minus}3} in the coarse fraction. Only two factors explained about 90% of the data variability for the fine and coarse aerosol fractions. These were soil dust (represented mainly by Al, Si, Ti, Mn, and Fe) and biogenic aerosol (represented by K, P, Cl, S, Zn, and the aerosol mass concentration). Biogenic particles account for 55-95% of the airborne concentrations and consisted of leaf fragments, pollen grains, fungi, algae, and other types of particles. It is possible that biogenic particles can play an important role in the global aerosol budget and in the global biogeochemical cycles of various elements.« less

Removal of Atmospheric Ethanol by Wet Deposition: A Global Flux Estimate

NASA Astrophysics Data System (ADS)

Felix, J. D. D.; Willey, J. D.; Avery, B.; Thomas, R.; Mullaugh, K.; Kieber, R. J.; Mead, R. N.; Helms, J. R.; Campos, L.; Shimizu, M. S.; Guibbina, F.

2017-12-01

Global ethanol fuel consumption has increased exponentially over the last two decades and the US plans to double annual renewable fuel production in the next five years as required by the renewable fuel standard. Regardless of the technology or feedstock used to produce the renewable fuel, the primary end product will be ethanol. Increasing ethanol fuel consumption will have an impact on the oxidizing capacity of the atmosphere and increase atmospheric concentrations of the secondary pollutant peroxyacetyl nitrate as well a variety of VOCs with relatively high ozone reactivities (e.g. ethanol, formaldehyde, acetaldehyde). Despite these documented effects of ethanol emissions on atmospheric chemistry, current global atmospheric ethanol budget models have large uncertainties in the magnitude of ethanol sources and sinks. The presented work investigates the global wet deposition sink by providing the first estimate of the global wet deposition flux of ethanol (2.4 ± 1.6 Tg/yr) based on empirical wet deposition data (219 samples collected at 12 locations). This suggests the wet deposition sink removes between 6 and 17% of atmospheric ethanol annually. Concentrations of ethanol in marine wet deposition (25 ± 6 nM) were an order of magnitude less than in the majority of terrestrial deposition (345 ± 280 nM). Terrestrial deposition collected in locations impacted by high local sources of biofuel usage and locations downwind from ethanol distilleries were an order of magnitude higher in ethanol concentration (3090 ± 448 nM) compared to deposition collected in terrestrial locations not impacted by these sources. These results indicate that wet deposition of ethanol is heavily influenced by local sources and ethanol emission impacts on air quality may be more significant in highly populated areas. As established and developing countries continue to rapidly increase ethanol fuel consumption and subsequent emissions, understanding the magnitude of all ethanol sources and

The use of bulk collectors in monitoring wet deposition at high-altitude sites in winter

USGS Publications Warehouse

Ranalli, A.J.; Turk, J.T.; Campbell, D.H.

1997-01-01

Concentrations of dissolved ions from samples collected by wet/dry collectors were compared to those collected by bulk collectors at Halfmoon Creek and Ned Wilson Lake in western Colorado to determine if bulk collectors can be used to monitor wet deposition chemistry in remote, high-altitude regions in winter. Hydrogen-ion concentration was significantly lower (p 0.05) at Halfmoon Creek. Wet deposition concentrations were predicated from bulk deposition concentrations through linear regression analysis. Results indicate that anions (chloride, nitrate and sulfate) can be predicted with a high degree of confidence. Lack of significant differences between seasonal (winter and summer) ratios of bulk to wet deposition concentrations indicates that at sites where operation of a wet/dry collector during the winter is not practical, wet deposition concentrations can be predicted from bulk collector samples through regression analysis of wet and bulk deposition data collected during the summer.

Comparison of SPECT aerosol deposition data with a human respiratory tract model.

PubMed

Fleming, John S; Epps, Ben P; Conway, Joy H; Martonen, Ted B

2006-01-01

Three-dimensional (3D) radionuclide imaging provides detailed information on the distribution of inhaled aerosol material within the body. Analysis of the data can provide estimates of the deposition per airway generation. In this study, two different nebulizers have been used to deliver radiolabeled aerosols of different particle size to 12 human subjects. Medical imaging has been used to assess the deposition in the body. The deposition pattern has also been estimated using the International Commission on Radiological Protection (ICRP) empirical model and compared to values obtained by experiment. The results showed generally good agreement between model and experiment for both aerosols for the deposition in the extrathoracic and conducting airways. However, there were significant differences in the fate of the remainder of the aerosol between the amount deposited in the alveolar region and that exhaled. The inter-subject variability of deposition predicted by the model was significantly less than that measured, for all regions of the body. The model predicted quite well the differences in deposition distribution pattern between the two aerosols. In conclusion, this study has shown that the ICPR model of inhaled aerosol deposition shows areas of good agreement with results from experiment. However, there are also areas of disagreement, which may be explained by hygroscopic particle growth and individual variation in airway anatomy.

The role of anisotropic expansion for pulmonary acinar aerosol deposition.

PubMed

Hofemeier, Philipp; Sznitman, Josué

2016-10-03

Lung deformations at the local pulmonary acinar scale are intrinsically anisotropic. Despite progress in imaging modalities, the true heterogeneous nature of acinar expansion during breathing remains controversial, where our understanding of inhaled aerosol deposition still widely emanates from studies under self-similar, isotropic wall motions. Building on recent 3D models of multi-generation acinar networks, we explore in numerical simulations how different hypothesized scenarios of anisotropic expansion influence deposition outcomes of inhaled aerosols in the acinar depths. While the broader range of particles acknowledged to reach the acinar region (d p =0.005-5.0μm) are largely unaffected by the details of anisotropic expansion under tidal breathing, our results suggest nevertheless that anisotropy modulates the deposition sites and fractions for a narrow band of sub-micron particles (d p ~0.5-0.75μm), where the fate of aerosols is greatly intertwined with local convective flows. Our findings underscore how intrinsic aerosol motion (i.e. diffusion, sedimentation) undermines the role of anisotropic wall expansion that is often attributed in determining aerosol mixing and acinar deposition. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recent Rainfall and Aerosol Chemistry From Bermuda

NASA Astrophysics Data System (ADS)

Landing, W. M.; Shelley, R.; Kadko, D. C.

2014-12-01

This project was devoted to testing the use of Be-7 as a tracer for quantifying trace element fluxes from the atmosphere to the oceans. Rainfall and aerosol samples were collected between June 15, 2011 and July 27, 2013 at the Bermuda Institute of Ocean Sciences (BIOS) located near the eastern end of the island of Bermuda. Collectors were situated near ground level, clear of surrounding vegetation, at a meteorological monitoring station in front of the BIOS laboratory, about 10 m above sea level. This is a Bermuda Air Quality Program site used for ambient air quality monitoring. To quantify the atmospheric deposition of Be-7, plastic buckets were deployed for collection of fallout over ~3 week periods. Wet deposition was collected for trace element analysis using a specially modified "GEOTRACES" N-CON automated wet deposition collector. Aerosol samples were collected with a Tisch TE-5170V-BL high volume aerosol sampler, modified to collect 12 replicate samples on acid-washed 47mm diameter Whatman-41 filters, using procedures identical to those used for the US GEOTRACES aerosol program (Morton et al., 2013). Aerosol and rainfall samples were analyzed for total Na, Mg, Al, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Zr, Cd, Sb, Ba, La, Ce, Nd, Pb, Th, and U using ICPMS. Confirming earlier data from Bermuda, strong seasonality in rainfall and aerosol loading and chemistry was observed, particularly for aerosol and rainfall Fe concentrations when Saharan dust arrives in July/August with SE trajectories.

[Nutrients in atmospheric wet deposition in the East China Sea].

PubMed

Zhu, Yu-Mei; Liu, Su-Mei

2011-09-01

92 rainwater samples were collected at Shengsi Archipelago from January 2008 to December 2009. The pH and the concentrations of nutrients (NH4(+), NO3(-) + NO2(-), PO4(3-), SiO3(2-)) were analyzed using spectrophotometry to understand the impacts of the atmospheric wet deposition on the ecosystem of the East China Sea. The results showed that the pH of 85% samples were less than 5.0, and had significant effect on the environment. There were significant differences among monthly average concentrations of nutrients and rainfall and seasonal average wet deposition of nutrients in investigation periods. The annual average wet deposition flux was 52.05 mmol x (m2 x a) (-1) for DIN, 0.08 mmol x (m2 x a) (-1) for PO4(3-), 2.05 mmol x (m2 x a) (-1) for SiO3(2-). The average molar ratios of NO3(-)/NH4(+) is 0.73, N: P ratio is 684: 1, indicating that nutrients composition in rainwater was different from seawater of the East China Sea Shelf (10-150). The wet deposition may change the nutrients structure, pH and lead to change the phytoplankton production in the surface seawater of the East China Sea, even lead to the red tide.

Improved mapping of National Atmospheric Deposition Program wet-deposition in complex terrain using PRISM-gridded data sets

USGS Publications Warehouse

Latysh, Natalie E.; Wetherbee, Gregory Alan

2012-01-01

High-elevation regions in the United States lack detailed atmospheric wet-deposition data. The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) measures and reports precipitation amounts and chemical constituent concentration and deposition data for the United States on annual isopleth maps using inverse distance weighted (IDW) interpolation methods. This interpolation for unsampled areas does not account for topographic influences. Therefore, NADP/NTN isopleth maps lack detail and potentially underestimate wet deposition in high-elevation regions. The NADP/NTN wet-deposition maps may be improved using precipitation grids generated by other networks. The Parameter-elevation Regressions on Independent Slopes Model (PRISM) produces digital grids of precipitation estimates from many precipitation-monitoring networks and incorporates influences of topographical and geographical features. Because NADP/NTN ion concentrations do not vary with elevation as much as precipitation depths, PRISM is used with unadjusted NADP/NTN data in this paper to calculate ion wet deposition in complex terrain to yield more accurate and detailed isopleth deposition maps in complex terrain. PRISM precipitation estimates generally exceed NADP/NTN precipitation estimates for coastal and mountainous regions in the western United States. NADP/NTN precipitation estimates generally exceed PRISM precipitation estimates for leeward mountainous regions in Washington, Oregon, and Nevada, where abrupt changes in precipitation depths induced by topography are not depicted by IDW interpolation. PRISM-based deposition estimates for nitrate can exceed NADP/NTN estimates by more than 100% for mountainous regions in the western United States.

Improved mapping of National Atmospheric Deposition Program wet-deposition in complex terrain using PRISM-gridded data sets.

PubMed

Latysh, Natalie E; Wetherbee, Gregory Alan

2012-01-01

High-elevation regions in the United States lack detailed atmospheric wet-deposition data. The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) measures and reports precipitation amounts and chemical constituent concentration and deposition data for the United States on annual isopleth maps using inverse distance weighted (IDW) interpolation methods. This interpolation for unsampled areas does not account for topographic influences. Therefore, NADP/NTN isopleth maps lack detail and potentially underestimate wet deposition in high-elevation regions. The NADP/NTN wet-deposition maps may be improved using precipitation grids generated by other networks. The Parameter-elevation Regressions on Independent Slopes Model (PRISM) produces digital grids of precipitation estimates from many precipitation-monitoring networks and incorporates influences of topographical and geographical features. Because NADP/NTN ion concentrations do not vary with elevation as much as precipitation depths, PRISM is used with unadjusted NADP/NTN data in this paper to calculate ion wet deposition in complex terrain to yield more accurate and detailed isopleth deposition maps in complex terrain. PRISM precipitation estimates generally exceed NADP/NTN precipitation estimates for coastal and mountainous regions in the western United States. NADP/NTN precipitation estimates generally exceed PRISM precipitation estimates for leeward mountainous regions in Washington, Oregon, and Nevada, where abrupt changes in precipitation depths induced by topography are not depicted by IDW interpolation. PRISM-based deposition estimates for nitrate can exceed NADP/NTN estimates by more than 100% for mountainous regions in the western United States.

High Mercury Wet Deposition at a "Clean Air" Site in Puerto Rico.

PubMed

Shanley, James B; Engle, Mark A; Scholl, Martha; Krabbenhoft, David P; Brunette, Robert; Olson, Mark L; Conroy, Mary E

2015-10-20

Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds, during two complete years the site averaged 27.9 μg m(-2) yr(-1) wet Hg deposition, or about 30% more than Florida and the Gulf Coast, the highest deposition areas within the U.S. These high Hg deposition rates are driven in part by high rainfall, which averaged 2855 mm yr(-1). The volume-weighted mean Hg concentration was 9.8 ng L(-1), and was highest during summer and lowest during the winter dry season. Rainout of Hg (decreasing concentration with increasing rainfall depth) was minimal. The high Hg deposition was not supported by gaseous oxidized mercury (GOM) at ground level, which remained near global background concentrations (<10 pg m(-3)). Rather, a strong positive correlation between Hg concentrations and the maximum height of rain detected within clouds (echo tops) suggests that droplets in high convective cloud tops scavenge GOM from above the mixing layer. The high wet Hg deposition at this "clean air" site suggests that other tropical areas may be hotspots for Hg deposition as well.

Modeling dry and wet deposition of sulfate, nitrate, and ammonium ions in Jiuzhaigou National Nature Reserve, China using a source-oriented CMAQ model: Part II. Emission sector and source region contributions.

PubMed

Qiao, Xue; Tang, Ya; Kota, Sri Harsha; Li, Jingyi; Wu, Li; Hu, Jianlin; Zhang, Hongliang; Ying, Qi

2015-11-01

A source-oriented Community Multiscale Air Quality (CMAQ) model driven by the meteorological fields generated by the Weather Research and Forecasting (WRF) model was used to study the dry and wet deposition of nitrate (NO3(-)), sulfate (SO4(2-)), and ammonium (NH4(+)) ions in the Jiuzhaigou National Nature Reserve (JNNR), China from June to August 2010 and to identify the contributions of different emission sectors and source regions that were responsible for the deposition fluxes. Contributions from power plants, industry, transportation, domestic, biogenic, windblown dust, open burning, fertilizer, and manure management sources to deposition fluxes in JNNR watershed and four EANET sites are determined. In JNNR, 96%, 82%, and 87% of the SO4(2-), NO3(-) and NH4(+) deposition fluxes are in the form of wet deposition of the corresponding aerosol species. Industry and power plants are the two major sources of SO4(2-) deposition flux, accounting for 86% of the total wet deposition of SO4(2-), and industry has a higher contribution (56%) than that of power plants (30%). Power plants and industry are also the top sources that are responsible for NO3(-) wet deposition, and contributions from power plants (30%) are generally higher than those from industries (21%). The major sources of NH4(+) wet deposition flux in JNNR are fertilizer (48%) and manure management (39%). Source-region apportionment confirms that SO2 and NOx emissions from local and two nearest counties do not have a significant impact on predicted wet deposition fluxes in JNNR, with contributions less than 10%. While local NH3 emissions account for a higher fraction of the NH4(+) deposition, approximately 70% of NH4(+) wet deposition in JNNR originated from other source regions. This study demonstrates that S and N deposition in JNNR is mostly from long-range transport rather than from local emissions, and to protect JNNR, regional emission reduction controls are needed. Copyright © 2015 Elsevier B.V. All

Deposition flux of aerosol particles and 15 polycyclic aromatic hydrocarbons in the North China Plain.

PubMed

Wang, Xilong; Liu, Shuzhen; Zhao, Jingyu; Zuo, Qian; Liu, Wenxin; Li, Bengang; Tao, Shu

2014-04-01

The present study examined deposition fluxes of aerosol particles and 15 polycyclic aromatic hydrocarbons (PAHs) associated with the particles in the North China Plain. The annual mean deposition fluxes of aerosol particles and 15 PAHs were 0.69 ± 0.46 g/(m(2) ×d) and 8.5 ± 6.2 μg/(m(2) ×d), respectively. Phenanthrene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[k]fluoranthene were the dominant PAHs bound to deposited aerosol particles throughout the year. The total concentration of 15 PAHs in the deposited aerosol particles was the highest in winter but lowest in spring. The highest PAH concentration in the deposited aerosol particles in winter was because the heating processes highly increased the concentration in atmospheric aerosol particles. Low temperature and weak sunshine in winter reduced the degradation rate of deposited aerosol particle-bound PAHs, especially for those with low molecular weight. The lowest PAH concentration in deposited aerosol particles in spring resulted from the frequently occurring dust storms, which diluted PAH concentrations. The mean deposition flux of PAHs with aerosol particles in winter (16 μg/[m(2) ×d]) reached 3 times to 5 times that in other seasons (3.5-5.0 μg/[m(2) ×d]). The spatial variation of the deposition flux of PAHs with high molecular weight (e.g., benzo[a]pyrene) was consistent with their concentrations in the atmospheric aerosol particles, whereas such a phenomenon was not observed for those with low molecular weight (e.g., phenanthrene) because of their distinct hydrophobicity, Henry's law constant, and the spatially heterogeneous meteorological conditions. © 2013 SETAC.

Monthly dynamics of atmospheric wet nitrogen deposition on different spatial scales in China.

PubMed

Zhang, Qiongyu; Wang, Qiufeng; Xu, Li; Zhu, Jianxing; He, Nianpeng

2018-06-16

China is one of three global hotspots for nitrogen (N) deposition, which has concerned scientists and the public. While previous studies on N deposition in China have focused on its composition, spatial pattern, and interannual dynamics, its monthly dynamics in different regions remain unclear, hindering our ability to evaluate its ecological effects. Therefore, we obtained monthly wet N deposition data from196 sites after continuous network observations and published data in China and analyzed the monthly dynamics of NH 4 + -N, NO 3 - -N, and dissolved inorganic N (DIN=NH 4 + -N+NO 3 - -N) deposition fluxes on site, regional, and national scales. We observed that the deposition fluxes of NH 4 + -N, NO 3 - -N, and DIN in China showed clear monthly patterns and regional differences. In Northern China, wet N deposition predominantly showed a unimodal trend, whereas in Southern China, it revealed a bimodal trend or irregular fluctuations. During 2000-2016, NH 4 + -N, NO 3 - -N, and DIN deposition fluxes were estimated as 9.09, 6.12, and 15.21 kg N ha -1  year. -1 , respectively. Our findings enhance our understanding of atmospheric wet N deposition, and can serve as a reference for N deposition simulation experiments in different regions, and for generating long-term N deposition data for model optimization. Regional differences in the monthly dynamics of wet N deposition should be emphasized to accurately evaluate its ecological effects on terrestrial ecosystems in different regions.

Investigation of shortcomings in simulated aerosol vertical profiles

NASA Astrophysics Data System (ADS)

Park, S.; Allen, R.

2017-12-01

The vertical distribution of aerosols is one important factor for aerosol radiative forcing. Previous studies show that climate models poorly reproduce the aerosol vertical profile, with too much aerosol aloft in the upper troposphere. This bias may be related to several factors, including excessive convective mass flux and wet removal. In this study, we evaluate the aerosol vertical profile from several Coupled Model Intercomparison Project 5 (CMIP5) models, as well as the Community Atmosphere Model 5 (CAM5), relative to the Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observation (CALIPSO). The results show that all models significantly underestimate extinction coefficient in the lower troposphere, while overestimating extinction coefficient in the upper troposphere. In addition, the majority of models indicate a land-ocean dependence in the relationship between aerosol extinction coefficient in the upper troposphere and convective mass flux. Over the continents, more convective mass flux is related to more aerosol aloft; over the ocean, more convective mass flux is associated with less aerosol in upper troposphere. Sensitivity experiments are conducted to investigate the role that convection and wet deposition have in contributing to the deficient simulation of the vertical aerosol profile, including the land-ocean dependence.

Inspiratory and expiratory aerosol deposition in the upper airway.

PubMed

Verbanck, S; Kalsi, H S; Biddiscombe, M F; Agnihotri, V; Belkassem, B; Lacor, C; Usmani, O S

2011-02-01

Aerosol deposition efficiency (DE) in the extrathoracic airways during mouth breathing is currently documented only for the inspiratory phase of respiration, and there is a need for quantification of expiratory DE. Our aim was to study both inspiratory and expiratory DE in a realistic upper airway geometry. This was done experimentally on a physical upper airway cast by scintigraphy, and numerically by computational fluid dynamic simulations using a Reynolds Averaged Navier?Stokes (RANS) method with a k-? SST turbulence model coupled with a stochastic Lagrangian approach. Experiments and simulations were carried out for particle sizes (3 and 6 μm) and flow rates (30 and 60 L/min) spanning the ranges of Stokes (Stk) and Reynolds (Re) number pertinent to therapeutic and environmental aerosols. We showed that inspiratory total deposition data obtained by scintigraphy fell onto a previously published deposition curve representative of a range of upper airway geometries. We also found that expiratory and inspiratory DE curves were almost identical. Finally, DE in different compartments of the upper airway model showed a very different distribution pattern of aerosol deposition during inspiration and expiration, with preferential deposition in oral and pharyngeal compartments, respectively. These compartmental deposition patterns were very consistent and only slightly dependent on particle size or flow rate. Total deposition for inspiration and expiration was reasonably well-mimicked by the RANS simulation method we employed, and more convincingly so in the upper range of the Stk and Re number. However, compartmental deposition patterns showed discrepancies between experiments and RANS simulations, particularly during expiration.

Atmospheric wet deposition of sulfur and nitrogen in Jiuzhaigou National Nature Reserve, Sichuan Province, China.

PubMed

Qiao, Xue; Xiao, Weiyang; Jaffe, Daniel; Kota, Sri Harsha; Ying, Qi; Tang, Ya

2015-04-01

In the last two decades, remarkable ecological changes have been observed in Jiuzhaigou National Nature Reserve (JNNR). Some of these changes might be related to excessive deposition of sulfur (S) and nitrogen (N), but the relationship has not been quantified due to lack of monitoring data, particularly S and N deposition data. In this study, we investigated the concentrations, fluxes, and sources of S and N wet deposition in JNNR from April 2010 to May 2011. The results show that SO4(2-), NO3-, and NH4+ concentrations in the wet deposition were 39.4-170.5, 6.2-34.8, and 0.2-61.2 μeq L(-1), with annual Volume-Weighted Mean (VWM) concentrations of 70.5, 12.7, and 13.4 μeq L(-1), respectively. Annual wet deposition fluxes of SO4(2-), NO3-, and NH4+ were 8.06, 1.29, and 1.39 kg S(N)ha(-1), respectively, accounting for about 90% of annual atmospheric inputs of these species at the monitoring site. The results of Positive Matrix Factorization (PMF) analysis show that fossil fuel combustion, agriculture, and aged sea salt contributed to 99% and 83% of annual wet deposition fluxes of SO4(2-) and NO3-, respectively. Agriculture alone contributed to 89% of annual wet deposition flux of NH4+. Although wet deposition in JNNR was polluted by anthropogenic acids, the acidity was largely neutralized by the Ca2+ from crust and 81% of wet deposition samples had a pH higher than 6.00. However, acid rain mainly caused by SO4(2-) continued to occur in the wet season, when ambient alkaline dust concentration was lower. Since anthropogenic emissions have elevated S and N deposition and caused acid rain in JNNR, further studies are needed to better quantify the regional sources and ecological effects of S and N deposition for JNNR. Copyright © 2014 Elsevier B.V. All rights reserved.

Aerosol chemical vapor deposition of metal oxide films

DOEpatents

Ott, Kevin C.; Kodas, Toivo T.

1994-01-01

A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said FIELD OF THE INVENTION The present invention relates to the field of film coating deposition techniques, and more particularly to the deposition of multicomponent metal oxide films by aerosol chemical vapor deposition. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

Wet and dry nitrogen deposition in the central Sichuan Basin of China

NASA Astrophysics Data System (ADS)

Kuang, Fuhong; Liu, Xuejun; Zhu, Bo; Shen, Jianlin; Pan, Yuepeng; Su, Minmin; Goulding, Keith

2016-10-01

Reactive nitrogen (Nr) plays a key role in the atmospheric environment and its deposition has induced large negative impacts on ecosystem health and services. Five-year continuous in-situ monitoring of N deposition, including wet (total nitrogen (WTN), total dissolved nitrogen (WTDN), dissolved organic nitrogen (WDON), ammonium nitrogen (WAN) and nitrate nitrogen (WNN)) and dry (DNH3, DHNO3, DpNH4+, DpNO3- and DNO2) deposition, had been conducted since August 2008 to December 2013 (wet) and May 2011 to December 2013 (dry) in Yan-ting, China, a typical agricultural area in the central Sichuan Basin. Mean annual total N deposition from 2011 to 2013 was 30.8 kg N ha-1 yr-1, and speculated that of 2009 and 2010 was averaged 28.2 kg N ha-1 yr-1, respectively. Wet and dry N deposition accounted for 76.3% and 23.7% of annual N deposition, respectively. Reduced N (WAN, DNH3 and DpNH4+) was 1.7 times of oxidized N (WNN, DHNO3, DNO2 and DpNO3-) which accounted for 50.9% and 30.3% of TN, respectively. Maximum loadings of all N forms of wet deposition, gaseous NH3, HNO3 and particulate NH4+ in dry deposition occurred in summer and minimum loadings in winter. Whether monthly, seasonal or annual averaged, dissolved N accounted for more than 70% of the total. N deposition in the central Sichuan Basin increased during the sampling period, especially that of ammonium compounds, and has become a serious threat to local aquatic ecosystems, the surrounding forest and other natural or semi-natural ecosystems in the upper reaches of the Yangtze River.

High mercury wet deposition at a “clean Air” site in Puerto Rico

USGS Publications Warehouse

Shanley, James B.; Engle, Mark A.; Scholl, Martha A.; Krabbenhoft, David P.; Brunette, Robert; Olson, Mark L.; Conroy, Mary E.

2015-01-01

Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds, during two complete years the site averaged 27.9 μg m–2 yr–1 wet Hg deposition, or about 30% more than Florida and the Gulf Coast, the highest deposition areas within the U.S. These high Hg deposition rates are driven in part by high rainfall, which averaged 2855 mm yr–1. The volume-weighted mean Hg concentration was 9.8 ng L–1, and was highest during summer and lowest during the winter dry season. Rainout of Hg (decreasing concentration with increasing rainfall depth) was minimal. The high Hg deposition was not supported by gaseous oxidized mercury (GOM) at ground level, which remained near global background concentrations (<10 pg m–3). Rather, a strong positive correlation between Hg concentrations and the maximum height of rain detected within clouds (echo tops) suggests that droplets in high convective cloud tops scavenge GOM from above the mixing layer. The high wet Hg deposition at this “clean air” site suggests that other tropical areas may be hotspots for Hg deposition as well.

The precision of wet atmospheric deposition data from national atmospheric deposition program/national trends network sites determined with collocated samplers

USGS Publications Warehouse

Nilles, M.A.; Gordon, J.D.; Schroder, L.J.

1994-01-01

A collocated, wet-deposition sampler program has been operated since October 1988 by the U.S. Geological Survey to estimate the overall sampling precision of wet atmospheric deposition data collected at selected sites in the National Atmospheric Deposition Program and National Trends Network (NADP/NTN). A duplicate set of wet-deposition sampling instruments was installed adjacent to existing sampling instruments at four different NADP/NTN sites for each year of the study. Wet-deposition samples from collocated sites were collected and analysed using standard NADP/NTN procedures. Laboratory analyses included determinations of pH, specific conductance, and concentrations of major cations and anions. The estimates of precision included all variability in the data-collection system, from the point of sample collection through storage in the NADP/NTN database. Sampling precision was determined from the absolute value of differences in the analytical results for the paired samples in terms of median relative and absolute difference. The median relative difference for Mg2+, Na+, K+ and NH4+ concentration and deposition was quite variable between sites and exceeded 10% at most sites. Relative error for analytes whose concentrations typically approached laboratory method detection limits were greater than for analytes that did not typically approach detection limits. The median relative difference for SO42- and NO3- concentration, specific conductance, and sample volume at all sites was less than 7%. Precision for H+ concentration and deposition ranged from less than 10% at sites with typically high levels of H+ concentration to greater than 30% at sites with low H+ concentration. Median difference for analyte concentration and deposition was typically 1.5-2-times greater for samples collected during the winter than during other seasons at two northern sites. Likewise, the median relative difference in sample volume for winter samples was more than double the annual median

Optical properties of aerosols over a tropical rain forest in Xishuangbanna, South Asia

NASA Astrophysics Data System (ADS)

Ma, Yongjing; Xin, Jinyuan; Zhang, Wenyu; Wang, Yuesi

2016-09-01

Observation and analysis of the optical properties of atmospheric aerosols in a South Asian tropical rain forest showed that the annual mean aerosol optical depth (AOD) and aerosol Ångström exponent (α) at 500 nm were 0.47 ± 0.30 (± value represents the standard deviation) and 1.35 ± 0.32, respectively, from 2012 to 2014, similar with that of Amazon region. Aerosol optical properties in this region varied significantly between the dry and wet seasons. The mean AOD and α were 0.50 ± 0.32 and 1.41 ± 0.28, respectively, in the dry season and 0.41 ± 0.20 and 1.13 ± 0.41 in the wet season. Because of the combustion of the rich biomass in the dry season, fine modal smoke aerosols increased, which led to a higher AOD and smaller aerosol control mode than in the wet season. The average atmospheric humidity in the wet season was 85.50%, higher than the 79.67% during the dry season. In the very damp conditions of the wet season, the aerosol control mode was relatively larger, while AOD appeared to be lower because of the effect of aerosol hygroscopic growth and wet deposition. The trajectories were similar both in dry and wet, but with different effects on the aerosol concentration. The highest AOD values 0.66 ± 0.34 (in dry) and 0.45 ± 0.21 (in wet) both occurred in continental air masses, while smaller (0.38-0.48 in dry and 0.30-0.35 in wet) in oceanic air masses. The range of AOD values during the wet season was relatively narrow (0.30-0.45), but the dry season range was wider (0.38-0.66). For the Ångström exponent, the range in the wet season (0.74-1.34) was much greater than that in the dry season (1.33-1.54).

Aerosol transport and wet scavenging in deep convective clouds: a case study and model evaluation using a multiple passive tracer analysis approach

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

Yang, Qing; Easter, Richard C.; Campuzano-Jost, Pedro

2015-08-20

The effect of wet scavenging on ambient aerosols in deep, continental convective clouds in the mid-latitudes is studied for a severe storm case in Oklahoma during the Deep Convective Clouds and Chemistry (DC3) field campaign. A new passive-tracer based transport analysis framework is developed to characterize the convective transport based on the vertical distribution of several slowly reacting and nearly insoluble trace gases. The passive gas concentration in the upper troposphere convective outflow results from a mixture of 47% from the lower level (0-3 km), 21% entrained from the upper troposphere, and 32% from mid-atmosphere based on observations. The transportmore » analysis framework is applied to aerosols to estimate aerosol transport and wet-scavenging efficiency. Observations yield high overall scavenging efficiencies of 81% and 68% for aerosol mass (Dp < 1μm) and aerosol number (0.03< Dp < 2.5μm), respectively. Little chemical selectivity to wet scavenging is seen among observed submicron sulfate (84%), organic (82%), and ammonium (80%) aerosols, while nitrate has a much lower scavenging efficiency of 57% likely due to the uptake of nitric acid. Observed larger size particles (0.15 - 2.5μm) are scavenged more efficiently (84%) than smaller particles (64%; 0.03 - 0.15μm). The storm is simulated using the chemistry version of the WRF model. Compared to the observation based analysis, the standard model underestimates the wet scavenging efficiency for both mass and number concentrations with low biases of 31% and 40%, respectively. Adding a new treatment of secondary activation significantly improves simulation results, so that the bias in scavenging efficiency in mass and number concentrations is reduced to <10%. This supports the hypothesis that secondary activation is an important process for wet removal of aerosols in deep convective storms.« less

Source apportionment of wet-deposited atmospheric mercury in Tampa, Florida

NASA Astrophysics Data System (ADS)

Michael, Ryan; Stuart, Amy L.; Trotz, Maya A.; Akiwumi, Fenda

2016-03-01

In this paper, sources of mercury deposition to the Tampa area (Florida, USA) are investigated by analysis of one year (March 2000-March 2001) of daily wet deposition data. HYSPLIT back-trajectory modeling was performed to assess potential source locations for high versus low concentration events in data stratified by precipitation level. Positive matrix factorization (PMF) was also applied to apportion the elemental compositions from each event and to identify sources. Increased total mercury deposition was observed during summer months, corresponding to increased precipitation. However, mercury concentration in deposited samples was not strongly correlated with precipitation amount. Back-trajectories show air masses passing over Florida land in the short (12 h) and medium (24 h) term prior to deposition for high mercury concentration events. PMF results indicate that eleven factors contribute to the deposited elements in the event data. Diagnosed elemental profiles suggest the sources that contribute to mercury wet deposition at the study site are coal combustion (52% of the deposited mercury mass), municipal waste incineration (23%), medical waste incineration (19%), and crustal dust (6%). Overall, results suggest that sources local to the county and in Florida likely contributed substantially to mercury deposition at the study site, but distant sources may also contribute.

Controlling Factors of Mercury Wet Deposition and Precipitation Concentrations in Upstate New York

NASA Astrophysics Data System (ADS)

Ye, Z.; Mao, H.; Driscoll, C. T.

2017-12-01

Observations from the Mercury Deposition Network (MDN) at Huntington Wildlife Forest (HWF) suggested that a significant decline in Hg concentrations in precipitation was linked to Hg emission decreases in the United States, especially in the Northeast and Midwest, and yet Hg wet deposition has remained fairly constant over the past two decades. The present study was aimed to investigate how climatic, terrestrial, and anthropogenic factors had influenced the Hg wet deposition flux in upstate New York (NY). To achieve this, an improved Community Multiscale Air Quality (CMAQ) model was employed, which included state-of-the-art Hg and halogen chemistry mechanisms. A base simulation and five sensitivity simulations were conducted. The base simulation used 2010 meteorology, U.S. EPA NEI 2011, and GEOS-Chem output as initial and boundary conditions (ICs and BCs). The five sensitivity runs each changed one condition at the time as follows: 1-3) 2004, 2005, and 2007 meteorology instead of 2010, 4) NEI 2005 Hg anthropogenic emission out of NYS instead of NEI 2011, and 5) no in-state Hg anthropogenic emission. The study period of all the simulations was March - November 2010, and the domain covered the northeastern United States at 12 km resolution. As a result, compared with rural areas in NYS, Hg wet deposition and ambient Hg concentrations in urban areas were affected more significantly by in-state anthropogenic Hg emission. The in-state anthropogenic Hg emissions contributed up to 20% of Hg wet deposition at urban sites and <1% at rural sites during the study period. Using 2005 anthropogenic Hg emissions, around twice of those in 2010, out-of-NYS emissions increased the total in-state Hg wet deposition by 2%. Hg wet deposition flux was greatly affected by meteorological conditions, causing changes varying from a 91% decrease to a factor of 5 increase in monthly accumulated wet deposition amounts. Possible affecting meteorological factors included, not limited to, solar

DEPOSITION OF SULFATE ACID AEROSOLS IN THE DEVELOPING HUMAN LUNG

EPA Science Inventory

Computations of aerosol deposition as affected by (i) aerosol hygroscopicity, (ii) human age, and (iii) respiratory intensity are accomplished using a validated mathematical model. he interactive effects are very complicated but systematic. ew general observations can be made; ra...

Atmospheric wet deposition of trace elements to a suburban environment, Reston, Virginia, USA

USGS Publications Warehouse

Conko, Kathryn M.; Rice, Karen C.; Kennedy, Margaret M.

2004-01-01

Wet deposition from a suburban area in Reston, Virginia was collected during 1998 and analyzed to assess the anion and trace-element concentrations and depositions. Suburban Reston, approximately 26 km west of Washington, DC, is densely populated and heavily developed. Wet deposition was collected bi-weekly in an automated collector using trace-element clean sampling and analytical techniques. The annual volume-weighted concentrations of As, Cd, and Pb were similar to those previously reported for a remote site on Catoctin Mt., Maryland (70 km northwest), which indicated a regional signal for these elements. The concentrations and depositions of Cu and Zn at the suburban site were nearly double those at remote sites because of the influence of local vehicular traffic. The 1998 average annual wet deposition (μg m−2 yr−1) was calculated for Al (52,000), As (94), Cd (54), Cr (160), Cu (700), Fe (23,000), Mn (2000), Ni (240), Pb (440), V (430), and Zn (4100). The average annual wet deposition (meq m−2 yr−1) was calculated for H+ (74), Cl− (8.5), NO3− (33), and SO42− (70). Analysis of digested total trace-element concentrations in a subset of samples showed that the refractory elements in suburban precipitation comprised a larger portion of the total deposition of trace elements than in remote areas.

A Novel Tool for Simulating Aerosol-cloud Interactions with a Sectional Model Implemented to a Large-Eddy Simulator

NASA Astrophysics Data System (ADS)

Tonttila, J.; Romakkaniemi, S.; Kokkola, H.; Maalick, Z.; Korhonen, H.; Liqing, H.

2015-12-01

A new cloud-resolving model setup for studying aerosol-cloud interactions, with a special emphasis on partitioning and wet deposition of semi-volatile aerosol species, is presented. The model is based on modified versions of two well-established model components: the Large-Eddy Simulator (LES) UCLALES, and the sectional aerosol model SALSA, previously employed in the ECHAM climate model family. Implementation of the UCLALES-SALSA is described in detail. As the basis for this work, SALSA has been extended to include a sectional representation of the size distributions of cloud droplets and precipitation. Microphysical processes operating on clouds and precipitation have also been added. Given our main motivation, the cloud droplet size bins are defined according to the dry particle diameter. The droplet wet diameter is solved dynamically through condensation equations, but represents an average droplet diameter inside each size bin. This approach allows for accurate tracking of the aerosol properties inside clouds, but minimizes the computational cost. Since the actual cloud droplet diameter is not fully resolved inside the size bins, processes such as precipitation formation rely on parameterizations. For realistic growth of drizzle drops to rain, which is critical for the aerosol wet deposition, the precipitation size bins are defined according to the actual drop size. With these additions, the implementation of the SALSA model replaces most of the microphysical and thermodynamical components within the LES. The cloud properties and aerosol-cloud interactions simulated by the model are analysed and evaluated against detailed cloud microphysical boxmodel results and in-situ aerosol-cloud interaction observations from the Puijo measurement station in Kuopio, Finland. The ability of the model to reproduce the impacts of wet deposition on the aerosol population is demonstrated.

Method development estimating ambient mercury concentration from monitored mercury wet deposition

NASA Astrophysics Data System (ADS)

Chen, S. M.; Qiu, X.; Zhang, L.; Yang, F.; Blanchard, P.

2013-05-01

Speciated atmospheric mercury data have recently been monitored at multiple locations in North America; but the spatial coverage is far less than the long-established mercury wet deposition network. The present study describes a first attempt linking ambient concentration with wet deposition using Beta distribution fitting of a ratio estimate. The mean, median, mode, standard deviation, and skewness of the fitted Beta distribution parameters were generated using data collected in 2009 at 11 monitoring stations. Comparing the normalized histogram and the fitted density function, the empirical and fitted Beta distribution of the ratio shows a close fit. The estimated ambient mercury concentration was further partitioned into reactive gaseous mercury and particulate bound mercury using linear regression model developed by Amos et al. (2012). The method presented here can be used to roughly estimate mercury ambient concentration at locations and/or times where such measurement is not available but where wet deposition is monitored.

Triple oxygen isotopes indicate urbanization affects sources of nitrate in wet and dry atmospheric deposition

NASA Astrophysics Data System (ADS)

Nelson, David M.; Tsunogai, Urumu; Ding, Dong; Ohyama, Takuya; Komatsu, Daisuke D.; Nakagawa, Fumiko; Noguchi, Izumi; Yamaguchi, Takashi

2018-05-01

Atmospheric nitrate deposition resulting from anthropogenic activities negatively affects human and environmental health. Identifying deposited nitrate that is produced locally vs. that originating from long-distance transport would help inform efforts to mitigate such impacts. However, distinguishing the relative transport distances of atmospheric nitrate in urban areas remains a major challenge since it may be produced locally and/or be transported from upwind regions. To address this uncertainty we assessed spatiotemporal variation in monthly weighted-average Δ17O and δ15N values of wet and dry nitrate deposition during one year at urban and rural sites along the western coast of the northern Japanese island of Hokkaido, downwind of the East Asian continent. Δ17O values of nitrate in wet deposition at the urban site mirrored those of wet and dry deposition at the rural site, ranging between ˜ +23 and +31 ‰ with higher values during winter and lower values in summer, which suggests the greater relative importance of oxidation of NO2 by O3 during winter and OH during summer. In contrast, Δ17O values of nitrate in dry deposition at the urban site were lower (+19 - +25 ‰) and displayed less distinct seasonal variation. Furthermore, the difference between δ15N values of nitrate in wet and dry nitrate deposition was, on average, 3 ‰ greater at the urban than rural site, and Δ17O and δ15N values were correlated for both forms of deposition at both sites with the exception of dry deposition at the urban site. These results suggest that, relative to nitrate in wet and dry deposition in rural environments and wet deposition in urban environments, nitrate in dry deposition in urban environments forms from relatively greater oxidation of NO by peroxy radicals and/or oxidation of NO2 by OH. Given greater concentrations of peroxy radicals and OH in cities, these results imply that dry nitrate deposition results from local NOx emissions more so than wet

Atmospheric wet and dry deposition of trace elements at ten sites in Northern China

NASA Astrophysics Data System (ADS)

Pan, Y. P.; Wang, Y. S.

2014-08-01

Atmospheric deposition is considered to be a major process that removes pollutants from the atmosphere and an important source of nutrients and contaminants for ecosystems. Trace elements (TEs), especially toxic metals deposited on plants and into soil and water, can cause substantial damage to the environment and human health due to their transfer and accumulation in food chains. Despite public concerns, quantitative knowledge of metal deposition from the atmosphere to ecosystems remains scarce. To advance our understanding of the spatio-temporal variations in the magnitudes, pathways, compositions and impacts of atmospherically deposited TEs, precipitation (rain and snow) and dry-deposited particles were collected simultaneously at ten sites in Northern China from December 2007 to November 2010. The measurements showed that the wet and dry depositions of TEs in the target areas were orders of magnitude higher than previous observations within and outside China, generating great concern over the potential risks. The spatial distribution of the total (wet plus dry) deposition flux was consistent with that of the dry deposition, with a significant decrease from industrial and urban areas to suburban, agricultural and rural sites. In contrast, the wet deposition exhibited less spatial variation. The seasonal variation of wet deposition was also different from that of dry deposition, although they were both governed by the precipitation and emission patterns. For the majority of TEs that exist as coarse particles, dry deposition dominated the total flux at each site. This was not the case for K, Ni, As, Pb, Zn, Cd, Se, Ag and Tl, for which the relative importance between wet and dry deposition fluxes varied by site. Whether wet deposition is the major atmospheric cleansing mechanism for the TEs depends on the size distribution and solubility of the particles. We found that atmospheric inputs of Cu, Pb, Zn, Cd, As and Se were of the same magnitude as their increases in

Atmospheric wet and dry deposition of trace elements at 10 sites in Northern China

NASA Astrophysics Data System (ADS)

Pan, Y. P.; Wang, Y. S.

2015-01-01

Atmospheric deposition is considered to be a major process that removes pollutants from the atmosphere and an important source of nutrients and contaminants for ecosystems. Trace elements (TEs), especially toxic metals deposited on plants and into soil or water, can cause substantial damage to the environment and human health due to their transfer and accumulation in food chains. Despite public concerns, quantitative knowledge of metal deposition from the atmosphere to ecosystems remains scarce. To advance our understanding of the spatiotemporal variations in the magnitudes, pathways, compositions and impacts of atmospherically deposited TEs, precipitation (rain and snow) and dry-deposited particles were collected simultaneously at 10 sites in Northern China from December 2007 to November 2010. The measurements showed that the wet and dry depositions of TEs in the target areas were orders of magnitude higher than previous observations within and outside China, generating great concern over the potential risks. The spatial distribution of the total (wet plus dry) deposition flux was consistent with that of the dry deposition, with a significant decrease from industrial and urban areas to suburban, agricultural and rural sites, while the wet deposition exhibited less spatial variation. In addition, the seasonal variation of wet deposition was also different from that of dry deposition, although they were both governed by the precipitation and emission patterns. For the majority of TEs that exist as coarse particles, dry deposition dominated the total flux at each site. This was not the case for potassium, nickel, arsenic, lead, zinc, cadmium, selenium, silver and thallium, for which the relative importance between wet and dry deposition fluxes varied by site. Whether wet deposition is the major atmospheric cleansing mechanism for the TEs depends on the size distribution of the particles. We found that atmospheric inputs of copper, lead, zinc, cadmium, arsenic and

Thunderstorms Increase Mercury Wet Deposition.

PubMed

Holmes, Christopher D; Krishnamurthy, Nishanth P; Caffrey, Jane M; Landing, William M; Edgerton, Eric S; Knapp, Kenneth R; Nair, Udaysankar S

2016-09-06

Mercury (Hg) wet deposition, transfer from the atmosphere to Earth's surface by precipitation, in the United States is highest in locations and seasons with frequent deep convective thunderstorms, but it has never been demonstrated whether the connection is causal or simple coincidence. We use rainwater samples from over 800 individual precipitation events to show that thunderstorms increase Hg concentrations by 50% relative to weak convective or stratiform events of equal precipitation depth. Radar and satellite observations reveal that strong convection reaching the upper troposphere (where high atmospheric concentrations of soluble, oxidized mercury species (Hg(II)) are known to reside) produces the highest Hg concentrations in rain. As a result, precipitation meteorology, especially thunderstorm frequency and total rainfall, explains differences in Hg deposition between study sites located in the eastern United States. Assessing the fate of atmospheric mercury thus requires bridging the scales of global transport and convective precipitation.

[Wet deposition of atmospheric nitrogen in Jiulong River Watershed].

PubMed

Chen, Neng-Wang; Hong, Hua-Sheng; Zhang, Luo-Ping

2008-01-01

Spatio-temporal distributions and sources of atmospheric nitrogen (N) in precipitation were examined for Jiulong River Watershed (JRW), an agricultural-dominated watershed located in southeastern China with a drainage area of 1.47 x 10(4) km2. During 2004-2005, 847 rain samples were collected in seventeen sites and analyzed for ammonium N, nitrate N and dissolved total N (DTN) followed by filtration through 0.45 microm nucleopore membranes. Atmospheric N deposition flux was calculated using GIS interpolation technique (Universal Kriging method for precipitation, Inverse distance weighted technique for N) based on measured N value and precipitation data from eight weather stations located in the JRW. ArcView GIS 3.2 was used for surface analysis, interpolation and statistical work. It was found that mean DTN concentration in all sites ranged between 2.20 +/- 1.69 and 3.26 +/- 1.37 mg x L(-1). Ammonium, nitrate and dissolved organic N formed 39%, 25% and 36% of DTN, respectively. N concentration decreased with precipitation intensity as a result of dilution, and showed a significant difference between dry season and wet season. The low isotope value of nitrate delta 15N ranging between -7.48 per thousand and -0.27 per thousand (mean: -3.61 per thousand) indicated that the increasing agricultural and soil emissions together with fossil combustions contributed to atmospheric nitrate sources. The annual wet deposition of atmospheric N flux amounted to 9.9 kg x hm(-2), which accounts for 66% of total atmospheric N deposition flux (14.9 kg x hm(-2)). About 91% of wet atmospheric deposition occurred in spring and summer. The spatio-temporal variation of atmospheric N deposition indicated that intensive precipitation, higher ammonia volatilization from fertilizer application in the growing season, and livestock productions together provided the larger N source.

Particle deposition in human respiratory system: deposition of concentrated hygroscopic aerosols.

PubMed

Varghese, Suresh K; Gangamma, S

2009-06-01

In the nearly saturated human respiratory tract, the presence of water-soluble substances in the inhaled aerosols can cause change in the size distribution of the particles. This consequently alters the lung deposition profiles of the inhaled airborne particles. Similarly, the presence of high concentration of hygroscopic aerosols also affects the water vapor and temperature profiles in the respiratory tract. A model is presented to analyze these effects in human respiratory system. The model solves simultaneously the heat and mass transfer equations to determine the size evolution of respirable particles and gas-phase properties within human respiratory tract. First, the model predictions for nonhygroscopic aerosols are compared with experimental results. The model results are compared with experimental results of sodium chloride particles. The model reproduces the major features of the experimental data. The water vapor profile is significantly modified only when a high concentration of particles is present. The model is used to study the effect of equilibrium assumptions on particle deposition. Simulations show that an infinite dilution solution assumption to calculate the saturation equilibrium over droplet could induce errors in estimating particle growth. This error is significant in the case of particles of size greater than 1 mum and at number concentrations higher than 10(5)/cm(3).

Development of a Sampler for Total Aerosol Deposition in the Human Respiratory Tract

PubMed Central

Koehler, Kirsten A.; Clark, Phillip; Volckens, John

2009-01-01

Studies that seek to associate reduced human health with exposure to occupational and environmental aerosols are often hampered by limitations in the exposure assessment process. One limitation involves the measured exposure metric itself. Current methods for personal exposure assessment are designed to estimate the aspiration of aerosol into the human body. Since a large proportion of inhaled aerosol is subsequently exhaled, a portion of the aspirated aerosol will not contribute to the dose. This leads to variable exposure misclassification (for heterogenous exposures) and increased uncertainty in health effect associations. Alternatively, a metric for respiratory deposition would provide a more physiologically relevant estimate of risk. To address this challenge, we have developed a method to estimate the deposition of aerosol in the human respiratory tract using a sampler engineered from polyurethane foam. Using a semi-empirical model based on inertial, gravitational, and diffusional particle deposition, a foam was engineered to mimic aerosol total deposition in the human respiratory tract. The sampler is comprised of commercially available foam with fiber diameter = 49.5 μm (equivalent to industry standard 100 PPI foam) of 8 cm thickness operating at a face velocity of 1.3 m s−1. Additionally, the foam sampler yields a relatively low-pressure drop, independent of aerosol loading, providing uniform particle collection efficiency over time. PMID:19638392

Five-year records of mercury wet deposition flux at GMOS sites in the Northern and Southern hemispheres

NASA Astrophysics Data System (ADS)

Sprovieri, Francesca; Pirrone, Nicola; Bencardino, Mariantonia; D'Amore, Francesco; Angot, Helene; Barbante, Carlo; Brunke, Ernst-Günther; Arcega-Cabrera, Flor; Cairns, Warren; Comero, Sara; Diéguez, María del Carmen; Dommergue, Aurélien; Ebinghaus, Ralf; Feng, Xin Bin; Fu, Xuewu; Garcia, Patricia Elizabeth; Gawlik, Bernd Manfred; Hageström, Ulla; Hansson, Katarina; Horvat, Milena; Kotnik, Jože; Labuschagne, Casper; Magand, Olivier; Martin, Lynwill; Mashyanov, Nikolay; Mkololo, Thumeka; Munthe, John; Obolkin, Vladimir; Ramirez Islas, Martha; Sena, Fabrizio; Somerset, Vernon; Spandow, Pia; Vardè, Massimiliano; Walters, Chavon; Wängberg, Ingvar; Weigelt, Andreas; Yang, Xu; Zhang, Hui

2017-02-01

The atmospheric deposition of mercury (Hg) occurs via several mechanisms, including dry and wet scavenging by precipitation events. In an effort to understand the atmospheric cycling and seasonal depositional characteristics of Hg, wet deposition samples were collected for approximately 5 years at 17 selected GMOS monitoring sites located in the Northern and Southern hemispheres in the framework of the Global Mercury Observation System (GMOS) project. Total mercury (THg) exhibited annual and seasonal patterns in Hg wet deposition samples. Interannual differences in total wet deposition are mostly linked with precipitation volume, with the greatest deposition flux occurring in the wettest years. This data set provides a new insight into baseline concentrations of THg concentrations in precipitation worldwide, particularly in regions such as the Southern Hemisphere and tropical areas where wet deposition as well as atmospheric Hg species were not investigated before, opening the way for future and additional simultaneous measurements across the GMOS network as well as new findings in future modeling studies.

Atmospheric Mg2+ wet deposition within the continental United States and implications for soil inorganic carbon sequestration

NASA Astrophysics Data System (ADS)

Goddard, Megan A.; Mikhailova, Elena A.; Post, Christopher J.; Schlautman, Mark A.

2007-02-01

Little is known about atmospheric magnesium ion (Mg2+) wet deposition in relation to soil inorganic carbon sequestration. Understanding the conversion of carbon dioxide (CO2) or organic carbon to a form having a long residence time within the soil (e.g., dolomite, magnesian calcite) will greatly benefit agriculture, industry, and society on a global scale. This preliminary study was conducted to analyze atmospheric Mg2+ wet deposition within the continental United States (U.S.) and to rank the twelve major soil orders in terms of average annual atmospheric Mg2+ wet deposition. The total average annual Mg2+ wet deposition for each soil order was estimated with geographic information systems (GIS) using the following data layers: (1) atmospheric Mg2+ wet deposition data layers covering the continental U.S. for a 10-yr period (1994-2003) and (2) a soil order data layer derived from a national soils database. A map of average annual Mg2+ wet deposition for 1994-2003 reveals that the highest deposition (0.75-1.41 kg ha-1) occurred in Oregon, Washington, parts of California, and the coastal areas of East Coast states due to magnesium enrichment of atmospheric deposition from sea salt. The Midwestern region of the U.S. received about 0.25-0.75 kg ha-1 Mg2+ wet deposition annually, which was associated with loess derived soils, occurrence of dust storms and possibly fertilization. The soil orders receiving the highest average annual atmospheric Mg2+ wet deposition from 1994 to 2003 were: (1) Mollisols (3.7 × 107 kg), (2) Alfisols (3.6 × 107 kg) and (3) Ultisols (2.8 × 107 kg). In terms of potential soil carbon sequestration, the average annual atmospheric Mg2+ wet deposition was equivalent to formation of the following theoretical amounts of dolomite: (1) Mollisols (2.8 × 108 kg of CaMg(CO3)2), (2) Alfisols (2.7 × 108 kg of CaMg(CO3)2) and (3) Ultisols (2.1 × 108 kg of CaMg(CO3)2). The soil orders receiving the lowest average annual atmospheric Mg2+ wet deposition

Distribution of Nitrogen Compounds in Marine Aerosol and Their Deposition Over the Pacific Ocean

NASA Astrophysics Data System (ADS)

Uematsu, M.; Narita, Y.; Sun, S. Y.

2016-02-01

Nutrient supply to the ocean surface layer is an important factor controlling the marine ecosystem. The major paths of supplies of nutrients have been considered as those from nutrient-rich deep waters and riverine input, which is mostly taken up near the estuary region, but the nutrients transported through the atmosphere recognize to be important for the open ocean, where the nutrients are limiting primary productivity. Because of rapid economic development surrounding the Pacific Ocean, anthropogenic NOx emissions increased by 2-3 times during the past decades. This rapid increase of NOx emission causes a large amount of N deposition mostly in the form of nitrate and ammonium over ocean surfaces, and strongly impacts their marine ecosystems. Especially, biological N2 fixation, riverine input and atmospheric deposition contribute to support "new production" and affect CO2 air-sea exchange. The concentration of nitrogen compounds in marine aerosol has been measured on the island stations and onboard of research vessels in the Pacific Ocean over a few decades. The temporal and spatial atmospheric distribution of water-soluble particulate nitrogen compounds is summarized in this study. As the transport of anthropogenic nitrogen compounds from land, high concentration is revealed over the marginal seas in the western North Pacific. Most of nitrate exists in the coarse aerosol associated with sea-salt particle while ammonium exists in the fine particle and showing a good relationship with non-sea-salt sulfate. This different particle size affects to estimate the deposition flux of nitrogen compounds to the ocean surface. Over the high primary productive areas such as the equatorial Pacific and the Southern Ocean, ammonia is released into the atmosphere and transported to other area. By wet and dry deposition, ammonium is removed to the ocean surface and modified the distribution of nitrogen compounds in the surface waters.

1988 Wet deposition temporal and spatial patterns in North America

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

Simpson, J.C.; Olsen, A.R.; Bittner, E.A.

1992-03-01

The focus of this report is on North American wet deposition temporal patterns from 1979 to 1988 and spatial patterns for 1988. It is the third in a series of reports that investigate the patterns of annual precipitation-weighted average concentration and annual deposition for nine ion species: hydrogen, sulfate, nitrate, ammonium, calcium, chloride, sodium, potassium, and magnesium. Mosaic maps, based on surface estimation using kriging, display concentration and deposition spatial patterns of pH, hydrogen, sulfate, nitrate, ammonium, and calcium ion species for 1988 annual, winter, and summer periods. Temporal pattern analyses use a subset of 35 sites over a 10-yearmore » (1979--1988) period and an expanded subset of 137 sites, with greater spatial coverage, over a 7-year (1982--1988) period. The 10-year period represents the longest period with wet deposition monitoring data available that has a sufficient number of sites with data of known quality to allow a descriptive summary of annual temporal patterns. Sen`s median trend estimate and Kendall`s seasonal tau (KST) test are calculated for each ion species concentration and deposition at each site in both subsets.« less

1988 Wet deposition temporal and spatial patterns in North America

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

Simpson, J.C.; Olsen, A.R.; Bittner, E.A.

1992-03-01

The focus of this report is on North American wet deposition temporal patterns from 1979 to 1988 and spatial patterns for 1988. It is the third in a series of reports that investigate the patterns of annual precipitation-weighted average concentration and annual deposition for nine ion species: hydrogen, sulfate, nitrate, ammonium, calcium, chloride, sodium, potassium, and magnesium. Mosaic maps, based on surface estimation using kriging, display concentration and deposition spatial patterns of pH, hydrogen, sulfate, nitrate, ammonium, and calcium ion species for 1988 annual, winter, and summer periods. Temporal pattern analyses use a subset of 35 sites over a 10-yearmore » (1979--1988) period and an expanded subset of 137 sites, with greater spatial coverage, over a 7-year (1982--1988) period. The 10-year period represents the longest period with wet deposition monitoring data available that has a sufficient number of sites with data of known quality to allow a descriptive summary of annual temporal patterns. Sen's median trend estimate and Kendall's seasonal tau (KST) test are calculated for each ion species concentration and deposition at each site in both subsets.« less

Unveiling aerosol-cloud interactions - Part 2: Minimising the effects of aerosol swelling and wet scavenging in ECHAM6-HAM2 for comparison to satellite data

NASA Astrophysics Data System (ADS)

Neubauer, David; Christensen, Matthew W.; Poulsen, Caroline A.; Lohmann, Ulrike

2017-11-01

constrained by satellite observations. In addition to aerosol swelling, wet scavenging and aerosol processing have an impact on liquid water path, cloud albedo and cloud droplet number susceptibilities. Aerosol processing leads to negative liquid water path susceptibilities to changes in aerosol index (AI) in ECHAM6-HAM2, likely due to aerosol-size changes by aerosol processing. Our results indicate that for statistical analysis of aerosol-cloud interactions the unwanted effects of aerosol swelling, wet scavenging and aerosol processing need to be minimised when computing susceptibilities of cloud variables to changes in aerosol.

The chemical composition and fluxes of atmospheric wet deposition at four sites in South Africa

NASA Astrophysics Data System (ADS)

Conradie, E. H.; Van Zyl, P. G.; Pienaar, J. J.; Beukes, J. P.; Galy-Lacaux, C.; Venter, A. D.; Mkhatshwa, G. V.

2016-12-01

South Africa is the economic hub of southern Africa and is regarded as an important source region of atmospheric pollutants. A nitrogen dioxide (NO2) hotspot is clearly visible from space over the South African Mpumalanga Highveld, while South Africa is also regarded as the 9th largest anthropogenic sulphur (S) emitting country. Notwithstanding the importance of South Africa with regard to nitrogen (N) and S emissions, very limited data has been published on the chemical composition of wet deposition for this region. This paper presents the concentrations of sodium (Na+), ammonium (NH4+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), nitrate (NO3-), chloride (Cl-), sulphate (SO42-) and water-soluble organic acids (OA) in the wet deposition samples collected between 2009 and 2014 at four South African IDAF (IGAC DEBITS Africa) sites, which are regarded as regional representatives of the north-eastern interior. Also, wet deposition fluxes of the ten ions are calculated and presented in this paper. The results show that the total ionic concentrations and fluxes of wet deposition were much higher at the two sites closer to anthropogenic emissions, while the pH of wet deposition at these two sites were lower compared to that of the two sites that were less impacted by anthropogenic emissions. . The major sources of the ten ions included marine, terrigenous (crust), fossil fuel combustion, agriculture and biomass burning. Significant contributions from fossil fuel combustion were determined for the two sites in close proximity to anthropogenic source regions. The results of back trajectory analysis, however, did indicate that the two remote sites are also affected by air masses passing over the source region through anti-cyclonic recirculation. The largest contributions at the two sites distant from the anthropogenic source regions were marine sources, while the impact of biomass burning was also more significant at the remote sites. Comparison to previous wet

Comparison of wet-only and bulk deposition at Chiang Mai (Thailand) based on rainwater chemical composition

NASA Astrophysics Data System (ADS)

Chantara, Somporn; Chunsuk, Nawarut

The chemical composition of 122 rainwater samples collected daily from bulk and wet-only collectors in a sub-urban area of Chiang Mai (Thailand) during August 2005-July 2006 has been analyzed and compared to assess usability of a cheaper and less complex bulk collector over a sophisticated wet-only collector. Statistical analysis was performed on log-transformed daily rain amount and depositions of major ions for each collector type. The analysis of variance (ANOVA) test revealed that the amount of rainfall collected from a rain gauge, bulk collector and wet-only collector showed no significant difference ( ∝=0.05). The volume weight mean electro-conductivity (EC) values of bulk and wet-only samples were 0.69 and 0.65 mS/m, respectively. The average pH of the samples from both types of collectors was 5.5. Scatter plots between log-transformed depositions of specific ions obtained from bulk and wet-only samples showed high correlation ( r>0.91). Means of log-transformed bulk deposition were 14% (Na + and K +), 13% (Mg 2+), 7% (Ca 2+), 4% (NO 3-), 3% (SO 42- and Cl -) and 2% (NH 4+) higher than that of wet-only deposition. However, multivariate analysis of variance (MANOVA) revealed that ion depositions obtained from bulk and wet-only collectors were not significantly different ( ∝=0.05). Therefore, it was concluded that a bulk collector can be used instead of a wet-only collector in a sub-urban area.

Atmospheric nitrogen deposition in south-east Scotland: Quantification of the organic nitrogen fraction in wet, dry and bulk deposition

NASA Astrophysics Data System (ADS)

González Benítez, Juan M.; Cape, J. Neil; Heal, Mathew R.; van Dijk, Netty; Díez, Alberto Vidal

Water soluble organic nitrogen (WSON) compounds are ubiquitous in precipitation and in the planetary boundary layer, and therefore are a potential source of bioavailable reactive nitrogen. This paper examines weekly rain data over a period of 22 months from June 2005 to March 2007 collected in 2 types of rain collector (bulk deposition and "dry + wet" deposition) located in a semi-rural area 15 km southwest of Edinburgh, UK (N55°51'44″, W3°12'19″). Bulk deposition collectors are denoted in this paper as "standard rain gauges", and they are the design used in the UK national network for monitoring precipitation composition. "Dry + wet" deposition collectors are flushing rain gauges and they are equipped with a rain detector (conductivity array), a spray nozzle, a 2-way valve and two independent bottles to collect funnel washings (dry deposition) and true wet deposition. On average, for the 27 weekly samples with 3 valid replicates for the 2 types of collectors, dissolved organic nitrogen (DON) represented 23% of the total dissolved nitrogen (TDN) in bulk deposition. Dry deposition of particles and gas on the funnel surface, rather than rain, contributed over half of all N-containing species (inorganic and organic). Some discrepancies were found between bulk rain gauges and flushing rain gauges, for deposition of both TDN and DON, suggesting biological conversion and loss of inorganic N in the flushing samplers.

Deposition of biomass combustion aerosol particles in the human respiratory tract.

PubMed

Löndahl, Jakob; Pagels, Joakim; Boman, Christoffer; Swietlicki, Erik; Massling, Andreas; Rissler, Jenny; Blomberg, Anders; Bohgard, Mats; Sandström, Thomas

2008-08-01

Smoke from biomass combustion has been identified as a major environmental risk factor associated with adverse health effects globally. Deposition of the smoke particles in the lungs is a crucial factor for toxicological effects, but has not previously been studied experimentally. We investigated the size-dependent respiratory-tract deposition of aerosol particles from wood combustion in humans. Two combustion conditions were studied in a wood pellet burner: efficient ("complete") combustion and low-temperature (incomplete) combustion simulating "wood smoke." The size-dependent deposition fraction of 15-to 680-nm particles was measured for 10 healthy subjects with a novel setup. Both aerosols were extensively characterized with regard to chemical and physical particle properties. The deposition was additionally estimated with the ICRP model, modified for the determined aerosol properties, in order to validate the experiments and allow a generalization of the results. The measured total deposited fraction of particles from both efficient combustion and low-temperature combustion was 0.21-0.24 by number, surface, and mass. The deposition behavior can be explained by the size distributions of the particles and by their ability to grow by water uptake in the lungs, where the relative humidity is close to saturation. The experiments were in basic agreement with the model calculations. Our findings illustrate: (1) that particles from biomass combustion obtain a size in the respiratory tract at which the deposition probability is close to its minimum, (2) that particle water absorption has substantial impact on deposition, and (3) that deposition is markedly influenced by individual factors.

Aerosol deposition in the human respiratory tract

NASA Astrophysics Data System (ADS)

Winchester, John W.; Jones, Donald L.; Mu-tian, Bi

1984-04-01

Rising sulfur dioxide emissions from increased coal combustion present risks, not only of acid rain, but also to health by inhalation of the SO 2 and acid to the lung. We are investigating human inhalation of ppm SO 2 concentrations mixed with aerosol of submicrometer aqueous salt droplets to determine the effects on lung function and body chemistry. Unlike some investigators, we emphasize ammonium sulfate and trace element aerosol composition which simulates ambient air; aerosol pH, relative humidity, and temperature control to reveal gas-particle reaction mechanisms; and dose estimates from length of exposure, SO 2 concentration, and a direct measurement of respiratory deposition of aerosol as a function of particle size by cascade impactor sampling and elemental analysis by PIXE. Exposures, at rest or during exercise, are in a walk-in chamber at body temperature and high humidity to simulate Florida's summer climate. Lung function measurement by spirometry is carried out immediately after exposure. The results are significant in relating air quality to athletic performance and to public health in the southeastern United States.

Effects of surface-active organic matter on carbon dioxide nucleation in atmospheric wet aerosols: a molecular dynamics study.

PubMed

Daskalakis, Vangelis; Charalambous, Fevronia; Panagiotou, Fostira; Nearchou, Irene

2014-11-21

Organic matter (OM) uptake in cloud droplets produces water-soluble secondary organic aerosols (SOA) via aqueous chemistry. These play a significant role in aerosol properties. We report the effects of OM uptake in wet aerosols, in terms of the dissolved-to-gas carbon dioxide nucleation using molecular dynamics (MD) simulations. Carbon dioxide has been implicated in the natural rainwater as well as seawater acidity. Variability of the cloud and raindrop pH is assumed in space and time, as regional emissions, local human activities and geophysical characteristics differ. Rain scavenging of inorganic SOx, NOx and NH3 plays a major role in rain acidity in terms of acid-base activity, however carbon dioxide solubility also remains a key parameter. Based on the MD simulations we propose that the presence of surface-active OM promotes the dissolved-to-gas carbon dioxide nucleation in wet aerosols, even at low temperatures, strongly decreasing carbon dioxide solubility. A discussion is made on the role of OM in controlling the pH of a cloud or raindrop, as a consequence, without involving OM ionization equilibrium. The results are compared with experimental and computational studies in the literature.

Deposition of Aerosols in the Lung: Physiological Factors

EPA Science Inventory

Ventilation and mechanics of breathing are an integral part of respiratory physiology that directly affect aerosol transport and deposition in the lung. Although natural breathing pattern varies widely among individuals, breathing pattern is controllable, and by using an appropri...

Characterizations of wet mercury deposition on a remote high-elevation site in the southeastern Tibetan Plateau.

PubMed

Huang, Jie; Kang, Shichang; Zhang, Qianggong; Guo, Junming; Sillanpää, Mika; Wang, Yongjie; Sun, Shiwei; Sun, Xuejun; Tripathee, Lekhendra

2015-11-01

Accurate measurements of wet mercury (Hg) deposition are critically important for the assessment of ecological responses to pollutant loading. The Hg in wet deposition was measured over a 3-year period in the southeastern Tibetan Plateau. The volume-weighted mean (VWM) total Hg (HgT) concentration was somewhat lower than those reported in other regions of the Tibetan Plateau, but the VWM methyl-Hg concentration and deposition flux were among the highest globally reported values. The VWM HgT concentration was higher in non-monsoon season than in monsoon season, and wet HgT deposition was dominated by the precipitation amount rather than the scavenging of atmospheric Hg by precipitation. The dominant Hg species in precipitation was mainly in the form of dissolved Hg, which indicates the pivotal role of reactive gaseous Hg within-cloud scavenging to wet Hg deposition. Moreover, an increasing trend in precipitation Hg concentrations was synchronous with the recent economic development in South Asia. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evaluating the effectiveness of pollution control measures via the occurrence of DDTs and HCHs in wet deposition of an urban center, China.

PubMed

Guo, Ling-Chuan; Bao, Lian-Jun; Li, Shao-Meng; Tao, Shu; Zeng, Eddy Y

2017-04-01

Wet deposition is not only a mechanism for removing atmospheric pollutants, but also a process which reflects loadings of atmospheric pollutants. Our previous study on wet deposition examined the effectiveness of short-term control measures on atmospheric particulate pollution, which were partly effective for organic pollutants of current input sources. In the present study, dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs), representative of legacy contaminants, were measured in the same samples collected throughout the entire year of 2010 in Guangzhou, a large urban center in South China. Concentrations of ∑DDT (sum of o,p' and p,p'-DDT, o,p' and p,p'-DDE, o,p' and p,p'-DDD, and p,p'-DDMU) and ∑HCH (sum of α-, β-, γ-, and δ-HCH) in wet deposition were in the ranges of nd-69 (average: 1.8 ng L -1 ) and nd-150 ng L -1 (average: 5.1 ng L -1 ), respectively. In addition, the results of source diagnostics and backward air mass trajectories appeared to suggest the transport of antifouling paint derived DDTs from the coastal region off South China to Guangzhou. The combined wet and dry deposition flux of ∑HCH in the first quarter (January to March) was greater than that in the fourth quarter (October to December), while those of ∑DDT were comparable in the first and fourth quarters. Similar trends were also observed for the concentrations of ∑HCH and ∑DDT in aerosol samples. These results suggested the short-term pollution control measures implemented during the 16th Asian Games and 10th Asian Para Games (held in November and December 2010, respectively) did not work well for DDTs. The reduced input of HCHs during the fourth quarter was probably associated with the strict ban on lindane for food safety, which also exposed the weakness of control measures focusing mainly on the removal of atmospheric particulate matter. Copyright © 2017 Elsevier Ltd. All rights reserved.

Aerosol-Assisted Chemical Vapor Deposited Thin Films for Space Photovoltaics

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; McNatt, Jeremiah; Dickman, John E.; Jin, Michael H.-C.; Banger, Kulbinder K.; Kelly, Christopher V.; AquinoGonzalez, Angel R.; Rockett, Angus A.

2006-01-01

Copper indium disulfide thin films were deposited via aerosol-assisted chemical vapor deposition using single source precursors. Processing and post-processing parameters were varied in order to modify morphology, stoichiometry, crystallography, electrical properties, and optical properties in order to optimize device-quality material. Growth at atmospheric pressure in a horizontal hot-wall reactor at 395 C yielded best device films. Placing the susceptor closer to the evaporation zone and flowing a more precursor-rich carrier gas through the reactor yielded shinier, smoother, denser-looking films. Growth of (112)-oriented films yielded more Cu-rich films with fewer secondary phases than growth of (204)/(220)-oriented films. Post-deposition sulfur-vapor annealing enhanced stoichiometry and crystallinity of the films. Photoluminescence studies revealed four major emission bands (1.45, 1.43, 1.37, and 1.32 eV) and a broad band associated with deep defects. The highest device efficiency for an aerosol-assisted chemical vapor deposited cell was 1.03 percent.

Evaluating Inter-Annual Climate Variability of Nitrogen Wet Deposition in the United States Using Wavelet Analysis

NASA Astrophysics Data System (ADS)

Nergui, T.; Thomas, N.; Liu, M.; Lamb, B. K.; Adam, J. C.; Chung, S. H.

2012-12-01

Human activities, primarily agricultural practices and fossil fuel combustion, have caused a significant increase in nitrogen (N) emissions into the atmosphere over the last 150 years. The increase in emission subsequently leads to elevated ozone concentration, haze, increased acid rain and N deposition at local and regional scales. Many ecosystems in the US are naturally N limited. These regions are highly vulnerable to increased N deposition which can lead to irreversible changes in biodiversity richness and composition of the ecosystems. Through the impact on atmospheric chemistry and scavenging by precipitation, climate variability can play a major role on N deposition rates. The El Niño/Southern Oscillation (ENSO), Northern Annular Mode/Arctic Oscillation (NAM/AO), North Atlantic Oscillation (NAO), and the Pacific-North American Pattern (PNA) indices are the key climate indices that characterize the climate in the contiguous US at inter-annual timescale. Here, we identify dominant periodic components (signal) in the N wet deposition and the climate index timeseries and examine their correlations and coherences using wavelet analysis. Seasonal precipitation and nitrogen (ammonium and nitrate) wet deposition data from the National Atmospheric Deposition Program (NADP), National Trends Network (NTN) for 87 sites across the United States are used for the study. The sites were selected based on data continuity of 21 years or more and NADP criteria for valid precipitation and wet deposition data. Precipitation data from the Parameter-elevation Regressions on Independent Slopes Model (PRISM) are also used to replicate and validate the general features of climate variability effects in different regions of US. Initial analysis reveals nitrate wet deposition has a dominant 1-4 year periodicity while ammonium wet deposition has a shorter periodicity (about 0.5-2 year) during 1979 to 2011. Precipitation and total N wet deposition are most correlated in the Great Plains

Laboratory exposure systems to simulate atmospheric degradation of building stone under dry and wet deposition conditions

NASA Astrophysics Data System (ADS)

Johnson, J. B.; Haneef, S. J.; Hepburn, B. J.; Hutchinson, A. J.; Thompson, G. E.; Wood, G. C.

The design philosophy, construction and use of two exposure test systems are described, in which the objective is to simulate the degradation of stone samples under, respectively, the 'dry' and 'wet' deposition of atmospheric pollutants. Some element of realistic acceleration is possible in certain experiments. Particular emphasis is placed upon using known presentation rates of the pollutants, both in respect of typical depositions of pollutants and their oxidation products appropriate for an industrial atmosphere. In the dry deposition rig, SO 2, NO 2, NO, HCl and the oxidant O 3 are presented individually or together at realistic deposition rates. In the wet deposition apparatus, SO 2-4, NO -3 and Cl - at a pH of 3.5, simulating 'acid rain' but in a more concentrated form, are deposited. The dry deposition chamber can be operated at constant relative humidity (typically 84%) with pre-dried or precisely wetted stones to simulate episodic rain wetting, or using other methods of wet/dry cycling, which are also a feature of the wet deposition chamber. Heating and cooling of the samples is also possible, as is the use of shaped or coupled stones of different kinds such as are found in a building facade. The results are illustrated in terms of data on the weight change, the anion content of stone and run-off, the pH change of run-off and the total calcium reacted, using Portland stone, as a prelude to later papers in which behaviour of a whole matrix of stone types and environments is presented and discussed. Such an approach permits the eventual production of 'pollutant-material response' relationships and damage functions for comparison with and prediction of external exposure results.

Determining atmospheric deposition in Wyoming with IMPROVE and other national programs

Treesearch

Karl Zeller; Debra Youngblood Harrington; Richard Fisher; Evgeny Donev

2000-01-01

Atmospheric deposition is the result of air pollution gases and aerosols leaving the atmosphere as "dry" or "wet" deposition. Little is known about just how much pollution is deposited onto soils, lakes and streams. To determine the extent and trends of forest exposure to air pollution, various types of monitoring have been conducted. In this study...

Diffusive deposition of aerosols in Phebus containment during FPT-2 test

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

Kontautas, A.; Urbonavicius, E.

2012-07-01

At present the lumped-parameter codes is the main tool to investigate the complex response of the containment of Nuclear Power Plant in case of an accident. Continuous development and validation of the codes is required to perform realistic investigation of the processes that determine the possible source term of radioactive products to the environment. Validation of the codes is based on the comparison of the calculated results with the measurements performed in experimental facilities. The most extensive experimental program to investigate fission product release from the molten fuel, transport through the cooling circuit and deposition in the containment is performedmore » in PHEBUS test facility. Test FPT-2 performed in this facility is considered for analysis of processes taking place in containment. Earlier performed investigations using COCOSYS code showed that the code could be successfully used for analysis of thermal-hydraulic processes and deposition of aerosols, but there was also noticed that diffusive deposition on the vertical walls does not fit well with the measured results. In the CPA module of ASTEC code there is implemented different model for diffusive deposition, therefore the PHEBUS containment model was transferred from COCOSYS code to ASTEC-CPA to investigate the influence of the diffusive deposition modelling. Analysis was performed using PHEBUS containment model of 16 nodes. The calculated thermal-hydraulic parameters are in good agreement with measured results, which gives basis for realistic simulation of aerosol transport and deposition processes. Performed investigations showed that diffusive deposition model has influence on the aerosol deposition distribution on different surfaces in the test facility. (authors)« less

Contribution of fungi to primary biogenic aerosols in the atmosphere: wet and dry discharged spores, carbohydrates, and inorganic ions

NASA Astrophysics Data System (ADS)

Elbert, W.; Taylor, P. E.; Andreae, M. O.; Pöschl, U.

2007-09-01

Biogenic aerosols play important roles in atmospheric chemistry physics, the biosphere, climate, and public health. Here, we show that fungi which actively discharge their spores with liquids into the air, in particular actively wet spore discharging Ascomycota (AAM) and actively wet spore discharging Basidiomycota (ABM), are a major source of primary biogenic aerosol particles and components. We present the first estimates for the global average emission rates of fungal spores. Measurement results and budget calculations based on investigations in Amazonia (Balbina, Brazil, July 2001) indicate that the spores of AAM and ABM may account for a large proportion of coarse particulate matter in tropical rainforest regions during the wet season (0.7-2.3 μg m-3). For the particle diameter range of 1-10 μm, the estimated proportions are ~25% during day-time, ~45% at night, and ~35% on average. For the sugar alcohol mannitol, the budget calculations indicate that it is suitable for use as a molecular tracer for actively wet discharged basidiospores (ABS). ABM emissions seem to account for most of the atmospheric abundance of mannitol (10-68 ng m-3), and can explain the observed diurnal cycle (higher abundance at night). ABM emissions of hexose carbohydrates might also account for a significant proportion of glucose and fructose in air particulate matter (7-49 ng m-3), but the literature-derived ratios are not consistent with the observed diurnal cycle (lower abundance at night). AAM emissions appear to account for a large proportion of potassium in air particulate matter over tropical rainforest regions during the wet season (17-43 ng m-3), and they can also explain the observed diurnal cycle (higher abundance at night). The results of our investigations and budget calculations for tropical rainforest aerosols are consistent with measurements performed at other locations. Based on the average abundance of mannitol reported for extratropical continental boundary layer air

Simulating the Effects of Semivolatile Compounds on Cloud Processing of Aerosol

NASA Astrophysics Data System (ADS)

Kokkola, H.; Kudzotsa, I.; Tonttila, J.; Raatikainen, T.; Romakkaniemi, S.

2017-12-01

Aerosol removal processes largely dictate how well aerosol is transported in the atmosphere and thus the aerosol load over remote regions depends on how effectively aerosol is removed during its transport from the source regions. This means that in order to model the global distribution aerosol, both in vertical and horizontal, wet deposition processes have to be properly modelled. However, in large scale models, the description of wet removal and the vertical redistribution of aerosol by cloud processes is often extremely simplified.Here we present a novel aerosol-cloud model SALSA, where the aerosol properties are tracked through different cloud processes. These processes include: cloud droplet activation, precipitation formation, ice nucleation, melting, and evaporation. It is a sectional model that includes separate size sections for non-activated aerosol, cloud droplets, precipitation droplets, and ice crystals. The aerosol-cloud model was coupled to a large eddy model UCLALES which simulates the boundary-layer dynamics. In this study, the model has been applied in studying the wet removal as well as interactions between aerosol, clouds, and semi-volatile compounds, ammonia and nitric acid. These semi-volative compounds are special in the sense that they co-condense together with water during cloud activation and have been suggested to form droplets that can be considered cloud-droplet-like already in subsaturated conditions. In our model, we calculate the kinetic partitioning of ammonia and sulfate thus explicitly taking into account the effect of ammonia and nitric acid in the cloud formation. Our simulations indicate that especially in polluted conditions, these compounds significantly affect the properties of cloud droplets thus significantly affecting the lifecycle of different aerosol compounds.

In vitro and in vivo lung deposition of coated magnetic aerosol particles.

PubMed

Xie, Yuanyuan; Longest, P Worth; Xu, Yun Hao; Wang, Jian Ping; Wiedmann, Timothy Scott

2010-11-01

The magnetic induced deposition of polydispersed aerosols composed of agglomerated superparamagnetic particles was measured with an in vitro model system and in the mouse trachea and deep lung for the purpose of investigating the potential of site specific respiratory drug delivery. Oleic acid coated superparamagnetic particles were prepared and characterized by TEM, induced magnetic moment, and iron content. The particles were dispersed in cyclohexane, aerosolized with an ultrasonic atomizer and dried by sequential reflux and charcoal columns. The fraction of iron deposited on glass tubes increased with particle size and decreasing flow rate. High deposition occurred with a small diameter tube, but the deposition fraction was largely independent of tube size at larger diameters. Results from computational fluid dynamics qualitatively agreed with the experimental results. Enhanced deposition was observed in the mouse lung but not in the trachea consistent with the analysis of the aerodynamic time allowed for deposition and required magnetic deposition time. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association

Sulfate-rich eolian and wet interdune deposits, erebus crater, meridiani Planum, Mars

USGS Publications Warehouse

Metz, J.M.; Grotzinger, J.P.; Rubin, D.M.; Lewis, K.W.; Squyres, S. W.; Bell, J.F.

2009-01-01

This study investigates three bedrock exposures at Erebus crater, an ?? 300 m diameter crater approximately 4 km south of Endurance crater on Mars. These outcrops, called Olympia, Payson, and Yavapai, provide additional evidence in support of the dune-interdune model proposed for the formation of the deposits at the Opportunity landing site in Meridiani Planum. There is evidence for greater involvement of liquid water in the Olympia outcrop exposures than was observed in Eagle or Endurance craters. The Olympia outcrop likely formed in a wet interdune and sand sheet environment. The facies observed within the Payson outcrop, which is likely stratigraphically above the Olympia outcrop, indicate that it was deposited in a damp-wet interdune, sand sheet, and eolian dune environment. The Yavapai outcrop, which likely stratigraphically overlies the Payson outcrop, indicates that it was deposited in primarily a sand sheet environment and also potentially in an eolian dune environment. These three outcrop exposures may indicate an overall drying-upward trend spanning the stratigraphic section from its base at the Olympia outcrop to its top at the Yavapai outcrop. This contrasts with the wetting-upward trend seen in Endurance and Eagle craters. Thus, the series of outcrops seen at Meridiani by Opportunity may constitute a full climatic cycle, evolving from dry to wet to dry conditions. ?? 2009, SEPM (Society for Sedimentary Geology).

Aerodynamics and deposition effects of inhaled submicron drug aerosol in airway diseases.

PubMed

Faiyazuddin, Md; Mujahid, Md; Hussain, Talib; Siddiqui, Hefazat H; Bhatnagar, Aseem; Khar, Roop K; Ahmad, Farhan J

2013-01-01

Particle engineering is the prime focus to improve pulmonary drug targeting with the splendor of nanomedicines. In recent years, submicron particles have emerged as prettyful candidate for improved fludisation and deposition. For effective deposition, the particle size must be in the range of 0.5-5 μm. Inhalers design for the purpose of efficient delivery of powders to lungs is again a crucial task for pulmonary scientists. A huge number of DPI devices exist in the market, a significant number are awaiting FDA approval, some are under development and a large number have been patented or applied for patent. Even with superior design, the delivery competence is still deprived, mostly due to fluidisation problems which cause poor aerosol generation and deposition. Because of the cohesive nature and poor flow characteristics, they are difficult to redisperse upon aerosolization with breath. These problems are illustrious in aerosol research, much of which is vastly pertinent to pulmonary therapeutics. A technical review is presented here of advances that have been utilized in production of submicron drug particles, their in vitro/in vivo evaluations, aerosol effects and pulmonary fate of inhaled submicron powders.

Urbanization in China changes the composition and main sources of wet inorganic nitrogen deposition.

PubMed

Huang, Juan; Zhang, Wei; Zhu, Xiaomin; Gilliam, Frank S; Chen, Hao; Lu, Xiankai; Mo, Jiangming

2015-05-01

Nowadays, nitrogen (N) deposition has become a growing global concern due to urbanization activities increasing the large amount of reactive N in the atmosphere. However, it remains unclear whether urbanization affects the composition and main sources of N deposition in rapidly urbanizing areas such as in China. One-year measurement of wet inorganic N deposition was conducted using ion-exchange resin (IER) columns in the range of 260 km from urban to rural areas in the Pearl River Delta (PRD) region, south China. An increasing pattern of wet inorganic deposition along the urbanization gradient was observed and it increased in the order: rural (15.26 ± 0.20 kg N ha(-1) year(-1)) < suburban/rural (21.45 ± 3.73 kg N ha(-1) year(-1)) < urban (31.16 ± 0.44 kg N ha(-1) year(-1)) < urban/suburban sites (34.15 ± 5.73 kg N ha(-1) year(-1)). Nitrate N (NO3 (-)-N) accounted for 53.5-79.1 % of total wet inorganic N deposition, indicating a significant negative correlation with distance from the urban core. Based on moss δ(15)N-values the main source of NO3 (-)-N was considered to be emitted from vehicles. Our results demonstrate that urbanization has large impacts on the regional pattern of wet inorganic N deposition. Thus, controlling NOx emission, especially vehicle emission will become an effective strategy for N pollution abatement in China.

Wet and dry atmospheric depositions of inorganic nitrogen during plant growing season in the coastal zone of Yellow River Delta.

PubMed

Yu, Junbao; Ning, Kai; Li, Yunzhao; Du, Siyao; Han, Guangxuan; Xing, Qinghui; Wu, Huifeng; Wang, Guangmei; Gao, Yongjun

2014-01-01

The ecological problems caused by dry and wet deposition of atmospheric nitrogen have been widespread concern in the world. In this study, wet and dry atmospheric depositions were monitored in plant growing season in the coastal zone of the Yellow River Delta (YRD) using automatic sampling equipment. The results showed that SO4 (2-) and Na(+) were the predominant anion and cation, respectively, in both wet and dry atmospheric depositions. The total atmospheric nitrogen deposition was ~2264.24 mg m(-2), in which dry atmospheric nitrogen deposition was about 32.02%. The highest values of dry and wet atmospheric nitrogen deposition appeared in May and August, respectively. In the studied area, NO3 (-)-N was the main nitrogen form in dry deposition, while the predominant nitrogen in wet atmospheric deposition was NH4 (+)-N with ~56.51% of total wet atmospheric nitrogen deposition. The average monthly attribution rate of atmospheric deposition of NO3 (-)-N and NH4 (+)-N was ~31.38% and ~20.50% for the contents of NO3 (-)-N and NH4 (+)-N in 0-10 cm soil layer, respectively, suggested that the atmospheric nitrogen was one of main sources for soil nitrogen in coastal zone of the YRD.

Assessment of atmospheric trace metal deposition in urban environments using direct and indirect measurement methodology and contributions from wet and dry depositions

NASA Astrophysics Data System (ADS)

Omrani, Mehrazin; Ruban, Véronique; Ruban, Gwenaël; Lamprea, Katerine

2017-11-01

Bulk Atmospheric Deposition (BAD), Wet Atmospheric Deposition (WAD) and Dry Atmospheric Deposition (DAD) were all measured within an urban residential area in Nantes (France) over a 9-month period (27 February - 10 December 2014). The objectives of this study were to compare 2 methods for measuring dry and wet atmospheric depositions in the urban environment (DAD and WAD: direct method; BAD and WAD: indirect one), and to characterize as well the variations and relative contributions of these depositions. Trace metals (As, Cd, Cr, Cu, Ni, Pt and V) were used to carry out these comparison and quantification. BAD was collected with two open polyethylene containers (72 × 54 × 21 cm), while WAD was collected by means of an automated rainwater collector and DAD was determined from both air measurements (recorded by an air sampler) and 7Be deposition velocities. The comparison based on a detailed evaluation of uncertainties showed a significant difference between the direct and indirect methods. Dry and wet depositions varied widely from one month to the next. Zn and Cu were the most abundant elements in both dry and wet depositions. The mean contribution of DAD to the bulk atmospheric deposition during this 9-month study was significant for Zn, Cu and V (about 25%) as well as for Pb (approx. 60%). For this relatively unpolluted urban residential catchment, the contribution of atmospheric deposition to global load at the catchment outlet was low, between 10% and 20% for Zn, Cu, V and Pb, 25% for Cr and about 30% for Ni. For other urban sites exhibiting high atmospheric pollution however, the atmospheric contribution to the global pollution load could be much greater. An accurate and representative estimation of DAD thus proves critical.

Effects of generation time on spray aerosol transport and deposition in models of the mouth-throat geometry.

PubMed

Worth Longest, P; Hindle, Michael; Das Choudhuri, Suparna

2009-06-01

For most newly developed spray aerosol inhalers, the generation time is a potentially important variable that can be fully controlled. The objective of this study was to determine the effects of spray aerosol generation time on transport and deposition in a standard induction port (IP) and more realistic mouth-throat (MT) geometry. Capillary aerosol generation (CAG) was selected as a representative system in which spray momentum was expected to significantly impact deposition. Sectional and total depositions in the IP and MT geometries were assessed at a constant CAG flow rate of 25 mg/sec for aerosol generation times of 1, 2, and 4 sec using both in vitro experiments and a previously developed computational fluid dynamics (CFD) model. Both the in vitro and numerical results indicated that extending the generation time of the spray aerosol, delivered at a constant mass flow rate, significantly reduced deposition in the IP and more realistic MT geometry. Specifically, increasing the generation time of the CAG system from 1 to 4 sec reduced the deposition fraction in the IP and MT geometries by approximately 60 and 33%, respectively. Furthermore, the CFD predictions of deposition fraction were found to be in good agreement with the in vitro results for all times considered in both the IP and MT geometries. The numerical results indicated that the reduction in deposition fraction over time was associated with temporal dissipation of what was termed the spray aerosol "burst effect." Based on these results, increasing the spray aerosol generation time, at a constant mass flow rate, may be an effective strategy for reducing deposition in the standard IP and in more realistic MT geometries.

QUALITY ASSURANCE PROGRAM FOR WET DEPOSITION SAMPLING AND CHEMICAL ANALYSES FOR THE NATIONAL TRENDS NETWORK.

USGS Publications Warehouse

Schroder, LeRoy J.; Malo, Bernard A.; ,

1985-01-01

The purpose of the National Trends Network is to delineate the major inorganic constituents in the wet deposition in the United States. The approach chosen to monitor the Nation's wet deposition is to install approximately 150 automatic sampling devices with at least one collector in each state. Samples are collected at one week intervals, removed from collectors, and transported to an analytical laboratory for chemical analysis. The quality assurance program has divided wet deposition monitoring into 5 parts: (1) Sampling site selection, (2) sampling device, (3) sample container, (4) sample handling, and (5) laboratory analysis. Each of these five components is being examined using existing designs or new designs. Each existing or proposed sampling site is visited and a criteria audit is performed.

Traffic aerosol lobar doses deposited in the human respiratory system.

PubMed

Manigrasso, Maurizio; Vernale, Claudio; Avino, Pasquale

2017-06-01

Aerosol pollution in urban environments has been recognized to be responsible for important pathologies of the cardiovascular and respiratory systems. In this perspective, great attention has been addressed to Ultra Fine Particles (UFPs < 100 nm), because they efficiently penetrate into the respiratory system and are capable of translocating from the airways into the blood circulation. This paper describes the aerosol regional doses deposited in the human respiratory system in a high-traffic urban area. The aerosol measurements were carried out on a curbside in downtown Rome, on a street characterized by a high density of autovehicular traffic. Aerosol number-size distributions were measured by means of a Fast Mobility Particle Sizer in the range from 5.6 to 560 nm with a 1 s time resolution. Dosimetry estimates were performed with the Multiple-Path Particle Dosimetry model by means of the stochastic lung model. The exposure scenario close to traffic is represented by a sequence of short-term peak exposures: about 6.6 × 10 10 particles are deposited hourly into the respiratory system. After 1 h of exposure in proximity of traffic, 1.29 × 10 10 , 1.88 × 10 10 , and 3.45 × 10 10 particles are deposited in the head, tracheobronchial, and alveolar regions. More than 95 % of such doses are represented by UFPs. Finally, according to the greater dose estimated, the right lung lobes are expected to be more susceptible to respiratory pathologies than the left lobes.

Air pollution: Tropospheric ozone, and wet deposition of sulfate and inorganic nitrogen

Treesearch

John W. Coulston

2009-01-01

The influence of air pollutants on ecosystems in the United States is an important environmental issue. The term “air pollution” encompasses a wide range of topics, but acid deposition and ozone are primary concerns in the context of forest health. Acid deposition partially results from emissions of sulfur dioxide, nitrogen oxides, and ammonia that are deposited in wet...

[Ammonia volatilization loss of nitrogen fertilizer from rice field and wet deposition of atmospheric nitrogen in rice growing season].

PubMed

Su, Chengguo; Yin, Bin; Zhu, Zhaoliang; Shen, Qirong

2003-11-01

Plot and field experiments showed that the NH3 volatilization loss from rice field reached its maximum in 1-3 days after N-fertilization, which was affected by the local climate conditions (e.g., sun illumination, temperature, humidity, wind speed, and rainfall), fertilization time, and ammonium concentration in surface water of the rice field. The wet deposition of atmospheric nitrogen was correlated with the application rate of N fertilizer and the rainfall. The amount of nitrogen brought into soil or surface water by the wet deposition in rice growing season reached 7.5 kg.hm-2. The percent of NH4(+)-N in the wet deposition was about 39.8%-73.2%, with an average of 55.5%. There was a significant correlation of total ammonia volatilization loss with the average concentration of NH4(+)-N in wet deposition and total amount of wet deposition in rice growing season.

Trace organic compounds in wet atmospheric deposition: an overview

USGS Publications Warehouse

Steinheimer, T.R.; Johnson, S.M.

1987-01-01

An overview of the occurrence of organic compounds in wet atmospheric deposition is given. Multiplicity of sources and problems associated with source identification are discussed. Available literature is reviewed by using citations from Chemical Abstracts and Water Resources Abstracts through June 1985 and includes reports published through December 1984 that summarize current knowledge. Approaches to the chemical determination of organic compounds in precipitation are examined in addition to aspects of sampling protocols. Best methods for sample collection and preparation for instrumental analysis continue to be discussed among various investigators. Automatic wet-deposition-only devices for collection and extraction are preferred. Classes of organic compounds that have been identified in precipitation include a spectrum of compounds with differing properties of acidity or basicity, polarity, and water solubility. Those compounds that have been reported in rainfall, snowfall, and ice include hydrocarbons (both aromatic and nonaromatic), chlorinated derivatives of these hydrocarbons, carbonyl compounds (both acidic and nonacidic), and carboxylic acids and esters. Formic and acetic are the most abundant organic acids present. Cloudwater, fogwater, and mist also have been collected and analyzed for organic composition.

Wet and Dry Atmospheric Depositions of Inorganic Nitrogen during Plant Growing Season in the Coastal Zone of Yellow River Delta

PubMed Central

Li, Yunzhao; Du, Siyao; Han, Guangxuan; Xing, Qinghui; Wu, Huifeng; Wang, Guangmei

2014-01-01

The ecological problems caused by dry and wet deposition of atmospheric nitrogen have been widespread concern in the world. In this study, wet and dry atmospheric depositions were monitored in plant growing season in the coastal zone of the Yellow River Delta (YRD) using automatic sampling equipment. The results showed that SO4 2− and Na+ were the predominant anion and cation, respectively, in both wet and dry atmospheric depositions. The total atmospheric nitrogen deposition was ~2264.24 mg m−2, in which dry atmospheric nitrogen deposition was about 32.02%. The highest values of dry and wet atmospheric nitrogen deposition appeared in May and August, respectively. In the studied area, NO3 −–N was the main nitrogen form in dry deposition, while the predominant nitrogen in wet atmospheric deposition was NH4 +–N with ~56.51% of total wet atmospheric nitrogen deposition. The average monthly attribution rate of atmospheric deposition of NO3 −–N and NH4 +–N was ~31.38% and ~20.50% for the contents of NO3 −–N and NH4 +–N in 0–10 cm soil layer, respectively, suggested that the atmospheric nitrogen was one of main sources for soil nitrogen in coastal zone of the YRD. PMID:24977238

Quality of wet deposition in the Grand Calumet River watershed, northwestern Indiana, October 17, 1995-November 12, 1996

USGS Publications Warehouse

Willoughby, Timothy C.

2000-01-01

In June 1992, a wet-deposition collection site was established at the Gary (Indiana) Regional Airport to monitor the quantity and chemical quality of wet deposition. During the first phase of sampling, 48 wet-deposition samples were collected between June 30, 1992, and August 31, 1993. A second phase of sampling began in October 1995. During the second phase of sampling, 40 wet-deposition samples were collected between October 17, 1995, and November 12, 1996. This report presents the findings for the second phase of sampling and compares those results to the first phase of sampling. Northwestern Indiana is a heavily industrialized area. Steel production and petroleum refining are two of the area?s predominant industries. High-temperature processes, such as fossil-fuel combustion and steel production, release contaminants to the atmosphere that may result in wet deposition being a major contributor to major-ion and trace-metal loadings in northwestern Indiana and Lake Michigan. Wet-deposition samples collected during the first and second phases of sampling were analyzed for pH, specific conductance, and selected major ions and trace metals. Forty weekly wet-deposition samples were collected at the Gary (Indiana) Regional Airport during the second phase of sampling. Approximately 1.2 times as much wet deposition was collected during the second phase of sampling compared to the first phase. Statistically significant increases (at the 5-percent significance level) in concentrations of potassium, iron, lead, and zinc were determined for samples collected during the second phase of sampling when compared to the first. No statistically significant differences were determined in constituent concentrations between samples collected during warm weather (April 1 through October 31) and during cold weather (November 1 through March 31). Annual loadings for the second phase of sampling were greater than 2 times the loadings determined during the first phase of sampling for

Rapid deceleration-driven wetting transition during pendant drop deposition on superhydrophobic surfaces.

PubMed

Kwon, Hyuk-Min; Paxson, Adam T; Varanasi, Kripa K; Patankar, Neelesh A

2011-01-21

A hitherto unknown mechanism for wetting transition is reported. When a pendant drop settles upon deposition, there is a virtual "collision" where its center of gravity undergoes rapid deceleration. This induces a high water hammer-type pressure that causes wetting transition. A new phase diagram shows that both large and small droplets can transition to wetted states due to the new deceleration driven and the previously known Laplace mechanisms, respectively. It is explained how the attainment of a nonwetted Cassie-Baxter state is more restrictive than previously known.

Rapid Deceleration-Driven Wetting Transition during Pendant Drop Deposition on Superhydrophobic Surfaces

NASA Astrophysics Data System (ADS)

Kwon, Hyuk-Min; Paxson, Adam T.; Varanasi, Kripa K.; Patankar, Neelesh A.

2011-01-01

A hitherto unknown mechanism for wetting transition is reported. When a pendant drop settles upon deposition, there is a virtual “collision” where its center of gravity undergoes rapid deceleration. This induces a high water hammer-type pressure that causes wetting transition. A new phase diagram shows that both large and small droplets can transition to wetted states due to the new deceleration driven and the previously known Laplace mechanisms, respectively. It is explained how the attainment of a nonwetted Cassie-Baxter state is more restrictive than previously known.

ZnS/diamond composite coatings for infrared transmission applications formed by the aerosol deposition method

NASA Astrophysics Data System (ADS)

Johnson, Scooter D.; Kub, Fritz J.; Eddy, Charles R.

2013-06-01

The deposition of nano-crystalline ZnS/diamond composite protective coatings on silicon, sapphire, and ZnS substrates, as a preliminary step to coating infrared transparent ZnS substrates from powder mixtures by the aerosol deposition method is presented. Advantages of the aerosol deposition method include the ability to form dense, nanocrystalline lms up to hundreds of microns thick at room temperature and at a high deposition rate on a variety of substrates. Deposition is achieved by creating a pressure gradient that accelerates micrometer- scale particles in an aerosol to high velocity. Upon impact with the target substrate the particles fracture and embed. Continued deposition forms the thick compacted lm. Deposition from an aerosolized mixture of ZnS and diamond powders onto all targets results in linear trend from apparent sputter erosion of the substrate at 100% diamond to formation of a lm with increasing fractions of ZnS. The crossover from abrasion to lm formation on sapphire occurs above about 50% ZnS and a mixture of 90% ZnS and 10% diamond forms a well-adhered lm of about 0.7 μm thickness at a rate of 0.14 μm/min. Resulting lms are characterized by scanning electron microscopy, pro lometry, infrared transmission spectroscopy, and x-ray photoemission spectroscopy. These initial lms mark progress toward the future goal of coating ZnS substrates for abrasion resistance.

Hygroscopic aerosol deposition in the human upper respiratory tract under various thermo-humidity conditions.

PubMed

Xi, Jinxiang; Kim, Jongwon; Si, Xiuhua A; Zhou, Yue

2013-01-01

The deposition of hygroscopic aerosols is highly complex in nature, which results from a cumulative effect of dynamic particle growth and the real-time size-specific deposition mechanisms. The objective of this study is to evaluate hygroscopic effects on the particle growth, transport, and deposition of nasally inhaled aerosols across a range of 0.2-2.5 μm in an adult image-based nose-throat model. Temperature and relative humidity fields were simulated using the LRN k-ω turbulence model and species transport model under a spectrum of thermo-humidity conditions. Particle growth and transport were simulated using a well validated Lagrangian tracking model coupled with a user-defined hygroscopic growth module. Results of this study indicate that the saturation level and initial particle size are the two major factors that determine the particle growth rate (d/d0), while the effect of inhalation flow rate is found to be not significant. An empirical correlation of condensation growth of nasally inhaled hygroscopic aerosols in adults has been developed based on a variety of thermo-humidity inhalation conditions. Significant elevated nasal depositions of hygroscopic aerosols could be induced by condensation growth for both sub-micrometer and small micrometer particulates. In particular, the deposition of initially 2.5 μm hygroscopic aerosols was observed to be 5-8 times that of inert particles under warm to hot saturated conditions. Results of this study have important implications in exposure assessment in hot humid environments, where much higher risks may be expected compared to normal conditions.

Wet deposition of brominated flame retardants to the Great Lakes basin--status and trends.

PubMed

Robson, Matthew; Melymuk, Lisa; Bradley, Lisa; Treen, Brenda; Backus, Sean

2013-11-01

This study examined the temporal and spatial trends in wet deposition of 19 legacy and emerging brominated flame retardants (14 polybrominated diphenyl ethers (PBDEs), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), decabromodiphenylethane (DBDPE), hexabromocyclododecane (HBCD) and pentabromoethylbenzene (PBEB)) at 9 sites in the Canadian Great Lakes between 2004 and 2010. Concentrations of BDE-209 in wet deposition declined significantly. This indicates that the voluntary actions taken to phase out the use of BDE 209 in North America are having an immediate effect on its environment concentrations. The analysis also revealed the presence of 22 short-term high concentration events that dominated overall wet deposition loadings of current-use BFRs to the lakes. For instance, one sample in 2007 was responsible for 37% of the total loadings of HBCD to Lake Huron over the entire six-year sampling period. This questions the current paradigm of how we believe such pollutants enter the environment. Copyright © 2013 Elsevier Ltd. All rights reserved.

Wet nitrogen deposition across the urban-intensive agricultural-rural transect of a small urban area in southwest China.

PubMed

Deng, Ouping; Zhang, Shirong; Deng, Liangji; Zhang, Chunlong; Fei, Jianbo

2018-03-01

Understanding of the spatial and temporal variation of the flux of atmospheric nitrogen (N) deposition is essential for assessment of its impact on ecosystems. However, little attention has been paid to the variability of N deposition across urban-intensive agricultural-rural transects. A continuous 2-year observational study (from January 2015 to December 2016) was conducted to determine wet N deposition across the urban-intensive agricultural-rural transect of a small urban area in southwest China. Significantly spatial and temporal variations were found in the research area. Along the urban-intensive agricultural-rural transect, the TN and NH 4 + -N deposition first increased and then decreased, and the NO 3 - -N and dissolved organic N (DON) deposition decreased continuously. Wet N deposition was mainly affected by the districts of agro-facilities, roads and build up lands. Wet NH 4 + -N deposition had non-seasonal emission sources including industrial emissions and urban excretory wastes in urban districts and seasonal emission sources such as fertilizer and manure volatilization in the other districts. However, wet NO 3 - -N deposition had seasonal emission sources such as industrial emissions and fireworks in urban district and non-seasonal emission sources such as transportation in the other districts. Deposition of DON was likely to have had similar sources to NO 3 - -N deposition in rural district, and high-temperature-dependent sources in urban and intensive agricultural districts. Considering the annual wet TN deposition in the intensive agricultural district was about 11.1% of the annual N fertilizer input, N fertilizer rates of crops should be reduced in this region to avoid the excessive application, and the risk of N emissions to the environment.

Seasonal and annual variations and regional characteristics of wet and dry deposition amounts in East Asian region

NASA Astrophysics Data System (ADS)

Sato, K.; Tsuyoshi, O.; Endo, T.; Yagoh, H.; Matsuda, K.

2011-12-01

Emission of sulfur and nitrogen compounds in Asian region has been remarkably increased with recent rapid economical growth (Ohara et al., 2007). To appropriately assess the influence of air pollutants on the ecosystem, it is important to quantitatively determine the atmospheric deposition of air pollutants. Here, Seasonal and annual variations and regional characteristics of estimated wet and dry deposition amounts at 27 monitoring sites of Acid Deposition Monitoring Network in East Asia (EANET) from 2003 to 2009 are discussed. Wet deposition sample was collected every 24 hours or 1 week by a wet only sampler. Wet deposition amounts were calculated by the product of the volume-weighted concentrations of ionic species (SO42-, NO3-, and NH4+) in the precipitation and precipitation amount measured by a standard rain gauge at each site. Dry deposition amount was estimated by the inferential method which was originated the model developed by Wesely and Hicks (1977) and modified by Matsuda (2008). The components examined for dry deposition were sulfur compounds (gaseous SO2 and particulate SO42-) and nitrogen compounds (gaseous HNO3 and NH3, particulate NO3- and NH4+). Dry deposition was calculated by the product of the deposition velocity estimated by the inferential method for forest and grass surfaces and the monitored air concentration of each compound. The mean annual dry deposition amounts for sulfur and nitrogen compounds in Japanese sites were in the range of 5-37 and 7-50 mmol m-2 year-1, respectively. The regional characteristics of dry deposition amounts in Japan were similar between sulfur and nitrogen compounds, which showed higher deposition in the Sea of Japan side and the western Japan. The mean annual total (wet + dry) deposition amounts for sulfur and nitrogen compounds in Japanese sites were in the range of 28-77 and 22-130 mmol m-2 year-1, respectively. The contributions of dry deposition to the total deposition amounts were 10-55% and 13-56% for

Development of the aerosol generation system for simulating the dry deposition behavior of radioaerosol emitted by the accident of FDNPP

NASA Astrophysics Data System (ADS)

Zhang, Z.

2015-12-01

A large amount of radioactivity was discharged by the accident of FDNPP. The long half-life radionuclide, 137Cs was transported through the atmosphere mainly as the aerosol form and deposited to the forests in Fukushima prefecture. After the dry deposition of the 137Cs, the foliar uptake process would occur. To evaluate environmental transfer of radionuclides, the dry deposition and following foliar uptake is very important. There are some pioneering studies for radionuclide foliar uptake with attaching the solution containing stable target element on the leaf, however, cesium oxide aerosols were used for these deposition study [1]. In the FDNPP case, 137Cs was transported in sulfate aerosol form [2], so the oxide aerosol behaviors could not represent the actual deposition behavior in this accident. For evaluation of whole behavior of 137Cs in vegetation system, fundamental data for deposition and uptake process of sulfate aerosol was desired. In this study, we developed aerosol generation system for simulating the dry deposition and the foliar uptake behaviors of aerosol in the different chemical constitutions. In this system, the method of aerosol generation based on the spray drying. Solution contained 137Cs was send to a nozzle by a syringe pump and spraying with a high speed air flow. The sprayed mist was generated in a chamber in the relatively high temperature. The solution in the mist was dried quickly, and micro size solid aerosols consisting 137Cs were generated. The aerosols were suctioned by an ejector and transported inside a tube by the dry air flow, then were directly blown onto the leaves. The experimental condition, such as the size of chamber, chamber temperature, solution flow rate, air flow rate and so on, were optimized. In the deposition experiment, the aerosols on leaves were observed by a SEM/EDX system and the deposition amount was evaluated by measuring the stable Cs remaining on leaf. In the presentation, we will discuss the detail

Precipitation chemistry and wet deposition in a remote wet savanna site in West Africa: Djougou (Benin)

NASA Astrophysics Data System (ADS)

Akpo, A. B.; Galy-Lacaux, C.; Laouali, D.; Delon, C.; Liousse, C.; Adon, M.; Gardrat, E.; Mariscal, A.; Darakpa, C.

2015-08-01

In the framework of the IDAF (IGAC/DEBITS/AFrica) international program, this study aims to study the chemical composition of precipitation and associated wet deposition at the rural site of Djougou in Benin, representative of a West and Central African wet savanna. Five hundred and thirty rainfall samples were collected at Djougou, Benin, from July 2005 to December 2009 to provide a unique database. The chemical composition of precipitation was analyzed for inorganic (Ca2+, Mg2+, Na+, NH4+, K+, NO3-, Cl-, SO42-) and organic (HCOO-, CH3COO-, C2H5COO-, C2O42-) ions, using ion chromatography. The 530 collected rain events represent a total of 5706.1 mm of rainfall compared to the measured pluviometry 6138.9 mm, indicating that the collection efficiency is about 93%. The order of total annual loading rates for soluble cations is NH4+ > Ca2+ > Mg2+ > K+. For soluble anions the order of loading is carbonates > HCOO- > NO3- > CH3COO- > SO42- > Cl- > C2O42- > C2H5COO-. In the wet savanna of Djougou, 86% of the measured pH values range between 4.7 and 5.7 with a median pH of 5.19, corresponding to a VWM (Volume Weighed Mean) H+ concentration of 6.46 μeq·L-1. This acidity results from a mixture of mineral and organic acids. The annual sea salt contribution was computed for K+, Mg2+, Ca2+ and SO42- and represents 4.2% of K+, 41% of Mg2+, 1.3% of Ca2+, and 7.4% of SO42-. These results show that K+, Ca2+, SO42-, and Mg2+ were mainly of non-marine origin. The marine contribution is estimated at 9%. The results of the chemical composition of rainwater of Djougou indicates that, except for the carbonates, ammonium has the highest VWM concentration (14.3 μeq·L-1) and nitrate concentration is 8.2 μeq·L-1. The distribution of monthly VWM concentration for all ions is computed and shows the highest values during the dry season, comparing to the wet season. Identified nitrogenous compound sources (NOx and NH3) are domestic animals, natural emissions from savanna soils, biomass

Trends in mercury wet deposition and mercury air concentrations across the U.S. and Canada

USGS Publications Warehouse

Weiss-Penzias, Peter S.; Gay, David A.; Brigham, Mark E.; Parsons, Matthew T.; Gustin, Mae S.; ter Shure, Arnout

2016-01-01

This study examined the spatial and temporal trends of mercury (Hg) in wet deposition and air concentrations in the United States (U.S.) and Canada between 1997 and 2013. Data were obtained from the National Atmospheric Deposition Program (NADP) and Environment Canada monitoring networks, and other sources. Of the 19 sites with data records from 1997–2013, 53% had significant negative trends in Hg concentration in wet deposition, while no sites had significant positive trends, which is in general agreement with earlier studies that considered NADP data up until about 2010. However, for the time period 2007–2013 (71 sites), 17% and 13% of the sites had significant positive and negative trends, respectively, and for the time period 2008–2013 (81 sites) 30% and 6% of the sites had significant positive and negative trends, respectively. Non-significant positive tendencies were also widespread. Regional trend analyses revealed significant positive trends in Hg concentration in the Rocky Mountains, Plains, and Upper Midwest regions for the recent time periods in addition to significant positive trends in Hg deposition for the continent as a whole. Sulfate concentration trends in wet deposition were negative in all regions, suggesting a lower importance of local Hg sources. The trend in gaseous elemental Hg from short-term datasets merged as one continuous record was broadly consistent with trends in Hg concentration in wet deposition, with the early time period (1998–2007) producing a significantly negative trend (− 1.5 ± 0.2% year− 1) and the recent time period (2008–2013) displaying a flat slope (− 0.3 ± 0.1% year− 1, not significant). The observed shift to more positive or less negative trends in Hg wet deposition primarily seen in the Central-Western regions is consistent with the effects of rising Hg emissions from regions outside the U.S. and Canada and the influence of long-range transport in the free troposphere.

Wet deposition and sources of inorganic nitrogen in the Three Gorges Reservoir Region, China.

PubMed

Wang, Huanbo; Shi, Guangming; Tian, Mi; Chen, Yang; Qiao, Baoqing; Zhang, Liuyi; Yang, Fumo; Zhang, Leiming; Luo, Qiong

2018-02-01

Precipitation samples were collected at five rural and one urban sites in the Three Gorges Reservoir Region (TGR), China from March 2014 to February 2016. The inorganic reactive nitrogen (Nr) contents were analysed to investigate their wet deposition flux, budget, and sources in the area. Annual Nr wet deposition varied from 7.1 to 23.4 kg N ha -1 yr -1 over the six sites during the two-year study campaign. The six-site average Nr wet deposition flux was 17.1 and 11.7 kg N ha -1 yr -1 in 2014 and 2015, respectively, with 71% from NH 4 + and 29% from NO 3 - . Dry deposition flux was estimated using the inferential method, which combined the measured ambient concentrations and modelled dry deposition velocities. The total (dry + wet) Nr deposition fluxes were estimated to be 21.4 kg N ha -1 yr -1 in 2014 and 16.0 kg N ha -1 yr -1 in 2015 at rural sites, and 31.4 and 25.3 kg N ha -1 yr -1 at the urban site. Annual average volume weighted mean (VWM) concentrations in precipitation at all the six sites differed little for NO 3 - but up to a factor of 2.0 for NH 4 + with the highest value at the urban site. Industrial emissions, agricultural emissions, soil dust, and biomass burning were identified as potential sources of the major inorganic ions in precipitation using factor analysis and correlation analysis. Conditional probability function (CPF) analysis indicated that the urban site was predominantly affected by industrial emissions from a power plant, cement manufactory, and salt chemical facility located ∼13 km southeast of the sampling site. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Simplified data assimilation for simulating wet deposition distribution of radioactive materials in FDNPP accident

NASA Astrophysics Data System (ADS)

Saya, A.; Yoshikane, T.; Chang, E. C.; Yoshimura, K.

2015-12-01

Due to the massive earthquakes and tsunami on March 11th 2011 in Eastern Japan, Fukushima Daiichi Nuclear Power Plant (FDNPP) was severely damaged. Radioactive materials were released and spread out by atmospheric advection-diffusion. Especially on March 21 - 23th when precipitation was observed, "hotspot" where the high concentration was detected locally. This area was formed in the metropolitan area in Kanto region. Thus, pollution at water treatment plants because of the deposition became a concern. Therefore, the reliable information of the hotspot is expected. Currently, atmospheric transport simulations by numerical models are developed for reproduction of the distribution. However, there are some uncertainties in the simulations. In the case of hotspot, accuracy of simulated precipitation have to be well considered because the hotspot seemed to be formed by wet deposition. We modified the stable isotope mode of Regional Spectral Model (IsoRSM) to enable to simulate the transport of the radioactive tracers, namely 131I and 137Cs, by including the dry and wet deposition processes. As the simplified data assimilation, simulated precipitation was replaced with Radar-AMeDAS precipitation data (RAP). RAP was assimilated in the post-process, after running simulations, to redistribute wet deposition of 137Cs. The ratio of 137Cs deposited from the cumulative vertical column with precipitation in the domain was not changed, however its pattern was redistributed corresponding with RAP and simulated concentration. As a result, the redistributed wet deposition was within factor 10 to 2 compared with the fallout data in Kanto region, and further data assimilation would be contributed. In addition, we found that due to the arrival time of the plume in the morning on 21st and the border time of daily observation data of fallout, validation result might be worse even though hourly distributions are well simulated.

Aerosol Fluxes over Amazon Rain Forest Measured with the Eddy Covariance Method

NASA Astrophysics Data System (ADS)

Ahlm, L.; Nilsson, E. D.; Krejci, R.; Mårtensson, E. M.; Vogt, M.; Artaxo, P.

2008-12-01

We present measurements of vertical aerosol fluxes over the Amazon carried out on top of K34, a 50 meter high tower in the Cuieiras Reserve about 50 km north of Manaus in northern Brazil. The turbulent fluxes were measured with the eddy covariance method. The covariance of vertical wind speed from a sonic anemometer Gill Windmaster and total aerosol number concentration from a condensation particle counter (CPC) TSI 3010 provided the total number flux (diameter >0.01 μm). The covariance of vertical wind speed and size resolved number concentrations from an optical particle counter (OPC) Grimm 1.109 provided size resolved number fluxes in 15 bins from 0.25 μm to 2.5 μm diameter. Additionally fluxes of CO2 and H2O were derived from Li-7500 observations. The observational period, from early March to early August, includes both wet and dry season. OPC fluxes generally show net aerosol deposition both during wet and dry season with the largest downward fluxes during midday. CPC fluxes show different patterns in wet and dry season. During dry season, when number concentrations are higher, downward fluxes clearly dominate. In the wet season however, when number concentrations are lower, our data indicates that upward and downward fluxes are quite evenly distributed during course of a day. On average there is a peak in upward flux during late morning and another peak during the afternoon. Since the OPC fluxes in the same time show net deposition, there is an indication of net source of primary aerosol particles with diameters between 10 and 250 nm emitted from the rain forest. Future data analysis will hopefully shed light on origin and formation mechanism of these particles and thus provide a deeper insight in the rain forest - atmosphere interactions. The aerosol flux measurements were carried out as a part of the AMAZE project in collaboration with University of Sao Paulo, Brazil, and financial support was provided by Swedish International Development Cooperation

Deposition of aerosol particles in human lungs: in vivo measurements and modeling

EPA Science Inventory

The deposition dose and site of inhaled particles within the lung are the key determinants in health risk assessment of particulate pollutants. Accurate dose estimation, however, is a formidable task because aerosol transport and deposition in the lung are governed by many factor...

Extraction of Aerosol-Deposited Yersinia pestis from Indoor Surfaces To Determine Bacterial Environmental Decay

PubMed Central

Bartlett, Ryan A.; Yeager, John J.; Leroux, Brian; Ratnesar-Shumate, Shanna; Dabisch, Paul

2016-01-01

ABSTRACT Public health and decontamination decisions following an event that causes indoor contamination with a biological agent require knowledge of the environmental persistence of the agent. The goals of this study were to develop methods for experimentally depositing bacteria onto indoor surfaces via aerosol, evaluate methods for sampling and enumerating the agent on surfaces, and use these methods to determine bacterial surface decay. A specialized aerosol deposition chamber was constructed, and methods were established for reproducible and uniform aerosol deposition of bacteria onto four coupon types. The deposition chamber facilitated the control of relative humidity (RH; 10 to 70%) following particle deposition to mimic the conditions of indoor environments, as RH is not controlled by standard heating, ventilation, and air conditioning (HVAC) systems. Extraction and culture-based enumeration methods to quantify the viable bacteria on coupons were shown to be highly sensitive and reproducible. To demonstrate the usefulness of the system for decay studies, Yersinia pestis persistence as a function of surface type at 21°C and 40% RH was determined to be >40%/min for all surfaces. Based upon these results, at typical indoor temperature and RH, a 6-log reduction in titer would expected to be achieved within 1 h as the result of environmental decay on surfaces without active decontamination. The developed approach will facilitate future persistence and decontamination studies with a broad range of biological agents and surfaces, providing agent decay data to inform both assessments of risk to personnel entering a contaminated site and decontamination decisions following biological contamination of an indoor environment. IMPORTANCE Public health and decontamination decisions following contamination of an indoor environment with a biological agent require knowledge of the environmental persistence of the agent. Previous studies on Y. pestis persistence have

Aerosol profiling with lidar in the Amazon Basin during the wet and dry season

NASA Astrophysics Data System (ADS)

Baars, H.; Ansmann, A.; Althausen, D.; Engelmann, R.; Heese, B.; Müller, D.; Artaxo, P.; Paixao, M.; Pauliquevis, T.; Souza, R.

2012-11-01

For the first time, multiwavelength polarization Raman lidar observations of optical and microphysical particle properties over the Amazon Basin are presented. The fully automated advanced Raman lidar was deployed 60 km north of Manaus, Brazil (2.5°S, 60°W) in the Amazon rain forest from January to November 2008. The measurements thus cover both the wet season (Dec-June) and the dry or burning season (July-Nov). Two cases studies of young and aged smoke plumes are discussed in terms of spectrally resolved optical properties (355, 532, and 1064 nm) and further lidar products such as particle effective radius and single-scattering albedo. These measurement examples confirm that biomass burning aerosols show a broad spectrum of optical, microphysical, and chemical properties. The statistical analysis of the entire measurement period revealed strong differences between the pristine wet and the polluted dry season. African smoke and dust advection frequently interrupt the pristine phases during the wet season. Compared to pristine wet season conditions, the particle scattering coefficients in the lowermost 2 km of the atmosphere were found to be enhanced, on average, by a factor of 4 during periods of African aerosol intrusion and by a factor of 6 during the dry (burning) season. Under pristine conditions, the particle extinction coefficients and optical depth for 532 nm wavelength were frequently as low as 10-30 Mm-1 and <0.05, respectively. During the dry season, biomass burning smoke plumes reached to 3-5 km height and caused a mean optical depth at 532 nm of 0.26. On average during that season, particle extinction coefficients (532 nm) were of the order of 100 Mm-1 in the main pollution layer (up to 2 km height). Ångström exponents were mainly between 1.0 and 1.5, and the majority of the observed lidar ratios were between 50-80 sr.

Wet deposition at the base of Mt Everest: Seasonal evolution of the chemistry and isotopic composition

NASA Astrophysics Data System (ADS)

Balestrini, Raffaella; Delconte, Carlo A.; Sacchi, Elisa; Wilson, Alana M.; Williams, Mark W.; Cristofanelli, Paolo; Putero, Davide

2016-12-01

The chemistry of wet deposition was investigated during 2012-2014 at the Pyramid International Laboratory in the Upper Khumbu Valley, Nepal, at 5050 m a.s.l., within the Global Atmosphere Watch (GAW) programme. The main hydro-chemical species and stable isotopes of the water molecule were determined for monsoon rain (July-September) and snow samples (October-June). To evaluate the synoptic-scale variability of air masses reaching the measurement site, 5 day back-trajectories were computed for the sampling period. Ion concentrations in precipitation during the monsoon were low suggesting that they represent global regional background concentrations. The associations between ions suggested that the principal sources of chemical species were marine aerosols, rock and soil dust, and fossil fuel combustion. Most chemical species exhibited a pattern during the monsoon, with maxima at the beginning and at the end of the season, partially correlated with the precipitation amount. Snow samples exhibited significantly higher concentrations of chemical species, compared to the monsoon rainfall observations. Particularly during 2013, elevated concentrations of NO3-, SO42- and NH4+ were measured in the first winter snow event, and in May at the end of the pre-monsoon season. The analysis of large-scale circulation and wind regimes as well as atmospheric composition observations in the region indicates the transport of polluted air masses from the Himalayan foothills and Indian sub-continent up to the Himalaya region. During the summer monsoon onset period, the greater values of pollutants can be attributed to air-mass transport from the planetary boundary layer (PBL) of the Indo-Gangetic plains. Isotopic data confirm that during the monsoon period, precipitation occurred from water vapor that originated from the Indian Ocean and the Bay of Bengal; by contrast during the non-monsoon period, an isotopic signature of more continental origin appeared, indicating that the higher

Trends in bromide wet deposition concentrations in the contiguous United States, 2001-2016.

PubMed

Wetherbee, Gregory A; Lehmann, Christopher M B; Kerschner, Brian M; Ludtke, Amy S; Green, Lee A; Rhodes, Mark F

2018-02-01

Bromide (Br - ) and other solute concentration data from wet deposition samples collected and analyzed by the National Atmospheric Deposition Program (NADP) from 2001 to 2016, were statistically analyzed for trends both geographically and temporally by precipitation type. Analysis was limited to NADP sites in the contiguous 48 United States. The Br - concentrations for this time period had a high number of values censored at the detection limits with greater than 86 percent of sample concentrations below analytical detection. Bromide was more frequently detected at NADP sites in coastal regions. Analysis using specialized statistical techniques for censored data revealed that Br - concentrations varied by precipitation type with higher concentrations usually observed in liquid versus precipitation containing snow. Negative temporal trends in Br - wet deposition concentrations were observed at a majority of NADP sites; approximately 25 percent of these trend values were statistically significant at less than 0.05 to 0.10 significance levels. Potential causes for the negative trends were explored, including annual and seasonal changes in precipitation depth, reduced emissions of methyl bromide (CH 3 Br) from coastal wetlands, and declining industrial use of bromine compounds. The results indicate that Br - in non-coastal wet-deposition comes mainly from long-range transport, not local sources. Correlations between Br - , chloride, and nitrate concentrations also were evaluated. Published by Elsevier Ltd.

Empirical model for conveniently predicting total and regional lung deposition of inhaled aerosols

EPA Science Inventory

Accurate estimate of a dose of inhaled aerosols is a key factor for estimating potential health risks to exposure to ambient pollutant particulate matter on the one hand, and the therapeutic efficacy of inhaled drug aerosols on the other hand. Particle deposition in the lung is d...

Meteorological effects on Hg wet deposition in a forested site in the Adirondack region of New York during 2000-2015

NASA Astrophysics Data System (ADS)

Mao, Huiting; Ye, Zhuyun; Driscoll, Charles

2017-11-01

An analysis of weekly measurement data of mercury (Hg) wet deposition was conducted for Huntington Wildlife Forest (HWF), a forest ecosystem in Upstate New York and a biological Hg hotspot, during 2000-2015. Annual accumulated Hg wet deposition flux was found to decrease at a rate of -0.13 μg m-2 yr-1 (2% yr-1) (p = 0.09), and volume weighted mean (VWM) Hg precipitation concentrations at -0.14 ng L-1 yr-1 (2.5% yr-1) (p = 0.00). In examining data by season, no trends were identified for the two variables. It was found that the North Atlantic Oscillation (NAO) affected Hg wet deposition predominantly in spring, as did the position of the U.S. East Coast trough in summer, which suggests different dominant mechanisms driving Hg wet deposition in different seasons. The impacts of such large scale circulation processes were facilitated via variations in precipitation amounts. This was manifested in spring 2011 with the strongest positive phase of NAO, resulting in the wettest spring with the largest Hg wet deposition flux, and in summer 2007 with the U.S. East Coast trough positioned the farthest out over the Atlantic Ocean, causing the driest summer with the lowest Hg wet deposition flux of the study period. Extreme precipitation amounts in spring could singularly drive the overall long-term trend in Hg wet deposition whereas in summer other factors could just be as important. Similar mechanisms were thought to control the long term variations of Hg wet deposition and precipitation concentrations in all seasons but summer as indicated in their significant correlation in all but summer. Atmospheric concentrations of gaseous oxidized mercury (GOM) and particulate borne mercury (PBM) at HWF over 2009-2015 hardly exhibited correlations with Hg wet deposition or precipitation concentrations. Chemical transport model simulations strongly supported efficient scavenging of oxidized Hg by precipitation resulting in the lowest concentration of GOM in the warm season despite the

Interlaboratory comparability, bias, and precision for four laboratories measuring analytes in wet deposition, October 1983-December 1984

USGS Publications Warehouse

Brooks, Myron H.; Schroder, LeRoy J.; Willoughby, Timothy C.

1987-01-01

Four laboratories involved in the routine analysis of wet-deposition samples participated in an interlaboratory comparison program managed by the U.S. Geological Survey. The four participants were: Illinois State Water Survey central analytical laboratory in Champaign, Illinois; U.S. Geological Survey national water-quality laboratories in Atlanta, Georgia, and Denver, Colorado; and Inland Waters Directorate national water-quality laboratory in Burlington, Ontario, Canada. Analyses of interlaboratory samples performed by the four laboratories from October 1983 through December 1984 were compared.Participating laboratories analyzed three types of interlaboratory samples--natural wet deposition, simulated wet deposition, and deionized water--for pH and specific conductance, and for dissolved calcium, magnesium, sodium, sodium, potassium, chloride, sulfate, nitrate, ammonium, and orthophosphate. Natural wet-deposition samples were aliquots of actual wet-deposition samples. Analyses of these samples by the four laboratories were compared using analysis of variance. Test results indicated that pH, calcium, nitrate, and ammonium results were not directly comparable among the four laboratories. Statistically significant differences between laboratory results probably only were meaningful for analyses of dissolved calcium. Simulated wet-deposition samples with known analyte concentrations were used to test each laboratory for analyte bias. Laboratory analyses of calcium, magnesium, sodium, potassium, chloride, sulfate, and nitrate were not significantly different from the known concentrations of these analytes when tested using analysis of variance. Deionized-water samples were used to test each laboratory for reporting of false positive values. The Illinois State Water Survey Laboratory reported the smallest percentage of false positive values for most analytes. Analyte precision was estimated for each laboratory from results of replicate measurements. In general, the

Characterization of wet and dry deposition in the downwind of industrial sources in a dry tropical area.

PubMed

Singh, R K; Agrawal, M

2001-12-19

An atmospheric deposition study was conducted in the downwind of Shaktinagar Thermal Power Plant (STPP), Renusagar Thermal Power Plant (RTPP), and Anpara Thermal Power Plant (ATPP), at Singrauli region, Uttar Pradesh (UP), India to characterize dry and wet deposition in relation to different pollution loading. During the study period, dry and wet depositions and levels of gaseous pollutants (SO2 and NO2) were estimated across the sites. Dry deposition was collected on a monthly basis and wet deposition on an event basis. Depositions were analyzed for pH, nitrate (NO3-), ammonium (NH4+), and sulphate (SO4(2-)) contents. Dry deposition rate both collected as clearfall and throughfall varied between 0.15 to 2.28 and 0.33 to 3.48 g m(-2) day(-1), respectively, at control and maximally polluted sites. The pH of dry deposition varied from 5.81 to 6.89 during winter and 6.09 to 7.02 during summer across the sites. During the rainy season, the mean pH of clear wet deposition varied from 6.56 to 7.04 and throughfall varied from 6.81 to 7.22. The concentrations of NO2 and SO2 pollutants were highest during the winter season. Mean SO2 concentrations varied from 18 to 75 g m(-3) at control and differently polluted sites during the winter season. The variation in NO2 concentrations did not show a pattern similar to that of SO2. The highest NO2 concentration during the winter season was 50 g m(-3), observed near RTPP. NO2 concentration did not show much variation among different sites, suggesting that the sources of NO2 emission are evenly distributed along the sites. The concentrations of NH4+, NO3-, and SO4(2-) ions in dry deposition were found to be higher in summer as compared to the winter season. In dry deposition (clearfall) the concentrations of NH4+, NO3-, and SO4(2-) varied from 0.13 to 1.0, 0.81 to 1.95, and 0.82 to 3.27 mg l(-1), respectively, during winter. In wet deposition (clearfall), the above varied from 0.14 to 0.74, 0.81 to 1.82, and 0.67 to 2.70 mg l(-1

A Hybrid Approach for Estimating Total Deposition in the ...

EPA Pesticide Factsheets

Atmospheric deposition of nitrogen and sulfur causes many deleterious effects on ecosystems including acidification and excess eutrophication. Assessments to support development of strategies to mitigate these effects require spatially and temporally continuous values of nitrogen and sulfur deposition. In the U.S., national monitoring networks exist that provide values of wet and dry deposition at discrete locations. While wet deposition can be interpolated between the monitoring locations, dry deposition cannot. Additionally, monitoring networks do not measure the complete suite of chemicals that contribute to total sulfur and nitrogen deposition. Regional air quality models provide spatially continuous values of deposition of monitored species as well as important unmeasured species. However, air quality modeling values are not generally available for an extended continuous time period. Air quality modeling results may also be biased for some chemical species. We developed a novel approach for estimating dry deposition using data from monitoring networks such as the Clean Air Status and Trends Network (CASTNET), the National Atmospheric Deposition Program (NADP) Ammonia Monitoring Network (AMoN), and the Southeastern Aerosol Research and Characterization (SEARCH) network and modeled data from the Community Multiscale Air Quality (CMAQ) model. These dry deposition values estimates are then combined with wet deposition values from the NADP National Trends Networ

A Novel Hybrid Approach for Estimating Total Deposition in ...

EPA Pesticide Factsheets

Atmospheric deposition of nitrogen and sulfur causes many deleterious effects on ecosystems including acidification and excess eutrophication. Assessments to support development of strategies to mitigate these effects require spatially and temporally continuous values of nitrogen and sulfur deposition. In the U.S., national monitoring networks exist that provide values of wet and dry deposition at discrete locations. While wet deposition can be interpolated between the monitoring locations, dry deposition cannot. Additionally, monitoring networks do not measure the complete suite of chemicals that contribute to total sulfur and nitrogen deposition. Regional air quality models provide spatially continuous values of deposition of monitored species as well as important unmeasured species. However, air quality modeling values are not generally available for an extended continuous time period. Air quality modeling results may also be biased for some chemical species. We developed a novel approach for estimating dry deposition using data from monitoring networks such as the Clean Air Status and Trends Network (CASTNET), the National Atmospheric Deposition Program (NADP) Ammonia Monitoring Network (AMoN), and the Southeastern Aerosol Research and Characterization (SEARCH) network and modeled data from the Community Multiscale Air Quality (CMAQ) model. These dry deposition values estimates are then combined with wet deposition values from the NADP National Trends Networ

Investigating the Impact of Aerosol Deposition on Snow Melt over the Greenland Ice Sheet Using a New Kernel

NASA Astrophysics Data System (ADS)

Li, Y.; Flanner, M.

2017-12-01

Accelerating surface melt on the Greenland Ice Sheet (GrIS) has led to a doubling of Greenland's contribution to global sea level rise during recent decades. The darkening effect due to black carbon (BC), dust, and other light absorbing impurities (LAI) enhances snow melt by boosting its absorption of solar energy. It is therefore important for coupled aerosol-climate and ice sheet models to include snow darkening effects from LAI, and yet most do not. In this study, we develop an aerosol deposition—snow melt kernel based on the Community Earth System Model (CESM) to investigate changes in melt flux due to variations in the amount and timing of aerosol deposition on the GrIS. The Community Land Model (CLM) component of CESM is driven with a large range of aerosol deposition fluxes to determine non-linear relationships between melt perturbation and deposition amount occurring in different months and location (thereby capturing variations in base state associated with elevation and latitude). The kernel product will include climatological-mean effects and standard deviations associated with interannual variability. Finally, the kernel will allow aerosol deposition fluxes from any global or regional aerosol model to be translated into surface melt perturbations of the GrIS, thus extending the utility of state-of-the-art aerosol models.

Osteogenic Responses to Zirconia with Hydroxyapatite Coating by Aerosol Deposition

PubMed Central

Cho, Y.; Hong, J.; Ryoo, H.; Kim, D.; Park, J.

2015-01-01

Previously, we found that osteogenic responses to zirconia co-doped with niobium oxide (Nb2O5) or tantalum oxide (Ta2O5) are comparable with responses to titanium, which is widely used as a dental implant material. The present study aimed to evaluate the in vitro osteogenic potential of hydroxyapatite (HA)-coated zirconia by an aerosol deposition method for improved osseointegration. Surface analysis by scanning electron microscopy and x-ray diffraction proved that a thin as-deposited HA film on zirconia showed a shallow, regular, crater-like surface. Deposition of dense and uniform HA films was measured by SEM, and the contact angle test demonstrated improved wettability of the HA-coated surface. Confocal laser scanning microscopy indicated that MC3T3-E1 pre-osteoblast attachment did not differ notably between the titanium and zirconia surfaces; however, cells on the HA-coated zirconia exhibited a lower proliferation than those on the uncoated zirconia late in the culture. Nevertheless, ALP, alizarin red S staining, and bone marker gene expression analysis indicated good osteogenic responses on HA-coated zirconia. Our results suggest that HA-coating by aerosol deposition improves the quality of surface modification and is favorable to osteogenesis. PMID:25586588

Simplified aerosol modeling for variational data assimilation

NASA Astrophysics Data System (ADS)

Huneeus, N.; Boucher, O.; Chevallier, F.

2009-11-01

We have developed a simplified aerosol model together with its tangent linear and adjoint versions for the ultimate aim of optimizing global aerosol and aerosol precursor emission using variational data assimilation. The model was derived from the general circulation model LMDz; it groups together the 24 aerosol species simulated in LMDz into 4 species, namely gaseous precursors, fine mode aerosols, coarse mode desert dust and coarse mode sea salt. The emissions have been kept as in the original model. Modifications, however, were introduced in the computation of aerosol optical depth and in the processes of sedimentation, dry and wet deposition and sulphur chemistry to ensure consistency with the new set of species and their composition. The simplified model successfully manages to reproduce the main features of the aerosol distribution in LMDz. The largest differences in aerosol load are observed for fine mode aerosols and gaseous precursors. Differences between the original and simplified models are mainly associated to the new deposition and sedimentation velocities consistent with the definition of species in the simplified model and the simplification of the sulphur chemistry. Furthermore, simulated aerosol optical depth remains within the variability of monthly AERONET observations for all aerosol types and all sites throughout most of the year. Largest differences are observed over sites with strong desert dust influence. In terms of the daily aerosol variability, the model is less able to reproduce the observed variability from the AERONET data with larger discrepancies in stations affected by industrial aerosols. The simplified model however, closely follows the daily simulation from LMDz. Sensitivity analyses with the tangent linear version show that the simplified sulphur chemistry is the dominant process responsible for the strong non-linearity of the model.

Extraction of Aerosol-Deposited Yersinia pestis from Indoor Surfaces To Determine Bacterial Environmental Decay.

PubMed

Gut, Ian M; Bartlett, Ryan A; Yeager, John J; Leroux, Brian; Ratnesar-Shumate, Shanna; Dabisch, Paul; Karaolis, David K R

2016-05-01

Public health and decontamination decisions following an event that causes indoor contamination with a biological agent require knowledge of the environmental persistence of the agent. The goals of this study were to develop methods for experimentally depositing bacteria onto indoor surfaces via aerosol, evaluate methods for sampling and enumerating the agent on surfaces, and use these methods to determine bacterial surface decay. A specialized aerosol deposition chamber was constructed, and methods were established for reproducible and uniform aerosol deposition of bacteria onto four coupon types. The deposition chamber facilitated the control of relative humidity (RH; 10 to 70%) following particle deposition to mimic the conditions of indoor environments, as RH is not controlled by standard heating, ventilation, and air conditioning (HVAC) systems. Extraction and culture-based enumeration methods to quantify the viable bacteria on coupons were shown to be highly sensitive and reproducible. To demonstrate the usefulness of the system for decay studies,Yersinia pestis persistence as a function of surface type at 21 °C and 40% RH was determined to be >40%/min for all surfaces. Based upon these results, at typical indoor temperature and RH, a 6-log reduction in titer would expected to be achieved within 1 h as the result of environmental decay on surfaces without active decontamination. The developed approach will facilitate future persistence and decontamination studies with a broad range of biological agents and surfaces, providing agent decay data to inform both assessments of risk to personnel entering a contaminated site and decontamination decisions following biological contamination of an indoor environment. Public health and decontamination decisions following contamination of an indoor environment with a biological agent require knowledge of the environmental persistence of the agent. Previous studies on Y. pestis persistence have utilized large liquid

Quantifying black carbon deposition over the Greenland ice sheet from forest fires in Canada

NASA Astrophysics Data System (ADS)

Thomas, J. L.; Polashenski, C. M.; Soja, A. J.; Marelle, L.; Casey, K. A.; Choi, H. D.; Raut, J.-C.; Wiedinmyer, C.; Emmons, L. K.; Fast, J. D.; Pelon, J.; Law, K. S.; Flanner, M. G.; Dibb, J. E.

2017-08-01

Black carbon (BC) concentrations observed in 22 snowpits sampled in the northwest sector of the Greenland ice sheet in April 2014 have allowed us to identify a strong and widespread BC aerosol deposition event, which was dated to have accumulated in the pits from two snow storms between 27 July and 2 August 2013. This event comprises a significant portion (57% on average across all pits) of total BC deposition over 10 months (July 2013 to April 2014). Here we link this deposition event to forest fires burning in Canada during summer 2013 using modeling and remote sensing tools. Aerosols were detected by both the Cloud-Aerosol Lidar with Orthogonal Polarization (on board CALIPSO) and Moderate Resolution Imaging Spectroradiometer (Aqua) instruments during transport between Canada and Greenland. We use high-resolution regional chemical transport modeling (WRF-Chem) combined with high-resolution fire emissions (FINNv1.5) to study aerosol emissions, transport, and deposition during this event. The model captures the timing of the BC deposition event and shows that fires in Canada were the main source of deposited BC. However, the model underpredicts BC deposition compared to measurements at all sites by a factor of 2-100. Underprediction of modeled BC deposition originates from uncertainties in fire emissions and model treatment of wet removal of aerosols. Improvements in model descriptions of precipitation scavenging and emissions from wildfires are needed to correctly predict deposition, which is critical for determining the climate impacts of aerosols that originate from fires.

Quantifying Black Carbon Deposition Over the Greenland Ice Sheet from Forest Fires in Canada

NASA Technical Reports Server (NTRS)

Thomas, J. L.; Polashenski, C. M.; Soja, Amber J.; Marelle, L.; Casey, K. A.; Choi, H. D.; Raut, J.-C.; Wiedinmyer, C.; Emmons, L. K.; Fast, J. D.;

Micron-sized and submicron-sized aerosol deposition in a new ex vivo preclinical model.

PubMed

Perinel, Sophie; Leclerc, Lara; Prévôt, Nathalie; Deville, Agathe; Cottier, Michèle; Durand, Marc; Vergnon, Jean-Michel; Pourchez, Jérémie

2016-07-07

The knowledge of where particles deposit in the respiratory tract is crucial for understanding the health effects associated with inhaled drug particles. An ex vivo study was conducted to assess regional deposition patterns (thoracic vs. extrathoracic) of radioactive polydisperse aerosols with different size ranges [0.15 μm-0.5 μm], [0.25 μm-1 μm] and [1 μm-9 μm]. SPECT/CT analyses were performed complementary in order to assess more precisely the regional deposition of aerosols within the pulmonary tract. Experiments were set using an original respiratory tract model composed of a human plastinated head connected to an ex vivo porcine pulmonary tract. The model was ventilated by passive expansion, simulating pleural depressions. Aerosol was administered during nasal breathing. Planar scintigraphies allowed to calculate the deposited aerosol fractions for particles in the three size ranges from sub-micron to micron The deposited fractions obtained, for thoracic vs. extra-thoracic regions respectively, were 89 ± 4 % vs. 11 ± 4 % for [0.15 μm-0.5 μm], 78 ± 5 % vs. 22 ± 5 % for [0.25 μm-1 μm] and 35 ± 11 % vs.65 ± 11 % for [1 μm-9 μm]. Results obtained with this new ex vivo respiratory tract model are in good agreement with the in vivo data obtained in studies with baboons and humans.

Comparison of secondary organic aerosol formation from toluene on initially wet and dry ammonium sulfate particles at moderate relative humidity

NASA Astrophysics Data System (ADS)

Liu, Tengyu; Huang, Dan Dan; Li, Zijun; Liu, Qianyun; Chan, ManNin; Chan, Chak K.

2018-04-01

The formation of secondary organic aerosol (SOA) has been widely studied in the presence of dry seed particles at low relative humidity (RH). At higher RH, initially dry seed particles can exist as wet particles due to water uptake by the seeds as well as the SOA. Here, we investigated the formation of SOA from the photooxidation of toluene using an oxidation flow reactor in the absence of NOx under a range of OH exposures on initially wet or dry ammonium sulfate (AS) seed particles at an RH of 68 %. The ratio of the SOA yield on wet AS seeds to that on dry AS seeds, the relative SOA yield, decreased from 1.31 ± 0.02 at an OH exposure of 4.66 × 1010 molecules cm-3 s to 1.01 ± 0.01 at an OH exposure of 5.28 × 1011 molecules cm-3 s. This decrease may be due to the early deliquescence of initially dry AS seeds after being coated by highly oxidized toluene-derived SOA. SOA formation lowered the deliquescence RH of AS and resulted in the uptake of water by both AS and SOA. Hence the initially dry AS seeds contained aerosol liquid water (ALW) soon after SOA formed, and the SOA yield and ALW approached those of the initially wet AS seeds as OH exposure and ALW increased, especially at high OH exposure. However, a higher oxidation state of the SOA on initially wet AS seeds than that on dry AS seeds was observed at all levels of OH exposure. The difference in mass fractions of m / z 29, 43 and 44 of SOA mass spectra, obtained using an aerosol mass spectrometer (AMS), indicated that SOA formed on initially wet seeds may be enriched in earlier-generation products containing carbonyl functional groups at low OH exposures and later-generation products containing acidic functional groups at high exposures. Our results suggest that inorganic dry seeds become at least partially deliquesced particles during SOA formation and hence that ALW is inevitably involved in the SOA formation at moderate RH. More laboratory experiments conducted with a wide variety of SOA

Deposition rates of fungal spores in indoor environments, factors effecting them and comparison with non-biological aerosols

NASA Astrophysics Data System (ADS)

Kanaani, Hussein; Hargreaves, Megan; Ristovski, Zoran; Morawska, Lidia

Particle deposition indoors is one of the most important factors that determine the effect of particle exposure on human health. While many studies have investigated the particle deposition of non-biological aerosols, few have investigated biological aerosols and even fewer have studied fungal spore deposition indoors. The purpose of this study was, for the first time, to investigate the deposition rates of fungal particles in a chamber of 20.4 m 3 simulating indoor environments by: (1) releasing fungal particles into the chamber, in sufficient concentrations so the particle deposition rates can be statistically analysed; (2) comparing the obtained deposition rates with non-bioaerosol particles of similar sizes, investigated under the same conditions; and (3) investigating the effects of ventilation on the particle deposition rates. The study was conducted for a wide size range of particle sizes (0.54-6.24 μm), at three different air exchange rates (0.009, 1.75 and 2.5 h -1). An Ultraviolet Aerodynamic Particle Sizer Spectrometer (UVAPS) was used to monitor the particle concentration decay rate. The study showed that the deposition rates of fungal spores ( Aspergillus niger and Penicillium species) and the other aerosols (canola oil and talcum powder) were similar, especially at very low air exchange rates (in the order of 0.009). Both the aerosol and the bioaerosol deposition rates were found to be a function of particle size. The results also showed increasing deposition rates with increasing ventilation rates, for all particles under investigation. These conclusions are important in understanding the dynamics of fungal spores in the air.

Deposition of amorphous carbon thin films by aerosol-assisted CVD method

NASA Astrophysics Data System (ADS)

Fadzilah, A. N.; Dayana, K.; Rusop, M.

2018-05-01

This paper reports on the deposition of amorphous carbon (a-C) by Aerosol-assisted Chemical Vapor Deposition (AACVD) using natural source of camphor oil as the precursor material. 4 samples were deposited at 4 different deposition flow rate from 15 sccm to 20 sccm, with 5 sccm interval for each sample. The analysis includes the electrical, optical and structural analysis of the data. The a-C structure which came from the manipulation of synthesis parameter was characterized by the solar simulator system, UV-VIS-NIR, Raman spectroscope and AFM. The properties of a-C are highly dependent on the deposition techniques and deposition parameters; hence the influences of gas flow rate were studied.

Deceleration-driven wetting transition of "gently" deposited drops on textured hydrophobic surfaces

NASA Astrophysics Data System (ADS)

Varanasi, Kripa; Kwon, Hyukmin; Paxson, Adam; Patankar, Neelesh

2010-11-01

Many applications of rough superhydrophobic surfaces rely on the presence of droplets in a Cassie state on the substrates. A well established understanding is that if sessile droplets are smaller than a critical size, then the large Laplace pressure induces wetting transition from a Cassie to a Wenzel state, i.e., the liquid impales the roughness grooves. Thus, larger droplets are expected to remain in the Cassie state. In this work we report a surprising wetting transition where even a "gentle" deposition of droplets on rough substrates lead to the transition of larger droplets to the Wenzel state. A hitherto unknown mechanism based on rapid deceleration is identified. It is found that modest amount of energy, during the deposition process, is channeled through rapid deceleration into high water hammer pressure which induces wetting transition. A new "phase" diagram is reported which shows that both large and small droplets can transition to Wenzel states due to the deceleration and Laplace mechanisms, respectively. This novel insight reveals for the first time that the attainment of a Cassie state is more restrictive than previous criteria based on the Laplace pressure transition mechanism.

AN EXAMINATION OF THE CMAQ SIMULATIONS OF THE WET DEPOSITION OF AMMONIUM FROM A BAYESIAN PERSPECTIVE

EPA Science Inventory

The objective of this study is to ascertain the effects of precipitation simulations and emissions on CMAQ simulations of deposition. In both seasons, CMAQ tends to underpredict the deposition amounts. Based on the co-located measurements of ammonium wet deposition and precipita...

Estimates of inorganic nitrogen wet deposition from precipitation for the conterminous United States, 1955-84

USGS Publications Warehouse

Gronberg, Jo Ann M.; Ludtke, Amy S.; Knifong, Donna L.

2014-01-01

The U.S. Geological Survey’s National Water-Quality Assessment program requires nutrient input information for analysis of national and regional assessment of water quality. Historical data are needed to lengthen the data record for assessment of trends in water quality. This report provides estimates of inorganic nitrogen deposition from precipitation for the conterminous United States for 1955–56, 1961–65, and 1981–84. The estimates were derived from ammonium, nitrate, and inorganic nitrogen concentrations in atmospheric wet deposition and precipitation-depth data. This report documents the sources of these data and the methods that were used to estimate the inorganic nitrogen deposition. Tabular datasets, including the analytical results, precipitation depth, and calculated site-specific precipitation-weighted concentrations, and raster datasets of nitrogen from wet deposition are provided as appendixes in this report.

Soluble Nutrient and Trace Metal Fluxes from Aerosol Dry Deposition to Elkhorn Slough, CA

NASA Astrophysics Data System (ADS)

Gray, E. T.; Paytan, A.; Haskins, J.

2009-12-01

Atmospheric deposition has been widely recognized as a source of pollutants and nutrients to coastal ecosystems. Specifically, deposition includes nitrogen compounds, sulfur compounds, mercury, pesticides, phosphate, trace metals and other toxic compounds that can travel great distances in aerosols. These components can come from both natural (volcanoes, mineral dust, forest fires) and anthropogenic (fossil fuels, chemical byproducts, incineration of waste) sources. These pollutants may affect ecosystem health and water quality with environmental impacts such as eutrophication, contaminated fish and harmful algal blooms. In this study we focus on dry deposition to Elkhorn Slough, California. Size fractionated aerosol samples (PM 2.5 and PM 10) collected continuously over a seven day period using a cascade impactor are used along with a deposition model to determine the soluble nutrient and trace metal fluxes on the Elkhorn Slough ecosystem. Atmospheric deposition inputs will be compared to other sources and their potential impact evaluated.

Characterizations of wet mercury deposition to a remote islet (Pengjiayu) in the subtropical Northwest Pacific Ocean

NASA Astrophysics Data System (ADS)

Sheu, Guey-Rong; Lin, Neng-Huei

2013-10-01

Thirty-four weekly rainwater samples were collected in 2009 at Pengjiayu, a remote islet in the subtropical Northwest (NW) Pacific Ocean, to study the distribution of rainwater mercury (Hg) concentrations and associated wet deposition fluxes. This is the first study concerning wet Hg deposition to the subtropical NW Pacific Ocean downwind of the East Asian continent, which is the major source region for Hg emissions worldwide. Sample Hg concentrations ranged from 2.25 to 22.33 ng L-1, with a volume-weighted mean (VWM) concentration of 8.85 ng L-1. The annual wet Hg deposition flux was 10.18 μg m-2, about 2.5 times the fluxes measured at sites on the Pacific coast of the USA, supporting the hypothesis that deposition is higher in the western than in the eastern Pacific. Seasonal VWM concentrations were 7.23, 11.58, 7.82, and 9.84 ng L-1, whereas seasonal wet deposition fluxes were 2.14, 3.45, 2.38, and 2.21 μg m-2, for spring, summer, fall and winter, respectively. Higher summer wet Hg deposition was a function of both higher rainwater Hg concentration and greater rainfall. The seasonal pattern of rainwater Hg concentrations was the opposite of the general seasonal pattern of the East Asian air pollutant export. Since there is no significant anthropogenic Hg emission source on the islet of Pengjiayu, the observed high summertime rainwater Hg concentration hints at the importance of Hg0 oxidation and/or scavenging of upper-altitude reactive gaseous Hg (RGM) by deep convection. Direct anthropogenic RGM emissions from the East Asian continent may not contribute significantly to the rainwater Hg concentrations, but anthropogenic Hg0 emissions could be transported to the upper troposphere or marine boundary layer (MBL) where they can be oxidized to produce RGM, which will then be effectively scavenged by cloud water and rainwater.

Aerosol pollution potential from major population centers

NASA Astrophysics Data System (ADS)

Kunkel, D.; Tost, H.; Lawrence, M. G.

2012-09-01

Major population centers (MPCs) or mega-cities represent the largest of growing urban agglomerations with major societal and environmental implications. In terms of air quality they are seen as localized but strong emission sources of aerosols and trace gases which in turn affect air pollution levels in the city or in downwind regions. In the state-of-the-art atmospheric chemistry general circulation model EMAC, generic aerosol and gas phase tracers with equal emission source strengths at 46 MPC locations are used to study the balance between local pollution build up and pollution export, either vertically into the upper troposphere or horizontally, but remaining in the lower atmosphere. The insoluble gas phase tracers with fixed lifetimes are transported with the atmospheric circulation, while the aerosol tracers also undergo gravitational sedimentation as well as dry and wet deposition processes. The strength of low-level tracer export depends on the location of the emission source and prevailing meteorology, in particular on atmospheric stability and the height of the boundary layer and the mixing out of this layer. In contrast, vertical transport of tracer mass depends on the tracer's solubility: the more soluble a tracer is the less mass reaches altitudes above five kilometers. Hence, the mass of insoluble gas phase tracer above five kilometers can be up to ten times higher than the hydrophilic aerosol mass from the same source. In the case of aerosol tracers, pollution build up around the source is determined by meteorological factors which have only indirect effects on tracer lifetime, like surface wind, boundary layer height, and turbulent mixing as well as those which affect the lifetime of the tracers such as precipitation. The longer a tracer stays in the atmosphere, the lower is the relative importance of the location of the source to the atmospheric mass and thus the lower is the relative local pollution build up. We further use aerosol deposition

Aerosol pollution potential from major population centers

NASA Astrophysics Data System (ADS)

Kunkel, D.; Tost, H.; Lawrence, M. G.

2013-04-01

Major population centers (MPCs), or megacities, represent the largest of growing urban agglomerations with major societal and environmental implications. In terms of air quality, they are seen as localized but strong emission sources of aerosols and trace gases which in turn affect air pollution levels in the city or in downwind regions. In the state-of-the-art atmospheric chemistry general circulation model EMAC, generic aerosol and gas-phase tracers with equal emission source strengths at 46 MPC locations are used to study the balance between local pollution build-up and pollution export, either vertically into the upper troposphere or horizontally in the lower troposphere. The insoluble gas-phase tracers with fixed lifetimes are transported with the atmospheric circulation, while the aerosol tracers also undergo gravitational sedimentation as well as dry and wet deposition processes. The strength of low-level tracer export depends on the location of the emission source and prevailing meteorology, in particular on atmospheric stability and the height of the boundary layer and the mixing out of this layer. In contrast, vertical transport of tracer mass depends on the tracer's solubility: the more soluble a tracer is, the less mass reaches altitudes above five kilometers. Hence, the mass of insoluble gas-phase tracer above five kilometers can be up to ten times higher than the hydrophilic aerosol mass from the same source. In the case of aerosol tracers, pollution build-up around the source is determined by meteorological factors which have only indirect effects on tracer lifetime, like surface wind, boundary layer height, and turbulent mixing, as well as those which affect the lifetime of the tracers such as precipitation. The longer a tracer stays in the atmosphere, the lower is the relative importance of the location of the source to the atmospheric mass, and thus the lower is the relative local pollution build-up. We further use aerosol deposition fields to

Quality of wet deposition in the Grand Calumet River watershed, northwestern Indiana, April 29, 1997-April 28, 1998

USGS Publications Warehouse

Willoughby, Timothy C.

2000-01-01

The Grand Calumet River, in northwestern Indiana, drains a heavily industrialized area along the southern shore of Lake Michigan. Steel production and petroleum refining are two of the area?s predominant industries. High-temperature processes, such as fossilfuel combustion and steel production, release contaminants to the atmosphere that may result in wet deposition being a major contributor to major-ion and trace-metal loadings in northwestern Indiana and Lake Michigan. A wet-deposition collection site was established at the Gary (Indiana) Regional Airport to monitor the quantity and chemical quality of wet deposition. During a first phase of sampling, 48 wet-deposition samples were collected weekly between June 30, 1992, and August 31, 1993. During a second phase of sampling, 40 wet-deposition samples were collected between October 17, 1995, and November 12, 1996. Forty-two wet-deposition samples were collected during a third phase of sampling, which began April 29, 1997, and was completed April 28, 1998. Wetdeposition samples were analyzed for pH, specific conductance, and selected major ions and trace metals. This report describes the quantity and quality of wet-deposition samples collected during the third sampling phase and compares these findings to the results of the first and second sampling phases. All of the samples collected during the third phase of sampling were of sufficient volumes for at least some of the analyses to be performed. Constituent concentrations from the third sampling phase were not significantly different (at the 5-percent significance level) from those for the second sampling phase. Significant increases, however, were observed in the concentrations of potassium, iron, lead, and zinc when compared to the concentrations observed in the first sampling phase. Weekly loadings were estimated for each constituent measured during the third sampling phase. If constituent concentrations were reported less than the method reporting limit, a

Enhancement of PM2.5 Concentrations by Aerosol-Meteorology Interactions Over China

NASA Astrophysics Data System (ADS)

Zhang, Xin; Zhang, Qiang; Hong, Chaopeng; Zheng, Yixuan; Geng, Guannan; Tong, Dan; Zhang, Yuxuan; Zhang, Xiaoye

2018-01-01

Aerosol-meteorology interactions can change surface aerosol concentrations via different mechanisms such as altering radiation budget or cloud microphysics. However, few studies investigated the impacts of different mechanisms on temporal and spatial distribution of PM2.5 concentrations over China. Here we used the fully coupled Weather Research and Forecasting model with online chemistry (WRF-Chem) to quantify the enhancement of PM2.5 concentrations by aerosol-meteorology feedback in China in 2014 for different seasons and separate the relative impacts of aerosol radiation interactions (ARIs) and aerosol-cloud interactions (ACIs). We found that ARIs and ACIs could increase population-weighted annual mean PM2.5 concentration over China by 4.0 μg/m3 and 1.6 μg/m3, respectively. We found that ARIs play a dominant role in aerosol-meteorology interactions in winter, while the enhancement of PM2.5 concentration by ARIs and ACIs is comparable in other three seasons. ARIs reduced the wintertime monthly mean wind speed and planetary boundary layer (PBL) height by up to 0.1 m/s and 160 m, respectively, but increased the relative humidity by up to 4%, leading to accumulation of pollutants within PBL. Also, ARIs reduced dry deposition velocity of aerosols by up to 20%, resulting in an increase in PM2.5 lifetime and concentrations. ARIs can increase wintertime monthly mean surface PM2.5 concentration by a maximum of 30 μg/m3 in Sichuan Basin. ACIs can also increase PM2.5 concentration with more significant impacts in wet seasons via reduced wet scavenging and enhanced in-cloud chemistry. Dominant processes in PM2.5 enhancement are also clarified in different seasons. Results show that physical process is more important than chemical processes in winter in ARIs, while chemical process of secondary inorganic aerosols production may be crucial in wet seasons via ACIs.

Wet Removal of Organic and Black Carbon Aerosols

NASA Astrophysics Data System (ADS)

Torres, A.; Bond, T. C.; Lehmann, C.

2012-12-01

Organic carbon (OC) and black carbon (BC) aerosols derived from the combustion of fossil fuels and biomass are significant atmospheric pollutants that alter the Earth's radiation balance and affect human health. Carbonaceous aerosol lifetime and extent of its effects are mainly controlled by its wet removal, especially by rain. Limited work has been done to measure both BC and OC from rain events even though these aerosols are co-emitted and exist together in the atmosphere. The choices of analytical techniques for measuring OC and BC in water are limited, and researchers often employ the same techniques used for measuring atmospheric carbon particles. There is no agreement in the methods employed for monitoring carbon concentration in precipitation. As part of the method development, the Single Particle Soot Photometer (SP2), Thermal-Optical Analysis (TOA), Ultraviolet/Visible (UV/VIS) Spectrophotometer, and the Total Organic Carbon (TOC) Analyzer were evaluated for measuring BC suspended in water, water insoluble OC (WIOC) and dissolved OC (DOC). The study also monitored the concentration of BC, WIOC, and DOC in rainwater collected at Bondville (Illinois) for 18 months. Results indicated that 34% (±3%) of the BC mass was lost in the SP2 analysis, most probably during the nebulization process. Filtration required for TOA also had large losses (>75%) because quartz fiber filters were ineffective for capturing BC particles from water. Addition of NH4H2PO4 as a coagulant improved (>95%) the capture efficiency of the filters. UV/VIS spectrophotometry had good linearity, but the sensitivity for detecting BC particles (±20 μg/L) suspended in water was inadequate. TOC analysis was a robust technique for measuring both DOC and total carbon (BC + OC). The chosen techniques were TOC analysis for DOC, and TOA with an optimized filtration procedure for BC and WIOC. The mean concentrations in rainwater were 8.72 (±9.84) μg/L of BC, 88.97 (±62.64) μg/L of WIOC, and 1

Organic nitrogen and carbon in atmospheric dry and wet depositions in the southern East China Sea: its implication for new production in coastal region

NASA Astrophysics Data System (ADS)

Chen, H. Y.; Yeh, J. X.; Lin, C. T.

2016-02-01

We collected 11 sets of size-segregated particulate aerosol (include coarse and fine particles) and 53 rain samples from January to December 2014 at a coastal city (Keelung) on the southern East China Sea. Here we present measurements of water-soluble inorganic/organic nitrogen and carbon (WSIN/WSON and WSIC/WSOC, respectively) in aerosol samples and dissolved inorganic/organic nitrogen and carbon (DIN/DON and DIC/DOC, respectively) in rain samples. In addition, 4-d back trajectories of air masses arriving daily at the sampling site were calculated to determine the potential aerosol source regions. The concentrations of water-soluble species in particulate aerosols were relatively high in March (WSON: 223±48 nmol m-3; WSOC: 203±51 nmol m-3) and dissolved species in rain samples were high in December (DON: 157±69 μM; DOC: 294±168 μM), which occur frequently during the spring and winter. The monsoon system of East Asia play a key role on the atmospheric composition of nitrogen and carbon, with higher loadings in northerly (winter to spring) than southerly (summer to autumn) monsoon periods, owing to strong emissions from the East Asian continent. Our results indicate that biomass burning and dust events yielded the largest concentrations of ON and OC not only on particulate aerosols but also in precipitations. For aerosols, the amounts of WSON and WSOC accounted for 42±8% and 80±7% of the water-soluble total nitrogen (WSTN) and carbon (WSTC), respectively. Additionally, the concentrations of DON and DOC accounted for 40±5% and 75±3% of total dissolved nitrogen (TDN) and carbon (TDC), respectively, for precipitations. By using dry and wet deposition flux estimations, we estimated that the fluxes of WSTN/TDN and WSTC/TDC were 47.1±24.4 / 266±20 mmol m-2 yr-1 and 23±9 / 153±3 mmol m-2 yr-1, respectively. These results suggest that atmospheric deposition contributed approximately 25-34% of the annual biological new production in the southern East China Sea.

COMPARISON OF MONODISPERSE AND POLYDISPERSE AEROSOL DEPOSITION IN A PACKED BED

EPA Science Inventory

COMPARISON OF MONODISPERSE AND POLYDISPERSE AEROSOL DEPOSITION IN A PACKED BED. Jacky A. Rosati, Dept. of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, NC 27599; Chong S. Kim, USEPA National Health and Environmental Effects Research Laboratory...

The Various Influences due to Aerosol Depositions

NASA Technical Reports Server (NTRS)

Yasunari, Teppei

2011-01-01

Recently the issue on glacier retreats comes up and many factors should be relevant to the issue. The absorbing aerosols such as dust and black carbon (BC) are considered to be one of the factors. After they deposited onto the snow surface, it will reduce snow albedo (called snow darkening effect) and probably contribute to further melting of glacier. The Goddard Earth Observing System version 5 (GEOS-5) has developed at NASA/GSFC. However, the original snowpack model used in the land surface model in the GEOS-5 did not consider the snow darkening effect. Here we developed the new snow albedo scheme which can consider the snow darkening effect. In addition, another scheme on calculating mass concentrations on the absorbing aerosols in snowpack was also developed, in which the direct aerosol depositions from the chemical transport model in the GEOS-5 were used. The scheme has been validated with the observed data obtained at backyard of the Institute of Low Temperature Science, Hokkaido University, by Dr. Teruo Aoki (Meteorological Research Institute) et al. including me. The observed data was obtained when I was Ph.D.caftdidate. The original GEOS-5 during 2007-2009 over the Himalayas and Tibetan Plateau region showed more reductions of snow than that of the new GEOS-5 because the original one used lower albedo settings. On snow cover fraction, the new GEOS-5 simulated more realistic snow-covered area comparing to the MODIS snow cover fraction. The reductions on snow albedo, snow cover fraction, and snow water equivalent were seen with statistically significance if we consider the snow darkening effect comparing to the results without the snow darkening effect. In the real world, debris cover, inside refreezing process, surface flow of glacier, etc. affect glacier mass balance and the simulated results immediately do not affect whole glacier retreating. However, our results indicate that some surface melting over non debris covered parts of the glacier would be

Wet deposition of fission-product isotopes to North America from the Fukushima Dai-ichi incident, March 2011

USGS Publications Warehouse

Wetherbee, Gregory A.; Gay, David A.; Debey, Timothy M.; Lehmann, Christopher M.B.; Nilles, Mark A.

2012-01-01

Using the infrastructure of the National Atmospheric Deposition Program (NADP), numerous measurements of radionuclide wet deposition over North America were made for 167 NADP sites before and after the Fukushima Dai-ichi Nuclear Power Station incident of March 12, 2011. For the period from March 8 through April 5, 2011, wet-only precipitation samples were collected by NADP and analyzed for fission-product isotopes within whole-water and filterable solid samples by the United States Geological Survey using gamma spectrometry. Variable amounts of 131I, 134Cs, or 137Cs were measured at approximately 21% of sampled NADP sites distributed widely across the contiguous United States and Alaska. Calculated 1- to 2-week individual radionuclide deposition fluxes ranged from 0.47 to 5100 Becquerels per square meter during the sampling period. Wet deposition activity was small compared to measured activity already present in U.S. soil. NADP networks responded to this complex disaster, and provided scientifically valid measurements that are comparable and complementary to other networks in North America and Europe.

Wet deposition of mercury at a remote site in the Tibetan Plateau: Concentrations, speciation, and fluxes

NASA Astrophysics Data System (ADS)

Huang, Jie; Kang, Shichang; Zhang, Qianggong; Yan, Haiyu; Guo, Junming; Jenkins, Matt G.; Zhang, Guoshuai; Wang, Kang

2012-12-01

Precipitation samples collected at a remote high elevation site (i.e., Nam Co Station, 4730 m a.s.l.) in the southern Tibetan Plateau were analyzed for total mercury (HgT) between July 2009 and 2011, particulate-bound mercury (HgP) between July 2010 and 2011 and methylmercury (MeHg) from July through August of 2009. The volume-weighted mean (VWM) concentrations and wet deposition fluxes of HgT and MeHg in precipitation were 4.8 ng L-1 and 1.75 μg m-2 yr-1, 0.031 ng L-1 and 0.01 μg m-2 yr-1, respectively. VWM HgT concentration was approximately two times higher during the non-monsoon season than during the monsoon season, while 83% of the HgT wet deposition fluxes occurred during the monsoon season. The HgT and MeHg concentrations are comparable to the reported data for some of the most remote alpine and polar regions worldwide (e.g., Churchill), but the wet deposition fluxes of HgT and MeHg were among the lowest in the world. Analysis of Hg speciation has presented that HgP and MeHg concentrations are high, making up 71.2% and 1.82% of the HgT on average (VWM), respectively. The high HgP%, as well as a significantly positive between HgT and HgP (R2 = 0.91; n = 44; p < 0.001), confirmed that atmospheric deposition of Hg in the Tibetan Plateau was occurring in the form of HgP. A decreasing trend in HgT concentrations with increasing amount of precipitation (R2 = 0.08; N = 101; p < 0.005) was found at Nam Co Station, indicative that scavenging of HgP from the atmosphere was an important mechanism contributing Hg to precipitation. The precipitation amount, rather than HgT concentration, was found to be the governing factor affecting HgT wet deposition flux. Moreover, a comparison between measured wet deposition flux of Hg at Nam Co Station and the estimates from environmental records indicated that both snowpits and lake sediments appear to be reliable archives for estimating historical Hg accumulation rates over the Tibetan Plateau.

Dense nanocrystalline yttrium iron garnet films formed at room temperature by aerosol deposition

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

Johnson, Scooter D., E-mail: scooter.johnson@nrl.navy.mil; Glaser, Evan R.; Cheng, Shu-Fan

Highlights: • We deposit yttrium iron garnet films at room temperature using aerosol deposition. • Films are 96% of theoretical density for yttrium iron garnet. • We report magnetic and structural properties post-deposition and post-annealing. • Low-temperature annealing decreases the FMR linewidth. • We discuss features of the FMR spectra at each anneal temperature. - Abstract: We have employed aerosol deposition to form polycrystalline yttrium iron garnet (YIG) films on sapphire at room temperature that are 90–96% dense. We characterize the structural and dynamic magnetic properties of the dense films using scanning electron microscopy, X-ray diffraction, and ferromagnetic resonance techniques.more » We find that the as-deposited films are pure single-phase YIG formed of compact polycrystallites ∼20 nm in size. The ferromagnetic resonance mode occurs at 2829 G with a linewidth of 308 G. We perform a series of successive anneals up to 1000 °C on a film to explore heat treatment on the ferromagnetic resonance linewidth. We find the narrowest linewidth of 98 G occurs after a 750 °C anneal.« less

Wet deposition of hydrocarbons in the city of Tehran-Iran

PubMed Central

Pardakhti, Alireza; Mohajeri, Leila; Bateni, Farshid

2009-01-01

Air pollution in the city of Tehran has been a major problem for the past three decades. The direct effects of hydrocarbon contaminants in the air are particularly important such as their carcinogenic, mutagenic, and teratogenic effects which can be transported to other environments via dry and wet deposition. In the present study, rainwater samples were collected and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethyl benzene, and xylene (BTEX) as well as fuel fingerprints in two ranges of gasoline (C5–C11) and diesel fuel (C12–C20) using a gas chromatograph equipped with a flame ionization detector (GC/FID). Mean concentrations of ∑16 PAHs varied between 372 and 527 µg/L and for BTEX was between 87 and 188 µg/L with maximum of 36 µg/L for toluene. Both gasoline range hydrocarbons (GRH) and diesel range hydrocarbons (DRH) were also present in the collected rainwater at concentrations of 190 and 950 µg/L, respectively. Hydrocarbon transports from air to soil were determined in this wet deposition. Average hydrocarbon transportation for ∑PAHs, BTEX, GRH, and DRH was 2,747, 627, 1,152, and 5,733 µg/m2, respectively. PMID:20495601

Comparison of snowpack and winter wet-deposition chemistry in the Rocky Mountains, USA: Implications for winter dry deposition

USGS Publications Warehouse

Clow, David W.; Ingersoll, George P.; Mast, M. Alisa; Turk, John T.; Campbell, Donald H.

2002-01-01

Depth-integrated snowpack chemistry was measured just prior to maximum snowpack depth during the winters of 1992-1999 at 12 sites co-located with National Atmospheric Deposition Program/National Trend Network (NADP/NTN) sites in the central and southern Rocky Mountains, USA. Winter volume-weighted mean wet-deposition concentrations were calculated for the NADP/NTN sites, and the data were compared to snowpack concentrations using the paired t-test and the Wilcoxon signed-rank test. No statistically significant differences were indicated in concentrations of SO42- or NO3- (p>0.1). Small, but statistically significant differences (p???0.03) were indicated for all other solutes analyzed. Differences were largest for Ca2+ concentrations, which on average were 2.3??eql-1 (43%) higher in the snowpack than in winter NADP/NTN samples. Eolian carbonate dust appeared to influence snowpack chemistry through both wet and dry deposition, and the effect increased from north to south. Dry deposition of eolian carbonates was estimated to have neutralized an average of 6.9??eql-1 and a maximum of 12??eql-1 of snowpack acidity at the southernmost sites. The good agreement between snowpack and winter NADP/NTN SO42- and NO3- concentrations indicates that for those solutes the two data sets can be combined to increase data density in high-elevation areas, where few NADP/NTN sites exist. This combination of data sets will allow for better estimates of atmospheric deposition of SO42- and NO3- across the Rocky Mountain region.

Comparison of snowpack and winter wet-deposition chemistry in the Rocky Mountains, USA: implications for winter dry deposition

NASA Astrophysics Data System (ADS)

Clow, David W.; Ingersoll, George P.; Mast, M. Alisa; Turk, John T.; Campbell, Donald H.

Depth-integrated snowpack chemistry was measured just prior to maximum snowpack depth during the winters of 1992-1999 at 12 sites co-located with National Atmospheric Deposition Program/National Trend Network (NADP/NTN) sites in the central and southern Rocky Mountains, USA. Winter volume-weighted mean wet-deposition concentrations were calculated for the NADP/NTN sites, and the data were compared to snowpack concentrations using the paired t-test and the Wilcoxon signed-rank test. No statistically significant differences were indicated in concentrations of SO 42- or NO 3- ( p>0.1). Small, but statistically significant differences ( p⩽0.03) were indicated for all other solutes analyzed. Differences were largest for Ca 2+ concentrations, which on average were 2.3 μeq l -1 (43%) higher in the snowpack than in winter NADP/NTN samples. Eolian carbonate dust appeared to influence snowpack chemistry through both wet and dry deposition, and the effect increased from north to south. Dry deposition of eolian carbonates was estimated to have neutralized an average of 6.9 μeq l -1 and a maximum of 12 μeq l -1 of snowpack acidity at the southernmost sites. The good agreement between snowpack and winter NADP/NTN SO 42- and NO 3- concentrations indicates that for those solutes the two data sets can be combined to increase data density in high-elevation areas, where few NADP/NTN sites exist. This combination of data sets will allow for better estimates of atmospheric deposition of SO 42- and NO 3- across the Rocky Mountain region.

Wet deposition of trace elements and radon daughter systematics in the South and equatorial Atlantic atmosphere

NASA Astrophysics Data System (ADS)

Kim, Guebuem; Church, Thomas M.

2002-09-01

Atmospheric samples were collected aboard ship in the South and equatorial Atlantic (35°S-10°N) between 19 May and 20 June 1996. We measured 222Rn in air, 210Pb in aerosol, and trace elements (Fe, Mn, Zn, Pb, Cu, Cd, Ni, and Cr), 210Pb, and 210Po in precipitation samples. The large variation of 222Rn in air suggests a significant change in the incursion of continental air with time and latitude in the remote Atlantic. In the equatorial and subtropical Atlantic (20°S-10°N), 222Rn activity was lower but 210Pb/222Rn ratios were higher than those at higher latitudes. The higher 210Pb/222Rn ratios in the equatorial Atlantic appear to be due to prevailing trade easterly winds which transport a supported source of 210Pb in Saharan dust from the African Sahel. The enrichment of noncrustal trace elements in precipitation samples from the remote equatorial Atlantic was small on account of the remoteness from the continental emission regions and as a result of dilution with Saharan dust. The wet depositional fluxes of major crustal elements (Fe and Mn) were two- to three-fold higher, while those of Cd and Zn were two- to ten-fold lower, in the South and equatorial Atlantic relative to the western North Atlantic (Bermuda) or North Atlantic coast (Lewes, Delaware). Thus, dominant wet precipitation of Saharan dust in the Intertropical Convergence Zone (ITCZ) areas of the equatorial Atlantic appears to be a large potential source of micronutrients (i.e., Fe) to surface seawater.

Effects of wet deposition on the abundance and size distribution of black carbon in East Asia

NASA Astrophysics Data System (ADS)

Kondo, Y.; Moteki, N.; Oshima, N.; Ohata, S.; Koike, M.; Shibano, Y.; Takegawa, N.; Kita, K.

2016-05-01

An improved understanding of the variations in the mass concentration and size distribution of black carbon (BC) in the free troposphere (FT) over East Asia, where BC emissions are very high, is needed to reliably estimate the radiative forcing of BC in climate models. We measured these parameters and the carbon monoxide (CO) concentration by conducting the Aerosol Radiative Forcing in East Asia (A-FORCE) 2013W aircraft campaign in East Asia in winter 2013 and compared these data with measurements made in the same region in spring 2009. The median BC concentrations in the FT originating from North China (NC) and South China (SC) showed different seasonal variations, which were primarily caused by variations in meteorological conditions. CO concentrations above the background were much higher in SC than in NC in both seasons, suggesting a more active upward transport of CO. In SC, precipitation greatly increased from winter to spring, leading to an increased wet deposition of BC. As a result, the median BC concentration in the FT was highest in SC air in winter. This season and region were optimal for the effective transport of BC from the planetary boundary layer to the FT. The count median diameters of the BC size distributions generally decreased with altitude via wet removal during upward transport. The altitude dependence of the BC size distributions was similar in winter and spring, in accord with the similarity in the BC mixing state. The observed BC concentrations and microphysical properties will be useful for evaluating the performance of climate models.

Exploring Climatology and Long-Term Variations of Aerosols from NASA Reanalysis MERRA-2 with Giovanni

NASA Technical Reports Server (NTRS)

Shen, Suhung; Ostrenga, Dana; Vollmer, Bruce; Li, Zhanqing

2016-01-01

Dust plays important roles in energy cycle and climate variations. The dust deposition is the major source of iron in the open ocean, which is an essential micronutrient for phytoplankton growth and therefore may influence the ocean uptake of atmospheric CO2. Mineral dust can also act as fertilizer for forests over long time periods. Over 35 years of simulated global aerosol products from NASA atmospheric reanalysis, second Modern-Era Retrospective analysis for Research and Applications (MERRA-2) are available from NASA Goddard Earth Science Data and Information Services Center (GES DISC). The MERRA-2 covers the period 1980-present, continuing as an ongoing climate analysis. Aerosol assimilation is included throughout the period, using MODIS, MISR, AERONET, and AVHRR (in the pre-EOS period). The aerosols are assimilated by using MERRA-2 aerosol model, which interact directly with the radiation parameterization, and radiatively coupled with atmospheric model dynamics in the Goddard Earth Observing System Model, Version 5 (GEOS-5). Dust deposition data along with other major aerosol compositions (e.g. black carbon, sea salt, and sulfate, etc.) are simulated as dry and wet deposition, respectively. The hourly and monthly data are available at spatial resolution of 0.5ox0.625o (latitude x longitude). Quick data exploration of climatology and interannual variations of MERRA-2 aerosol can be done through the online visualization and analysis tool, Giovanni. This presentation, using dust deposition as an example, demonstrates a number of MERRA-2 data services at GES DISC. Global distributions of dust depositions, and their seasonal and inter-annual variations are investigated from MERRA-2 monthly aerosol products.

Long-term atmospheric deposition wet-dry fluxes. Critical loads exceedences in an urban area.

PubMed

Morselli, L; Brusori, B; Cecchini, M; Olivieri, P; Silingardi, D; Passarini, F

2001-01-01

The present work provides an overview of the most relevant results concerning a five years monitoring programme of wet and dry deposition (1995-1999) in the city of Bologna. The aim of this research is to get an overall picture of atmospheric pollutants deposition inventory in an urban territory and to allow an assessment of the vulnerability of the area by comparing actual fluxes of acidity and nutrient nitrogen with the respective "critical loads" associated to the territory, in the framework of the UNECE LRTAP (Long Range Transboundary Air Pollution Convention). This comparison, for the Bologna monitoring station, shows "exceedance classes" from 4 to 6 for acidity and from 1 to 5 for nutrient nitrogen, reflecting an urban-industrial context, though a trend in reducing occurs from 1995 to 1999. A water layer surface sampler (DAS-MTX sampler) was employed for "surrogate" dry deposition collection. The contribute of dry fraction to the total deposition fluxes appears to prevail on wet fraction for many pollutants (up to more than 90% for total calcium and alkalinity). A comparison with long term monitoring results from some stations in Italian territory, shows that the differences among chemical species deposition fluxes may be ascribed both to the long distance aerial transport of pollutants and to site characteristics.

Source attribution, physicochemical properties and spatial distribution of wet deposited mercury to the Ohio River valley

NASA Astrophysics Data System (ADS)

White, Emily Mae

Mercury (Hg) is a bioaccumulative neurotoxin that is emitted from anthropogenic sources through fossil fuel combustion. The spatial scale of atmospheric transport prior to deposition is dependent on the chemical and physical form of Hg emissions, and has yet to be quantitatively defined. A five-year comprehensive Hg monitoring and source apportionment study was conducted in Steubenville, Ohio to investigate atmospheric Hg deposition to the highly industrialized Ohio River Valley region. Long-term event-precipitation measurements revealed a significant 30% to three-fold enrichment of Hg concentrations and total Hg deposition flux to the Steubenville site over other Great Lakes regional sites. Multivariate receptor models attributed ˜70% of Hg wet deposition to local coal combustion sources. While local stagnant atmospheric conditions led to moderately high volume-weighted mean Hg concentrations and the majority of Hg wet deposition flux, regional transport from the Chicago/Gary and Detroit/Windsor urban areas also led to elevated precipitation Hg concentrations, but did not contribute significantly to the overall Hg deposition. The degree of local source influence was established during a summertime field intensive study in which a local scale network of concurrently collected rain samples revealed that 42% of Hg wet deposition measured less than one km from the base of coal fired utilities could be attributed to the adjacent source, corresponding to 170% Hg concentration enhancement over regionally representative precipitation collected concurrently. In addition, 69+/-37% of the Hg collected in rain was in a soluble form, entering the precipitation as reactive gas phase or fine particle associated Hg. The Hg scavenging coefficient (rate of concentration reduction throughout a single precipitation event) was particularly low when compared to other trace elements. Furthermore, when compared to an upwind but non-locally source impacted site, the scavenging

Wet and Dry Atmospheric Mercury Deposition Accumulates in Watersheds of the Northeastern United States

NASA Astrophysics Data System (ADS)

Boyer, E. W.; Grant, C.; Grimm, J.; Drohan, P. J.; Bennett, J.; Lawler, D.

2013-12-01

Mercury emissions to the atmosphere from coal-fired power plants and other sources such as waste incineration can be deposited to landscapes in precipitation and in dry fallout. Some mercury reaches watersheds and streams, where it can accumulate in sediments and biota. Human exposure to mercury occurs primarily through fish consumption, and currently mercury fish eating advisories are in place for many of the streams and lakes in the state. Here, we explored mercury in air, soils, water, and biota. To quantify atmospheric mercury deposition, we measured both wet and dry mercury deposition at over 10 locations in Pennsylvania, from which we present variation in mercury deposition and initial assessments of factors affecting the patterns. Further, we simulated mercury deposition at unmonitored locations in Pennsylvania and the northeastern United States over space and time with a high-resolution modeling technique that reflects storm tracks and air flow patterns. To consider mercury accumulation in watersheds, we collected data on soil mercury concentrations in a set of soil samples, and collected baseline data on mercury in streams draining 35 forested watersheds across Pennsylvania, spanning gradients of atmospheric deposition, climate and geology. Mercury concentrations were measured in stream water under base-flow conditions, in streambed sediments, aquatic mosses, and in fish tissues from brook trout. Results indicate that wet and dry atmospheric deposition is a primary source of mercury that is accumulating in watersheds of Pennsylvania and the northeastern United States.

Reactive nitrogen deposition to South East Asian rainforest

NASA Astrophysics Data System (ADS)

di Marco, Chiara F.; Phillips, Gavin J.; Thomas, Rick; Tang, Sim; Nemitz, Eiko; Sutton, Mark A.; Fowler, David; Lim, Sei F.

2010-05-01

The supply of reactive nitrogen (N) to global terrestrial ecosystems has doubled since the 1960s as a consequence of human activities, such as fertilizer application and production of nitrogen oxides by fossil-fuel burning. The deposition of atmospheric N species constitutes a major nutrient input to the biosphere. Tropical forests have been undergoing a radical land use change by increasing cultivation of sugar cane and oil palms and the remaining forests are increasingly affected by anthropogenic activities. Yet, quantifications of atmospheric nitrogen deposition to tropical forests, and nitrogen cycling under near-pristine and polluted conditions are rare. The OP3 project ("Oxidant and Particle Photochemical Processes above a Southeast Asian Tropical Rainforest") was conceived to study how emissions of reactive trace gases from a tropical rain forest mediate the regional scale production and processing of oxidants and particles, and to better understand the impact of these processes on local, regional and global scale atmospheric composition, chemistry and climate. As part of this study we have measured reactive, nitrogen containing trace gas (ammonia, nitric acid) and the associated aerosol components (ammonium, nitrate) at monthly time resolution using a simple filter / denuder for 16 months. These measurements were made at the Bukit Atur Global Atmospheric Watch tower near Danum Valley in the Malaysian state of Sabah, Borneo. In addition, the same compounds were measured at hourly time-resolution during an intensive measurement period, with a combination of a wet-chemistry system based on denuders and steam jet aerosol collectors and an aerosol mass spectrometer (HR-ToF-AMS), providing additional information on the temporal controls. During this period, concentrations and fluxes of NO, NO2 and N2O were also measured. The measurements are used for inferential dry deposition modelling and combined with wet deposition data from the South East Asian Acid

[Wet deposition of atmospheric nitrogen of the Jinshui watershed in the upper Hanjiang River].

PubMed

Wang, Jin-Jie; Zhang, Ke-Rong; Wu, Chuan; Zhang, Quan-Fa

2014-01-01

The Jinshui River, a tributary of the Hanjiang River, is an important region of water conservation for the Middle Route of South to North Water Transfer Project. However, water quality has been deteriorated in recent years, in particular nitrogen increasing pollution. In this study, the wet deposition of atmospheric nitrogen in the Jinshui watershed was investigated between Feb. 2012-Feb. 2013, and the corresponding contribution to the river N loading was calculated using N retention model. The results indicated that the volume-weighted concentration of dissolved total nitrogen (DTN) was 0.24-2.89 mg x L(-1), consisting of ammonium (NH(4+)-N) (42.8%), nitrate (NO3- N) (13.3%) and dissolved organic nitrogen (DON) (43.9%), which decreased with rainfall volume as a result of dilution. The wet deposition of atmospheric N was mainly from anthropogenic pollution and the flux was between 4.97-7.00 kg x (hm2 x a)(-1), dominated by seasonal rainfall, of which about 81% occurred in spring and summer and the flux in a decreasing order of upstream, downstream, and middlestream. The wet deposition contributed approximately 34,000-46,000 kg N to the river, accounting for only 5.05%-6.78% of the contribution by fertilizers, which was too small to be the main source of the river N loading.

Studies on aerosols. I. Reduction of dust deposition in lungs of rabbits by aqueous aerosols

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

Dautrebande, L.; Highman, B.; Alford, W.C.

1948-01-01

Rabbits were exposed to air containing 0.01 to 0.04 mg/liter zinc silicate dust with a mean diameter of 0.9 ..mu..m. Irregular breathing with some cyanosis after 2 hr was observed. Pulmonary changes after 4.5 to 5 hr included bronchitis, patchy atelectasis, emphysema, interstitial pneumonitis (thickening of septa, moderate congestion, infiltration of mononuclear cells and polymorphonuclear leukocytes). After 1, 7, or 14 days recovery there were no or only slight pulmonary problems. There was localization of particles at surfaces facing, deflecting or slowing air currents, particularly near pleura and hilus and less in central portion of lobes. Rabbits exposed to abovemore » dust plus aqueous wetting agent aerosol averaging 0.5 ..mu..m in diameter showed no cyanosis or marked respiratory difficulty. Rabbits showed less of above pulmonary changes and lesser amount of dust in lungs, particularly in alveoli and alveolar ducts. Most particles were cleared in 1 day in both groups, especially aerosol group, and essentially were all gone after 7 days. Differences were primarily due to coating of particles with liquid (increased size) and aggregation.« less

The influence of outliers on results of wet deposition measurements as a function of measurement strategy

NASA Astrophysics Data System (ADS)

Slanina, J.; Möls, J. J.; Baard, J. H.

The results of a wet deposition monitoring experiment, carried out by eight identical wet-only precipitation samplers operating on the basis of 24 h samples, have been used to investigate the accuracy and uncertainties in wet deposition measurements. The experiment was conducted near Lelystad, The Netherlands over the period 1 March 1983-31 December 1985. By rearranging the data for one to eight samplers and sampling periods of 1 day to 1 month both systematic and random errors were investigated as a function of measuring strategy. A Gaussian distribution of the results was observed. Outliers, detected by a Dixon test ( a = 0.05) influenced strongly both the yearly averaged results and the standard deviation of this average as a function of the number of samplers and the length of the sampling period. The systematic bias in bulk elements, using one sampler, varies typically from 2 to 20% and for trace elements from 10 to 500%, respectively. Severe problems are encountered in the case of Zn, Cu, Cr, Ni and especially Cd. For the sensitive detection of trends generally more than one sampler per measuring station is necessary as the standard deviation in the yearly averaged wet deposition is typically 10-20% relative for one sampler. Using three identical samplers, trends of, e.g. 3% per year will be generally detected in 6 years.

Influence of aerosol dry deposition on photosynthetically active radiation available to plants: A case study in the Yangtze Delta Region of China

NASA Astrophysics Data System (ADS)

Bergin, M. H.; Greenwald, R.; Xu, J.; Berta, Y.; Chameides, W. L.

In this paper, a new mechanism is proposed by which aerosols decrease the amount of photosynthetically active radiation (PAR) available to plants for photosynthesis. The mechanism involves the scattering and absorption of PAR by water insoluble aerosol particles (WIA) which deposit on leaves and are not washed off by precipitation. A simple model is developed that predicts the change in the transmittance of PAR, TPAR, for plant leaves due to WIA dry deposition as a function of aerosol chemical, physical, and optical properties. Model estimates for the agricultural Yangtze delta region of China indicate that over a 2-month period during a growing season, dry deposition of WIA may account for a ∼35% reduction in PAR available for plant photosynthesis. Although, the estimate is sensitive to several factors that are uncertain including aerosol dry deposition velocity, leaf area index, and removal rate of particles by precipitation. Results suggest that impacts on crop yields due to aerosol dry deposition could be considerable in this region and suggest a previously neglected economic incentive for China to mitigate air pollution. Additionally, WIA dry deposition may influence carbon uptake by plants in other locations that experience regional haze.

Variation of wet deposition chemistry in Sequoia National Park, California

USGS Publications Warehouse

Stohlgren, Thomas J.; Parsons, David J.

1987-01-01

Sequoia National Park has monitored wet deposition chemistry in conjunction with the National Atmospheric Deposition Program and National Trends Network (NADP/NTN), on a weekly basis since July, 1980. Annual deposition of H, NO3 and SO4 (0.045, 3.6, and 3.9 kg ha−1 a−1, respectively) is relatively low compared to that measured in the eastern United States, or in the urban Los Angeles and San Francisco areas. Weekly ion concentrations are highly variable. Maximum concentrations of 324,162, and 156 μeq ol−1 of H, NO3 and SO4 have been recorded for one low volume summer storm (1.4 mm). Summer concentrations of NO3 and SO4 average two and five times higher, respectively, than concentrations reported for remote areas in the world. There is considerable variability in the ionic concentration of low volume samples, and much less variability in moderate and high volume samples.

ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED AMBIENT AEROSOLS FOR DIFFERENT DOSE METRICS

EPA Science Inventory

ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED AMBIENT AEROSOLS FOR DIFFERENT DOSE METRICS.
Chong S. Kim, SC. Hu**, PA Jaques*, US EPA, National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC 27711; **IIT Research Institute, Chicago, IL; *South...

Solid aerosol generator

DOEpatents

Prescott, Donald S.; Schober, Robert K.; Beller, John

1992-01-01

An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates.

A novel hybrid approach for estimating total deposition in the United States

NASA Astrophysics Data System (ADS)

Schwede, Donna B.; Lear, Gary G.

2014-08-01

Atmospheric deposition of nitrogen and sulfur causes many deleterious effects on ecosystems including acidification and excess eutrophication. Assessments to support development of strategies to mitigate these effects require spatially and temporally continuous values of nitrogen and sulfur deposition. In the U.S., national monitoring networks exist that provide values of wet and dry deposition at discrete locations. While wet deposition can be interpolated between the monitoring locations, dry deposition cannot. Additionally, monitoring networks do not measure the complete suite of chemicals that contribute to total sulfur and nitrogen deposition. Regional air quality models provide spatially continuous values of deposition of monitored species as well as important unmeasured species. However, air quality modeling values are not generally available for an extended continuous time period. Air quality modeling results may also be biased for some chemical species. We developed a novel approach for estimating dry deposition using data from monitoring networks such as the Clean Air Status and Trends Network (CASTNET), the National Atmospheric Deposition Program (NADP) Ammonia Monitoring Network (AMoN), and the Southeastern Aerosol Research and Characterization (SEARCH) network and modeled data from the Community Multiscale Air Quality (CMAQ) model. These dry deposition values estimates are then combined with wet deposition values from the NADP National Trends Network (NTN) to develop values of total deposition of sulfur and nitrogen. Data developed using this method are made available via the CASTNET website.

A comparative sensitivity analysis focused on wet deposition models for the Fukushima and Chernobyl atmospheric dispersion events

NASA Astrophysics Data System (ADS)

Quérel, Arnaud; Roustan, Yelva; Quélo, Denis; Bocquet, Marc; Winiarek, Victor

2014-05-01

In order to model the transport of radionuclides bound to atmospheric particles and the ground contamination at the synoptic scale, the wet deposition is a crucial point. Usually, the wet deposition is divided in two different mechanisms, the below-cloud scavenging (washout) and the in-cloud scavenging (rainout). Since the micro-physics of both deposition processes is not well known yet, the modeling of the wet deposition of particles at the synoptic scale is uncertain and difficult to validate. This leads to an abundance of wet deposition models, none of them being fully adequate. The existing models of particle scavenging can be distinguished by the nature and the number of physical parameters they rely on. For instance the scavenging coefficient variability can be determined only by the rainfall intensity or take into account the rainfall intensity and the particle size distribution. Beyond their intrinsic formulations, the deposition models are sensitive to the input data necessary to use them, cloud height for instance. Finally, the simulated ground deposition is more or less sensitive to the choices of the overall-models involved in the atmospheric transport of particles and the meteorology in general. For accidental atmospheric releases, the uncertainties linked to the source-term are for instance crucial, what justifies the use of different ones in the study. The Polyphemus air quality system is used to perform the simulations of the radioactive dispersion, considering Caesium-137 as particulate matter for the accidental releases from the Fukushima and Chernobyl nuclear power plants. In this study, two different approaches are used. In the first one, the influence of the different components taking part in the scavenging modeling are confronted separately (whether the scavenging models or the overall models). The second approach is a global sensitivity analysis computed both on the Chernobyl and Fukushima cases. It relies on simulations performed with

In Vitro Surfactant and Perfluorocarbon Aerosol Deposition in a Neonatal Physical Model of the Upper Conducting Airways

PubMed Central

Goikoetxea, Estibalitz; Murgia, Xabier; Serna-Grande, Pablo; Valls-i-Soler, Adolf; Rey-Santano, Carmen; Rivas, Alejandro; Antón, Raúl; Basterretxea, Francisco J.; Miñambres, Lorena; Méndez, Estíbaliz; Lopez-Arraiza, Alberto; Larrabe-Barrena, Juan Luis; Gomez-Solaetxe, Miguel Angel

2014-01-01

Objective Aerosol delivery holds potential to release surfactant or perfluorocarbon (PFC) to the lungs of neonates with respiratory distress syndrome with minimal airway manipulation. Nevertheless, lung deposition in neonates tends to be very low due to extremely low lung volumes, narrow airways and high respiratory rates. In the present study, the feasibility of enhancing lung deposition by intracorporeal delivery of aerosols was investigated using a physical model of neonatal conducting airways. Methods The main characteristics of the surfactant and PFC aerosols produced by a nebulization system, including the distal air pressure and air flow rate, liquid flow rate and mass median aerodynamic diameter (MMAD), were measured at different driving pressures (4–7 bar). Then, a three-dimensional model of the upper conducting airways of a neonate was manufactured by rapid prototyping and a deposition study was conducted. Results The nebulization system produced relatively large amounts of aerosol ranging between 0.3±0.0 ml/min for surfactant at a driving pressure of 4 bar, and 2.0±0.1 ml/min for distilled water (H2Od) at 6 bar, with MMADs between 2.61±0.1 µm for PFD at 7 bar and 10.18±0.4 µm for FC-75 at 6 bar. The deposition study showed that for surfactant and H2Od aerosols, the highest percentage of the aerosolized mass (∼65%) was collected beyond the third generation of branching in the airway model. The use of this delivery system in combination with continuous positive airway pressure set at 5 cmH2O only increased total airway pressure by 1.59 cmH2O at the highest driving pressure (7 bar). Conclusion This aerosol generating system has the potential to deliver relatively large amounts of surfactant and PFC beyond the third generation of branching in a neonatal airway model with minimal alteration of pre-set respiratory support. PMID:25211475

Satellite observations and EMAC model calculations of sulfate aerosols from Kilauea: a study of aerosol formation, processing, and loss

NASA Astrophysics Data System (ADS)

Penning de Vries, Marloes; Beirle, Steffen; Brühl, Christoph; Dörner, Steffen; Pozzer, Andrea; Wagner, Thomas

2016-04-01

The currently most active volcano on Earth is Mount Kilauea on Hawaii, as it has been in a state of continuous eruption since 1983. The opening of a new vent in March 2008 caused half a year of strongly increased SO2 emissions, which in turn led to the formation of a sulfate plume with an extent of at least two thousand kilometers. The plume could be clearly identified from satellite measurements from March to November, 2008. The steady trade winds in the region and the lack of interfering sources allowed us to determine the life time of SO2 from Kilauea using only satellite-based measurements (no a priori or model information). The current investigation focuses on sulfate aerosols: their formation, processing and subsequent loss. Using space-based aerosol measurements by MODIS, we study the evolution of aerosol optical depth, which first increases as a function of distance from the volcano due to aerosol formation from SO2 oxidation, and subsequently decreases as aerosols are deposited to the surface. The outcome is compared to results from calculations using the EMAC (ECHAM/MESSy Atmospheric Chemistry) model to test the state of understanding of the sulfate aerosol life cycle. For this comparison, a particular focus is on the role of clouds and wet removal processes.

Recent bright gully deposits on Mars: Wet or dry flow?

USGS Publications Warehouse

Pelletier, J.D.; Kolb, K.J.; McEwen, A.S.; Kirk, R.L.

2008-01-01

Bright gully sediments attributed to liquid water flow have been deposited on Mars within the past several years. To test the liquid water flow hypothesis, we constructed a high-resolution (1 m/pixel) photogrammetric digital elevation model of a crater in the Centauri Montes region, where a bright gully deposit formed between 2001 and 2005. We conducted one-dimensional (1-D) and 2-D numerical flow modeling to test whether the deposit morphology is most consistent with liquid water or dry granular How. Liquid water flow models that incorporate freezing can match the runout distance of the flow for certain freezing rates but fail to reconstruct the distributary lobe morphology of the distal end of the deposit. Dry granular flow models can match both the observed runout distance and the distal morphology. Wet debris flows with high sediment concentrations are also consistent with the observed morphology because their rheologies are often similar to that of dry granular flows. As such, the presence of liquid water in this flow event cannot be ruled out, but the available evidence is consistent with dry landsliding. ?? 2008 The Geological Society of America.

Solid aerosol generator

DOEpatents

Prescott, D.S.; Schober, R.K.; Beller, J.

1992-03-17

An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration is disclosed. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates. 2 figs.

Aerosol and precipitation chemistry measurements in a remote site in Central Amazonia: the role of biogenic contribution

NASA Astrophysics Data System (ADS)

Pauliquevis, T.; Lara, L. L.; Antunes, M. L.; Artaxo, P.

2012-06-01

ones observed in other remote sites in tropical forests. The volume-weighted mean (VWM) pH was 4.90. The most important contribution to acidity was from weak organic acids. The organic acidity was predominantly associated with the presence of acetic acid instead of formic acid, which is more often observed in pristine tropical areas. Wet deposition rates for major species did not differ significantly between dry and wet season, except for NH4+, citrate and acetate, which had smaller deposition rates during dry season. While biomass burning emissions were clearly identified in the aerosol component, it did not present a clear signature in rainwater. The biogenic component and the long-range transport of sea salt were observed both in aerosols and rainwater composition. The results shown here indicate that in Central Amazonia it is still possible to observe quite pristine atmospheric conditions, relatively free of anthropogenic influences.

Total and regional deposition of inhaled aerosols in supine healthy subjects and subjects with mild-to-moderate COPD

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

Darquenne, Chantal; Lamm, Wayne J.; Fine, Janelle M.

Despite substantial development of sophisticated subject-specific computational models of aerosol transport and deposition in human lungs, experimental validation of predic- tions from these new models is sparse. We collected aerosol retention and exhalation profiles in seven healthy volunteers and six subjects with mild-to-moderate COPD (FEV1 ¼ 50–80%predicted) in the supine posture. Total deposition was measured during continuous breathing of 1 and 2.9 mm-diameter particles (tidal volume of 1 L, flow rate of 0.3 L/s and 0.75 L/s). Bolus inhalations of 1 mm particles were performed to penetration volumes of 200, 500 and 800 mL (flow rate of 0.5 L/s). Aerosolmore » bolus dispersion (H), deposition, and mode shift (MS) were calculated from these data. There was no significant difference in total deposition between healthy subjects and those with COPD. Total deposition increased with increasing particle size and also with increasing flow rate. Similarly, there was no significant difference in aerosol bolus deposition between subject groups. Yet, the rate of increase in dispersion and of decrease in MS with increasing penetration volume was higher in subjects with COPD than in healthy volunteers (H: 0.79870.205 vs. 0.52770.122 mL/mL, p¼ 0.01; MS: - 0.27170.129 vs. - 0.145 70.076 mL/mL, p¼ 0.05) indicating larger ventilation inhomogeneities (based on H) and increased flow sequencing (based on MS) in the COPD than in the healthy group. In conclusion, in the supine posture, deposition appears to lack sensitivity for assessing the effect of lung morphology and/or ventilation distribution alteration induced by mild-to- moderate lung disease on the fate of inhaled aerosols. However, other parameters such as aerosol bolus dispersion and mode shift may be more sensitive parameters for evaluating models of lungs with moderate disease.« less

Chemical composition and sources of atmospheric aerosols at Djougou (Benin)

NASA Astrophysics Data System (ADS)

Ouafo-Leumbe, Marie-Roumy; Galy-Lacaux, Corinne; Liousse, Catherine; Pont, Veronique; Akpo, Aristide; Doumbia, Thierno; Gardrat, Eric; Zouiten, Cyril; Sigha-Nkamdjou, Luc; Ekodeck, Georges Emmanuel

2017-06-01

In the framework of the INDAAF (International Network to study Deposition and Atmospheric chemistry in AFrica) program, atmospheric aerosols were collected in PM2.5 and PM10 size fractions at Djougou, Benin, in the West Africa, from November, 2005 to October, 2009. Particulate carbon, ionic species, and trace metals were analyzed. Weekly PM2.5 and PM10 total mass concentrations varied between 0.7 and 47.3 µg m-3 and 1.4-148.3 µg m-3, respectively. We grouped the aerosol chemical compounds into four classes: dust, particulate organic matter (POM), elemental carbon (EC), and ions. We studied the annual variation of each class to determine their contribution in the total aerosol mass concentration and finally to investigate their potential emission sources. On an annual basis, the species presented a well-marked seasonality, with the peak of mass concentration for both sizes registered in dry season, 67 ± 2 to 86 ± 9 versus 14 ± 9 to 34 ± 5% in wet season. These values emphasized the seasonality of the emissions and the relative weak interannual standard deviation indicates the low variability of the seasonality. At the seasonal scale, major contributions to the aerosol chemistry in the dry season are: dust (26-59%), POM (30-59%), EC (5-9%), and ions (3-5%), suggesting a predominance of Sahelian and Saharan dust emissions and biomass burning source in this season. In the wet season, POM is predominant, followed by dust, EC, and ions. These results point out the contribution of surrounded biofuel combustion used for cooking and biogenic emissions during the wet season.

Volatility dependence of Henry's law constants of condensable organics: Application to estimate depositional loss of secondary organic aerosols

NASA Astrophysics Data System (ADS)

Hodzic, A.; Aumont, B.; Knote, C.; Lee-Taylor, J.; Madronich, S.; Tyndall, G.

2014-07-01

The water solubility of oxidation intermediates of volatile organic compounds that can condense to form secondary organic aerosol (SOA) is largely unconstrained in current chemistry-climate models. We apply the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere to calculate Henry's law constants for these intermediate species. Results show a strong negative correlation between Henry's law constants and saturation vapor pressures. Details depend on precursor species, extent of photochemical processing, and NOx levels. Henry's law constants as a function of volatility are made available over a wide range of vapor pressures for use in 3-D models. In an application using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) over the U.S. in summer, we find that dry (and wet) deposition of condensable organic vapors leads to major reductions in SOA, decreasing surface concentrations by ~50% (10%) for biogenic and ~40% (6%) for short chain anthropogenic precursors under the considered volatility conditions.

Airflow, transport and regional deposition of aerosol particles during chronic bronchitis of human central airways.

PubMed

Farkhadnia, Fouad; Gorji, Tahereh B; Gorji-Bandpy, Mofid

2016-03-01

In the present study, the effects of airway blockage in chronic bronchitis disease on the flow patterns and transport/deposition of micro-particles in a human symmetric triple bifurcation lung airway model, i.e., Weibel's generations G3-G6 was investigated. A computational fluid and particle dynamics model was implemented, validated and applied in order to evaluate the airflow and particle transport/deposition in central airways. Three breathing patterns, i.e., resting, light activity and moderate exercise, were considered. Using Lagrangian approach for particle tracking and random particle injection, an unsteady particle tracking method was performed to simulate the transport and deposition of micron-sized aerosol particles in human central airways. Assuming laminar, quasi-steady, three-dimensional air flow and spherical non-interacting particles in sequentially bifurcating rigid airways, airflow patterns and particle transport/deposition in healthy and chronic bronchitis (CB) affected airways were evaluated and compared. Comparison of deposition efficiency (DE) of aerosols in healthy and occluded airways showed that at the same flow rates DE values are typically larger in occluded airways. While in healthy airways, particles deposit mainly around the carinal ridges and flow dividers--due to direct inertial impaction, in CB affected airways they deposit mainly on the tubular surfaces of blocked airways because of gravitational sedimentation.

Tracing the Sources of Atmospheric Phosphorus Deposition to a Tropical Rain Forest in Panama Using Stable Oxygen Isotopes.

PubMed

Gross, A; Turner, B L; Goren, T; Berry, A; Angert, A

2016-02-02

Atmospheric dust deposition can be a significant source of phosphorus (P) in some tropical forests, so information on the origins and solubility of atmospheric P is needed to understand and predict patterns of forest productivity under future climate scenarios. We characterized atmospheric dust P across a seasonal cycle in a tropical lowland rain forest on Barro Colorado Nature Monument (BCNM), Republic of Panama. We traced P sources by combining remote sensing imagery with the first measurements of stable oxygen isotopes in soluble inorganic phosphate (δ(18)OP) in dust. In addition, we measured soluble inorganic and organic P concentrations in fine (<1 μm) and coarse (>1 μm) aerosol fractions and used this data to estimate the contribution of P inputs from dust deposition to the forest P budget. Aerosol dry mass was greater in the dry season (December to April, 5.6-15.7 μg m(-3)) than the wet season (May to November, 3.1-7.1 μg m(-3)). In contrast, soluble P concentrations in the aerosols were lower in the dry season (980-1880 μg P g(-1)) than the wet season (1170-3380 μg P g(-1)). The δ(18)OP of dry-season aerosols resembled that of nearby forest soils (∼19.5‰), suggesting a local origin. In the wet season, when the Trans-Atlantic Saharan dust belt moves north close to Panama, the δ(18)OP of aerosols was considerably lower (∼15.5‰), suggesting a significant contribution of long-distance dust P transport. Using satellite retrieved aerosol optical depth (AOD) and the P concentrations in aerosols we sampled in periods when Saharan dust was evident we estimate that the monthly P input from long distance dust transport during the period with highest Saharan dust deposition is 88 ± 31 g P ha(-1) month(-1), equivalent to between 10 and 29% of the P in monthly litter fall in nearby forests. These findings have important implications for our understanding of modern nutrient budgets and the productivity of tropical forests in the region under future

Aerosol chemical vapor deposition of metal oxide films

DOEpatents

Ott, K.C.; Kodas, T.T.

1994-01-11

A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said substrate.

Analysis of remotely sensed and surface data of aerosols and meteorology for the Mexico Megalopolis Area between 2003 and 2015.

PubMed

Mora, Marco; Braun, Rachel A; Shingler, Taylor; Sorooshian, Armin

2017-08-27

This paper presents an aerosol characterization study from 2003 to 2015 for the Mexico City Metropolitan Area using remotely sensed aerosol data, ground-based measurements, air mass trajectory modeling, aerosol chemical composition modeling, and reanalysis data for the broader Megalopolis of Central Mexico region. The most extensive biomass burning emissions occur between March and May concurrent with the highest aerosol optical depth, ultraviolet aerosol index, and surface particulate matter (PM) mass concentration values. A notable enhancement in coarse PM levels is observed during vehicular rush hour periods on weekdays versus weekends owing to nonengine-related emissions such as resuspended dust. Among wet deposition species measured, PM 2.5 , PM 10 , and PM coarse (PM 10 -PM 2.5 ) were best correlated with NH 4 + , SO 4 2- , and Ca 2+ , suggesting that the latter three constituents are important components of the aerosol seeding raindrops that eventually deposit to the surface in the study region. Reductions in surface PM mass concentrations were observed in 2014-2015 owing to reduced regional biomass burning as compared to 2003-2013.

Analysis of remotely sensed and surface data of aerosols and meteorology for the Mexico Megalopolis Area between 2003 and 2015

PubMed Central

Mora, Marco; Braun, Rachel A.; Shingler, Taylor; Sorooshian, Armin

2017-01-01

This paper presents an aerosol characterization study from 2003 to 2015 for the Mexico City Metropolitan Area using remotely sensed aerosol data, ground-based measurements, air mass trajectory modeling, aerosol chemical composition modeling, and reanalysis data for the broader Megalopolis of Central Mexico region. The most extensive biomass burning emissions occur between March and May concurrent with the highest aerosol optical depth, ultraviolet aerosol index, and surface particulate matter (PM) mass concentration values. A notable enhancement in coarse PM levels is observed during vehicular rush hour periods on weekdays versus weekends owing to nonengine-related emissions such as resuspended dust. Among wet deposition species measured, PM2.5, PM10, and PMcoarse (PM10−PM2.5) were best correlated with NH4+, SO42−, and Ca2+, suggesting that the latter three constituents are important components of the aerosol seeding raindrops that eventually deposit to the surface in the study region. Reductions in surface PM mass concentrations were observed in 2014–2015 owing to reduced regional biomass burning as compared to 2003–2013. PMID:28955600

Aerosol deposition in the human lung following administration from a microprocessor controlled pressurised metered dose inhaler.

PubMed Central

Farr, S. J.; Rowe, A. M.; Rubsamen, R.; Taylor, G.

1995-01-01

BACKGROUND--Gamma scintigraphy was employed to assess the deposition of aerosols emitted from a pressurised metered dose inhaler (MDI) contained in a microprocessor controlled device (SmartMist), a system which analyses an inspiratory flow profile and automatically actuates the MDI when predefined conditions of flow rate and cumulative inspired volume coincide. METHODS--Micronised salbutamol particles contained in a commercial MDI (Ventolin) were labelled with 99m-technetium using a method validated by the determination of (1) aerosol size characteristics of the drug and radiotracer following actuation into an eight stage cascade impactor and (2) shot potencies of these non-volatile components as a function of actuation number. Using nine healthy volunteers in a randomised factorial interaction design the effect of inspiratory flow rate (slow, 30 l/min; medium, 90 l/min; fast, 270 l/min) combined with cumulative inspired volume (early, 300 ml; late, 3000 ml) was determined on total and regional aerosol lung deposition using the technique of gamma scintigraphy. RESULTS--The SmartMist firing at the medium/early setting (medium flow and early in the cumulative inspired volume) resulted in the highest lung deposition at 18.6 (1.42)%. The slow/early setting gave the second highest deposition at 14.1 (2.06)% with the fast/late setting resulting in the lowest (7.6 (1.15)%). Peripheral lung deposition obtained for the medium/early (9.1 (0.9)%) and slow/early (7.5 (1.06)%) settings were equivalent but higher than those obtained with the other treatments. This reflected the lower total lung deposition at these other settings as no difference in regional deposition, expressed as a volume corrected central zone:peripheral zone ratio, was apparent for all modes of inhalation studied. CONCLUSIONS--The SmartMist device allowed reproducible actuation of an MDI at a preprogrammed point during inspiration. The extent of aerosol deposition in the lung is affected by a change in

Impacts of aerosol-cloud interactions on past and future changes in tropospheric composition

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

Unger, N.; Menon, S.; Shindell, D. T.

2009-02-02

The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, aerosol-cloud interactions (ACI). The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI) to present day (PD) and future impacts from PD to 2050 (for the moderate IPCC A1B scenario) that embracemore » a wide spectrum of precursor emission changes and consequential ACI. The aerosol indirect effect (AIE) is estimated to be -2.0 Wm{sup -2} for PD-PI and -0.6 Wm{sup -2} for 2050-PD, at the high end of current estimates. Inclusion of ACI substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of ACI leads to 20% enhancements in in-cloud sulfate production and {approx}10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions ({approx}10-30%). Nitric acid wet deposition is dampened by 15-20% across the industrialized regions due to ACI allowing additional re-release of reactive nitrogen that contributes to 1-2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that ACI must be considered in studies of methane trends and projections of future changes to particulate matter air quality.« less

Putative cryomagma interaction with aerosols deposit at Titan's surface

NASA Astrophysics Data System (ADS)

Coll, Patrice; Navarro-Gonzalez, Rafael; Raulin, Francois; Coscia, David; Ramirez, Sandra I.; Buch, Arnaud; Szopa, Cyril; Poch, Olivier; Cabane, Michel; Brassé, Coralie

The largest moon of Saturn, Titan, is known for its dense, nitrogen-rich atmosphere. The organic aerosols which are produced in Titan’s atmosphere are of great astrobiological interest, particularly because of their potential evolution when they reach the surface and may interact with putative ammonia-water cryomagma [1]. In this context we have followed the evolution of alkaline pH hydrolysis (25wt% ammonia-water) of Titan aerosol analogues, that have been qualified as representative of Titan’s aerosols [2]. Indeed the first results obtained by the ACP experiment onboard Huygens probe revealed that the main products obtained after thermolysis of Titan’s collected aerosols, were ammonia (NH3) and hydrogen cyanide (HCN). Then performing a direct comparison of the volatiles produced after a thermal treatment done in conditions similar to the ones used by the ACP experiment, we may estimate that the tholins we used are relevant to chemical analogues of Titan’s aerosols, and to note free of oxygen. Taking into account recent studies proposing that the subsurface ocean may contain a lower fraction of ammonia (about 5wt% or less [3]), and assuming the presence of specific gas species [4, 5], in particular CO2 and H2S, trapped in likely internal ocean, we determine a new probable composition of the cryomagma which could potentially interact with deposited Titan’s aerosols. We then carried out different hydrolyses, taking into account this composition, and we established the influence of the hydrolysis temperature on the organic molecules production. References: [1] Mitri et al., 2008. Resurfacing of Titan by ammonia-water cryomagma. Icarus. 196, 216-224. [2] Coll et al. 2013, Can laboratory tholins mimic the chemistry producing Titan's aerosols? A review in light of ACP experimental results, Planetary and Space Science 77, 91-103. [3] Tobie et al. 2012. Titan’s Bulk Composition Constrained by Cassini-Huygens: implication for internal outgassing. The

Compact Layers of Hybrid Halide Perovskites Fabricated via the Aerosol Deposition Process-Uncoupling Material Synthesis and Layer Formation.

PubMed

Panzer, Fabian; Hanft, Dominik; Gujar, Tanaji P; Kahle, Frank-Julian; Thelakkat, Mukundan; Köhler, Anna; Moos, Ralf

2016-04-08

We present the successful fabrication of CH₃NH₃PbI₃ perovskite layers by the aerosol deposition method (ADM). The layers show high structural purity and compactness, thus making them suitable for application in perovskite-based optoelectronic devices. By using the aerosol deposition method we are able to decouple material synthesis from layer processing. Our results therefore allow for enhanced and easy control over the fabrication of perovskite-based devices, further paving the way for their commercialization.

Investigation of Mercury Wet Deposition Physicochemistry in the Ohio River Valley through Automated Sequential Sampling

EPA Science Inventory

Intra-storm variability and soluble fractionation was explored for summer-time rain events in Steubenville, Ohio to evaluate the physical processes controlling mercury (Hg) in wet deposition in this industrialized region. Comprehensive precipitation sample collection was conducte...

Trace element and isotope deposition across the air–sea interface: progress and research needs

PubMed Central

Landing, W. M.; Bucciarelli, E.; Cheize, M.; Fietz, S.; Hayes, C. T.; Kadko, D.; Morton, P. L.; Rogan, N.; Sarthou, G.; Shelley, R. U.; Shi, Z.; Shiller, A.; van Hulten, M. M. P.

2016-01-01

The importance of the atmospheric deposition of biologically essential trace elements, especially iron, is widely recognized, as are the difficulties of accurately quantifying the rates of trace element wet and dry deposition and their fractional solubility. This paper summarizes some of the recent progress in this field, particularly that driven by the GEOTRACES, and other, international research programmes. The utility and limitations of models used to estimate atmospheric deposition flux, for example, from the surface ocean distribution of tracers such as dissolved aluminium, are discussed and a relatively new technique for quantifying atmospheric deposition using the short-lived radionuclide beryllium-7 is highlighted. It is proposed that this field will advance more rapidly by using a multi-tracer approach, and that aerosol deposition models should be ground-truthed against observed aerosol concentration data. It is also important to improve our understanding of the mechanisms and rates that control the fractional solubility of these tracers. Aerosol provenance and chemistry (humidity, acidity and organic ligand characteristics) play important roles in governing tracer solubility. Many of these factors are likely to be influenced by changes in atmospheric composition in the future. Intercalibration exercises for aerosol chemistry and fractional solubility are an essential component of the GEOTRACES programme. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035268

Trace element and isotope deposition across the air-sea interface: progress and research needs

NASA Astrophysics Data System (ADS)

Baker, A. R.; Landing, W. M.; Bucciarelli, E.; Cheize, M.; Fietz, S.; Hayes, C. T.; Kadko, D.; Morton, P. L.; Rogan, N.; Sarthou, G.; Shelley, R. U.; Shi, Z.; Shiller, A.; van Hulten, M. M. P.

2016-11-01

The importance of the atmospheric deposition of biologically essential trace elements, especially iron, is widely recognized, as are the difficulties of accurately quantifying the rates of trace element wet and dry deposition and their fractional solubility. This paper summarizes some of the recent progress in this field, particularly that driven by the GEOTRACES, and other, international research programmes. The utility and limitations of models used to estimate atmospheric deposition flux, for example, from the surface ocean distribution of tracers such as dissolved aluminium, are discussed and a relatively new technique for quantifying atmospheric deposition using the short-lived radionuclide beryllium-7 is highlighted. It is proposed that this field will advance more rapidly by using a multi-tracer approach, and that aerosol deposition models should be ground-truthed against observed aerosol concentration data. It is also important to improve our understanding of the mechanisms and rates that control the fractional solubility of these tracers. Aerosol provenance and chemistry (humidity, acidity and organic ligand characteristics) play important roles in governing tracer solubility. Many of these factors are likely to be influenced by changes in atmospheric composition in the future. Intercalibration exercises for aerosol chemistry and fractional solubility are an essential component of the GEOTRACES programme. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Trace element and isotope deposition across the air-sea interface: progress and research needs.

PubMed

Baker, A R; Landing, W M; Bucciarelli, E; Cheize, M; Fietz, S; Hayes, C T; Kadko, D; Morton, P L; Rogan, N; Sarthou, G; Shelley, R U; Shi, Z; Shiller, A; van Hulten, M M P

2016-11-28

The importance of the atmospheric deposition of biologically essential trace elements, especially iron, is widely recognized, as are the difficulties of accurately quantifying the rates of trace element wet and dry deposition and their fractional solubility. This paper summarizes some of the recent progress in this field, particularly that driven by the GEOTRACES, and other, international research programmes. The utility and limitations of models used to estimate atmospheric deposition flux, for example, from the surface ocean distribution of tracers such as dissolved aluminium, are discussed and a relatively new technique for quantifying atmospheric deposition using the short-lived radionuclide beryllium-7 is highlighted. It is proposed that this field will advance more rapidly by using a multi-tracer approach, and that aerosol deposition models should be ground-truthed against observed aerosol concentration data. It is also important to improve our understanding of the mechanisms and rates that control the fractional solubility of these tracers. Aerosol provenance and chemistry (humidity, acidity and organic ligand characteristics) play important roles in governing tracer solubility. Many of these factors are likely to be influenced by changes in atmospheric composition in the future. Intercalibration exercises for aerosol chemistry and fractional solubility are an essential component of the GEOTRACES programme.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2015 The Authors.

Improved solid aerosol generator

DOEpatents

Prescott, D.S.; Schober, R.K.; Beller, J.

1988-07-19

An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates. 2 figs.

Year-round atmospheric wet and dry deposition of nitrogen and phosphorus on water and land surfaces in Nanjing, China.

PubMed

Sun, Liying; Li, Bo; Ma, Yuchun; Wang, Jinyang; Xiong, Zhengqin

2013-06-01

The dry deposition of ammonium, nitrate, and total phosphorus (TP) to both water (DW) and land (DD) surfaces, along with wet deposition, were simultaneously monitored from March 2009 to February 2011 in Nanjing, China. Results showed that wet deposition of total phosphorus was 1.1 kg phosphorus ha (-1)yr(-1), and inorganic nitrogen was 28.7 kg nitrogen ha (-1)yr(-1), with 43% being ammonium nitrogen. Dry deposition of ammonium, nitrate, and total phosphorus, measured by the DW/DD method, was 7.5/2.2 kg nitrogen ha (-1)yr(-1), 6.3/ 4.9 kg nitrogen ha (-1)yr(-1), and 1.9/0.4 kg phosphorus ha (-1)yr(-1), respectively. Significant differences between the DW and DD methods indicated that both methods should be employed simultaneously when analyzing deposition to aquatic and terrestrial ecosystems in watershed areas. The dry deposition of ammonium, nitrate, and total phosphorus contributed 38%, 28%, and 63%, respectively, to the total deposition in the simulated aquatic ecosystem; this has significance for the field of water eutrophication control.

Atmospheric wet deposition of nitrogen and sulfur to a typical red soil agroecosystem in Southeast China during the ten-year monsoon seasons (2003-2012)

NASA Astrophysics Data System (ADS)

Cui, Jian; Zhou, Jing; Peng, Ying; He, Yuanqiu; Yang, Hao; Mao, Jingdong

2014-01-01

Biological processes in agroecosystems have been affected by atmospheric nitrogen (N) and sulfur (S) deposition, but there is uncertainty about their deposition characteristics in the monsoon season. We collected rain samples using an ASP-2 sampler, recorded rainfall and rain frequency by an auto-meteorological experiment sub-station, and determined total N, NO3--N and NH4+-N levels in precipitation with an AutoAnalyzer 3 and SO42--S with a chromatography, in order to characterize the wet deposition of N and S to a typical red soil agroecosystem by a ten-year monitoring experiment in Southeast China. The results indicated that N and S wet deposition had an increased trend with the flux of total N (3.34-65.17 kg ha-1 N) and total S (SO42--S) (7.17-23.44 kg ha-1 S) during the monsoon seasons. The additional applications of pig mature in 2006 and 2007 led to the peaks of DON (dissolved organic nitrogen) and total N wet deposition. On average, NH4+-N was the major N form, accounting for 48.5% of total N wet deposition and DON was not a negligible N form, accounting for 20.8% during the ten-year monsoon seasons (except 2006 and 2007). Wet deposition of N and S has been intensively influenced by human activities in the monsoon season, and would increase the potential ecological risk in the red soil agricultural ecosystem.

Cardiogenic mixing increases aerosol deposition in the human lung in the absence of gravity.

PubMed

Prisk, G Kim; Sá, Rui Carlos; Darquenne, Chantal

2013-11-01

Exposure to extraterrestrial dusts is an almost inevitable consequence of any proposed planetary exploration. Previous studies in humans showed reduced deposition in low-gravity compared with normal gravity (1G). However, the reduced sedimentation means that fewer particles deposit in the airways, increasing the number of particles transported to the lung periphery where they eventually deposit albeit at a smaller rate than in 1G. In this study, we determined the role that gravity and other mechanisms such as cardiogenic mixing play in peripheral lung deposition during breath holds. Eight healthy subjects inhaled boluses of 0.5 μm-diameter particles to penetration volumes (V p ) of 300 and 1200ml that were followed by breath holds of up to 10 sec. Tests were performed in 1G and during short periods of microgravity (μG) aboard the NASA Microgravity Research Aircraft. Aerosol deposition and dispersion were calculated from these data. Results show that, for both V p , deposition in 1G was significantly higher than in μG. In contrast, while dispersion was significantly higher in 1G compared to μG at V p =1200ml, there was no significant gravitational effect on dispersion at V p =300ml. Finally, for each G level and V p , deposition and dispersion significantly increased with increasing breath-hold time. The most important finding of this study is that, even in the absence of gravity, aerosol deposition in the lung periphery increased with increasing residence time. Because the particles used in this study were too large to be significantly affected by Brownian diffusion, the increase in deposition is likely due to cardiogenic motion effects.

Long term aerosol and trace gas measurements in Central Amazonia

NASA Astrophysics Data System (ADS)

Artaxo, Paulo; Barbosa, Henrique M. J.; Ferreira de Brito, Joel; Carbone, Samara; Rizzo, Luciana V.; Andreae, Meinrat O.; Martin, Scot T.

2016-04-01

The central region of the Amazonian forest is a pristine region in terms of aerosol and trace gases concentrations. In the wet season, Amazonia is actually one of the cleanest continental region we can observe on Earth. A long term observational program started 20 years ago, and show important features of this pristine region. Several sites were used, between then ATTO (Amazon Tall Tower Observatory) and ZF2 ecological research site, both 70-150 Km North of Manaus, receiving air masses that traveled over 1500 km of pristine tropical forests. The sites are GAW regional monitoring stations. Aerosol chemical composition (OC/EC and trace elements) is being analysed using filters for fine (PM2.5) and coarse mode aerosol as well as Aerodyne ACSM (Aerosol Chemical Speciation Monitors). VOCs are measured using PTR-MS, while CO, O3 and CO2 are routinely measured. Aerosol absorption is being studied with AE33 aethalometers and MAAP (Multi Angle Absorption Photometers). Aerosol light scattering are being measured at several wavelengths using TSI and Ecotech nephelometers. Aerosol size distribution is determined using scanning mobility particle sizer at each site. Lidars measure the aerosol column up to 12 Km providing the vertical profile of aerosol extinction. The aerosol column is measures using AERONET sun photometers. In the wet season, organic aerosol comprises 75-85% of fine aerosol, and sulfate and nitrate concentrations are very low (1-3 percent). Aerosols are dominated by biogenic primary particles as well as SOA from biogenic precursors. Black carbon in the wet season accounts for 5-9% of fine mode aerosol. Ozone in the wet season peaks at 10-12 ppb at the middle of the day, while carbon monoxide averages at 50-80 ppb. Aerosol optical thickness (AOT) is a low 0.05 to 0.1 at 550 nm in the wet season. Sahara dust transport events sporadically enhance the concentration of soil dust aerosols and black carbon. In the dry season (August-December), long range transported

Evaluating WRF-Chem aerosol indirect effects in Southeast Pacific marine stratocumulus during VOCALS-REx

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

Saide, Pablo; Spak, S. N.; Carmichael, Gregory

2012-03-30

We evaluate a regional-scale simulation with the WRF-Chem model for the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), which sampled the Southeast Pacific's persistent stratocumulus deck. Evaluation of VOCALS-REx ship-based and aircraft observations focuses on analyzing how aerosol loading affects marine boundary layer (MBL) dynamics and cloud microphysics. We compare local time series and campaign averaged longitudinal gradients, and highlight differences in model simulations with (W) and without wet (NW) deposition processes. The higher aerosol loadings in the NW case produce considerable changes in MBL dynamics and cloud microphysics, in accordance with the established conceptualmore » model of aerosol indirect effects. These include increase in cloud albedo, increase in MBL and cloud heights, drizzle suppression, increase in liquid water content, and increase in cloud lifetime. Moreover, better statistical representation of aerosol mass and number concentration improves model fidelity in reproducing observed spatial and temporal variability in cloud properties, including top and base height, droplet concentration, water content, rain rate, optical depth (COD) and liquid water path (LWP). Together, these help to quantify confidence in WRF-Chem's modeled aerosol-cloud interactions, while identifying structural and parametric uncertainties including: irreversibility in rain wet removal; overestimation of marine DMS and sea salt emissions and accelerated aqueous sulfate conversion. Our findings suggest that WRF-Chem simulates marine cloud-aerosol interactions at a level sufficient for applications in forecasting weather and air quality and studying aerosol climate forcing, including the reliability required for policy analysis and geo-engineering applications.« less

Sensitivity study of the wet deposition schemes in the modelling of the Fukushima accident.

NASA Astrophysics Data System (ADS)

Quérel, Arnaud; Quélo, Denis; Roustan, Yelva; Mathieu, Anne; Kajino, Mizuo; Sekiyama, Thomas; Adachi, Kouji; Didier, Damien; Igarashi, Yasuhito

2016-04-01

The Fukushima-Daiichi release of radioactivity is a relevant event to study the atmospheric dispersion modelling of radionuclides. Actually, the atmospheric deposition onto the ground may be studied through the map of measured Cs-137 established consecutively to the accident. The limits of detection were low enough to make the measurements possible as far as 250km from the nuclear power plant. This large scale deposition has been modelled with the Eulerian model ldX. However, several weeks of emissions in multiple weather conditions make it a real challenge. Besides, these measurements are accumulated deposition of Cs-137 over the whole period and do not inform of deposition mechanisms involved: in-cloud, below-cloud, dry deposition. A comprehensive sensitivity analysis is performed in order to understand wet deposition mechanisms. It has been shown in a previous study (Quérel et al, 2016) that the choice of the wet deposition scheme has a strong impact on the assessment of the deposition patterns. Nevertheless, a "best" scheme could not be highlighted as it depends on the selected criteria: the ranking differs according to the statistical indicators considered (correlation, figure of merit in space and factor 2). A possibility to explain the difficulty to discriminate between several schemes was the uncertainties in the modelling, resulting from the meteorological data for instance. Since the move of the plume is not properly modelled, the deposition processes are applied with an inaccurate activity in the air. In the framework of the SAKURA project, an MRI-IRSN collaboration, new meteorological fields at higher resolution (Sekiyama et al., 2013) were provided and allows to reconsider the previous study. An updated study including these new meteorology data is presented. In addition, a focus on several releases causing deposition in located areas during known period was done. This helps to better understand the mechanisms of deposition involved following the

Development of AN Atmospheric Aerosol Model for Studies of Global Budgets and Effects of Airborne Particulate Material

NASA Astrophysics Data System (ADS)

Giorgi, Filippo

A microphysics-removal Atmospheric Aerosol Model (AAM) is developed for use in General Circulation Models (GCM) to study global budgets and effects of particulate material. In this model the particle population is assumed to be composed of a set of log-normal modes whose time evolution due to microphysical processes is described via prognostic equations for an appropriate number of moments of the particle size distribution. This newly devised technique, by making use of a small number of prognostic equations for the aerosol variables and utilizing optimized numerical procedures, renders the model computationally efficient, hence particularly suitable for use in complex 3D GCMs. Detailed parameterizations of particle coagulation, sedimentation, dry deposition, and wet removal are incorporated into the AAM. The coagulation term includes only intramodal Brownian coagulation; the sedimentation term is proportional to the vertical divergence of the gravitational settling flux; dry depositions is calculated in terms of a surface deposition velocity dependent upon surface wind speed, surface drag coefficient, particle size and density, and characteristics of the surface roughness elements; wet removal is included as an in-cloud scavenging term dependent upon the local GCM-produced precipitation rates. The AAM is incorporated into a GCM and is applied to two types of studies: (1) Characteristics of the particle wet and dry removal processes. The rainout-determined lifetimes of soluble particulate (or gaseous) compounds are found to depend, because of the episodic and asymmetric nature of precipitation, not only on the amount of precipitation but also on the characteristics of the storm cycle and the direction of the species' main flow. Calculated dry deposition velocities are sensitive, in a complicated fashion, to both meteorological factors and particle dynamics. (2) Climatic and environmental impact of massive particulate injections following a full-scale nuclear war

Quality of wet deposition in the Grand Calumet River watershed, northwestern Indiana, June 30, 1992-August 31, 1993

USGS Publications Warehouse

Willoughby, T.C.

1995-01-01

Northwestern Indiana is one of the most heavily industrialized and largest steel-producing areas in the United States. High temperature processes, such as fossil-fuel combustion and steel production, release contaminants to the atmosphere that may result in wet deposition being a major contributor to major ion and trace-metal loadings in north- western Indiana and Lake Michigan. A wet-deposition collection site was established at the Gary (Indiana) Regional Airport in June 1992 to monitor the chemical quality of wet deposition. Weekly samples were collected at this site from June 30, 1992, through August 31, 1993, and were analyzed for pH, specific conductance, and selected major ions and trace metals. Forty-eight samples collected during the study were of sufficient volumes for some of the determinations to be performed. Median constituent concentrations were determined for samples collected during warm weather and cold weather (November 1 through March 31). Median concentrations were substituted for missing values from samples with insufficient volumes for analysis of all the constituents of interest. Constituent concentrations were converted to weekly loadings. Two values were calculated to provide a range for the weekly loading for samples with measured concentrations of constituents less than the method reporting limit. The minimum weekly loading was computed by substituting zero for the constituent concentration; the maximum weekly loading was computed by substituting the method reporting limit for the concentration. If all of the sample concentrations measured were greater than the method reporting limit, an annual loading value was computed. The annual loadings could be used to assist in estimating the contribution of wet deposition to the total annual constituent loadings in the Grand Calumet River in northwestern Indiana.

Water-soluble nitrogen and phosphorus in aerosols and dry deposition in Jiaozhou Bay, North China: Deposition velocities, origins and biogeochemical implications

NASA Astrophysics Data System (ADS)

Xing, Jianwei; Song, Jinming; Yuan, Huamao; Wang, Qidong; Li, Xuegang; Li, Ning; Duan, Liqin; Qu, Baoxiao

2018-07-01

To probe the deposition velocities (Vd), fluxes, origins and biogeochemical significance of atmospheric dry deposition (ADD) of nutrients in coastal waters, aerosol and dry deposition samples were collected in Jiaozhou Bay (JZB) from June 2015 to May 2016. We measured water-soluble inorganic nitrogen (WSIN; including ammonium (NH4sbnd N), nitrate (NO3sbnd N) and nitrite (NO2sbnd N)), organic nitrogen (WSON), inorganic phosphorus (WSIP; including reactive phosphate (PO4sbnd P)) and organic phosphorus (WSOP) for all samples. The concentrations of aerosol N species were comparatively higher than those in other aquatic ecosystems worldwide. Although WSIN and WSIP represented relatively large percentages of species, WSON ( 16%) and WSOP ( 35%) cannot be ignored in aerosols. The dry deposition fluxes for NH4sbnd N, NO3sbnd N, NO2sbnd N, WSON, PO4sbnd P and WSOP were 29.4, 29.9, 0.058, 15.4, 0.099 and 0.165 mmol m-2 yr-1, respectively, with apparent seasonal variations. The average annual Vd values of NH4sbnd N, NO3sbnd N, NO2sbnd N, WSON, PO4sbnd P and WSOP were indirectly calculated as 0.17 ± 0.11, 0.35 ± 0.20, 0.34 ± 0.25, 0.30 ± 0.22, 0.43 ± 0.28 and 0.91 ± 0.60 cm s-1, respectively. The considerable differences between the percentages of corresponding nutrient concentrations and ADD fluxes were mainly attributed to Vd variations. Anthropogenic emissions were the most common source of WSON and WSIN based on a correlation analysis. WSIP was highly correlated with WSOP, suggesting that they may share similar sources. Additionally, the long-range transport of natural and anthropogenic pollutants, especially the air-masses originating from the northwest direction, exerted greater effects than local emissions on aerosol N and P species in JZB based on an air mass backward trajectory analysis. The increasing ADD flux may have non-negligible biogeochemical effects on JZB by increasing primary productivity and altering the nutrient structure due to the high WSIN

Seasonality of Forcing by Carbonaceous Aerosols

NASA Astrophysics Data System (ADS)

Habib, G.; Bond, T.; Rasch, P. J.; Coleman, D.

2006-12-01

Aerosols can influence the energy balance of Earth-Atmosphere system with profound effect on regional climate. Atmospheric processes, such as convection, scavenging, wet and dry deposition, govern the lifetime and location of aerosol; emissions affect its quantity and location. Both affect climate forcing. Here we investigate the effect of seasonality in emissions and atmospheric processes on radiative forcing by carbonaceous aerosols, focusing on aerosol from fossil fuel and biofuel. Because aerosol lifetime is seasonal, ignoring the seasonality of sources such as residential biofuel may introduce a bias in aerosol burden and therefore in predicted climate forcing. We present a global emission inventory of carbonaceous aerosols with seasonality, and simulate atmospheric concentrations using the Community Atmosphere Model (CAM). We discuss where and when the seasonality of emissions and atmospheric processes has strong effects on atmospheric burden, lifetime, climate forcing and aerosol optical depth (AOD). Previous work has shown that aerosol forcing is higher in summer than in winter, and has identified the importance of aerosol above cloud in determining black carbon forcing. We show that predicted cloud height is a very important factor in determining normalized radiative forcing (forcing per mass), especially in summer. This can affect the average summer radiative forcing by nearly 50%. Removal by cloud droplets is the dominant atmospheric cleansing mechanism for carbonaceous aerosols. We demonstrate the modeled seasonality of removal processes and compare the importance of scavenging by warm and cold clouds. Both types of clouds contribute significantly to aerosol removal. We estimate uncertainty in direct radiative forcing due to scavenging by tagging the aerosol which has experienced cloud interactions. Finally, seasonal variations offer an opportunity to assess modeled processes when a single process dominates variability. We identify regions where aerosol

Wash effect of atmospheric trace metals wet deposition and its source characteristic in subtropical watershed in China.

PubMed

Gao, Yang; Hao, Zhuo; Yang, Tiantian; He, Nianpeng; Tian, Jing; Wen, Xuefa

2016-10-01

In order to better understand air pollution in deve-loping regions, such as China, it is important to investigate the wet deposition behavior of atmospheric trace metals and its sources in the subtropical watershed. This paper studies the seasonal change of trace metal concentrations in precipitation and other potential sources in a typical subtropical watershed (Jiazhuhe watershed) located in the downstream of the Yangtze River of China. The results show that typical crustal elements (Al, Fe) and trace element (Zn) have high seasonal variation patterns and these elements have higher contents in precipitation as compared to other metals in Jiazhuhe watershed. In addition, there is no observed Pb in base flow in this study, and the concentration magnitudes of Al, Ba, Fe, Mn, Sr, and Zn in base flow are significantly higher than that of other metals. During different rainfall events, the dynamic export processes are also different for trace metals. The various trace metals dynamic export processes lead to an inconsistent mass first flush and a significant accumulative variance throughout the rainfall events. It is found that in this region, most of the trace metals in precipitation are from anthropogenic emission and marine aerosols brought by typhoon and monsoon.

Aerosol and Surface Deposition Characteristics of Two Surrogates for Bacillus anthracis Spores

PubMed Central

Stapleton, Helen L.

2016-01-01

ABSTRACT Spores of an acrystalliferous derivative of Bacillus thuringiensis subsp. kurstaki, termed Btcry−, are morphologically, aerodynamically, and structurally indistinguishable from Bacillus anthracis spores. Btcry− spores were dispersed in a large, open-ended barn together with spores of Bacillus atrophaeus subsp. globigii, a historically used surrogate for Bacillus anthracis. Spore suspensions (2 × 1012 CFU each of B. atrophaeus subsp. globigii and Btcry−) were aerosolized in each of five spray events using a backpack misting device incorporating an air blower; a wind of 4.9 to 7.6 m s−1 was also flowing through the barn in the same direction. Filter air samplers were situated throughout the barn to assess the aerosol density of the spores during each release. Trays filled with a surfactant in aqueous buffer were placed on the floor near the filter samplers to assess spore deposition. Spores were also recovered from arrays of solid surfaces (concrete, aluminum, and plywood) that had been laid on the floor and set up as a wall at the end of the barn. B. atrophaeus subsp. globigii spores were found to remain airborne for significantly longer periods, and to be deposited on horizontal surfaces at lower densities, than Btcry− spores, particularly near the spray source. There was a 6-fold-higher deposition of Btcry− spores than of B. atrophaeus subsp. globigii spores on vertical surfaces relative to the surrounding airborne density. This work is relevant for selecting the best B. anthracis surrogate for the prediction of human exposure, hazard assessment, and hazard management following a malicious release of B. anthracis. IMPORTANCE There is concern that pathogenic bacteria could be maliciously disseminated in the air to cause human infection and disruption of normal life. The threat from spore-forming organisms, such as the causative agent of anthrax, is particularly serious. In order to assess the extent of this risk, it is important to have a

¹¹¹Indium-labeled ultrafine carbon particles; a novel aerosol for pulmonary deposition and retention studies.

PubMed

Sanchez-Crespo, Alejandro; Klepczynska-Nyström, Anna; Lundin, Anders; Larsson, Britt Marie; Svartengren, Magnus

2011-02-01

Continuous environmental or occupational exposure to airborne particulate pollution is believed to be a major hazard for human health. A technique to characterize their deposition and clearance from the lungs is fundamental to understand the underlying mechanisms behind their negative health effects. In this work, we describe a method for production and follow up of ultrafine carbon particles labeled with radioactive ¹¹¹Indium (¹¹¹In). The physicochemical and biological properties of the aerosol are described in terms of particle size and concentration, agglomeration rate, chemical bonding stability, and human lung deposition and retention. Preliminary in vivo data from a healthy human pilot exposure and 1-week follow up of the aerosol is presented. More than 98% of the generated aerosol was labeled with Indium and with particle sizes log normally distributed around 79  nm count median diameter. The aerosol showed good generation reproducibility and chemical stability, about 5% leaching 7 days after generation. During human inhalation, the particles were deposited in the alveolar space, with no central airways involvement. Seven days after exposure, the cumulative activity retention was 95.3%. Activity leaching tests from blood and urine samples confirmed that the observed clearance was explained by unbound activity, suggesting that there was no significant elimination of ultrafine particles. Compared to previously presented methods based on Technegas, ¹¹¹In-labelled ultrafine carbon particles allow for extended follow-up assessments of particulate pollution retention in healthy and diseased lungs.

Evaluation of a new microphysical aerosol module in the ECMWF Integrated Forecasting System

NASA Astrophysics Data System (ADS)

Woodhouse, Matthew; Mann, Graham; Carslaw, Ken; Morcrette, Jean-Jacques; Schulz, Michael; Kinne, Stefan; Boucher, Olivier

2013-04-01

The Monitoring Atmospheric Composition and Climate II (MACC-II) project will provide a system for monitoring and predicting atmospheric composition. As part of the first phase of MACC, the GLOMAP-mode microphysical aerosol scheme (Mann et al., 2010, GMD) was incorporated within the ECMWF Integrated Forecasting System (IFS). The two-moment modal GLOMAP-mode scheme includes new particle formation, condensation, coagulation, cloud-processing, and wet and dry deposition. GLOMAP-mode is already incorporated as a module within the TOMCAT chemistry transport model and within the UK Met Office HadGEM3 general circulation model. The microphysical, process-based GLOMAP-mode scheme allows an improved representation of aerosol size and composition and can simulate aerosol evolution in the troposphere and stratosphere. The new aerosol forecasting and re-analysis system (known as IFS-GLOMAP) will also provide improved boundary conditions for regional air quality forecasts, and will benefit from assimilation of observed aerosol optical depths in near real time. Presented here is an evaluation of the performance of the IFS-GLOMAP system in comparison to in situ aerosol mass and number measurements, and remotely-sensed aerosol optical depth measurements. Future development will provide a fully-coupled chemistry-aerosol scheme, and the capability to resolve nitrate aerosol.

Annual wet and dry deposition of sulfur and nitrogen in the Snowy Range, Wyoming

Treesearch

Karl Zeller; Debra Harrington; Al Riebau; Evgeny Donev

2000-01-01

The collocation of three national networked programs NADP, EPA's CASTNET, and the Forest Service's IMPROVE Module A, within a few hundred meters of each other in the pristine Medicine Bow forest of Wyoming has made it possible to assess the total amount of sulfur and nitrogen deposition, both wet and dry for this alpine/subalpine ecosystem. Additional sites...

Constraints Pb-210 and Be-7 on Wet Deposition and Transport in a Global Three-Dimensional Chemical Tracer Model Driven by Assimilated Meteorological Fields

NASA Technical Reports Server (NTRS)

Liu, Hong-Yu; Jacob, Daniel J.; Bey, Isabelle; Yantosca, Robert M.

2001-01-01

The atmospheric distributions of the aerosol tracers Pb-210 and Be-7 are simulated with a global three-dimensional model driven by assimilated meteorological observations for 1991-1996 from the NASA Goddard Earth Observing System (GEOSl). The combination of terrigenic Pb-210 and cosmogenic Be-7 provides a sensitive test of wet deposition and vertical transport in the model. Our simulation of moist transport and removal includes scavenging in wet convective updrafts (40% scavenging efficiency per kilometer of updraft), midlevel entrainment and detrainment, first-order rainout and washout from both convective anvils and large-scale precipitation, and cirrus precipitation. Observations from surface sites in specific years are compared to model results for the corresponding meteorological years, and observations from aircraft missions over the Pacific are compared to model results for the days of the flights. Initial simulation of Be-7 showed that cross-tropopause transport in the GEOSl meteorological fields is too fast by a factor of 3-4. We adjusted the stratospheric Be-7 source to correct the tropospheric simulation. Including this correction, we find that the model gives a good simulation of observed Pb-210 and Be-7 concentrations and deposition fluxes at surface sites worldwide, with no significant global bias and with significant success in reproducing the observed latitudinal and seasonal distributions. We achieve several improvements over previous models; in particular, we reproduce the observed Be-7 minimum in the tropics and show that its simulation is sensitive to rainout from convective anvils. Comparisons with aircraft observations up to 12-km altitude suggest that cirrus precipitation could be important for explaining the low concentrations in the middle and upper troposphere.

An Analysis of Simulated Wet Deposition of Mercury from the North American Mercury Model Intercomparison Study

EPA Science Inventory

A previous intercomparison of atmospheric mercury models in North America has been extended to compare simulated and observed wet deposition of mercury. Three regional-scale atmospheric mercury models were tested; CMAQ, REMSAD and TEAM. These models were each employed using thr...

Evaluating WRF-Chem aerosol indirect effects in Southeast Pacific marine stratocumulus during VOCALS-REx

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

Saide P. E.; Springston S.; Spak, S. N.

2012-03-29

We evaluate a regional-scale simulation with the WRF-Chem model for the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), which sampled the Southeast Pacific's persistent stratocumulus deck. Evaluation of VOCALS-REx ship-based and three aircraft observations focuses on analyzing how aerosol loading affects marine boundary layer (MBL) dynamics and cloud microphysics. We compare local time series and campaign-averaged longitudinal gradients, and highlight differences in model simulations with (W) and without (NW) wet deposition processes. The higher aerosol loadings in the NW case produce considerable changes in MBL dynamics and cloud microphysics, in accordance with the established conceptualmore » model of aerosol indirect effects. These include increase in cloud albedo, increase in MBL and cloud heights, drizzle suppression, increase in liquid water content, and increase in cloud lifetime. Moreover, better statistical representation of aerosol mass and number concentration improves model fidelity in reproducing observed spatial and temporal variability in cloud properties, including top and base height, droplet concentration, water content, rain rate, optical depth (COD) and liquid water path (LWP). Together, these help to quantify confidence in WRF-Chem's modeled aerosol-cloud interactions, especially in the activation parameterization, while identifying structural and parametric uncertainties including: irreversibility in rain wet removal; overestimation of marine DMS and sea salt emissions, and accelerated aqueous sulfate conversion. Our findings suggest that WRF-Chem simulates marine cloud-aerosol interactions at a level sufficient for applications in forecasting weather and air quality and studying aerosol climate forcing, and may do so with the reliability required for policy analysis.« less

Modeling wet deposition of acid substances over the PRD region in China

NASA Astrophysics Data System (ADS)

Lu, Xingcheng; Fung, Jimmy Chi Hung; Wu, Dongwei

2015-12-01

The Pearl River Delta (PRD) region in southern China has suffered heavily from acid rain in the last 10 years due to the anthropogenic emission of sulfur dioxide and nitrogen dioxide. Several measurement-based studies about this issue have been conducted to analyze the chemical composition of precipitation in this area. However, no detailed, high resolution numerical simulation regarding this topic has ever been done in this region. In this study, the WRF-SMOKE-CMAQ system was applied to simulate the wet deposition of acid substances (SO42- and NO3-) in the PRD region from 2009 to 2011 with a resolution of 3 km. The simulation output agreed well with the observation data. Our results showed that Guangzhou was the city most affected by acid rain in this region. The ratio of non-sea-salt sulfate to nitrate indicated that the acid rain in this region belonged to the sulfate-nitrate mixed type. The source apportionment result suggests that point source and super regional source are the ones that contribute the pollutants most in the rain water over PRD Region. The sulfate and nitrate input to some reservoirs via wet deposition was also estimated based on the model simulation. Our results suggest that further cross-city cooperation and emission reduction are needed to further curb acid rain in this region.

Atmospheric Residence Times of Continental Aerosols.

NASA Astrophysics Data System (ADS)

Balkanski, Yves Jacques

The global atmospheric distributions of ^{222}Rn and ^{210 }Pb are simulated with a three-dimensional model of atmospheric transport based on the meteorology of the NASA GISS^1>=neral circulation model. The short-lived radioactive gas ^ {222}Rn (half-life = 3.8d) is emitted almost exclusively from land, at a relatively uniform rate; hence it is an excellent tracer of continental influences. Lead -210 is produced by decay of ^{222} Rn and immediately condenses to preexisting aerosol surfaces. It provides an excellent measure of aerosol residence times in the atmosphere because its source is accurately defined by the ^{222} Rn distribution. Results from the three-dimensional model are compared to measurements of ^ {222}Rn and ^{210 }Pb atmospheric concentrations to evaluate model's long-range transport over oceanic regions and to study the deposition mechanisms of atmospheric aerosols. Model results for ^{222} Rn are used to examine the long-range transport of continental air over two selected oceanic regions, the subantartic Indian Ocean and the North Pacific. It is shown that fast transport of air from southern Africa causes substantial continental pollution at southern mid-latitudes, a region usually regarded as pristine. Air over the North Pacific is heavily impacted by continental influences year round, but the altitude at which the transport occurs varies seasonally. Observations of aerosols at island sites, which are commonly used as diagnostics of continental influences, may be misleading because they do not account for influences at high altitude and because aerosols are efficiently scavenged by deposition during transport. The study of ^{210}Pb focuses on defining the residence times of submicron aerosols in the troposphere. Scavenging in wet convective updrafts is found to provide the dominant sink on a global scale. The globally averaged residence time for ^{210 }Pb-containing aerosols in the troposphere is 7 days. The average increase in residence time

Modeling dry and wet deposition of sulfate, nitrate, and ammonium ions in Jiuzhaigou National Nature Reserve, China using a source-oriented CMAQ model: Part I. Base case model results.

PubMed

Qiao, Xue; Tang, Ya; Hu, Jianlin; Zhang, Shuai; Li, Jingyi; Kota, Sri Harsha; Wu, Li; Gao, Huilin; Zhang, Hongliang; Ying, Qi

2015-11-01

A source-oriented Community Multiscale Air Quality (CMAQ) model driven by the meteorological fields generated by the Weather Research and Forecasting (WRF) model was used to study the dry and wet deposition of nitrate (NO3(-)), sulfate (SO4(2-)), and ammonium (NH4(+)) ions in the Jiuzhaigou National Nature Reserve (JNNR), China from June to August 2010 and to identify the contributions of different emission sectors and source regions that were responsible for the deposition fluxes. The model performance is evaluated in this paper and the source contribution analyses are presented in a companion paper. The results show that WRF is capable of reproducing the observed precipitation rates with a Mean Normalized Gross Error (MNGE) of 8.1%. Predicted wet deposition fluxes of SO4(2-) and NO3(-) at the Long Lake (LL) site (3100 m a.s.l.) during the three-month episode are 2.75 and 0.34 kg S(N) ha(-1), which agree well with the observed wet deposition fluxes of 2.42 and 0.39 kg S(N) ha(-1), respectively. Temporal variations in the weekly deposition fluxes at LL are also well predicted. Wet deposition flux of NH4(+) at LL is over-predicted by approximately a factor of 3 (1.60 kg N ha(-1)vs. 0.56 kg N ha(-1)), likely due to missing alkaline earth cations such as Ca(2+) in the current CMAQ simulations. Predicted wet deposition fluxes are also in general agreement with observations at four Acid Deposition Monitoring Network in East Asia (EANET) sites in western China. Predicted dry deposition fluxes of SO4(2-) (including gas deposition of SO2) and NO3(-) (including gas deposition of HNO3) are 0.12 and 0.12 kg S(N) h a(-1) at LL and 0.07 and 0.08 kg S(N) ha(-1) at Jiuzhaigou Bureau (JB) in JNNR, respectively, which are much lower than the corresponding wet deposition fluxes. Dry deposition flux of NH4(+) (including gas deposition of NH3) is 0.21 kg N ha(-1) at LL, and is also much lower than the predicted wet deposition flux. For both dry and wet deposition fluxes, predictions

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates.

PubMed

Longest, P Worth; Tian, Geng; Khajeh-Hosseini-Dalasm, Navvab; Hindle, Michael

2016-12-01

The objective of this study was to compare aerosol deposition predictions of a new whole-airway CFD model with available in vivo data for a dry powder inhaler (DPI) considered across multiple inhalation waveforms, which affect both the particle size distribution (PSD) and particle deposition. The Novolizer DPI with a budesonide formulation was selected based on the availability of 2D gamma scintigraphy data in humans for three different well-defined inhalation waveforms. Initial in vitro cascade impaction experiments were conducted at multiple constant (square-wave) particle sizing flow rates to characterize PSDs. The whole-airway CFD modeling approach implemented the experimentally determined PSDs at the point of aerosol formation in the inhaler. Complete characteristic airway geometries for an adult were evaluated through the lobar bronchi, followed by stochastic individual pathway (SIP) approximations through the tracheobronchial region and new acinar moving wall models of the alveolar region. It was determined that the PSD used for each inhalation waveform should be based on a constant particle sizing flow rate equal to the average of the inhalation waveform's peak inspiratory flow rate (PIFR) and mean flow rate [i.e., AVG(PIFR, Mean)]. Using this technique, agreement with the in vivo data was acceptable with <15% relative differences averaged across the three regions considered for all inhalation waveforms. Defining a peripheral to central deposition ratio (P/C) based on alveolar and tracheobronchial compartments, respectively, large flow-rate-dependent differences were observed, which were not evident in the original 2D in vivo data. The agreement between the CFD predictions and in vivo data was dependent on accurate initial estimates of the PSD, emphasizing the need for a combination in vitro-in silico approach. Furthermore, use of the AVG(PIFR, Mean) value was identified as a potentially useful method for characterizing a DPI aerosol at a constant flow rate.

Atmospheric dry and wet nitrogen deposition on three contrasting land use types of an agricultural catchment in subtropical central China

NASA Astrophysics Data System (ADS)

Shen, Jianlin; Li, Yong; Liu, Xuejun; Luo, Xiaosheng; Tang, Hong; Zhang, Yangzhu; Wu, Jinshui

2013-03-01

Atmospheric emissions of reactive nitrogen (N) species are at high levels in China in recent years, but few studies have employed N deposition monitoring techniques that measure both dry and wet deposition for comprehensive evaluation of the impacts of N deposition on ecosystems. In this study, to quantify the total N deposition, both dry and wet N depositions were monitored using denuder/filter pack systems, passive samplers and wet-only samplers at three sites with different land use types (forest, paddy field and tea field) in a 135-km2 catchment in subtropical central China from September 2010 to August 2011. At the three sampling sites, the annual mean concentrations of total N (the sum of NH, NO and DON) in rainwater were 1.2-1.6 mg N L-1, showing small variation across sites. Annual mean concentrations of total N (the sum of NH3, NO2, HNO3, particulate NH and NO) in the air were 13-18 μg N m-3. High NH3 concentrations in the air were observed at the agricultural sites of tea and paddy fields, indicating significant NH3 emissions from N fertiliser application; and high NO2 concentrations were found at the upland sites of forest and tea field, suggesting high NO emissions from soils due to high N deposition or high N fertiliser input. The annual total N deposition for the three sites of paddy field, tea field and forest was estimated as 22, 34 and 55 kg N ha-1 yr-1, in which the dry N deposition components contributed to 21%, 36% and 63% of the annual total N deposition, respectively. The annual deposition of reduced N species was 1.1-1.8 times of the annual deposition of oxidised N species. To minimise the adverse effects of atmospheric N deposition on natural/semi-natural ecosystems, it is crucial to reduce the reactive N emissions from anthropogenic activities (e.g., N fertiliser application, animal production and fossil fuel combustion) in subtropical central China.

Continental-scale assessment of long-term trends in wet deposition trajectories: Role of anthropogenic and hydro-climatic drivers

NASA Astrophysics Data System (ADS)

Park, J.; Gall, H. E.; Niyogi, D.; Rao, S.

2012-12-01

The global trend of increased urbanization, and associated increased intensity of energy and material consumption and waste emissions, has contributed to shifts in the trajectories of aquatic, terrestrial, and atmospheric environments. Here, we focus on continental-scale spatiotemporal patterns in two atmospheric constituents (nitrate and sulfate), whose global biogeochemical cycles have been dramatically altered by emissions from mobile and fixed sources in urbanized and industrialized regions. The observed patterns in wet deposition fluxes of nitrate and sulfate are controlled by (1) natural hydro-climatic forcing, and (2) anthropogenic forcing (emissions and regulatory control), both of which are characterized by stochasticity and non-stationarity. We examine long-term wet deposition records in the U.S., Europe, and East Asia to evaluate how anthropogenic and natural forcing factors jointly contributed to the shifting temporal patterns of wet deposition fluxes at continental scales. These data offer clear evidence for successful implementation of regulatory controls and widespread adoption of technologies contributed to improving water quality and mitigation of adverse ecological impacts. We developed a stochastic model to project the future trajectories of wet deposition fluxes in emerging countries with fast growing urban areas. The model generates ellipses within which projected wet deposition flux trajectories are inscribed, similar to the trends in observational data. The shape of the ellipses provides information regarding the relative dominance of anthropogenic (e.g., industrial and urban emissions) versus hydro-climatic drivers (e.g., rainfall patterns, aridity index). Our analysis facilitates projections of the trajectory shift as a result of urbanization and other land-use changes, climate change, and regulatory enforcement. We use these observed data and the model to project likely trajectories for rapidly developing countries (BRIC), with a

Properties of zinc tin oxide thin film by aerosol assisted chemical vapor deposition (AACVD)

NASA Astrophysics Data System (ADS)

Riza, Muhammad Arif; Rahman, Abu Bakar Abd; Sepeai, Suhaila; Ludin, Norasikin Ahmad; Teridi, Mohd Asri Mat; Ibrahim, Mohd Adib

2018-05-01

This study focuses on the properties of ZTO which have been deposited by a low-cost method namely aerosol assisted chemical vapor deposition (AACVD). The precursors used in this method were zinc acetate dihidrate and tin chloride dihydrate for ZTO thin film deposition. Both precursors were mixed and stirred until fully dissolved before deposition. The ZTO was deposited on borosilicate glass substrate for the investigation of optical properties. The films deposited have passed the scotch tape adherence test. XRD revealed that the crystal ZTO is slightly in the form of perovskite structure but several deteriorations were also seen in the spectrum. The UV-Vis analysis showed high transmittance of ˜85% and the band gap was calculated to be 3.85 eV. The average thickness of the film is around 284 nm. The results showed that the ZTO thin films have been successfully deposited by the utilization of AACVD method.

Strong influence of deposition and vertical mixing on secondary organic aerosol concentrations in CMAQ and CAMx

NASA Astrophysics Data System (ADS)

Shu, Qian; Koo, Bonyoung; Yarwood, Greg; Henderson, Barron H.

2017-12-01

Differences between two air quality modeling systems reveal important uncertainties in model representations of secondary organic aerosol (SOA) fate. Two commonly applied models (CMAQ: Community Multiscale Air Quality; CAMx: Comprehensive Air Quality Model with extensions) predict very different OA concentrations over the eastern U.S., even when using the same source data for emissions and meteorology and the same SOA modeling approach. Both models include an option to output a detailed accounting of how each model process (e.g., chemistry, deposition, etc.) alters the mass of each modeled species, referred to as process analysis. We therefore perform a detailed diagnostic evaluation to quantify simulated tendencies (Gg/hr) of each modeled process affecting both the total model burden (Gg) of semi-volatile organic compounds (SVOC) in the gas (g) and aerosol (a) phases and the vertical structures to identify causes of concentration differences between the two models. Large differences in deposition (CMAQ: 69.2 Gg/d; CAMx: 46.5 Gg/d) contribute to significant OA bias in CMAQ relative to daily averaged ambient concentration measurements. CMAQ's larger deposition results from faster daily average deposition velocities (VD) for both SVOC (g) (VD,cmaq = 2.15 × VD,camx) and aerosols (VD,cmaq = 4.43 × Vd,camx). Higher aerosol deposition velocity would be expected to cause similar biases for inert compounds like elemental carbon (EC), but this was not seen. Daytime low-biases in EC were also simulated in CMAQ as expected but were offset by nighttime high-biases. Nighttime high-biases were a result of overly shallow mixing in CMAQ leading to a higher fraction of EC total atmospheric mass in the first layer (CAMx: 5.1-6.4%; CMAQ: 5.6-6.9%). Because of the opposing daytime and nighttime biases, the apparent daily average bias for EC is reduced. For OA, there are two effects of reduced vertical mixing: SOA and SVOC are concentrated near the surface, but SOA yields are reduced

Photochemistry of Glyoxal in Wet Aerosols: Smog Chamber Study

NASA Astrophysics Data System (ADS)

Lim, Y. B.; Kim, H.; Turpin, B. J.

2015-12-01

Aqueous chemistry is an important pathway for the formation of secondary organic aerosol (SOA). Reaction vessel studies provide evidence that in the aqueous phase photooxidation of water soluble organic compounds (e.g., glyoxal, methylglyoxal) form multifunctional organic products and oligomers. In this work, we extend this bulk-phase chemistry to the condensed-phase chemistry that occurs in/on aerosols by conducting smog chamber experiments — photooxidation of ammonium sulfate and sulfuric acid aerosols containing glyoxal and hydrogen peroxide in the presence of NOx under dry/humid conditions. Particles were analyzed using ultra performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). In the irradiated chamber, photooxidation products of glyoxal as seen in reaction vessel experiments (e.g., oxalic acids and tartaric acids) were also formed in both ammonium sulfate aerosols and sulfuric acid aerosols at humid and even dry conditions. However, the major products were organosulfurs (CHOS), organonitrogens (CHON), and nitrooxy-organosulfates (CHONS), which were also dominantly formed in the dark chamber. These products were formed via non-radical reactions, which depend on acidity and humidity. However, the real-time profiles in the dark chamber and the irradiated chamber were very different, suggesting photochemistry substantially affects non-radical formation in the condensed phase.

Enhanced Deposition by Electrostatic Field-Assistance Aggravating Diesel Exhaust Aerosol Toxicity for Human Lung Cells.

PubMed

Stoehr, Linda C; Madl, Pierre; Boyles, Matthew S P; Zauner, Roland; Wimmer, Monika; Wiegand, Harald; Andosch, Ancuela; Kasper, Gerhard; Pesch, Markus; Lütz-Meindl, Ursula; Himly, Martin; Duschl, Albert

2015-07-21

Air pollution is associated with increased risk of cardiovascular and pulmonary diseases, but conventional air quality monitoring gives no information about biological consequences. Exposing human lung cells at the air-liquid interface (ALI) to ambient aerosol could help identify acute biological responses. This study investigated electrode-assisted deposition of diesel exhaust aerosol (DEA) on human lung epithelial cells (A549) in a prototype exposure chamber. A549 cells were exposed to DEA at the ALI and under submerged conditions in different electrostatic fields (EFs) and were assessed for cell viability, membrane integrity, and IL-8 secretion. Qualitative differences of the DEA and its deposition under different EFs were characterized using scanning mobility particle sizer (SMPS) measurements, transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). Upon exposure to DEA only, cell viability decreased and membrane impairment increased for cells at the ALI; submerged cells were unaffected. These responses were enhanced upon application of an EF, as was DEA deposition. No adverse effects were observed for filtered DEA or air only, confirming particle-induced responses. The prototype exposure chamber proved suitable for testing DEA-induced biological responses of cells at the ALI using electrode-assisted deposition and may be useful for analysis of other air pollutants.

A new approach to chemically-speciated submicron aerosol fluxes over tropical and temperate forests.

NASA Astrophysics Data System (ADS)

Farmer, D. K.; Kimmel, J. R.; Nemitz, E.; Phillips, G.; Docherty, K.; Chen, Q.; Martin, S.; Cubison, M.; Jimenez, J.

2008-12-01

Aerosols play an important role in the planet's radiation balance; however, their sources and sinks remain highly uncertain. In particular, due to instrumental limitations, there are few measurements of particle fluxes over the Earth's surface. Particles are expected to deposit over forests, leading not only to an aerosol sink, but also to an ecosystem source of nutrients and acids. However, forests emit volatile organic compounds (VOCs) that are known to produce secondary organic aerosol, thus also acting as aerosol sources. We have developed a new approach to measure biosphere-atmosphere exchange of chemically-speciated aerosol using a High Resolution-Time of Flight-Aerosol Mass Spectrometer (HR-ToF-AMS; DeCarlo et al., Anal. Chem., 2006) in a new Eddy Covariance Flux mode (10 Hz). This approach allows us to directly measure fluxes of non-refractory organic, sulphate, nitrate and ammonium in submicron particles. Measurements have been carried out over two forests: a temperate ponderosa pine plantation at Blodgett Forest (BEARPEX-I campaign, 2007) and a tropical rain forest in the Brazilian Amazon during the wet season (AMAZE campaign, 2008). Data collected at these sites allows us to demonstrate that the flux mode of the HR-ToF-AMS meets the rigorous instrumental requirements of the eddy covariance approach and that fluxes of different chemical species can be quantified. Aerosol fluxes under clean and anthropogenically-impacted conditions are compared. These measurements allow us to better constrain dry deposition over forested environments and to understand the potential of flux measurements to constrain the biogenic SOA budget.

A Fast and Efficient Version of the TwO-Moment Aerosol Sectional (TOMAS) Global Aerosol Microphysics Model

NASA Technical Reports Server (NTRS)

Lee, Yunha; Adams, P. J.

2012-01-01

This study develops more computationally efficient versions of the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithms, collectively called Fast TOMAS. Several methods for speeding up the algorithm were attempted, but only reducing the number of size sections was adopted. Fast TOMAS models, coupled to the GISS GCM II-prime, require a new coagulation algorithm with less restrictive size resolution assumptions but only minor changes in other processes. Fast TOMAS models have been evaluated in a box model against analytical solutions of coagulation and condensation and in a 3-D model against the original TOMAS (TOMAS-30) model. Condensation and coagulation in the Fast TOMAS models agree well with the analytical solution but show slightly more bias than the TOMAS-30 box model. In the 3-D model, errors resulting from decreased size resolution in each process (i.e., emissions, cloud processing wet deposition, microphysics) are quantified in a series of model sensitivity simulations. Errors resulting from lower size resolution in condensation and coagulation, defined as the microphysics error, affect number and mass concentrations by only a few percent. The microphysics error in CN70CN100 (number concentrations of particles larger than 70100 nm diameter), proxies for cloud condensation nuclei, range from 5 to 5 in most regions. The largest errors are associated with decreasing the size resolution in the cloud processing wet deposition calculations, defined as cloud-processing error, and range from 20 to 15 in most regions for CN70CN100 concentrations. Overall, the Fast TOMAS models increase the computational speed by 2 to 3 times with only small numerical errors stemming from condensation and coagulation calculations when compared to TOMAS-30. The faster versions of the TOMAS model allow for the longer, multi-year simulations required to assess aerosol effects on cloud lifetime and precipitation.

The influence of continental air masses on the aerosols and nutrients deposition over the western North Pacific

NASA Astrophysics Data System (ADS)

Fu, Jiangping; Wang, Bo; Chen, Ying; Ma, Qingwei

2018-01-01

The air masses transported from East Asia have a strong impact on the aerosol properties and deposition in the marine boundary layer of the western North Pacific (WNP) during winter and spring. We joined a cruise between 17 Mar. and 22 Apr. 2014 and investigated the changes of aerosol composition and size distribution over the remote WNP and marginal seas. Although the secondary aerosol species (SO42-, NO3- and NH4+) in remote WNP were influenced significantly by the continental transport, NH4+ concentrations were lower than 2.7 μg m-3 in most sampling days and not correlated with non-sea-salt (nss)-SO42- suggesting that the ocean could be a primary source of NH4+. Moderate Cl- depletion (23%) was observed in remote WNP, and the inverse relationship between Cl- depletion percentages and nss-K+ in aerosols suggested that the transport of biomass burning smoke from East Asia might be a vital extra source of Cl-. Both Asian dust and haze events were encountered during the cruise. Asian dust carried large amounts of crustal elements such as Al and Ti to the WNP, and the dusty Fe deposition may double its background concentration in seawater. Differently, a dramatic increase of dry deposition flux of dissolved particulate inorganic nitrogen was observed during the haze event. Our study reveals that the transport of different continental air masses may have distinct biogeochemical impacts on the WNP by increasing the fluxes of different nutrient elements and potentially changing the nutrient stoichiometry.

Estimation of carbon sequestration in China’s forests induced by atmospheric wet nitrogen deposition using the principles of ecological stoichiometry

NASA Astrophysics Data System (ADS)

Zhu, Jianxing; He, Nianpeng; Zhang, Jiahui; Wang, Qiufeng; Zhao, Ning; Jia, Yanlong; Ge, Jianping; Yu, Guirui

2017-11-01

The worldwide development of industry and agriculture has generated noticeable increases in atmospheric nitrogen (N) deposition, significantly altering the global N cycle. These changes might affect the global carbon (C) cycle by enhancing forest C sequestration. Here, we used a series of datasets from eight typical forests along the north-south transect of eastern China (NSTEC). These datasets contained information on community structure, C and N concentrations in the soil and the organs (leaf, branch, stem, and fine-root) of 877 plant species, and atmospheric wet N deposition. Using the biomass weighting method, we scaled up the C:N ratios from the organ level to the ecosystem level, and evaluated the C sequestration rate (CSRN) in response to wet N deposition and N use efficiency (NUE) in China’s forests based on the principles of ecological stoichiometry. Our results showed that atmospheric wet N deposition had a modest impact on forest C storage. Specifically, mean CSRN was estimated as 231 kg C ha-1 yr-1 (range: 32.7-507.1 kg C ha-1 yr-1), accounting for 2.1% of NPP and 4.6% of NEP at the ecosystem level. The NUEeco of atmospheric N deposition ranged from 9.6-27.7 kg C kg-1 N, and increased with increasing latitude from subtropical to cold-temperate forests in China (P < 0.05). This study provides a new approach for estimating the effect of atmospheric deposition on forest C sequestration based on the principles of ecological stoichiometry.

Desiccation by Foliar Deposition of Hygroscopic Aerosols may link Air Pollution to Forest Decline and Tree Mortality associated with Global-Change-Type Drought

NASA Astrophysics Data System (ADS)

Burkhardt, J.; Grantz, D. A.; Hunsche, M.; Pariyar, S.; Sutton, M. A.; Zinsmeister, D.

2016-12-01

Leaf surfaces are a major sink for atmospheric aerosol deposition. Plants benefit from aerosol associated nutrients and are able to increase deposition by leaf surface micromorphology. Recent studies have shown that deposited hygroscopic aerosols can also influence plant water relations. This might be an important issue even for remote forest ecosystems, given the strong anthropogenic influence on aerosol production and efficient atmospheric transport. We study processes of aerosol deposition to plant surfaces and their impact on water relations and drought tolerance, both for experimental particle amendment and for aerosol exclusion in filtered air (FA). FA plants experience an environment with < 10% concentration of hygroscopic aerosols compared to ambient air (AA), but no difference in trace gases. Increasing particle concentration leads to decreasing water use efficiency and increasing minimum epidermal conductance (gmin; a measure of uncontrolled water loss inversely related to drought tolerance). After particle amendment, anisohydric beech seedlings increased transpiration and maintained photosynthesis, while isohydric pine seedlings maintained transpiration and tended to reduce photosynthesis. FA seedlings of pine, oak, and fir showed lower gmin than corresponding AA seedlings. The results support the concept of hydraulic activation of stomata (HAS) and an associated wick action caused by leaf surface particles. Concentrated salt solutions formed by hygroscopicity even in unsaturated air may create a thin liquid film that penetrates the stomatal pore, allowing evaporation of liquid water at the leaf surface. Increased gmin suggests the significance of this process under ambient conditions. The direct impact of air pollution on plant drought tolerance is poorly integrated in current scenarios of forest decline and tree mortality, but might represent an important component.

Intranasal Deposition of Accuspray™ Aerosol in Anatomically Correct Models of 2-, 5-, and 12-Year-Old Children.

PubMed

Laube, Beth L; Sharpless, Gail; Vikani, Ami R; Harrand, Vincent; Zinreich, Simeon J; Sedberry, Keith; Knaus, Darin; Barry, James; Papania, Mark

2015-10-01

To our knowledge, quantification of intranasal deposition of aerosol generated by Accuspray(™) (AS) in children has never been published. We hypothesized that deposition would vary significantly with age and with placement of the device within, or outside, of the nostril. We tested these hypotheses in anatomically-correct physical models based on CT scans of 2-, 5-, and 12-year-old children with normal, intranasal airways. Models included a removable anterior nose (AN) with exterior facial features and interior nasal vestibule and nasal valve area and a main nasal airway (MNA), subdivided into upper (superior turbinates and olfactory area), middle (middle turbinates), and lower (inferior turbinates and nasopharynx) thirds. Aerosol was generated from distilled water admixed with (99m)technetium pertechnetate and administered during static airflow by AS inserted inside the right nostril (eight runs/model), or outside the right nostril (six runs/model). Mean aerosol Dv(50) ± standard deviation was 67.8 ± 24.7 μm. Deposition was quantified by 2D gamma scintigraphy and expressed as percentage of the emitted dose. When placed inside the nostril, mean (± standard deviation) deposition within the MNA was significantly less in the 2-year-old, compared to the 5- and 12-year-old, averaging 46.8 ± 33.8% (AN:55.4 ± 29.9%), 75.4 ± 26.7% (AN:23.3 ± 13.6%), and 72.1 ± 18.5% (AN:25.8 ± 18.5%), respectively (p<0.05). When placed outside the nostril, MNA was significantly less in the 2- and 5-year-old compared to the 12-year-old, with 1.4 ± 2.5% (AN:69.7 ± 40.7%), 7.4 ± 9.0% (AN:77.8 ± 32.8%), and 21.1 ± 29.1% (AN:29.2 ± 19.3%), respectively (p<0.05). Deposition in the MNA of all age models was highest when AS was placed inside the nostril (p<0.05). Deposition in the lower third was significantly increased for the 5- and 12-year-old and in the middle third of the 5-year-old when AS was placed inside the nostril. These results indicate that age and device placement

Microfog lubricant application system for advanced turbine engine components, phase 3. [wetting characteristics and deposit forming tendencies of lubricants

NASA Technical Reports Server (NTRS)

Petrucco, R. J.; Leonardi, S. J.

1973-01-01

The wetting characteristics and deposit forming tendencies of a series of lubricants were evaluated using a microfog jet delivery system to wet a flat heated rotating disc. The performances of the nine lubricants are discussed in terms of the various testing parameters which include temperature, disc speed and lubricant gas flow rates. Also discussed are the heat transfer characteristics of two of the lubricants on that same plane disc specimen. The wetting characteristics and heat transfer characteristics of one of the lubricants on a complex disc simulating bearing geometry are also discussed.

Mobilization and distribution of lead originating from roof dust and wet deposition in a roof runoff system.

PubMed

Yu, Jianghua; Yu, Haixia; Huang, Xiaogu

2015-12-01

In this research, the mobilization and distribution of lead originating in roof dust and wet deposition were investigated within a roof dust-rooftop-runoff system. The results indicated that lead from roof dust and wet deposition showed different transport dynamics in runoff system and that this process was significantly influenced by the rainfall intensity. Lead present in the roof dust could be easily washed off into the runoff, and nearly 60 % of the total lead content was present in particulate form. Most of the lead from the roof dust was transported during the late period of rainfall; however, the lead concentration was higher for several minutes at the rainfall beginning. Even though some of the lead from wet deposition, simulated with a standard isotope substance, was adsorbed onto adhered roof dust and/or retained on rooftop in runoff system, most of it (50-82 %) remained as dissolved lead in the runoff for rainfall events of varying intensity. Regarding the distribution of lead in the runoff system, the results indicated that it could be carried in the runoff in dissolved and particulate form, be adsorbed to adhered roof dust, or remain on the rooftop because of adsorption to the roof material. Lead from the different sources showed different distribution patterns that were also related to the rainfall intensity. Higher rainfall intensity resulted in a higher proportion of lead in the runoff and a lower proportion of lead remaining on the rooftop.

The stability of hydrogen ion and specific conductance in filtered wet-deposition samples stored at ambient temperatures

USGS Publications Warehouse

Gordon, J.D.; Schroder, L.J.; Morden-Moore, A. L.; Bowersox, V.C.

1995-01-01

Separate experiments by the U.S. Geological Survey (USGS) and the Illinois State Water Survey Central Analytical Laboratory (CAL) independently assessed the stability of hydrogen ion and specific conductance in filtered wet-deposition samples stored at ambient temperatures. The USGS experiment represented a test of sample stability under a diverse range of conditions, whereas the CAL experiment was a controlled test of sample stability. In the experiment by the USGS, a statistically significant (?? = 0.05) relation between [H+] and time was found for the composited filtered, natural, wet-deposition solution when all reported values are included in the analysis. However, if two outlying pH values most likely representing measurement error are excluded from the analysis, the change in [H+] over time was not statistically significant. In the experiment by the CAL, randomly selected samples were reanalyzed between July 1984 and February 1991. The original analysis and reanalysis pairs revealed that [H+] differences, although very small, were statistically different from zero, whereas specific-conductance differences were not. Nevertheless, the results of the CAL reanalysis project indicate there appears to be no consistent, chemically significant degradation in sample integrity with regard to [H+] and specific conductance while samples are stored at room temperature at the CAL. Based on the results of the CAL and USGS studies, short-term (45-60 day) stability of [H+] and specific conductance in natural filtered wet-deposition samples that are shipped and stored unchilled at ambient temperatures was satisfactory.

Simulating Aerosol Size Distribution and Mass Concentration with Simultaneous Nucleation, Condensation/Coagulation, and Deposition with the GRAPES-CUACE

NASA Astrophysics Data System (ADS)

Zhou, Chunhong; Shen, Xiaojing; Liu, Zirui; Zhang, Yangmei; Xin, Jinyuan

2018-04-01

A coupled aerosol-cloud model is essential for investigating the formation of haze and fog and the interaction of aerosols with clouds and precipitation. One of the key tasks of such a model is to produce correct mass and number size distributions of aerosols. In this paper, a parameterization scheme for aerosol size distribution in initial emission, which took into account the measured mass and number size distributions of aerosols, was developed in the GRAPES-CUACE [Global/Regional Assimilation and PrEdiction System-China Meteorological Administration (CMA) Unified Atmospheric Chemistry Environment model]—an online chemical weather forecast system that contains microphysical processes and emission, transport, and chemical conversion of sectional multi-component aerosols. In addition, the competitive mechanism between nucleation and condensation for secondary aerosol formation was improved, and the dry deposition was also modified to be in consistent with the real depositing length. Based on the above improvements, the GRAPES-CUACE simulations were verified against observational data during 1-31 January 2013, when a series of heavy regional haze-fog events occurred in eastern China. The results show that the aerosol number size distribution from the improved experiment was much closer to the observation, whereas in the old experiment the number concentration was higher in the nucleation mode and lower in the accumulation mode. Meanwhile, the errors in aerosol number size distribution as diagnosed by its sectional mass size distribution were also reduced. Moreover, simulations of organic carbon, sulfate, and other aerosol components were improved and the overestimation as well as underestimation of PM2.5 concentration in eastern China was significantly reduced, leading to increased correlation coefficient between simulated and observed PM2.5 by more than 70%. In the remote areas where bad simulation results were produced previously, the correlation coefficient

2013 Monitoring and tracking wet nitrogen deposition at Rocky Mountain National Park

USGS Publications Warehouse

Morris, Kristi; Mast, M. Alisa; Clow, David W.; Wetherbee, Gregory A.; Baron, Jill S.; Taipale, Curt; Blett, Tamara; Gay, David A.; Bowker, Daniel

2015-01-01

In 2004, multiple agencies including the Colorado Department of Public Health and Environment (CDPHE), the National Park Service (NPS), and the U.S. Environmental Protection Agency (U.S. EPA) met to address the effects and trends of nitrogen deposition and related air quality issues at Rocky Mountain National Park (RMNP). These agencies signed a Memorandum of Understanding (MOU) to facilitate interagency coordination, calling the effort the “Rocky Mountain National Park Initiative.” After much collaboration, the MOU agencies (CDPHE, NPS, and U.S. EPA) issued the Nitrogen Deposition Reduction Plan (NDRP) in 2007, which was endorsed by the three agencies and the Colorado Air Quality Control Commission (AQCC). The NDRP and other related documents are available on the CDPHE website: http://www.colorado.gov/cdphe/rmnpinitiative. The purpose of this report is to inform the MOU agencies, stakeholders, and the public about the status and trends of wet nitrogen deposition at RMNP through 2013. In addition to other types of evidence, the MOU agencies use the information provided in this annual report to determine interim milestone achievements.

Long-Term Wet and Dry Deposition of Total and Methyl Mercury in the Remote Boreal Ecoregion of Canada

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

Graydon, Jennifer A; Louis, Vincent; Hintelmann, Holger

2008-11-01

Although a positive relationship between atmospheric loadings of inorganic mercury (Hg(II)) to watersheds and concentrations of methyl mercury (MeHg) in fish has now been established, net wet and dry deposition of Hg(II) and MeHg to watersheds remains challenging to quantify. In this study, concentrations and loadings of total mercury (THg; all forms of Hg in a sample) and MeHg in open area wet deposition, throughfall, and litterfall were quantified at the remote Experimental Lakes Area in the boreal ecoregion, NW Ontario, Canada. Between 1992 and 2006, mean annual THg and MeHg loadings in the open were 36 17 and 0.5more » 0.2 mg ha 1, respectively. Throughfall THg and MeHg loadings were generally 2 4 times and 0.8 2 times higher, respectively, than loadings in the open. Loadings of both THg and MeHg were highest under an old growth spruce/fir canopy and lowest under a deciduous maple canopy, whereas loadings under young jack pine and wetland spruce/pine/alder canopies were intermediate. Litterfall generally represented the largest input of THg (86 105 mg ha 1) and MeHg (0.7 0.8 mg ha 1) to the landscape on an annual basis. Using the direct method of estimating dry deposition (thoughfall + litterfall open loadings), we calculated that annual dry deposition of THg and MeHg under forest canopies ranged from 105 to 201 mg ha 1, whereas dry deposition of MeHg ranged from 0.7 to 1.2 mg ha 1. Photoreduction and emission of wet-deposited Hg(II) from canopy foliage were accounted for, resulting in 3 5% (5 6 mg ha 1) higher annual estimates of dry deposition than via the direct method alone. Net THg and MeHg loadings to this remote landscape were lower than at any other previously studied forested site globally. This study shows that THg and MeHg loading can be extremely variable within a heterogeneous boreal landscape and that processes such as Hg photoreduction and emission from foliage should be considered when estimating dry deposition of Hg.« less

Precipitation effects on aerosol concentration in the background EMEP station of Zarra (Valencia), Spain

NASA Astrophysics Data System (ADS)

Calvo, Ana Isabel; San Martín, Isabel; Castro, Amaya; Alonso-Blanco, Elisabeth; Alves, Célia; Duarte, Márcio; Fernández-González, Sergio; Fraile, Roberto

2014-05-01

Aerosols and precipitation are closely related, presenting a bidirectional influence and constituting an important source of uncertainties on climate change studies. However, they are usually studied independently and in general are only linked to one another for the development or validation of cloud models. The primary and secondary pollutants may be removed by wet and dry deposition. Wet deposition, including in-cloud and below-cloud scavenging processes, can efficiently remove atmospheric aerosols and it is considered a critical process for determining aerosol concentrations in the atmosphere. In this study, aerosols and precipitation data from a background Spanish EMEP (Cooperative Programme for the Monitoring and Evaluation of Long Range Transmission of Air Pollutants in Europe) station located in Zarra, Valencia (Spain) were analyzed (1° 06' W and 39° 05' N, 885 m asl). The effect of precipitation on aerosol concentration was studied and the correlation between the intensity of precipitation and scavenging effect was investigated. In order to evaluate the effects of precipitation on different aerosol size ranges three different aerosol fractions were studied: PM10, PM10-2.5 and PM2.5. In order to eliminate the influence of the air mass changes, only the days in which the air mass of the precipitation day and the previous day had the same origin were considered. Thus, from a total of 3586 rainy days registered from March 2001 to December 2010, 34 precipitation days satisfied this condition and were analyzed. During the period of study, daily precipitation ranged between 0.2 and 28.8 mm, with a mean value of 4 mm. Regarding the origin of the air masses, those from west were dominant at the three height levels investigated (500, 1500 and 3000 m). In order to obtain additional information, aerosol and precipitation chemical composition were also studied in relation to the days of precipitation and the previous days. Furthermore, in order to identify the type

Investigating the impact of local urban sources on total atmospheric mercury wet deposition in Cleveland, Ohio, USA

EPA Science Inventory

Event-based precipitation samples were collected at a downtown industrial and a predominantly upwind rural location in the Cleveland, Ohio metropolitan area from July 2009 through December 2010 to investigate the potential local total mercury (Hg) wet deposition enhancement in a ...

Aqueous-Phase Reactions of Isoprene with Sulfoxy Radical Anions as a way of Wet Aerosol Formation in the Atmosphere

NASA Astrophysics Data System (ADS)

Kuznietsova, I.; Rudzinski, K. J.; Szmigielski, R.; Laboratory of the Environmental Chemistry

2011-12-01

Atmospheric aerosols exhibit an important role in the environment. They have implications on human health and life, and - in the larger scale - on climate, the Earth's radiative balance and the cloud's formation. Organic matter makes up a significant fraction of atmospheric aerosols (~35% to ~90%) and may originate from direct emissions (primary organic aerosol, POA) or result from complex physico-chemical processes of volatile organic compounds (secondary organic aerosol, SOA). Isoprene (2-methyl-buta-1,3-diene) is one of the relevant volatile precursor of ambient SOA in the atmosphere. It is the most abundant non-methane hydrocarbon emitted to the atmosphere as a result of living vegetation. According to the recent data, the isoprene emission rate is estimated to be at the level of 500 TgC per year. While heterogeneous transformations of isoprene have been well documented, aqueous-phase reactions of this hydrocarbon with radical species that lead to the production of new class of wet SOA components such as polyols and their sulfate esters (organosulfates), are still poorly recognized. The chain reactions of isoprene with sulfoxy radical-anions (SRA) are one of the recently researched route leading to the formation of organosulfates in the aqueous phase. The letter radical species originate from the auto-oxidation of sulfur dioxide in the aqueous phase and are behind the phenomenon of atmospheric acid rain formation. This is a complicated chain reaction that is catalyzed by transition metal ions, such as manganese(II), iron(III) and propagated by sulfoxy radical anions . The presented work addresses the chemical interaction of isoprene with sulfoxy radical-anions in the water solution in the presence of nitrite ions and nitrous acid, which are important trace components of the atmosphere. We showed that nitrite ions and nitrous acid significantly altered the kinetics of the auto-oxidation of SO2 in the presence of isoprene at different solution acidity from 2 to 8

Applying super-droplets as a compact representation of warm-rain microphysics for aerosol-cloud-aerosol interactions

NASA Astrophysics Data System (ADS)

Arabas, S.; Jaruga, A.; Pawlowska, H.; Grabowski, W. W.

2012-12-01

Clouds may influence aerosol characteristics of their environment. The relevant processes include wet deposition (rainout or washout) and cloud condensation nuclei (CCN) recycling through evaporation of cloud droplets and drizzle drops. Recycled CCN physicochemical properties may be altered if the evaporated droplets go through collisional growth or irreversible chemical reactions (e.g. SO2 oxidation). The key challenge of representing these processes in a numerical cloud model stems from the need to track properties of activated CCN throughout the cloud lifecycle. Lack of such "memory" characterises the so-called bulk, multi-moment as well as bin representations of cloud microphysics. In this study we apply the particle-based scheme of Shima et al. 2009. Each modelled particle (aka super-droplet) is a numerical proxy for a multiplicity of real-world CCN, cloud, drizzle or rain particles of the same size, nucleus type,and position. Tracking cloud nucleus properties is an inherent feature of the particle-based frameworks, making them suitable for studying aerosol-cloud-aerosol interactions. The super-droplet scheme is furthermore characterized by linear scalability in the number of computational particles, and no numerical diffusion in the condensational and in the Monte-Carlo type collisional growth schemes. The presentation will focus on processing of aerosol by a drizzling stratocumulus deck. The simulations are carried out using a 2D kinematic framework and a VOCALS experiment inspired set-up (see http://www.rap.ucar.edu/~gthompsn/workshop2012/case1/).

Atmospheric aerosol deposition influences marine microbial communities in oligotrophic surface waters of the western Pacific Ocean

NASA Astrophysics Data System (ADS)

Maki, Teruya; Ishikawa, Akira; Mastunaga, Tomoki; Pointing, Stephen B.; Saito, Yuuki; Kasai, Tomoaki; Watanabe, Koichi; Aoki, Kazuma; Horiuchi, Amane; Lee, Kevin C.; Hasegawa, Hiroshi; Iwasaka, Yasunobu

2016-12-01

Atmospheric aerosols contain particulates that are deposited to oceanic surface waters. These can represent a major source of nutrients, trace metals, and organic compounds for the marine environment. The Japan Sea and the western Pacific Ocean are particularly affected by aerosols due to the transport of desert dust and industrially derived particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) from continental Asia. We hypothesized that supplementing seawater with aerosol particulates would lead to measurable changes in surface water nutrient composition as well as shifts in the marine microbial community. Shipboard experiments in the Pacific Ocean involved the recovery of oligotrophic oceanic surface water and subsequent supplementation with aerosol particulates obtained from the nearby coastal mountains, to simulate marine particulate input in this region. Initial increases in nitrates due to the addition of aerosol particulates were followed by a decrease correlated with the increase in phytoplankton biomass, which was composed largely of Bacillariophyta (diatoms), including Pseudo-nitzschia and Chaetoceros species. This shift was accompanied by changes in the bacterial community, with apparent increases in the relative abundance of heterotrophic Rhodobacteraceae and Colwelliaceae in aerosol particulate treated seawater. Our findings provide empirical evidence revealing the impact of aerosol particulates on oceanic surface water microbiology by alleviating nitrogen limitation in the organisms.

Aerosol Emissions from Fuse-Deposition Modeling 3D Printers in a Chamber and in Real Indoor Environments.

PubMed

Vance, Marina E; Pegues, Valerie; Van Montfrans, Schuyler; Leng, Weinan; Marr, Linsey C

2017-09-05

Three-dimensional (3D) printers are known to emit aerosols, but questions remain about their composition and the fundamental processes driving emissions. The objective of this work was to characterize the aerosol emissions from the operation of a fuse-deposition modeling 3D printer. We modeled the time- and size-resolved emissions of submicrometer aerosols from the printer in a chamber study, gained insight into the chemical composition of emitted aerosols using Raman spectroscopy, and measured the potential for exposure to the aerosols generated by 3D printers under real-use conditions in a variety of indoor environments. The average aerosol emission rates ranged from ∼10 8 to ∼10 11 particles min -1 , and the rates varied over the course of a print job. Acrylonitrile butadiene styrene (ABS) filaments generated the largest number of aerosols, and wood-infused polylactic acid (PLA) filaments generated the smallest amount. The emission factors ranged from 6 × 10 8 to 6 × 10 11 per gram of printed part, depending on the type of filament used. For ABS, the Raman spectra of the filament and the printed part were indistinguishable, while the aerosol spectra lacked important peaks corresponding to styrene and acrylonitrile, which are both present in ABS. This observation suggests that aerosols are not a result of volatilization and subsequent nucleation of ABS or direct release of ABS aerosols.

Spatial patterns and temporal trends in mercury concentrations, precipitation depths, and mercury wet deposition in the North American Great Lakes region, 2002-2008

USGS Publications Warehouse

Risch, Martin R.; Gay, David A.; Fowler, Kathleen K.; Keeler, Gerard J.; Backus, Sean M.; Blanchard, Pierrette; Barres, James A.; Dvonch, J. Timothy

2012-01-01

Annual and weekly mercury (Hg) concentrations, precipitation depths, and Hg wet deposition in the Great Lakes region were analyzed by using data from 5 monitoring networks in the USA and Canada for a 2002-2008 study period. High-resolution maps of calculated annual data, 7-year mean data, and net interannual change for the study period were prepared to assess spatial patterns. Areas with 7-year mean annual Hg concentrations higher than the 12 ng per liter water-quality criterion were mapped in 4 states. Temporal trends in measured weekly data were determined statistically. Monitoring sites with significant 7-year trends in weekly Hg wet deposition were spatially separated and were not sites with trends in weekly Hg concentration. During 2002-2008, Hg wet deposition was found to be unchanged in the Great Lakes region and its subregions. Any small decreases in Hg concentration apparently were offset by increases in precipitation.

An automatic collector to monitor insoluble atmospheric deposition: application for mineral dust deposition

NASA Astrophysics Data System (ADS)

Laurent, B.; Losno, R.; Chevaillier, S.; Vincent, J.; Roullet, P.; Bon Nguyen, E.; Ouboulmane, N.; Triquet, S.; Fornier, M.; Raimbault, P.; Bergametti, G.

2015-07-01

Deposition is one of the key terms of the mineral dust cycle. However, dust deposition remains poorly constrained in transport models simulating the atmospheric dust cycle. This is mainly due to the limited number of relevant deposition measurements. This paper aims to present an automatic collector (CARAGA), specially developed to sample the total (dry and wet) atmospheric deposition of insoluble dust in remote areas. The autonomy of the CARAGA can range from 25 days to almost 1 year depending on the programmed sampling frequency (from 1 day to 2 weeks respectively). This collector is used to sample atmospheric deposition of Saharan dust on the Frioul islands in the Gulf of Lions in the Western Mediterranean. To quantify the mineral dust mass in deposition samples, a weighing and ignition protocol is applied. Almost 2 years of continuous deposition measurements performed on a weekly sampling basis on Frioul Island are presented and discussed with air mass trajectories and satellite observations of dust. Insoluble mineral deposition measured on Frioul Island was 2.45 g m-2 for February to December 2011 and 3.16 g m-2 for January to October 2012. Nine major mineral deposition events, measured during periods with significant MODIS aerosol optical depths, were associated with air masses coming from the southern Mediterranean Basin and North Africa.

Sensitivity of atmospheric aerosol scavenging to precipitation intensity and frequency in the context of global climate change

NASA Astrophysics Data System (ADS)

Hou, Pei; Wu, Shiliang; McCarty, Jessica L.; Gao, Yang

2018-06-01

Wet deposition driven by precipitation is an important sink for atmospheric aerosols and soluble gases. We investigate the sensitivity of atmospheric aerosol lifetimes to precipitation intensity and frequency in the context of global climate change. Our sensitivity model simulations, through some simplified perturbations to precipitation in the GEOS-Chem model, show that the removal efficiency and hence the atmospheric lifetime of aerosols have significantly higher sensitivities to precipitation frequencies than to precipitation intensities, indicating that the same amount of precipitation may lead to different removal efficiencies of atmospheric aerosols. Combining the long-term trends of precipitation patterns for various regions with the sensitivities of atmospheric aerosol lifetimes to various precipitation characteristics allows us to examine the potential impacts of precipitation changes on atmospheric aerosols. Analyses based on an observational dataset show that precipitation frequencies in some regions have decreased in the past 14 years, which might increase the atmospheric aerosol lifetimes in those regions. Similar analyses based on multiple reanalysis meteorological datasets indicate that the changes of precipitation intensity and frequency over the past 30 years can lead to perturbations in the atmospheric aerosol lifetimes by 10 % or higher at the regional scale.

Enhanced photo response of mesoporous nanostructured CdS thin film via electrospray aerosol deposition technique

NASA Astrophysics Data System (ADS)

Logu, T.; Soundarrajan, P.; Sankarasubramanian, K.; Sethuraman, K.

2018-04-01

In this work, a high crystalline and mesoporous nanostructured cadmium sulfide (CdS) thin film was successfully grown on the FTO substrates using facile Electrospray Aerosol Deposition (ESAD) technique. The structural, optical, morphological and electrical properties of CdS thin film have been systematically examined. CdS thin film exhibits the hexagonal wurtzite crystal structure with polycrystalline nature. The optical band gap energy of the prepared film was estimated from the Tauc plot and is 2.43 eV. The SEM and AFM images show that the well-interconnected CdS nanoparticles gives mesoporous like morphology. The fine aerosol generated from the ESAD process induces the alteration in the surface morphological structure of deposited CdS film that consequences in enhanced electrical and photo-physical properties. The photoconductivity of the sample has been studied which demonstrates significant photo current. The present study predicts that mesoporous nanostructured CdS thin film would be given a special interest for optoelectronic applications.

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates

PubMed Central

Tian, Geng; Khajeh-Hosseini-Dalasm, Navvab; Hindle, Michael

2016-01-01

Abstract Background: The objective of this study was to compare aerosol deposition predictions of a new whole-airway CFD model with available in vivo data for a dry powder inhaler (DPI) considered across multiple inhalation waveforms, which affect both the particle size distribution (PSD) and particle deposition. Methods: The Novolizer DPI with a budesonide formulation was selected based on the availability of 2D gamma scintigraphy data in humans for three different well-defined inhalation waveforms. Initial in vitro cascade impaction experiments were conducted at multiple constant (square-wave) particle sizing flow rates to characterize PSDs. The whole-airway CFD modeling approach implemented the experimentally determined PSDs at the point of aerosol formation in the inhaler. Complete characteristic airway geometries for an adult were evaluated through the lobar bronchi, followed by stochastic individual pathway (SIP) approximations through the tracheobronchial region and new acinar moving wall models of the alveolar region. Results: It was determined that the PSD used for each inhalation waveform should be based on a constant particle sizing flow rate equal to the average of the inhalation waveform's peak inspiratory flow rate (PIFR) and mean flow rate [i.e., AVG(PIFR, Mean)]. Using this technique, agreement with the in vivo data was acceptable with <15% relative differences averaged across the three regions considered for all inhalation waveforms. Defining a peripheral to central deposition ratio (P/C) based on alveolar and tracheobronchial compartments, respectively, large flow-rate-dependent differences were observed, which were not evident in the original 2D in vivo data. Conclusions: The agreement between the CFD predictions and in vivo data was dependent on accurate initial estimates of the PSD, emphasizing the need for a combination in vitro–in silico approach. Furthermore, use of the AVG(PIFR, Mean) value was identified as a potentially useful method

Climatic Effects of 1950-2050 Changes in US Anthropogenic Aerosols. Part 1; Aerosol Trends and Radiative Forcing

NASA Technical Reports Server (NTRS)

Leibensperger, E. M.; Mickley, L. J.; Jacob, D. J.; Chen, W.-T.; Seinfeld, J. H.; Nenes, A.; Adams, P. J.; Streets, D. G.; Kumar, N.; Rind, D.

2012-01-01

We calculate decadal aerosol direct and indirect (warm cloud) radiative forcings from US anthropogenic sources over the 1950-2050 period. Past and future aerosol distributions are constructed using GEOS-Chem and historical emission inventories and future projections from the IPCC A1B scenario. Aerosol simulations are evaluated with observed spatial distributions and 1980-2010 trends of aerosol concentrations and wet deposition in the contiguous US. Direct and indirect radiative forcing is calculated using the GISS general circulation model and monthly mean aerosol distributions from GEOS-Chem. The radiative forcing from US anthropogenic aerosols is strongly localized over the eastern US. We find that its magnitude peaked in 1970-1990, with values over the eastern US (east of 100 deg W) of -2.0Wm(exp-2 for direct forcing including contributions from sulfate (-2.0Wm-2), nitrate (-0.2Wm(exp-2), organic carbon (-0.2Wm(exp-2), and black carbon (+0.4Wm(exp-2). The uncertainties in radiative forcing due to aerosol radiative properties are estimated to be about 50 %. The aerosol indirect effect is estimated to be of comparable magnitude to the direct forcing. We find that the magnitude of the forcing declined sharply from 1990 to 2010 (by 0.8Wm(exp-2) direct and 1.0Wm(exp-2 indirect), mainly reflecting decreases in SO2 emissions, and project that it will continue declining post-2010 but at a much slower rate since US SO2 emissions have already declined by almost 60% from their peak. This suggests that much of the warming effect of reducing US anthropogenic aerosol sources has already been realized. The small positive radiative forcing from US BC emissions (+0.3Wm(exp-2 over the eastern US in 2010; 5% of the global forcing from anthropogenic BC emissions worldwide) suggests that a US emission control strategy focused on BC would have only limited climate benefit.

ULTRAFINE AEROSOL INFLUENCE ON THE SAMPLING BY CASCADE IMPACTOR.

PubMed

Vasyanovich, M; Mostafa, M Y A; Zhukovsky, M

2017-11-01

Cascade impactors based on inertial deposition of aerosols are widely used to determine the size distribution of radioactive aerosols. However, there are situations where radioactive aerosols are represented by particles with a diameter of 1-5 nm. In this case, ultrafine aerosols can be deposited on impactor cascades by diffusion mechanism. The influence of ultrafine aerosols (1-5 nm) on the response of three different types of cascade impactors was studied. It was shown that the diffusion deposition of ultrafine aerosols can distort the response of the cascade impactor. The influence of diffusion deposition of ultrafine aerosols can be considerably removed by the use of mesh screens or diffusion battery installed before cascade impactor during the aerosol sampling. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Improved light-extraction efficiency from organic light-emitting diodes using hazy SiO2 thin films created by using an aerosol-deposition method

NASA Astrophysics Data System (ADS)

Moon, Byung Seuk; Lee, Soo-Hyoung; Huh, Yoon Ho; Kwon, O. Eun; Park, Byoungchoo; Lee, Bumjoo; Lee, Seung-Hyun; Hwang, Inchan

2015-04-01

We herein report an investigation of the effect of rough thin films of SiO2 granules deposited on glass substrates of organic light-emitting devices (OLEDs) by using a simple, low-cost and scalable process based on a powder spray of SiO2 granules in vacuum, known as the aerosol-deposition method, with regard to their external light-extraction capabilities. The rough and hazy thin SiO2 films produced by using aerosol-deposition and acting as scattering centers were able to efficiently reduce the light-trapping loss in the glass substrate (glass mode) for internally-generated photons and to enhance the external quantum efficiency (EQE) of the OLEDs. Based on aerosol-deposited silica films with a thickness of 800 nm and a haze of 22% on glass substrates, the EQE of phosphorescent green OLEDs was found to be enhanced by 17%, from an EQE of 7.0% for smooth bare glass substrates to an EQE of 8.2%. Furthermore, the EQEs of fluorescent blue and phosphorescent red OLEDs were shown to be enhanced by 16%, from an EQE of 3.7% to 4.3%, and by 16%, from an EQE of 9.3% to 10.8%, respectively. These improvements in the EQEs without serious changes in the emission spectra or the Lambertian emitter property clearly indicate the high potential of the aerosol-deposition technique for the realization of highly-efficient light extraction in colorful OLED lighting.

Lung deposition analyses of inhaled toxic aerosols in conventional and less harmful cigarette smoke: a review.

PubMed

Kleinstreuer, Clement; Feng, Yu

2013-09-23

Inhaled toxic aerosols of conventional cigarette smoke may impact not only the health of smokers, but also those exposed to second-stream smoke, especially children. Thus, less harmful cigarettes (LHCs), also called potential reduced exposure products (PREPs), or modified risk tobacco products (MRTP) have been designed by tobacco manufacturers to focus on the reduction of the concentration of carcinogenic components and toxicants in tobacco. However, some studies have pointed out that the new cigarette products may be actually more harmful than the conventional ones due to variations in puffing or post-puffing behavior, different physical and chemical characteristics of inhaled toxic aerosols, and longer exposure conditions. In order to understand the toxicological impact of tobacco smoke, it is essential for scientists, engineers and manufacturers to develop experiments, clinical investigations, and predictive numerical models for tracking the intake and deposition of toxicants of both LHCs and conventional cigarettes. Furthermore, to link inhaled toxicants to lung and other diseases, it is necessary to determine the physical mechanisms and parameters that have significant impacts on droplet/vapor transport and deposition. Complex mechanisms include droplet coagulation, hygroscopic growth, condensation and evaporation, vapor formation and changes in composition. Of interest are also different puffing behavior, smoke inlet conditions, subject geometries, and mass transfer of deposited material into systemic regions. This review article is intended to serve as an overview of contributions mainly published between 2009 and 2013, focusing on the potential health risks of toxicants in cigarette smoke, progress made in different approaches of impact analyses for inhaled toxic aerosols, as well as challenges and future directions.

Lacustrine responses to decreasing wet mercury deposition rates: results from a case study in northern Minnesota

USGS Publications Warehouse

Brigham, Mark E.; Sandheinrich, Mark B.; Gay, David A.; Maki, Ryan P.; Krabbenhoft, David P.; Wiener, James G.

2014-01-01

We present a case study comparing metrics of methylmercury (MeHg) contamination for four undeveloped lakes in Voyageurs National Park to wet atmospheric deposition of mercury (Hg), sulfate (SO4–2), and hydrogen ion (H+) in northern Minnesota. Annual wet Hg, SO4–2, and H+ deposition rates at two nearby precipitation monitoring sites indicate considerable decreases from 1998 to 2012 (mean decreases of 32, 48, and 66%, respectively). Consistent with decreases in the atmospheric pollutants, epilimnetic aqueous methylmercury (MeHgaq) and mercury in small yellow perch (Hgfish) decreased in two of four lakes (mean decreases of 46.5% and 34.5%, respectively, between 2001 and 2012). Counter to decreases in the atmospheric pollutants, MeHgaq increased by 85% in a third lake, whereas Hgfish increased by 80%. The fourth lake had two disturbances in its watershed during the study period (forest fire; changes in shoreline inundation due to beaver activity); this lake lacked overall trends in MeHgaq and Hgfish. The diverging responses among the study lakes exemplify the complexity of ecosystem responses to decreased loads of atmospheric pollutants.

Criteria for significance of simultaneous presence of both condensible vapors and aerosol particles on mass transfer (deposition) rates

NASA Technical Reports Server (NTRS)

Gokoglu, S. A.

1987-01-01

The simultaneous presence of aerosol particles and condensible vapors in a saturated boundary layer which may affect deposition rates to subcooled surfaces because of vapor-particle interactions is discussed. Scavenging of condensible vapors by aerosol particles may lead to increased particle size and decreased vapor mass fraction, which alters both vapor and particle deposition rates. Particles, if sufficiently concentrated, may also coagulate. Criteria are provided to assess the significance of such phenomena when particles are already present in the mainstream and are not created inside the boundary layer via homogeneous nucleation. It is determined that there is direct proportionality with: (1) the mass concentration of both condensible vapors and aerosol particles; and (2) the square of the boundary layer thickness to particle diameter ratio (delta d sub p) square. Inverse proportionality was found for mainstream to surface temperature difference if thermophoresis dominates particle transport. It is concluded that the square of the boundary layer thickness to particle diameter ratio is the most critical factor to consider in deciding when to neglect vapor-particle interactions.

Criteria for significance of simultaneous presence of both condensible vapors and aerosol particles on mass transfer (deposition) rates

NASA Technical Reports Server (NTRS)

Gokoglu, S. A.

1986-01-01

The simultaneous presence of aerosol particles and condensible vapors in a saturated boundary layer which may affect deposition rates to subcooled surfaces because of vapor-particle interactions is discussed. Scavenging of condensible vapors by aerosol particles may lead to increased particle size and decreased vapor mass fraction, which alters both vapor and particle deposition rates. Particles, if sufficiently concentrated, may also coagulate. Criteria are provided to assess the significance of such phenomena when particles are already present in the mainstream and are not created inside the boundary layer via homogeneous nucleation. It is determined that there is direct proportionality with: (1) the mass concentration of both condensible vapors and aerosol particles; and (2) the square of the boundary layer thickness to particle diameter ratio (delta d sub p) square. Inverse proportionality was found for mainstream to surface temperature difference if thermophoresis dominates particle transport. It is concluded that the square of the boundary layer thickness to particle diameter ratio is the most critical factor to consider in deciding when to neglect vapor-particle interactions.

CuInS2 Films Deposited by Aerosol-Assisted Chemical Vapor Deposition Using Ternary Single-Source Precursors

NASA Technical Reports Server (NTRS)

Jin, Michael; Banger, Kal; Harris, Jerry; Hepp, Aloysius

2003-01-01

Polycrystalline CuInS2 films were deposited by aerosol-assisted chemical vapor deposition using both solid and liquid ternary single-source precursors (SSPs) which were prepared in-house. Films with either (112) or (204/220) preferred orientation, had a chalcopyrite structure, and (112)-oriented films contained more copper than (204/220)-oriented films. The preferred orientation of the film is likely related to the decomposition and reaction kinetics associated with the molecular structure of the precursors at the substrate. Interestingly, the (204/220)-oriented films were always In-rich and were accompanied by a secondary phase. From the results of post-growth annealing, etching experiments, and Raman spectroscopic data, the secondary phase was identified as an In-rich compound. On the contrary, (112)-oriented films were always obtained with a minimal amount of the secondary phase, and had a maximum grain size of about 0.5 micron. Electrical and optical properties of all the films grown were characterized. They all showed p-type conduction with an electrical resistivity between 0.1 and 30 Omega-cm, and an optical band gap of approximately 1.46 eV +/- 0.02, as deposited. The material properties of deposited films revealed this methodology of using SSPs for fabricating chalcopyrite-based solar cells to be highly promising.

High T(sub c) superconductors fabricated by plasma aerosol mist deposition technique

NASA Technical Reports Server (NTRS)

Wang, X. W.; Vuong, K. D.; Leone, A.; Shen, C. Q.; Williams, J.; Coy, M.

1995-01-01

We report new results on high T(sub c) superconductors fabricated by a plasma aerosol mist deposition technique, in atmospheric environment. Materials fabricated are YBaCuO, BiPbSrCaCuO, BaCaCuO precursor films for TlBaCaCuO, and other buffers such as YSZ. Depending on processing conditions, sizes of crystallites and/or particles are between dozens of nano-meters and several micrometers. Superconductive properties and other material characteristics can also be tailored.

A graphical method for determining the dry-depositional component of aerosol samples and their field blanks

NASA Astrophysics Data System (ADS)

Huang, Suilou; Rahn, Kenneth A.; Arimoto, Richard

During the Atmosphere/Ocean Chemistry Experiment (AEROCE), field blanks of certain elements in aerosol samples occasionally increased abruptly, always during periods of unusually high atmospheric concentrations. We hypothesized that the anomalous blanks were created by coarse aerosol entering the sampling shelters and depositing onto the blank filters. If so, samples taken nearby should have been similarly affected. To test this hypothesis, we developed a simple graphical method in which elemental masses in field blanks are plotted against elemental masses in pumped samples, and zones of proportionality between the two are sought. Data from Bermuda and Mace Head (coastal western Ireland) confirmed that depositional zones did indeed appear, but only for coarse-particle elements and only under certain conditions. Actual increases of crustal and pollution-derived elements agreed well with values predicted from settling velocities and sampling rates: blanks increased up to an order of magnitude or more but samples by less than 1%. Marine elements behaved like crustal elements in most samples but occasionally were much more enriched: blanks increased up to 30-fold and samples up to about 3%. It thus appears that when coarse-particle elements are present in high concentrations, their field blanks and samples may be measurably affected by dry deposition. Depending on the elements of interest, this dry deposition may have to be measured and the concentrations corrected.

Spatial Variability of Mercury Wet Deposition in Eastern Ohio: Summertime Meteorological Case Study Analysis of Local Source Influences

EPA Science Inventory

Extensive exploration of event precipitation data in the Ohio River Valley indicates that coal combustion emissions play an important role in mercury (Hg) wet deposition. During July-September 2006, an intensive study was undertaken to discern the degree of local source influence...

Wet deposition of mercury in Qingdao, a coastal urban city in China: Concentrations, fluxes, and influencing factors

NASA Astrophysics Data System (ADS)

Chen, Lufeng; Li, Yanbin; Liu, Chang; Guo, Lina; Wang, Xiulin

2018-02-01

Mercury (Hg) is a global pollutant of public concern because of its high toxicity and capability for worldwide distribution via long-range atmospheric transportation. Wet atmospheric deposition is an important source of Hg in both terrestrial and aquatic environments. Concentrations of various Hg species in precipitation were monitored from March 2016 to February 2017 in a coastal urban area of Qingdao, and their wet deposition fluxes were estimated. The results showed that the volume-weighted mean (VWM) concentrations of total mercury (THg), reactive mercury (RHg), dissolved THg (DTHg), particulate THg (PTHg), total methylmercury (TMeHg), and dissolved and particulate MeHg (DMeHg and PMeHg) in Qingdao's precipitation were 13.6, 1.5, 5.4, 8.2, 0.38, 0.15, and 0.22 ng L-1, respectively, and their annual deposition fluxes were estimated to be 5703.0 (THg), 666.6 (RHg), 2304.0 (DTHg), 3470.4 (PTHg), 161.6 (TMeHg), 64.0 (DMeHg), and 95.7 (PMeHg) ng m-2 y-1, respectively. A relatively high proportion of MeHg in THg was observed in precipitation (3.0 ± 2.6%) possibly due to higher methylation and contributions from an oceanic source to MeHg in the precipitation. Obvious seasonal variations in Hg concentrations and deposition fluxes were observed in the precipitation in Qingdao. Correlation analyses and multiple regression analyses showed that SO2, pH, and NO3- were the controlling factors for THg in precipitation, whereas the MeHg concentration was primarily controlled by the SO2, WS, Cl-, and THg concentrations. PM2.5 and Cl- were the major controlling factors for PMeHg/TMeHg, whereas the TMeHg/THg ratio was mainly influenced by Cl-. The THg and MeHg fluxes were primarily controlled by precipitation, whereas Cl- was also an important factor for the MeHg wet deposition flux. The results of a 72-h backward trajectory analysis in the study region with the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model indicated that Hg deposition in Qingdao mainly

Development studies towards an 11-year global gridded aerosol optical thickness reanalysis for climate and applied applications

NASA Astrophysics Data System (ADS)

Lynch, P.; Reid, J. S.; Westphal, D. L.; Zhang, J.; Hogan, T. F.; Hyer, E. J.; Curtis, C. A.; Hegg, D. A.; Shi, Y.; Campbell, J. R.; Rubin, J. I.; Sessions, W. R.; Turk, F. J.; Walker, A. L.

2015-12-01

While standalone satellite and model aerosol products see wide utilization, there is a significant need in numerous climate and applied applications for a fused product on a regular grid. Aerosol data assimilation is an operational reality at numerous centers, and like meteorological reanalyses, aerosol reanalyses will see significant use in the near future. Here we present a standardized 2003-2013 global 1° × 1° and 6 hourly modal aerosol optical thickness (AOT) reanalysis product. This dataset can be applied to basic and applied earth system science studies of significant aerosol events, aerosol impacts on numerical weather prediction, and electro-optical propagation and sensor performance, among other uses. This paper describes the science of how to develop and score an aerosol reanalysis product. This reanalysis utilizes a modified Navy Aerosol Analysis and Prediction System (NAAPS) at its core and assimilates quality controlled retrievals of AOT from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Multi-angle Imaging SpectroRadiometer (MISR) on Terra. The aerosol source functions, including dust and smoke, were regionally tuned to obtain the best match between the model fine and coarse mode AOTs and the Aerosol Robotic Network (AERONET) AOTs. Other model processes, including deposition, were tuned to minimize the AOT difference between the model and satellite AOT. Aerosol wet deposition in the tropics is driven with satellite retrieved precipitation, rather than the model field. The final reanalyzed fine and coarse mode AOT at 550 nm is shown to have good agreement with AERONET observations, with global mean root mean square error around 0.1 for both fine and coarse mode AOTs. This paper includes a discussion of issues particular to aerosol reanalyses that make them distinct from standard meteorological reanalyses, considerations for extending such a reanalysis outside of the NASA A-Train era, and examples of how the

Lung Deposition Analyses of Inhaled Toxic Aerosols in Conventional and Less Harmful Cigarette Smoke: A Review

PubMed Central

Kleinstreuer, Clement; Feng, Yu

2013-01-01

Inhaled toxic aerosols of conventional cigarette smoke may impact not only the health of smokers, but also those exposed to second-stream smoke, especially children. Thus, less harmful cigarettes (LHCs), also called potential reduced exposure products (PREPs), or modified risk tobacco products (MRTP) have been designed by tobacco manufacturers to focus on the reduction of the concentration of carcinogenic components and toxicants in tobacco. However, some studies have pointed out that the new cigarette products may be actually more harmful than the conventional ones due to variations in puffing or post-puffing behavior, different physical and chemical characteristics of inhaled toxic aerosols, and longer exposure conditions. In order to understand the toxicological impact of tobacco smoke, it is essential for scientists, engineers and manufacturers to develop experiments, clinical investigations, and predictive numerical models for tracking the intake and deposition of toxicants of both LHCs and conventional cigarettes. Furthermore, to link inhaled toxicants to lung and other diseases, it is necessary to determine the physical mechanisms and parameters that have significant impacts on droplet/vapor transport and deposition. Complex mechanisms include droplet coagulation, hygroscopic growth, condensation and evaporation, vapor formation and changes in composition. Of interest are also different puffing behavior, smoke inlet conditions, subject geometries, and mass transfer of deposited material into systemic regions. This review article is intended to serve as an overview of contributions mainly published between 2009 and 2013, focusing on the potential health risks of toxicants in cigarette smoke, progress made in different approaches of impact analyses for inhaled toxic aerosols, as well as challenges and future directions. PMID:24065038

AEROSOL DEPOSITION EFFICIENCIES AND UPSTREAM RELEASE POSITIONS FOR DIFFERENT INHALATION MODES IN AN UPPER BRONCHIAL AIRWAY MODELS

EPA Science Inventory

Aerosol Deposition Efficiencies and Upstream Release Positions for Different Inhalation Modes in an Upper Bronchial Airway Model

Zhe Zhang, Clement Kleinstreuer, and Chong S. Kim

Center for Environmental Medicine and Lung Biology, University of North Carolina at Ch...

The thermal infrared radiance properties of dust aerosol over ocean

NASA Astrophysics Data System (ADS)

Hao, Zengzhou; Pan, Delu; Tu, Qianguang; Gong, Fang; Chen, Jianyu

2015-10-01

Asian dust storms, which can long-range transport to ocean, often occur on spring. The present of Asian dust aerosols over ocean makes some difficult for other studies, such as cloud detection, and also take some advantage for ocean, such as take nutrition into the ocean by dry or wet deposition. Therefore, it is important to study the dust aerosol and retrieve the properties of dust from satellite observations that is mainly from the thermal infrared radiance. In this paper, the thermal infrared radiance properties of dust aerosol over ocean are analyzed from MODIS and MTSAT2 observations and Streamer model simulations. By analyzing some line samples and a series of dust aerosol region, it shows that the dust aerosol brightness temperature at 12μm (BT12) is always greater than BT11 and BT8.5, and BT8.5 is general greater than BT11. The brightness temperature different between 11μm and 12μm (BTD11-12) increases with the dust intensity. And the BTD11-12 will become positive when the atmospheric relative humidity is greater than 70%. The BTD11-12 increases gradually with the surface temperature while the effect on BTD11-12 of dust layer temperature is not evident. Those are caused by the transmission of the dust aerosol is different at the two thermal infrared channels. During daytime, dust infrared brightness temperature at mid-infrared bands should reduce the visual radiance, which takes about 25K or less. In general, BT3.7 is greater than BT11 for dust aerosol. Those results are helpful to monitor or retrieve dust aerosol physical properties over ocean from satellite.

Preliminary Results from an Assimilation of TOMS Aerosol Observations Into the GOCART Model

NASA Technical Reports Server (NTRS)

daSilva, Arlindo; Weaver, Clark J.; Ginoux, Paul; Torres, Omar; Einaudi, Franco (Technical Monitor)

2000-01-01

At NASA Goddard we are developing a global aerosol data assimilation system that combines advances in remote sensing and modeling of atmospheric aerosols. The goal is to provide high resolution, 3-D aerosol distributions to the research community. Our first step is to develop a simple assimilation system for Saharan mineral aerosol. The Goddard Chemistry and Aerosol Radiation model (GOCART) provides accurate 3-D mineral aerosol size distributions that compare well with TOMS satellite observations. Surface, mobilization, wet and dry deposition, convective and long-range transport are all driven by assimilated fields from the Goddard Earth Observing System Data Assimilation System, GEOS-DAS. Our version of GOCART transports sizes from.08-10 microns and only simulates Saharan dust. TOMS radiance observations in the ultra violet provide information on the mineral and carbonaceous aerosol fields. We use two main observables in this study: the TOMS aerosol index (AI) which is directly related to the ratio of the 340 and 380 radiances and the 380 radiance. These are sensitive to the aerosol optical thickness, the single scattering albedo and the height of the aerosol layer. The Goddard Aerosol Assimilation System (GAAS) uses the Data Assimilation Office's Physical-space Statistical Analysis System (PSAS) to combine TOMS observations and GOCART model first guess fields. At this initial phase we only assimilate observations into the the GOCART model over regions of Africa and the Atlantic where mineral aerosols dominant and carbonaceous aerosols are minimal, Our preliminary results during summer show that the assimilation with TOMS data modifies both the aerosol mass loading and the single scattering albedo. Assimilated aerosol fields will be compared with assimilated aerosol fields from GOCART and AERONET observations over Cape Verde.

Wet deposition of mercury at a New York state rural site: Concentrations, fluxes, and source areas

NASA Astrophysics Data System (ADS)

Lai, Soon-onn; Holsen, Thomas M.; Hopke, Philip K.; Liu, Peng

Event-based mercury (Hg) precipitation samples were collected with a modified MIC-B sampler between September 2003 and April 2005 at Potsdam, NY to investigate Hg in wet deposition and identify potential source areas using the potential source contribution function (PCSF) and residence time weighted concentration (RTWC) models. The volume-weighted mean (VWM) concentration and wet deposition flux were 5.5ngL-1 and 7.6μgm-2 during the study period, and 5.5ngL-1 and 5.9μgm-2 in 2004, respectively, and show seasonal trends with larger values in the spring and summer. The PSCF model results matched known source areas based on an emission inventory better than did the RTWC results based on the spatial correlation index. Both modeling results identified large Hg source areas that contain a number of coal-fired power plants located in the Upper Ohio River Valley and in southeastern Michigan, as well as in Quebec and Ontario where there are metal production facilities, waste incinerators and paper mills. Emissions from the Atlantic Ocean were also determined to be a potential source.

Simulating ozone dry deposition at a boreal forest with a multi-layer canopy deposition model

NASA Astrophysics Data System (ADS)

Zhou, Putian; Ganzeveld, Laurens; Rannik, Üllar; Zhou, Luxi; Gierens, Rosa; Taipale, Ditte; Mammarella, Ivan; Boy, Michael

2017-01-01

A multi-layer ozone (O3) dry deposition model has been implemented into SOSAA (a model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) to improve the representation of O3 concentration and flux within and above the forest canopy in the planetary boundary layer. We aim to predict the O3 uptake by a boreal forest canopy under varying environmental conditions and analyse the influence of different factors on total O3 uptake by the canopy as well as the vertical distribution of deposition sinks inside the canopy. The newly implemented dry deposition model was validated by an extensive comparison of simulated and observed O3 turbulent fluxes and concentration profiles within and above the boreal forest canopy at SMEAR II (Station to Measure Ecosystem-Atmosphere Relations II) in Hyytiälä, Finland, in August 2010. In this model, the fraction of wet surface on vegetation leaves was parametrised according to the ambient relative humidity (RH). Model results showed that when RH was larger than 70 % the O3 uptake onto wet skin contributed ˜ 51 % to the total deposition during nighttime and ˜ 19 % during daytime. The overall contribution of soil uptake was estimated about 36 %. The contribution of sub-canopy deposition below 4.2 m was modelled to be ˜ 38 % of the total O3 deposition during daytime, which was similar to the contribution reported in previous studies. The chemical contribution to O3 removal was evaluated directly in the model simulations. According to the simulated averaged diurnal cycle the net chemical production of O3 compensated up to ˜ 4 % of dry deposition loss from about 06:00 to 15:00 LT. During nighttime, the net chemical loss of O3 further enhanced removal by dry deposition by a maximum ˜ 9 %. Thus the results indicated an overall relatively small contribution of airborne chemical processes to O3 removal at this site.

Mixed-phase aerosol particles

NASA Astrophysics Data System (ADS)

Corti, T.; Krieger, U. K.; Koop, T.; Peter, T.

2003-04-01

Within a liquid aerosol particle a solid phase may coexist with the liquid over a wide range of ambient conditions. The optical properties of such particles are of interest for a number of reasons. They will affect the scattering albedo of atmospheric aerosols, may cause depolarisation in lidar measurements, and potentially open a window for studying the internal morphology and physical properties (e.g. wetting properties, diffusion constants) of composite particles in laboratory experiments. In this contribution, we will present results of experimental and theoretical work on mixed-phase aerosol particles. The optical properties of mixed-phase particles depend on the location of the inclusion in the liquid phase, which is determined by the surface tensions of the involved interfaces. In the case of complete wetting, the energetically favoured position of the inclusion is in the volume of the liquid phase. For partial wetting, a position at the surface of the liquid phase is favoured, with the contact angle between the solid, liquid and air being described by Young's equation. For systems with small contact angles, the difference in energy between an inclusion situated at the droplets surface and in its volume may be so small that the thermal energy kT is sufficient to displace the inclusion from the droplet surface into its volume. The critical contact angle depends on the size of the inclusion and the droplet and ranges from 0.1 to 10 degrees. Examples of mixed-phase aerosol particles are aged soot particles and sea salt particles at low relative humidity. For aged soot, contact angles on sulphuric acid clearly above 10 degrees have been reported, so that soot inclusions are expected to be located at the surface of aerosol particles. For mixed-phase sea salt particles, consisting of a solid NaCl inclusion and an aqueous solution of mainly NaCl and MgCl2, our measurements on macroscopic NaCl crystals show a contact angle clearly below 10 degrees and possibly as

Atmospheric aerosols in Amazonia and land use change: from natural biogenic to biomass burning conditions.

PubMed

Artaxo, Paulo; Rizzo, Luciana V; Brito, Joel F; Barbosa, Henrique M J; Arana, Andrea; Sena, Elisa T; Cirino, Glauber G; Bastos, Wanderlei; Martin, Scot T; Andreae, Meinrat O

2013-01-01

In the wet season, a large portion of the Amazon region constitutes one of the most pristine continental areas, with very low concentrations of atmospheric trace gases and aerosol particles. However, land use change modifies the biosphere-atmosphere interactions in such a way that key processes that maintain the functioning of Amazonia are substantially altered. This study presents a comparison between aerosol properties observed at a preserved forest site in Central Amazonia (TT34 North of Manaus) and at a heavily biomass burning impacted site in south-western Amazonia (PVH, close to Porto Velho). Amazonian aerosols were characterized in detail, including aerosol size distributions, aerosol light absorption and scattering, optical depth and aerosol inorganic and organic composition, among other properties. The central Amazonia site (TT34) showed low aerosol concentrations (PM2.5 of 1.3 +/- 0.7 microg m(-3) and 3.4 +/- 2.0 microg m(-3) in the wet and dry seasons, respectively), with a median particle number concentration of 220 cm(-3) in the wet season and 2200 cm(-3) in the dry season. At the impacted site (PVH), aerosol loadings were one order of magnitude higher (PM2.5 of 10.2 +/- 9.0 microg m(-3) and 33.0 +/- 36.0 microg m(-3) in the wet and dry seasons, respectively). The aerosol number concentration at the impacted site ranged from 680 cm(-3) in the wet season up to 20 000 cm(-3) in the dry season. An aerosol chemical speciation monitor (ACSM) was deployed in 2013 at both sites, and it shows that organic aerosol account to 81% to the non-refractory PM1 aerosol loading at TT34, while biomass burning aerosols at PVH shows a 93% content of organic particles. Three years of filter-based elemental composition measurements shows that sulphate at the impacted site decreases, on average, from 12% of PM2.5 mass during the wet season to 5% in the dry season. This result corroborates the ACSM finding that the biomass burning contributed overwhelmingly to the organic

Nasal deposition of ciclesonide nasal aerosol and mometasone aqueous nasal spray in allergic rhinitis patients.

PubMed

Emanuel, Ivor A; Blaiss, Michael S; Meltzer, Eli O; Evans, Philip; Connor, Alyson

2014-01-01

Sensory attributes of intranasal corticosteroids, such as rundown to the back of the throat, may influence patient treatment preferences. This study compares the nasal deposition and nasal retention of a radiolabeled solution of ciclesonide nasal aerosol (CIC-hydrofluoroalkane [HFA]) with a radiolabeled suspension of mometasone furoate monohydrate aqueous nasal spray (MFNS) in subjects with either perennial allergic rhinitis (AR) or seasonal AR. In this open-label, single-dose, randomized, crossover scintigraphy study, 14 subjects with symptomatic AR received a single dose of radiolabeled 74-μg CIC-HFA (37 μg/spray, 1 spray/each nostril) via a nasal metered-dose inhaler or a single dose of radiolabeled 200-μg MFNS (50 μg/spray, 2 sprays/each nostril), with a minimum 5-day washout period between treatments. Initial deposition (2 minutes postdose) of radiolabeled CIC-HFA and MFNS in the nasal cavity, nasopharynx, and on nasal wipes, and retention of radioactivity in the nasal cavity and nasal run-out on nasal wipes at 2, 4, 6, 8, and 10 minutes postdose were quantified with scintigraphy. At 2 and 10 minutes postdose, deposition of radiolabeled CIC-HFA was significantly higher in the nasal cavity versus radiolabeled MFNS (99.42% versus 86.50% at 2 minutes, p = 0.0046; and 81.10% versus 54.31% at 10 minutes, p < 0.0001, respectively; p values unadjusted for multiplicity). Deposition of radioactivity on nasal wipes was significantly higher with MFNS versus CIC-HFA at all five time points, and posterior losses of radiolabeled formulation were significantly higher with MFNS at 6, 8, and 10 minutes postdose. In this scintigraphic study, significantly higher nasal deposition and retention of radiolabeled aerosol CIC-HFA were observed versus radiolabeled aqueous MFNS in subjects with AR.

Toxicity of atmospheric aerosols on marine phytoplankton

USGS Publications Warehouse

Paytan, A.; Mackey, K.R.M.; Chen, Y.; Lima, I.D.; Doney, S.C.; Mahowald, N.; Labiosa, R.; Post, A.F.

2009-01-01

Atmospheric aerosol deposition is an important source of nutrients and trace metals to the open ocean that can enhance ocean productivity and carbon sequestration and thus influence atmospheric carbon dioxide concentrations and climate. Using aerosol samples from different back trajectories in incubation experiments with natural communities, we demonstrate that the response of phytoplankton growth to aerosol additions depends on specific components in aerosols and differs across phytoplankton species. Aerosol additions enhanced growth by releasing nitrogen and phosphorus, but not all aerosols stimulated growth. Toxic effects were observed with some aerosols, where the toxicity affected picoeukaryotes and Synechococcus but not Prochlorococcus.We suggest that the toxicity could be due to high copper concentrations in these aerosols and support this by laboratory copper toxicity tests preformed with Synechococcus cultures. However, it is possible that other elements present in the aerosols or unknown synergistic effects between these elements could have also contributed to the toxic effect. Anthropogenic emissions are increasing atmospheric copper deposition sharply, and based on coupled atmosphere-ocean calculations, we show that this deposition can potentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia.

Aerosol Delivery for Amendment Distribution in Contaminated Vadose Zones

NASA Astrophysics Data System (ADS)

Hall, R. J.; Murdoch, L.; Riha, B.; Looney, B.

2011-12-01

Remediation of contaminated vadose zones is often hindered by an inability to effectively distribute amendments. Many amendment-based approaches have been successful in saturated formations, however, have not been widely pursued when treating contaminated unsaturated materials due to amendment distribution limitations. Aerosol delivery is a promising new approach for distributing amendments in contaminated vadose zones. Amendments are aerosolized and injected through well screens. During injection the aerosol particles are transported with the gas and deposited on the surfaces of soil grains. Resulting distributions are radially and vertically broad, which could not be achieved by injecting pure liquid-phase solutions. The objectives of this work were A) to characterize transport and deposition behaviors of aerosols; and B) to develop capabilities for predicting results of aerosol injection scenarios. Aerosol transport and deposition processes were investigated by conducting lab-scale injection experiments. These experiments involved injection of aerosols through a 2m radius, sand-filled wedge. A particle analyzer was used to measure aerosol particle distributions with time, and sand samples were taken for amendment content analysis. Predictive capabilities were obtained by constructing a numerical model capable of simulating aerosol transport and deposition in porous media. Results from tests involving vegetable oil aerosol injection show that liquid contents appropriate for remedial applications could be readily achieved throughout the sand-filled wedge. Lab-scale tests conducted with aqueous aerosols show that liquid accumulation only occurs near the point of injection. Tests were also conducted using 200 g/L salt water as the aerosolized liquid. Liquid accumulations observed during salt water tests were minimal and similar to aqueous aerosol results. However, particles were measured, and salt deposited distal to the point of injection. Differences between

The Effect of Aerosol Hygroscopicity and Volatility on Aerosol Optical Properties During Southern Oxidant and Aerosol Study

NASA Astrophysics Data System (ADS)

Khlystov, A.; Grieshop, A. P.; Saha, P.; Subramanian, R.

2014-12-01

Secondary organic aerosol (SOA) from biogenic sources can influence optical properties of ambient aerosol by altering its hygroscopicity and contributing to light absorption directly via formation of brown carbon and indirectly by enhancing light absorption by black carbon ("lensing effect"). The magnitude of these effects remains highly uncertain. A set of state-of-the-art instruments was deployed at the SEARCH site near Centerville, AL during the Southern Oxidant and Aerosol Study (SOAS) campaign in summer 2013 to measure the effect of relative humidity and temperature on aerosol size distribution, composition and optical properties. Light scattering and absorption by temperature- and humidity-conditioned aerosols was measured using three photo-acoustic extinctiometers (PAX) at three wavelengths (405 nm, 532 nm, and 870 nm). The sample-conditioning system provided measurements at ambient RH, 10%RH ("dry"), 85%RH ("wet"), and 200 C ("TD"). In parallel to these measurements, a long residence time temperature-stepping thermodenuder (TD) and a variable residence time constant temperature TD in combination with three SMPS systems and an Aerosol Chemical Speciation Monitor (ACSM) were used to assess aerosol volatility and kinetics of aerosol evaporation. We will present results of the on-going analysis of the collected data set. We will show that both temperature and relative humidity have a strong effect on aerosol optical properties. SOA appears to increase aerosol light absorption by about 10%. TD measurements suggest that aerosol equilibrated fairly quickly, within 2 s. Evaporation varied substantially with ambient aerosol loading and composition and meteorology.

Inhalation Anthrax (Ames aerosol) in Naive and Vaccinated New Zealand Rabbits: Characterizing the Spread of Bacteria from Lung Deposition to Bacteremia

DTIC Science & Technology

2012-06-28

York City anthrax investigation working group. (2003). Isolated case of bioterrorism-related inhalational anthrax, New York City , 2001. Emerg. Infect...ORIGINAL RESEARCH ARTICLE published: 28 June 2012 doi: 10.3389/fcimb.2012.00087 Inhalational anthrax(Ames aerosol) in naïve and vaccinated New ...Inhalation Antrax (Ames aerosol) In Naive and Vaccinated New Zealand Rabbits: Characterizing The Spread Of Bacteria From Lung Deposition To Bacteremia

Temperature-dependent evolution of the wetting layer thickness during Ge deposition on Si(001).

PubMed

Bergamaschini, R; Brehm, M; Grydlik, M; Fromherz, T; Bauer, G; Montalenti, F

2011-07-15

The evolution of the wetting layer (WL) thickness during Ge deposition on Si(001) is analyzed with the help of a rate-equation approach. The combined role of thickness, island volume and shape-dependent chemical potentials is considered. Several experimental observations, such as WL thinning following the pyramid-to-dome transformation, are captured by the model, as directly demonstrated by a close comparison with photoluminescence measurements (PL) on samples grown at three different temperatures. The limitations of the model in describing late stages of growth are critically addressed.

Development of an aerosol surface inoculation method for bacillus spores.

PubMed

Lee, Sang Don; Ryan, Shawn P; Snyder, Emily Gibb

2011-03-01

A method was developed to deposit Bacillus subtilis spores via aerosolization onto various surface materials for biological agent decontamination and detection studies. This new method uses an apparatus coupled with a metered dose inhaler to reproducibly deposit spores onto various surfaces. A metered dose inhaler was loaded with Bacillus subtilis spores, a surrogate for Bacillus anthracis. Five different material surfaces (aluminum, galvanized steel, wood, carpet, and painted wallboard paper) were tested using this spore deposition method. This aerosolization method deposited spores at a concentration of more than 10(7) CFU per coupon (18-mm diameter) with less than a 50% coefficient of variation, showing that the aerosolization method developed in this study can deposit reproducible numbers of spores onto various surface coupons. Scanning electron microscopy was used to probe the spore deposition patterns on test coupons. The deposition patterns observed following aerosol impaction were compared to those of liquid inoculation. A physical difference in the spore deposition patterns was observed to result from the two different methods. The spore deposition method developed in this study will help prepare spore coupons via aerosolization fast and reproducibly for bench top decontamination and detection studies.

[Characteristics of Atmospheric Nitrogen Wet Deposition and Associated Impact on N Transport in the Watershed of Red Soil Area in Southern China].

PubMed

Hao, Zhuo; Gao, Yang; Zhang, Jin-zhong; Xu, Ya-juan; Yu, Gui-rui

2015-05-01

In this study, Qianyanzhou Xiangxi River Basin in the rainy season was monitored to measure different nitrogen form concentrations of rainfall and rainfall-runoff process, in order to explore the southern red soil region of nitrogen wet deposition characteristics and its influence on N output in watershed. The results showed that there were 27 times rainfall in the 2014 rainy season, wherein N wet deposition load reached 43.64-630.59 kg and N deposition flux were 0.44-6.43 kg · hm(-2), which presented a great seasonal variability. We selected three rainfall events to make dynamic analysis. The rainfall in three rainfall events ranged from 8 to 14mm, and the deposition load in the watershed were from 18.03 to 41.16 kg and its flux reached 0.18 to 0.42 kg · hm(-2). Meanwhile, this three rainfall events led to 4189.38 m3 of the total runoff discharge, 16.72 kg of total nitrogen (TN) load and 4.64 kg · hm(-2) of flux, wherein dissolved total nitrogen (DTN) were 9.64 kg and 2.68 kg · hm(-2), ammonium-nitrogen (NH(4+)-N) were 2.93 kg and 0.81 kg · hm(-2), nitrate-nitrogen (NO(3-)-N) were 5.60 kg and 1.56 kg · hm(-2). The contribution rate of N wet deposition to N output from watershed reached 56%-94% , implying that the rainfall-runoff had tremendous contribution to N loss in this small watershed. The concentrations of TN in water had exceeded 1.5 mg · L(-1) of eutrophication threshold, which existed an eutrophication potential.

Improving organic aerosol treatments in CESM/CAM5: Development, application, and evaluation

NASA Astrophysics Data System (ADS)

Glotfelty, Timothy; He, Jian; Zhang, Yang

2017-06-01

New treatments for organic aerosol (OA) formation have been added to a modified version of the CESM/CAM5 model (CESM-NCSU). These treatments include a volatility basis set treatment for the simulation of primary and secondary organic aerosols (SOAs), a simplified treatment for organic aerosol (OA) formation from glyoxal, and a parameterization representing the impact of new particle formation (NPF) of organic gases and sulfuric acid. With the inclusion of these new treatments, the concentration of oxygenated organic aerosol increases by 0.33 µg m-3 and that of primary organic aerosol (POA) decreases by 0.22 µg m-3 on global average. The decrease in POA leads to a reduction in the OA direct effect, while the increased OOA increases the OA indirect effects. Simulations with the new OA treatments show considerable improvement in simulated SOA, oxygenated organic aerosol (OOA), organic carbon (OC), total carbon (TC), and total organic aerosol (TOA), but degradation in the performance of HOA. In simulations of the current climate period, despite some deviations from observations, CESM-NCSU with the new OA treatments significantly improves the magnitude, spatial pattern, seasonal pattern of OC and TC, as well as, the speciation of TOA between POA and OOA. Sensitivity analysis reveals that the inclusion of the organic NPF treatment impacts the OA indirect effects by enhancing cloud properties. The simulated OA level and its impact on the climate system are most sensitive to choices in the enthalpy of vaporization and wet deposition of SVOCs, indicating that accurate representations of these parameters are critical for accurate OA-climate simulations.

Influence of high temperature annealing on the dielectric properties of alumina films prepared by the aerosol deposition method

NASA Astrophysics Data System (ADS)

Leupold, Nico; Schubert, Michael; Kita, Jaroslaw; Moos, Ralf

The aerosol deposition method (ADM) is a novel coating technique that allows to fabricate dense and nanocrystalline ceramic films at room temperature. To investigate the dielectric properties of aerosol deposited alumina films at high temperatures and the influence of annealing on them, the temperature was increased in steps of 100∘C from 200∘C to 900∘C and subsequently cooled down stepwise again. At each step, the dielectric properties were measured by impedance spectroscopy between 50mHz and 200kHz. During the heating steps, the relative permittivity and also the loss tangent showed a disordered behavior with various maxima in the loss tangent. After reaching 900∘C, during cooling, the behavior was more ordered, and the loss tangent exhibited only one maximum that appeared at lower frequencies. Overall, the annealing reduces the loss tangent at low frequencies and low temperatures. The origin of this behavior could lie in the annealing of defects, which are incorporated into the layer when the particles hit the surface of the substrate and crack while being deposited via ADM following the room temperature impact consolidation mechanism (RTIC).

Influence of Oxygen Partial Pressure during Processing on the Thermoelectric Properties of Aerosol-Deposited CuFeO₂.

PubMed

Stöcker, Thomas; Exner, Jörg; Schubert, Michael; Streibl, Maximilian; Moos, Ralf

2016-03-24

In the field of thermoelectric energy conversion, oxide materials show promising potential due to their good stability in oxidizing environments. Hence, the influence of oxygen partial pressure during synthesis on the thermoelectric properties of Cu-Delafossites at high temperatures was investigated in this study. For these purposes, CuFeO₂ powders were synthetized using a conventional mixed-oxide technique. X-ray diffraction (XRD) studies were conducted to determine the crystal structures of the delafossites associated with the oxygen content during the synthesis. Out of these powders, films with a thickness of about 25 µm were prepared by the relatively new aerosol-deposition (AD) coating technique. It is based on a room temperature impact consolidation process (RTIC) to deposit dense solid films of ceramic materials on various substrates without using a high-temperature step during the coating process. On these dense CuFeO₂ films deposited on alumina substrates with electrode structures, the Seebeck coefficient and the electrical conductivity were measured as a function of temperature and oxygen partial pressure. We compared the thermoelectric properties of both standard processed and aerosol deposited CuFeO₂ up to 900 °C and investigated the influence of oxygen partial pressure on the electrical conductivity, on the Seebeck coefficient and on the high temperature stability of CuFeO₂. These studies may not only help to improve the thermoelectric material in the high-temperature case, but may also serve as an initial basis to establish a defect chemical model.

Aerosol impacts on regional trends in atmospheric stagnation

NASA Astrophysics Data System (ADS)

Mascioli, N. R.; Fiore, A. M.; Previdi, M. J.

2017-12-01

Extreme pollution events pose a significant threat to human health and are a leading cause of premature mortality worldwide. While emissions of atmospheric pollutants and their precursors are projected to decrease in the future due to air quality legislation, future climate change may affect the underlying meteorological conditions that contribute to extreme pollution events. Stagnation events, characterized by weak winds and an absence of precipitation, contribute to extreme pollution by halting the removal of pollutants via advection and wet deposition. Here, we use a global climate model (GFDL-CM3) to show that regional stagnation trends over the historical period (1860-2005) are driven by changes in anthropogenic aerosol emissions, rather than rising greenhouse gases. In the northeastern and central United States, aerosol-induced changes in surface and upper level winds have produced significant decreases in the number of stagnant summer days, while decreasing precipitation in the southeast US has increased the number of stagnant summer days. Significant drying over eastern China in response to aerosol forcing contributed to increased stagnation. Additionally, this region was found to be particularly sensitive to changes in local emissions, indicating that improving air quality will also lessen stagnation. In Europe, we find a dipole pattern wherein stagnation decreases over southern Europe and increases over northern Europe in response to global increases in aerosol emissions. We hypothesize that this is due to changes in the large-scale circulation patterns associated with a poleward shift of the North Atlantic storm track. We find that in the future, the combination of declining aerosol emissions and the continued rise of greenhouse gas emissions will lead to a reversal of the historical stagnation trends.

An 11-year global gridded aerosol optical thickness reanalysis (v1.0) for atmospheric and climate sciences

NASA Astrophysics Data System (ADS)

Lynch, Peng; Reid, Jeffrey S.; Westphal, Douglas L.; Zhang, Jianglong; Hogan, Timothy F.; Hyer, Edward J.; Curtis, Cynthia A.; Hegg, Dean A.; Shi, Yingxi; Campbell, James R.; Rubin, Juli I.; Sessions, Walter R.; Turk, F. Joseph; Walker, Annette L.

2016-04-01

While stand alone satellite and model aerosol products see wide utilization, there is a significant need in numerous atmospheric and climate applications for a fused product on a regular grid. Aerosol data assimilation is an operational reality at numerous centers, and like meteorological reanalyses, aerosol reanalyses will see significant use in the near future. Here we present a standardized 2003-2013 global 1 × 1° and 6-hourly modal aerosol optical thickness (AOT) reanalysis product. This data set can be applied to basic and applied Earth system science studies of significant aerosol events, aerosol impacts on numerical weather prediction, and electro-optical propagation and sensor performance, among other uses. This paper describes the science of how to develop and score an aerosol reanalysis product. This reanalysis utilizes a modified Navy Aerosol Analysis and Prediction System (NAAPS) at its core and assimilates quality controlled retrievals of AOT from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Multi-angle Imaging SpectroRadiometer (MISR) on Terra. The aerosol source functions, including dust and smoke, were regionally tuned to obtain the best match between the model fine- and coarse-mode AOTs and the Aerosol Robotic Network (AERONET) AOTs. Other model processes, including deposition, were tuned to minimize the AOT difference between the model and satellite AOT. Aerosol wet deposition in the tropics is driven with satellite-retrieved precipitation, rather than the model field. The final reanalyzed fine- and coarse-mode AOT at 550 nm is shown to have good agreement with AERONET observations, with global mean root mean square error around 0.1 for both fine- and coarse-mode AOTs. This paper includes a discussion of issues particular to aerosol reanalyses that make them distinct from standard meteorological reanalyses, considerations for extending such a reanalysis outside of the NASA A-Train era, and examples of how

Solubility of aerosol trace elements: Sources and deposition fluxes in the Canary Region

NASA Astrophysics Data System (ADS)

López-García, Patricia; Gelado-Caballero, María Dolores; Collado-Sánchez, Cayetano; Hernández-Brito, José Joaquín

2017-01-01

African dust inputs have important effects on the climate and marine biogeochemistry of the subtropical North Atlantic Ocean. The impact of dust inputs on oceanic carbon uptake and climate is dependent on total dust deposition fluxes as well as the bioavailability of nutrients and metals in the dust. In this work, the solubility of trace metals (Fe, Al, Mn, Co and Cu) and ions (Ca, sulphate, nitrate and phosphate) has been estimated from the analysis of a long-time series of 109 samples collected over a 3-year period in the Canary Islands. Solubility is primarily a function of aerosol origin, with higher solubility values corresponding to aerosols with more anthropogenic influence. Using soluble fractions of trace elements measured in this work, atmospheric deposition fluxes of soluble metals and nutrients have been calculated. Inputs of dissolved nutrients (P, N and Fe) have been estimated for the mixed layer. Considering that P is the limiting factor when ratios of these elements are compared with phytoplankton requirements, an increase of 0.58 nM of P in the mixed layer (∼150 m depth) and in a year can be estimated, which can support an increase of 0.02 μg Chla L-1 y-1. These atmospheric inputs of trace metals and nutrients appear to be significant relative to the concentrations reported in this region, especially during the summer months when the water column is more stratified and deep-water nutrient inputs are reduced.

Oxidation Kinetics of Chemically Vapor-Deposited Silicon Carbide in Wet Oxygen

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.

1994-01-01

The oxidation kinetics of chemically vapor-deposited SiC in dry oxygen and wet oxygen (P(sub H2O) = 0.1 atm) at temperatures between 1200 C and 1400 C were monitored using thermogravimetric analysis. It was found that in a clean environment, 10% water vapor enhanced the oxidation kinetics of SiC only very slightly compared to rates found in dry oxygen. Oxidation kinetics were examined in terms of the Deal and Grove model for oxidation of silicon. It was found that in an environment containing even small amounts of impurities, such as high-purity Al2O3 reaction tubes containing 200 ppm Na, water vapor enhanced the transport of these impurities to the oxidation sample. Oxidation rates increased under these conditions presumably because of the formation of less protective sodium alumino-silicate scales.

Atmospheric transport and wet deposition of ammonium in North Carolina

NASA Astrophysics Data System (ADS)

Walker, John T.; Aneja, Viney P.; Dickey, David A.

Wet deposition and transport analysis has been performed for ammonium (NH 4+) in North Carolina, USA. Multiple regression analysis is employed to model the temporal trend and seasonality in monthly volume-weighted mean NH 4+ concentrations in precipitation from 1983 to 1996 at six National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites. A significant ( p<0.01) increasing trend beginning in 1990, which corresponds to an annual concentration increase of approximately 9.5%, is detected at the rural Sampson County site (NC35), which is located within a densely populated network of swine and poultry operations. This trend is positively correlated with increasing ammonia (NH 3) emissions related to the vigorous growth of North Carolina's swine population since 1990, particularly in the state's Coastal Plain region. A source-receptor regression model, which utilizes weekly NH 4+ concentrations in precipitation in conjunction with boundary layer air mass back trajectories, is developed to statistically test for the influence of a particular NH 3 source region on NH 4+ concentrations at surrounding NADP/NTN sites for the years 1995-1996. NH 3 emissions from this source region, primarily evolving from swine and poultry operations, are found to increase NH 4+ concentration in precipitation at sites up to ≈80 km away. At the Scotland County (NC36) and Wake County (NC41) sites, mean NH 4+ concentrations show increases of at least 44% for weeks during which 25% or more back trajectories are influenced by this source region.

Study of particulate matter from Primary/Secondary Marine Aerosol and anthropogenic sources collected by a self-made passive sampler for the evaluation of the dry deposition impact on built heritage.

PubMed

Morillas, Héctor; Maguregui, Maite; García-Florentino, Cristina; Marcaida, Iker; Madariaga, Juan Manuel

2016-04-15

Dry deposition is one of the most dangerous processes that can take place in the environment where the compounds that are suspended in the atmosphere can react directly on different surrounding materials, promoting decay processes. Usually this process is related with industrial/urban fog and/or marine aerosol in the coastal areas. Particularly, marine aerosol transports different types of salts which can be deposited on building materials and by dry deposition promotes different decay pathways. A new analytical methodology based on the combined use of Raman Spectroscopy and SEM-EDS (point-by-point and imaging) was applied. For that purpose, firstly evaporated seawater (presence of Primary Marine Aerosol (PMA)) was analyzed. After that, using a self-made passive sampler (SMPS), different suspended particles coming from marine aerosol (transformed particles in the atmosphere (Secondary Marine Aerosol (SMA)) and metallic airborne particulate matter coming from anthropogenic sources, were analyzed. Finally in order to observe if SMA and metallic particles identified in the SMPS can be deposited on a building, sandstone samples from La Galea Fortress (Getxo, north of Spain) located in front of the sea and in the place where the passive sampler was mounted were analyzed. Copyright © 2016 Elsevier B.V. All rights reserved.

Altitudinal characteristics of atmospheric deposition of aerosols in mountainous regions: Lessons from the Fukushima Daiichi Nuclear Power Station accident.

PubMed

Sanada, Yukihisa; Katata, Genki; Kaneyasu, Naoki; Nakanishi, Chika; Urabe, Yoshimi; Nishizawa, Yukiyasu

2018-03-15

To understand the formation process of radiologically contaminated areas in eastern Japan caused by the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, the deposition mechanisms over complex topography are the key factors to be investigated. To characterize the atmospheric deposition processes of radionuclides over complex mountainous topography, we investigated the altitudinal distributions of the radiocesium deposited during the accident. In five selected areas, altitudinal characteristics of the air dose rates observed using airborne surveys were analyzed. To examine the deposition mechanisms, we supplementarily used vertical profiles of radiocesium deposition in each area calculated in the latest atmospheric dispersion model. In southern Iwate, the vertical profile of the observed air dose rate was uniform regardless of altitude. In western Tochigi, the areas with the highest levels of contamination were characteristically distributed in the middle of the mountains, while in southern Fukushima, the areas with the highest contamination levels were enhanced near the summits of mountains. In central Fukushima, high air dose rates were limited to the bottoms of basin-like valley. In the region northwest of FDNPS, the air dose rate was the highest at the bottom of valley topography and decreased gradually with altitude. The simulation results showed that calculated wet deposition and observed vertical profiles of total deposition were similar in areas of southern Iwate and northwest of FDNPS qualitatively, suggesting that the dominant deposition mechanism was wet deposition. In contrast, the atmospheric dispersion model failed to reproduce either the timing of precipitation events or vertical profiles of radiocesium deposition in three other areas. Although it was difficult to elucidate the deposition mechanisms in these areas due to uncertainties of the present model results, potential mechanisms such as cloud water deposition were still proposed based on

The Many Problems with Geoengineering Using Stratospheric Aerosols

NASA Astrophysics Data System (ADS)

Robock, Alan

2009-05-01

In response to the global warming problem, there has been a recent renewed call for geoengineering ``solutions'' involving injecting particles into the stratosphere or blocking sunlight with satellites between the Sun and Earth. While volcanic eruptions have been suggested as innocuous examples of stratospheric aerosols cooling the planet, the volcano analog actually argues against geoengineering because of ozone depletion and regional hydrologic and temperature responses. In this talk, I consider the suggestion to create an artificial stratospheric aerosol layer. No systems to conduct geoengineering now exist, but a comparison of different proposed stratospheric injection schemes, airplanes, balloons, artillery, and a space elevator, shows that using airplanes would not be that expensive. We simulated the climate response to both tropical and Arctic stratospheric injection of sulfate aerosol precursors using a comprehensive atmosphere-ocean general circulation model, the National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE. We simulated the injection of SO2 and the model converts it to sulfate aerosols, transports them and removes them through dry and wet deposition, and calculates the climate response to the radiative forcing from the aerosols. We conducted simulations of future climate with the Intergovernmental Panel on Climate Change A1B business-as-usual scenario both with and without geoengineering, and compare the results. We found that if there were a way to continuously inject SO2 into the lower stratosphere, it would produce global cooling. Acid deposition from the sulfate would not be enough to disturb most ecosystems. Tropical SO2 injection would produce sustained cooling over most of the world, with more cooling over continents. Arctic SO2 injection would not just cool the Arctic. But both tropical and Arctic SO2 injection would disrupt the Asian and African summer monsoons, reducing precipitation to the food supply

Development of an Aerosol Surface Inoculation Method for Bacillus Spores ▿

PubMed Central

Lee, Sang Don; Ryan, Shawn P.; Snyder, Emily Gibb

2011-01-01

A method was developed to deposit Bacillus subtilis spores via aerosolization onto various surface materials for biological agent decontamination and detection studies. This new method uses an apparatus coupled with a metered dose inhaler to reproducibly deposit spores onto various surfaces. A metered dose inhaler was loaded with Bacillus subtilis spores, a surrogate for Bacillus anthracis. Five different material surfaces (aluminum, galvanized steel, wood, carpet, and painted wallboard paper) were tested using this spore deposition method. This aerosolization method deposited spores at a concentration of more than 107 CFU per coupon (18-mm diameter) with less than a 50% coefficient of variation, showing that the aerosolization method developed in this study can deposit reproducible numbers of spores onto various surface coupons. Scanning electron microscopy was used to probe the spore deposition patterns on test coupons. The deposition patterns observed following aerosol impaction were compared to those of liquid inoculation. A physical difference in the spore deposition patterns was observed to result from the two different methods. The spore deposition method developed in this study will help prepare spore coupons via aerosolization fast and reproducibly for bench top decontamination and detection studies. PMID:21193670

Biogenic cloud nuclei in the central Amazon during the transition from wet to dry season

NASA Astrophysics Data System (ADS)

Whitehead, James D.; Darbyshire, Eoghan; Brito, Joel; Barbosa, Henrique M. J.; Crawford, Ian; Stern, Rafael; Gallagher, Martin W.; Kaye, Paul H.; Allan, James D.; Coe, Hugh; Artaxo, Paulo; McFiggans, Gordon

2016-08-01

The Amazon basin is a vast continental area in which atmospheric composition is relatively unaffected by anthropogenic aerosol particles. Understanding the properties of the natural biogenic aerosol particles over the Amazon rainforest is key to understanding their influence on regional and global climate. While there have been a number of studies during the wet season, and of biomass burning particles in the dry season, there has been relatively little work on the transition period - the start of the dry season in the absence of biomass burning. As part of the Brazil-UK Network for Investigation of Amazonian Atmospheric Composition and Impacts on Climate (BUNIAACIC) project, aerosol measurements, focussing on unpolluted biogenic air masses, were conducted at a remote rainforest site in the central Amazon during the transition from wet to dry season in July 2013. This period marks the start of the dry season but before significant biomass burning occurs in the region. Median particle number concentrations were 266 cm-3, with size distributions dominated by an accumulation mode of 130-150 nm. During periods of low particle counts, a smaller Aitken mode could also be seen around 80 nm. While the concentrations were similar in magnitude to those seen during the wet season, the size distributions suggest an enhancement in the accumulation mode compared to the wet season, but not yet to the extent seen later in the dry season, when significant biomass burning takes place. Submicron nonrefractory aerosol composition, as measured by an aerosol chemical speciation monitor (ACSM), was dominated by organic material (around 81 %). Aerosol hygroscopicity was probed using measurements from a hygroscopicity tandem differential mobility analyser (HTDMA), and a quasi-monodisperse cloud condensation nuclei counter (CCNc). The hygroscopicity parameter, κ, was found to be low, ranging from 0.12 for Aitken-mode particles to 0.18 for accumulation-mode particles. This was consistent

Control of Alq3 wetting layer thickness via substrate surface functionalization.

PubMed

Tsoi, Shufen; Szeto, Bryan; Fleischauer, Michael D; Veinot, Jonathan G C; Brett, Michael J

2007-06-05

The effects of substrate surface energy and vapor deposition rate on the initial growth of porous columnar tris(8-hydroxyquinoline)aluminum (Alq3) nanostructures were investigated. Alq3 nanostructures thermally evaporated onto as-supplied Si substrates bearing an oxide were observed to form a solid wetting layer, likely caused by an interfacial energy mismatch between the substrate and Alq3. Wetting layer thickness control is important for potential optoelectronic applications. A dramatic decrease in wetting layer thickness was achieved by depositing Alq3 onto alkyltrichlorosilane-derivatized Si/oxide substrates. Similar effects were noted with increasing deposition rates. These two effects enable tailoring of the wetting layer thickness.

Decadal trend of black carbon and refractory carbonaceous aerosol in the western rim of the North Pacific Ocean: atmospheric concentration and the retrieved record of deposition flux

NASA Astrophysics Data System (ADS)

Kaneyasu, Naoki; Yamaguchi, Takashi; Noguchi, Izumi; Akiyama, Masayuki; Matsumoto, Kiyoshi

2013-04-01

The long-term trend of light absorbing carbonaceous aerosols (or black carbon: BC) or refractory carbonaceous aerosol (or elemental carbon: EC) concentration is reported at European background sites such as Mace Head, and that of aerosol absorption coefficient are monitored in many GAW sites. On the contrary, such long-term data are relatively scarce at around the western part of the North Pacific Ocean. Thus, to understand the long-term variation of in the area, BC in fine aerosol fraction has been measured at Chichi-jima Islands, Japan. Chichi-jima Island is located 1000 km south of the Japanese mainland, and 1800 km west of the coast line of the Asian continent. BC has been measured with an Aethalometer (Magee, AE-16 and AE-30) since December, 1998 with 1 hr time resolution. Mass flowmeter embedded inside the Aethalometer is calibrated with a rotational dry gas-meter once a year. Monthly averaged BC concentration shows an obvious seasonal variation, i.e. high concentration during late autumn-winter-spring period resulting from the transport from East Asia, with maximum daily concentration above 500 ng m-3. In summer, daily concentration was usually less than 20 ng m-3, due to the clean background airmass originating from the North Pacific Anticyclone. Decadal trend of the annual averaged BC concentration showed a increasing trend from 2000 to 2007 and started to decrease after 2008, which roughly coincides with the reported emission trend of SO2 in China (Lu et al., 2010). In addition, total (i.e., wet + dry) deposition record of refractory carbon at two sites in the northern Japan (Rishiri Island: a remote island site, and Sapporo City: an urban site) are retrieved. At these sites, the local government have been measuring the chemical components in precipitation water collected by deposition gauges. In the deposition gauge, a membrane filter made of cellulose-acetate is fixed at the bottom of the funnel to remove water-insoluble particles from the precipitated

MODELING DEPOSITION OF INHALED PARTICLES

EPA Science Inventory

Modeling Deposition of Inhaled Particles: ABSTRACT

The mathematical modeling of the deposition and distribution of inhaled aerosols within human lungs is an invaluable tool in predicting both the health risks associated with inhaled environmental aerosols and the therapeut...

Aerosol tests conducted at Aberdeen Proving Grounds MD.

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

Brockmann, John E.; Lucero, Daniel A.; Servantes, Brandon Lee

Test data are reported that demonstrate the deposition from a spray dispersion system (Illinois Tool Works inductively charging rotary atomization nozzle) for application of decontamination solution to various surfaces in the passenger cabin of a Boeing 737 aircraft. The decontamination solution (EnviroTru) was tagged with a known concentration of fluorescein permitting determination of both airborne decontaminant concentration and surface deposited decontaminant solution so that the effective deposition rates and surface coverage could be determined and correlated with the amount of material sprayed. Six aerosol dispersion tests were conducted. In each test, aluminum foil deposition coupons were set out throughout themore » passenger area and the aerosol was dispersed. The aerosol concentration was measured with filter samplers as well as with optical techniques Average aerosol deposition ranged from 3 to 15 grams of decontamination solution per square meter. Some disagreement was observed between various instruments utilizing different measurement principles. These results demonstrate a potentially effective method to disperse decontaminant to interior surfaces of a passenger aircraft.« less

Estimation of atmospheric nutrient inputs to the Atlantic Ocean from 50°N to 50°S based on large-scale field sampling: Fixed nitrogen and dry deposition of phosphorus

NASA Astrophysics Data System (ADS)

Baker, A. R.; Lesworth, T.; Adams, C.; Jickells, T. D.; Ganzeveld, L.

2010-09-01

Atmospheric nitrogen inputs to the ocean are estimated to have increased by up to a factor of three as a result of increased anthropogenic emissions over the last 150 years, with further increases expected in the short- to mid-term at least. Such estimates are largely based on emissions and atmospheric transport modeling, because, apart from a few island sites, there is very little observational data available for atmospheric nitrogen concentrations over the remote ocean. Here we use samples of rainwater and aerosol we obtained during 12 long-transect cruises across the Atlantic Ocean between 50°N and 50°S as the basis for a climatological estimate of nitrogen inputs to the basin. The climatology is for the 5 years 2001-2005, during which almost all of the cruises took place, and includes dry and wet deposition of nitrate and ammonium explicitly, together with a more uncertain estimate of soluble organic nitrogen deposition. Our results indicate that nitrogen inputs into the region were ˜850-1420 Gmol (12-20 Tg) N yr-1, with ˜78-85% of this in the form of wet deposition. Inputs were greater in the Northern Hemisphere and in wet regions, and wet regions had a greater proportion of input via wet deposition. The largest uncertainty in our estimate of dry inputs is associated with variability in deposition velocities, while the largest uncertainty in our wet nitrogen input estimate is due to the limited amount and uneven geographic distribution of observational data. We also estimate a lower limit of dry deposition of phosphate to be ˜0.19 Gmol P yr-1, using data from the same cruises. We compare our results to several recent estimates of N and P deposition to the Atlantic and discuss the likely sources of uncertainty, such as the potential seasonal bias introduced by our sampling, on our climatology.

Improving organic aerosol treatments in CESM/CAM5: Development, application, and evaluation

PubMed Central

Glotfelty, Timothy; He, Jian

2017-01-01

Abstract New treatments for organic aerosol (OA) formation have been added to a modified version of the CESM/CAM5 model (CESM‐NCSU). These treatments include a volatility basis set treatment for the simulation of primary and secondary organic aerosols (SOAs), a simplified treatment for organic aerosol (OA) formation from glyoxal, and a parameterization representing the impact of new particle formation (NPF) of organic gases and sulfuric acid. With the inclusion of these new treatments, the concentration of oxygenated organic aerosol increases by 0.33 µg m−3 and that of primary organic aerosol (POA) decreases by 0.22 µg m−3 on global average. The decrease in POA leads to a reduction in the OA direct effect, while the increased OOA increases the OA indirect effects. Simulations with the new OA treatments show considerable improvement in simulated SOA, oxygenated organic aerosol (OOA), organic carbon (OC), total carbon (TC), and total organic aerosol (TOA), but degradation in the performance of HOA. In simulations of the current climate period, despite some deviations from observations, CESM‐NCSU with the new OA treatments significantly improves the magnitude, spatial pattern, seasonal pattern of OC and TC, as well as, the speciation of TOA between POA and OOA. Sensitivity analysis reveals that the inclusion of the organic NPF treatment impacts the OA indirect effects by enhancing cloud properties. The simulated OA level and its impact on the climate system are most sensitive to choices in the enthalpy of vaporization and wet deposition of SVOCs, indicating that accurate representations of these parameters are critical for accurate OA‐climate simulations. PMID:29104733

Drivers of Seasonal Variability in Marine Boundary Layer Aerosol Number Concentration Investigated Using a Steady State Approach

NASA Astrophysics Data System (ADS)

Mohrmann, Johannes; Wood, Robert; McGibbon, Jeremy; Eastman, Ryan; Luke, Edward

2018-01-01

Marine boundary layer (MBL) aerosol particles affect the climate through their interaction with MBL clouds. Although both MBL clouds and aerosol particles have pronounced seasonal cycles, the factors controlling seasonal variability of MBL aerosol particle concentration are not well constrained. In this paper an aerosol budget is constructed representing the effects of wet deposition, free-tropospheric entrainment, primary surface sources, and advection on the MBL accumulation mode aerosol number concentration (Na). These terms are then parameterized, and by assuming that on seasonal time scales Na is in steady state, the budget equation is rearranged to form a diagnostic equation for Na based on observable variables. Using data primarily collected in the subtropical northeast Pacific during the MAGIC campaign (Marine ARM (Atmospheric Radiation Measurement) GPCI (GCSS Pacific Cross-Section Intercomparison) Investigation of Clouds), estimates of both mean summer and winter Na concentrations are made using the simplified steady state model and seasonal mean observed variables. These are found to match well with the observed Na. To attribute the modeled difference between summer and winter aerosol concentrations to individual observed variables (e.g., precipitation rate and free-tropospheric aerosol number concentration), a local sensitivity analysis is combined with the seasonal difference in observed variables. This analysis shows that despite wintertime precipitation frequency being lower than summer, the higher winter precipitation rate accounted for approximately 60% of the modeled seasonal difference in Na, which emphasizes the importance of marine stratocumulus precipitation in determining MBL aerosol concentrations on longer time scales.

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Average Atmospheric (Wet) Deposition of Inorganic Nitrogen, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the average atmospheric (wet) deposition, in kilograms per square kilometer, of inorganic nitrogen for the year 2002 compiled for every catchment for MRB_E2RF1 of Major River Basins (MRBs, Crawford and others, 2006). The source data set for wet deposition was from the USGS's raster data set atmospheric (wet) deposition of inorganic nitrogen for 2002 (Gronberg, 2005). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every catchment of MRB_E2RF1 catchments for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Aerosol Chemical and Physical Characterization in Central Amazonia during the 2013 Dry Season

NASA Astrophysics Data System (ADS)

Artaxo, P.; Stern, R.; Brito, J.; Carbone, S.

2015-12-01

During the dry season, the central Amazon forest is highly influenced by forest fires transported through large distances, changing drastically the atmospheric composition even in remote places. This work focuses on a physical-chemical characterization of the aerosol population over a pristine site in Central Amazonia during the dry season. The submicrometer organic aerosols were measured with the Aerodyne ACSM (Aerosol Chemical Speciation Monitor, Aerodyne Inc). Optical properties, size distribution and other micro-physical characteristics were also analyzed. Other instruments were simultaneously used. The measurements were taken during the dry season of 2013 in the Cuieiras ecological reserve (ZF2), northwest of Manaus. The statistical analysis of the data was done with the PMF (Positive Matrix Factorization) technique, in which the organic aerosol was separated into different factors, and then its sources and forming processes were attributed. Results show that the mean aerosol loading was 5,91 μg m-3, from which 78% are of organic composition, 8.5% are sulfate, 6.5% are equivalent black carbon, 4% are ammonium and 3% are nitrate. The mass spectra variability can be explained by 3 factors only, determined with the PMF technique. They were identified as BBOA (Biomass Burning Organic Aerosol), representing 12% of the total organic mass, OOA (Oxygenated Organic Aerosol), representing 66% of the total organic mass and IEPOX-SOA (Isoprene derived Epoxydiol-Secondary Organic Aerosol), representing 21% of the total organic mass. Even in remote and pristine regions, Central Amazonia is highly impacted by biomass burning. Biogenic secondary organic aerosols are also present during the dry season, and the suppression of its wet deposition processes increases their concentration. The oxidation level and other physical-chemical characteristics indicate that the long range transport is responsible for the regional range of this impact.

A Preliminary Assessment of Wet Deposition and Eposodic Transport of Total and Methyl Metcury From Low Order Blue Ridge Watersheds, S.E. U.S.A.

Treesearch

C.J. Allan; A. Heyes

1998-01-01

Abstract. Results from a preliminary sampling program designed to investigate total (THg) and methyl Hg (MeHg) deposition, cycling and transport at the Coweeta Hydrologic Laboratory western North Carolina are presented. Wet deposition samples were collected in June and July 1994 and throughfall, seep and streamwaters were intensively collected during...

A Multi-Resolution Assessment of the Community Multiscale Air Quality (CMAQ) Model v4.7 Wet Deposition Estimates for 2002 - 2006

EPA Science Inventory

This paper examines the operational performance of the Community Multiscale Air Quality (CMAQ) model simulations for 2002 - 2006 using both 36-km and 12-km horizontal grid spacing, with a primary focus on the performance of the CMAQ model in predicting wet deposition of sulfate (...

Joint analysis of deposition fluxes and atmospheric concentrations of inorganic nitrogen and sulphur compounds predicted by six chemistry transport models in the frame of the EURODELTAIII project

NASA Astrophysics Data System (ADS)

Vivanco, M. G.; Bessagnet, B.; Cuvelier, C.; Theobald, M. R.; Tsyro, S.; Pirovano, G.; Aulinger, A.; Bieser, J.; Calori, G.; Ciarelli, G.; Manders, A.; Mircea, M.; Aksoyoglu, S.; Briganti, G.; Cappelletti, A.; Colette, A.; Couvidat, F.; D'Isidoro, M.; Kranenburg, R.; Meleux, F.; Menut, L.; Pay, M. T.; Rouïl, L.; Silibello, C.; Thunis, P.; Ung, A.

2017-02-01

In the framework of the UNECE Task Force on Measurement and Modelling (TFMM) under the Convention on Long-range Transboundary Air Pollution (LRTAP), the EURODELTAIII project is evaluating how well air quality models are able to reproduce observed pollutant air concentrations and deposition fluxes in Europe. In this paper the sulphur and nitrogen deposition estimates of six state-of-the-art regional models (CAMx, CHIMERE, EMEP MSC-W, LOTOS-EUROS, MINNI and CMAQ) are evaluated and compared for four intensive EMEP measurement periods (25 Feb-26 Mar 2009; 17 Sep-15 Oct 2008; 8 Jan-4 Feb 2007 and 1-30 Jun 2006). For sulphur, this study shows the importance of including sea salt sulphate emissions for obtaining better model results; CMAQ, the only model considering these emissions in its formulation, was the only model able to reproduce the high measured values of wet deposition of sulphur at coastal sites. MINNI and LOTOS-EUROS underestimate sulphate wet deposition for all periods and have low wet deposition efficiency for sulphur. For reduced nitrogen, all the models underestimate both wet deposition and total air concentrations (ammonia plus ammonium) in the summer campaign, highlighting a potential lack of emissions (or incoming fluxes) in this period. In the rest of campaigns there is a general underestimation of wet deposition by all models (MINNI and CMAQ with the highest negative bias), with the exception of EMEP, which underestimates the least and even overestimates deposition in two campaigns. This model has higher scavenging deposition efficiency for the aerosol component, which seems to partly explain the different behaviour of the models. For oxidized nitrogen, CMAQ, CAMx and MINNI predict the lowest wet deposition and the highest total air concentrations (nitric acid plus nitrates). Comparison with observations indicates a general underestimation of wet oxidized nitrogen deposition by these models, as well as an overestimation of total air concentration for

A rapid and repeatable method to deposit bioaerosols on material surfaces.

PubMed

Calfee, M Worth; Lee, Sang Don; Ryan, Shawn P

2013-03-01

A simple method for repeatably inoculating surfaces with a precise quantity of aerosolized spores was developed. Laboratory studies were conducted to evaluate the variability of the method within and between experiments, the spatial distribution of spore deposition, the applicability of the method to complex surface types, and the relationship between material surface roughness and spore recoveries. Surface concentrations, as estimated by recoveries from wetted-wipe sampling, were between 5×10(3) and 1.5×10(4)CFUcm(-2) across the entire area (930cm(2)) inoculated. Between-test variability (Cv) in spore recoveries was 40%, 81%, 66%, and 20% for stainless steel, concrete, wood, and drywall, respectively. Within-test variability was lower, and did not exceed 33%, 47%, 52%, and 20% for these materials. The data demonstrate that this method is repeatable, is effective at depositing spores across a target surface area, and can be used to dose complex materials such as concrete, wood, and drywall. In addition, the data demonstrate that surface sampling recoveries vary by material type, and this variability can partially be explained by the material surface roughness index. This deposition method was developed for use in biological agent detection, sampling, and decontamination studies, however, is potentially beneficial to any scientific discipline that investigates surfaces containing aerosol-borne particles. Published by Elsevier B.V.

Predicting the mineral composition of dust aerosols - Part 1: Representing key processes

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Pérez García-Pando, C.; Miller, R. L.

2015-10-01

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to

Atmospheric deposition as a source of carbon and nutrients to an alpine catchment of the Colorado Rocky Mountains

NASA Astrophysics Data System (ADS)

Mladenov, N.; Williams, M. W.; Schmidt, S. K.; Cawley, K.

2012-08-01

Many alpine areas are experiencing deglaciation, biogeochemical changes driven by temperature rise, and changes in atmospheric deposition. There is mounting evidence that the water quality of alpine streams may be related to these changes, including rising atmospheric deposition of carbon (C) and nutrients. Given that barren alpine soils can be severely C limited, atmospheric deposition sources may be an important source of C and nutrients for these environments. We evaluated the magnitude of atmospheric deposition of C and nutrients to an alpine site, the Green Lake 4 catchment in the Colorado Rocky Mountains. Using a long-term dataset (2002-2010) of weekly atmospheric wet deposition and snowpack chemistry, we found that volume weighted mean dissolved organic carbon (DOC) concentrations were 1.12 ± 0.19 mg l-1, and weekly concentrations reached peaks as high at 6-10 mg l-1 every summer. Total dissolved nitrogen concentration also peaked in the summer, whereas total dissolved phosphorus and calcium concentrations were highest in the spring. To investigate potential sources of C in atmospheric deposition, we evaluated the chemical quality of dissolved organic matter (DOM) and relationships between DOM and other solutes in wet deposition. Relationships between DOC concentration, fluorescence, and nitrate and sulfate concentrations suggest that pollutants from nearby urban and agricultural sources and organic aerosols derived from sub-alpine vegetation may influence high summer DOC wet deposition concentrations. Interestingly, high DOC concentrations were also recorded during "dust-in-snow" events in the spring, which may reflect an association of DOM with dust. Detailed chemical and spectroscopic analyses conducted for samples collected in 2010 revealed that the DOM in many late spring and summer samples was less aromatic and polydisperse and of lower molecular weight than that of winter and fall samples. Our C budget estimates for the Green Lake 4 catchment

Deposition and rainwater concentrations of trifluoroacetic acid in the United States from the use of HFO-1234yf

NASA Astrophysics Data System (ADS)

Kazil, J.; McKeen, S.; Kim, S.-W.; Ahmadov, R.; Grell, G. A.; Talukdar, R. K.; Ravishankara, A. R.

2014-12-01

Currently, HFC-134a (1,1,1,2-tetrafluoroethane) is the most common refrigerant in automobile air conditioners. This high global warming potential substance (100 year GWP of 1370) will likely be phased out and replaced with HFO-1234yf (2,3,3,3-tetrafluoropropene) that has a 100 year GWP of 4. HFO-1234yf will be oxidized to produce trifluoroacetic acid (TFA) in clouds. TFA, a mildly toxic substance with detrimental effects on some aquatic organisms at high concentrations (≥100μgL-1), would be transported by rain to the surface and enter bodies of water. We investigated the dry and wet deposition of TFA from HFO-1234yf over the contiguous USA using the Advanced Research Weather Research and Forecasting model (ARW) with interactive chemical, aerosol, and cloud processes (WRF/Chem) model. Special focus was placed on emissions from three continental USA regions with different meteorological characteristics. WRF/Chem simulated meteorology, cloud processes, gas and aqueous phase chemistry, and dry and wet deposition between May and September 2006. The model reproduced well the multimonth total sulfate wet deposition (4% bias) and its spatial variability (r = 0.86) observed by the National Atmospheric Deposition Program. HFO-1234yf emissions were obtained by assuming the number of automobile air conditioners to remain unchanged, and substituting HFO-1234yf, mole-per-mole for HFC-134a. Our estimates of current HFC-134a emissions were in agreement with field data. Average TFA rainwater concentration was 0.89μgL-1, with peak values of 7.8μgL-1, for the May-September 2006 period over the contiguous USA. TFA rainwater concentrations over the dry western USA were often significantly higher, but wet-deposited TFA amounts remained relatively low at such locations.

Quantifying black carbon deposition over the Greenland ice sheet from forest fires in Canada: BC DEPOSITION FROM FOREST FIRES

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

Thomas, J. L.; Polashenski, C. M.; Soja, A. J.

We identify an important Black Carbon (BC) aerosol deposition event that was observed in snow stratigraphy and dated to between 27 July 2013 – 2 August 2013. This event comprises a significant portion (~60%) of total deposition over a 10 month period (July 2013 – April 2014). Here we link this event to forest fires burning in Canada during summer 2013 using modeling and remote sensing tools. Aerosols were detected by both the CALIOP and MODIS instruments during transport between Canada and Greenland, confirming that this event involved emissions from forest fires in Canada. We use high-resolution regional chemical transportmore » mod-eling (WRF-Chem) combined with high-resolution fire emissions (FINNv1.5) to study aerosol emissions, transport, and deposition during this event. The model accurately captures the timing of the BC deposition event and shows that the major contribution to deposition during this event is emissions originating from fires in Canada. However, the model under-predicts aerosol deposition compared to measurements at all sites by a factor of 2–100. Under-prediction of modeled BC deposition originates from uncertainties in fire emissions combined with uncertainties in aerosol scavenging by clouds. This study suggests that it is possible to describe the transport of an exceptional smoke event on regional and continental scales. Improvements in model descriptions of precipitation scavenging and emissions from wildfires are needed to correctly predict deposition, which is critical for determining the climate impacts of aerosols that originate from fires.« less

Evaluating the Contributions of Atmospheric Deposition of Carbon and Other Nutrients to Nitrification in Alpine Environments

NASA Astrophysics Data System (ADS)

Oldani, K. M.; Mladenov, N.; Williams, M. W.

2013-12-01

The Colorado Front Range of the Rocky Mountains contains undeveloped, barren soils, yet in this environment there is strong evidence for a microbial role in increased nitrogen (N) export. Barren soils in alpine environments are severely carbon-limited, which is the main energy source for microbial activity and sustenance of life. It has been shown that atmospheric deposition can contain high amounts of organic carbon (C). Atmospheric pollutants, dust events, and biological aerosols, such as bacteria, may be important contributors to the atmospheric organic C load. In this stage of the research we evaluated seasonal trends in the chemical composition and optical spectroscopic (fluorescence and UV-vis absorbance) signatures of snow, wet deposition, and dry deposition in an alpine environment at Niwot Ridge in the Rocky Mountains of Colorado to obtain a better understanding of the sources and chemical character of atmospheric deposition. Our results reveal a positive trend between dissolved organic carbon concentrations and calcium, nitrate and sulfate concentrations in wet and dry deposition, which may be derived from such sources as dust and urban air pollution. We also observed the presence of seasonally-variable fluorescent components that may be attributed to fluorescent pigments in bacteria. These results are relevant because atmospheric inputs of carbon and other nutrients may influence nitrification in barren, alpine soils and, ultimately, the export of nitrate to alpine watersheds.

Atmospheric Nitrogen Deposition to the Oceans: Observation- and Model-Based Estimates

NASA Astrophysics Data System (ADS)

Baker, Alex; Altieri, Katye; Okin, Greg; Dentener, Frank; Uematsu, Mitsuo; Kanakidou, Maria; Sarin, Manmohan; Duce, Robert; Galloway, Jim; Keene, Bill; Singh, Arvind; Zamora, Lauren; Lamarque, Jean-Francois; Hsu, Shih-Chieh

2014-05-01

The reactive nitrogen (Nr) burden of the atmosphere has been increased by a factor of 3-4 by anthropogenic activity since the industrial revolution. This has led to large increases in the deposition of nitrate and ammonium to the surface waters of the open ocean, particularly downwind of major human population centres, such as those in North America, Europe and Southeast Asia. In oligotrophic waters, this deposition has the potential to significantly impact marine productivity and the global carbon cycle. Global-scale understanding of N deposition to the oceans is reliant on our ability to produce effective models of reactive nitrogen emission, atmospheric chemistry, transport and deposition (including deposition to the land surface). The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) recently completed a multi-model analysis of global N deposition, including comparisons to wet deposition observations from three regional networks in North America, Europe and Southeast Asia (Lamarque et al., Atmos. Chem. Phys., 13, 7977-8018, 2013). No similar datasets exist which would allow observation - model comparisons of wet deposition for the open oceans, because long-term wet deposition records are available for only a handful of remote island sites and rain collection over the open ocean itself is very difficult. In this work we attempt instead to use ~2600 observations of aerosol nitrate and ammonium concentrations, acquired chiefly from sampling aboard ships in the period 1995 - 2012, to assess the ACCMIP N deposition fields over the remote ocean. This database is non-uniformly distributed in time and space. We selected four ocean regions (the eastern North Atlantic, the South Atlantic, the northern Indian Ocean and northwest Pacific) where we considered the density and distribution of observational data is sufficient to provide effective comparison to the model ensemble. Two of these regions are adjacent to the land networks used in the ACCMIP

Mercury in the global atmosphere: Chemistry, deposition, and land-atmosphere interactions

NASA Astrophysics Data System (ADS)

Selin, Noelle Eckley

This thesis uses a global 3-D chemical transport model (GEOS-Chem), in conjunction with worldwide atmospheric observations, to better understand and quantify biogeochemical cycling and deposition of mercury. GEOS-Chem includes gaseous elemental (Hg(0)), divalent (Hg(II)), and particulate (Hg(P)) mercury in the atmosphere, and includes coupling with the ocean, developed at University of Washington, and with land, developed in this work. Observed concentrations and seasonal variation of total gaseous mercury (TGM) are consistent with photochemical oxidation for Hg(0) partly balanced by in-cloud photochemical reduction of Hg(II). High TGM concentrations from ship cruises in the Northern Hemisphere are not reproduced, implying a problem either in measurements or our understanding of sources. Model results, supported by observations, suggest Hg(II) to be dominant at higher altitudes. Diurnal variability observed at marine sites suggests uptake by sea salt aerosols is a major deposition mechanism. Global biogeochemical cycles of mercury are constructed for pre-industrial and present-day using the first fully-coupled, global 3-D land-atmosphere-ocean mercury model. Atmosphere-surface cycling increases the effective mercury lifetime more than threefold against transfer to long-lived soil and ocean reservoirs. It is estimated that 68% of deposition to the U.S. is anthropogenic, including 16% from the legacy of anthropogenic mercury accumulated in soils and the deep ocean. Observed seasonal variations in U.S. wet deposition are used to constrain redox and deposition processes influencing the fate of North American and international emissions. The model reproduces the seasonal variation and latitudinal gradient of wet deposition flux measured in the eastern U.S., with a maximum in the Southeast and higher fluxes in summer and at lower latitudes. Seasonal variation is attributed to variations in oxidation and wet deposition rates at northern latitudes, and to seasonal

Predicting the mineral composition of dust aerosols - Part 1: Representing key processes

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Pérez García-Pando, C.; Miller, R. L.

2015-02-01

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, coating by heterogeneous uptake of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the resulting aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent in a soil whose aggregates are dispersed by wet sieving during analysis. We reconstruct the undispersed size distribution of the original soil that is subject to wind erosion. An empirical constraint upon the relative emission of clay and silt is applied that further differentiates the soil and aerosol mineral composition. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to measurements from North Africa shows that the extension brings the model into better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles.

Influence of Oxygen Partial Pressure during Processing on the Thermoelectric Properties of Aerosol-Deposited CuFeO2

PubMed Central

Stöcker, Thomas; Exner, Jörg; Schubert, Michael; Streibl, Maximilian; Moos, Ralf

2016-01-01

In the field of thermoelectric energy conversion, oxide materials show promising potential due to their good stability in oxidizing environments. Hence, the influence of oxygen partial pressure during synthesis on the thermoelectric properties of Cu-Delafossites at high temperatures was investigated in this study. For these purposes, CuFeO2 powders were synthetized using a conventional mixed-oxide technique. X-ray diffraction (XRD) studies were conducted to determine the crystal structures of the delafossites associated with the oxygen content during the synthesis. Out of these powders, films with a thickness of about 25 µm were prepared by the relatively new aerosol-deposition (AD) coating technique. It is based on a room temperature impact consolidation process (RTIC) to deposit dense solid films of ceramic materials on various substrates without using a high-temperature step during the coating process. On these dense CuFeO2 films deposited on alumina substrates with electrode structures, the Seebeck coefficient and the electrical conductivity were measured as a function of temperature and oxygen partial pressure. We compared the thermoelectric properties of both standard processed and aerosol deposited CuFeO2 up to 900 °C and investigated the influence of oxygen partial pressure on the electrical conductivity, on the Seebeck coefficient and on the high temperature stability of CuFeO2. These studies may not only help to improve the thermoelectric material in the high-temperature case, but may also serve as an initial basis to establish a defect chemical model. PMID:28773351

Seasonal aerosol characteristics in the Amazon rain forest

NASA Astrophysics Data System (ADS)

Baars, H.; Althausen, D.; Ansmann, A.; Engelmann, R.; Heese, B.; Müller, D.; Pauliquevis, T.; Souza, R.; Artaxo, P.

2012-04-01

For the first time in Amazonia, continuous measurements of the vertical aerosol structure were carried out in the framework of EUCAARI (European Integrated Project on Aerosol, Cloud, Climate, Air Quality Interactions) and AMAZE-08 (Amazonian Aerosol Characterization Experiment). The observations were performed 60 km north of Manaus, Brazil (at 2° 35.5' S and 60° 2.3' W) in the central northern part of the Amazon rain forest from January to November 2008 with the automated multi-wavelength-Raman-polarization-lidar PollyXT. With this instrument, vertical profiles of the particle backscatter coefficient at 355, 532, and 1064 nm, of the particle extinction coefficient at 355 and 532 nm, and of the particle linear depolarization ratio at 355 nm can be determined. During the 10-months observational period, measurements were performed on 211 days resulting in more than 2500 hours of tropospheric aerosol and cloud profile observations. The analysis of the long-term data set revealed strong differences in the aerosol characteristics between the wet and the dry season. In the wet season, very clean atmospheric conditions occurred in ca. 50% of all observation cases. During these clean conditions, the aerosol optical depth (AOD) at 532 nm was less than 0.05 and the aerosol was trapped in the lowermost 2 km of the troposphere. However, also intrusions of Saharan dust and African biomass-burning aerosol (BBA) - characterized by a significantly increased AOD and particle depolarization ratio - were observed in about one third (32%) of all lidar observations. These African aerosol plumes extended usually from the surface up to about 3.5 km agl. During the dry season, BBA from fires on the South American continent was the dominant aerosol species. The mean AOD of the dry season was found to be a factor of 3 higher than the mean AOD of the wet season (0.26 compared to 0.08 at 532 nm). This is due to the high BBA concentration in the atmosphere. Maximum AOD values were less than 0

Aerosol delivery of liposome-encapsulated ciprofloxacin: aerosol characterization and efficacy against Francisella tularensis infection in mice.

PubMed

Conley, J; Yang, H; Wilson, T; Blasetti, K; Di Ninno, V; Schnell, G; Wong, J P

1997-06-01

The aerosol delivery of liposome-encapsulated ciprofloxacin by using 12 commercially available jet nebulizers was evaluated in this study. Aerosol particles containing liposome-encapsulated ciprofloxacin generated by the nebulizers were analyzed with a laser aerodynamic particle sizer. Mean mass aerodynamic diameters (MMADs) and geometric standard deviations (GSDs) were determined, and the drug contents of the sampling filters from each run onto which aerosolized liposome-encapsulated ciprofloxacin had been deposited were analyzed spectrophotometrically. The aerosol particles of liposome-encapsulated ciprofloxacin generated by these nebulizers ranged from 1.94 to 3.5 microm, with GSDs ranging from 1.51 to 1.84 microm. The drug contents of the sampling filters exposed for 1 min to aerosolized liposome-encapsulated ciprofloxacin range from 12.7 to 40.5 microg/ml (0.06 to 0.2 mg/filter). By using the nebulizer selected on the basis of most desirable MMADs, particle counts, and drug deposition, aerosolized liposome-encapsulated ciprofloxacin was used for the treatment of mice infected with 10 times the 50% lethal dose of Francisella tularensis. All mice treated with aerosolized liposome-encapsulated ciprofloxacin survived the infection, while all ciprofloxacin-treated or untreated control mice succumbed to the infection (P < 0.001). These results suggest that aerosol delivery of liposome-encapsulated ciprofloxacin to the lower respiratory tract is feasible and that it may provide an effective therapy for the treatment of respiratory tract infections.

Predicting the mineral composition of dust aerosols – Part 1: Representing key processes

DOE PAGES

Perlwitz, J. P.; Perez Garcia-Pando, C.; Miller, R. L.

2015-10-21

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accountsmore » for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. Finally, a

Effects of Heat and Moisture Exchangers and Exhaled Humidity on Aerosol Deposition in a Simulated Ventilator-Dependent Adult Lung Model.

PubMed

Ari, Arzu; Alwadeai, Khalid S; Fink, James B

2017-05-01

Many in vitro models report higher inhaled dose with dry versus heated humidity. Heat-and-moisture exchangers (HMEs) provide passive humidity in ventilator-dependent patients but act as a barrier to aerosol. The HMEs designed to allow aerosol delivery (HME-ADs) have not been well described. The purpose of this study is to determine the impact on aerosol deposition of HME-ADs with and without active exhaled humidity in a simulated ventilator-dependent adult model. We used an in vitro lung model consisting of an intubated teaching mannequin with an endotracheal tube of 8.0 mm inner diameter with bronchi directly attached to a collecting filter and passive rubber test lung to provide testing without active exhaled humidity. To simulate exhaled humidity, a Cascade humidifier (37°C and 100% relative humidity) was placed between the collecting filter and test lung, simulating body temperature and pressure saturated exhaled humidity at the bronchi. Albuterol sulfate (2.5 mg/3 mL) was administered with a mesh nebulizer (Aerogen Solo) placed in the inspiratory limb of the ventilator circuit at the Y-piece, with no HME in place (control) and with 3 HME-AD devices, including the CircuVent, Humid-Flo, and AirLife, with and without exhaled humidity. Drug was eluted from the collecting filter and analyzed with spectrophotometry. Student t tests and analysis of variance were used for data analysis ( P < .05). The percentage of drug dose delivered (mean ± SD) distal to the bronchi in the control experiments was greater than all of the HME-ADs without exhaled humidity 18 ± 0.7 and with active exhaled humidity 10.8 ± 0.2% ( P < .005). Without exhaled humidity, aerosol delivery with the CircuVent (12.6 ± 0.8), Humid-Flo (15.3 ± 0.8), and AirLife (12.0 ± 0.5) was less than control ( P < .001, P = .01 and P < .001, respectively). In contrast, with exhaled humidity, no difference was found between control and HME-ADs ( P = .89). Also, a greater variation between control and the 3

Drivers of Seasonal Variability in Marine Boundary Layer Aerosol Number Concentration Investigated Using a Steady State Approach

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

Mohrmann, Johannes; Wood, Robert; McGibbon, Jeremy

Marine boundary layer (MBL) aerosol particles affect the climate through their interaction with MBL clouds. Although both MBL clouds and aerosol particles have pronounced seasonal cycles, the factors controlling seasonal variability of MBL aerosol particle concentration are not well-constrained. In this paper an aerosol budget is constructed representing the effects of wet deposition, free-tropospheric entrainment, primary surface sources, and advection on the MBL accumulation mode aerosol number concentration (N a). These terms are further parameterized, and by assuming that on seasonal timescales N a is in steady state, the budget equation is rearranged to form a diagnostic equation for Nmore » a based on observable variables. Using data primarily collected in the subtropical northeast Pacific during the MAGIC campaign (Marine ARM (Atmospheric Radiation Measurement) GPCI (GCSS Pacific Cross-section Intercomparison) Investigation of Clouds), estimates of both mean summer and winter N a concentrations are made using the simplified steady-state model and seasonal mean observed variables, and are found to match well with the observed N a. To attribute the modeled difference between summer and winter aerosol concentrations to individual observed variables (e.g. precipitation rate, free-tropospheric aerosol number concentration), a local sensitivity analysis is combined with the seasonal difference in observed variables. This analysis shows that despite wintertime precipitation frequency being lower than summer, the higher winter precipitation rate accounted for approximately 60% of the modeled seasonal difference in N a, which emphasizes the importance of marine stratocumulus precipitation in determining MBL aerosol concentrations on longer time scales.« less

Drivers of Seasonal Variability in Marine Boundary Layer Aerosol Number Concentration Investigated Using a Steady State Approach

DOE PAGES

Mohrmann, Johannes; Wood, Robert; McGibbon, Jeremy; ...

2018-01-21

Marine boundary layer (MBL) aerosol particles affect the climate through their interaction with MBL clouds. Although both MBL clouds and aerosol particles have pronounced seasonal cycles, the factors controlling seasonal variability of MBL aerosol particle concentration are not well-constrained. In this paper an aerosol budget is constructed representing the effects of wet deposition, free-tropospheric entrainment, primary surface sources, and advection on the MBL accumulation mode aerosol number concentration (N a). These terms are further parameterized, and by assuming that on seasonal timescales N a is in steady state, the budget equation is rearranged to form a diagnostic equation for Nmore » a based on observable variables. Using data primarily collected in the subtropical northeast Pacific during the MAGIC campaign (Marine ARM (Atmospheric Radiation Measurement) GPCI (GCSS Pacific Cross-section Intercomparison) Investigation of Clouds), estimates of both mean summer and winter N a concentrations are made using the simplified steady-state model and seasonal mean observed variables, and are found to match well with the observed N a. To attribute the modeled difference between summer and winter aerosol concentrations to individual observed variables (e.g. precipitation rate, free-tropospheric aerosol number concentration), a local sensitivity analysis is combined with the seasonal difference in observed variables. This analysis shows that despite wintertime precipitation frequency being lower than summer, the higher winter precipitation rate accounted for approximately 60% of the modeled seasonal difference in N a, which emphasizes the importance of marine stratocumulus precipitation in determining MBL aerosol concentrations on longer time scales.« less

Use of multivariate analysis for determining sources of solutes found in wet atmospheric deposition in the United States

USGS Publications Warehouse

Hooper, R.P.; Peters, N.E.

1989-01-01

A principal-components analysis was performed on the major solutes in wet deposition collected from 194 stations in the United States and its territories. Approximately 90% of the components derived could be interpreted as falling into one of three categories - acid, salt, or an agricultural/soil association. The total mass, or the mass of any one solute, was apportioned among these components by multiple linear regression techniques. The use of multisolute components for determining trends or spatial distribution represents a substantial improvement over single-solute analysis in that these components are more directly related to the sources of the deposition. The geographic patterns displayed by the components in this analysis indicate a far more important role for acid deposition in the Southeast and intermountain regions of the United States than would be indicated by maps of sulfate or nitrate deposition alone. In the Northeast and Midwest, the acid component is not declining at most stations, as would be expected from trends in sulfate deposition, but is holding constant or increasing. This is due, in part, to a decline in the agriculture/soil factor throughout this region, which would help to neutralize the acidity.

The smog-fog-smog cycle and acid deposition

NASA Astrophysics Data System (ADS)

Pandis, Spyros N.; Seinfeld, John H.; Pilinis, Christodoulos

1990-10-01

A model including descriptions of aerosol and droplet microphysics, gas and aqueous-phase chemistry, and deposition is used to study the transformation of aerosol to fog droplets and back to aerosol in an urban environment. Fogs in polluted environments have the potential to increase aerosol sulfate concentrations but at the same time to cause reductions in the aerosol concentration of nitrate, chloride, ammonium and sodium and well as in the total aerosol mass concentration. The sulfate produced during fog episodes favors the aerosol particles that have access to most of the fog liquid water which are usually the large particles. Aerosol scavenging efficiencies of around 80 percent are calculated for urban fogs. Sampling and subsequent mixing of fog droplets of different sizes may result in measured concentrations that are not fully representative of the fogwater chemical composition and can introduce errors in the reported values of the ionic species deposition velocities. Differences in the major ionic species deposition velocities can be explained by their distribution over the droplet size spectrum and can be correlated with the species average diameter. Two different expressions are derived for use in fog models for the calculation of the liquid water deposition velocity during fog growth and dissipation stages.

An assessment of the variability in performance of wet atmospheric deposition samplers

USGS Publications Warehouse

Graham, R.C.; Robertson, J.K.; Obal, John

1987-01-01

The variability in performance of two brands of wet/dry atmospheric deposition samplers were compared for 1 year at a sincle site. A total of nine samplers were used. Samples were collected weekly and analyzed for pH, specific conductance, common chemical constituents, and sample volume. Additionally, data on the duration of each sampler opening were recorded using a microdatalogger. These data disprove the common perception that samplers remain open throughout a precipitation event. The sensitivity of sampler sensors within the range tested did not have a defineable impact on sample collection. The nonnormal distribution within the data set necessitated application of the nonparametric Friedman Test to assess comparability of sample chemical composition and volume between and within sampler brands. Statistically significant differences existed for most comparisons, however the test did not permit quantification of their magnitudes. Differences in analyte concentrations between samplers were small. (USGS)

The impact of precipitation evaporation on the atmospheric aerosol distribution in EC-Earth v3.2.0

NASA Astrophysics Data System (ADS)

de Bruine, Marco; Krol, Maarten; van Noije, Twan; Le Sager, Philippe; Röckmann, Thomas

2018-04-01

The representation of aerosol-cloud interaction in global climate models (GCMs) remains a large source of uncertainty in climate projections. Due to its complexity, precipitation evaporation is either ignored or taken into account in a simplified manner in GCMs. This research explores various ways to treat aerosol resuspension and determines the possible impact of precipitation evaporation and subsequent aerosol resuspension on global aerosol burdens and distribution. The representation of aerosol wet deposition by large-scale precipitation in the EC-Earth model has been improved by utilising additional precipitation-related 3-D fields from the dynamical core, the Integrated Forecasting System (IFS) general circulation model, in the chemistry and aerosol module Tracer Model, version 5 (TM5). A simple approach of scaling aerosol release with evaporated precipitation fraction leads to an increase in the global aerosol burden (+7.8 to +15 % for different aerosol species). However, when taking into account the different sizes and evaporation rate of raindrops following Gong et al. (2006), the release of aerosols is strongly reduced, and the total aerosol burden decreases by -3.0 to -8.5 %. Moreover, inclusion of cloud processing based on observations by Mitra et al. (1992) transforms scavenged small aerosol to coarse particles, which enhances removal by sedimentation and hence leads to a -10 to -11 % lower aerosol burden. Finally, when these two effects are combined, the global aerosol burden decreases by -11 to -19 %. Compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations, aerosol optical depth (AOD) is generally underestimated in most parts of the world in all configurations of the TM5 model and although the representation is now physically more realistic, global AOD shows no large improvements in spatial patterns. Similarly, the agreement of the vertical profile with Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP

Addressing the ice nucleating abilities of marine aerosol: A combination of deposition mode laboratory and field measurements

NASA Astrophysics Data System (ADS)

Ladino, L. A.; Yakobi-Hancock, J. D.; Kilthau, W. P.; Mason, R. H.; Si, M.; Li, J.; Miller, L. A.; Schiller, C. L.; Huffman, J. A.; Aller, J. Y.; Knopf, D. A.; Bertram, A. K.; Abbatt, J. P. D.

2016-05-01

This study addresses, through two types of experiments, the potential for the oceans to act as a source of atmospheric ice-nucleating particles (INPs). The INP concentration via deposition mode nucleation was measured in situ at a coastal site in British Columbia in August 2013. The INP concentration at conditions relevant to cirrus clouds (i.e., -40 °C and relative humidity with respect to ice, RHice = 139%) ranged from 0.2 L-1 to 3.3 L-1. Correlations of the INP concentrations with levels of anthropogenic tracers (i.e., CO, SO2, NOx, and black carbon) and numbers of fluorescent particles do not indicate a significant influence from anthropogenic sources or submicron bioaerosols, respectively. Additionally, the INPs measured in the deposition mode showed a poor correlation with the concentration of particles with sizes larger than 500 nm, which is in contrast with observations made in the immersion freezing mode. To investigate the nature of particles that could have acted as deposition INP, laboratory experiments with potential marine aerosol particles were conducted under the ice-nucleating conditions used in the field. At -40 °C, no deposition activity was observed with salt aerosol particles (sodium chloride and two forms of commercial sea salt: Sigma-Aldrich and Instant Ocean), particles composed of a commercial source of natural organic matter (Suwannee River humic material), or particle mixtures of sea salt and humic material. In contrast, exudates from three phytoplankton (Thalassiosira pseudonana, Nanochloris atomus, and Emiliania huxleyi) and one marine bacterium (Vibrio harveyi) exhibited INP activity at low RHice values, down to below 110%. This suggests that the INPs measured at the field site were of marine biological origins, although we cannot rule out other sources, including mineral dust.

Processes Controlling the Seasonal Cycle of Arctic Aerosol Number and Size Distributions

NASA Astrophysics Data System (ADS)

Wentworth, G.; Croft, B.; Martin, R.; Leaitch, W. R.; Tunved, P.; Breider, T. J.; D'Andrea, S.; Pierce, J. R.; Murphy, J. G.; Kodros, J.; Abbatt, J.

2015-12-01

Measurements at high-Arctic sites show a strong seasonal cycle in aerosol number and size. The number of aerosols with diameters larger than 20 nm exhibits a maximum in late spring associated with a dominant accumulation mode, and a second maximum in the summer associated with a dominant Aitken mode. Seasonal-mean aerosol effective diameter ranges from about 160 nm in summer to 250 nm in winter. This study interprets these seasonal cycles with the GEOS-Chem-TOMAS global aerosol microphysics model. We find improved agreement with in situ measurements (SMPS) of aerosol size at both Alert, Nunavut, and Mt. Zeppelin, Svalbard following model developments: 1) increase the efficiency of wet scavenging in the Arctic summer and 2) represent coagulation between interstitial aerosols and aerosols activated to form cloud droplets. Our simulations indicate that the dominant summer-time Aitken mode is associated with increased efficiency of wet removal, which limits the number of larger aerosols and promotes local new-aerosol formation. We also find an important role of interstitial coagulation in clouds in the Arctic, which limits the number of Aitken-mode aerosols in the non-summer seasons when direct wet removal of these aerosols is inefficient. The summertime Arctic atmosphere is particularly pristine and strongly influenced by natural regional emissions which have poorly understood climate impacts. Especially influenced are the climatic roles of atmospheric particles and clouds. Here we present evidence that ammonia (NH3) emissions from migratory-seabird guano (dung) are the primary contributor to summertime free ammonia levels recently measured in the Canadian Arctic atmosphere. These findings suggest that ammonia from seabird guano is a key factor contributing to bursts of new-particle formation, which are observed every summer in the near-surface atmosphere at Alert, Canada. Chemical transport model simulations show that these newly formed particles can grow by vapour

Cloud condensation nuclei activity and droplet activation kinetics of wet processed regional dust samples and minerals

NASA Astrophysics Data System (ADS)

Kumar, P.; Sokolik, I. N.; Nenes, A.

2011-08-01

This study reports laboratory measurements of particle size distributions, cloud condensation nuclei (CCN) activity, and droplet activation kinetics of wet generated aerosols from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. The dependence of critical supersaturation, sc, on particle dry diameter, Ddry, is used to characterize particle-water interactions and assess the ability of Frenkel-Halsey-Hill adsorption activation theory (FHH-AT) and Köhler theory (KT) to describe the CCN activity of the considered samples. Wet generated regional dust samples produce unimodal size distributions with particle sizes as small as 40 nm, CCN activation consistent with KT, and exhibit hygroscopicity similar to inorganic salts. Wet generated clays and minerals produce a bimodal size distribution; the CCN activity of the smaller mode is consistent with KT, while the larger mode is less hydrophilic, follows activation by FHH-AT, and displays almost identical CCN activity to dry generated dust. Ion Chromatography (IC) analysis performed on regional dust samples indicates a soluble fraction that cannot explain the CCN activity of dry or wet generated dust. A mass balance and hygroscopicity closure suggests that the small amount of ions (from low solubility compounds like calcite) present in the dry dust dissolve in the aqueous suspension during the wet generation process and give rise to the observed small hygroscopic mode. Overall these results identify an artifact that may question the atmospheric relevance of dust CCN activity studies using the wet generation method. Based on the method of threshold droplet growth analysis, wet generated mineral aerosols display similar activation kinetics compared to ammonium sulfate calibration aerosol. Finally, a unified CCN activity framework that accounts for concurrent effects of solute and adsorption is developed to describe the CCN activity of aged or hygroscopic dusts.

Role of Climate Change in Global Predictions of Future Tropospheric Ozone and Aerosols

NASA Technical Reports Server (NTRS)

Liao, Hong; Chen, Wei-Ting; Seinfeld, John H.

2006-01-01

A unified tropospheric chemistry-aerosol model within the Goddard Institute for Space Studies general circulation model II is applied to simulate an equilibrium CO2-forced climate in the year 2100 to examine the effects of climate change on global distributions of tropospheric ozone and sulfate, nitrate, ammonium, black carbon, primary organic carbon, secondary organic carbon, sea salt, and mineral dust aerosols. The year 2100 CO2 concentration as well as the anthropogenic emissions of ozone precursors and aerosols/aerosol precursors are based on the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (SRES) A2. Year 2100 global O3 and aerosol burdens predicted with changes in both climate and emissions are generally 5-20% lower than those simulated with changes in emissions alone; as exceptions, the nitrate burden is 38% lower, and the secondary organic aerosol burden is 17% higher. Although the CO2-driven climate change alone is predicted to reduce the global O3 concentrations over or near populated and biomass burning areas because of slower transport, enhanced biogenic hydrocarbon emissions, decomposition of peroxyacetyl nitrate at higher temperatures, and the increase of O3 production by increased water vapor at high NOx levels. The warmer climate influences aerosol burdens by increasing aerosol wet deposition, altering climate-sensitive emissions, and shifting aerosol thermodynamic equilibrium. Climate change affects the estimates of the year 2100 direct radiative forcing as a result of the climate-induced changes in burdens and different climatological conditions; with full gas-aerosol coupling and accounting for ozone and direct radiative forcings by the O2, sulfate, nitrate, black carbon, and organic carbon are predicted to be +0.93, -0.72, -1.0, +1.26, and -0.56 W m(exp -2), respectively, using present-day climate and year 2100 emissions, while they are predicted to be +0.76, -0.72, 0.74, +0.97, and -0.58 W m(exp -2

Using stable isotopes of reactive N in dry and wet deposition to investigate the source, transport, and fate of NOx and NH3

NASA Astrophysics Data System (ADS)

Felix, J.; Elliott, E. M.

2011-12-01

Reactive N emissions (NH3 and NOx) can reach the land surfaces via both wet (NH4+, NO3) and dry (NOx, HNO3, NH3, NH4+) depositional processes. Together, these reactive N compounds are important global contributors to air and water quality degradation. Although nitrate concentrations in wet deposition have decreased in the U.S. during the last two decades due to NOx emission regulations set forth by the Clean Air Act, ammonium concentrations in wet deposition have recently increased. In order to further decrease NOx emissions and decrease NH3 emissions, additional tools for reactive N source apportionment are essential. The stable isotopic composition of reactive N may be one such tool for characterizing source, transport, and fate of reactive N emissions. Here, we present results from a comprehensive inventory of the isotopic composition of reactive N emission sources, focusing mainly on agricultural and fossil fuel sources. We build on these inventory results by tracing reactive N emissions across multiple landscapes including: a dairy operation, a conventionally managed cornfield, a tallgrass prairie, and a concentrated animal feeding operation. We then use two examples to illustrate how reactive N isotopes can be used in a regional context. First, we illustrate how passive NH3 samplers deployed at nine U.S. monitoring sites reflect spatial variations in predominant NH3 sources. Secondly, we reconstruct the regional influence of agricultural NOx emissions to nitrate deposition recorded in an ice core from Summit, Greenland. These results reveal significant evidence that the trend in the N isotopic composition of 20th century nitrate deposition in Greenland was driven by increasing biogenic soil NOx emissions induced by fertilizer application in the US over the last century. Together, these studies demonstrate the isotopic composition of reactive N emissions can be an additional tool for investigators to source and trace reactive N emissions in both historical and

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.

A Review of Spatial Variation of Inorganic Nitrogen (N) Wet Deposition in China

PubMed Central

Liu, Lei; Zhang, Xiuying; Wang, Shanqian; Lu, Xuehe; Ouyang, Xiaoying

2016-01-01

Atmospheric nitrogen (N) deposition (Ndep), an important component of the global N cycle, has increased sharply in recent decades in China. Although there were already some studies on Ndep on a national scale, there were some gaps on the magnitude and the spatial patterns of Ndep. In this study, a national-scale Ndep pattern was constructed based on 139 published papers from 2003 to 2014 and the effects of precipitation (P), energy consumption (E) and N fertilizer use (FN) on spatial patterns of Ndep were analyzed. The wet deposition flux of NH4+-N, NO3--N and total Ndep was 6.83, 5.35 and 12.18 kg ha-1 a-1, respectively. Ndep exhibited a decreasing gradient from southeast to northwest of China. Through accuracy assessment of the spatial Ndep distribution and comparisons with other studies, the spatial Ndep distribution by Lu and Tian and this study both gained high accuracy. A strong exponential function was found between P and Ndep, FN and Ndep and E and Ndep, and P and FN had higher contribution than E on the spatial variation of Ndep. Fossil fuel combustion was the main contributor for NO3--N (86.0%) and biomass burning contributed 5.4% on the deposition of NO3--N. The ion of NH4+ was mainly from agricultural activities (85.9%) and fossil fuel combustion (6.0%). Overall, Ndep in China might be considerably affected by the high emissions of NOx and NH3 from fossil fuel combustion and agricultural activities. PMID:26731264

Influence of anthropogenic combustion emissions on the deposition of soluble aerosol iron to the ocean: Empirical estimates for island sites in the North Atlantic

NASA Astrophysics Data System (ADS)

Sholkovitz, Edward R.; Sedwick, Peter N.; Church, Thomas M.

2009-07-01

The results of several recent studies challenge the reigning paradigm that continental soil dust provides the only significant atmospheric source of dissolved iron to the surface ocean. This evidence includes correlations between the operational solubility of aerosol iron and atmospheric loadings of black carbon and aluminum-normalized vanadium and nickel, each of which are associated with emissions from the combustion of fossil fuel oil. These observations suggest that the relative solubility of aerosol iron, hence the eolian flux of soluble iron to the surface ocean, may be significantly impacted by anthropogenic oil combustion products. Using recent field data from the Bermuda region, we have developed an empirical method to estimate the solubility of aerosol iron using bulk aerosol concentrations of Fe, V and Al. We apply this method to a large body of published data from the AEROCE program for North Atlantic island sites on Tenerife, Barbados, Bermuda and Ireland, where the relative proportions of anthropogenic aerosols range from minor to major, respectively. Our aerosol iron solubility estimates suggest that anthropogenic emissions contribute approximately 70% and 85% of the annual dry deposition of soluble iron to the surface ocean near Bermuda and Ireland, respectively, implying that human activities have profoundly affected the iron budget of the North Atlantic region. The annual mean dry deposition of soluble iron at Barbados and Izana is dominated by soil dust. The anthropogenic contribution at these two sites ranges from 12% to 30% and is highly dependent on the soil dust solubility of Fe employed in the model. The low end (˜12%) estimate appears to be more representative of these high-dust sites.

Aerosol delivery of liposome-encapsulated ciprofloxacin: aerosol characterization and efficacy against Francisella tularensis infection in mice.

PubMed Central

Conley, J; Yang, H; Wilson, T; Blasetti, K; Di Ninno, V; Schnell, G; Wong, J P

1997-01-01

The aerosol delivery of liposome-encapsulated ciprofloxacin by using 12 commercially available jet nebulizers was evaluated in this study. Aerosol particles containing liposome-encapsulated ciprofloxacin generated by the nebulizers were analyzed with a laser aerodynamic particle sizer. Mean mass aerodynamic diameters (MMADs) and geometric standard deviations (GSDs) were determined, and the drug contents of the sampling filters from each run onto which aerosolized liposome-encapsulated ciprofloxacin had been deposited were analyzed spectrophotometrically. The aerosol particles of liposome-encapsulated ciprofloxacin generated by these nebulizers ranged from 1.94 to 3.5 microm, with GSDs ranging from 1.51 to 1.84 microm. The drug contents of the sampling filters exposed for 1 min to aerosolized liposome-encapsulated ciprofloxacin range from 12.7 to 40.5 microg/ml (0.06 to 0.2 mg/filter). By using the nebulizer selected on the basis of most desirable MMADs, particle counts, and drug deposition, aerosolized liposome-encapsulated ciprofloxacin was used for the treatment of mice infected with 10 times the 50% lethal dose of Francisella tularensis. All mice treated with aerosolized liposome-encapsulated ciprofloxacin survived the infection, while all ciprofloxacin-treated or untreated control mice succumbed to the infection (P < 0.001). These results suggest that aerosol delivery of liposome-encapsulated ciprofloxacin to the lower respiratory tract is feasible and that it may provide an effective therapy for the treatment of respiratory tract infections. PMID:9174185

Influence of Carrier Gas Composition on the Stress of Al₂O₃ Coatings Prepared by the Aerosol Deposition Method.

PubMed

Schubert, Michael; Exner, Jörg; Moos, Ralf

2014-08-05

Al₂O₃ films were prepared by the aerosol deposition method at room temperature using different carrier gas compositions. The layers were deposited on alumina substrates and the film stress of the layer was calculated by measuring the deformation of the substrate. It was shown that the film stress can be halved by using oxygen instead of nitrogen or helium as the carrier gas. The substrates were annealed at different temperature steps to gain information about the temperature dependence of the reduction of the implemented stress. Total relaxation of the stress can already be achieved at 300 °C. The XRD pattern shows crystallite growth and reduction of microstrain while annealing.

Effect of tubing deposition, breathing pattern, and temperature on aerosol mass distribution measured by cascade impactor.

PubMed

Gurses, Burak K; Smaldone, Gerald C

2003-01-01

Aerosols produced by nebulizers are often characterized on the bench using cascade impactors. We studied the effects of connecting tubing, breathing pattern, and temperature on mass-weighted aerodynamic particle size aerosol distributions (APSD) measured by cascade impaction. Our experimental setup consisted of a piston ventilator, low-flow (1.0 L/min) cascade impactor, two commercially available nebulizers that produced large and small particles, and two "T"-shaped tubes called "Tconnector(cascade)" and "Tconnector(nebulizer)" placed above the impactor and the nebulizer, respectively. Radiolabeled normal saline was nebulized using an airtank at 50 PSIG; APSD, mass balance, and Tconnector(cascade) deposition were measured with a gamma camera and radioisotope calibrator. Flow through the circuit was defined by the air tank (standing cloud, 10 L/min) with or without a piston pump, which superimposed a sinusoidal flow on the flow from the air tank (tidal volume and frequency of breathing). Experiments were performed at room temperature and in a cooled environment. With increasing tidal volume and frequency, smaller particles entered the cascade impactor (decreasing MMAD; e.g., Misty-Neb, 4.2 +/- 0.9 microm at lowest ventilation and 2.7 +/- 0.1 microm at highest, p = 0.042). These effects were reduced in magnitude for the nebulizer that produced smaller particles (AeroTech II, MMAD 1.8 +/- 0.1 to 1.3 +/- 0.1 microm; p = 0.0044). Deposition on Tconnector(cascade) increased with ventilation but was independent of cascade impactor flow. Imaging of the Tconnector(cascade) revealed a pattern of deposition unaffected by cascade impactor flow. These measurements suggest that changes in MMAD with ventilation were not artifacts of tubing deposition in the Tconnector(cascade). At lower temperatures, APSD distributions were more polydisperse. Our data suggest that, during patient inhalation, changes in particle distribution occur that are related to conditions in the tubing and

Characteristics of wet dissolved carbon deposition in a semi-arid catchment at the Loess Plateau, China

NASA Astrophysics Data System (ADS)

Wang, Linhua; Yen, Haw; Chen, Liding; E, Xinhui; Wang, Yafeng

2018-06-01

Wet dissolved carbon deposition is a critical node of the global carbon cycle, but little is known about dissolved organic and inorganic carbon (DOC and DIC) concentrations and fluxes in the semi-arid areas of the Loess Plateau Region (LPR). In this study, we measured variations in DOC and DIC concentrations in rainfalls at Yangjuangou Ecological Restoration and Soil and Water Observatory. Rainwater samples were collected in 16 rainfall events from July to September and the event-based, monthly concentrations and fluxes of DOC and DIC were quantified. The results showed that the event-based concentrations and fluxes of DOC and DIC were highly variable, ranging from 0.56 to 28.71 mg C L-1 and from 3.47 to 17.49 mg C L-1, respectively. The corresponding event-based fluxes ranged from 0.21-258.36 mg C m-2 and from 4.12 to 42.32 mg C m-2. The monthly concentrations of DOC and DIC were 24.62 and 4.30 (July), 3.58 and 10.52 (August), and 1.01 and 5.89 (September) mg C L-1, respectively. Thus, the monthly deposition fluxes of DOC and DIC were 541.64/94.60, 131.03/385.03, and 44.44/259.16 mg C m-2 for July, August, and September, respectively. In addition, the concentrations of DOC and DIC for the concentrated rainfall season (July-September) in the studied catchment were 7.06 and 7.00 mg C L-1, respectively. The estimated annual wet dissolved carbon depositions were 1.91 and 1.89 g C m-2 yr-1 for DOC and DIC, respectively. The results of this study suggest the variation in concentrations and fluxes of DOC and DIC and explore that these variation may be related to the dissolved carbon source and the rainfall characteristics during the concentrated rainfall season in the semi-arid catchment of the LPR. Furthermore, these results also suggest that dissolved carbon may be an important external input of carbon into terrestrial ecosystems.

Optimal Delivery of Aerosols to Infants During Mechanical Ventilation

PubMed Central

Azimi, Mandana; Hindle, Michael

2014-01-01

Abstract Purpose: The objective of this study was to determine optimal aerosol delivery conditions for a full-term (3.6 kg) infant receiving invasive mechanical ventilation by evaluating the effects of aerosol particle size, a new wye connector, and timing of aerosol delivery. Methods: In vitro experiments used a vibrating mesh nebulizer and evaluated drug deposition fraction and emitted dose through ventilation circuits containing either a commercial (CM) or new streamlined (SL) wye connector and 3-mm endotracheal tube (ETT) for aerosols with mass median aerodynamic diameters of 880 nm, 1.78 μm, and 4.9 μm. The aerosol was released into the circuit either over the full inhalation cycle (T1 delivery) or over the first half of inhalation (T2 delivery). Validated computational fluid dynamics (CFD) simulations and whole-lung model predictions were used to assess lung deposition and exhaled dose during cyclic ventilation. Results: In vitro experiments at a steady-state tracheal flow rate of 5 L/min resulted in 80–90% transmission of the 880-nm and 1.78-μm aerosols from the ETT. Based on CFD simulations with cyclic ventilation, the SL wye design reduced depositional losses in the wye by a factor of approximately 2–4 and improved lung delivery efficiencies by a factor of approximately 2 compared with the CM device. Delivery of the aerosol over the first half of the inspiratory cycle (T2) reduced exhaled dose from the ventilation circuit by a factor of 4 compared with T1 delivery. Optimal lung deposition was achieved with the SL wye connector and T2 delivery, resulting in 45% and 60% lung deposition for optimal polydisperse (∼1.78 μm) and monodisperse (∼2.5 μm) particle sizes, respectively. Conclusions: Optimization of selected factors and use of a new SL wye connector can substantially increase the lung delivery efficiency of medical aerosols to infants from current values of <1–10% to a range of 45–60%. PMID:24299500

Chemical aging of single and multicomponent biomass burning aerosol surrogate-particles by OH: Implications for cloud condensation nucleus activity

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

Thalman, R.; Thalman, R.; Wang, J.

Multiphase OH and O₃ oxidation reactions with atmospheric organic aerosol (OA) can influence particle physicochemical properties including composition, morphology, and lifetime. Chemical aging of initially insoluble or low soluble single-component OA by OH and O₃ can increase their water-solubility and hygroscopicity, making them more active as cloud condensation nuclei (CCN) and susceptible to wet deposition. However, an outstanding problem is whether the effects of chemical aging on their CCN activity are preserved when mixed with other organic or inorganic compounds exhibiting greater water-solubility. In this work, the CCN activity of laboratory-generated biomass burning aerosol (BBA) surrogate-particles exposed to OH andmore » O₃ is evaluated by determining the hygroscopicity parameter, κ, as a function of particle type, mixing state, and OH/O₃ exposure applying a CCN counter (CCNc) coupled to an aerosol flow reactor (AFR). Levoglucosan (LEV), 4-methyl-5-nitrocatechol (MNC), and potassium sulfate (KS) serve as representative BBA compounds that exhibit different hygroscopicity, water solubility, chemical functionalities, and reactivity with OH radicals, and thus exemplify the complexity of mixed inorganic/organic aerosol in the atmosphere. The CCN activities of all of the particles were unaffected by O₃ exposure. Following exposure to OH, κ of MNC was enhanced by an order of magnitude, from 0.009 to ~0.1, indicating that chemically-aged MNC particles are better CCN and more prone to wet deposition than pure MNC particles. No significant enhancement in κ was observed for pure LEV particles following OH exposure. κ of the internally-mixed particles was not affected by OH oxidation. Furthermore, the CCN activity of OH exposed MNC-coated KS particles is similar to the OH unexposed atomized 1:1 by mass MNC: KS binary-component particles. Our results strongly suggest that when OA is dominated by water-soluble organic carbon (WSOC) or inorganic ions

Chemical aging of single and multicomponent biomass burning aerosol surrogate particles by OH: implications for cloud condensation nucleus activity

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

Slade, J. H.; Thalman, R.; Wang, J.

Multiphase OH and O 3 oxidation reactions with atmospheric organic aerosol (OA) can influence particle physicochemical properties including composition, morphology, and lifetime. Chemical aging of initially insoluble or low-soluble single-component OA by OH and O 3 can increase their water solubility and hygroscopicity, making them more active as cloud condensation nuclei (CCN) and susceptible to wet deposition. However, an outstanding problem is whether the effects of chemical aging on their CCN activity are preserved when mixed with other organic or inorganic compounds exhibiting greater water solubility. In this work, the CCN activity of laboratory-generated biomass burning aerosol (BBA) surrogate particlesmore » exposed to OH and O 3 is evaluated by determining the hygroscopicity parameter, κ, as a function of particle type, mixing state, and OH and O 3 exposure applying a CCN counter (CCNc) coupled to an aerosol flow reactor (AFR). Levoglucosan (LEV), 4-methyl-5-nitrocatechol (MNC), and potassium sulfate (KS) serve as representative BBA compounds that exhibit different hygroscopicity, water solubility, chemical functionalities, and reactivity with OH radicals, and thus exemplify the complexity of mixed inorganic/organic aerosol in the atmosphere. The CCN activities of all of the particles were unaffected by O 3 exposure. Following exposure to OH, κ of MNC was enhanced by an order of magnitude, from 0.009 to ~ 0.1, indicating that chemically aged MNC particles are better CCN and more prone to wet deposition than pure MNC particles. No significant enhancement in κ was observed for pure LEV particles following OH exposure. κ of the internally mixed particles was not affected by OH oxidation. Furthermore, the CCN activity of OH-exposed MNC-coated KS particles is similar to the OH unexposed atomized 1 : 1 by mass MNC : KS binary-component particles. Our results strongly suggest that when OA is dominated by water-soluble organic carbon (WSOC) or inorganic ions

Chemical aging of single and multicomponent biomass burning aerosol surrogate particles by OH: implications for cloud condensation nucleus activity

DOE PAGES

Slade, J. H.; Thalman, R.; Wang, J.; ...

2015-09-14

Multiphase OH and O 3 oxidation reactions with atmospheric organic aerosol (OA) can influence particle physicochemical properties including composition, morphology, and lifetime. Chemical aging of initially insoluble or low-soluble single-component OA by OH and O 3 can increase their water solubility and hygroscopicity, making them more active as cloud condensation nuclei (CCN) and susceptible to wet deposition. However, an outstanding problem is whether the effects of chemical aging on their CCN activity are preserved when mixed with other organic or inorganic compounds exhibiting greater water solubility. In this work, the CCN activity of laboratory-generated biomass burning aerosol (BBA) surrogate particlesmore » exposed to OH and O 3 is evaluated by determining the hygroscopicity parameter, κ, as a function of particle type, mixing state, and OH and O 3 exposure applying a CCN counter (CCNc) coupled to an aerosol flow reactor (AFR). Levoglucosan (LEV), 4-methyl-5-nitrocatechol (MNC), and potassium sulfate (KS) serve as representative BBA compounds that exhibit different hygroscopicity, water solubility, chemical functionalities, and reactivity with OH radicals, and thus exemplify the complexity of mixed inorganic/organic aerosol in the atmosphere. The CCN activities of all of the particles were unaffected by O 3 exposure. Following exposure to OH, κ of MNC was enhanced by an order of magnitude, from 0.009 to ~ 0.1, indicating that chemically aged MNC particles are better CCN and more prone to wet deposition than pure MNC particles. No significant enhancement in κ was observed for pure LEV particles following OH exposure. κ of the internally mixed particles was not affected by OH oxidation. Furthermore, the CCN activity of OH-exposed MNC-coated KS particles is similar to the OH unexposed atomized 1 : 1 by mass MNC : KS binary-component particles. Our results strongly suggest that when OA is dominated by water-soluble organic carbon (WSOC) or inorganic ions

Chemical aging of single and multicomponent biomass burning aerosol surrogate-particles by OH: Implications for cloud condensation nucleus activity

DOE PAGES

Thalman, R.; Thalman, R.; Wang, J.; ...

2015-03-06

Multiphase OH and O₃ oxidation reactions with atmospheric organic aerosol (OA) can influence particle physicochemical properties including composition, morphology, and lifetime. Chemical aging of initially insoluble or low soluble single-component OA by OH and O₃ can increase their water-solubility and hygroscopicity, making them more active as cloud condensation nuclei (CCN) and susceptible to wet deposition. However, an outstanding problem is whether the effects of chemical aging on their CCN activity are preserved when mixed with other organic or inorganic compounds exhibiting greater water-solubility. In this work, the CCN activity of laboratory-generated biomass burning aerosol (BBA) surrogate-particles exposed to OH andmore » O₃ is evaluated by determining the hygroscopicity parameter, κ, as a function of particle type, mixing state, and OH/O₃ exposure applying a CCN counter (CCNc) coupled to an aerosol flow reactor (AFR). Levoglucosan (LEV), 4-methyl-5-nitrocatechol (MNC), and potassium sulfate (KS) serve as representative BBA compounds that exhibit different hygroscopicity, water solubility, chemical functionalities, and reactivity with OH radicals, and thus exemplify the complexity of mixed inorganic/organic aerosol in the atmosphere. The CCN activities of all of the particles were unaffected by O₃ exposure. Following exposure to OH, κ of MNC was enhanced by an order of magnitude, from 0.009 to ~0.1, indicating that chemically-aged MNC particles are better CCN and more prone to wet deposition than pure MNC particles. No significant enhancement in κ was observed for pure LEV particles following OH exposure. κ of the internally-mixed particles was not affected by OH oxidation. Furthermore, the CCN activity of OH exposed MNC-coated KS particles is similar to the OH unexposed atomized 1:1 by mass MNC: KS binary-component particles. Our results strongly suggest that when OA is dominated by water-soluble organic carbon (WSOC) or inorganic ions

Contributions of wastewater, runoff and sewer deposit erosion to wet weather pollutant loads in combined sewer systems.

PubMed

Gasperi, J; Gromaire, M C; Kafi, M; Moilleron, R; Chebbo, G

2010-12-01

An observatory of urban pollutants was created in Paris for the purpose of assessing the dynamics of wastewater and wet weather flow (WW and WWF) pollutant loads within combined sewers. This observatory is composed of six urban catchments, covering land areas ranging in size from 42 ha to 2581 ha. For a wide array of parameters including total suspended solids (TSS), chemical and biochemical oxygen demand (COD and BOD(5)), total organic carbon (TOC), total Kjeldahl nitrogen (TKN), heavy metals (Cu and Zn) and polycyclic aromatic hydrocarbons (PAHs), this article is intended to evaluate the contributions of wastewater, runoff and in-sewer processes to WWF pollutant loads through the use of an entry-exit mass balance approach. To achieve this objective, a total of 16 rain events were sampled on these sites between May 2003 and February 2006. This study has confirmed that at the considered catchment scale (i.e. from 42 ha to 2581 ha) the production and transfer processes associated with WWF pollutant loads do not vary with basin scale. Entry-exit chemical mass balances over all catchments and for a large number of rain events indicate that wastewater constitutes the main source of organic and nitrogenous pollution, while runoff is the predominant source of Zn. For Cu, PAHs and TSS, the calculation underscores the major role played by in-sewer processes, specifically by sediment erosion, as a source of WWF pollution. A significant loss of dissolved metals was also observed during their transfer within the sewer network, likely as a consequence of the adsorption of dissolved metals on TSS and/or on sewer deposits. Moreover, the nature of eroded particles was examined and compared to the various sewer deposits. This comparison has highlighted that such particles exhibit similar organic and PAH contents to those measured in the organic layer, thus suggesting that the deposit eroded during a wet weather period is organic and of a nature comparable to the organic layer

Development and evaluation of the aerosol dynamics and gas phase chemistry model ADCHEM

NASA Astrophysics Data System (ADS)

Roldin, P.; Swietlicki, E.; Schurgers, G.; Arneth, A.; Lehtinen, K. E. J.; Boy, M.; Kulmala, M.

2011-06-01

The aim of this work was to develop a model suited for detailed studies of aerosol dynamics, gas and particle phase chemistry within urban plumes, from local scale (1 × 1 km2) to regional scale. This article describes and evaluates the trajectory model for Aerosol Dynamics, gas and particle phase CHEMistry and radiative transfer (ADCHEM). The model treats both vertical and horizontal dispersion perpendicular to an air mass trajectory (2-space dimensions). The Lagrangian approach enables a more detailed representation of the aerosol dynamics, gas and particle phase chemistry and a finer spatial and temporal resolution compared to that of available regional 3D-CTMs. These features make it among others well suited for urban plume studies. The aerosol dynamics model includes Brownian coagulation, dry deposition, wet deposition, in-cloud processing, condensation, evaporation, primary particle emissions and homogeneous nucleation. The organic mass partitioning was either modeled with a 2-dimensional volatility basis set (2D-VBS) or with the traditional two-product model approach. In ADCHEM these models consider the diffusion limited and particle size dependent condensation and evaporation of 110 and 40 different organic compounds respectively. The gas phase chemistry model calculates the gas phase concentrations of 61 different species, using 130 different chemical reactions. Daily isoprene and monoterpene emissions from European forests were simulated separately with the vegetation model LPJ-GUESS, and included as input to ADCHEM. ADCHEM was used to simulate the ageing of the urban plumes from the city of Malmö in southern Sweden (280 000 inhabitants). Several sensitivity tests were performed concerning the number of size bins, size structure method, aerosol dynamic processes, vertical and horizontal mixing, coupled or uncoupled condensation and the secondary organic aerosol formation. The simulations show that the full-stationary size structure gives accurate results

Development and evaluation of the aerosol dynamic and gas phase chemistry model ADCHEM

NASA Astrophysics Data System (ADS)

Roldin, P.; Swietlicki, E.; Schurgers, G.; Arneth, A.; Lehtinen, K. E. J.; Boy, M.; Kulmala, M.

2010-08-01

The aim of this work was to develop a model ideally suited for detailed studies on aerosol dynamics, gas and particle phase chemistry within urban plumes, from local scale (1×1 km2) to regional or global scale. This article describes and evaluates the trajectory model for Aerosol Dynamics, gas and particle phase CHEMistry and radiative transfer (ADCHEM), which has been developed and used at Lund University since 2007. The model treats both vertical and horizontal dispersion perpendicular to an air mass trajectory (2-space dimensions), which is not treated in Lagrangian box-models (0-space dimensions). The Lagrangian approach enables a more detailed representation of the aerosol dynamics, gas and particle phase chemistry and a finer spatial and temporal resolution compared to that of available regional 3D-CTMs. These features make it among others ideally suited for urban plume studies. The aerosol dynamics model includes Brownian coagulation, dry deposition, wet deposition, in-cloud processing, condensation, evaporation, primary particle emissions and homogeneous nucleation. The gas phase chemistry model calculates the gas phase concentrations of 63 different species, using 119 different chemical reactions. Daily isoprene and monoterpene emissions from European forests were simulated separately with the vegetation model LPJ-GUESS, and included as input to ADCHEM. ADCHEM was used to simulate the ageing of the urban plumes from the city of Malmö in Southern Sweden (280 000 inhabitants). Several sensitivity tests were performed concerning the number of size bins, size structure method, coupled or uncoupled condensation, the volatility basis set (VBS) or traditional 2-product model for secondary organic aerosol formation, different aerosol dynamic processes and vertical and horizontal mixing. The simulations show that the full-stationary size structure gives accurate results with little numerical diffusion when more than 50 size bins are used between 1.5 and 2500 nm

Aerosol processing in stratiform clouds in ECHAM6-HAM

NASA Astrophysics Data System (ADS)

Neubauer, David; Lohmann, Ulrike; Hoose, Corinna

2013-04-01

chemical components as well as 5 tracers for aerosol particles in ice crystals. This allows simulations of aerosol processing in warm, mixed-phase (e.g. through the Bergeron-Findeisen process) and ice clouds. The fixed scavenging ratios used for wet deposition in clouds in standard HAM are replaced by an explicit treatment of collision of cloud droplets/ice crystals with interstitial aerosol particles. Nucleation scavenging of aerosol particles by acting as cloud condensation nuclei or ice nuclei, freezing and evaporation of cloud droplets and melting and sublimation of ice crystals are treated explicitly. In extension to previous studies, aerosol particles from evaporating precipitation are released to modes which correspond to their size. Cloud processing of aerosol particles changes their size distribution and hence influences cloud droplet and ice crystal number concentrations as well as precipitation rate, which in turn affects aerosol concentrations. Results will be presented at the conference. Hoose et al., JGR, 2008a, doi: 10.1029/2007JD009251 Hoose et al., ACP, 2008b, doi: 10.5194/acp-8-6939-2008 Stevens et al., 2013, submitted Stier et al., ACP, 2005, doi: 10.5194/acp-5-1125-2005

Aerosol optical characteristics and their vertical distributions under enhanced haze pollution events: effect of the regional transport of different aerosol types over eastern China

NASA Astrophysics Data System (ADS)

Sun, Tianze; Che, Huizheng; Qi, Bing; Wang, Yaqiang; Dong, Yunsheng; Xia, Xiangao; Wang, Hong; Gui, Ke; Zheng, Yu; Zhao, Hujia; Ma, Qianli; Du, Rongguang; Zhang, Xiaoye

2018-03-01

The climatological variation of aerosol properties and the planetary boundary layer (PBL) during 2013-2015 over the Yangtze River Delta (YRD) region were investigated by employing ground-based Micro Pulse Lidar (MPL) and CE-318 sun-photometer observations. Combining Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite products, enhanced haze pollution events affected by different types of aerosol over the YRD region were analyzed through vertical structures, spatial distributions, backward trajectories, and the potential source contribution function (PSCF) model. The results show that aerosols in the YRD are dominated by fine-mode particles, except in March. The aerosol optical depth (AOD) in June and September is higher due to high single scattering albedo (SSA) from hygroscopic growth, but it is lower in July and August due to wet deposition from precipitation. The PBL height (PBLH) is greater (means ranging from 1.23 to 1.84 km) and more variable in the warmer months of March to August, due to the stronger diurnal cycle and exchange of heat. Northern fine-mode pollutants are brought to the YRD at a height of 1.5 km. The SSA increases, blocking the radiation to the surface, and cooling the surface, thereby weakening turbulence, lowering the PBL, and in turn accelerating the accumulation of pollutants, creating a feedback to the cooling effect. Originated from the deserts in Xinjiang and Inner Mongolia, long-range transported dust masses are seen at heights of about 2 km over the YRD region with an SSA440 nm below 0.84, which heat air and raise the PBL, accelerating the diffusion of dust particles. Regional transport from biomass-burning spots to the south of the YRD region bring mixed aerosol particles at a height below 1.5 km, resulting in an SSA440 nm below 0.89. During the winter, the accumulation of the local emission layer is facilitated by stable weather conditions

The Increasing Importance of Deposition of Reduced Nitrogen ...

EPA Pesticide Factsheets

Rapid development of agricultural activities and fossil fuel combustion in the United States has led to a great increase in reactive nitrogen (Nr) emissions in the second half of the twentieth century. These emissions have been linked to excess nitrogen (N) deposition (i.e. deposition exceeding critical loads) in natural ecosystems through dry and wet deposition pathways. U.S. efforts to reduce nitrogen oxides (NOx) emissions since the 1970s have substantially reduced nitrate deposition, as evidenced by decreasing trends in long-term wet deposition data. These decreases in nitrate deposition along with increases in wet ammonium deposition have altered the balance between oxidized (nitrate) and reduced (ammonium) nitrogen deposition. Across most of the U.S., wet deposition has transitioned from being nitrate dominated in the 1980s to ammonium dominated in recent years. Because ammonia has not been a regulated air pollutant in the U.S., it has historically not been commonly measured. Recent measurement efforts, however, provide a more comprehensive look at ammonia concentrations across several regions of the U.S. These data, along with more routine measurements of gas phase nitric acid and fine particle ammonium and nitrate, permit new insight into the balance of oxidized and reduced nitrogen in the total (wet + dry) U.S. inorganic reactive nitrogen deposition budget. Utilizing two years of N-containing gas and fine particle observations from 37 U.S. monitoring si

Below-cloud wet scavenging of soluble inorganic ions by rain in Beijing during the summer of 2014.

PubMed

Xu, Danhui; Ge, Baozhu; Wang, Zifa; Sun, Yele; Chen, Yong; Ji, Dongshen; Yang, Ting; Ma, Zhiqiang; Cheng, Nianliang; Hao, Jianqi; Yao, Xuefeng

2017-11-01

Wet deposition is one of the most important and efficient removal mechanisms in the reduction of air pollution. As a key parameter determining wet deposition, the wet scavenging coefficient (WSC) is widely used in chemical transport models (CTMs) and reported values have large uncertainties. In this study, a high-resolution observational dataset of the soluble inorganic aerosols (SO 4 2- , NO 3 - and NH 4 + , hereafter SNA) in the air and in rainwater during multiple precipitation events was collected using sequential sampling and used to estimate the below-cloud WSC in Beijing during the summer of 2014. The average concentrations of SNA in precipitation during the observational period were 7.9 mg/L, 6.2 mg/L and 4.6 mg/L, with the contributions from below-cloud scavenging constituting 56%, 61% and 47% of this, respectively. The scavenging ratios of SNA (i.e., the ratio of the concentrations in rain to concentrations in the air) were used with the height of the cloud base and the precipitation intensity to estimate the WSC. The estimated WSC of SO 4 2- is comparable to that reported elsewhere. The relationship between the below-cloud WSC and the precipitation intensity followed an exponential power distribution (K=aP b ) for SNA. In contrast to previous studies, this study considers the differences between the chemical compositions of the SNA, with the highest WSC for NO 3 - , followed by those of SO 4 2- and NH 4 + . Therefore, we recommend that CTMs include ion specific WSCs in the future. Copyright © 2017 Elsevier Ltd. All rights reserved.

Long-term Chemical Characterization of Submicron Aerosol Particles in the Amazon Forest - ATTO Station

NASA Astrophysics Data System (ADS)

Carbone, S.; Brito, J.; Rizzo, L. V.; Holanda, B. A.; Cirino, G. G.; Saturno, J.; Krüger, M. L.; Pöhlker, C.; Ng, N. L.; Xu, L.; Andreae, M. O.; Artaxo, P.

2015-12-01

The study of the chemical composition of aerosol particles in the Amazon forest represents a step forward to understand the strong coupling between the atmosphere and the forest. For this reason submicron aerosol particles were investigated in the Amazon forest, where biogenic and anthropogenic aerosol particles coexist at the different seasons (wet/dry). The measurements were performed at the ATTO station, which is located about 150 km northeast of Manaus. At ATTO station the Aerosol chemical speciation monitor (ACSM, Aerodyne) and the Multiangle absorption photometer (MAAP, Thermo 5012) have been operated continuously from March 2014 to July 2015. In this study, long-term measurements (near-real-time, ~30 minutes) of PM1 chemical composition were investigated for the first time in this environment.The wet season presented lower concentrations than the dry season (~5 times). In terms of chemical composition, both seasons were dominated by organics (75 and 63%) followed by sulfate (11 and 13%). Nitrate presented different ratio values between the mass-to-charges 30 to 46 (main nitrate fragments) suggesting the presence of nitrate as inorganic and organic nitrate during both seasons. The results indicated that about 75% of the nitrate signal was from organic nitrate during the dry season. In addition, several episodes with elevated amount of chloride, likely in the form of sea-salt from the Atlantic Ocean, were observed during the wet season. During those episodes, chloride comprised up to 7% of the PM1. During the dry season, chloride was also observed; however, with different volatility, which suggested that Chloride was present in different form and source. Moreover, the constant presence of sulfate and BC during the wet season might be related to biomass burning emissions from Africa. BC concentration was 2.5 times higher during the dry season. Further characterization of the organic fraction was accomplished with the positive matrix factorization (PMF), which

Impact of absorbing aerosol deposition on snow albedo reduction over the southern Tibetan plateau based on satellite observations

NASA Astrophysics Data System (ADS)

Lee, Wei-Liang; Liou, K. N.; He, Cenlin; Liang, Hsin-Chien; Wang, Tai-Chi; Li, Qinbin; Liu, Zhenxin; Yue, Qing

2017-08-01

We investigate the snow albedo variation in spring over the southern Tibetan Plateau induced by the deposition of light-absorbing aerosols using remote sensing data from moderate resolution imaging spectroradiometer (MODIS) aboard Terra satellite during 2001-2012. We have selected pixels with 100 % snow cover for the entire period in March and April to avoid albedo contamination by other types of land surfaces. A model simulation using GEOS-Chem shows that aerosol optical depth (AOD) is a good indicator for black carbon and dust deposition on snow over the southern Tibetan Plateau. The monthly means of satellite-retrieved land surface temperature (LST) and AOD over 100 % snow-covered pixels during the 12 years are used in multiple linear regression analysis to derive the empirical relationship between snow albedo and these variables. Along with the LST effect, AOD is shown to be an important factor contributing to snow albedo reduction. We illustrate through statistical analysis that a 1-K increase in LST and a 0.1 increase in AOD indicate decreases in snow albedo by 0.75 and 2.1 % in the southern Tibetan Plateau, corresponding to local shortwave radiative forcing of 1.5 and 4.2 W m-2, respectively.

[Atmospheric depositions of biogenic elements and their ecological effects on marine ecosystem of Jiaozhou Bay: A review].

PubMed

Xing, Jian Wei; Song, Jin Ming; Yuan, Hua Mao; Li, Xue Gang; Li, Ning; Duan, Li Qin; Qu, Bao Xiao; Kang, Xu Ming

2017-01-01

As a typical semi-closed bay, Jiaozhou Bay, is remarkably affected by human activities. Biogenic elements transported into the oceans by the atmospheric deposition of anthropogenic particles can lead to profound impacts on the ecosystem of Jiaozhou Bay. In this paper, the researches of atmospheric dry and wet depositions in the Jiaozhou Bay were systematically summarized from the following three aspects: study methods, variation characteristics of the fluxes and their influencing factors and the ecological effects of atmospheric deposition. The concentrations and fluxes of nitrogen species in atmospheric dry and wet depositions were very high in the Jiaozhou Bay compared with other bays, estuaries and marginal seas around the world. The dissolved inorganic nitrogen (DIN) was the main component of the total dissolved nitrogen (TDN) and the dissolved organic nitrogen (DON) accounted for 22%-31% of TDN. However, the concentrations and fluxes of phosphate and silicate species were very low. The atmospheric deposition fluxes of (NO 3 - -N+NO 2 - -N) were slightly higher than terrestrial inputs, while the fluxes of NH 4 + -N, PO 4 3- -P and SiO 3 2- -Si were very low compared with terrestrial inputs. The concentration of total suspended particulates (TSP) in the air, the intensity of the emission sources, precipitation amount and meteorological conditions are the major factors influencing the atmospheric depositions of biogenic elements, which can increase the primary productivity, change the structure of nutrients and the structure of phytoplankton communities in surface seawater and further promote the succession of phytoplankton dominant species from diatom to dinoflagellate in the Jiaozhou Bay. On that basis, the future research should be focused on constructing the monitoring network for atmospheric dry and wet depositions, accurately quantifying the deposition rates of aerosol particles of different forms and sizes, recognizing the ecological effects and

Regional background aerosols over the Balearic Islands over the last 3 years: ground-based concentrations, atmospheric deposition and sources

NASA Astrophysics Data System (ADS)

Cerro, Jose Carlos; Pey, Jorge; Bujosa, Carles; Caballero, Sandra; Alastuey, Andres; Sicard, Michael; Artiñano, Begoña; Querol, Xavier

2013-04-01

In the context of the ChArMEx (The Chemistry-Aerosol Mediterranean Experiment, https://charmex.lsce.ipsl.fr) initiative, a 3-year study over a regional background environment (Can Llompart, CLP) in Mallorca has been conducted. Ground-based PM mass concentrations, gaseous pollutants and meteorological parameters were continuously registered from 2010 to 2012. Since the beginning of the campaign, PM10 daily samples for chemical determinations were obtained every 4 days, and dry and wet deposition samples were collected every week. Moreover, additional instruments (condensation particle counter, multi-angle absorption photometer, airpointer, sequential high and low volume samplers) were deployed during intensive filed campaigns in 2011 and 2012, as well as the sampling frequency was intensified. In the laboratory, PM samples were analyzed for inorganic compounds, and organic and elemental carbon following different approaches. In addition, n-alkanes, iso-alkanes, antiso-alkanes, levoglucosan, alkanoic acids and cholesterol were determined by GC-MS chromatography in a selection of 30 samples. Mean PM10, PM2.5 and PM1 concentrations in the period 2010-2012 reached 17, 11, and 8 µg/m3 respectively. Mass concentrations displayed marked seasonal trends, with much higher background levels in summer due to stagnant conditions over the western Mediterranean and increased frequency of Saharan dust events. Likewise, diverse-intensity peaks of coarse PM due to African dust inputs were observed along the year. On average, African dust in PM10 accounted for 1.0-1.5 µg/m3. Sporadic pollution events, characterized by most of the particles in the fine mode, were related to the transport of anthropogenic polluted air masses from central and eastern Europe. Wet and dry atmospheric deposition samples are being analyzed to quantify the deposition fluxes for different soluble and insoluble compounds. On average, PM10 composition is made up of organic matter (23%), mineral components (17

Predicting the Mineral Composition of Dust Aerosols. Part 1; Representing Key Processes

NASA Technical Reports Server (NTRS)

Perlwitz, J. P.; Garcia-Pando, C. Perez; Miller, R. L.

2015-01-01

Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wetsieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to

The Aerosol Coarse Mode Initiative

NASA Astrophysics Data System (ADS)

Arnott, W. P.; Adhikari, N.; Air, D.; Kassianov, E.; Barnard, J.

2014-12-01

Many areas of the world show an aerosol volume distribution with a significant coarse mode and sometimes a dominant coarse mode. The large coarse mode is usually due to dust, but sea salt aerosol can also play an important role. However, in many field campaigns, the coarse mode tends to be ignored, because it is difficult to measure. This lack of measurements leads directly to a concomitant "lack of analysis" of this mode. Because, coarse mode aerosols can have significant effects on radiative forcing, both in the shortwave and longwave spectrum, the coarse mode -- and these forcings -- should be accounted for in atmospheric models. Forcings based only on fine mode aerosols have the potential to be misleading. In this paper we describe examples of large coarse modes that occur in areas of large aerosol loading (Mexico City, Barnard et al., 2010) as well as small loadings (Sacramento, CA; Kassianov et al., 2012; and Reno, NV). We then demonstrate that: (1) the coarse mode can contribute significantly to radiative forcing, relative to the fine mode, and (2) neglecting the coarse mode may result in poor comparisons between measurements and models. Next we describe -- in general terms -- the limitations of instrumentation to measure the coarse mode. Finally, we suggest a new initiative aimed at examining coarse mode aerosol generation mechanisms; transport and deposition; chemical composition; visible and thermal IR refractive indices; morphology; microphysical behavior when deposited on snow and ice; and specific instrumentation needs. Barnard, J. C., J. D. Fast, G. Paredes-Miranda, W. P. Arnott, and A. Laskin, 2010: Technical Note: Evaluation of the WRF-Chem "Aerosol Chemical to Aerosol Optical Properties" Module using data from the MILAGRO campaign, Atmospheric Chemistry and Physics, 10, 7325-7340. Kassianov, E. I., M. S. Pekour, and J. C. Barnard, 2012: Aerosols in Central California: Unexpectedly large contribution of coarse mode to aerosol radiative forcing

Increased exposure to pollutant aerosols under high voltage power lines.

PubMed

Fews, A P; Henshaw, D L; Keitch, P A; Close, J J; Wilding, R J

1999-12-01

To assess increased exposure to airborne pollutants near power lines by investigating theoretically and experimentally the behaviour of 222Rn decay product marker aerosols in the 50 Hz electric field under power lines. The behaviour of aerosols in outdoor air including those carrying 222Rn decay products was modelled theoretically in the presence of an AC field. TASTRAK alpha-particle spectroscopy was used to characterize 218Po and 214Po aerosols outdoors. Sampling points were chosen along a line at right angles up to 200 m from a number of high voltage power (transmission) lines. Each sampling point comprised an arrangement of mutually orthogonal TASTRAK detectors. Exposures were carried out at different power line locations in various weather conditions. The model predicts a two- to three-fold increase in deposition of aerosols on spherical surfaces mimicking the human head under high voltage power lines. Experimental measurements using detectors mounted on grounded metal spheres showed an enhanced deposition of both 218Po and 214Po aerosols. Enhanced 218Po deposition on 400 kV lines ranged from 1.96+/-0.15 to 2.86+/-0.32. Enhanced 214Po deposition on 275 kV and 132 kV lines were 1.43+/-0.07 and 1.11+/-0.21, respectively, where the latter value was not significant. The observations demonstrate a mode of increased exposure to pollutant aerosols under high voltage power lines by increased deposition on the body. The total (indoor + outdoor) 218Po and 214Po dose to the basal layer of facial skin is estimated to be increased by between 1.2 and 2.0 for 10% of time spent outdoors under high voltage power lines.

A novel ultrasonic aerosol generator.

PubMed

Davies, A; Hudson, N; Pirie, L

1995-07-01

An ultrasonic aerosol generator constructed from a domestic humidifier is described which has been used to produce liquid aerosols for physiological investigations. The instrument was constructed from a Pifco domestic humidifier modified to include an energy guide to direct the oscillations of the transducer through the coupling water, which would normally be aerosolized, onto a small membrane based sample chamber containing the liquid to be aerosolized. The size distribution of the aerosol produced was found to be between 2 and 6 mm, optimum for diffuse intrapulmonary deposition. Up to 4 ml/min of aqueous liquid was used; however the sample chamber could be made small enough to contain economic amounts of expensive material to administer by inhalation. The instrument has proved to be reliable over a period of three years.