Hydrochemical analysis and quality comprehensive assessment of groundwater in the densely populated coastal industrial city

In densely populated and industrially developed areas, contaminated groundwater poses significant risks to human health, leads to economic losses, and harms the ecological environment. This study focused on a typical coastal industrial city in Shandong Province, utilizing a comprehensive research method that involved analyzing hydrochemical characteristics and conducting a comprehensive quality evaluation to investigate the groundwater situation thoroughly. The hydrochemical study revealed that the groundwater in the study area is primarily characterized by weakly alkaline hard fresh water, with hydrochemical types mainly consisting of HCO3·Cl·SO4-Ca and HCO3·Cl-Ca. Hydrochemical composition is primarily controlled by carbonate rock dissolution and rock weathering. Stronger positive cation exchange results in the replacement of Na+ and K+ ions in groundwater by Ca2+ and Mg2+ ions. The comprehensive evaluation of water quality shows that the groundwater in the study area is divided into four categories: good (14 %), medium (54 %), poor (18 %), and extremely poor (14 %), with 32 % of groundwater deemed unsuitable for drinking. The groundwater vulnerability level is classified as IV, with poor antifouling ability. Approximately 59 % of the groundwater shows varying degrees of pollution, with excessive NO3−, Mn, and NH4-N significant contributors to severe groundwater contamination. The results of this study provide scientific guidance for local groundwater prevention and control work and provide a reference for the development of groundwater research.