Identification of sources and transformations of nitrate in the Xijiang River using nitrate isotopes and Bayesian model
| Autor: | Sen Xu, Jing Liu, Fu-Jun Yue, Si-Liang Li, Cai Li, Jun Zhong, Zhifeng Yan, Zhong-Jun Wang, Ruochun Zhang |
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| Rok vydání: | 2019 |
| Předmět: |
Environmental Engineering
Denitrification 010504 meteorology & atmospheric sciences Soil chemistry chemistry.chemical_element 010501 environmental sciences engineering.material 01 natural sciences Pollution Manure Nitrogen Isotopes of oxygen chemistry.chemical_compound Nitrate chemistry Environmental chemistry engineering Environmental Chemistry Environmental science Fertilizer Waste Management and Disposal 0105 earth and related environmental sciences Isotope analysis |
| Zdroj: | Science of The Total Environment. 646:801-810 |
| ISSN: | 0048-9697 |
| DOI: | 10.1016/j.scitotenv.2018.07.345 |
| Popis: | Coupled nitrogen and oxygen isotopes of nitrate have proven useful in identifying nitrate sources and transformation in rivers. However, isotopic fractionation and low-resolution monitoring limit the accurate estimation of nitrate dynamics. In the present study, the spatio-temporal variations of nitrate isotopes (N-15 and O-18) and hydrochemical compositions (NO3- and Cl-) of river water were examined to understand nitrate sources in the Xijiang River, China. High-frequency sampling campaigns and isotopic analysis were performed at the mouth of the Xijiang River to capture temporal nitrate variabilities. The overall values of delta N-15-NO3- and delta O-18-NO3- ranged from +4.4% to +14.1% and from -0.3% to +6.8%, respectively. The results of nitrate isotopes indicated that NO3- mainly originated from soil organic nitrogen (SON), chemical fertilizer (CF), and manure and sewage wastes (MS whereas approximately 58% of nitrate was derived from anthropogenic inputs (M&S and CF) in the dry season. The nitrate flux was 2.08 x 10(5) tons N yr(-1) during one hydrologic year between 2013 and 2014, with 86% occurring in the wet season. Long-term fluctuations in nitrate flux indicated that nitrate export increased significantly over the past 35 years, and was significantly correlated with nitrate concentrations. The seasonal pattern of nitrate dynamics indicated the mixing of nitrified NO3- and denitrified NO3- between surface flow and groundwater flow under different hydrological conditions. Overall, the present study quantitatively evaluates the spatio-temporal variations in nitrate sources in a subtropical watershed, and the high-frequency monitoring gives a better estimate of nitrate exports and proportional contributions of nitrate sources. |
| Databáze: | OpenAIRE |
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