The biotransformation mechanism of chloroform in landfill cover
LIU Shuai1, XING Zhi-lin1,2, LI Chen1, ZHANG Hao1, HU Wen-qing1, ZHANG Li-jie1, ZHANG Yun-ru1, ZHAO Tian-tao1,2
1. College of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400050, China;
2. College of Urban Construction and Environmental Engineering, Chongqing University, Chongqing 400045, China
It is important to deeply understanding the degradation mechanism of chloroform (CF) along the depth of a soil layer. In this study, the simulated landfill cover system (SLCS) was set up and biotransformation mechanism of CF was firstly investigated by the method of diversity sequencing. The results showed that the landfill cover was divided into three zones along the depth, aerobic zone (0~20cm), anoxic zone (20~40cm) and anaerobic zone (>40cm), based on the oxygen content. The analysis of diversity sequencing revealed that methanotrophs were dominant bacteria in aerobic zone, including type I methanotrophs Methylobacter and type Ⅱ methanotrophs Methylosinus. While Anaeromyxobacter was the dominant bacteria for CF biodegradation by reductive dechlorination in anoxic and anaerobic zone. In addition, the relative abundance of methanotrophs in the anoxic zone was about 13%. These results suggested that CF was firstly degraded effectively in aerobic, anoxic and anoxic zone. Previous studies reported that CF can be degraded into dichloromethane reductive dechlorination in the anoxic and anaerobic zone, and part of dichloromethane would be transformed into acetate, H2 and CO2 due to the activity of Dehalobacter, which agreed with this study. The metabolic product dichloromethane was then completely degraded by through co-metabolism by methanotrophs in aerobic and anoxic zone. Moreover, the relationship between biodegradation capacity and gas flux was also studied. With the change of inlet flux, there was a negative correlation between methane removal efficiency and flux (R2=0.80), while the positive correlation was found between methane biodegradation rate and flux (R2=0.86). Similarly, CF biodegradation efficiency decreased with increase of inlet gas flux (R2=0.86), while biodegradation rate increased with increase of inlet gas flux (R2=0.89). Therefore, aerobic co-metabolism contributed more in in removal of CF than reductive dichlorination. These results provided theoretical basis for in situ bioremediation of chlorinated aliphatic hydrocarbons pollutants.
Heidrich S, Weiss H, Kaschl A. Attenuation reactions in a multiple contaminated aquifer in Bitterfeld (Germany)[J]. Environmental Pollution, 2004,129(2):277-288.
Wreford K A, Atwater J W, Lavkulich L M. The effects of moisture inputs on landfill gas production and composition and leachate characteristics at the Vancouver Landfill Site at Burns Bog[J]. Waste Management & Research, 2000,18(4):386-392.
Xing Z, Zhao T, Gao Y, et al. Real-time monitoring of methane oxidation in a simulated landfill cover soil and MiSeq pyrosequencing analysis of the related bacterial community structure.[J]. Waste Management, 2017,68(10):369-377.
Scheutz C, Bogner J, Chanton JP, et al. Atmospheric emissions and attenuation of non-methane organic compounds in cover soils at a French landfill[J]. Waste Management, 2008,28(10):1892-1908.
[14]
Scheutz C, Mosbaek H, Kjeldsen P. Attenuation of methane and volatile organic compounds in landfill soil covers[J]. Journal of Environmental Quality, 2004,33(1):61-71.
Yao S, Xuan Z, Xiao-Meng W, et al. Evaluation of simultaneous biodegradation of methane and toluene in landfill covers[J]. Journal of Hazardous Materials, 2014,274(12):367-375.
[18]
Scheutz C, Kjeldsen P. Capacity for biodegradation of CFCs and HCFCs in a methane oxidative counter-gradient laboratory system simulating landfill soil covers[J]. Environmental Science & Technology, 2003,37(22):5143-5149.
Scheutz C, Kjeldsen P. Environmental factors influencing attenuation of methane and hydrochlorofluorocarbons in landfill cover soils[J]. Soil Mechanics & Foundation Engineering, 2004,7(2):113-116.
Scheutz C, Kjeldsen P. Biodegradation of trace gases in simulated landfill soil[J]. Journal of the Air & Waste Management Association, 2005,55(7):878-885.
Bouwer E J, Mccarty P L. Transformations of 1-and 2-carbon halogenated aliphatic organic compounds under methanogenic conditions[J]. Applied & Environmental Microbiology, 1983,45(4):1286-1294.
[25]
Egli C, Tschan T, Scholtz R, et al. Transformation of tetrachloromethane to dichloromethane and carbon dioxide by Acetobacterium woodii.[J]. Applied & Environmental Microbiology, 1988,54(11):2819-2824.
[26]
Shan H, Jr K H, Mykytczuk N, et al. Anaerobic biotransformation of high concentrations of chloroform by an enrichment culture and two bacterial isolates[J]. Applied & Environmental Microbiology, 2010, 76(19):6463-6469.
[27]
Gälli R, Mccarty P L. Biotransformation of 1,1,1-trichloroethane, trichloromethane, and tetrachloromethane by a Clostridium sp[J]. Applied & Environmental Microbiology, 1989,55(4):837-844.
[28]
Grostern A, Duhamel M, Dworatzek S, et al. Chloroform respiration to dichloromethane by a Dehalobacter population[J]. Environmental Microbiology, 2010,12(4):1053-1060.
[29]
Nijenhuis I, Kuntze K. Anaerobic microbial dehalogenation of organohalides-state of the art and remediation strategies[J]. Current Opinion in Biotechnology, 2016,38(4):33-38.
[30]
Nonaka H, Keresztes G, Shinoda Y, et al. Complete genome sequence of the dehalorespiring bacterium Desulfitobacterium hafniense Y51 and comparison with Dehalococcoides ethenogenes 195[J]. Journal of Bacteriology, 2006,188(6):2262-2274.
[31]
Thomas S H, Wagner R D, Arakaki A K, et al. The mosaic genome of anaeromyxobacter dehalogenans strain 2CP-C suggests an aerobic common ancestor to the Delta-Proteobacteria[J]. PloS one, 2008, 3(5):2103-2115.
[32]
Wagner D D, Hug L A, Hatt J K, et al. Genomic determinants of organohalide-respiration in Geobacter lovleyi, an unusual member of the Geobacteraceae [J]. Bmc Genomics, 2012,13(1):1471-1488.
[33]
Sharma P K, Mccarty P L. Isolation and characterization of a facultatively aerobic bacterium that reductively dehalogenates tetrachloroethene to cis-1,2-dichloroethene[J]. Applied & Environmental Microbiology, 1996,62(3):761-765.
[34]
Seshadri R, Adrian L, Fouts DE, et al. Genome sequence of the PCE-dechlorinating bacterium Dehalococcoides ethenogenes[J]. Science, 2005,307(5706):105-109.
[35]
Siddaramappa S, Challacombe J F, Delano S F, et al. Complete genome sequence of Dehalogenimonas lykanthroporepellens type strain (BL-DC-9(T)) and comparison to "Dehalococcoides" strains[J]. Standards in Genomic Sciences, 2012,6(2):251-264.
[36]
Lee M, Low A, Zemb O, et al. Complete chloroform dechlorination by organochlorine respiration and fermentation[J]. Environmental Microbiology, 2012,14(4):883-894.
[37]
Trotsenko Y A, Torgonskaya M L. The aerobic degradation of dichloromethane:Structural-functional aspects (a review)[J]. Applied Biochemistry & Microbiology, 2009,45(3):233-247.
