基于氮氧同位素技术的黄河上游清水河硝酸盐来源解析

对清水河灌溉季和非灌溉季各采样点位的水化学指标和硝酸盐的时空分布特征进行分析,运用贝叶斯混合模型MixSIAR模型定量识别了该河流硝酸盐来源,以期了解灌溉对地表水硝酸盐含量的影响.结果表明,清水河水体呈弱碱性,水体氮类以硝酸盐为主,Cl^-和SO₄^2-时空变化特征一致,通过NO₃^-/Cl^-比值和Cl^-浓度的关系,结合清水河地区土地利用、工农业生产的实际情况,揭示了清水河水体硝酸盐受生活污水、畜禽养殖和化学氮肥源的影响较大.MixSIAR模型计算结果表明土壤有机氮、化学氮肥和畜禽养殖对灌溉季水体的贡献率较大,分别为24.8%、24.5%和22.8%,生活污水和大气氮沉降的贡献率分别为14.4%和13.6%;而生活污水、畜禽养殖和土壤有机氮对非灌溉季水体的贡献率较大,分别为26.7%、23.4%和20.4%,大气氮沉降和化学氮肥贡献率分别为16.5%和12.9%.农业灌溉增加了地表水硝酸盐的含量,灌溉季中农用氮肥的施用率较高,贡献了主要的硝酸盐;非灌溉季生活污水的贡献率较高.

Analysis of nitrate sources in the Qingshui River of the Yellow River with nitrogen and oxygen isotope technique

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.