[Enzymatic activities of phenanthrene contaminated soil in wheat and clover intercropping system]

The dynamic changes of soil enzymatic activities during remediation of phenanthrene contaminated soil with clover or clover and wheat were investigated with pot experiments. Clover and wheat increased the activities of soil sucrase, polyphenol oxidase, urease and phosphatase with an increase rate in the range of 14.72%-46.52%, but inhibited the catalase activity with an inhibition rate in the range of 36.13%-94.79%. Sucrase and polyphenol oxidase reached the maximum activity values at the 14th day, and urease and phosphatase at the 21th day. Catalase got to the minimum activity value at the 7th day. In the light of these, catalase was relatively more sensitive to phenanthrene than the other enzymes, and could be employed as a key indicator to evaluate the risk of polycyclic aromatic hydrocarbon contaminated soil during remedying. Sucrase and polyphenol oxidase activities in wheat and clover intercropping system were significantly higher than in wheat or clover single-cropping system. Furthermore, there was a good negative correlation between catalase and sucrase (r = - 0.482), and polyphenol oxidase (r = -0.599), and urease (r = -0.329), and phosphatase (r = -0.297). Nonetheless, a good positive correlation existed among sucrase, polyphenol oxidase, urease and phosphatase. It is concluded that in the process of phytoremediation, soil enzymes can be employed as indicators for soil quality, it is not necessary to monitor each enzymatic activity, but to the activity of a key enzyme.