| This thesis examines the small-scale gold mining area of Tongguan County in Shanxi Province (Xiaoqinling region), as a case study of an area using amalgamation for gold extraction. The distributions of mercury and methylmercury are studied in air, water, soil and some crops in that region affected by gold mining activities, from the point of view of environmental geochemistry. The environmental geochemistry behaviors and modes of transport involving the transformation and enrichment of mercury in gold mining environments are thoroughly discussed. The total mercury emissions due to gold mining activities in the past over twenty years in Tongguan County are approximated and extrapolated for the whole of China. In addition, feasible recommendations on how to improve the environmental management of gold mining areas are proposed. Through the detailed studies reported in this thesis, some main conclusions are as follows:1.The spatial variability pattern of airborne mercury is clearly presented in Tongguan County: the airborne mercury concentrations in the zone where gold mills are densely distributed are higher than that in other zones, and decrease with increasing distance away from the gold mills. The mean airborne mercury concentration is 18,047 ng/m3, with the maximum of 33,080 ng/m3, found in an amalgamation workshop of a larger gold mill. The average concentrations in areas near gold mills and in areas moderately distant from gold mills are 385 ng/m3 and 77 ng/m3 respectively; while the mean airborne mercury concentration is down to 29 ng/m3 in areas distant from gold mills, and 2 ng/m3 in background level areas along the banks of the Yellow River which are little affected by air movements from the gold mining region. In Tongguan County, every miner living in the study area would inhale an estimated 72,804-75,268 ng of mercury per day, and every local inhabitant (adult) would inhale 924-4,620 ng of mercury per day.2.In Tongguan County, the mean total mercury concentration in spring and well water samples is 329.2 ng/L and the mercury concentrations of all different species of them are all extremely high, which possibly shows the higher mercury background levels in gold mine areas, and indicates that the local groundwater has suffered mercury contamination from gold mining activities. Dissolvedmercury concentrations in river .water samples collected in cold and warm seasons and methylmercury concentrations in warm season water are several times higher than that in spring and well water samples, and also several hundreds times higher for other mercury species. There is a positive correlation between the reactive and dissolved mercury concentration in water. The mean concentrations of reactive and dissolved mercury in water in cold season are marginally higher than that in warm season water, but the opposite is true of particulate mercury. In a few water samples, reactive mercury levels are higher than dissolved mercury, but particulate mercury is the predominant species in total mercury levels and in most samples exceeds 50 %.3.In sediment samples collected during cold and warm seasons, the mean total mercury concentrations are up to 151.1 and 44.6 ng/g, respectively, and the mean methylmercury concentrations are 7.1 and 3.6 ng/g, respectively. There is a positive correlation between the total mercury and methyl mercury concentrations in warm season sediments. Particles in water and sediments are derived mainly from waste residues and tailings emitted from gold mills, so they have a common lithological origin and both of them contain high heavy metals (Hg, Fe, Mn and Cu) levels. However, all heavy metals are found in particles characterized by small particle diameter, large surface area, organic material and strong adsorption ability, arid thus the mercury levels are obviously higher than that in ordinary sediments. There are positive correlations between Hg and other heavy metals levels in particles, but not in sediments, and the only tight correlation is found between the concentrations of Hg an...
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