Using Carbon-14 Tracing To Investigate The Fate And Transformation Of Decabromodiphenyl Ether In Soil And Soil Organsim

Decabromodiphenyl ether（DBDE）is one of the’ most important class of brominated flame retardants（BFR）that are used extensively in both commercial and household products.During the past decades.DBDEs have been frequently detected and persistented in environment.In recent years,numerous studies on DBDE have been conducted to assess its risks to the environment and ecosystems i.e.,bioavailability,transformation,degradation and toxicity.However,lack of labled DBDE most of the existing studies about DBDEs are based on traditional technology,which can be overlooked the concertation in environment,and can not provide more information about the environment fate of DBDE.In this paper,the ¹⁴C-DBDE was self-synthesized,and used to track its fate and transportation in soil and soil-earthworm system basing on the mass balance of ¹⁴C.We think it could provide more information about the environment fate for DBDE,which could help to fully understand the environment risks for DBDE1)Decabromodiphenyl ether(¹⁴C-DBDE)was synthesized from uniformly radiolabeled with ¹⁴C phenol and purified in the lab.The reaction conditions for intermediates Diphenyl ether was:Cs2CO3（5.66 g,17.37 mmol）,CuBr(0.¹⁴78 g.1.03 mmol),2-oxocyclohexanecarboxylate（0.3311 g,9.73 mmol）,iodobenzene（1.699 g.8.32 mmol）,phenol（0.7301 g,7.7 mmol）,¹⁴C phenol（24.096 mg,0.251 mmol）.The reaction mixture was resulted Diphenyl ether 1.0177 g.The labeled Diphenyl ether was used as starting materials for ¹⁴C Decabromodiphenyl ether.The reaction conditions for ¹⁴C Decabromodiphenyl ether was:Diphenyl ether 0.5311 g,Bromide 3 ml、Dichloride carbon 3.5 mL、Aluminium trichloride 0.25 g.The reaction mixture was stirred at the temperature for 7 h,which resulted in 2.0788 g ¹⁴C Decabromodiphenyl ether.Chemical（98.4%）and radiochemical purities（98.6%）and special activities（1.25 mCi/mmol）of the radiolabeled compound were determined by GC-MS,IR or HPLC-LSC.2)The self-synthesized ¹⁴C-DBDE was used to track its fate and transportation in soil basing on the mass balance of ¹⁴C.Throughout the 130-day incubation,negligible radioactivity was detected in the traps for volatile products or cumulative ¹⁴CO2 production in all treatments.The bound-residue（BR）and extractable residues（ER）formation in neutral yellow field soil（S-3）was 97.4%and 2.6%;in acidic red sand soil（S-1）was 99.65%and 0.35%;in alkaline light slime of land soil（S-4）was 1.3%and 98.7%;in sterile biosoild amend（5%-20%）yellow pine soil（S-2）was 0.79%-98.87%and 1.13%-3.21%;in unsterile biosoild amend（5%-2 0%）in sterile and unsterile yellow pine soil（S-2）was 98.4%-98.7%and 1.3%-1.6%.The bound-residue（BR）formation in all treatments was<4%and BR concentration was generally considered to be correlated with organic carbon and biosoild amend.3)Three strains of DBDE degrading bacteria were screened,isolated and separated from soils by applying modern molecular biological technique with traditional microbiological method.The degradation rate for strain CZ-1、PT-12 and HZ-4 at 20 mg/L were 11.0%,15.8 2%and 21.04%.The strain HZ-4 was identified as Rhodococcus erythropoli.by physiological,biochemical tests and 16s rDNA sequence and renamed as HNS209-1.The 34 kinds of representative drugs were selected to test the drug resistance for HNS209-1,the results show that the strain was sensitive to 11 test drugs and resistance for 2 drugs,and there is no biological toxicity for fish（Carassius auratus gibelio）.The strain HNS209-1 was applied to soil was to evaulate the affection of yellow pine soil（S-2）.The results showed the BR in strain amend soil rised from 0.45%to 1.75%,but no degradation of DBDE was observed.4)However,the fate of DBDE and its transportation in an earthworm-soil system with and without a DBDE-degrading was rarely evaluated.In this study,the ¹⁴C-DBDE was self-synthesized,and strain Rhodococcus erythropolis.was used.DBDE showed limited degradation and mineralization after 35 days in all treatments.The bound-residue（BR）formation in soil was<2.5%with earthworms,which was significantly higher（p<0.05）than without earthworms（<0.45%）.The DBDE could be absorbed but not bioaccumulated in the earthworm（BSAF ≤ 0.31）.The distribution of ¹⁴C-DBDE concentrations in worm roughly followed the pattern of crop gizzard>digestive system>head>tail>body wall,suggesting uptake of DBDE was mainly through ingestion.Up to 31%of the ¹⁴C-DBDE was non-extractable in the earthworms,revealing that the total accumulation concentration was underestimated.The results also showed that the DBDE-degrading bacteria did not significantly affect the fate of DBDE and its accumulation in earthworms.These results indicate that the conventional assessment of bioaccumulation and risk based on the extractable concentrations only yield underestimates and require modifications,and the concentrations in worm guts should receive attention.