THE PAILAVIRI TAILINGS DEPOSIT, POTOSÍ, BOLIVIA: EXTREME ACID ROCK DRAINAGE GENERATION

Abstract

The historic mining center of Cerro Rico de Potos, Bolivia is marked with many tailing piles, with the Pailaviri tailings deposit being of great concern. These polymetallic sulfide tailings release some of the highest concentrations of ecotoxic metals observed in natural waters. In order to obtain a deeper understanding of the deposit, water samples were taken in transects throughout the deposit. Total metal concentrations in the waters were extremes: Al (25-2.9 g/L), As (1700-330 mg/L), Cu (850-140 mg/L), Fe (100-24 g/L), Mn (110-70 mg/L), Pb (36-21 mg/L), and Zn (3.1-1.9 g/L). Dissolved concentrations were essentially equivalent indicating these metals were in aqueous phase. Sulfate ranged from 136 to 400 g/L. Due to the extremely acidic nature of the water, the pH probes quickly degraded and became inoperable, rendering accurate pH measurements impossible. These results provided evidence of highly toxic conditions and likely downstream impacts due to close proximity of Rio Huayna Mayu. The extremely elevated concentrations of metals indicate that the Pailaviri deposit may be reprocessed at a profit and safely disposed of, an option which should be investigated.