Groundwater Chemistry Characteristics and the Analysis of Influence Factors in the Luochuan Loess Tablelands

Abstract

Groundwater is of great importance to the loess area, and its hydrochemical characteristics and control factors are of great significance for the utilization and management of groundwater resources. In this study, groundwater hydrochemical characteristics and their controlling factors were analyzed using descriptive statistical analysis, Piper diagrams, Gibbs diagrams, forward derivation modeling, and correlation analysis. The results show that:① Groundwater is weakly alkaline, has low salinity, and has the water chemical type Ca-Mg-HCO3; the dominant anions and cations were HCO3- and Ca2+, which accounted for 58% to 59% of the anions and 40% to 80% of the cations, respectively; ② The ion content of the groundwater, particularly the dominant anions and cations, varied, which may have been affected by factors such as precipitation leaching of soil, cation exchange, and the horizontal flow of groundwater; ③ The main factors affecting the ion content of the groundwater are the weathering of carbonate and silicate rock, while the contribution of evaporite dissolution, human activity, and atmospheric input is very small. Carbonate weathering is a dominant source of ions in the groundwater, having an average contribution of 47%-85%, while the contribution of silicate rock weathering is between 6% and 38%. The dissolution of evaporite as a solute source was not important, contributing an average of 3%. Based on these results, it appears that the deep loess provides favorable conditions for the storage of high-quality groundwater, and the existing water quality is dominated by natural factors.