Production of methyl bromide by terrestrial higher plants

Abstract

Methyl bromide ( CH 3 Br ) is considered to play an important role in stratospheric ozone depletion, but its sources are currently not well defined. We have observed that Brassica plants can take up Br − from soil, produce CH 3 Br and release it into the air. Emission of CH 3 Br was detected from plants grown in natural soils containing 0.06–0.31 mg/kg Br − ; the emission increases with increasing soil Br − level. We estimate that cabbage produces 0.4±0.2 Gg/yr, and rapeseed plants 6.6±1.8 Gg/yr. Given the ubiquitous distribution of Br − in soil, CH 3 Br production by terrestrial higher plants is likely a large source for atmospheric CH 3 Br .