Relationship between organic matter content of soil and the sequestration of phenanthrene

A study was conducted to determine the relationship between organic matter content of soil and the availability of aged phenanthrene. Phenanthrene was aged for 200 days in sterile samples of dissimilar soils, soils treated with H2O2 to reduce the content of organic matter, and sand. Sequestration as measured by the extent of mineralization of phenanthrene by an added bacterium was appreciable in samples with >2.0% organic C, and the bioavailability of the hydrocarbon declined with time of aging. Sequestration was not evident in soils or sand with <2.0% organic C. Phenanthrene aged for 200 days was more slowly degraded than the freshly added compound in soils with >2.0% organic C, but a small effect on rate was evident in soil and sand with <2.0% organic C. More of the compound remained after biodegradation of the hydrocarbon aged for 200 days than if it was not aged, with the largest amount remaining in soils with >2.0% organic C and the least in sand. Aging as measured by a decline in extractability of l-butanol was evident in all soils, although the rate was fastest in soil with >2.0% organic C. The volume occupied by pores of <10-mu m diameter was higher in soils containing more organic matter and was negligible in sand. We suggest that the organic matter content of soil is a major determinant of sequestration.