Abstract
This study was carried out to find out the source of nitrate-nitrogen (NO$_3$-N) contamination in the groundwater in Cheju Island. Among the sites which have exceeded or may exceed the criterion level (10 mg/L) of NO$_3$-N in drinking water, seven sampling sites including two reference sites were chosen. The former regions are mainly agricultural ones (A-1 to A-6) and residential (R). The latter regions are forest (F-1 and F-2). The predicted major source and its contribution to NO$_3$-N concentration at each site, using $\delta$$\^$15/N and NO$_3$-N concentration, were as follow; Those at A-1, R and F-1 was 61.1%, 50.0% and 20.0% to manure or domestic sewage, 27.8%, 45.7% and 40.0% to chemical fertilizers and 11.1%, 4.3% and 40.0% to natural soil, respectively. Those at A-2 to A-6 were 37.8%, 25.0%, 40.9%, 26.2% and 35.7% to manure or domestic sewage, 59.6%, 71.7%, 53.0%, 71.5% and 60.2% to chemical fertilizers and 2.6%, 3.3%, 6.1%, 2.3% and 4.1% to natural soil, respectively.
제주도 지하수중의 $\delta$$^{15}$ N값을 이용하여 질산성질소의 오염원을 추정하기 위해 질산성질소농도가 먹는물 최대허용농도를 초과하거나 초과할 우려가 있는 지역중 7개 지점을 선정했으며, 대조지역으로 질산성 질소가 1 mg/ι 미만인 1개 지역을 선정하였다 질산성질소의 오염원은 $\delta$$^{15}$ N와의 관계를 비교하여 자연토양, 화학비료, 가정하수, 축산폐기물이나 퇴비등에서 유래되는 것으로 구분하였다. 질산성 질소농도와 $\delta$$^{15}$ N에 의한 주요 기원별 구성비에서는 A-1, R 및 F-1이 각각 61.1%, 50.0% 및 20.0%가 축산분뇨.생활하수 로 27,8%, 45.7% 및 40.0%가 화학비료로 11.1%, 4.3% 및 40.0%가 자연토양으로 구별되였고, A-2에서 A-6은 각각 37.8%, 25.0%, 40.9%, 26.2% 및 35.7%가 축산분뇨.생활하수로 2.6%, 3.3%, 6.1%, 2.3% 및 4.1%가 자연 토양으로 59.6%, 71.7%, 53.0%, 71.5% 및 60.2%가 화학비료로 추정되었다.
