Application of a groundwater contamination index in Finland and Slovakia

A methodology is presented for evaluating and mapping the degree of groundw ater contamination by applying the contamination index C-d. The applicabili ty of the contamination index was tested in two distinctly different geolog ical regions: the area between Uusikaupunki and Ylane in southwestern Finla nd and the Brezno area in central Slovakia. The index takes into account bo th the number of parameters that exceed the upper permissible concentration s of contaminants or potentially harmful elements and the part of the conce ntrations exceeding those values. The water-quality parameters reflect the effect of diverse natural (topographical, climatical, geological, biologica l) and anthropogenic (type of land use, local pollution) environmental fact ors on groundwater quality. In Finland, technical-aesthetic contamination w as found over more than half the test area. These quality problems were mos t often related to acidity and high concentrations of organic carbon and Al and Fe in wells. Health-risk-based contamination, mainly caused by elevate d concentrations of fluoride, radon, or nitrate, was found in only a few se parate areas. In Slovakia, naturally contaminated and anthropogenically pol luted groundwaters could be distinguished. The geogenic pollution is mainly derived from sulfide mineralizations. In both countries the strongest anth ropogenic pollution was found in intensively cultivated areas.