engleski

Distribution of arsenic in the groundwater in Osječko-baranjska County, Eastern Croatia

The presence of elevated concentrations of arsenic in drinking and stream water of Eastern Croatia has been recently evidenced (Ćavar et al., 2005 ; Salminen et al., 2005). However, the extent of As contamination was poorly known, as well as the processes that might explain groundwater As enrichment. The aim of this study was to investigate the As concentration and speciation in the groundwater of Osječko-baranjska County. Row water samples were taken from 30 groundwater wells used for public supply (more than 50m in depth) in March-April 2007. The wells were electrically pumped and samples were taken in the wellhead. Where it was not possible to reach a wellhead the samples were taken in the houses nearest to the wells, in which tap water was consumed without any treatment. In order to determine arsenic concentrations in shallow aquifers, the samples were taken from 9 private shallow wells (up to 15m in depth). Total arsenic concentrations were determined as well as pH, conductivity, dissolved O2, alkalinity, NH4, NO3-, Fe, Mn, SO42- and other major dissolved species. Water samples from ten wells were collected again in July 2007 for monitoring temporal variations in the groundwater composition and the As speciation. Results showed that the shallow wells were not polluted by arsenic (<1 µ ; ; g/L). However, in the deep groundwater wells, total dissolved arsenic concentration ranged from <1 µ ; ; g/L to 305 µ ; ; g/L. Arsenite, the dominant form of As, ranged from below the method detection limit to 287 µ ; ; g/L. Arsenate As(V) concentrations ranged from <1µ ; ; g/L to 170 µ ; ; g/L. It seems that the occurrence of arsenic in the groundwater of Eastern Croatia depend on the local geology, hydrogeology, and geochemical characteristics of the aquifer. The relative amount of As(III) and As(V) at residential tap water probably depend on the time of water retaining in the pipeline.

arsenic; groundwater; Osječko-baranjska County

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