• Journal of Microbiology and Biotechnology
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• 제25권4호
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• pp.423-430
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• 2015

Aerobic CH₄ oxidation is an important CH₄ sink in landfills. To investigate the distribution and community diversity of methanotrophs and link with soil characteristics and operational parameters (e.g., concentrations of O₂, CH₄), cover soil samples were collected at different locations and depths from the Mengzi semi-aerobic landfill (SAL) in Yunnan Province of southern China. Specific PCR followed by denaturing gradient gel electrophoresis and realtime PCR were used to examine methanotrophs in the landfill cover soils. The results showed that different locations did harbor distinct methanotroph communities. Methanotrophs were more abundant in areas near the venting pipes because of the higher O₂ concentrations. The depth of 20-25 cm, where the ratio of the CH₄ to O₂ was within the range from 1.3 to 8.6, was more conducive to the growth of CH₄-oxidizing bacteria. Type II methanotrophs dominated in all samples compared with Type I methanotrophs, as evidenced by the high ratio of Type II to Type I methanotrophic copy numbers (from 1.76 to 11.60). The total copy numbers of methanotrophs detected were similar to other ecosystems, although the CH₄ concentration was much higher in SAL cover soil. Methylobacter and Methylocystis were the most abundant Type I and Type II methanotrophs genera, respectively, in the Mengzi SAL. The results suggested that SALs could provide a special environment with both high concentrations of CH₄ and O₂ for methanotrophs, especially around the vertical venting pipes.

• Membrane and Water Treatment
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• 제8권2호
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• pp.171-184
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• 2017

This study presents the effect of hydraulic retention time (HRT) on the characteristics of emission of three major greenhouse gases (GHGs) including $CH_4$, $CO_2$ and $N_2O$ during operation of a sequencing batch reactor for aerobic oxidation of methane with denitrification (AeOM-D SBR). Dissolved $N_2O$ concentration increased, leveled-off and slightly decreased as the HRT increased from 0.25 to 1d. Concentration of the dissolved $N_2O$ was higher at the shorter HRT, which was highly associated with the lowered C/N ratio. A longer HRT resulted in a higher C/N ratio with a sufficient carbon source produced by methanotrophs via methane oxidation, which provided a favorable condition for reducing $N_2O$ formation. With a less formation of the dissolved $N_2O$, $N_2O$ emission rate was lower at a longer HRT condition due to the lower C/N ratio. Opposite to the $N_2O$ emission, emission rates of $CH_4$ and $CO_2$ were higher at a longer HRT. Longer HRT resulted in the greater total GHGs emission as $CO_2$ equivalent which was doubled when the HRT increased from 0.5d to 1.0 d. Contribution of $CH_4$ onto the total GHGs emission was most dominant accounting for 98 - 99% compared to that of $N_2O$ (< 2%).

• Bulletin of the Korean Chemical Society
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• 제14권4호
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• pp.439-444
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• 1993

The aerobic oxidation of the Fe(II) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)$(CH_3CN)_2](ClO_4)_2$, in MeCN in the presence of a few drops of $HClO_4$ leads to low spin Fe(III) species [Fe(cyclam)$(CH_3CN)_2](ClO_4)_3$. The Fe(III) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(II) complex $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$. The Fe(II) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$ crystallizes in the monoclinic space group $P2_1/n$ with a= 13.099 (1) ${\AA}$, b= 10.930 (1) ${\AA}$, c= 17.859 (1) ${\AA}$, ${\beta}$= 95.315 $(7)^{\circ}$, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and $R_w$= 0.0702 for 1819 observed reflections with F > $4{\sigma}$ (F) measured with Mo K${\alpha}$ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of ${\beta}$-diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of $Fe(II)-N_{imine}$, $Fe(II)-N_{amine}$, and $Fe(II)-N_{MeCN}$ are 1.890 (5), 2.001 (5), and 1.925 (6) ${\AA}$, respectively. The complex is diamagnetic, containing two low spin Fe(II) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ${\varepsilon}$= 25,000 $M^{-1}cm^{-1}$. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in $MeNO_2$ to form carbonyl adducts, whose $v_{CO}$ value (2010 $cm^{-1}$) indicates the ${\pi}$-accepting property of the present bismacrocyclic ligand.

• 한국미생물·생명공학회지
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• 제37권4호
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• pp.293-305
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• 2009

메탄은 온실효과가 이산화탄소 보다 20배 이상인 대표적인 non-$CO_2$ 온실가스이다. 매립지는 주요 인위적 메탄 발생원으로, 매립지의 메탄 발생량은 연간 35~73 Tg(tera gram)으로 추정된다. 바이오커버(개방형 시스템)과 바이오필터(폐쇄형 시스템)을 이용하는 생물학적 방법은 메탄을 회수하여 자원화하기에는 메탄 농도가 너무 낮거나 가스 포집정이 설치되어 있지 않는 노후화된 매립지나 소규모 매립지로부터 메탄 배출을 저감할 수 있는 유용한 방법이다. 메탄을 유일탄소원과 에너지원으로 활용하는 메탄산화세균은 이러한 생물학적 방법에 있어 메탄을 산화시켜 제거하는데 매우 중요한 역할을 담당한다. 토양, compost, 지렁이 분변토 등과 같은 다양한 충전재를 이용하여 실험실 규모의 바이오커버/바이오필터의 메탄산화효율에 관한 많은 연구가 진행되었다. 이 중에서 compost는 가장 많이 이용되고 있는 충전재이고, compost를 이용한 바이오커버/바이오필터의 메탄산화속도는 50에서 $700\;g-CH_4\;m^{-2}\;d^{-1}$로 보고되고 있다. 또한, 실제 매립지에 파일럿 규모의 바이오커버/바이오필터를 설치하여 메탄 배출 저감 효과에 관한 연구도 진행되고 있다. 매립지의 메탄 배출 저감은 탄소배출권 거래와 연관될 수 있으므로, 바이오커버/바이오필터에 의한 메탄 저감량을 정확하게 평가하는 것이 매우 중요하다. 그러므로, 매립지 현장에 설치된 바이오커버/바이오필터의 성능을 평가하는 방법은 표준화되어야 하며, 메탄 저감량을 정확하게 정량화할 수 있는 방법 개발이 필요하다.