Environmental geochemistry of an active Hg mine in Xunyang, Shaanxi Province, China

摘要

The Xunyang Hg mine (XMM) situated in Shaanxi Province is an active Hg mine in China. Gaseous elemental Hg (GEM) concentrations in ambient air were determined to evaluate its distribution pattern as a consequence of the active mining and retorting in the region. Total Hg (HgT) and methylmercury (MeHg) concentrations in riparian soil, sediment and rice grain samples (polished) as well as Hg speciation in surface water samples were measured to show local dispersion of Hg contamination. As expected, elevated concentrations of GEM were found, ranging from 7.4 to 410ngm ~(-3). High concentrations of HgT and MeHg were also obtained in riparian soils, ranged from 5.4 to 120mgkg ~(-1) and 1.2 to 11μgkg ~(-1), respectively. Concentrations of HgT and MeHg in sediment samples varied widely from 0.048 to 1600mgkg ~(-1) and 1.0 to 39μgkg ~(-1), respectively. Surface water samples showed elevated HgT concentrations, ranging from 6.2 to 23,500ngL ~(-1), but low MeHg concentrations, ranging from 0.022 to 3.7ngL ~(-1). Rice samples exhibited high concentrations of 50-200μgkg ~(-1) in HgT and of 8.2-80μgkg ~(-1) in MeHg. The spatial distribution patterns of Hg speciation in the local environmental compartments suggest that the XMM is the source of Hg contaminations in the study area.