Effects of aging on the bioavailability and sorption/desorption behavior of biphenyl in soils

The effects of aging (soil-chemical contact time) on bioavailability, one of the main variables for determining the persistence of organic chemicals in the environment, is poorly understood. There are few studies that have tested the effects of long-term aging on chemical dynamics in soils and have related these effects to bioavailability tests of these aged compounds. In this study, sorption/desorption behavior of biphenyl (BP) on two soil types (Capac A and Capac B) was evaluated for aging times of 24 hours and 8 months. Then bioavailability experiments of BP on the same soils were performed after aging times of 24 hours to 6 months. Sorption isotherms and desorption kinetic profiles were prepared to analyze changes in uptake and release, respectively, due to aging of BP. Mineralization kinetics of BP to ¹⁴CO₂ by a strain of Pseudomonas putida was used to assess changes in bioavailability due to aging. Data indicates that there was an increase in sorption with aging time for BP on both soil types. The rate of BP desorption did not much change with increased aging time. The extent of BP mineralization was found to decrease with aging time.