Trace Element Groundwater Pollution Hazard in Regional Hydrogeological Systems (Empordà Basin, NE Spain)

Abstract

Trace elements appear in natural waters as a result of rock weathering and human activities. Their occurrence is governed by a complex set of geochemical conditions which finally may induce trace element concentrations above health standards. In regional, large-scale aquifers, their presence is representative of the hydrogeological setting of the overall flow path from the recharge zone to the sampling well. In this study, we analyze hydrochemical, including major components and trace elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Sb, Sn, Sr, Pb, Zn), and stable isotopic data from exploitation wells in the Empordà basin (NE Spain). Our goal is to explore the hydrogeological meaning of trace elements as a means to contribute to the understanding of the regional flow dynamics as an initial step to face trace element pollution events. Groundwater data is hence described in the context of each aquifer relating the major hydrochemical facies with their accompanying trace elements. Results point out some expected geochemical relationships as well as some trace element associations that cannot be envisaged from the usual incomplete lithological information of the aquifer. Multivariate statistical analysis, as PCA, provides complementary information about geochemical processes (loadings) and regional occurrence (scores). Such statistical information can be taken as indicative of potential health hazard associated to trace element in groundwater. From a management perspective, such analysis points out which elements should a priori be considered for analysis according to the geological formation that holds the water supply well