Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 21
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
Sci Total Environ ; 707: 136031, 2020 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-31869604

RESUMO

Remediation of mercury (Hg) contaminated sites has long relied on traditional approaches, such as removal and containment/capping. Here we review contemporary practices in the assessment and remediation of industrial-scale Hg contaminated sites and discuss recent advances. Significant improvements have been made in site assessment, including the use of XRF to rapidly identify the spatial extent of contamination, Hg stable isotope fractionation to identify sources and transformation processes, and solid-phase characterization (XAFS) to evaluate Hg forms. The understanding of Hg bioavailability for methylation has been improved by methods such as sequential chemical extractions and porewater measurements, including the use of diffuse gradient in thin-film (DGT) samplers. These approaches have shown varying success in identifying bioavailable Hg fractions and further study and field applications are needed. The downstream accumulation of methylmercury (MeHg) in biota is a concern at many contaminated sites. Identifying the variables limiting/controlling MeHg production-such as bioavailable inorganic Hg, organic carbon, and/or terminal electron acceptors (e.g. sulfate, iron) is critical. Mercury can be released from contaminated sites to the air and water, both of which are influenced by meteorological and hydrological conditions. Mercury mobilized from contaminated sites is predominantly bound to particles, highly correlated with total sediment solids (TSS), and elevated during stormflow. Remediation techniques to address Hg contamination can include the removal or containment of Hg contaminated materials, the application of amendments to reduce mobility and bioavailability, landscape/waterbody manipulations to reduce MeHg production, and food web manipulations through stocking or extirpation to reduce MeHg accumulated in desired species. These approaches often rely on knowledge of the Hg forms/speciation at the site, and utilize physical, chemical, thermal and biological methods to achieve remediation goals. Overall, the complexity of Hg cycling allows many different opportunities to reduce/mitigate impacts, which creates flexibility in determining suitable and logistically feasible remedies.

2.
Atmosphere (Basel) ; 10(4): 176, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31456887

RESUMO

We report on the continuous ambient measurements of total gaseous mercury (TGM) and several ancillary air quality parameters that were collected in Colorado Springs, CO. This urban area, which is located adjacent to the Front Range of the Rocky Mountains, is the second largest metropolitan area in Colorado and has a centrally located coal-fired power plant that installed mercury (Hg) emission controls the year prior to our study. There are few other Hg point sources within the city. Our results, which were obtained from a measurement site < 1 km from the power plant, show a distinct diel pattern in TGM, with peak concentrations occurring during the night (1.7 ± 0.3 ng m-3) and minimum concentrations mid-day (1.5 ± 0.2 ng m-3). The TGM concentrations were not correlated with wind originating from the direction of the plant or with sulfur dioxide (SO2) mixing ratios, and they were not elevated when the atmospheric mixing height was above the effective stack height. These findings suggest that the current Hg emissions from the CFPP did not significantly influence local TGM, and they are consistent with the facility's relatively low reported annual emissions of 0.20 kg Hg per year. Instead, variability in the regional signal, diurnal meteorological conditions, and/or near-surface emission sources appears to more greatly influence TGM at this urban site.

3.
Environ Pollut ; 253: 636-645, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31330355

RESUMO

Timber harvest has many effects on aquatic ecosystems, including changes in hydrological, biogeochemical, and ecological processes that can influence mercury (Hg) cycling. Although timber harvest's influence on aqueous Hg transformation and transport are well studied, the effects on Hg bioaccumulation are not. We evaluated Hg bioaccumulation, biomagnification, and food web structure in 10 paired catchments that were either clear-cut in their entirety, clear-cut except for an 8-m wide riparian buffer, or left unharvested. Average mercury concentrations in aquatic biota from clear-cut catchments were 50% higher than in reference catchments and 165% higher than in catchments with a riparian buffer. Mercury concentrations in aquatic invertebrates and salamanders were not correlated with aqueous THg or MeHg concentrations, but rather treatment effects appeared to correspond with differences in the utilization of terrestrial and aquatic basal resources in the stream food webs. Carbon and nitrogen isotope data suggest that a diminished shredder niche in the clear-cut catchments contributed to lower basal resource diversity compared with the reference of buffered treatments, and that elevated Hg concentrations in the clear-cut catchments reflect an increased reliance on aquatic resources in clear-cut catchments. In contrast, catchments with riparian buffers had higher basal resource diversity than the reference catchments, indicative of more balanced utilization of terrestrial and aquatic resources. Further, following timber harvest THg concentrations in riparian songbirds were elevated, suggesting an influence of timber harvest on Hg export to riparian food webs. These data, coupled with comparisons of individual feeding guilds, indicate that changes in organic matter sources and associated effects on stream food web structure are important mechanisms by which timber harvest modifies Hg bioaccumulation in headwater streams and riparian consumers.


Assuntos
Cadeia Alimentar , Agricultura Florestal/métodos , Mercúrio/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Biota , Carbono , Ecossistema , Invertebrados , Mercúrio/análise , Compostos de Metilmercúrio , Isótopos de Nitrogênio , Rios/química , Poluentes Químicos da Água/análise
4.
Environ Sci Technol ; 52(17): 9556-9561, 2018 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-30067020

RESUMO

Mercury is a global pollutant released into the biosphere by varied human activities including coal combustion, mining, artisanal gold mining, cement production, and chemical production. Once released to air, land and water, the addition of carbon atoms to mercury by bacteria results in the production of methylmercury, the toxic form that bioaccumulates in aquatic and terrestrial food chains resulting in elevated exposure to humans and wildlife. Global recognition of the mercury contamination problem has resulted in the Minamata Convention on Mercury, which came into force in 2017. The treaty aims to protect human health and the environment from human-generated releases of mercury curtailing its movement and transformations in the biosphere. Coincident with the treaty's coming into force, the 13th International Conference of Mercury as a Global Pollutant (ICMGP-13) was held in Providence, Rhode Island USA. At ICMGP-13, cutting edge research was summarized and presented to address questions relating to global and regional sources and cycling of mercury, how that mercury is methylated, the effects of mercury exposure on humans and wildlife, and the science needed for successful implementation of the Minamata Convention. Human activities have the potential to enhance mercury methylation by remobilizing previously released mercury, and increasing methylation efficiency. This synthesis concluded that many of the most important factors influencing the fate and effects of mercury and its more toxic form, methylmercury, stem from environmental changes that are much broader in scope than mercury releases alone. Alterations of mercury cycling, methylmercury bioavailability and trophic transfer due to climate and land use changes remain critical uncertainties in effective implementation of the Minamata Convention. In the face of these uncertainties, important policy and management actions are needed over the short-term to support the control of mercury releases to land, water and air. These include adequate monitoring and communication on risk from exposure to various forms of inorganic mercury as well as methylmercury from fish and rice consumption. Successful management of global and local mercury pollution will require integration of mercury research and policy in a changing world.


Assuntos
Poluentes Ambientais , Mercúrio , Compostos de Metilmercúrio , Animais , Poluição Ambiental , Humanos , Rhode Island
6.
Ambio ; 47(2): 141-169, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29388127

RESUMO

The environmental cycling of mercury (Hg) can be affected by natural and anthropogenic perturbations. Of particular concern is how these disruptions increase mobilization of Hg from sites and alter the formation of monomethylmercury (MeHg), a bioaccumulative form of Hg for humans and wildlife. The scientific community has made significant advances in recent years in understanding the processes contributing to the risk of MeHg in the environment. The objective of this paper is to synthesize the scientific understanding of how Hg cycling in the aquatic environment is influenced by landscape perturbations at the local scale, perturbations that include watershed loadings, deforestation, reservoir and wetland creation, rice production, urbanization, mining and industrial point source pollution, and remediation. We focus on the major challenges associated with each type of alteration, as well as management opportunities that could lessen both MeHg levels in biota and exposure to humans. For example, our understanding of approximate response times to changes in Hg inputs from various sources or landscape alterations could lead to policies that prioritize the avoidance of certain activities in the most vulnerable systems and sequestration of Hg in deep soil and sediment pools. The remediation of Hg pollution from historical mining and other industries is shifting towards in situ technologies that could be less disruptive and less costly than conventional approaches. Contemporary artisanal gold mining has well-documented impacts with respect to Hg; however, significant social and political challenges remain in implementing effective policies to minimize Hg use. Much remains to be learned as we strive towards the meaningful application of our understanding for stakeholders, including communities living near Hg-polluted sites, environmental policy makers, and scientists and engineers tasked with developing watershed management solutions. Site-specific assessments of MeHg exposure risk will require new methods to predict the impacts of anthropogenic perturbations and an understanding of the complexity of Hg cycling at the local scale.


Assuntos
Mercúrio/análise , Poluentes do Solo/análise , Poluentes Químicos da Água/análise , Exposição Ambiental , Monitoramento Ambiental , Humanos , Compostos de Metilmercúrio , Mineração , Solo
7.
Environ Sci Technol ; 52(4): 1971-1980, 2018 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-29366328

RESUMO

Land-use activities can alter hydrological and biogeochemical processes that can affect the fate, transformation, and transport of mercury (Hg). Previous studies in boreal forests have shown that forestry operations can have profound but variable effects on Hg export and methylmercury (MeHg) formation. The Pacific Northwest is an important timber producing region that receives large atmospheric Hg loads, but the impact of forest harvesting on Hg mobilization has not been directly studied and was the focus of our investigation. Stream discharge was measured continuously, and Hg and MeHg concentrations were measured monthly for 1.5 years following logging in three paired harvested and unharvested (control) catchments. There was no significant difference in particulate-bound Hg concentrations or loads in the harvested and unharvested catchments which may have resulted from forestry practices aimed at minimizing erosion. However, the harvested catchments had significantly higher discharge (32%), filtered Hg concentrations (28%), filtered Hg loads (80%), and dissolved organic carbon (DOC) loads (40%) compared to forested catchments. MeHg concentrations were low (mostly <0.05 ng L-1) in harvested, unharvested, and downstream samples due to well-drained/unsaturated soil conditions and steep slopes with high energy eroding stream channels that were not conducive to the development of anoxic conditions that support methylation. These results have important implications for the role forestry operations have in affecting catchment retention and export of Hg pollution.


Assuntos
Mercúrio , Compostos de Metilmercúrio , Poluentes Químicos da Água , Monitoramento Ambiental , Noroeste dos Estados Unidos , Oregon , Movimentos da Água
8.
Environ Pollut ; 222: 32-41, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28104341

RESUMO

Reservoirs typically have elevated fish mercury (Hg) levels compared to natural lakes and rivers. A unique feature of reservoirs is water-level management which can result in sediment exposure to the air. The objective of this study is to identify how reservoir water-level fluctuations impact Hg cycling, particularly the formation of the more toxic and bioaccumulative methylmercury (MeHg). Total-Hg (THg), MeHg, stable isotope methylation rates and several ancillary parameters were measured in reservoir sediments (including some in porewater and overlying water) that are seasonally and permanently inundated. The results showed that sediment and porewater MeHg concentrations were over 3-times higher in areas experiencing water-level fluctuations compared to permanently inundated sediments. Analysis of the data suggest that the enhanced breakdown of organic matter in sediments experiencing water-level fluctuations has a two-fold effect on stimulating Hg methylation: 1) it increases the partitioning of inorganic Hg from the solid phase into the porewater phase (lower log Kd values) where it is more bioavailable for methylation; and 2) it increases dissolved organic carbon (DOC) in the porewater which can stimulate the microbial community that can methylate Hg. Sulfate concentrations and cycling were enhanced in the seasonally inundated sediments and may have also contributed to increased MeHg production. Overall, our results suggest that reservoir management actions can have an impact on the sediment-porewater characteristics that affect MeHg production. Such findings are also relevant to natural water systems that experience wetting and drying cycles, such as floodplains and ombrotrophic wetlands.


Assuntos
Inundações , Sedimentos Geológicos/análise , Compostos de Metilmercúrio/análise , Poluentes do Solo/análise , Poluentes Químicos da Água/análise , Lagos/química , Oregon , Rios/química , Áreas Alagadas
9.
Sci Total Environ ; 568: 1213-1226, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27320732

RESUMO

Western North America is a region defined by extreme gradients in geomorphology and climate, which support a diverse array of ecological communities and natural resources. The region also has extreme gradients in mercury (Hg) contamination due to a broad distribution of inorganic Hg sources. These diverse Hg sources and a varied landscape create a unique and complex mosaic of ecological risk from Hg impairment associated with differential methylmercury (MeHg) production and bioaccumulation. Understanding the landscape-scale variation in the magnitude and relative importance of processes associated with Hg transport, methylation, and MeHg bioaccumulation requires a multidisciplinary synthesis that transcends small-scale variability. The Western North America Mercury Synthesis compiled, analyzed, and interpreted spatial and temporal patterns and drivers of Hg and MeHg in air, soil, vegetation, sediments, fish, and wildlife across western North America. This collaboration evaluated the potential risk from Hg to fish, and wildlife health, human exposure, and examined resource management activities that influenced the risk of Hg contamination. This paper integrates the key information presented across the individual papers that comprise the synthesis. The compiled information indicates that Hg contamination is widespread, but heterogeneous, across western North America. The storage and transport of inorganic Hg across landscape gradients are largely regulated by climate and land-cover factors such as plant productivity and precipitation. Importantly, there was a striking lack of concordance between pools and sources of inorganic Hg, and MeHg in aquatic food webs. Additionally, water management had a widespread influence on MeHg bioaccumulation in aquatic ecosystems, whereas mining impacts where relatively localized. These results highlight the decoupling of inorganic Hg sources with MeHg production and bioaccumulation. Together the findings indicate that developing efforts to control MeHg production in the West may be particularly beneficial for reducing food web exposure instead of efforts to simply control inorganic Hg sources.


Assuntos
Poluentes Ambientais/metabolismo , Mercúrio/metabolismo , Compostos de Metilmercúrio/metabolismo , Vertebrados/metabolismo , Animais , Canadá , Monitoramento Ambiental , Poluentes Ambientais/análise , Peixes/metabolismo , Mercúrio/análise , Compostos de Metilmercúrio/análise , México , Estados Unidos
10.
Sci Total Environ ; 568: 727-738, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27130329

RESUMO

Large-scale assessments are valuable in identifying primary factors controlling total mercury (THg) and monomethyl mercury (MeHg) concentrations, and distribution in aquatic ecosystems. Bed sediment THg and MeHg concentrations were compiled for >16,000 samples collected from aquatic habitats throughout the West between 1965 and 2013. The influence of aquatic feature type (canals, estuaries, lakes, and streams), and environmental setting (agriculture, forest, open-water, range, wetland, and urban) on THg and MeHg concentrations was examined. THg concentrations were highest in lake (29.3±6.5µgkg(-1)) and canal (28.6±6.9µgkg(-1)) sites, and lowest in stream (20.7±4.6µgkg(-1)) and estuarine (23.6±5.6µgkg(-1)) sites, which was partially a result of differences in grain size related to hydrologic gradients. By environmental setting, open-water (36.8±2.2µgkg(-1)) and forested (32.0±2.7µgkg(-1)) sites generally had the highest THg concentrations, followed by wetland sites (28.9±1.7µgkg(-1)), rangeland (25.5±1.5µgkg(-1)), agriculture (23.4±2.0µgkg(-1)), and urban (22.7±2.1µgkg(-1)) sites. MeHg concentrations also were highest in lakes (0.55±0.05µgkg(-1)) and canals (0.54±0.11µgkg(-1)), but, in contrast to THg, MeHg concentrations were lowest in open-water sites (0.22±0.03µgkg(-1)). The median percent MeHg (relative to THg) for the western region was 0.7%, indicating an overall low methylation efficiency; however, a significant subset of data (n>100) had percentages that represent elevated methylation efficiency (>6%). MeHg concentrations were weakly correlated with THg (r(2)=0.25) across western North America. Overall, these results highlight the large spatial variability in sediment THg and MeHg concentrations throughout western North America and underscore the important roles that landscape and land-use characteristics have on the MeHg cycle.


Assuntos
Monitoramento Ambiental/métodos , Sedimentos Geológicos/análise , Mercúrio/análise , Compostos de Metilmercúrio/análise , Poluentes Químicos da Água/análise , Territórios do Noroeste , Noroeste dos Estados Unidos
11.
Sci Total Environ ; 568: 638-650, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27015962

RESUMO

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.

12.
Sci Total Environ ; 568: 651-665, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-26936663

RESUMO

Mercury (Hg) emission and deposition can occur to and from soils, and are an important component of the global atmospheric Hg budget. This paper focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A database of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were detectable among the field studies, with the chamber material and sampling flushing flow rate influencing the magnitude of calculated emissions. The spatiotemporal scaling of soil-air Hg fluxes identified that the largest emissions occurred from irrigated agricultural landscapes in California. Vegetation was shown to have a large impact on surface-air Hg fluxes due to both a reduction in solar radiation reaching the soil as well as from direct uptake of Hg in foliage. Despite high soil Hg emissions from some forested and other heavily vegetated regions, the net ecosystem flux (soil flux+vegetation uptake) was low. Conversely, sparsely vegetated regions showed larger net ecosystem emissions, which were similar in magnitude to atmospheric Hg deposition (except for the Mediterranean California region where soil emissions were higher). The net ecosystem flux results highlight the important role of landscape characteristics in effecting the balance between Hg sequestration and (re-)emission to the atmosphere.

13.
Environ Sci Technol ; 49(16): 9750-7, 2015 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-26189758

RESUMO

Prior to its closure, the base-metal smelter in Flin Flon, Manitoba, Canada was one of the North America's largest mercury (Hg) emission sources. Our project objective was to understand the exchange of Hg between the soil and the air before and after the smelter closure. Field and laboratory Hg flux measurements were conducted to identify the controlling variables and used for spatial and temporal scaling. Study results showed that deposition from the smelter resulted in the surrounding soil being enriched in Hg (up to 99 µg g(-1)) as well as other metals. During the period of smelter operation, air concentrations were elevated (30 ± 19 ng m(-3)), and the soil was a net Hg sink (daily flux: -3.8 ng m(-2) h(-1)). Following the smelter closure, air Hg(0) concentrations were reduced, and the soils had large emissions (daily flux: 108 ng m(-2) h(-1)). The annual scaling of soil Hg emissions following the smelter closure indicated that the landscape impacted by smelter deposition emitted or re-emitted almost 100 kg per year. Elevated soil Hg concentrations and emissions are predicted to continue for hundreds of years before background concentrations are re-established. Overall, the results indicate that legacy Hg deposition will continue to cycle in the environment long after point-source reductions.


Assuntos
Poluentes Atmosféricos/análise , Ar , Indústrias , Mercúrio/análise , Poluentes do Solo/análise , Solo/química , Geografia , Manitoba
14.
Environ Sci Technol ; 49(15): 9143-9, 2015 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-26151306

RESUMO

Soil mercury (Hg) emissions are an important component of the global Hg cycle. Sunlight induced photoreduction of oxidized Hg to gaseous elemental Hg is an important mechanism controlling emissions from the soil surface, however we currently understand little about how subsurface Hg stores participate in gaseous Hg cycling. Our study objective was to investigate the ability of Hg at deeper soil depths to participate in emissions. Soil fluxes were measured under controlled laboratory conditions utilizing an enriched stable Hg isotope tracer buried at 0, 1, 2, and 5 cm below the surface. Under dry and low-light conditions, the Hg isotope tracer buried at the different depths participated similarly in surface emissions (median flux: 7.5 ng m(-2) h(-1)). When the soils were wetted, Hg isotope tracer emissions increased significantly (up to 285 ng m(-2) h(-1)), with the highest fluxes (76% of emissions) originating from the surface 1 cm amended soils and decreasing with depth. Mercury associated with sandy soil up to 6 cm below the surface can be emitted, clearly demonstrating that volatilization can occur via processes unrelated to sunlight. These results have important implications for considering how long older, legacy soil Hg contamination continues to cycle between soil and atmosphere.


Assuntos
Gases/análise , Mercúrio/análise , Poluentes do Solo/análise , Solo/química , Isótopos de Mercúrio , Estatísticas não Paramétricas , Luz Solar , Molhabilidade
15.
Environ Sci Technol ; 47(18): 10339-48, 2013 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-23978035

RESUMO

The Flin Flon, Manitoba copper smelter was Canada's largest point source of mercury emissions until its closure in 2010 after ~80 years of operation. The objective of this study was to understand the variables controlling the local ground-level air mercury concentrations before and after this major point source reduction. Total gaseous mercury (TGM) in air, mercury in precipitation, and other ancillary meteorological and air quality parameters were measured pre- and postsmelter closure, and mercury speciation measurements in air were collected postclosure. The results showed that TGM was significantly elevated during the time period when the smelter operated (4.1 ± 3.7 ng m(-3)), decreased only 20% during the year following its closure, and remained ~2-fold above background levels. Similar trends were observed for mercury concentrations in precipitation. Several lines of evidence indicated that while smelter stack emissions would occasionally mix down to the surface resulting in large spikes in TGM concentrations (up to 61 ng m(-3)), the largest contributor to elevated TGM concentrations before and after smelter closure was from surface-air fluxes from mercury-enriched soils and/or tailings. These findings highlight the ability of legacy mercury, deposited to local landscapes over decades from industrial activities, to significantly affect local air concentrations via emissions/re-emissions.


Assuntos
Poluentes Atmosféricos/análise , Mercúrio/análise , Cobre , Monitoramento Ambiental , Manitoba , Metalurgia , Material Particulado/análise , Dióxido de Enxofre/análise
16.
Environ Pollut ; 161: 291-8, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21719170

RESUMO

Rates of surface-air elemental mercury (Hg(0)) fluxes in the literature were synthesized for the Great Lakes Basin (GLB). For the majority of surfaces, fluxes were net positive (evasion). Digital land-cover data were combined with representative evasion rates and used to estimate annual Hg(0) evasion for the GLB (7.7 Mg/yr). This value is less than our estimate of total Hg deposition to the area (15.9 Mg/yr), suggesting the GLB is a net sink for atmospheric Hg. The greatest contributors to annual evasion for the basin are agricultural (∼55%) and forest (∼25%) land cover types, and the open water of the Great Lakes (∼15%). Areal evasion rates were similar across most land cover types (range: 7.0-21.0 µg/m(2)-yr), with higher rates associated with urban (12.6 µg/m(2)-yr) and agricultural (21.0 µg/m(2)-yr) lands. Uncertainty in these estimates could be partially remedied through a unified methodological approach to estimating Hg(0) fluxes.


Assuntos
Poluentes Ambientais/análise , Poluição Ambiental/estatística & dados numéricos , Mercúrio/análise , Atmosfera/química , Monitoramento Ambiental , Great Lakes Region , Ontário , Quebeque
17.
Sci Total Environ ; 409(19): 3879-86, 2011 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-21741677

RESUMO

The state of Nevada has extensive mineral resources, and is the largest producer of gold in the USA as well as fourth in world gold production. Mercury (Hg) is often present in the hydrothermal systems that produce gold deposits, and can be found in elevated concentrations in gold ore. As a result, mining of gold ore in Nevada has been shown to release Hg to the atmosphere from point and non-point sources. This project focused on measurement of air-soil Hg exchange associated with undisturbed soils and bedrock outcrops in the vicinity of two large gold mines. Field and laboratory data collected were used to identify the important variables controlling Hg flux from these surfaces, and to estimate a net flux from the areas adjacent to the active mines as well as that occurring from the mined area pre-disturbance. Mean daily flux by substrate type ranged from 9 ng m(-2) day(-1) to 140 ng m(-2) day(-1). Periods of net deposition of elemental Hg were observed when air masses originating from a mine site moved over sampling locations. Based on these observations and measured soil Hg concentrations we suggest that emissions from point and non-point sources at the mines are a source of Hg to the surrounding substrates with the amount deposited not being of an environmental concern but of interest mainly with respect to the cycling of atmospheric elemental Hg. Observations indicate that while some component of the deposited Hg is sequestered in the soil, this Hg is gradually released back to the atmosphere over time. Estimated pre-disturbance emissions from the current mine footprints based on field data were 0.1 and 1.7 kg yr(-1), compared to that estimated for the current non-point mining sources of 19 and 109 kg yr(-1), respectively.


Assuntos
Monitoramento Ambiental , Poluentes Ambientais/análise , Ouro , Mercúrio/análise , Mineração , Nevada , Solo/química
18.
Can J Diet Pract Res ; 71(1): 41-5, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20205977

RESUMO

Pregnant women's fish consumption provides both benefits and risks to the developing fetus. Docosahexaenoic acid (DHA) from fish may enhance fetal neurodevelopment, while methylmercury (MeHg) can have detrimental effects. Dietitians would benefit from information on the frequency with which fish species may be consumed to increase DHA intake among Canadian women of childbearing age, and on minimizing the risks from MeHg, especially for those who consume fish frequently. Eighteen fish species were selected for DHA and mercury analysis from retail markets in the Toronto area. Consumption scenarios using analytical results for these fish species indicate that women of childbearing age can consume nine of 18 fish species every day (14 servings a week) or often (up to four servings a week) and remain below toxicological benchmarks for mercury. Moreover, women can also attain the recommended DHA level by consuming six of those nine fish: four 75-g servings of smelt, porgie, or bluefish a week, or two 75-g servings of milkfish, silver pomfret, or tilapia a day. Our analysis indicates that the DHA level recommended for childbearing women can be attained through fish consumption alone, without the need for supplementation and without posing a risk to the woman (or the fetus) from mercury.


Assuntos
Peixes , Contaminação de Alimentos/análise , Alimentos Marinhos/análise , Adolescente , Adulto , Animais , Canadá , Dieta , Dietética , Ácidos Docosa-Hexaenoicos/análise , Ácidos Graxos Ômega-3/análise , Feminino , Desenvolvimento Fetal/efeitos dos fármacos , Humanos , Troca Materno-Fetal/efeitos dos fármacos , Mercúrio/análise , Compostos de Metilmercúrio/análise , Pessoa de Meia-Idade , Gravidez , Medição de Risco , Fatores de Risco , Adulto Jovem
19.
Water Res ; 43(15): 3635-46, 2009 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-19576611

RESUMO

This research focuses on mercury (Hg) mobilization in stormwater runoff from an urban roadway. The objectives were to determine: how the transport of surface-derived Hg changes during an event hydrograph; the influence of antecedent dry days on the runoff Hg load; the relationship between total suspended sediments (TSS) and Hg transport, and; the fate of new Hg input in rain and its relative importance to the runoff Hg load. Simulated rain events were used to control variables to elucidate transport processes and a Hg stable isotope was used to trace the fate of Hg inputs in rain. The results showed that Hg concentrations were highest at the beginning of the hydrograph and were predominantly particulate bound (HgP). On average, almost 50% of the total Hg load was transported during the first minutes of runoff, underscoring the importance of the initial runoff on load calculations. Hg accumulated on the road surface during dry periods resulting in the Hg runoff load increasing with antecedent dry days. The Hg concentrations in runoff were significantly correlated with TSS concentrations (mean r(2)=0.94+/-0.09). The results from the isotope experiments showed that the new Hg inputs quickly become associated with the surface particles and that the majority of Hg in runoff is derived from non-event surface-derived sources.


Assuntos
Mercúrio/análise , Chuva , Movimentos da Água , Poluentes Químicos da Água/análise , Cidades , Drenagem Sanitária , Modelos Químicos , Transportes
20.
Sci Total Environ ; 403(1-3): 164-77, 2008 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-18582918

RESUMO

Urban stormwater runoff has been identified as a leading cause of waterway impairment for many pollutants, but there has been a lack of research that directly measures Hg in urban stormwater runoff. The objectives of this research were: to use high frequency sampling to characterize the Hg export dynamics from an urban micro-catchment (i.e. a parking lot) during individual rain events; determine the relationship between suspended sediments and Hg transport; assemble event-scale mass balances of atmospheric Hg inputs, surface storage, and Hg export in runoff to evaluate the relative importance of rainfall-derived Hg and surface-derived Hg in runoff; and finally, to compare the yield of Hg from the urban micro-catchment to that of a larger mixed land-use urban catchment to evaluate the feasibility of scaling the results. The results found that the highest Hg concentrations in runoff were observed during the rising limb of the hydrograph (first flush effect), which was dominated by particulate bound Hg (84+/-8%). There was a significant relationship between the Hg and total suspended solids (TSS) concentrations in runoff. For all events, the largest Hg flux occurred during the period of peak discharge, even though the Hg concentrations were substantially lower during this period. The catchment surface Hg load (i.e. street dust) varied over the course of the study, but the changes were not clearly linked to the rain events. The mass balance of the Hg inputs and outputs from the catchment showed that it could act as a Hg sink or a source depending on the rainfall characteristics. The export of Hg from the larger mixed land-cover catchment were all within the range of the values from the parking-lot catchment, though tended to be lower as a result of increased retention and fewer sources/disturbance within the catchment.


Assuntos
Cidades , Compostos de Mercúrio/análise , Poluentes Químicos da Água/análise , Poluição da Água/análise , Canadá , Poeira/análise , Monitoramento Ambiental/métodos , Água Doce , Emissões de Veículos/análise , Movimentos da Água
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA