Abstract: An experiment was conducted on the effect of surfactant TW 80 on biodegradation of polycyclic aromatic hydrocarbons (PAHs) in soil for 150 days. Samples were collected in the intermittence of 30, 60 and 150 days to monitor the degradation rate of PAHs. The results indicate that after 30 days, the degradation rate reached 90%, approximately 30% higher than that of control. After 60 days, the degradation rate with a concentration of TW 80 at 1000mg·kg^-1 and the control reached from 65.1% and 60.0% to 93.8% and 79.2%, respectively; but the average degradation of PAHs in other treatements increased only by 4%, compared with results of 30 days. One hundred and fifty days later, the degradation rate in all treatments was over 90%. It is suggested that surfactant can improve the bioavailability of PAHs and speed up the degradation rate, therefore, reduce the exposure time of pollutants. But, surfactant at high concentration can inhibit the activity of microbes. It was also found that the soil with surfactant TW-80 contained dominant fungi which were identified as Penicillium freguentant, P.vermiculatum, P.lilacinum and Cephalosporium acremonium, indicating that these fungi were the driving force for rapid degradation of PAHs in soil.

Key words: Contaminated soil, Polycyclic aromatic hydrocarbons(PAHs), Surfactant TW-80, Degradation rate, Dominant fungi