Hydrochemical Formation Mechanisms and Source Apportionment in Multi-Aquifer Systems of Coastal Cities: A Case Study of Qingdao City, China

Mingming Li, Xinfeng Wang, Jiangong You, Yueqi Wang, Mingyue Zhao, Ping Sun, Jiani Fu, Yang Yu () and Kuanzhen Mao ()
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Mingming Li: Langfang Integrated Natural Resources Survey Center, China Geological Survey, Langfang 065000, China
Xinfeng Wang: Langfang Integrated Natural Resources Survey Center, China Geological Survey, Langfang 065000, China
Jiangong You: Langfang Integrated Natural Resources Survey Center, China Geological Survey, Langfang 065000, China
Yueqi Wang: Qingdao Key Laboratory of Groundwater Resources Protection and Rehabilitation, Qingdao Geo-Engineering Surveying Institute, Qingdao 266101, China
Mingyue Zhao: Qingdao Key Laboratory of Groundwater Resources Protection and Rehabilitation, Qingdao Geo-Engineering Surveying Institute, Qingdao 266101, China
Ping Sun: Qingdao Key Laboratory of Groundwater Resources Protection and Rehabilitation, Qingdao Geo-Engineering Surveying Institute, Qingdao 266101, China
Jiani Fu: Qingdao Key Laboratory of Groundwater Resources Protection and Rehabilitation, Qingdao Geo-Engineering Surveying Institute, Qingdao 266101, China
Yang Yu: Qingdao Key Laboratory of Groundwater Resources Protection and Rehabilitation, Qingdao Geo-Engineering Surveying Institute, Qingdao 266101, China
Kuanzhen Mao: Langfang Integrated Natural Resources Survey Center, China Geological Survey, Langfang 065000, China

Sustainability, 2025, vol. 17, issue 13, 1-18

Abstract: This study systematically unravels the hydrochemical evolution mechanisms and driving forces in multi-aquifer systems of Qingdao, a coastal economic hub. Integrated hydrochemical analysis of porous, fissured, and karst water, combined with PHREEQC modeling and Positive Matrix Factorization (PMF), deciphers water–rock interactions and anthropogenic perturbations. Groundwater exhibits weak alkalinity (pH 7.2–8.4), with porous aquifers showing markedly higher TDS (161.1–8203.5 mg/L) than fissured (147.7–1224.8 mg/L) and karst systems (361.1–4551.5 mg/L). Spatial heterogeneity reveals progressive hydrochemical transitions (HCO 3 -Ca → SO 4 -Ca·Mg → Cl-Na) in porous aquifers across the Dagu River Basin. While carbonate (calcite) and silicate weathering govern natural hydrochemistry, evaporite dissolution and seawater intrusion drive severe groundwater salinization in the western Pingdu City and the Dagu River Estuary (localized TDS up to 8203.5 mg/L). PMF source apportionment identifies acid deposition-enhanced dissolution of carbonate/silicate minerals, with nitrate contamination predominantly sourced from agricultural runoff and domestic sewage. Landfill leachate exerts pronounced impacts in Laixi and adjacent regions. This study offering actionable strategies for salinity mitigation and contaminant source regulation, thereby providing a scientific framework for sustainable groundwater management in rapidly urbanizing coastal zones.

Keywords: groundwater chemistry; water–rock interaction; anthropogenic contamination; source apportionment; Qingdao (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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