| Brominated flame retardants(BFRs) are a group of brominated organic compounds with persistent, lipophilic, and bioaccumulative properties. Duo to their ubiquitous presence in various matrices, including water, air, soil and sediment, even biota as well as their potential adverse effects on wildlife and human, these organic compounds are of great concern for environmental researchers. Thus, in this thesis, the pollution profiles and risk assessment of BFRs in an electronic-waste dismantiling area were investigated and the relationships between the pollution profiles and the corresponding microbial community structure were also carried out. To avoid the problematic redistribution of these contaminants, and decrease the cost of sediments management, the biostimulation and bioaugmentation were employed to remove these BFRs. Three kinds of bacteria used in the biostimulation and bioaugmentation microcosms were previously isolated and inoculated by our group from BFRs contaminated sludge. That is, Ochrobactrum sp. T, Bacillus sp. GZT and Bacillus sp. GZB can be used to degrade and mineralize tetrabromobisphenol A(TBBPA), 2,4-dibromophenol(2,4-DBP) and 2,4,6-tribromophenol(TBP), and bisphenol A(BPA), respectively. In addition, to better understand the biodegradation enhancement of these compounds in the bioaugmentation experiments, the evolution of bacterial community were also investigated during the biodegradation process. Furthermore, a methodology was developed for the determination of carbon isotope ratios using gas chromatography/combustion/isotope ratio mass spectrometry(GC/C/IRMS), and then the method was applied to measure the δ13C values of phenolic BFRs and BPA during the biodegradation processes. In addition, these values can also be used to identify the source and fate of phenolic BFRs and BPA in environments. Main results of this thesis are listed as follows:(1) It is found that a big river, the Beijiang River, was not very polluted by brominated flame retardants and bisphenol A, although an electronic-waste dismantiling area was located near the river. The Σ20PBDEs(the sum of 20 polybrominated biphenyl ethers(PBDEs) congneners studied) concentrations ranged from nd(not detected) to 2.2 ng L-1 and 0.3 to 5.6 ng g-1 in water and sediments, respectively. Compared with the concentrations of Σ20PBDEs in small reviers near another electronic-waste recycling area, the concentrations of Σ20PBDEs in Beijiang River were three orders of magnitude lower. The concentrations of phenolic BFRs and BPA were lower than 1 ng L-1 in water and were lower than 1ng g-1 in sediments.(2) In small reviers near another electronic-waste recycling area, PBDEs, TBP, pentabromophenol(Pe BP), TBBPA and BPA were present in all samples, suggesting widespread contamination across the electronic-waste recycling area and the surrounding environment. In water, Σ20PBDEs concentrations ranged from 0.31 to 8.9×102 ng L-1, with an average of 1.6×102 ng L-1, and the low bromine PBDE congeners were found to be the dominant polluted species, while high bromine PBDE congeners and BDE-209 were below the detectable line or very low. In sediments, Σ20PBDEs concentrations ranged from nd to 6.0×103 ng g-1, with an average of 2.8×103 ng g-1, and BDE-209 was the dominant congener. In water, the concentrations of TBP, Pe BP, TBBPA and BPA ranged from nd to 3.2×102 ng L-1 for TBP; from nd to 37.0 ng L-1 for Pe BP; from nd to 9.2×102 ng L-1 for TBBPA; from nd to 8.6×102 ng L-1 for BPA. While in sediments, the concentrations of TBP, Pe BP, TBBPA and BPA ranged from nd to 47.0 ng g-1 for TBP; from nd to 25.0 ng g-1 for Pe BP; from nd to 2.4×102 ng g-1 for TBBPA; from nd to 5.6×102 ng g-1 for BPA. In water, the eco-toxicity assessment results showed that the total eco-toxicity of PBDEs, phenolic BFRs and BPA at three trophic levels(green algae, daphnia and fish) exhibited expected potential adverse effects(RQTotal≥100, except for S1 and S10). While in sediments, total eco-toxicity of these compounds at three trophic levels exhibited difference levels adverse effects. The estrogenic activity assessment results showed that the total estrogenic activity of TBBPA and BPA was far less than the threshold of endocrine disrupting(1 ng E2 L-1).(3) The diversity of microbes in water and sediments from rivers near an the electronic-waste recycling area was studied. Results showed that the microbes have very high species evenness and abundance(the range of H’ values were 2.6 to 3.4) in water, while have relatively low species evenness and abundance(the range of H’ values were 1.6 to 2.9) in sediments. The denatured gradient gel electrophoresis(DGGE) bands showed that the similarity coefficients of bacterial community were from 60% to 80% in water, while from 30% to 50% in sediments. The results of Ribosomal Database Project(RDP) classification of the DGGE bands sequenced showed that there were main four different phylogenetic groups at the phylum taxonomic rank, including Proteobacteria, Firmicutes, Bacteroidetes and Acidobacteria, except for few unclassified phylum, and the dominating bacterial phylum was found to be Proteobacteria. The corresponding matches(BLASTN) using the NCBI database showed that many DGGE bands sequenced had high similarity percentages of sources of origin with the reported dehalogenation microbes.(4) These results of bioremediation showed that:(a) No degradation was observed in the sterile controls and a small amount(3.4%) of TBBPA was degraded in the unamended controls. In contrast, 52.1% of TBBPA could be degraded in the bioaugmentation with Ochrobactrum sp. T strain, after ten weeks of incubation. Therefore, the native microbes existing in the BFRs contaminanted sediments can degrade TBBPA, and the bioaugmentation with the addition of Ochrobactrum sp. T strain in the sediment microcosms can improve the degradation efficiency of TBBPA. The addition of 2,4-DBP, TBP, and BPA as a co-substrate separately could degrade 36.2%, 35.7% and 30.1% of TBBPA in the sediments microcosm plus the bioaugmentation with Ochrobactrum sp. T. The biostimulating of 2,4-DBP, TBP or BPA could inhibit the degradation of TBBPA with the bioaugmentation of the Ochrobactrum sp. T strain. The composition of microbial community showed that the Ochrobactrum genus was the absolutely dominant genus and increased from 34.08% to 55.80% with the increasing of the incubation time from week zero to week ten. While Parasegetibacter(from 2.28% to 9.92%), Thermithiobacillus(from 0.20% to 6.49%), Phenylobacterium(from 0.82% to 4.33%) and Sphingomonas(from 0.90% to 2.39%) were found to be the minor genera. So microbes from genera Ochrobactrum have been mainly relative with the removal of TBBPA.(b) The biostimulating and bioaugmentation can obviously enhance the degradation efficiency of TBP in sediments microcosms. The biostimulating effects of yeast extract, sodium chloride, humic acid, sodium lactate, glucose and propionic acid on TBP degradation were evident within seven weeks incubation. That is, within seven weeks incubation, 54.0%, 46.6%, 46.0%, 44.3%, 59.0%, and 47.0% of TBP could be degraded in the sediments microcosms with the bioaugmentation with Bacillus sp. GZT when the yeast extract, sodium chloride, humic acid, sodium lactate, glucose or propionic acid was co-substrate, respectively. Particularly, yeast extract and glucose were more effective for enhancing the degradation efficiency of TBP than other co-substrates. The metagenomic analysis of total 16 S r RNA genes showed that the phylum of Proteobacteria(52.08-66.22%), Actinobacteria(20.03-5.47%), Bacteroidetes(6.68-13.68%) and Firmicutes(4.53-20.83%) were the predominant phylum. Bacillus sp. GZT strain belongs to phylum Firmicutes, which increased from 4.53% to 20.83% with the increasing of degradation time from week zero to seven weeks. Bacillus sp. GZT strain might mainly be associated with the enhanced degradation of TBP;(c) About 35.9% of BPA could be degraded in the bioaugmentation with Bacillus sp. GZB strain after seven weeks of incubation. As such, the bioaugmentation with the addition of Bacillus sp. GZB strain could improve the degradation efficiency of BPA in sediments microcosms. The biostimulating effects of yeast extract, sodium chloride, humic acid and glucose on BPA degradation were also evident within seven weeks incubation. About 56.3%, 44.4%, 47.6% and 56.6% of BPA could be degraded in sediments microcosms with the bioaugmentation with Bacillus sp. GZB strain and yeast extract, sodium chloride, humic acid or glucose as co-substrates, respectively. Yeast extract and glucose also were more effective for enhancing the degradation efficiency of BPA than other co-substrates. The metagenomic analysis of total 16 S r RNA genes showed that the phylum of Proteobacteria(37.54-59.05%), Firmicutes(11.59-33.97%), Bacteroidetes(8.56-21.84%), Actinobacteria(5.54-12.44%) and Acidobacteria(1.57-3.54%) were the predominant phylum. The Bacillus sp. GZB strain used in the bioaugmentation belongs to phylum Firmicutes, which increased from 11.59% to 33.97% as the degradation time increased from week zero to seven weeks. Therefore, Bacillus sp. GZB strain might mainly be relative with the enhanced degradation of BPA.(5) A methodology for the determination of carbon isotope compositions of phenolic BFRs and BPA was developed using gas chromatography/combustion/isotope ratio mass spectrometry(GC/C/IRMS). And this method can be used to accurately and precisely measure the δ13C values of BFRs and BPA. Subsequently, this method was validated in our laboratory for determination of the δ13C values of BFRs and BPA during the biodegradation processes. Results indicated that no obvious carbon isotopic fractionation was observed during the biodegradation of BFRs and BPA. Thus, the relatively constant isotopic compositions may provide additional evidence to understand the parent/daughter relationships and the sources of these brominated phenolic compounds in the natural environments. |
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