Characterization and Cause Analysis of Shallow Groundwater Hydrochemistry in the Plains of Henan Province, China

With the development of the human population and society, groundwater environmental problems have become an important factor limiting global socioeconomic development, and the study of groundwater hydrochemical characteristics and pollution is a current hot issue. In this study, data regarding shallow groundwater quality in 76 instances were used to evaluate the quality of shallow groundwater in the plains of Henan Province, China, by using a combination of subjective and objective assignments, mathematical statistics, Piper trilinear diagram, Gibbs diagram, ion ratio analysis, and other methods to study the hydrochemical characteristics of groundwater and its formation mechanism. The results showed that the groundwater quality in most areas of Henan Plain is in good condition, and the proportion of samples with excellent grades and good grades is as high as 43.42% and 35.53%. The range of poor and extremely poor water quality is small, and only five samples are judged as poor and extremely poor grades, mainly distributed in Jiaozuo City, Xinxiang City, Zhoukou City, and Puyang City. The groundwater anionic hydrochemistry is mainly of the HCO3 type, accounting for 61.84% of the samples and locally transformed downstream to HCO3 & BULL;SO4, HCO3 & BULL;SO4 & BULL;Cl, HCO3 & BULL;Cl & BULL;SO4, and Cl & BULL;SO4 & BULL;HCO3. Cations are predominantly of the Ca/Mg and Ca-Mg/Mg-Ca type, and gradually transformed to the Na-Ca/Ca-Na and Na-Mg/Mg-Na type along the runoff direction. Water-rock interactions and anthropogenic factors dominate the hydrochemistry evolution, with major geochemical processes involving the precipitation of calcite and dolomite as well as the weathering dissolution of rock salt and fluorite. Human activity is an important factor affecting the distribution of NO3-N and Fe3+. It is recommended that groundwater be continuously monitored to provide scientific data for sustainable groundwater quality management and that appropriate measures be developed to prevent further degradation of the groundwater environment.