The influence of soil environmental variables on the degradation and volatility of methyl bromide in soil

Recent controversy over the potential role of methyl bromide (MeBr) in damaging the ozone layer has spurred interest in qualitatively increasing our understanding of the transformation and movement of this fumigant. In contrast to the extensive uses of this common agricultural fumigant, a paucity of data exits on the environmental fate of MeBr. Our research indicates that MeBr is rapidly volatilized from fumigated soil (within the first 24 h) and volatility significantly increases with temperature (35°C > 25°C > 15°C) and moisture (-3 kPa > -33 kPa > -300 kPa). Degradation of MeBr, measured by production of bromide ion (Br^-), was also positively related to temperature and moisture. Undisturbed soil column studies indicated that MeBr rapidly volatilized (>50% of the MeBr flux occurred in 48 h) and did not leach into subsurface soil. Residual MeBr was degraded in the soil column, as evident by the high concentrations of Br in the leachate watch. These studies provide valuable information for assessing the fate of MeBr in soil, which should lead to more informed decisions for regulating its use.