Soil Mercury Concentrations Research Articles

Mercury concentrations in paddy field soil and freshwater snails around a small-scale gold mining area, West Java, Indonesia

To estimate the impact of mercury released from an artisanal small-scale gold mining (ASGM) activities on the ecosystem. Total and organic mercury concentrations in paddy field soil and freshwater snails around an artisanal small-scale gold mining area were investigated. Paddy field soil samples and freshwater snails were collected from ten sites along the Cikaniki River. A site located in a national park, which was approximately 12 km upstream from the ASGM site, was considered the reference site for this study. The organic mercury concentration in soil samples collected at the ASGM site was n.d.–0.018 mg kg−1 and that at the reference site was 0.005–0.008 mg kg−1. The organic mercury concentrations in the freshwater snails collected at the ASGM and reference sites were 0.38 ± 0.21 mg kg−1 (31.0 ± 26.6% of total mercury, n = 38) and 0.056 ± 0.032 mg kg−1 (40.5 ± 11.5% of total mercury, n = 16), respectively. Although the original form of mercury in the mining waste was elemental mercury and/or Hg2+, the mercury form changed to organic mercury in environment and the organic mercury was concentrated two orders of magnitude, even in low-order organisms.

Contaminación por mercurio en árboles de carpes (Carpinus betulus) en espacios verdes en el área del parque industrial (Irán)

El mercurio es un metal tóxico que puede acumularse en los órganos de las plantas en grandes cantidades ocasionando toxicidad a los humanos. Carpinus betulus es una especies de los bosques mixtos hircanos del Caspio. En esta investigación, se estudió la cantidad de mercurio que pueden absorber los árboles de carpes del ambiente. Veinticinco árboles fueron seleccionados al azar, las distancias entre árboles fueron de 10 a 15 m en un parque industrial en el norte de Irán. De cada árbol seleccionado, se cosecharon 15 g de hojas y 15 g de raíz con tijeras hortícolas, y 15 g de tierra a partir de 30 cm de profundidad. Se seleccionaron cuatro estaciones cerca de la fábrica de acero. Se seleccionó una estación de control ubicada a 2 km de la fábrica de acero y se ubicaron tres estaciones cerca de la fábrica de acero. Las muestras de hojas, tierra y raíces se prepararon y codificaron, se colocan en sobres de papel y se transfirieron al laboratorio. La cantidad de mercurio en las muestras de plantas se preparó mediante digestión en seco con espectroscopía de absorción atómica. Para comparar el efecto de la concentración de mercurio en la hoja y la raíz, se utilizó la prueba de Tukey. La concentración promedio de mercurio en el suelo fue de 0.96 mg/kg, en la raíz 0.551 mg/kg y en la hoja 0.28 mg/kg. Se observó que con el aumento de mercurio la cantidad de clorofila en la hoja disminuye. Se puede concluir que la cantidad de acumulación de metales mercurio en el árbol Carpinus betulus es adecuada para absorber la contaminación del mercurio de la contaminación del suelo.

Response mechanism of microbial community to the environmental stress caused by the different mercury concentration in soils.

Despite the toxicity of mercury for mammal has been widely studied in recent years, little is known on its impact on the soil microbiome. In this paper, the effects of mercury in soils microbial communities along a gradient of contamination from no to high concentration was assessed by the richness and diversity of microbial community using high throughput sequencing method. The richness of microbial community decreased gradually with the increase of culture time, while the low and medium concentration of mercury had little effect on the evenness of soil microbial community. Proteobacteria tolerated the mercury contamination, while Acidobacteria, Planctomycetes and Chloroflexi were sensitive to mercury pollution in phylum level. Omnitrophica and Ignavibacteriae microorganisms were very sensitive to mercury contamination and dead quickly when contaminated with mercury. Mercury contamination selected two mercury tolerance genuses which were Massilia and Burkholderia in genus level and at least 22 microorganisms such as Alkanindiges, Geothrix, Polycyclovorans and Sporichthya in genus which mainly from the Acidobacteria, Proteobacteria, Bacteroides, Chloroflexi and Omnitrophica phylum were sensitive to mercury. The bacteria tolerant to mercury in soil were Massilia and Burkholderia from Betaproteobacteria and Lysobacter, Luteimonas from Gammaproteobacteria, separately, they were Gram-negative bacteria with thin cell walls and complex ingredients that responded quickly to pollution stress.

Simultaneous Analysis of Heavy Metal Concentration in Soil Samples

The application of Fourier transform infrared spectroscopy to the simultaneous analysis of heavy metal concentration in soil samples was demonstrated in this paper. Two spectral techniques, namely, attenuated total reflectance (ATR) and diffuse reflectance (DRIFT), were applied and the whole infrared spectral region, i.e., far IR, mid IR, and near IR were considered in this work. Spectral data with reference to the results of laboratory analysis enabled the development of calibration partial least squares (PLS) models. The PLS models for the ATR near IR were characterized by a good fit and good prediction abilities. According to the results obtained, the most accurate description and prediction were realized in the case of mid/far and near IR for the mercury and nickel concentration in soil. Application of far IR slightly improved the prediction possibilities of the model. The construction of PLS models based on the Fourier-transform infrared (FT-IR) spectra enables the perception of FT-IR spectroscopy as a supplementary method that is useful in the estimation and monitoring of the contamination level in soils.

Comparison of spatial interpolation methods for mercury content in soil of contaminated farmland in Tongren

Taking mercury-contaminated farmland in Tongren city, Guizhou province as study area, we conducted five interpolation methods, including inverse distance weight, radial basis function, global polynomial, local polynomial and kriging, for the collected soil mercury content data. The interpolation results were evaluated by cross validation. The results indicated that the five methods can accurately reflect the spatial distribution characteristics of the study area and the interpolation effect and precision of kriging method are optimal. In kriging method, the accuracy of removing second-order trends is highest, and the interpolation effect of exponential model is the best. The variation function model of kriging method shows that soil mercury content in this region is mainly affected by natural factors, but less affected by random factors.

Phytoremediation potential of Miscanthus sinensis for mercury-polluted sites and its impacts on soil microbial community.

Phytoremediation potential of Miscanthus sinensis and its impacts on soil microbial community and nutrients were evaluated by pot experiment at soil mercury concentration from 1.48 to 706 mg kg-1. The changes in biomass yield in dry mass, chlorophyll content, and SOD activity indicated Miscanthus sinensis was tolerant to higher levels of soil mercury exposure, and could grow even if at soil mercury up to 706 mg kg-1. Mercury bioconcentration and translocation factors were close to or greater than 1 when exposed to soil mercury up to 183 mg kg-1, demonstrating Miscanthus sinensis a potential phytoremediator for mercury-polluted soils. Miscanthus sinensis planting could significantly improve the diversity and abundance of soil microbial community, but might cause potential loss of soil nitrogen and phosphorus in the early and middle of its growth. In a word, the study indicated Miscanthus sinensis was a promising energy crop linking biofuel production and phytoremediation of mercury-contaminated sites.

Mercury resistance and bioremediation mediated by endophytic fungi

The present study proposes the use of endophytic fungi for mercury bioremediation in in vitro and host-associated systems. We examined mercury resistance in 32 strains of endophytic fungi grown in culture medium supplemented with toxic metal concentrations. The residual mercury concentrations were quantified after mycelial growth. Aspergillus sp. A31, Curvularia geniculata P1, Lindgomycetaceae P87, and Westerdykella sp. P71 were selected and further tested for mercury bioremediation and bioaccumulation in vitro, as well as for growth promotion of Aeschynomene fluminensis and Zea mays in the presence or absence of the metal. Aspergillus sp. A31, C. geniculata P1, Lindgomycetaceae P87 and Westerdykella sp. P71 removed up to 100% of mercury from the culture medium in a species-dependent manner and they promoted A. fluminensis and Z. mays growth in substrates containing mercury or not (Dunnett's test, p < 0.05). Lindgomycetaceae P87 and C. geniculata P1 are dark septate endophytic fungi that endophytically colonize root cells of their host plants. The increase of host biomass correlated with the reduction of soil mercury concentration due to the metal bioaccumulation in host tissues and its possible volatilization. The soil mercury concentration was decreased by 7.69% and 57.14% in A. fluminensis plants inoculated with Lindgomycetaceae P87 + Aspergillus sp. A31 and Lindgomycetaceae P87, respectively (Dunnet's test, p < 0.05). The resistance mechanisms of mercury volatilization and bioaccumulation in plant tissues mediated by these endophytic fungi can contribute to bioremediation programs. The biochemical and genetic mechanisms involved in bioaccumulation and volatilization need to be elucidated in the future.

REKLAMASI LAHAN KRITIS BEKAS PENAMBANGAN EMAS MENGGUNAKAN METODE BIOREMEDIASI DAN FITOREMEDIASI

Degraded land caused by gold mining activities in Central Kalimantan requires reclamation efforts, in order to restore of soil conditions, due to the damage of topsoil layer, lack of soil nutrients, and reduced of soil fertility. This research aim was to find an appropriate method of biological reclamation in ex gold mining area, by utilizing a combination of several types of microorganisms and mercury phytoremediator plants. The research is an experiment on a pilot scale at an ex gold mining site in Central Kalimantan. Bioremediation method has used a consortium of local isolates Klebsiella sp. and Pseudomonas sp., and the phytoremediation method was used Melastoma sp. and Cyperus sp. Dependent variables were soil mercury concentration and soil nutrients. The results showed the application of consortium microorganisms and mercury phytoremediator, were able to reduce soil mercury concentrations in averages 2.5 ppm, soil nutrient levels increased in averages 33%. These increased soil nutrients consist of potassium in averaged 73%, Mg in average 21%, Na in average 19.5%, and Fe in averaged 71%, when compared to controls. The application of consortium of microorganisms combined with mercury plant phytoremediator type Melastoma sp., able more to improve soil conditions in ex gold mining area compared to Cyperus sp.

Occurrence, Distribution and Risk Assessment of Mercury in Multimedia of Soil-Dust-Plants in Shanghai, China.

The urban environment is a complex ecosystem influenced by strong human disturbances in multi-environmental media, so it is necessary to analyze urban environmental pollutants through the comprehensive analysis of different media. Soil, road dust, foliar dust, and camphor leaves from 32 sample sites in Shanghai were collected for the analysis of mercury contamination in soil–road dust–leaves–foliar dust systems. Mercury concentrations in surface soils in Shanghai were the highest, followed by road dust, foliar dust, and leaves, successively. The spatial distribution of mercury in the four environmental media presented different distribution patterns. Except for the significant correlation between mercury concentrations in road dust and mercury concentrations in leaves (r = 0.56, p < 0.001), there was no significant correlation between the other groups in the four media. Besides this, there was no significant correlation between mercury concentrations and land types. The LUR (Land use regression) model was used to assess the impact of urbanization factors on mercury distribution in the environment. The results showed that soil mercury was affected by factories and residential areas. Foliar dust mercury was affected by road density and power plants. Leaf mercury was affected by power plants and road dust mercury was affected by public service areas. The highest average HI (Hazard index) value of mercury in Shanghai was found in road dust, followed by surface soil and foliar dust. The HI values for children were much higher than those for adults. However, the HI values of mercury exposure in all sampling sites were less than one, suggesting a lower health risk level. The microscopic mechanism of mercury in different environmental media was suggested to be studied further in order to learn the quantitative effects of urbanization factors on mercury concentrations.

Mercury and methylmercury levels in soils associated with coal-fired power plants in central-northern Chile

Mercury pollution is a worldwide problem, and is associated with a number of natural and anthropogenic processes. The present work, conducted in Chile, a country that has traditionally depended heavily on fossil fuels for power generation, examines total mercury (THg) and monomethylmercury (MMHg) concentrations in soils across different sites exposed to coal fired power plant emissions. Samples from four selected (Renca, Laguna Verde, Las Ventanas, Huasco) and 1 control (Quintay) sites were analyzed using cold vapour and fluorescence spectroscopy (CV-AFS) for THg determination and chromatographic separation with atomic fluorescence detection (DI-GC-AFS) was followed for speciation analysis.From the sites analyzed, Renca and Las Ventanas showed high concentrations of total mercury, exhibiting ranges between 135 – 568 and 94–464 ng g−1 respectively, while Laguna Verde and Huasco exhibited lower values ranged 5–27 and 9–44 ng g−1 respectively. Conversely, analysis of MMHg concentrations showed that only Renca site possessed high values, ranging between 0.1 and 3.0 ng g−1, resulting in this site being considered contaminated. Conversely, other sites showed minimal values comparable to the control site (0.024 ± 0.003 ng g−1) in terms of MMHg concentrations. An analysis of the differences between MMHg and THg concentrations in contaminated sites, suggests an overall absence of methylation in soils of Las Ventanas, probably related to the very high levels of soil heavy metals, especially copper. Moreover, the influence of the composition and physicochemical properties of the different soils on the mobility of the species was assessed. Results obtained (as Log Kd) were 3.5 and 4.1 for Renca and Las Ventanas respectively, suggesting low mobility of mercury species in the environment for both sites.Finally, the data obtained allowed us to establish a first approximation of the differences in concentration and mobility of total and MMHg associated with coal fired power plants emission in central-northern Chile, an area previously understudied in a country heavily dependent on fossil-fuels.

A Review for the Long-Term Trend and Spatial Distribution of Soil Mercury Concentration in South Korea

A Review for the Long-Term Trend and Spatial Distribution of Soil Mercury Concentration in South Korea

Measurement and Scaling of Mercury on Soil and Air in a Historical Artisanal Gold Mining Area in Northeastern China

The Jiapigou gold mine area, located in the upper reaches of the Songhua River, was the first and largest artisanal gold mine once in China, and it used to be prominent in two marking years (1870 and 1974). Jiapigou area had a gold mining history of more than 190 years, which was first opened in 1820. Gold extraction with algamation was applied as the dominant method of excavation from 1940 to 2008, and a total of more than 100 t of gold were extracted from the mine using this method and it was estimated that 100–200 t Hg were released, thus causing severe mercury environmental pollution in the mining area. In the experimental campaigns of this study, in situ air and soil Hg concentrations and air-soil Hg fluxes were measured from April 2009 to December 2011. The results showed that in the study area the total gaseous mercury (TGM) concentration exhibited remarkable spatial and temporal distribution patterns, i.e. the TGM gradually decreased following the increase in distance to gold mining sites in space, and the values in spring, summer and autumn were elevated by 1–2 orders of magnitude in comparison with those in winter. Furthermore, at other sampling sites the total soil mercury (TSM) concentration in spring was higher than that in autumn, except for the contrary laws demonstrated at the Erdaogou mining site. However, in spring and winter the Hg flux between air and soil was under the control of different environmental factors, and the characteristics were clear and distinct. In spring the Hg flux between air and soil was directly under the control of solar irradiation, and the releasing process was predominant with a remarkable positive correlation to solar irradiation. Nevertheless, in winter the Hg fluxes were indirectly under the control of solar irradiation, which caused thermal inversion due to the thick snow cover. The depositing process was predominant and the correlations between Hg flux and air temperature was remarkably negative, and there was a positive correlation between Hg flux and solar irradiation.

Critical mercury concentration in tropical soils: Impact on plants and soil biological attributes

Mercury is a toxic element that becomes a problem when present at high concentrations in soils. Mercury toxicity in soils varies depending on chemical species, concentration, exposure routes, and organism vulnerability. There is little information regarding the toxicity of Hg in tropical soils, especially for establishing safe levels of this pollutant. The purpose of this study was to investigate Hg concentrations in two tropical soils and their effect on oats and common beans, as well as on soil biological attributes. The experiment was carried out in a greenhouse, following ISO 11.269-2 and OECD-208 guidelines. Oat and common bean were cultivated in a Typic Hapludox (TyHpx) and Rhodic Acrudox (RhAcx) contaminated with HgCl2 at the following concentrations: 0, 2.5, 5.0, 10.0, 20.0, 40.0, and 80.0 mg of Hg kg−1 of dry soil. The biological variables analyzed were seedling emergence, vegetative growth, chlorophyll content (SPAD index), gas exchange (photosynthetic rate, internal CO2 concentration, transpiration rate, and stomatal conductance), and Hg concentration and accumulation in shoot dry matter. Microbial biomass carbon, soil basal respiration, and metabolic quotient (qCO2) were also analyzed. Due to the sorptive characteristics of TyHpx, it had higher Hg concentrations than RhAcx. Mercury showed toxic effects on both oat and common bean species. However, common bean was affected only at concentrations higher than 20 mg kg−1. The microbial community showed high sensitivity to soil Hg concentrations, but external factors, such as the plant species cultivated, influenced the sensitivity of the community. The microbiota was most sensitive in pots with common bean, and this effect was more pronounced at low clay and low organic matter contents (TyHpx). In this study, the concentration of 0.36 mg kg−1 was critical for Hg in these soils, based on its deleterious effects on oat and common bean and on biological soil attributes.

Consequences of Mercury Used by Artisanal and Small-Scale Gold Mining Processes – A Case of River Nile State Sudan

On the discovery of gold reserves in 14 states in Sudan, traditional gold mining suddenly started to flourish and hundreds of thousands of laymen became engaged in gold extraction. The use of mercury in gold extraction poses much threat to the environment and general health of miners and the surrounding areas. The investigation includes: The effects of extraction methods on the environment and general health, The level of education and its distribution within the miners and how it affected the awareness of the miners about the dangers of mining activities, The period of stay that miners spend in the mining area and its contribution on the awareness about the dangers and diseases inflicted on the miners, The effects of traditional gold mining activities on natural environmental and The effects of the meteorological and topographical factors, the distribution and concentration of mercury in the area and their effects on the environment and general health. The research adopted the techniques of using random sampling and quantitative qualitative in addition to the analytical techniques. The research finally concluded that the mercury has potential to distribution and transport from study area to neighboring places by two meteorological and topographical factors, the wind directions and speed, those two meteorological elements affect the transport of pollutants from the highest to the lowest boundary layers. The area is characterized by high temperatures during most of year for ten months (50c) and low temperatures during winter months to (5c). Mercury starts to evaporate at temperature exceeding (25c). hence areas of higher temperatures are subjected to higher mercury concentration than other area of low temperatures. The study area is located at a height of (372 meters) above sea level, and that the River Nile to the West is located at an altitude of (340 meters), Topographically contour lines retreat towards in the River Nile, the fact which means that the surface run-off water will flow towards in River Nile and carry mercury concentration because of the natural slope of the area. But a portion of the Western area slopes towards the residents within the surrounding communities. Artisanal and small-scale gold mining has positive effects on the economic side and negative effects on the environment and general health. Keywords: artisanal and small-scale gold mining, Workers occupationally exposed (WOE), Residents in surrounding communities (RSC), Distribution of mercury concentration in surface soil and surface water, Meteorological and topographical factors.

Экогеохимия ртути в почвах и углях юга Кузбасса

Assessment for content of mercury as a toxic component of coal combustion by-product in rocks and deposit environments is aimed at identification of risks caused by impact of hazardous activities on the environment in full concordance with green chemistry concept. In this paper have been presented results of mercury content determination for the South Kuzbass coals and soils of the coal-mining area. The mercury contents in soils (30 samples) and coals (30 samples) were determined by atomic absorption method on the RA‑915+ mercury analyzer with pyrolytic attachment. The mercury content in Mezhdurechensk strip mines’ coals varies from 0.13 to 2.46 mg/kg with the average concentration of 0.57±0.10 mg/kg. The determined content exceeds the Clarke of mercury in coals by factor of 1.3 to 24.6. The mercury content in soil samples varies from 0.012 to 0.173 mg/kg with the average value of 0.057±0.007 mg/kg, which is by 1.7 times more than the average mercury content in the Earth crust. There are five locations within Mezhdurechensk city area where the mercury content in the soil exceeds 3.1–5.3 times the Clark value. During past 25 years the average mercury content in the soil has been decreased by 2.8 times. The solubility of mercury from technogenic landscapes’ soils has been studied by methods of successive acetate-ammonium and hydrochloric acid extracts. The solubility of mercury in aqueous extracts from Mezhdurechensk soils is by 2.2–2.9 times higher than the ones taken from undisturbed landscapes, in acetate-hydrochloric acid and alkaline extracts it is within the limits of content in natural soils; in strongly acidic extracts has been found the maximum solubility of mercury (30.6–84.8% from the total amount). Based on the major contribution of coal dust in the gross input of mercury into the environment of Mezhdurechensk, it is possible to expect the increasing of mercury background in and around the city caused by the growth of coal mining in the area without implementation of modern and effective methods for dust suppression.

Estimation Methods for Soil Mercury Content Using Hyperspectral Remote Sensing

Mercury is one of the five most toxic heavy metals to the human body. In order to select a high-precision method for predicting the mercury content in soil using hyperspectral techniques, 75 soil samples were collected in Guangdong Province to obtain the soil mercury content by chemical analysis and hyperspectral data based on an indoor hyperspectral experiment. A multiple linear regression (MLR), a back-propagation neural network (BPNN), and a genetic algorithm optimization of the BPNN (GA-BPNN) were used to establish a relationship between the hyperspectral data and the soil mercury content and to predict the soil mercury content. In addition, the feasibility and modeling effects of the three modeling methods were compared and discussed. The results show that the GA-BPNN provided the best soil mercury prediction model. The modeling R2 is 0.842, the root mean square error (RMSE) is 0.052, and the mean absolute error (MAE) is 0.037; the testing R2 is 0.923, the RMSE is 0.042, and the MAE is 0.033. Thus, the GA-BPNN method is the optimum method to predict soil mercury content and the results provide a scientific basis and technical support for the hyperspectral inversion of the soil mercury content.

Low-thermal remediation of mercury-contaminated soil and cultivation of treated soil

In this study, low-thermal technology was used to treat the mercury contaminated farmland soil from a chemical plant in Guizhou Province, China. A series of field planting experiments were also aimed at determining the content of total and methyl-Hg in crop plants after thermal treatment. The results showed that the mercury concentration in soils was reduced about 70% from 255.74mg/kg to 80.63mg/kg when treated at 350°C for 30min in engineering-scale experiments, and the treated soil retained most of its original soil. Organic-bound and residual mercury in treated soil were reduced by 64.1 and 56.4% by means of a sequential extraction procedure, respectively. The total and methyl-mercury concentrations in crops decreased significantly, and the degree of soil mercury accumulation to crop roots has been reduced significantly. The total Hg concentrations in potato and corn were lower than the mercury tolerance limits for food in China, and the Hg concentration of radish was close to the limit. The technology provides a more sustainable remediation method for treating mercury-contaminated farmland soil in future engineering applications.

Are the existing guideline values adequate to protect soil health from inorganic mercury contamination?

Currently, data that guide safe concentration ranges for inorganic mercury in the soil are lacking and subsequently, threaten soil health. In the present study, a species sensitivity distribution (SSD) approach was applied to estimate critical mercury concentration that has little (HC5) or no effect (PNEC) on soil biota. Recently published terrestrial toxicity data were incorporated in the approach. Considering total mercury content in soils, the estimated HC5 was 0.6 mg/kg, and the PNEC was 0.12–0.6 mg/kg. Whereas, when only water-soluble mercury fractions were considered, these values were 0.04 mg/kg and 0.008–0.04 mg/kg, respectively.

Mercury sink in Amazon rainforest: soil geochemical data from the Tapajos National Forest, Brazil

Atmospheric mercury sink in Amazonian rainforest was tested in this work. Forest soil was analyzed for 11 soil profiles at depths of 0–40 cm in the northern portion of the Tapajos National Forest, Brazilian Amazon. Major oxides and Hg contents in soil and rock were determined by XRF and by Zeeman AAS, respectively. A mercury content of 146 μg kg−1 was found in the bedrock, whereas the mercury content in soil averaged 240 μg kg−1. The soil pH varied from 4.4 to 5.2 and the organic matter contents varied from 1.4 to 7.5%. Enrichment factors of Hg for soil were calculated in relation to the parental bedrock assuming aluminum as immobile element. The lower soil layers presented mercury enrichment of 29–98% in comparison to the bedrock. The upper soil layers showed mercury enrichment of 4–24% in comparison to lower soil layers. Mercury in soil was highly correlated with Al, Fe, and Ti; however, no significant correlation was observed between Hg and organic matter contents. All results pointed to mercury retention in forest soils as a result of the combined action of rock weathering processes and continuous input of metal from the atmosphere, estimated to be between 31 and 46% of the total Hg in the upper soil layers. These results are consistent with the hypothesis that the Amazon rainforest is a sink for atmospheric Hg and they also highlight the role of rainforest as a barrier for a number of substances associated with suspended atmospheric particulate.

Senegalese artisanal gold mining leads to elevated total mercury and methylmercury concentrations in soils, sediments, and rivers

The largest source of global mercury (Hg) anthropogenic inputs to the environment is derived from artisanal and small-scale gold mining (ASGM) activities in developing countries. While our understanding of global Hg emissions from ASGM is growing, there is limited empirical documentation about the levels of total mercury (THg) and methylmercury (MeHg) contamination near ASGM sites. We measured THg and MeHg concentrations in soil (n = 119), sediment (n = 22), and water (n = 25) from four active ASGM villages and one non-ASGM reference village in Senegal, West Africa. Nearly all samples had THg and MeHg concentrations that exceeded the reference village concentrations and USEPA regulatory standards. The highest median THg concentrations were found in huts where mercury-gold amalgams were burned (7.5 μg/g), while the highest median MeHg concentrations and percent Hg as MeHg were found in river sediments (4.2 ng/g, 0.41%). Median river water concentrations of THg and MeHg were also elevated compared to values at the reference site (22 ng THg/L, 0.037 ng MeHg/L in ASGM sites). This study provides direct evidence that Hg from ASGM is entering both the terrestrial and aquatic ecosystems where it is converted in soils, sediment, and water to the neurotoxic and bioavailable form of MeHg.