Water-rock interaction simulation of artificial recharge in the groundwater over-exploited area of the Hutuo River Basin
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Abstract:
The water-rock interaction in the recharge water and groundwater mixed zone of aquifer under artificial recharge is the key process that determines the evolution of groundwater quality and leads to the chemical clogging of aquifer. To study the effect of artificial recharge on the groundwater quality evolution in the groundwater over-exploited area of the Hutuo River Basin, taking the groundwater artificia recharge site in Shijiazhuang as an example and using the Shijin irrigation canal water as the recharge water, we revealed the mechanism of water-rock interaction of surface water and groundwater mixed zone in the aquifer by carrying out the laboratory experiments and reverse hydrogeochemical simulation. The results show that the evolution characteristics of total dissolved solids(TDS) in the mixed zone firstly increase and then slowly decrease. The larger the proportion of surface water mixed with water is and the smaller the particle size of medium is, the larger the variation amplitude of TDS is. The change of main ion concentrations is controlled by mixing action, carbonic acid balance, dissolution-precipitation, cation exchange and nitrification. Among them, the concentrations of K+, Ca2+and SO42- are mainly controlled by dissolution-precipitation, the concentrations of Na+, Cl-, HCO3-, NO3- are mainly controlled by mixing action, and the concentration of Mg2+ is mainly controlled by cation exchange. In the water-rock reaction, the dissolved minerals include anhydrite, albite, K-feldspar and halite, whereas the precipitated minerals included calcite, calcium montmorillonite and quartz. Moreover, in the aquifer with larger proportion of surface water and finer particle size of medium, the calcite precipitation is greater, indicating that there is a high risk of carbonate chemical clogging in the recharge aquifer with fine particle size when the surface water is the recharge source.
