Equilibrium studies of the adsorption of dichlorprop on three Swedish soil profiles
1991
Ghorayshi, M. | Bergstroem, L. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Markvetenskap)
Adsorption of the herbicide dichlorprop (2,4-DP) (2-(2,4-dichlorophenoxy) propionic acid) to 10 horizons of three representative Swedish soils was measured in batch experiments. The Freundlich equation was used to analyze the data. The adsorption coefficients of 9 horizons ranged between 0.5 and 1. However, one subsoil horizon of Mellby sandy loam (greater than 115 cm depth) with pH=3.7 and a high content of exchangeable and water soluble Fe (83 mg/kg soil) showed a significantly (at the 0.05 level) higher adsorption coefficient, namely 3. No significant correlation (p greater than 0.05) between adsorption coefficients of dichlorprop and either the organic matter or clay content was found. A significant negative correlation between adsorption coefficients and pH (r=-0.86, p less than 0.05) was found. An increase of the adsorption of dichlorprop with decrease in soil pH is stated to be the result of I) increased anion exchange capacity of the soil particles due to protonation of iron oxide/hydroxide surfaces and II) enhanced clay-hydrogen-dichlorprop anion bonding due to the protonation of exchange sites.
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