中国地质科学院水文地质环境地质研究所
中央级公益性科研院所基本科研项目（SK202003；YYWF201728），国家十三五重点研发计划课题（2016YFC0502601）。
1.The Institute of Hydrogeology and Environmental Geology, CAGS,;2.The Institute of Hydrogeology and Environmental Geology, CAGS
人工回灌条件下回灌水与地下水混合带的水-岩相互作用，是决定地下水水质演化和含水层发生化学堵塞的关键过程。为研究人工回灌对滹沱河地下水超采区水质演化的影响，以石家庄市人工回灌场地为例，利用石津灌渠水作为回灌水源，通过室内实验结合反向水文地球化学模拟揭示回灌层位地表水与地下水混合带的水-岩相互作用机理。结果显示：混合带水的TDS变化特征表现为先增大后缓慢降低，且地表水占比越大、含水介质粒径越细，则其变幅越大；混合带水中主要离子浓度变化特征受混合、碳酸平衡、溶解-沉淀、阳离子交换及硝化作用控制，其中K+、Ca2+、SO42-浓度主要受溶解-沉淀作用控制，Na+、Cl-、HCO3-、NO3-浓度主要受混合作用控制，Mg2+浓度主要受阳离子交换作用控制；水-岩相互作用过程中溶解的矿物有石膏、钠长石、钾长石及盐岩，析出的矿物有方解石、钙蒙脱石及石英，且在地表水占比越大、含水介质粒径越细的层位，方解石的沉淀量越大，表明在粒径较细的回灌层位存在碳酸岩盐的化学堵塞风险。研究结果可为安全高效地开展地下水人工回灌工程提供科学依据。
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, took the groundwater artificial recharge site in Shijiazhuang as an example , the Shijin irrigation canal water were used as the recharge water ， the laboratory experiments and reverse hydrogeochemical simulation were used to reveal the mechanism of water-rock interaction of surface water and groundwater mixed zone in the aquifer. The results showed that the evolution characteristics of TDS in the mixed zone was firstly increasing and then slowly decreasing, if the proportion of surface water mixed with water was larger and the particle size of medium was smaller, the variation amplitude of TDS is larger. Mixing action, carbonic acid balance, dissolution-precipitation and nitrification controlled the change of main ion concentration, whereas the concentration of K+, Ca2+and SO42- were mainly controlled by solution-precipitation, the concentration of Na+, Cl-, HCO3-, NO3- is mainly controlled by mixing, 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 include calcite, calcium montmorillonite and quartz. Moreover, in the larger the proportion of surface water, the finer the particle size of medium, and the more the calcite precipitation, indicated that the risk of carbonate chemical clogging is high in the aquifer with fine particle size, as the surface water was the recharge source. The results can provide scientific basis for the safe and efficient artificial recharge engineering.
