Study on coupling of typical elements in surface water and groundwater in the middle reaches of the Yangtze River, China

• Published in: Journal of hydrology (Amsterdam) 2023-11, Vol.626, p.130298, Article 130298
• Main Authors: Hu, Meiyan, Zhou, Peijiang, Chen, Chaoqi
• Format: Article
• Language: English
• Subjects: Coupling relationship; Environment pollution; Groundwater; Surface water; Yangtze River
• ISSN: 0022-1694
• DOI: 10.1016/j.jhydrol.2023.130298

[Display omitted] •There is a close relationship between SW and GW in the middle reaches of the Yangtze River.•SW and GW may have a common major source of Cl-.•Almost the same water-carbonate reaction may occur in PGW and CGW.•Sources of nitrogen or phosphorus may be similar in SW and GW.•CGW is affected by SW and PGW by 29%–33% and 67%–71%, respectively. Understanding the coupling relationship of typical elements between surface water (SW) and groundwater (GW) is helpful to the prevention of regional water environment pollution. In this study, the coupling of typical elements (C, N, P) of SW and GW in the middle reaches of the Yangtze River was comprehensively analyzed using multiple statistics and hydrogeochemical modeling methods. SW chemical characteristics was found similar with that of GW in the middle reaches of the Yangtze River with cluster analysis, and all sampling points was divided into two principal components based on principal component analysis. One principal component was more affected by the water-carbonate mineral interaction, the other one was greatly affected by anthropogenic activities. More interestingly, no fixed replenishment and discharge relationship was found between SW and GW in different seasons, which laid a foundation for the coupling of typical elements between SW and GW. Cl- in SW and GW had the same major source. In addition, almost identical water-carbonate reactions was found occurred in phreatic water (PGW) and confined water (CGW). As a link between SW and CGW, PGW may accept the supplies of the two waters at the same time, resulting the concentrations of δD, Cl-, DOC and HCO3– in PGW ranking between SW and CGW. Furthermore, Nitrogen and phosphorus were found to migrate between SW and GW, and a potential ammonium source in shallow aquitard which generated a large amount of ammonium. The coupling effect of nitrogen source input and transformation occurred in the process of nitrogen coupling between SW and GW, which increased the ecological risk of water environment. This study provided a scientific basis for the control of SW-GW pollution in the middle reaches of the Yangtze River, and supported the security of the water ecological environment in the Yangtze River Basin.