The Comparison Study of Water-Rock Interaction Before and During the Artificial Recharge

The water-rock interaction during the artificial recharge is an important influencing factor of groundwater environment quality in the recharged aquifer. The hydrogeochemical simulation and indoor experiment were used to study the mechanism of water- rock interaction in the recharge aquifer before and during the artificial recharge respectively. The results of the research showed that the original water- rock interaction during the groundwater runoff in the recharged aquifer before the artificial recharge were dissolution of dolomite, k- feldspar, anorthite, halite, gypsum and precipitation of calcite and illite and the reaction amounts were 0.1207 similar to 0.2300nmol/ L, 0.1721 similar to 0.5074 nmol/L, 0.0975 similar to 0.1053 nmol/L, 0.3363 similar to 0.3673 nmol/L, 0.0021 similar to 0.0063 nmol/L, 0.1117 similar to 0.3011 nmol/L and 0.2868 similar to 0.8457 nmol/L respectively; During the artificial recharge, the TDS(Total Dissolved Solids) of the mixed water decreased and the water type became Na-Ca-HCO3-Cl from Na-Cl-HCO3 with the increase of proportion of the recharge water affected by the mixing and in the same proportion of the recharge water, the TDS of the mixed water increased and the concentrations of the major ions showed increasing trend affected by the water- rock interaction; during the artificial recharge, Ca2+ and HCO3 originated from the dissolution of calcite and dolomite, but before the the artificial recharge, Ca2+ originated from the dissolution of anorthite, Mg2+ originated from the dissolution of dolomite and Na+ originated from the dissolution of halite both during and before the artificial recharge; with the increase of proportion of the recharge water, pH decreased and pE increased nonlinearly in the mixed water and there was a negative correlation and the correlation coefficient was 0.99 between the pH and pE in the mixed water. This study provides necessary basis for the overall developing of artificial recharge technology and the guarantee of security and stability of the groundwater environment.