我国主要河流水系硝态氮污染特征及定量源解析

Nitrate Pollution Characteristics and Its Quantitative Source Identification of Major River Systems in China

准确定量污染来源组成是有效控制水体硝态氮污染的关键科学基础.采用荟萃分析的方法,收集了2000~2022年我国167条主要水系河流的硝态氮浓度和硝态氮的氮氧同位素等数据,分析了七大主要河流水系硝态氮污染的时空变异规律及其转化特征,定量识别了河流硝态氮的污染来源组成.结果表明,我国主要河流水系ρ(NO_(3)^(-)-N)平均值为(4.54±3.99)mg·L_(-1),其中9.6%的河流硝态氮浓度超过我国地表水环境质量标准(GB 3838-2002)规定的限值(10.0 mg·L_(-1)),海河水系的硝态氮污染最为严重.东部地区河流水系的硝态氮浓度总体高于西部,各大河流水系支流的硝态氮浓度高于干流.除黄河水系以外,其他水系枯水期的硝态氮浓度总体高于丰水期.珠江水系、黄河水系中下游地区、辽河水系中游地区、松花江水系,以及海河水系河流水体存在显著的硝化作用,而长江水系、淮河水系和珠江水系下游地区存在显著的反硝化作用.污水/粪肥是长江水系、海河水系、辽河水系,以及东南诸河水系硝态氮的主要来源(>50%),土壤氮是松花江水系硝态氮的主要来源(56.4%),化肥氮、土壤氮和污水/粪肥对珠江水系、淮河水系和黄河水系硝态氮的污染贡献为20%~40%.污水/粪肥对水系支流硝态氮贡献率总体大于干流的,土壤氮对干流硝态氮的贡献总体大于支流的.土壤氮、化肥氮和大气沉降氮对丰水期河流硝态氮的贡献率高于枯水期,而污水/粪肥对枯水期河流硝态氮的污染贡献率高于丰水期.因此,海河水系、长江水系、辽河水系、黄河水系支流与下游干流地区和珠江水系下游地区应重点控制生活和生产的污水排放等点源污染,而淮河水系、松花江水系、黄河水系中游干流地区和珠江水系中上游地区要重点控制化肥和土壤氮等流失造成的非点源污染.研究结果可为有效控制我国各河流水系硝态氮的污染提供科学依据.

Accurate source identification/apportionment is essential for optimizing water NO_(3)^(-)-N pollution control strategies.This study conducted a meta-analysis based on data from 167 rivers across China from 2000 to 2022 to analyze the spatial and temporal variation patterns of nitrate pollution in seven major river systems and to quantitatively identify the source composition of riverine nitrate.The averageρ(NO_(3)^(-)-N)in the seven major river systems was(4.54±3.99)mg·L^(-1),with 9.6% of riverρ(NO_(3)^(-)-N)exceeding 10 mg·L^(-1).The riverineρ(NO_(3)^(-)-N)in eastern China were higher than that in western China,and the highest concentration was observed in the Haihe River system.Additionally,tributaries experienced more serious NO_(3)^(-)-N pollution than that in the main stream.Theρ(NO_(3)^(-)-N)in most river systems in the dry season was higher than that in the wet season,except in the Yellow River system.There was significant nitrification in the Pearl River system,the middle and lower reaches of the Yellow River system,the middle reaches of the Liaohe River system,the Songhua River system,and the Haihe River system,whereas there was significant denitrification in the Yangtze River system,the Huaihe River system,and the lower reaches of the Pearl River system.Based on the dual stable isotopes-based MixSIAR model,the major NO_(3)^(-)-N source was sewage/manure(>50%)in the Yangtze River system,Haihe River system,Liaohe River system,and Southeast River system.Soil nitrogen was the main NO_(3)^(-)-N source in the Songhua River system(56.4%),and the contribution of fertilizer nitrogen,soil nitrogen,and sewage/manure to NO_(3)^(-)-N pollution in the Pearl River system,Huai River system,and Yellow River system was 20%-40%.The contribution rate of sewage/manure to NO_(3)^(-)-N in the tributaries was higher than that in the main stream,whereas the contribution rate of soil nitrogen to NO_(3)^(-)-N in the main stream was higher than that in the tributaries.The contribution rate of soil nitrogen,fertilizer nitrogen,and atmospheric deposition nitrogen to nitrate nitrogen in the wet season was higher than that in the dry season,whereas the contribution rate of sewage/manure to NO_(3)^(-)-N pollution in the dry season was higher than that in the wet season.Therefore,point source pollution such as domestic and production sewage discharge should be controlled in the Haihe River system,the Yangtze River system,the Liaohe River system,the tributaries and the downstream main stream areas of Yellow River system,and the downstream area of the Pearl River system,whereas non-point source pollution caused by the loss of fertilizer and soil nitrogen should be controlled in the Huaihe River system,the Songhua River system,the middle reaches of the main stream area of the Yellow River system,and the middle and upper reaches of the Pearl River system.The results can provide a scientific basis for the effective control of nitrate pollution in the river systems in China.