Degradation of Soil Fumigants as Affected by Initial Concentration and Temperature
- 1 January 2001
- journal article
- Published by Wiley in Journal of Environmental Quality
- Vol. 30 (4), 1278-1286
- https://doi.org/10.2134/jeq2001.3041278x
Abstract
Soil fumigation using shank injection creates high fumigant concentration gradients in soil from the injection point to the soil surface. A temperature gradient also exists along the soil profile. We studied the degradation of methyl isothiocyanate (MITC) and 1,3-dichloropropene (1,3-D) in an Arlington sandy loam (coarse-loamy, mixed, thermic Haplic Durixeralf) at four temperatures and four initial concentrations. We then tested the applicability of first-order, half-order, and second-order kinetics, and the Michaelis–Menten model for describing fumigant degradation as affected by temperature and initial concentration. Overall, none of the models adequately described the degradation of MITC and 1,3-D isomers over the range of the initial concentrations. First-order and half-order kinetics adequately described the degradation of MITC and 1,3-D isomers at each initial concentration, with the correlation coefficients greater than 0.78 (r 2 > 0.78). However, the derived rate constant was dependent on the initial concentration. The first-order rate constants varied between 6 and 10× for MITC for the concentration range of 3 to 140 mg kg−1, and between 1.5 and 4× for 1,3-D isomers for the concentration range of 0.6 to 60 mg kg−1, depending on temperature. For the same initial concentration range, the variation in the half-order rate constants was between 1.4 and 1.7× for MITC and between 3.1 and 6.1× for 1,3-D isomers, depending on temperature. Second-order kinetics and the Michaelis–Menten model did not satisfactorily describe the degradation at all initial concentrations. The degradation of MITC and 1,3-D was primarily biodegradation, which was affected by temperature between 20 and 40°C, following the Arrhenius equation (r 2 > 0.74). Copyright © 2001. American Society of Agronomy, Crop Science Society of America, Soil Science Society . Published in J. Environ. Qual.30:1278–1286.Keywords
Funding Information
- USDA-National Research Initiative (98-35316-6450)
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