Colloid Deposition and Release in Soils and Their Association With Heavy Metals

Abstract

Colloid transport in subsurface has received considerable atten-tion recently because mobile colloids can facilitate the transport of heavy metals in soils to contaminate groundwater. Many studies on colloid mobility in the subsurface consider soils as well-defined porous media. Though similar in many aspects, soils are differ-ent from well-defined porous media. The authors emphasize the impacts of soil properties on soil-colloid deposition, release, and as-sociation with heavy metals to provide an overview of colloidal dynamics in natural soils. The electrical double layer and Derjaguin-Landau-Verwey-Overbeek (DVLO) theories are summa-rized in Section II as theoretical bases for further discussions of colloid dynamics in soils, and their interactions with heavy metals. After discussions of theory developments and experimental results on the characteristics of soil colloids in Section III and soil porous media in Section IV, the authors compares the deposition of col-loidal particles in well-defined porous media with that in natural soils in Section V. In Section VI, processes that affect colloid release in soils are summarized and theories of ion transfer processes in soils during colloid release are reviewed and discussed. Finally, the authors give a brief overview of the adsorption and precipita-tion of heavy metals to soil colloidal particles and their influences on colloid surface charge development in Section VII. The authors conclude with remarks on the importance of colloid deposition and release in soils and their association with heavy metals.