Toxicity Of Lambda-cyhalothrin And Cadmium On Earthworms

Lambda-Cyhalothrin(LCT),also known as?-cyhalothrin,is mainly used for contact killing and stomach poisoning injurious insects on cotton,cruciferous vegetables,fruit trees and tea trees.It can prevent insects by inhibiting their nerve conduction.LCT is widely used at home and abroad,but excessive and frequent use of LCT will increase the environmental risk of non-target organisms.Cadmium(Cadmium,Cd)is a heavy metal that is difficult to degrade and extremely toxic.It can accumulate in organisms and cause serious damage to agricultural safety and human health.Previous research has been shown that the effect of LCT on insect behavior such as bees,residue analysis in soil and plants,and acute toxicity to organisms.With the aim of evaluating the ecotoxicological effects of LCT and its combined pollution with Cd,this paper selected Eisenia foetida as biological indicator for 28 days of poisoning,and used artificial soil method to study the exposure concentration design.The concentration series of LCT was set to 0,5,10,20,40 mg·kg^-1 and the concentration of Cd to 5 mg·kg^-1.The indexes of antioxidant enzyme system(the activities of superoxide dismutase SOD,peroxidase POD,catalase CAT),the activity of detoxification enzyme GST,the content of lipid peroxidation product MDA,the content of reactive oxygen species ROS and the degree of DNA damage were measure on day 7,14,21 and 28.And the main results obtained from the experiment are as follows:(1)When LCT exposed to earthworms,the activities of SOD and POD showed a tendency to activate first and then inhibit during the entire experimental cycle.The activity of CAT in earthworms were significantly activated in the early stage of experiment.The activity of CAT in the treatment of high concentration was initially inhibited in late stage of experiment.The activity of GST always showed an activated state.During the entire exposure period,the contents of MDA and ROS in earthworms were higher than the blank groups.The results indicate that LCT induces oxidative stress on earthworms,leading to the antioxidant system activated and produced excessive ROS in the organism.(2)When LCT single exposed,the DNA of treatment groups were damaged to different degrees.There is a dose-effect relationship between LCT concentration and the degree of DNA damage.And the DNA damage degree of earthworm is also related to the exposure time.(3)In the case of LCT-Cd combined pollution,the activity SOD and POD showed a tendency to activate first and then inhibit during the entire exposure cycle.The activity of CAT was always significantly activated.Coexposed to LCT-Cd,the activity of GST was always activated in low concentration treatments.In the stage of late exposure,the activity of GST showed a tendency to inhitir in high concentration treatments.The contents of MDA and ROS both increased significantly.(4)When the LCT-Cd compound exposed,the OTM value of the compound group is always higher than that of the LCT group.There is a dose-effect relationship between the OTM value of earthworm cells and the LCT concentration.There was also a correlation with the exposure time,indicating that the LCT-Cd compound caused damage to the DNA of earthworms,showing a certain synergistic effect.