Enhancing the bioavailability of organic compounds sequestered in soil andaquifer solids

A study was conducted to find ways to increase the biodegradability of comp ounds that have aged in soil or aquifer material and become less bioavailab le. Slurrying enhanced the rate and extent of biodegradation by individual bacterial strains of aged and unaged phenanthrene and di(2-ethylhexyl) phth alate in soils and aquifer solids. After bacterial degradation of aged phen anthrene in unslurried soil had largely ceased, the residual compound was m etabolized if the soil was slurried and reinoculated with a phenanthrene-de grading bacterium. The rate and extent of biodegradation of aged phenanthre ne by Pseudomonas sp. were enhanced when anthracene or pyrene was added to the soil at the same rime as the bacterium, although the organism could not metabolize anthracene or pyrene. Moreover, anthracene or pyrene increased the amount of aged phenanthrene removed from soil by a mild extractant. The data show that the bioavailability of organic compounds that become seques tered by aging can be altered by appropriate soil treatments.