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Soil type and tillage effects on sorption of cyanazine and degradation products
Published online by Cambridge University Press: 12 June 2017
Abstract
The hydrolytic and dealkylation products of cyanazine have been detected in soils, but the sorption of these products in soil has not been well studied. We examined sorption characteristics of five cyanazine degradation products in relation to cyanazine in Norfolk loamy sand, Tunica silty clay, and Dundee silt loam soils. Sorption was determined using a batch equilibrium method. Air-dried soil (3 g) was shaken in 6 ml of solution containing cyanazine or one of its degradation products for 48 h at 4 C. Five concentrations (2.04 to 54.67 μmol L−1) of each chemical were evaluated. The cyanazine Freundlich coefficient (Kf) ranged from 0.64 in Norfolk soil to 4.75 in Dundee no-tillage (NT) soil, and was higher in Dundee NT than in Dundee conventional-tillage (CT) soil. The Freundlich exponent (N) values for cyanazine were less than 0.85 in all soils, indicating nonlinearity of the sorption isotherm. In general, cyanazine sorption among the soils increased in the order of Norfolk << Dundee CT < Tunica < Dundee NT. Cyanazine sorption among the soils was correlated with fine texture and higher organic carbon content. Sorption of cyanazine degradation products was less than cyanazine sorption in all soils. Isotherms were nonlinear, with sorption decreasing in the order of cyanazine > desmethylpropanenitrile cyanazine > hydroxyacid cyanazine > desethyl cyanazine > cyanazine amide >> chloroacid cyanazine. The Kf for chloroacid cyanazine ranged from 0.21 in Norfolk soil to 0.42 in Dundee NT soil. Sorption patterns of five degradation products among the soils were generally similar to that of cyanazine. Our data indicate that under field conditions, cyanazine degradation products (especially cyanazine amide and chloroacid cyanazine) are more likely to remain in the aqueous phase and thus have a greater potential to move with water compared to cyanazine.
Keywords
- Type
- Soil, Air, and Water
- Information
- Copyright
- Copyright © 1997 by the Weed Science Society of America