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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASAE. Vol. 44(2): 251–258 . (doi: 10.13031/2013.4686) @2001
Authors:   D. Shinde, M. R. Savabi, P. Nkedi–Kizza, A. Vázquez
Keywords:   Sorption, Transport, Non–Equilibrium, Models, Water, Pesticides, Tracers

A study was carried out on water and pesticide transport in three calcareous soils (Perrine, Krome, and Chekika) of South Florida. Tritium and bromide were used as tracers for water flow and atrazine (2chloro4ethylamino6 isopropylamino1,3,5triazine) was used as a probe chemical representing neutral organic compounds. Atrazine sorption isotherms were linear for all soils, and atrazine transport through watersaturated soil columns during steady water flow exhibited chemical nonequilibrium for Perrine and Krome soils columns. Apart from nonequilibrium chemical sorption, Chekika soil columns also had an added effect of mobile and immobile water zones that induced physical non equilibrium during water movement. Simulation of leaching data revealed that the ConvectiveDispersive Equilibrium (CDE) model could describe tracer breakthrough curves (BTCs) for Perrine and Krome soils, and the Two Site NonEquilibrium (TSNE) model described atrazine BTCs. However, tracer BTCs from Chekika soil were described by the Two Region NonEquilibrium (TRNE) model. None of the nonequilibrium models could describe atrazine BTCs obtained from Chekika soil due to the presence of both physical and chemical nonequilibrium in the system.

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