Extractability of arsenic, copper, and lead in soils of a mining and agricultural zone in central Chile

Copper (Cu) mining activities are very important in central Chile. The present study consists in determining the distribution and availability of copper, arsenic (As), and lead (Pb) in soils near a smelting facility, in the VI Administrative Region of Chile, which are subjected to risk of contamination by emissions and by irrigation with contaminated water. In order to determine the distribution of these elements in their various chemical forms in soils, two sequential extraction methods (SEM) were applied. A five stage SEM was used for Cu and Pb, and a four stage one for As. Single extraction methods were also carried. out using 1 M HCl, 0.005 M DTPA and 0.005 M EDTA for As, Cu, and Pb, respectively. Furthermore, a 0.1 M malic-citric acid solution (MC) was used as simple extractant for the three elements to simulate the conditions of root environment of the plant. The soils showed the following order of total metal concentration: Cu > As > Pb. Copper was extracted in higher amount than the other metals, both with the sequential and with the simple extraction method. Single correlation analysis was applied between the amount of metal in the single extraction method and the different fraction obtained with the sequential technique. Significant positive correlations were obtained, especially for copper and lead.