Biological Monitoring And Ecological Risk Assessment Of Pb And Decabromodiphenyl Ethane

Lead（Plumbum,Pb）and Decabromodiphenylethane（DBDPE）,as two typical pollutants in the soil,may enter animals and plants and accumulate in the human body,and cause potential harm to animals,plants and human health.In this paper,earthworms（Eisenia vulgaris）were used as the test organism for evaluating the pollution state of Pb and DBDPE in the soil as well as the potential ecotoxicity.（1）The 48-h avoidance experiments showed no significant avoidance behavior for earthworms in Pb and DBDPE-contaminated soil.With the increase of concentration and exposure time,the mortality and growth inhibition rates of earthworm in Pb-contaminated soil increased in the 21-day soil toxicity tests.After 21 d of exposure,the mortality and growth inhibition rates of earthworms in the highest Pb treatment group（2000 mg/kg）increased to the highest levels.The effects of DBDPE on mortality and growth inhibition rates of earthworms were less significant than that of Pb.The combined effects of Pb and DBDPE were studied by dose effect diagram and nonlinear joint toxicity evaluation methods.The results showed that the specific type of joint toxicity was concentration dependent.The aging effects（0.7,14,21 d）on mortality and growth inhibition rates of earthworms in Pb and DBDPE treatment groups were also studied.With the increase of aging time,the mortality and growth inhibition rates of earthworm in high concentrations of Pb groups were significantly lower than those in control group,while no significant effects were observed in most DBDPE groups.（2）The effects of Pb and DBDPE on the activities of antioxidant enzymes（SOD,CAT,MDA）,glutathione-S transferase（GST）,acid phosphatase（ACP）and acetylcholinesterase（AChE）in earthworms were as follows:①With the increase of exposure time,the SOD activity in earthworms was decreased and then increased by exposure to Pb compared to the control,while the MDA contents increased significantly.The activity of GST was also significantly inhibited at 7 and 21 d.② With the increase of exposure time,the MDA contents in earthworms in DBDPEcontaminated soils were increased significantly compared with those in the control.The activity of GST was significantly inhibited at 7 and 21 d after exposure,and a downward trend was observed with increasing concentrations of DBDPE.Except for 1 mg/kg DBDPE group,the activities of ACP in all groups were higher than those in the control group.The AChE activity in the 0.25 and 0.75 mg/kg groups reached the highest levels 21 d after exposure,while AChE activity of 1 mg/kg group was inhibited at 21 d.③Effects of Pb and DBDPE on the enzyme activities of earthworms were dependent on concentrations and time.The MDA contents in all treated groups were higher than that in the control group,and increased with the increase of concentrations.The GST activity was significantly lower than that of the control group after exposure for 7 and 21 d.The activity of SOD and ACP was decreased by prolonged exposure time.The ACP activity in the treatment groups was stimulated at 7 d and inhibited at 21 d.Coexposre to Pb and DBDPE seemed to have no significant effects on CAT activity.There were also no significant changes in AChE activity at 7 and 21 d,but significant inhibition was observed at 14 d.④Factor analysis was used to obtain the main indicators that affect earthworm oxidative stress under different exposure time.Under single Pb stress,TP and GST were the most important indicators,whileCAT and AChE are the most important indicators for earthworms under DBDEP single stress.（3）Different amounts of biochar were added to the Pb and DBDPE-contaminated soil.The results showed that biochar had a certain inhibitory effect on the avoidance behavior of earthworms in soil polluted by Pb and DBDPE.When 5%biochar was added,the avoidance rates of earthworms in Pb treatment groups（400 and 800 mg/kg）were significantly decreased compared with the control group.Biochar had better remediation effect on Pb-contaminated soil than DBDPE-contaminated soil.（4）To study the ecological risks of Pb in the soil,the Log-logistic function was used to fit the species sensitivity distribution（SSD）curves of 10 species in four typical soils in China,and the HC5 were calculated.Results showed that the sensitivity of the 10 species was soil microorganism>Eisenia vulgaris>plants.