Study On Toxic Effects Of Phenanthrene And Pyrene To Eisenia Foetida

In this study, the acute and chronic tests of Phenanthrene (Phe) and Pyrene (Pyr) to earthworms were performed in order to know the toxicity and mechanism of toxicosis of these typical organic pollutants on environmental organisms. Effects of combined pollution between Phe and Pyr were also studied. The results are showed as follow:1.The toxic effects of single and joint stress of Phe and Pyr on earthworms (Eisenia foetida) were investigated by natural soil tests. The results showed that the single toxic sequence of Phe and Pyr was Phe> Pyr. The difference may depend on the biological mechanisms of the earthworm population. The value LC50 of Phe was 45.95 mg/kg. There was a positive correlation between mortality and the concentration of pollutant added to soil. Also, the more exposed to single or joint Phe and Pyr, the more morality. For joint pollution, Phe was the main contributive factor of toxic effects, the different concentration and interaction of Phe and Pyr significantly influenced mortality. Pyr at all concentration, it could increase the toxicity of Phe, and the toxicity of Phe increased with the increase of Pyr concentration. When Phe at low concentration, it could decrease the toxicity of 300 mg·kg-1 Pyr. At medium and high Phe concentration, it could increase the toxicity of Pyr. Therefore, the component and different concentration of combined pollutant are the significant factors to determine the toxicity of combined pollutant.2.The toxic effects of single and joint stress of Phe and Pyr on earthworms weight were studied by natural soil tests. The results showed that there was a positive correlation between weight reduction and the concentration of pollutant added to soil. After a 28d exposure,12 mg·kg-1 Phe group reached the maximum inhibition rate of earthworm weight, indicating that Phe had a accumulated toxic effects on earthworm. Also, Pyr had significant inhibitory effects on the earthworm weight. In the experiments of combined pollution, the inhibition rate of earthworm weight was higher than single experiment of Pyr. The interactive effects between Phe and Pyr were synergistic. It suggested that organic compound contamination enhance the toxic effects of pollutants.3. Enzymatic activities are regarded as fast and prognostic indices of individual reaction to the environmental stress, and should allow prediction of the consequences of pollution at population and ecosystem levels. Our objective was to investigate whether their superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were influenced by Phe and Pyr at different concentrations and exposure times. Three replicates of adult earthworms(Eisenia foetida) were exposed to exposure times ranging from 2d to 28d. Different changes in SOD, CAT activity and MDA content in the tested earthworms were observed for application of Phe or Pyr alone. SOD activity showed a concentration-dependent effect with the PAHs:it increased in the low concentration group, while it decreased in the high concentration group compared to the controls. MDA content in the earthworms varied over the 28 day exposure time. When only Phe was applied to the soil, CAT activity in earthworms varied over the 28 day exposure time. No obvious effects of Pyr on CAT activity were observed in this study. When soil was treated with multiple concentrations of Pyr and a fixed concentration of Phe, SOD activity was restrained significantly. After 28 days of exposure the MDA content of all groups reached their maximum, and the combined stress could promote lipid peroxidation in the earthworms. When the soil was treated with 0.5 mg·kg-1 Phe, lower Pyr additions caused the CAT activity to vary over the 28 day exposure time. The application of 2.5 mg·kg-1 Phe in soil caused an increase of CAT in the presence of Pyr. The effects of combined Phe and Pyr pollution differed among the various treatments and were closely related to the applied PAHs doses. The results of this study indicated that compound treatment of Phe and Pyr caused more serious oxidative threat to the tested earthworms.