摘要
滨海含水层中地下水流动、胶体与溶质的协同运移具有复杂性,而含水层孔隙结构中胶体运移所诱发的孔隙尺寸排阻(size exclusion)效应对整体运移过程影响深远.本研究采用长江口砂质含水层,基于土柱渗透试验,分析盐分梯度驱动胶体运移的过程,利用Hydrus-1D和Acualntrusion Transport对溶质运移的穿透过程进行数值模拟并获取溶质运移参数,以探究胶体释放诱发的孔隙尺寸排阻效应与盐分梯度之间的响应关系,揭示孔隙排阻效应与含水层相关水文地质参数的响应机制.结果表明,海水入侵使地下水离子强度增大,同时抑制胶体释放;反之,淡水驱替时则促进胶体的释放.胶体释放峰值及总量与该过程的盐分梯度呈正相关,当0.5%~1.5%的NaCl溶液被淡水洗脱的过程中,胶体浓度穿透曲线的零阶时间矩从77.79 mg增至220.52 mg,释放峰值从209.7μg·mL^(-1)增至688.5μg·mL^(-1),释放量显著增大.数据表明在胶体颗粒释放后,介质孔隙结构改变,所释放的带负电胶体颗粒与固体基质表面的静电斥力诱发了尺寸排阻效应,使胶体颗粒选择性地通过部分孔隙,并在连通孔隙中增加了胶体颗粒的迁移速度.本研究结果对地下水-污染物-胶体在复杂孔隙结构中的多相协同渗流模拟有借鉴意义.
The co-transport of groundwater flow,colloids,and solutes in coastal aquifers represents a highly intricate phenomenon,profoundly influenced by the pore size exclusion effect triggered by colloid transport within the porous structure.The research centered on column experiments utilizing sandy aquifer samples extracted from the Yangtze River estuary.The study analyzed the salt gradient-driven colloid transport process and employed numerical simulations through Hydrus-1D and Acuaintrusion Transport to obtain solute transport parameters.The primary objective was to investigate the relationship between the pore size exclusion effect induced by colloid release and the salt gradient,thereby revealing how this effect responds to hydrogeological parameters relevant to the aquifer.The findings demonstrated that seawater intrusion heightened groundwater ionic strength,concurrently inhibiting colloid release.Conversely,during freshwater displacement,colloid release was enhanced.Notably,both the peak value and total colloid release exhibited a positive correlation with the salt gradient.Specifically,when freshwater displaced 0.5%to 1.5%NaCl solution,the zero-order moment of the colloid concentration breakthrough curve increased significantly from 77.79 mg to 220.52 mg.The release peak value escalated from 209.7μg·mL^(-1) to 688.5μg·mL^(-1),indicating a substantial rise in colloid release.The data suggested that post-colloid particle release,alterations occurred in the pore structure.The electrostatic repulsion between the released negatively charged colloid particles and the solid matrix surface induced the size exclusion effect.Consequently,colloid particles selectively traversed certain pores,thereby augmenting their transport velocity in the interconnected pores.These findings offer valuable insights into the multiphase flow simulation of groundwater-pollutant-colloid systems within intricate porous structures.
作者
阙智林
庄文化
谭博
QUE Zhilin;ZHUANG Wenhua;TAN Bo(State Key Laboratory of Hydraulics and Mountain River Engineering,Chengdu 610065;College of Water Resource and Hydropower,Sichuan University,Chengdu 610065)
出处
《环境科学学报》
CAS
CSCD
北大核心
2024年第2期248-254,共7页
Acta Scientiae Circumstantiae
基金
国家自然科学基金资助项目(No.42102291)。
关键词
多孔介质
土柱试验
胶体释放
尺寸排阻
数值模拟
porous media
soil column test
colloidal release
size exclusion
numerical simulation
