Kinetics and mechanisms of soil biogeochemical processes

The application of kinetic studies to soil chemistry is useful to determine reaction mechanisms and fate of nutrients and environmental contaminants. This chapter develops the principles of kinetics into a framework to solve problems related to soil chemistry. It is important to first distinguish between overall and elementary reactions. An elementary reaction occurs in a single molecular process with no intermediate species appearing before product formation and describes an exact reaction mechanism or pathway. The kinetics of sorption and desorption are extremely important in regulating the solubility and fate of many plant nutrients, trace metals, and organic compounds in soil environments. Ion exchange reactions are crucial in nutrient dynamics in soils and involve mixtures of inorganic and organic components. Linkage of mechanistic data obtained viakinetic and spectroscopic studies to field-scale transport processes will provide abetter prediction of contaminant and nutrient fate in natural soil environments.