Groundwater quality and main influencing factors in the northeast of Zhanjiang City, Guangdong Province

Objective Investigate the quality of groundwater in the northeastern coastal area of Zhanjiang, study the formation mechanisms of its main influencing factors, and assess its development and utilization potential, providing a theoretical basis for regional water resource development, utilization, and protection management.

Methods A total of 50 groundwater samples were collected within the area for comprehensive analysis, and pH levels were measured on−site in 168 private wells. Groundwater quality was evaluated and classified using a combination of methods including Shukalev classification, descriptive statistical analysis, Pearson correlation analysis, Gibbs diagrams, end−member mixing analysis, and ion ratio methods. The study analyzed the formation mechanisms of key factors affecting groundwater quality and assessed the potential for groundwater development and utilization.

Results The comprehensive evaluation indicates that groundwater quality is predominantly classified as Class IV and Class V. Source analysis shows that the groundwater chemistry is primarily influenced by the weathering of silicate minerals, followed by atmospheric precipitation. The pH of groundwater in the area is jointly affected by acid rain, the acid buffering capacity of the aquifer media, iron−bearing minerals in the strata, and tidal influences from rivers and seawater. Iron (Fe) and manganese (Mn) in groundwater exhibit a strong positive correlation; the aquifer media provide the source material for Fe and Mn, while leaching processes, acidic groundwater conditions, and reducing environments control their concentrations. Selenium mainly originates from selenium−enriched sandstone and shale in the upper reaches of Jianjiang River, and its concentration is also influenced by the groundwater's pH and Fe content. The impact of selenium on groundwater quality remains unclear. The study area holds significant groundwater development potential. , with Wuchuan City having greater potential than Potou District.

Conclusions The primary factors affecting groundwater quality in the study area are pH, iron (Fe), manganese (Mn), and selenium (Se), which are collectively influenced by the native geological environment, regional hydrogeological conditions, and climatic factors. Loose rock−type pore water is suitable for dispersed extraction, while loose rock−type pore confined water is suitable for centralized extraction, facilitating enhanced development of underground water resources in Wuchuan City.