Metal Pollution by Gold Mining Activities in the Sunchulli Mining District of Apolobamba (Bolivia)

The Sunchulli district is located inside of the National Integrated Management Area of Apolobamba in Bolivia where intense gold mining activities have been carried out since ancient times to the present but with very poor gold extraction and mineral processing technology where mercury is still being used in the amalgamation processes. The aim of this work thus was to evaluate the heavy metal pollution by gold mining activities in the area. Soil samples were taken and Hg, Pb, Cu, Zn and Cd were analysed. Total DTPA and water extractable metals were also determined along with soil organic carbon, total nitrogen, calcium carbonates, exchangeable bases (Na, Mg, K), pH, electric conductivity and texture. The results show that the mining activities do not increase heavy metals levels, except for Hg that presents high concentrations surpassing the Holland reference levels. Also, the decreased TOC and TN in the zone located near the mining operation site could give rise to the extinction of the plant cover affecting biodiversity, soil stability and accelerating soil erosion processes.