Contamination trend at flooded mines: 20 y time-series at Casargiu, Sardinia

At Casargiu, Pb-Zn ores were exploited for a century. After mine closure, pumping systems were shut down allowing rebound. First outflow of contaminated water occurred in 1997. This study reports contamination trends based on 26 hydrogeochemical surveys carried out from 1997 to 2016. Results showed contamination peaks at the first flushing. After 20 y, concentrations of Ni and Co showed marked decreases, followed by Mn, sulfate, Pb, Zn and Cd. Although a decrease of contaminants has been occurring, high contamination persists at Casargiu. This suggests the need of remediation actions for preventing dispersion of contaminants downstream of abandoned mines.