other potential hazards of sludge application. S. C. Wilson and colleagues used a pilot-scale column to quantify loss of VOCs (toluene, ethyl benzene, and xylene) from sludgeamended soils. After 150 h, they found that ~ 9% of total VOCs was emitted, almost none was leached, and 23% of total VOCs remained in the soil. They presume that most of the unaccounted-for 68% is the result of biodegradation. The unaccounted amount was compound dependent. The results show that a column experiment C3.il QUcintify VOC losses from sludge-treated soils. {Chemosphere 1996 33 ,261-72)
PAH degradation Sorption of organic compounds in soil can affect the transport of toxic compounds to distant sites and reduce biodegradation by making the compounds unavailable. Polycyclic aromatic hydrocarbons (PAHs) adsorbed to soils can become resistant to desorption with time, potentially inhibiting biodegradation. J. C. White and M. Alexander incubated different soils and aquifer solids with phenanthrene and naphthalene to determine the availability of the desorption-resistant fractions to microorganisms. The rate and extent of degradation were less for the desorption-resistant fraction than for the freshly added fraction of the PAHs Greater mineralization of the desorotion-resistant fraction occurred in soils with lower organic matter content The authors concluded that decreased biodeeradation indicates micropore entraDment of Dartitionine into soil organic matter (Fnviron Toxical Chem 1996 15 1973-781
Mineralization rates Several chemical and physical factors influence the biodegradation of organic compounds in soils. D. B. Knaebel and co-workers studied interactions between organic chemicals and components of the soil matrix and their effects on microbial mineralization kinetics. Five 14 Clabeled compounds were sorbed to six purified soil constituents. They added these chemical-soil constituent materials to agricultural soil and measured microbial mineralization over periods of 60-70 days. Generally, mineralization occurred in the following order: Scind K. kaolinite
