Factors controlling the release of metals and a metalloid from the tailings of a gold mine in Thailand

This study focused on assessing the release potential of various metals and a metalloid (arsenic; As) leached from gold mine tailings under three different degrees of acidity (pH 2, 4 and 6.5) using a synthetic precipitation leaching procedure (SPLP). Tailings were collected from four pits from 0 to 16 m depth, approximately. The samples were divided into the three types, based on their position in the tailings and on other physical characteristics, of the sulphide (c. 5 m depth), mixing (c.1 m depth) and oxide (c. 10 m depth) zones. This study was primarily concerned with the concentrations of As and Mn, which were found to exceed the Thailand Industrial Effluent Standard (TIES) in the tailings from all zones. Principal component analysis revealed that the release of metals and As from the tailings under acidic conditions, as well as the metals and As mobility, was mainly controlled by the pH and redox conditions. Moreover, the first principal component had high positive loadings of Mn, Pb, Co and Ni (R2 > 0.80), indicating that these four metals are either released into the environment from a common source or/and their geochemical behaviour in the aqueous phase is similar.