| Title |
Quantifying nitrogen source contribution ratios using stable isotope method: Application of Bayesian mixing model |
| Authors |
남태희 ( Tae-hui Nam ) ; 류희성 ( Hui-seoung Ryu ) ; 강태우 ( Tae-woo Kang ) ; 한영운 ( Yeong-un Han ) ; 김지현 ( Jihyun Kim ) ; 이경희 ( Kyounghee Lee ) ; 황순홍 ( Soonhong Hwang ) ; 김경현 ( Kyunghyun Kim ) |
| DOI |
https://doi.org/10.15681/KSWE.2019.35.6.510 |
| Keywords |
Bayesian isotope mixing model; End-member; Isotopic fractionation; SIAR; Yeongsan River |
| Abstract |
The ‘Stable Isotope Analysis in R’ (SIAR), one of the Bayesian mixing models for stable isotopes, has been proven to be useful for source apportionment of nitrates in rivers. In this study, the contribution ratios of nitrate sources were quantified by using the SIAR based on nitrogen and oxygen stable isotope measurements in the Yeongsan River. From the measurements, it was found that the values of δ15N-NO3 and δ18O-NO3 ranged from -8.2‰ to +13.4‰ and from +2.2‰ to +9.8‰, respectively. We further analyzed the contribution ratios of the five nitrate sources by using the SIAR. From the modeling results, the main nitrate source was found to be soil N (29.3 %), followed by sewage (26.7 %), manure (19.6 %), chemical fertilizer (17.9 %) and precipitation (6.3 %). From the results, it was found that the anthropogenic sources, i.e., sewage, manure and chemical fertilizer contribute 64.2% of the total nitrate inflow from the watershed. Due to the significant correlation of δ15N-NO3 and lnNO3- in this study, the fractionation factors reflecting the biogeochemical processes of stable isotope ratios could be directly obtained. This may make the contribution ratios obtained in this study more precise. The fractionation factors were identified as +3.64 ± 0.91‰ for δ15N-NO3 (p<0.01) and -5.67 ± 1.73 ‰ for δ18O-NO3(p<0.01), respectively, and were applied in using the SIAR. The study showed that the stable isotope method using the SIAR could be applied to quantitatively calculate the contribution ratios of nitrate sources in the Yeongsan River. |