硝酸盐氮同位素指示的青海湟水河中可能的氮污染来源

The Possible Sources of Nitrogen Pollution Indicated by Nitrate Nitrogen Isotopes from Huangshui River,Qinghai

中文关键词:  氮污染  湟水河  硝酸盐  氮同位素

英文关键词:Nitrogen pollution  Huangshui river  Nitrate  Nitrogen isotopes

中文摘要:

      系统测定了青海湟水河枯水期河水的硝酸盐(NO-₃)含量及其氮同位素组成(δ¹⁵N-NO-₃),详细分析了青海湟水河流域硝酸盐浓度及氮同位素组成的变化特征,基于此初步探讨了河水中可能的氮污染来源。结果显示,研究时段内湟水河河水的NO-₃浓度范围为0.1~38.0 mg/L,平均值为15.9 mg/L,约56%的河水样品中的NO-₃含量超过我国《地表水环境质量标准》中V类水氮含量的标准限值。湟水河河水δ¹⁵N-NO-₃值的变化范围为+2.7‰~+16.8‰,平均值为+8.5‰,反映出受不同氮来源的影响。总体而言,湟水河NO-₃浓度自源头至下游整体呈增大趋势,但各区段δ¹⁵N-NO-₃值的变化幅度却存在较大差异。对比分析发现,流域内河水较高的δ¹⁵N-NO-₃值可能指示河水中的硝态氮主要来源于工业生产以及人类生活排放的污水或粪便；而较低的δ¹⁵N-NO-₃值指示河水中的硝态氮主要来源于大气氮沉降或与农业活动有关的土壤。

英文摘要:

      Based on the results of NO-₃contents and δ¹⁵N-NO-₃compositions of river water from Huangshui River during the dry season,we analyzed the variation characteristics of nitrate concentrations and nitrogen isotope compositions,and preliminarily discussed the possible sources of nitrogen pollution in the river.The results showed that the nitrate concentrations of river water ranged from 0.1 mg/L to 38.0 mg/L in the study period,with an average value of 15.9 mg/L.The NO-₃contents in about 56% of river water samples exceeded the limit value of nitrogen concentration of Class V Water Standard in China’s Environmental Quality Standard for Surface Water.The δ¹⁵N-NO-₃values ranged from +2.7‰ to +16.8‰ in the study period,with an average value of +8.5‰,reflecting the influence of different nitrate sources.In general,the concentrations of NO-₃ increased from the source to the downstream as a whole,but the δ¹⁵N-NO-₃values varied greatly in each section.The comparative analysis showed that the relatively higher δ¹⁵N-NO-₃values indicated that the nitrate nitrogen of river water were mainly derived from the industrial production and sewage or feces discharged from human activities,while the relatively lower δ¹⁵N-NO-₃values indicated that the nitrate nitrogen of river water were mainly derived from the atmospheric deposition or soil nitrogen.