title: Transport of bromide and pesticides through an undisturbed soil column: a modeling study with global optimization analysis.
abstract: The fate of pesticides in tropical soils is still not understood as well as it is for soils in temperate regions. In this study, water flow and transport of bromide tracer and five pesticides (atrazine, imazaquin, sulfometuron methyl, S-metolachlor, and imidacloprid) through an undisturbed soil column of tropical Oxisol were analyzed using a one-dimensional numerical model. The numerical model is based on Richards' equation for solving water flow, and the advection-dispersion equation for solving solute transport. Data from a laboratory column leaching experiment were used in the uncertainty analysis using a global optimization methodology to evaluate the model's sensitivity to transport parameters. All pesticides were found to be relatively mobile (sorption distribution coefficients lower than 2 cm(3) g(-1)). Experimental data indicated significant non-conservative behavior of bromide tracer. All pesticides, with the exception of imidacloprid, were found less persistent (degradation half-lives smaller than 45 days). Three of the five pesticides (atrazine, sulfometuron methyl, and S-metolachlor) were better described by the linear kinetic sorption model, while the breakthrough curves of imazaquin and imidacloprid were more appropriately approximated using nonlinear instantaneous sorption. Sensitivity analysis suggested that the model is most sensitive to sorption distribution coefficient. The prediction limits contained most of the measured points of the experimental breakthrough curves, indicating adequate model concept and model structure for the description of transport processes in the soil column under study. Uncertainty analysis using a physically-based Monte Carlo modeling of pesticide fate and transport provides useful information for the evaluation of chemical leaching in Hawaii soils.
authors.affiliation: Czech Technical University in Prague, Faculty of Civil Engineering, Prague, Czech Republic. Electronic address: dusek@mat.fsv.cvut.cz.
authors.forename: Jaromir
authors.initials: J
authors.lastname: Dusek
authors.affiliation: Czech Technical University in Prague, Faculty of Civil Engineering, Prague, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Dohnal
authors.affiliation: Czech Technical University in Prague, Faculty of Civil Engineering, Prague, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Snehota
authors.affiliation: Czech Technical University in Prague, Faculty of Civil Engineering, Prague, Czech Republic.
authors.forename: Martina
authors.initials: M
authors.lastname: Sobotkova
authors.affiliation: Civil and Environmental Engineering, Water Resources Research Center, University of Hawaii at Manoa, Honolulu, HI, USA; Nebraska Water Center, University of Nebraska, Lincoln, NE, USA.
authors.forename: Chittaranjan
authors.initials: C
authors.lastname: Ray
authors.affiliation: Czech Technical University in Prague, Faculty of Civil Engineering, Prague, Czech Republic.
authors.forename: Tomas
authors.initials: T
authors.lastname: Vogel
mesh_terms: D001965:Bromides / Q000737:chemistry*; D006254:Hawaii; D006540:Herbicides / Q000737:chemistry*; D007306:Insecticides / Q000737:chemistry*; D008962:Models, Theoretical; D012989:Soil Pollutants / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D001965:Bromides; D006540:Herbicides; D007306:Insecticides; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical
keywords: Flow interruption; Herbicides; Latin hypercube sampling; Miscible displacement experiment; Monte Carlo; Parameter sensitivity