Behavior of 2,4-D in Belgian Soils1
- A. Moreale and
- R. Van Bladel2
This investigation was conducted to determine the physicochemical parameters of soils useful in predicting the adsorption and movement of 2,4-D ([2,4-dichlorophenoxy] acetic acid) in selected soils (surface and subhorizons) from the sandy and loam regions of Belgium. A statistical analysis showed that organic matter, soil pH (surface horizons), and exchangeable aluminum (subhorizons) could be used as key characteristics in the quantitative determination of the percentage of 2,4-D adsorbed. Adsorption isotherms demonstrated that changing the initial concentration of 2,4-D in solution (0.01–10 ppm) was of negligible importance in determining key soil properties related to the percentage of 2,4-D adsorbed. Desorption data were significantly correlated (r = −0.96) with the percentage of 2,4-D initially adsorbed. The overall effect of increasing the ionic strength of the calcium chloride (CaCl2) solution was to enhance 2,4-D adsorption. However, this effect was relatively small between 0.075 and 0.75 ionic strength. Degradation of 2,4-D added at a rate of 10 µg/g of soil (soil/solution ratio 1:1) was followed by CO2 evolution resulting from the oxidation of [Carboxyl-14C] 2,4-D. Within 1 month of incubation, extensive degradation occurred in neutral soils, but the degradation rate was considerably lower in acid soils. Leaching experiments indicated that 2,4-D mobility was inversely related to the amount of 2,4-D adsorbed. After 62-days of leaching in a Podzol soil column, 1 m long, the recovery of 2,4.D nondegraded in the profile was only 7% of the initial application rate. No trace of the herbicide was detected in the column effluent for this period.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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