Cheng Tao, Saiers James E
Department of Earth Sciences, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador A1B 3X5, Canada.
School of Forestry & Environmental Studies, Yale University, New Haven, CT 06511, USA.
J Contam Hydrol. 2015 Jun-Jul;177-178:148-57. doi: 10.1016/j.jconhyd.2015.04.005. Epub 2015 Apr 20.
Colloid-facilitated transport of contaminants in the vadose zone has important implications to groundwater quality, and has received considerable attention. Natural organic matter (NOM) is ubiquitous in subsurface environments, and its influence on mineral colloids and solute transport has been well documented. However, research on the influence of NOM on colloid-facilitated transport is limited. The objective of this paper is to elucidate the effects of NOM on colloid-facilitated transport of a radioactive contaminant (Cs-137) within partially-saturated sediments. Measurements made with re-packed columns reveal that Cs-137 mobility was low when mineral colloids were absent and was unaffected by the presence of NOM. The addition of mineral colloids to influent increased Cs-137 mobility, and effluent Cs-137 was dominated by the colloid-associated form. When NOM was added to systems that contained mineral colloids and Cs-137, the mobility of Cs-137 further increased. A mathematical model simulating colloid-facilitated transport showed that NOM increases Cs-137 transport by increasing colloid mobility and reducing the rate of Cs-137 adsorption to the porous medium.
胶体促进的污染物在非饱和带中的运移对地下水质量具有重要影响，并已受到广泛关注。天然有机物（NOM）在地下环境中普遍存在，其对矿物胶体和溶质运移的影响已有充分记录。然而，关于NOM对胶体促进运移影响的研究却很有限。本文的目的是阐明NOM对放射性污染物（Cs-137）在部分饱和沉积物中胶体促进运移的影响。用重新装填的柱体进行的测量表明，当不存在矿物胶体时，Cs-137的迁移率较低，且不受NOM存在的影响。向进水添加矿物胶体增加了Cs-137的迁移率，流出液中的Cs-137以胶体结合形式为主。当向含有矿物胶体和Cs-137的体系中添加NOM时，Cs-137的迁移率进一步增加。一个模拟胶体促进运移的数学模型表明，NOM通过增加胶体迁移率和降低Cs-137在多孔介质上的吸附速率来增加Cs-137的运移。
