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 nes can enhance or retard the mobility and dispersion of various contaminants in groundwater ows (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 ndings 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 nes emerged in the 1980s (Eneld and Bengtsson, 1988; McCarthy and Zachara, 1989). Our knowledge and understanding of the colloidal nes-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 nes, sampling methods and characterization, and their role in groundwater contamination. This has been
5.1 Introduction .......................................................................................................................... 413 5.2 Subsurface Colloidal Fines and Their Classication ............................................................ 414 5.3 Classication of Subsurface Environment and Importance on Colloid-Contaminant
Transport ............................................................................................................................... 415 5.4 Sampling and Characterization ............................................................................................ 417
5.4.1 Particle Size .............................................................................................................. 420 5.4.2 Surface Charge and Zeta Potential ........................................................................... 421 5.4.3 Chemical Characterization of Fines ......................................................................... 427
5.5 Brief Description of the Role of Inorganic Colloidal Fines-Associated Contaminant Transport in Groundwater Flows and Associated Health Effect .......................................... 427
5.6 Brief Description of the Role of Biocolloids in Groundwater Contamination and Associated Health Effect ...................................................................................................... 428
5.7 Conclusions ........................................................................................................................... 431 References ...................................................................................................................................... 431
evidenced by various experimental, modeling, and eld studies, which have been briey compiled here and also partially updated in Chapter 4 (Sen and Khilar, 2009). Finally, authors here briey discussed subsurface inorganic/organic colloid-associated contaminant transport in groundwater and their associated health effects.
