AZOTANY W WODACH PODZIEMNYCH ZLEWNI GÓRNEJ LISWARTY

Abstract

NITRATES IN GROUNDWATER OF THE UPPER LISWARTA RIVER BASIN

Abstract. The upper Liswarta River basin is situated in the drainage area of the Warta River. The chemical composition of groundwater in the investigated area is the result of natural and anthropogenic factors. Lithology of the aeration and saturation zones and the differentiation of oxidation-reduction conditions along the path of water circulation have the main influence on groundwater quality. The worsening quality of groundwater in the area of the upper Liswarta River basin is due to the influence of anthropogenic factors including the leaching migration of nitrates from surface contamination spots as a result of soil cultivation and fertilisation, animal farming and social-living activities within rural areas. An important factor influencing the water quality is hydrogeochemical changes in water consumption conditions. The assessments of groundwater chemistry and quality of the Quaternary aquifer within the upper Liswarta River basin were determined from the results of 74 chemical analyses. The study results indicate that groundwater in the area is represented by multi-ion fresh waters, slightly acid to slightly basic (pH values range from 5.35 to 9.56). The TDS of these waters reaches up to 672.35 mg/l, with average of 295.36 mg/l. The tested waters show the presence of increased concentrations of nitrates, sulfates, and sometimes chlorides, which are the indicators of anthropogenic contaminations. Nitrate concentrations in the groundwaters are up to 189.00 mg/l, and the content of sulfates ranges from 5.47 to 178.00 mg/l. The mosaic concentration distribution of nitrates in groundwater can suggest local contamination of single water intakes. The differentiated distribution of the nitrates concentration in some wells and observation boreholes, especially in rural area, is probably related the type of land use and land development.