Assessment of mercury erosion by surface water in Wanshan mercury mining area

• Spatial distribution of environmental Hg in mining region was investigated.
• Atmospheric Hg in ambient air was elevated.
• Total Hg and MeHg in rice impacted by mining tailings and calcines were highly elevated.
• The upstream calcines and tailings were sources of Hg contamination in the environment of an abandoned Hg mine.

Soil erosion is a main cause of land degradation, and in its accelerated form is also one of the most serious ecological environmental problems. Moreover, there are few studies on migration of mercury (Hg) induced by soil erosion in seriously Hg-polluted districts. This paper selected Wanshan Hg mining area, SW China as the study area. Revised universal soil loss equation (RUSLE) and Geographic information system (GIS) methods were applied to calculate soil and Hg erosion and to classify soil erosion intensity. Our results show that the soil erosion rate can reach up to 600,884 t km−2 yr−1. Surfaces associated with very slight and extremely severe erosion include 76.6% of the entire land in Wanshan. Furthermore, the cumulative erosion rates in the area impacted by extremely severe erosion make up 90.5% of the total. On an annual basis, Hg surface erosion load was predicted to be 505 kg yr−1 and the corresponding mean migration flux of Hg was estimated to be 3.02 kg km−2 yr−1. The erosion loads of Hg resulting from farmland and meadow soil were 175 and 319 kg yr−1 respectively, which were enhanced compared to other landscape types due to the fact that they are generally located in the steep zones associated with significant reclamation. Contributing to establish a mass balance of Hg in Wanshan Hg mining area, this study supplies a dependable scientific basis for controlling soil and water erosion in the local ecosystems. Land use change is the most effective way for reducing Hg erosion load in Wanshan mining area.