Effects Of Combined Pollution Of Heavy Metals In Soil On Biomarkers Of Earthworms

In recent years,with the improvement of China's industrialization level,a large number of toxic and harmful metals have been discharged into the environment,making the situation of heavy metal soil pollution in China grim.Since metal lead(Pb)and metal cadmium(Cd)are one of eight common inorganic heavy metal pollutants in China,their combined pollution has gradually become the focus of risk assessment and remediation of contaminated soil.Earthworm,as one of the most widely distributed invertebrates in the soil environment,is often used as an indicator for the ecotoxicity experiment of soil Pb and Cd combined pollution.In this study,the effects of combined pollution of Pb and Cd on biomarkers in earthworms under low-concentration conditions were analyzed,and the dose-response relationship between heavy metals and biomarkers was established by analyzing the environmental sensitivity of each biomarker.The main research results are as follows:1.At low concentration level,when Pb and CD compound pollution occurs in soil,the weight,mortality and avoidance behavior of earthworm will not be significantly affected.However,the physical and chemical properties of the soil in which earthworms are cultivated can largely affect the macroscopical life performance of earthworms.According to the suitability of the soil,the results are moisture soil>red soil>saline soil.2.For earthworms cultivated in moisture soil,when the soil is contaminated with low concentrations of lead(Pb)and cadmium(Cd),SOD activity,POD activity,CAT activity,AchE activity,GSH-Px activity will influences.With the increase of the content of Cd and Pb in the moisture soil in each experimental group,the activities of SOD,CAT,and AchE in earthworms first increased and then decreased,and the activities of POD and GSH-Px showed a trend of first decrease and then increased.In the course of exposure time in moisture soil,the activities of SOD,CAT,POD,and AchE in earthworms generally showed a gradual decline trend,and the activity of GSH-Px changed little.3.For earthworms cultivated in red soil,when the soil is contaminated with low concentrations of lead(Pb)and cadmium(Cd),SOD activity,POD activity,CAT activity,AchE activity,GSH-Px activity will be affected.With the increase of the content of Cd and Pb in the red soil in each experimental group,the SOD activity of earthworms showed a trend of first increase and then decrease,POD and GSH-Px activities showed a trend of first decrease and then increase,CAT activity generally showed an upward trend and AchE activity is generally on the decline;With the exposure time of earthworm in red soil,the SOD and AchE activity of earthworm decreased gradually,GSH-Px activity decreased first and then increased,while CAT and POD activity did not change obviously.4.According to the test results,for earthworms cultivated in moisture soil,when earthworms are subjected to the combined stress of lead(Pb)and cadmium(Cd),the sensitivity of GSH-Px in the body is the best,and the sensitivity of SOD and POD are the second.CAT has the worst sensitivity.AchE has a obvious trend of change,but the activity level is the lowest.For earthworms cultivated in red soil,when earthworms are subjected to the combined stress of lead(Pb)and cadmium(Cd),the sensitivity of GSH-Px is the best in vivo,followed by POD and SOD,and the sensitivity of CAT and AchE are the worst.In addition,comparing the absolute values,it can be found that when subjected to the combined stress of low concentrations of lead(Pb)and cadmium(Cd),the activity levels of GSH-Px,SOD,CAT,POD,and AchE are ranked as GSH-Px>SOD>POD>CAT>AchE.In summary,the biomarkers in earthworms can still show obvious changes,and a relatively stable dose-effect relationship can be formed between vitality and heavy metal elements.The absolute value of the biomarker's vitality will be affected by soil type and exposure time.Each biomarker has different environmental sensitivities,and the order of sensitivity of each biomarker can be obtained by comparison.The research results of this paper can provide a theoretical reference for environmental risk assessment of low-level heavy metal contaminated sites.