[Effects of copper pollution on Trifolium repens growth and soil enzyme activities]

The study with pot experiment showed that with increasing Cu concentration, soil urease, invertase, catalase and polyphenol oxidase activities decreased gradually. There was a significant correlation between Cu concentration and soil enzyme activities, with the correlated degree followed the order of invertase > polyphenol oxidase > urease > catalase. Under a fixed Cu concentration, soil enzyme activities changed with time, and the changes were different between high and low Cu concentrations, being increased slightly under low Cu concentration (< 500 mg x kg(-1)), but decreased gradually as Cu concentration increased (500-3000 mg x kg(-1)). Statistical analysis indicated that within the range of test Cu concentrations, the activities of test soil enzymes were significantly different among different Cu concentration (P < 0.01), which was accorded with the seedlings growth status. Soil pH was decreased, while electric conductivity was increased with increasing Cu concentration (500-3000 mg x kg(-1)), but they were increased with time under a fixed Cu concentration, with significant difference among different Cu concentration (P < 0.01) . Soil pH and electric conductivity were highly related to soil enzyme activities, with the order of polyphenol oxidase > invertase > catalase > urease. The test soil enzyme activities could be used as the indices of soil environment quality.