[Effects of combined pollution of Cd, Cu and Pb on antioxidant enzyme activities of earthworm in soils].

Recently,soil heavy metal contamination becomes more and more serious in certain areas in China. Adverse effect caused by heavy metals in contaminated soils has been a wide concern for many years. In this study,a bioassay experiment with the earthworm( Eisenia foetida) was conducted to investigate the effects of compound application of Cd,Cu and Pb in soil on surperoxide dismutase( SOD),glutathione S-transferase( GST) and acid phosphatase( AP) activity in earthworms. Through a method of greenhouse soil experiment,this study utilized a uniform design method of three factors and six levels( Cd: 0-15 mg·kg- 1,Cu: 0-175 mg·kg- 1,Pb:0-600 mg·kg- 1) to research the physiological property and enrichment characteristics of earthworm in soils with Cd,Cu and Pb compound pollution. The activity of SOD,GST and AP were inhibited significantly under Cd,Cu and Pb compound pollution. And they were impacted by both time and heavy metal contents in the soil. Compared with the control sample,the activity of SOD increased by 7. 4%-240. 5% in the first eight days under the stress of heavy metals. But owing to the extremely severe stress,it was suppressed and descended by 19. 4%-69. 7%. Compared with the control sample,the activity of GST increased by 104. 3%-217. 3% in the first sixteen days under the stress of heavy metals. But owing to the extremely severe stress,it was suppressed and descended by 1. 2%-40. 3%. The activity of AP changed over time in a trend of "increase,decrease,increase,decrease". Compared with the control sample,the activity of AP decreased by 9. 2%-37. 8% in the first eight days,then increased by 37. 2%-117. 2% in sixteenth days and decreased by 24. 3%-34. 0% to the last day. The analysis demonstrates that Pb and Cd-Cu-Pb is the dominant factor to the activity of SOD,while Cd and Cu were the dominant factors to the activity of GST and AP.