S16 Mercury in contaminated sites: Biogeochemistry and human health

Tuesday, 26 July, 2011

TS16-P1 — 11:00-12:00 and 17:30-18:30
Authors: CESAR, Ricardo1, COLONESE, Juan2, SILVA, Marianna2, BERTOLINO, Luiz Carlos3, EGLER, Silvia3, CASTILHOS, Zuleica3, POLIVANOV, Helena4, BIDONE, Edison5, PEREZ, Daniel6
(1) Federal Fluminense University (UFF), Niterói, RJ, Brazil., geo_ricardocesar@yahoo.com.br; (2) Centre for Mineral Technology (CETEM), Rio de Janeiro, RJ, Brazil; (3) Centre for Mineral Technology (CETEM), RJ, Brazil; (4) Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil; (5) Federal Fluminense University (UFF), Niterói (RJ); (6) Brazilian Company for Agropecuary Research (EMBRAPA), Rio de Janeiro, RJ, Brazil.

Mercury is one the most toxic heavy metals and the contamination of soils has been causing serious damages on biota. This investigation proposes the study of mercury bioaccumulation by earthworms (Eisenia andrei) exposed to an artificially contaminated tropical soil (yellow ferralsol). The bioaccumulation assay was performed according to ASTM (2004). The test was conducted with five replicates and composed by two steps: (i) bioaccumulation step, when 540 organisms are exposed on the test-soil during 28 days (ASTM, 2004); (ii) depuration step, when the survival worms are transferred to a non-contaminated artificial soil, where they remain for 28 days (ASTM, 2004). In order to evaluate temporal variability of mercury uptake and depuration rates, 30 organisms were taken from the soil in previously defined days, and sent to total mercury analysis. Bioconcentrations factors (BCF) were calculated through the ration between mercury content in the organisms and the concentration in the soil. The contamination of the soil was performed with a solution divalent mercury. Mercury concentration in the soil was 5.00mg/kg, which is much higher than the limits established by WHO and Brazilian legislation (0.05mg/kg). By the end of the bioaccumulation step, 30% of the organisms were dead. This observation suggests that this dose (5.00mg/kg) seems to be very toxic under chronic exposure (28 days), although it has not provoked significant lethal effects under acute exposure (14 days). Another aspect which may indicate such high chronic ecotoxicity is the absence of cocoons by the of the bioaccumulation step, suggesting that the presence of mercury was able to affect the reproduction of the earthworms. Mercury concentration in worm’s tissues had an increment of 120 times in comparison with the naturally content observed in the control sample (0.02mg/kg). Thus, BCFs were relatively high (between 2 and 20 units), suggesting that the organisms were able to absorb and accumulate mercury. Such high bioavailability may be justified by the acid pH value of the soil sample (4.8 units), low organic matter contents and mineralogy essentially composed by kaolinite. On the other hand, the earthworms were only able to eliminate about ¼ of the bioaccumulated mercury amount, suggesting the existence of internal fixation mechanisms, possibly into the intestinal tract.

TS16-P2 — 11:00-12:00 and 17:30-18:30
Authors: CESAR, Ricardo1, SANTOS, Maria Carla2, SENDEROWITZ, Stephanie3, COLONESE, Juan3, BERTOLINO, Luiz Carlos3, EGLER, Silvia3, CASTILHOS, Zuleica2, MADDOCK, John2
(1) Federal Fluminense University (UFF), Niterói, RJ, Brazil., geo_ricardocesar@yahoo.com.br; (2) Federal Fluminense University (UFF), Niterói, RJ, Brazil; (3) Centre for Mineral Technology (CETEM), RJ, Brazil.;

The CENTRES (Queimados Municipality, Rio de Janeiro State, Brazil) should be a temporary area for industrial wastes storage. However, over the two last decades the wastes have not been receiving an appropriated disposal, thus contaminating soils with heavy metals, including mercury. This work proposes the ecotoxicological assessment and the study of mercury bioavailability levels in superficial soils from the CENTRES. Soil samples were collected in November/2009. Granulometric analysis was conducted with nylon sieves of 0.075mm and 1.7mm. Mercury concentration was quantified in the two fractions: <0.075mm and 1.7-0.075mm. Acute bioassays (14 days) with earthworms (Eisenia andrei) were performed with bulk soil samples, following ASTM (2004). Survival organisms were sent to total mercury determination. Bioconcentrations factors (BCF) were calculated though the ratio between mercury content in the organisms and the concentration in the soil. Total mercury determination was executed with LUMEX, a portable Atomic Absorption. The granulometric analysis revealed very sandy materials. Although the fine fraction (<0.075mm) corresponds about 7% of the granulometric distribution, it is able to fix around 66.9% of the total mercury (mean mercury concentration = 894.36 ± 596.60 ng/g). Such affinity between mercury retention and fine fractions is possibly related to the increase of the specific surface contact, as well as to the presence of expansive clay minerals (vermiculite) in these soils. Total mercury contents in the bulk samples were higher than the limits established by Brazilian legislation (50ng/g). The acute bioassay revealed the absence of significant lethal effects of the organisms. This observation may be associated with the actuation of expansive clay minerals, which are able to reduce mercury (and other heavy metals) concentrations in the soil solution, decreasing the bioavailability for the earthworms (though dermal contact). However, the animals had a significant biomass loss after 14 days of exposure, suggesting that the contaminants were able to provoke some stress. In general, mercury determination in the earthworm’s tissues revealed BCFs values lower than one unit; suggesting low bioavailability levels of mercury (as previously indicated such low lethality levels). Just one sample presented BCF higher than one unit, possibly due to its low pH value (pH = 4.6) that tends to increase mercury bioavailability for the earthworms.

TS16-P3 — 11:00-12:00 and 17:30-18:30
Authors: ESBRÍ, José M1, DIEZ, Sergi2, TOBÍAS, Aurelio3, HIGUERAS, Pablo L.4, MARTÍNEZ-CORONADO, Alba5
(1) Instituto de Geología Aplicada, UCLM. Pl. Manuel Meca, 1. 13400 Almadén (Ciudad Real), Spain, josemaria.esbri@uclm.es; (2) Environmental Chemistry Department, IDAEA-CSIC. 08034 Barcelona, Spain; (3) Geosciences Department, IDAEA-CSIC; (4) Instituto de Geología Aplicada, Universidad de Castilla-La Mancha; (5) Instituto de Geología Aplicada, Universidad de Castilla-La Mancha.

Mercury exposure of local population was assessed in two areas of Castilla-La Mancha region (Spain): Almadén mercury mining district, which has been the World’s largest producer of this element, and localities within a radius of 2 hundred Kilometers away. These two studied groups are exposed to different sources of mercury: a point source in Almadén and a diffuse source hundreds of km away on the same region. Total mercury (THg) in human hair was analysed by means of atomic absorption spectrometry with Zeeman effect, by mean of a LUMEX RA-915 equipment, and results ranged from 0.20 to 9.35 mg kg-1 with a mean value of 2.64 mg·kg-1. About 87% of subjects had THg levels in excess of the EPA reference dose (RfD=1.0 mg·kg-1), while a high percentage (68%) of them are living in Almadén. In this group, the women of child-bearing age had a mean hair mercury level of 2.12 mg·kg-1, which is twofold higher than the RfD. There was a clear increase in hair Hg with reported fish consumption and the highest mean hair mercury level was 4 times the RfD in a group who has reported the higher consumption of fish. For the whole group there was a significant effect of age, gender, and fish consumption in relation to Hg concentration in the hair. Nevertheless, when both groups were tested separately by means of a multivariate regression model, there is a significant exposure for those living near the mine area. Several factors such as age, gender, and fish consumption remained statistically significant and are associated with Hg contents in the hair. The main conclusion is that people living close to the hot spot are more impacted by mercury than people living further away. The intake of Hg through consumption of fish is an important parameter for Hg exposure; however, in case of the people living close to the hot spot, their levels are related to the highly Hg-impacted living environment.

TS16-P4 — 11:00-12:00 and 17:30-18:30
Authors: CESAR, Ricardo1, SILVA, Marianna2, COLONESE, Juan2, EGLER, Silvia3, CASTILHOS, Zuleica3, POLIVANOV, Helena4, BIDONE, Edison5
(1) Federal Fluminense University (UFF), Niterói, RJ, Brazil., geo_ricardocesar@yahoo.com.br; (2) Centre for Mineral Technology (CETEM), Rio de Janeiro, RJ, Brazil; (3) Centre for Mineral Technology (CETEM), RJ, Brazil; (4) Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil; (5) Federal Fluminense University (UFF), Niterói, RJ, Brazil.

Sewage sludge (SL) is a waste produced by Effluents Treatment Stations. Since it contains high concentrations of organic matter and nutrients, its agricultural recycle has become an important alternative of disposal. However, SL also contains high levels of metals, including mercury, which can cause damages on biota. This work proposes the determination of mercury content in earthworm’s tissues exposed to sewage sludge-amended ferralsols and chernosols. Acute bioassays (14 days) with Eisenia andrei were performed according ASTM (2004). Mercury determination in survival worms was performed with LUMEX (a portable Atomic Absorption). The following SL doses were tested: 6.66, 13.12, 19.98, 26.14 and 33%. Lethal dose on 50% of the organisms (DL50) was estimated with the software Trimmed Spearmen Karbet. The bioaccumulation test (56 days - ASMT, 2004) was only performed with the ferralsol, using a sub-lethal dose previously defined in the acute assays. Mercury content in the SL samples was 1.8 mg/kg. All doses applied on the chernosol were not able to provoke significant lethal effects on the organisms. In the ferralsol, higher levels of lethality were observed (DL50 = 12.30mg/kg), suggesting that soil properties (in this case, especially clay minerals, fertility and pH) played a vital role in the contaminants bioavailability. Mercury determination in the survival worms indicated BCFs lower than one unit, suggesting that the organisms absorbed the contaminant. Mercury contents were higher in the organisms exposed to chernosol. In this respect, high nutrients concentrations in the chernosol (more availability of food for the organisms) possibly contributed for a great uptake of mercury by the organisms, since healthier animals tend to support higher levels of metals in the tissues. SL tested dose in the bioaccumulation test was 8.14%. Results revealed a lethality level of 20% by the end of the bioaccumulation step. Thus, although this dose of SL has caused no lethal effects under acute exposure, it was able to cause significant lethal effects under chronic exposure. The absence of cocoons by the end of the bioaccumulation step confirms such high chronic ecotoxicity, suggesting the occurrence of adverse effects on the reproduction. The BCFs showed that mercury uptake rates were higher during the first days of exposure. Mercury mass balance revealed that the animals could eliminate about 50% of the bioaccumulated amount, indicating possible retentions in the intestinal tract.

TS16-P5 — 11:00-12:00 and 17:30-18:30
Authors: NISI, Barbara1, TASSI, Franco1, HIGUERAS, Pablo L.2, VASELLI, Orlando1, RAPPUOLI, Daniele3, ESBRÍ, José M.2, MARTÍNEZ-CORONADO, Alba4
(1)Dipartimento di Scienze della Terra, Via G. Pira, 4, 50121 Firenze (Italy), barbara.nisi@unifi.it; (2) Instituto de Geología Aplicada, Universidad de Castilla-La Mancha; (3) Comunità Montana Amiata-Val D’Orcia, Via Hamman, 98 53021 Abbadia San Salvatore, Siena (Italy); (4) Instituto de Geología Aplicada, Universidad de Castilla-La Mancha. Almadén (Spain).

The Mt. Amiata area is the youngest and largest volcanic edifice in Tuscany (central-northern Italy) and is characterized by a geothermal field, exploited for the production of electrical energy. The Mt. Amiata volcano is mainly constituted by trachydacitic rocks, and hosts the world first class mercury deposit close to the city of Abbadia San Salvarore. Besides, the area is rich in hypogenic activity, including thermal waters and CO2 rich emissions, some of them used as touristic resorts (e.g. Bagni San Filippo).

In the present work we describe some preliminary data on mercury emissions related to both former mercury mine facilities and hypogene activity. Surveys were carried out by car for long distance regional surveys, and by feet for local scale surveys.

We have carried out the surveys by means of a LUMEX RA-915+ device, an Atomic Absorption Spectrometer with Zeeman effect, able to measure atmospheric mercury concentrations with a measuring range between 2 and 25000 ng m-3, and with data acquisition every second.

Results put forward that both the decommissioned mines and the CO2-rich emissions generate atmospheric mercury concentrations that occasionally reach over 25.000 ng m-3, well above the reference levels for chronic exposure to this pollutant (1000 ng m-3, WHO, 2000), fortunately not affecting the urban areas. It is to mention that even away from the mining activity, high Hg concentrations are found, particularly close to degassing vents that show values comparable to those in the mining zones. This suggests that other than the mineralized zones from where Hg was extracted and converted to industrial product, the Mt. Amiata volcanic complex is de facto an anomalous geological container of mercury as a whole. Consequently, further investigations are needed to both better define the real zone of Hg anomaly and characterize the background values of gaseous Hg in this region. There are few doubts that far from the Mt. Amiata area the concentrations of atmospheric Hg are comparable to the standard background level worldwide even in those areas that have similar chemical features, i.e. high CO2-rich vents, such as the Calatrava Volcanic Field in Central Spain, to those investigated in the Tuscan volcano.

WHO, 2000. Air quality guidelines for Europe. WHO Regional Publications European Series 91, World Health Organization Regional Office for Europe, Copenhagen, 288pp.

TS16-P6 — 11:00-12:00 and 17:30-18:30
Author: RANDALL, Paul1
(1)USEPA, randall.paul@epa.gov

Mercury (Hg) can accumulate in sediment from point and non-point sources, depending on a number of physical, chemical, biological, geological and anthropogenic environmental processes. It is believed that the associated Hg contamination in aquatic systems can be decreased by imposing effective management and monitoring strategies of contaminated sediment. Environmental project managers face several challenges in the management of contaminated sediment sites, primarily due to the large volumes of sediment that are typically involved. The complexities and high costs associated with characterization and cleanup are magnified by evolving regulatory requirements and the difficulties inherent in tracking the contaminants in aquatic environments. Generally, four basic options for remediation of contaminated sediments exist for environmental project managers; they are: (1)Containment in-place, (2) Treatment in-place, (3)Removal and containment, and (4)Removal and treatment. Existing technologies for remediating Hg-contaminated sites focus primarily on highly polluted areas, and are not suitable for remediating vast, diffusely polluted sediment areas where pollutants occur at relatively low concentrations. The speciation of Hg, which concerns the identification and quantitation of specific forms of Hg, is a critical determinant of its mobility, reactivity, and potential bioavailability in Hg-impacted sediment-water systems. Common Hg-contaminated sediment remediation strategies include dredging, capping and natural attenuation. Since each remedial action can result in a change in the physical, chemical and biological conditions of the sediment, it is expected that the speciation and transport properties of Hg might change as the result of implementing a remedial action. However, the effectiveness of such remediation practices has not been adequately assessed and long-term reliability has not been proven. The aim of this poster is to discuss the characterization, assessment, and approaches for the cleanup of mercury contaminated sediments from past industrial operations, contaminated rivers, lakes, swamps, coastal areas, and gold and mercury mines. Case studies include characterization, assessment, and remediation efforts made at Lavaca Bay, Texas, Onondaga Lake in Syracuse, New York, Lake Turingen, Sweden, Sulphur Banks Mercury Mine near Clear Lake, California, a mercury cell chlor-alkali plant in the Southeastern U.S. and other characterization and assessment efforts at the Nura River and Lake Balkyldak in Kazakhstan.

TS16-P7 — 11:00-12:00 and 17:30-18:30
Author: RANDALL, Paul1
(1)USEPA, randall.paul@epa.gov

Fate and transport of mercury (Hg) and methylmercury (MeHg) within the aquatic environment involves many complex and interconnected pathways. MeHg is formed mainly at the sediment-water interface, just below which there is a transition from oxic to anoxic conditions. The formation of MeHg is mediated by the complex interaction of inorganic Hg and microorganisms. Transport of Hg and MeHg into the overlying water, particularly in lacustrine environments, can be mitigated by the placement of a sediment cap. Traditional caps are used as physical isolation barriers between the source sediments and the sensitive ecological receptors of the overlying aquatic ecosystem. Contaminant transport from source sediments through a sediment cap and into the overlying water is promoted by groundwater upwelling and processes that contribute to sediment re-suspension, such as bioturbation and gas ebullition. The function, capacity and longevity of traditional isolation caps can be augmented through the strategic use of both permeability control and reactive materials. Reactive capping materials, in metals-impacted sediments, typically have high sorptive capacities, hypothetically rendering the metals non-bioavailable and limiting the transport of contaminants into overlying surface water. In the case of Hg, a reactive cap with requisite sorptive characteristics can also render the Hg non-bioavailable and thereby mitigate the rate and extent of methylation.

The aim of this project is to characterize the extent of mercury methylation under conditions simulating those at a mercury-contaminated superfund site in Alabama, both during baseline (non-reactive capping) conditions and with the implementation of reactive capping materials. In order to evaluate the performance of each reactive capping material, a three-stage experimental study was developed. The adsorption of Hg and MeHg onto the five materials (bauxite, AquaBlok®, local soil, local dredged sediment, and Ottawa sand as a control) was evaluated in Stage 1 (Sorption Study). The ability of two candidate capping materials (local soil and local dredge material) to inhibit the methylation of Hg relative to the quantity of MeHg produced during the incubation conditions was evaluated in Stage 2 (Incubation Study). The capacity of one candidate capping material (local soil) to inhibit translocation of Hg and MeHg with respect to ebullition-facilitated contaminant transport was evaluated in Stage 3 (Column Study). This presentation will report the results of this study.

TS16-P8 — 11:00-12:00 and 17:30-18:30
Authors: DESROCHERS, Krista A.N.1, PTACEK, Carol J.1
(1) University of Waterloo, k2desroc@uwaterloo,ca

Erosion and redeposition of mercury (Hg) contaminated bank sediment into the South River, Virginia can provide a source of Hg, which may convert to methyl-Hg in stagnant, organic-carbon rich reaches of the river. This study entails characterization of solid-phase forms of Hg, mechanisms leading to Hg release, and development of approaches for stabilizing Hg in the South River sediments. Samples of sediment were collected along two transects perpendicular to the riverbed at distances of 0.1 and 3.5 river miles downstream from the Hg release zone. Resuspension experiments were conducted to assess the potential for Hg release from sediment due to erosion from the banks through a series of time dependent and mass dependent modified elutriate tests. Variations of the water-sediment ratio resulted in a non-linear response in total Hg release with increasing mass of sediment, suggesting a possible solid-phase solubility control on aqueous Hg concentrations. Column experiments were conducted to simulate Hg release into slowly advecting river water through the bank sediments. The column experiments, which evaluated the effects of varying flow rates to evaluate the influence of velocity fluctuations on Hg release, showed elevated concentrations of total Hg in response to increases in flow velocity and following periods of stagnation. Filter size-fractionation of water samples collected from the column and resuspension experiments suggest that approximately 50% of total Hg leached was present in dissolved and colloidal phases. Sequential extraction analyses suggest that the majority of the solid-phase sediment Hg (79-93%) was present in the form of insoluble sulfides . However a significant portion of sediment Hg was observed to be in the water soluble fraction (2-9%), which is consistent with the elevated total aqueous Hg concentrations observed from the resuspension and column experiments. The results of the sediment characterization experiments were used to develop techniques to optimize reductions in aqueous concentrations of Hg in sediment porewater and river water. Solid-phase reactive media, including complexing agents, carbon-based adsorbents, and strong reductants, were co-blended with the riverbank sediment. Mercury immobilization was evaluated by batch and column experiments to assess time-dependent and mass- dependent variability, with aqueous Hg reductions ranging from 0-99% . The results of the experiments will be used to develop field-scale approaches to minimize Hg release and potentially lower biotic uptake of Hg within the South River watershed.

TS16-P9 — 11:00-12:00 and 17:30-18:30
Authors: DYER, James A.1, LANDIS, Richard C.1, GROSSO, Nancy R.2, MURPHY, Gregory 3, FLANDERS, J. R.3, HARRIS, Reed4
(1) DuPont Engineering Research and Technology, james.a.dyer@usa.dupont.com; (2) DuPont Corporate Remediation Group; (3) URS Corporation; (4) Reed Harris Environmental Ltd..

Historic point-source releases of anthropogenic mercury to the South River, Waynesboro, Virginia, USA, a high-gradient fluvial ecosystem, present unique challenges to scientists and engineers tasked with identifying, developing, and implementing remedial options for reducing mercury concentrations to safe levels in both aquatic and terrestrial biota. Inorganic mercury releases from a former rayon acetate fiber manufacturing facility more than 60 years ago have made their way from surface water into sediments, bank and floodplain soils, and aquatic and terrestrial biota inhabiting the fluvial ecosystem. As a result, methylmercury concentrations in fish tissue along a 25-mile river reach downstream of the manufacturing facility have not declined as expected, even though ongoing point sources have largely been eliminated. The working hypothesis for the absence of a decline in fish-tissue mercury is that mercury-contaminated soil particles from eroding river banks and floodplain soil are an ongoing long-term source of bioavailable mercury to the aquatic ecosystem. A second, but related, working hypothesis for the absence of a decline is that mercury-rich, fine-grained sediment particles, which accumulate in near-bank areas and in sand/gravel/cobble beds within the river channel, continue to supply pore water with dissolved and colloidal inorganic mercury that diffuses to sites of methylation.

A challenge for fluvial systems like the South River is how to effectively deploy remedial technologies in a high-energy, sinuous, bedrock, and gravel-bed river. As an essential first step in this effort, conceptual pathway and exposure diagrams were developed that highlight the abiotic and biotic processes involved in the supply, methylation, and bioaccumulation of mercury in contaminated reaches of the South River. More specifically, the diagrams identify and quantify (1) the sources of and abiotic pathways by which inorganic mercury moves through the aquatic system to sites of methylation; (2) the methylmercury production compartments that supply biota at the base of the food web; and (3) the biotic pathways by which methylmercury bioaccumulates up the food web to smallmouth bass.

TS16-P10 — 11:00-12:00 and 17:30-18:30
Authors: RIBEIRO GUEVARA, Sergio1, STERGARŠEK, Andrej2, FRKAL, Peter2, HORVAT, Milena2
(1) Centro Atómico Bariloche, Bariloche, Argentina, ribeiro@cab.cnea.gov.ar; (2) Jožef Stefan Institute, Ljubljana, Slovenia;

The understanding of mercury transformations and transport processes in natural and contaminated environments provides basic data for the evaluation of the overall mercury impact. There are few analytical techniques available for these studies, which combined with the direct measurements and speciation, allow a comprehensive understanding of mercury impact in the system under study. These techniques are based in spiking labelled mercury, following it throughout the processes. The mercury can be labelled by changing the natural isotopic composition or by a radioactive isotope. The mercury radiotracer most frequently used is 203Hg; however, the short live 197Hg can be employed successfully.

The high specific activity achieved by producing 197Hg from enriched 196Hg targets enables extremely low spikes (e.g. 1-10 ng L-1 in waters, 0.01 ng g-1 in sediments), allowing the evaluation of recoveries as low as 0.001 to 1 % of the spike. This radiotracer can be spiked in concentrations spanning several orders of magnitude (e.g. spikes from 0.02 to 2000 ng g-1 in sediments studies). With a proper standard, design and HPGe detector, the 197Hg radiotracer can be measured in very different arrangements, materials and geometries, without complex devices or procedures.

Nowadays, the main source of antrophic mercury emissions to the atmosphere is associated with flue gases generated in coal power plants. The flue gas desulphurisation system of these plants retains mercury, but the undergoing chemical processes are not completely understood. The 197Hg radiotracer was employed to study these processes, evaluating the Hg2+ retention capacity of Gypsum and mercury transformations after an Hg0 input in a water-air mixed system in different conditions.

Moreover, the understanding of the processes associated with the transformation of Hg2+ to organic species is basic in assessing the impact of mercury inputs. The 197Hg radiotracer enables simultaneous measurements of mercury methylation and reduction in sediments, soils and waters, reproducing natural and disturbed conditions.

TS16-P11 — 11:00-12:00 and 17:30-18:30
Authors: IGNACIO, Aurea Regina Alves1, LONDERO, Henriette Cevada1, KEHRIG, Helena do Amaral2, MALM, Olaf2, DÍEZ, Sergi3, DA SILVA, Carolina Joana1
(1)UNEMAT, aurea@unemat.br; (2) UFRJ; (3) CSIC;

Pantanal is a lowland plateau periodically flooded during rainy season, it has a rich biodiversity of fauna and flora, traditional folklore and human activity, including gold mining. The history of gold mining at Poconé in Mato Grosso State, starts back in the last century, reaching its peak in the 80s. Human populations are exposed to the organic form of mercury, methylmercury, when feeding on contaminated fish. Riverside people in Pantanal eat fish as the main source of animal protein on a daily basis. Hair is considered a bioindicator of mercury contamination, for when Hg is deposited is not eliminated and effectively shows bioaccumulation. This study quantifies THg levels on the hair of riverside people in Pantanal at Mato Grosso State, Brazil. Study area includes Cuiabá Mirim Traditional Community, Pantanal National Park and municipality of Poconé, at the banks of Cuiabá River, Paraguay River and Bento Gomes River, respectively. This study involved 160 people, 45 men, 34 women, 26 boys and 35 girls. Hair samples (0.05g) were placed in paper bags, subsequently undergoing acid digestion and THg concentrations were assessed using atomic absorption spectrometry with Flow Injection Mercury System (FIMS) and FIA 400 (Perkin Elmer, USA), with auto-sampler AS90. International reference certification was done according to the National Research Council-Canada (Dorm-3). Mercury concentrations assessed in reference samples were between 95 and 98% of average certified values showing high precision in the analyses. Coefficient of variation in duplicates was less than 10%. The detection limit is 0.01 ppb. The highest concentrations of THg were collected from individuals from Cuiabá Mirim (3.059 ± 1.913), followed by individuals from Pantanal National Park (2.353 ± 1.536) and Poconé (0.6168 ± 0.7168). At these communities, adults had higher concentrations of mercury compared to children (P<0.05). Similarly, men had higher concentrations of mercury (2.612 ± 2.237) compared to women (1.344 ± 1.353).

TS16-P12 — 11:00-12:00 and 17:30-18:30
Authors: LLANOS, Wiilians R1, KOCMAN, David2, HIGUERAS, Pablo L1, HORVAT, Milena2
(1) Instituto de Geología Aplicada, UCLM. Pl. Manuel Meca, 1. 13400 Almadén (Ciudad Rea)., Willians.Llanos@uclm.es; (2) Jožef Stefan Institute, Department of Environmental Sciences, Jamova 39, 1000 Ljubljana, Slovenia;

Results obtained by a laboratory flux measurement system (LFMS) focused on investigating the kinetics of the mercury emission flux (MEF) from contaminated soils are presented. Representative soil samples with respect to total Hg concentration (26-9770 µg g-1) surrounding decommissioned mercury-mining area (Las Cuevas Mine), and former mercury smelter (Cerco Metalúrgico de Almadenejos), in the Almadén mercury Mining District, Spain were collected. Altogether, 14 samples were analyzed to determine the variation in MEF versus distance from the sources, regulating two major environmental parameters comprising soil temperature and solar radiation. In addition, the fraction of the water-soluble mercury in these samples was determined in order to assess how MEF from soil is related to the mercury in the aqueous soil phase. Measured MEFs ranged from less than 140 to over 10000 ng m-2 h-1, with the highest emissions from contaminated soils adjacent to point sources. A significant decrease of MEF was then observed with increasing distance from these sites. The results revealed a strong positive effect of all three parameters investigated on momentum MEF. The light-induced flux was shown to be independent of the soil temperature, while Hg associated with the soil aqueous phase seems to be responsible for recharging the pool of mercury in the soil available for both the light- and thermally-induced flux. The overall flux response to simulated environmental conditions depends greatly on the form of Hg in the soil. Higher activation energies are required for the overall process to occur in soils where insoluble cinnabar prevails compared to soils where more mobile Hg forms and are present. Based on the calculated Hg emission rates and with the support of geographical information system (GIS) tools and ISC AERMOD software, dispersion models for atmospheric mercury were implemented. In this way, gaseous mercury plume generated by the soil-originated emissions at different seasons was modeled. Modeling efforts revealed that much higher emissions and larger mercury plumes are generated in dry and warm periods (summer), while the plume is smaller and associated with lower concentrations of atmospheric mercury during colder periods with higher wind activity (fall). Based on the calculated emissions and the model implementation, yearly emissions from the CMA metallurgical precinct (Cerco Metalúrgico de Almadenejos) were estimated at 16.4 kg Hg y-1, with significant differences between seasons.

TS16-P13 — 11:00-12:00 and 17:30-18:30
Authors: ALIEVA, Vera I.1, PASTUKHOV , Mikhail V.1, EPOV, Vladimir N.2, PERROT, Vincent3
(1) Institute of Geochemistry SB RAS, Irkutsk, Russia, alieva@igc.irk.ru; (2) LCABIE, IPREM, CNRS-UMR-5254, Pau, France; (3) LCABIE, IPREM, UPPA-UMR-5254, Pau, France.

Mercury contamination of the Bratsk Water-Reservoir (BWR), artificially created on the Angara River, the only outflow from Lake Baikal, is one of the ecological problems of the region. Mercury was used by the factory “Usoliechimprom” for the production of chlorine and caustic soda. Total amount of mercury had been discharged to the BWR during the functioning of the factory was about 80 tons.

By comparing mercury distribution in water, water suspension, pore water, bottom sediments, higher water plants, plankton and fish of the BWR basin, we distinguished sites, where mercury migration rate and mercury accumulation rate changes abruptly. These sites play the role of geochemical barriers, at which mercury was accumulated and stored.

The most important area is a barrier near the Konniy (Horse) Island, located 55 km downstream the factory “Usoliechimprom”; it takes a substantial part of anthropogenic load upon itself. We distinguished this area as a barrier, based on a set of factors, both direct (geochemical study of biotic and abiotic elements components in BWR), as well as indirect (the faster rate of sedimentation, landscape and geochemical relief, geological and hydrological conditions, etc.). Major portion of mercury is adsorbed by water suspension and precipitated to the sediments of the geochemical barrier. As a result, this area of the BWR demonstrates the highest mercury concentration in core sediments (up to 9 mg/kg) and in plankton (up to 0.722 mg/kg). Mercury in food-species of fish was also found to be high (up to 7.3 mg/kg), that threaten human health.

The study demonstrates that the geochemical barrier in the area of Konniy Island has physico-chemical, mechanical and biological importance. We also found out that borders of the barrier are not permanent; they vary with the variation of the reservoir water level.

This geochemical barrier has double influence on the mercury migration in BWR. From one side, it prevents mercury diffusion into water of the reservoir. From other side, mercury transformation, which occurs in anaerobic conditions of the barrier, leads to the secondary contamination of water and biological species.

TS16-P15 — 11:00-12:00 and 17:30-18:30
Authors: LIANG, Lian1, HWANG, David2, YOUNG, Lyman2, AULTMAN, Elizabeth A1, PANG, Patrick1
(1) Cebam Analytical, Inc., liang@cebam.net; (2) Chevron Energy Technology Company;

Alkylatable mercury (AHg) based on the ethylation reaction is a scientifically-reproducible and reliable measure of reactive Hg2+(RHg) in the environment, and it can be a particularly useful species of risk in assessments of contaminated sites. Recently, AHg and its link with RHg determined by Sn2+ reduction were investigated with respect to chemical principle, analytical methodology, and field testing results. AHg and Sn2+reducible Hg are the same target in nature for representing RHg, but they are operationally defined based on two different analytical methods. While RHg is an important species of methylation potential in biogeochemical Hg cycling, this species is not widely analyzed or discussed. This may be due to irreproducible results caused by analytical problems using Sn2+ reduction method. After these problems were discovered and solved, results by Sn2+ reduction method were found to agree with those by AHg method for various water samples. In addition, AHg method was used for analysis of Hg2+ in crude oils, and the results agreed with those based on speciated isotope dilution ICPMS. Due to its significant advantages over methods including Sn2+ reduction, ICPMS, and others, AHg is recommended for characterization of RHg.

Methylmercury (MeHg)/methylation/demethylation of Hg have been the subject of numerous studies. At Hg contaminated sites, there is no doubt that biota MeHg levels can reflect Hg risk levels, however, using water, soil and sediment Hg levels can be more direct and more immediate than using biota Hg levels to characterize contaminated points. MeHg is typically a very small fraction of total Hg (THg) in water, soil and sediment, and when THg is even higher, the MeHg/THg ratio is even lower, suggesting that MeHg is not a useful species for the purpose. AHg can provide more useful information for site evaluation and risk assessment. AHg directly reflects risk levels of contaminated water, soils, and sediments due to its high solubility, mobility, bioavailability, and reactivity at points downstream from contaminated sites. The final goal of Hg remediation at such sites will be better met by converting reactive Hg to inactive Hg rather than removing Hg. The criteria for determining the success of such remediation efforts involve determining how much reactive Hg is converted to inactive Hg, and, for this purpose, AHg may be the best species to evaluate.

TS16-P16 — 11:00-12:00 and 17:30-18:30
Author: LODENIUS, Martin1
(1)University of Helsinki, martin.lodenius@helsinki.fi

Mercury is deposited to terrestrial ecosystems by dry and wet deposition processes. The interaction between air and vegetation includes many processes which are not fully known. Emissions and deposition have been successfully monitored by using different methods, e.g. mosses, lichens and moss transplants. The methods may be standardized and they give repeatable results. The information from biological monitoring may however differ from that obtained by using mechanical/technical devices which are based on deposition on glass or Teflon surfaces or gold amalgamation. Physical, chemical and biological parameters should be known in more detail if we want reliable quantitative estimates of mercury deposition.

TS16-P17 — 11:00-12:00 and 17:30-18:30
Authors: DE JESUS, Iracina M.1, LIMA, Marcelo Oliveira1, FAIAL, Kleber Raimundo Freitas1, PINHEIRO, Maria da Conceição Nascimento2, NAKAMURA, Masaaki3, AKAGI, Hirokatsu4, SAKAMOTO, Mineshi3, SANTOS, Elisabeth Conceição Oliveira1
(1) Evandro Chagas Institute, iracinajesus@iec.pa.gov.br; (2) Federal University of Pará; (3) National Institute for Minamata Disease; (4) International Mercury Lab. Inc.;

Different patterns of mercury (Hg) exposure has been found in the Amazon populations and it has been related to the sources of mercury release to the environment until reaching alimentary resources as fish. The riverside communities represent a large number of those populations and they present high vulnerability due to the route exposure to the methylmercury (MeHg) since they are consumers of aquatic food. This study aimed at to contribute for the health surveillance of a riverside community located in Tapajós river basin, Brasilian Amazon assessing the epidemiological current status of MeHg exposure. Comparative study was developed in Maranhão village, a community of the Pará river, without previous data of Hg exposure. The analyses of total and methylmercury in hair were accomplished respectively by CVAAS and GC-ECD, according Akagi method (2004). A total of 104 resident from Barreiras village, 12 to 72 years old participated in the study. The average of THg in hair was of 12.23 ± 7.83 µg g-1 and geometric mean of 9.34 ± 2.13 µg g-1. Methylmercury average of 87 individuals was of 10.20 ± 6.62 µg g-1 and geometric mean of 7.55 ± 2.23 µg g-1. Correlation between THg and MeHg was positive and very strong (r=0.9043, p<0.0001). Concerning fish consumption the correlation was positive and weak (THg rs=0.2987, p=0.0021; MeHg rs=0.2298, p=0.0322). Maranhão village presented average of THg of 2.12 ± 1.45 µg g-1 and geometric mean of 1.62 ± 1.78 µg g-1. In Barreiras and Maranhão the average of fish consumption was of 8.7 and 3.0 times per week, respectively. Hair samples of 62 women of Barreiras were analyzed in six consecutive segments of two cm to verify possible variation along the last year, considering a growth of the hair about a cm a month. The THg average varied from 8.77 to 11.68 µg g-1, geometric mean from 6.51 to 8.84 µg g-1 and there was not significant difference among the periods (Anova one way, Dunn’s post test). The results suggest a high and continuous exposure to MeHg, supporting the need of strengthenning the health surveillance in riverside populations.

TS16-P18 — 11:00-12:00 and 17:30-18:30
Authors: POULIN, Brett A.1, AIKEN, George R.1, RYAN, Joseph N.2, NAGY, Kathryn L.3
(1) United States Geological Survey, poulinbrett@gmail.com; (2) University of Colorado at Boulder; (3) University of Illinois at Chicago.

Mercury transport from contaminated East Fork Poplar Creek floodplain soils in Oak Ridge, TN contributes to downstream mercury pools available for methylation, but the environmental controls of soil-to-stream mercury release are not well understood. Factors such as fluctuations in soil redox status, soil geochemistry, dissolved organic matter and mineral colloids likely control the mobilization and subsequent transport of mercury from contaminated soils to nearby streams. In this study, mercury release was assessed from two Oak Ridge soils, a stream bank site and a floodplain site. Soil characterization of each site included total mercury concentration, mercury physiochemical speciation via selective sequential extraction, organic matter content, elemental composition, cation exchange capacity, and soil mineralogy. Undisturbed, intact soil cores were collected at the sample sites from the O/A (0-30 cm depth) and subsurface B (35-65 cm depth) soil horizons. In the laboratory, soil cores were flooded with deionized water. To simulate the effects of a fluctuating water table, flooded cores were drained, allowed to dry for 7 d, and subjected to second and third flooding events. During flooding events, which lasted a period of 21 d, porewater was sampled at 6-48 h intervals. Porewater analyses included pH, total dissolved mercury (0.2 µm-filtered), total dissolved iron, dissolved iron(II), dissolved sulfate and sulfide, dissolved organic carbon (DOC), DOC specific ultraviolet absorbance, and colloid characterization. Analysis of porewater colloids included elemental and mineralogical composition, morphology, and size. Soil characterization data identified significant differences between the two sample sites including total mercury concentration, mercury speciation, and organic matter content. Our results aim to identify the dominant source(s) of the mobile soil mercury pool by comparing mercury release dynamics (in soil cores) between sample sites and soil horizons. Under reducing conditions, we observed a relationship between changes in soil geochemistry and the subsequent effect on porewater composition and mercury release. Data from second and third flooding events showed evidence of mercury desorption, diffusion, and precipitation dynamics driven by a fluctuating water table.

TS16-P19 — 11:00-12:00 and 17:30-18:30
Authors: MILLER, Matthieu1, GUSTIN, Mae1
(1) UNR, matthieum@unr.edu

Mercury (Hg) is often naturally enriched in rocks hosting gold mineralization, and consequently can be released during the mining and processing of gold ore. Hg emissions from non-point sources at industrial open pit gold mines, which include spatially extensive areas of ore in varying stages of processing as well as waste rock material, can be significant. Recent work suggested that Hg releases are highest from materials being actively leached for gold and from the tailings impoundments that contain residual rock waste from mill processing. Field data suggested that reclamation and dust control techniques already commonly applied at mining operations may substantially reduce Hg emissions. This project investigated potential reductions in Hg emission using two of these techniques: capping of high Hg mine process materials with low Hg substrates, and application of dust control solutions. Oxide ore rock, tailings waste, and capping substrate materials were collected from four open pit gold mines in north-central Nevada, and flux data were collected using dynamic flux chambers in a controlled environment at the University of Nevada, Reno. Preliminary results indicate that depending on substrate characteristics, capping high Hg materials with low Hg substrates can reduce Hg emissions significantly, under both wet and dry conditions. Both low-grade oxide ore and tailings waste material showed low Hg flux when dry (mean 0.7 and 4.6 ng m-2 hr-1, respectively), and small difference in flux between capped and uncapped samples. Wet materials showed much higher fluxes (100s ng m-2 hr-1) and a greater difference in flux for capped versus uncapped.

TS16-P20 — 11:00-12:00 and 17:30-18:30
Authors: STECKLING, Nadine1, BOSE-O’REILLY, Stephan2, GRADEL, Cornelia1, DRASCH, Gustav3, SIEBERT, Uwe2, HORNBERG, Claudia1
(1) Faculty of Health Sciences, Bielefeld School of Public Health, Bielefeld University, Bielefeld, Germany, nadine.steckling@uni-bielefeld.de; (2) Institute of Public Health, Medical Decision Making and Health Technology Assessment, UMIT (University for Health Sciences, Medical Informatics and Technology), Hall in Tirol, Austria; (3) Department of Forensic Toxicology, Institute of Forensic Medicine, University of Munich, Munich, Germany;

Artisanal small-scale gold mining (ASGM) is a poverty-driven activity in developing countries. Since the 1990s gold mining became the main livelihood for people in Mongolia who lost their jobs during the economic transition as well as for nomadic herders who lost their livestock during a particularly harsh winter. Poor rural inhabitants try to improve their situation by extracting gold by amalgamation - a simple and available technology. Mercury is discharged into the environment, where it poses a hazard for human health.

In September 2008, an environmental epidemiological study was conducted in Mongolia to assess the human exposure: Urine, blood and hair samples were collected from 156 exposed and 42 unexposed Mongolian women. The human specimens were analyzed for mercury. Three subgroups were formed, depending on the different dimension of mercury exposure: (1) occupational exposure (medium/high exposed group, n= 64); (2) environmental exposure (low exposed group, n= 92); and (3) no exposure (control group, n= 42). Internal mercury distributions of the subgroups were compared using the Kruskal–Wallis and Mann–Whitney U-test. The Chi-square test and likelihood ratio proportion were used to compare the results with threshold limits (German Human Biomonitoring (HBM) values).

The highest values and the greatest differences in the subgroups were seen in the urine samples (p<0.001, Kruskal–Wallis), with a maximum of 78.5 µg/l urine. The occupational exposed group showing the highest exposure with a median mercury level of 4.36 µg/l urine (control group: 0.10 µg/l, p<0.001), 7.18 µg/g creatinine and 12 results above the threshold limit HBM I. Even participants from the low-exposure subgroup showed elevated mercury levels (median 2.88 µg/l urine; 2.98 µg/g creatinine, p<0.001), with 10 individuals above the HBM I threshold limits.

The body burden resulting from the use of mercury in ASGM is high not only within the group of active miners. An increased hazard was also found for inhabitants of mining areas who were not actively involved in mining. In some cases, environmental exposed residents exceed occupational guidance values. Women of child-bearing age represent a particular group at-risk, because of secondary mercury exposure of fetuses and infants. Public health support measures are urgently needed to improve the situation by supporting the population groups thus affected.

TS16-P21 — 11:00-12:00 and 17:30-18:30
Authors: GASCON DIEZ, Elena1, GRAHAM, Neil David1, LOIZEAU, Jean-Luc1
(1) University of Geneva, elena.gascon@unige.ch

Elevated concentrations of mercury found in the sediments of the Bay of Vidy renders this area a hot spot in Lake Geneva (Switzerland). This persistent loading of mercury to the bay is due to the effluent of the Waste Water Treatment Plant (WWTP) of the city of Lausanne. Previous studies have shown a higher concentration of total mercury and methylmercury near the WWTP outlet pipe as compared to sampling points further from the outlet pipe. This study attempts to determine i) the dispersal of mercury from the lake coastal zone to the deep lake, ii) the main currents responsible for sediment focusing in this area, and iii) the fate of mercury deposited in the bay. Surface sediments were collected around the WWTP effluent, and towards the deepest part of the lake. Subsequent analyses comprised total mercury (THg), methylmercury (MHg), grain size, and organic matter. Similar analyses were performed to sediment trap particles collected over a period of one year, on a monthly basis, at two sites off the bay. Finally a sediment core has been retrieved from the bay to reconstruct the Hg history.

Results show a clear impact of the WWTP, high Hg concentrations (up to 12 mg THg/kg) being observed at the onset of the WWTP. Although current mercury concentrations in the bay are lower than those exhibited in the past, concentrations are still found to be high around the WWTP outlet. Total mercury has been found to be 1.32 mg/kg around the outlet whereas the natural background of the lake, prior to the implementation of the WWTP, was 0.04mg/kg, and concentrations observed in the major lake sediment surface were 0.2 mg/kg. Moreover, THg and MHg results from both sediment surface and settling particles aid in identifying possible remobilization of mercury from the sediments to the water column and its subsequent transport further deep, and/or the release of particle-bound mercury from the WWTP.

TS16-P22 — 11:00-12:00 and 17:30-18:30
Authors: GIBSON, Blair D1, DAUGHERTY, Shannon D1, LINDSAY, Matthew BJ1, PTACEK, Carol J1, BLOWES, David W1, LANDIS, Richard C2, DYER, James A2
(1) University of Waterloo, bgibson@uwaterloo.ca; (2) DuPont Company;

Mitigation strategies for contaminated sediment include monitored natural attenuation, in situ capping, and sediment removal by dredging operations. Although sediment removal prevents future releases into the surrounding aquatic environment, dredging operations may result in the resuspension of anoxic sediment and induce the release of heavy metals through oxidative dissolution processes. This study involved collection of core samples from various locations within a mercury-contaminated lake which were characterized using physical and chemical methods. Sequential extraction analyses suggested that mercury is mainly present as an organo-chelate or mercuric sulfide/selenide, with trace amounts of water soluble mercury. Micro-X-ray absorption near edge spectroscopy (µ-XANES) and micro-X-ray fluorescence (µ-XRF) analyses using synchrotron-based radiation suggested a correlation between mercury, selenium, and copper. Resuspension tests, performed in both oxic and anoxic environments to assess the effects of air entrainment during a simulated dredging operation, showed that mixing under oxic conditions generally induced a larger release of aqueous mercury compared to anoxic mixing, presumably due to the oxidation of mercury-chelates and/or mercury sulfide/selenide. Four different treatment media were assessed in batch and column experiments for their potential to stabilize mercury in the sediment. The treatment media were chosen to induce aqueous mercury removal through either adsorption or chemical binding. Experimental conditions, including reaction time, treatment media mass, and redox conditions, were varied to evaluate treatment effectiveness over a range of geochemical conditions. Results from the batch experiments indicated a general mass dependence on treatment effectiveness, with greater mercury removal observed with increased treatment media mass. Aqueous mercury concentrations were reduced from > 800 ng L-1 in a non-amended control sample to < 50 ng L-1 in the amended samples. Results from the column experiments indicated that the sediment did not release environmentally-significant mercury concentrations in the column effluent if maintained under anoxic and constant flow conditions. However, after column flow had been stagnated for prolonged times, subsequent reinitiation of flow resulted in the release of elevated concentrations of mercury. These increases in concentration were not observed in the columns containing sediment co-blended with elemental sulfur and iron or attapulgite clay following reinitiation of flow.

TS16-P23 — 11:00-12:00 and 17:30-18:30
Authors: WATSON, David1, CARRIE, Miller1, LOWE, Kenneth1, BRIAN, Lester2, SOUTHWORTH, George1, BOGLE, Mary Anna1, LIANG, Liyuan1
(1) Oak Ridge National Laboratory, watsondb@ornl.gov; (2) ;

During past operations at industrial facilities like the Department of Energy (DOE) Y-12 National Security Complex (NSC), and Oak Ridge National Laboratory in Oak Ridge, Tennessee, large quantities of elemental mercury (Hg) were inadvertently released to the environment resulting in extensive soil and groundwater contamination. Subsequent transport of Hg into nearby surface water has resulted in uptake by fish and other biota. The exact location of past Hg spills and the spatial subsurface distribution of Hg at these sites are poorly understood, making it difficult to select effective remedial actions and assess their potential effectiveness and cost. The Y-12 NSC site has many aging facilities in need of decommissioning. One of the largest areas of risk and therefore cost contingency is related to the uncertainty in the nature and extent of the Hg releases. The current estimated Hg cleanup cost at the Y-12 NSC is $1 billion, based on the assumption that large volumes of mercury contaminated soils will have to be stored, treated and/or disposed in landfills. Development and demonstration of reliable measurement tools that can detect and help quantify the nature and extent of mercury in the subsurface are needed to reduce these uncertainties and increase the effectiveness of remedial actions. Our recent laboratory and field tests at the Y-12 NSC have shown that sampling and analysis of Hg vapors in the shallow subsurface (<0.3 m depth) can be an excellent indicator of the location and extent of Hg(0) releases in the subsurface. We constructed a rigid PVC pushprobe assembly, which was driven into the ground. Soil gas samples were collected through a sealed inner tube of the assembly and analyzed immediately in the field with a Jerome or Lumex Hg analyzer. Time-series sampling showed that Hg vapor concentrations were fairly stable over time suggesting that the vapor phase Hg was not being depleted and that the results were not very sensitive to the purge volume. Controlled head space analysis of Hg contaminated core material in the laboratory provided data on the Hg vapor concentrations that indicate the presence of Hg(0). Hg vapor data collected at over 200 pushprobe locations at 3 different release sites correlated well to areas of known Hg(0) contamination. These results suggest that soil gas sampling and analysis can be conducted rapidly and inexpensively at a large scale to help identify areas contaminated with elemental Hg.

TS16-P24 — 11:00-12:00 and 17:30-18:30
Authors: KOCMAN, David1, BROOKS, Scott1, MILLER, Carrie1, BOGLE, Mary Anna1, YIN, Xiangping1, LIANG, Liyuan1
(1) Oak Ridge National Laboratory, kocmand@ornl.gov

Mercury use at the Oak Ridge Y-12 National Security Complex (Y-12 NSC) between 1950- 1963 resulted in contamination of the East Fork Poplar Creek (EFPC) ecosystems. Hg continues to be released into EFPC creek from point sources and diffuse contaminated soil and groundwater sources within the Y-12 NSC and outside the facility boundary. In general, methylmercury (MeHg) concentrations in water and in fish have not declined in response to improvements in water quality and exhibit trends of increasing concentration in some cases. Therefore, our study focuses on identifying ecosystem compartments and/or characteristics that favor the production, as well as degradation, of MeHg in the EFPC. Detailed geochemical characterization of the surface water, interstitial pore water, and creek sediments were performed during quarterly sampling campaigns in 2010 and 2011 at two locations in the EFPC. The two sites in EFPC were located 3.7 km (NOAA) and 20 km (NH) downstream of the headwaters. Vertical profiles of interstitial water collected from fine-grained deposits at the creek margin showed decreases in nitrate, sulfate, and oxidation-reduction potential (ORP) with depth as well as increases in dissolved manganese, iron, and small increases in sulfide. The results indicate the progression of terminal electron accepting processes with depth in the upper 30 cm of these fine grained sediments. Interstitial MeHg concentration also increased with depth in August 2010 suggesting these areas served as a source of MeHg. In contrast, interstitial water collected from the center channel of the creek did not exhibit these redox gradients. The observed constant or decreasing MeHg concentrations with depth suggest that the interstitial water in the fast flowing sections of the creek is rapidly exchanging with the surface water and these sections do not serve as MeHg sources. Total Hg concentration in sediment cores from the creek margin was variable, 0.057-24 mg/kg and 0.02-155 mg/kg, at NH and NOAA respectively. MeHg measured on a subset of these sectioned cores ranged from 1.6-3.1 µg/kg at NH and 0.08-9.5 µg/kg at NOAA. Large intra- and inter-site variability of Hg distribution in these samples is partly attributed to the very heterogeneous sediment texture that ranged from coarse- to fine-grained. Methylation and demethylation potentials are also being examined using intact sediment cores and enriched stable isotopes to quantify zones of net MeHg production.

TS16-P25 — 11:00-12:00 and 17:30-18:30
Authors: VU, Loi D1, MINESHI, Sakamoto2, DUONG, Hung T3
(1) Institute of Chemistry- Vietnam Academy of Science and Technology, ducloi@ich.vast.ac.vn; (2) Natinal Institute for Minamata Disease; (3) Institute of Chemistry.

The purpose of this study was to assess of human exposure to mercury (Hg) due to gold mining activities in Vietnam. Mercury vapor is one of the most risky substances occurring through inhalation due to the easy vaporization of metallic mercury, and mercury concentration in plasma is the best biomarker of mercury vapor exposure. The total mercury (T-Hg) as well as methyl mercury (Me-Hg) was determined in human hair, plasma, and urine samples collected from 51 miners who have been working at the two gold mines located in the northern and the central Vietnam. The total mercury concentrations in plasma and hair of miners were 14.86±7.82 ppb and 33.54±12.74 ppm, respectively which was significantly (P<0.01) higher than that of control group (0.98±0.50 ppb) and (0.95±0.22 ppm). The differences of methyl mercury content in hair between miners and control group were not found, whereas a significant correlation was observed between T-Hg and Me-Hg in hair from control group (R2 =0.91, p<0.01). These results confirm that T-Hg in plasma is a good biomarker for assessment of mercury vapor exposure.

TS16-P26 — 11:00-12:00 and 17:30-18:30
Authors: LIU, Peng1, WANG, Ou1, PTACEK, Carol J.1, BLOWES, David W.1, BERTI, William R.2, LANDIS, Richard C.2
(1) University of Waterloo, p26liu@uwaterloo.ca; (2) DuPont Co.;

Biochar is the generic name for stable, carbon-rich charcoal produced by thermal decomposition of organic material (biomass pyrolysis) under low/no oxygen conditions at relatively low temperature (<700°C). Among the many potential benefits attributed to its use, we are studying its potential to adsorb mercury in river water as a way to reduce mercury (bio)availability. Three biochars made from mushroom soil (MS), poultry manure (PO) and pine wood-chips (WC), were prepared by charring at 225 oC for 2-3 hours. They were then characterized and evaluated for their ability to remove mercury from river water. A series of batch-style experiments was conducted, which included addition of biochar (<2 mm) to Hg(II)-spiked (as HgCl2) river water at a 1:75 ratio. The water chemistry was monitored at 2 and 14 days after equilibrating the biochar and water mixtures. The removal of mercury was 96 %, 80 % and 96 % at 2 days and 99 %, 97 %, and 99 % at 14 days for MS, WC, and PO for a mercury initial concentration of 7780 ng/L. Solid-phase characterization of the biochar by scanning electron microscope/energy dispersion X-ray spectroscopy (SEM/EDX) indicated the presence of porous structure and high surface area that likely contributed to the high mercury removal capacity. Fourier Transform Infrared Spectroscopy (FT-IR) spectra showed -OH, -CH, -CH2, CH3, R(CO)R, quinone, -C=C-, -C-O-C-, and unknown structures in all three biochars. Carbonyl groups play an important role in Hg sorption. However, carboxylic-carbonate structure was not observed in WC, which could explain why mercury removal by WC was less than PO and MS after 2 days. The FT-IR analyses of PO and MS indicated the presence of carbonate groups (CO32-), which was consistent with the high measured alkalinity in aqueous solution. FT-IR analyses also confirmed the presence of sulfate groups (SO42-) on PO, which is consistent with elevated aqueous concentrations for this material. The results of this study suggest that biochars may be highly effective for removing Hg from contaminated water.

TS16-P27 — 0
Authors: TODOROVA, Svetoslava1, DRISCOLL, Charles1, MATTHEWS, David2
(1)Syracuse University, stodorov@maxwell.syr.edu; (2) Upstate Freshwater Institute.

Zooplankton are an essential link between the upper and the lower trophic positions in aquatic food chains. They are the critical species for initial bioaccumulation of mercury and its subsequent trophic transfer to predator fish and humans. This study focused on understanding the drivers of long-term and seasonal changes in the zooplankton mercury (Hg) concentrations in Onondaga Lake, NY, USA. The water column and sediments of Onondaga Lake are contaminated with Hg as a result of discharge of ionic Hg from a chlor-alkali plant, which was in operation between 1940 and 1988. The lake is culturally eutrophic, historically receiving elevated nitrogen and phosphorus inputs from a regional wastewater treatment facility. The level of Hg contamination in the lake ecosystem has substantially improved due to closure of the industrial facilities and shifts in electron acceptor availability in the anoxic waters.

In this study we present a comprehensive 30-year record of total and methyl Hg concentrations in mixed zooplankton collected from the pelagic zone. Zooplankton data were supplemented with detailed seasonal analysis of mercury species in the epilimnion of the lake during the open water period of 2006, 2007, and 2009. Total Hg concentrations in the zooplankton were positively correlated with the concentrations of total Hg in the upper mixed water. Episodic peak concentrations in zooplankton total Hg corresponded to spikes in epilimnetic inputs due to high runoff events, wind-driven mixing, and fall turnover. Long-term decreases in peak Hg concentrations in the water column and zooplankton were observed, following reductions in Hg load and decreases in nutrient concentrations. The changes in methyl Hg concentrations in zooplankton were driven primarily by changes in the zooplankton community, changes within the food web (i.e., invasion of zebra mussels, appearance of new fish species), as well as by changes in water quality. The applicability of the bio-dilution hypothesis was assessed. Under eutrophic conditions and with prevailing large-bodied zooplankton species, the biodilution hypothesis was confirmed. However, improvements in the nutrient status and shift to small zooplankton species changed the relationship.

Tuesday, 26 July, 2011