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Model Interpretation of Field-Scale Herbicide Transport through Preferential Flow Paths

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

Citation:  Pp. 113-116 in Preferential Flow, Water Movement and Chemical Transport in the Environment, Proc. 2nd Int. Symp. (3-5 January 2001, Honolulu, Hawaii, USA), eds. D. D. Bosch and K. W. King. St. Joseph, Michigan: ASAE  701P0006.(doi:10.13031/2013.2112)
Authors:   E. Simic, B. Lennartz and G. Destouni
Keywords:   stochastic modeling, preferential flow, herbicides, tracer tests, bromide, isoproturon, terbuthylazine, adsorption kinetics, degradation

We analyze transport of bromide, terbuthylazine and isoproturon through 99 undisturbed soil columns representing a 1.8-ha field site in regular agricultural use. We quantify the preferential flow effects on transport of both the conservative (bromide) and the reactive (herbicides) compounds by use of a Lagrangian stochastic advective-reactive approach to modeling observed field-scale breakthrough curves. We show that the most pronounced preferential flow effects are localized in one part (about 0.66 ha) of the investigated field plot, whereas preferential flow through the remaining part (about 1.14 ha) manifests itself differently. Distinction between the areas with different preferential flow manifestations is important for relevant and reproducible quantification of preferential flow effects on non-reactive transport. The herbicide transport modeling is less sensitive to the details of the preferential flow quantification. However, the main effects of the relatively fast transport through preferential flow paths must be accounted for. This fast transport increased the total leached mass of isoproturon by 350% and the total leached mass of terbutyazine by 810% in one part (0.66 ha) of the considered field-plot, and by 100% and 130%, respectively, in the other part (1.14 ha).

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