Chemical Stoichiometry and Molecular Level Mechanisms as Support for Future Predictive Engineering Calculations

Gamble, Donald S.; Langford, Cooper H.; Bruccoleri, Aldo G.

doi:10.1007/1-4020-3252-8_3

Cited by 2 publications

(9 citation statements)

References 47 publications

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“…Significant effects of organic matter, clays, and pH have been reported by other authors, for sorption parameters other than θ C (15)(16)(17)(18)(19)(20)(21). As previously reported (1,5,13,14), protonated carboxyl groups in undissolved soil organic matter contribute to the labile sorption of hydrophobic molecules while carboxylate anions do not. The solution concentration of H + , as indicated by pH, does not directly influence θ C .…”

Section: Resultssupporting

confidence: 62%

“…It would not, however, be the correct equilibrium function for the calculation of thermodynamic functions or for molecular level interpretations. The differential equilibrium function K 1 defined by eq 9 is more correct for those purposes (13,14). The extent to which K 1 differs from the weighted average equilibrium function in a particular case depends on the nature of the mixture of reactants.…”

Section: Resultsmentioning

confidence: 99%

“…For soils and sediments with mixtures of surface sorption sites, the presaturation sections of the titration curves yield a law of mass action equilibrium function K j 1 . This is a weighted average equilibrium function that is measured experimentally for the whole mixture of sorption sites (13,14). Sorption equilibrium is governed by the law of mass action, as described by eq 3.…”

Section: Theorymentioning

confidence: 99%

“…Sorption equilibrium is governed by the law of mass action, as described by eq 3. The theory previously developed for cations and humic materials has been adapted here for hydrophobic molecules in immersed soils (13,14). In terms of the concentrations of dissolved chemical M S and water filled sorption sites M W as reactants, the equilibrium can be described by eq 1.…”

Section: Theorymentioning

confidence: 99%

“…Second, equilibrium as a limiting condition can be described by adapting the law of mass action to the mixture of sorption sites found in a natural soil. Versions of the theory already exist for cations in soils and soil components (13,14).…”

Section: Introductionmentioning

confidence: 99%

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

Gamble

2009

Environ. Sci. Technol.

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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.

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Section: Resultssupporting

confidence: 62%

Section: Resultsmentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Gamble

2009

Environ. Sci. Technol.

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Atrazine Sorption Kinetics In A Characterized Soil: Predictive Calculations

Gamble

2008

Environ. Sci. Technol.

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The use and risks of agricultural pesticides will continue. It is proposed here that better control and possibly some prevention of environmental and health problems should replace the arbitrary standards and post- event monitoring that are still current practice. Mathematical models have been developed for atrazine in a characterized soil from outside Ottawa, Ontario. Experimental data obtained bythe on line HPLC microextraction method were used for the development of the models. The labile sorption sites were treated as a reactant and the number of sites per gram of soil was used to define stoichiometry. This allowed a second-order kinetics integral rate law to be used for sorption from solution onto labile sorption sites, and a first order kinetics integral rate law to be used for bound residue formation. An experimental check and error analyses indicate that the type of model can be used for predictive calculations. The physical meaning of the distribution coefficient K(D) is also considered. The model suggests some practical implications for leaching through soil and for transport by storm runoff. The type of model would be best used for providing input data for fate and transport hydrology models.

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Chemical Stoichiometry and Molecular Level Mechanisms as Support for Future Predictive Engineering Calculations

Cited by 2 publications

References 47 publications

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

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

Atrazine Sorption Kinetics In A Characterized Soil: Predictive Calculations

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