Nitrate concentrations in excess of national drinking-water standards (10mg/L as N) have been found in unconfined groundwater at Kaneko upland area.
To investigate the nitrate-nitrogen sources in the groundwater, nitrogen-isotopic compositions of nitrate-nitrogen and dissolved ion concentrations were measured in the groundwater from 15 wells. Along the flow of groundwater in each topographical surface, the relationship among the changes of dissolved ion concentrations, nitrogen-isotopic compositions, land use and position of the area with sewerage system were also examined. As a result, it was suggested that chemical fertilizer and domestic waste have an influence on the groundwater quality in a part of the researching area. Also it was suggested that the rise of nitrogen-isotopic compositions with the flow of groundwater in the part of the researching area should be attributed to the denitrification.