Environmental Stable Isotopes of the sistema de Las Encadenadas de Chascomús?

C. DA PEÑA, P. MIRETZKY, H. PANARELLO AND A. FERNÁNDEZ CIRELLI

Santiago de Chile

Jornada; Third South American Symposium on Isotope Geology.; 2001

Universidad de Chile

The Sistema de las Encadenadas de Chascomús lies in the geomorphologic unit called Pampa Deprimida in the Buenos Aires province, that has a wet climate with annual precipitation about 900 mm and annual temperature ranking 13-16 0C and are formed by interconnected shallow lakes. Pampasic lakes are shallow alkaline systems with nearly continuous vertical mixing that promotes a high concentration of suspended particulate matter and low water transparency. Water column is almost always thermally homogeneous, saturated with dissolved oxygen and high organic matter, mainly humic substances. The aim of this work is to study the relation between the superficial and shallow groundwater by means of environmental stable isotopes (2H and 18O). The isotopic results suggest that during the summer, when the precipitation-evaporation balance is negative, the surface water hydrochemistry is governed by the evaporation process. It has been also demonstrated that the origin of the groundwater is meteoric and the shallow groundwater constitutes the base flow of surficial water.