Submitted to: Handbook of Soil Science
Publication Type: Book / Chapter
Publication Acceptance Date: February 11, 2010
Publication Date: January 1, 2012
Repository URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2292.pdf
Citation: Goldberg, S.R., Lebron, I., Seaman, J.C., Suarez, D.L. 2012. Soil colloidal behavior. In: P.M. Huang, Y. Li and M.E. Sumner (eds.) Handbook of Soil Sciences Properties and Processes (2nd Edition). CRC Press, Taylor and Francis Group. Boca Raton, FL. Chapter 15. pp: 15-1 - 15-39. Technical Abstract: Recent understanding that organic and inorganic contaminants are often transported via colloidal particles has increased interest in colloid science. The primary importance of colloids in soil science stems from their surface reactivity and charge characteristics. Characterizations of size, shape, surface area, and surface charge density are required for understanding the processes of adsorption, flocculation, dispersion, and transport in soils and the resultant changes in soil hydraulic properties, as well as chemical migration. Colloids are reactive not only because of their total surface area but because of enhanced reactivity related to rough surfaces and highly energetic sites, as well as the effects of electrostatic charge. Colloid charge is associated with substitution of lower charge cations for those of higher charge in the mineral lattice, as well as surface charge associated with broken bonds. The charge associated with broken bonds is characterized as variable charge, in as much as the solution influences the surface speciation. In addition to these chemical processes, colloids are mobile in soils and thus affect not only the transport of otherwise immobile chemicals but also exert a strong influence on soil hydraulic properties. Predictions of transport of pathogens (viruses and bacteria), radionuclides, heavy metals, and organic contaminants require consideration of colloid mobility and thus understanding of both physical processes, as well as surface chemistry. We will review the general principles pertaining to these processes.