Measuring release and biodegradation kinetics of aged hydrocarbons from soils

A laboratory protocol was used to estimate the Rate of Release (ROR) of hydrocarbons from aged soils over extended periods of time (months). The data collected were analyzed with an empirical two-site model consisting of two first order rate constants (k(1) and k(2)), describing fast and slow releases, respectively, and F, the fraction that is rapidly released. This protocol was applied to six manufactured gas plant (MGP) soils. A large fraction of the hydrocarbons was only released slowly (k(2) on the order of 0.0001hr(-1)). Biodegradation studies using some of the same soils were conducted over extended periods (months) and the loss curves displayed a pattern similar to those observed in the ROR experiments. A coupled process model was applied to the ROR and biodegradation data to estimate a first order aqueous phase biodegradation coefficient (k(bio)).