Origin of arsenic in surface water in the southern extreme of the Chaco-Pampean region, Argentina. Facts and speculations

M. PUNTORIERO; A. VOLPEDO; A. FERNÁNDEZ CIRELLI

Ciudad Autónoma de Buenos Aires

Taller; El arsénico como factor limitante en la producción agrícolo-ganadera; 2011

Centro de Estudios Transdisciplinarios del Agua

The Chaco-Pampa Plain of central Argentina is one of the largest regions of high Arsenicgroundwater known. Studies of As occurrence in surface water are scarce. High values weredetermined in two hydrographic regions in the southern extreme of the Chaco-Pampeanregion: SW Endorheic Basin (ESO) and Bahía Blanca (BB). Surface and groundwater ofthese two areas were evaluated for As, F and V content. A significant correlation was foundbetween As and F, both in surface and groundwater, while As and V, only showed asignificant correlation in groundwater. The principal geochemical processes determining thechemical composition of surface waters was analyzed through ionic relations. A cationexchange reaction between calcium and sodium takes place in the hydrochemical evolutionof groundwater through Pampean loessic sediments, with groundwater being one of thesources of surface water. Therefore, the occurrence of As and related elements in surfacewater may be explained by its relation with groundwater.