Effect of additives on biodegradation of PAH in soils

In a series of experiments with soil samples of contaminated sites we investigated the effect of special surfactant combinations and other additives on the kinetics and extent of solubilization and degradation of PAH. Biodegradation tests showed a positive effect of adding surfactant combinations T10 and T15. The effect was more pronounced when samples exhibited low degradation effectivity without surfactants. Addition of surfactants counterbalanced the dependence of bioavailability of the individual PAH compounds on their solubility in pure water. Changing the composition of surfactant combinations different tendencies were observed for the extent of solubilization and degradation, i.e. very high concentrations of PAH in the liquid phase may have toxic effects on the soil microflora. However, addition of a sorbent had the most remarkable effect on residual pyrene concentration in a sandy soil, whereby the contamination was transferred to the sorbent phase. Sorption to the sorptive phase and solubilization are substantially faster processes than degradation.