Selective Inhibition of Ammonium Oxidation and Nitrification-Linked N ₂ O Formation by Methyl Fluoride and Dimethyl Ether

Methyl fluoride (CH(3)F) and dimethyl ether (DME) inhibited nitrification in washed-cell suspensions of Nitrosomonas europaea and in a variety of oxygenated soils and sediments. Headspace additions of CH(3)F (10% [vol/vol]) and DME (25% [vol/vol]) fully inhibited NO(2) and N(2)O production from NH(4) in incubations of N. europaea, while lower concentrations of these gases resulted in partial inhibition. Oxidation of hydroxylamine (NH(2)OH) by N. europaea and oxidation of NO(2) by a Nitrobacter sp. were unaffected by CH(3)F or DME. In nitrifying soils, CH(3)F and DME inhibited N(2)O production. In field experiments with surface flux chambers and intact cores, CH(3)F reduced the release of N(2)O from soils to the atmosphere by 20- to 30-fold. Inhibition by CH(3)F also resulted in decreased NO(3) + NO(2) levels and increased NH(4) levels in soils. CH(3)F did not affect patterns of dissimilatory nitrate reduction to ammonia in cell suspensions of a nitrate-respiring bacterium, nor did it affect N(2)O metabolism in denitrifying soils. CH(3)F and DME will be useful in discriminating N(2)O production via nitrification and denitrification when both processes occur and in decoupling these processes by blocking NO(2) and NO(3) production.