title: Photometric hydroxyl radical scavenging analysis of standard natural organic matter isolates.
abstract: Hydroxyl radical (˙OH) scavenging reaction rate constants of standard natural organic matter (NOM) isolates (k˙OH,NOM) were measured with a rapid background scavenging method, to expand the dataset of published k˙OH,NOM values. The proposed method relies on ˙OH generation with a simple UV/H₂O₂ AOP-based system. The associated decay of a ˙OH probe compound is monitored with a field-deployable spectrophotometer and k˙OH,NOM is determined through competition kinetics. The resulting k˙OH,NOM values for the six NOM standard isolates ranged from 1.02 (±0.10) × 10(8) MC(-1) s(-1) for Suwannee River Fulvic Acid I Standard to 2.03 (±0.12) × 10(8) MC(-1) s(-1) for Pony Lake Fulvic Acid Reference NOM, which is within the range reported with more elaborate and time-consuming k˙OH,NOM methods. A slight correlation between nitrogen content and scavenging rate constant was evident while no significant correlation between k˙OH,NOM and atomic composition, carbon structure, weight-average molecular weight, UV absorbance (SUVA₂₅₄), or fluorescence index (FI) was observed. Overall, the results demonstrate that k˙OH,NOM can be rapidly assessed in NOM isolate samples. The results suggest that this type of rapid field-deployable spectrophotometric method may minimize the need for expensive and time-consuming background scavenging methods, and for models that predict k˙OH,NOM based on other NOM characteristics.
authors: University of Maryland - Department of Civil and Environmental Engineering, College Park, Maryland, USA.
authors: J E
authors: JE
authors: Donham
authors: E J
authors: EJ
authors: Rosenfeldt
authors: K R
authors: KR
authors: Wigginton
mesh_terms: D001578:Benzopyrans / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical
chemical_list: D001578:Benzopyrans; D016166:Free Radical Scavengers; D017665:Hydroxyl Radical; C005023:fulvic acid