| Abstract
| - This study was carried out to assess the influence ofphysicochemical properties on PAH sequestration in sterilesewage sludge-amended arable soil. Radiolabeledphenanthrene (14C-9-Phe), pyrene (14C-4,5,9,10-Pyr), and benzo[a]pyrene (14C-7-B[a]P) were spiked and aged for up to525 days in sterile soil microcosms. The degree of compoundsequestration at various sampling times was determinedby their extractability with organic solvents and release fromsoil residues by base saponification extraction. Theamount of PAH extractable by butanol and dichloromethanedecreased with compound aging in the soil. The decreasein PAH extractability with aging, and the formation ofnonextractable bound residues, increased with compoundmolecular weight, Kow and Koc. The amount of totalextractable PAH determined by sequential dichloromethanesoxtec and methanolic saponification extraction decreasedfrom 98%, 97%, and 94% at day 10 to 95%, 91%, and77%, respectively for 14C-9-Phe, 14C-4,5,9,10-Pyr, and 14C-7-B[a]P after 525 days aging. During the same agingperiod there was an increase in the amount of PAHreleased from the soil by base saponification extraction,suggesting a progressive diffusion of PAHs into hydrolyzableand recalcitrant organic matter and mineral phases ofsoil. Calculated half-lives for the apparent loss of PAHsby sequestration in this experiment were dependent on themethod used to extract them from soil. These half-livesranged from 96 to 1789 days depending on the compound,and are in agreement with values obtained from previousspiking experiments using nonsterile soils. These resultssuggest that a considerable fraction of PAHs assumeddegraded in previous studies may have been sequesteredwithin the organic carbon and, to a lesser extent, mineralphases of soil.
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