Immobilization of mercury and arsenic in a mine tailing from a typical Carlin-type gold mining site in southwestern part of China

Abstract

Abstract The potential of chicken manure and ferrous sulfate in immobilizing both mercury (Hg) and arsenic (As) in a tailing collected from Danzhai gold (Au) mine in southwestern part of China was investigated. A laboratory leaching experiment was conducted firstly to study the effectiveness of 30 tons ha−1 to 90 tons ha−1 chicken manure, or its combination with 1.5 tons ha−1 to 15 tons ha−1 ferrous sulfate, on the mobilization of Hg and As in the tailing. Results showed that the sole application of chicken manure at dose of 30 tons ha−1 to 90 tons ha−1 to the tailing removed approximately 94%–99% and 49%–85% of Hg and As, respectively, from the leachate over three months. These reductions might be attributed to the formation of hardly soluble Hg sulfides (e.g., HgS) and As sulfides in the tailing. Addition of chicken manure and ferrous sulfate to the tailing decreased Hg and As concentrations by 60%–85% and 31%–60%, respectively, in the leachate as compared to sole treatment of chicken manure. The mechanisms of Hg and As removal might be linked to their adsorption by iron oxides and chicken manure. The co-application of 30 tons ha−1 chicken manure and 15 tons ha−1 ferrous sulfate to the tailing showed promising results in reducing Hg and As concentrations as compared to the other treatments. The results from field trial showed that about 73% of Hg and 82% of As were removed from the leachate by the selected amendments (30 tons ha−1 chicken manure and 15 tons ha−1 ferrous sulfate), as compared to the control. In summary, the co-application of 30 tons ha−1 chicken manure and 15 tons ha−1 ferrous sulfate was promising in mitigating risk of both Hg and As from tailings, and the knowledge provided might deepen our understanding of mobilization of Hg and As in the tailing in Carlin-type gold mining regions.