Vesna Fajon

Total mercury, methylmercury and selenium in mercury polluted areas in the province Guizhou, China

The province of Guizhou in Southwestern China is currently one of the worlds most important mercury production areas. Emissions of mercury from the province to the global atmosphere have been estimated to be approximately 12% of the world total anthropogenic emissions. The main objective of this study was to assess the level of contamination with Hg in two geographical areas of Guizhou province. Mercury pollution in the areas concerned originates from mercury mining and ore processing in the area of Wanshan, while in the area of Quingzhen mercury pollution originates from the chemical industry discharging Hg through wastewaters and emissions to the atmosphere due to coal burning for electricity production. The results of this study confirmed high contamination with Hg in soil, sediments and rice in the Hg mining area in Wanshan. High levels of Hg in soil and rice were also found in the vicinity of the chemical plant in Quingzhen. The concentrations of Hg decreased with distance from the main sources of pollution considerably. The general conclusion is that Hg contamination in Wanshan is geographically more widespread, due to deposition and scavenging of Hg from contaminated air and deposition on land. In Quingzhen Hg contamination of soil is very high close to the chemical plant but the levels reach background concentrations at a distance of several km. Even though the major source of Hg in both areas is inorganic Hg, it was observed that active transformation of inorganic Hg to organic Hg species (MeHg) takes place in water, sediments and soils. The concentration of Hg in rice grains can reach up to 569 microg/kg of total Hg of which 145 microg/kg was in MeHg form. The percentage of Hg as MeHg varied from 5 to 83%. The concentrations of selenium can reach up to 16 mg/kg in soil and up to 1 mg/g in rice. A correlation exists between the concentration of Se in soil and rice, indicating that a portion of Se is bioavailable to plants. No correlation between Hg and Se in rice was found. Exposure of the local population to Hg may occur due to inhalation of Hg present in air (in particular in Hg mining area) and consumption of Hg contaminated food (in particular rice and fish) and water. Comparison of intake through these different routes showed that the values of Hg considerably exceed the USA EPA Reference Concentration (RfC) for chronic Hg exposure (RfC is 0.0004 mg/m(3)) close to the emission sources. Intake of Hg through food consumption, particularly rice and fish, is also an important route of Hg exposure in study area. In general, it can be concluded that the population mostly at risk is located in the vicinity of smelting facilities, mining activities and close to the waste disposal sites in the wider area of Wanshan. In order to assess the real level of contamination in the local population, it is recommended that biomonitoring should be performed, including Hg and MeHg measurements in hair, blood and urine samples.

Mercury and methylmercury in the Gulf of Trieste (northern Adriatic Sea)

The distribution, sources and fate of mercury (Hg) in the water column of the Gulf of Trieste (northern Adriatic Sea), affected by the Hg polluted river Soca/Isonzo for centuries draining the cinnabar-rich deposits of the Idrija mining district (NW Slovenia), were studied in terms of total and dissolved Hg, reactive Hg, total and dissolved methylmercury (MeHg), mesozooplankton Hg and MeHg, and sedimentation rates of particulate Hg. Higher total Hg concentrations in the surface layer were restricted to the area of the Gulf in front of the river plume expanding in a westerly direction. Higher concentrations in bottom water layers were the consequence of sediment resuspension. Dissolved Hg exhibited higher concentrations in the surface layer in the area in front of the river plume. Higher bottom concentrations of dissolved Hg observed at some stations were probably due to remobilization from sediments, including resuspension and benthic recycling. The relationship between dissolved Hg in the surface layer and salinity showed nonconservative mixing in June 1995 during higher riverine inflow and nearly conservative mixing in September 1995 during lower riverine inflow. Both mixing curves confirm the river Soca/Isonzo to be the most important source of total and dissolved Hg, which are significantly correlated, in the Gulf. Reactive Hg is significantly correlated with dissolved Hg, indicating that the majority of dissolved Hg is reactive and potentially involved in biogeochemical transformations. The higher total MeHg in the bottom layer is the result of remobilization of MeHg from sediments including benthic fluxes. Strong seasonal variation of sedimentation rates of particulate Hg was found during a 2-year study in the central part of the Gulf. These variations followed those of total sedimented matter, indicating that sedimented Hg is mostly associated with inorganic matter. About a 2.5-fold higher fluxes of particulate Hg were observed at the depth of 20 m relative to 10 m which is attributed to bottom sediment resuspension. Temporal variability of mesozooplankton Hg and MeHg is the consequence of biomass and species variations, and grazing behaviour. From the preliminary Hg mass balance it appears that the Gulf is an efficient trap for total Hg and a net source of MeHg.

Mercury distribution in water, sediment and soil in the Idrijca and SoĉAhca river systems

Although the production of mercury (Hg) at the Idrija mercury mine, Slovenia, stopped in 1994, the tailings and contaminated soils in the mining region are continuously eroded and serve as a permanent source of Hg to the downstream rivers, flood plains and the Gulf of Trieste. The present article describes measurements of total Hg and monomethylmercury (MeHg) in various environmental compartments in the rivers Idrijca and So|

Heavy metals in the vicinity of a chlor-alkali factory in the Upper Negro River ecosystem, Northern Patagonia, Argentina.

|Ahca and the Gulf of Trieste during the period 1998–2000. Total Hg in the Idrijca river water upstream of the mercury mine varied between 2.8 and 6.9 ng l−1 and increased to 197 ng l−1 downstream of the mercury mine and remained elevated further downstream along the rivers Idrijca and So|

Remediation of Mercury Polluted Sites Due to Mining Activities

|Ahca (from c. 10 to 59 ng l−1), with lowest concentrations found in marine waters (from 0.2 to 2.0 ng l−1). The concentrations of total Hg were higher after the rain, which caused erosion and transport of particles enriched with Hg. Concentrations of MeHg were quite variable and did not follow the same trend as total Hg. The concentrations of MeHg in August 1999 were significantly higher than in June 1998, indicating the importance of seasonal effects, as well as hydrological conditions, on the production of MeHg. Above the mercury mine, MeHg was 0.1–0.2 ng l−1 and doubled below the mercury mine. Downstream, in the rivers Idrijca and So|

Mercury in Small Freshwater Lakes: A Case Study: Lake Velenje, Slovenia

|Ahca, MeHg varied from 0.05 to 0.53 ng l−1 and in marine waters from 0.06 to 0.08 ng l−1. Concentrations of Hg in sediments also increased downstream several fold with a value of 5.39 μg g−1 above the mercury mine to a maximum of 727 μg g−1 below the mine in the silt and clay fraction. The coarser-grained fraction (0.063 < d < 1.4 mm) frequently exceeded the value of total Hg in the silt and clay fraction due to the presence of particles of cinnabar. The concentrations of MeHg in sediments did not follow the same trend as total mercury. Highest concentrations of 14.1 and 10.0 ng g−1 were found downstream of the peak total Hg concentration in sediments. In general, higher MeHg concentrations were associated with the silt and clay fraction, and accounted for 0.001–0.144% of total Hg. Total Hg in flood plain surficial soils varied from 60 to 150 μg g−1 with less than 0.01% of mercury as MeHg. The results confirmed the fact that beside soils that are naturally elevated in Hg due to the high levels of Hg in geological materials in the Idrija district, there are also Hg-laden materials and tailings that are continuously eroded and deposited in flood plains downstream and serve as an important additional source of Hg to the rivers and the Gulf of Trieste. Important transformation mechanisms take place during fluvial transport, evidenced by the presence of MeHg in the various samples analyzed.

Mercury in an ultraoligotrophic North Patagonian Andean lake (Argentina): concentration patterns in different components of the water column.

The main objectives of our study were to estimate the impact of a mercury cell chlor-alkali (MCCA) complex in Rosignano Solvay (Tuscany, Italy) on the local environment and to assess mercury exposure of inhabitants living near the plant. Measurement campaigns of atmospheric Hg near the MCCA plant showed that the impact of the emitted Hg from the industry on the terrestrial environment is restricted to a close surrounding area. Total gaseous mercury concentrations in ambient air of inhabited area around the MCCA plant were in the range of 8.0-8.7 ng/m3 in summer and 2.8-4.2 ng/m3 in winter. Peaks of up to 100 ng/m3 were observed at particular meteorological conditions. Background levels of 2 ng/m3 were reached within a radius of 3 km from the plant. Reactive gaseous mercury emissions from the plant constituted around 4.2% of total gaseous mercury and total particulate mercury emission constituted around 1.0% of total gaseous mercury emitted. Analysis of local vegetables and soil samples showed relatively low concentrations of total mercury (30.1-2919 microgHg/kg DW in the soil; <0.05-111 microgHg/kg DW in vegetables) and methylmercury (0.02-3.88 microgHg/kg DW in the soil; 0.03-1.18 microgHg/kg DW in vegetables). Locally caught marine fish and fresh marine fish from the local market had concentrations of total Hg from 0.049 to 2.48 microgHg/g FW, of which 37-100% were in the form of methylmercury. 19% of analysed fish exceeded 1.0 microgHg/g FW level, which is a limit set by the European Union law on Hg concentrations in edible marine species for tuna, swordfish and shark, while 39% of analysed fish exceeded the limit of 0.5 microgHg/g FW set for all other edible marine species. Risk assessment performed by calculating ratio of probable daily intake (PDI) and provisional tolerable daily intake (PTDI) for mercury species for various exposure pathways showed no risks to human health for elemental and inorganic mercury, except for some individuals with higher number of amalgam fillings, while PDI/PTDI ratio for methylmercury and total mercury exceeded the toxicologically tolerable value due to the potential consumption of contaminated marine fish.