Examination of total mercury inputs by precipitation and litterfall in a remote upland forest of Southwestern China

China is regarded as one of the largest anthropogenic mercury (Hg) emission source regions over the world. However, wet and dry deposition of atmospheric Hg in China has not been well investigated. In the present study, wet and litterfall depositions of total mercury (THg) were continuously measured from June 2011 to May 2012 at a high-altitude site in Mt. Ailao area, Southwestern China. The annual volume-weighted mean concentration of THg and reactive mercury (RHg) in precipitation was 2.98 and 0.92 ng L−1, respectively. The mean THg concentration in litterfall was 52 ng g−1 (dry weight). Atmospheric deposition was highly elevated in forest in the study area, with the annual mean THg deposition fluxes of 76.7 μg m−2 yr−1. Litterfall Hg depositions were the major pathway for Hg loading to the forest catchment, which were 71.2 μg m−2 yr−1 (about 92.8% of total input for THg). Forest ecosystem in the study area was a large pool of atmospheric Hg, and the average storage of Hg in forest soil (0–80 cm depth) was 191.3 mg m−2.