基于氮氧同位素技术的黄河上游清水河硝酸盐来源解析

In order to understand the influence of irrigation on nitrate concentration in surface water, the temporal and spatial distribution characteristics of nitrate and hydrochemical indexes at each sampling point in the Qingshui River during irrigation- and non-irrigation seasons were analyzed to identify the sources of nitrate with Bayesian mixed model (MixSIAR) in this study. The results show that the water body of the Qingshui River was of weakly alkaline and dominated with nitrate that was mainly attributed to domestic sewage, livestock and poultry breeding, and chemical nitrogen sources. The MixSIAR model show that soil organic nitrogen, chemical nitrogen fertilizer, and livestock breeding also contributed greatly to the major nitrate content in irrigation season, accounting for 24.8%, 24.5%, and 22.8%, and the contribution of domestic sewage and atmospheric nitrogen deposition were 14.4% and 13.6%, respectively. In addition, in non-irrigation season, the contribution of domestic sewage, livestock breeding, and soil organic nitrogen were 26.7%, 23.4% and 20.4%, and the contribution of atmospheric nitrogen deposition and chemical nitrogen fertilizer were 16.5% and 12.9%, respectively. Furthermore, in the irrigation season, agricultural irrigation increased the nitrate concentration in surface water, and the application of agricultural nitrogen fertilizers was higher, contributing to the major nitrate content; in the non-irrigation season, the contribution ratio of domestic sewage was higher.