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 increa sing our understanding of the transformation and movement of this fumi gant. In contrast to the extensive uses of this common agricultural fu migant, a paucity of data exits on the environmental fate of MeBr. Our research indicates that MeBr is rapidly volatilized from fumigated so il (within the first 24 h) and volatility significantly increases with temperature (35 degrees C > 25 degrees C > 15 degrees C) and moisture (-3 kPa > -33 kPa > -300 kPa). Degradation of MeBr, measured by produ ction of bromide ion (Br-), was also positively related to temperature and moisture. Undisturbed soil column studies indicated that MeBr rap idly volatilized (>50% of the MeBr flux occurred in 48 h) and did not leach into subsurface soil. Residual MeBr was degraded in the soil col umn, as evident by the high concentrations of Br- in the leachate wate r. These studies provide valuable information for assessing the fate o f MeBr in soil, which should lead to more informed decisions for regul ating its use.