填海条件下地下水氮素污染的动力学特征

Dynamic characteristics of nitrogen contamination in groundwater under land reclamation

为系统研究滨海地下水环境中氮素污染的动态变化特征,以青岛欢乐滨海城填海区为研究对象,在改进和完善氮素反应动力学方程的基础上,构建了变密度条件下反应性溶质运移模型,定量分析了填海长度和填海区含水层渗透系数对地下水中氮素的迁移转化影响效应。结果表明:填海造陆加剧了地下水中的硝酸盐污染,地下水中NH_(4)^(+)-N质量浓度逐渐升高,NH_(4)^(+)-N在初始含水层底部小范围聚集,其质量浓度可以达到饮用水标准的3倍;随着填海长度的增加,NO_(3)^(-)-N和NH_(4)^(+)-N的分布范围不断扩大,而初始含水层中NO_(3)^(-)-N的平均质量浓度和增加幅度不断升高,NH_(4)^(+)-N的平均质量浓度呈先升高后降低的变化趋势;当填海区含水层渗透系数高于初始含水层时,在稳态条件下填海材料渗透性对初始含水层中NO_(3)^(-)-N和NH_(4)^(+)-N的平均质量浓度影响不大,当填海区含水层渗透系数低于初始含水层时,初始含水层中NO_(3)^(-)-N的平均质量浓度明显升高,而NH_(4)^(+)-N的平均质量浓度显著降低。

This study systematically investigated the dynamic variations of nitrogen contamination in coastal aquifers,focusing on the land reclamation area of Qingdao Happy Sea Town.Based on improved and refined nitrogen reaction kinetic equations,a reactive solute transport model under variable density conditions was developed.The model was used to quantitatively analyze the impacts of reclamation length and permeability of reclamation aquifers on the migration and transformation of nitrogen in groundwater.The results indicated that reclamation intensified nitrate pollution in groundwater.The mass concentration of NH_(4)^(+)-N gradually increased,with NH_(4)^(+)-N accumulating in a small range at the bottom of the initial aquifer,and its mass concentration could reach three times of the drinking water standard.As the reclamation length increased,the distribution range of NO_(3)^(-)-N and NH_(4)^(+)-N expanded.In the initial aquifer,the average mass concentration of NO_(3)^(-)-N and its increase amplitude rose continuously,and the average mass concentration of NH_(4)^(+)-N exhibited a trend of first increasing and then decreasing.When the permeability of reclamation aquifer was higher than that of the initial aquifer,the permeability of reclamation material had little effect on the average mass concentrations of NO_(3)^(-)-N and NH_(4)^(+)-N in the initial aquifer under steady state condition.However,when the permeability of reclamation aquifer was lower than that of the initial aquifer,the average mass concentration of NO_(3)^(-)-N in the initial aquifer increased significantly,while the average mass concentration of NH_(4)^(+)-N decreased significantly.