人工回灌过程中的水-岩相互作用模拟

Modeling of Water-Rock Interaction During the Artificial Recharge

人工回灌过程中所发生的水-岩相互作用是影响回灌层位地下水环境质量的重要因素。采用室内实验和水文地球化学模拟等技术对人工回灌过程中的水-岩相互作用机理进行了分析。研究结果表明:受混合作用影响,随着回灌水比例的增加,混合水中TDS质量浓度降低,水化学类型由Cl·HCO3-Na型水逐渐转变为HCO3·Cl-Na·Ca型水;受水-岩作用影响,在同一混合比例条件下,随着水-岩作用的进行,混合水中TDS质量浓度升高,各主要离子质量浓度呈现升高的趋势,但只有回灌水比例占10%时,混合水TDS质量浓度才大于原始地下水(涨幅约5%)。实验介质溶解于水的离子中,Ca2+、Mg2+和HCO3-主要来源于碳酸盐矿物的溶解,Na+主要来自岩盐的溶解。在人工回灌过程中,发生的水-岩相互作用主要包括方解石、白云石、钾长石、岩盐、CO2的溶解和伊利石的沉淀。其中:钾长石溶解量与伊利石沉淀量、碳酸盐矿物溶解量与CO2溶解量的相关性较强,其相关系数分别为1.00和0.78(显著性水平为0.05);硅酸盐矿物反应量和回灌水比例之间的相关系数为0.97(显著性水平为0.01),相关性极强;而碳酸盐矿物反应量和回灌水比例之间的相关系数为0.52(显著性水平为0.01),相关性较弱。上述相关性分析为确定人工回灌过程中的水-岩相互作用机理、地下水中主要离子组分的来源途径以及定量分析人工回灌对含水层介质的影响提供了依据。

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 C1- Na Ca from C1 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 HCO3 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.