NITRATE AND CHLORIDE LOADINGS AS ANTHROPOGENIC INDICATORS

Agricultural, urban, forest and groundwater protection areas as well as nitrate and chloride concentrations are documented in maps. Areal distribution shows regionally elevated nitrate and chloride concentrations in connection with urban areas and agricultural use. Transport of nitrate and chloride tends to be conservative in the groundwater of the investigated area. Therefore, the elevated concentrations of these anions are suitable as indicators of anthropogenic impact on the groundwater. The average concentration of nitrate and chloride from all surveyed wells amounts to 26 and 17 mg L-1, respectively. It is shown that wells recharged through forests have lower nitrate and chloride concentrations (average: 21 and 13 mg L-1, respectively). Wells affected by waste deposits have an average nitrate concentration of 35 mg L-1 and chloride concentration of 24 mg L-1. Urban use results in an average value of 28 mg L-1 nitrate and 24 mg L-1 chloride. As nitrate and chloride concentrations are stable with respect to the depth of the groundwater table, degradation processes or other protective effects of the unsaturated zone can be omitted.