Copper and selenium in rainwater, soils and alfalfa from agricultural ecosystems of valparaiso region, Chile
Résumé
Total copper and selenium concentrations were determined in rainwater, soils and alfalfa samples collected on April-May 1997 at various sites from three different zones of Valparaiso region, in Chile: Puchuncavi and Catemu valleys, both impacted by mining activities and Casablanca valley (reference site). In rainwater Cu and Se concentrations clearly decreased exponentially with the distance from the sources and 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 those found for samples from the reference site. In Puchuncavi valley Cu concentrations in soils and alfalfa show close correlation and were function on the distance from the smelter. The selenium concentration in soils and alfalfa show a very different behaviour. They were relatively constant in these matrices and do not present a 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 very high and do not seem to state problems to livestock grazing in these zones.