Survey of trace elements in agricultural resources of Chile. Waters and soils of the Elqui and Limari valleys, IV Region

Sergio González M.1

The quality of surface waters and soils of the Elqui and Limarí valleys (IV Region, Chile). with emphasis on trace elements, were surveyed, between November'87 and December'88. The study included the detection of active environmental degradation processes. Waters of the Limarí basin as well as those of the Claro, in the Elqui system, showed low chemical charges, having good irrigation quality. The Turbio, the other component of the Elqui system, produced waters with higher contents of dissolved salts and metalic elements (Cu, Mn, Pb, Zn); this charge is properly diluted by the Claro river. Total Mn and Cu contents in Elqui and Na% values in the lower Límarí, seldomly exceeded their respective maximum allowances, staulished by the official Chilean norms. Excesses in total Cu, were the most common. Total trace element contents in the upper layer of soils were relatively high, but lower than expected by climatic onditions. They seem to be inherited from the Andes parent materials. EDTA-extractable fractions were closely related to total contents; water-soluble fractions were a extremely low part and not related with the total contents. The main degradation problem is the extremely high amount of sediments in the surface waters, mainIy during the snow-smelting season. In Elqui, part of them are retai[led by the soils, whereas in Limarí, they are deposited in the dams built to regulate this basin, shortening their useful lives. No relevant evidences of antropic pollution were detected in both valleys; nevertheless, its occurrence cannot be discarded, as some potentially present pollutants, as As, B and cyanide, were not included in this survey.

1 Estación Experimental La Platina (INIA), Casilla 439, Correo 3, Santiago, Chile.