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南水北调中线工程通水后,将有部分结余水量用于补给潮白河地下水调蓄区。由于南方地表水(以下简称南水)与北京当地地下水的水质存在一定差异,回灌过程中很有可能发生水岩相互作用。研究以潮白河地下水回灌区为例,通过静态摇瓶实验和水文地球化学模拟等研究方法,对南水补给北京深层地下水过程中产生的水岩作用过程和水质影响程度进行分析评价。研究结果表明:南水回灌过程中,地下水的主要离子成分会受到硝化作用、阳离子交换作用及包气带矿物质溶解等作用的综合影响。两种水混合过程中,土壤矿物相中的方解石和白云石不断溶解,Ca2+、Mg2+浓度逐渐升高,反应过程中还伴随强烈的阳离子交换作用,主要为Na+与Ca2+、Mg2+的交换。南水比例越大,溶解氧促进硝化作用越明显;在硝化作用和碳酸平衡的共同影响下,地下水的pH值呈现先降低后升高的趋势。
After passing through the mid-route of the South-to-North Water Diversion Project, part of the remaining water will be used to recharge the Chaobai River groundwater storage area. Due to the difference in water quality between the South China Surface Water (hereinafter referred to as “South Water”) and the local groundwater in Beijing, water-rock interaction is likely to occur during recharge. Taking the recharge area of Chaobaihe groundwater as an example, this paper analyzes and evaluates the process of water-rock interaction and the influence of water quality during deep groundwater recharge from Beijing to Beijing through static shake flask experiment and hydrogeochemical simulation. The results show that the main ionic components of groundwater will be affected by the combination of nitrification, cation exchange and dissolution of mineral in aeration zone. During the mixing process of two kinds of water, the calcite and dolomite in the soil mineral phase continuously dissolved, and the concentrations of Ca2 + and Mg2 + increased gradually. During the reaction, intense cation exchange was also observed, mainly the exchange of Na + with Ca2 + and Mg2 +. The higher the proportion of South Water, the more obvious the role of dissolved oxygen in nitrification. Under the common influence of nitrification and carbonation, the pH value of groundwater firstly decreased and then increased.