为研究硝酸盐在不同pH值条件下通过弱透水层的越流迁移机理及转化形式设计了室内试验,用天然黏土模拟弱透水层渗透介质,配制硝酸盐溶液作为渗透液,在高渗透压条件下,观察NO-3通过弱透水层的迁移转化过程.结果表明:不同pH值条件下硝酸盐通过弱透水层向下迁移的能力很弱;由于黏土的pH值为5.8,土壤中分布的正电荷多于负电荷,所以硝酸盐大量减少是因为结合水强化的电性吸附造成的.硝酸盐在弱透水层中的迁移过程表现为大部分被弱透水层吸附,在试验后期发生了异化还原作用.硝酸盐浓度随时间的增加呈指数下降.同时发现硫酸盐对硝酸盐的异化还原反应具有较弱的阻滞作用,氯离子与硝酸盐之间显示微弱竞争吸附关系.%In order to study the cross-flow migration mechanism and the transformation form of the nitrate through the aquitard under different pH conditions, laboratory test was designed using natural clay as a permeating medium and using nitrate solution as the liquid of infiltration, and the process of migration and transformation of the NO3- in groundwater through the aquitard under the high osmotic pressure conditions was observed. The results showed that the capacity of nitrates migrating downward through the aquitard was weak under different pH conditions. As the clay' s pH was 5.8, the positive charge was more than negative charge, so great decrease of nitrate was due to bound water enhancing electric adsorption. Most of the nitrate was adsorped by aquitard, and in the latter part of the test, the dissimilation-deoxidization was taken place. The nitrate concentrations index decreased exponentially with time. It was found simultaneously that blocking effect of sulfate on nitrate' s dissimilation-deoxidization was weak, and a weak competitive adsorption was showed between chloride and nitrate.
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