Effect Of La, Cu Single And Combined Pollution On Several Important Enzyme Activities Of Arthworms

Earthworms directly exposed to contaminants in soil, through the digestive system and surface in contact with contaminated materials,and it is more sensitive to pollution, so often used as an important indicator of earthworm biological evaluation of environmental pollution. Natural soil test method was used to study La, Cu Single and Combined Pollution on enzyme activitiy of earthworms, including protein content,superoxide dismutase (SOD),catalase (CAT),peroxidase (POD) and malondialdehyde (MDA). The results were as follows:For lanthanum single stress:the lanthanum stress had a certain impact on several important activity of earthworms. With exposure time increasing, Protein content, SOD and POD activity showed "Hormesis effect", which means promotion at low concentration and suppression at high concentration, CAT activity fluctuated and MDA content increased. Cellulase activity decreased firstly and then increased at low concentration of lanthanum, and it continuous increased at high concentration of lanthanum.For heavy metals copper single stress:the overall protein content showed a slightly increasing trend, with prolonged exposure, earthworm protein content decreased. POD activity showing a trend fluctuations. CAT activity reduced with increasing exposure time. At low concentrations Cu2+ Stress POD activity increased, under high concentration of Cu2+ stress decreased, showing a "low and promote high suppression" phenomenon. Under Cu2+ Stress,the MDA content increased firstly and then declined.For lanthanum-copper composite stress:When La was combined with different concentrations of Cu, there are different joint effects, when different concentrations of La combined with 50 mg·kg-1 Cu, protein content increased, It indicated that La reduced the toxic effect of 50 mg·kg-1 Cu for earthworms. Different concentrations of La combined with 200 mg·kg-1 Cu and 600 mg·kg-1 Cu strengthened the environmental stress of earthworms. The activity of SOD showed the rising trend with low-dose La, while the rising trend firstly and then the declining trend with high-dose La. It indicated that combined stress strengthened the environmental stress of earthworms and combined stress exceeded their tolerance threshold. The activity of POD fluctuated obviously; in general, it showed rising trend, which indicated that combined stress strengthened the environmental stress of earthworms. For CAT, when different concentrations of La combined with 50 mg·kg-1 Cu, the activity of CAT increased firstly and then declined. It indicated that La reduced the toxic effect of 50 mg·kg-1 Cu for earthworms. Different concentrations of La combined with 200 mg·kg-1 Cu and 600 mg·kg-1 Cu strengthened the environmental stress of earthworms. MDA content in the rising trend overall,indicating that combined stress strengthened the environmental stress of earthworms and combined stress exceeded their tolerance threshold.