Integration of Photolysis and Biodegradation for the Degradation of Polychlorinated Biphenyl Mizture
Polychlorinated biphenyls (PCBs) are ubiquitous toxic pollutants in our environment. Although the production of PCBs was banned by the US Congress in 1976, they persist in the environment because of their resistance to physicochemical and biological degradation. Upon entering the marine environment, PCBs will associate with sediment due to their hydrophobic nature. Thus marine sediment becomes a sink for PCBs and exerts a threat to marine organisms. In this study, photolysis was used to dechlorinate the selected PCB congeners, namely, 2 , 4, 4’-trichlorobiphenyl (PCB 28), 2, 2’, 5, 5’- tetrachlorobiphenyl (PCB 52), 2, 2’, 4, 5, 5’-pentachlorobiphenyl (PCB 101), 2, 2’, 4, 4’, 5, 5’-hexachlorobiphenyl (PCB 153) and 2, 2’, 3, 4, 4’, 5, 5’- heptachlorobiphenyl (PCB 180), in the selected organic solvent, and produced less chlorinated PCBs and ultimately biphenyl (BP) which could be further degraded (mineralized) by the selected bacterium. Thus integration of photolysis and biodegradation is a feasible remediation for PCB contaminat ed marine sediment. To optimize the conditions for photolytic dechlorination, a “clean marine sediment was collected and spiked with the selected PCB congeners individually or in combination. Sediment extraction was performed by accelerated solvent extraction (ASE) and cleanups using sulphuric acid, activated copper granule and C-18 solid phase extraction (SPE) were conducted. Results from spiked “clean sediment indicated that the cleanups could effectively remove coextracted organics. The photolytic intermediates and products were identified by gas chromatography-mass spectrometry (GC-MS). Less chlorinated congeners and BP were found, indicating stepwise dechlorination of PCB was the major pathway and lead to the final production of biphenyl (BP). In addition, the toxicity of the photolytic intermediates and product were also monitored by the Microtoxa test. The toxicity of the treatment sample increased after initial illumination, and then decreased when photolysis proceed. Then A BP-degrading bacterium was isolated from a greenhouse soil sample and biodegradation was optimised with respect to temperature, initial pH, agitation rate and initial biphenyl concentration. Results showed that the isolated bacterium was Rhodococcus rhodochrous and the optimal temperature, initial pH, agitation rate and initial biphenyl concentration were 30 , pH 7, 200 rpm and 100 mg/L, respectively. Integration of photolysis and biodegradation was performed using a “clean sediment collected spiked with mixture of PCB congeners. Biodegradation of photolytic product (mainly BP) indicated that the photolysis of pure congeners did not produce inhibitory compounds. Close to 100% of BP was degraded biologically. Results in this study indicate that integration of photolysis and biodegradation is an effective treatment for PCBs in marine sediment.
polychlorinated biphenyls photolysis biodegradation integration pathway
WONG Kin Hang WONG Po Keung
Department of Biology,the Chinese University of Hong Kong,Shatin,New Territories,Hong Kong SAR,China
国际会议
2009 International Symposium on Environmental Science and Technology(2009环境科学与技术国际会议)
上海
英文
2470-2479
2009-06-02（万方平台首次上网日期，不代表论文的发表时间）