Mercury Mine Research Articles

A New Plant Indicator (Artemisia lavandulaefolia DC.) of Mercury in Soil Developed by Fourier-Transform Near-Infrared Spectroscopy Coupled with Least Squares Support Vector Machine.

A rapid indicator of mercury in soil using a plant (Artemisia lavandulaefolia DC., ALDC) commonly distributed in mercury mining area was established by fusion of Fourier-transform near-infrared (FT-NIR) spectroscopy coupled with least squares support vector machine (LS-SVM). The representative samples of ALDC (stem and leaf) were gathered from the surrounding and distant areas of the mercury mines. As a reference method, the total mercury contents in soil and ALDC samples were determined by a direct mercury analyzer incorporating high-temperature decomposition, catalytic adsorption for impurity removal, amalgamation capture, and atomic absorption spectrometry (AAS). Based on the FT-NIR data of ALDC samples, LS-SVM models were established to distinguish mercury-contaminated and ordinary soil. The results of reference analysis showed that the mercury level of the areas surrounding mercury mines (0–3 kilometers, 7.52–88.59 mg/kg) was significantly higher than that of the areas distant from mercury mines (>5 kilometers, 0–0.75 mg/kg). The LS-SVM classification model of ALDC samples was established based on the original spectra, smoothed spectra, second-derivative (D2) spectra, and standard normal transformation (SNV) spectra, respectively. The prediction accuracy of D2-LS-SVM was the highest (0.950). FT-NIR combined with LS-SVM modeling can quickly and accurately identify the contaminated ALDC. Compared with traditional methods which rely on naked eye observation of plants, this method is objective and more sensitive and applicable.

Newly deposited atmospheric mercury in a simulated rice ecosystem in an active mercury mining region: High loading, accumulation, and availability

Mercury (Hg) mining activities are an important anthropogenic source of atmospheric Hg. The Xunyang Hg mine located in Shaanxi Province is the largest active Hg producing centre in China. To understand the biogeochemical processes of atmospheric Hg through Hg mining activities, six groups of experimental pots were carefully designed to investigate the effect of Hg mining activities on Hg contamination from atmospheric deposition in the local surface soils. Based on the variations of Hg in the soil from the experimental pots, the deposition flux and loading of Hg in the Xunyang Hg mining district were investigated. The results showed that the average concentration of total gaseous mercury (TGM) as high as 193 ± 122 ng m-3 was observed in the ambient air, which was orders of magnitude higher than that in remote areas. The average deposition flux and annual loading of atmospheric Hg were 72 mg m-2 y-1 and 10 t y-1, respectively. The dominant atmospheric Hg deposition is within a distance range of 6.0-12 km from the Hg retorting facility, accounting for approximately 85% of the total Hg loading. After 14 months of exposure, total mercury (THg) concentrations in the soil from the experimental pots increased 0.35-9.5 times, and the highest concentrations of methylmercury (MeHg) (3.7 ± 2.9 μg kg-1) in soil were observed in February. Concentrations as high as 643 μg kg-1 THg and 13 μg kg-1 MeHg in rice were observed in the second experimental year. Elevated concentrations of both THg and MeHg in rice indicated that the newly deposited atmospheric Hg was bioavailable, readily methylated, and taken up by rice, suggesting that the ongoing Hg mining activities cause serious Hg contamination in the soil-rice ecosystem and posed a threat to local residents in the Xunyang Hg mining area.

Dimethylmercury in Floodwaters of Mercury Contaminated Rice Paddies.

Dimethyl mercury (CH3HgCH3, DMeHg) has been observed in upwelling marine environments and the deep ocean. However, little is known about the occurrence and mechanisms of DMeHg formation in freshwater environments. In this study, concentrations of dissolved gaseous DMeHg were investigated in floodwaters of rice paddies in China that have been contaminated by mercury from mining. Values of DMeHg in rice paddies were compared with measurements from nearshore surface seawater in the Bohai Gulf. High concentrations of dissolved gaseous DMeHg occurred in rice paddies. Average DMeHg concentration was 12 ± 22 pg L-1 with range of 0.39 to 91 pg L-1 in rice paddies at Shuijing, China, a site impacted by an abandoned mercury mine. These concentrations are comparable to those previously observed in the deep seawater and coastal upwelling environments (2.3-115pg L-1). An alkaline environment was found to be necessary for DMeHg formation in rice paddies. Associated incubation experiments showed that production of DMeHg in paddy soil was limited by Hg availability. Although iron amendments accelerated the production of gaseous methylmercury (MeHg) species to floodwaters, available Hg2+ is crucial for this production in flooded rice paddies. These observations are the first to demonstrate the occurrence of DMeHg and reveal factors affecting DMeHg production in rice paddies. Given the high volatility of DMeHg, these measurements also suggest a source for observations of MeHg in atmospheric deposition and advance understanding of a potentially important aspect of the biogeochemical cycling of Hg.

Fluid properties and sources of Sixiangchang carbonate-associated mercury deposit, southwest China

Mercury mines in Guizhou province are the main base of mercury production and the most important resource base in China. The San-Dan mercury belt in Guizhou province contains a series of important mercury deposits. However, the source of metallogenic materials and the properties of metallogenic fluid of these mercury deposits have long been a controversial issue. In this study, we used cathode luminescence techniques to distinguish different stages of dolomite and calcite, laser ablation inductively coupled plasma mass spectrometry to analyze the trace elements, and stable isotope mass spectrometry techniques to analyze C–O isotopes compositions of dolomite and calcite in the Sixiangchang mercury deposit in San-Dan mercury belt. We also measured the sulfur isotope composition of cinnabar. Our study showed that dolomite can be divided into two stages, the lumpy dolomite associated with cinnabar in Dol 1 stage and dolomite vein in Dol 2 stage, which is associated with Cal 2 stage calcite vein. With the progress of mineralization, Al, As, Mo, Sb, and Sr elements were gradually enriched in the ore-forming fluid. The rare earth element (REE) partition curve of Dol 1 stage dolomite showed a trend of light REE enrichment. Cal 2 stage calcite and Dol 2 stage dolomite exhibited a flat-type REE partition curve, and Dol 2 stage dolomite showed a strong negative anomaly for Eu. δ13C of carbonate mineral variation ranges from − 6.89 to − 2.16 ‰, while δ18O variation ranges from 13.80 to 23.09 ‰, and the δ34S variation range of cinnabar is 16.51–24.28 ‰. Carbonate mineral trace elements and C–O isotopes compositions suggested that early ore-forming fluid was reduced, and late ore-forming fluid was oxidized. The ore-forming fluid of the Sixiangchang mercury deposit is a mixture of deep crustal fluid and meteoric water in deep thermal circulation, and involved in the oxidation of organic matter. The cinnabar δ34S results showed that sulfur mainly came from seawater sulfate with the participation of microbial reduction. Sulfur is sedimentary in origin and was derived mainly from the host-rock strata.

Mercury concentration and speciation in mine wastes in Tongren mercury mining area, southwest China and environmental effects

Mercury mines cause mercury (Hg) contamination to local environment, because mine wastes are not properly disposed during long-term large scale Hg mining activities. This study investigated Hg concentration and speciation in mine wastes collected from Tongren Hg mining area, and evaluated the impact of Hg mines subjected to different remediation measures on the surrounding environment. Total Hg (THg) concentrations in the mine wastes varied from 4.15 to 825 mg/kg, and Hg0 was the dominant form of Hg in the mine wastes. No obvious deformation was observed in the mineral boundaries by TEM analysis, which indicated that the smelting process was incomplete. Nanometer-scale Hg compounds were observed in the mine wastes using EDS microtopography analysis, which may pose risks for the local environment. The average concentration of total soluble Hg (TSHg) in mine waste leachates was 11.27 μg/L. The THg concentrations in surrounding surface waters varied from 0.038 to 10.6 μg/L, and THg concentrations in 21.1% of samples exceeded level Ⅴ of the national standards (1 μg/L). There was a significant negative correlation between THg concentration and pH in the surface water, indicating that Hg was more mobile under acidic conditions. The total gaseous mercury (TGM) concentration above the mine waste piles varied from 13.5 to 309 ng/m3; these values are significantly lower than those recorded in previous studies. These data demonstrate that restoration and proper treatment are required for the mine waste.

Study of mercury behavior and earthworm bioassays in three solid environment components from selected areas of Eastern Slovakia

<p>A 28-day bioassay with the earthworm (Dendrobaena veneta) was used to assessing the ecotoxic effect of mercury in study soils and sediments. This article deals with quality evaluation of the soils, sediments and plants (assimilation organs) from three localities, Rudňany, Krompachy, and water reservoir of Ružín, Eastern Slovakia (Europe) in consideration of their toxic effect on the environment. These areas are well - known for its mercury mining and metallurgical activities for several centuries. Within the frame of evaluation it was found that the concentrations of mercury exceeded some of the MPC (Max. Tolerable Risk) and IV (Serious Risk) values. The samples Rudňany tailing-SED (188.5mg/kg), Krompachy a-SED (69.4mg/kg), and Krompachy b-SED (93.4mg/kg) were the most polluted by mercury, which is evident according to it is the highest mortality on the earthworm (Dendrobaena veneta). The high mercury concentrations were obtained in the soils of the Rudňany-tailing-S (82.5mg/kg), Rudňany-tailing, valley-S (57.8mg/kg), and Krompachy 4KO-S (20.6mg/kg). A significant positive correlation is found between highest concentrations of mercury Rudňany-tailing SED Hg=188.5mg/kg (r=0.87) with the highest mortality of Dendrobaena veneta after 28 days bioassay.</p>

The impact of former mining activity on soils and plants in the vicinity of an old mercury mine (Vallalta, Belluno, NE Italy)

Exploitation of ore minerals (cinnabar, chalcopyrite, sphalerite) from the old mine in Vallalta (Belluno, NE Italy) has resulted in serious environmental impacts, including the acidification of water, and the contamination of soils and plants. Forty-eight soil samples and four wild plants were examined at four sites in the vicinity of the mine (<100 m), where mine waste was discharged. After digestion with aqua regia, chemical analyses were carried out on both soils and plants by inductively coupled plasma-optical emission spectroscopy (ICP-OES) for potentially harmful elements (Cr, Cu, Ni, Pb, Zn, Fe, Mn); the mercury concentration was directly ascertained by atomic absorption spectrometry (AAS). The levels of Ni, Cr, Mn and Zn in the soils were generally below the ‘normal’ levels for uncontaminated sites. Conversely, more than 50% of the examined samples presented Cu and Pb concentrations higher than the phytotoxic level (10 mg kg −1 ). Iron concentrations exceeded normal values (<300 mg kg −1 ) in 65% of the examined samples. The mercury concentration was high (6–21 mg kg −1 ) in all soil samples, mostly above the phytotoxicity limit (10 mg kg −1 ). Chaerophyllum hirsutum presented the highest Hg levels in roots, up to the phytotoxicity level (10 mg kg −1 ). Micronutrients Cu, Zn, Fe and Mn showed translocation factors (TFs) of between 0.5 and 1, suggesting that these elements are taken up to a critical concentration and are then arrested in the roots. Iron is less mobile, particularly in C. hirsutum , with the lowest TF of 0.38 . The TF for Mn and Hg is >1 in S. nemorum and C. hirsutum ; a TF of <0.5 in P. braunii , and particularly in T. officinale , suggests that these metals are most likely to be arrested in their roots. Soil contamination is confined to the proximity (<100 m) of the mine waste. Among the investigated plants, Chaerophyllum seems to be most suitable for phytoremediation of Hg-contaminated sites.

The use of a geostatistical model supported by multivariate analysis to assess the spatial distribution of mercury in soils from historical mining areas: Karcz\xf3wka Mt., Miedzianka Mt., and Rudki (south-central Poland)

For the purpose of this study, 181 soil samples were collected from three post-mining areas (Miedzianka Mt. (62), Karczówka Mt. (61), and Rudki (58)) in the Holy Cross Mountains, south-central Poland. Collected samples were dried, disaggregated, and digested in a closed microwave system. All solutions were analyzed for Hg concentrations with cold vapor-atomic absorption spectroscopy (CV-AAS) technique using a continuous flow vapor accessory. The average Hg concentrations and the upper limits of geochemical background (UBG) were as follows: Miedzianka Mt. Hg 0.501 mg kg−1, UBG 0.312 mg kg−1; Karczówka Mt. Hg 0.150 mg kg−1, UBG 0.180 mg kg−1; Rudki area Hg 0.216 mg kg−1, UBG 0.193 mg kg−1. The use of a spatial distribution map of mercury concentrations integrated with computed geochemical factors and results of cluster analysis showed a direct relationship between mercury contents and mining activity conducted in these areas. Only in the case of Miedzianka Mt., this relationship was visible and probably resulted from the presence of tennantite (Cu,Fe)12As4S13 in soil samples, which was also confirmed with the factor analysis. Higher Hg concentrations in soil samples from Karczówka Mt. and Rudki resulted from the presence of clay and other secondary minerals that increase the mercury adsorption from atmospheric deposition. Fossil fuel and biomass combustion was classified as the main anthropogenic source of the metal, but the neighborhood of a cement factory may be taken under consideration. Our results showed that the use of integrated geostatistical models allows for better data visualization and interpretation.

Do bacteria occupying important ecological niches contribute to the entrance of mercury into the food webs?

Bioavailable mercury represents a major threat locally to wildlife and also contributes to the global Hg pool and cycling of Hg. In this study, we focused on bacterial mobilization of inorganic Hg contained in sediment collected from the river Idrijca near the site of UNESCO's Idrija Mercury Mine. At the lowest trophic level, bacteria have an important role in Hg mobilization due to the cumulative nature of Hg in the food chain. Ignoring the most commonly studied sulfate reducing and methanogenic bacteria, we focused, among others, on the ubiquitous mineral weathering bacteria, Bacillus and Pseudomonas, the nitrifying Nitrobacter sp., the nitrogen fixing Rhizobium and Azotobacter, the aerobic Brevundimonas and the exoelectrogenic Schewanella to examine their potential for the mobilization of total (tHg) and the bioavailable Hg (bHg) fraction. We showed that several bacterial groups are able to mobilize the less soluble formes of Hg, i.e. HgS and smelting calcine in the sediment, either via close contact between cells and sediment particles or by the cell- excreted exudates resulting in increased levels of tHg and bHg in solution or in the cell biomass. The diversity of bacterial groups capable of mobilizing Hg implies that many different more general pathways and consequently many mobilization mechanisms, are possible apart from the Hg specific routes. In particular, the bacterial groups Pseudomonas and Bacillus, with their mineral weathering capabilities, were shown to be able to increase or decrease the availability of bHg depending on the peculiarities of their respective metabolisms and the nature of their exposure to the river sediment. Additionally, we showed that accumulation of Hg in the biofilm biomass is one type of mechanism influencing the bioavailability of Hg and can act as a point at which the insoluble Hg can enter into the foodweb.

Impacts of selenium supplementation on soil mercury speciation, and inorganic mercury and methylmercury uptake in rice (Oryza sativa L.)

Rice grain is known to accumulate methylmercury (MeHg) and has been confirmed to be the major pathway of MeHg exposure to residents in mercury (Hg) mining areas in China. Selenium (Se) supplementation has been proven to be effective in mitigating the toxicity of Hg. To understand how Se supplementation influences soil Hg speciation, a wide range of Se (0–500 mg/kg) was applied to Hg polluted paddy soils in this study, which decreased MeHg concentration in soil from 2.95 ± 0.36 to 0.69 ± 0.16 μg/kg (or 77%). After Se addition, humic acid state Hg (F4) was transformed into strong-complexed state Hg (F5), indicating that Hg bound up to the non-sulfur functional groups of humic acid (non-RSH) was released and reabsorbed by strong binding Se functional group (F5). As a result, inorganic Hg (IHg) was reduced by >48%, 18%, and 80% in root, stem, and grain, respectively, however, the reduction was not apparent in leaf. Substantial reductions were also found for MeHg in grain and root, but not in stem and leaf. Soil is suggested to be the main source of both MeHg and IHg in rice grain. Such a finding may provide an idea for improving Hg-polluted paddies through controlling soil IHg and MeHg. Further research on the molecular structure of the strong-complexed Hg in F5 should be conducted to elucidate the mechanism of Hg-Se antagonism.

Diurnal fluxes of gaseous elemental mercury from the water-air interface in coastal environments of the northern Adriatic Sea

A crucial step towards developing a more complete understanding of mercury (Hg) biogeochemical cycling in coastal environments is the measurement of the fluxes of gaseous elemental mercury (GEM), at the water-air interface (W-A interface). A floating flux chamber coupled with a real-time atomic adsorption spectrometer (Lumex-RA 915M) was applied to measure GEM concentrations, and to estimate the diurnal evasion flux at the W-A interface during three seasonal campaigns at four selected sites: two in a lagoon-based fish farm, one in an open lagoon environment highly impacted by long-term activities from the Idrija mercury mine (Slovenia), and an uncontaminated area of the Gulf of Trieste, the Bay of Piran (Slovenia). In this study, the regional background concentration measured at the uncontaminated site of atmospheric GEM (from 1.60 ± 0.95 to 2.87 ± 1.52 ng m−3) was determined. GEM fluxes at the W-A interface were found to be significantly higher during the summer (from 51.2 ± 8.8 ng m−2 h−1 to 79.9 ± 11.4 ng m−2 h−1) and correlated to incident solar radiation and water temperature. This finding confirms the importance of these two parameters in the photoreduction and biotic reduction of Hg2+ to dissolved gaseous mercury (DGM), which is volatile and easily released to the atmosphere in the form of GEM. These new insights will be of help for future estimates of Hg mass balance in one of the most contaminated areas in the Adriatic Sea.

Effects of Selenium on Mercury Bioaccumulation in a Terrestrial food Chain from an Abandoned Mercury Mining Region.

Few reports of the relationship exist between mercury (Hg) and selenium (Se) from locations of severe Hg contamination in terrestrial environments. Here, we report the concentrations of Hg and Se as well as Se:Hg molar ratios in biotic samples collected from a region with a long history of Hg mining. Nitrogen isotopes (δ15N) were analyzed to confirm the trophic levels. Results showed that bird feathers at the top trophic level exhibited the highest Hg concentrations, while the lowest concentrations were found in herbivorous insects, demonstrating a significant biomagnification across the food chain. In contrast, herbivorous insects of different types (generalists vs. specialized rice pests) exhibited both the highest and the lowest concentrations of Se, indicating a lack of biomagnification. Indeed, Se was correlated positively with Hg when Se:Hg ratios were greater than one, suggesting Se:Hg molar ratios can be a controlling influence on Hg in terrestrial organisms.

Health Risk Assessment of Inorganic Mercury and Methylmercury via Rice Consumption in the Urban City of Guiyang, Southwest China.

Rice consumption is the main methylmercury (MeHg) exposure route for residents in mercury (Hg) mining areas. However, there is limited studies on mercury in commercial rice, which has high liquidity and can be directly consumed by urban residents. This study measured the total Hg (THg) and MeHg concentrations in 146 rice samples purchased from the markets in Guiyang city, southwest China, and both the inorganic Hg (IHg) and MeHg estimated daily intakes (EDIs) and hazard quotients (HQs) were calculated according to rice consumption. The THg concentrations in all rice samples (range: 0.97 to 13.10 μg·kg−1; mean: 3.88 μg·kg−1) were lower than the Chinese national standard (20 μg·kg−1). The average MeHg concentration in rice was 1.16 μg·kg−1. The total HQs (THQs) ranged from 0.0106 to 0.1048, with a mean of 0.0462, which was far lower than 1. This result suggests that there were low Hg exposure levels through consumption of commercial rice in residents of Guiyang.

Arsenic accumulation and speciation in epilithic moss collected from an abandoned mercury mining area, south-western China

Arsenic (As) is considered a carcinogenic toxin, and nonferrous metal smelting activities can release significant quantities of As, causing an increase in As levels in the environment. A total of 221 samples of moss belonging to 5 species in 4 families were collected from the Wanshan District, the world third largest mercury mining area, in Guizhou Province, southwestern China, for analysis of total As (tAs) concentrations and As speciation. The results indicated that the tAs concentrations in these mosses ranged from 0.67 to 9.6 mg kg−1, with an average of 2.4 ± 1.7 mg kg−1. The dominant species of As in these mosses were inorganic forms of arsenite (As(III)) and arsenate (As(V)) with a total percentage of 87%, whereas the concentrations of organic forms (monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) were relatively low, with percentages of 11.8% and 6.0%, respectively. A significant correlation (r = 0.766, p < 0.01) was observed between As(V) and tAs. In the spatial distribution pattern of As, high concentrations of As in mosses were centralized around historical Hg retorting sites in the town of Wanshan, the villages of Gouxi and Yanwuping and sites downwind of these locations, suggesting that historical intensive Hg mining activities might be the most possible source of atmospheric As.

Mechanism of Accumulation of Methylmercury in Rice ( Oryza sativa L.) in a Mercury Mining Area.

Rice consumption is the primary pathway for methylmercury (MeHg) exposure at inland mercury (Hg) mining areas of China. The sources and processes of formation and translocation for MeHg in rice plant are complex and remain largely unknown. In this study, rice ( Oryza sativa L.) was exposed to isotopically labeled dimethylmercury (DMe199Hg) in field experiments using open top chambers to explore the response of MeHg accumulation in rice tissues to different levels of DMe199Hg in air. Rice leaves assimilated DMeHg from air, which was subsequently largely stored in aboveground tissues, including the rice grain, with only a small amount reaching the root. Combining these experimental results with field investigations of DMeHg concentrations in air beneath the rice canopy in a Hg mining area, we estimate that 15.5%, 10.8%, and 8.50% MeHg in the brown rice, the leaf, and the upper stalk, respectively, could be derived from atmospheric sources of DMeHg, while 99.5% of MeHg in rice root originated from the rice soil-water system. These findings help refine the mechanism of MeHg accumulation in rice that, in addition to soil, a fraction of MeHg in rice plants can be derived from DMeHg emissions from flooded rice paddies in Hg mining areas.

A new graphic methodology to interpret the multivariate data analysis of hydrochemical data in orphan mine areas

Orphan mine areas around the world are sources of potential toxic elements (PTEs) in environmental compartments. The weathering of sulphide minerals plays an important role in PTEs' fate, especially in humid climates. Orphan metal mines in Asturias are principal sources of water metal(oid) pollution in small watersheds. Several abandoned mercury mines were found in the upper Nalon Catchment. Small mining-impacted watersheds exhibit significant metal(oid) pollution, especially arsenic (As), from the seepage of mine waste and metallurgical slug dumps. Low flow and high metal(oid) pollution are characteristic of small mining-impacted watersheds, in contrast to high flow and low metal(oid)s content in principal streams. The systematic monitoring of surface water across watersheds showed that mine-influenced water (MIW) was found in several micro basins in the study area. Circumneutral water, calcium sulphate type, predominant in mine-polluted areas did not generate social alarm by its non-acid character, even presenting high concentrations of metal(oid)s. Multivariate data analysis of the surface water dataset was conducted to delimitate polluted waters and to reduce it to the most important parameters, as hydrochemical factor (defined by relation of As, Pb, Zn, SO4, … vs OD and pH) or base ion-exchange water. A new graphic representation for principal components from multivariate analysis is defined to explain water quality evolution using the concept of multivariate facies, which is a visual way of PCA interpretation.

Effects of soil properties on production and bioaccumulation of methylmercury in rice paddies at a mercury mining area, China

Rice paddy soil is recognized as the hotspot of mercury (Hg) methylation, which is mainly a biotic process mediated by many abiotic factors. In this study, effects of key soil properties on the production and bioaccumulation of Hg and methylmercury (MeHg) in Hg-contaminated rice paddies were investigated. Rice and soil samples were collected from the active Hg smelting site and abandoned Hg mining sites (a total of 124 paddy fields) in the Wanshan Mercury Mine, China. Total Hg (THg) and MeHg in soils and rice grains, together with sulfur (S), selenium (Se), organic matter (OM), nitrogen (N), phosphorus (P), mineral compositions (e.g., SiO2, Al2O3 and Fe2O3) and pH in soils were quantified. The results showed that long-term Hg mining activities had resulted in THg and MeHg contaminations in soil-rice system. The newly-deposited atmospheric Hg was more readily methylated relative to the native Hg already in soils, which could be responsible for the elevated MeHg levels in soils and rice grains around the active artificial Hg smelting site. The MeHg concentrations in soils and rice grains showed a significantly negative relationship with soil N/Hg, S/Hg and OM/Hg ratio possibly due to the formation of low-bioavailability Hg–S(N)–OM complexes in rhizosphere. The Hg–Se antagonism undoubtedly occurred in soil-rice system, while its role in bioaccumulation of MeHg in the MeHg-contaminated rice paddies was minor. However, other soil properties showed less influence on the production and bioaccumulation of MeHg in rice paddies located at the Wanshan Mercury Mine zone.

Mercury species accumulation and distribution in Typha domingensis under real field conditions (Almadén, Spain).

Monomethylmercury (MeHg) is one of the most toxic and the most commonly occurring organomercury compound and the wetlands are one of the main areas of generation of this Hg form. Concretely, it is in the macrophyte root system where better conditions are given for its generation. However, the knowledge of absorption and subsequent distribution of mercury (Hg) and monomethylmercury in aquatic plants is still limited. Mercury mining district such as Almadén (Ciudad Real, Spain) is a natural laboratory where different rivers flow and the species Typha domingensis Pers. is a common macrophyte which grows in their riverbanks. The aim of the present work is to apply a recently developed method specially designed to analyze Hg species in plant tissues to the different fractions of T. domingensis under real field conditions and to study the accumulation and distribution of Hg species (inorganic Hg and MeHg) within the plant. The results proved that whatever Hg species has preference to be accumulated in the belowground fractions and demonstrated a high efficiency in the accumulation of MeHg.

Diversity of microbial communities potentially involved in mercury methylation in rice paddies surrounding typical mercury mining areas in China.

Mercury can be a serious hazard to human health, especially in paddy soils surrounding mining areas. In this study, mercury (Hg)‐methylating microbes with the potential biomarker gene hgcA were obtained from 45 paddy soil samples in mercury mining areas in Fenghuang, Wanshan, and Xunyang. In different areas, the abundance of the hgcA gene was affected by different environmental factors, including organic matter, pH, total carbon content, total nitrogen content, and total mercury content. Phylogenetic analysis showed that hgcA microbes in paddy soils were potentially members of the phyla Proteobacteria, Euryarchaeota, Chloroflexi, and two unnamed groups. Canonical correspondence analysis showed that pH and organic matter impacted the hgcA gene diversity and the microbial community structures in paddy soils. The identification of Hg‐methylating microbes may be crucial for understanding mercury methylation/demethylation processes, which would be helpful in assessing the risk of methylmercury contamination in the food chain.

Hg and CO2 emissions from soil diffuse degassing and fumaroles at Furnas Volcano (São Miguel Island, Azores): Gas flux and thermal energy output

Gaseous elemental mercury (Hg0g or GEM) and CO2 are emitted from active hydrothermal systems in volcanic areas mostly through diffuse degassing. Here, data from about 400 simultaneous measurements of soil GEM and CO2 flux performed within the caldera of Furnas Volcano, São Miguel Island (Azores) are discussed for the first time. This survey aimed at providing a new insight into the origin and magnitude of GEM in the investigated hydrothermal/volcanic environment and its relation with CO2 release. The distribution of GEM and CO2 emissions over an area of about 0.04 km2 are correlated with soil temperature, and measurements have provided total CO2 and GEM output of 39 t d−1 and 1.8 × 10−6 t d−1, respectively. These results are similar to the emission from currently active volcanic/hydrothermal areas elsewhere, as well as from important non-volcanic areas, such as Sulphur Bank Mercury Mine (California, USA) and Idrija Mercury Mine (Slovenia, EU), pointing out the relevance of diffuse degassing processes at Furnas Volcano. Atmospheric spot measurements in the most vigorous fumarole vents of the geothermal field have shown that the fumarolic GEM contribution (9.2 × 10−7 t d−1) represents a minor fraction of the total (fumarolic + diffusive) GEM output (2.7 × 10−6 t d−1) for the study area of this volcano. Basing upon the integration of the hydrothermal CO2 released and the H2O/CO2 ratio in the fumarolic gas, we have also estimated the thermal energy release associated with diffuse degassing at Furnas Volcano. Our estimates are ∼7.8 MW and 9.8 MW, respectively for Furnas Lake and Furnas Village fumaroles.