Spatial patterns of methane oxidation and methanotrophic diversity in landfill cover soils of southern China

Abstract

Aerobic CH 4 oxidation is an important CH 4 sink in landfills. To investigate the distribution and community diversity of methanotrophs and link with soil characteristics and operational parameters (e.g., concentrations of O 2, CH 4), 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 O 2 concentrations. The depth of 20-25 cm, where the ratio of the CH 4 to O 2 was within the range from 1.3 to 8.6, was more conducive to the growth of CH 4 -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 CH 4 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 CH 4 and O 2 for methanotrophs, especially around the vertical venting pipes.