Impact of chemical and biochemical reactions on transport of environmental pollutants in porous media

The transport and fate of contaminants or pollutants in subsurface systems has become one of the major research areas in the environmental-hydrological-earth sciences. An understanding of how contaminants move in the subsurface is required to address environmental pollution problems. This chapter reviews how chemical and biochemical reactions influence transport. Four processes that control the movement of contaminants in porous media are advection, dispersion, interphase mass transfer, and transformation reactions. Transformation reactions cause a loss of contaminant mass from the soil system by transforming the contaminant. Numerous experimental and theoretical studies have shown that rate-limited sorption-desorption can cause nonideal transport. This nonideality can take the form of asymmetrical breakthrough curves exhibiting early breakthrough and tailing, as well as decelerating contaminant plumes. Knowledge of how contaminants move through porous media also is critical to successful development and evaluation of plans for cleaning up contaminated sites.