Volatility, adsorption, and degradation of propargyl bromide as a soil fumigant

During the 1960s, propargyl bromide (3-bromopropyne, C3H3Br, or 3BP) was used in a soil fumigant Trizone, a combination of chloropicrin, methyl bromide, and propargyl bromide. Since a great deal of attention is being placed on finding replacements for methyl bromide (CH3Br, MeBr) in soil fumigation, there is a revived interest in developing propargyl bromide as an alternative fumigant. However, at present, no information exists for assessing its behavior and safety in the environment. In this study, several important parameters needed to determine its environmental fate are obtained. These include basic parameters such as solubility, saturated vapor density, the Henry's law constant, adsorption, and degradation. These parameters are compared to MeBr and 1,3-dichloropropene (1,3-D); a methyl bromide alternative. At 25 degrees C, the Henry's law constant, K-H, for 3-bromopropyne is 0.046, which is smaller than that for MeBr and similar in magnitude to that for 1,3-D. In water at 25 degrees C, the solubility is approximate to 1.5% and 3BP slowly degrades with a hydrolysis half-life of 47 days. In soil, the degradation half-life ranged from 1.2 to 5 days, depending on the soil type. Under typical agricultural conditions, 3BP will move readily in soils, a desirable characteristic for fumigants, but, due to its short soil degradation time, should not pose a serious environmental risk.