Chapter 16 - Soil Organic Matter as a Factor Influencing the Fate of Organic Chemicals in the Soil Environment

Abstract

The behavior of organic chemicals in the soil environment is complicated due to interactions with the solid, aqueous, and gaseous phases, and with the living part of soils. Sorption to soil and soil constituents plays an important role in retention, degradation, and mobility of organic chemicals in soils. This chapter describes the distribution of organic chemicals between solid and liquid phases either in terms of the solute partitioning in soil organic matter like the nonionic compounds or by the adsorption isotherms. The correlation between adsorption and physicochemical characteristics of the sorbent (soil or its constituents) is also discussed in the chapter. It leads to the proliferation of prediction models for estimating the extent of adsorption of organic chemicals in soils. Among the factors influencing the rate of degradation of organic chemicals, one must include soil temperature, moisture content, and organic matter content. An increase in organic matter enhances the rates of degradation in mineral soils up to a limiting value, above which the rate of decomposition can be retarded.