Mercury and Arsenic Storage Estimation, Source Apportion, and Pollution Assessment in the Greater Khingan Mountains Wetlands, Northeast China.

The Greater Khingan Mountains (GKM) regions have the second-largest areas of permafrost in China and serve as sinks of heavy metals like mercury (Hg) and arsenic (As). However, to date, we lack detailed information on Hg and As reserves, sources, and pollution assessment in the region, and this may bring increasing uncertainty when studying Hg and As cycle. By investing Hg and As contents of soil, plant, and litter samples from 22 typical wetlands in the GKM, we found that the average Hg content was 0.11 mg/kg in the soil, higher than the soil background value. The geo-accumulation index (I_geo) showed that Hg pollution degree ranged from mild to moderate grade. The average soil As content was 16.1 mg/kg. Hg and As storage in wetland soils, vegetation biomass, and litter were estimated to be 4.32 mg/m² and 995 mg/m², 159 μg/m² and 494 μg/m², and 13.9 μg/m² and 113 μg/m², respectively. About 61% As was from endogenous sources contribution, and about 84% Hg was derived from exogenous sources. A positive correlation was observed between Hg in the litter and temperature and the precipitation-to-temperature ratio. This implied that Hg accumulation in the litter should be paid more attention to considering current climatic warming in the GKM. [ABSTRACT FROM AUTHOR]