Abstract
Abstract. The legacy of long-term mining activities in Wanshan mercury (Hg) mining area (WMMA), Guizhou, China including a series of environmental issues related to Hg pollution. The spatial distribution of gaseous elemental mercury (Hg0) concentrations in ambient air were monitored using a mobile RA-915+ Zeeman Mercury Analyzer during daytime and night time in May 2010. The data imply 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 WMMA. For a full year (May 2010 to May 2011), sampling of precipitation and throughfall were conducted on a weekly basis at three sites (Shenchong, Dashuixi, and Supeng) within WMMA. Hg in deposition was characterized by analysis of total Hg (THg) and dissolved Hg (DHg) concentrations. The corresponding data exhibit a high degree of variability, both temporarily and spatially. The volume-weighted mean 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−1and 9641.5 ng l−1 at Supeng, respectively. THg was enhanced in throughfall compared to wet deposition samples by up to a factor of 7. 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 WMMA 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 WMMA.
Highlights
An assessment of the primary mercury (Hg) sources to terrestrial ecosystems is imperative to evaluate its biogeochemical cycling (Landis and Keeler, 2002; Rolfhus et al, 2003; Wiener et al, 2003)
It is demonstrated that the calcine heaps continued to release Hg0 to ambient air and Hg emission fluxes were significantly positively correlated to ambient air temperature and solar radiation (Wang et al, 2005; Qiu, 2005; Feng and Qiu, 2008), which may explain the diurnal variations in Hg0 observations
In comparison with the Idrijca catchment of Idrija Hg mining area in Slovenia, which is the second largest Hg mine in the world, we found that the concentration of Hg0 in ambient air in Wanshan mercury (Hg) mining area (WMMA) was similar with the values reported in Idrija in 1999 (Kotnik et al, 2005)
Summary
An assessment of the primary mercury (Hg) sources to terrestrial ecosystems is imperative to evaluate its biogeochemical cycling (Landis and Keeler, 2002; Rolfhus et al, 2003; Wiener et al, 2003). Atmospheric transport and transformation and its eventual deposition constitutes an important source of mercury to pristine areas. Deposition is in-turn linked to the levels of bioavailable and neurotoxic form methylmercury (MeHg) in the aquatic food-web (Lindberg et al, 2001; Miller et al, 2005). There are three species of mercury in atmosphere, including gaseous elemental mercury, semi-volatile oxidized species (acronym: GOM) and non-volatile particulate form (PHg, Schroeder and Munthe, 1998). Compared with Hg0, PHg and GOM fractions are more prone to undergo physical removal and are readily scavenged via wet and dry deposition (Guentzel et al, 2001)
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