| Title |
Estimation of Pollution Sources of Oenam Watershed in Juam Lake using Nitrogen Concentration and Isotope Analysis |
| Authors |
최유진 ( Yu Jin Choi ) ; 정재운 ( Jae Woon Jung ) ; 최우정 ( Woo Jung Choi ) ; 윤광식 ( Kwang Sik Yoon ) ; 최동호 ( Dong Ho Choi ) ; 임상선 ( Sang Sun Lim ) ; 정주홍 ( Ju Hong Jeong ) ; 임병진 ( Byung Jin Lim ) ; 장남익 ( Nam Ik Chang ) |
| Keywords |
Nitrogen isotope; Pollution source; Water quality; Watershed |
| Abstract |
In an effort to investigate water pollution characteristics of Juam lake, water samples were collected from three sites (Sites A, B, and C) of Oenam stream which is a typical tributary of rural watershed in the lake and analyzed for N concentration and the corresponding isotope ratio (δ15N) of NO3-. Concentrations of NO3- were not dramatically different among the sites; 0.8±0.2 mg N L-1 (range: 0.0~4.3 mg N L-1) for Site A, 1.1±0.2 mg N L-1 (0.0~4.3 mg N L-1) for Site B, and 1.1±0.1 mg N L-1 (0.1~2.6 mg N L-1) for Site C. Meanwhile, δ15N tended to decrease with river flow; it was highest for Site A (45.5±5.3‰) followed by Site B (19.7±2.0‰) and Site C (8.7±1.5‰). Such high δ15N values of NO3- in Site A suggested that NO3- derived from livestock feedlot (specifically livestock excrete of which δ15N is higher than 10‰) is the predominant pollution sources despite mountainous area occupied the most of land-use in the watershed. Using the two-sources isotope mixing model, it was estimated that the contribution of cropping activities (i.e. fertilization) became greater in down-stream area (Sites B and C) due to the higher agricultural land-use than the up-stream area (Site A). Particularly, during the active cropping season, the low contribution of organic pollution sources indicated that domestic sewage was not the predominant pollution source. Therefore, it was suggested that agricultural sources such as livestock farming and cropping rather than mountainous and residential are the dominant sources of water pollution in the study area. These results could be effectively utilized in elucidating water pollution sources in rural areas and selecting water management practices. |