Abstract
Abstract The riverbed sedimentation zone is an important zone of hydrochemistry, and the biogeochemical action in this zone has a significant impact on groundwater quality. As the main area where hydrochemistry occurs, studying the law of hydrochemical evolution within 1 m below the riverbed is of great significance for understanding the migration and removal of river pollutants. In this study, a combination of onsite monitoring and indoor experiments was used to analyze the variation characteristics of the hydrochemical composition of pore water during riverbank infiltration, as well as the main hydrochemical effects and influencing factors. The results show that in the process of river water infiltration, a series of redox reactions occur in the riverbed sedimentation zone, and there are differences in different infiltration depths. From 0 to 20 cm below the riverbed, strong respiration and denitrification mainly occurred. Reductive dissolution of manganese minerals mainly occurred from 20 to 60 cm, and reductive dissolution of iron minerals mainly occurred from 60 to 90 cm. River water level, dissolved organic carbon content and microbial activity had varying degrees of influence on these redox effects. The recharge of river water infiltration ensures the exploitation amount of the pumping wells, but it also leads to the increase of some components in groundwater, and the extracted water cannot be directly drunk.
Highlights
As an important source of water supply, groundwater plays an important role in ensuring residents’ lives, industrial and agricultural production, and ecological environment construction (Sophocleous ; Bekkoussa et al ; Tsanov et al )
The reductive dissolution of iron–manganese minerals will cause the release of toxic substances adsorbed on the surface and lattice of the iron–manganese minerals, and the redox effect in the riverbed sedimentation zone has a great impact on the groundwater quality (Lu et al )
Affected by oxygen-enriched river water and redox in the riverbed sedimentation zone, strong respiration and denitrification occurred from 0 to 20 cm below the riverbed, which consumed a large amount of O2 and NO3À in the river
Summary
As an important source of water supply, groundwater plays an important role in ensuring residents’ lives, industrial and agricultural production, and ecological environment construction (Sophocleous ; Bekkoussa et al ; Tsanov et al ). The reductive dissolution of iron–manganese minerals will cause the release of toxic substances adsorbed on the surface and lattice of the iron–manganese minerals, and the redox effect in the riverbed sedimentation zone has a great impact on the groundwater quality (Lu et al ). On the basis of onsite monitoring and indoor column simulation experiments, study on hydrochemical evolution of pore water in the riverbed sedimentation zone had been carried out, and the characteristics of the redox process during riverbank infiltration were analyzed, which will help to reveal the mechanism of biogeochemical evolution in the process of river water infiltration and provide a scientific basis for ensuring the safety of the groundwater source area
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