Groundwater arsenic variations:: the role of local geology and rainfall

High concentrations of As were detected in the aquifer system of Zimapan Valley, Mexico. Arsenic is related to a multisource system, both natural and anthropogenic. The main source is As bearing-rocks. Groundwater As variations were detected in the more polluted urban deep well. Variations were correlated with the precipitation regime and with the hydrogeologic and geologic framework. An induced As transport mechanism related mainly with the rainfall regime is proposed. (C) 2003 Elsevier Ltd. All rights reserved.