华北平原东部浅层咸水与深层淡水构成“上咸下淡”的区域性水质结构。相关调查研究表明，浅层咸水越流补给深层淡水的过程并未使得深层水矿化度显著提高。为研究黏性土层是否能截留水中盐分，通过渗透试验计算分析了咸水通过黏性土层时的弥散作用。结果表明：（1）黏性土可有效截留咸水中的大部分盐分，证实了前人提出的华北平原东部深层弱透水层滤盐现象的存在；（2）黏性土截留盐分的能力随渗透系数和弥散度的减小而增大。据推测，黏性土滤盐的原因可能是咸水中Na+被土壤胶体颗粒吸附或与土壤胶体吸附的一些组分发生了阳离子交换作用。

Regional water quality structure is constituted by deep freshwater and shallow salt water in the east of North China Plain (NCP). Evidences showed that salinity of deep freshwater did not increase significantly when it was supplied by shallow saline water. To examine whether the clay-bearing soil can intercept the salt from water, this study conducted the permeability tests to analyze the dispersion effects of saline water flowing through the clay-bearing soil. The results showed that (1) clay-bearing soil can intercept most of salt in the saline water, which confirms the existence of salt-filtering phenomenon in the eastern deep aquitard of NCP; (2) the intercept capacity of clay-bearing soil increases with the decreasing of permeability and dispersivity. ; and (3) the possible reason of salt-filtering is that Na+ in saline water is adsorbed by solid colloid particles or has cation exchange interaction with some components absorbed by soil colloids.

国家自然科学基金“华北平原区咸水越流过程中水-岩作用研究”（40772157）；国家重点基础研究发展计划（973）课题2010CB428803