High altitude artisanal small-scale gold mines are hot spots for Mercury in soils and plants

Mercury releases from artisanal and small-scale gold mines (ASGM) condense and settle on plants, soils and water bodies. We collected soil and plant samples to add knowledge to the likely transfer of Hg from soils into plants and eventually predict Hg accumulation in livestock around ASGM in Bolivia. Mean contents of Hg in soils range from 0.5 to 48.6 mg Hg kg−1 soil (5× to 60× more compared to control sites) and exceeded the soil Hg threshold levels in some European countries. The Hg contents ranged from 0.6 to 18 and 0.2 to 28.3 mg Hg kg−1 leaf and root, respectively. The high Hg in Poaceae and Rosaceae may elevate Hg accumulation into the food chain because llama and alpaca solely thrive on these plants for food. Erosion of soils around ASGM in Bolivia contributes to the Hg contamination in lower reaches of the Amazon basin.

► Hg in soils ranged from 0.5 to 48.6 mg Hg kg−1 soil, and at least 5× to 60× more than control sites.
► Plants near gold mines exceed the 0.1 mg Hg kg−1 plant material European limit for feed quality.
► Camelids feeding on plants with high Hg may elevate Hg levels in foods (meats) for the miners.
► Soils with high Hg can be significant Hg sources to the contamination of the Amazon basin.