School of Geography and Ocean Science, Nanjing University, Nanjing, Jiangsu province 210023, China.
Center for Water and Ecology, State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
Sci Total Environ. 2023 May 1;871:162026. doi: 10.1016/j.scitotenv.2023.162026. Epub 2023 Feb 7.
Groundwater and rivers in Chinese cities suffer from severe nitrate pollution. The accurate identification of nitrate sources throughout aquatic systems is key to the water nitrate pollution management. This study investigated nitrogen components of groundwater for twelve years and analyzed the sources of nitrate in the aquatic system based on dual isotopes (δN-NO and δO-NO) in the city of Nanjing, a core city of the Yangtze River Delta region, China. Our results showed that the ratio of nitrate to the sum of ammonia and nitrate in groundwater show an increasing trend during 2010-2021. The nitrate concentration was positively correlated with the proportion of cultivated land and negatively correlated with the proportion of forest land in the buffer zone. The relationship between Cl and NO/ Cl showed that agriculture and sewage sources increased during 2010-2015, sewage sources increased during 2016-2018, agriculture sources increased during 2019-2021. Manure and sewage were the primary sources of groundwater nitrate (72 %). There was no significant difference between the developed land (78 %), cultivated land (69 %), and aquaculture area (72 %). This indicates that dense population and intensive aquaculture in the suburbs have a significant impact on nitrate pollution. The contributions of manure and sewage to the fluvial nitrate sources in the lower reaches of the Qinhuai River Basin were 61 %. The non-point sources, including groundwater N (39 %) and soil N (35 %), were 74 % over the upper reaches. This study highlights the necessity of developing different N pollution management strategies for different parts of highly urbanized watersheds and considers groundwater restoration and soil nitrogen management as momentous, long-term tasks.
中国城市的地下水和河流遭受着严重的硝酸盐污染。准确识别水生系统中的硝酸盐来源是水硝酸盐污染管理的关键。本研究调查了南京市十二年的地下水氮成分，并基于双同位素（δN-NO 和 δO-NO）分析了该水系中硝酸盐的来源。南京市是中国长三角地区的核心城市。结果表明，2010-2021 年期间，地下水硝酸盐与氨氮和硝酸盐总和的比值呈上升趋势。硝酸盐浓度与缓冲区耕地比例呈正相关，与林地比例呈负相关。Cl 和 NO/Cl 的关系表明，2010-2015 年农业和污水源增加，2016-2018 年污水源增加，2019-2021 年农业源增加。粪肥和污水是地下水硝酸盐的主要来源（72%）。发达用地（78%）、耕地（69%）和养殖区（72%）之间没有显著差异。这表明郊区密集的人口和集约化养殖对硝酸盐污染有重大影响。粪肥和污水对秦淮河下游流域河流硝酸盐源的贡献分别为 61%。非点源，包括地下水 N（39%）和土壤 N（35%），在上游占 74%。本研究强调了在高度城市化流域的不同部分制定不同的 N 污染管理策略的必要性，并认为地下水修复和土壤氮管理是重大的、长期的任务。
