The distribution of total and methylmercury concentrations in soils near the Idrija mercury mine, Slovenia, and the dependence of the mercury concentrations on the chemical composition and organic carbon levels of the soil

Abstract

Although the mining activity of the Idrija mine in Slovenia ceased in 1995, a large amount of mining dregs containing high concentrations of mercury remains in the area. The mining dregs were transported with river flow and deposition along the Idrija River. To estimate the dispersion and change in the chemical form of mercury, a total of 28 soil core samples were taken around the river. The individual core samples were separated into layers for the analysis of their chemical composition, carbon contents, total mercury (T-Hg) and methylmercury (MeHg) concentrations. The chemical composition measured by X-ray fluorescence spectrometry was useful to estimate the dispersion of tailings: the fluvial terrace soil had a chemical composition similar to that of the tailings and could be distinguished clearly from the forest soil. The highest T-Hg concentration, 1,100 mg kg -1 , was observed in the fluvial terrace soil near the mine. Although the concentration decreased gradually along with distance from the mine, concentrations higher than 200 mg kg -1 of T-Hg were still observed in the fluvial terrace soil approximately 20 km downstream from the mine. In the vertical distribution of T-Hg in the hillslope soil, a higher value was observed in the upper layers, which suggests the recent atmospheric deposition of mercury. The concentration of MeHg was the lowest at the riverside and higher in the hillslope soil, which was the opposite of the T-Hg distribution. The total organic carbon content tracked similarly with the distribution of MeHg and a linear relation with a significantly high correlation coefficient was obtained. The distinction may be related to the different dispersion process of mercury, and the organic carbon contents may be an important factor for MeHg formation.

Mercury concentrations and distribution in soil, water, mine waste leachates, and air in and around mercury mines in the Big Bend region, Texas, USA

“…Soil samples collected in this study show a correlation between methyl-Hg and TOC ( r 2 = 0.57, p < 0.001; Fig. 4 ), which is consistent with the affinity of methyl-Hg for organic matter and similar to results found in other studies of Hg mined areas (Rimondi et al 2012 ; Tomiyasu et al 2012 ). The methyl-Hg data for soil indicate generally low conversion of inorganic Hg (dominantly HgS) to the highly toxic methyl-Hg.…”

Toward an Assessment of the Global Inventory of Present-Day Mercury Releases to Freshwater Environments

“…We distribute releases associated with mining activities along the locations of Hg mines obtained from mineral resources data system (MRDS) [ 35 ] and gold deposits [ 36 ], similar to the approach used by Selin et al [ 37 ] for distribution of geogenic Hg emissions. A 10 km buffer zone surrounding Hg and Au mines was used to delineate the contributing area, based on reported extent of pollution in various studies [ 38 , 39 , 40 , 41 ]. Different ranges of Hg releases were then considered depending on the climatic position of the site: 10–100, 100–1000 and 1000–3000 g·Hg·km −2 ·a −1 in case of primary Hg mining [ 41 , 42 ] for arid, temperate and humid climate zone [ 30 ], respectively, while order of magnitude lower loads were considered for Au mining sites.…”

Total mercury, organic mercury and mercury fractionation in soil profiles from the Almadén mercury mine area

“…The same behavior has been recently found in soils near an old mercury mine. 76 However, the strongest correlation was found between organic Hg and Hg concentrations in fraction F3. It has been suggested that elemental Hg present in mine sites, through time, can be converted to Hg(II) compounds, mostly by oxidation, and further methylated by methylating bacteria.…”