土壤孔径分布对污染物迁移过程中弥散系数的影响

弥散作用主要受土体孔隙结构影响,基于孔隙结构特征对弥散作用的影响这一问题,通过压汞实验确定土样孔径分布,以水动力弥散理论为基础,以3种不同粒径组分砂土作土样,以氯化钠作为示踪剂,进行一维土柱水动力弥散和扩散实验。并由实验结果计算出各土样的机械弥散和扩散系数,得出以下结论:随着特征孔径d60或者不均匀系数Pu增大,分子扩散系数只有很小程度的增加,但机械弥散系数却有大幅度的增大,而且扩散作用在整个水动力弥散作用中所占的比例也越来越小,机械弥散受孔隙结构特征影响程度较分子扩散而言要大的多。

Effect of distribution of soil pore size on dispersion coefficient in migration process of pollutant

The role of dispersion is mainly affected by soil pore structure. Based on the problem, the paper determined the pore size distribution of sandy soil samples by mercury intrusion porosimetry (MIP).Based on the hydrodynamic dispersion theory, one dimensional sand column diffusion experiments were carried out in laboratory. Three sandy soils with different particle size distribution were used as the samples and NaCl solution was used as tracer material in the experiments. The mechanical dispersion coefficient and diffusion coefficient of each soil sample were calculated according to the experiment. The results show that with the increase of d₆₀ or P_u coefficient, the coefficient of molecule diffusion increases little, but the coefficient of machinery dispersion has obvious increase, and the proportion of diffusion role in the whole role of hydrodynamic dispersion become smaller and smaller.The influence of pore structure characteristics on mechanical dispersion is greater than on molecule diffusion.