title: Estimating hydroxyl radical photochemical formation rates in natural waters during long-term laboratory irradiation experiments.
abstract: In this study it was observed that, during long-term irradiations (>1 day) of natural waters, the methods for measuring hydroxyl radical (˙OH) formation rates based upon sequentially determined cumulative concentrations of photoproducts from probes significantly underestimate actual ˙OH formation rates. Performing a correction using the photodegradation rates of the probe products improves the ˙OH estimation for short term irradiations (<1 day), but not long term irradiations. Only the 'instantaneous' formation rates, which were obtained by adding probes to aliquots at each time point and irradiating these sub-samples for a short time (≤2 h), were found appropriate for accurately estimating ˙OH photochemical formation rates during long-term laboratory irradiation experiments. Our results also showed that in iron- and dissolved organic matter (DOM)-rich water samples, ˙OH appears to be mainly produced from the Fenton reaction initially, but subsequently from other sources possibly from DOM photoreactions. Pathways of ˙OH formation in long-term irradiations in relation to H2O2 and iron concentrations are discussed.
authors: Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA, USA. kmopper@odu.edu.
authors: Luni
authors: L
authors: Sun
authors: Hongmei
authors: H
authors: Chen
authors: Hussain A
authors: HA
authors: Abdulla
authors: Kenneth
authors: K
authors: Mopper
mesh_terms: D005618:Fresh Water / Q000737:chemistry*; D006861:Hydrogen Peroxide; D017665:Hydroxyl Radical / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008956:Models, Chemical; D055668:Photochemical Processes; D014466:Ultraviolet Rays
chemical_list: D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D007501:Iron