Abstract
Fluctuation of nitrate concentration in spring water at the Nogawa basin was studied during 1976-1977, and the possible source of nitrate nitrogen was discussed. Nitrate concentration in spring water at the station N-0 in Kokubunji, Tokyo ranged from 360 to 574 μg at/1 with an average value of 502 μg at/1. It seemed that the effluent of spring water at N-0 was influenced by rainfall within a short period. A laboratory experiment on production of nitrate in soil showed that ammonium nitrogen added to fresh soil was transformed quantitatively to nitrate nitrogen during 23 days incu- bation. Thd δ15N value of nitrate nitrogen in spring water (+8.9‰) was similar to that of ammonium nitrogen in sewage (+8.2‰) discharging into the Nogawa River. In the area near N-0, domestic wastes have been discharged into the Nogawa River by simple sewers or percolated downward through the soil. These results suggest that one of the main source of nitrate nitrogen in spring water is ammonium and organic nitrogen in domestic wastes.
