Groundwater serves as a vital water source in Zhanjiang City. This study analyzed the chemical components of 35 samples to understand the hydrochemical characteristics and evolution mechanism of groundwater in Zhanjiang City. A comprehensive analysis was conducted using statistical methods, including the use of Piper trilinear diagrams, the Gibbs method, ion ratios, and other techniques, to investigate the sources and control factors of the main ions in groundwater in the area. The findings reveal that all the groundwater is freshwater, with the main cations and anions being Na⁺ and HCO₃⁻, respectively. Shallow water is mainly of the Cl•SO₄ mixed cation type, followed by the HCO₃•ClNa•Ca type. Middle and deep pore water is mainly of the HCO₃Na type, followed by the HCO₃Na•Mg type and HCO₃Na•Ca type. The hydrochemical classifications of pore and fissure water are Cl•HCO₃Mg•Na type and Cl•HCO₃Na type water. The primary hydrogeochemical process is water–rock interaction, particularly the dissolution of silicate minerals. Additionally, evaporation and concentration contribute significantly to the chemical composition of shallow water, and ion exchange is also an important hydrogeochemical process affecting middle and deep pore water. Shallow water commonly contains nitrates, with 37.5% of shallow water showing contamination with NO₃⁻. This study aims to provide insights into the development and utilization of local water resources.

To comprehensively explore the research hotpots and trends in soil salinization in China, CiteSpace software (version 6.3.R1) was used to visualize the knowledge graph and bibliometric analysis of relevant literature from 2000 to 2024 in the China Knowledge Network (CNKI) database and Web of Science (WoS) database. Analysis of 1963 CNKI documents and 2134 WoS documents published by 249 units for annual publications, research institutions, authors, and keyword graph revealed that the annual publication volume of the literature in the field of salinization shows an upward trend and the volume of quality English publications is higher than that of Chinese. The cooperation network of authors and institutions had already been formed in the field. The cooperation among research institutes was stable, and a core group of authors had already been formed. Since 2020, “spectral index”, “machine learning”, “remote sensing inversion”, “spatial and temporal changes”, “inter-root”, “simulation”, “oasis”, “ rainy season”, and “soil water content” have become hot words in research. The visualization of spatial and temporal distribution of soil salts based on big data and artificial intelligence has become the focus of attention of the academic community. Therefore, the challenges of salinization should be better addressed through scientific and technological innovation and comprehensive measures. The results of the study are expected to provide scientific references for the field of salinization in China.

The muddy coastal region of North Shandong, China, including Laizhou Bay and the Huanghe River (Yellow River) Delta, is a complex depositional environment where land and sea intersect, creating diverse water types and intricate coastal groundwater formation and evolution. This study focuses on the shallow Holocene aquifer (SHA) and the deep Pleistocene aquifer (DPA) groundwater, using hydrogeochemical, isotope analysis and numerical simulation methods to infer the source of water and salt and hydrogeological chemical processes. The results reveal that the groundwater is a mix of seawater, freshwater, and brine, with significant differences in hydrochemical types and isotopic signatures between the SHA and DPA aquifers. The SHA groundwater is dominated by low salinity (TDS ≈ 8 g/L), with the freshwater dominated by Cl-Na and Cl-Na·Mg hydrochemical types. In contrast, the DPA groundwater is characterised primarily by high salinity (TDS ≈ 72 g/L) and the Cl-Na type. δ¹⁸O-δ²H deviates from the precipitation line and is close to the seawater evaporation line, indicating stronger seawater intrusion and salt accumulation processes. Interestingly, δ¹⁸O and δ²H stable isotopes' relative abundance in the DPA brine samples from the Huanghe River Delta (at a burial depth of ~260 m) and Huanghe River water samples bear a resemblance, suggesting a strong correlation between the river water and the subsurface brine water source in the EPA. The Hydrochemical Facies Evolution Diagram (HFE–Diagram) analysis shows 63.77% of SHA samples underwent desalination, while 79.31% of DPA samples experienced seawater intrusion, this was restricted by structural constraints and rock salt dissolution. This study provides new insights into the hydrogeochemical evolution of coastal aquifers.