Release of metals and arsenic from various mine tailings by Eriophorum angustifolium
Previous investigations have found that plants grown on sulphide-rich mine tailings have phytostabilising effects on acid mine drainage (AMD) by decreasing the pH and preventing the release of metals. The possibility of similar effects on tailings containing other minerals was investigated here. The aim was to examine the effects of Eriophorum angustifolium on four water-covered mine tailings with different mineralogy – i.e. the plants’ effect on the release of elements from the tailings and the uptake of elements – to reveal if E. angustifolium is suitable for phytostabilisation in various tailings. Seeds of E. angustifolium were sown in different tailings amended with sewage sludge. Arsenic, Cd, Cu, Fe, Pb and Zn levels in the drainage water and in plant tissues were examined. pH, alkalinity, SO2-4 and organic acid concentrations were measured in drainage water, and redox potential and O2 levels in the pore water. The effect of E. angustifolium on the release of metals from the tailings varied with the composition of the tailings. In tailings with a low buffering capacity and low element and sulphide levels, compared with the other tailings, E. angustifolium increased the release of metals, which was shown by the high concentrations of elements and low pH in the drainage water and high concentrations of elements in the shoots, thereby generating a bio-concentration factor (BCF) >1. In tailings with a high concentration of elements, the plants had little effect on the levels of the elements in the drainage water, likely due to the presence of buffering agents in the tailings (added prior to the experiment). In this case, the pH did not decrease in the presence of plants and the shoot BCF was <1.
Keywords: Eriophorum angustifolium - Organic acids - Phytostabilisation - Redox potential - Water-covered mine tailings