Comparative study of copper and selenium pollution in agricultural ecosystems from Valparaiso region, Chile

Total copper and selenium concentrations were determined in rain waters, soils and alfalfa samples collected during April-May 1997 at various sites from different zones of Valparaiso region, in Chile: Puchuncavi and Catemu valleys, (both impacted by mining activities) and Casablanca valley (reference site). In rain waters. Cu and Se concentrations clearly decreased exponentially with distance from the sources ana were significantly correlated. The results obtained demonstrate that the mining activities have contributed to increase the contamination by copper in the agricultural ecosystems, particularly those located near the smelters. In all matrices from Puchuncavi and Catemu valleys copper concentrations were higher than in the reference site. In Puchuncavi valley, Cu concentrations in soils and alfalfa show close correlation and were a function of the distance from the smelter. Selenium concentration in soils and alfalfa follows a different pattern, being relatively constant in these matrices and presenting no clear dependency on the distance from the sources. In alfalfa they ranged between 0.10 and 0.40 mg kg(-1); these concentrations are not high and do not represent a problem to livestock grazing in these areas.