The Bioaccumulation,Transformation And Toxicity Of Novel Brominated Flame Retardants Decabromodiphenyl Ethane In A Soil System

As a novel brominated flame retardant(NBFR),decabromodiphenyl ethane(DBDPE)has attracted widespread attention due to its large-scale production and high detection rate in environment.However,little was currently known about the toxic effects of DBDPE in terrestrial ecosystems.In this study,the bioaccumulation and transformation regularity of DBDPE in earthworms as well as its toxic effects in soil system were investigated at different DBDPE exposure(5,10,20,50 and 100 mg kg-1).The main research results were as follows:(1)DBDPE could accumulate in earthworms and the bioaccumulation factors(BAFs)were 0.028-0.213(gdw,worm/gdw,soil),while the concentrations of DBDPE in cast were about 2.84-37.95 times of that in earthworms.In addition,the clearance process fitted well with the first-order kinetic model(R2>0.81).The elimination rate constant(ke)values ranged from 0.323 to 0.452 d-1,and the half-life(t1/2)was between 1.53 and 2.14 d.The bioaccumulation and elimination results showed that the bioaccumulation capacity of DBDPE in earthworms was low.According to the GC-ENCI-MS analysis,at least four debrominated products were detected,indicating that DBDPE biotransformation occurred in earthworms.Histopathological and microscopic observations classified that DBDPE stress caused different degrees of damage,such as skin surface shrinkage,annular muscular atrophy,cytoplasmic concentration and vacuolation.(2)The growth and avoidance behaviors of earthworms were not significantly influenced by DBDPE stress,but the response of cellular and molecular level indicators suggested that DBDPE could affect the physiological and biochemical processes of earthworms.In general,after exposure to 0-14 d,superoxide dismutase(SOD),catalase(CAT)and total antioxidant capacity(T-AOC)were significantly induced(p<0.05),while MDA had no significant change.However,with the prolonged exposure time,the activities of all three indicators decreased as compared with 0-14 d,that the induction effect of DBDPE was weakened and even inhibited,however,the MDA contents increased significantly(p<0.05).On the context of 10 mg kg-1 DBDPE exposure,the ROS contents in earthworms increased obviously(p<0.05),and the ROS contents increased at first and then stabilized with increasing exposure concentrations.In addition,comparing with the control group,cytochrome P450(CYP450)and glutathione transferase(GST)were significantly induced(p<0.05),and the induction effect increased firstly and then decreased with the subsequent increase of time.The response of CYP450 to DBDPE stress was more sensitive.Thus,the CYP450,GST,ROS and MDA were selected as more sensitive indexes by time/dose-effect and correlation analysis.(3)During the whole exposure period,the microbial biomass carbon(MBC)contents and soil basal respiration(SBR)intensity were generally higher than those in the control group,while the metabolic entropy(qCO2)value increased firstly and then decreased with time elapsed.In addition,urease(US)activity did not change significantly overall,but was inhibited by DBDPE at high concentrations(50 and 100 mg kg-1)on 28 d.Compared with US,luciferin diacetate hydrolase(FDA)was more sensitive to DBDPE,and its activity was significantly increased after 21 d induction(p<0.05).Besides,DBDPE stress did not reduce the diversity of the microbial community,but the composition of the microbial community was changed after 60 days of exposure,and ?-proteobacteria in Proteobacteria had a greater influence.Compared with the control group,the abundance of ?-proteobacteria in different treatment groups decreased by 8.42-11.56%.