Responses of methanotrophic activity, community and EPS production to CH_4 and O_2 concentrations in waste biocover soils

摘要

Biocover soils are known to be a good alternative material to mitigate CH_4 emissions from landfills to the atmosphere. In this study, 16 treatments with four O_2 concentrations (～0%, 5%, 10% and 21%) and four CH_4 concentrations (i.e. 1%, 10%, 20% and 50%) were conducted to estimate extracellular polymeric substances (EPS) production, methanotrophic activity and community in response to CH_4 and O_2 concentrations in waste biocover soil (WBS). When the CH_4 concentration was saturated for CH_4 oxidation in the WBS, the continuous exposure of CH_4 above the saturated concentrations could not obviously enhance CH_4 oxidation activity. In the WBS, extracellular protein (ECP) production was negatively related with the tested CH_4 concentrations, while both ECP and extracellular polysaccharides (ECPS) productions were positively related with the tested O_2 concentrations. Cloning and terminal restriction fragment length polymorphism analyses showed that type Ⅰ methanotrophs (Methytocaldum, Methylococcaceae, Methylomicrobium and Methylobacter) and type Ⅱ methanotrophs (Methylosinus) dominated in the WBS. Among them, Methylocaldum and/or Methylococcaceae were sensitive to low O_2 concentrations of ～0%. Methylobacter had propensity to grow at low O_2 concentrations of ～0% and 5%, while Methylosinus preferred environments with high concentrations of CH_4 (≥ 10%) and O_2 (21%). In the tested five environmental variables of ECPS, O_2, EPS, CH_4 and ECP, only ECPS and O_2 concentrations had significant effect on the methanotrophic communities. These results suggested that O_2 concentration in landfill covers should be paid more attention to optimize and sustain CH_4 oxidation for mitigating CH_4 emission from landfills.