DIFLUOROMETHANE, A NEW AND IMPROVED INHIBITOR OF METHANOTROPHY

Difluoromethane (HFC-32; DFM) is compared to acetylene and methyl fluo ride as an inhibitor of methanotrophy in cultures and soils. DFM was f ound to be a reversible inhibitor of CH4 oxidation by Methylococcus ca psulatus (Bath). Consumption of CH4 in soil was blocked by additions o f low levels of DFM (0.03 kPa), and this inhibition was reversed by DF M removal. Although a small quantity of DFM was consumed during these incubations, its remaining concentration was sufficiently elevated to sustain inhibition. Methanogenesis in anaerobic soil slurries, includi ng acetoclastic methanogenesis, was unaffected by levels of DFM which inhibit methanotrophy. Low levels of DFM (0.03 kPa) also inhibited nit rification and N2O production by soils. DFM is proposed as an improved inhibitor of CH4 oxidation over acetylene and/or methyl fluoride on t he basis of its reversibility, its efficacy at low concentrations, its lack of inhibition of methanogenesis, and its low cost.