Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 41
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
Sci Total Environ ; 743: 140695, 2020 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-32679494

RESUMO

Tree-ring records are a potential archive for reconstructing long-term historical trends in atmospheric mercury (Hg) concentrations. Although Hg preserved in tree rings has been shown to be derived largely from the atmosphere, quantitative relationships linking atmospheric concentrations to those in tree rings are limited. In addition, few tree-ring-based Hg records have been evaluated against co-located proxies of atmospheric Hg deposition or direct atmospheric measurements. Here we develop long-term Hg records extending from 1800 to 2018 CE using cores collected from two stands of whitebark pine located near the Upper Fremont Glacier in the Wind River Range, Wyoming, where a long-term record of atmospheric Hg deposition previously was developed from an ice core. The tree ring record showed that Hg concentrations increased beginning in 1800 CE to a broad peak centered at ~1960 CE, before decreasing to present, generally paralleling the ice-core record of Hg deposition. The exact timing and magnitude of the Hg increases in the trees, however, is offset earlier relative to the ice-core record. These discrepancies potentially arise from biotic processes that impact Hg uptake and preservation in whitebark pine, and results from an advection-diffusion model indicate that the temporal differences are consistent with radial movement of Hg within the trees. The forms of atmospheric Hg and seasonality may also impact the Hg record preserved by each archive, but are less likely to affect long-term trends. Further work is needed to assess radial Hg translocation in more controlled studies with larger sample sizes.

2.
Environ Sci Technol ; 54(13): 7922-7931, 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32506903

RESUMO

To advance our understanding of the mercury (Hg) biogeochemical cycle, concentrations and chemistry of gaseous oxidized Hg (GOM), particulate-bound Hg (PBM), and reactive Hg (RM = GOM + PBM) need to be known. The UNR-RMAS 2.0 provides a solution that will advance knowledge. From 11/2017 to 02/2019, the RMAS 2.0 was deployed in Hawai'i, Nevada, Maryland, and Utah to test system performance and develop an understanding of RM at locations impacted by different atmospheric oxidants. Mauna Loa Observatory, Hawai'i, impacted by the free troposphere and the marine boundary layer, had primarily -Br/Cl RM compounds. The Nevada location, directly adjacent to a major interstate highway and experiences inputs from the free troposphere, exhibited -Br/Cl, -N, -S, and organic compounds. In Maryland, compounds observed were -N, -S, and organic-Hg. This site is downwind of coal-fired power plants and located in a forested area. The location in Utah is in a basin impacted by oil and natural gas extraction, multiday wintertime inversion episodes, and inputs from the free troposphere. Compounds were -Br/Cl or -O, -N, and -Br/Cl. The chemical forms of RM identified were consistent with the air source areas, predominant ion chemistry, criterion air pollutants, and meteorology.

4.
Environ Sci Technol ; 53(24): 14489-14495, 2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31742397

RESUMO

The atmosphere is an important (1) pathway by which mercury (Hg) is transported around the globe and (2) source of Hg to ecosystems. Thus, understanding Hg atmospheric chemistry is critical for understanding the biogeochemical cycle and impacts to human and ecosystem health. Work over the past 13 years has demonstrated that the standard instrument used to measure atmospheric Hg does not accurately quantify gaseous oxidized mercury (GOM) or particulate bound mercury (PBM). This study focused on comparing four methods for quantifying atmospheric Hg and identifying Hg(II) compounds. Data from two automated systems, the Tekran 2537/1130 system and the University of Nevada, Reno-Dual Channel System (DCS), were compared with two University of Nevada, Reno-Reactive Mercury Active Systems (RMAS 2.0). One RMAS 2.0 included cation exchange membranes (CEMs) and nylon membranes, and the second included a polytetrafluoroethylene (PTFE) membrane upstream of the CEM and nylon membranes. The Tekran system and the DCS underestimated GOM concentrations with respect to that measured using the RMAS 2.0. The RMAS 2.0 with the upstream PTFE provided a means of distinguishing GOM and PBM. Thermal desorption of nylon membrane data identified a variety of GOM and PBM compounds present.


Assuntos
Poluentes Atmosféricos , Mercúrio , Ecossistema , Monitoramento Ambiental , Gases
5.
Sci Total Environ ; 684: 276-280, 2019 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-31153074

RESUMO

Commercial pet foods should be safe for long-term feeding. However, recent recalls and lawsuits have eroded public trust in pet food companies and products. Recent studies have identified high concentrations of mercury, a potent neurotoxin, in pet food products. Here we posit that pet food products require independent testing to verify safety and compliance with developed Food and Drug Administration and Association of American Feed Control Officials standards, and initiate a discussion as to why including quantification of mercury and methylmercury, as well as the identification of adulteration, are important to such testing protocols. The outcomes of these discussions will be multi-faceted: initiating the impetus to investigate the quality and label accuracy of pet foods; ensuring product safety; promoting transparency within the pet food industry; informing veterinary practices regarding pet food recommendations; providing data for evidence-based policy and regulatory enforcement; and working toward fulfilling the National Research Council's call for research that identifies levels of contaminants in animal feeds and residues in human foods.


Assuntos
Ração Animal/análise , Exposição Ambiental , Poluentes Ambientais/análise , Contaminação de Alimentos/análise , Mercúrio/análise , Animais , Gatos , Cães , Monitoramento Ambiental
6.
Environ Sci Technol ; 53(7): 3663-3671, 2019 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-30865434

RESUMO

This study investigated the methodology and utility of dendrochemistry in the assessment of spatial and temporal concentrations of gaseous elemental mercury. Tree cores from the Pinus species in California and Nevada, U.S.A. were collected from previously sampled areas to test the stability of tree ring concentrations over time. Cores were collected from 2 new locations to assess spatial variability among trees within and between stands located at two elevations in the same watershed. Results indicated that using 2 to 3 cores from ∼10 or more trees provided the best framework for understanding tree ring concentrations within a population of trees located in uncontaminated areas. At the least 2 sides of a tree should be cored to account for radially asymmetric variations associated with growing conditions or injury. An agreement of concentrations and trends measured in trees cored with previous research indicated that tree rings are suitable proxies for historical air mercury concentrations and that mercury concentrations have increased since the Industrial Revolution. Data collected demonstrate that tree rings record regional gradients in GEM concentrations. In addition, temporal consistency may vary within a geographic location due to differing biotic and abiotic factors influencing ring growth since trees are active samplers of atmospheric Hg.


Assuntos
Poluentes Atmosféricos , Mercúrio , California , Monitoramento Ambiental , Poluição Ambiental , Nevada
7.
Sci Total Environ ; 615: 1411-1427, 2018 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-29751446

RESUMO

Ambient air particulate matter (<2.5µm in diameter) samples were collected on two different filter types in 2014 and 2015 over 24h periods and analyzed for reactive mercury (gaseous oxidized mercury+particulate bound mercury) concentrations and lead isotopes to determine sources of pollution to three sites in Nevada, USA. Two sites were located on the western edge of Nevada (Reno, urban, 1370m and Peavine Peak, rural, high elevation, 2515m); the third location was ~485km east in rural Great Basin National Park, NV (2061m). Reactive mercury samples were collected on cation exchange membranes simultaneously with lead samples, collected on Teflon membranes. Lead isotopic ratios have previously identified trans-Pacific lead sources based on the 206/207 and 208/207 lead ratios. Influence from trans-Pacific air masses was higher from March to June associated with long-range transport of pollutants. Spring months are well known for increased transport across the Pacific; however, fall months were also influenced by trans-Pacific air masses in this study. Western North American background ozone concentrations have been measured and modeled at 50 to 55ppbv. Median ozone concentrations at both rural sites in Nevada were within this range. Sources leading to enhancements in ozone of 2 to 18ppbv above monthly medians in Nevada included emissions from Eurasia, regional urban centers, and global and regional wildfires, resulting in concentrations close to the USA air quality standard. At the high elevation locations, ozone was derived from pollutants being transported in the free troposphere that originate around the globe; however, Eurasia and Asia were dominant sources to the Western USA. Negative correlations between reactive mercury and percent Asian lead, Northern Eurasia and East Asia trajectories indicated reactive mercury concentrations at the two high elevation sites were produced by oxidants from local, regional, and marine boundary layer sources.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Mercúrio/análise , Ozônio/análise , Material Particulado/análise , Poluição do Ar/estatística & dados numéricos , Isótopos , Chumbo , Nevada
8.
Environ Sci Technol ; 52(3): 1174-1182, 2018 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-29232509

RESUMO

To determine whether trees are reliable biomonitors of air mercury (Hg) pollution concentrations were measured in bark, foliage, and tree rings. Data were developed using 4-year old Pinus and Populus trees grown from common genetic stock in Oregon and subsequently transferred to four air treatments differing in gaseous oxidized mercury (GOM) chemistry and total gaseous Hg (TGM) concentrations. Soil of a subset of trees was spiked with HgBr2 in solution to test for root uptake. Results indicate no significant effect of the soil spike or GOM compounds on tree tissue Hg concentrations. TGM treatment had a significant effect on Pinus and Populus foliage, and Pinus year 5 growth ring concentrations. Populus foliar Hg concentrations were highest in the exposure where 24 h TGM concentrations were highest, indicating the importance of the nonstomatal pathway for uptake. Pinus tree ring concentrations were correlated to day time TGM concentrations suggesting Hg accumulation into tree rings is by way of the stomata and subsequent translocation by way of phloem. Populus leaves and Pinus rings can be used as biomonitors for TGM concentrations over space. However, the use of trees as temporal proxies requires further investigation due to radial translocation observed in active sapwood tree rings.


Assuntos
Mercúrio , Pinus , Áustria , Monitoramento Ambiental , Oregon
9.
Environ Sci Technol ; 51(1): 436-445, 2017 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-27966905

RESUMO

The Teledyne Advanced Pollution Instrumentation (TAPI) model 602 BetaPlus particulate system provides nondestructive analysis of particulate matter (PM2.5) mass concentration. This instrument was used to determine if measurements made with cation exchange membranes (CEM) were comparable to standard methods, the ß attenuation method at two locations in Reno, NV and an environmental ß attenuation method and gravimetric method at Great Basin National Park, NV. TAPI PM2.5 CEM measurements were statistically similar to the other three PM2.5 methods. Once this was established, the second objective, a destructive method for measurement of reactive mercury (RM = gaseous oxidized and particulate bound Hg), was tested. Samples collected at 16.7 L per min (Lpm) for 24 h on CEM from the TAPI were compared to those measured by the University of Nevada, Reno-Reactive Mercury Active System (UNRRMAS, 1 Lpm) CEM and a Tekran 2537/1130/1135 system (7 Lpm). Given the use of CEM in the TAPI and UNRRMAS, we hypothesized that both should collect RM. Due to the high flow rate and different inlets, TAPI data were systematically lower than the UNRRMAS. Correlation between RM concentrations demonstrated that the TAPI may be used to estimate 24 h resolution RM concentrations in Nevada.


Assuntos
Poluentes Atmosféricos , Mercúrio , Monitoramento Ambiental , Poluição Ambiental , Material Particulado
10.
Environ Sci Technol ; 50(23): 12921-12927, 2016 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-27934266

RESUMO

The atmosphere is an important reservoir for mercury pollution, and understanding of oxidation processes is essential to elucidating the fate of atmospheric mercury. Several recent studies have shown that a low bias exists in a widely applied method for atmospheric oxidized mercury measurements. We developed an automated, permeation tube-based calibrator for elemental and oxidized mercury, and we integrated this calibrator with atmospheric mercury instrumentation (Tekran 2537/1130/1135 speciation systems) in Reno, Nevada and at Mauna Loa Observatory, Hawaii, U.S.A. While the calibrator has limitations, it was able to routinely inject stable amounts of HgCl2 and HgBr2 into atmospheric mercury measurement systems over periods of several months. In Reno, recovery of injected mercury compounds as gaseous oxidized mercury (as opposed to elemental mercury) decreased with increasing specific humidity, as has been shown in other studies, although this trend was not observed at Mauna Loa, likely due to differences in atmospheric chemistry at the two locations. Recovery of injected mercury compounds as oxidized mercury was greater in Mauna Loa than in Reno, and greater still for a cation-exchange membrane-based measurement system. These results show that routine calibration of atmospheric oxidized mercury measurements is both feasible and necessary.


Assuntos
Poluentes Atmosféricos , Mercúrio , Calibragem , Monitoramento Ambiental , Compostos de Mercúrio
13.
Sci Total Environ ; 530-531: 519-525, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-25934382

RESUMO

Ozone as an atmospheric pollutant is largely produced by anthropogenic precursors and can significantly impact human and ecosystem health, and climate. The U.S. Environmental Protection Agency has recently proposed lowering the ozone standard from 75 ppbv (MDA8 = Maximum Daily 8-Hour Average) to between 65 and 70 ppbv. This will result in remote areas of the Intermountain West that includes many U.S. National Parks being out of compliance, despite a lack of significant local sources. We used Pb isotope fingerprinting and back-trajectory analysis to distinguish sources of imported ozone to Great Basin National Park in eastern Nevada. During discrete Chinese Pb events (> 1.1 ng/m(3) & > 80% Asian Pb) trans-Pacific transported ozone was 5 ± 5.5 ppbv above 19 year averages for those dates. In contrast, concentrations during regional transport from the Los Angeles and Las Vegas areas were 15 ± 2 ppbv above the long-term averages, and those characterized by high-altitude transport 3 days prior to sampling were 19 ± 4ppbv above. However, over the study period the contribution of trans-Pacific transported ozone increased at a rate of 0.8 ± 0.3 ppbv/year, suggesting that Asian inputs will exceed regional and high altitude sources by 2015-2020. All of these sources will impact regulatory compliance with a new ozone standard, given increasing global background.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Chumbo/análise , Ozônio/análise , Poluição do Ar/estatística & dados numéricos , Atmosfera/química , Política Ambiental , Los Angeles , Nevada , Estados Unidos , United States Environmental Protection Agency
14.
Sci Total Environ ; 530-531: 526-533, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-25895623

RESUMO

Measurements of O3 at relatively remote monitoring sites are useful for quantifying baseline O3, and subsequently the magnitude of O3 not controllable by local regulations. As the National Ambient Air Quality Standard (NAAQS) for O3 becomes more stringent, there is an increased need to quantify baseline O3 particularly in the Western US, where regional and global sources can significantly enhance O3 measured at surface sites, yielding baseline mixing ratios approaching or exceeding the NAAQS threshold. Past work has indicated that meteorological conditions as well as site specific spatial characteristics (e.g. elevation, basin size, gradient) are significantly correlated with O3 intercepted at rural monitoring sites. Here, we use 3 years of measurements from sites throughout rural Nevada to develop a categorical tree model to identify spatial and meteorological characteristics that are associated with elevated baseline O3. Data from other sites in the Intermountain Western US are used to test the applicability of the model for sites throughout the region. Our analyses indicate that increased elevation and basin size were associated with increased frequency of elevated O3. On a daily time scale, relative humidity had the strongest association with observed MDA8 O3. Seventy-four percent of MDA8 O3 observations>60 ppbv occurred when daily minimum relative humidity was <15%. Further, we found that including ancillary pollutant data did not improve the predictive accuracy for measurements >60 ppbv whereas including upper air meteorological measurements improved the accuracy of predicting periods when O3 was >60 ppbv. These findings indicate that transport, rather than local production, influences O3 measurements in Nevada, and that high elevation sites in rural Nevada, are representative of baseline conditions in the Intermountain Western US.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Monitoramento Ambiental , Modelos Estatísticos , Ozônio/análise , Conceitos Meteorológicos , Modelos Químicos , Nevada
15.
Chemosphere ; 131: 209-16, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25880343

RESUMO

Deposition of mercury (Hg) from the atmosphere is an important source of this contaminant to terrestrial ecosystems. Once deposited, all forms of Hg can be retained or emitted back to the atmosphere. Distinguishing between volatilization of geogenic or indigenous Hg and that deposited from the atmosphere is difficult. Field flux measurements in the general area of two industrial scale gold mining operations, showed local deposition of Hg emitted from point and nonpoint sources, and subsequent re-emission. The work presented in this paper investigated deposition/emission of elemental Hg to and from alluvium and two mine materials before, during, and after exposure to high air concentrations, for both wet and dry conditions, using a laboratory gas exchange chamber and a Hg permeation source. In general, results showed a range in mean elemental Hg deposition velocities ranging from 0.13 to 0.46 cm s(-1) that varied with material. A significant influence of atmospheric ozone (O3) on flux was observed that depended on the material and whether wet or dry. A synergistic relationship existed between O3 and light promoting Hg flux, and flux was also influenced by material grain size, chemistry, and primary mineralogy.


Assuntos
Resíduos Perigosos , Mercúrio/análise , Mineração , Atmosfera , Monitoramento Ambiental/métodos , Ouro , Volatilização
16.
Environ Sci Technol ; 49(10): 6102-8, 2015 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-25877790

RESUMO

Quantifying the concentration of gaseous oxidized mercury (GOM) and identifying the chemical compounds in the atmosphere are important for developing accurate local, regional, and global biogeochemical cycles. The major hypothesis driving this work was that relative humidity affects collection of GOM on KCl-coated denuders and nylon membranes, both currently being applied to measure GOM. Using a laboratory manifold system and ambient air, GOM capture efficiency on 3 different collection surfaces, including KCl-coated denuders, nylon membranes, and cation-exchange membranes, was investigated at relative humidity ranging from 25 to 75%. Recovery of permeated HgBr2 on KCl-coated denuders declined by 4-60% during spikes of relative humidity (25 to 75%). When spikes were turned off GOM recoveries returned to 60 ± 19% of permeated levels. In some cases, KCl-coated denuders were gradually passivated over time after additional humidity was applied. In this study, GOM recovery on nylon membranes decreased with high humidity and ozone concentrations. However, additional humidity enhanced GOM recovery on cation-exchange membranes. In addition, reduction and oxidation of elemental mercury during experiments was observed. The findings in this study can help to explain field observations in previous studies.


Assuntos
Poluentes Atmosféricos/análise , Gases/análise , Membranas Artificiais , Mercúrio/análise , Cátions , Monitoramento Ambiental , Umidade , Nylons , Oxirredução , Ozônio , Cloreto de Potássio
17.
Sci Total Environ ; 530-531: 505-518, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-25864796

RESUMO

The proposed revision of the United States (US) air quality standard for ozone will result in violations in sparsely populated remote rural areas in the Western US. Replicating air quality as measured at surface monitoring sites by modeling is particularly difficult in this region due to complex terrain, poorly represented in regional and global models, and uncertainties in emission rates and timing at all scales (locally as well as hundreds to thousands of km upwind). As an alternative method, a fully empirical, receptor-based scheme using in situ aerosol composition and simple meteorological variables to simulate ozone (O3) measurements was tested and found to produce O3 simulation results comparable in uncertainty to regional modeling, and supporting trajectory-based identification of O3 source regions. This approach was tested using two widely-separated (650 km) high altitude (approx. 2 km above sea level) monitoring sites, Lassen Volcanic National Park, in northern California (LAVO) and Great Basin National Park in eastern Nevada (GRBA). Comparing correlations between observed O3 and aerosols, and examining back-trajectories associated with peak concentrations for the two sites permitted distinguishing among local, distant North American, and Asian sources of particulate matter (PM2.5) and O3. This analysis indicates that anthropogenic enhancement of O3 at LAVO is primarily due to transport from Asia. Asia is also the dominant source of anthropogenic O3 at GRBA in spring, but regional North American sources of O3 appear to drive additional ozone peaks in late summer and fall at this more interior site.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Ozônio/análise , Aerossóis/análise , Poluição do Ar/estatística & dados numéricos , California , Modelos Químicos , Nevada , Material Particulado/análise
18.
Sci Total Environ ; 530-531: 493-504, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-25845306

RESUMO

The current United States (US) National Ambient Air Quality Standard (NAAQS) for O3 (75 ppb) is expected to be revised to between 60 and 70 ppb. As the NAAQS becomes more stringent, characterizing the extent of O3 and precursors transported into the US is increasingly important. Given the high elevation, complex terrain, and location in the Intermountain West, the State of Nevada is ideally situated to intercept air transported into the US. Until recently, measurements of O3 and associated pollutants were limited to areas in and around the cities of Las Vegas and Reno. In 2011, the Nevada Rural Ozone Initiative began and through this project 13 surface monitoring sites were established. Also in 2011, the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) began making routine aircraft measurements of O3 and other greenhouse gases in Nevada. The availability of aircraft and surface measurements in a relatively rural, remote setting in the Intermountain West presented a unique opportunity to investigate sources contributing to the O3 observed in Nevada. Our analyses indicate that stratosphere to troposphere transport, long-range transport of Asian pollution, and regional emissions from urban areas and wildfires influence surface observations. The complexity of sources identified here along with the fact that O3 frequently approaches the threshold being considered for a revised NAAQS indicate that interstate and international cooperation will be necessary to achieve compliance with a more stringent regulatory standard. Further, on a seasonal basis we found no significant difference between daily 1-h maximum O3 at surface sites, which ranged in elevation from 888 to 2307 m, and aircraft measurements of O3 <2500 m which suggests that similar processes influence daytime O3 across rural Nevada and indicates that column measurements from Railroad Valley, NV are useful in understanding these processes.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Ozônio/análise , Poluição do Ar/estatística & dados numéricos , Atmosfera/química , Modelos Químicos , Nevada
19.
Sci Total Environ ; 530-531: 455-470, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-25840481

RESUMO

The Nevada Rural Ozone Initiative (NVROI) was established to better understand O3 concentrations in the Western United States (US). The major working hypothesis for development of the sampling network was that the sources of O3 to Nevada are regional and global. Within the framework of this overarching hypothesis, we specifically address two conceptual meteorological hypotheses: (1) The high elevation, complex terrain, and deep convective mixing that characterize Nevada, make this state ideally located to intercept polluted parcels of air transported into the US from the free troposphere; and (2) site specific terrain features will influence O3 concentrations observed at surface sites. Here, the impact of complex terrain and site location on observations are discussed. Data collected in Nevada at 6 sites (1385 to 2082 m above sea level (asl)) are compared with that collected at high elevation sites in Yosemite National Park and the White Mountains, California. Average daily maximum 1-hour concentrations of O3 during the first year of the NVROI ranged from 58 to 69 ppbv (spring), 53 to 62 ppbv (summer), 44 to 49 ppbv (fall), and 37 to 45 ppbv (winter). These were similar to those measured at 3 sites in Yosemite National Park (2022 to 3031 m asl), and at 4 sites in the White Mountains (1237 to 4342 m asl) (58 to 67 ppbv (summer) and 47 to 58 ppbv (fall)). Results show, that in complex terrain, collection of data should occur at high and low elevation sites to capture surface impacts, and site location with respect to topography should be considered. Additionally, concentrations measured are above the threshold reported for causing a reduction in growth and visible injury for plants (40 ppbv), and sustained exposure at high elevation locations in the Western USA may be detrimental for ecosystems.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Ozônio/análise , Poluição do Ar/estatística & dados numéricos , Atmosfera/química , Nevada
20.
Environ Sci Technol ; 49(1): 432-41, 2015 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-25485926

RESUMO

To understand gaseous oxidized mercury (GOM) sources to the Western US, data were collected with passive samplers for ambient GOM concentrations and dry deposition at 10 sites from the coast of the Pacific Ocean to Great Basin National Park. Tests were done to better understand the samplers and the materials used. Measured dry deposition of GOM was significantly higher at sites >2000 m elevation relative to those below due to high GOM concentrations and atmospheric turbulence. At these high elevation sites, GOM dry deposition was higher in spring due to long-range transport from Asia (air parcels from the free troposphere) and some high GOM dry deposition events were related to regional emissions. Dry deposition of GOM at two sites was calculated using the passive sampler data and a multiple-resistance model. A previously developed relationship between the sampling rate of the passive sampler and GOM concentrations was used to estimate dry deposition and a scaling factor of 3 was used to adjust GOM concentrations, due to underestimation by KCl-coated denuder measurements. With the scaling factor of 3, modeled deposition was in the range of results estimated from two different models settings. However, dry deposition did not correlate consistently with either model. The disagreement could be due to uncertainties associated with measurements and/or modeling, or different GOM compounds existing in the atmosphere. If the atmospheric GOM compounds are known, dry deposition velocities could be estimated more accurately. Lastly, we investigated the potential for use of a new sampling material for GOM and checked the efficiency of the passive sampler.


Assuntos
Poluentes Atmosféricos/análise , Compostos de Mercúrio/análise , Mercúrio/análise , Modelos Teóricos , Altitude , Atmosfera , California , Monitoramento Ambiental/métodos , Gases/análise , Nevada , Oxirredução , Oceano Pacífico , Estações do Ano , Incerteza
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA