Controles hidrogeoquímicos sobre la concentración de arsénico en el acuífero somero de la región pampeana

Abstract

Se muestran los resultados de una perforación con extracción de testigos continuos destinada al estudio de la hidrogeoquímica del arsénico (As) en la zona no saturada y acuífero somero. La misma se realizó en la ciudad de Azul, provincia de Buenos Aires y tuvo como objetivo al acuífero pampeano. Sobre los testigos se realizaron análisis texturales y mineralógicos, extracciones secuenciales y se obtuvieron muestras del agua poral, las que se analizaron químicamente. Los resultados indican que el As se encuentra mayormente adsorbido sobre los óxidos de hierro amorfos y, a su vez, guardan relación con el As presente en el agua poral. Existe un aumento de las concentraciones en la zona de interacción entre la zona no saturada y el acuífero.This study deals with arsenic (As) hydrogeochemistry in the unsaturated zone and the shallow Pampeano aquifer. This system was studied by a borehole with undisturbed soil core extraction. These cores were subjected to mineralogical and textural analysis as well as sequential extraction procedures and chemical analysis of extracted pore waters. Results show that As in the sediments is mainly adsorbed onto amorphous iron (hydr)oxides and concentrations in pore waters are correlated with the adsorbed mass of As into the aquifer. This may indicate that larger As concentrations in groundwater are associated with sediments with larger amounts of adsorbed As. An increase in As concentrations was observed in the interface between unsaturated zone and the upper part of the aquifer by means of water mixing processes.