Hydrochemical evolution of groundwater and soils in the water-level-fluctuation zone

Groundwater level fluctuations have a significant effect on the hydrogeochemical processes in the aeration zone and aquifers, which is closely related to human daily life. To better determine the details of hydrogeochemical evolution during groundwater level fluctuations, a large column simulation experiment was carried out. Results show that Ca2+, Na+, NO3- and HCO3- are more susceptible to water level fluctuations than Mg2+, K+, Cl- and SO42-. Groundwater level fluctuations have an especially large effect on concentrations of NO3- in both water and soil. As water level rises, NO3- concentration of groundwater increases and NO3- concentration of soil decreases. Concentrations of Ca2+ and Na+ are negatively correlated with water level. Concentrations of soluble salts in soils at different depths additionally vary, and the variation trends for different constituents were different. Hydrogeochemical processes in the groundwater fluctuation zone formed distinctive and complex patterns. Elucidating these patterns and their causes is, therefore, extremely significant for fully evaluating groundwater-affected soils and environments.