Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2002
Publication Date: 9/9/2002
Citation: Papiernik, S.K., Gan, J., Yates, S.R. 2002. Characterization of propargyl bromide transformation in soil.. Pest Management Science. 58:1055-1062. Interpretive Summary: Soil fumigants are used for broad-spectrum pest control in high-value crops. Concerns of stratospheric ozone depletion has mandated the discontinuation of a popular soil fumigant, methyl bromide (MeBr). Currently-existing alternative fumigants lack the broad-spectrum activity of MeBr, leading to a search for additional fumigant compounds. Propargyl bromide (PrBr, 3-bromopropyne) is being investigated for its potential to serve as an additional MeBr alternative. An evaluation of PrBr's efficacy and environmental fate are required to determine its value as a soil fumigant. These experiments further characterized the rate and mechanism of transformation of PrBr in soil. This information is required for a more extensive evaluation of PrBr's potential to serve effectively as a soil fumigant. We assessed the potential for PrBr degradation by soil microorganisms and the effect of soil and application conditions on the rate of PrBr transformation in soil. The time required for half of the PrB added to soil to be degraded ranged from a few hours to 10 days, depending on the soil type and initial PrBr concentration. Transformation of PrBr in soil is primarily abiotic except at low concentrations. These results will allow more accurate predictions of soil concentrations that may occur following soil fumigation with PrBr and aid in the development of management practices for PrBr use.
Technical Abstract: Propargyl bromide (PrBr) is being investigated for its potential as a soil fumigant. Characterization of the fate of PrBr in soil is important in determining both efficacy and the threat of environmental contamination. These experiments investigated some of the factors affecting the rate of PrBr degradation in soil and quantified some of the products formed as a result of PrBr degradation in four soils of differing composition and at three initial PrBr concentrations. In all soils at all initial PrBr concentrations, equimolar formation of bromide was observed during PrBr degradation, but little propargyl alcohol (product of hydrolysis) was formed. The apparent first-order degradation coefficient (k) increased with decreasing initial PrBr concentration in all soils, but the mass degraded per unit time increased with increasing PrBr concentration. The rate of PrBr degradation increased with increasing soil organic matter content, and dthe k was correlated to the organic carbon content of the soil (correlatio coefficient 0.97 for all concentrations). Repeated application of PrBr did not increase the rate of PrBr degradation in soil. Addition of bromide did not affect the rate of PrBr transformation in soil, so accumulation of bromide in the soil is not expected to impede PrBr degradation.