Estimation of Nitrate Sources in Cheju Island Groundwater using $\delta$$^{15}$ N

$\delta$$^{15}$ N을 이용한 제주도 지하수 중의 질산염 오염원 조사

18 boreholes with nitrate contaminated were selected. Samples were collected 4 times between both 1995 and 1996. Stable nitrogen isotope ratio for them all was measured and the contribution to contamination from several sources like fertilizer, sewage, cropland. and landfill was analysed. Nitrogen source for 11 sampling sites of T-3, L-1. O-1∼O-4, F-2∼F-5, and G-2 considered to come from chemical fertilizer and its contribution was around 60% or more. T-4. T-5 were located downward the downtown, which were influenced bydomestic sewage and its contribution were 70.7% and 54.7%. Nitrate concentration of G-2 was 17.7 mg/L, among which 60.7% was estimated to come from landfill leachate. T-1 and T-2 were located in the small village, in which 42.2 and 43.4% of nitrogen was to come from domestic sewage but 52.8% and 56.0% were from fertilizer sprayed in the cropland. L-2 was near livestock by which it was estimated to be influenced, in which 59.9% of nitrogen was from cropland. F-1 was in the cropland, by which 50.0% was influenced and 49.5% was estimated from organic matter of animals.

제주도 지하수중 질산염농도가 높은 지점을 선정하여 1995년부터 1996년까지 4차에 걸쳐 질소안정등위원소의 자연존재를 측정하고. 오염원별 기여율을 계산한 결과는 다음과 같다. 화학비료에 의한 영향이 뚜렸하게 나타나는 지점은 T-3, L-1. O-1∼O-4. F-2∼F-5. G-2의 11개소로써 화학비료 질소성분이 지하수 질산염농도 중 약 60% 이상을 차지하는 것으로 조사되었다. 그리고. 동물성 유기물질에 의한 영향이 많은 지하수는 T-4, T-5. G-2지점 3개소이며, T-4, T-5지점은 생활하수에 의한 영향으로, G-2지점은 쓰레기매립장 침출수의 영향으로 사료된다. 또한. 화학비료와 동물성 유기물질에 의한 영향을 비슷하게 받는 지하수는 T-1, T-2. L-2. F-1지점 4개소로 조사되었다.