Toxicological Effects Of Decabromodiphenyl Ether And Nanoscale Zero-valent Iron In The Earthworm-soil System

Decabromodiphenyl ether(BDE209)is the typical contaminant at e-waste recycling sites(EWRSs).In recent years,nanoscale zero-valent iron(nZVI)has been extensively used in situ remediation(i.e.,soil and groundwater).The combined toxic effects of two chemicals on soil organisms are becoming a research hotspot.In this study,the toxicological effects of nZVI and BDE209 on earthworm(Eisenia fetida)were studied under laboratory conditions.The results are as follows:(1)The results have demonstrated that addition of nZVI can affect accumulation and transformation of BDE209 in earthworms.After mid-and long-term exposure(14 and 28 days),BDE209 uptake was generally enhanced after simultaneous exposure to nZVI(100 mg kg-1)and BDE209(10 mg kg-1),but under middle and high doses of nZVI(500 or 1000 mg kg-1),BDE209 uptake was inhibited.In addition,according to the detected results by GC-MS,BDE208,BDE207,BDE206,BDE203,BDE153,BDE99,and BDE28 were the debrominated congeners of BDE209 metabolites in earthworms.Furthermore,low BDEs could be attacked by hydroxyl radicals in the presence of nZVI and generate the hydroxylated products.(2)In the acute toxicity tests(natural soil assay),the mortality of earthworms was lower than 50%in different treated groups of nZVI during 14 days of exposure.Results of sub-acute toxicity showed that compared to the controls,being exposed to nZVI(1000 mg kg-1)significantly inhibited growth,respiration,and reproduction and increased avoidance response in earthworms(P<0.05).Moreover,addition of BDE209(10 mg kg-1)significantly(P<0.05)reduced the activity of physiological indicator in earthworms under exposure to nZVI(1000 mg kg-1).(3)Superoxide dismutase(SOD)showed a significantly induction trend(P<0.05)under short-term(7 days)exposure to nZVI,while it was significantly inhibited(P<0.05)under long-term(28 days)exposure.However,catalase(CAT)activity was barely(P>0.05)affected by pollutants relative to the controls during 7 and 14 days of exposure,whereas it was significantly(P<0.05)induced after 21 days of exposure.The increased generation of reactive oxygen species(ROS)led to the perturbations of antioxidant enzyme activities(e.g.SOD and CAT)and marked enhancement trend of MDA content in earthworms after being co-exposed to 1000 mg nZVI kg-1 and 10 mg BDE209 kg-1,confirming the lipid peroxidation occurred.(4)Expression levels of annetocin(ANN)gene indicated remarkable(P<0.05)down-regulation in earthworms after co-exposure to nZVI and BDE209,and supported the dose-response relationship.Moreover,it exhibited a positive correlation with reproductive response.Iron contents in earthworms were also associated with the reproductive response and ANN expression(R>0.80).In conclusion,ROS,respiration,and reproductive gene in earthworms were the relatively sensitive indicators in response to the stress caused by pollutants.