title: Predicting Reactive Intermediate Quantum Yields from Dissolved Organic Matter Photolysis Using Optical Properties and Antioxidant Capacity.
abstract: The antioxidant capacity and formation of photochemically produced reactive intermediates (RI) was studied for water samples collected from the Florida Everglades with different spatial (marsh versus estuarine) and temporal (wet versus dry season) characteristics. Measured RI included triplet excited states of dissolved organic matter (3DOM*), singlet oxygen (1O2), and the hydroxyl radical (•OH). Single and multiple linear regression modeling were performed using a broad range of extrinsic (to predict RI formation rates, RRI) and intrinsic (to predict RI quantum yields, ΦRI) parameters. Multiple linear regression models consistently led to better predictions of RRIand ΦRIfor our data set but poor prediction of ΦRIfor a previously published data set,1 probably because the predictors are intercorrelated (Pearson's r > 0.5). Single linear regression models were built with data compiled from previously published studies (n ≈ 120) in which E2:E3, S, and ΦRIvalues were measured, which revealed a high degree of similarity between RI-optical property relationships across DOM samples of diverse sources. This study reveals that•OH formation is, in general, decoupled from3DOM* and1O2formation, providing supporting evidence that3DOM* is not a•OH precursor. Finally, ΦRIfor1O2and3DOM* correlated negatively with antioxidant activity (a surrogate for electron donating capacity) for the collected samples, which is consistent with intramolecular oxidation of DOM moieties by3DOM*.
authors.affiliation: Department of Environmental Engineering, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Garrett
authors.initials: G
authors.lastname: Mckay
authors.forename: Wenxi
authors.initials: W
authors.lastname: Huang
authors.forename: Cristina
authors.initials: C
authors.lastname: Romera-Castillo
authors.affiliation: Department of Environmental Engineering, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Jenna E
authors.initials: JE
authors.lastname: Crouch
authors.affiliation: Department of Environmental Engineering, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Fernando L
authors.identifier: http://orcid.org/0000-0002-3311-9089
authors.initials: FL
authors.lastname: Rosario-Ortiz
authors.forename: Rudolf
authors.identifier: http://orcid.org/0000-0001-6153-248X
authors.initials: R
authors.lastname: Jaffé
mesh_terms: D005431:Florida; D017665:Hydroxyl Radical; D009930:Organic Chemicals; D010084:Oxidation-Reduction; D010782:Photolysis; D026082:Singlet Oxygen; D053833:Wetlands
chemical_list: D009930:Organic Chemicals; D026082:Singlet Oxygen; D017665:Hydroxyl Radical