Herbicide Sorption by Immersed Soils: Stoichiometry and the Law of Mass Action in Support of Predictive Kinetics

Abstract

The stoichiometry of labile herbicide sorption on immersed soils has been determined for a few herbicides and a number of soils (Gamble, D. S.; Khan, S. U. Atrazine in organic soil: Chemical speciation during heterogeneous catalysis. J. Agric. Food Chem. 1990, 38, 297-308; Gamble, D. S.; Ismaily, L. A. Atrazine in mineral soil: The analytical chemistry of speciation. Can. J. Chem. 1992, 70, 1590-1596; Gamble, D. S.; Khan, S. U. Atrazine in mineral soil: Chemical species and catalysed hydrolysis. Can. J. Chem. 1992, 70, 1597-1603; Gilchrist, G. F. R.; Gamble, D. S.; Khan, S. U. Atrazine interactions with clay minerals: Kinetics and equilibria of sorption. J. Agric. Food Chem. 1993, 41, 1748-1755; Gamble, D. S. Physical chemistry parameters that control pesticide persistence and leaching in watershed soils. Final report submitted to the Great Lakes Water Quality Program Committee, Guelph, Ontario, June, 1994; Li, J.; Langford, C. H.; Gamble, D. S. Atrazine sorption by a mineral soil: Processes of labile and nonlabile uptake. J. Agric. Food Chem. 1996, 44, 3672-3679; Li, J.; Langford, C. H.; Gamble, D. S. Atrazine sorption by a mineral soil: The effects of size fractions and temperature. J. Agric. Food Chem. 1996, 44, 3680-3684; Gamble, D. S. Pesticide-soil research for the behaviour of chlorothalonil and its metabolite SD-3701 in soil. Final report submitted to Ricerca Inc., Sept 15, 1998; Gamble, D. S. Atrazine sorption kinetics in a characterized soil: Predictive calculations. Environ. Sci. Technol. 2008, 42, 1537-1541). This was done by using equilibrium titrations forthe measurement of labile sorption capacities thetaC. The titrations were made possible by resolving total sorption into its labile and unrecovered fractions. But equilibrium was not also necessary for unrecovered fractions. The site saturation at titration plateaus defined thetaC. The first purpose of determining the stoichiometry is to permitthe use of second-order kinetics instead of unpredictive pseudo-first-order kinetics for sorption modeling. Another purpose is to replace empirical distribution coefficients such as K(D) with the law of mass action for describing equilibria as limiting states. Temperature trends and a comparison with EGME vapor deposition data from the literature indicate a control of herbicide sorption by sorbed water. A preliminary examination of limited data from different sources suggests that future research should investigate some additional correlations. ThetaC and equilibrium functions might both be influenced by soil organic matter carboxyls and carboxylate anions, as well as inorganic materials. Some disadvantages of K(D) are noted.

Quantitative Prediction of Atrazine Sorption in a Manitoba Soil Using Conventional Chemical Kinetics Instead of Empirical Parameters

“…This has recently been confirmed experimentally. 5,19 Since the original 1966 report by Hamaker, 13 several authors have confirmed the existence of intraparticle diffusion from surface sites into particle interiors. An HPLC method that resolves total sorption into recoverable and unrecoverable fractions has revealed labile sorption capacities.…”

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

“…The on line HPLC m extraction method for sorption-reaction kinetics in soil slurries has been previously described. 11,15,[19][20][21][23][24][25]36 It is the only experimental method available for resolving total extractable chemical into dissolved and labile sorbed fractions. Sorption-reaction experimental samples are prepared with slurries of pre-wetted soils in aqueous pesticide solutions.…”

“…The variables that are measurable in the laboratory directly support the determination of molecular level reaction mechanisms. [19][20][21][22][23] Some of the critical variables are not obtainable from field trials. 22,23 Models of such mechanisms are needed for quantitative predictions.…”

“…The predictions were successfully tested experimentally. 20,21 On line HPLC m extraction made this possible by resolving total sorption into recoverable and unrecoverable fractions of pesticides. [24][25][26] But for such practical applications as chemical input for pesticide fate and transport hydrology models, soil remediation, and regulatory practice, chemical reactions also need to be accounted for.…”

The Longitudinal Profile of a Stream Contaminated With 2,4-D and its Effects on Non-Target Species

“…While pesticide applications aim to eliminate undesirable species, this process also puts non-target organisms at risk across different environmental compartments (Turetta et al 2017;Frimpong et al 2018). Upon reaching rivers and streams, pesticides are subject to a combination of physical, chemical, and biological processes, as they can be continuously transported longitudinally downstream (Nowell et al 2010), retained in the sediments (Gamble 2009), assimilated, Isabele Baima Ferreira Freitas and Allan Pretti Ogura have equally contributed to this work.…”