Role of organic matter and nanopores in the bioavailability and sequestration of phenanthrene in soil and model solids

Some organic compounds in soil become progressively less bioavailable as they persist in soil. This study was conducted to determine whether the organic matter content and nanopores of soil are related to the sequestration of organic compounds. In addition, the effect of biodegradation rate on sequestration was investigated.; Tests with hydrophilic and hydrophobic beads with or without nanopores showed that only beads having nanopores and hydrophobic surfaces markedly reduced the availability of phenanthrene for biodegradation. Beads with either nanopores or hydrophobic surfaces alone did not reduce bioavailability. The data with model solids suggest that hydrophobic nanopores are a prerequisite for sequestration of phenanthrene.; Experiments with soils varying in organic matter content demonstrated that biological and chemical availability of phenanthrene declined with time of aging. The decrease in availability was more pronounced in soils with higher organic matter content than in soils with lower organic matter content. The data suggest that soil organic matter may be an important determinant of sequestration of phenanthrene. More of the compound remained after biodegradation of the aged than of the unaged hydrocarbon.; Competition between biodegradation and sequestration in soil was studied. More phenanthrene remained in soils with low than with high phenanthrene-degrading activity. The amount of the compound remaining in soil was inversely related to the initial rate of its disappearance. Some of the hydrocarbon remaining in soil was biodegraded by successive inocula of bacteria. However, a significant amount of the compound was still biologically unavailable even after successive inoculations.