<p>Groundwater is a critical freshwater resource in Weihai, a coastal city in North China, yet its hydrochemical evolution and associated pollution risks under the combined influence of seawater intrusion and human activities remain insufficiently understood. This study established an integrated framework to characterize groundwater chemistry, quantify source contributions, evaluate water quality, and assess non-carcinogenic health risks. A total of 72 shallow groundwater samples collected during the dry season were analyzed using Piper and Gibbs diagrams, ion-ratio analysis, principal component analysis coupled with the absolute principal component score-multiple linear regression model, the entropy-weighted water quality index, and human health risk assessment. Groundwater was classified into four major hydrochemical facies: HCO₃-Ca·Mg, SO₄-Ca·Mg, Cl-Na, and Cl·SO₄-Ca·Mg. Multiple lines of evidence indicated that marine-related salinization is a major control on groundwater chemistry, particularly in southern Wendeng and coastal Rongcheng. Source apportionment identified five principal contributors: carbonate dissolution (27.7%), seawater intrusion (22.4%), anthropogenic disturbance (20.5%), sulfate-bearing evaporite dissolution with minor silicate weathering contribution (16.4%), and unidentified sources (13.0%). Groundwater quality was generally acceptable, with 79.17% of samples classified as excellent to good, although deterioration was concentrated in southeastern Wendeng and central-eastern Rongcheng. TDS, Na⁺, NO₃⁻, Ca²⁺, Cl⁻, and F⁻ were the principal factors associated with groundwater quality decline. Health risk assessment showed that nitrate posed the main non-carcinogenic risk, with children more vulnerable than adults. This study provides an integrated process-to-risk framework for disentangling marine and anthropogenic controls on coastal groundwater, thereby providing a scientific basis for management and governance in vulnerable coastal zones.</p>