Sedimentological controls in distribution of arsenic in the Claromecó basin, Argentina

摘要

The aim of the present work is to demonstrate the preliminary results of the study of the arsenic concentrations in the sediments of the Claromecó river basin. A variation of As content related to lithogenic factors is presented in the study: the Miocene-Pliocene fluvial facies have a reduced arsenic concentration (~2.6 mg/kg) compared with the Late Pleistocene fluvial facies (~11.6 mg/kg). These differences are probably attributed to a major hydraulic gradient during the Pliocene, which is reflected in grain size and in fluvial structures that probably washed out the sediments. Volcanic glass shards probably represent one of the main arsenic sources, especially in the fine silt grain size. On the other hand, different paleo sols show different As concentrations due to the presence of amorphous Fe-Mn oxides-hydroxides. Topography is controlling the As concentrations as shown by the increasing of this element in sediments and groundwater in the downgradient of the basin.