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

Total copper and selenium concentrations were determined in rain waters, so ils and alfalfa samples collected during April-May 1997 at various sites fr om different zones of Valparaiso region, in Chile: Puchuncavi and Catemu va lleys, (both impacted by mining activities) and Casablanca valley (referenc e site). In rain waters. Cu and Se concentrations clearly decreased exponen tially with distance from the sources ana were significantly correlated. Th e results obtained demonstrate that the mining activities have contributed to increase the contamination by copper in the agricultural ecosystems, par ticularly 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 clo se correlation and were a function of the distance from the smelter. Seleni um concentration in soils and alfalfa follows a different pattern, being re latively constant in these matrices and presenting no clear dependency on t he 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.