Role of Clay and Organic Matter in the Biodegradation of Organics in Soil

Abstract

The fate of organic contaminants such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, nitroaromatic compounds, chlorinated aliphatics, and other xenobiotics in soils is an issue of significant environmental and ­regulatory interest. Such chemicals are known to possess a variety of carcinogenic, mutagenic and toxic properties, making their destruction and/or removal from all environmental domains a highly desired end-point. In soil, the decomposition of organic contaminants occurs primarily through attack by the vast populations of microorganisms (Cerniglia 1992), an occurrence that is exploited for the purposes of land remediation. However, the biodegradation of organic compounds is a dynamic and complicated process. The viability and capability of a soil microbial population to degrade the target contaminant is essential. The physicochemical properties of the contaminant and their interaction with various soil components both influence a given contaminant’s potential to be biodegraded, as well as the length of contaminant residence time (Semple et al. 2003). Soils are a heterogeneous assemblage of organic/inorganic constituents, organo-mineral complexes, ions, biota and other compounds (Fig. 17.1) which result in an array of mechanisms and reactions that all contribute to the fate and behaviour of organic contaminants (Reid et al. 2000, Stokes et al. 2005). Predicting the biodegradation end points in a given soil is therefore inherently difficult (Semple et al. 2007).