Propanil in a Manitoba soil: an interactive spreadsheet model based on conventional chemical kinetics

Abstract

An interactive spreadsheet model has been created for quantitative predictions of propanil sorption and reaction in a slurried Manitoba clay soil. Based on experimental values for the numbers of empty and filled sorption sites as reactants and products, the reaction mechanism has been described with conventional chemical kinetics. The on line HPLC μ extraction method revealed labile sorption, intraparticle diffusion, and a chemical reaction. Laidler's integral rate law for second order kinetics describes the labile sorption. Desorption, intraparticle diffusion, and the chemical reaction are all described by first order kinetics. The time dependent effects of initial concentration and amount of slurried soil can be predicted for sorption, intraparticle diffusion, and the amount of reaction product. Suggested applications include storm runoff and inputs for fate and transport hydrology models.

The Physical Chemistry of Pesticides in Soil and Water

“…Proof of concept has been published for the experimentally supported theory that reveals the kinetics and mechanisms of pesticides in soil and water [1][2][3][4][5][6][7][8][9]. For a soil immersed in a pesticide solution, the starting point was the answer to a critical question.…”

“…Costs could be reduced. Secondly, the number of labile sorption sites has to be measured for kinetics calculations [1,2]. Experimental time-dependent kinetic rate coefficients are necessary for predictions [1][2][3][4].…”

A Quantitative LC-MS/MS Study of the Partitioning, Transport, and Fate of Pesticide Residues on Soil

“…These mod-els predict the uptake rates and sorption capacities of select pesticides on characterized soils, using the experimentally determined fundamental rate coefficients. Descriptions and testing have been published for three of them [3]- [6]. These ab initio calculations based on rate coefficients from first principles are much more accurate for prediction and extrapolation than more empirically based distribution coefficients, in which the fundamental chemistry can be obscured.…”

“…From an environmental perspective, these decomposition products can be either more or less benign than the parent compounds. Experimental techniques exist which can resolve these fractions [2]. Sorption site stoichiometry can be revealed by titrating the analyte onto the labile sorption sites.…”

“…Models which use fundamental kinetic rate coefficients to accurately predict the rate of uptake of specific pesticides, and their total sorption capacities, on recognized soils already exist and are well documented [1] [2]. They are based on the fundamental premise that sorption-desorption is a labile process that can be written as a reaction between the analyte M (e.g.…”