Mercury speciation and distribution in a glacierized mountain environment and their relevance to environmental risks in the inland Tibetan Plateau.

Glacierized mountain environments can preserve and release mercury (Hg) and play an important role in regional Hg biogeochemical cycling. However, the behavior of Hg in glacierized mountain environments and its environmental risks remain poorly constrained. In this research, glacier meltwater, runoff and wetland water were sampled in Zhadang-Qugaqie basin (ZQB), a typical glacierized mountain environment in the inland Tibetan Plateau, to investigate Hg distribution and its relevance to environmental risks. The total mercury (THg) concentrations ranged from 0.82 to 6.98ng·L-1 , and non-parametric pairwise multiple comparisons of the THg concentrations among the three different water samples showed that the THg concentrations were comparable. The total methylmercury (TMeHg) concentrations ranged from 0.041 to 0.115ng·L-1 , and non-parametric pairwise multiple comparisons of the TMeHg concentrations showed a significant difference. Both the THg and MeHg concentrations of water samples from the ZQB were comparable to those of other remote areas, indicating that Hg concentrations in the ZQB watershed are equivalent to the global background level. Particulate Hg was the predominant form of Hg in all runoff samples, and was significantly correlated with the total suspended particle (TSP) and not correlated with the dissolved organic carbon (DOC) concentration. The distribution of mercury in the wetland water differed from that of the other water samples. THg exhibited a significant correlation with DOC as well as TMeHg, whereas neither THg nor TMeHg was associated with TSP. Based on the above findings and the results from previous work, we propose a conceptual model illustrating the four Hg distribution zones in glacierized environments. We highlight that wetlands may enhance the potential hazards of Hg released from melting glaciers, making them a vital zone for investigating the environmental effects of Hg in glacierized environments and beyond.