Abstract:

The water-rock interaction during the artificial recharge is an important influencing factor of groundwater environment quality in the recharge aquifer. The laboratory experiment and hydrogeochemical modeling were used to study the mechanism of water-rock interaction during the artificial recharge. The results of the research showed that the TDS of the mixed water decreased and the water type became HCO₃·Cl-Na·Ca from Cl·HCO₃-Na with the increase in the proportion of the recharge water affected by the mixing; the TDS of the mixed water increased and the concentrations of the major ions showed increasing trend as the water-rock interaction proceeded in the same proportion of the recharge water affected by the water-rock interaction, but the TDS of the mixed water was more than original groundwater when the proportion of recharge water was 10% only(up 5%). The sources of major ions dissolved from the experimental medium: Ca²⁺, Mg²⁺ and HCO^-₃ originated from the dissolution of carbonate minerals and Na⁺ originated from the dissolution of halite. The water-rock interaction included the dissolution of calcite, dolomite, potash feldspar, halite, CO₂ and the precipitation of illite during the artificial recharge. The correlation between the dissolved quantity of potash feldspar and the precipitated quantity of illite and the correlation between the dissolved quantity of carbonate minerals and the dissolved quantity of CO₂ were strong with the correlation coefficient 1.00 and 0.78 respectively with a significance level of 0.05. The correlation coefficient was 0.97 between the reacted quantity of silicate minerals and the proportion of the recharge water that showed extremely strong correlation, but the correlation coefficient was 0.52 with a significance level of 0.01 between the reacted quantity of carbonate minerals and the proportion of the recharge water that showed weak correlation. This correlation study above provided basis for determining the mechanism of waterrock interaction， the original way of major ions in the groundwater and the quantitative analysis of the impact on the aquifer medium during the artificial recharge.

Key words: artificial recharge, water-rock interaction, hydrogeochemical modeling, groundwater