The Removal Of 2,2′,4,4′-tetrabromodiphenyl Ether (BDE-47) In Contaminated Soil By Agricultural Waste Composting

Polybrominated diphenyl ethers(PBDEs) are a variety of persistent organic pollutants(POPs) which belong to the group of brominated flame retardants(BFRs). Among them, BDE-47 is main component, and it usually can cause great concern due to its extensive occurrence and unfavorable effects.BDE-47 contaminated soil by aerobic composting with agricultural wastes were investigated in this paper. Physico-chemical properties were selected to evaluate the effect of BDE-47 addition on aerobic composting process and microbial community composition. The experiment chose straw stalks, leaves, bran and soil as composting materials. Two composting piles were prepared:(i) pile A was free from BDE-47 contamination(ii) pile B contained BDE-47 with initial concentration of 0.366 mg/L(dry weight). Pile C only contained soil without any other composting materials as control group(BDE-47 initial concentration was 0.369 mg/L). The results showed that the degradation rate of BDE-47 was significantly higher in agricultural waste composting pile compared with control group, which was enhanced up to almost 15% at the end of composting, meanwhile the degradation rate of BDE-47 in control group was only 3%.This result indicated that repairing BDE-47 polluted soil by composting is feasible. The difference of two composting piles’ parameters indicated significant effects of BDE-47 on composting process,and the addition of BDE-47 led to an inferior quality in pile B.The microbial communities were determined by polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE): Total genomic DNA was extracted from obtained compost samples. The fragments of 16 S r DNA and 18 S rDNA genes were amplified with universal primers(bacteria: GC-338F/518 R and fungi: GC-Fung/NS1). Then denaturing gradient gel electrophoresis was used to obtain the information of bacterial and fungal communities.The relationships between the DGGE results and physico-chemical parameters were evaluated by redundancy analysis(RDA) and heatmap clustering analysis. The analysis results showed that there were different environmental factors which affected the distribution of composting bacterial and fungal community. The bacterial community composition was more significantly affected by the addition of BDE-47 compared with other physico-chemical parameters, and BDE-47 had stronger influences on bacterial community than fungal community during the composting. Meanwhile, the most variation in distribution of fungal community was explained by pile temperature.