Hydrochemistry characteristics and genesis of shallow groundwater in diverse industrial agglomeration areas in typical alluvial plain of the Yellow River

The groundwater environment in the middle and upper reaches of the Yellow River in China has attracted extensive attention. But, the hydrochemistry characteristics and genesis of shallow groundwater in diverse industrial agglomeration areas in typical alluvial plain of the Yellow River are still unknown. In this study, geochemical analysis methods, the positive matrix factorisation model, and the geodetector model were used to multidimensional analyze. The results showed that 78 % of the groundwater samples had high-alkalinity-risk and high-salinity-risk, and the water quality was poor and unsuitable for irrigation. "Very poor" and "undrinkable" samples accounted for 26.31 %. The weathering of calcium magnesium minerals and the dissolution of soluble sulfate were important sources of the main chemical components of the groundwater. However, evaporation and concentration gradually dominated from the inclined plain of the piedmont to the alluvial plain of the Yellow River. Domestic and agricultural activities were important sources of nitrogen species (NO₃^-, NO₂^-, and NH₄⁺). The presence of Al, Mn, Zn, and Pb was caused by the production activities of various enterprises. The pollution contributors of natural sources, domestic and agricultural activities, industrial production and other sources were 29.49 %, 17.05 %, 31.41 %, and 22.05 %, respectively. Groundwater velocity and enterprise type were the main factors driving groundwater pollution by these four metal substances. The interaction between enterprise type and groundwater velocity had the greatest influence on the concentrations of Al, Mn, and Zn. Moreover, the interaction between enterprise type and the distance from enterprise had the greatest influence on Pb levels. Overall, groundwater pollution in the study area was the result of both natural and human factors. The findings of this study can offer valuable insights and theoretical support for preventing groundwater pollution in other industrial agglomeration areas in the alluvial plain of the Yellow River.