DISTRIBUTION AND SPECIATION OF ARSENIC IN GROUNDWATERS AND TAP WATERS OF EASTERN CROATIA

The presence of arsenic in the groundwater of Eastern Croatia was found almost 20 years ago; however, the extent of this anomaly is still unknown. There is a growing need to improve the knowledge of arsenic distribution in the region as well as of As speciation since As(III) is more toxic and less strongly retained in water treatment processes. Different methods for the determination of As speciation and species preservation have been proposed in the literature, but preservation of As species is still subject of scientific debate. In the present study, two analytical approaches (HPLC-ICP-MS and field speciation) have been used to study arsenic speciation in raw groundwater (at 31 different locations) and tap water (at 11 locations). Samples for laboratory speciation were preserved with EDTA, a commonly used preservative when using HPLC-ICP-MS technique. It was shown that EDTA conservation alone is not sufficient for species preservation, at least not for long (230 days) periods of storage. It was shown that shallow aquifers were not contaminated by arsenic, while deeper aquifers were generally more affected. Arsenic in the tested groundwater was present predominantly in dissolved form as As(III). As(V) was the predominant species in the residents' tap water. These results contribute to a greater understanding of hydrogeochemical settings in the area. They also have important implications on the protection of public health and will be helpful for the choice of a cost-effective arsenic removal technology.