Vertical profiles of community and activity of methanotrophs in landfill cover soils of different age

Aerobic CH4 oxidation is an important process controlling CH4 release from landfills to the atmosphere. The aim of this study was to investigate the link between CH4 oxidation activity and methanotrophs abundance and diversity in landfill cover soils of different age.Among the three investigated sites, the highest CH4 emission occurred at the active landfill area with the range of 1371-2242 mg m(-2) day. The CH4 oxidation activities of landfill cover soils were 1·07-1·21 μmol g(-1) h(-1) in the landfill area of 7-16 years, which was 7-17 times higher than those in the active landfill area. The relative abundance of methanotrophs assessed by quantification of pmoA gene was about 1·7 × 10(6) -2·4 × 10(7) copies g(-1) in the landfill cover soils. The CH4 oxidation activity was positively correlated with pmoA copy number in the landfill cover soil of each site, respectively. Type II methanotrophs (Methylocystis) and type I methanotrophs including Methylosoma, Methylocaldum and Methylococcus were all present in the landfill cover soils. Compared to type I methanotroph, type II methanotroph, Methylocystis, was more abundant in the acidic landfill cover soils.Oxidation activity and community structure of methanotrophs varied with depth and age of landfill cover soils.These findings provide new fundamental information regarding the activity and diversity of methanotrophs in landfill cover soils of different age that may aid predicting and modelling CH4 flux from landfills.