The degradation rates of a mixture of volatile and semi-volatile organic compounds (N = 16) were determined by monitoring the removal of parent chemicals from two different soil types, a Captina silt loam (Typic Fragiudult) and a McLaurin sandy loam (Typic Paleudults), over a 7-day period. The compounds were applied to the soil in a mixture such that the concentration of each individual chemical was 100 ..mu..g/g soil (dry weight). Soil samples, along with sterile (autoclaved) controls, were incubated in the dark at 20/degree/C in 8 /times/ 5-cm glass jars equipped with teflon-lined stoppers and charcoal traps. Samples were disassembled, extracted with methanol, and analyzed on days 0, 2, 3, 6, and 7 of the experiment. Linear regression analysis was used to model the disappearance of the compounds from the soils. First-order degradation rate constants and half-lives were calculated. half-lives for the 16 organic compounds were relatively short (<23 days). Correlations between physicochemical parameters and half-lives were poor (r less than or equal to 0.63) for the entire data set (N = 16), however, a group of structurally related benzene derivatives (N = 7) gave good correlations in both soil types with log/sub 10/ octanol-water partition coefficient (r greater thanmore » or equal to 0.89), log/sub 10/ molecular weight (r greater than or equal to 0.84), log/sub 10/ water solubility (r greater than or equal to 0.77), and molecular connectivity (r greater than or equal to 0.83). 81 refs., 3 figs., 13 tabs.« less