title: Formation of Light Absorbing Soluble Secondary Organics and Insoluble Polymeric Particles from the Dark Reaction of Catechol and Guaiacol with Fe(III).
abstract: Transition metals such as iron are reactive components of environmentally relevant surfaces. Here, dark reaction of Fe(III) with catechol and guaiacol was investigated in an aqueous solution at pH 3 under experimental conditions that mimic reactions in the adsorbed phase of water. Using UV-vis spectroscopy, liquid chromatography, mass spectrometry, elemental analysis, dynamic light scattering, and electron microscopy techniques, we characterized the reactants, intermediates, and products as a function of reaction time. The reactions of Fe(III) with catechol and guaiacol produced significant changes in the optical spectra of the solutions due to the formation of light absorbing secondary organics and colloidal organic particles. The primary steps in the reaction mechanism were shown to include oxidation of catechol and guaiacol to hydroxy- and methoxy-quinones. The particles formed within a few minutes of reaction and grew to micron-size aggregates after half an hour reaction. The mass-normalized absorption coefficients of the particles were comparable to those of strongly absorbing brown carbon compounds produced by biomass burning. These results could account for new pathways that lead to atmospheric secondary organic aerosol formation and abiotic polymer formation on environmental surfaces mediated by transition metals.
authors.affiliation: †Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada.
authors.forename: Samantha
authors.initials: S
authors.lastname: Slikboer
authors.affiliation: †Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Grandy
authors.affiliation: ‡Department of Chemistry, University of California, Irvine, California 92697, United States.
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Blair
authors.affiliation: ‡Department of Chemistry, University of California, Irvine, California 92697, United States.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Nizkorodov
authors.affiliation: §University of Waterloo Mass Spectrometry Facility, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Smith
authors.affiliation: †Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada.
authors.forename: Hind A
authors.initials: HA
authors.lastname: Al-Abadleh
mesh_terms: D000327:Adsorption; D000336:Aerosols / Q000737:chemistry; D018533:Biomass; D002396:Catechols / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry; D000067493:Dynamic Light Scattering; D006139:Guaiacol / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D008027:Light; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D011108:Polymers; D011809:Quinones / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D002396:Catechols; D003102:Colloids; D011108:Polymers; D011809:Quinones; D012996:Solutions; D014867:Water; D006139:Guaiacol; D007501:Iron; C034221:catechol