Degradation of Soil Fumigants as Affected by Initial Concentration and Temperature
2001
Ma, Q.L. | Gan, J. | Papiernik, S.K. | Becker, Jo | Yates, S.R.
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).
Show more [+] Less [-]AGROVOC Keywords
Bibliographic information
This bibliographic record has been provided by National Agricultural Library