Sorption of Pesticides and its Dependence on Soil Properties: Chemometrics Approach for Estimating Sorption

Sorption is one of the major processes that determine the fate, effects, efficacy and ecological risks of pesticides in terrestrial and aquatic environments. In this chapter we provide an overview of sorption and its dependence on soil properties. Soil solid phase consists of mineral and organic matter; both in strong association with each other make a contribution towards sorption of pesticides, depending on their relative abundance in soil/sediments, chemistry and the chemical nature of the pesticide molecule. We discuss the roles of organic matter and clay contents as well their chemistries in determining sorption of pesticides, and assess the partition theory in terms of its adequacy in describing the observed sorption behavior of pesticides in soil. The complex interactions and heterogeneities associated with the soil solid phase contribute to the large degree of variation in K-oc., a parameter that is often used to extrapolate the pesticide sorption estimate, among soils. A more comprehensive approach incorporating soil organic matter as well as soil minerals (both contents as well as their chemistries) is therefore desirable to fully incorporate the role of soil surfaces in sorption of organic compounds. Therefore, we introduce some emerging approaches based on chemometrics and infrared spectroscopy that appear promising for comprehensive representations of the combined role of organic matter, mineralogy and other soil properties in estimating pesticide sorption in soil.