Spatial distribution of mercury deposition fluxes in Wanshan Hg mining area, Guizhou, China

Abstract. A long-term mining history introduced a series of environmental problems in Wanshan Hg mining area, Guizhou, China. The spatial distribution of gaseous elemental Hg (Hg0) concentrations in ambient air were investigated using RA-915+ Zeeman Mercury Analyzer during day time and night time in May 2010, which showed that calcines and mine wastes piles located at Dashuixi and on-going artisanal Hg mining activities at Supeng were major sources of atmospheric mercury in Wanshan Hg mining area. Meanwhile, both precipitation and throughfall samples were collected weekly at Shenchong, Dashuixi, and Supeng from May 2010 to May 2011, respectively. Our data showed that the concentrations of different Hg species varied with a large range, and the annual volume-weighted mean total mercury (THg) concentrations in precipitation and throughfall samples were 502.6 ng L−1 and 977.8 ng L−1 at Shenchong, 814.1 ng L−1and 3392.1 ng L−1 at Dashuixi, 7490.1 ng L−1 and 9641.5 ng L−1 at Supeng, respectively. Besides, THg concentrations in all throughfall samples were 1–7 folds higher than those in precipitation samples. The annual wet Hg deposition fluxes were 29.1, 68.8 and 593.1 μg m−2 yr−1 at Shenchong, Dashuixi and Supeng, respectively, while the annual dry Hg deposition fluxes were estimated to be 378.9, 2613.6 and 6178 μg m−2 yr−1 at these sites, respectively. Dry deposition played a dominant role in total atmospheric Hg deposition in Wanshan Hg mining area since the dry deposition fluxes were 10.4–37.9 times higher than the wet deposition fluxes during the whole sample period. Our data showed that air deposition was still an important pathway of Hg contamination to the local environment in Wanshan Hg mining area.