State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, 710061, Xi'an, China.
School of Water and Environment, Chang' an University, 710054, Xi'an, China.
Environ Sci Pollut Res Int. 2024 Oct;31(50):60126-60140. doi: 10.1007/s11356-024-35209-2. Epub 2024 Oct 7.
Urban rivers worldwide have been increasingly threatened by nitrate (NO) pollution. The Xianyang-Xi'an segment of the Weihe River, located in the loess plateau with serious soil erosion, has been highly urbanized and with intensive agricultural activities. Tracing the sources and transformations of NO is particularly challenging for this watershed which has multiple N sources and variable environmental factors. In this study, integrating antecedent studies with multiple stable isotopes and MixSIAR models, these river basins can be categorized into three classes: (1) urban areas, sewage, and manure were the predominant sources of NO in the Weihe River's mainstream, accounting for 73.4 ± 12.8%; (2) suburban areas, sewage and manure (Fenghe River, 58.0 ± 14.0%; Bahe River, 53.9 ± 15.0%) were recognized as the main sources of NO; (3) and the rural areas, ammonium nitrogen fertilizers were identified as the primary source of NO in the Heihe and Laohe Rivers. In addition, nitrification dominated the mainstream of the Weihe, Fenghe, and Bahe Rivers, while neither denitrification nor nitrification was evident in the Heihe and Laohe Rivers. In conclusion, this study is important for the improvement of surface water quality of rivers with different land use types and the development of targeted water environment management.
世界范围内的城市河流受到硝酸盐（NO）污染的威胁日益增加。渭河流域的咸阳-西安段位于水土流失严重的黄土高原，城市化程度高，农业活动密集。对于这个具有多种氮源和多变环境因素的流域，追踪 NO 的来源和转化尤为具有挑战性。在这项研究中，通过整合先前的研究以及多种稳定同位素和 MixSIAR 模型，这些河流流域可以分为三类：（1）城市地区，污水和粪便是渭河主流中 NO 的主要来源，占 73.4±12.8%；（2）郊区地区，污水和粪便（沣河，58.0±14.0%；北河，53.9±15.0%）被认为是 NO 的主要来源；（3）以及农村地区，黑河流和老河流中铵态氮肥是 NO 的主要来源。此外，硝化作用主导了渭河、沣河和北河的主流，而黑河流和老河流中既没有反硝化作用也没有硝化作用。总之，这项研究对于改善不同土地利用类型的河流地表水质量和制定有针对性的水环境管理具有重要意义。
