Chinese Research Academy of Environmental Sciences, Beijing 100012, China; College of Water Sciences, Beijing Normal University, Beijing 100875, China.
Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Sci Total Environ. 2023 Jan 10;855:158500. doi: 10.1016/j.scitotenv.2022.158500. Epub 2022 Sep 8.
Anthropogenic reactive nitrogen (Nr) emissions from agricultural production and food consumption in city clusters have caused water quality degradation and scarcity. In this study, anthropogenic Nr emissions to the water environment were quantitatively evaluated in the Yangtze River Delta city cluster from 2011 to 2020 using coupling nitrogen (N) flow analysis and the grey water footprint (GWF) method. The spatiotemporal characteristics of the GWF and the relative contributions of natural and human factors to the water pollution level (WPL) were analyzed. The results showed that from 2011 to 2020, the total N-related GWF decreased by 12.1 %, mainly driven by reduced fertilizer application and livestock numbers. In 2020, the primary pollution source changed from livestock to humans; however, non-point sources still dominated the GWF. The spatial clustering trend of the GWF was significant: high and low GWF were mainly concentrated in the northeast and southwest regions, respectively. From 2011 to 2020, the mean center of the GWF moved west due to the decrease and increase in the eastern and western regions, respectively, supporting the pollution haven hypothesis. The WPL ranged from 2.67 to 5.03 and fluctuated due to variations in precipitation. The relative contributions of natural and human factors to the WPL evolution were 72.9 % and 27.1 %, respectively. According to the scenario analysis, increasing the N use efficiency to 50 %, manure recycling rate to 80 %, and sewage treatment rate in urban and rural regions to 98 % and 40 %, respectively, could decrease GWF by 39.6 %. The present study establishes an open framework to evaluate anthropogenic N emissions to water, and the outcomes provide valuable references for sustainable N management in city clusters.
人为氮（Nr）排放物来自农业生产和城市集群的食品消费，导致水质恶化和短缺。本研究采用耦合氮（N）流分析和灰水足迹（GWF）方法，定量评估了 2011 年至 2020 年长三角城市群向水环境排放的人为 Nr。分析了 GWF 的时空特征以及自然和人为因素对水污染水平（WPL）的相对贡献。结果表明，2011 年至 2020 年，与 N 相关的 GWF 总量减少了 12.1%，主要是由于化肥施用量和牲畜数量减少所致。2020 年，主要污染源由牲畜变为人类，但非点源仍占 GWF 的主导地位。GWF 的空间聚类趋势明显：高 GWF 和低 GWF 主要集中在东北和西南地区。2011 年至 2020 年，由于东部和西部的减少和增加，GWF 的平均中心向西移动，支持污染避难所假说。WPL 范围为 2.67 至 5.03，受降水变化影响而波动。自然和人为因素对 WPL 演变的相对贡献分别为 72.9%和 27.1%。根据情景分析，将 N 利用率提高到 50%，将粪肥回收率提高到 80%，将城乡地区污水处理率提高到 98%和 40%，可使 GWF 减少 39.6%。本研究建立了一个评估人为 N 向水排放的开放框架，研究结果为城市集群可持续 N 管理提供了有价值的参考。
