ABSTRACT
Contaminants dissolved in the water film surrounding soil particles in the unsaturated zone. This locus includes only the water that exists as a thin film around, or in narrow pores between, soil particles. As such, it represents the relatively immobile water retained in a well-drained soil. The sorption equilibrium is not easily changed by parameters that can be adjusted during common remediation activities. It is, in fact, easier to enhance the desorption process via addition of water, detergents, solvents or—in some cases—heat. Biodegradation by microbes occurs most readily when microbes, organic contaminants and other nutrient substrates come in close physical contact. Humic substances are brown to black colored organic acids which have high molecular weight and are structurally complex. Humic substances play a significant role in both the biotic and abiotic transformation of introduced hydrocarbons as well as being formed from the degradation of the hydrocarbons.
