Coupling hydrochemistry and stable isotopes (d2H and d18O) to identify the major factors affecting the hydrochemical evolution of groundwater in the Western Yellow Sea Coast, China

Groundwater, as an invaluable freshwater resource, has a significant impact on the social and economic development of coastal areas. The Western Yellow Sea coast (WYSC), located in the eastern part of China, is considered one of the most prosperous areas in terms of economic development, with considerable demand for water. In this study, a total of 160 groundwater samples were collected in the field, for which the Ca2+, Mg2+, Na+, K+, Cl-, SO42-, HCO3-, F-, Br-, delta H-2 , and delta O-18 contents were determined. We studied the chemical characteristics, sources of dissolved substances, hydrogeochemical processes, and the difference between the chemical characteristics of groundwater in two areas of the WYSC, the Shandong part (SDP) and Jiangsu part (JSP). The results indicate that the major sources of dissolved substances in the groundwater of WYSC were mineral dissolution and seawater intrusion (SWI). SDP was mainly affected by mineral dissolution, whereas JSP was significantly affected by SWI. The major source of groundwater recharge in the WYSC was precipitation; moreover, the groundwater recharge was affected by seawater and evaporation. The groundwater in the SDP was affected by modern SWI, whereas that in JSP was affected by palaeo SWI. SWI not only directly changes the chemical composition of groundwater via mixing but also indirectly changes it by influencing the hydrogeochemical processes. SWI can also lead to the formation of high-fluoride groundwater. Therefore, feasible measures should be incorporated to prevent SWI and ensure drinking water safety for the inhabitants.

Automated summary

This study investigates the chemical characteristics, sources of dissolved substances, hydrogeochemical processes, and the differences between two areas of groundwater in the Western Yellow Sea coast of China. The study finds that mineral dissolution and seawater intrusion are the major sources of dissolved substances in the groundwater, with different impacts on the two areas. The study also highlights the importance of preventing seawater intrusion and ensuring drinking water safety.