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This article in JEQ

  1. Vol. 12 No. 4, p. 553-558

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Kinetics of the Microbial Degradation of 2,4-D in Soil: Effects of Temperature and Moisture1

  1. L. W. Parker and
  2. K. G. Doxtader2



The effects of soil moisture tension and temperature on the kinetics of the degradation of (2,4-dichlorophenoxy)acetic acid (2,4-D) in an Ascalon sandy loam were studied under laboratory conditions to develop a simulation model. Degradation occurred by a slow, first-order reaction (slow phase) which, under some conditions, was followed by a rapid, first-order reaction (fast phase). The optimum temperature and moisture tension were 27°C and 0.1 bar, respectively. Degradation rates under optimum conditions were 0.230 and 2.234 µg g−1 soil for the slow and fast phases, respectively. At temperatures above the optimum, no fast phase was observed. The activation energy (EA) values increased from 22.96 to 45.46 kcal mole−1, with increasing soil moisture tension in the range from 0.1 to 1.0 bar. The rate of decomposition of 2,4-D decreased with increasing soil moisture tension for temperatures between 20 and 35°C. This decrease was a result of the reduced activity of the 2,4-D-degrading microorganisms arising from decreased water availability and increased 2,4-D solution concentration.

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