Subsurface Colloidal Fines, Behavior, Characterization, and Their Role in Groundwater Contamination

Abstract

There are several classes of subsurface colloids—abiotic and biotic. The mobilization and migration of these subsurface colloidal particles take place under different physical and geochemical conditions (Massoudieh and Ginn, 2010; Sen, 2011; Sen and Khilar, 2006). Therefore, subsurface colloidal fines can enhance or retard the mobility and dispersion of various contaminants in groundwater flows (Sen and Khilar, 2009). There are two categories of colloid-induced subsurface contaminant transport: (a) colloid-associated contaminant transport and (b) transport of biocolloids. General research on subsurface colloid transport originated in the early 1930s (Kretzschmar and Schafer, 2005). First findings on the partitioning of aqueous solution constituents onto colloids appeared in the late 1970s, as summarized by Gustafasson and Gschwend (1987). Subsequently, reports on the transport facilitation of contaminants via association with subsurface colloidal fines emerged in the 1980s (Enfield and Bengtsson, 1988; McCarthy and Zachara, 1989).Our knowledge and understanding of the colloidal fines–associated contaminant transport in subsurface porous media have increased substantially over the last three decades, which is reviewed by various researchers from time to time such as Kretzschmar et al. (1999), Elimelech and Ryan (2002), Sen and Khilar (2006, 2009), and Bin et al. (2011). The focus of this chapter is to review subsurface colloidal fines, sampling methods and characterization, and their role in groundwater contamination. This has been evidenced by various experimental, modeling, and field studies, which have been briefly compiled here and also partially updated in the author’s earlier book chapter publication (Sen and Khilar, 2009). Finally, authors here briefly discussed subsurface inorganic/organic colloid–associated contaminant transport in groundwater and their associated health effects.