Aerosol properties and meteorological conditions in the city of Buenos Aires, Argentina, during the resuspension of volcanic ash from the Puyehue-Cordón Caulle eruption

NASA Astrophysics Data System (ADS)

Graciela Ulke, Ana; Torres Brizuela, Marcela M.; Raga, Graciela B.; Baumgardner, Darrel

2016-09-01

The eruption in June 2011 of the Puyehue-Cordón Caulle Volcanic Complex in Chile impacted air traffic around the Southern Hemisphere for several months after the initial ash emissions. The ash deposited in vast areas of the Patagonian Steppe was subjected to the strong wind conditions prevalent during the austral winter and spring experiencing resuspension over various regions of Argentina. In this study we analyze the meteorological conditions that led to the episode of volcanic ash resuspension which impacted the city of Buenos Aires and resulted in the closure of the two main airports in Buenos Aires area (Ezeiza and Aeroparque) on 16 October 2011. A relevant result is that resuspended material (volcanic ash plus dust) imprints a distinguishable feature within the atmospheric thermodynamic vertical profiles. The thermodynamic soundings show the signature of "pulses of drying" in layers associated with the presence of hygroscopic ash in the atmosphere that has already been reported in similar episodes after volcanic eruptions in other parts of the world. This particular footprint can be used to detect the probable existence of volcanic ash layers. This study also illustrates the utility of ceilometers to detect not only cloud base at airports but also volcanic ash plumes at the boundary layer and up to 7 km altitude. Aerosol properties measured in the city during the resuspension episode indicate the presence of enhanced concentrations of aerosol particles in the boundary layer along with spectral signatures in the measurements at the Buenos Aires AERONET site typical of ash plus dust advected towards the city. The mandatory aviation reports from the National Weather Service about airborne and deposited volcanic ash at the airport near the measurement site (Aeroparque) correlate in time with the enhanced concentrations. The presence of the resuspended material was detected by the CALIOP lidar overpassing the region. Since the dynamics of ash resuspension and

Atmospheric deposition maps for the Rocky Mountains

USGS Publications Warehouse

Nanus, L.; Campbell, D.H.; Ingersoll, G.P.; Clow, D.W.; Mast, M.A.

2003-01-01

Variability in atmospheric deposition across the Rocky Mountains is influenced by elevation, slope, aspect, and precipitation amount and by regional and local sources of air pollution. To improve estimates of deposition in mountainous regions, maps of average annual atmospheric deposition loadings of nitrate, sulfate, and acidity were developed for the Rocky Mountains by using spatial statistics. A parameter-elevation regressions on independent slopes model (PRISM) was incorporated to account for variations in precipitation amount over mountainous regions. Chemical data were obtained from the National Atmospheric Deposition Program/National Trends Network and from annual snowpack surveys conducted by the US Geological Survey and National Park Service, in cooperation with other Federal, State and local agencies. Surface concentration maps were created by ordinary kriging in a geographic information system, using a local trend and mathematical model to estimate the spatial variance. Atmospheric-deposition maps were constructed at 1-km resolution by multiplying surface concentrations from the kriged grid and estimates of precipitation amount from the PRISM model. Maps indicate an increasing spatial trend in concentration and deposition of the modeled constituents, particularly nitrate and sulfate, from north to south throughout the Rocky Mountains and identify hot-spots of atmospheric deposition that result from combined local and regional sources of air pollution. Highest nitrate (2.5-3.0kg/ha N) and sulfate (10.0-12.0kg/ha SO4) deposition is found in northern Colorado.

Observations of Near-Bed Deposition and Resuspension Processes at the Fluvial-Tidal Transition Using High Resolution Adcp, Adv, and Lisst

NASA Astrophysics Data System (ADS)

Haught, D. R.; Stumpner, P.

2012-12-01

Processes that determine deposition and resuspension of sediment in fluvial and tidal systems are complicated and difficult to predict because of turbulence-sediment interaction. In fluvial systems net sediment deposition rates near the bed are determined by shear stresses that occur when turbulence interacts with the bed and the entrained sediment above. In tidal systems, processes are driven primarily by the confounding factors of slack water and reversing flow. In this study we investigate near-bed sediment fluxes, settling velocities and sediment size distributions during a change from a fluvial signal to a tidal signal. In order to examine these processes a high resolution, high frequency ADCP, ADV, water quality sonde and LISST data were collocated at the fluvial-tidal transition in the Sacramento River at Freeport, CA. Data were collected at 15-30 minute increments for a month`. Data were dissevered into fluvial and tidal components. Acoustic backscatterence was used as a surrogate to sediment concentration and sediment flux () was calculated from the turbulence properties. Settling velocities were computed from the diffusion-advection equation assuming equilibrium of settling and re-suspension fluxes. Particle density was back-calculated from median particle diameter and calculated settling velocities (Reynolds number<0.5) using Stokes' law. Preliminary results suggest that during peak fluvial discharge that the diffusion-advection gives poor estimates of settling velocities as inferred from particle densities above 3500 kg/m3. During the transition from fluvial to tidal signal and throughout the tidal signal particle densities range from 2650 kg/m3 to 1000 kg/m3, suggesting that settling velocities were accurately estimated. Thus the equilibrium assumption appears poor during high fluvial discharge and reasonable during low fluvial discharge when tidal signal is dominant.

Evaluation of Resuspension from Propeller Wash in DoD Harbors

DTIC Science & Technology

2016-05-01

RESUSPENSION CHARACTERIZATION ............................................................. 11 5.3 DEEP -DRAFT RESUSPENSION STUDY IN PEARL HARBOR...RESUSPENSION FROM A DEEP -DRAFT VESSEL .............................................. 21 6.4.1 Field Observations Using ADCP...event resulted in validation of the FANS model for prediction of sediment resuspension by a deep draft vessel. While working on the resuspension

Near-Bottom Turbulence and Sediment Resuspension Induced by Nonlinear Internal Waves

DTIC Science & Technology

2011-09-30

boundary layer (BBL) turbulence and particulate resuspension leading to benthic nepheloid layer ( BNL ) formation. OBJECTIVES The specific...identify mechanisms for the capturing of nearbed particles by the BBL-turbulence and their transport/deposition into BNLs . • Analyze field...resuspended particle distributions under NLIWs, a reliable proxy of BNLs , can be used to quantify the transmission or backscatter of optical/acoustic

Short-term variability of mineral dust, metals and carbon emission from road dust resuspension

NASA Astrophysics Data System (ADS)

Amato, Fulvio; Schaap, Martijn; Denier van der Gon, Hugo A. C.; Pandolfi, Marco; Alastuey, Andrés; Keuken, Menno; Querol, Xavier

2013-08-01

Particulate matter (PM) pollution in cities has severe impact on morbidity and mortality of their population. In these cities, road dust resuspension contributes largely to PM and airborne heavy metals concentrations. However, the short-term variation of emission through resuspension is not well described in the air quality models, hampering a reliable description of air pollution and related health effects. In this study we experimentally show that the emission strength of resuspension varies widely among road dust components/sources. Our results offer the first experimental evidence of different emission rates for mineral dust, heavy metals and carbon fractions due to traffic-induced resuspension. Also, the same component (or source) recovers differently in a road in Barcelona (Spain) and a road in Utrecht (The Netherlands). This finding has important implications on atmospheric pollution modelling, mostly for mineral dust, heavy metals and carbon species. After rain events, recoveries were generally faster in Barcelona rather than in Utrecht. The largest difference was found for the mineral dust (Al, Si, Ca). Tyre wear particles (organic carbon and zinc) recovered faster than other road dust particles in both cities. The source apportionment of road dust mass provides useful information for air quality management.

Wind Induced Sediment Resuspension in a Microtidal Estuary

NASA Technical Reports Server (NTRS)

Booth, J. G.; Miller, R. L.; McKee, B. A.; Leathers, R. A.

1999-01-01

Bottom sediment resuspension frequency, duration and extent (% of bottom sediments affected) were characterized for the fifteen month period from September 1995 to January 1997 for the Barataria Basin, LA. An empirical model of sediment resuspension as a function of wind speed, direction, fetch and water depth was derived from wave theory. Water column turbidity was examined by processing remotely sensed radiance information from visible and near-IR AVHRR imagery. Based on model predictions, wind induced resuspension occurred during all seasons of this study. Seasonal characteristics for resuspension reveal that late fall, winter and early spring are the periods of most frequent and intense resuspension. Model predictions of the critical wind speed required to induce resuspension indicate that winds of 4 m/s (averaged over all wind directions resuspend approximately 50% of bottom sediments in the water bodies examined. Winds of this magnitude (4 m/s) occurred for 80% of the time during the late fall, winter and early spring and for approximately 30% of the time during the summer. More than 50% of the bottom sedimets are resuspended throughout the year, indicating the importance of resuspension as a process affecting sediment and biogeochemical fluxes in the Barataria Basin.

Impact of Natural (Storm) and Anthropogenic (Trawl) Resuspension the Sediment Transport on the Gulf of Lion's Shelf (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Ferre, B.; Durrieu de Madron, X.; Estournel, C.; Ulses, C.; Le Corre, G.

2006-12-01

Modern sediment deposits on continental margins form a vast reservoir of particulate matter that is regularly affected by resuspension processes. On shelves with strong fishing activity, resuspension by bottom trawling processes can modify the scale of natural disturbance by waves and currents. Recent field data shows that the impact of bottom trawls on the resuspension of the fine sediments per unit surface is comparable with that of the largest storms. We assessed the impact of both natural and anthropogenic processes on the dispersal of river-borne particles and shelf sediments on the Gulf of Lion's Shelf. Realistic numerical simulations of resuspension and transport forced by currents and waves or by a fleet of bottom trawlers were developed. Simulations were conducted for a 16-month period to characterize the seasonal variability. The sediment dynamics takes into account bed armoring, ripple geometry and the cohesive and non-cohesive characteristics of the sediment. Essential but uncertain parameters (clay content, erosion fluxes and critical shear stress for cohesive sediment) were set with existing data. Resuspension by waves and currents is controlled by the shear stress, whereas resuspension by the bottom trawler fleet is controlled by its density and distribution. Natural resuspension by waves and currents mostly occurs during short winter episodes, and is concentrated on the inner-shelf. Trawling-induced resuspension, in contrast, occurs regularly throughout the year and is concentrated on the outer shelf. The total annual net resuspension by trawls (8×106 T y-1 is four orders of magnitude lower than the resuspension induced by waves and currents (4×1010 T y-1. However, because trawled regions are located on the outer shelf, closer to the continental slope, export of fine sediment resuspended by trawls (0.6×106 T y-1 is only one order of magnitude lower than export associated with natural resuspension (8×106 T y-1. A simulation combining both

Near-Bottom Turbulence and Sediment Resuspension Induced by Nonlinear Internal Waves

DTIC Science & Technology

2012-09-30

boundary layer (BBL) turbulence and particulate resuspension leading to benthic nepheloid layer ( BNL ) formation. OBJECTIVES The specific objectives...capturing of nearbed particles by the BBL-turbulence and their transport/deposition into BNLs . • Analyze field observations from the New Jersey shelf to...generated resuspended particle distributions under NLIWs, a reliable proxy of BNLs , can be used to quantify the transmission or backscatter of optical

Near-Bottom Turbulence and Sediment Resuspension Induced by Nonlinear Internal Waves

DTIC Science & Technology

2014-09-30

boundary layer (BBL) turbulence and particulate resuspension leading to benthic nepheloid layer ( BNL ) formation. OBJECTIVES The specific objectives...identify mechanisms for the capturing of near-bed particles by the BBL-turbulence and their transport/deposition into BNLs . • Analyze field...distributions under NLIWs, a reliable proxy of BNLs , can be used to quantify the transmission or backscatter of optical/acoustic signals of importance to

Near Bottom Turbulence and Sediment Resuspension Induced by Nonlinear Internal Waves

DTIC Science & Technology

2013-09-30

boundary layer (BBL) turbulence and particulate resuspension leading to benthic nepheloid layer ( BNL ) formation. OBJECTIVES The specific...capturing of nearbed particles by the BBL-turbulence and their transport/deposition into BNLs . • Analyze field observations from the New Jersey shelf to...distributions under NLIWs, a reliable proxy of BNLs , can be used to quantify the transmission or backscatter of optical/acoustic signals of importance to

MEAD Marine Effects of Atmospheric Deposition

NASA Astrophysics Data System (ADS)

Jickells, T.; Spokes, L.

2003-04-01

The coastal seas are one of the most valuable resources on the planet but they are threatened by human activity. We rely on the coastal area for mineral resources, waste disposal, fisheries and recreation. In Europe, high population densities and high levels of industrial activity mean that the pressures arising from these activities are particularly acute. One of the main problems concerning coastal seas is the rapid increase in the amounts of nitrogen-based pollutants entering the water. They come from many sources, the most important ones being traffic, industry and agriculture. These pollutants can be used by algae as nutrients. The increasing concentrations of these nutrients have led to excessive growth of algae, some of which are harmful. When algae die and decay, oxygen in the water is used up and the resulting lower levels of oxygen may lead to fish kills. Human activity has probably doubled the amount of chemically and biologically reactive nitrogen present globally. In Europe the increases have been greater than this, leading to real concern over the health of coastal waters. Rivers have, until recently, been thought to be the most important source of reactive nitrogen to the coastal seas but we now know that inputs from the atmosphere are large and can equal, or exceed, those from the rivers. Our initial hypothesis was that atmospheric inputs are important and potentially different in their effect on coastal ecosystems to riverine inputs and hence require different management strategies. However, we had almost no information on the direct effects of atmospheric deposition on marine ecosystems, though clearly such a large external nitrogen input should lead to enhanced phytoplankton growth The aim of this European Union funded MEAD project has been to determine how inputs of nitrogen from the atmosphere affect the chemistry and biology of coastal waters. To try to answer this, we have conducted field experiments in the Kattegat, an area where we know

Effect of the resuspension technique on distribution of the heavy metals in sediment and suspended particulate matter.

PubMed

Pourabadehei, Mehdi; Mulligan, Catherine N

2016-06-01

Harbour areas play important roles in the economy worldwide. Human activities, however, in those areas, generate contamination, which mostly accumulates in sediments. On the other hand, harbour areas have been facing deposition of significant amounts of sediment each year. As a consequence, shallowness and accumulation of contaminants in sediment become challenging issues in harbours. Among the various management options for remediation of contaminated sediments in harbours, resuspension technique was introduced as a new approach to address those issues. The concept of the resuspension method is that finer sediments have a greater tendency to adsorb the contamination. Therefore, removing the finer sediments instead of dredging the whole contaminated area is the main goal of the resuspension technique. The objective of this paper was to evaluate the effect of the resuspension method on reducing the concentration of contamination and distribution of heavy metals in sediment and suspended particulate matter. The resuspension method was successful in reducing the concentration of seven selected heavy metals (Cr, Ni, Cu, Zn, As, Cd and Pb) by removing just 4% of the contaminated sediment. The contamination intensity in the sediment, presented by geoaccumulation index, was reduced for Cd and Pb as the main contaminants by 26 and 28 percent and the rest of the selected heavy metals returned to the natural level. The results of the sequential extraction tests and enrichment factor implied that the resuspension technique is capable of decreasing the risk of remobilization of heavy metals in the aquatic ecosystem. Copyright © 2016 Elsevier Ltd. All rights reserved.

Atmospheric deposition to forests in the eastern USA

USGS Publications Warehouse

Risch, Martin R.; DeWild, John F.; Gay, David A.; Zhang, Leiming; Boyer, Elizabeth W.; Krabbenhoft, David P.

2017-01-01

Atmospheric mercury (Hg) deposition to forests is important because half of the land cover in the eastern USA is forest. Mercury was measured in autumn litterfall and weekly precipitation samples at a total of 27 National Atmospheric Deposition Program (NADP) monitoring sites in deciduous and mixed deciduous-coniferous forests in 16 states in the eastern USA during 2007–2014. These simultaneous, uniform, repeated, annual measurements of forest Hg include the broadest area and longest time frame to date. The autumn litterfall-Hg concentrations and litterfall mass at the study sites each year were combined with annual precipitation-Hg data. Rates of litterfall-Hg deposition were higher than or equal to precipitation-Hg deposition rates in 70% of the annual data, which indicates a substantial contribution from litterfall to total atmospheric-Hg deposition. Annual litterfall-Hg deposition in this study had a median of 11.7 μg per square meter per year (μg/m2/yr) and ranged from 2.2 to 23.4 μg/m2/yr. It closely matched modeled dry-Hg deposition, based on land cover at selected NADP Hg-monitoring sites. Mean annual atmospheric-Hg deposition at forest study sites exhibited a spatial pattern partly explained by statistical differences among five forest-cover types and related to the mapped density of Hg emissions. Forest canopies apparently recorded changes in atmospheric-Hg concentrations over time because litterfall-Hg concentrations decreased year to year and litterfall-Hg concentrations were significantly higher in 2007–2009 than in 2012–2014. These findings reinforce reported decreases in Hg emissions and atmospheric elemental-Hg concentrations during this same time period. Methylmercury (MeHg) was detected in all litterfall samples at all sites, compared with MeHg detections in less than half the precipitation samples at selected sites during the study. These results indicate MeHg in litterfall is a pathway into the terrestrial food web where it can

The investigation of atmospheric deposition distribution of organochlorine pesticides (OCPs) in Turkey

NASA Astrophysics Data System (ADS)

Cindoruk, S. Sıddık; Tasdemir, Yücel

2014-04-01

Atmospheric deposition is a significant pollution source leading to contamination of remote and clean sites, surface waters and soils. Since persistent organic pollutants (POPs) stay in atmosphere without any degradation, they can be transported and deposited to clean surfaces. Organochlorine pesticides are an important group of POPs which have toxic and harmful effects to living organisms and environment. Therefore, atmospheric deposition levels and characteristics are of importance to determine the pollution quantity of water and soil surfaces in terms of POPs. This study reports the distribution quantities of atmospheric deposition including bulk, dry, wet and air-water exchange of particle and gas phase OCPs as a result of 1-year sampling campaign. Atmospheric deposition distribution showed that the main mechanism for OCPs deposition is wet processes with percentage of 69 of total deposition. OCP compounds' deposition varied according to atmospheric concentration and deposition mechanism. HCH compounds were dominant pesticide species for all deposition mechanisms. HCH deposition constituted the 65% of Σ10OCPs.

The contribution of ice cover to sediment resuspension in a shallow temperate lake: possible effects of climate change on internal nutrient loading.

PubMed

Niemistö, Juha P; Horppila, Jukka

2007-01-01

The effect of ice cover on sediment resuspension and internal total P (Tot-P) loading was studied in the northern temperate Kirkkojärvi basin in Finland. The gross sedimentation and resuspension rates were estimated with sediment traps during ice-cover and ice-free periods. After ice break, the average gross sedimentation rate increased from 1.4 to 30.0 g dw m(-2) d(-1). Resuspension calculations showed clearly higher values after ice break as well. Under ice cover, resuspension ranged from 50 to 78% of the gross sedimentation while during the ice-free period it constituted from 87 to 97% of the gross sedimentation. Consequently, the average resuspension rate increased from 1.0 g dw m(-2) d(-1) under ice-cover to 27.0 g dw m(-2) d(-1) after thaw, indicating the strong effect of ice cover on sediment resuspension. To estimate the potential effect of climate change on internal P loading caused by resuspension we compared the Tot-P loading calculations between the present climate and the climate with doubled atmospheric CO2 concentration relative to the present day values (ice cover reduced from current 165 to 105 d). The annual load increased from 7.4 to 9.4 g m(-2). In conclusion, the annual internal Tot-P loading caused by resuspension will increase by 28% in the Kirkkojärvi basin if the 2xCO2 climate scenario comes true.

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.

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

Increasing rates of atmospheric mercury deposition in midcontinental North America

USGS Publications Warehouse

Swain, Edward B.; Engstrom, Daniel R.; Brigham, Mark E.; Henning, Thomas A.; Brezonik, P.L.

1992-01-01

Mercury contamination of remote lakes has been attributed to increasing deposition of atmospheric mercury, yet historic deposition rates and inputs from terrestrial sources are essentially unknown. Sediments of seven headwater lakes in Minnesota and Wisconsin were used to reconstruct regional modern and preindustrial deposition rates of mercury. Whole-basin mercury fluxes, determined from lake-wide arrays of dated cores, indicate that the annual deposition of atmospheric mercury has increased from 3.7 to 12.5 micrograms per square meter since 1850 and that 25 percent of atmospheric mercury deposition to the terrestrial catchment is exported to the lake. The deposition increase is similar among sites, implying regional or global sources for the mercury entering these lakes.

Environmental hazard assessment of a marine mine tailings deposit site and potential implications for deep-sea mining.

PubMed

Mestre, Nélia C; Rocha, Thiago L; Canals, Miquel; Cardoso, Cátia; Danovaro, Roberto; Dell'Anno, Antonio; Gambi, Cristina; Regoli, Francesco; Sanchez-Vidal, Anna; Bebianno, Maria João

2017-09-01

Portmán Bay is a heavily contaminated area resulting from decades of metal mine tailings disposal, and is considered a suitable shallow-water analogue to investigate the potential ecotoxicological impact of deep-sea mining. Resuspension plumes were artificially created by removing the top layer of the mine tailings deposit by bottom trawling. Mussels were deployed at three sites: i) off the mine tailings deposit area; ii) on the mine tailings deposit beyond the influence from the resuspension plumes; iii) under the influence of the artificially generated resuspension plumes. Surface sediment samples were collected at the same sites for metal analysis and ecotoxicity assessment. Metal concentrations and a battery of biomarkers (oxidative stress, metal exposure, biotransformation and oxidative damage) were measured in different mussel tissues. The environmental hazard posed by the resuspension plumes was investigated by a quantitative weight of evidence (WOE) model that integrated all the data. The resuspension of sediments loaded with metal mine tails demonstrated that chemical contaminants were released by trawling subsequently inducing ecotoxicological impact in mussels' health. Considering as sediment quality guidelines (SQGs) those indicated in Spanish action level B for the disposal of dredged material at sea, the WOE model indicates that the hazard is slight off the mine tailings deposit, moderate on the mine tailings deposit without the influence from the resuspension plumes, and major under the influence of the resuspension plumes. Portmán Bay mine tailings deposit is a by-product of sulphide mining, and despite differences in environmental setting, it can reflect the potential ecotoxic effects to marine fauna from the impact of resuspension of plumes created by deep-sea mining of polymetallic sulphides. A similar approach as in this study could be applied in other areas affected by sediment resuspension and for testing future deep-sea mining sites in

Total dissolved atmospheric nitrogen deposition in the anoxic Cariaco basin

NASA Astrophysics Data System (ADS)

Rasse, R.; Pérez, T.; Giuliante, A.; Donoso, L.

2018-04-01

Atmospheric deposition of total dissolved nitrogen (TDN) is an important source of nitrogen for ocean primary productivity that has increased since the industrial revolution. Thus, understanding its role in the ocean nitrogen cycle will help assess recent changes in ocean biogeochemistry. In the anoxic Cariaco basin, the place of the CARIACO Ocean Time-Series Program, the influence of atmospherically-deposited TDN on marine biogeochemistry is unknown. In this study, we measured atmospheric TDN concentrations as dissolved organic (DON) and inorganic (DIN) nitrogen (TDN = DIN + DON) in atmospheric suspended particles and wet deposition samples at the northeast of the basin during periods of the wet (August-September 2008) and dry (March-April 2009) seasons. We evaluated the potential anthropogenic N influences by measuring wind velocity and direction, size-fractionated suspended particles, chemical traces and by performing back trajectories. We found DIN and DON concentration values that ranged between 0.11 and 0.58 μg-N m-3 and 0.11-0.56 μg-N m-3 in total suspended particles samples and between 0.08 and 0.54 mg-N l-1 and 0.02-1.3 mg-N l-1 in wet deposition samples, respectively. Continental air masses increased DON and DIN concentrations in atmospheric suspended particles during the wet season. We estimate an annual TDN atmospheric deposition (wet + particles) of 3.6 × 103 ton-N year-1 and concluded that: 1) Atmospheric supply of TDN plays a key role in the C and N budget of the basin because replaces a fraction of the C (20% by induced primary production) and N (40%) removed by sediment burial, 2) present anthropogenic N could contribute to 30% of TDN atmospheric deposition in the basin, and 3) reduced DON (gas + particles) should be a significant component of bulk N deposition.

Atmospheric mercury deposition to forests in the eastern USA.

PubMed

Risch, Martin R; DeWild, John F; Gay, David A; Zhang, Leiming; Boyer, Elizabeth W; Krabbenhoft, David P

2017-09-01

Atmospheric mercury (Hg) deposition to forests is important because half of the land cover in the eastern USA is forest. Mercury was measured in autumn litterfall and weekly precipitation samples at a total of 27 National Atmospheric Deposition Program (NADP) monitoring sites in deciduous and mixed deciduous-coniferous forests in 16 states in the eastern USA during 2007-2014. These simultaneous, uniform, repeated, annual measurements of forest Hg include the broadest area and longest time frame to date. The autumn litterfall-Hg concentrations and litterfall mass at the study sites each year were combined with annual precipitation-Hg data. Rates of litterfall-Hg deposition were higher than or equal to precipitation-Hg deposition rates in 70% of the annual data, which indicates a substantial contribution from litterfall to total atmospheric-Hg deposition. Annual litterfall-Hg deposition in this study had a median of 11.7 μg per square meter per year (μg/m 2 /yr) and ranged from 2.2 to 23.4 μg/m 2 /yr. It closely matched modeled dry-Hg deposition, based on land cover at selected NADP Hg-monitoring sites. Mean annual atmospheric-Hg deposition at forest study sites exhibited a spatial pattern partly explained by statistical differences among five forest-cover types and related to the mapped density of Hg emissions. Forest canopies apparently recorded changes in atmospheric-Hg concentrations over time because litterfall-Hg concentrations decreased year to year and litterfall-Hg concentrations were significantly higher in 2007-2009 than in 2012-2014. These findings reinforce reported decreases in Hg emissions and atmospheric elemental-Hg concentrations during this same time period. Methylmercury (MeHg) was detected in all litterfall samples at all sites, compared with MeHg detections in less than half the precipitation samples at selected sites during the study. These results indicate MeHg in litterfall is a pathway into the terrestrial food web where it can

Impact of natural (waves and currents) and anthropogenic (trawl) resuspension on the export of particulate matter to the open ocean: Application to the Gulf of Lion (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Ferré, B.; Durrieu de Madron, X.; Estournel, C.; Ulses, C.; Le Corre, G.

2008-08-01

Modern sediment deposits on continental margins form a vast reservoir of particulate matter that is regularly affected by resuspension processes. Resuspension by bottom trawling on shelves with strong fishing activity can modify the scale of natural disturbance by waves and currents. Recent field data show that the impact of bottom trawls on fine sediment resuspension per unit surface is comparable with that of the largest storms. We assessed the impact of both natural and anthropogenic processes on the dispersal of riverborne particles and shelf sediments on the Gulf of Lion shelf. We performed realistic numerical simulations of resuspension and transport forced by currents and waves or by a fleet of bottom trawlers. Simulations were conducted for a 16-month period (January 1998-April 1999) to characterise the seasonal variability. The sediment dynamics takes into account bed armoring, ripple geometry and the cohesive and non-cohesive characteristics of the sediments. Essential but uncertain parameters (clay content, erosion fluxes and critical shear stress for cohesive sediment) were set with existing data. Resuspension by waves and currents was controlled by shear stress, whereas resuspension by trawls was controlled by density and distribution of the bottom trawler fleet. Natural resuspension by waves and currents mostly occurred during short seasonal episodes, and was concentrated on the inner shelf. Trawling-induced resuspension, in contrast, occurred regularly throughout the year and was concentrated on the outer shelf. The total annual erosion by trawls (5.6×10 6 t y -1, t for metric tonnes) was four orders of magnitude lower than the erosion induced by waves and currents (35.3×10 9 t y -1). However the net resuspension (erosion/deposition budget) for trawling (0.4×10 6 t y -1) was only one order of magnitude lower than that for waves and currents (9.2×10 6 t y -1). Off-shelf export concerned the finest fraction of the sediment (clays and fine silts

Ecological geochemical assessment and source identification of trace elements in atmospheric deposition of an emerging industrial area: Beibu Gulf economic zone.

PubMed

Zhong, Cong; Yang, Zhongfang; Jiang, Wei; Hu, Baoqing; Hou, Qingye; Yu, Tao; Li, Jie

2016-12-15

Industrialization and urbanization have led to a deterioration in air quality and provoked some serious environmental concerns. Fifty-four samples of atmospheric deposition were collected from an emerging industrial area and analyzed to determine the concentrations of 11 trace elements (As, Cd, Cu, Fe, Hg, Mn, Mo, Pb, Se, S and Zn). Multivariate geostatistical analyses were conducted to determine the spatial distribution, possible sources and enrichment degrees of trace elements in atmospheric deposition. Results indicate that As, Fe and Mo mainly originated from soil, their natural parent materials, while the remaining trace elements were strongly influenced by anthropogenic or natural activities, such as coal combustion in coal-fired power plants (Pb, Se and S), manganese ore (Mn, Cd and Hg) and metal smelting (Cu and Zn). The results of ecological geochemical assessment indicate that Cd, Pb and Zn are the elements of priority concern, followed by Mn and Cu, and other heavy metals, which represent little threat to local environment. It was determine that the resuspension of soil particles impacted the behavior of heavy metals by 55.3%; the impact of the coal-fired power plants was 18.9%; and the contribution of the local manganese industry was 9.6%. The comparison of consequences from various statistical methods (principal component analysis (PCA), cluster analysis (CA), enrichment factor (EF) and absolute principle component score (APCS)-multiple linear regression (MLR)) confirmed the credibility of this research. Copyright © 2016 Elsevier B.V. All rights reserved.

ATMOSPHERIC MERCURY TRANSPORT AND DEPOSITION

EPA Science Inventory

The current state of our scientific understanding the mercury cycle tells us that most of the mercury getting into fish comes from atmospheric deposition, but methylation of that mercury in aquatic systems is required for the concentrations in fish to reach harmful levels. We st...

Resuspension of sediment, a new approach for remediation of contaminated sediment.

PubMed

Pourabadehei, Mehdi; Mulligan, Catherine N

2016-06-01

Natural events and anthropogenic activities are the reasons of undesirable resuspension of contaminated sediments in aquatic environment. Uncontrolled resuspension could remobilize weakly bound heavy metals into overlying water and pose a potential risk to aquatic ecosystem. Shallow harbours, with contaminated sediments are subjected to the risk of uncontrolled resuspension. Remediation of sediments in these areas cannot be performed by conventional in situ methods (e.g. capping with or without reactive amendment). Ex situ remediation also requires dredging of sediment, which could increase the risk of spreading contaminants. Alternatively, the resuspension technique was introduced to address these issues. The concept of the resuspension method is that finer sediments have a greater tendency to adsorb the contamination. Therefore, finer sediments, believed carry more concentration of contaminants, were targeted for removal from aquatic environment by a suspension mechanism in a confined water column. The objective of this study was to evaluate the feasibility of the resuspension technique as a new approach for remediation of contaminated sediment and a viable option to reduce the risk of remobilization of contaminants in harbours due to an undesirable resuspension event. Unlike the common in situ techniques, the resuspension method could successfully reduce the total concentration of contaminants in almost all samples below the probable effect level (PEL) with no significant change in the quality of overlying water. The results indicated that removal efficiency could be drastically enhanced for metals in sediment with a higher enrichment factor. Moreover, availability of metals (e.g. Cd and Pb) with a high concentration in labile fractions was higher in finer sediments with a high enrichment factor. Consequently, removal of contaminants from sediment through the resuspension method could reduce the risk of mobility and availability of metals under changing

The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

NASA Astrophysics Data System (ADS)

Moriarty, Julia M.; Harris, Courtney K.; Fennel, Katja; Friedrichs, Marjorie A. M.; Xu, Kehui; Rabouille, Christophe

2017-04-01

Observations indicate that resuspension and associated fluxes of organic material and porewater between the seabed and overlying water can alter biogeochemical dynamics in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabed-water-column interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; fluxes of this material between the seabed and the water column via erosion, deposition, and diffusion at the sediment-water interface; and biogeochemical reactions within the seabed. A one-dimensional version of HydroBioSed was then implemented for the Rhône subaqueous delta in France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a 2-month period that included three resuspension events; also, the supply of organic matter, oxygen, and nutrients to the model was held constant in time. Consistent with time series observations from the Rhône Delta, model results showed that erosion increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabed-water interface. This enhanced supply of oxygen to the seabed, as well as resuspension-induced increases in ammonium availability in surficial sediments, allowed seabed oxygen consumption to increase via nitrification. This increase in nitrification compensated for the decrease in seabed oxygen consumption due to aerobic remineralization that occurred as organic matter was entrained into the water

[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.

The influence of human physical activity and contaminated clothing type on particle resuspension.

PubMed

McDonagh, A; Byrne, M A

2014-01-01

A study was conducted to experimentally quantify the influence of three variables on the level of resuspension of hazardous aerosol particles from clothing. Variables investigated include physical activity level (two levels, low and high), surface type (four different clothing material types), and time i.e. the rate at which particles resuspend. A mixture of three monodisperse tracer-labelled powders, with median diameters of 3, 5, and 10 microns, was used to "contaminate" the samples, and the resuspended particles were analysed in real-time using an Aerodynamic Particle Sizer (APS), and also by Neutron Activation Analysis (NAA). The overall finding was that physical activity resulted in up to 67% of the contamination deposited on clothing being resuspended back into the air. A detailed examination of the influence of physical activity level on resuspension, from NAA, revealed that the average resuspended fraction (RF) of particles at low physical activity was 28 ± 8%, and at high physical activity was 30 ± 7%, while the APS data revealed a tenfold increase in the cumulative mass of airborne particles during high physical activity in comparison to that during low physical activity. The results also suggest that it is not the contaminated clothing's fibre type which influences particle resuspension, but the material's weave pattern (and hence the material's surface texture). Investigation of the time variation in resuspended particle concentrations indicated that the data were separable into two distinct regimes: the first (occurring within the first 1.5 min) having a high, positive rate of change of airborne particle concentration relative to the second regime. The second regime revealed a slower rate of change of particle concentration and remained relatively unchanged for the remainder of each resuspension event. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

Observation of sediment resuspension in Old Tampa Bay, Florida

USGS Publications Warehouse

Schoellhamer, David H.; ,

1990-01-01

Equipment and methodology have been developed to monitor sediment resuspension at two sites in Old Tampa Bay. Velocities are measured with electromagnetic current meters and suspended solids and turbidity are monitored with optical backscatterance sensors. In late November 1989, a vertical array of instrument pairs was deployed from a permanent platform at a deep-water site, and a submersible instrument package with a single pair of instruments was deployed at a shallow-water site. Wind waves caused resuspension at the shallow-water site, but not at the deeper platform site, and spring tidal currents did not cause resuspension at either site.

Sensitivity of terrestrial N2O emission to atmospheric nitrogen deposition

NASA Astrophysics Data System (ADS)

Ito, A.; Sudo, K.; Nishina, K.; Ishijima, K.; Inatomi, M. I.

2015-12-01

Terrestrial N2O emission is generated from several nitrogen sources including biological fixation, agricultural fertilizer, and atmospheric deposition. There remain large uncertainties how much N2O is produced from atmospheric deposition. This is a crosscutting issue between global warming and atmospheric pollution. In this study, we assessed the sensitivity of global terrestrial N2O emission to atmospheric deposition, using a process-based model VISIT. In the model, N2O emission is estimated separately for nitrification and denitrfication with the NGAS parameterization. The global simulations were conducted from 1901 to 2014 at spatial resolution of 0.5 degree. Atmospheric deposition of ammonium, NOy, and organic nitrogen simulated by the atmospheric chemistry model CHASER from the pre-industrial time to the present was used. Annual total nitrogen deposition was estimated to increase from 27 Tg N in 1901 to 77 Tg N in 2014. The total N2O emission was also estimated to increase in the period, but it was largely attributable to the increased emission from croplands. We need further investigations for the N2O emission from natural soils, which may be nitrogen-limited.

Sulfur accumulation and atmospherically deposited sulfate in the Lake States.

Treesearch

Mark B. David; George Z. Gernter; David F. Grigal; Lewis F. Ohmann

1989-01-01

Characterizes the mass of soil sulfur (adjusted for nitrogen), and atmospherically deposited sulfate along an acid precipitation gradient from Minnesota to Michigan. The relationship of these variables, presented graphically through contour mapping, suggests that patterns of atmospheric wet sulfate deposition are reflected in soil sulfur pools.

Loess as an environmental archive of atmospheric trace element deposition

NASA Astrophysics Data System (ADS)

Blazina, T.; Winkel, L. H.

2013-12-01

Environmental archives such as ice cores, lake sediment cores, and peat cores have been used extensively to reconstruct past atmospheric deposition of trace elements. These records have provided information about how anthropogenic activities such as mining and fossil fuel combustion have disturbed the natural cycles of various atmospherically transported trace elements (e.g. Pb, Hg and Se). While these records are invaluable for tracing human impacts on such trace elements, they often provide limited information about the long term natural cycles of these elements. An assumption of these records is that the observed variations in trace element input, prior to any assumed anthropogenic perturbations, represent the full range of natural variations. However, records such as those mentioned above which extend back to a maximum of ~400kyr may not capture the potentially large variations of trace element input occurring over millions of years. Windblown loess sediments, often representing atmospheric deposition over time scales >1Ma, are the most widely distributed terrestrial sediments on Earth. These deposits have been used extensively to reconstruct continental climate variability throughout the Quaternary and late Neogene periods. In addition to being a valuable record of continental climate change, loess deposits may represent a long term environmental archive of atmospheric trace element deposition and may be combined with paleoclimate records to elucidate how fluctuations in climate have impacted the natural cycle of such elements. Our research uses the loess-paleosol deposits on the Chinese Loess Plateau (CLP) to quantify how atmospheric deposition of trace elements has fluctuated in central China over the past 6.8Ma. The CLP has been used extensively to reconstruct past changes of East Asian monsoon system (EAM). We present a suite of trace element concentration records (e.g. Pb, Hg, and Se) from the CLP which exemplifies how loess deposits can be used as an

Direct and indirect atmospheric deposition of PCBs to the Delaware River watershed.

PubMed

Totten, Lisa A; Panangadan, Maya; Eisenreich, Steven J; Cavallo, Gregory J; Fikslin, Thomas J

2006-04-01

Atmospheric deposition can be an important source of PCBs to aquatic ecosystems. To develop the total maximum daily load (TMDL) for polychlorinated biphenyls (PCBs) for the tidal Delaware River (water-quality Zones 2-5), estimates of the loading of PCBs to the river from atmospheric deposition were generated from seven air-monitoring sites along the river. This paper presents the atmospheric PCB data from these sites, estimates direct atmospheric deposition fluxes, and assesses the importance of atmospheric deposition relative to other sources of PCBs to the river. Also, the relationship between indirect atmospheric deposition and PCB loads from minor tributaries to the Delaware River is discussed. Data from these sites revealed high atmospheric PCB concentrations in the Philadelphia/Camden urban area and lower regional background concentrations in the more remote areas. Wet, dry particle, and gaseous absorption deposition are estimated to contribute about 0.6, 1.8, and 6.5 kg year-(-1) sigmaPCBs to the River, respectively, exceeding the TMDL of 0.139 kg year(-1) by more than an order of magnitude. Penta-PCB watershed fluxes were obtained by dividing the tributary loads by the watershed area. The lowest of these watershed fluxes are less than approximately 1 ng m(-2) day(-1) for penta-PCB and probably indicates pristine watersheds in which PCB loads are dominated by atmospheric deposition. In these watersheds, the pass-through efficiency of PCBs is estimated to be on the order of 1%.

Atmospheric nitrogen in the Mississippi River Basin - Amissions, deposition and transport

USGS Publications Warehouse

Lawrence, G.B.; Goolsby, D.A.; Battaglin, W.A.; Stensland, G.J.

2000-01-01

Atmospheric deposition of nitrogen has been cited as a major factor in the nitrogen saturation of forests in the north-eastern United States and as a contributor to the eutrophication of coastal waters, including the Gulf of Mexico near the mouth of the Mississippi River. Sources of nitrogen emissions and the resulting spatial patterns of nitrogen deposition within the Mississippi River Basin, however, have not been fully documented. An assessment of atmospheric nitrogen in the Mississippi River Basin was therefore conducted in 1998-1999 to: (1) evaluate the forms in which nitrogen is deposited from the atmosphere; (2) quantify the spatial distribution of atmospheric nitrogen deposition throughout the basin; and (3) relate locations of emission sources to spatial deposition patterns to evaluate atmospheric transport. Deposition data collected through the NADP/NTN (National Atmospheric Deposition Program/National Trends Network) and CASTNet (Clean Air Status and Trends Network) were used for this analysis. NO(x) Tier 1 emission data by county was obtained for 1992 from the US Environmental Protection Agency (Emissions Trends Viewer CD, 1985-1995, version 1.0, September 1996) and NH3 emissions data was derived from the 1992 Census of Agriculture (US Department of Commerce. Census of Agriculture, US Summary and County Level Data, US Department of Commerce, Bureau of the Census. Geographic Area series, 1995:1b) or the National Agricultural Statistics Service (US Department of Agriculture. National Agricultural Statistics Service Historical Data. Accessed 7/98 at URL, 1998. http://www.usda.gov/nass/pubs/hisdata.htm). The highest rates of wet deposition of NO3- were in the north-eastern part of the basin, downwind of electric utility plants and urban areas, whereas the highest rates of wet deposition of NH4+ were in Iowa, near the center of intensive agricultural activities in the Midwest. The lowest rates of atmospheric nitrogen deposition were on the western (windward

Resuspension of biological particles from indoor surfaces: Effects of humidity and air swirl.

PubMed

Salimifard, Parichehr; Rim, Donghyun; Gomes, Carlos; Kremer, Paul; Freihaut, James D

2017-04-01

Human exposure to airborne particles can lead to adverse health outcomes such as respiratory and allergic symptoms. Understanding the transport mechanism of respirable particles in occupied spaces is a first step towards assessing inhalation exposure. Several studies have contributed to the current knowledge of particle resuspension from indoor surfaces; however, few published studies are available on resuspension of biological particles from indoor surfaces. The objective of this study is to investigate the impacts of humidity and air swirl on resuspension of biological particles from floor and duct surfaces. Controlled laboratory experiments were conducted under varying degrees of humidity and airflow conditions. Resuspension rates of five types of particles (quartz, dust mite, cat fur, dog fur, and bacterial spore-Bacillus thuringiensis as an anthrax simulant) were determined for two types of floor surface (carpet and linoleum) and a duct surface (galvanized sheet metal). The results show that the particle property of being hydrophilic or hydrophobic plays an important role in particle resuspension rate. Resuspension rates of hydrophilic dust mite particles increase up to two orders of magnitude as relative humidity (RH) decreased from 80% to 10% at 25°C. However, resuspension rates of cat fur and dog fur particles that are hydrophobic are within the measurement error range (±15%) over 10-80% RH. With regard to resuspension of bacterial spores (Bacillus thuringiensis) from a duct surface, the resuspension rates are substantially affected by air swirl velocity and particle size. However, no discernible increase in particle resuspension was observed with duct vibration. Copyright © 2017 Elsevier B.V. All rights reserved.

Sediment resuspension and transport patterns on a fringing reef flat, Molokai, Hawaii

USGS Publications Warehouse

Ogston, A.S.; Storlazzi, C.D.; Field, M.E.; Presto, M.K.

2004-01-01

Corals are known to flourish in various turbid environments around the world. The quantitative distinction between clear and turbid water in coral habitats is not well defined nor are the amount of sediment in suspension and rates of sedimentation used to evaluate the condition of reef environments well established. This study of sediment resuspension, transport, and resulting deposition on a fringing reef flat off Molokai, Hawaii, uses a year of time-series data from a small, instrumented tripod. It shows the importance of trade winds and ocean wave heights in controlling the movement of sediment. Sediment is typically resuspended daily and the dominant controls on the magnitude of events (10-25 mg/l) are the trade-wind-generated waves and currents and tidal elevation on the reef flat. The net flux of sediment on this reef is primarily along the reef flat in the direction of the prevailing trade winds (to the west), with a secondary direction of slightly offshore, towards a zone of low coral abundance. These results have application to reef studies and reef management in other areas in several ways. First, the observed resuspension and turbidity results from fine-grained terrigenous sediment that appears to be trapped and recycled on the reef flat. Thus corals are subjected to light attenuation by the same particles repeatedly, however small the amount. Secondly, the measurements show high temporal variability (from daily to seasonal scales) of sediment resuspension, indicating that single measurements are inadequate to accurately describe conditions on a reef flat. ?? Springer-Verlag 2004.

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...

Residual β activity of particulate (234)Th as a novel proxy for tracking sediment resuspension in the ocean.

PubMed

Lin, Wuhui; Chen, Liqi; Zeng, Shi; Li, Tao; Wang, Yinghui; Yu, Kefu

2016-06-02

Sediment resuspension occurs in the global ocean, which greatly affects material exchange between the sediment and the overlying seawater. The behaviours of carbon, nutrients, heavy metals, and other pollutants at the sediment-seawater boundary will further link to climate change, eutrophication, and marine pollution. Residual β activity of particulate (234)Th (RAP234) is used as a novel proxy to track sediment resuspension in different marine environments, including the western Arctic Ocean, the South China Sea, and the Southern Ocean. Sediment resuspension identified by high activity of RAP234 is supported by different lines of evidence including seawater turbidity, residence time of total (234)Th, Goldschmidt's classification, and ratio of RAP234 to particulate organic carbon. A conceptual model is proposed to elucidate the mechanism for RAP234 with dominant contributions from (234)Th-(238)U and (212)Bi-(228)Th. The 'slope assumption' for RAP234 indicated increasing intensity of sediment resuspension from spring to autumn under the influence of the East Asian monsoon system. RAP234 can shed new light on (234)Th-based particle dynamics and should benefit the interpretation of historical (234)Th-(238)U database. RAP234 resembles lithophile elements and has broad implications for investigating particle dynamics in the estuary-shelf-slope-ocean continuum and linkage of the atmosphere-ocean-sediment system.

Residual β activity of particulate 234Th as a novel proxy for tracking sediment resuspension in the ocean

PubMed Central

Lin, Wuhui; Chen, Liqi; Zeng, Shi; Li, Tao; Wang, Yinghui; Yu, Kefu

2016-01-01

Sediment resuspension occurs in the global ocean, which greatly affects material exchange between the sediment and the overlying seawater. The behaviours of carbon, nutrients, heavy metals, and other pollutants at the sediment-seawater boundary will further link to climate change, eutrophication, and marine pollution. Residual β activity of particulate 234Th (RAP234) is used as a novel proxy to track sediment resuspension in different marine environments, including the western Arctic Ocean, the South China Sea, and the Southern Ocean. Sediment resuspension identified by high activity of RAP234 is supported by different lines of evidence including seawater turbidity, residence time of total 234Th, Goldschmidt’s classification, and ratio of RAP234 to particulate organic carbon. A conceptual model is proposed to elucidate the mechanism for RAP234 with dominant contributions from 234Th-238U and 212Bi-228Th. The ‘slope assumption’ for RAP234 indicated increasing intensity of sediment resuspension from spring to autumn under the influence of the East Asian monsoon system. RAP234 can shed new light on 234Th-based particle dynamics and should benefit the interpretation of historical 234Th-238U database. RAP234 resembles lithophile elements and has broad implications for investigating particle dynamics in the estuary-shelf-slope-ocean continuum and linkage of the atmosphere-ocean-sediment system. PMID:27252085

Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments

NASA Astrophysics Data System (ADS)

Drevnick, Paul E.; Yang, Handong; Lamborg, Carl H.; Rose, Neil L.

2012-11-01

In this study we used lake sediments, which faithfully record Hg inputs, to derive estimates of net atmospheric Hg deposition to Svalbard, Norwegian Arctic. With the exception of one site affected by local pollution, the study lakes show twofold to fivefold increases in sedimentary Hg accumulation since 1850, likely due to long-range atmospheric transport and deposition of anthropogenic Hg. Sedimentary Hg accumulation in these lakes is a linear function of the ratio of catchment area to lake area, and we used this relationship to model net atmospheric Hg flux: preindustrial and modern estimates are 2.5 ± 3.3 μg m-2 y-1 and 7.0 ± 3.0 μg m-2 y-1, respectively. The modern estimate, by comparison with data for Hg wet deposition, indicates that atmospheric mercury depletion events (AMDEs) or other dry deposition processes contribute approximately half (range 0-70%) of the net flux. Hg from AMDEs may be moving in significant quantities into aquatic ecosystems, where it is a concern because of contamination of aquatic food webs.

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

ULTRASONIC MEASUREMENT OF SEDIMENT RESUSPENSION

EPA Science Inventory

Recognizing the need for improved measurement and parameterization of sediment resuspension, this paper presents a review of the major methods now in use for alleviating this need. Special attention is devoted to reviewing methods for obtaining sediment concentration profiles by ...

Total Suspended Matter (TSM) and Maximum Signal Depth (Z90_max) for Monitoring the Evolution of Sediment Resuspension Process in Shallow Coastal Environments

NASA Astrophysics Data System (ADS)

Filipponi, Federico; Zucca, Francesco; Taramelli, Andrea; Valentini, Emiliana

2015-12-01

Monitoring sediment fluxes patterns in coastal area, like dispersion, sedimentation and resuspension processes, is a relevant topic for scientists, decision makers and natural resources management. Time series analysis of Earth Observation (EO) data may contribute to the understanding and the monitoring of processes in sedimentary depositional marine environment, especially for shallow coastal areas. This research study show the ability of optical medium resolution imagery to interpret the evolution of sediment resuspension from seafloor in coastal areas during intense wind forcings. Intense bora wind events in northern Adriatic Sea basin during winter season provoke considerable wave-generated resuspension of sediments, which cause variation in water column turbidity. Total Suspended Matter (TSM) product has been selected as proxy for qualitative and quantitative analysis of resuspended sediments. In addition, maximum signal depth (Z90_max), has been used to evaluate the evolution of sediment concentration in the water column.

Simple Approaches for Measuring Dry Atmospheric Nitrogen Deposition to Watersheds

EPA Science Inventory

Assessing the effects of atmospheric nitrogen (N) deposition on surface water quality requires accurate accounts of total N deposition (wet, dry, and cloud vapor); however, dry deposition is difficult to measure and is often spatially variable. Affordable passive sampling methods...

Spatial variation in the flux of atmospheric deposition and its ecological effects in arid Asia

NASA Astrophysics Data System (ADS)

Jiao, Linlin; Wang, Xunming; Li, Danfeng

2018-06-01

Atmospheric deposition is one of the key land surface processes, and plays important roles in regional ecosystems and global climate change. Previous studies have focused on the magnitude of and the temporal and spatial variations in the flux of atmospheric deposition, and the composition of atmospheric deposition on a local scale. However, there have been no comprehensive studies of atmospheric deposition on a regional scale and its ecological effects in arid Asia. The temporal and spatial patterns, composition of atmospheric deposition, and its potential effects on regional ecosystems in arid Asia are investigated in this study. The results show that the annual deposition flux is high on the Turan Plain, Aral Sea Desert, and Tarim Basin. The seasonal deposition flux also varies remarkably among different regions. The Tarim Basin shows higher deposition flux in both spring and summer, southern Mongolian Plateau has a higher deposition flux in spring, and the deposition flux of Iran Plateau is higher in summer. Multiple sources of elements in deposited particles are identified. Calcium, iron, aluminum, and magnesium are mainly derived from remote regions, while zinc, copper and lead have predominantly anthropogenic sources. Atmospheric deposition can provide abundant nutrients to vegetation and consequently play a role in the succession of regional ecosystems by affecting the structure, function, diversity, and primary production of the vegetation, especially the exotic or short-lived opportunistic species in arid Asia. Nevertheless, there is not much evidence of the ecological effects of atmospheric deposition on the regional and local scale. The present results may help in further understanding the mechanism of atmospheric deposition as well as providing a motivation for the protection of the ecological environment in arid Asia.

Deposition rates of viruses and bacteria above the atmospheric boundary layer.

PubMed

Reche, Isabel; D'Orta, Gaetano; Mladenov, Natalie; Winget, Danielle M; Suttle, Curtis A

2018-04-01

Aerosolization of soil-dust and organic aggregates in sea spray facilitates the long-range transport of bacteria, and likely viruses across the free atmosphere. Although long-distance transport occurs, there are many uncertainties associated with their deposition rates. Here, we demonstrate that even in pristine environments, above the atmospheric boundary layer, the downward flux of viruses ranged from 0.26 × 10 9 to >7 × 10 9  m -2 per day. These deposition rates were 9-461 times greater than the rates for bacteria, which ranged from 0.3 × 10 7 to >8 × 10 7  m -2 per day. The highest relative deposition rates for viruses were associated with atmospheric transport from marine rather than terrestrial sources. Deposition rates of bacteria were significantly higher during rain events and Saharan dust intrusions, whereas, rainfall did not significantly influence virus deposition. Virus deposition rates were positively correlated with organic aerosols <0.7 μm, whereas, bacteria were primarily associated with organic aerosols >0.7 μm, implying that viruses could have longer residence times in the atmosphere and, consequently, will be dispersed further. These results provide an explanation for enigmatic observations that viruses with very high genetic identity can be found in very distant and different environments.

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.

The Measurement of Atmospheric Concentrations and Deposition of Semi-Volatile Organic Compounds.

ERIC Educational Resources Information Center

Lee, David S.; Nicholson, Ken W.

1994-01-01

Provides a physical description of semivolatile organic compounds (SVOCs), both in terms of their characteristic nature in the atmosphere and the processes which control their deposition. Contains a summary of the requirements for a full assessment of atmospheric SVOCs and their deposition. (LZ)

Effect of atmospheric electricity on dry deposition of airborne particles from atmosphere

NASA Astrophysics Data System (ADS)

Tammet, H.; Kimmel, V.; Israelsson, S.

The electric mechanism of dry deposition is well known in the case of unattached radon daughter clusters that are unipolar charged and of high mobility. The problematic role of the electric forces in deposition of aerosol particles is theoretically examined by comparing the fluxes of particles carried by different deposition mechanisms in a model situation. The electric mechanism of deposition appears essential for particles of diameter 10-200 nm in conditions of low wind speed. The electric flux of fine particles can be dominant on the tips of leaves and needles even in a moderate atmospheric electric field of a few hundred V m -1 measured over the plane ground surface. The electric deposition is enhanced under thunderclouds and high voltage power lines. Strong wind suppresses the relative role of the electric deposition when compared with aerodynamic deposition. When compared with diffusion deposition the electric deposition appears less uniform: the precipitation particulate matter on the tips of leaves and especially on needles of top branches of conifer trees is much more intensive than on the ground surface and electrically shielded surfaces of plants. The knowledge of deposition geometry could improve our understanding of air pollution damage to plants.

Trade-Induced Atmospheric Mercury Deposition over China and Implications for Demand-Side Controls.

PubMed

Chen, Long; Meng, Jing; Liang, Sai; Zhang, Haoran; Zhang, Wei; Liu, Maodian; Tong, Yindong; Wang, Huanhuan; Wang, Wei; Wang, Xuejun; Shu, Jiong

2018-02-20

Mercury (Hg) is of global concern because of its adverse effects on humans and the environment. In addition to long-range atmospheric transport, Hg emissions can be geographically relocated through economic trade. Here, we investigate the effect of China's interregional trade on atmospheric Hg deposition over China, using an atmospheric transport model and multiregional input-output analysis. In general, total atmospheric Hg deposition over China is 408.8 Mg yr -1 , and 32% of this is embodied in China's interregional trade, with the hotspots occurring over Gansu, Henan, Hebei, and Yunnan provinces. Interprovincial trade considerably redistributes atmospheric Hg deposition over China, with a range in deposition flux from -104% to +28%. Developed regions, such as the Yangtze River Delta (Shanghai, Jiangsu, and Zhejiang) and Guangdong, avoid Hg deposition over their geographical boundaries, instead causing additional Hg deposition over developing provinces. Bilateral interaction among provinces is strong over some regions, suggesting a need for joint mitigation, such as the Jing-Jin-Ji region (Beijing, Tianjin, and Hebei) and the Yangtze River Delta. Transferring advanced technology from developed regions to their developing trade partners would be an effective measure to mitigate China's Hg pollution. Our findings are relevant to interprovincial efforts to reduce trans-boundary Hg pollution in China.

Climate-change signals in national atmospheric deposition program precipitation data

USGS Publications Warehouse

Wetherbee, Gregory A.; Mast, M. Alisa

2016-01-01

National Atmospheric Deposition Program (NADP)/National Trends Network precipitation type, snow-season duration, and annual timing of selected chemical wet-deposition maxima vary with latitude and longitude within a 35-year (1979–2013) data record for the contiguous United States and Alaska. From the NADP data collected within the region bounded by 35.6645°–48.782° north latitude and 124°–68° west longitude, similarities in latitudinal and longitudinal patterns of changing snow-season duration, fraction of annual precipitation recorded as snow, and the timing of chemical wet-deposition maxima, suggest that the chemical climate of the atmosphere is linked to physical changes in climate. Total annual precipitation depth has increased 4–6 % while snow season duration has decreased from approximately 7 to 21 days across most of the USA, except in higher elevation regions where it has increased by as much as 21 days. Snow-season precipitation is increasingly comprised of snow, but annually total precipitation is increasingly comprised of liquid precipitation. Meanwhile, maximum ammonium deposition occurs as much as 27 days earlier, and the maximum nitrate: sulfate concentration ratio in wet-deposition occurs approximately 10–21 days earlier in the year. The maximum crustal (calcium + magnesium + potassium) cation deposition occurs 2–35 days earlier in the year. The data suggest that these shifts in the timing of atmospheric wet deposition are linked to a warming climate, but the ecological consequences are uncertain.

Biomonitors of atmospheric nitrogen deposition: potential uses and limitations.

PubMed

Díaz-Álvarez, Edison A; Lindig-Cisneros, Roberto; de la Barrera, Erick

2018-01-01

Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha -1 year -1 , well above the threshold for physiological damage of 12-20 kg of N ha -1 year -1 , depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1‰ per kilogram of N ha -1 year -1 . The isotopic signature, δ 15 N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g. 5‰) of plants from natural environments can become very negative (-11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments or passive

Biomonitors of atmospheric nitrogen deposition: potential uses and limitations

PubMed Central

Díaz-Álvarez, Edison A; Lindig-Cisneros, Roberto

2018-01-01

Abstract Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha−1 year−1, well above the threshold for physiological damage of 12–20 kg of N ha−1 year−1, depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1‰ per kilogram of N ha−1 year−1. The isotopic signature, δ15N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g. 5‰) of plants from natural environments can become very negative (−11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments

Atmospheric Nitrogen Deposition in the Western United States: Sources, Sinks and Changes over Time

NASA Astrophysics Data System (ADS)

Anderson, Sarah Marie

Anthropogenic activities have greatly modified the way nitrogen moves through the atmosphere and terrestrial and aquatic environments. Excess reactive nitrogen generated through fossil fuel combustion, industrial fixation, and intensification of agriculture is not confined to anthropogenic systems but leaks into natural ecosystems with consequences including acidification, eutrophication, and biodiversity loss. A better understanding of where excess nitrogen originates and how that changes over time is crucial to identifying when, where, and to what degree environmental impacts occur. A major route into ecosystems for excess nitrogen is through atmospheric deposition. Excess nitrogen is emitted to the atmosphere where it can be transported great distances before being deposited back to the Earth's surface. Analyzing the composition of atmospheric nitrogen deposition and biological indicators that reflect deposition can provide insight into the emission sources as well as processes and atmospheric chemistry that occur during transport and what drives variation in these sources and processes. Chapter 1 provides a review and proof of concept of lichens to act as biological indicators and how their elemental and stable isotope composition can elucidate variation in amounts and emission sources of nitrogen over space and time. Information on amounts and emission sources of nitrogen deposition helps inform natural resources and land management decisions by helping to identify potentially impacted areas and causes of those impacts. Chapter 2 demonstrates that herbaria lichen specimens and field lichen samples reflect historical changes in atmospheric nitrogen deposition from urban and agricultural sources across the western United States. Nitrogen deposition increases throughout most of the 20 th century because of multiple types of emission sources until the implementation of the Clean Air Act Amendments of 1990 eventually decrease nitrogen deposition around the turn of

Atmospheric deposition exposes Qinling pandas to toxic pollutants.

PubMed

Chen, Yi-Ping; Zheng, Ying-Juan; Liu, Qiang; Song, Yi; An, Zhi-Sheng; Ma, Qing-Yi; Ellison, Aaron M

2017-03-01

The giant panda (Ailuropoda melanoleuca) is one of the most endangered animals in the world, and it is recognized worldwide as a symbol for conservation. A previous study showed that wild and captive pandas, especially those of the Qinling subspecies, were exposed to toxicants in their diet of bamboo; the ultimate origin of these toxicants is unknown. Here we show that atmospheric deposition is the most likely origin of heavy metals and persistent organic pollutants (POPs) in the diets of captive and wild Qinling pandas. Average atmospheric deposition was 199, 115, and 49 g·m -2 ·yr -1 in the center of Xi'an City, at China's Shaanxi Wild Animal Research Center (SWARC), and at Foping National Nature Reserve (FNNR), respectively. Atmospheric deposition of heavy metals (As, Cd, Cr, Pb, Hg, Co, Cu, Zn, Mn, and Ni) and POPs was highest at Xi'an City, intermediate at SWARC, and lowest at FNNR. Soil concentrations of the aforementioned heavy metals other than As and Zn also were significantly higher at SWARC than at FNNR. Efforts to conserve Qinling pandas may be compromised by air pollution attendant to China's economic development. Improvement of air quality and reductions of toxic emissions are urgently required to protect China's iconic species. © 2017 by the Ecological Society of America.

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

Use of a size-resolved 1-D resuspension scheme to evaluate resuspended radioactive material associated with mineral dust particles from the ground surface.

PubMed

Ishizuka, Masahide; Mikami, Masao; Tanaka, Taichu Y; Igarashi, Yasuhito; Kita, Kazuyuki; Yamada, Yutaka; Yoshida, Naohiro; Toyoda, Sakae; Satou, Yukihiko; Kinase, Takeshi; Ninomiya, Kazuhiko; Shinohara, Atsushi

2017-01-01

A size-resolved, one-dimensional resuspension scheme for soil particles from the ground surface is proposed to evaluate the concentration of radioactivity in the atmosphere due to the secondary emission of radioactive material. The particle size distributions of radioactive particles at a sampling point were measured and compared with the results evaluated by the scheme using four different soil textures: sand, loamy sand, sandy loam, and silty loam. For sandy loam and silty loam, the results were in good agreement with the size-resolved atmospheric radioactivity concentrations observed at a school ground in Tsushima District, Namie Town, Fukushima, which was heavily contaminated after the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. Though various assumptions were incorporated into both the scheme and evaluation conditions, this study shows that the proposed scheme can be applied to evaluate secondary emissions caused by aeolian resuspension of radioactive materials associated with mineral dust particles from the ground surface. The results underscore the importance of taking soil texture into account when evaluating the concentrations of resuspended, size-resolved atmospheric radioactivity. Copyright © 2016 Elsevier Ltd. All rights reserved.

Projections of Atmospheric Nutrient Deposition to the Chesapeake Bay Watershed

EPA Science Inventory

Atmospheric deposition remains one of the largest loadings of nutrients to the Chesapeake Bay watershed. The interplay between future land use, climate, and emission changes, however, will cause shifts in the future nutrient deposition regime (e.g., oxidized vs. reduced nitrogen...

Resuspension and settling of helminth eggs in water: Interactions with cohesive sediments.

PubMed

Sengupta, Mita E; Andersen, Thorbjørn J; Dalsgaard, Anders; Olsen, Annette; Thamsborg, Stig M

2012-08-01

Helminth parasite eggs in low quality water represent main food safety and health hazards and are therefore important indicators used to determine whether such water can be used for irrigation. Through sedimentation helminth eggs accumulate in the sediment, however resuspension of deposited helminth eggs will lead to increased concentration of suspended eggs in the water. Our study aimed to determine the erodibility (erosion rate and erosion threshold) and settling velocity of Ascaris and Trichuris eggs as well as cohesive sediment at different time points after incorporation into the sediment. Cohesive sediment collected from a freshwater stream was used to prepare a sediment bed onto which helminth eggs were allowed to settle. The erodibility of both sediment and helminth eggs was found to decrease over time indicating that the eggs were incorporated into the surface material of the bed and that this material was stabilized through time. This interaction between eggs and bulk sediment was further manifested in an increased settling velocity of suspended eggs when sediment was present in the suspension as compared to a situation with settling in clean water. The incorporation into the sediment bed and the aggregation with sediment particles decrease the mobility of both helminth egg types. Our findings document that helminth eggs should not be viewed as single entities in water systems when modelling the distribution of eggs since both erodibility and settling velocity of eggs are determined by mobility of the sediment present in the water stream. Recalculation of the erosion threshold for helminth eggs and sediment showed that even at relatively low current velocities i.e. 0.07-0.12ms(-1) newly deposited eggs will be mobile in open irrigation channels. These environmental factors affecting resuspension must be taken into account when developing models for sedimentation of helminth eggs in different water systems. Copyright © 2012 Elsevier Ltd. All rights

Western Pacific atmospheric nutrient deposition fluxes, their impact on surface ocean productivity

NASA Astrophysics Data System (ADS)

Martino, M.; Hamilton, D.; Baker, A. R.; Jickells, T. D.; Bromley, T.; Nojiri, Y.; Quack, B.; Boyd, P. W.

2014-07-01

The atmospheric deposition of both macronutrients and micronutrients plays an important role in driving primary productivity, particularly in the low-latitude ocean. We report aerosol major ion measurements for five ship-based sampling campaigns in the western Pacific from ~25°N to 20°S and compare the results with those from Atlantic meridional transects (~50°N to 50°S) with aerosols collected and analyzed in the same laboratory, allowing full incomparability. We discuss sources of the main nutrient species (nitrogen (N), phosphorus (P), and iron (Fe)) in the aerosols and their stoichiometry. Striking north-south gradients are evident over both basins with the Northern Hemisphere more impacted by terrestrial dust sources and anthropogenic emissions and the North Atlantic apparently more impacted than the North Pacific. We estimate the atmospheric supply rates of these nutrients and the potential impact of the atmospheric deposition on the tropical western Pacific. Our results suggest that the atmospheric deposition is P deficient relative to the needs of the resident phytoplankton. These findings suggest that atmospheric supply of N, Fe, and P increases primary productivity utilizing some of the residual excess phosphorus (P*) in the surface waters to compensate for aerosol P deficiency. Regional primary productivity is further enhanced via the stimulation of nitrogen fixation fuelled by the residual atmospheric iron and P*. Our stoichiometric calculations reveal that a P* of 0.1 µmol L-1 can offset the P deficiency in atmospheric supply for many months. This study suggests that atmospheric deposition may sustain ~10% of primary production in both the western tropical Pacific.

Atmospheric mercury deposition and its contribution of the regional atmospheric transport to mercury pollution at a national forest nature reserve, southwest China.

PubMed

Ma, Ming; Wang, Dingyong; Du, Hongxia; Sun, Tao; Zhao, Zheng; Wei, Shiqing

2015-12-01

Atmospheric mercury deposition by wet and dry processes contributes to the transformation of mercury from atmosphere to terrestrial and aquatic systems. Factors influencing the amount of mercury deposited to subtropical forests were identified in this study. Throughfall and open field precipitation samples were collected in 2012 and 2013 using precipitation collectors from forest sites located across Mt. Jinyun in southwest China. Samples were collected approximately every 2 weeks and analyzed for total (THg) and methyl mercury (MeHg). Forest canopy was the primary factor on THg and MeHg deposition. Simultaneously, continuous measurements of atmospheric gaseous elemental mercury (GEM) were carried out from March 2012 to February 2013 at the summit of Mt. Jinyun. Atmospheric GEM concentrations averaged 3.8 ± 1.5 ng m(-3), which was elevated compared with global background values. Sources identification indicated that both regional industrial emissions and long-range transport of Hg from central, northeast, and southwest China were corresponded to the elevated GEM levels. Precipitation deposition fluxes of THg and MeHg in Mt. Jinyun were slightly higher than those reported in Europe and North America, whereas total fluxes of MeHg and THg under forest canopy on Mt. Jiuyun were 3 and 2.9 times of the fluxes of THg in wet deposition in the open. Highly elevated litterfall deposition fluxes suggest that even in remote forest areas of China, deposition of atmospheric Hg(0) via uptake by vegetation leaf may be a major pathway for the deposition of atmospheric Hg. The result illustrates that areas with greater atmospheric pollution can be expected to have greater fluxes of Hg to soils via throughfall and litterfall.

Seasonal atmospheric deposition and air-sea gas exchange of polycyclic aromatic hydrocarbons over the Yangtze River Estuary, East China Sea: Implications for source-sink processes

NASA Astrophysics Data System (ADS)

Jiang, Yuqing; Lin, Tian; Wu, Zilan; Li, Yuanyuan; Li, Zhongxia; Guo, Zhigang; Yao, Xiaohong

2018-04-01

In this work, air samples and surface seawater samples covering four seasons from March 2014 to January 2015 were collected from a background receptor site in the YRE to explore the seasonal fluxes of air-sea gas exchange and dry and wet deposition of 15 polycyclic aromatic hydrocarbons (PAHs) and their source-sink processes at the air-sea interface. The average dry and wet deposition fluxes of 15 PAHs were estimated as 879 ± 1393 ng m-2 d-1 and 755 ± 545 ng m-2 d-1, respectively. Gaseous PAH release from seawater to the atmosphere averaged 3114 ± 1999 ng m-2 d-1 in a year round. The air-sea gas exchange of PAHs was the dominant process at the air-sea interface in the YRE as the magnitude of volatilization flux of PAHs exceeded that of total dry and wet deposition. The gas PAH exchange flux was dominated by three-ring PAHs, with the highest value in summer and lowest in winter, indicating a marked seasonal variation owing to differences in Henry's law constants associated with temperature, as well as wind speed and gaseous-dissolved gradient among seasons. Based on the simplified mass balance estimation, a net 11 tons y-1 of PAHs (mainly three-ring PAHs) were volatilized from seawater to the atmosphere in a ∼20,000 km2 area in the YRE. Other than the year-round Yangtze River input and ocean ship emissions, the selective release of low-molecular-weight PAHs from bottom sediments in winter due to resuspension triggered by the East Asian winter monsoon is another potential source of PAHs. This work suggests that the source-sink processes of PAHs at the air-sea interface in the YRE play a crucial role in regional cycling of PAHs.

Atmospheric deposition, CO2, and change in the land carbon sink.

PubMed

Fernández-Martínez, M; Vicca, S; Janssens, I A; Ciais, P; Obersteiner, M; Bartrons, M; Sardans, J; Verger, A; Canadell, J G; Chevallier, F; Wang, X; Bernhofer, C; Curtis, P S; Gianelle, D; Grünwald, T; Heinesch, B; Ibrom, A; Knohl, A; Laurila, T; Law, B E; Limousin, J M; Longdoz, B; Loustau, D; Mammarella, I; Matteucci, G; Monson, R K; Montagnani, L; Moors, E J; Munger, J W; Papale, D; Piao, S L; Peñuelas, J

2017-08-29

Concentrations of atmospheric carbon dioxide (CO 2 ) have continued to increase whereas atmospheric deposition of sulphur and nitrogen has declined in Europe and the USA during recent decades. Using time series of flux observations from 23 forests distributed throughout Europe and the USA, and generalised mixed models, we found that forest-level net ecosystem production and gross primary production have increased by 1% annually from 1995 to 2011. Statistical models indicated that increasing atmospheric CO 2 was the most important factor driving the increasing strength of carbon sinks in these forests. We also found that the reduction of sulphur deposition in Europe and the USA lead to higher recovery in ecosystem respiration than in gross primary production, thus limiting the increase of carbon sequestration. By contrast, trends in climate and nitrogen deposition did not significantly contribute to changing carbon fluxes during the studied period. Our findings support the hypothesis of a general CO 2 -fertilization effect on vegetation growth and suggest that, so far unknown, sulphur deposition plays a significant role in the carbon balance of forests in industrialized regions. Our results show the need to include the effects of changing atmospheric composition, beyond CO 2 , to assess future dynamics of carbon-climate feedbacks not currently considered in earth system/climate modelling.

Tracing Fallout Radionuclide Behavior During Atmospheric Deposition and Pedogenesis

NASA Astrophysics Data System (ADS)

Landis, J. D.

2017-12-01

Short-lived fallout radionuclides 7Be (54 day half-life) and 210Pbexcess (22.3 year half-life) inform problems in geomorphology covering timespans of days to decades. Linking these radionuclides together is a powerful strategy, since the ratio 7Be:210Pb can control for changes in the activity of each, provided that the tracers have similar behavior through relevant chemical and physical processes such as interception, sorption, dilution, transport, etc. To investigate the extent to which 7Be and 210Pbxs share a common behavior, I measured these radionuclides in atmospheric deposition, vegetation, and stable soil, sediment and peat profiles. Bulk deposition of 7Be and 210Pb was measured in weekly intervals for 6 years of continuous record. Samples of red oak leaves (Quercus rubra) were collected regularly over 4 years at a site co-located with precipitation collection. Soil pits were sampled by high resolution methods at regional, undisturbed sites. In all samples 7Be, 210Pb, and other nuclides were measured by high-precision gamma spectrometry. Depositional fluxes of 7Be and 210Pb were highly correlated, with 7Be:210Pb converging to the long-term mean activity ratio of ca. 10.5 over intervals of 7 to 14 days. Red oak foliage accumulated 7Be and 210Pb at a linear rate during both growth and senescence, and appeared to maintain a dynamic equilibrium with atmospheric deposition. Canopies of both forest and grass intercepted on the order of 50% of deposition; the remainder reached underlying soil, where 7Be activity showed an exponential decline due to rapid hydrologic penetration of soil surface. Features of 210Pbxs soil profiles, including a subsurface maximum, reflect the same penetration pattern integrated over decades of deposition. Application of the Linked Radionuclide aCcumulation (LRC) model demonstrated that 210Pb moves through soil, peat and fluvial sediment profiles at rates on the order of 1 mm per year, similar to other atmospherically-derived metals

Human health risk assessment of lead pollution in atmospheric deposition in Baoshan District, Shanghai.

PubMed

Chen, Yuanyuan; Wang, Jun; Shi, Guitao; Sun, Xiaojing; Chen, Zhenlou; Xu, Shiyuan

2011-12-01

The lead (Pb) content in atmospheric deposition was determined at 42 sampling sites in Baoshan District of Shanghai, China. Based on exposure and dose-response assessments, the health risk caused by Pb exposure in atmospheric deposition was investigated. The results indicated that Pb was significantly accumulated in atmospheric deposition. The spatial distribution of Pb was mapped by geostatistical analysis, and the results showed that pollution hotspots were present at traffic and industrial zones. Ingestion was the main route of Pb exposure in both adults and children. For children the risk value was above 1, whereas it was below 1 for the adult group. Therefore, children belong to the high-risk group for Pb exposure from atmospheric deposition in the observed area of Shanghai, China.

Measurement of forest condition and response along the Pennsylvania atmospheric deposition gradent

Treesearch

D.D. David; J.M. Skelly; J.A. Lynch; L.H. McCormick; B.L. Nash; M. Simini; E.A. Cameron; J.R. McClenahen; R.P. Long

1991-01-01

Research in the oak-hickory forest of northcentral Pennsylvania is being conducted to detect anomalies in forest condition that may be due to atmospheric deposition, with the intent that such anomalies will be further studied to determine the role, if any, of atmospheric deposition. This paper presents the status of research along a 160-km gradient of sulfate/nitrate...

Atmospheric Deposition of Heavy Metals in Soil Affected by Different Soil Uses of Southern Spain

NASA Astrophysics Data System (ADS)

Acosta, J. A.; Faz, A.; Martínez-Martínez, S.; Bech, J.

2009-04-01

Heavy metals are a natural constituent of rocks, sediments and soils. However, the heavy metal content of top soils is also dependent on other sources than weathering of the indigenous minerals; input from atmospheric deposition seems to be an important pathway. Atmospheric deposition is defined as the process by which atmospheric pollutants are transferred to terrestrial and aquatic surfaces and is commonly classified as either dry or wet. The interest in atmospheric deposition has increased over the past decade due to concerns about the effects of deposited materials on the environment. Dry deposition provides a significant mechanism for the removal of particles from the atmosphere and is an important pathway for the loading of heavy metals into the soil ecosystem. Within the last decade, an intensive effort has been made to determine the atmospheric heavy metal deposition in both urban and rural areas. The main objective of this study was to identification of atmospheric heavy metals deposition in soil affected by different soil uses. Study area is located in Murcia Province (southeast of Spain), in the surroundings of Murcia City. The climate is typically semiarid Mediterranean with an annual average temperature of 18°C and precipitation of 350 mm. In order to determine heavy metals atmospheric deposition a sampling at different depths (0-1 cm, 1-5 cm, 5-15 cm and 15-30 cm) was carried out in 7 sites including agricultural soils, two industrial areas and natural sites. The samples were taken to the laboratory where, dried, passed through a 2 mm sieve, and grinded. For the determination of the moisture the samples were weighed and oven dried at 105 °C for 24 h. The total amounts of metals (Pb, Cu, Pb, Zn, Cd, Mn, Ni and Cr) were determined by digesting the samples with nitric/perchoric acids and measuring with ICP-MS. Results showed that zinc contamination in some samples of industrial areas was detected, even this contamination reaches 30 cm depth; thus it is

Atmospheric deposition of phthalate esters in a subtropical city

NASA Astrophysics Data System (ADS)

Zeng, Feng; Lin, Yujun; Cui, Kunyan; Wen, Jiaxin; Ma, Yongqin; Chen, Hongli; Zhu, Fang; Ma, Zhiling; Zeng, Zunxiang

2010-02-01

In Chinese cities, air pollution has become a serious and aggravating environmental problem undermining the sustainability of urban ecosystems and the quality of urban life. Bulk atmospheric deposition samples were collected two-weekly, from February 2007 to January 2008, at three representative areas, one suburban and two urbanized, in the subtropical city, Guangzhou, China, to assess the deposition fluxes and seasonal variations of phthalate esters (PAEs). Sixteen PAE congeners in bulk deposition samples were measured and the depositional fluxes of ∑ 16PAEs ranged from 3.41 to 190 μg m -2 day -1, and were highly affected by local anthropogenic activities. The significant relationship between PAEs and particulate depositional fluxes (correlation coefficient R2 = 0.72, P < 0.001) showed PAEs are associated primarily with particles. Temporal flux variations of PAEs were influenced by seasonal changes in meteorological parameters, and the deposition fluxes of PAEs were obviously higher in wet season than in dry season. Diisobutyl phthalate (D iBP), Di- n-butyl phthalate (D nBP), and Di(2-ethylhexyl) phthalate (DEHP) dominated the PAE pattern in bulk depositions, which is consistent with a high consumption of the plasticizer market in China. PAE profiles in bulk deposition showed similarities exhibited in both time and space, and a weak increase of high molecular weight PAE (HMW PAE) contribution in the wet season compared to those in the dry season. Average atmospheric deposition fluxes of PAEs in the present study were significantly higher than those from other studies, reflecting strong anthropogenic inputs as a consequence of rapid industrial and urban development in the region.

Oceanic Emissions and Atmospheric Depositions of Volatile Organic Compounds

NASA Astrophysics Data System (ADS)

Yang, M.; Blomquist, B.; Beale, R.; Nightingale, P. D.; Liss, P. S.

2015-12-01

Atmospheric volatile organic compounds (VOCs) affect the tropospheric oxidative capacity due to their ubiquitous abundance and relatively high reactivity towards the hydroxyal radical. Over the ocean and away from terrestrial emission sources, oxygenated volatile organic compounds (OVOCs) make up a large fraction of VOCs as airmasses age and become more oxidized. In addition to being produced or destroyed in the marine atmosphere, OVOCs can also be emitted from or deposited to the surface ocean. Here we first present direct air-sea flux measurements of three of the most abundant OVOCs - methanol, acetone, and acetaldehyde, by the eddy covariance technique from two cruises in the Atlantic: the Atlantic Meridional Transect in 2012 and the High Wind Gas Exchange Study in 2013. The OVOC mixing ratios were quantified by a high resolution proton-reaction-transfer mass spectrometer with isotopically labeled standards and their air-sea (net) fluxes were derived from the eddy covariance technique. Net methanol flux was consistently from the atmosphere to the surface ocean, while acetone varied from supersaturation (emission) in the subtropics to undersaturation (deposition) in the higher latitudes of the North Atlantic. The net air-sea flux of acetaldehyde is near zero through out the Atlantic despite the apparent supersaturation of this compound in the surface ocean. Knowing the dissolved concentrations and in situ production rates of these compounds in seawater, we then estimate their bulk atmospheric depositions and oceanic emissions. Lastly, we summarize the state of knowledge on the air-sea transport of a number of organic gasses, and postulate the magnitude and environmental impact of total organic carbon transfer between the ocean and the atmosphere.

A sediment resuspension and water quality model of Lake Okeechobee

USGS Publications Warehouse

James, R.T.; Martin, J.; Wool, T.; Wang, P.-F.

1997-01-01

The influence of sediment resuspension on the water quality of shallow lakes is well documented. However, a search of the literature reveals no deterministic mass-balance eutrophication models that explicitly include resuspension. We modified the Lake Okeeehobee water quality model - which uses the Water Analysis Simulation Package (WASP) to simulate algal dynamics and phosphorus, nitrogen, and oxygen cycles - to include inorganic suspended solids and algorithms that: (1) define changes in depth with changes in volume; (2) compute sediment resuspension based on bottom shear stress; (3) compute partition coefficients for ammonia and ortho-phosphorus to solids; and (4) relate light attenuation to solids concentrations. The model calibration and validation were successful with the exception of dissolved inorganic nitrogen species which did not correspond well to observed data in the validation phase. This could be attributed to an inaccurate formulation of algal nitrogen preference and/or the absence of nitrogen fixation in the model. The model correctly predicted that the lake is lightlimited from resuspended solids, and algae are primarily nitrogen limited. The model simulation suggested that biological fluxes greatly exceed external loads of dissolved nutrients; and sedimentwater interactions of organic nitrogen and phosphorus far exceed external loads. A sensitivity analysis demonstrated that parameters affecting resuspension, settling, sediment nutrient and solids concentrations, mineralization, algal productivity, and algal stoichiometry are factors requiring further study to improve our understanding of the Lake Okeechobee ecosystem.

Lichen-based critical loads for atmospheric nitrogen deposition in Western Oregon and Washington forests, USA

Treesearch

Linda H. Geiser; Sarah E. Jovan; Doug A. Glavich; Matthew K. Porter

2010-01-01

Critical loads (CLs) define maximum atmospheric deposition levels apparently preventative of ecosystem harm. We present first nitrogen CLs for northwestern North America's maritime forests. Using multiple linear regression, we related epiphytic-macrolichen community composition to: 1) wet deposition from the National Atmospheric Deposition Program, 2) wet, dry,...

MEASURING CONTAMINANT RESUSPENSION RESULTING FROM SEDIMENT CAPPING

EPA Science Inventory

This Sediment Issue summarizes two studies undertaken at marine sites by the National Risk Management Research Laboratory of U.S. EPA to evaluate the resuspension of surface materials contaminated with polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) b...

Atmospheric bulk deposition of polycyclic aromatic hydrocarbons in Shanghai: Temporal and spatial variation, and global comparison.

PubMed

Feng, Daolun; Liu, Ying; Gao, Yi; Zhou, Jinxing; Zheng, Lirong; Qiao, Gang; Ma, Liming; Lin, Zhifen; Grathwohl, Peter

2017-11-01

Atmospheric deposition leads to accumulation of atmospheric polycyclic aromatic hydrocarbons (PAHs) on urban surfaces and topsoils. To capture the inherent variability of atmospheric deposition of PAHs in Shanghai's urban agglomeration, 85 atmospheric bulk deposition samples and 7 surface soil samples were collected from seven sampling locations during 2012-2014. Total fluxes of 17 PAHs were 587-32,300 ng m -2 day -1 , with a geometric mean of 2600 ng m -2 day -1 . The deposition fluxes were categorized as moderate to high on a global scale. Phenanthrene, fluoranthene and pyrene were major contributors. The spatial distribution of deposition fluxes revealed the influence of urbanization/industrialization and the relevance of local emissions. Meteorological conditions and more heating demand in cold season lead to a significant increase of deposition rates. Atmospheric deposition is the principal pathway of PAHs input to topsoils and the annual deposition load in Shanghai amounts to ∼4.5 tons (0.7 kg km -2 ) with a range of 2.5-10 tons (0.4-1.6 kg km -2 ). Copyright © 2017 Elsevier Ltd. All rights reserved.

Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies.

PubMed

Behera, Sailesh N; Sharma, Mukesh; Aneja, Viney P; Balasubramanian, Rajasekhar

2013-11-01

Gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH3 emissions is agriculture, including animal husbandry and NH3-based fertilizer applications. Other sources of NH3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH3. Over the last two decades, a number of research papers have addressed pertinent issues related to NH3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH3 from the literature in a systematic manner, describes the environmental implications of unabated NH3 emissions and provides a scientific basis for developing effective control strategies for NH3.

Decreased atmospheric sulfur deposition across the southeastern U.S.: When will watersheds release stored sulfate?

Treesearch

Karen C. Rice; Todd M. Scanlon; Jason A. Lynch; Bernard J. Cosby

2014-01-01

Emissions of sulfur dioxide (SO2) to the atmosphere lead to atmospheric deposition of sulfate (SO42-), which is the dominant strong acid anion causing acidification of surface waters and soils in the eastern United States. Since passage of the Clean Air Act and its Amendments, atmospheric deposition...

ANALYSIS OF ATMOSPHERE DEPOSITION SAMPLES FROM EASTON, PA

EPA Science Inventory

The report gives results of an analysis of samples of tenacious atmospheric deposits on exposed surfaces (e.g., automobiles and houses) in an industrial area near Easton, PA. The analysis was made at the request of the State of Pennsylvania. The Pennsylvania Department of Environ...

ANALYSIS OF ATMOSPHERE DEPOSITION SAMPLES FROM EASTON, PA

EPA Science Inventory

The report gives results of an analysis of samples of tenacious atmospheric deposits on exposed surfaces (e.g., automobiles and houses) in an industrial area near Easton, PA. he analysis was made at the request of the State of Pennsylvania. he Pennsylvania Department of Environme...

Complementary Pu Resuspension Study at Palomares, Spain

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

Shinn, J

2002-10-01

Soil in an area near Palomares, Spain, was contaminated with plutonium as a result of a mid-air collision of U.S. military aircraft in January 1966. The assessment for potential inhalation dose can be found in Iranzo et al., (1987). Long-term monitoring has been used to evaluate remedial actions (Iranzo et al., 1988) and there are many supporting studies of the Pu contamination at Palomares that have been carried out by the Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT) in Madrid. The purpose of this study is to evaluate the resuspension of Pu from the soil in terms of Pu-concentrationsmore » in air and resuspension rates in a complementary investigation to those of CIEMAT but in an intensive short-term field effort. This study complements the resuspension studies of CIEMAT at Palomares with additional information, and with confirmation of their previous studies. Observed mass loadings (M) were an average of 70 mg/m{sup 3} with peaks in the daytime of 130 mg/m{sup 3} and low values at night below 30 {micro}g/m{sup 3}. The Pu-activity of aerosols (A) downwind of plot 2-1 was 0.12 Bq/g and the enhancement factor (E{sub f}) had a value of 0.3, which is low but similar to a typical value of 0.7 for other undisturbed sites. This E{sub f} value may increase further away from ground zero. The particle size distribution of the Pu in air measured by cascade impactors was approximately lognormal with a median aerodynamic diameter of 3.7 {micro}m and a geometric standard deviation of 3.5 in the respirable range. This peak midway between 1 ? m and 10 {micro}m in the respirable range is commonly observed. Daily fluctuations in the Pu concentration in air (C) detected by the UHV were lognormally distributed with a geometric standard deviation of 4.9 indicating that the 98th percentile would be 24 times as high as the median. Downwind of plot 2-1 the mean Pu concentration in air, C, was 8.5 {micro}Bq/m{sup 3}. The resuspension factor (Sf) was 2

A 3D parameterization of nutrients atmospheric deposition to the global ocean

NASA Astrophysics Data System (ADS)

Myriokefalitakis, S.; Nenes, A.; Baker, A. R.; Mihalopoulos, N.; Kanakidou, M.

2016-12-01

Atmospheric deposition of trace constituents, both of natural and anthropogenic origin, can act as a nutrient source into the open ocean and affect marine ecosystem functioning and subsequently the exchange of CO2 between the atmosphere and the global ocean. Dust is known as a major source of nutrients (such as iron and phosphorus) to the global ocean, but only a fraction of these nutrients is released in soluble form that can be assimilated by the ecosystems. The global atmospheric iron (Fe) and phosphorus (P) cycles are here parameterized in a global 3-D chemical transport model. Both primary emissions of total and soluble Fe and P associated with dust and combustion processes are taken into account. The impact of atmospheric acidity on nutrient solubility is parameterised based on experimental findings and model results are evaluated by comparison with available observations. The effect of air-quality changes on soluble nutrient deposition is studied by performing sensitivity simulations using preindustrial, present and future emission scenarios. The link between the soluble Fe and P atmospheric deposition and anthropogenic sources is also investigated. Overall, the response of the chemical composition of nutrient-containing aerosols to environmental changes is demonstrated and quantified.

Comparison of Mercury Mass Loading in Streams to Wet and Dry Atmospheric Deposition in Watersheds of the Western US: Evidence for Non-Atmospheric Mercury Sources

NASA Astrophysics Data System (ADS)

Domagalski, J. L.; Majewski, M. S.; Alpers, C. N.; Eckley, C.

2015-12-01

Many streams in the western United States (US) are listed as impaired by mercury (Hg), and it is important to understand the magnitudes of the various sources in order to implement management strategies. Atmospheric deposition of Hg and can be a major source of aquatic contamination, along with mine wastes, and other sources. Prior studies in the eastern US have shown that streams deliver less than 50% of the atmospherically deposited Hg on an annual basis. In this study, we compared annual stream Hg loads for 20 watersheds in the western US to measured wet and modeled dry deposition. Land use varies from undisturbed to mixed (agricultural, urban, forested, mining). Data from the Mercury Deposition Network was used to estimate Hg input from precipitation. Dry deposition was not directly measured, but can be modeled using the Community Multi-scale Air Quality model. At an undeveloped watershed in the Rocky Mountains, the ratio of stream Hg load to atmospheric deposition was 0.2 during a year of average precipitation. In contrast, at the Carson River in Nevada, with known Hg contamination from historical silver mining with Hg amalgamation, stream export exceeded atmospheric deposition by a factor of 60, and at a small Sierran watershed with gold mining, the ratio was 70. Larger watersheds with mixed land uses, tend to have lower ratios of stream export relative to atmospheric deposition suggesting storage of Hg. The Sacramento River was the largest watershed for which Hg riverine loads were available with an average ratio of stream Hg export to atmospheric deposition of 0.10. Although Hg was used in upstream historical mining operations, the downstream river Hg load is partially mitigated by reservoirs, which trap sediment. This study represents the first compilation of riverine Hg loads in comparison to atmospheric deposition on a regional scale; the approach may be useful in assessing the relative importance of atmospheric and non-atmospheric Hg sources.

Pulsed laser deposition of plasmonic nanostructured gold on flexible transparent polymers at atmospheric pressure

NASA Astrophysics Data System (ADS)

McCann, Ronán; Hughes, Cian; Bagga, Komal; Stalcup, Apryll; Vázquez, Mercedes; Brabazon, Dermot

2017-06-01

In this paper, we outline a novel technique for the deposition of nanostructured thin films utilizing a modified form of pulsed laser deposition (PLD). We demonstrate confined atmospheric PLD (CAP) for the deposition of gold on cyclic olefin polymer substrates. The deposition process is a simplified form of conventional PLD, with deposition conducted under atmospheric conditions and the substrate and target in close proximity. It was found that this confinement results in the deposition of nanostructured thin films on the substrate. Infrared spectroscopy showed no significant change of polymer surface chemistry as a result of the deposition process, and optical spectroscopy revealed plasmonic behavior of the resulting thin film. The effect of laser fluence on the deposition process was also examined with more uniform films deposited at higher fluences.

Atmospheric Deposition of Indium in the Northeastern United States: Flux and Historical Trends.

PubMed

White, Sarah Jane O; Keach, Carrie; Hemond, Harold F

2015-11-03

The metal indium is an example of an increasingly important material used in electronics and new energy technologies, whose environmental behavior and toxicity are poorly understood despite increasing evidence of detrimental health impacts and human-induced releases to the environment. In the present work, the history of indium deposition from the atmosphere is reconstructed from its depositional record in an ombrotrophic bog in Massachusetts. A novel freeze-coring technique is used to overcome coring difficulties posed by woody roots and peat compressibility, enabling retrieval of relatively undisturbed peat cores dating back more than a century. Results indicate that long-range atmospheric transport is a significant pathway for the transport of indium, with peak concentrations of 69 ppb and peak fluxes of 1.9 ng/cm2/yr. Atmospheric deposition to the bog began increasing in the late 1800s/early 1900s, and peaked in the early 1970s. A comparison of deposition data with industrial production and emissions estimates suggests that both coal combustion and the smelting of lead, zinc, copper, and tin sulfides are sources of indium to the atmosphere in this region. Deposition appears to have decreased considerably since the 1970s, potentially a visible effect of particulate emissions controls instated in North America during that decade.

Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering

NASA Astrophysics Data System (ADS)

Stark, C. R.; Diver, D. A.

2018-04-01

Context. In contemporary sub-stellar model atmospheres, dust growth occurs through neutral gas-phase surface chemistry. Recently, there has been a growing body of theoretical and observational evidence suggesting that ionisation processes can also occur. As a result, atmospheres are populated by regions composed of plasma, gas and dust, and the consequent influence of plasma processes on dust evolution is enhanced. Aim. This paper aims to introduce a new model of dust growth and destruction in sub-stellar atmospheres via plasma deposition and plasma sputtering. Methods: Using example sub-stellar atmospheres from DRIFT-PHOENIX, we have compared plasma deposition and sputtering timescales to those from neutral gas-phase surface chemistry to ascertain their regimes of influence. We calculated the plasma sputtering yield and discuss the circumstances where plasma sputtering dominates over deposition. Results: Within the highest dust density cloud regions, plasma deposition and sputtering dominates over neutral gas-phase surface chemistry if the degree of ionisation is ≳10-4. Loosely bound grains with surface binding energies of the order of 0.1-1 eV are susceptible to destruction through plasma sputtering for feasible degrees of ionisation and electron temperatures; whereas, strong crystalline grains with binding energies of the order 10 eV are resistant to sputtering. Conclusions: The mathematical framework outlined sets the foundation for the inclusion of plasma deposition and plasma sputtering in global dust cloud formation models of sub-stellar atmospheres.

Nutrient availability and phytoplankton nutrient limitation across a gradient of atmospheric nitrogen deposition

USGS Publications Warehouse

Elser, J.J.; Kyle, M.; Steuer, L.; Nydick, K.R.; Baron, Jill S.

2009-01-01

Atmospheric nitrogen (N) deposition to lakes and watersheds has been increasing steadily due to various anthropogenic activities. Because such anthropogenic N is widely distributed, even lakes relatively removed from direct human disturbance are potentially impacted. However, the effects of increased atmospheric N deposition on lakes are not well documented, We examined phytoplankton biomass, the absolute and relative abundance of limiting nutrients (N and phosphorus [P]), and phytoplankton nutrient limitation in alpine lakes of the Rocky Mountains of Colorado (USA) receiving elevated (>6 kg N??ha-1??yr-1) or low (<2 kg N??ha-1??yr-1) levels of atmospheric N deposition. Highdeposition lakes had higher NO3-N and total N concentrations and higher total N : total P ratios. Concentrations of chlorophyll and seston carbon (C) were 2-2.5 times higher in highdeposition relative to low-deposition lakes, while high-deposition lakes also had higher seston C:N and C:P (but not N:P) ratios. Short-term enrichment bioassays indicated a qualitative shift in the nature of phytoplankton nutrient limitation due to N deposition, as highdeposition lakes had an increased frequency of primary P limitation and a decreased frequency and magnitude of response to N and to combined N and P enrichment. Thus elevated atmospheric N deposition appears to have shifted nutrient supply from a relatively balanced but predominantly N-deficient regime to a more consistently P-limited regime in Colorado alpine lakes. This adds to accumulating evidence that sustained N deposition may have important effects on lake phytoplankton communities and plankton-based food webs by shifting the quantitative and qualitative nature of nutrient limitation. ?? 2009 by the Ecological Society of America.

Response of global soil consumption of atmospheric methane to changes in atmospheric climate and nitrogen deposition

USGS Publications Warehouse

Zhuang, Qianlai; Chen, Min; Xu, Kai; Tang, Jinyun; Saikawa, Eri; Lu, Yanyu; Melillo, Jerry M.; Prinn, Ronald G.; McGuire, A. David

2013-01-01

Soil consumption of atmospheric methane plays an important secondary role in regulating the atmospheric CH4 budget, next to the dominant loss mechanism involving reaction with the hydroxyl radical (OH). Here we used a process-based biogeochemistry model to quantify soil consumption during the 20th and 21st centuries. We estimated that global soils consumed 32–36 Tg CH4 yr−1 during the 1990s. Natural ecosystems accounted for 84% of the total consumption, and agricultural ecosystems only consumed 5 Tg CH4 yr−1 in our estimations. During the twentieth century, the consumption rates increased at 0.03–0.20 Tg CH4 yr−2 with seasonal amplitudes increasing from 1.44 to 3.13 Tg CH4 month−1. Deserts, shrublands, and xeric woodlands were the largest sinks. Atmospheric CH4 concentrations and soil moisture exerted significant effects on the soil consumption while nitrogen deposition had a moderate effect. During the 21st century, the consumption is predicted to increase at 0.05-1.0 Tg CH4 yr−2, and total consumption will reach 45–140 Tg CH4 yr−1 at the end of the 2090s, varying under different future climate scenarios. Dry areas will persist as sinks, boreal ecosystems will become stronger sinks, mainly due to increasing soil temperatures. Nitrogen deposition will modestly reduce the future sink strength at the global scale. When we incorporated the estimated global soil consumption into our chemical transport model simulations, we found that nitrogen deposition suppressed the total methane sink by 26 Tg during the period 1998–2004, resulting in 6.6 ppb higher atmospheric CH4 mixing ratios compared to without considering nitrogen deposition effects. On average, a cumulative increase of every 1 Tg soil CH4 consumption decreased atmospheric CH4 mixing ratios by 0.26 ppb during the period 1998–2004.

Source apportionment of atmospheric bulk deposition in the Belgrade urban area using Positive Matrix factorization

NASA Astrophysics Data System (ADS)

Tasić, M.; Mijić, Z.; Rajšić, S.; Stojić, A.; Radenković, M.; Joksić, J.

2009-04-01

The primary objective of the present study was to assess anthropogenic impacts of heavy metals to the environment by determination of total atmospheric deposition of heavy metals. Atmospheric depositions (wet + dry) were collected monthly, from June 2002 to December 2006, at three urban locations in Belgrade, using bulk deposition samplers. Concentrations of Fe, Al, Pb, Zn, Cu, Ni, Mn, Cr, V, As and Cd were analyzed using atomic absorption spectrometry. Based upon these results, the study attempted to examine elemental associations in atmospheric deposition and to elucidate the potential sources of heavy metal contaminants in the region by the use of multivariate receptor model Positive Matrix Factorization (PMF).

Elevated atmospheric deposition and dynamics of mercury in a remote upland forest of southwestern China.

PubMed

Fu, Xuewu; Feng, Xinbin; Zhu, Wanze; Rothenberg, S; Yao, Heng; Zhang, Hui

2010-06-01

Mt. Gongga area in southwest China was impacted by Hg emissions from industrial activities and coal combustion, and annual means of atmospheric TGM and PHg concentrations at a regional background station were 3.98 ng m(-3) and 30.7 pg m(-3), respectively. This work presents a mass balance study of Hg in an upland forest in this area. Atmospheric deposition was highly elevated in the study area, with the annual mean THg deposition flux of 92.5 microg m(-2) yr(-1). Total deposition was dominated by dry deposition (71.8%), and wet deposition accounted for the remaining 28.2%. Forest was a large pool of atmospheric Hg, and nearly 76% of the atmospheric input was stored in forest soil. Volatilization and stream outflow were identified as the two major pathways for THg losses from the forest, which yielded mean output fluxes of 14.0 and 8.6 microg m(-2) yr(-1), respectively. Copyright 2010 Elsevier Ltd. All rights reserved.

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.

[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

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.

Mosses as an integrating tool for monitoring PAH atmospheric deposition: comparison with total deposition and evaluation of bioconcentration factors. A year-long case-study.

PubMed

Foan, Louise; Domercq, Maria; Bermejo, Raúl; Santamaría, Jesús Miguel; Simon, Valérie

2015-01-01

Polycyclic aromatic hydrocarbon (PAH) atmospheric deposition was evaluated at a remote site in Northern Spain using moss biomonitoring with Hylocomium splendens (Hedw.) Schimp., and by measuring the total deposition fluxes of PAHs. The year-long study allowed seasonal variations of PAH content in mosses to be observed, and these followed a similar trend to those of PAH fluxes in total deposition. Generally, atmospheric deposition of PAHs is greater in winter than in summer, due to more PAH emissions from domestic heating, less photoreactivity of the compounds, and intense leaching of the atmosphere by wet deposition. However, fractionation of these molecules between the environmental compartments occurs: PAH fluxes in total deposition and PAH concentrations in mosses are correlated with their solubility (r=0.852, p<0.01) and lipophilic properties (KOW, r=0.768, p<0.01), respectively. This annual study therefore showed that atmospheric PAH fluxes can be estimated with moss biomonitoring data if the bioconcentration or 'enriching' factors are known. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

Toward Synchronous Evaluation of Source Apportionments for Atmospheric Concentration and Deposition of Sulfate Aerosol Over East Asia

NASA Astrophysics Data System (ADS)

Itahashi, S.

2018-03-01

Source apportionments for atmospheric concentration, dry deposition, and wet deposition of sulfate aerosol (SO42-) were synchronously evaluated over East Asia, a main source of anthropogenic sulfur dioxide (SO2) emissions. Estimating dry deposition was difficult owing to the difficulty of measuring deposition velocity directly; therefore, sensitivity simulations using two dry deposition schemes were conducted. Moreover, sensitivity simulations for different emission inventories, the largest uncertainty source in the air quality model, were also conducted. In total, four experimental settings were used. Model performance was verified for atmospheric concentration and wet deposition using a ground-based observation network in China, Korea, and Japan, and all four model settings captured the observations. The underestimation of wet deposition over China was improved by an adjusted approach that linearly scaled the modeled precipitation values to observations. The synchronous evaluation of source apportionments for atmospheric concentration and dry and wet deposition showed the dominant contribution of anthropogenic emissions from China to the atmospheric concentration and deposition in Japan. The contributions of emissions from volcanoes were more important for wet deposition than for atmospheric concentration. Differences in the dry deposition scheme and emission inventory did not substantially influence the relative ratio of source apportionments over Japan. Because the dry deposition was more attributed to local factors, the differences in dry deposition may be an important determinant of the source contributions from China to Japan. Verification of these findings, including the dry deposition velocity, is necessary for better understanding of the behavior of sulfur compound in East Asia.

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.

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) in Shanghai: the spatio-temporal variation and source identification

NASA Astrophysics Data System (ADS)

Cheng, Chen; Bi, Chunjuan; Wang, Dongqi; Yu, Zhongjie; Chen, Zhenlou

2018-03-01

This study investigated the dry and wet deposition fluxes of atmospheric polycyclic aromatic hydrocarbons (PAHs) in Shanghai, China. The flux sources were traced based on composition and spatio-temporal variation. The results show that wet deposition concentrations of PAHs ranged from 0.07 to 0.67 mg·L-1 and were correlated with temperature ( P<0.05). Dry deposition of PAHs concentrations ranged from 3.60-92.15 mg·L-1 and were higher in winter and spring than in summer and autumn. The annual PAH average fluxes were 0.631 mg·m-2·d-1 and 4.06 mg·m-2·d-1 for wet and dry deposition, respectively. The highest wet deposition of PAH fluxes was observed in summer, while dry deposition fluxes were higher in winter and spring. Atmospheric PAHs were deposited as dry deposition in spring and winter, yet wet deposition was the dominant pathway during summer. Total atmospheric PAH fluxes were higher in the northern areas than in the southern areas of Shanghai, and were also observed to be higher in winter and spring. Annual deposition of atmospheric PAHs was about 10.8 t in across all of Shanghai. Wet deposition of PAHs was primarily composed of two, three, or four rings, while dry deposition of PAHs was composed of four, five, or six rings. The atmospheric PAHs, composed of four, five, or six rings, primarily existed in the form of particulates. Coal combustion and vehicle emissions were the dominant sources of PAH in the observed area of downtown Shanghai. In suburban areas, industrial pollution, from sources such as coke oven, incinerator, and oil fired power plant, was as significant as vehicle emissions in contributing to the deposition of PAHs.

Atmospheric deposition of mercury and cadmium impacts on topsoil in a typical coal mine city, Lianyuan, China.

PubMed

Liang, Jie; Feng, Chunting; Zeng, Guangming; Zhong, Minzhou; Gao, Xiang; Li, Xiaodong; He, Xinyue; Li, Xin; Fang, Yilong; Mo, Dan

2017-12-01

Mercury (Hg) and cadmium (Cd) in the atmosphere from coal combustion emissions play an important role in soil pollution. Therefore, the purposes of this study were to quantitatively evaluate the atmospheric Hg and Cd deposition and to determine the influence of atmospheric deposition on Hg and Cd contents in surface soil in a typical coal mine city. Atmospheric deposition samples were collected from May 2015 to May 2016 at 17 sites located in industrial, agricultural and forest areas in the Lianyuan city. Atmospheric Hg and Cd deposition fluxes in the different land use types showed high variability. Curvilinear regression analysis suggested that the atmospheric Hg deposition fluxes were positively related with Hg contents in soils (R 2  = 0.86359, P < 0.001). In addition, atmospheric Cd deposition fluxes were also positively correlated with Cd contents in soils when the site LY02, LY04 and LY05 (all belong to agricultural land) were not included in the fitting (R 2  = 0.82458, P < 0.001). When they were included, there was no significant relationship between them (R 2  = 0.2039, P = 0.05). The accumulation of Hg and Cd concentration in topsoil due to the influence of atmospheric deposition will increase rapidly in the next 30 years, and the mean value of the increment will reach 2.6007 and 33.344 mg kg -1 . After 30 years, the Hg and Cd concentration will increase slowly. The present study advocates that much attention should be paid to the potential ecological hazards in soil resulting from the atmospheric Hg and Cd deposition. Copyright © 2017 Elsevier Ltd. All rights reserved.

Two dimensional radial gas flows in atmospheric pressure plasma-enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kim, Gwihyun; Park, Seran; Shin, Hyunsu; Song, Seungho; Oh, Hoon-Jung; Ko, Dae Hong; Choi, Jung-Il; Baik, Seung Jae

2017-12-01

Atmospheric pressure (AP) operation of plasma-enhanced chemical vapor deposition (PECVD) is one of promising concepts for high quality and low cost processing. Atmospheric plasma discharge requires narrow gap configuration, which causes an inherent feature of AP PECVD. Two dimensional radial gas flows in AP PECVD induces radial variation of mass-transport and that of substrate temperature. The opposite trend of these variations would be the key consideration in the development of uniform deposition process. Another inherent feature of AP PECVD is confined plasma discharge, from which volume power density concept is derived as a key parameter for the control of deposition rate. We investigated deposition rate as a function of volume power density, gas flux, source gas partial pressure, hydrogen partial pressure, plasma source frequency, and substrate temperature; and derived a design guideline of deposition tool and process development in terms of deposition rate and uniformity.

The release of dissolved nutrients and metals from coastal sediments due to resuspension

USGS Publications Warehouse

Kalnejais, Linda H.; Martin, William R.; Bothner, Michael H.

2010-01-01

Coastal sediments in many regions are impacted by high levels of contaminants. Due to a combination of shallow water depths, waves, and currents, these sediments are subject to regular episodes of sediment resuspension. However, the influence of such disturbances on sediment chemistry and the release of solutes is poorly understood. The aim of this study is to quantify the release of dissolved metals (iron, manganese, silver, copper, and lead) and nutrients due to resuspension in Boston Harbor, Massachusetts, USA. Using a laboratory-based erosion chamber, a range of typical shear stresses was applied to fine-grained Harbor sediments and the solute concentration at each shear stress was measured. At low shear stress, below the erosion threshold, limited solutes were released. Beyond the erosion threshold, a release of all solutes, except lead, was observed and the concentrations increased with shear stress. The release was greater than could be accounted for by conservative mixing of porewaters into the overlying water, suggesting that sediment resuspension enhances the release of nutrients and metals to the dissolved phase. To address the long-term fate of resuspended particles, samples from the erosion chamber were maintained in suspension for 90. h. Over this time, 5-7% of the particulate copper and silver was released to the dissolved phase, while manganese was removed from solution. Thus resuspension releases solutes both during erosion events and over a longer timescale due to reactions of suspended particles in the water column. The magnitude of the annual solute release during erosion events was estimated by coupling the erosion chamber results with a record of bottom shear stresses simulated by a hydrodynamic model. The release of dissolved copper, lead, and phosphate due to resuspension is between 2% and 10% of the total (dissolved plus particulate phase) known inputs to Boston Harbor. Sediment resuspension is responsible for transferring a significant

Atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver with flowing gas and flowing atmospheric plasma

NASA Astrophysics Data System (ADS)

Khan, T. M.; Pokle, A.; Lunney, J. G.

2018-04-01

Two methods of atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver are described. In both methods the ablation plume, produced by a 248 nm, 20 ns excimer laser in gas, is strongly confined near the target and forms a nanoparticle aerosol. For both the flowing gas, and the atmospheric plasma from a dielectric barrier discharge plasma source, the aerosol is entrained in the flow and carried to a substrate for deposition. The nanoparticle films produced by both methods were examined by electron microscopy and optical absorption spectroscopy. With plasma assistance, the deposition rate was significantly enhanced and the film morphology altered. With argon gas, isolated nanoparticles of 20 nm size were obtained, whereas in argon plasma, the nanoparticles are aggregated in clusters of 90 nm size. Helium gas also leads to the deposition of isolated nanoparticles, but with helium plasma, two populations of nanoparticles are observed: one of rounded particles with a mean size of 26 nm and the other of faceted particles with a mean size 165 nm.

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

A 3D parameterization of iron atmospheric deposition to the global ocean

NASA Astrophysics Data System (ADS)

Myriokefalitakis, Stelios; Krol, Maarten C.; van Noije, Twan P. C.; Le Sager, Philippe

2017-04-01

Atmospheric deposition of trace constituents, both of natural and anthropogenic origin, can act as a nutrient source into the open ocean and affect marine ecosystem functioning and subsequently the exchange of CO2 between the atmosphere and the global ocean. Dust is known as a major source of nutrients to the global ocean, but only a fraction of these nutrients is released in soluble form that can be assimilated by the ecosystems. Iron (Fe) is a key micronutrient that significantly modulates gross primary production in High-Nutrient-Low-Chlorophyll (HNLC) oceans, where macronutrients like nitrate are abundant but primary production is limited by Fe scarcity. The global atmospheric Fe cycle is here parameterized in the state-of-the-art global Earth System Model EC-Earth. The model takes into account the primary emissions of both insoluble and soluble Fe, associated with dusts and combustion processes. The impact of atmospheric acidity on mineral solubility is parameterized based on updated experimental and theoretical findings, and model results are evaluated against available observations. The link between the soluble Fe atmospheric deposition and anthropogenic sources is also investigated. Overall, the response of the chemical composition of nutrient containing aerosols to atmospheric composition changes is demonstrated and quantified. This work has been financed by the Marie-Curie H2020-MSCA-IF-2015 grant (ID 705652) ODEON (Online DEposition over OceaNs: Modeling the effect of air pollution on ocean bio-geochemistry in an Earth System Model).

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

Atmospheric lead deposition to Okefenokee Swamp, Georgia, USA

USGS Publications Warehouse

Jackson, B.P.; Winger, P.V.; Lasier, P.J.

2004-01-01

'Capsule:' Coal combustion emissions appear to be a major source of Pb in the Okefenokee wetland. Contamination of the environment from atmospheric deposition during the twentieth century is pervasive even in areas ostensibly considered pristine or remote from point sources. In this study, Pb concentrations in a Pb-210-dated peat core collected from the Okefenokee Swamp, GA were used to assess historical contaminant input via atmospheric deposition. Lead isotope ratios were determined by dynamic reaction cell ICP-MS (DRC-ICP-MS). Increases in Pb concentration occurred in the late nineteenth century and a marked rise in Pb concentrations pre-dated the widespread use of leaded gasoline within the US. The Pb-206/Pb-207 ratios of 1.19 during this period were consistent with coal combustion emissions. A later increase in Pb concentration, concurrent with a trend toward more radiogenic Pb-206/Pb-207 ratios in gasoline is consistent with an increased input of Pb from leaded gasoline emissions. However, it appears that coal combustion emissions remain a major source of Pb to the Okefenokee.

Seasonal atmospheric deposition and air-sea gaseous exchange of polycyclic aromatic hydrocarbons over the Yangtze River Estuary, East China Sea: Implication for the source-sink processes

NASA Astrophysics Data System (ADS)

Jiang, Y.; Guo, Z.

2017-12-01

As the home of the largest port in the world, the Yangtze River Estuary (YRE) in the East China Sea (ECS) is adjacent to the largest economic zone in China with more than 10% of Chinese population and provides one-fifth of national GDP. The YRE is under the path of contaminated East Asian continental outflow. These make the YRE unique for the pollutant biogeochemical cycling in the world. In this work, 94 pairs of air samples and 20 surface seawater samples covering four seasons were collected from a remote receptor site in the YRE from March 2014 to January 2015, in order to explore the seasonal fluxes of air-sea gaseous exchange and atmospheric dry and wet deposition of 15 polycyclic aromatic hydrocarbons (PAHs) and their source-sink processes at the air-sea interface. The average dry and wet deposition fluxes of 15 PAHs were estimated as 879 ± 1393 ng m-2 d-1 and 755 ± 545 ng m-2 d-1, respectively. The gaseous PAHs were released from seawater to atmosphere during the whole year with an average of 3039 ± 2030 ng m-2 d-1. The gaseous exchange of PAHs was referred as the dominant process at the air-sea interface in the YRE as the magnitude of volatilization flux of PAHs exceeded that of the total dry and wet deposition. The gaseous PAH exchange flux was dominated by 3-ring PAHs, with the highest value in summer while lowest in winter, depicting a strong seasonal variation due to temperature, wind speed and air-sea concentration gradient difference among seasons. Based on the simplified mass balance estimation, net 9.6 tons/y of PAHs was volatilized from seawater to atmosphere with an area of approximately 20000 km2 in the YRE. Apart from Yangtze River input and ocean ship emissions in the entire year, the selective release of low molecular weight PAHs from sediments in winter due to re-suspension triggered by the East Asian winter monsoon could be another possible source for dissolved PAHs. This work suggests that the source-sink processes of PAHs at air

Sediment Resuspension and Deposition on Seagrass Leaves Impedes Internal Plant Aeration and Promotes Phytotoxic H2S Intrusion.

PubMed

Brodersen, Kasper E; Hammer, Kathrine J; Schrameyer, Verena; Floytrup, Anja; Rasheed, Michael A; Ralph, Peter J; Kühl, Michael; Pedersen, Ole

2017-01-01

HIGHLIGHTS: Sedimentation of fine sediment particles onto seagrass leaves severely hampers the plants' performance in both light and darkness, due to inadequate internal plant aeration and intrusion of phytotoxic H 2 S. Anthropogenic activities leading to sediment re-suspension can have adverse effects on adjacent seagrass meadows, owing to reduced light availability and the settling of suspended particles onto seagrass leaves potentially impeding gas exchange with the surrounding water. We used microsensors to determine O 2 fluxes and diffusive boundary layer (DBL) thickness on leaves of the seagrass Zostera muelleri with and without fine sediment particles, and combined these laboratory measurements with in situ microsensor measurements of tissue O 2 and H 2 S concentrations. Net photosynthesis rates in leaves with fine sediment particles were down to ~20% of controls without particles, and the compensation photon irradiance increased from a span of 20-53 to 109-145 μmol photons m -2 s -1 . An ~2.5-fold thicker DBL around leaves with fine sediment particles impeded O 2 influx into the leaves during darkness. In situ leaf meristematic O 2 concentrations of plants exposed to fine sediment particles were lower than in control plants and exhibited long time periods of complete meristematic anoxia during night-time. Insufficient internal aeration resulted in H 2 S intrusion into the leaf meristematic tissues when exposed to sediment resuspension even at relatively high night-time water-column O 2 concentrations. Fine sediment particles that settle on seagrass leaves thus negatively affect internal tissue aeration and thereby the plants' resilience against H 2 S intrusion.

Worldwide dispersion and deposition of radionuclides produced in atmospheric tests.

PubMed

Bennett, Burton G

2002-05-01

Radionuclides produced in atmospheric nuclear tests were widely dispersed in the global environment. From the many measurements of the concentrations in air and the deposition amounts, much was learned of atmospheric circulation and environmental processes. Based on these results and the reported fission and total yields of individual tests, it has been possible to devise an empirical model of the movement and residence times of particles in the various atmospheric regions. This model, applied to all atmospheric weapons tests, allows extensive calculations of air concentrations and deposition amounts for the entire range of radionuclides produced throughout the testing period. Especially for the shorter-lived fission radionuclides, for which measurement results at the time of the tests are less extensive, a more complete picture of levels and isotope ratios can be obtained, forming a basis for improved dose estimations. The contributions to worldwide fallout can be inferred from individual tests, from tests at specific sites, or by specific countries. Progress was also made in understanding the global hydrological and carbon cycles from the tritium and 14C measurements. A review of the global measurements and modeling results is presented in this paper. In the future, if injections of materials into the atmosphere occur, their anticipated motions and fates can be predicted from the knowledge gained from the fallout experience.

Estimating Chemical Exchange between Atmospheric Deposition and Forest Canopy in Guizhou, China.

PubMed

Li, Wei; Gao, Fang; Liao, Xueqin

2013-01-01

To evaluate the effects of atmospheric deposition on forest ecosystems, wet-only precipitation and throughfall samples were collected in two forest types (Masson pine [ Lamb.] forests and mixed conifer and broadleaf forests) in the Longli forest in the Guizhou province of southwestern China for a period of 21 successive months from April 2007 to December 2008. The pH and chemical components of precipitation and throughfall were analyzed. In addition, the canopy budget model was applied to distinguish between in-canopy and atmospheric sources of chemical compounds. Canopy leaching and total potentially acidifying deposition fluxes were calculated. The results showed that the average pH and the concentration of ions in throughfall were higher than those in precipitation, with the exception of the NH concentration. Dry deposition of S and N accumulated more in Masson pine forests than in mixed conifer and broadleaf forests. Canopy leaching was the most significant source of base cations in forest throughfall, which was higher in the mixed forests than in the coniferous forests. Anions in throughfall deposition in Masson pine forests exceeded those in the mixed forests. Higher total potentially acidifying deposition fluxes reflected the more effective amounts of acid delivered to Masson pine forests compared with mixed conifer and broadleaf forests. In addition, acid deposition induced the leaching and loss of nutrient ions such as Mg, K, and Ca. Although the trees of the studied areas have not shown any symptoms of cation loss, a potentially harmful influence was engendered by atmospheric deposition in the two forest types in the Longli area. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Watershed-scale changes in terrestrial nitrogen cycling during a period of decreased atmospheric nitrate and sulfur deposition

USGS Publications Warehouse

Sabo, Robert D.; Scanga, Sara E.; Lawrence, Gregory B.; Nelson, David M.; Eshleman, Keith N.; Zabala, Gabriel A.; Alinea, Alexandria A.; Schirmer, Charles D.

2016-01-01

Recent reports suggest that decreases in atmospheric nitrogen (N) deposition throughout Europe and North America may have resulted in declining nitrate export in surface waters in recent decades, yet it is unknown if and how terrestrial N cycling was affected. During a period of decreased atmospheric N deposition, we assessed changes in forest N cycling by evaluating trends in tree-ring δ15N values (between 1980 and 2010; n = 20 trees per watershed), stream nitrate yields (between 2000 and 2011), and retention of atmospherically-deposited N (between 2000 and 2011) in the North and South Tributaries (North and South, respectively) of Buck Creek in the Adirondack Mountains, USA. We hypothesized that tree-ring δ15N values would decline following decreases in atmospheric N deposition (after approximately 1995), and that trends in stream nitrate export and retention of atmospherically deposited N would mirror changes in tree-ring δ15N values. Three of the six sampled tree species and the majority of individual trees showed declining linear trends in δ15N for the period 1980–2010; only two individual trees showed increasing trends in δ15N values. From 1980 to 2010, trees in the watersheds of both tributaries displayed long-term declines in tree-ring δ15N values at the watershed scale (R = −0.35 and p = 0.001 in the North and R = −0.37 and p <0.001 in the South). The decreasing δ15N trend in the North was associated with declining stream nitrate concentrations (−0.009 mg N L−1 yr−1, p = 0.02), but no change in the retention of atmospherically deposited N was observed. In contrast, nitrate yields in the South did not exhibit a trend, and the watershed became less retentive of atmospherically deposited N (−7.3% yr−1, p < 0.001). Our δ15N results indicate a change in terrestrial N availability in both watersheds prior to decreases in atmospheric N deposition, suggesting that decreased atmospheric N deposition was not the sole driver of

Particulate Matter Resuspension in Mississippi Bight Evaluated with CONCORDE's Synthesis Model

NASA Astrophysics Data System (ADS)

O'Brien, S. J.; Quas, L. M.; Miles, T. N.; Pan, C.; Cambazoglu, M. K.; Soto Ramos, I. M.; Greer, A. T.; Church, I.; Wiggert, J. D.

2017-12-01

The CONsortium for oil spill exposure pathways in COastal River-Dominated Ecosystems (CONCORDE) was established to investigate the complex fine-scale biological, chemical and physical interactions in a marine system controlled by pulsed-river plume dynamics. During CONCORDE's spring 2016 field campaign, the In Situ Ichthyoplankton Imaging System (ISIIS) on the R/V Point Sur and the Scanfish on the R/V Pelican comprehensively characterized the physical and biological structure in the region. Increased suspended particulate matter was observed by the ISIIS, with concentrations at depth sufficient to completely occlude the in situ images of planktonic organisms. Data was also collected on the continental shelf during the spring cruise by the RU31 glider in the proximity of the Mississippi River Delta, east of the ISIIS / Scanfish transects. Backscatter and salinity observed by the Scanfish and glider showed elevated suspended particulate matter and increased salinity, suggesting a linkage to shoreward advection from the continental shelf of oceanic waters that are sufficiently energetic to drive sediment resuspension. As part of the CONCORDE research effort, a four-dimensional biogeochemical/lower trophic level synthesis model for Mississippi Sound and Bight has been developed, based on the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System. This study utilizes CONCORDE's synthesis model to investigate the physical forcing mechanisms affecting the increased suspended particulate matter concentration observed in the Mississippi Bight during spring 2016, and advection pathways between estuarine and shelf waters in the northern Gulf of Mexico. The results show that episodic, advection-driven resuspension is a critical aspect controlling suspended sediment distributions in Mississippi Bight, which has implications for observed spatio-temporal patterns of planktonic species.

Sediment Resuspension and Transport in Water Distribution ...

EPA Pesticide Factsheets

Journal article This journal article addresses the question of how likely tank sediments are to be resuspended and to drain from the tank, potentially impacting human health. AUsing computational fluid dynamics software, and sediment models from the literature, a variety of normal tank operating conditions are assessed to evaluate the likelihood of tank sediment resuspension.

Estimated variability of National Atmospheric Deposition Program/Mercury Deposition Network measurements using collocated samplers

USGS Publications Warehouse

Wetherbee, G.A.; Gay, D.A.; Brunette, R.C.; Sweet, C.W.

2007-01-01

The National Atmospheric Deposition Program/Mercury Deposition Network (MDN) provides long-term, quality-assured records of mercury in wet deposition in the USA and Canada. Interpretation of spatial and temporal trends in the MDN data requires quantification of the variability of the MDN measurements. Variability is quantified for MDN data from collocated samplers at MDN sites in two states, one in Illinois and one in Washington. Median absolute differences in the collocated sampler data for total mercury concentration are approximately 11% of the median mercury concentration for all valid 1999-2004 MDN data. Median absolute differences are between 3.0% and 14% of the median MDN value for collector catch (sample volume) and between 6.0% and 15% of the median MDN value for mercury wet deposition. The overall measurement errors are sufficiently low to resolve between NADP/MDN measurements by ??2 ng??l-1 and ??2 ????m-2?? year-1, which are the contour intervals used to display the data on NADP isopleths maps for concentration and deposition, respectively. ?? Springer Science+Business Media B.V. 2007.

Conditional vulnerability of plant diversity to atmospheric nitrogen deposition across the United States

Treesearch

Samuel M. Simkin; Edith B. Allen; William D. Bowman; Christopher M. Clark; Jayne Belnap; Matthew L. Brooks; Brian S. Cade; Scott L. Collins; Linda H. Geiser; Frank S. Gilliam; Sarah E. Jovan; Linda H. Pardo; Bethany K. Schulz; Carly J. Stevens; Katharine N. Suding; Heather L. Throop; Donald M. Waller

2016-01-01

Atmospheric nitrogen (N) deposition has been shown to decrease plant species richness along regional deposition gradients in Europe and in experimental manipulations. However, the general response of species richness to N deposition across different vegetation types, soil conditions, and climates remains largely unknown even though responses may be contingent on these...

Modeling study of deposition locations in the 291-Z plenum

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

Mahoney, L.A.; Glissmeyer, J.A.

The TEMPEST (Trent and Eyler 1991) and PART5 computer codes were used to predict the probable locations of particle deposition in the suction-side plenum of the 291-Z building in the 200 Area of the Hanford Site, the exhaust fan building for the 234-5Z, 236-Z, and 232-Z buildings in the 200 Area of the Hanford Site. The Tempest code provided velocity fields for the airflow through the plenum. These velocity fields were then used with TEMPEST to provide modeling of near-floor particle concentrations without particle sticking (100% resuspension). The same velocity fields were also used with PART5 to provide modeling ofmore » particle deposition with sticking (0% resuspension). Some of the parameters whose importance was tested were particle size, point of injection and exhaust fan configuration.« less

CO2 deficit in temperate forest soils receiving high atmospheric N-deposition.

PubMed

Fleischer, Siegfried

2003-02-01

Evidence is provided for an internal CO2 sink in forest soils, that may have a potential impact on the global CO2-budget. Lowered CO2 fraction in the soil atmosphere, and thus lowered CO2 release to the aboveground atmosphere, is indicated in high N-deposition areas. Also at forest edges, especially of spruce forest, where additional N-deposition has occurred, the soil CO2 is lowered, and the gradient increases into the closed forest. Over the last three decades the capacity of the forest soil to maintain the internal sink process has been limited to a cumulative supply of approximately 1000 and 1500 kg N ha(-1). Beyond this limit the internal soil CO2 sink becomes an additional CO2 source, together with nitrogen leaching. This stage of "nitrogen saturation" is still uncommon in closed forests in southern Scandinavia, however, it occurs in exposed forest edges which receive high atmospheric N-deposition. The soil CO2 gradient, which originally increases from the edge towards the closed forest, becomes reversed.

Plutonium in the atmosphere: A global perspective.

PubMed

Thakur, P; Khaing, H; Salminen-Paatero, S

2017-09-01

A number of potential source terms have contributed plutonium isotopes to the atmosphere. The atmospheric nuclear weapon tests conducted between 1945 and 1980 and the re-entry of the burned SNAP-9A satellite in 1964, respectively. It is generally believed that current levels of plutonium in the stratosphere are negligible and compared with the levels generally found at surface-level air. In this study, the time trend analysis and long-term behavior of plutonium isotopes ( 239+240 Pu and 238 Pu) in the atmosphere were assessed using historical data collected by various national and international monitoring networks since 1960s. An analysis of historical data indicates that 239+240 Pu concentration post-1984 is still frequently detectable, whereas 238 Pu is detected infrequently. Furthermore, the seasonal and time-trend variation of plutonium concentration in surface air followed the stratospheric trends until the early 1980s. After the last Chinese test of 1980, the plutonium concentrations in surface air dropped to the current levels, suggesting that the observed concentrations post-1984 have not been under stratospheric control, but rather reflect the environmental processes such as resuspension. Recent plutonium atmospheric air concentrations data show that besides resuspension, other environmental processes such as global dust storms and biomass burning/wildfire also play an important role in redistributing plutonium in the atmosphere. Copyright © 2017 Elsevier Ltd. All rights reserved.

Contributions of atmospheric nitrogen deposition to U.S. estuaries: Summary and conclusions: Chapter 8

USGS Publications Warehouse

Stacey, Paul E.; Greening, Holly; Kremer, James N.; Peterson, David; Tomasko, David A.; Valigura, Richard A.; Alexander, Richard B.; Castro, Mark S.; Meyers, Tilden P.; Paerl, Hans W.; Stacey, Paul E.; Turner, R. Eugene

2001-01-01

A NOAA project was initiated in 1998, with support from the U.S. EPA, to develop state-of-the-art estimates of atmospheric N deposition to estuarine watersheds and water surfaces and its delivery to the estuaries. Work groups were formed to address N deposition rates, indirect (from the watershed) yields from atmospheric and other anthropogenic sources, and direct deposition on the estuarine waterbodies, and to evaluate the levels of uncertainty within the estimates. Watershed N yields were estimated using both a land-use based process approach and a national (SPARROW) model, compared to each other, and compared to estimates of N yield from the literature. The total N yields predicted by the national model were similar to values found in the literature and the land-use derived estimates were consistently higher. Atmospheric N yield estimates were within a similar range for the two approaches, but tended to be higher in the land-use based estimates and were not wellcorrelated. Median atmospheric N yields were around 15% of the total N yield for both groups, but ranged as high as 60% when both direct and indirect deposition were considered. Although not the dominant source of anthropogenic N, atmospheric N is, and will undoubtedly continue to be, an important factor in culturally eutrophied estuarine systems, warranting additional research and management attention.

Detection of Atmospheric Water Deposits in Porous Media Using the TDR Technique

PubMed Central

Nakonieczna, Anna; Kafarski, Marcin; Wilczek, Andrzej; Szypłowska, Agnieszka; Janik, Grzegorz; Albert, Małgorzata; Skierucha, Wojciech

2015-01-01

Investigating the intensity of atmospheric water deposition and its diurnal distribution is essential from the ecological perspective, especially regarding dry geographic regions. It is also important in the context of monitoring the amount of moisture present within building materials in order to protect them from excessive humidity. The objective of this study was to test a constructed sensor and determine whether it could detect and track changes in the intensity of atmospheric water deposition. An operating principle of the device is based on the time-domain reflectometry technique. Two sensors of different plate volumes were manufactured. They were calibrated at several temperatures and tested during field measurements. The calibration turned out to be temperature independent. The outdoor measurements indicated that the upper limits of the measurement ranges of the sensors depended on the volumes of the plates and were equal to 1.2 and 2.8 mm H2O. The respective sensitivities were equal to 3.2 × 10−3 and 7.5 × 10−3 g·ps−1. The conducted experiments showed that the construction of the designed device and the time-domain reflectometry technique were appropriate for detecting and tracing the dynamics of atmospheric water deposition. The obtained outcomes were also collated with the readings taken in an actual soil sample. For this purpose, an open container sensor, which allows investigating atmospheric water deposition in soil, was manufactured. It turned out that the readings taken by the porous ceramic plate sensor reflected the outcomes of the measurements performed in a soil sample. PMID:25871717

Mapping Critical Loads of Atmospheric Nitrogen Deposition in the Rocky Mountains, USA

NASA Astrophysics Data System (ADS)

Nanus, L.; Clow, D. W.; Stephens, V. C.; Saros, J. E.

2010-12-01

Atmospheric nitrogen (N) deposition can adversely affect sensitive aquatic ecosystems at high-elevations in the western United States. Critical loads are the amount of deposition of a given pollutant that an ecosystem can receive below which ecological effects are thought not to occur. GIS-based landscape models were used to create maps for high-elevation areas across the Rocky Mountain region showing current atmospheric deposition rates of nitrogen (N), critical loads of N, and exceedances of critical loads of N. Atmospheric N deposition maps for the region were developed at 400 meter resolution using gridded precipitation data and spatially interpolated chemical concentrations in rain and snow. Critical loads maps were developed based on chemical thresholds corresponding to observed ecological effects, and estimated ecosystem sensitivities calculated from basin characteristics. Diatom species assemblages were used as an indicator of ecosystem health to establish critical loads of N. Chemical thresholds (concentrations) were identified for surface waters by using a combination of in-situ growth experiments and observed spatial patterns in surface-water chemistry and diatom species assemblages across an N deposition gradient. Ecosystem sensitivity was estimated using a multiple-linear regression approach in which observed surface water nitrate concentrations at 530 sites were regressed against estimates of inorganic N deposition and basin characteristics (topography, soil type and amount, bedrock geology, vegetation type) to develop predictive models of surface water chemistry. Modeling results indicated that the significant explanatory variables included percent slope, soil permeability, and vegetation type (including barren land, shrub, and grassland) and were used to predict high-elevation surface water nitrate concentrations across the Rocky Mountains. Chemical threshold concentrations were substituted into an inverted form of the model equations and applied to

Glider Observations of Sediment Resuspension in a Middle Atlantic Bight Fall Transition Storm

DTIC Science & Technology

2008-06-14

response within the lower water column only was observed for sediment resuspension on the outer shelf during Tropical Storm Ernesto , which also occurred when...sediment types in the MAB was summarized by Amato (1994) using data mostly from U.S. Geological Survey databases or state geological surveys and...shelf ( Amato 1994) and suggests that the storm resuspended the sediment from the sandy bottom. Physical processes driving the sediment resuspension

Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources.

PubMed

Domagalski, Joseph; Majewski, Michael S; Alpers, Charles N; Eckley, Chris S; Eagles-Smith, Collin A; Schenk, Liam; Wherry, Susan

2016-10-15

Annual stream loads of mercury (Hg) and inputs of wet and dry atmospheric Hg deposition to the landscape were investigated in watersheds of the Western United States and the Canadian-Alaskan Arctic. Mercury concentration and discharge data from flow gauging stations were used to compute annual mass loads with regression models. Measured wet and modeled dry deposition were compared to annual stream loads to compute ratios of Hg stream load to total Hg atmospheric deposition. Watershed land uses or cover included mining, undeveloped, urbanized, and mixed. Of 27 watersheds that were investigated, 15 had some degree of mining, either of Hg or precious metals (gold or silver), where Hg was used in the amalgamation process. Stream loads in excess of annual Hg atmospheric deposition (ratio>1) were observed in watersheds containing Hg mines and in relatively small and medium-sized watersheds with gold or silver mines, however, larger watersheds containing gold or silver mines, some of which also contain large dams that trap sediment, were sometimes associated with lower load ratios (<0.2). In the non-Arctic regions, watersheds with natural vegetation tended to have low ratios of stream load to Hg deposition (<0.1), whereas urbanized areas had higher ratios (0.34-1.0) because of impervious surfaces. This indicated that, in ecosystems with natural vegetation, Hg is retained in the soil and may be transported subsequently to streams as a result of erosion or in association with dissolved organic carbon. Arctic watersheds (Mackenzie and Yukon Rivers) had a relatively elevated ratio of stream load to atmospheric deposition (0.27 and 0.74), possibly because of melting glaciers or permafrost releasing previously stored Hg to the streams. Overall, our research highlights the important role of watershed characteristics in determining whether a landscape is a net source of Hg or a net sink of atmospheric Hg. Published by Elsevier B.V.

Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources

USGS Publications Warehouse

Domagalski, Joseph L.; Majewski, Michael S.; Alpers, Charles N.; Eckley, Chris S.; Eagles-Smith, Collin A.; Schenk, Liam N.; Wherry, Susan

2016-01-01

Annual stream loads of mercury (Hg) and inputs of wet and dry atmospheric Hg deposition to the landscape were investigated in watersheds of the Western United States and the Canadian-Alaskan Arctic. Mercury concentration and discharge data from flow gauging stations were used to compute annual mass loads with regression models. Measured wet and modeled dry deposition were compared to annual stream loads to compute ratios of Hg stream load to total Hg atmospheric deposition. Watershed land uses or cover included mining, undeveloped, urbanized, and mixed. Of 27 watersheds that were investigated, 15 had some degree of mining, either of Hg or precious metals (gold or silver), where Hg was used in the amalgamation process. Stream loads in excess of annual Hg atmospheric deposition (ratio > 1) were observed in watersheds containing Hg mines and in relatively small and medium-sized watersheds with gold or silver mines, however, larger watersheds containing gold or silver mines, some of which also contain large dams that trap sediment, were sometimes associated with lower load ratios (< 0.2). In the non-Arctic regions, watersheds with natural vegetation tended to have low ratios of stream load to Hg deposition (< 0.1), whereas urbanized areas had higher ratios (0.34–1.0) because of impervious surfaces. This indicated that, in ecosystems with natural vegetation, Hg is retained in the soil and may be transported subsequently to streams as a result of erosion or in association with dissolved organic carbon. Arctic watersheds (Mackenzie and Yukon Rivers) had a relatively elevated ratio of stream load to atmospheric deposition (0.27 and 0.74), possibly because of melting glaciers or permafrost releasing previously stored Hg to the streams. Overall, our research highlights the important role of watershed characteristics in determining whether a landscape is a net source of Hg or a net sink of atmospheric Hg.

Optimizing best management practices to control anthropogenic sources of atmospheric phosphorus deposition to inland lakes.

PubMed

Weiss, Lee; Thé, Jesse; Winter, Jennifer; Gharabaghi, Bahram

2018-04-18

Excessive phosphorus loading to inland freshwater lakes around the globe has resulted in nuisance plant growth along the waterfronts, degraded habitat for cold water fisheries, and impaired beaches, marinas and waterfront property. The direct atmospheric deposition of phosphorus can be a significant contributing source to inland lakes. The atmospheric deposition monitoring program for Lake Simcoe, Ontario indicates roughly 20% of the annual total phosphorus load (2010-2014 period) is due to direct atmospheric deposition (both wet and dry deposition) on the lake. This novel study presents a first-time application of the Genetic Algorithm (GA) methodology to optimize the application of best management practices (BMPs) related to agriculture and mobile sources to achieve atmospheric phosphorus reduction targets and restore the ecological health of the lake. The novel methodology takes into account the spatial distribution of the emission sources in the airshed, the complex atmospheric long-range transport and deposition processes, cost and efficiency of the popular management practices and social constraints related to the adoption of BMPs. The optimization scenarios suggest that the optimal overall capital investment of approximately $2M, $4M, and $10M annually can achieve roughly 3, 4 and 5 tonnes reduction in atmospheric P load to the lake, respectively. The exponential trend indicates diminishing returns for the investment beyond roughly $3M per year and that focussing much of this investment in the upwind, nearshore area will significantly impact deposition to the lake. The optimization is based on a combination of the lowest-cost, most-beneficial and socially-acceptable management practices that develops a science-informed promotion of implementation/BMP adoption strategy. The geospatial aspect to the optimization (i.e. proximity and location with respect to the lake) will help land managers to encourage the use of these targeted best practices in areas that

Sediment Resuspension and Deposition on Seagrass Leaves Impedes Internal Plant Aeration and Promotes Phytotoxic H2S Intrusion

PubMed Central

Brodersen, Kasper E.; Hammer, Kathrine J.; Schrameyer, Verena; Floytrup, Anja; Rasheed, Michael A.; Ralph, Peter J.; Kühl, Michael; Pedersen, Ole

2017-01-01

HIGHLIGHTS: Sedimentation of fine sediment particles onto seagrass leaves severely hampers the plants' performance in both light and darkness, due to inadequate internal plant aeration and intrusion of phytotoxic H2S. Anthropogenic activities leading to sediment re-suspension can have adverse effects on adjacent seagrass meadows, owing to reduced light availability and the settling of suspended particles onto seagrass leaves potentially impeding gas exchange with the surrounding water. We used microsensors to determine O2 fluxes and diffusive boundary layer (DBL) thickness on leaves of the seagrass Zostera muelleri with and without fine sediment particles, and combined these laboratory measurements with in situ microsensor measurements of tissue O2 and H2S concentrations. Net photosynthesis rates in leaves with fine sediment particles were down to ~20% of controls without particles, and the compensation photon irradiance increased from a span of 20–53 to 109–145 μmol photons m−2 s−1. An ~2.5-fold thicker DBL around leaves with fine sediment particles impeded O2 influx into the leaves during darkness. In situ leaf meristematic O2 concentrations of plants exposed to fine sediment particles were lower than in control plants and exhibited long time periods of complete meristematic anoxia during night-time. Insufficient internal aeration resulted in H2S intrusion into the leaf meristematic tissues when exposed to sediment resuspension even at relatively high night-time water-column O2 concentrations. Fine sediment particles that settle on seagrass leaves thus negatively affect internal tissue aeration and thereby the plants' resilience against H2S intrusion. PMID:28536583

Toxicological effects of short-term resuspension of metal-contaminated freshwater and marine sediments.

PubMed

Fetters, Kyle J; Costello, David M; Hammerschmidt, Chad R; Burton, G Allen

2016-03-01

Sediments in navigation-dominated waterways frequently are contaminated with a variety of particle-associated pollutants and are subject to frequent short-term resuspension events. There is little information documenting whether resuspension of metal-contaminated sediments has adverse ecological effects on resident aquatic organisms. Using a novel laboratory approach, the authors examined the mobilization of Zn, Cu, Cd, Pb, Ni, and Cr during resuspension of 1 freshwater and 2 coastal marine sediments and whether resuspension and redeposition resulted in toxicity to model organisms. Sediment flux exposure chambers were used to resuspend metal-contaminated sediments from 1 site in Lake DePue, Illinois (USA), and 2 sites in Portsmouth Naval Shipyard, Maine (USA). Short-term (4-h) resuspension of sediment at environmentally relevant suspended particulate matter concentrations (<1 g/L) resulted in metal mobilization to water that was sediment and metal specific. Overall, the net release of metals from suspended particles was limited, likely because of scavenging by organic matter and Fe oxides that formed during sediment interaction with oxic water. Minimal toxicity to organisms (survival of Hyalella azteca and Daphnia magna; survival, growth, and tissue metal concentration of Neanthes arenaceodentata; bioluminescence of Pyrocystis lunula) was observed during 4-h exposure to resuspended sediments and during 4-d to 10-d post-exposure recovery periods in uncontaminated water. Redeposited suspended particles exhibited increased metal bioavailability and toxicity to H. azteca, highlighting the potential for adverse ecological impacts because of changes in metal speciation. It is important to consider interactions between organisms' life histories and sediment disturbance regimes when assessing risks to ecosystems. © 2015 SETAC.

The silica cycle in a Northeast Pacific fjord; the role of biological resuspension

NASA Astrophysics Data System (ADS)

Katz, Timor; Yahel, Gitai; Tunnicliffe, Verena; Herut, Barak; Whitney, Frank; Snelgrove, Paul V. R.; Lazar, Boaz

2016-09-01

This study is a quantitative assessment of the role fish-induced bio-resuspension plays in the silica cycle of coastal waters. We used new, published and archived oceanographic data to construct a comprehensive silica budget for Saanich Inlet (Vancouver Island, Canada), a highly productive Northeast Pacific fjord, where siliceous diatoms dominate primary productivity. Anoxia in the deep water of the inlet persists during most of the year, precluding animal life, whereas abundant groundfish continuously rework and resuspend bottom sediments in the shallower, oxygenated margins. This resuspension transfers settled biogenic silica fragments from the sediment, where they are immersed in porewater that is rich with dissolved silica, to the overlying water, where the much lower concentrations accelerate their dissolution rate. The budget shows that Saanich Inlet sediments constitute a sink for approximately 250 × 106 mol Si y-1. Most of this Si enters the inlet in advected, siliceous phytoplankton. Sediment resuspension by groundfish in the oxygenated margins of Saanich Inlet generates about 50% of the total flux of dissolved silica from the inlet seafloor. This resuspension also facilitates a massive transport of biogenic silica from the margins to the anoxic basin, where approximately 90% of all the biogenic silica is buried. The excess dissolution caused by fish activity reduces the burial efficiency of biogenic silica in the entire inlet sediments by about 20%. This case study emphasizes the link between the silica cycle and groundfish activity. Based on this study and because biological resuspension occurs in most regions of the ocean, we recommend that it will be taken into account when budgeting the silica cycle, and potentially other geochemical cycles, in marine environments.

Characteristics and impacts of trace elements in atmospheric deposition at a high-elevation site, southern China.

PubMed

Nie, Xiaoling; Wang, Yan; Li, Yaxin; Sun, Lei; Li, Tao; Yang, Minmin; Yang, Xueqiao; Wang, Wenxing

2017-10-01

To investigate the regional background trace element (TE) level in atmospheric deposition (dry and wet), TEs (Fe, Al, V, Cr, Mn, Ni, Cu, Zn, As, Se, Mo, Cd, Ba, and Pb) in 52 rainwater samples and 73 total suspended particles (TSP) samples collected in Mt. Lushan, Southern China, were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The results showed that TEs in wet and dry deposition of the target area were significantly elevated compared within and outside China and the volume weight mean pH of rainwater was 4.43. The relative contributions of wet and dry depositions of TEs vary significantly among elements. The wet deposition fluxes of V, As, Cr, Se, Zn, and Cd exceeded considerably their dry deposition fluxes while dry deposition dominated the removal of pollution elements such as Mo, Cu, Ni, Mn, and Al. The summed dry deposition flux was four times higher than the summed wet deposition flux. Prediction results based on a simple accumulation model found that the content of seven toxic elements (Cr, Ni, Cu, Zn, As, Cd, and Pb) in soils could increase rapidly due to the impact of annual atmospheric deposition, and the increasing amounts of them reached 0.063, 0.012, 0.026, 0.459, 0.076, 0.004, and 0.145 mg kg -1 , respectively. In addition, the annual increasing rates ranged from 0.05% (Cr and Ni) to 2.08% (Cd). It was also predicted that atmospheric deposition induced the accumulation of Cr and Cd in surface soils. Cd was the critical element with the greatest potential ecological risk among all the elements in atmospheric deposition.

Atmospheric deposition and re-emission of mercury estimated in a prescribed forest-fire experiment in Florida, USA

Treesearch

Ralph J. DiCosty; Mac A. Callaham; John A. Stanturf

2006-01-01

Prescribed fires are likely to re-emit atmospherically deposited mercury (Hg), and comparison of soil Hg storage in areas affected by prescribed fire to that in similar unburned areas may provide cross-validating estimates of atmospheric Hg deposition. Prescribed fires are common in the southeastern United States (US), a region of relatively high Hg deposition compared...

Shifts in lake N: P stoichiometry and nutrient limitation driven by atmospheric nitrogen deposition

USGS Publications Warehouse

Elser, J.J.; Andersen, T.; Baron, Jill S.; Bergstrom, A.-K.; Jansson, M.; Kyle, M.; Nydick, K.R.; Steger, L.; Hessen, D.O.

2009-01-01

Human activities have more than doubled the amount of nitrogen (N) circulating in the biosphere. One major pathway of this anthropogenic N input into ecosystems has been increased regional deposition from the atmosphere. Here we show that atmospheric N deposition increased the stoichiometric ratio of N and phosphorus (P) in lakes in Norway, Sweden, and Colorado, United States, and, as a result, patterns of ecological nutrient limitation were shifted. Under low N deposition, phytoplankton growth is generally N-limited; however, in high-N deposition lakes, phytoplankton growth is consistently P-limited. Continued anthropogenic amplification of the global N cycle will further alter ecological processes, such as biogeochemical cycling, trophic dynamics, and biological diversity, in the world's lakes, even in lakes far from direct human disturbance.

Estimation of carbon sequestration in China's forests induced by atmospheric nitrogen deposition: Principles of ecological stoichiometry

NASA Astrophysics Data System (ADS)

Zhu, J.; He, N.; Zhang, J.; Wang, Q.; Zhao, N.; Jia, Y.; Ge, J.; Yu, G.

2017-12-01

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 measured 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 different organs of 877 plant species (leaf, branch, stem, and fine-root), and atmospheric 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 N deposition and N use efficiency (NUE) in China's forests on the principles of ecological stoichiometry. Our results showed that atmospheric N deposition had a modest impact on forest C storage. Specifically, 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 NUE (NUEeco) of atmospheric N deposition ranged from 9.6 to 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 principle of ecological stoichiometry.

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.

AIRSHED DOMAINS FOR MODELING ATMOSPHERIC DEPOSITION OF OXIDIZED AND REDUCED NITROGEN TO THE NEUSE/PAMLICO SYSTEM OF NORTH CAROLINA

EPA Science Inventory

Atmospheric deposition is important to nutrient loadings to coastal estuaries. Atmospheric emissions of nitrogen travel hundreds of kilometers as they are removed via atmospheric deposition. Long-range transport from outside the Neuse/Pamlico system in North Carolina is an impo...

Atmospheric CO and hydrogen uptake and CO oxidizer phylogeny for miyake-jima, Japan volcanic deposits.

PubMed

King, Gary M; Weber, Carolyn F; Nanba, Kenji; Sato, Yoshinori; Ohta, Hiroyuki

2008-01-01

We have assayed rates of atmospheric CO and hydrogen uptake, maximum potential CO uptake and the major phylogenetic composition of CO-oxidizing bacterial communities for a variety of volcanic deposits on Miyake-jima, Japan. These deposits represented different ages and stages of plant succession, ranging from unvegetated scoria deposited in 1983 to forest soils on deposits >800 yr old. Atmospheric CO and hydrogen uptake rates varied from -2.0±1.8-6.3±0.1 mg CO m(-2) d(-1) and 0.0±0.4-2.0±0.2 mg H(2) m(-2) d(-1), respectively, and were similar to or greater than values reported for sites on Kilauea volcano, Hawaii, USA. At one of the forested sites, CO was emitted to the atmosphere, while two vegetated sites did not consume atmospheric hydrogen, an unusual observation. Although maximum potential CO uptake rates were also comparable to values for Kilauea, the relationship between these rates and organic carbon contents of scoria or soil indicated that CO oxidizers were relatively more abundant in Miyake-jima deposits. Phylogenetic analyses based on the large sub-unit gene for carbon monoxide dehydrogenase (coxL) indicated that many novel lineages were present on Miyake-jima, that CO-oxidizing Proteobacteria were prevalent in vegetated sites and that community structure appeared to vary more than composition among sites.

Atmospheric deposition patterns of (210)Pb and (7)Be in Cienfuegos, Cuba.

PubMed

Alonso-Hernández, Carlos M; Morera-Gómez, Yasser; Cartas-Águila, Héctor; Guillén-Arruebarrena, Aniel

2014-12-01

The radiometric composition of bulk deposition samples, collected monthly for one year, February 2010 until January 2011, at a site located in Cienfuegos (22° 03' N, 80° 29' W) (Cuba), are analysed in this paper. Measurement of (7)Be and (210)Pb activity concentrations were carried out in 12 bulk deposition samples. The atmospheric deposition fluxes of (7)Be and (210)Pb are in the range of 13.2-132 and 1.24-8.29 Bq m(-2), and their mean values are: 56.6 and 3.97 Bq m(-2), respectively. The time variations of the different radionuclide have been discussed in relation with meteorological factors and the mean values have been compared to those published in recent literature from other sites located at different latitudes. The annual average flux of (210)Pb and (7)Be were 47 and 700 Bq m(-2) y(-1), respectively. Observed seasonal variations of deposition data are explained in terms of different environmental features. The atmospheric deposition fluxes of (7)Be and (210)Pb were moderately well correlated with precipitation and well correlated with one another. The (210)Pb/(7)Be ratios in the monthly depositions samples varied in the range of 0.05-0.10 and showed a strong correlation with the number of rainy days. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evidence for the Importance of Atmospheric Nitrogen Deposition to Eutrophic Lake Dianchi, China

NASA Astrophysics Data System (ADS)

Zhan, X.; Bo, Y.; Zhou, F.; Liu, X.; Paerl, H. W.; Shen, J.; Wang, R.; Li, F. R.; Tao, S.; Yanjun, D.; Tang, X.

2017-12-01

Elevated atmospheric nitrogen (N) deposition has significantly influenced aquatic ecosystems, especially with regard to their N budgets and phytoplankton growth potentials. Compared to a considerable number of studies on oligotrophic lakes and oceanic waters, little evidence for the importance of N deposition has been generated for eutrophic lakes, even though emphasis has been placed on reducing external N inputs to control eutrophication in these lakes. Our high-resolution observations of atmospheric depositions and riverine inputs of biologically reactive N species into eutrophic Lake Dianchi (the sixth largest freshwater lake in China) shed new light onto the contribution of N deposition to total N loads. Annual N deposition accounted for 15.7% to 16.6% of total N loads under variable precipitation conditions, 2-fold higher than previous estimates (7.6%) for the Lake Dianchi. The proportion of N deposition to total N loads further increased to 27-48% in May and June when toxic blooms of the ubiquitous non-N2 fixing cyanobacteria Microcystis spp. are initiated and proliferate. Our observations reveal that reduced N (59%) contributes a greater amount than oxidized N to total N deposition, reaching 56-83% from late spring to summer. Progress toward mitigating eutrophication in Lake Dianchi and other bloom-impacted eutrophic lakes will be difficult without reductions in ammonia emissions and subsequent N deposition.

Atmospheric nitrogen deposition budget in a subtropical hydroelectric reservoir (Nam Theun II case study, Lao PDR)

NASA Astrophysics Data System (ADS)

Adon, Marcellin; Galy-Lacaux, Corinne; Serça, Dominique; Guerin, Frederic; Guedant, Pierre; Vonghamsao, Axay; Rode, Wanidaporn

2016-04-01

With 490 km² at full level of operation, Nam Theun 2 (NT2) is one of the largest hydro-reservoir in South East Asia. NT2 is a trans-basin hydropower project that diverts water from the Nam Theun river (a Mekong tributary) to the Xe Ban Fai river (another Mekong tributary). Atmospheric deposition is an important source of nitrogen (N), and it has been shown that excessive fluxes of N from the atmosphere has resulted in eutrophication of many coastal waters. A large fraction of atmospheric N input is in the form of inorganic N. This study presents an estimation of the atmospheric inorganic nitrogen budget into the NT2 hydroelectric reservoir based on a two-year monitoring (July 2010 to July 2012) including gas concentrations and precipitation. Dry deposition fluxes are calculated from monthly mean surface measurements of NH3, HNO3 and NO2 concentrations (passive samplers) together with simulated deposition velocities, and wet deposition fluxes from NH4+ and NO3- concentrations in single event rain samples (automated rain sampler). Annual rainfall amount was 2500 and 3160 mm for the two years. The average nitrogen deposition flux is estimated at 1.13 kgN.ha-1.yr-1 from dry processes and 5.52 kgN.ha-1.yr-1 from wet ones, i.e., an average annual total nitrogen flux of 6.6 kgN.ha-1.yr-1 deposited into the NT2 reservoir. The wet deposition contributes to 83% of the total N deposition. The nitrogen deposition budget has been also calculated over the rain tropical forest surrounding the reservoir. Due to higher dry deposition velocities above forested ecosystems, gaseous dry deposition flux is estimated at 4.0 kgN.ha-1.yr-1 leading to a total nitrogen deposition about 9.5 kgN.ha-1.yr-1. This result will be compared to nitrogen deposition in the African equatorial forested ecosystems in the framework of the IDAF program (IGAC-DEBITS-AFrica).

[Pollution evaluation and health risk assessment of heavy metals from atmospheric deposition in Lanzhou].

PubMed

Li, Ping; Xue, Su-Yin; Wang, Sheng-Li; Nan, Zhong-Ren

2014-03-01

In order to evaluate the contamination and health risk of heavy metals from atmospheric deposition in Lanzhou, samples of atmospheric deposition were collected from 11 sampling sites respectively and their concentrations of heavy metals were determined. The results showed that the average contents of Cu, Pb, Cd, Cr, Ni, Zn and Mn were 82.22, 130.31, 4.34, 88.73, 40.64, 369.23 and 501.49 mg x kg(-1), respectively. There was great difference among different functional areas for all elements except Mn. According to the results, the enrichment factor score of Mn was close to 1, while the enrichment of Zn, Ni, Cu and Cr was more serious, and Pb and Cd were extremely enriched. The assessment results of geoaccumulation index of potential ecological risk indicated that the pollution of Cd in the atmospheric deposition of Lanzhou should be classified as extreme degree, and that of Cu, Ni, Zn, Pb as between slight and extreme degrees, and Cr as practically uncontaminated. Contaminations of atmospheric dust by heavy metals in October to the next March were more serious than those from April to August. Health risk assessment indicated that the heavy metals in atmospheric deposition were mainly ingested by human bodies through hand-mouth ingestion. The non-cancer risk was higher for children than for adults. The order of non-cancer hazard indexes of heavy metals was Pb > Cr > Cd > Cu > Ni > Zn. The non-cancer hazard indexes and carcinogen risks of heavy metals were both lower than their threshold values, suggesting that they will not harm the health.

STURM: Resuspension mesocosms with realistic bottom shear stress and water column turbulence for benthic-pelagic coupling studies: Design and Applications

NASA Astrophysics Data System (ADS)

Sanford, L. P.; Porter, E.; Porter, F. S.; Mason, R. P.

2016-02-01

Shear TUrbulence Resuspension Mesocosm (STURM) tanks, with high instantaneous bottom shear stress and realistic water column mixing in a single system, allow more realistic benthic-pelagic coupling studies that include sediment resuspension. The 1 m3 tanks can be programmed to produce tidal or episodic sediment resuspension over extended time periods (e.g. 4 weeks), over muddy sediments with or without infaunal organisms. The STURM tanks use a resuspension paddle that produces uniform bottom shear stress across the sediment surface while gently mixing a 1 m deep overlying water column. The STURM tanks can be programmed to different magnitudes, frequencies, and durations of bottom shear stress (and thus resuspension) with proportional water column turbulence levels over a wide range of mixing settings for benthic-pelagic coupling experiments. Over eight STURM calibration settings, turbulence intensity ranged from 0.55 to 4.52 cm s-1, energy dissipation rate from 0.0032 to 2.65 cm2 s-3, the average bottom shear stress from 0.0068 to 0.19 Pa, and the instantaneous bottom shear stress from 0.07 to 2.0 Pa. Mixing settings can be chosen as desired and/or varied over the experiment, based on the scientific question at hand. We have used the STURM tanks for four 4-week benthic-pelagic coupling ecosystem experiments with tidal resuspension with or without infaunal bivalves, for stepwise erosion experiments with and without infaunal bivalves, for experiments on oyster biodeposit resuspension, to mimic storms overlain on tidal resuspension, and for experiments on the effects of varying frequency and duration of resuspension on the release of sedimentary contaminants. The large size of the tanks allows water quality and particle measurements using standard oceanographic instrumentation. The realistic scale and complexity of the contained ecosystems has revealed indirect feedbacks and responses that are not observable in smaller, less complex experimental systems.

Seasonal atmospheric deposition variations of polychlorinated biphenyls (PCBs) and comparison of some deposition sampling techniques.

PubMed

Birgül, Askın; Tasdemir, Yücel

2011-03-01

Ambient air and bulk deposition samples were collected between June 2008 and June 2009. Eighty-three polychlorinated biphenyl (PCB) congeners were targeted in the samples. The average gas and particle PCB concentrations were found as 393 ± 278 and 70 ± 102 pg/m(3), respectively, and 85% of the atmospheric PCBs were in the gas phase. Bulk deposition samples were collected by using a sampler made of stainless steel. The average PCB bulk deposition flux value was determined as 6,020 ± 4,350 pg/m(2) day. The seasonal bulk deposition fluxes were not statistically different from each other, but the summer flux had higher values. Flux values differed depending on the precipitation levels. The average flux value in the rainy periods was 7,480 ± 4,080 pg/m(2) day while the average flux value in dry periods was 5,550 ± 4,420 pg/m(2) day. The obtained deposition values were lower than the reported values given for the urban and industrialized areas, yet close to the ones for the rural sites. The reported deposition values were also influenced by the type of the instruments used. The average dry deposition and total deposition velocity values calculated based on deposition and concentration values were found as 0.23 ± 0.21 and 0.13 ± 0.13 cm/s, respectively.

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

REGIONAL MODELING OF THE ATMOSPHERIC TRANSPORT AND DEPOSITION OF ATRAZINE

EPA Science Inventory

A version of the Community Multiscale Air Quality (CMAQ) model has been developed by the U.S. EPA that is capable of addressing the atmospheric fate, transport and deposition of some common trace toxics. An initial, 36-km rectangular grid-cell application for atrazine has been...

Estimation of the contribution of ultrafine particles to lung deposition of particle-bound mutagens in the atmosphere.

PubMed

Kawanaka, Youhei; Matsumoto, Emiko; Sakamoto, Kazuhiko; Yun, Sun-Ja

2011-02-15

The present study was performed to estimate the contributions of fine and ultrafine particles to the lung deposition of particle-bound mutagens in the atmosphere. This is the first estimation of the respiratory deposition of atmospheric particle-bound mutagens. Direct and S9-mediated mutagenicity of size-fractionated particulate matter (PM) collected at roadside and suburban sites was determined by the Ames test using Salmonella typhimurium strain TA98. Regional deposition efficiencies in the human respiratory tract of direct and S9-mediated mutagens in each size fraction were calculated using the LUDEP computer-based model. The model calculations showed that about 95% of the lung deposition of inhaled mutagens is caused by fine particles for both roadside and suburban atmospheres. Importantly, ultrafine particles were shown to contribute to the deposition of mutagens in the alveolar region of the lung by as much as 29% (+S9) and 26% (-S9) for the roadside atmosphere and 11% (+S9) and 13% (-S9) for the suburban atmosphere, although ultrafine particles contribute very little to the PM mass concentration. These results indicated that ultrafine particles play an important role as carriers of mutagens into the lung. Copyright © 2010 Elsevier B.V. All rights reserved.

Biomagnetic monitoring of heavy metals contamination in deposited atmospheric dust, a case study from Isfahan, Iran.

PubMed

Norouzi, Samira; Khademi, Hossein; Cano, Angel Faz; Acosta, Jose A

2016-05-15

Tree leaves are considered as one of the best biogenic dust collectors due to their ability to trap and retain particulate matter on their surfaces. In this study, the magnetic susceptibility (MS) and the concentration of selected heavy metals of plane tree (Platanus orientalis L.) leaves and deposited atmospheric dust, sampled by an indirect and a direct method, respectively, were determined to investigate the relationships between leaf magnetic parameters and the concentration of heavy metals in deposited atmospheric dust. The objective was to develop a biomagnetic method as an alternative to the common ones used for determining atmospheric heavy metal contaminations. Plane tree leaves were monthly sampled on the 19th of May to November, 2012 (T1-T7), for seven months from 21 different sites in the city of Isfahan, central Iran. Deposited atmospheric dust samples were also collected using flat glass surfaces from the same sites on the same dates, except for T1. MS (χlf, χhf) values in washed (WL) and unwashed leaves (UL) as well as Cu, Fe, Mn, Ni, Pb, and Zn concentrations in UL and deposited atmospheric dust samples were determined. The results showed that the MS content with a biogenic source was low with almost no significant change during the sampling period, while an increasing trend was observed in the MS content of UL samples due to the deposition of heavy metals and magnetic particles on leaf surfaces throughout the plant growth. The latter type of MS content could be reduced through washing off by rain. Most heavy metals examined, as well as the Tomlinson pollution load index (PLI) in UL, showed statistically significant correlations with MS values. The correlation between heavy metals content in atmospheric dust deposited on glass surfaces and leaf MS values was significant for Cu, Fe, Pb, and Zn. Moreover, the similarity observed between the spatial distribution maps of leaf MS and deposited atmospheric dust PLI provided convincing evidence regarding

Uncertainty and perspectives in studies of atmospheric nitrogen deposition in China: A response to Liu et al. (2015).

PubMed

He, Nianpeng; Zhu, Jianxing; Wang, Qiufeng

2015-07-01

In this paper, we have formally responded to the speculation in "Liu et al. suspect that Zhu et al. (2015) may have underestimated dissolved organic N but overestimated total particulate N in wet deposition in China" by Liu et al. (2015). Here, we first discussed the uncertainty and plausible reasons of atmospheric deposition in China, which have been reported in different studies. We disagree with their interpretation on some points. Firstly, the difficulties in quality control from sampling to analyzing are common to all studies regarding atmospheric deposition, including the studies cited by Liu et al. (2015). More importantly, their discussion did not fully consider the apparent influence of different scaling-up methods (from an observation site scale to a national scale) on estimations of atmospheric N deposition in China. Furthermore, we provided the optimal approaches to resolve these challenges discussed in order to promote the related studies of atmospheric N deposition in China in the future. Copyright © 2015 Elsevier B.V. All rights reserved.

Spatial patterns and temporal changes in atmospheric-mercury deposition for the midwestern USA, 2001–2016

USGS Publications Warehouse

Risch, Martin R.; Kenski, Donna M.

2018-01-01

the study area between the periods 2001–2013 and 2014–2016 were observed, coinciding with reported reductions in Hg emissions in the USA required by implementation of national Hg emissions-control rules. These decreases in atmospheric-Hg concentrations are believed to have resulted in the reduced atmospheric-Hg deposition recorded because precipitation depths between the two periods were not significantly different. The Hg-monitoring data for the study area identified an atmospheric deposition response to decreased local and regional Hg emissions.

A quantitative estimation of the exhaust, abrasion and resuspension components of particulate traffic emissions using electron microscopy

NASA Astrophysics Data System (ADS)

Weinbruch, Stephan; Worringen, Annette; Ebert, Martin; Scheuvens, Dirk; Kandler, Konrad; Pfeffer, Ulrich; Bruckmann, Peter

2014-12-01

The contribution of the three traffic-related components exhaust, abrasion, and resuspension to kerbside and urban background PM10 and PM1 levels was quantified based on the analysis of individual particles by scanning electron microscopy. A total of 160 samples was collected on 38 days between February and September 2009 at a kerbside and an urban background station in the urban/industrial Ruhr area (Germany). Based on size, morphology, chemical composition and stability under electron bombardment, the 111,003 particles studied in detail were classified into the following 14 particle classes: traffic/exhaust, traffic/abrasion, traffic/resuspension, carbonaceous/organic, industry/metallurgy, industry/power plants, secondary particles, (aged) sea salt, silicates, Ca sulfates, carbonates, Fe oxides/hydroxides, biological particles, and other particles. The traffic/exhaust component consists predominantly of externally mixed soot particles and soot internally mixed with secondary particles. The traffic/abrasion component contains all particles with characteristic tracer elements (Fe, Cu, Ba, Sb, Zn) for brake and tire abrasion. The traffic/resuspension component is defined by the mixing state and comprises all internally mixed particles with a high proportion of silicates or Fe oxides/hydroxides which contain soot or abrasion particles as minor constituent. In addition, silicates and Fe oxides/hydroxides internally mixed with chlorine and sulphur containing particles were also assigned to the traffic/resuspension component. The total contribution of traffic to PM10 was found to be 27% at the urban background station and 48% at the kerbside station, the corresponding values for PM1 are 15% and 39%. These values lie within the range reported in previous literature. The relative share of the different traffic components for PM10 at the kerbside station was 27% exhaust, 15% abrasion, and 58% resuspension (38%, 8%, 54% for PM1). For the urban background, the following

A 270-year Ice Core Record of Atmospheric Mercury Deposition to Western North America

NASA Astrophysics Data System (ADS)

Schuster, P. F.; Krabbenhoft, D. P.; Naftz, D. L.; Cecil, L. D.; Olson, M. L.; DeWild, J. F.; Susong, D. D.; Green, J. R.

2001-05-01

The Upper Fremont Glacier (UFG), a mid-latitude glacier in the Wind River Range, Wyoming, U.S.A., contains a record of atmospheric mercury deposition. Although some polar ice-core studies have provided a limited record of past mercury deposition, polar cores are, at best, proxy indicators of historic mercury deposition in the mid-latitudes. Two ice cores removed from the UFG in 1991 and 1998 (totaling 160 meters in length) provided a chronology and paleoenvironmental framework. This aids in the interpretation of the mercury deposition record. For the first time reported from a mid-latitude ice core, using low-level procedures, 97 ice core samples were analyzed to reconstruct a 270-year atmospheric mercury deposition record based in the western United States. Trends in mercury concentration from the UFG record major releases to the atmosphere of both natural and anthropogenic mercury from regional and global sources. We find that mercury concentrations are significantly, but for relatively short time intervals, elevated during periods corresponding to volcanic eruptions with global impact. This indicates that these natural events "punctuate" the record. Anthropogenic activities such as industrialization (global scale), gold mining and war-time manufacturing (regional scale), indicate that chronic levels of elevated mercury emissions have a greater influence on the historical atmospheric deposition record from the UFG. In terms of total mercury deposition recorded by the UFG during approximately the past 270 years: anthropogenic inputs contributed 52 percent; volcanic events contributed 6 percent; and pre-industrialization or background accounted for 42 percent of the total input. More significantly, during the last 100 years, anthropogenic sources contributed 70 percent of the total mercury input. A declining trend in mercury concentrations is obvious during the past 20 years. Declining mercury concentrations in the upper section of the ice core are corroborated by

Long-Term Simulated Atmospheric Nitrogen Deposition Alters ...

EPA Pesticide Factsheets

Atmospheric nitrogen deposition has been suggested to increase forest carbon sequestration across much of the Northern Hemisphere; slower organic matter decomposition could contribute to this increase. At four sugar maple (Acer saccharum)-dominated northern hardwood forests, we previously observed that 10 years of chronic simulated nitrogen deposition (30 kg N ha-1 yr-1) increased soil organic carbon. Over three years at these sites, we investigated the effects of nitrogen additions on decomposition of two substrates with documented differences in biochemistry: leaf litter (more labile) and fine roots (more recalcitrant). Further, we combined decomposition rates with annual leaf and fine root litter production to estimate how nitrogen additions altered the accumulation of soil organic matter. Nitrogen additions marginally stimulated early-stage decomposition of leaf litter, a substrate with little acid-insoluble material (e.g., lignin). In contrast, nitrogen additions inhibited the late stage decomposition of fine roots, a substrate with high amount of acid insoluble material and a change consistent with observed decreases in lignin-degrading enzyme activities with nitrogen additions at these sites. At the ecosystem scale, the slower fine root decomposition led to additional root mass retention (g m-2), which explained 5, 48, and 52 % of previously-documented soil carbon accumulation due to nitrogen additions. Our results demonstrated that nitrogen deposition ha

Atmospheric nitrogen deposition to the northwestern Pacific: seasonal variation and source attribution

NASA Astrophysics Data System (ADS)

Zhao, Y.; Zhang, L.; Pan, Y.; Wang, Y.; Paulot, F.; Henze, D. K.

2015-09-01

Rapid Asian industrialization has led to increased downwind atmospheric nitrogen deposition threatening the marine environment. We present an analysis of the sources and processes controlling atmospheric nitrogen deposition to the northwestern Pacific, using the GEOS-Chem global chemistry model and its adjoint model at 1/2° × 2/3° horizontal resolution over East Asia and its adjacent oceans. We focus our analyses on the marginal seas: the Yellow Sea and the South China Sea. Asian nitrogen emissions in the model are 28.6 Tg N a-1 as NH3 and 15.7 Tg N a-1 as NOx. China has the largest sources with 12.8 Tg N a-1 as NH3 and 7.9 Tg N a-1 as NOx; the high-NH3 emissions reflect its intensive agricultural activities. We find Asian NH3 emissions are a factor of 3 higher in summer than winter. The model simulation for 2008-2010 is evaluated with NH3 and NO2 column observations from satellite instruments, and wet deposition flux measurements from surface monitoring sites. Simulated atmospheric nitrogen deposition to the northwestern Pacific ranges 0.8-20 kg N ha-1 a-1, decreasing rapidly downwind of the Asian continent. Deposition fluxes average 11.9 kg N ha-1 a-1 (5.0 as reduced nitrogen NHx and 6.9 as oxidized nitrogen NOy) to the Yellow Sea, and 5.6 kg N ha-1 a-1 (2.5 as NHx and 3.1 as NOy) to the South China Sea. Nitrogen sources over the ocean (ship NOx and oceanic NH3) have little contribution to deposition over the Yellow Sea, about 7 % over the South China Sea, and become important (greater than 30 %) further downwind. We find that the seasonality of nitrogen deposition to the northwestern Pacific is determined by variations in meteorology largely controlled by the East Asian monsoon and in nitrogen emissions. The model adjoint further estimates that nitrogen deposition to the Yellow Sea originates from sources over China (92 % contribution) and the Korean peninsula (7 %), and by sectors from fertilizer use (24 %), power plants (22 %), and transportation (18

Investigating the importance of sediment resuspension in Alexandrium fundyense cyst population dynamics in the Gulf of Maine

USGS Publications Warehouse

Butman, Bradford; Aretxabaleta, Alfredo L.; Dickhudt, Patrick J.; Dalyander, P. Soupy; Sherwood, Christopher R.; Anderson, Donald M.; Keafer, Bruce A.; Signell, Richard P.

2014-01-01

Cysts of Alexandrium fundyense, a dinoflagellate that causes toxic algal blooms in the Gulf of Maine, spend the winter as dormant cells in the upper layer of bottom sediment or the bottom nepheloid layer and germinate in spring to initiate new blooms. Erosion measurements were made on sediment cores collected at seven stations in the Gulf of Maine in the autumn of 2011 to explore if resuspension (by waves and currents) could change the distribution of over-wintering cysts from patterns observed in the previous autumn; or if resuspension could contribute cysts to the water column during spring when cysts are viable. The mass of sediment eroded from the core surface at 0.4 Pa ranged from 0.05 kg m−2 near Grand Manan Island, to 0.35 kg m−2 in northern Wilkinson Basin. The depth of sediment eroded ranged from about 0.05 mm at a station with sandy sediment at 70 m water depth on the western Maine shelf, to about 1.2 mm in clayey–silt sediment at 250 m water depth in northern Wilkinson Basin. The sediment erodibility measurements were used in a sediment-transport model forced with modeled waves and currents for the period October 1, 2010 to May 31, 2011 to predict resuspension and bed erosion. The simulated spatial distribution and variation of bottom shear stress was controlled by the strength of the semi-diurnal tidal currents, which decrease from east to west along the Maine coast, and oscillatory wave-induced currents, which are strongest in shallow water. Simulations showed occasional sediment resuspension along the central and western Maine coast associated with storms, steady resuspension on the eastern Maine shelf and in the Bay of Fundy associated with tidal currents, no resuspension in northern Wilkinson Basin, and very small resuspension in western Jordan Basin. The sediment response in the model depended primarily on the profile of sediment erodibility, strength and time history of bottom stress, consolidation time scale, and the current in the water

Swept Away: Resuspension of Bacterial Mats Regulates Benthic-Pelagic Exchange of Sulfur

NASA Astrophysics Data System (ADS)

Grant, Jonathan; Bathmann, Ulrich V.

1987-06-01

Filaments and extracellular material from colorless sulfur bacteria (Beggiatoa spp.) form extensive white sulfur mats on surface sediments of coastal, oceanic, and even deep-sea environments. These chemoautotrophic bacteria oxidize soluble reduced sulfur compounds and deposit elemental sulfur, enriching the sulfur content of surface sediment fivefold over that of deeper sediments. Laboratory flume experiments with Beggiatoa mats from an intertidal sandflat (Nova Scotia) demonstrated that even slight erosion of sediment causes a flux of 160 millimoles of sulfur per square meter per hour, two orders of magnitude greater than the flux produced by sulfur transformations involving either sulfate reduction or sulfide oxidation by benthic bacteria. These experiments indicate that resuspension of sulfur bacterial mats by waves and currents is a rapid mechanism by which sediment sulfur is recycled to the water column. Benthic communities thus lose an important storage intermediate for reduced sulfur as well as a high-quality bacterial food source for benthic grazers.

Engineering of pulsed laser deposited calcium phosphate biomaterials in controlled atmospheres

NASA Astrophysics Data System (ADS)

Drukteinis, Saulius E.

Synthetic calcium phosphates (CAP) such as hydroxyapatite (HA) have been used as regenerative bone graft materials and also as thin films to improve the integration of biomedical implant devices within skeletal tissue. Pulsed laser deposition (PLD) can deposit crystalline HA with significant adhesion on titanium biomaterials. However, there are PLD processing constraints due to the complex physical and chemical interactions occurring simultaneously during PLD, which influence ablation plume formation and development. In this investigation PLD CAP films were engineered with a focus on novel decoupling of partial pressure of H2O (g) ( PH2O ) from total background pressure, in combination with substrate heat treatment and laser energy density control. Characterization of these films was performed with X-ray Diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy, and Optical Profilometry. In vitro cellular adhesion testing was also performed using osteoblast (MC3T3) cell lines to evaluate adhesion of bone-forming cells on processed PLD CAP samples. Preferred a-axis orientation films were deposited in H2O (g) saturated atmospheres with reduced laser fluence (< 4 J/cm2). Crystalline HA/tetracalcium phosphate (TTCP) films were deposited in H2O ( g)-deficient atmospheres with higher laser fluence (> 3 J/cm 2). Varied PH2O resulted in control of biphasic HA/TTCP composition with increasing TTCP at lower PH2O . These were dense continuous films composed of micron-scale particles. Cellular adhesion assays did not demonstrate a significant difference between osteoblast adhesion density on HA films compared with biphasic HA/TTCP films. Room temperature PLD at varied PH2O combined with furnace heat treatment resulted in controlled variation in surface amplitude parameters including surface roughness (S a), root mean square (Sq), peak to valley height (St), and ten-point height ( Sz). These discontinuous films were

Characteristics of sediment resuspension in Lake Taihu, China: A wave flume study

NASA Astrophysics Data System (ADS)

Ding, Yanqing; Sun, Limin; Qin, Boqiang; Wu, Tingfeng; Shen, Xia; Wang, Yongping

2018-06-01

Lake Taihu is a typical shallow lake which frequently happens sediment resuspension induced by wind-induced waves. The experiments are carried on to simulate the wave disturbance processes in wave flume by setting a series of wave periods (1.2 s, 1.5 s, 1.8 s) and wave heights (2 cm, 10 cm). It aims to analyze the characteristics of sediment resuspension and the mechanisms of nutrients release and to evaluate the effects of sediment dredging on sediment resuspension and nutrients release in Lake Taihu. The results show that wave shear stress during 2 cm and 10 cm wave height processes ranges 0.018-0.023 N/m2 and 0.221-0.307 N/m2, respectively. Wave shear stress has no significant differences between wave periods. Wave height has much more effects on sediment resuspension. Wave height of 2 cm could induce total suspended solids (TSS) reaching up to 5.21 g/m2 and resuspension flux of sediment (M) up to 1.74 g/m2. TSS sharply increases to 30.33-52.41 g/m2 and M reached up to 48.94 g/m2 when wave height reaches to 10 cm. The disturbance depth under different sediment bulk weights ranges from 0.089 to 0.161 mm. Variation of suspended solids in 3 layers (1 cm, 5 cm, 20 cm above sediment interface) has no significant differences. Organic matter, TN and TP have positive relationship with SS. Organic matter is only accounted for 5.7%-7.3% of SS. The experiments under different sediment bulk densities (1.34 g/cm3, 1.47 g/cm3 and 1.59 g/cm3) find that TSS and M fall by 44.2% and 39.8% with sediment bulk density increasing, respectively. Total TN, DTN, TP and DTP decrease by 24.3%-33.6%. It indicates that sediment dredging could effectively reduce SS concentration and nutrient levels in water column. The researches provide a theoretical basis for sediment dredging to control the shore zone of Lake Taihu for lake management.

Status and trends in atmospheric deposition and emissions near Atlanta, Georgia, 1986-99

USGS Publications Warehouse

Peters, N.E.; Meyers, T.P.; Aulenbach, Brent T.

2002-01-01

Wet and dry atmospheric deposition were investigated from weekly data, 1986-99 (1986-97 for dry deposition) at the Panola Mountain Research Watershed (PMRW), a forested research site 25 km, southeast of Atlanta, Georgia. Furthermore, the wet deposition was compared to that at three adjacent National Atmospheric Deposition Program's National Trends Network (NTN) sites (GA41, 50 km south of PMRW; AL99, 175 km northwest; NC25, 175 km north-northeast) and dry deposition was compared to that at adjacent Clean Air Status and Trends Network (CASTNET) sites, co-located at the NTN sites. The pH of precipitation is acidic and the dominant acid anion is SO4; the pH (derived from the volume-weighted mean H concentration) averages 4.44 for 1986-99, and varies seasonally with average lowest values in summer (4.19) and highest in winter (4.63). From 1986-99, the annual wet deposition of sulfur (S) and nitrogen (N) averaged 400 and 300 eq ha-1 (6.4 and 4.2 kg ha-1), respectively. Inferential model estimates of annual dry S and N deposition from 1986-97 averaged 130 and 150 eq ha-1 (2.1 and 2.1 kg ha-1), respectively. From 1993-99, net S deposition (dry deposition plus canopy interactions) for coniferous and deciduous throughfall (throughfall minus wet-only deposition) averaged 400 and 150 eq ha-1 (6.4 and 2.1 kg ha-1), respectively. The annual wet deposition of S and N species at PMRW was comparable to that at NTN sites, with the exception of higher N species deposition at AL99 and relatively lower H, SO4 and NO3 deposition at GA41. Dry S deposition at PMRW differed markedly from the CASTNET sites despite similarity in S concentrations for all but NC25; the differences are attributed to differences in model parameters associated with the landscape and vegetation characteristics at the sites. At PMRW, atmospheric deposition trends were not detected for the entire sampling period, but were detected for shorter periods (4-5yr). Annual S and N deposition increased from 1986 to 1991

Zn isotope study of atmospheric emissions and dry depositions within a 5 km radius of a Pb-Zn refinery

NASA Astrophysics Data System (ADS)

Mattielli, Nadine; Petit, Jérôme C. J.; Deboudt, Karine; Flament, Pascal; Perdrix, Esperanza; Taillez, Aurélien; Rimetz-Planchon, Juliette; Weis, Dominique

The present paper examines the use of zinc isotopes as tracers of atmospheric sources and focuses on the potential fractionation of Zn isotopes through anthropogenic processes. In order to do so, Zn isotopic ratios are measured in enriched ores and airborne particles associated with pyrometallurgical activities of one of the major Pb-Zn refineries in France. Supporting the isotopic investigation, this paper also compares morphological and chemical characteristics of Zn particles collected on dry deposition plates ("environmental samples") placed within a 5 km radius of the smelter, with those of Zn particles collected inside the plant ("process samples"), i.e. dust collected from the main exhaust system of the plant. To ensure a constant isotopic "supply", the refinery processed a specific set of ores during the sampling campaigns, as agreed with the executive staff of the plant. Enriched ores and dust produced by the successive Zn extraction steps show strong isotope fractionation (from -0.66 to +0.22‰) mainly related to evaporation processes within the blast furnaces. Dust from the main chimney displays a δ 66Zn value of -0.67‰. Application of the Rayleigh equation to evaluate the fractionation factor associated with the Zn vapor produced after a free evaporation gives a range of αore/vapor from 1.0004 to 1.0008. The dry deposits, collected on plates downwind of the refinery, display δ 66Zn variations of up to +0.7‰. However, it is to be noted that between 190 and 1250 m from the main chimney of the refinery, the dry deposits show a high level of large (>10 μm) Zn, S, Fe and O bearing aggregates characterized by positive δ 66Zn values (+0.02 to +0.19‰). These airborne particles probably derive from the re-suspension of slag heaps and local emissions from the working-units. In contrast, from 1720 to 4560 m, the dry deposits are comprised of small (PM10) particles, including spherical Zn-bearing aggregates, showing negative δ 66Zn values (-0.52 to -0

Dissemination, resuspension, and filtration of carbon fibers. [aircraft fires

NASA Technical Reports Server (NTRS)

Elber, W.

1980-01-01

Carbon fiber transport was studied using mathematical models established for other pollution problems. It was demonstrated that resuspension is not a major factor contributing to the risk. Filtration and fragmentation tests revealed that fiber fragmentation shifts the fiber spectrum to shorter mean lengths in high velocity air handling systems.

Concentration, solubility and deposition flux of atmospheric particulate nutrients over the Yellow Sea

NASA Astrophysics Data System (ADS)

Shi, Jin-Hui; Zhang, Jing; Gao, Hui-Wang; Tan, Sai-Chun; Yao, Xiao-Hong; Ren, Jing-Ling

2013-12-01

Satellite images showed that two large dust storms swept over the Yellow Sea from 31 Mach to 1 April 2007; both were accompanied by precipitation. Three to four days after the dust episodes, blooms occurred in the Yellow Sea. As an important and potential controlling factor of the bloom, nutrients in the total suspended particle (TSP) and size-segregated particle samples during the cruise campaign were measured and their atmospheric deposition fluxes of nutrients are reported in this paper. Concentrations of total P and TIN (NH4+, NO2- and NO3-) in TSP varied from 0.01 to 1.05 μg m-3, and from 1.21 to 22.28 μg m-3, with the maximum occurring concurrently with the dust storm events. In addition, the measured solubility of Fe in these particles varied from 1.0 to 20.1%, while it ranged from 0.8 to 15% for Al. The total deposition fluxes of Asian dust as well as the contained nutrients were estimated on the basis of an episodic increment of the measured concentration of dissolved Al in the surface ocean during the dust events. The estimated fluxes of atmospheric deposition of soluble Fe, P and inorganic nitrogen over the Yellow Sea during the dust episodes were 42.5±10.9, 10.3±2.6 and 772.0±198.0 mg m-2, respectively. The estimated fluxes of nutrients via dry atmospheric deposition accounted for only ~2% of the total fluxes. The deposition fluxes of particulate Fe and P during the two dust storm events associated with precipitation were about 500-1000 times of that daily averaged flux during non-dust days, indicating the importance of the episodic inputs to the annual budget of these metals deposited into the ocean.

Atmospheric nitrogen deposition to the northwestern Pacific: seasonal variation and source attribution

NASA Astrophysics Data System (ADS)

Zhao, Yuanhong; Zhang, Lin; Pan, Yuepeng; Wang, Yuesi; Paulot, Fabien; Henze, Daven

2016-04-01

Rapid Asian industrialization has lead to increased atmospheric nitrogen deposition downwind threatening the marine environment. We present an analysis of the sources and processes controlling atmospheric nitrogen deposition to the northwestern Pacific, using the GEOS-Chem global chemistry model and its adjoint model at 1/2°× 2/3° horizontal resolution over the East Asia and its adjacent oceans. We focus our analyses on the marginal seas: the Yellow Sea and the South China Sea. Asian nitrogen emissions in the model are 28.6 Tg N a-1 as NH3 and 15.7 Tg N a-1 as NOx. China has the largest sources with 12.8 Tg N a-1 as NH3 and 7.9 Tg N a-1 as NOx; the much higher NH3 emissions reflect its intensive agricultural activities. We improve the seasonality of Asian NH3 emissions; emissions are a factor of 3 higher in summer than winter. The model simulation for 2008-2010 is evaluated with NH3 and NO2 column observations from satellite instruments, and wet deposition flux measurements from surface monitoring sites. Simulated atmospheric nitrogen deposition to the northwestern Pacific ranges 0.8-20 kg N ha-1 a-1, decreasing rapidly downwind the Asian continent. Deposition fluxes average 11.9 kg N ha-1 a-1 (5.0 as reduced nitrogen NHx and 6.9 as oxidized nitrogen NOy) to the Yellow Sea, and 5.6 kg N ha-1 a-1 (2.5 as NHx and 3.1 as NOy) to the South China Sea. Nitrogen sources over the ocean (ship NOx and oceanic NH3) have little contribution to deposition over the Yellow Sea, about 7% over the South China Sea, and become important (greater than 30%) further downwind. We find that the seasonality of nitrogen deposition to the northwestern Pacific is determined by variations in meteorology largely controlled by the East Asian Monsoon and in nitrogen emissions. The model adjoint further points out that nitrogen deposition to the Yellow Sea originates from sources over China (92% contribution) and the Korean peninsula (7%), and by sectors from fertilizer use (24%), power plants

Heavy metals in atmospheric surrogate dry deposition

PubMed

Morselli; Cecchini; Grandi; Iannuccilli; Barilli; Olivieri

1999-02-01

This paper describes a methodological approach for the assessment of the amount of surrogate dry deposition of several toxic heavy metals (Cd, Cr, Cu, Ni, Pb, V, Zn) associated with atmospheric particulate matter at ground level. The objectives of the study were twofold: i) the evaluation of several techniques for the digestion of dry deposition samples for trace metal analysis; ii) the comparison of the results from two samplers with different collecting surfaces. A dry solid surface sampler (DRY sampler, Andersen--USA) and a water layer surface sampler (DAS sampler--MTX Italy) were employed. The samples were collected over a one-year period in an urban site of Bologna (northern Italy). A description is given of the complete procedure, from sampling to data elaboration, including sample storage, digestion and analytical methods. According to the results obtained with three different digestion techniques (Teflon bomb, microwave digester and Teflon flask with vapour cooling system), the highest recovery rate was achieved by the Teflon bomb procedure employing an NBS 1648 Standard Reference Material; 90-95% of the elements considered were recovered by dissolution in a pressurized Teflon bomb with an HNO3-HF mixture. Given these results, the technique was adopted for dry deposition sample digestion. On the basis of the amount of heavy metals measured as monthly deposition fluxes (microg/m2), the collecting efficiency of the DAS sampler for a number of elements was found to be as much as two to three times greater than that of the DRY sampler.

Fission products in National Atmospheric Deposition Program—Wet deposition samples prior to and following the Fukushima Dai-Ichi Nuclear Power Plant incident, March 8?April 5, 2011

USGS Publications Warehouse

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

2012-01-01

Radioactive isotopes I-131, Cs-134, or Cs-137, products of uranium fission, were measured at approximately 20 percent of 167 sampled National Atmospheric Deposition Program monitoring sites in North America (primarily in the contiguous United States and Alaska) after the Fukushima Dai-Ichi Nuclear Power Plant incident on March 12, 2011. Samples from the National Atmospheric Deposition Program were analyzed for the period of March 8-April 5, 2011. Calculated 1- or 2-week radionuclide deposition fluxes at 35 sites from Alaska to Vermont ranged from 0.47 to 5,100 Becquerels per square meter during the sampling period of March 15-April 5, 2011. No fission-product isotopes were measured in National Atmospheric Deposition Program samples obtained during March 8-15, 2011, prior to the arrival of contaminated air in North America.

Atmospheric Nitrogen Deposition and the Properties of Soils in Forests of Vologda Region

NASA Astrophysics Data System (ADS)

Kudrevatykh, I. Yu.; Ivashchenko, K. V.; Ananyeva, N. D.; Ivanishcheva, E. A.

2018-02-01

Twenty plots (20 m2 each) were selected in coniferous and mixed forests of the industrial Vologda district and the Vytegra district without developed industries in Vologda region. In March, snow cores corresponding to the snow cover depth were taken on these plots. In August, soil samples from the 0- to 20-cm layer of litter-free soddy-podzolic soil (Albic Retisol (Ochric)) were taken on the same plots in August. The content of mineral nitrogen (Nmin), including its ammonium (NH+ 4) and nitrate (NO- 3) forms, was determined in the snow (meltwater) and soil. The contents of total organic carbon, total nitrogen, and elements (Al, Ca); pH; particle size distribution; and microbiological parameters―carbon of microbial biomass (Cmic) and microbial respiration (MR)―were determined in the soil. The ratio MR/Cmic = qCO2 (specific respiration of microbial biomass, or soil microbial metabolic quotient) was calculated. The content of Nmic in meltwater of two districts was 1.7 mg/L on the average (1.5 and 0.3 mg/L for the NH+ 4 and NO- 3 forms, respectively). The annual atmospheric deposition was 0.6-8.9 kg Nmin/ha, the value of which in the Vologda district was higher than in the Vytegra district by 40%. Reliable correlations were found between atmospheric NH+ 4 depositions and Cmic (-0.45), between NH+ 4 and qCO2 (0.56), between atmospheric NO- 3 depositions and the soil NO- 3 (-0.45), and between NO- 3 and qCO2 (-0.58). The content of atmospheric Nmin depositions correlated with the ratios C/N (-0.46) and Al/Ca (-0.52) in the soil. In forests with the high input of atmospheric nitrogen (>2.0 kg NH+ 4/(ha yr) and >6.4 kg Nmin/(ha yr)), a tendency of decreasing Cmic, C/N, and Al/Ca, as well as increasing qCO2, was revealed, which could be indicative of deterioration in the functioning of microbial community and the chemical properties of the soil.

Analysis of Atmospheric Nitrate Deposition in Lake Tahoe Using Multiple Oxygen Isotopes

NASA Astrophysics Data System (ADS)

McCabe, J. R.; Michalski, G. M.; Hernandez, L. P.; Thiemens, M. H.; Taylor, K.; Kendall, C.; Wankel, S. D.

2002-12-01

Lake Tahoe in the Sierra Nevada Mountain Range is world renown for its depth and water clarity bringing 2.2 million visitors per year resulting in annual revenue of \\1.6 billion from tourism. In past decades the lake has suffered from decreased water clarity (from 32 m plate depth to less than 20), which is believed to be largely the result of algae growth initiated by increased nutrient loading. Lake nutrients have also seen a shift from a nitrogen limited to a phosphorous limited system indicating a large increase in the flux of fixed nitrogen. Several sources of fixed nitrogen of have been suggested including surface runoff, septic tank seepage from ground water and deposition from the atmosphere. Bio-available nitrogen in the form of nitrate (NO_{3}$-) is a main component of this system. Recent studies have estimated that approximately 50% of the nitrogen input into the lake is of atmospheric origin (Allison et al. 2000). However, the impact and magnitude of atmospheric deposition is still one of the least understood aspects of the relationship between air and water quality in the Basin (TRPA Threshold Assessment 2002). The utility of stable isotopes as tracers of nitrate reservoirs has been shown in several studies (Bohlke et al. 1997, Kendall and McDonnell 1998, Durka et al. 1994). Stable nitrogen (δ15N) and oxygen (δ18O) isotopes have been implemented in a dual isotope approach to characterize the various nitrate sources to an ecosystem. While δ18O distinguishes between atmospheric and soil sources of nitrate, processes such as denitrification can enrich the residual nitrate in δ18O leaving a misleading atmospheric signature. The benefit of δ15N as a tracer for NO3- sources is the ability to differentiate natural soil, fertilizer, and animal or septic waste, which contain equivalent δ18O values. The recent implementation of multiple oxygen isotopes to measure Δ17O in nitrate has proven to be a more sensitive tracer of atmospheric deposition. The

External quality assurance project report for the National Atmospheric Deposition Program’s National Trends Network and Mercury Deposition Network, 2013–14

USGS Publications Warehouse

Wetherbee, Gregory A.; Martin, RoseAnn

2016-07-05

The Mercury Deposition Network programs include the system blank program and an interlaboratory comparison program. System blank results indicated that maximum total mercury contamination concentrations in samples were less than the third percentile of all Mercury Deposition Network sample concentrations. The Mercury Analytical Laboratory produced chemical concentration results with low bias and variability compared with other domestic and international laboratories that support atmospheric-deposition monitoring.

Linking pulses of atmospheric deposition to DOC release in an upland peat-covered catchment

NASA Astrophysics Data System (ADS)

Worrall, F.; Burt, T. P.; Adamson, J. K.

2008-12-01

Changes in atmospheric deposition have been proposed as one possible explanation of the widespread increase in DOC concentration observed in many Northern Hemisphere catchments. This study uses detailed, long-term, monthly monitoring records of pH, conductivity SO4, and DOC in precipitation, soil water, and runoff chemistry from an upland peat-covered catchment in northern England. By deriving impulse transfer functions this study explores whether changes in deposition lead to significant changes in the occurrence of each component in the soil and runoff water; especially significant changes in DOC. The study shows that (1) impulses in the deposition of acidity have no significant effect upon pH or DOC in soil water or runoff. (2) DOC in soil water and runoff is responsive to impulses in SO4 and conductivity, but only when those impulses are changes in soil water chemistry and not when they are in atmospheric deposition. (3) The effects of changes in SO4 and/or conductivity can easily be overemphasized if memory effects are not accounted for, and their effect is limited to only 1 or 2 months after a severe drought. This study can support the view that changes in ionic strength can result in changes in DOC concentration in soil water or runoff, but the system studied is unresponsive to changes in atmospheric deposition. Impulses in soil water SO4 do not lead to increases in DOC concentrations, and so this mechanism does not provide an explanation for DOC increases.

Exploring lag times between monthly atmospheric deposition and stream chemistry in Appalachian forests using cross-correlation

NASA Astrophysics Data System (ADS)

DeWalle, David R.; Boyer, Elizabeth W.; Buda, Anthony R.

2016-12-01

Forecasts of ecosystem changes due to variations in atmospheric emissions policies require a fundamental understanding of lag times between changes in chemical inputs and watershed response. Impacts of changes in atmospheric deposition in the United States have been documented using national and regional long-term environmental monitoring programs beginning several decades ago. Consequently, time series of weekly NADP atmospheric wet deposition and monthly EPA-Long Term Monitoring stream chemistry now exist for much of the Northeast which may provide insights into lag times. In this study of Appalachian forest basins, we estimated lag times for S, N and Cl by cross-correlating monthly data from four pairs of stream and deposition monitoring sites during the period from 1978 to 2012. A systems or impulse response function approach to cross-correlation was used to estimate lag times where the input deposition time series was pre-whitened using regression modeling and the stream response time series was filtered using the deposition regression model prior to cross-correlation. Cross-correlations for S were greatest at annual intervals over a relatively well-defined range of lags with the maximum correlations occurring at mean lags of 48 months. Chloride results were similar but more erratic with a mean lag of 57 months. Few high-correlation lags for N were indicated. Given the growing availability of atmospheric deposition and surface water chemistry monitoring data and our results for four Appalachian basins, further testing of cross-correlation as a method of estimating lag times on other basins appears justified.

700 years reconstruction of mercury and lead atmospheric deposition in the Pyrenees (NE Spain)

NASA Astrophysics Data System (ADS)

Corella, J. P.; Valero-Garcés, B. L.; Wang, F.; Martínez-Cortizas, A.; Cuevas, C. A.; Saiz-Lopez, A.

2017-04-01

Geochemical analyses in varved lake sediment cores (Lake Montcortès, Pre-Pyrenees) allowed reconstruction of mercury (Hg) and lead (Pb) atmospheric deposition over the past seven centuries in the Pyrenees (NE Spain). Accumulation Rates (AR) from the Middle Ages to the Industrial Period ranged from 2500 to 26130 μg m2.y-1 and 15-152 μg m2.y-1 for Pb and Hg respectively. Significant metal pollution started ca CE 1550 during a period of increased exploitation of ore resources in Spain. Colder and humid conditions in the Pyrenees during the Little Ice Age may have also favoured Hg and Pb atmospheric deposition in the lake. Therefore, the interplay between increased rainfall (wet deposition) and mining activities in the Iberian Peninsula has driven Hg and Pb AR during the Pre-industrial Period. More recently, the use of leaded gasoline in Europe in the mid-20th century may explain the highest Pb AR between CE 1953 and 1971. The highest Hg AR occurred in CE 1940 synchronous with the highest Hg production peak in Almadén mining district (southern Spain) and the Second World War. The record of Hg enrichment in Lake Montcortès shows a decrease during the last decades in Western Europe similar to other regional records and global emission models. This study highlights the exceptional quality of varved sequences to tease apart pollutants depositional mechanisms, identify historical periods of increased atmospheric pollution and provide a historical context for pollutant baseline values to make correct assessments of recent (atmospheric) pollution in lake ecosystems.

Assessment of dry and wet atmospheric deposits of radioactive aerosols: application to Fukushima radiocaesium fallout.

PubMed

Gonze, Marc-André; Renaud, Philippe; Korsakissok, Irène; Kato, Hiroaki; Hinton, Thomas G; Mourlon, Christophe; Simon-Cornu, Marie

2014-10-07

The Fukushima Dai-ichi nuclear accident led to massive atmospheric deposition of radioactive substances onto the land surfaces. The spatial distribution of deposits has been estimated by Japanese authorities for gamma-emitting radionuclides through either airborne monitoring surveys (since April 2011) or in situ gamma-ray spectrometry of bare soil areas (since summer 2011). We demonstrate that significant differences exist between the two surveys for radiocaesium isotopes and that these differences can be related to dry deposits through the use of physically based relationships involving aerosol deposition velocities. The methodology, which has been applied to cesium-134 and cesium-137 deposits within 80-km of the nuclear site, provides reasonable spatial estimations of dry and wet deposits that are discussed and compared to atmospheric numerical simulations from the Japanese Atomic Energy Agency and the French Institute of Radioprotection and Nuclear Safety. As a complementary approach to numerical simulations, this field-based analysis has the possibility to contribute information that can be applied to the understanding and assessment of dose impacts to human populations and the environment around Fukushima.

RECOVERY OF SURFACE WATERS IN THE NORTHEASTERN U.S. FROM DECREASES IN ATMOSPHERIC DEPOSITION OF SULFUR

EPA Science Inventory

A simple mass flux model was developed to simulate the response of SO concentrations in surface waters to past and anticipated future changes in atmospheric deposition of SO . Values of bulk (or wet) SO deposition and dry deposition of S determined from measured air concentrat...

Uncertainty analysis of atmospheric deposition simulation of radiocesium and radioiodine from Fukushima Daiichi Nuclear Power Plant

NASA Astrophysics Data System (ADS)

Morino, Yu; Ohara, Toshimasa; Yumimoto, Keiya

2014-05-01

Chemical transport models (CTM) played key roles in understanding the atmospheric behaviors and deposition patterns of radioactive materials emitted from the Fukushima Daiichi nuclear power plant (FDNPP) after the nuclear accident that accompanied the great Tohoku earthquake and tsunami on 11 March 2011. In this study, we assessed uncertainties of atmospheric simulation by comparing observed and simulated deposition of radiocesium (137Cs) and radioiodine (131I). Airborne monitoring survey data were used to assess the model performance of 137Cs deposition patterns. We found that simulation using emissions estimated with a regional-scale (~500 km) CTM better reproduced the observed 137Cs deposition pattern in eastern Japan than simulation using emissions estimated with local-scale (~50 km) or global-scale CTM. In addition, we estimated the emission amount of 137Cs from FDNPP by combining a CTM, a priori source term, and observed deposition data. This is the first use of airborne survey data of 137Cs deposition (more than 16,000 data points) as the observational constraints in inverse modeling. The model simulation driven by a posteriori source term achieved better agreements with 137Cs depositions measured by aircraft survey and at in-situ stations over eastern Japan. Wet deposition module was also evaluated. Simulation using a process-based wet deposition module reproduced the observations well, whereas simulation using scavenging coefficients showed large uncertainties associated with empirical parameters. The best-available simulation reproduced the observed 137Cs deposition rates in high-deposition areas (≥10 kBq m-2) within one order of magnitude. Recently, 131I deposition map was released and helped to evaluate model performance of 131I deposition patterns. Observed 131I/137Cs deposition ratio is higher in areas southwest of FDNPP than northwest of FDNPP, and this behavior was roughly reproduced by a CTM if we assume that released 131I is more in gas phase

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 deposition of mercury in central Poland: Sources and seasonal trends

NASA Astrophysics Data System (ADS)

Siudek, Patrycja; Kurzyca, Iwona; Siepak, Jerzy

2016-03-01

Atmospheric deposition of total mercury was studied at two sites in central Poland, between April 2013 and October 2014. Hg in rainwater (bulk deposition) was analyzed in relation to meteorological parameters and major ions (H+, NO3-, Cl-, SO42 -) in order to investigate seasonal variation, identify sources and determine factors affecting atmospheric Hg chemistry and deposition. Total mercury concentrations varied between 1.24 and 22.1 ng L- 1 at the urban sampling site (Poznań) and between 0.57 and 18.3 ng L- 1 in the woodland protected area (Jeziory), with quite similar mean values of 6.96 and 6.37 ng L- 1, respectively. Mercury in precipitation exhibited lower spatial variability within the study domain (urban/forest transect) than the concentrations determined during other similar observations, reflecting the predominant influence of the same local sources. In our study, a significant seasonal pattern of Hg deposition was observed at both sampling sites, with higher and more variable concentrations of Hg reported for the urban area. In particular, deposition values of Hg were higher in the samples attributed to relatively large precipitation amounts in the summer and in those collected during the winter season (the result of higher contributions from combustion sources, i.e. intensive combustion of fossil fuels in residential and commercial boilers, individual power/heat-generating plants). In addition, a significant relationship between Hg concentration and precipitation amount was found while considering different types of wintertime samples (i.e. rain, snow and mixed precipitation). The analysis of backward trajectories showed that air masses arriving from polluted regions of western Europe and southern Poland largely affected the amount of Hg in rainwater. A seasonal variation in Hg deposition fluxes was also observed, with the maximum value of Hg in spring and minimum in winter. Our results indicated that rainwater Hg and, consequently, the wet deposition

Atmospheric deposition and critical loads for nitrogen and metals in Arctic Alaska: Review and current status

USGS Publications Warehouse

Linder, Greg L.; Brumbaugh, William G.; Neitlich, Peter; Little, Edward

2013-01-01

To protect important resources under their bureau’s purview, the United States National Park Service’s (NPS) Arctic Network (ARCN) has developed a series of “vital signs” that are to be periodically monitored. One of these vital signs focuses on wet and dry deposition of atmospheric chemicals and further, the establishment of critical load (CL) values (thresholds for ecological effects based on cumulative depositional loadings) for nitrogen (N), sulfur, and metals. As part of the ARCN terrestrial monitoring programs, samples of the feather moss Hylocomium splendens are being col- lected and analyzed as a cost-effective means to monitor atmospheric pollutant deposition in this region. Ultimately, moss data combined with refined CL values might be used to help guide future regulation of atmospheric contaminant sources potentially impacting Arctic Alaska. But first, additional long-term studies are needed to determine patterns of contaminant deposition as measured by moss biomonitors and to quantify ecosystem responses at particular loadings/ ranges of contaminants within Arctic Alaska. Herein we briefly summarize 1) current regulatory guidance related to CL values 2) derivation of CL models for N and metals, 3) use of mosses as biomonitors of atmospheric deposition and loadings, 4) preliminary analysis of vulnerabilities and risks associated with CL estimates for N, 5) preliminary analysis of existing data for characterization of CL values for N for interior Alaska and 6) implications for managers and future research needs.

Modeling Planetary Atmospheric Energy Deposition By Energetic Ions

NASA Astrophysics Data System (ADS)

Parkinson, Christopher; Bougher, Stephen; Gronoff, Guillaume; Barthelemy, Mathieu

2016-07-01

The structure, dynamics, chemistry, and evolution of planetary upper atmospheres are in large part determined by the available sources of energy. In addition to the solar EUV flux, the solar wind and solar energetic particle (SEP) events are also important sources. Both of these particle populations can significantly affect an atmosphere, causing atmospheric loss and driving chemical reactions. Attention has been paid to these sources from the standpoint of the radiation environment for humans and electronics, but little work has been done to evaluate their impact on planetary atmospheres. At unmagnetized planets or those with crustal field anomalies, in particular, the solar wind and SEPs of all energies have direct access to the atmosphere and so provide a more substantial energy source than at planets having protective global magnetic fields. Additionally, solar wind and energetic particle fluxes should be more significant for planets orbiting more active stars, such as is the case in the early history of the solar system for paleo-Venus and Mars. Therefore quantification of the atmospheric energy input from the solar wind and SEP events is an important component of our understanding of the processes that control their state and evolution. We have applied a full Lorentz motion particle transport model to study the effects of particle precipitation in the upper atmospheres of Mars and Venus. Such modeling has been previously done for Earth and Mars using a guiding center precipitation model. Currently, this code is only valid for particles with small gyroradii in strong uniform magnetic fields. There is a clear necessity for a Lorentz formulation, hence, a systematic study of the ionization, excitation, and energy deposition has been conducted, including a comparison of the influence relative to other energy sources (namely EUV photons). The result is a robust examination of the influence of energetic ion transport on the Venus and Mars upper atmosphere which

Suspending sediment transport, sedimentation, and resuspension in Lake Houston, Texas: Implications for water quality

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

Matty, J.M.; Anderson, J.B.; Dunbar, R.B.

1987-01-01

Lake Houston is a man-made reservoir located northeast of Houston, Texas. The purpose of this investigation was to document suspended sediment transport, sedimentation, and resuspension in the lake with a view towards estimating the influence of sedimentation on water quality. Sediment traps were placed in strategic locations in the lake to collect suspended sediments. Samples were analyzed for bulk density, grain size, organic carbon, and a number of trace elements. These data were analyzed along with meteorological data to examine those factors which regulate suspended sediment input and dispersal, and the role of suspended sediments in controlling water quality withinmore » the lake. Sediment input to the lake depends primarily on the intensity of rainfall in the watershed. Sediment movement within the lake is strongly influenced by wave activity, which resuspends sediments from shallow areas, and by wind-driven circulation. The increased residence time of suspended sediments due to resuspension allows greater decomposition of organic matter and the release of several trace elements from sediments to the water column. Virtually all samples from sediment traps suspended between 1 and 5 m above the lake bottom contain medium to coarse silt, and even some very fine sand-sized material. This implies that circulation in Lake Houston is periodically intense enough to transport this size material in suspension. During winter, northerly winds with sustained velocities of greater than 5 m/sec provide the most suitable condition for rapid (< 1 d) transport of suspended sediment down the length of the lake. Fluctuations in current velocities and the subsequent suspension/deposition of particles may explain variations in the abundance of coliform bacteria in Lake Houston.« less

Rapid atmospheric transport and large-scale deposition of recently synthesized plant waxes

NASA Astrophysics Data System (ADS)

Nelson, Daniel B.; Ladd, S. Nemiah; Schubert, Carsten J.; Kahmen, Ansgar

2018-02-01

Sedimentary plant wax 2H/1H ratios are important tools for understanding hydroclimate and environmental changes, but large spatial and temporal uncertainties exist about transport mechanisms from ecosystem to sediments. To assess atmospheric pathways, we collected aerosol samples for two years at four locations within a ∼60 km radius in northern Switzerland. We measured n-alkane distributions and 2H/1H ratios in these samples, and from local plants, leaf litter, and soil, as well as surface sediment from six nearby lakes. Increased concentrations and 2H depletion of long odd chain n-alkanes in early summer aerosols indicate that most wax aerosol production occurred shortly after leaf unfolding, when plants synthesize waxes in large quantities. During autumn and winter, aerosols were characterized by degraded n-alkanes lacking chain length preferences diagnostic of recent biosynthesis, and 2H/1H values that were in some cases more than 100‰ higher than growing season values. Despite these seasonal shifts, modeled deposition-weighted average 2H/1H values of long odd chain n-alkanes primarily reflected summer values. This was corroborated by n-alkane 2H/1H values in lake sediments, which were similar to deposition-weighted aerosol values at five of six sites. Atmospheric deposition rates for plant n-alkanes on land were ∼20% of accumulation rates in lakes, suggesting a role for direct deposition to lakes or coastal oceans near similar production sources, and likely a larger role for deposition on land and transport in river systems. This mechanism allows mobilization and transport of large quantities of recently produced waxes as fine-grained material to low energy sedimentation sites over short timescales, even in areas with limited topography. Widespread atmospheric transfer well before leaf senescence also highlights the importance of the isotopic composition of early season source water used to synthesize waxes for the geologic record.

Critical Loads of Atmospheric Nitrogen Deposition for Aquatic Ecosystems in Yosemite and Sequoia and Kings Canyon National Parks

NASA Astrophysics Data System (ADS)

Nanus, L.; Clow, D. W.; Sickman, J. O.

2016-12-01

High-elevation aquatic ecosystems in Yosemite (YOSE) and Sequoia and Kings Canyon (SEKI) National Parks are impacted by atmospheric nitrogen (N) deposition associated with local and regional air pollution. Documented effects include elevated surface water nitrate concentrations, increased algal productivity, and changes in diatom species assemblages. Annual wet inorganic N deposition maps, developed at 1-km resolution for YOSE and SEKI to quantify N deposition to sensitive high-elevation ecosystems, range from 1.0 to over 5.0 kg N ha-1 yr-1. Critical loads of N deposition for nutrient enrichment of aquatic ecosystems were quantified and mapped using a geostatistical approach, with N deposition, topography, vegetation, geology, and climate as potential explanatory variables. Multiple predictive models were created using various combinations of explanatory variables; this approach allowed us to better quantify uncertainty and more accurately identify the areas most sensitive to atmospherically deposited N. The lowest critical loads estimates and highest exceedances identified within YOSE and SEKI occurred in high-elevation basins with steep slopes, sparse vegetation, and areas of neoglacial till and talus. These results are consistent with previous analyses in the Rocky Mountains, and highlight the sensitivity of alpine ecosystems to atmospheric N deposition.

Synergy of rising nitrogen depositions and atmospheric CO2 on land carbon uptake moderately offsets global warming

NASA Astrophysics Data System (ADS)

Churkina, Galina; Brovkin, Victor; von Bloh, Werner; Trusilova, Kristina; Jung, Martin; Dentener, Frank

2009-12-01

Increased carbon uptake of land in response to elevated atmospheric CO2 concentration and nitrogen deposition could slow down the rate of CO2 increase and facilitate climate change mitigation. Using a coupled model of climate, ocean, and land biogeochemistry, we show that atmospheric nitrogen deposition and atmospheric CO2 have a strong synergistic effect on the carbon uptake of land. Our best estimate of the global land carbon uptake in the 1990s is 1.34 PgC/yr. The synergistic effect could explain 47% of this carbon uptake, which is higher than either the effect of increasing nitrogen deposition (29%) or CO2 fertilization (24%). By 2030, rising carbon uptake on land has a potential to reduce atmospheric CO2 concentration by about 41 ppm out of which 16 ppm reduction would come from the synergetic response of land to the CO2 and nitrogen fertilization effects. The strength of the synergy depends largely on the cooccurrence of high nitrogen deposition regions with nonagricultural ecosystems. Our study suggests that reforestation and sensible ecosystem management in industrialized regions may have larger potential for climate change mitigation than anticipated.

Spatial Variability of Benthic-Pelagic Coupling in an Estuary Ecosystem: Consequences for Microphytobenthos Resuspension Phenomenon

PubMed Central

Ubertini, Martin; Lefebvre, Sébastien; Gangnery, Aline; Grangeré, Karine; Le Gendre, Romain; Orvain, Francis

2012-01-01

The high degree of physical factors in intertidal estuarine ecosystem increases material processing between benthic and pelagic compartments. In these ecosystems, microphytobenthos resuspension is a major phenomenon since its contribution to higher trophic levels can be highly significant. Understanding the sediment and associated microphytobenthos resuspension and its fate in the water column is indispensable for measuring the food available to benthic and pelagic food webs. To identify and hierarchize the physical/biological factors potentially involved in MPB resuspension, the entire intertidal area and surrounding water column of an estuarine ecosystem, the Bay des Veys, was sampled during ebb tide. A wide range of physical parameters (hydrodynamic regime, grain size of the sediment, and suspended matter) and biological parameters (flora and fauna assemblages, chlorophyll) were analyzed to characterize benthic-pelagic coupling at the bay scale. Samples were collected in two contrasted periods, spring and late summer, to assess the impact of forcing variables on benthic-pelagic coupling. A mapping approach using kriging interpolation enabled us to overlay benthic and pelagic maps of physical and biological variables, for both hydrological conditions and trophic indicators. Pelagic Chl a concentration was the best predictor explaining the suspension-feeders spatial distribution. Our results also suggest a perennial spatio-temporal structure of both benthic and pelagic compartments in the ecosystem, at least when the system is not imposed to intense wind, with MPB distribution controlled by both grain size and bathymetry. The benthic component appeared to control the pelagic one via resuspension phenomena at the scale of the bay. Co-inertia analysis showed closer benthic-pelagic coupling between the variables in spring. The higher MPB biomass observed in summer suggests a higher contribution to filter-feeders diets, indicating a higher resuspension effect in

Long-Term Simulated Atmospheric Nitrogen Deposition Alters Leaf and Fine Root Decomposition

EPA Science Inventory

Atmospheric nitrogen deposition has been suggested to increase forest carbon sequestration across much of the Northern Hemisphere; slower organic matter decomposition could contribute to this increase. At four sugar maple (Acer saccharum)-dominated northern hardwood forests, we p...

Spatial and temporal variability of Alexandrium cyst fluxes in the Gulf of Maine: Relationship to seasonal particle export and resuspension.

PubMed

Pilskaln, C H; Anderson, D M; McGillicuddy, D J; Keafer, B A; Hayashi, K; Norton, K

2014-05-01

Quantification of Alexandrium cyst fluxes through the Gulf of Maine water column is central to understanding the linkage between the source and fate of annual Alexandrium blooms in the offshore waters. These blooms often lead to paralytic shellfish poisoning (PSP) and extensive closures of shellfish beds. We report here on time-series sediment trap deployments completed at four offshore locations in the gulf between 2005 and 2010 as components of two ECOHAB-GOM field programs. Data presented documents the substantial spatial and temporal fluctuations in Alexandrium fundyense cyst fluxes in the gulf. Cyst delivery out of the euphotic zone peaked primarily between July and August following annual spring-summer Alexandrium blooms and was greatest in the western gulf. At all sites, cyst flux maxima to the subsurface waters were rarely coincident with seasonal peaks in the total mass export of particulate material indicating that cyst delivery was primarily via individually sinking cysts. Where persistent benthic nepheloid layers (BNLs) exist, significant sediment resuspension input of cysts to the near-bottom water column was evidenced by deep cyst fluxes that were up to several orders of magnitude greater than that measured above the BNL. The largest cyst fluxes in the BNL were observed in the eastern gulf, suggesting greater resuspension energy and BNL cyst inventories in this region. Temporal similarities between peak cyst export out of the upper ocean and peak cyst fluxes in the BNL were observed and document the contribution of seasonal, newly formed cysts to the BNL. The data however also suggest that many Alexandrium cells comprising the massive, short-lived blooms do not transition into cysts. Time-series flow measurements and a simple 1D model demonstrate that the BNL cyst fluxes reflect the combined effects of tidal energy-maintained resuspension, deposition, and input of cysts from the overlying water column.

Spatial and temporal variability of Alexandrium cyst fluxes in the Gulf of Maine: Relationship to seasonal particle export and resuspension

PubMed Central

Pilskaln, C.H.; Anderson, D.M.; McGillicuddy, D.J.; Keafer, B.A.; Hayashi, K.; Norton, K.

2014-01-01

Quantification of Alexandrium cyst fluxes through the Gulf of Maine water column is central to understanding the linkage between the source and fate of annual Alexandrium blooms in the offshore waters. These blooms often lead to paralytic shellfish poisoning (PSP) and extensive closures of shellfish beds. We report here on time-series sediment trap deployments completed at four offshore locations in the gulf between 2005 and 2010 as components of two ECOHAB–GOM field programs. Data presented documents the substantial spatial and temporal fluctuations in Alexandrium fundyense cyst fluxes in the gulf. Cyst delivery out of the euphotic zone peaked primarily between July and August following annual spring–summer Alexandrium blooms and was greatest in the western gulf. At all sites, cyst flux maxima to the subsurface waters were rarely coincident with seasonal peaks in the total mass export of particulate material indicating that cyst delivery was primarily via individually sinking cysts. Where persistent benthic nepheloid layers (BNLs) exist, significant sediment resuspension input of cysts to the near-bottom water column was evidenced by deep cyst fluxes that were up to several orders of magnitude greater than that measured above the BNL. The largest cyst fluxes in the BNL were observed in the eastern gulf, suggesting greater resuspension energy and BNL cyst inventories in this region. Temporal similarities between peak cyst export out of the upper ocean and peak cyst fluxes in the BNL were observed and document the contribution of seasonal, newly formed cysts to the BNL. The data however also suggest that many Alexandrium cells comprising the massive, short-lived blooms do not transition into cysts. Time-series flow measurements and a simple 1D model demonstrate that the BNL cyst fluxes reflect the combined effects of tidal energy-maintained resuspension, deposition, and input of cysts from the overlying water column. PMID:25431527

Atmospheric deposition of organochlorine contaminants to Galveston Bay, Texas

NASA Astrophysics Data System (ADS)

Park, June-Soo; Wade, Terry L.; Sweet, Stephen

Atmospheric monitoring of PCBs and chlorinated pesticides (e.g., HCHs, chlordanes, and DDTs) in Galveston Bay was conducted at Seabrook, Texas. Air and wet deposition samples were collected from 2 February 1995 and continued through 6 August 1996. Vapor total PCB ( tPCB) concentrations in air ranged from 0.21 to 4.78 ng m -3 with a dominance of tri-chlorinated PCBs. Dissolved tPCBs in rain ranged from 0.08 to 3.34 ng l -1, with tetra-chlorinated PCBs predominating. The predominant isomers found in air and rain were α- and γ-HCH, α- and γ-chlordanes, 4,4'-DDT, and dieldrin. The concentrations of PCBs and pesticides in the air and rain revealed no clear seasonal trend. Elevated levels of PCBs in the air occurred when temperatures were high and wind came from urban and industrialized areas (S, SW, NW, and W of the site). Concentrations of HCHs were elevated in April, May, and October, perhaps due to local and/or regional applications of γ-HCH (lindane). Other pesticides showed no notable temporal variation. When winds originated from the Gulf of Mexico (southeasterly), lower concentrations of organochlorines were detected in the air. The direct deposition rate (wet+dry) of PCBs to Galveston Bay (6.40 μg m -2 yr -1) was significantly higher than that of pesticides by a factor of 5-10. The net flux from gas exchange estimated for PCBs was from Galveston Bay water to the atmosphere (78 μg m -2 yr -1). Gas exchange of PCBs from bay water to the atmosphere was the dominant flux.

Comparison of atmospheric mercury speciation and deposition at nine sites across central and eastern North America

USGS Publications Warehouse

Engle, Mark A.; Tate, Michael T.; Krabbenhoft, David P.; Schauer, James J; Kolker, Allan; Shanley, James B.; Bothner, Michael

2010-01-01

was observed but was highly dependant upon inclusion of data from two sites with exceptionally high deposition. Findings from this study highlight the importance of environmental setting on atmospheric Hg cycling and deposition rates.

Contribution of atmospheric nitrogen deposition to diffuse pollution in a typical hilly red soil catchment in southern China.

PubMed

Shen, Jianlin; Liu, Jieyun; Li, Yong; Li, Yuyuan; Wang, Yi; Liu, Xuejun; Wu, Jinshui

2014-09-01

Atmospheric nitrogen (N) deposition is currently high and meanwhile diffuse N pollution is also serious in China. The correlation between N deposition and riverine N export and the contribution of N deposition to riverine N export were investigated in a typical hilly red soil catchment in southern China over a two-year period. N deposition was as high as 26.1 to 55.8kgN/(ha·yr) across different land uses in the studied catchment, while the riverine N exports ranged from 7.2 to 9.6kgN/(ha·yr) in the forest sub-catchment and 27.4 to 30.3kgN/(ha·yr) in the agricultural sub-catchment. The correlations between both wet N deposition and riverine N export and precipitation were highly positive, and so were the correlations between NH4(+)-N or NO3(-)-N wet deposition and riverine NH4(+)-N or NO3(-)-N exports except for NH4(+)-N in the agricultural sub-catchment, indicating that N deposition contributed to riverine N export. The monthly export coefficients of atmospheric deposited N from land to river in the forest sub-catchment (with a mean of 14%) presented a significant positive correlation with precipitation, while the monthly contributions of atmospheric deposition to riverine N export (with a mean of 18.7% in the agricultural sub-catchment and a mean of 21.0% in the whole catchment) were significantly and negatively correlated with precipitation. The relatively high contribution of N deposition to diffuse N pollution in the catchment suggests that efforts should be done to control anthropogenic reactive N emissions to the atmosphere in hilly red soil regions in southern China. Copyright © 2014. Published by Elsevier B.V.

Enhanced acid rain and atmospheric deposition of nitrogen, sulfur and heavy metals in Northern China

NASA Astrophysics Data System (ADS)

Pan, Y.; Wang, Y.

2013-12-01

Atmospheric deposition is known to be important mechanism reducing air pollution. In response to the growing concern on the potential effects of the deposited material entering terrestrial and aquatic environments as well as their subsequent health effects, since 2007 we have established a 10-site monitoring network in Northern China, where particularly susceptible to severe air pollution. Wet and dry deposition was collected using an automatic wet-dry sampler. The presentation will focus on the new results of atmospheric deposition flux for a number of chemical species, such as nutrients (e.g. nitrogen and phosphorus), acidic matters (e.g. sulfur and proton), heavy metals and Polycyclic Aromatic Hydrocarbons, etc. This is to our knowledge the first detailed element budget study in the atmosphere across Northern China. We find that: (1) Over the 3 year period, 26% of precipitation events in the target area were more acid than pH 5.60 and these acidic events occurred in summer and autumn. The annual volume-weighted mean (VWM) pH value of precipitation was lower than 5.60 at most sites, which indicated the acidification of precipitation was not optimistic. The primary ions in precipitation were NH4+, Ca2+, SO42- and NO3-, with 10-sites-average concentrations of 221, 216, 216 and 80 μeq L-1, respectively. The ratio of SO42- to NO3- was 2.7; suggesting SO42- was the dominant acid component. (2) The deposited particles were neutral in general and the pH value increased from rural area to industrial and coastal sites. It is not surprising to note that the annual VWM pH value of precipitation was higher than 5.60 at three urban sites (Beijing and Tianjin mega cities) and one coastal site near the Bohai Bay, considering the fact that high buffer capacity of alkaline component, gas NH3 and mineral aerosols, at these sites compared to other places. (3) The 10-sites annual total deposition amounts for sulfur and nitrogen compounds were 60 and 65 kg N/S ha-1 yr-1

Contemporary rates of atmospheric inorganic nitrogen (N) deposition to Latin American cities

EPA Science Inventory

Recent efforts to develop and evaluate regional and global chemical transport models reveal major gaps in atmospheric deposition monitoring. First, in contrast to northern North America, western Europe, and Asia, vast land areas in Latin America, Africa, and Australia remain unde...

Atmospheric deposition as a source of carbon and nutrients to barren, alpine soils of the Colorado Rocky Mountains

NASA Astrophysics Data System (ADS)

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

2012-03-01

Many alpine areas are experiencing intense 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, we evaluated the magnitude and chemical quality 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 approximately 1.0 mg L-1and 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. Relationships among DOC concentration, dissolved organic matter (DOM) fluorescence properties, 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. 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 and, therefore, likely to be more bioavailable to microbes in barren alpine soils. Bioavailability experiments with different types of atmospheric C sources are needed to better evaluate the substrate quality of atmospheric C inputs. Our C budget estimates for the Green Lake 4 catchment suggest that atmospheric deposition represents an

Atmospheric deposition of methanol over the Atlantic Ocean

PubMed Central

Yang, Mingxi; Nightingale, Philip D.; Beale, Rachael; Liss, Peter S.; Blomquist, Byron; Fairall, Christopher

2013-01-01

In the troposphere, methanol (CH3OH) is present ubiquitously and second in abundance among organic gases after methane. In the surface ocean, methanol represents a supply of energy and carbon for marine microbes. Here we report direct measurements of air–sea methanol transfer along a ∼10,000-km north–south transect of the Atlantic. The flux of methanol was consistently from the atmosphere to the ocean. Constrained by the aerodynamic limit and measured rate of air–sea sensible heat exchange, methanol transfer resembles a one-way depositional process, which suggests dissolved methanol concentrations near the water surface that are lower than what were measured at ∼5 m depth, for reasons currently unknown. We estimate the global oceanic uptake of methanol and examine the lifetimes of this compound in the lower atmosphere and upper ocean with respect to gas exchange. We also constrain the molecular diffusional resistance above the ocean surface—an important term for improving air–sea gas exchange models. PMID:24277830

Atmospheric deposition of methanol over the Atlantic Ocean.

PubMed

Yang, Mingxi; Nightingale, Philip D; Beale, Rachael; Liss, Peter S; Blomquist, Byron; Fairall, Christopher

2013-12-10

In the troposphere, methanol (CH3OH) is present ubiquitously and second in abundance among organic gases after methane. In the surface ocean, methanol represents a supply of energy and carbon for marine microbes. Here we report direct measurements of air-sea methanol transfer along a ∼10,000-km north-south transect of the Atlantic. The flux of methanol was consistently from the atmosphere to the ocean. Constrained by the aerodynamic limit and measured rate of air-sea sensible heat exchange, methanol transfer resembles a one-way depositional process, which suggests dissolved methanol concentrations near the water surface that are lower than what were measured at ∼5 m depth, for reasons currently unknown. We estimate the global oceanic uptake of methanol and examine the lifetimes of this compound in the lower atmosphere and upper ocean with respect to gas exchange. We also constrain the molecular diffusional resistance above the ocean surface-an important term for improving air-sea gas exchange models.

Dry atmospheric deposition rates of metals along a coastal transect in southern California

NASA Astrophysics Data System (ADS)

Sabin, Lisa D.; Schiff, Kenneth C.

While recent studies indicate atmospheric deposition is a significant source of metals to the Santa Monica Bay and coastal river systems of the Los Angeles area, the spatial extent of the atmospheric source along the entire southern California coast has not been measured in 30 years. This study provides measurements of dry atmospheric deposition of chromium, copper, lead, nickel and zinc at eight sites located along the coast between Santa Barbara and San Diego, and compares these data to historic measurements from the 1970s. Median dry deposition fluxes across sites ranged between 0.23 and 3.6 (chromium), 0.21 and 5.4 (nickel), 0.52 and 14 (lead), 0.89 and 29 (copper), and 4.8 and 160 (zinc) μg m -2 day -1. Differences in metal dry deposition rates observed between sites were dominated by proximity to urban areas and/or other nearby sources, with the highest metal fluxes observed near the Los Angeles Harbor (LAH) and San Diego Bay (SDB) sites. Compared with data from the 1970s, lead fluxes were typically one to two orders of magnitude lower in the present study (2006), indicating atmospheric sources of this metal have decreased over the past three decades in southern California. Chromium fluxes were also lower in 2006 compared with the 1970s, although to a lesser extent than for lead. In contrast, copper and zinc fluxes were typically within the same order of magnitude between the two time periods, with some higher measurements observed in 2006 compared with the 1970s at the LAH and SDB sites. This result indicates atmospheric sources of copper and zinc have not decreased over the past three decades in southern California, and have increased near our harbor/urban sites. Differences in sampling conditions (e.g., Santa Ana winds) and measurement techniques may also explain, in part, the differences observed in metal flux rates for these time periods. However, these limitations were most important for those metals with the smallest difference in flux rates measured

Stable isotope evidence for an atmospheric origin of desert nitrate deposits in northern Chile and southern California, U.S.A.

USGS Publications Warehouse

Böhlke, J.K.; Ericksen, G.E.; Revesz, K.

1997-01-01

Natural surficial accumulations of nitrate-rich salts in the Atacama Desert, northern Chile, and in the Death Valley region of the Mojave Desert, southern California, are well known, but despite many geologic and geochemical studies, the origins of the nitrates have remained controversial. N and O isotopes in nitrate, and S isotopes in coexisting soluble sulfate, were measured to determine if some proposed N sources could be supported or rejected, and to determine if the isotopic signature of these natural deposits could be used to distinguish them from various types of anthropogenic nitrate contamination that might be found in desert groundwaters. High-grade caliche-type nitrate deposits from both localities have ??15N values that range from -5 to +5???, but are mostly near 0???. Values of ??15N near 0??? are consistent with either bulk atmospheric N deposition or microbial N fixation as major sources of the N in the deposits. ??18O values of those desert nitrates with ??15N near 0??? range from about +31 to + 50??? (V-SMOW), significantly higher than that of atmospheric O2 (+ 23.5???). Such high values of ??18O are considered unlikely to result entirely from nitrification of reduced N, but rather resemble those of modern atmospheric nitrate in precipitation from some other localities. Assuming that limited modern atmospheric isotope data are applicable to the deposits, and allowing for nitrification of co-deposited ammonium, it is estimated that the fraction of the nitrate in the deposits that could be accounted for isotopically by atmospheric N deposition may be at least 20% and possibly as much as 100%. ??34S values are less diagnostic but could also be consistent with atmospheric components in some of the soluble sulfates associated with the deposits. The stable isotope data support the hypothesis that some high-grade caliche-type nitrate-rich salt deposits in some of the Earth's hyperarid deserts represent long-term accumulations of atmospheric deposition

Persistent toxic substance inputs to the river Seine basin (France) via atmospheric deposition and urban sludge application.

PubMed

Blanchard, M; Teil, M-J; Guigon, E; Larcher-Tiphagne, K; Ollivon, D; Garban, B; Chevreuil, M

2007-04-01

Paris constitutes a major direct and indirect source of persistent toxic substances (PTS) to the river Seine, its tributaries and its basin, by atmospheric depositions and sewage sludge land-filling. The contaminant cycle and transfer pathways were investigated from 1999 to 2003 at local and inter regional scales in order to determine the respective importance of the main input and diffusion processes (wastewater, rainwater and runoff) from urban to rural areas. Paris constitutes an atmospheric emission hot spot for PAHs and PCBs. For example, for 2002, atmospheric concentrations ranged from 0.5 to 3 ng m(-3) for PAHs (Sigma 6 WHO) and from 0.06 to 0.69 ng m(-3) for PCBs (Sigma 7, EEC) and concentrations in bulk deposition ranged from 6.6 to 647 ng L(-1) for PAHs (Sigma 14) and from 0.6 to 8.1 ng L(-1) for PCBs. At Paris, annual atmospheric deposition inputs of PAHs (Sigma 6) and PCBs (Sigma 7) reached 104 g km(-2) and 35 g km(-2), respectively. PAHs followed a marked seasonal cycle in relation with winter domestic heating and bulk deposition concentrations were 5 to 15 times lower in remote areas. No seasonal cycle was observed for PCBs which varied little according to the area considered. PCB deposition fluxes were ruled by the rainfall amount, while for PAHs, the fluxes depended on local anthropogenic characteristics. At the scale of the Seine-Aval treatment plant comparison of annual inputs of PTS in wet period indicated that PCBs essentially come from atmospheric sources whereas PAHs are derived from both atmospheric and urban runoff sources. At the scale of the sub-basin, atmospheric inputs to the soil (Sigma 3 PAHs: 14-25 g km(-2), Sigma 7 PCBs: 5.6-25 g km(-2)) represent the prevailing source for PAHs and PCBs, as compared to that from the disposal of urban sludge on agricultural plots (Sigma 3 PAHs: 3-8 g km(-2), Sigma 7 PCBs: 0.5-2 g km(-2)).

Trace-element evidence for the origin of desert varnish by direct aqueous atmospheric deposition

NASA Astrophysics Data System (ADS)

Thiagarajan, Nivedita; Aeolus Lee, Cin-Ty

2004-07-01

Smooth rock surfaces in arid environments are often covered with a thin coating of Fe-Mn oxyhydroxides known as desert varnish. It is debated whether such varnish is formed (a) by slow diagenesis of dust particles deposited on rock surfaces, (b) by leaching from the underlying rock substrate, or (c) by direct deposition of dissolved constituents in the atmosphere. Varnishes collected from smooth rock surfaces in the Mojave Desert and Death Valley, California are shown here to have highly enriched and fractionated trace-element abundances relative to upper continental crust (UCC). They are highly enriched in Co, Ni, Pb and the rare-earth elements (REEs). In particular, they have anomalously high Ce/La and low Y/Ho ratios. These features can only be explained by preferential scavenging of Co, Ni, Pb and the REEs by Fe-Mn oxyhydroxides in an aqueous environment. High field strength elements (HFSEs: Zr, Hf, Ta, Nb, Th), however, show only small enrichments despite the fact that these elements should also be strongly scavenged by Fe-Mn oxyhydroxides. This suggests that their lack of enrichment is a feature inherited from a solution initially poor in HFSEs. The first two scenarios for varnish formation can be ruled out as follows. The high enrichment factors of Fe, Mn and many trace elements cannot be generated by mass loss associated with post-depositional diagenesis of dust particles because such a process predicts only a small increase in concentration. In addition, the highly fractionated abundance patterns of particle reactive element pairs (e.g., Ce/La and Y/Ho) rules out leaching of the rock substrate. This is because if leaching were to occur, varnishes would grow from the inside to the outside, and thus any particle-reactive trace element leached from the substrate would be quantitatively sequestered in the Fe-Mn oxyhydroxide layers, prohibiting any significant elemental fractionations. One remaining possibility is that the Fe, Mn and trace metals in varnish are

The effects of atmospheric nitrogen deposition on terrestrial and freshwater biodiversity

USGS Publications Warehouse

Baron, Jill S.; Barber, Mary C.; Adams, Mark; Agboola, Julius I.; Allen, Edith B.; Bealey, William J.; Bobbink, Roland; Bobrovsky, Maxim V.; Bowman, William D.; Branquinho, Cristina; Bustamente, Mercedes M. C.; Clark, Christopher M.; Cocking, Edward C.; Cruz, Cristina; Davidson, Eric A.; Denmead, O. Tom; Dias, Teresa; Dise, Nancy B.; Feest, Alan; Galloway, James N.; Geiser, Linda H.; Gilliam, Frank S.; Harrison, Ian J.; Khanina, Larisa G.; Lu, Xiankai; Manrique, Esteban; Ochoa-Hueso, Raul; Ometto, Jean P. H. B.; Payne, Richard; Scheuschner, Thomas; Sheppard, Lucy J.; Simpson, Gavin L.; Singh, Y. V.; Stevens, Carly J.; Strachan, Ian; Sverdrup, Harald; Tokuchi, Naoko; van Dobben, Hans; Woodin, Sarah

2014-01-01

This chapter reports the findings of a Working Group on how atmospheric nitrogen (N) deposition affects both terrestrial and freshwater biodiversity. Regional and global scale impacts on biodiversity are addressed, together with potential indicators. Key conclusions are that: the rates of loss in biodiversity are greatest at the lowest and initial stages of N deposition increase; changes in species compositions are related to the relative amounts of N, carbon (C) and phosphorus (P) in the plant soil system; enhanced N inputs have implications for C cycling; N deposition is known to be having adverse effects on European and North American vegetation composition; very little is known about tropical ecosystem responses, while tropical ecosystems are major biodiversity hotspots and are increasingly recipients of very high N deposition rates; N deposition alters forest fungi and mycorrhyzal relations with plants; the rapid response of forest fungi and arthropods makes them good indicators of change; predictive tools (models) that address ecosystem scale processes are necessary to address complex drivers and responses, including the integration of N deposition, climate change and land use effects; criteria can be identified for projecting sensitivity of terrestrial and aquatic ecosystems to N deposition. Future research and policy-relevant recommendations are identified.

Benthic fluxes of oxygen and inorganic nutrients in the archipelago of Gulf of Finland, Baltic Sea - Effects of sediment resuspension measured in situ

NASA Astrophysics Data System (ADS)

Niemistö, Juha; Kononets, Mikhail; Ekeroth, Nils; Tallberg, Petra; Tengberg, Anders; Hall, Per O. J.

2018-05-01

Benthic fluxes of oxygen and dissolved inorganic nutrients; phosphate (DIP), ammonium (NH4), nitrate + nitrite (NOx), and silicate (DSi); and the effects of resuspension on these were studied in situ with the Göteborg benthic landers in the Gulf of Finland archipelago, Baltic Sea. The benthic fluxes were examined at two shallow stations at depths of 7 m and 20 m in May and August 2014. Resuspension altered benthic fluxes of oxygen and nutrients in most of the experiments in August, but not in May, which was mainly due to weaker resuspension treatments in spring. Additionally, the benthic nutrient regeneration rates were higher and redox conditions lower in August when the water was warmer. In August, resuspension increased the benthic oxygen uptake by 33-35%, which was, in addition to stronger resuspension treatment, attributed to higher amounts of dissolved reduced substances in the sediment pore water in comparison to conditions in May. Adsorption onto newly formed iron oxyhydroxides could explain the uptake of DIP by the sediment at the 20 m station and the lowering of the DSi efflux by 31% at the 7 m station during resuspension in August. In addition, resuspension promoted nitrification, as indicated by increased NOx fluxes at both stations (by 30% and 27% at the 7 m and 20 m station, respectively) and a lowered NH4 flux (by 48%) at the 7 m station. Predicted increases in the magnitude and frequency of resuspension will thus markedly affect the transport of phosphorus and silicon and the cycling of nitrogen in the shallow areas of the Gulf of Finland.

Atmospheric deposition, retention, and stream export of dioxins and PCBs in a pristine boreal catchment.

PubMed

Bergknut, Magnus; Laudon, Hjalmar; Jansson, Stina; Larsson, Anna; Gocht, Tilman; Wiberg, Karin

2011-06-01

The mass-balance between diffuse atmospheric deposition of organic pollutants, amount of pollutants retained by the terrestrial environment, and levels of pollutants released to surface stream waters was studied in a pristine northern boreal catchment. This was done by comparing the input of atmospheric deposition of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and PCBs with the amounts exported to surface waters. Two types of deposition samplers were used, equipped with a glass fibre thimble and an Amberlite sampler respectively. The measured fluxes showed clear seasonality, with most of the input and export occurring during winter and spring flood, respectively. The mass balance calculations indicates that the boreal landscape is an effective sink for PCDD/Fs and PCBs, as 96.0-99.9 % of received bulk deposition was retained, suggesting that organic pollutants will continue to impact stream water in the region for an extended period of time. Copyright © 2011 Elsevier Ltd. All rights reserved.

Impacts of atmospheric nitrogen deposition on vegetation and soils in Joshua Tree National Park

Treesearch

E.B. Allen; L. Rao; R.J. Steers; A. Bytnerowicz; M.E. Fenn

2009-01-01

The western Mojave Desert is downwind of nitrogen emissions from coastal and inland urban sources, especially automobiles. The objectives of this research were to measure reactive nitrogen (N) in the atmosphere and soils along a N-deposition gradient at Joshua Tree National Park and to examine its effects on invasive and native plant species. Atmospheric nitric acid (...

Impacts of large-scale atmospheric circulation changes in winter on black carbon transport and deposition to the Arctic

NASA Astrophysics Data System (ADS)

Pozzoli, Luca; Dobricic, Srdan; Russo, Simone; Vignati, Elisabetta

2017-10-01

Winter warming and sea-ice retreat observed in the Arctic in the last decades may be related to changes of large-scale atmospheric circulation pattern, which may impact the transport of black carbon (BC) to the Arctic and its deposition on the sea ice, with possible feedbacks on the regional and global climate forcing. In this study we developed and applied a statistical algorithm, based on the maximum likelihood estimate approach, to determine how the changes of three large-scale weather patterns associated with increasing temperatures in winter and sea-ice retreat in the Arctic impact the transport of BC to the Arctic and its deposition. We found that two atmospheric patterns together determine a decreasing winter deposition trend of BC between 1980 and 2015 in the eastern Arctic while they increase BC deposition in the western Arctic. The increasing BC trend is mainly due to a pattern characterized by a high-pressure anomaly near Scandinavia favouring the transport in the lower troposphere of BC from Europe and North Atlantic directly into to the Arctic. Another pattern with a high-pressure anomaly over the Arctic and low-pressure anomaly over the North Atlantic Ocean has a smaller impact on BC deposition but determines an increasing BC atmospheric load over the entire Arctic Ocean with increasing BC concentrations in the upper troposphere. The results show that changes in atmospheric circulation due to polar atmospheric warming and reduced winter sea ice significantly impacted BC transport and deposition. The anthropogenic emission reductions applied in the last decades were, therefore, crucial to counterbalance the most likely trend of increasing BC pollution in the Arctic.

Atmospheric nitrogen deposition on petals enhances seed quality of the forest herb Anemone nemorosa.

PubMed

De Frenne, P; Blondeel, H; Brunet, J; Carón, M M; Chabrerie, O; Cougnon, M; Cousins, S A O; Decocq, G; Diekmann, M; Graae, B J; Hanley, M E; Heinken, T; Hermy, M; Kolb, A; Lenoir, J; Liira, J; Orczewska, A; Shevtsova, A; Vanneste, T; Verheyen, K

2018-05-01

Elevated atmospheric input of nitrogen (N) is currently affecting plant biodiversity and ecosystem functioning. The growth and survival of numerous plant species is known to respond strongly to N fertilisation. Yet, few studies have assessed the effects of N deposition on seed quality and reproductive performance, which is an important life-history stage of plants. Here we address this knowledge gap by assessing the effects of atmospheric N deposition on seed quality of the ancient forest herb Anemone nemorosa using two complementary approaches. By taking advantage of the wide spatiotemporal variation in N deposition rates in pan-European temperate and boreal forests over 2 years, we detected positive effects of N deposition on the N concentration (percentage N per unit seed mass, increased from 2.8% to 4.1%) and N content (total N mass per seed more than doubled) of A. nemorosa seeds. In a complementary experiment, we applied ammonium nitrate to aboveground plant tissues and the soil surface to determine whether dissolved N sources in precipitation could be incorporated into seeds. Although the addition of N to leaves and the soil surface had no effect, a concentrated N solution applied to petals during anthesis resulted in increased seed mass, seed N concentration and N content. Our results demonstrate that N deposition on the petals enhances bioaccumulation of N in the seeds of A. nemorosa. Enhanced atmospheric inputs of N can thus not only affect growth and population dynamics via root or canopy uptake, but can also influence seed quality and reproduction via intake through the inflorescences. © 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

E. coli Resuspension During an Artificial High-flow Event in a Small First-order Creek

NASA Astrophysics Data System (ADS)

Pachepsky, Y. A.; Guber, A. K.; Shelton, D. R.; Hill, R. L.

2009-04-01

Stream, pond, and lake sediments can serve as environmental reservoirs for E. coli, including pathogenic strains. Substantial increases in E. coli concentrations observed in stream water during rainfall events are often attributed exclusively to runoff from agricultural fields, pastures, and riparian areas. However, this increase can, to various extents, be caused by the resuspension of E. coli from sediment. The separation of runoff vs. sediment E. coli sources is not possible based exclusively on creek water sampling during natural rainfalls. The objectives of this work were (a) to create and monitor an artificial high-flow event that would cause E. coli concentration changes solely due to resuspension and settling, (b) to develop a model of E. coli transport in creek water as affected by resuspension and settling. The study site, at the USDA-Beltsville Agricultural Research Center, is in the mid-Atlantic coastal plain of Maryland. The site contains a small first-order stream that is instrumented with four stations for monitoring stream flow and bacteria concentrations. The creek runs within a riparian corridor of variable width from about 65 m at its narrowest point, to more than 100 m. The creek bed is from 100 to 150 cm wide. Prior to the high-flow experiment, the creek sediment was grab-sampled weekly for 2 months for E. coli concentrations at three locations downstream from stations 1, 2 and 4. Time and sample position across the creek were not significant factors affecting E. coli concentrations in sediment; location along the creek was a significant factor. Initial E. coli concentrations in top 1 cm (just prior to flow) averaged 4500, 2500, and 500 cell per g of sediment at locations 1 and 2 and 4, respectively. The E. coli concentrations in sediments decreased exponentially with depth by about one order of magnitude per 2 cm. The artificial flow event was created by releasing 80 tons of tap water on a tarp-covered stream bank at 11 m above the station 1

Forest canopy uptake of atmospheric nitrogen deposition at eastern U.S. conifer sites: Carbon storage implications?

Treesearch

Herman Sievering; Ivan Fernandez; John Lee; John Hom; Lindsey Rustad

2000-01-01

Dry deposition determinations, along with wet deposition and throughfall (TF) measurements, at a spruce fir forest in central Maine were used to estimate the effect of atmospherically deposited nitrogen (N) uptake on forest carbon storage. Using nitric acid and particulate N as well as TF ammonium and nitrate data, the growing season (May-October) net canopy uptake of...

RELATING THE 4 RS OF ENVIRONMENTAL DREDGING: RESUSPENSION, RELEASE, RESIDUAL, AND RISK

EPA Science Inventory

This presentation summarizes discussions at an EPA/Corps of Engineers' Workshop which summarizind the state of the science in regard to understanding and predicting resuspension, release, residuals, and risk associated with remedial dredging.

Estimating the deposition of urban atmospheric NO2 to the urban forest in Portland-Vancouver USA

NASA Astrophysics Data System (ADS)

Rao, M.; Gonzalez Abraham, R.; George, L. A.

2016-12-01

Cities are hotspots of atmospheric emissions of reactive nitrogen oxides, including nitrogen dioxide (NO2), a US EPA criteria pollutant that affects both human and environmental health. A fraction of this anthropogenic, atmospheric NO2 is deposited onto the urban forest, potentially mitigating the impact of NO2 on respiratory health within cities. However, the role of the urban forest in removal of atmospheric NO2 through deposition has not been well studied. Here, using an observationally-based statistical model, we first estimate the reduction of NO2 associated with the urban forest in Portland-Vancouver, USA, and the health benefits accruing from this reduction. In order to assess if this statistically observed reduction in NO2 associated with the urban forest is consistent with deposition, we then compare the amount of NO2 removed through deposition to the urban forest as estimated using a 4km CMAQ simulation. We further undertake a sensitivity analysis in CMAQ to estimate the range of NO2removed as a function of bulk stomatal resistance. We find that NO2 deposition estimated by CMAQ accounts for roughly one-third of the reduction in NO2 shown by the observationally-based statistical model (Figure). Our sensitivity analysis shows that a 3-10 fold increase in the bulk stomatal resistance parameter in CMAQ would align CMAQ-estimated deposition with the statistical model. The reduction of NO2 by the urban forest in the Portland-Vancouver area may yield a health benefit of at least $1.5 million USD annually, providing strong motivation to better understand the mechanism through which the urban forest may be removing air pollutants such as NO2and thus helping create healthier urban atmospheres. Figure: Comparing the amount of NO2 deposition as estimated by CMAQ and the observationally-based statistical model (LURF). Each point corresponds to a single 4 x 4km CMAQ grid cell.

Anthropogenic 129I in the atmosphere: overview over major sources, transport processes and deposition pattern.

PubMed

Reithmeier, H; Lazarev, V; Rühm, W; Nolte, E

2010-10-01

Wet and, to a lesser extent, dry deposition of atmospheric (129)I are known to represent the dominating processes responsible for (129)I in continental environmental samples that are remote from (129)I sources and not directly influenced by any liquid (129)I release of nuclear installations. Up to now, however, little is known about the major emitters and the related global deposition pattern of (129)I. In this work an overview over major sources of (129)I is given, and hitherto unknown time-dependent releases from these were estimated. Total gaseous (129)I releases from the US and former Soviet reprocessing facilities Hanford, Savannah River, Mayak, Seversk and Zheleznogorsk were found to have been 0.53, 0.27, 1.05, 0.23 and 0.14TBq, respectively. These facilities were thus identified as major airborne (129)I emitters. The global deposition pattern due to the (129)I released, depending on geographic latitude and longitude, and on time was studied using a box model describing the global atmospheric transport and deposition of (129)I. The model predictions are compared to (129)I concentrations measured by means of Accelerator Mass Spectrometry (AMS) in water samples that were collected from various lakes in Asia, Africa, America and New Zealand, and to published values. As a result, both pattern and temporal evolution of (129)I deposition values measured in and calculated for different types of environmental samples are, in general, in good agreement. This supports our estimate on atmospheric (129)I releases and the considered substantial transport and deposition mechanisms in our model calculations. Copyright 2010 Elsevier B.V. All rights reserved.

Resuspension and redistribution of radionuclides during grassland and forest fires in the Chernobyl exclusion zone: part II. Modeling the transport process.

PubMed

Yoschenko, V I; Kashparov, V A; Levchuk, S E; Glukhovskiy, A S; Khomutinin, Yu V; Protsak, V P; Lundin, S M; Tschiersch, J

2006-01-01

To predict parameters of radionuclide resuspension, transport and deposition during forest and grassland fires, several model modules were developed and adapted. Experimental data of controlled burning of prepared experimental plots in the Chernobyl exclusion zone have been used to evaluate the prognostic power of the models. The predicted trajectories and elevations of the plume match with those visually observed during the fire experiments in the grassland and forest sites. Experimentally determined parameters could be successfully used for the calculation of the initial plume parameters which provide the tools for the description of various fire scenarios and enable prognostic calculations. In summary, the model predicts a release of some per thousand from the radionuclide inventory of the fuel material by the grassland fires. During the forest fire, up to 4% of (137)Cs and (90)Sr and up to 1% of the Pu isotopes can be released from the forest litter according to the model calculations. However, these results depend on the parameters of the fire events. In general, the modeling results are in good accordance with the experimental data. Therefore, the considered models were successfully validated and can be recommended for the assessment of the resuspension and redistribution of radionuclides during grassland and forest fires in contaminated territories.

Long-term atmospheric deposition of nitrogen, phosphorus and sulfate in a large oligotrophic lake

PubMed Central

Craft, James A.; Stanford, Jack A.

2015-01-01

We documented significantly increasing trends in atmospheric loading of ammonium (NH4) and nitrate/nitrite (NO2/3) and decreasing trends in total phosphorus (P) and sulfate (SO4) to Flathead Lake, Montana, from 1985 to 2004. Atmospheric loading of NO2/3 and NH4 increased by 48 and 198% and total P and SO4 decreased by 135 and 39%. The molar ratio of TN:TP also increased significantly. Severe air inversions occurred periodically year-round and increased the potential for substantial nutrient loading from even small local sources. Correlations between our loading data and various measures of air quality in the basin (e.g., particulate matter <10 µm in size, aerosol fine soil mass, aerosol nutrient species, aerosol index, hectares burned) suggest that dust and smoke are important sources. Ammonium was the primary form of N in atmospheric deposition, whereas NO3 was the primary N form in tributary inputs. Atmospheric loading of NH4 to Flathead Lake averaged 44% of the total load and on some years exceeded tributary loading. Primary productivity in the lake is colimited by both N and P most of the year; and in years of high atmospheric loading of inorganic N, deposition may account for up to 6.9% of carbon converted to biomass. PMID:25802810

Long-term atmospheric deposition of nitrogen, phosphorus and sulfate in a large oligotrophic lake.

PubMed

Ellis, Bonnie K; Craft, James A; Stanford, Jack A

2015-01-01

We documented significantly increasing trends in atmospheric loading of ammonium (NH4) and nitrate/nitrite (NO2/3) and decreasing trends in total phosphorus (P) and sulfate (SO4) to Flathead Lake, Montana, from 1985 to 2004. Atmospheric loading of NO2/3 and NH4 increased by 48 and 198% and total P and SO4 decreased by 135 and 39%. The molar ratio of TN:TP also increased significantly. Severe air inversions occurred periodically year-round and increased the potential for substantial nutrient loading from even small local sources. Correlations between our loading data and various measures of air quality in the basin (e.g., particulate matter <10 µm in size, aerosol fine soil mass, aerosol nutrient species, aerosol index, hectares burned) suggest that dust and smoke are important sources. Ammonium was the primary form of N in atmospheric deposition, whereas NO3 was the primary N form in tributary inputs. Atmospheric loading of NH4 to Flathead Lake averaged 44% of the total load and on some years exceeded tributary loading. Primary productivity in the lake is colimited by both N and P most of the year; and in years of high atmospheric loading of inorganic N, deposition may account for up to 6.9% of carbon converted to biomass.

Atmospheric deposition of inorganic nitrogen in Spanish forests of Quercus ilex measured with ion-exchange resins and conventional collectors

Treesearch

Héctor García-Gomez; Sheila Izquieta-Rojano; Laura Aguillaume; Ignacio González-Fernández; Fernando Valiño; David Elustondo; Jesús M. Santamaría; Anna Àvila; Mark E. Fenn; Rocío Alonso

2016-01-01

Atmospheric nitrogen deposition is one of the main threats for biodiversity and ecosystem functioning. Measurement techniques like ion-exchange resin collectors (IECs), which are less expensive and time-consuming than conventional methods, are gaining relevance in the study of atmospheric deposition and are recommended to expand monitoring networks. In the present work...

Oxygen in the Martian atmosphere: Regulation of PO2 by the deposition of iron formations on Mars

NASA Technical Reports Server (NTRS)

Burns, Roger G.

1992-01-01

During Earth's early history, and prior to the evolution of its present day oxygenated atmosphere, extensive iron rich siliceous sedimentary rocks were deposited, consisting of alternating layers of silica (chert) and iron oxide minerals (hematite and magnetite). The banding in iron formations recorded changes of atmosphere-hydrosphere interactions near sea level in the ancient ocean, which induced the oxidation of dissolved ferrous iron, precipitation of insoluble ferric oxides and silica, and regulation of oxygen in Earth's early atmosphere. Similarities between the Archean Earth and the composition of the present day atmosphere on Mars, together with the pervasive presence of ferric oxides in the Martian regolith suggest that iron formation might also have been deposited on Mars and influenced the oxygen content of the Martian atmosphere. Such a possibility is discussed here with a view to assessing whether the oxygen content of the Martian atmosphere has been regulated by the chemical precipitation of iron formations on Mars.

[Laboratory simulation study on the influence of resuspension on the release of mercury from Yangtze estuarine tidal flat].

PubMed

Li, Meng; Bi, Chun-Juan; Zhang, Jing-Jing; Lü, Jin-Gang; Chen, Zhen-Lou

2011-11-01

Using a Particle Environment Simulator, laboratory simulation experiment on the influence of resuspension on the release of mercury from sediments collected from medium tidal flat and low tidal flat in Chongming Dongtan was conducted. Results indicated that the conditions of overlying water changed significantly during resuspension. The concentrations of HgD and HgP were mainly in the rang of 0.152-2.657 microg x L(-1), 0.080-2.722 microg x L(-1) separately. In the resuspension processes, mercury was released from the medium intertidal sediments under the salinity condition of 4.1 per thousand, 8.0 per thousand, 10.0 per thousand, 13.0 per thousand, and from the low intertidal sediments under the salinity condition of 13.0 per thousand. However, the release of mercury from the medium intertidal sediments is not significant under the salinity condition of 4.1 per thousand, 8.0 per thousand, 10.0 per thousand. The salinity of overlying water had an important effect on resuspension. In different salinity condition, the release of mercury was different. And the release of mercury from medium tidal flat and low tidal flat was different during the resuspension periods, the release of mercury from the medium intertidal sediment was significantly higher than the release from the low intertidal sediment. When the rotate speed was (210 +/- 5) r x min(-1), the desorption of mercury significantly increased, thereby the rotate speed had an effect on the release of mercury.

Influence of combustion-originated dioxins in atmospheric deposition on water quality of an urban river in Japan.

PubMed

Minomo, Kotaro; Ohtsuka, Nobutoshi; Nojiri, Kiyoshi; Matsumoto, Rie

2018-02-01

Bulk (wet and dry) deposition samples were collected in Saitama Prefecture, Japan throughout a year (February 8, 2012 to February 7, 2013) to estimate the influence of dioxins emitting from waste incinerators on river water quality. The annual deposition flux of dioxins was 3.3ng-toxic equivalent (TEQ)/m 2 /year. Source identification using indicative congeners estimated that 82% of dioxin TEQ in the bulk deposition (2.7ng-TEQ/m 2 /year) was combustion-originated, indicating that most of the dioxins in the deposition were derived from waste incinerators. In Saitama prefecture the annual flux of combustion-originated dioxins in depositions was apparently consistent with that of dioxin emission into the air from waste incinerators. The TEQ of combustion-originated dioxins in the deposition per rainfall was 2.4pg-TEQ/L on annual average, exceeding the environmental quality standard (EQS) for water in Japan of 1pg-TEQ/L. This suggests there is a possibility that dioxins in atmospheric deposition have a significant influence on the water quality of urban rivers which rainwater directly flows into because of many paved areas in the basins. The influence of combustion-originated dioxin in the deposition on the water quality of Ayase River, an urban river heavily polluted with dioxins, was estimated at 0.29pg-TEQ/L on annual average in 2015. It seems that dioxins in atmospheric deposition from waste incinerators have a significant influence on water quality of some urban rivers via rainwater though the dioxins in the ambient air have achieved the EQS for atmosphere at all monitoring sites in Japan. Copyright © 2017. Published by Elsevier B.V.

Atmospheric dry deposition of sulfur and nitrogen in the Athabasca Oil Sands Region, Alberta, Canada

Treesearch

Yu-Mei Hsu; Andrzej Bytnerowicz; Mark E. Fenn; Kevin E. Percy

2016-01-01

Due to the potential ecological effects on terrestrial and aquatic ecosystems from atmospheric deposition in the Athabasca Oil Sands Region (AOSR), Alberta, Canada, this study was implemented to estimate atmospheric nitrogen (N) and sulfur (S) inputs. Passive samplers were used to measure ambient concentrations of ammonia (NH3), nitrogen dioxide...

Estimates of the atmospheric deposition of sulfur and nitrogen species: Clean Air Status and Trends Network 1990-2000.

PubMed

Baumgardner, Ralph E; Lavery, Thomas F; Rogers, Christopher M; Isil, Selma S

2002-06-15

The Clean Air Status and Trends Network (CASTNet) was established by the U.S. EPA in response to the requirements of the 1990 Clean Air Act Amendments. To satisfy these requirements CASTNet was designed to assess and report on geographic patterns and long-term, temporal trends in ambient air pollution and acid deposition in order to gauge the effectiveness of current and future mandated emission reductions. This paper presents an analysis of the spatial patterns of deposition of sulfur and nitrogen pollutants for the period 1990-2000. Estimates of deposition are provided for two 4-yr periods: 1990-1993 and 1997-2000. These two periods were selected to contrast deposition before and after the large decrease in SO2 emissions that occurred in 1995. Estimates of dry deposition were obtained from measurements at CASTNet sites combined with deposition velocities that were modeled using the multilayer model, a 20-layer model that simulates the various atmospheric processes that contribute to dry deposition. Estimates of wet deposition were obtained from measurements at sites operated bythe National Atmospheric Deposition Program. The estimates of dry and wet deposition were combined to calculate total deposition of atmospheric sulfur (dry SO2, dry and wet SO4(2-)) and nitrogen (dry HNO3, dry and wet NO3-, dry and wet NH4+). An analysis of the deposition estimates showed a significant decline in sulfur deposition and no change in nitrogen deposition. The highest rates of sulfur deposition were observed in the Ohio River Valley and downwind states. This region also observed the largest decline in sulfur deposition. The highest rates of nitrogen deposition were observed in the Midwest from Illinois to southern New York State. Sulfur and nitrogen deposition fluxes were significantly higher in the eastern United States as compared to the western sites. Dry deposition contributed approximately 38% of total sulfur deposition and 30% of total nitrogen deposition in the eastern

Exploring lag times between monthly atmospheric deposition and stream chemistry in Appalachian Forest using cross-correlation

USDA-ARS?s Scientific Manuscript database

Although long-term reductions in surface water nitrogen and sulfate concentrations have been widely observed in response to reductions in atmospheric deposition, documenting and inter-relating transient variations in deposition and stream time series has proven problematical due to low signal-to-noi...

Calibration of the MDCO dust collector and of four versions of the inverted frisbee dust deposition sampler

NASA Astrophysics Data System (ADS)

Sow, Mamadou; Goossens, Dirk; Rajot, Jean Louis

2006-12-01

Wind tunnel experiments were conducted to determine the efficiency of sediment samplers designed to measure the deposition of aeolian dust. Efficiency was ascertained relative to a water surface, which was considered the best alternative for simulating a perfectly absorbent surface. Two types of samplers were studied: the Marble Dust Collector (MDCO) and the inverted frisbee sampler. Four versions of the latter catcher were tested: an empty frisbee, an empty frisbee surrounded by an aerodynamic flow deflector ring, a frisbee filled with glass marbles, and a frisbee filled with glass marbles and surrounded by a flow deflector ring. Efficiency was ascertained for five wind velocities (range: 1-5 m s - 1 ) and eight grain size classes (range: 10-89 μm). The efficiency of dust deposition catchers diminishes rapidly as the wind speed increases. It also diminishes as the particles caught become coarser. Adding a flow deflector ring to a catcher substantially improves the catcher's efficiency, by up to 100% in some cases. The addition of glass marbles to a catcher, on the other hand, does not seem to increase the efficiency, at least not at wind velocities inferior to the deflation threshold. For higher velocities the marbles protect the settled particles from resuspension, keeping them in the catcher. The following five parameters determine the accumulation of aeolian dust in a catcher: the horizontal dust flux, the weight of the particles, atmospheric turbulence, resuspension, and the dust shadow effect created by the catcher. The final accumulation flux depends on the combination of these parameters. The catchers tested in this study belong to the best catchers currently in use in earth science and have been the subject of various aerodynamic studies to improve their efficiency. Nevertheless the catching efficiency remains low, in the order of 20-40% for wind speeds above 2 m s - 1 . Other catchers suffer from the same low efficiencies. There is, thus, evidence to

High-O2, low-CO2 atmosphere on early Mars inferred from manganese oxide deposits

NASA Astrophysics Data System (ADS)

Sekine, Y.; Imanura, S.; Noda, N.; Takahashi, Y.; Uesugi, S.; Kurisu, M.; Hartmann, J.

2017-12-01

The atmospheric composition and its redox state are central to understanding of geochemical cycles, aqueous environment, and habitability on early Mars. Findings of manganese (Mn) oxide deposits together with some trace metals (e.g., Zn and Ni) by the Curiosity and Opportunity rovers suggest a more oxidizing surface environments on early Mars, possibly with higher amount of O2, than in the present day [Lanza et al., 2016; Arvidson et al., 2016; Hurowitz et al., 2017]. However, the abundance and formation mechanism of O2 have been poorly constrained. In the present study, we report results of laboratory experiments to constrain the redox state of the aqueous environment and atmospheric composition responsible for formation of the Mn oxides on early Mars. Our results of scavenging pattern of trace metals show that the Mn oxides found by the rovers are MnO2, which requires highly oxidizing water (Eh > 0.4 V at pH 7-8) and high atmospheric O2 (> a few mbar) for deposition. We suggest that a low-CO2 condition are also required to prevent formation of Mn carbonate in the aqueous environments. We suggest a low CO2/O2 atmosphere, e.g., CO2/O2 < 1, on early Mars at the time of deposition. This in turn implies that O2 would not have been derived mainly from CO2 photolysis and may require more effective paths (e.g., H2O photolysis and effective atmospheric escape) for producing O2 in the very early stage of Mars' history.

Atmospheric nitrogen deposition in the Rocky Mountains of Colorado and southern Wyoming - A review and new analysis of past study results

USGS Publications Warehouse

Burns, Douglas A.

2003-01-01

The Rocky Mountain region of Colorado and southern Wyoming receives as much as 7kgha-1yr-1 of atmospheric nitrogen (N) deposition, an amount that may have caused changes in aquatic and terrestrial life in otherwise pristine ecosystems. Results from published studies indicate a long-term increase in the rate of atmospheric N deposition during the 20th century, but data from the National Atmospheric Deposition Program and Clean Air Status and Trends Network show no region-wide increase during the past 2 decades. Nitrogen loads in atmospheric wet deposition have increased since the mid-1980s, however, at three high elevation (>3000m) sites east of the Continental Divide in the Front Range. Much of this increase is the result of increased ammonium (NH4+) concentrations in wet deposition. This suggests an increase in contributions from agricultural areas or from vehicles east of the Rocky Mountains and is consistent with the results of previous studies that have suggested a significant eastern source for atmospheric N deposition to the Front Range. The four sites with the highest NH4+ concentrations in wet deposition were among the six easternmost NADP sites, which is also consistent with a source to the east of the Rockies. This analysis found an increase in N loads in wet deposition at Niwot Ridge of only 0.013kgha-1yr-1, more than an order of magnitude less than previously reported for this site. This lower rate of increase results from application of the non-parametric Seasonal Kendall trend test to mean monthly data, which failed a test for normality, in contrast to linear regression, which was applied to mean annual data in a previous study. Current upward trends in population growth and energy use in Colorado and throughout the west suggest a need for continued monitoring of atmospheric deposition of N, and may reveal more widespread trends in N deposition in the future.

Atmospheric concentrations and dry deposition fluxes of particulate trace metals in Salvador, Bahia, Brazil

NASA Astrophysics Data System (ADS)

de P. Pereira, Pedro A.; Lopes, Wilson A.; Carvalho, Luiz S.; da Rocha, Gisele O.; de Carvalho Bahia, Nei; Loyola, Josiane; Quiterio, Simone L.; Escaleira, Viviane; Arbilla, Graciela; de Andrade, Jailson B.

Respiratory system is the major route of entry for airborne particulates, being the effect on the human organism dependent on chemical composition of the particles, exposure time and individual susceptibility. Airborne particulate trace metals are considered to represent a health hazard since they may be absorbed into human lung tissues during breathing. Fossil fuel and wood combustion, as well as waste incineration and industrial processes, are the main anthropic sources of metals to the atmosphere. In urban areas, vehicular emissions—and dust resuspension associated to road traffic—become the most important manmade source. This work investigated the atmospheric concentrations of TSP, PM 10 and elements such as iron, manganese, copper and zinc, from three different sites around Salvador Region (Bahia, Brazil), namely: (i) Lapa Bus Station, strongly impacted by heavy-duty diesel vehicles; (ii) Aratu harbor, impacted by an intense movement of goods, including metal ores and concentrates and near industrial centers and; (iii) Bananeira Village located on Maré Island, a non-vehicle-influenced site, with activities such as handcraft work and fishery, although placed near the port. Results have pointed out that TSP concentrations ranged between 16.9 (Bananeira) and 354.0 μg m -3 (Aratu#1), while for PM 10 they ranged between 30.9 and 393.0 μg m -3, both in the Lapa Bus Station. Iron was the major element in both Lapa Station and Aratu (#1 and #2), with average concentrations in the PM 10 samples of 148.9, 79.6 and 205.0 ng m -3, respectively. Zinc, on the other hand, was predominant in samples from Bananeira, with an average concentration of 145.0 ng m -3 in TSP samples, since no PM 10 sample was taken from this site. The main sources of iron in the Lapa Station and Aratu harbor were, respectively, soil resuspension by buses and discharge of solid granaries, as fertilizers and metal ores. On the other hand, zinc and copper in the bus station were mainly from

Energy Deposition Processes in Titan's Upper Atmosphere

NASA Technical Reports Server (NTRS)

Sittler, Edward C., Jr.; Bertucci, Cesar; Coates, Andrew; Cravens, Tom; Dandouras, Iannis; Shemansky, Don

2008-01-01

Most of Titan's atmospheric organic and nitrogen chemistry, aerosol formation, and atmospheric loss are driven from external energy sources such as Solar UV, Saturn's magnetosphere, solar wind and galactic cosmic rays. The Solar UV tends to dominate the energy input at lower altitudes of approximately 1100 km but which can extend down to approximately 400 km, while the plasma interaction from Saturn's magnetosphere, Saturn's magnetosheath or solar wind are more important at higher altitudes of approximately 1400 km, but the heavy ion plasma [O(+)] of approximately 2 keV and energetic ions [H(+)] of approximately 30 keV or higher from Saturn's magnetosphere can penetrate below 950km. Cosmic rays with energies of greater than 1 GeV can penetrate much deeper into Titan's atmosphere with most of its energy deposited at approximately 100 km altitude. The haze layer tends to dominate between 100 km and 300 km. The induced magnetic field from Titan's interaction with the external plasma can be very complex and will tend to channel the flow of energy into Titan's upper atmosphere. Cassini observations combined with advanced hybrid simulations of the plasma interaction with Titan's upper atmosphere show significant changes in the character of the interaction with Saturn local time at Titan's orbit where the magnetosphere displays large and systematic changes with local time. The external solar wind can also drive sub-storms within the magnetosphere which can then modify the magnetospheric interaction with Titan. Another important parameter is solar zenith angle (SZA) with respect to the co-rotation direction of the magnetospheric flow. Titan's interaction can contribute to atmospheric loss via pickup ion loss, scavenging of Titan's ionospheric plasma, loss of ionospheric plasma down its induced magnetotail via an ionospheric wind, and non-thermal loss of the atmosphere via heating and sputtering induced by the bombardment of magnetospheric keV ions and electrons. This

Modeling the biogeochemical impact of atmospheric phosphate deposition from desert dust and combustion sources to the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Richon, Camille; Dutay, Jean-Claude; Dulac, François; Wang, Rong; Balkanski, Yves

2018-04-01

Daily modeled fields of phosphate deposition to the Mediterranean from natural dust, anthropogenic combustion and wildfires were used to assess the effect of this external nutrient on marine biogeochemistry. The ocean model used is a high-resolution (1/12°) regional coupled dynamical-biogeochemical model of the Mediterranean Sea (NEMO-MED12/PISCES). The input fields of phosphorus are for 2005, which are the only available daily resolved deposition fields from the global atmospheric chemical transport model LMDz-INCA. Traditionally, dust has been suggested to be the main atmospheric source of phosphorus, but the LMDz-INCA model suggests that combustion is dominant over natural dust as an atmospheric source of phosphate (PO4, the bioavailable form of phosphorus in seawater) for the Mediterranean Sea. According to the atmospheric transport model, phosphate deposition from combustion (Pcomb) brings on average 40.5×10-6 mol PO4 m-2 yr-1 over the entire Mediterranean Sea for the year 2005 and is the primary source over the northern part (e.g., 101×10-6 mol PO4 m-2 yr-1 from combustion deposited in 2005 over the north Adriatic against 12.4×10-6 from dust). Lithogenic dust brings 17.2×10-6 mol PO4 m-2 yr-1 on average over the Mediterranean Sea in 2005 and is the primary source of atmospheric phosphate to the southern Mediterranean Basin in our simulations (e.g., 31.8×10-6 mol PO4 m-2 yr-1 from dust deposited in 2005 on average over the south Ionian basin against 12.4×10-6 from combustion). The evaluation of monthly averaged deposition flux variability of Pdust and Pcomb for the 1997-2012 period indicates that these conclusions may hold true for different years. We examine separately the two atmospheric phosphate sources and their respective flux variability and evaluate their impacts on marine surface biogeochemistry (phosphate concentration, chlorophyll a, primary production). The impacts of the different phosphate deposition sources on the biogeochemistry of the

Accounting for the effect of temperature in clarifying the response of foliar nitrogen isotope ratios to atmospheric nitrogen deposition.

PubMed

Chen, Chongjuan; Li, Jiazhu; Wang, Guoan; Shi, Minrui

2017-12-31

Atmospheric nitrogen deposition affects nitrogen isotope composition (δ 15 N) in plants. However, both negative effect and positive effect have been reported. The effects of climate on plant δ 15 N have not been corrected for in previous studies, this has impeded discovery of a true effect of atmospheric N deposition on plant δ 15 N. To obtain a more reliable result, it is necessary to correct for the effects of climatic factors. Here, we measured δ 15 N and N contents of plants and soils in Baiwangshan and Mount Dongling, north China. Atmospheric N deposition in Baiwangshan was much higher than Mount Dongling. Generally, however, foliar N contents showed no difference between the two regions and foliar δ 15 N was significantly lower in Baiwangshan than Mount Dongling. The corrected foliar δ 15 N after accounting for a predicted value assumed to vary with temperature was obviously more negative in Baiwangshan than Mount Dongling. Thus, this suggested the necessity of temperature correction in revealing the effect of N deposition on foliar δ 15 N. Temperature, soil N sources and mycorrhizal fungi could not explain the difference in foliar δ 15 N between the two regions, this indicated that atmospheric N deposition had a negative effect on plant δ 15 N. Additionally, this study also showed that the corrected foliar δ 15 N of bulk data set increased with altitude above 1300m in Mount Dongling, this provided an another evidence for the conclusion that atmospheric N deposition could cause 15 N-depletion in plants. Copyright © 2017 Elsevier B.V. All rights reserved.

The effects of atmospheric nitrogen deposition in the Rocky Mountains of Colorado and southern Wyoming - A synthesis and critical assessment of published results

USGS Publications Warehouse

Burns, Douglas A.

2002-01-01

The Rocky Mountain region of Colorado and southern Wyoming receives as much as 7 kilograms per hectare per year ((kg/ha)/yr) of atmospheric nitrogen (N) deposition, an amount that may have caused changes in aquatic and terrestrial life in otherwise pristine ecosystems. The Rocky Mountain National Park, in its role of protecting air-quality related values under provisions of the Clean Air Act Amendments of 1977, has provided support for this synthesis and critical assessment of published literature on the effects of atmospheric N deposition. Results from published studies indicate a long-term increase in the rate of atmospheric N deposition during the 20th century, but no region-wide increase during the past 2 decades, although the rate of atmospheric N deposition has increased at three sites east of the Continental Divide in the Front Range region since the mid-1980s. Much of the increase in atmospheric N deposition at all three sites has resulted from an increase in the ammonium concentrations of wet deposition; this suggests an increase in contributions from agricultural areas or from vehicle traffic east of the Rocky Mountains. Lakes at two study sites in the Front Range (Loch Vale and Green Lakes Valley) had NO3- concentrations of 30 to 40 micromoles per liter (µmol/L) during early spring snowmelt and remained at 5 to 10 µmol/L during summer. Retention of N in atmospheric wet deposition in some sub-catchments of these lakes was less than 50 percent, which reflects an advanced stage of N saturation. Nitrate concentrations in surface waters west of the Continental Divide were lower—often less than 10 µmol/L during snowmelt and less than 2 µmol/L during summer -- than surface waters east of the Divide, except in areas such as the Mt. Zirkel Wilderness that receive elevated amounts of atmospheric N deposition of 4 to 5 (kg/ha)/yr. Atmospheric N deposition in the Front Range east of the Divide may have altered the composition of alpine tundra-plant communities

Atmospheric Deposition of Trace Elements in Ombrotrophic Peat as a Result of Anthropic Activities

NASA Astrophysics Data System (ADS)

Fabio Lourençato, Lucio; Cabral Teixeira, Daniel; Vieira Silva-Filho, Emmanoel

2014-05-01

Ombrotrophic peat can be defined as a soil rich in organic matter, formed from the partial decomposition of vegetable organic material in a humid and anoxic environment, where the accumulation of material is necessarily faster than the decomposition. From the physical-chemical point of view, it is a porous and highly polar material with high adsorption capacity and cation exchange. The high ability of trace elements to undergo complexation by humic substances happens due to the presence of large amounts of oxygenated functional groups in these substances. Since the beginning of industrialization human activities have scattered a large amount of trace elements in the environment. Soil contamination by atmospheric deposition can be expressed as a sum of site contamination by past/present human activities and atmospheric long-range transport of trace elements. Ombrotrophic peat records can provide valuable information about the entries of trace metals into the atmosphere and that are subsequently deposited on the soil. These trace elements are toxic, non-biodegradable and accumulate in the food chain, even in relatively low quantities. Thus studies on the increase of trace elements in the environment due to human activities are necessary, particularly in the southern hemisphere, where these data are scarce. The aims of this study is to evaluate the concentrations of mercury in ombrotrophic peat altomontanas coming from atmospheric deposition. The study is conducted in the Itatiaia National Park, Brazilian conservation unit, situated between the southeastern state of Rio de Janeiro, São Paulo and Minas Gerais. An ombrotrophic peat core is being sampled in altitude (1980m), to measure the trace elements concentrations of this material. As it is conservation area, the trace elements found in the samples is mainly from atmospheric deposition, since in Brazil don't exist significant lithology of trace elements. The samples are characterized by organic matter content which

Spatial distribution and seasonal variations of atmospheric sulfur deposition over Northern China

NASA Astrophysics Data System (ADS)

Pan, Y. P.; Wang, Y. S.; Tang, G. Q.; Wu, D.

2012-09-01

The increasing anthropogenic emissions of acidic compounds have induced acid deposition accompanied by acidification in the aquatic and terrestrial ecosystems worldwide. However, comprehensive assessment of spatial patterns and long-term trends of acid deposition in China remains a challenge due to a paucity of field-based measurement data, in particular for dry deposition. Here we quantify the sulfur (S) deposition on a regional scale via precipitation, particles and gases during a 3-yr observation campaign at ten selected sites in Northern China. Results show that the total S deposition flux in the target area ranged from 35.0 to 100.7 kg S ha-1 yr-1, categorized as high levels compared to those documented in Europe, North America, and East Asia. The ten-site, 3-yr average total S deposition was 64.8 kg S ha-1 yr-1, with 32% attributed to wet deposition, and the rest attributed to dry deposition. Compared with particulate sulfate, gaseous SO2 was the major contributor of dry-deposited S, contributing approximately 49% to the total flux. Wet deposition of sulfate showed pronounced seasonal variations with maximum in summer and minimum in winter, corresponding to precipitation patterns in Northern China. However, the spatial and inter-annual differences in the wet deposition were not significant, which were influenced by the precipitation amount, scavenging ratio and the concentrations of atmospheric S compounds. In contrast, the relatively large dry deposition of SO2 and sulfate during cold season, especially at industrial areas, was reasonably related to the local emissions from home heating. Although seasonal fluctuations were constant, clear spatial differences were observed in the total S deposition flux and higher values were also found in industrial areas with huge emissions of SO2. These findings indicate that human activity has dramatically altered the atmospheric S deposition and thus regional S cycles. To systematically illustrate the potential effects

Increased atmospheric deposition of mercury in reference lakes near major urban areas

USGS Publications Warehouse

Van Metre, P.C.

2012-01-01

Atmospheric deposition of Hg is the predominant pathway for Hg to reach sensitive ecosystems, but the importance of emissions on near-field deposition remains unclear. To better understand spatial variability in Hg deposition, mercury concentrations were analyzed in sediment cores from 12 lakes with undeveloped watersheds near to (<50 km) and remote from (>150 km) several major urban areas in the United States. Background and focusing corrected Hg fluxes and flux ratios (modern to background) in the near-urban lakes (68 ?? 6.9 ??g m -2 yr -1 and 9.8 ?? 4.8, respectively) greatly exceed those in the remote lakes (14 ?? 9.3 ??g m -2 yr -1 and 3.5 ?? 1.0) and the fluxes are strongly related to distance from the nearest major urban area (r 2 = 0.87) and to population and Hg emissions within 50-100 km of the lakes. Comparison to monitored wet deposition suggests that dry deposition is a major contributor of Hg to lakes near major urban areas. ?? 2011 Elsevier Ltd. All rights reserved.

[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.

Decreased atmospheric sulfur deposition across the southeastern U.S.: When will watersheds release stored sulfate?

USGS Publications Warehouse

Rice, Karen C.; Scanlon, Todd M.; Lynch, Jason A.; Cosby, Bernard J.

2014-01-01

Emissions of sulfur dioxide (SO2) to the atmosphere lead to atmospheric deposition of sulfate (SO42-), which is the dominant strong acid anion causing acidification of surface waters and soils in the eastern United States (U.S.). Since passage of the Clean Air Act and its Amendments, atmospheric deposition of SO2 in this region has declined by over 80%, but few corresponding decreases in stream-water SO42- concentrations have been observed in unglaciated watersheds. We calculated SO42- mass balances for 27 forested, unglaciated watersheds from Pennsylvania to Georgia, by using total atmospheric deposition (wet plus dry) as input. Many of these watersheds still retain SO42-, unlike their counterparts in the northeastern U.S. and southern Canada. Our analysis showed that many of these watersheds should convert from retaining to releasing SO42- over the next two decades. The specific years when the watersheds crossover from retaining to releasing SO42- correspond to a general geographical pattern of later net watershed release from north to south. The single most important variable that explained the crossover year was the runoff ratio, defined as the ratio of annual mean stream discharge to precipitation. Percent clay content and mean soil depth were secondary factors in predicting crossover year. The conversion of watersheds from net SO42- retention to release anticipates more widespread reductions in stream-water SO42- concentrations in this region.

Decreased atmospheric sulfur deposition across the Southeastern U.S.: when will watersheds release stored sulfate?

PubMed

Rice, Karen C; Scanlon, Todd M; Lynch, Jason A; Cosby, Bernard J

2014-09-02

Emissions of sulfur dioxide (SO2) to the atmosphere lead to atmospheric deposition of sulfate (SO4(2-)), which is the dominant strong acid anion causing acidification of surface waters and soils in the eastern United States. Since passage of the Clean Air Act and its Amendments, atmospheric deposition of SO2 in this region has declined by over 80%, but few corresponding decreases in streamwater SO4(2-) concentrations have been observed in unglaciated watersheds. We calculated SO4(2-) mass balances for 27 forested, unglaciated watersheds from Pennsylvania to Georgia, by using total atmospheric deposition (wet plus dry) as input. Many of these watersheds still retain SO4(2-), unlike their counterparts in the northeastern U.S. and southern Canada. Our analysis showed that many of these watersheds should convert from retaining to releasing SO4(2-) over the next two decades. The specific years when the watersheds crossover from retaining to releasing SO4(2-) correspond to a general geographical pattern of later net watershed release from north to south. The single most important variable that explained the crossover year was the runoff ratio, defined as the ratio of annual mean stream discharge to precipitation. Percent clay content and mean soil depth were secondary factors in predicting crossover year. The conversion of watersheds from net SO4(2-) retention to release anticipates more widespread reductions in streamwater SO4(2-) concentrations in this region.

ATMOSPHERIC MERCURY DEPOSITION TO LAKE MICHIGAN DURING THE LAKE MICHIGAN MASS BALANCE STUDY

EPA Science Inventory

Wet and dry mercury (Hg) deposition were calculated to Lake Michigan using a hybrid receptor modeling framework. The model utilized mercury monitoring data collected during the Lake Michigan Mass Balance Study and the Atmospheric Exchange Over Lakes and Oceans Study together w...

A model of the atmospheric metal deposition by cosmic dust particles

NASA Astrophysics Data System (ADS)

McNeil, W. J.

1993-11-01

We have developed a model of the deposition of meteoric metals in Earth's atmosphere. The model takes as input the total mass influx of material to the Earth and calculates the deposition rate at all altitudes through solution of the drag and subliminal equations in a Monte Carlo-type computation. The diffusion equation is then solved to give steady state concentration of complexes of specific metal species and kinetics are added to calculate the concentration of individual complexes. Concentrating on sodium, we calculate the Na(D) nightglow predicted by the model, and by introduction of seasonal variations in lower tropospheric ozone based on experimental results, we are able to duplicate the seasonal variation of mid-latitude nightglow data.

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.

Future monitoring of charged particle energy deposition into the upper atmosphere and comments on possible relationships between atmospheric phenomena and solar and/or geomagnetic activity

NASA Technical Reports Server (NTRS)

Williams, D. J.; Grubb, R. N.; Evans, D. S.; Sauer, H. H.

1975-01-01

Monitoring of earth's atmosphere was conducted for several years utilizing the ITOS series of low-altitude, polar-orbiting weather satellites. A space environment monitoring package was included in these satellites to perform measurements of a portion of earth's charged particle environment. The charged particle observations proposed for the low-altitude weather satellite TIROS N, are described which will provide the capability of routine monitoring of the instantaneous total energy deposition into the upper atmosphere by the precipitation of charged particles from higher altitudes. Such observations may be of use in future studies of the relationships between geomagnetic activity and atmospheric weather pattern developments. Estimates are given to assess the potential importance of this type of energy deposition. Discussion and examples are presented illustrating the importance of distinguishing between solar and geomagnetic activity as possible causative sources. Such differentiation is necessary because of the widely different spatial and time scales involved in the atmospheric energy input resulting from these various sources of activity.

Spatial variation of mercury bioaccumulation in bats of Canada linked to atmospheric mercury deposition.

PubMed

Chételat, John; Hickey, M Brian C; Poulain, Alexandre J; Dastoor, Ashu; Ryjkov, Andrei; McAlpine, Donald; Vanderwolf, Karen; Jung, Thomas S; Hale, Lesley; Cooke, Emma L L; Hobson, Dave; Jonasson, Kristin; Kaupas, Laura; McCarthy, Sara; McClelland, Christine; Morningstar, Derek; Norquay, Kaleigh J O; Novy, Richard; Player, Delanie; Redford, Tony; Simard, Anouk; Stamler, Samantha; Webber, Quinn M R; Yumvihoze, Emmanuel; Zanuttig, Michelle

2018-06-01

Wildlife are exposed to neurotoxic mercury at locations distant from anthropogenic emission sources because of long-range atmospheric transport of this metal. In this study, mercury bioaccumulation in insectivorous bat species (Mammalia: Chiroptera) was investigated on a broad geographic scale in Canada. Fur was analyzed (n=1178) for total mercury from 43 locations spanning 20° latitude and 77° longitude. Total mercury and methylmercury concentrations in fur were positively correlated with concentrations in internal tissues (brain, liver, kidney) for a small subset (n=21) of little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus), validating the use of fur to indicate internal mercury exposure. Brain methylmercury concentrations were approximately 10% of total mercury concentrations in fur. Three bat species were mainly collected (little brown bats, big brown bats, and northern long-eared bats [M. septentrionalis]), with little brown bats having lower total mercury concentrations in their fur than the other two species at sites where both species were sampled. On average, juvenile bats had lower total mercury concentrations than adults but no differences were found between males and females of a species. Combining our dataset with previously published data for eastern Canada, median total mercury concentrations in fur of little brown bats ranged from 0.88-12.78μg/g among 11 provinces and territories. Highest concentrations were found in eastern Canada where bats are most endangered from introduced disease. Model estimates of atmospheric mercury deposition indicated that eastern Canada was exposed to greater mercury deposition than central and western sites. Further, mean total mercury concentrations in fur of adult little brown bats were positively correlated with site-specific estimates of atmospheric mercury deposition. This study provides the largest geographic coverage of mercury measurements in bats to date and indicates that atmospheric

Variation in mineral content of red maple sap across an atmospheric deposition gradient

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

McCormick, L.H.

1997-11-01

Xylem sap was collected from red maple (Acer rubrum L.) trees during the spring of 1988 and 1989 at seven forest sites along an atmospheric deposition gradient in north central Pennsylvania and analyzed for pH and twelve mineral constituents. The objectives of the study were to examine the sources and patterns of variation in red maple sap chemistry across an atmospheric deposition gradient and to assess the feasibility of using sap analysis as an indicator of nutrient bioavailability. For most sap constituents, there was considerable spatial and temporal variation in concentration. Sources of variation included within and between site variation,more » date, and year of collection. The nature and extent of variation varied for different constituents. Site differences were similar in 1988 and 1989 for most sap constituents and for some constituents corresponded with differences in soil levels.« less

ATMOSPHERIC DRY PARTICLE DEPOSITION OF POPS AND TRACE METALS IN AN URBAN- AND INDUSTRIALLY-IMPACTED MID-ATLANTIC ESTUARY (AEOLOS B MID-ATLANTIC)

EPA Science Inventory

Emissions of hazardous air pollutants into the coastal urban-industrial atmosphere increase atmospheric depositional fluxes to proximate water bodies. Dry deposition of large particles containing persistent organic pollutants (POPs) and trace metals were a major contribu...

Self-organization of SiO{sub 2} nanodots deposited by chemical vapor deposition using an atmospheric pressure remote microplasma

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

Arnoult, G.; Belmonte, T.; Henrion, G.

Self-organization of SiO{sub 2} nanodots is obtained by chemical vapor deposition out of hexamethyldisiloxane (HMDSO) and atmospheric pressure remote Ar-O{sub 2} plasma operating at high temperature (1200-1600 K). The dewetting of the film being deposited when it is still thin enough (<500 nm) is found to be partly responsible for this self-organization. When the coating becomes thicker (approx1 mum), and for relatively high contents in HMDSO, SiO{sub 2} walls forming hexagonal cells are obtained on a SiO{sub 2} sublayer. For thicker coatings (>1 mum), droplet-shaped coatings with a Gaussian distribution in thickness over their width are deposited. The coatings aremore » submitted to high compressive stress. When it is relaxed, 'nestlike structures' made of nanoribbons are synthesized.« less

Developing Oxidized Nitrogen Atmospheric Deposition Source Attribution from CMAQ for Air-Water Trading for Chesapeake Bay

NASA Astrophysics Data System (ADS)

Dennis, R. L.; Napelenok, S. L.; Linker, L. C.; Dudek, M.

2012-12-01

Estuaries are adversely impacted by excess reactive nitrogen, Nr, from many point and nonpoint sources, including atmospheric deposition to the watershed and the estuary itself as a nonpoint source. For effective mitigation, trading among sources of Nr is being considered. The Chesapeake Bay Program is working to bring air into its trading scheme, which requires some special air computations. Airsheds are much larger than watersheds; thus, wide-spread or national emissions controls are put in place to achieve major reductions in atmospheric Nr deposition. The tributary nitrogen load reductions allocated to the states to meet the TMDL target for Chesapeake Bay are large and not easy to attain via controls on water point and nonpoint sources. It would help the TMDL process to take advantage of air emissions reductions that would occur with State Implementation Plans that go beyond the national air rules put in place to help meet national ambient air quality standards. There are still incremental benefits from these local or state-level controls on atmospheric emissions. The additional air deposition reductions could then be used to offset water quality controls (air-water trading). What is needed is a source to receptor transfer function that connects air emissions from a state to deposition to a tributary. There is a special source attribution version of the Community Multiscale Air Quality model, CMAQ, (termed DDM-3D) that can estimate the fraction of deposition contributed by labeled emissions (labeled by source or region) to the total deposition across space. We use the CMAQ DDM-3D to estimate simplified state-level delta-emissions to delta-atmospheric-deposition transfer coefficients for each major emission source sector within a state, since local air regulations are promulgated at the state level. The CMAQ 4.7.1 calculations are performed at a 12 km grid size over the airshed domain covering Chesapeake Bay for 2020 CAIR emissions. For results, we first present

Deposition of Atmospheric Nitrogen to Coastal Ecosystems (DANCE): A study in seasonally oligotrophic waters off the eastern U.S.

NASA Astrophysics Data System (ADS)

Najjar, R.; Sedwick, P.; Mulholland, M. R.; Friedrichs, M. A.; Thompson, A. M.; Martins, D. K.; Bernhardt, P. W.; Herrmann, M.; Price, L. M.; Sohst, B. M.; Sookhdeo, C.; St-Laurent, P.; Widner, B.

2016-02-01

We carried out a program of process-oriented field measurements and biogeochemical modeling in oligotrophic coastal waters off the eastern U.S.—a region that currently receives high levels of atmospheric nitrogen deposition (AND)—to test whether wet AND events stimulate primary productivity and accumulation of algal biomass in coastal waters following summer storms. Our results from shipboard incubations and numerical modeling indicate that nitrogen in rain stimulated primary production in these waters during the summer of 2014. We will present isotopic, tracer, and modeling analyses that determine the relative roles of vertical mixing and atmospheric deposition during the wet AND events in two anticyclonic eddies north and south of the Gulf Stream. 3-D atmospheric and oceanic modeling results will also be presented, which allow the understanding gained during the summer 2014 field campaign to be applied to quantifying the role of atmospheric deposition throughout coastal waters of the eastern US over many years.

Control of Toxic Chemicals in Puget Sound, Phase 3: Study of Atmospheric Deposition of Air Toxics to the Surface of Puget Sound

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

Brandenberger, Jill M.; Louchouarn, Patrick; Kuo, Li-Jung

2010-07-05

The results of the Phase 1 Toxics Loading study suggested that runoff from the land surface and atmospheric deposition directly to marine waters have resulted in considerable loads of contaminants to Puget Sound (Hart Crowser et al. 2007). The limited data available for atmospheric deposition fluxes throughout Puget Sound was recognized as a significant data gap. Therefore, this study provided more recent or first reported atmospheric deposition fluxes of PAHs, PBDEs, and select trace elements for Puget Sound. Samples representing bulk atmospheric deposition were collected during 2008 and 2009 at seven stations around Puget Sound spanning from Padilla Bay southmore » to Nisqually River including Hood Canal and the Straits of Juan de Fuca. Revised annual loading estimates for atmospheric deposition to the waters of Puget Sound were calculated for each of the toxics and demonstrated an overall decrease in the atmospheric loading estimates except for polybrominated diphenyl ethers (PBDEs) and total mercury (THg). The median atmospheric deposition flux of total PBDE (7.0 ng/m2/d) was higher than that of the Hart Crowser (2007) Phase 1 estimate (2.0 ng/m2/d). The THg was not significantly different from the original estimates. The median atmospheric deposition flux for pyrogenic PAHs (34.2 ng/m2/d; without TCB) shows a relatively narrow range across all stations (interquartile range: 21.2- 61.1 ng/m2/d) and shows no influence of season. The highest median fluxes for all parameters were measured at the industrial location in Tacoma and the lowest were recorded at the rural sites in Hood Canal and Sequim Bay. Finally, a semi-quantitative apportionment study permitted a first-order characterization of source inputs to the atmosphere of the Puget Sound. Both biomarker ratios and a principal component analysis confirmed regional data from the Puget Sound and Straits of Georgia region and pointed to the predominance of biomass and fossil fuel (mostly liquid petroleum

Natural or anthropogenic? On the origin of atmospheric sulfate deposition in the Andes of southeastern Ecuador

NASA Astrophysics Data System (ADS)

Makowski Giannoni, S.; Rollenbeck, R.; Trachte, K.; Bendix, J.

2014-10-01

Atmospheric sulfur deposition above certain limits can represent a threat to tropical forests, causing nutrient imbalances and mobilizing toxic elements that impact biodiversity and forest productivity. Atmospheric sources of sulfur deposited by precipitation have been roughly identified in only a few lowland tropical forests. Even scarcer are studies of this type in tropical mountain forests, many of them mega-diversity hotspots and especially vulnerable to acidic deposition. In these places, the topographic complexity and related streamflow conditions affect the origin, type, and intensity of deposition. Furthermore, in regions with a variety of natural and anthropogenic sulfur sources, like active volcanoes and biomass burning, no source emission data has been used for determining the contribution of each source to the deposition. The main goal of the current study is to evaluate sulfate (SO4- deposition by rain and occult precipitation at two topographic locations in a tropical mountain forest of southern Ecuador, and to trace back the deposition to possible emission sources applying back-trajectory modeling. To link upwind natural (volcanic) and anthropogenic (urban/industrial and biomass-burning) sulfur emissions and observed sulfate deposition, we employed state-of-the-art inventory and satellite data, including volcanic passive degassing as well. We conclude that biomass-burning sources generally dominate sulfate deposition at the evaluated sites. Minor sulfate transport occurs during the shifting of the predominant winds to the north and west. Occult precipitation sulfate deposition and likely rain sulfate deposition are mainly linked to biomass-burning emissions from the Amazon lowlands. Volcanic and anthropogenic emissions from the north and west contribute to occult precipitation sulfate deposition at the mountain crest Cerro del Consuelo meteorological station and to rain-deposited sulfate at the upriver mountain pass El Tiro meteorological station.

Natural or anthropogenic? On the origin of atmospheric sulfate deposition in the Andes of southeastern Ecuador

NASA Astrophysics Data System (ADS)

Makowski Giannoni, S.; Rollenbeck, R.; Trachte, K.; Bendix, J.

2014-05-01

Atmospheric sulfur deposition above certain limits can represent a threat to tropical forests, causing nutrient imbalances and mobilizing toxic elements that impact biodiversity and forest productivity. Atmospheric sources of sulfur deposited by precipitation have being roughly identified in only a few lowland tropical forests. Even scarcer are these type of studies in tropical mountain forests, many of them megadiversity hotspots and especially vulnerable to acidic deposition. Here, the topographic complexity and related streamflow condition the origin, type, and intensity of deposition. Furthermore, in regions with a variety of natural and anthropogenic sulfur sources, like active volcanoes and biomass-burning, no source-emission data has been used for determining the contribution of each of them to the deposition. The main goal of the current study is to evaluate sulfate (SO4-) deposition by rain and occult precipitation at two topographic locations in a tropical mountain forest of southern Ecuador, and to trace back the deposition to possible emission sources applying back trajectory modeling. To link upwind natural (volcanic) and anthropogenic (urban/industrial and biomass-burning) sulfur emissions and observed sulfate deposition, we employed state of the art inventory and satellite data, including volcanic passive degassing as well. We conclude that biomass-burning sources generally dominate sulfate deposition at the evaluated sites. Minor sulfate transport occurs during the shifting of the predominant winds to the north and west. Occult precipitation sulfate deposition and likely rain sulfate deposition are mainly linked to biomass-burning emissions from the Amazon lowlands. Volcanic and anthropogenic emissions from the north and west contribute to occult precipitation sulfate deposition at the mountain crest Cerro del Consuelo meteorological station and to rain-deposited sulfate at the upriver mountain-pass El Tiro meteorological station.

Methods for measuring atmospheric nitrogen deposition inputs in arid and montane ecosystems of western North America

Treesearch

M.E. Fenn; J.O. Sickman; A. Bytnerowicz; D.W. Clow; N.P. Molotch; J.E. Pleim; G.S. Tonnesen; K.C. Weathers; P.E. Padgett; D.H. Campbell.

2009-01-01

Measuring atmospheric deposition in arid and snow-dominated regions presents unique challenges. Throughfall, the flux of nutrients transported in solution to the forest floor, is generally the most practical method of estimating below-canopy deposition, particularly when monitoring multiple forest sites or over multiple years. However, more studies are needed to relate...

Atmospheric Energy Deposition Modeling and Inference for Varied Meteoroid Structures

NASA Technical Reports Server (NTRS)

Wheeler, Lorien; Mathias, Donovan; Stokan, Edward; Brown, Peter

2018-01-01

Asteroids populations are highly diverse, ranging from coherent monoliths to loosely-bound rubble piles with a broad range of material and compositional properties. These different structures and properties could significantly affect how an asteroid breaks up and deposits energy in the atmosphere, and how much ground damage may occur from resulting blast waves. We have previously developed a fragment-cloud model (FCM) for assessing the atmospheric breakup and energy deposition of asteroids striking Earth. The approach represents ranges of breakup characteristics by combining progressive fragmentation with releases of variable fractions of debris and larger discrete fragments. In this work, we have extended the FCM to also represent asteroids with varied initial structures, such as rubble piles or fractured bodies. We have used the extended FCM to model the Chelyabinsk, Benesov, Kosice, and Tagish Lake meteors, and have obtained excellent matches to energy deposition profiles derived from their light curves. These matches provide validation for the FCM approach, help guide further model refinements, and enable inferences about pre-entry structure and breakup behavior. Results highlight differences in the amount of small debris vs. discrete fragments in matching the various flare characteristics of each meteor. The Chelyabinsk flares were best represented using relatively high debris fractions, while Kosice and Benesov cases were more notably driven by their discrete fragmentation characteristics, perhaps indicating more cohesive initial structures. Tagish Lake exhibited a combination of these characteristics, with lower-debris fragmentation at high altitudes followed by sudden disintegration into small debris in the lower flares. Results from all cases also suggest that lower ablation coefficients and debris spread rates may be more appropriate for the way in which debris clouds are represented in FCM, offering an avenue for future model refinement.

Deposition of Suspended Clay to Open and Sand-Filled Framework Gravel Beds in a Laboratory Flume

NASA Astrophysics Data System (ADS)

Mooneyham, Christian; Strom, Kyle

2018-01-01

Pulses of fine sediment composed of sand, silt, and clay can be introduced to gravel bed rivers through runoff from burn-impacted hillslopes, landslides, bank failure, or the introduction of reservoir sediment as a result of sluicing or dam decommissioning. Here we present a study aimed at quantifying exchange between suspensions of clay and gravel beds. The questions that motivate the work are: how do bed roughness and pore space characteristics, shear velocity (u∗), and initial concentration (C0) affect clay deposition on or within gravel beds? Where does deposition within these beds occur, and can deposited clay be resuspended while the gravel is immobile? We examine these questions in a laboratory flume using acrylic, open-framework gravel, and armored sand-gravel beds under conditions of varying u∗ and C0. Deposition of clay occurred to all beds (even with Rouse numbers ˜ 0.01). We attribute deposition under full suspension conditions to be an outcome of localized protected zones where clay can settle and available pore space in the bed. For smooth wall cases, protection came from the viscous wall region and the development of bed forms; for the rough beds, protection came from separation zones and low-velocity pore spaces. Bed porosity was the strongest influencer of nondimensional deposition rate; deposition increased with porosity. Deposition was inversely related to u∗ for the acrylic bed runs; no influence of u∗ was found for the porous bed runs. Increases in discharge resulted in resuspension of clay from acrylic beds; no resuspension was observed in the porous bed runs.

The importance of source configuration in quantifying footprints of regional atmospheric sulphur deposition.

PubMed

Vieno, M; Dore, A J; Bealey, W J; Stevenson, D S; Sutton, M A

2010-01-15

An atmospheric transport-chemistry model is applied to investigate the effects of source configuration in simulating regional sulphur deposition footprints from elevated point sources. Dry and wet depositions of sulphur are calculated for each of the 69 largest point sources in the UK. Deposition contributions for each point source are calculated for 2003, as well as for a 2010 emissions scenario. The 2010 emissions scenario has been chosen to simulate the Gothenburg protocol emission scenario. Point source location is found to be a major driver of the dry/wet deposition ratio for each deposition footprint, with increased precipitation scavenging of SO(x) in hill areas resulting in a larger fraction of the emitted sulphur being deposited within the UK for sources located near these areas. This reduces exported transboundary pollution, but, associated with the occurrence of sensitive soils in hill areas, increases the domestic threat of soil acidification. The simulation of plume rise using individual stack parameters for each point source demonstrates a high sensitivity of SO(2) surface concentration to effective source height. This emphasises the importance of using site-specific information for each major stack, which is rarely included in regional atmospheric pollution models, due to the difficulty in obtaining the required input data. The simulations quantify how the fraction of emitted SO(x) exported from the UK increases with source magnitude, effective source height and easterly location. The modelled reduction in SO(x) emissions, between 2003 and 2010 resulted in a smaller fraction being exported, with the result that the reductions in SO(x) deposition to the UK are less than proportionate to the emission reduction. This non-linearity is associated with a relatively larger fraction of the SO(2) being converted to sulphate aerosol for the 2010 scenario, in the presence of ammonia. The effect results in less-than-proportional UK benefits of reducing in SO(2

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

Active moss biomonitoring of trace elements with Sphagnum girgensohnii moss bags in relation to atmospheric bulk deposition in Belgrade, Serbia.

PubMed

Anicić, M; Tasić, M; Frontasyeva, M V; Tomasević, M; Rajsić, S; Mijić, Z; Popović, A

2009-02-01

Active biomonitoring with wet and dry moss bags was used to examine trace element atmospheric deposition in the urban area of Belgrade. The element accumulation capability of Sphagnum girgensohnii Russow was tested in relation to atmospheric bulk deposition. Moss bags were mounted for five 3-month periods (July 2005-October 2006) at three representative urban sites. For the same period monthly bulk atmospheric deposition samples were collected. The concentrations of Al, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb were determined by instrumental neutron activation analyses and atomic absorption spectrometry. Significant accumulation of most elements occurred in the exposed moss bags compared with the initial moss content. High correlations between the elements in moss and bulk deposits were found for V, Cu, As, and Ni. The enrichment factors of the elements for both types of monitor followed the same pattern at the corresponding sites.

Development of ion-exchange collectors for monitoring atmospheric deposition of inorganic pollutants in Alaska parklands

USGS Publications Warehouse

Brumbaugh, William G.; Arms, Jesse W.; Linder, Greg L.; Melton, Vanessa D.

2016-09-19

Between 2010 and 2014, the U.S. Geological Survey completed a series of laboratory and field experiments designed to develop methodology to support the National Park Service’s long-term atmospheric pollutant monitoring efforts in parklands of Arctic Alaska. The goals of this research were to develop passive sampling methods that could be used for long-term monitoring of inorganic pollutants in remote areas of arctic parklands and characterize relations between wet and dry deposition of atmospheric pollutants to that of concentrations accumulated by mosses, specifically the stair-step, splendid feather moss, Hylocomium splendens. Mosses and lichens have been used by National Park Service managers as atmospheric pollutant biomonitors since about 1990; however, additional research is needed to better characterize the dynamics of moss bioaccumulation for various classes of atmospheric pollutants. To meet these research goals, the U.S. Geological Survey investigated the use of passive ionexchange collectors (IECs) that were adapted from the design of Fenn and others (2004). Using a modified IEC configuration, mulitple experiments were completed that included the following: (a) preliminary laboratory and development testing of IECs, (b) pilot-scale validation field studies during 2012 with IECs at sites with instrumental monitoring stations, and (c) deployment of IECs in 2014 at sites in Alaska having known or suspected regional sources of atmospheric pollutants where samples of Hylocomium splendens moss also could be collected for comparison. The targeted substances primarily included ammonium, nitrate, and sulfate ions, and certain toxicologically important trace metals, including cadmium, cobalt, copper, nickel, lead, and zinc.Deposition of atmospheric pollutants is comparatively low throughout most of Alaska; consequently, modifications of the original IEC design were needed. The most notable modification was conversion from a single-stage mixed-bed column to a two

Paleolimnological evidence of variations in deposition of atmosphere-borne Polycyclic Aromatic Hydrocarbons (PAHs) in Ireland.

PubMed

O'Dwyer, B; Taylor, D

2009-11-01

Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous in the environment and are produced by both natural and anthropogenic processes, principally from the incomplete combustion of organic matter. Levels of emissions of PAHs from the combustion of fossil fuels have increased rapidly over the last ca. 200 years. As PAHs have detrimental environmental and human health impacts, assessing spatial and temporal variations in environmental loadings has become a pressing issue in many industrialised and industrializing countries. The current paper reports spatial and temporal variations in levels of atmospheric deposition of PAHs recorded in sediment cores from three lakes in Ireland, the locations of which were selected on the basis of known geographic differences in the deposition of atmospheric pollutants. Thirteen PAH compounds were analysed for in samples of lake sediment that were assumed to represent contemporary/recent and historical (possibly reference) levels of deposition. A third sample was selected from each core on the basis of measured levels of spheroidal carbonaceous particles, which are regarded as a direct indicator of depositions from the industrial-level combustion of fossil fuels. Chronological control was provided by the (210)Pb dating technique which also allowed for the calculation of PAH flux. For the most part, and when compared with the limited published data, measured levels of PAH depositions were relatively low. However, levels of deposition of PAHs in the west of Ireland are higher now than previously, which is in contrast to a general trend of decreasing levels in Europe.

Energy deposition rates by charged particles. [in upper atmosphere

NASA Technical Reports Server (NTRS)

Torkar, K. M.; Urban, A.; Bjordal, J.; Lundblad, J. A.; Soraas, F.; Smith, L. G.; Dumbs, A.; Grandal, B.; Ulwick, J. C.; Vancour, R. P.

1985-01-01

A summary of measurements of the precipitation of electrons and positive ions (in the keV-MeV range) detected aboard eight rockets launched within the Energy Budget Campaign from Northern Scandinavia is given, together with corresponding satellite data. In some cases strong temporal variations of the downgoing integral fluxes were observed. The fluxes provide the background for the calculated ion production rates and altitude profiles of the energy deposition into the atmosphere at different levels of geomagnetic disturbance and cosmic noise absorption. The derived ion production rates by eneretic particles are compared to other night-time ionisation sources.

Atmospheric deposition and ozone levels in Swiss forests: are critical values exceeded?

PubMed

Waldner, Peter; Schaub, Marcus; Graf Pannatier, Elisabeth; Schmitt, Maria; Thimonier, Anne; Walthert, Lorenz

2007-05-01

Air pollution affects forest health through atmospheric deposition of acidic and nitrogen compounds and elevated levels of tropospheric ozone (O3). In 1985, a monitoring network was established across Europe and various research efforts have since been undertaken to define critical values. We measured atmospheric deposition of acidity and nitrogen as well as ambient levels of O3 on 12, 13, and 14 plots, respectively, in the framework of the Swiss Long-Term Forest Ecosystem Research (LWF) in the period from 1995 to 2002. We estimated the critical loads of acidity and of nitrogen, using the steady state mass balance approach, and calculated the critical O3 levels using the AOT40 approach. The deposition of acidity exceeded the critical loads on 2 plots and almost reached them on 4 plots. The median of the measured molar ratio of base nutrient cations to total dissolved aluminium (Bc/Al) in the soil solution was higher than the critical value of 1 for all depths, and also at the plots with an exceedance of the critical load of acidity. For nitrogen, critical loads were exceeded on 8 plots and deposition likely represents a long-term ecological risk on 3 to 10 plots. For O3, exceedance of critical levels was recorded on 12 plots, and led to the development of typical O3-induced visible injury on trees and shrubs, but not for all plots due to (1) the site specific composition of O3 sensitive and tolerant plant species, and (2) the influence of microclimatic site conditions on the stomatal behaviour, i.e., O3 uptake.

Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

NASA Astrophysics Data System (ADS)

Hemawan, Kadek W.; Gou, Huiyang; Hemley, Russell J.

2015-11-01

Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C2, Ar, N2, CH, Hβ, and Hα were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T2g phonon at 1333 cm-1 peak relative to the Raman features of graphitic carbon. Field emission scanning electron microscopy images reveal that, depending on the growth conditions, the carbon microstructures of grown films exhibit "coral" and "cauliflower-like" morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.

Impact of natural (storm) and anthropogenic (trawling) sediment resuspension on particulate organic matter in coastal environments

NASA Astrophysics Data System (ADS)

Pusceddu, A.; Grémare, A.; Escoubeyrou, K.; Amouroux, J. M.; Fiordelmondo, C.; Danovaro, R.

2005-12-01

In order to assess the impact of natural and anthropogenic sediment resuspension on quantity, biochemical composition and bioavailability of particulate organic matter (POM), two field investigations were carried out in two shallow coastal areas of the Mediterranean Sea. In the Gulf of Lions, we investigated the impact of a storm resuspension of sediment, whereas in the Thermaikos Gulf we investigated the impact of bottom trawling. Resuspension in the Gulf of Lions determined the increase of sedimentation rates, modified the composition of the organic fraction of settling particles and decreased the labile fraction of POM, as indicated by a drop in the enzymatically hydrolysable amino acid fraction. The increase in the refractory fraction, following short-term storm-induced resuspension, increased also the contribution of glycine and decreased the contribution of aspartic acid contents to the total amino acid pools. Trawling activities in Thermaikos Gulf determined a significant increase in suspended POM concentrations and important changes in its biochemical composition. After trawling, the protein to carbohydrate ratio decreased (as a result of a major input of sedimentary carbohydrates at the water-sediment interface) and the fraction of enzymatically hydrolysable biopolymeric C decreased by ≈30%, thus reducing the bioavailability of resuspended organic particles. Results of the present study indicate that changes in suspended POM, induced by storms and trawling activities, can have similar consequences on benthic systems and on food webs. In fact, the potential benefit of increased organic particle concentration for suspension feeders, is depressed by the shift of suspended food particles towards a more refractory composition.

Challenges in tracing the fate and effects of atmospheric polycyclic aromatic hydrocarbon deposition in vascular plants.

PubMed

Desalme, Dorine; Binet, Philippe; Chiapusio, Geneviève

2013-05-07

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants that raise environmental concerns because of their toxicity. Their accumulation in vascular plants conditions harmful consequences to human health because of their position in the food chain. Consequently, understanding how atmospheric PAHs are taken up in plant tissues is crucial for risk assessment. In this review we synthesize current knowledge about PAH atmospheric deposition, accumulation in both gymnosperms and angiosperms, mechanisms of transfer, and ecological and physiological effects. PAHs emitted in the atmosphere partition between gas and particulate phases and undergo atmospheric deposition on shoots and soil. Most PAH concentration data from vascular plant leaves suggest that contamination occurs by both direct (air-leaf) and indirect (air-soil-root) pathways. Experimental studies demonstrate that PAHs affect plant growth, interfering with plant carbon allocation and root symbioses. Photosynthesis remains the most studied physiological process affected by PAHs. Among scientific challenges, identifying specific physiological transfer mechanisms and improving the understanding of plant-symbiont interactions in relation to PAH pollution remain pivotal for both fundamental and applied environmental sciences.

Statistical characterization of wind-wave induced sediment resuspension events in shallow tidal basins

NASA Astrophysics Data System (ADS)

D'Alpaos, A.; Carniello, L.; Rinaldo, A.

2013-12-01

Wind-wave induced erosion processes play a critical role on the morphodynamic evolution of shallow tidal landscapes. Both in the horizontal and in the vertical planes, patterns of wind-induced bottom shear stresses contribute to control the morphological and biological features of the tidal landscape, through the erosion of tidal-flat surfaces and of salt-marsh margins, the disruption of the polymeric microphytobenthic biofilm, and the increase in suspended sediment concentration which affects the stability of intertidal ecosystems. Towards the goal of developing a synthetic theoretical framework to represent wind wave-induced resuspension events and account for their erosional effects on the long-term biomorphodynamic evolution of tidal systems, we have employed a complete, coupled finite element model accounting for the role of wind waves and tidal currents on the hydrodynamic circulation in shallow basins. Our analysis of the characteristics of combined current and wave-induced exceedances in bottom shear stress over a given threshold for erosion, suggest that wind wave-induced resuspension events can be modeled as a marked Poisson process. Moreover, the analysis of wind-wave induced resuspension events for different historical configurations of the Venice Lagoon shows that the interarrival times of erosion events have decreased through the last two centuries, whereas the intensities of erosion events have increased. This allows us to characterize the threatening erosion and degradation processes that the Venice Lagoon has been experiencing since the beginning of the last century.

Atmospheric mercury deposition during the last 270 years--A glacial ice core record of natural and anthropogenic sources

USGS Publications Warehouse

Schuster, Paul F.; Krabbenhoft, David P.; Naftz, David L.; Cecil, L. DeWayne; Olson, Mark L.; DeWild, John F.; Susong, David D.; Green, Jaromy R.; Abbott, Michael L.

2002-01-01

Mercury (Hg) contamination of aquatic ecosystems and subsequent methylmercury bioaccumulation are significant environmental problems of global extent. At regional to global scales, the primary mechanism of Hg contamination is atmospheric Hg transport. Thus, a better understanding of the long-term history of atmospheric Hg cycling and quantification of the sources is critical for assessing the regional and global impact of anthropogenic Hg emissions. Ice cores collected from the Upper Fremont Glacier (UFG), Wyoming, contain a high-resolution record of total atmospheric Hg deposition (ca. 1720−1993). Total Hg in 97 ice-core samples was determined with trace-metal clean handling methods and low-level analytical procedures to reconstruct the first and most comprehensive atmospheric Hg deposition record of its kind yet available from North America. The record indicates major atmospheric releases of both natural and anthropogenic Hg from regional and global sources. Integrated over the past 270-year ice-core history, anthropogenic inputs contributed 52%, volcanic events 6%, and background sources 42%. More significantly, during the last 100 years, anthropogenic sources contributed 70% of the total Hg input. Unlike the 2−7-fold increase observed from preindustrial times (before 1840) to the mid-1980s in sediment-core records, the UFG record indicates a 20-fold increase for the same period. The sediment-core records, however, are in agreement with the last 10 years of this ice-core record, indicating declines in atmospheric Hg deposition.

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.

Conditional vulnerability of plant diversity to atmospheric nitrogen deposition across the United States

USGS Publications Warehouse

Simkin, Samuel M.; Allen, Edith B.; Bowman, William D.; Clark, Christopher M.; Belnap, Jayne; Brooks, Matthew L.; Cade, Brian S.; Collins, Scott L.; Geiser, Linda H.; Gilliam, Frank S.; Jovan, Sarah E.; Pardo, Linda H.; Schulz, Bethany K.; Stevens, Carly J.; Suding, Katharine N.; Throop, Heather L.; Waller, Donald M.

2016-01-01

Atmospheric nitrogen (N) deposition has been shown to decrease plant species richness along regional deposition gradients in Europe and in experimental manipulations. However, the general response of species richness to N deposition across different vegetation types, soil conditions, and climates remains largely unknown even though responses may be contingent on these environmental factors. We assessed the effect of N deposition on herbaceous richness for 15,136 forest, woodland, shrubland, and grassland sites across the continental United States, to address how edaphic and climatic conditions altered vulnerability to this stressor. In our dataset, with N deposition ranging from 1 to 19 kg N⋅ha−1⋅y−1, we found a unimodal relationship; richness increased at low deposition levels and decreased above 8.7 and 13.4 kg N⋅ha−1⋅y−1 in open and closed-canopy vegetation, respectively. N deposition exceeded critical loads for loss of plant species richness in 24% of 15,136 sites examined nationwide. There were negative relationships between species richness and N deposition in 36% of 44 community gradients. Vulnerability to N deposition was consistently higher in more acidic soils whereas the moderating roles of temperature and precipitation varied across scales. We demonstrate here that negative relationships between N deposition and species richness are common, albeit not universal, and that fine-scale processes can moderate vegetation responses to N deposition. Our results highlight the importance of contingent factors when estimating ecosystem vulnerability to N deposition and suggest that N deposition is affecting species richness in forested and nonforested systems across much of the continental United States.

Synthesis of Diamond-Like Carbon Films on Planar and Non-Planar Geometries by the Atmospheric Pressure Plasma Chemical Vapor Deposition Method

NASA Astrophysics Data System (ADS)

Noborisaka, Mayui; Hirako, Tomoaki; Shirakura, Akira; Watanabe, Toshiyuki; Morikawa, Masashi; Seki, Masaki; Suzuki, Tetsuya

2012-09-01

Diamond-like carbon (DLC) films were synthesized by the dielectric barrier discharge-based plasma deposition at atmospheric pressure and their hardness and gas barrier properties were measured. A decrease in size of grains and heating substrate temperature improved nano-hardness up to 3.3 GPa. The gas barrier properties of DLC-coated poly(ethylene terephthalate) (PET) sheets were obtained by 3-5 times of non-coated PET with approximately 0.5 µm in film thickness. The high-gas-barrier DLC films deposited on PET sheets are expected to wrap elevated bridge of the super express and prevent them from neutralization of concrete. We also deposited DLC films inside PET bottles by the microwave surface-wave plasma chemical vapor deposition (CVD) method at near-atmospheric pressure. Under atmospheric pressure, the films were coated uniformly inside the PET bottles, but did not show high gas barrier properties. In this paper, we summarize recent progress of DLC films synthesized at atmospheric pressure with the aimed of food packaging and concrete pillar.

Measurement of atmospheric dry deposition at Emerald Lake in Sequoia National Park. Final report

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

Bytnerowicz, A.; Olszyk, D.

1988-04-11

The primary objective of the study was to evaluate atmospheric dry deposition of major anions and cations to trees in the Emerald Lake area of Sequoia National Park. The field work was performed between July 15 and September 10, 1987. Teflon-coated and non-coated branches of native lodgepole pine (Pinus concorta) and western white pine (P. monticola), and potted seedlings of Coulter pine (P. coulteri) were rinsed using deionized-distilled water. Nylon and paper filters were exposed along with the vegetation, and were extracted in deionized-distilled water. The rinses and extracts were analyzed for concentrations of nitrate, sulfate, phosphate, chloride, fluoride, ammonium,more » and metallic cations. The deposition of nitrate to paper filters and to Coulter pine branches was significantly higher than deposition to the native conifers. Deposition of nitrate was significantly greater than deposition of sulfate, supporting earlier studies of chapparal in the South Coast Air Basin. Ammonium deposition was also quite high, suggesting that transport from the valley may be a significant source of dry deposition in the Sierra.« less

Depositional fluxes and residence time of atmospheric radioiodine (131I) from the Fukushima accident.

PubMed

Yang, Weifeng; Guo, Laodong

2012-11-01

Activities of radioiodine ((131)I) along with (210)Pb and (210)Po in time series precipitation samples were measured to determine the depositional fluxes of (131)I in the Southern United States and its removal rate and residence time in the atmosphere during the Fukushima nuclear accident. Radioiodine released from the Fukushima accident reached the Southern United States within 11 days, giving rise to a concurrent (131)I peak and anomalous (210)Po/(210)Pb ratios in the precipitation samples. The cumulative (131)I depositional flux was 4.6 ± 0.2 Bq m(-2) during the maximum fallout. The removal rate of (131)I out of the atmosphere, derived from a definite (131)I integral model, ranged from 0.03 to 0.14 d(-1) with an average of 0.08 ± 0.02 d(-1), which corresponds to a residence time of (131)I in the atmosphere of 12 ± 3 days, consistent with the resident timescale constrained by the (210)Po/(210)Pb disequilibrium technique. These results support our hypothesis that radioiodine was removed from the atmosphere by precipitation within two weeks. It seemed that regions reachable by (131)I transport within two weeks from Fukushima Japan would receive much more fallout, whereas places outside that distance would be relatively less polluted with radionuclides. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Correlation Between Atmospheric Dust Deposition to the Surface Ocean and SeaWiFS Ocean Color: A Global Satellite-Based Analysis

NASA Technical Reports Server (NTRS)

Erickson, D. J., III; Hernandez, J.; Ginoux, P.; Gregg, W.; Kawa, R.; Behrenfeld, M.; Esaias, W.; Einaudi, Franco (Technical Monitor)

2000-01-01

Since the atmospheric deposition of iron has been linked to primary productivity in various oceanic regions, we have conducted an objective study of the correlation of dust deposition and satellite remotely sensed surface ocean chlorophyll concentrations. We present a global analysis of the correlation between atmospheric dust deposition derived from a satellite-based 3-D atmospheric transport model and SeaWiFs estimates of ocean color. We use the monthly mean dust deposition fields of Ginoux et al. which are based on a global model of dust generation and transport. This model is driven by atmospheric circulation from the Data Assimilation Office (DAO) for the period 1995-1998. This global dust model is constrained by several satellite estimates of standard circulation characteristics. We then perform an analysis of the correlation between the dust deposition and the 1998 SeaWIFS ocean color data for each 2.0 deg x 2.5 deg lat/long grid point, for each month of the year. The results are surprisingly robust. The region between 40 S and 60 S has correlation coefficients from 0.6 to 0.95, statistically significant at the 0.05 level. There are swaths of high correlation at the edges of some major ocean current systems. We interpret these correlations as reflecting areas that have shear related turbulence bringing nitrogen and phosphorus from depth into the surface ocean, and the atmospheric supply of iron provides the limiting nutrient and the correlation between iron deposition and surface ocean chlorophyll is high. There is a region in the western North Pacific with high correlation, reflecting the input of Asian dust to that region. The southern hemisphere has an average correlation coefficient of 0.72 compared that in the northern hemisphere of 0.42 consistent with present conceptual models of where atmospheric iron deposition may play a role in surface ocean biogeochemical cycles. The spatial structure of the correlation fields will be discussed within the context

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.

Evaluation of Resuspension from Propeller Wash in DoD Harbors

DTIC Science & Technology

2016-09-01

Environmental Research and Development Center FANS FOV ICP-MS Finite Analytical Navier-Stoker Solver Field of View Inductively Coupled Plasma with...Model (1984) and the Finite Analytical Navier- Stoker Solver (FANS) model (Chen et al., 2003) were set up to simulate and evaluate flow velocities and...model for evaluating the resuspension potential of propeller wash by a tugboat and the FANS model for a DDG. The Finite -Analytic Navier-Stokes (FANS

A new sampler for collecting separate dry and wet atmospheric depositions of trace organic chemicals

NASA Astrophysics Data System (ADS)

Waite, Don T.; Cessna, Allan J.; Gurprasad, Narine P.; Banner, James

Studies conducted in Saskatchewan and elsewhere have demonstrated the atmospheric transport of agricultural pesticides and other organic contaminants and their deposition into aquatic ecosystems. To date these studies have focused on ambient concentrations in the atmosphere and in wet precipitation. To measure the dry deposition of organic chemicals, a new sampler was designed which uses a moving sheet of water to passively trap dry particles and gasses. The moving sheet of water drains into a reservoir and, during recirculation through the sampler, is passed through an XAD-2 resin column which adsorbs the trapped organic contaminants. All surfaces which contact the process water are stainless steel or Teflon. Chemicals collected can be related to airborne materials depositing into aquatic ecosystems. The sampler has received a United States patent (number 5,413,003 - 9 May 1996) with the Canadian patent pending. XAD-2 resin adsorption efficiencies for 10 or 50 μg fortifications of ten pesticides ranged from 76% for atrazine (2-chloro-4-ethylamino-6-isopropylamino- S-triazine) to 110% for triallate [ S-(2,3,3-trichloro-2-phenyl)bis(1-methylethyl)carbamothioate], dicamba (2-methoxy-3,6-dichlorobenzoic acid) and toxaphene (chlorinated camphene mixture). Field testing using duplicate samplers showed good reproducibility and amounts trapped were consistent with those from high volume and bulk pan samplers located on the same site. Average atmospheric dry deposition rates of three chemicals, collected for 5 weeks in May and June, were: dicamba, 69 ng m -2 da -1; 2,4-D (2,4-dichlorophenoxyacetic acid), 276 ng m -2 da -1: and, γ-HCH ( γ-1, 2, 3, 4, 5, 6-hexachlorocyclohexane), 327 ng m -2 da -1.

Atmospheric Nitrogen Deposition at Two Sites in an Arid Environment of Central Asia.

PubMed

Li, Kaihui; Liu, Xuejun; Song, Wei; Chang, Yunhua; Hu, Yukun; Tian, Changyan

2013-01-01

Arid areas play a significant role in the global nitrogen cycle. Dry and wet deposition of inorganic nitrogen (N) species were monitored at one urban (SDS) and one suburban (TFS) site at Urumqi in a semi-arid region of central Asia. Atmospheric concentrations of NH3, NO2, HNO3, particulate ammonium and nitrate (pNH4 (+) and pNO3 (-)) concentrations and NH4-N and NO3-N concentrations in precipitation showed large monthly variations and averaged 7.1, 26.6, 2.4, 6.6, 2.7 µg N m(-3) and 1.3, 1.0 mg N L(-1) at both SDS and TFS. Nitrogen dry deposition fluxes were 40.7 and 36.0 kg N ha(-1) yr(-1) while wet deposition of N fluxes were 6.0 and 8.8 kg N ha(-1) yr(-1) at SDS and TFS, respectively. Total N deposition averaged 45.8 kg N ha(-1) yr(-1)at both sites. Our results indicate that N dry deposition has been a major part of total N deposition (83.8% on average) in an arid region of central Asia. Such high N deposition implies heavy environmental pollution and an important nutrient resource in arid regions.

Controllable growth of shaped graphene domains by atmospheric pressure chemical vapour deposition

NASA Astrophysics Data System (ADS)

Fan, Lili; Li, Zhen; Li, Xiao; Wang, Kunlin; Zhong, Minlin; Wei, Jinquan; Wu, Dehai; Zhu, Hongwei

2011-12-01

Graphene domains in different shapes have been grown on copper substrates via atmospheric pressure chemical vapour deposition by controlling the growth process parameters. Under stabilized conditions, graphene domains tend to be six-fold symmetric hexagons under low flow rate methane with some domains in an irregular hexagonal shape. After further varying the growth duration, methane flow rate, and temperature, graphene domains have developed shapes from hexagon to shovel and dendrite. Two connecting modes, through overlap and merging of adjacent graphene domains, are proposed.Graphene domains in different shapes have been grown on copper substrates via atmospheric pressure chemical vapour deposition by controlling the growth process parameters. Under stabilized conditions, graphene domains tend to be six-fold symmetric hexagons under low flow rate methane with some domains in an irregular hexagonal shape. After further varying the growth duration, methane flow rate, and temperature, graphene domains have developed shapes from hexagon to shovel and dendrite. Two connecting modes, through overlap and merging of adjacent graphene domains, are proposed. Electronic supplementary information (ESI) available: Schematics of CVD setups for graphene growth, Raman spectra and SEM images. See DOI: 10.1039/c1nr11480h

Sediment resuspension characteristics in Baltimore Harbor, Maryland

USGS Publications Warehouse

Maa, J.P.-Y.; Sanford, L.; Halka, J.P.

1998-01-01

Critical bed shear stress for sediment resuspension and sediment erosion rate were measured in-situ at sites from inner to outer Baltimore Harbor using the VIMS Sea Carousel. Clay mineral contents and biological conditions were almost the same at the four study sites. The experimental results indicated that the erosion rate increased from the outer harbor toward the inner harbor with a maximum difference of about 10 times at an excess bed shear stress of 0.1 Pa. The measured critical bed shear stress strongly depended on the existence of a fluff layer. It was approximately 0.05 Pa if a fluff layer existed, and increases to about 0.1 Pa in the absence of a fluff layer.

Atmospheric nitrogen deposition influences denitrification and nitrous oxide production in lakes.

PubMed

McCrackin, Michelle L; Elser, James J

2010-02-01

Microbially mediated denitrification is an important process that may ameliorate the effects of nitrogen (N) loading by permanently removing excess N inputs. In this study, we measured the rate of denitrification and nitrous oxide (N2O) production during denitrification in sediments from 32 Norwegian lakes at the high and low ends of a gradient of atmospheric N deposition. Denitrification and N2O production rates averaged 41.7 and 1.1 micromol N x m(-2) x h(-1), respectively, for high-deposition lakes. There was no detectable denitrification or N2O production in low-deposition lakes. Epilimnetic nitrate concentration was strongly correlated with denitrification rate (r2 = 0.67). We also measured the denitrification rate in response to experimental additions of organic carbon, nitrate, and phosphorus. Experimental nitrate additions stimulated denitrification in sediments of all lakes, regardless of N deposition level. In fact, the rate of denitrification in nitrate-amended treatments was the same magnitude for lakes in both deposition areas. These findings suggest that lake sediments possess considerable capacity to remove nitrate and that this capacity has not been saturated under conditions of chronic N loading. Further, nitrous oxide was nearly 3% of the total gaseous product during denitrification in high-deposition lakes, a fraction that is comparable to polluted marine sediments. Our findings suggest that, while lakes play an important role in N removal in the landscape, they may be a source of N2O emissions, especially in areas subject to elevated N inputs.

Interactions between atmospheric circulation, nutrient deposition, and tropical forest primary production (Invited)

NASA Astrophysics Data System (ADS)

Randerson, J. T.; Chen, Y.; Rogers, B. M.; Morton, D. C.; van der Werf, G.; Mahowald, N. M.

2010-12-01

Tropical forests influence regional and global climate by means of several pathways, including by modifying surface energy exchange and by forming clouds. High levels of precipitation, leaching, and soil weathering limit nutrient availability in these ecosystems. Phosphorus (P) is a key element limiting net primary production, and in some areas, including forests recovering from prior disturbance, nitrogen (N) also may limit some components of production. Here we quantified atmospheric P and N inputs to these forests from fires using satellite-derived estimates of emissions and atmospheric models. In Africa and South America, cross-biome transport of fire-emitted aerosols and reactive N gases from savannas and areas near the deforestation frontier increased deposition of P and N in interior forests. Equatorward atmospheric transport during the dry (fire) season in one hemisphere was linked with surface winds moving toward the inter-tropical convergence zone (ITCZ) in the other hemisphere. Deposition levels were higher in tropical forests in Africa than in South America because of large savanna areas with high levels of fire emissions in both southern and northern Africa. We conclude by describing a potential feedback loop by which equatorward transport of fire emissions, dust, and spores sustains the productivity of tropical forests. We specifically assessed evidence that savanna-to-forest atmospheric transport of nutrients increases forest productivity, height, and rates of evapotranspiration (ET). In parallel, we examined the degree to which increases in ET and surface roughness in tropical forests have the potential to strengthen several components of the Hadley circulation, including deep convection, equatorward return flow (near the surface), and the intensity of seasonal drought in the subtropics (thereby increasing fires). These interactions are important for understanding biogeochemical - climate interactions on millennial timescales and for quantifying how

Open Air Silicon Deposition by Atmospheric Pressure Plasma under Local Ambient Gas Control

NASA Astrophysics Data System (ADS)

Naito, Teruki; Konno, Nobuaki; Yoshida, Yukihisa

2015-09-01

In this paper, we report open air silicon (Si) deposition by combining a silane free Si deposition technology and a newly developed local ambient gas control technology. Recently, material processing in open air has been investigated intensively. While a variety of materials have been deposited, there were only few reports on Si deposition due to the susceptibility to contamination and the hazardous nature of source materials. Since Si deposition is one of the most important processes in device fabrication, we have developed open air silicon deposition technologies in BEANS project. For a clean and safe process, a local ambient gas control head was designed. Process gas leakage was prevented by local evacuation, and air contamination was shut out by inert curtain gas. By numerical and experimental investigations, a safe and clean process condition with air contamination less than 10 ppm was achieved. Si film was deposited in open air by atmospheric pressure plasma enhanced chemical transport under the local ambient gas control. The film was microcrystalline Si with the crystallite size of 17 nm, and the Hall mobility was 2.3 cm2/V .s. These properties were comparable to those of Si films deposited in a vacuum chamber. This research has been conducted as one of the research items of New Energy and Industrial Technology Development Organization ``BEANS'' project.

Atmospheric behavior, deposition, and budget of radioactive materials from the Fukushima Daiichi nuclear power plant in March 2011

NASA Astrophysics Data System (ADS)

Morino, Y.; Ohara, T.; Nishizawa, M.

2011-12-01

To understand the atmospheric behavior of radioactive materials emitted from the Fukushima Daiichi nuclear power plant after the nuclear accident that accompanied the great Tohoku earthquake and tsunami on 11 March 2011, we simulated the transport and deposition of iodine-131 and cesium-137 using a chemical transport model. The model roughly reproduced the observed temporal and spatial variations of deposition rates over 15 Japanese prefectures (60-400 km from the plant), including Tokyo, although there were some discrepancies between the simulated and observed rates. These discrepancies were likely due to uncertainties in the simulation of emission, transport, and deposition processes in the model. A budget analysis indicated that approximately 13% of iodine-131 and 22% of cesium-137 were deposited over land in Japan, and the rest was deposited over the ocean or transported out of the model domain (700 × 700 km2). Radioactivity budgets are sensitive to temporal emission patterns. Accurate estimation of emissions to the air is important for estimation of the atmospheric behavior of radionuclides and their subsequent behavior in land water, soil, vegetation, and the ocean.

Atmospheric behavior, deposition, and budget of radioactive materials from the Fukushima Daiichi nuclear power plant in March 2011

NASA Astrophysics Data System (ADS)

Morino, Yu; Ohara, Toshimasa; Nishizawa, Masato

2011-09-01

To understand the atmospheric behavior of radioactive materials emitted from the Fukushima Daiichi nuclear power plant after the nuclear accident that accompanied the great Tohoku earthquake and tsunami on 11 March 2011, we simulated the transport and deposition of iodine-131 and cesium-137 using a chemical transport model. The model roughly reproduced the observed temporal and spatial variations of deposition rates over 15 Japanese prefectures (60-400 km from the plant), including Tokyo, although there were some discrepancies between the simulated and observed rates. These discrepancies were likely due to uncertainties in the simulation of emission, transport, and deposition processes in the model. A budget analysis indicated that approximately 13% of iodine-131 and 22% of cesium-137 were deposited over land in Japan, and the rest was deposited over the ocean or transported out of the model domain (700 × 700 km2). Radioactivity budgets are sensitive to temporal emission patterns. Accurate estimation of emissions to the air is important for estimation of the atmospheric behavior of radionuclides and their subsequent behavior in land water, soil, vegetation, and the ocean.

ATMOSPHERIC MERCURY SIMULATION USING THE CMAQ MODEL: FORMULATION DESCRIPTION AND ANALYSIS OF WET DEPOSITION RESULTS

EPA Science Inventory

The Community Multiscale Air Quality (CMAQ) modeling system has recently been adapted to simulate the emission, transport, transformation and deposition of atmospheric mercury in three distinct forms; elemental mercury gas, reactive gaseous mercury, and particulate mercury. Emis...

Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

DOE PAGES

Gou, Huiyang; Hemley, Russell J.; Hemawan, Kadek W.

2015-11-02

Polycrystalline diamond has been successfully synthesized on silicon substrates at atmospheric pressure using a microwave capillary plasma chemical vapor deposition technique. The CH 4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C 2, Ar, N 2, CH, H β and H α were observed in emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T 2g phonon at 1333 cm -1 peak relative to the Raman features of graphitic carbon. Furthermore, fieldmore » emission scanning electron microscopy (SEM) images reveal that, depending on the on growth conditions, the carbon microstructures of grown films exhibit “coral” and “cauliflower-like” morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.« less

Atmospheric deposition having been one of the major source of Pb in Jiaozhou Bay

NASA Astrophysics Data System (ADS)

Yang, Dongfang; Miao, Zhenqing; Zhang, Xiaolong; Wang, Qi; Li, Haixia

2018-03-01

Many marine bays have been polluted by Pb due to the rapid development of industry, and identifying the major source of Pb is essential to pollution control. This paper analyzed the distribution and pollution source of Pb in Jiaozhou Bay in 1988. Results showed that Pb contents in surface waters in Jiaozhou Bay in April, July and October 1988 were 5.52-24.61 μg L‑1, 7.66-38.62 μg L‑1 and 6.89-19.30 μg L‑1, respectively. The major Pb sources in this bay were atmospheric deposition, and marine current, whose source strengths were 19.30-24.61μg L‑1 and 38.62 μg L‑1, respectively. Atmospheric deposition had been one of the major Pb sources in Jiaozhou Bay, and the source strengths were stable and strong. The pollution level of Pb in this bay in 1988 was moderate to heavy, and the source control measurements were necessary.

Reconstruction of 20th Century Atmospheric Deposition Rates in the Sierra Nevada (California) using Spheroidal Carbonaceous Particles

NASA Astrophysics Data System (ADS)

Heard, A.; Sickman, J. O.; Rose, N.

2012-12-01

Atmospheric nitrogen deposition is altering biogeochemical cycles and ecological processes in high-elevation aquatic ecosystems. A need for stricter standards based on measurable ecological effects has been identified as an important step towards their long-term protection. One of the challenges with identifying ecological thresholds is a lack of knowledge of background conditions (pre- industrial) and changes that may have occurred prior to extensive monitoring programs. However, this information can be obtained using paleolimnological approaches. We are investigating historic atmospheric deposition in the Sierra Nevada using spheroidal carbonaceous particles (SCPs) in lake sediments. SCPs are strong geochemical indicators of anthropogenic atmospheric deposition because they are only produced by industrial combustion of fossil fuels---there are no natural sources. We detected SCPs as early as 1870 at Moat Lake in the eastern Sierra Nevada. SCP concentrations increased over time, peaking in the mid-1980's (2,399 gDM-1) while SCP accumulation rates peaked in the early 1920's (105 no, cm-2 yr-1) (Figure 1). Lakes along the western slope of the Sierra (Pear and Emerald) show similar patterns although differences vary by site and are likely explained by watershed characteristics and proximity to emission sources. SCP concentrations at Pear and Emerald lakes peak 10-15 years earlier than Moat. A consistent decrease was observed at Pear and Moat following the peak concentrations until present. Present day concentrations are 556 gDM-1 at Moat and 473 gDM-1 at Pear. At Emerald lake SCPs also initially decreased starting in 1964, but an increasing trend is observed from 1995 through present. These data improve our understanding of historic atmospheric deposition patterns and are being used to inform additional palaeolimnological research, including diatom analyses, with the broader objective of reconstructing historic nitrogen deposition and estimating critical loads for

Aquatic Ecosystem Exposure Associated with Atmospheric Mercury Deposition: Importance of Watershed and Water Body Hot Spots and Hot Moments

EPA Science Inventory

Atmospheric deposition of divalent mercury (Hg(II)) is often the primary driving force for mercury contamination in fish tissue, resulting in mercury exposure to wildlife and humans. Transport and transformation of the deposited mercury into the environmentally relevant form, met...

Critical loads of nitrogen deposition and critical levels of atmospheric ammonia for mediterranean evergreen woodlands

NASA Astrophysics Data System (ADS)

Pinho, P.; Theobald, M. R.; Dias, T.; Tang, Y. S.; Cruz, C.; Martins-Loução, M. A.; Máguas, C.; Sutton, M.; Branquinho, C.

2011-11-01

Nitrogen (N) has emerged in recent years as a key factor associated with global changes, with impacts on biodiversity, ecosystems functioning and human health. In order to ameliorate the effects of excessive N, safety thresholds have been established, such as critical loads (deposition fluxes) and levels (concentrations). For Mediterranean ecosystems, few studies have been carried out to assess these parameters. Our objective was therefore to determine the critical loads of N deposition and long-term critical levels of atmospheric ammonia for Mediterranean evergreen woodlands. For that we have considered changes in epiphytic lichen communities, which have been shown to be one of the most sensitive to excessive N. Based on a classification of lichen species according to their tolerance to N we grouped species into response functional groups, which we used as a tool to determine the critical loads and levels. This was done under Mediterranean climate, in evergreen cork-oak woodlands, by sampling lichen functional diversity and annual atmospheric ammonia concentrations and modelling N deposition downwind from a reduced N source (a cattle barn). By modelling the highly significant relationship between lichen functional groups and N deposition, the critical load was estimated to be below 26 kg (N) ha-1 yr-1, which is within the upper range established for other semi-natural ecosystems. By modelling the highly significant relationship of lichen functional groups with annual atmospheric ammonia concentration, the critical level was estimated to be below 1.9 μg m-3, in agreement with recent studies for other ecosystems. Taking into account the high sensitivity of lichen communities to excessive N, these values should be taken into account in policies that aim at protecting Mediterranean woodlands from the initial effects of excessive N.

Depositional characteristics of atmospheric polybrominated diphenyl ethers on tree barks.

PubMed

Chun, Man Young

2014-07-17

This study was conducted to determine the depositional characteristics of several tree barks, including Ginkgo (Ginkgo biloba), Pine (Pinus densiflora), Platanus (Platanus), and Metasequoia (Metasequoia glyptostroboides). These were used as passive air sampler (PAS) of atmospheric polybrominated diphenyl ethers (PBDEs). Tree barks were sampled from the same site. PBDEs were analyzed by highresolution gas chromatography/high-resolution mass spectrometer, and the lipid content was measured using the gravimetric method by n-hexane extraction. Gingko contained the highest lipid content (7.82 mg/g dry), whereas pine (4.85 mg/g dry), Platanus (3.61 mg/g dry), and Metasequoia (0.97 mg/g dry) had relatively lower content. The highest total PBDEs concentration was observed in Metasequoia (83,159.0 pg/g dry), followed by Ginkgo (53,538.4 pg/g dry), Pine (20,266.4 pg/g dry), and Platanus (12,572.0 pg/g dry). There were poor correlations between lipid content and total PBDE concentrations in tree barks (R(2)=0.1011, p =0.682). Among the PBDE congeners, BDE 206, 207 and 209 were highly brominated PBDEs that are sorbed to particulates in ambient air, which accounted for 90.5% (84.3-95.6%) of the concentration and were therefore identified as the main PBDE congener. The concentrations of particulate PBDEs deposited on tree barks were dependent on morphological characteristics such as surface area or roughness of barks. Therefore, when using the tree barks as the PAS of the atmospheric PBDEs, samples belonging to same tree species should be collected to reduce errors and to obtain reliable data.

ESTIMATING GASEOUS EXCHANGES BETWEEN THE ATMOSPHERE AND PLANTS USING A COUPLED BIOCHEMICAL DRY DEPOSITION MODEL

EPA Science Inventory

To study gaseous exchanges between the soil, biosphere and atmosphere, a biochemical model was coupled with the latest version of Meyers Multi-Layer Deposition Model. The biochemical model describes photosynthesis and respiration and their coupling with stomatal resistance for...

The impact of atmospheric dust deposition and trace elements levels on the villages surrounding the former mining areas in a semi-arid environment (SE Spain)

NASA Astrophysics Data System (ADS)

Sánchez Bisquert, David; Matías Peñas Castejón, José; García Fernández, Gregorio

2017-03-01

It is understood that particulate matter in the atmosphere from metallic mining waste has adverse health effects on populations living nearby. Atmospheric deposition is a process connecting the mining wasteswith nearby ecosystems. Unfortunately, very limited information is available about atmospheric deposition surrounding rural metallic mining areas. This article will focus on the deposition from mining areas, combined with its impact on nearby rural built areas and populations. Particle samples were collected between June 2011 and March 2013. They were collected according to Spanish legislation in ten specialised dust collectors. They were located near populations close to a former Mediterranean mining area, plus a control, to assess the impact of mining waste on these villages. This article and its results have been made through an analysis of atmospheric deposition of these trace elements (Mn, Zn, As, Cd and Pb). It also includes an analysis of total dust flux. Within this analysis it has considered the spatial variations of atmospheric deposition flux in these locations. The average annual level of total bulk deposition registered was 42.0 g m-2 per year. This was higher than most of the areas affected by a Mediterranean climate or in semi-arid conditions around the world. Regarding the overall analysis of trace elements, the annual bulk deposition fluxes of total Zn far exceeded the values of other areas. While Mn, Cd and Pb showed similar or lower values, and in part much lower than those described in other Mediterranean mining areas. This study confirmed some spatial variability of dust and trace elements, contained within the atmospheric deposition. From both an environmental and a public health perspective, environmental managers must take into account the cumulative effect of the deposition of trace elements on the soil and air quality around and within the villages surrounding metallic mining areas.

Ecological and Human Health Risk Assessment of Heavy Metal Content of Atmospheric Dry Deposition, a Case Study: Kermanshah, Iran.

PubMed

Sobhanardakani, Soheil

2018-05-12

The present study was intended to investigate the ecological and human health risk of cobalt, nickel, and vanadium in the atmospheric dry deposition of the Kermanshah city, Iran, in 2015. Totally 54 samples of atmospheric dry deposition were collected from the three regions of the city with different traffic intensity, and after acid digestion of the samples with ultrapure concentrated HNO 3 , the total contents of the metals were determined using inductively coupled plasma optical emission spectrometer (ICP-OES). Also, all statistical analyses were performed using the SPSS statistical package. The atmospheric dry deposition element contents increase according to the following descending order for both autumn seasons: Ni > Co > V. The results of potential ecological risk analysis demonstrated that metals in the samples are in low ecological risk levels, whereas the results of human health risk assessment showed that ingestion is the main exposure pathway of heavy metals in the dust to the local residents compared with inhalation and dermal pathways. Also, the upper limit of the 95% confidence interval (95% UCL) of hazard indices for non-carcinogenic risks of all analyzed metals in the dust samples was within the safe level for both children and adults. On the other hand, the carcinogenic risk levels of Co and Ni were all lower than the acceptable range (10 -6 -10 -4 ) to local citizens. Consequently, the results advocate the necessity of understanding the heavy metal content of atmospheric dry deposition and regular monitoring of air pollution.

Critical loads of nitrogen deposition and critical levels of atmospheric ammonia for semi-natural Mediterranean evergreen woodlands

NASA Astrophysics Data System (ADS)

Pinho, P.; Theobald, M. R.; Dias, T.; Tang, Y. S.; Cruz, C.; Martins-Loução, M. A.; Máguas, C.; Sutton, M.; Branquinho, C.

2012-03-01

Nitrogen (N) has emerged in recent years as a key factor associated with global changes, with impacts on biodiversity, ecosystems functioning and human health. In order to ameliorate the effects of excessive N, safety thresholds such as critical loads (deposition fluxes) and levels (concentrations) can be established. Few studies have assessed these thresholds for semi-natural Mediterranean ecosystems. Our objective was therefore to determine the critical loads of N deposition and long-term critical levels of atmospheric ammonia for semi-natural Mediterranean evergreen woodlands. We have considered changes in epiphytic lichen communities, one of the most sensitive comunity indicators of excessive N in the atmosphere. Based on a classification of lichen species according to their tolerance to N we grouped species into response functional groups, which we used as a tool to determine the critical loads and levels. This was done for a Mediterranean climate in evergreen cork-oak woodlands, based on the relation between lichen functional diversity and modelled N deposition for critical loads and measured annual atmospheric ammonia concentrations for critical levels, evaluated downwind from a reduced N source (a cattle barn). Modelling the highly significant relationship between lichen functional groups and annual atmospheric ammonia concentration showed the critical level to be below 1.9 μg m-3, in agreement with recent studies for other ecosystems. Modelling the highly significant relationship between lichen functional groups and N deposition showed that the critical load was lower than 26 kg (N) ha-1 yr-1, which is within the upper range established for other semi-natural ecosystems. Taking into account the high sensitivity of lichen communities to excessive N, these values should aid development of policies to protect Mediterranean woodlands from the initial effects of excessive N.

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.

The Influence of Climate Change on Atmospheric Deposition of Mercury in the Arctic—A Model Sensitivity Study

PubMed Central

Hansen, Kaj M.; Christensen, Jesper H.; Brandt, Jørgen

2015-01-01

Mercury (Hg) is a global pollutant with adverse health effects on humans and wildlife. It is of special concern in the Arctic due to accumulation in the food web and exposure of the Arctic population through a rich marine diet. Climate change may alter the exposure of the Arctic population to Hg. We have investigated the effect of climate change on the atmospheric Hg transport to and deposition within the Arctic by making a sensitivity study of how the atmospheric chemistry-transport model Danish Eulerian Hemispheric Model (DEHM) reacts to climate change forcing. The total deposition of Hg to the Arctic is 18% lower in the 2090s compared to the 1990s under the applied Special Report on Emissions Scenarios (SRES-A1B) climate scenario. Asia is the major anthropogenic source area (25% of the deposition to the Arctic) followed by Europe (6%) and North America (5%), with the rest arising from the background concentration, and this is independent of the climate. DEHM predicts between a 6% increase (Status Quo scenario) and a 37% decrease (zero anthropogenic emissions scenario) in Hg deposition to the Arctic depending on the applied emission scenario, while the combined effect of future climate and emission changes results in up to 47% lower Hg deposition. PMID:26378551

The Influence of Climate Change on Atmospheric Deposition of Mercury in the Arctic—A Model Sensitivity Study.

PubMed

Hansen, Kaj M; Christensen, Jesper H; Brandt, Jørgen

2015-09-10

Mercury (Hg) is a global pollutant with adverse health effects on humans and wildlife. It is of special concern in the Arctic due to accumulation in the food web and exposure of the Arctic population through a rich marine diet. Climate change may alter the exposure of the Arctic population to Hg. We have investigated the effect of climate change on the atmospheric Hg transport to and deposition within the Arctic by making a sensitivity study of how the atmospheric chemistry-transport model Danish Eulerian Hemispheric Model (DEHM) reacts to climate change forcing. The total deposition of Hg to the Arctic is 18% lower in the 2090s compared to the 1990s under the applied Special Report on Emissions Scenarios (SRES-A1B) climate scenario. Asia is the major anthropogenic source area (25% of the deposition to the Arctic) followed by Europe (6%) and North America (5%), with the rest arising from the background concentration, and this is independent of the climate. DEHM predicts between a 6% increase (Status Quo scenario) and a 37% decrease (zero anthropogenic emissions scenario) in Hg deposition to the Arctic depending on the applied emission scenario, while the combined effect of future climate and emission changes results in up to 47% lower Hg deposition.

Negative effects of temperature and atmospheric depositions on the seed viability of common juniper (Juniperus communis).

PubMed

Gruwez, R; De Frenne, P; De Schrijver, A; Leroux, O; Vangansbeke, P; Verheyen, K

2014-02-01

Environmental change is increasingly impacting ecosystems worldwide. However, our knowledge about the interacting effects of various drivers of global change on sexual reproduction of plants, one of their key mechanisms to cope with change, is limited. This study examines populations of poorly regenerating and threatened common juniper (Juniperus communis) to determine the influence of four drivers of global change (rising temperatures, nitrogen deposition, potentially acidifying deposition and altering precipitation patterns) on two key developmental phases during sexual reproduction, gametogenesis and fertilization (seed phase two, SP2) and embryo development (seed phase three, SP3), and on the ripening time of seeds. In 42 populations throughout the distribution range of common juniper in Europe, 11,943 seeds of two developmental phases were sampled. Seed viability was determined using seed dissection and related to accumulated temperature (expressed as growing degree-days), nitrogen and potentially acidifying deposition (nitrogen plus sulfur), and precipitation data. Precipitation had no influence on the viability of the seeds or on the ripening time. Increasing temperatures had a negative impact on the viability of SP2 and SP3 seeds and decreased the ripening time. Potentially acidifying depositions negatively influenced SP3 seed viability, while enhanced nitrogen deposition led to lower ripening times. Higher temperatures and atmospheric deposition affected SP3 seeds more than SP2 seeds. However, this is possibly a delayed effect as juniper seeds develop practically independently, due to the absence of vascular communication with the parent plant from shortly after fertilization. It is proposed that the failure of natural regeneration in many European juniper populations might be attributed to climate warming as well as enhanced atmospheric deposition of nitrogen and sulfur.

MOBILIZATION OF PAHS AND PCBS FROM IN-PLACE CONTAMINATED MARINE SEDIMENTS DURING SIMULATED RESUSPENSION EVENTS

EPA Science Inventory

A particle entrainment simulator was used to experimentally produce representative estuarine resuspension conditions to investigate the resulting transport of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) to the overlying water column. Contaminants ...

Reoxidation of estuarine sediments during simulated resuspension events: Effects on nutrient and trace metal mobilisation

NASA Astrophysics Data System (ADS)

Vidal-Durà, Andrea; Burke, Ian T.; Stewart, Douglas I.; Mortimer, Robert J. G.

2018-07-01

Estuarine environments are considered to be nutrient buffer systems as they regulate the delivery of nutrients from rivers to the ocean. In the Humber Estuary (UK) seawater and freshwater mixing during tidal cycles leads to the mobilisation of oxic surface sediments (0-1 cm). However, less frequent seasonal events can also mobilise anoxic subsurface (5-10 cm) sediments, which may have further implications for the estuarine geochemistry. A series of batch experiments were carried out on surface and subsurface sediments taken from along the salinity gradient of the Humber Estuary. The aim was to investigate the geochemical processes driving major element (N, Fe, S, and Mn) redox cycling and trace metal behaviour during simulated resuspension events. The magnitude of major nutrient and metal release was significantly greater during the resuspension of outer estuarine sediments rather than from inner estuarine sediments. When comparing resuspension of surface versus subsurface sediment, only the outer estuary experiments showed significant differences in major nutrient behaviour with sediment depth. In general, any ammonium, manganese and trace metals (Cu and Zn) released during the resuspension experiments were rapidly removed from solution as new sorption sites (i.e. Fe/Mn oxyhydroxides) formed. Therefore Humber estuary sediments showed a scavenging capacity for these dissolved species and hence may act as an ultimate sink for these elements. Due to the larger aerial extent of the outer estuary intertidal mudflats in comparison with the inner estuary area, the mobilisation of the outer estuary sediments (more reducing and richer in sulphides and iron) may have a greater impact on the transport and cycling of nutrients and trace metals. Climate change-associated sea level rise combined with an increasing frequency of major storm events in temperate zones, which are more likely to mobilise deeper sediment regions, will impact the nutrient and metal inputs to the

Atmospheric deposition of PBDEs and DPs in Dongjiang River Basin, South China.

PubMed

Wu, Xiaowei; Wang, Yan; Hou, Minmin; Luo, Chunling; Zhao, Hongxia; Zhang, Gan

2017-02-01

The atmospheric deposition fluxes of polybrominated diphenyl ethers (PBDEs) and Dechlorane Plus (DPs) in Dongjiang River Basin of the Pearl River Delta in South China were investigated during winter and summer, respectively. The total deposition fluxes varied from 4.74 to 27.0 ng/m 2 /day for PBDEs and 8.77 to 206 ng/m 2 /day for DPs, respectively. The fractions of anti-DP to the total DPs (f anti ) varied from 0.28 to 0.63 (mean = 0.43 ± 0.06), i.e., generally lower than those in commercial products, which might be attributed to the different environmental fates of the two isomers. Significant seasonal and spatial variations of PBDEs and DPs were observed. The deposition fluxes in summer were generally higher than those in winter, which may be due to the relatively high temperature and rainfall in summer under the influence of prevailing subtropical monsoon climate. Moreover, high deposition fluxes of PBDEs and DPs in urban areas and significant urban/rural gradient implied that local industrial activities in the urban areas were primary sources, which were further confirmed by the results of principal component analysis. The highest deposition of PBDE and DP fluxes was found at different sampling sites, suggesting PBDEs and DPs may be derived from different industries or products.

Short-term variability of 7Be atmospheric deposition and watershed response in a Pacific coastal stream, Monterey Bay, California, USA.

PubMed

Conaway, Christopher H; Storlazzi, Curt D; Draut, Amy E; Swarzenski, Peter W

2013-06-01

Beryllium-7 is a powerful and commonly used tracer for environmental processes such as watershed sediment provenance, soil erosion, fluvial and nearshore sediment cycling, and atmospheric fallout. However, few studies have quantified temporal or spatial variability of (7)Be accumulation from atmospheric fallout, and parameters that would better define the uses and limitations of this geochemical tracer. We investigated the abundance and variability of (7)Be in atmospheric deposition in both rain events and dry periods, and in stream surface-water samples collected over a ten-month interval at sites near northern Monterey Bay (37°N, 122°W) on the central California coast, a region characterized by a rainy winters, dry summers, and small mountainous streams with flashy hydrology. The range of (7)Be activity in rainwater samples from the main sampling site was 1.3-4.4 Bq L(-1), with a mean (±standard deviation) of 2.2 ± 0.9 Bq L(-1), and a volume-weighted average of 2.0 Bq L(-1). The range of wet atmospheric deposition was 18-188 Bq m(-2) per rain event, with a mean of 72 ± 53 Bq m(-2). Dry deposition fluxes of (7)Be ranged from less than 0.01 up to 0.45 Bq m(-2) d(-1), with an estimated dry season deposition of 7 Bq m(-2) month(-1). Annualized (7)Be atmospheric deposition was approximately 1900 Bq m(-2) yr(-1), with most deposition via rainwater (>95%) and little via dry deposition. Overall, these activities and deposition fluxes are similar to values found in other coastal locations with comparable latitude and Mediterranean-type climate. Particulate (7)Be values in the surface water of the San Lorenzo River in Santa Cruz, California, ranged from <0.01 Bq g(-1) to 0.6 Bq g(-1), with a median activity of 0.26 Bq g(-1). A large storm event in January 2010 characterized by prolonged flooding resulted in the entrainment of (7)Be-depleted sediment, presumably from substantial erosion in the watershed. There were too few particulate (7)Be data over the storm to

Short-term variability of 7Be atmospheric deposition and watershed response in a Pacific coastal stream, Monterey Bay, California, USA

USGS Publications Warehouse

Conaway, Christopher H.; Storlazzi, Curt D.; Draut, Amy E.; Swarzenski, Peter W.

2013-01-01

Beryllium-7 is a powerful and commonly used tracer for environmental processes such as watershed sediment provenance, soil erosion, fluvial and nearshore sediment cycling, and atmospheric fallout. However, few studies have quantified temporal or spatial variability of 7Be accumulation from atmospheric fallout, and parameters that would better define the uses and limitations of this geochemical tracer. We investigated the abundance and variability of 7Be in atmospheric deposition in both rain events and dry periods, and in stream surface-water samples collected over a ten-month interval at sites near northern Monterey Bay (37°N, 122°W) on the central California coast, a region characterized by a rainy winters, dry summers, and small mountainous streams with flashy hydrology. The range of 7Be activity in rainwater samples from the main sampling site was 1.3–4.4 Bq L−1, with a mean (±standard deviation) of 2.2 ± 0.9 Bq L−1, and a volume-weighted average of 2.0 Bq L−1. The range of wet atmospheric deposition was 18–188 Bq m−2 per rain event, with a mean of 72 ± 53 Bq m−2. Dry deposition fluxes of 7Be ranged from less than 0.01 up to 0.45 Bq m−2 d−1, with an estimated dry season deposition of 7 Bq m−2 month−1. Annualized 7Be atmospheric deposition was approximately 1900 Bq m−2 yr−1, with most deposition via rainwater (>95%) and little via dry deposition. Overall, these activities and deposition fluxes are similar to values found in other coastal locations with comparable latitude and Mediterranean-type climate. Particulate 7Be values in the surface water of the San Lorenzo River in Santa Cruz, California, ranged from −1 to 0.6 Bq g−1, with a median activity of 0.26 Bq g−1. A large storm event in January 2010 characterized by prolonged flooding resulted in the entrainment of 7Be-depleted sediment, presumably from substantial erosion in the watershed. There were too few particulate 7Be data over the storm to accurately model a 7Be load

Effect of wave-current interactions on sediment resuspension in large shallow Lake Taihu, China.

PubMed

Li, Yiping; Tang, Chunyan; Wang, Jianwei; Acharya, Kumud; Du, Wei; Gao, Xiaomeng; Luo, Liancong; Li, Huiyun; Dai, Shujun; Mercy, Jepkirui; Yu, Zhongbo; Pan, Baozhu

2017-02-01

The disturbance of the water-sediment interface by wind-driven currents and waves plays a critical role in sediment resuspension and internal nutrient release in large, shallow lakes. This study analyzed the effects of the interactions between wind-induced currents an1d waves on the driving mechanism of sediment resuspension in Lake Taihu, the third largest freshwater lake in China, using acoustic and optic techniques to collect long-term, high-frequency, synchronous in situ measurements of wind, currents, waves, and suspended solid concentrations (SSCs). The results suggested that water turbidity started to increase at wind speeds of approximately 4 m/s and significantly increased when wind speeds exceeded 6 m/s. In most cases, wind-induced waves were the main energy source for changes in turbidity. Wave-generated shear stress contributed more than 95% to sediment resuspension and that only in weak wind conditions (<4 m/s) did the lake bottom shear stresses generated by currents and waves contributed equally. The relationship between SSC and bottom shear stress generated by wave was established by fitting the observed results. The processes of sediment dynamics were divided into four stages (A through D) according to three shear-stress thresholds. In stage A, SSC remained stable (about 45 mg/L) and τ w was less than 0.02 N/m 2 . In stage B, the sediment bed was starting to be activated (SSC 45∼60 mg/L) and τ w was in the range of 0.02∼0.07 N/m 2 . In stage C, a medium amount of sediment was suspended (SSC 60∼150 mg/L) and τ w ranged from 0.07 to 0.3 N/m 2 . In stage D, large amount of sediment was suspended (SSC 150∼300 mg/L) and τ w was larger than 0.3 N/m 2 . The findings of this paper reveal the driving mechanism of sediment resuspension, which may further help to evaluate internal nutrient release in large shallow Lake Taihu.

Simulation of trace metals and PAH atmospheric pollution over Greater Paris: Concentrations and deposition on urban surfaces

NASA Astrophysics Data System (ADS)

Thouron, L.; Seigneur, C.; Kim, Y.; Legorgeu, C.; Roustan, Y.; Bruge, B.

2017-10-01

Urban areas can be subject not only to poor air quality, but also to contamination of other environmental media by air pollutants. Here, we address the potential transfer of selected air pollutants (two metals and three PAH) to urban surfaces. To that end, we simulate meteorology and air pollution from Europe to a Paris suburban neighborhood, using a four-level one-way nesting approach. The meteorological and air quality simulations use urban canopy sub-models in order to better represent the effect of the urban morphology on the air flow, atmospheric dispersion, and deposition of air pollutants to urban surfaces. This modeling approach allows us to distinguish air pollutant deposition among various urban surfaces (roofs, roads, and walls). Meteorological model performance is satisfactory, showing improved results compared to earlier simulations, although precipitation amounts are underestimated. Concentration simulation results are also satisfactory for both metals, with a fractional bias <0.5. Concentrations of benzo[a]pyrene are overestimated, probably because continental emissions may be overestimated. Concentrations of benzo[b]fluoranthene and indeno[1,2,3,cd]pyrene are underestimated, in part because of null boundary conditions. PAH deposition fluxes are consistent with earlier measurements obtained in the Greater Paris region. The model simulation results suggest that both wet and dry deposition processes need to be considered when estimating the transfer of air pollutants to other environmental media. Dry deposition fluxes to various urban surfaces are mostly uniform for PAH, which are entirely present in fine particles. However, there is significantly less wall deposition compared to deposition to roofs and roads for trace metals, due to their coarse fraction. Meteorology, particle size distribution, and urban morphology are all important factors affecting air pollutant deposition. Future work should focus on the collection of data suitable to evaluate the

Re-suspension of the radioactive fallout after the Fukushima accident: risk of internal dose during the first week and the first two months

NASA Astrophysics Data System (ADS)

Yamauchi, M.; Takeda, M.; Makino, M.; Owada, T.

2012-04-01

The nuclear accident at the Fukushima Dai-ichi Nuclear Power Plant in March 2011 contaminated an area of more than 100 km in diameter by radioactive material with amount of about 10-20% of that by the Chernobyl accident. According to the Chernobyl experience, a part of fallout radionuclide is expected to be re-suspended by wind, causing possible risk of internal dose. However, this re-suspension process and its amounts have not been studied very much due to the difficulty of direct measurement of low-density dusts. To estimate forms and periods of the re-suspension of the radioactive fallout, we used both the radiation dose rate data and vertical (downward) component of the DC electric field near the ground, or potential gradient (PG) at Kakioka, 150 km away from the accident site. The data indicates: (1) During 14-15 March, the radioactive dust is most likely suspended in the air near the ground. (2) During 2-7 UT on 16 March, the radioactive dust is most likely blown up from the surface by the strong wind from the non-contaminated area. (3) During 16-20 March, the radioactive dust most likely stayed re-suspended. (4) After the wet contamination on 20 March until late April, the radioactive fallout on the ground are re-suspended during daytime by daily convection due to sunshine, and transported to downwind direction. (5) At more than 30 km distance from the accident site, the re-suspension most likely ceased by the end of April. However, no data is available within 20 km distance from the accident site. Yamauchi, et al. (2012): Settlement process of radioactive dust to the ground inferred from the atmospheric electric field measurement, Ann. Geophys., 30, 49-56, doi:10.5194/angeo-30-49-2012. Yamauchi (2012): Secondary wind transport of radioactive materials after the Fukushima accident, Earth Planet Space, accepted for publication.

A sub-atmospheric chemical vapor deposition process for deposition of oxide liner in high aspect ratio through silicon vias.

PubMed

Lisker, Marco; Marschmeyer, Steffen; Kaynak, Mehmet; Tekin, Ibrahim

2011-09-01

The formation of a Through Silicon Via (TSV) includes a deep Si trench etching and the formation of an insulating layer along the high-aspect-ratio trench and the filling of a conductive material into the via hole. The isolation of the filling conductor from the silicon substrate becomes more important for higher frequencies due to the high coupling of the signal to the silicon. The importance of the oxide thickness on the via wall isolation can be verified using electromagnetic field simulators. To satisfy the needs on the Silicon dioxide deposition, a sub-atmospheric chemical vapor deposition (SA-CVD) process has been developed to deposit an isolation oxide to the walls of deep silicon trenches. The technique provides excellent step coverage of the 100 microm depth silicon trenches with the high aspect ratio of 20 and more. The developed technique allows covering the deep silicon trenches by oxide and makes the high isolation of TSVs from silicon substrate feasible which is the key factor for the performance of TSVs for mm-wave 3D packaging.

[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.

Depositional characteristics of atmospheric polybrominated diphenyl ethers on tree barks

PubMed Central

Chun, Man Young

2014-01-01

Objectives This study was conducted to determine the depositional characteristics of several tree barks, including Ginkgo (Ginkgo biloba), Pine (Pinus densiflora), Platanus (Platanus), and Metasequoia (Metasequoia glyptostroboides). These were used as passive air sampler (PAS) of atmospheric polybrominated diphenyl ethers (PBDEs). Methods Tree barks were sampled from the same site. PBDEs were analyzed by highresolution gas chromatography/high-resolution mass spectrometer, and the lipid content was measured using the gravimetric method by n-hexane extraction. Results Gingko contained the highest lipid content (7.82 mg/g dry), whereas pine (4.85 mg/g dry), Platanus (3.61 mg/g dry), and Metasequoia (0.97 mg/g dry) had relatively lower content. The highest total PBDEs concentration was observed in Metasequoia (83,159.0 pg/g dry), followed by Ginkgo (53,538.4 pg/g dry), Pine (20,266.4 pg/g dry), and Platanus (12,572.0 pg/g dry). There were poor correlations between lipid content and total PBDE concentrations in tree barks (R2=0.1011, p =0.682). Among the PBDE congeners, BDE 206, 207 and 209 were highly brominated PBDEs that are sorbed to particulates in ambient air, which accounted for 90.5% (84.3-95.6%) of the concentration and were therefore identified as the main PBDE congener. The concentrations of particulate PBDEs deposited on tree barks were dependent on morphological characteristics such as surface area or roughness of barks. Conclusions Therefore, when using the tree barks as the PAS of the atmospheric PBDEs, samples belonging to same tree species should be collected to reduce errors and to obtain reliable data. PMID:25116365

Negative effects of temperature and atmospheric depositions on the seed viability of common juniper (Juniperus communis)

PubMed Central

Gruwez, R.; De Frenne, P.; De Schrijver, A.; Leroux, O.; Vangansbeke, P.; Verheyen, K.

2014-01-01

Background and Aims Environmental change is increasingly impacting ecosystems worldwide. However, our knowledge about the interacting effects of various drivers of global change on sexual reproduction of plants, one of their key mechanisms to cope with change, is limited. This study examines populations of poorly regenerating and threatened common juniper (Juniperus communis) to determine the influence of four drivers of global change (rising temperatures, nitrogen deposition, potentially acidifying deposition and altering precipitation patterns) on two key developmental phases during sexual reproduction, gametogenesis and fertilization (seed phase two, SP2) and embryo development (seed phase three, SP3), and on the ripening time of seeds. Methods In 42 populations throughout the distribution range of common juniper in Europe, 11 943 seeds of two developmental phases were sampled. Seed viability was determined using seed dissection and related to accumulated temperature (expressed as growing degree-days), nitrogen and potentially acidifying deposition (nitrogen plus sulfur), and precipitation data. Key Results Precipitation had no influence on the viability of the seeds or on the ripening time. Increasing temperatures had a negative impact on the viability of SP2 and SP3 seeds and decreased the ripening time. Potentially acidifying depositions negatively influenced SP3 seed viability, while enhanced nitrogen deposition led to lower ripening times. Conclusions Higher temperatures and atmospheric deposition affected SP3 seeds more than SP2 seeds. However, this is possibly a delayed effect as juniper seeds develop practically independently, due to the absence of vascular communication with the parent plant from shortly after fertilization. It is proposed that the failure of natural regeneration in many European juniper populations might be attributed to climate warming as well as enhanced atmospheric deposition of nitrogen and sulfur. PMID:24284814

Spatial patterns of atmospheric deposition of nitrogen and sulfur using ion-exchange resin collectors in Rocky Mountain National Park, USA

USGS Publications Warehouse

Clow, David W.; Roop, Heidi; Nanus, Leora; Fenn, Mark; Sexstone, Graham A.

2015-01-01

Lakes and streams in Class 1 wilderness areas in the western United States (U.S.) are at risk from atmospheric deposition of nitrogen (N) and sulfur (S), and protection of these resources is mandated under the Federal Clean Air Act and amendments. Assessment of critical loads, which are the maximum exposure to pollution an area can receive without adverse effects on sensitive ecosystems, requires accurate deposition estimates. However, deposition is difficult and expensive to measure in high-elevation wilderness, and spatial patterns in N and S deposition in these areas remain poorly quantified. In this study, ion-exchange resin (IER) collectors were used to measure dissolved inorganic N (DIN) and S deposition during June 2006–September 2007 at approximately 20 alpine/subalpine sites spanning the Continental Divide in Rocky Mountain National Park. Results indicated good agreement between deposition estimated from IER collectors and commonly used wet + dry methods during summer, but poor agreement during winter. Snowpack sampling was found to be a more accurate way of quantifying DIN and S deposition during winter. Summer DIN deposition was significantly greater on the east side of the park than on the west side (25–50%; p ≤ 0.03), consistent with transport of pollutants to the park from urban and agricultural areas to the east. Sources of atmospheric nitrate (NO3−) were examined using N isotopes. The average δ15N of NO3− from IER collectors was 3.5‰ higher during winter than during summer (p < 0.001), indicating a seasonal shift in the relative importance of regional NOxsources, such as coal combustion and vehicular sources of atmospheric NO3−. There were no significant differences in δ15N of NO3− between east and west sides of the park during summer or winter (p = 0.83), indicating that the two areas may have similar sources of atmospheric NO3−. Results from this study indicate that a combination of IER collectors and snowpack

Expanding atmospheric acid deposition in China from the 1990s to the 2010s

NASA Astrophysics Data System (ADS)

Yu, Haili; Wang, Qiufeng

2017-04-01

Atmospheric acid deposition is considered a global environmental issue. China has been experiencing serious acid deposition, which is anticipated to be more serious with the country's economic development and increasing consumption of fossil fuels in recent decades. By collecting nationwide data on pH and concentrations of sulfate (SO42-) and nitrate (NO3-) in precipitation between 1980 and 2014 in China, we explored the spatiotemporal variations of precipitation acid deposition (bulk deposition) and their influencing factors. Our results showed that average precipitation pH values were 4.86 and 4.84 in the 1990s and 2010s, respectively. This suggests that precipitation acid deposition in China has not seriously changes. Average SO42- deposition declined from 30.73 to 28.61 kg S ha-1 yr-1 but average NO3- deposition increased from 4.02 to 6.79 kg N ha-1 yr-1. Specifically, the area of severe precipitation acid deposition in southern China has shrunk to some extent as a result of decreasing pollutant emissions, whereas the area of moderate precipitation acid deposition has expanded in northern China, associated with rapid industrial and transportation development. Significant positive correlations have been found between precipitation acid deposition, energy consumption, and rainfall. Our findings provide a comprehensive evaluation of the spatiotemporal dynamics of precipitation acid deposition in China over past three decades, and confirm the idea that strategies implemented to save energy and reduce pollutant emissions in China have been effective in alleviating precipitation acid deposition. These findings might be used to demonstrate how developing countries could achieve economic development and environmental protection through the implementation of advanced technologies to reduce pollutant emissions.

Atmospheric Pressure Spray Chemical Vapor Deposited CuInS2 Thin Films for Photovoltaic Applications

NASA Technical Reports Server (NTRS)

Harris, J. D.; Raffaelle, R. P.; Banger, K. K.; Smith, M. A.; Scheiman, D. A.; Hepp, A. F.

2002-01-01

Solar cells have been prepared using atmospheric pressure spray chemical vapor deposited CuInS2 absorbers. The CuInS2 films were deposited at 390 C using the single source precursor (PPh3)2CuIn(SEt)4 in an argon atmosphere. The absorber ranges in thickness from 0.75 - 1.0 micrometers, and exhibits a crystallographic gradient, with the leading edge having a (220) preferred orientation and the trailing edge having a (112) orientation. Schottky diodes prepared by thermal evaporation of aluminum contacts on to the CuInS2 yielded diodes for films that were annealed at 600 C. Solar cells were prepared using annealed films and had the (top down) composition of Al/ZnO/CdS/CuInS2/Mo/Glass. The Jsc, Voc, FF and (eta) were 6.46 mA per square centimeter, 307 mV, 24% and 0.35%, respectively for the best small area cells under simulated AM0 illumination.

Future monitoring of charged particle energy deposition into the upper atmosphere and comments on possible relationships between atmospheric phenomena and solar and/or geomagnetic activity

NASA Technical Reports Server (NTRS)

Williams, D. J.; Grubb, R. N.; Evans, D. S.; Sauer, H. H.

1974-01-01

The charged particle observations proposed for the new low altitude weather satellites, TIROS-N, are described that will provide the capability of routine monitoring of the instantaneous total energy deposition into the upper atmosphere by the precipitation of charged particles from higher altitudes. Estimates are given to assess the potential importance of this type of energy deposition. Discussion and examples are presented illustrating the importance in distinguishing between solar and geomagnetic activity as possible causative sources.

Sediment resuspension in a shallow lake with muddy substrates: St Lucia, South Africa

NASA Astrophysics Data System (ADS)

Zikhali, Vulindlela; Tirok, Katrin; Stretch, Derek

2015-10-01

Wind-driven sediment resuspension affects the physical and biological environment of the water column in shallow estuarine lakes. This study investigated the relationship between wind-driven waves and suspended sediment concentration (SSC) using the 33 km2 South Lake basin of Lake St Lucia, South Africa as a case study. Five wave poles measuring significant wave height and turbidity were deployed over an aggregate period of twenty days at distributed locations where sediment substrate compositions varied from muddy to sandy and depths ranged from 0.7 m to 2.1 m. The resulting turbidity dynamics were used to test a simple depth-averaged model of suspended sediment concentrations. The model performed best in the muddy regions of the lake and was able to simulate the resuspension dynamics more accurately than the settling dynamics. Peak suspended sediment concentration levels were best captured for the deeper muddy locations. The model provides a means to make spatially explicit predictions of suspended sediment concentrations that can be used to understand the forcing mechanisms for primary producer growth and distribution or to improve sediment budget calculations.

Influence of bottom trawling on sediment resuspension in the `Grande-Vasière' area (Bay of Biscay, France)

NASA Astrophysics Data System (ADS)

Mengual, Baptiste; Cayocca, Florence; Le Hir, Pierre; Draye, Robin; Laffargue, Pascal; Vincent, Benoit; Garlan, Thierry

2016-09-01

Sea trials were performed on two zones with different fishing efforts on the continental shelf of the Bay of Biscay (`Grande-Vasière' area of muddy sand) in order to assess particulate matter resuspension and seabed disturbances (i.e., penetration, reworking, grain size changes) induced by different types of trawls. Optical and acoustic measurements made in the water column indicate a significant trawling-induced resuspension mainly due to the scraping action of doors. It manifests as a highly dynamic turbid plume confined near the seabed, where suspended sediment concentrations can reach 200 mg l-1. Concentration levels measured behind an "alternative" configuration (trawls with jumper doors instead of classical doors penetrating the sediment) are significantly lower (around 10-20 mg l-1), which indicates a potential limiting impact regarding the seabed. Grain size analyses of the surficial sediment led to highlight a potential reworking influence of bottom trawling. On the intensively trawled zone, this reworking manifests as an upward coarsening trend in the first 5 cm of the cores. A significant decrease in mud content (30 %) has been also witnessed on this zone between 1967 and 2014, which suggests an influence on the seabed evolution. The geometric analysis of bottom tracks (4-5-cm depth, 20-cm width) observed with a benthic video sledge was used to compute an experimental trawling-induced erosion rate of 0.13 kg m-2. This erosion rate was combined with fishing effort data, in order to estimate trawling-induced erosion fluxes which were then compared to natural erosion fluxes over the Grande-Vasière at monthly, seasonal and annual scales. Winter storms control the annual resuspended load and trawling contribution to annual resuspension is in the order of 1 %. However, results show that trawling resuspension can become dominant during the fishing high season (i.e., until several times the natural one in summer). In addition, the contribution of trawling

Climate, not atmospheric deposition, drives the biogeochemical mass-balance of a mountain watershed

USGS Publications Warehouse

Baron, Jill S.; Heath, Jared

2014-01-01

Watershed mass-balance methods are valuable tools for demonstrating impacts to water quality from atmospheric deposition and chemical weathering. Owen Bricker, a pioneer of the mass-balance method, began applying mass-balance modeling to small watersheds in the late 1960s and dedicated his career to expanding the literature and knowledge of complex watershed processes. We evaluated long-term trends in surface-water chemistry in the Loch Vale watershed, a 660-ha. alpine/subalpine catchment located in Rocky Mountain National Park, CO, USA. Many changes in surface-water chemistry correlated with multiple drivers, including summer or monthly temperature, snow water equivalent, and the runoff-to-precipitation ratio. Atmospheric deposition was not a significant causal agent for surface-water chemistry trends. We observed statistically significant increases in both concentrations and fluxes of weathering products including cations, SiO2, SO4 2−, and ANC, and in inorganic N, with inorganic N being primarily of atmospheric origin. These changes are evident in the individual months June, July, and August, and also in the combined June, July, and August summer season. Increasingly warm summer temperatures are melting what was once permanent ice and this may release elements entrained in the ice, stimulate chemical weathering with enhanced moisture availability, and stimulate microbial nitrification. Weathering rates may also be enhanced by sustained water availability in high snowpack years. Rapid change in the flux of weathering products and inorganic N is the direct and indirect result of a changing climate from warming temperatures and thawing cryosphere.

Deposition of shallow water sponges in response to seasonal changes

NASA Astrophysics Data System (ADS)

Ávila, Enrique; Carballo, José Luis; Vega, Cristina; Camacho, Leonardo; Barrón-Álvarez, José J.; Padilla-Verdín, Claudia; Yáñez-Chávez, Benjamín

2011-08-01

Removal of organisms from the subtidal zone plays an important role in shaping benthic communities in shallow bays. The main objective of this research was to quantify the biomass of sponges washed up on the beach at Mazatlan Bay (Mexico, eastern Pacific Ocean), and to determine its relationship with local weather and oceanographic conditions. To know whether this process has a significant effect on the sponge populations, changes in abundance of the species washed into the beach were also quantified in adjoining sublittoral areas. The sponges that were washed ashore were mainly branching ( Mycale ramulosa), massive ( Haliclona caerulea) and cushion-shaped ( Callyspongia californica) species. Species with high content of spongin in their structure (e.g. Hyattella intestinalis) were common in the subtidal zone but were rarely found on the beach. Encrusting species were never found. Four-year data of sponge deposition on the beach showed that the total annual sponge biomass ranged from 30 to 60 g DW m - 2 with an inter-annual range from 0.1 to 17.3 g DW m - 2 . The highest deposition of sponges was during the spring-summer transition (from April to July), which was associated with a change in wind direction (from NW to WSW). This change also matched with low tides and a high resuspension of bottom sediments, suggesting a high-energy environment during this transition. The increase in sponge biomass washed on the beach coincided with a decrease in the density of adjacent sponge populations. A multiple regression analysis showed that 68.48% of the variation on sponge biomass on the beach could be statistically explained using a combination of environmental factors (wind speed, sediment resuspension and tides). Thus, seasonal changes in wind direction combined with the effect of low tides and sediment resuspension could serve to predict fragmentation/detachment events of benthic organisms in shallow sublittoral areas worldwide. This study also provides insights to

Carbon nanotubes synthesized by Ni-assisted atmospheric pressure thermal chemical vapor deposition

NASA Astrophysics Data System (ADS)

Choi, G. S.; Cho, Y. S.; Hong, S. Y.; Park, J. B.; Son, K. H.; Kim, D. J.

2002-03-01

A detailed systematic study on the growth morphology of carbon nanotubes (CNTs) on Si in atmospheric pressure thermal chemical vapor deposition was undertaken. The role of NH3 for vertical alignment of CNTs was investigated. The direct cause for the alignment was a dense distribution of the catalytic metal particles, but that the particles are maintained catalytically active under amorphous carbon deposits was established by NH3. It allows a dense nucleation of the CNTs, and consequently, assists vertical alignment through entanglement and mechanical leaning among the tubes. The CNTs grew in a base growth mode. Since Ni is consumed both by silicide reaction and by capture into the growing tube, the growth stops when Ni is totally depleted. It occurs earlier for smaller particles, and thus a long time of growth results in a thin bottom with poor adhesion.

Atmospheric dry deposition on pines in the Eastern Brook Lake Watershed, Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Bytnerowicz, Andrzej; Dawson, P. J.; Morrison, C. L.; Poe, M. P.

Atmospheric dry deposition to branches of Pinus contorta and P. albicaulis was measured during summer 1987 in a sub-alpine zone at Eastern Brook Lake Watershed (EBLW), eastern Sierra Nevada, California. Results are presented as deposition fluxes of NO 3-, SO 42-, PO 43-, Cl -, F -, NH 4+, Ca 2+, Mg 2+, Na +, K +, Zn 2+, Fe 3+, Mn 2+, Pb 2+ and H +, and compared with other locations in California and elsewhere. Deposition fluxes of anions and cations to the pine branches were low, several times lower than the values determined near the Emerald Lake Watershed (ELW), another sub-alpine location in the western Sierra Nevada. The sums of deposition fluxes of the measured cations and anions to pine surfaces were similar, in contrast to the ELW location where the sums of cation fluxes were much higher than the sums of anion fluxes. A strong positive correlation between depositions of NO 3- and NH 4+, as well as SO 42- and Ca 2+, suggested that large portions of these ions might have originated from particulate NH 4NO 3 and CaSO 4 deposited on pine surfaces. An estimated total N dry deposition (surface deposition of NO 3- and NH 4+ and internal uptake of NO 2 and HNO 3) to the forested area of the EBLW was 29.54 eq ha -1 yr - (about 414 g H ha -1 yr -1).

Computations of Lifshitz-van der Waals interaction energies between irregular particles and surfaces at all separations for resuspension modelling

NASA Astrophysics Data System (ADS)

Priye, Aashish; Marlow, William H.

2013-10-01

The phenomenon of particle resuspension plays a vital role in numerous fields. Among many aspects of particle resuspension dynamics, a dominant concern is the accurate description and formulation of the van der Waals (vdW) interactions between the particle and substrate. Current models treat adhesion by incorporating a material-dependent Hamaker's constant which relies on the heuristic Hamaker's two-body interactions. However, this assumption of pairwise summation of interaction energies can lead to significant errors in condensed matter as it does not take into account the many-body interaction and retardation effects. To address these issues, an approach based on Lifshitz continuum theory of vdW interactions has been developed to calculate the principal many-body interactions between arbitrary geometries at all separation distances to a high degree of accuracy through Lifshitz's theory. We have applied this numerical implementation to calculate the many-body vdW interactions between spherical particles and surfaces with sinusoidally varying roughness profile and also to non-spherical particles (cubes, cylinders, tetrahedron etc) orientated differently with respect to the surface. Our calculations revealed that increasing the surface roughness amplitude decreases the adhesion force and non-spherical particles adhere to the surfaces more strongly when their flatter sides are oriented towards the surface. Such practical shapes and structures of particle-surface systems have not been previously considered in resuspension models and this rigorous treatment of vdW interactions provides more realistic adhesion forces between the particle and the surface which can then be coupled with computational fluid dynamics models to improve the predictive capabilities of particle resuspension dynamics.

Contribution of atmospheric dry deposition to stormwater loads for PAHs and trace metals in a small and highly trafficked urban road catchment.

PubMed

Al Ali, Saja; Debade, Xavier; Chebbo, Ghassan; Béchet, Béatrice; Bonhomme, Céline

2017-12-01

A deep understanding of pollutant buildup and wash-off is essential for accurate urban stormwater quality modeling and for the development of stormwater management practices, knowing the potential adverse impacts of runoff pollution on receiving waters. In the context of quantifying the contribution of airborne pollutants to the contamination of stormwater runoff and assessing the need of developing an integrated AIR-WATER modeling chain, loads of polycyclic aromatic hydrocarbons (PAHs) and metal trace elements (MTEs) are calculated in atmospheric dry deposits, stormwater runoff, and surface dust stock within a small yet highly trafficked urban road catchment (~ 30,000 vehicles per day) near Paris. Despite the important traffic load and according to the current definition of "atmospheric" source, atmospheric deposition did not account for more than 10% of the PAHs and trace metal loads in stormwater samples for the majority of the events, based on the ratio of deposition to stormwater. This result shows that atmospheric deposition is not a major source of pollutants in stormwater, and thus, linking the air and water compartment in a modeling chain to have more accurate estimates of pollutant loads in stormwater runoff might not be relevant. Comparison of road dust with water samples demonstrates that only the fine fraction of the available stock is eroded during a rainfall event. Even if the atmosphere mostly generates fine particles, the existence of other sources of fine particles to stormwater runoff is highlighted.

Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model

NASA Astrophysics Data System (ADS)

Katata, G.; Chino, M.; Kobayashi, T.; Terada, H.; Ota, M.; Nagai, H.; Kajino, M.; Draxler, R.; Hort, M. C.; Malo, A.; Torii, T.; Sanada, Y.

2015-01-01

Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate the detailed atmospheric releases during the accident using a reverse estimation method which calculates the release rates of radionuclides by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric and oceanic transport, dispersion and deposition models. The atmospheric and oceanic models used are WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN-FDM (Finite difference oceanic dispersion model), both developed by the authors. A sophisticated deposition scheme, which deals with dry and fog-water depositions, cloud condensation nuclei (CCN) activation, and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The results revealed that the major releases of radionuclides due to the FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, midnight of 14 March when the SRV (safety relief valve) was opened three times at Unit 2, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of release rates. The simulation by WSPEEDI-II using the new source term reproduced the local and regional patterns of cumulative

External quality assurance project report for the National Atmospheric Deposition Program’s National Trends Network and Mercury Deposition Network, 2015–16

USGS Publications Warehouse

Wetherbee, Gregory A.; Martin, RoseAnn

2018-06-29

The U.S. Geological Survey Precipitation Chemistry Quality Assurance project operated five distinct programs to provide external quality assurance monitoring for the National Atmospheric Deposition Program’s (NADP) National Trends Network and Mercury Deposition Network during 2015–16. The National Trends Network programs include (1) a field audit program to evaluate sample contamination and stability, (2) an interlaboratory comparison program to evaluate analytical laboratory performance, and (3) a colocated sampler program to evaluate bias and variability attributed to automated precipitation samplers. The Mercury Deposition Network programs include the (4) system blank program and (5) an interlaboratory comparison program. The results indicate that NADP data continue to be of sufficient quality for the analysis of spatial distributions and time trends for chemical constituents in wet deposition.The field audit program results indicate increased sample contamination for calcium, magnesium, and potassium relative to 2010 levels, and slight fluctuation in sodium contamination. Nitrate contamination levels dropped slightly during 2014–16, and chloride contamination leveled off between 2007 and 2016. Sulfate contamination is similar to the 2000 level. Hydrogen ion contamination has steadily decreased since 2012. Losses of ammonium and nitrate resulting from potential sample instability were negligible.The NADP Central Analytical Laboratory produced interlaboratory comparison results with low bias and variability compared to other domestic and international laboratories that support atmospheric deposition monitoring. Significant absolute bias above the magnitudes of the detection limits was observed for nitrate and sulfate concentrations, but no analyte determinations exceeded the detection limits for blanks.Colocated sampler program results from dissimilar colocated collectors indicate that the retrofit of the National Trends Network with N-CON Systems Company

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

Influence of variable rates of neritic carbonate deposition on atmospheric carbon dioxide and pelagic sediments

NASA Technical Reports Server (NTRS)

Walker, J. C.; Opdyke, B. C.

1995-01-01

Short-term imbalances in the global cycle of shallow water calcium carbonate deposition and dissolution may be responsible for much of the observed Pleistocene change in atmospheric carbon dioxide content. However, any proposed changes in the alkalinity balance of the ocean must be reconciled with the sedimentary record of deep-sea carbonates. The possible magnitude of the effect of shallow water carbonate deposition on the dissolution of pelagic carbonate can be tested using numerical simulations of the global carbon cycle. Boundary conditions can be defined by using extant shallow water carbonate accumulation data and pelagic carbonate deposition/dissolution data. On timescales of thousands of years carbonate deposition versus dissolution is rarely out of equilibrium by more than 1.5 x 10(13) mole yr-1. Results indicate that the carbonate chemistry of the ocean is rarely at equilibrium on timescales less than 10 ka. This disequilibrium is probably due to sea level-induced changes in shallow water calcium carbonate deposition/dissolution, an interpretation that does not conflict with pelagic sedimentary data from the central Pacific.

Comparison of Atmospheric Deposition Among Three Sites In and Near the Flat Tops Wilderness Area, Colorado, 2003-2005

USGS Publications Warehouse

Ingersoll, George P.; Campbell, Donald H.; Mast, M. Alisa

2008-01-01

Atmospheric deposition was monitored for ammonium, nitrate, and sulfate concentrations and precipitation amounts in the Flat Tops Wilderness Area of northwestern Colorado at Ned Wilson Lake beginning in 1984 to detect changes that might result from future emissions associated with development of oil-shale resources in northwestern Colorado. Renewed monitoring, by the U.S. Geological Survey, in cooperation with Rio Blanco County, to determine the current status of atmospheric deposition has been ongoing since 2003 at Ned Wilson Lake. Two new monitoring sites were located near Ripple Creek Pass near the Flat Tops Wilderness area and about 12 kilometers north of Ned Wilson Lake because access to the area near Ripple Creek Pass is less difficult and less expensive, particularly in winter and spring. The intent of this study was to establish whether the new deposition data being collected near Ripple Creek Pass, near the northern boundary of the Flat Tops Wilderness Area, would be representative of deposition at sensitive sites within the wilderness such as Ned Wilson Lake and to compare more current (2003 through 2005) deposition data with earlier data (1984 through 1991). At Ned Wilson Lake, bulk ammonium and nitrate concentrations collected from 1984 through 1991 were similar to those from 2003 through 2005. However, in the same comparison significant differences in sulfate concentrations were observed, indicating a decrease consistent with other regional findings for similar periods. Comparison of concentrations of constituents at two bulk-deposition sites located at Ned Wilson Lake (NWLB) and near Ripple Creek Pass (RCPB) showed only one significant difference (p = 0.05) with the winter bulk nitrate concentrations for NWLB significantly lower than winter concentrations from RCPB. Another comparison of concentrations of constituents between the bulk deposition site RCPB and a wet deposition site 100 meters away (RCPW) showed no significant differences for

Deposition and Effects of Atmospheric Nitrogen and Ozone in Holm Oak Forests in Spain

NASA Astrophysics Data System (ADS)

González Fernández, I.; García Gómez, H.; Calvete Sogo, H.; Bermejo, V.; Valiño, F.; Elvira, S.; Rábago, I.; Sanz, J.; Alonso, R.

2013-12-01

Atmospheric nitrogen (N) emissions in Spain, in the western Mediterranean basin, have followed an increasing trend since 1990 and have only started to decline recently. These trends have resulted in growing N depositions in some areas and in N enrichment of ecosystems, as described in previous studies by increasing records of nitrophilous species in herbaria and raising N content both in bryophytes and in leaves of forest trees. Tropospheric ozone (O3) background concentrations, formed as a result of photochemical reactions of N compounds in the atmosphere, have also increased during the last decades. Despite these evidences, limited information is available on N and O3 deposition and effects in Holm oak forests, important ecosystems in Spain. New studies are being developed to address this lack of data. First results on N deposition in a Holm oak forest in central Spain stress the importance of seasonal variations of N inputs in Mediterranean environments. Spring and autumn rainfall events added up to 80% of total annual bulk deposition and losses of NO3- in the soil water were detected when throughfall N pulses occurred during periods of low plant physiological activity. N uptake in the tree canopy was also observed. High O3 concentrations were also measured in this study. The exposure to both N and O3 is a common situation in Holm oak forests. The combined effect of N and O3 deposition on the annual pasture of the Holm oak forest understory has been studied in an open-top chamber study using a simplified community of six species. Results show that O3 can potentially reduce pasture growth, decrease its nutritive value for herbivores and cause shifts in species abundance. N deposition can partially counterbalance O3-induced effects on the pasture biomass, thus both O3 and N need to be considered together when studying air pollution impacts in these ecosystems. The studies presented here are intended for developing N and O3 critical loads and levels for the

Atomic layer deposited high-k dielectric on graphene by functionalization through atmospheric plasma treatment

NASA Astrophysics Data System (ADS)

Shin, Jeong Woo; Kang, Myung Hoon; Oh, Seongkook; Yang, Byung Chan; Seong, Kwonil; Ahn, Hyo-Sok; Lee, Tae Hoon; An, Jihwan

2018-05-01

Atomic layer-deposited (ALD) dielectric films on graphene usually show noncontinuous and rough morphology owing to the inert surface of graphene. Here, we demonstrate the deposition of thin and uniform ALD ZrO2 films with no seed layer on chemical vapor-deposited graphene functionalized by atmospheric oxygen plasma treatment. Transmission electron microscopy showed that the ALD ZrO2 films were highly crystalline, despite a low ALD temperature of 150 °C. The ALD ZrO2 film served as an effective passivation layer for graphene, which was shown by negative shifts in the Dirac voltage and the enhanced air stability of graphene field-effect transistors after ALD of ZrO2. The ALD ZrO2 film on the functionalized graphene may find use in flexible graphene electronics and biosensors owing to its low process temperature and its capacity to improve device performance and stability.

Atomic layer deposited high-k dielectric on graphene by functionalization through atmospheric plasma treatment.

PubMed

Shin, Jeong Woo; Kang, Myung Hoon; Oh, Seongkook; Yang, Byung Chan; Seong, Kwonil; Ahn, Hyo-Sok; Lee, Tae Hoon; An, Jihwan

2018-05-11

Atomic layer-deposited (ALD) dielectric films on graphene usually show noncontinuous and rough morphology owing to the inert surface of graphene. Here, we demonstrate the deposition of thin and uniform ALD ZrO 2 films with no seed layer on chemical vapor-deposited graphene functionalized by atmospheric oxygen plasma treatment. Transmission electron microscopy showed that the ALD ZrO 2 films were highly crystalline, despite a low ALD temperature of 150 °C. The ALD ZrO 2 film served as an effective passivation layer for graphene, which was shown by negative shifts in the Dirac voltage and the enhanced air stability of graphene field-effect transistors after ALD of ZrO 2 . The ALD ZrO 2 film on the functionalized graphene may find use in flexible graphene electronics and biosensors owing to its low process temperature and its capacity to improve device performance and stability.

Four studies on effects of environmental factors on the quality of National Atmospheric Deposition Program measurements

USGS Publications Warehouse

Wetherbee, Gregory A.; Latysh, Natalie E.; Lehmann, Christopher M.B.; Rhodes, Mark F.

2011-01-01

Selected aspects of National Atmospheric Deposition Program / National Trends Network (NADP/NTN) protocols are evaluated in four studies. Meteorological conditions have minor impacts on the error in NADP/NTN sampling. Efficiency of frozen precipitation sample collection is lower than for liquid precipitation samples. Variability of NTN measurements is higher for relatively low-intensity deposition of frozen precipitation than for higher-intensity deposition of liquid precipitation. Urbanization of the landscape surrounding NADP/NTN sites is not affecting trends in wet-deposition chemistry data to a measureable degree. Five NADP siting criteria intended to preserve wet-deposition sample integrity have varying degrees of effectiveness. NADP siting criteria for objects within the 90 degrees cones and trees within the 120 degrees cones projected from the collector bucket to sky are important for protecting sample integrity. Tall vegetation, fences, and other objects located within 5 meters of the collectors are related to the frequency of visible sample contamination, indicating the importance of these factors in NADP siting criteria.

Spatial Patterns of Atmospherically Deposited Organic Contaminants at High Elevation in the Southern Sierra Nevada Mountains, California

EPA Science Inventory

Atmospherically deposited contaminants in the Sierra Nevada mountains of California have been implicated as adversely affecting amphibians and fish, yet the distributions of contaminants within the mountains are poorly known, particularly at high elevation. We tested the hypothe...

Spatial Patterns of Atmospherically Deposited Organic Contaminants at High Elevation in the Southern Sierra Nevada Mountains, California

EPA Science Inventory

Atmospherically deposited contaminants in the Sierra Nevada mountains of California have been implicated as a factor adversely affecting biological resources such as amphibians and fish, yet the distributions of contaminants within the mountains are poorly known, particularly at...

Microorganisms and heavy metals associated with atmospheric deposition in a congested urban environment of a developing country: Sri Lanka.

PubMed

Weerasundara, Lakshika; Amarasekara, R W K; Magana-Arachchi, D N; Ziyath, Abdul M; Karunaratne, D G G P; Goonetilleke, Ashantha; Vithanage, Meththika

2017-04-15

The presence of bacteria and heavy metals in atmospheric deposition were investigated in Kandy, Sri Lanka, which is a typical city in the developing world with significant traffic congestion. Atmospheric deposition samples were analyzed for Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb which are heavy metals common to urban environments. Al and Fe were found in high concentrations due to the presence of natural sources, but may also be re-suspended by vehicular traffic. Relatively high concentrations of toxic metals such as Cr and Pb in dissolved form were also found. High Zn loads can be attributed to vehicular emissions and the wide use of Zn coated roofing materials. The metal loads in wet deposition showed higher concentrations compared to dry deposition. The metal concentrations among the different sampling sites significantly differ from each other depending on the traffic conditions. Industrial activities are not significant in Kandy City. Consequently, the traffic exerts high influence on heavy metal loadings. As part of the bacterial investigations, nine species of culturable bacteria, namely; Sphingomonas sp., Pseudomonas aeruginosa, Pseudomonas monteilii, Klebsiella pneumonia, Ochrobactrum intermedium, Leclercia adecarboxylata, Exiguobacterium sp., Bacillus pumilus and Kocuria kristinae, which are opportunistic pathogens, were identified. This is the first time Pseudomonas monteilii and Ochrobactrum intermedium has been reported from a country in Asia. The culturable fraction constituted ~0.01 to 10%. Pigmented bacteria and endospore forming bacteria were copious in the atmospheric depositions due to their capability to withstand harsh environmental conditions. The presence of pathogenic bacteria and heavy metals creates potential human and ecosystem health risk. Copyright © 2017 Elsevier B.V. All rights reserved.

Mixing behavior of a model cellulosic biomass slurry during settling and resuspension

DOE PAGES

Crawford, Nathan C.; Sprague, Michael A.; Stickel, Jonathan J.

2016-01-29

Thorough mixing during biochemical deconstruction of biomass is crucial for achieving maximum process yields and economic success. However, due to the complex morphology and surface chemistry of biomass particles, biomass mixing is challenging and currently it is not well understood. This study investigates the bulk rheology of negatively buoyant, non-Brownian α-cellulose particles during settling and resuspension. The torque signal of a vane mixer across two distinct experimental setups (vane-in-cup and vane-in-beaker) was used to understand how mixing conditions affect the distribution of biomass particles. During experimentation, a bifurcated torque response as a function of vane speed was observed, indicating thatmore » the slurry transitions from a “settling-dominant” regime to a “suspension-dominant” regime. The torque response of well-characterized fluids (i.e., DI water) were then used to empirically identify when sufficient mixing turbulence was established in each experimental setup. The predicted critical mixing speeds were in agreement with measured values, suggesting that secondary flows are required in order to keep the cellulose particles fully suspended. In addition, a simple scaling relationship was developed to model the entire torque signal of the slurry throughout settling and resuspension. Furthermore, qualitative and semi-quantitative agreement between the model and experimental results was observed.« less

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.

Atmospheric pressure plasma deposition of antimicrobial coatings on non-woven textiles

NASA Astrophysics Data System (ADS)

Nikiforov, Anton Yu.; Deng, Xiaolong; Onyshchenko, Iuliia; Vujosevic, Danijela; Vuksanovic, Vineta; Cvelbar, Uros; De Geyter, Nathalie; Morent, Rino; Leys, Christophe

2016-08-01

A simple method for preparation of nanoparticle incorporated non-woven fabric with high antibacterial efficiency has been proposed based on atmospheric pressure plasma process. In this work direct current plasma jet stabilized by fast nitrogen flow was used as a plasma deposition source. Three different types of the nanoparticles (silver, copper and zinc oxide nanoparticles) were employed as antimicrobial agents. X-ray photoelectron spectroscopy (XPS) measurements have shown a positive chemical shift observed for Ag 3d 5/2 (at 368.1 eV) suggests that silver nanoparticles (AgNPs) are partly oxidized during the deposition. The surface chemistry and the antibacterial activity of the samples against Staphylococcus aureus and Escherichia coli were investigated and analyzed. It is shown that the samples loaded with nanoparticles of Ag and Cu and having the barrier layer of 10 nm characterized by almost 97% of bacterial reduction whereas the samples with ZnO nanoparticles provide 86% reduction of Staphylococcus aureus. Contribution to the topical issue "6th Central European Symposium on Plasma Chemistry (CESPC-6)", edited by Nicolas Gherardi, Ester Marotta and Cristina Paradisi

Recent increases in atmospheric deposition of mercury to North-Central Wisconsin lakes inferred from sediment analyses

USGS Publications Warehouse

Rada, R.G.; Wiener, J.G.; Winfrey, M.R.; Powell, D.E.

1989-01-01

Profiles of total mercury (Hg) concentrations in sediments were examined in 11 lakes in north-central Wisconsin having a broad range of pH (5.1 to 7.8) and alkalinity (-12 to 769 μeq/L). Mercury concentrations were greatest in the top 15 cm of the cores and were much lower in the deeper strata. The Hg content in the most enriched stratum of individual cores ranged from 0.09 to 0.24 μg/g dry weight, whereas concentrations in deep, precolonial strata ranged from 0.04 to 0.07 μg/g. Sediment enrichment factors varied from 0.8 to 2.8 and were not correlated with lake pH. The increase in the Hg content of recent sediments was attributed to increased atmospheric deposition of the metal. Eight of the 11 systems studied were low-alkalinity lakes that presumably received most (≥90%) of their hydrologic input from precipitation falling directly onto the lake surface. Thus, the sedimentary Hg in these lakes seems more likely linked to direct atmospheric deposition onto the lake surfaces than to influxes from the watershed. The data imply that a potentially significant fraction of the high Hg burdens measured in game fish in certain lakes in north-central Wisconsin originated from atmospheric sources.

Atmospheric deposition, water-quality, and sediment data for selected lakes in Mount Rainer, North Cascades, and Olympic National Parks, Washington, 2008-10

USGS Publications Warehouse

Sheibley, Rich W.; Foreman, James R.; Moran, Patrick W.; Swarzenski, Peter W.

2012-01-01

To evaluate the potential effect from atmospheric deposition of nitrogen to high-elevation lakes, the U.S. Geological Survey partnered with the National Park Service to develop a "critical load" of nitrogen for sediment diatoms. A critical load is defined as the level of a given pollutant (in this case, nitrogen) at which detrimental effects to a target endpoint (sediment diatoms) result. Because sediment diatoms are considered one of the "first responders" to ecosystem changes from nitrogen, they are a sensitive indicator for nitrogen deposition changes in natural areas. This report presents atmospheric deposition, water quality, sediment geochronology, and sediment diatom data collected from July 2008 through August 2010 in support of this effort.

High Elevation Lakes of the Western US: Are we Studying Systems Recovering from Excess Atmospheric Deposition of Acids and Nutrients?

NASA Astrophysics Data System (ADS)

Sickman, J. O.

2011-12-01

Instrumental records and monitoring of high elevation lakes began in most areas of the western US in the early 1980s. Much effort has been devoted to detecting changes in these aquatic ecosystems resulting from increased atmospheric deposition of acids and nutrients. However, there is growing evidence that thresholds for atmospheric pollutants were crossed much earlier in the 20th Century and that some of the subsequent hydrochemical and ecological changes observed in these lakes may be the result of recovery from earlier atmospheric forcing. We examine responses of high elevation lakes to atmospheric deposition on annual to century timescales using data from a 29-year study of Emerald Lake (Sequoia National Park) and paleolimnological analyses of other high elevation lakes incorporating diatom species analyses and geochemical proxies for fossil-fuel burning. At Emerald Lake, we have observed multiple transitions between nitrogen and phosphorus limitation of phytoplankton, the earliest of which occurred in the beginning of the 1980s and may be the result of reduction in N deposition due to the Clean Air Act. Critical loads analyses incorporating diatom species in lake sediments suggest that thresholds for N deposition were crossed in the period of 1950-1980 in the Rocky Mountains and likely much earlier, 1900-1920, in the Sierra Nevada. Diatom species composition is strongly controlled by acid neutralizing capacity (ANC) in the Sierra Nevada and we have observed a pronounced decline and recovery of ANC over the period of 1920-1980 in some Sierra Nevada lakes that coincides with the abundance of spheroidal carbonaceous particles (i.e., a diagnostic tracer of fossil fuel combustion) preserved in lake sediments; these patterns appear to be driven by increased emissions of oxidized N and S in the mid-20th Century and reductions in acid precursor levels caused by the Clean Air Act in the 1970s. Thus, when interpreting observational records from western high elevation

Atmospheric deposition and solute export in giant sequoia: mixed conifer watersheds in the Sierra Nevada, California

USGS Publications Warehouse

Stohlgren, Thomas J.; Melack, John M.; Esperanza, Anne M.; Parsons, David J.

1991-01-01

Atmospheric depostion and stream discharge and solutes were measured for three years (September 1984 - August 1987) in two mixed conifer watersheds in Sequoia National Park, in the southern Sierra Nevada of California. The Log Creek watershed (50 ha, 2067-2397 m elev.) is drained by a perennial stream, while Tharp's Creek watershed (13 ha, 2067-2255 m elev.) contains an intermittent stream. Dominant trees in the area include Abies concolor (white fir), Sequoiadendron giganteum (giant sequoia), A. magnifica (red fir), and Pinus lambertiana (sugar pine). Bedrock is predominantly granite and granodiorite, and the soils are mostly Pachic Xerumbrepts. Over the three year period, sulfate (SO42-), nitrate (NO3-), and chloride (Cl-) were the major anions in bulk precipitation with volume-weighted average concentrations of 12.6, 12.3 and 10.0 μeq/1, respectively. Annual inputs of NO3-N, NH4-N and SO4-S from wet deposition were about 60 to 75% of those reported from bulk deposition collectors. Discharge from the two watersheds occurs primarily during spring snowmelt. Solute exports from Log and Tharp's Creeks were dominated by HCO3-, Ca2+ and Na+, while H+, NO3-, NH4+ and PO43- outputs were relatively small. Solute concentrations were weakly correlated with instantaneous stream flow for all solutes (r2 3- (Log Cr. r2=0.72; Tharp's Cr. r2=0.38), Na+ (Log Cr. r2=0.56; Tharp's Cr. r2=0.47), and silicate (Log Cr. r2=0.71; Tharp's Cr. r2=0.49). Mean annual atmospheric contributions of NO3-N (1.6 kg ha-1), NH4-N (1.7 kg ha-1), and SO4-S (1.8 kg ha-1), which are associated with acidic deposition, greatly exceed hydrologic losses. Annual watershed yields (expressed as eq ha-1) of HCO3- exceeded by factors of 2.5 to 37 the annual atmospheric deposition of H+.

Atmospheric Nitrogen Deposition Threatens Biodiversity: Development of Novel Mitigation Policies in California

NASA Astrophysics Data System (ADS)

Weiss, S. B.

2011-12-01

Atmospheric nitrogen deposition threatens biodiversity in many parts of the world. In California, 20% of the land surface receives > 5 kg-N ha-1 year-1, with hotspots receiving > 50 kg-N ha-1 year-1. Documented impacts of N-deposition include increased growth of annual grass and other invasives in coastal sage scrub, serpentine grasslands, vernal pools, and deserts, altered nutrient cycling and fuel accumulation of montane forests, enhanced fire cycles, nitrate leaching into surface and groundwater, and eutrophication of montane lakes such as Lake Tahoe. 40% of listed threatened and endangered plants are exposed to > 5 kg-N ha-1 year-1, and N-deposition is arguably a greater immediate threat to biodiversity than is climate change. Appropriate policy responses are lagging, because the magnitude of N-deposition impacts on biodiversity is poorly known in the broader conservation/regulatory community and the general public. Policies to decrease emissions and deposition are clearly the ultimate solution on a decadal time scale. In the interim, habitat management is critical to preventing extinction of many species. This presentation reviews recent policies and regulatory actions in California that address N-deposition impacts on biodiversity. The immediate and long-term needs for invasive weed management are overwhelming and require long-term endowment funding. Mitigation requirements under the US Endangered Species Act have been used to secure land and management resources. The on-going story of the threatened Bay checkerspot butterfly, from the first precedent setting mitigation in 2001 through a regional Habitat Conservation Plan (HCP), illustrates the development of these novel policies based on science, regulatory authority, grassroots activism, public education, habitat restoration, and legal actions. The 50-year HCP will ultimately result in a network of conserved lands with management endowments. Eventually N-deposition may be reduced below critical loads

Ahead of his time: Jacob Lipman's 1930 estimate of atmospheric sulfur deposition for the conterminous United States

USGS Publications Warehouse

Landa, Edward R.; Shanley, James B.

2015-01-01

A 1936 New Jersey Agricultural Experiment Station Bulletin provided an early quantitative assessment of atmospheric deposition of sulfur for the United States that has been compared in this study with more recent assessments. In the early 20th century, anthropogenic sulfur additions from the atmosphere to the soil by the combustion of fossil fuels were viewed as part of the requisite nutrient supply of crops. Jacob G. Lipman, the founding editor of Soil Science, and his team at Rutgers University, made an inventory of such additions to soils of the conterminous United States during the economic depression of the 1930s as part of a federally funded project looking at nutrient balances in soils. Lipman's team gathered data compiled by the US Bureau of Mines on coal and other fuel consumption by state and calculated the corresponding amounts of sulfur emitted. Their work pioneered a method of assessment that became the norm in the 1970s to 1980s—when acid rain emerged as a national issue. Lipman's estimate of atmospheric sulfur deposition in the 1930 is in reasonable agreement with recent historic reconstructions.

Influence of sediment resuspension on the efficacy of geoengineering materials in the control of internal phosphorous loading from shallow eutrophic lakes.

PubMed

Yin, Hongbin; Kong, Ming; Han, Meixiang; Fan, Chengxin

2016-12-01

Modified clay-based solid-phase phosphorous (P) sorbents are increasingly used as lake geoengineering materials for lake eutrophication control. However, some still dispute the feasibility of using these materials to control internal P loading from shallow eutrophic lakes. The lack of information about P behavior while undergoing frequent sediment resuspension greatly inhibits the modified minerals' use. In this study, a sediment resuspension generating system was used to simulate the effect of both moderate winds (5.1 m/s) and strong winds (8.7 m/s) on the stability of sediment treated by two geoengineering materials, Phoslock ® (a lanthanum modified bentonite) and thermally-treated calcium-rich attapulgite. This study also presents an analysis of the P dynamics across the sediment-water interface of two shallow eutrophic lakes. In addition, the effect of wind velocity on P forms and P supply from the treated sediment were studied using chemical extraction and diffusive gradients in thin films (DGT) technique, respectively. Results showed that adding geoengineering materials can enhance the stability of surface sediment and reduce the erosion depth caused by wind accordingly. All treatments can effectively reduce soluble reactive phosphorus (SRP) concentration in overlying water when sediment is capped with thermally-treated calcium-rich attapulgite, which performs better than sediment mixed with modified attapulgite but not as well as sediment treated with Phoslock ® . However, their efficiency decreased with the increase in occurrences of sediment resuspension. The addition of the selected geoengineering materials effectively reduced the P fluxes across sediment-water interface and lowered P supply ability from the treated sediment during sediment resuspension. The reduction of mobile P and enhancement of calcium bound P and residual P fraction in the treated sediment was beneficial to the long-term lake internal P loading management. All of the results

Modeling of temporal patterns and sources of atmospherically transported and deposited pesticides in ecosystems of concern: A case study of toxaphene in the Great Lakes

NASA Astrophysics Data System (ADS)

Li, Rong; Jin, Jiming

2013-10-01

have adverse effects on human health and the environment and can be transported through the atmosphere from application sites and deposited to sensitive ecosystems. This study applies a comprehensive multimedia regional pesticide fate and chemical transport modeling system that we developed to investigate the atmospheric transport and deposition of toxaphene to the Great Lakes. Simulated results predict a significant amount of toxaphene (~350 kg) being transported through the atmosphere and deposited into the Great Lakes in the simulation year. Results also show that U.S. residues and global background are major sources to toxaphene deposition into the Great Lakes and atmospheric concentrations in the region. While the U.S. residues are the dominant source in warm months, the background dominates during winter months. In addition, different sources have different influences on the individual Great Lakes due to their proximity and relative geographical positions to the sources; U.S. residues are the dominant source to Lakes Ontario, Erie, Huron, and Michigan, but they are a much less important source to Lake Superior. These results shed light on the mystery that observed toxaphene concentrations in Great Lakes' lake trout and smelt declined between 1982 and 1992 in four of the Great Lakes except Lake Superior. While monthly total depositions to Lakes Ontario, Erie, Huron, and Michigan have clear seasonal variability with much greater values in April, May, and June, monthly total depositions to Lake Superior are more uniformly distributed over the year with comparatively greater levels in cold months.

Development of atmospheric acid deposition in China from the 1990s to the 2010s.

PubMed

Yu, Haili; He, Nianpeng; Wang, Qiufeng; Zhu, Jianxing; Gao, Yang; Zhang, Yunhai; Jia, Yanlong; Yu, Guirui

2017-12-01

Atmospheric acid deposition is a global environmental issue. China has been experiencing serious acid deposition, which is anticipated to become more severe with the country's economic development and increasing consumption of fossil fuels in recent decades. We explored the spatiotemporal variations of acid deposition (wet acid deposition) and its influencing factors by collecting nationwide data on pH and concentrations of sulfate (SO 4 2- ) and nitrate (NO 3 - ) in precipitation between 1980 and 2014 in China. Our results showed that average precipitation pH values were 4.59 and 4.70 in the 1990s and 2010s, respectively, suggesting that precipitation acid deposition in China has not seriously worsened. Average SO 4 2- deposition declined from 40.54 to 34.87 kg S ha -1 yr -1 but average NO 3 - deposition increased from 4.44 to 7.73 kg N ha -1 yr -1 . Specifically, the area of severe precipitation acid deposition in southern China has shrunk to some extent as a result of controlling the pollutant emissions; but the area of moderate precipitation acid deposition has expanded in northern China, associated with rapid industrial and transportation development. Furthermore, we found significant positive correlations between precipitation acid deposition, energy consumption, and rainfall. Our findings provide a relatively comprehensive evaluation of the spatiotemporal dynamics of precipitation acid deposition in China over past three decades, and confirm the idea that strategies implemented to save energy and control pollutant emissions in China have been effective in alleviating precipitation acid deposition. These findings might be used to demonstrate how developing countries could achieve economic development and environmental protection through the implementation of advanced technologies to reduce pollutant emissions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Atmospheric dry deposition in the vicinity of the Salton Sea, California - I: Air pollution and deposition in a desert environment

USGS Publications Warehouse

Alonso, R.; Bytnerowicz, A.; Boarman, W.I.

2005-01-01

Air pollutant concentrations and atmospheric dry deposition were monitored seasonally at the Salton Sea, southern California. Measurements of ozone (O 3), nitric acid vapor (HNO3), ammonia (NH3), nitric oxide (NO), nitrogen dioxide (NO2) and sulfur dioxide (SO 2) were performed using passive samplers. Deposition rates of NO 3-, NH4+, Cl-, SO 42-, Na+, K+ and Ca2+ to creosote bush branches and nylon filters as surrogate surfaces were determined for one-week long exposure periods. Maximum O3 values were recorded in spring with 24-h average values of 108.8 ??g m-3. Concentrations of NO and NO2 were low and within ranges of the non-urban areas in California (0.4-5.6 and 3.3-16.2 ??g m-3 ranges, respectively). Concentrations of HNO3 (2.0-6.7 ??g m-3) and NH 3 (6.4-15.7 ??g m-3) were elevated and above the levels typical for remote locations in California. Deposition rates of Cl-, SO42-, Na+, K+ and Ca2+ were related to the influence of sea spray or to suspended soil particles, and no strong enrichments caused by ions originated by human activities were detected. Dry deposition rates of NO3- and NH4+ were similar to values registered in areas where symptoms of nitrogen saturation and changes in species composition have been described. Deposition of nitrogenous compounds might be contributing to eutrophication processes at the Salton Sea. ?? 2005 Elsevier Ltd. All rights reserved.

Monitoring Atmospheric Deposition of Nitrogen in Alpine Environments in Rocky Mountain and Yosemite National Parks, USA

NASA Astrophysics Data System (ADS)

Roop, H. A.; Clow, D. W.; Mills, J.; Fenn, M. E.

2011-12-01

Recent increases in atmospheric deposition of nitrogen (N) in the western U.S. have adversely impacted surface water quality and changed the composition of aquatic biota in high-elevation lakes. Existing N deposition data are generally not spatially diverse; representation of remote wilderness areas and high-elevation watersheds is often lacking, making it difficult to assess the importance of variations in N deposition on water quality impacts. This study aims to better understand N deposition in remote environments, particularly in alpine environments, where both the quantity and environmental impact of atmospheric N deposition are poorly understood. Understanding the impacts of N deposition on these environments is important for National Park resource and water-quality managers. Using ion-exchange resin (IER) collectors, seasonal through-fall of nitrogen was measured at 29 sites in the Rocky Mountains and 21 sites in the Sierra Nevada from 2006-2011. The IER collectors, deployed in pairs, represent geographically diverse transects aimed to quantify the spatial distribution of nitrogen deposition. Placed on talus slopes or in areas of exposed bedrock, the IER collectors were installed immediately following snowmelt (June/July) and replaced with new collectors prior to the first snowfall (September). Following spring melt, the collectors deployed over the winter were exchanged with new collectors. These seasonal swaps capture winter/spring and summer/fall deposition. A majority of the sites were paired with seasonal surface-water quality samples, allowing for comparison with nitrate levels in surface waters. In the lab, N compounds are eluted from the resins, then diluted and analyzed on an ion- chromatograph. Preliminary data from 2006, representing 16 sites with uncontaminated samples in Rocky Mountain National Park, suggest higher nitrogen deposition on the east side of the park. Average summer N deposition for an 85-day exposure period at the eastern slope

Derivation of Effective Resuspension Factors in Scenarios for Inhalation Exposure Involving Resuspension of Previously Deposited Fallout by Nuclear Detonations at Nevada Test Site

DTIC Science & Technology

2009-11-30

generate exposure-rate contours at the fixed time is not an additional source of uncertainty when relative activities of radionuclides on the ground are...deposition or transit and other target organs or tissues, and calculations of radiation transport between a source and target. These uncertainties are...Beck, H., and de Planque, G., 1968. The Radiation Field in Air Due to Distributed Gamma-Ray Sources in the Ground, HASL-195, Health and Safety

Nitrogen cycling in ombrotrophic peat bogs in the Czech Republic: Is microbial N-fixation occurring at atmospheric depositions of reactive N higher than 10 kg/ha/yr?

NASA Astrophysics Data System (ADS)

Novak, Martin; Jackova, Ivana; Cejkova, Bohuslava; Buzek, Frantisek; Curik, Jan; Stepanova, Marketa; Prechova, Eva; Veselovsky, Frantisek; Komarek, Arnost

2017-04-01

Biogeochemical cycling of carbon (C) and nitrogen (N) in peat bogs are coupled. Whereas at low pollution levels, reactive nitrogen (Nr, mainly nitrate- and ammonium-N) inputs may positively affect C storage, high Nr deposition may have a detrimental effect on C storage. We have previously reported N isotope systematics at two ombrotrophic peat bogs in the Czech Republic, receiving medium levels of Nr of about 10 kg/ha/yr via atmospheric deposition. Nitrogen of living Sphagnum was systematically heavier than N of the atmospheric input (p < 0.001), and close to the N isotope signature of atmospheric N2 (del15N-N2 of 0.0 per mil). We argued that even at medium Nr pollution, such as that in the Czech Republic, the amount of Nr in rainfall becomes minute toward the end of major precipitation events, possible triggering off microbial N-fixation. This process may be responsible for the del15N shift in Sphagnum from negative values of atmospheric deposition to the zero value of N2. In 2016, we conducted a laboratory study in which living Sphagnum from sites receiving annually slightly over 10 kg Nr/ha/yr via atmospheric deposition was incubated in an atmosphere enriched in 15N-N2. At the end of the incubation, we detected a 1 to 3 per mil increase in del15N of Sphagnum. Rinsing Sphagnum capitula in deionized water prior to the 15N-N2 incubation has led to a slight further increase in del15N of Sphagnum. Also in 2016, we monitored del15N of atmospheric deposition at three medium Nr-polluted peat bogs. Open-area precipitation had the following mean del 15N values: Uhlirska -6.1 per mil (NH4) and -6.2 per mil (NO3); Brumiste -1.7 per mil (NH4) and -3.4 per mil (NO3); Male Mechove Jezirko -3.3 per mil (NH4) and -3.9 per mil (NO3). At all sites, atmospheric Nr deposition was made up by NO3-N and NH4-N in a roughly 1.1 ratio. We found that N of winter-time deposition became isotopically extremely light (less than -10.0 per mil). During the growing season, del15N of total

VALDRIFT 1.0: A valley atmospheric dispersion model with deposition

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

Allwine, K.J.; Bian, X.; Whiteman, C.D.

1995-05-01

VALDRIFT version 1.0 is an atmospheric transport and diffusion model for use in well-defined mountain valleys. It is designed to determine the extent of ddft from aedal pesticide spraying activities, but can also be applied to estimate the transport and diffusion of various air pollutants in valleys. The model is phenomenological -- that is, the dominant meteorological processes goveming the behavior of the valley atmosphere are formulated explicitly in the model, albeit in a highly parameterized fashion. The key meteorological processes treated are: (1) nonsteady and nonhomogeneous along-valley winds and turbulent diffusivities, (2) convective boundary layer growth, (3) inversion descent,more » (4) noctumal temperature inversion breakup, and (5) subsidence. The model is applicable under relatively cloud-free, undisturbed synoptic conditions and is configured to operate through one diumal cycle for a single valley. The inputs required are the valley topographical characteristics, pesticide release rate as a function of time and space, along-valley wind speed as a function of time and space, temperature inversion characteristics at sunrise, and sensible heat flux as a function of time following sunrise. Default values are provided for certain inputs in the absence of detailed observations. The outputs are three-dimensional air concentration and ground-level deposition fields as a function of time.« less

Atmospheric deposition of particles at a sensitive alpine lake: Size-segregated daily and annual fluxes from passive sampling techniques.

PubMed

Tai, Anna Y-C; Chen, L-W Antony; Wang, Xiaoliang; Chow, Judith C; Watson, John G

2017-02-01

Lake Tahoe, a North American alpine lake long appreciated for its clear water and geographic setting, has experienced a trend of declining water clarity due to increasing nutrient and particle inputs. Contributions from atmospheric deposition of particulate matter (PM) could be important, yet they are inadequately quantified. This study established a yearlong deposition monitoring network in the northern Lake Tahoe Basin. Dry deposition was quantified on surrogate surfaces while wet deposition was based on particles suspended in precipitation at 24-hour resolution. The particle size ranges by these passive techniques were 1-64μm and 0.5-20μm in diameter for dry and wet deposition, respectively. Dry deposition of submicrometer (0.5-1μm) particles was also estimated by extrapolation of a lognormal size distribution. Higher daily number deposition fluxes (NDF dry and NDF wet ) were found at a near-shore site, confirming substantial impacts of commercial and tourist activities. The two more isolated sites indicated a uniform regional background. On average, daily NDF dry is about one order of magnitude lower than daily NDF wet . Dry deposition velocities increased rapidly with particle size, as evidenced by collocated measurements of NDF dry and ambient particle number concentrations, though it seems less so for wet deposition due to different scavenging mechanisms. Despite fewer "wet" days than "dry" days during the monitoring period, wet processes dominated seasonal particle deposition, particularly in winter and spring when most precipitation occurred. Adopting sediment (insoluble, inorganic) particle fraction estimates from the literature, this study reports an annual particle flux of 2.9-5.2×10 10 #m -2 yr -1 for sediment particles with 1-20μm diameter and 6.1-11×10 10 #m -2 yr -1 for those with 0.5-20μm diameter. Implications of these findings to the current knowledge of atmospheric deposition in the Lake Tahoe Total Maximum Daily Load (TMDL) are discussed

Re-suspension of Cesium-134/137 into the Canadian Environment and the Contribution Stemming from the Fukushima-Daiichi Nuclear Incident

NASA Astrophysics Data System (ADS)

Mercier, Jean-Francois; Zhang, Weihua; Loignon-Houle, Francis; Cooke, Michael W.; Ungar, Kurt R.; Pellerin, Eric R.

2013-04-01

Cesium-137 (t1/2 = 30 yr) and cesium-134 (t1/2 = 2yr) constitute major fission by-products observed as the result of a nuclear incident. Such radioisotopes become integrated into the soil and biomass, and can therefore undergo re-suspension into the environment via activities such as forest fires. The Canadian Radiological Monitoring Network (CRMN), which consists of 26 environmental monitoring stations spread across the country, commonly observes cesium-137 in air filters due to re-suspension of material originating from long-past weapons testing. Cesium-134 is not observed owing to its relatively short half-life. The Fukushima-Daiichi nuclear power plant incident of March 2011 caused a major release of radioactive materials into the environment. In Canada, small quantities of both cesium-137 and cesium-134 fallout were detected with great frequency in the weeks which followed, falling off rapidly beginning in July 2011. Since September 2011, the CRMN has detected both cesium-137 and cesium-134 from air filters collected at Yellowknife, Resolute, and Quebec City locations. Using the known initial cesium-134/cesium-137 ratio stemming from this incident, along with a statistical assessment of the normality of the data distribution, we herein present evidence that strongly suggests that these activity spikes are due to re-suspended hot particles originating from the Fukushima-Daiichi nuclear power plant incident. Moreover, we have evidence to suggest that this re-suspension is localized in nature. This study provided empirical insight into the transport and uptake of radionuclides over vast distances, and it demonstrates that the CRMN was able to detect evidence of a re-suspension of Fukushima-Daiichi related isotopes.

Watershed processing of atmospheric polychlorinated biphenyl inputs.

PubMed

Rowe, Amy A; Totten, Lisa A; Cavallo, Gregory I; Yagecic, John R

2007-04-01

Indirect atmospheric deposition of PCBs was examined in subwatersheds of the Delaware River Estuary. Tributary PCB loads and atmospheric PCB concentrations were used to understand the pass-through efficiencies for nine rivers/ creeks for which PCB inputs appeared to be dominated by atmospheric deposition. The pass-through efficiency, E, was calculated from tributary loads and atmospheric deposition fluxes. Unfortunately, uncertainties in the gaseous and dry particle deposition velocities, vg and vd, respectively, render the calculated atmospheric deposition fluxes highly uncertain. In order to circumvent this problem, export of PCBs from the watershed was related directly to atmospheric PCB concentrations via a new mass transfer coefficient, the watershed delivery rate or vws, which describes the process by which the watershed transfers PCBs from the airto the River's main stem. vws increases with increasing chlorination and is significantly correlated with vapor pressure. This trend suggests that the transfer of PCBs from the atmosphere to the River via the watershed is more efficient for high molecular weight PCBs than for low molecular weight PCBs. This may indicate that the selected watersheds are at or close to equilibrium with respect to gaseous exchange of PCBs, such that lower molecular weight congeners undergo substantial revolatilization after deposition. The magnitude of the pass-through efficiency, E, depends on the deposition velocities used to calculate the atmospheric deposition flux, but when congener-specific deposition velocities are used, E is independent of vapor pressure and is relatively constant at about 3%.

Data for atmospheric arsenic deposition: A case study- northeast of Iran.

PubMed

Atarodi, Zahra; Alinezhad, Javad; Amiri, Reza; Safari, Yahya; Yoosefpour, Nasrin

2018-08-01

Air pollution is the major health concern in modern societies, especially in countries with arid and aggressive climate. Nowadays extensive research has been carried out to identify air pollution and its control. The main aim of this study is determine the atmospheric arsenic deposition concentration in Gonabad County in northeast Iran. In this cross-sectional study, the concentration of arsenic was measured by collecting of PM 10 deposition from the ambient air of Gonabad urban areas. Samples were firstly taken by jar test method in four one-month periods in 2016 from Taleghani st., Imam Khomeini sq., Mend sq., Ghaffari st., and Sadi st., and arsenic concentration in the particles were determined by the Graphite furnace atomic absorption spectroscopy (GFAAS). The results indicated that the maximum and minimum concentrations (average) of particles PM 10 depositing was observed in Taleghani st. about 10.395 ± 1.183 µg/kg and Imam Khomeini sq. about 4.394 ± 0.961 µg/kg, respectively. The maximum and minimum concentration of arsenic concentrations were estimated to be respectively 12.080 and 3.560 µg/kg in December and September, respectively. The results showed that in the northern part of the city, due to the wind blow, there are more particles in the air and people living in these areas are more exposed to arsenic. Therefore, residents of these areas need more actions that are preventive.

Spatial and temporal variation in sources of atmospheric nitrogen deposition in the Rocky Mountains using nitrogen isotopes

USGS Publications Warehouse

Nanus, Leora; Campbell, Donald H.; Lehmann, Christopher M.B.; Mast, M. Alisa

2018-01-01

Variation in source areas and source types of atmospheric nitrogen (N) deposition to high-elevation ecosystems in the Rocky Mountains were evaluated using spatially and temporally distributed N isotope data from atmospheric deposition networks for 1995-2016. This unique dataset links N in wet deposition and snowpack to mobile and stationary emissions sources, and enhances understanding of the impacts of anthropogenic activities and environmental policies that mitigate effects of accelerated N cycling across the Rocky Mountain region. δ15N−NO3− at 50 U.S. Geological Survey Rocky Mountain Snowpack (Snowpack) sites ranged from −3.3‰ to +6.5‰, with a mean value of +1.4‰. At 15 National Atmospheric Deposition Program (NADP)/National Trends Network wet deposition (NADP Wetfall) sites, summer δ15N−NO3− is significantly lower ranging from −7.6‰ to −1.3‰ while winter δ15N−NO3− ranges from −2.6‰ to +5.5‰, with a mean value of +0.7‰ during the cool season. The strong seasonal difference in NADP Wetfall δ15N−NO3− is due in part to variation in the proportion of N originating from source regions at different times of the year due to seasonal changes in weather patterns. Snowpack NO3− and δ15N−NO3− are significantly related to NADP Wetfall (fall and winter) suggesting that bulk snowpack samples provide a reliable estimate at high elevations. Spatial trends show higher NO3−concentrations and δ15N−NO3− in the Southern Rocky Mountains located near larger anthropogenic N emission sources compared to the Northern Rocky Mountains. NADP Wetfall δ15N−NH4+ ranged from −10‰ to 0‰, with no observed spatial pattern. However, the lowest δ15N−NH4+(−9‰), and the highest NH4+ concentration (35 μeq/L) were observed at a Utah site dominated by local agricultural activities, whereas the higher δ15N−NH4+observed in Colorado and Wyoming are likely due to mixed sources, including fossil fuel combustion and

Spatial and temporal variation in sources of atmospheric nitrogen deposition in the Rocky Mountains using nitrogen isotopes

NASA Astrophysics Data System (ADS)

Nanus, Leora; Campbell, Donald H.; Lehmann, Christopher M. B.; Mast, M. Alisa

2018-03-01

Variation in source areas and source types of atmospheric nitrogen (N) deposition to high-elevation ecosystems in the Rocky Mountains were evaluated using spatially and temporally distributed N isotope data from atmospheric deposition networks for 1995-2016. This unique dataset links N in wet deposition and snowpack to mobile and stationary emissions sources, and enhances understanding of the impacts of anthropogenic activities and environmental policies that mitigate effects of accelerated N cycling across the Rocky Mountain region. δ15N-NO3- at 50 U.S. Geological Survey Rocky Mountain Snowpack (Snowpack) sites ranged from -3.3‰ to +6.5‰, with a mean value of +1.4‰. At 15 National Atmospheric Deposition Program (NADP)/National Trends Network wet deposition (NADP Wetfall) sites, summer δ15N-NO3- is significantly lower ranging from -7.6‰ to -1.3‰ while winter δ15N-NO3- ranges from -2.6‰ to +5.5‰, with a mean value of +0.7‰ during the cool season. The strong seasonal difference in NADP Wetfall δ15N-NO3- is due in part to variation in the proportion of N originating from source regions at different times of the year due to seasonal changes in weather patterns. Snowpack NO3- and δ15N-NO3- are significantly related to NADP Wetfall (fall and winter) suggesting that bulk snowpack samples provide a reliable estimate at high elevations. Spatial trends show higher NO3- concentrations and δ15N-NO3- in the Southern Rocky Mountains located near larger anthropogenic N emission sources compared to the Northern Rocky Mountains. NADP Wetfall δ15N-NH4+ ranged from -10‰ to 0‰, with no observed spatial pattern. However, the lowest δ15N-NH4+(-9‰), and the highest NH4+ concentration (35 μeq/L) were observed at a Utah site dominated by local agricultural activities, whereas the higher δ15N-NH4+ observed in Colorado and Wyoming are likely due to mixed sources, including fossil fuel combustion and agricultural sources. These findings show spatial and

Particle deposition onto people in a transit venue

DOE PAGES

Liljegren, James C.; Brown, David F.; Lunden, Melissa M.; ...

2016-07-11

Following the release of an aerosolized biological agent in a transit venue, material deposited on waiting passengers and subsequently shed from their clothing may significantly magnify the scope and consequences of such an attack. Published estimates of the relevant particle deposition and resuspension parameters for complex, real-world environments such as a transit facility are non-existent. In this study, measurements of particle deposition velocity onto cotton fabric samples affixed to stationary and walking persons in a large multimodal transit facility were obtained for tracer particle releases carried out as part of a larger study of subway airflows and particulate transport. Depositionmore » velocities onto cotton and wool were also obtained using a novel automated sampling mechanism deployed at locations in the transit facility and throughout the subway. The data revealed higher deposition velocities than have been previously reported for people exposed in test chambers or office environments. Furthermore, the relatively high rates of deposition onto people in a transit venue obtained in this study suggest it is possible that fomite transport by subway and commuter/regional rail passengers could present a significant mechanism for rapidly dispersing a biological agent throughout a metropolitan area and beyond.« less

Particle deposition onto people in a transit venue

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

Liljegren, James C.; Brown, David F.; Lunden, Melissa M.

Following the release of an aerosolized biological agent in a transit venue, material deposited on waiting passengers and subsequently shed from their clothing may significantly magnify the scope and consequences of such an attack. Published estimates of the relevant particle deposition and resuspension parameters for complex, real-world environments such as a transit facility are non-existent. In this study, measurements of particle deposition velocity onto cotton fabric samples affixed to stationary and walking persons in a large multimodal transit facility were obtained for tracer particle releases carried out as part of a larger study of subway airflows and particulate transport. Depositionmore » velocities onto cotton and wool were also obtained using a novel automated sampling mechanism deployed at locations in the transit facility and throughout the subway. The data revealed higher deposition velocities than have been previously reported for people exposed in test chambers or office environments. Furthermore, the relatively high rates of deposition onto people in a transit venue obtained in this study suggest it is possible that fomite transport by subway and commuter/regional rail passengers could present a significant mechanism for rapidly dispersing a biological agent throughout a metropolitan area and beyond.« less

Deep sediment resuspension and thick nepheloid layer generation by open-ocean convection

NASA Astrophysics Data System (ADS)

Durrieu de Madron, X.; Ramondenc, S.; Berline, L.; Houpert, L.; Bosse, A.; Martini, S.; Guidi, L.; Conan, P.; Curtil, C.; Delsaut, N.; Kunesch, S.; Ghiglione, J. F.; Marsaleix, P.; Pujo-Pay, M.; Séverin, T.; Testor, P.; Tamburini, C.

2017-03-01

The Gulf of Lions in the northwestern Mediterranean is one of the few sites around the world ocean exhibiting deep open-ocean convection. Based on 6 year long (2009-2015) time series from a mooring in the convection region, shipborne measurements from repeated cruises, from 2012 to 2015, and glider measurements, we report evidence of bottom thick nepheloid layer formation, which is coincident with deep sediment resuspension induced by bottom-reaching convection events. This bottom nepheloid layer, which presents a maximum thickness of more than 2000 m in the center of the convection region, probably results from the action of cyclonic eddies that are formed during the convection period and can persist within their core while they travel through the basin. The residence time of this bottom nepheloid layer appears to be less than a year. In situ measurements of suspended particle size further indicate that the bottom nepheloid layer is primarily composed of aggregates between 100 and 1000 µm in diameter, probably constituted of fine silts. Bottom-reaching open ocean convection, as well as deep dense shelf water cascading that occurred concurrently some years, lead to recurring deep sediments resuspension episodes. They are key mechanisms that control the concentration and characteristics of the suspended particulate matter in the basin, and in turn affect the bathypelagic biological activity.

Atmospheric deposition fluxes and solubility over the Southern Indian Ocean: time series on Kerguelen and Crozet Islands.

NASA Astrophysics Data System (ADS)

Heimburger, Alexie; Losno, Remi; Triquet, Sylvain; Bon Nguyen, Elisabeth

2013-04-01

Atmospheric supplies bringing trace metals are suspected to have a significant impact on biogeochemical processes in High-Nutrient-Low-Chlorophyll waters of the open ocean, such as the Southern Ocean. We recorded time series of atmospheric deposition samples continuously collected over two years on Kerguelen and Crozet Islands in the Southern Indian Ocean. Dust deposition flux and scavenging ratio on Kerguelen Islands were reported in a previous publication [Heimburger et al., GBC, 2012]. Here, we present results of total atmospheric deposition fluxes for a large suite of elements (Al, As, Ba, Ca, Ce, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Na, Nd, Ni, Pb including isotopes, Rb, S, Si, Sr, Ti, U, V, Zn), which are identified as coming either from sea-salt, crustal or anthropogenic sources. Enrichment factor variabilities for Pb, As, Cr, Cu and V and Pb isotopic ratios highlight the anthropogenic contribution during the austral winter only. For Al, Fe, Mn and Si, deposition fluxes are similar for both Kerguelen and Crozet Islands, which are situated 1300 km apart, and so can be extrapolated for the entire Southern Indian Ocean. Over the entire sampling period, those fluxes are on average equal to 53 ± 2 µg/m²/d, 33 ± 1 µg/m²/d, 0.83 ± 0.04 µg/m²/d and 88 ± 14 µg/m²/d respectively. For the other non-sea-salt elements, we observed differences between flux values from a factor of two to a factor of five with a decreasing gradient from Crozet to Kerguelen Islands. One-month field experiments were also performed during four different austral summers in order to collect rain water on an event basis. Soluble and insoluble fractions were directly separated by filtration and analysed using High Resolution - Inductively Coupled Plasma - Mass Spectrometry and Inductively Coupled Plasma-Atomic Emission Spectrometry as done for deposition samples. Concentrations in rain water samples are very low and difficult to measure accurately mainly because of possible contamination

Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of atmospheric dispersion model with improved deposition scheme and oceanic dispersion model

NASA Astrophysics Data System (ADS)

Katata, G.; Chino, M.; Kobayashi, T.; Terada, H.; Ota, M.; Nagai, H.; Kajino, M.; Draxler, R.; Hort, M. C.; Malo, A.; Torii, T.; Sanada, Y.

2014-06-01

Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Dai-ichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate a detailed time trend of atmospheric releases during the accident by combining environmental monitoring data with atmospheric model simulations from WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information), and simulations from the oceanic dispersion model SEA-GEARN-FDM, both developed by the authors. A sophisticated deposition scheme, which deals with dry and fogwater depositions, cloud condensation nuclei (CCN) activation and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The fallout to the ocean surface calculated by WSPEEDI-II was used as input data for the SEA-GEARN-FDM calculations. Reverse and inverse source-term estimation methods based on coupling the simulations from both models was adopted using air dose rates and concentrations, and sea surface concentrations. The results revealed that the major releases of radionuclides due to FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, the morning of 13 March after the venting event at Unit 3, midnight of 14 March when the SRV (Safely Relief Valve) at Unit 2 was opened three times, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of

Lake-specific responses to elevated atmospheric nitrogen deposition in the Colorado Rocky Mountains, U.S.A.

USGS Publications Warehouse

Nydick, K.R.; LaFrancois, B.M.; Baron, Jill S.; Johnson, B.M.

2003-01-01

We explored variability among subalpine lakes sharing very similar climate and atmospheric conditions, but differing in watershed characteristics, hydrology, and food web structure. Special attention was given to nitrogen (N) dynamics because the study area receives some of the highest levels of atmospheric N deposition in the Rocky Mountains. We asked if the effect of regional N deposition would be manifested uniformly among neighboring lakes both in terms of ambient conditions and responses to greater nutrient inputs. Catchment vegetation appeared to be the main determinant of ambient nitrate (NO3), phosphate (PO4), and dissolved organic carbon (DOC) concentrations, although in-lake differences in recycling produced variable and contrasting NH4 levels. Phytoplankton chlorophyll a temporarily responded to early season NO3 peaks in the lakes with rocky watersheds, but chlorophyll means over the ice-free season were remarkably similar among lakes despite differences in both nutrient supply and zooplankton grazing. In most cases, phosphorus was limiting to phytoplankton growth, although the importance of N deficiencies was greater in lakes with forested watersheds and fringing wetlands.

Lake-specific responses to elevated atmospheric nitrogen deposition in the Colorado Rocky Mountains, U.S.A

USGS Publications Warehouse

Nydick, K.R.; LaFrancois, B.M.; Baron, Jill S.; Johnson, B.M.

2003-01-01

We explored variability among subalpine lakes sharing very similar climate and atmospheric conditions, but differing in watershed characteristics, hydrology, and food web structure. Special attention was given to nitrogen (N) dynamics because the study area receives some of the highest levels of atmospheric N deposition in the Rocky Mountains. We asked if the effect of regional N deposition would be manifested uniformly among neighboring lakes both in terms of ambient conditions and responses to greater nutrient inputs. Catchment vegetation appeared to be the main determinant of ambient nitrate (NO3), phosphate (PO4), and dissolved organic carbon (DOC) concentrations, although in-lake differences in recycling produced variable and contrasting NH4 levels. Phytoplankton chlorophyll atemporarily responded to early season NO3 peaks in the lakes with rocky watersheds, but chlorophyll means over the ice-free season were remarkably similar among lakes despite differences in both nutrient supply and zooplankton grazing. In most cases, phosphorus was limiting to phytoplankton growth, although the importance of N deficiencies was greater in lakes with forested watersheds and fringing wetlands.

Deposition of carbon-free silicon dioxide from pure hexamethyldisiloxane using an atmospheric microplasma jet

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

Raballand, V.; Benedikt, J.; Keudell, A. von

2008-03-03

Carbon-free silicon dioxide has been deposited at room temperature by injection of pure hexamethyldisiloxane (HMDSO) into an atmospheric pressure microplasma jet from argon. At low HMDSO flow rates [<0.1 SCCM (SCCM denotes cubic centimeter per minute at STP)], the SiO{sub x}H{sub z} films contain no carbon and exhibit an oxygen to silicon ratio close to 2 according to x-ray photoelectron spectroscopy. At high HMDSO flow rates (>0.1 SCCM), SiO{sub x}C{sub y}H{sub z} films with a carbon content of up to 21% are obtained. The transition between organic to inorganic film is confirmed by Fourier transformed infrared spectroscopy. The deposition ofmore » inorganic films without oxygen admixture is explained by an ion-induced polymerization scheme of HMDSO.« less

Temporal and Spatial Variation of Atmospherically Deposited Organic Contaminants at High Elevation in Yosemite National Park, California, USA

EPA Science Inventory

Atmospherically deposited organic contaminants in the Sierra Nevada mountains of California, USA, have exceeded some thresholds of concern, but the spatial and temporal distributions of contaminants in the mountains are not well known. The present study evaluated (1) whether the...

Energy deposition and middle atmosphere electrodynamic response to a highly relativistic electron precipitation event

NASA Technical Reports Server (NTRS)

Goldberg, R. A.; Baker, D. N.; Herrero, F. A.; Mccarthy, S. P.; Twigg, P. A.; Croskey, C. L.; Hale, L. C.

1994-01-01

Rocket data have been used to evaluate the characteristics of precipitating relativistic electrons and their effects on the electrodynamic structure of the middle atmosphere. These data were obtained at Poker Flat, Alaska, on May 13 and 14, 1990, during a midday, highly relativistic electron (HRE) precipitation event. Solid state detectors were used to measure the electron fluxes and their energy spectra. An X ray scintillator was included on each flight to measure bremsstrahlung X rays produced by energetic electrons impacting on the upper atmosphere. However, these were found the be of negligible importance for this particular event. The energy deposition by the electrons has been determined from the flux measurements and compared with in situ measurements of the atmospheric electrical response. The electrodynamic measurements were obtained by the same rockets and additionally on May 13, with an accompanying rocket. The impact flux was highly irregular, containing short-lived bursts of relativistic electrons, mainly with energies below 0.5 MeV and with fluxes most enhanced between pitch angles of 0 deg - 20 deg. Although the geostationary counterpart of this measured event was considered to be of relatively low intensity and hardness, energy deposition peaked near 75 km with fluxes approaching an ion pair production rate in excess of 100/cu cm s. This exceeds peak fluxes in relativistic electron precipitation (REP) events as observed by us in numerous rocket soundings since 1976. Conductivity measurements from a blunt probe showed that negative electrical conductivities exceeded positive conductivities down to 50 km or lower, consistent with steady ionization by precipitating electrons above 1 MeV. These findings imply that the electrons from the outer radiation zone can modulate the electrical properties of the middle atmosphere to altitudes below 50 km. During the decline and activity minimum of the current solar cycle, we anticipate the occurence of similar

Energy deposition and middle atmosphere electrodynamic response to a highly relativistic electron precipitation event

NASA Astrophysics Data System (ADS)

Goldberg, R. A.; Baker, D. N.; Herrero, F. A.; McCarthy, S. P.; Twigg, P. A.; Croskey, C. L.; Hale, L. C.

1994-10-01

Rocket data have been used to evaluate the characteristics of precipitating relativistic electrons and their effects on the electrodynamic structure of the middle atmosphere. These data were obtained at Poker Flat, Alaska, on May 13 and 14, 1990, during a midday, highly relativistic electron (HRE) precipitation event. Solid state detectors were used to measure the electron fluxes and their energy spectra. An X ray scintillator was included on each flight to measure bremsstrahlung X rays produced by energetic electrons impacting on the upper atmosphere. However, these were found the be of negligible importance for this particular event. The energy deposition by the electrons has been determined from the flux measurements and compared with in situ measurements of the atmospheric electrical response. The electrodynamic measurements were obtained by the same rockets and additionally on May 13, with an accompanying rocket. The impact flux was highly irregular, containing short-lived bursts of relativistic electrons, mainly with energies below 0.5 MeV and with fluxes most enhanced between pitch angles of 0 deg - 20 deg. Although the geostationary counterpart of this measured event was considered to be of relatively low intensity and hardness, energy deposition peaked near 75 km with fluxes approaching an ion pair production rate in excess of 100/cu cm s. This exceeds peak fluxes in relativistic electron precipitation (REP) events as observed by us in numerous rocket soundings since 1976. Conductivity measurements from a blunt probe showed that negative electrical conductivities exceeded positive conductivities down to 50 km or lower, consistent with steady ionization by precipitating electrons above 1 MeV. These findings imply that the electrons from the outer radiation zone can modulate the electrical properties of the middle atmosphere to altitudes below 50 km. During the decline and activity minimum of the current solar cycle, we anticipate the occurence of similar

Manganese deposition in drinking water distribution systems.

PubMed

Gerke, Tammie L; Little, Brenda J; Barry Maynard, J

2016-01-15

This study provides a physicochemical assessment of manganese deposits on brass and lead components from two fully operational drinking water distributions systems. One of the systems was maintained with chlorine; the other, with secondary chloramine disinfection. Synchrotron-based in-situ micro X-ray adsorption near edge structure was used to assess the mineralogy. In-situ micro X-ray fluorescence mapping was used to demonstrate the spatial relationships between manganese and potentially toxic adsorbed metal ions. The Mn deposits ranged in thickness from 0.01 to 400 μm. They were composed primarily of Mn oxides/oxhydroxides, birnessite (Mn(3+) and Mn(4+)) and hollandite (Mn(2+) and Mn(4+)), and a Mn silicate, braunite (Mn(2+) and Mn(4+)), in varying proportions. Iron, chromium, and strontium, in addition to the alloying elements lead and copper, were co-located within manganese deposits. With the exception of iron, all are related to specific health issues and are of concern to the U.S. Environmental Protection Agency (U.S. EPA). The specific properties of Mn deposits, i.e., adsorption of metals ions, oxidation of metal ions and resuspension are discussed with respect to their influence on drinking water quality. Copyright © 2015 Elsevier B.V. All rights reserved.

Multiscale Framework for Assessing Critical Loads of Atmospheric Nitrogen Deposition for Aquatic Ecosystems in Wilderness Areas of the Western United States

NASA Astrophysics Data System (ADS)

Nanus, Leora; Clow, David; Saros, Jasmine; McMurray, Jill; Blett, Tamara; Sickman, James

2017-04-01

High-elevation aquatic ecosystems in Wilderness areas of the western United States are impacted by current and historic atmospheric nitrogen (N) deposition associated with local and regional air pollution. Documented effects include elevated surface water nitrate concentrations, increased algal productivity, and changes in diatom species assemblages. A predictive framework was developed for sensitive high-elevation basins across the western United States at multiple spatial scales including the Rocky Mountain Region (Rockies), the Greater Yellowstone Area (GYA), and Yosemite (YOSE) and Sequoia & Kings Canyon (SEKI) National Parks. Spatial trends in critical loads of N deposition for nutrient enrichment of aquatic ecosystems were quantified and mapped using a geostatistical approach, with modeled N deposition, topography, vegetation, geology, and climate as potential explanatory variables. Multiple predictive models were created using various combinations of explanatory variables; this approach allowed for better quantification of uncertainty and identification of areas most sensitive to high atmospheric N deposition (> 3 kg N ha-1 yr-1). For multiple spatial scales, the lowest critical loads estimates (<1.5 + 1 kg N ha-1 yr-1) occurred in high-elevation basins with steep slopes, sparse vegetation, and exposed bedrock and talus. Based on a nitrate threshold of 1 μmol L-1, estimated critical load exceedances (>1.5 + 1 kg N ha-1 yr-1) correspond with areas of high N deposition and vary spatially ranging from less than 20% to over 40% of the study area for the Rockies, GYA, YOSE, and SEKI. These predictive models and maps identify sensitive aquatic ecosystems that may be impacted by excess atmospheric N deposition and can be used to help protect against future anthropogenic disturbance. The approach presented here may be transferable to other remote and protected high-elevation ecosystems at multiple spatial scales that are sensitive to adverse effects of pollutant

Critical loads of atmospheric deposition to Adirondack lake watersheds: A guide for policymakers

USGS Publications Warehouse

Burns, Douglas A.; Sullivan, Timothy J.

2015-01-01

Acid deposition is sometimes referred to as “acid rain,” although part of the acid load reaches the surface by means other than rainfall. In the eastern U.S., acid deposition consists of several forms of sulfur and nitrogen that largely originate as emissions to the atmosphere from sources such as electricity-generating facilities (coal, oil, and natural gas), diesel- and gasoline-burning vehicles, some agricultural activities, and smokestack industries. Acid deposition is known to cause deleterious effects to sensitive ecosystems of which the Adirondack region of New York State provides several well-known and well-studied examples. This largely forested region includes abundant lakes, streams, and wetlands and possesses several landscape features that result in high ecosystem sensitivity to acid deposition. These features include bedrock that weathers slowly, steep slopes, and thin, naturally acidic soils. An ecosystem is described as sensitive to, or affected by, acid deposition if prolonged exposure to acid deposition has resulted in detrimental ecosystem effects. Soils, streams, and lakes that are less sensitive are better able to buffer acid deposition. A principal reason that acidification is a concern for resource managers is because of the changes induced in native biota and their habitat on land and in water. As the chemistry of soils and surface waters in sensitive landscapes changes in response to prolonged exposure to acid deposition, organisms that cannot tolerate high acidity, such as sugar maple trees and many species of fish and aquatic insects, may be gradually eliminated from the ecosystem. Other biota such as red spruce may experience increased stress and reduced growth rates as a result of acidification, exposing these species to increased susceptibility to disease and other natural stressors and perhaps increased mortality. The ecological effects of acid deposition have been documented by extensive research that began in the U.S. in the

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.

Use of fallout radionuclides ((7)Be, (210)Pb) to estimate resuspension of Escherichia coli from streambed sediments during floods in a tropical montane catchment.

PubMed

Ribolzi, Olivier; Evrard, Olivier; Huon, Sylvain; Rochelle-Newall, Emma; Henri-des-Tureaux, Thierry; Silvera, Norbert; Thammahacksac, Chanthamousone; Sengtaheuanghoung, Oloth

2016-02-01

Consumption of water polluted by faecal contaminants is responsible for 2 million deaths annually, most of which occur in developing countries without adequate sanitation. In tropical aquatic systems, streambeds can be reservoirs of persistent pathogenic bacteria and high rainfall can lead to contaminated soils entering streams and to the resuspension of sediment-bound microbes in the streambed. Here, we present a novel method using fallout radionuclides ((7)Be and (210)Pbxs) to estimate the proportions of Escherichia coli, an indicator of faecal contamination, associated with recently eroded soil particles and with the resuspension of streambed sediments. We show that using these radionuclides and hydrograph separations we are able to characterize the proportion of particles originating from highly contaminated soils and that from the resuspension of particle-attached bacteria within the streambed. We also found that although overland flow represented just over one tenth of the total flood volume, it was responsible for more than two thirds of the downstream transfer of E. coli. We propose that data obtained using this method can be used to understand the dynamics of faecal indicator bacteria (FIB) in streams thereby providing information for adapted management plans that reduce the health risks to local populations. Graphical Abstract Graphical abstract showing (1) the main water flow processes (i.e. overland flow, groundwater return flow, blue arrows) and sediment flow components (i.e. resuspension and soil erosion, black arrows) during floods in the Houay Pano catchment; (2) the general principle of the method using fallout radionuclide markers (i.e. (7)Be and (210)Pbxs) to estimate E. coli load from the two main sources (i.e. streambed resuspension vs soil surface washoff); and 3) the main results obtained during the 15 May 2012 storm event (i.e. relative percentage contribution of each process to the total streamflow, values in parentheses).

Increasing and decreasing trends of the atmospheric deposition of organochlorine compounds in European remote areas during the last decade

NASA Astrophysics Data System (ADS)