title: Modeling concentration-dependent sorption-desorption hysteresis of atrazine in a loam soil.
abstract: Nonequilibrium sorption plays an active role in the transport of organic contaminants in soil. We applied a two-stage, one-rate model (2S1R) and a new, nonlinear variant (2S1RN) of this model to examine the effects of wastewater irrigation on the sorption kinetics of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) in soil. The models were applied to previously published sorption-desorption data sets, which showed pronounced deviations between sorption curves and desorption curves (sorption-desorption hysteresis). Moreover, the slopes of the desorption curves decreased with decreasing concentration. Different treatments had been used, and two experimental time steps (2 and 14 d) were used. Treatments considered were lipid removal, fulvic and humic acid removal, and untreated soil. The 2S1R model was unable to reproduce the observed type of hysteresis, but the 2S1RN model, which assumes that the sorption-desorption process follows a power function relationship, was able to reproduce the observed type of hysteresis. Visually, applying the new model improved the model fits in all test cases. Statistically, as tested by an extra sum of squares analysis, the new model performed significantly better in 50% of all test cases. According to an example simulation, the choice of the sorption model has a considerable impact on the prediction of atrazine transport in soil.
authors.affiliation: Institute of Soil Science and Land Evaluation, Biogeophysics section, Univ. of Hohenheim (310), 70593 Stuttgart, Germany. ihuakuo@yahoo.com
authors.forename: Ihuaku
authors.initials: I
authors.lastname: Anagu
authors.forename: Joachim
authors.initials: J
authors.lastname: Ingwersen
authors.forename: Yaron
authors.initials: Y
authors.lastname: Drori
authors.forename: Benny
authors.initials: B
authors.lastname: Chefetz
authors.forename: Thilo
authors.initials: T
authors.lastname: Streck
mesh_terms: D000327:Adsorption; D001280:Atrazine / Q000378:metabolism*; D005618:Fresh Water; D006540:Herbicides / Q000378:metabolism*; D008962:Models, Theoretical; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000378:metabolism*; D014865:Waste Disposal, Fluid; D014872:Water Movements
chemical_list: D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D001280:Atrazine