抄録
A new separation index (SNI) was proposed to estimate the source of nitrogen in nitrogen contaminated water. SNI is defined as the equivalent ratio of SO42- to a total of NO2-, NO3-, and NH4+. SNI values of typical land use areas were measured in order to estimate actual SNI values. As a result, the ratio of S and N for chemical fertilizer was about 1 but the ratio for livestock manure, domestic waste water and organic nitrogen derivation was extremely low. Then, a mixing ratio of nitrogen derived from chemical fertilizer to total nitrogen was calculated from the SNI values of the sampled groundwater using representative SNI values for fertilizer and livestock waste. The mixing ratio was calculated for heavily nitrate contaminated groundwater in the North West of Kyushu. Each nitrogen origin determined by SNI analysis was in agreement with the actual land use. Therefore SNI analysis is a useful indicator for determining the ratio of nitrogen source to total nitrogen.
