Abstract: This simulation study deals with the biodegradation processes of petroleum hydrocarbons and phenol substances in soil and their relations with soil enzyme activities. Results show that the biodegradation rates of these pollutants are higher when in low concentra tions and under normal soil moisture condition than in high concentrations and under waterlogged. Chemical structures of pollutants also give an influence to the rates:a lower biodegradation rate can be found for the pollutant having a more stable and complex chemical structure. The biodegradation process of hydrocarbons and phenol relates closely with the activities of soil invertase and polyphenoloxidase respectively, and hence, the intensity of these activities could be respectively used as an index indicating the pollu tion degree of soil by petroleum hydrocarbons and phenol substances. To say the least, a certain extent of pollution by these pollutants does not exert an obvious influence un favourable to the biological activities or transformations of C, N, and Pin soil under normal soil moisture condition. Based on these results, suggestions on land treatment of these pollutants are put forward.

Key words: Biodegradation, Petroleum hydrocarbons, Phenolsubstance, Soil enzyme, Land treatment