Electron Pulse Radiolysis Determination of Hydroxyl Radical Rate Constants with Suwannee River Fulvic Acid and Other Dissolved Organic Matter Isolates

Department of Civil and Environmental Engineering, Arizona State University, Box 5306, Tempe, Arizona 85287-5306, USA.
Environmental Science and Technology (Impact Factor: 5.33). 08/2007; 41(13):4640-6. DOI: 10.1021/es062529n
Source: PubMed


Pulse radiolysis experiments were conducted on dissolved organic matter (DOM) samples isolated as hydrophobic and hydrophilic acids and neutrals from different sources (i.e., stream, lake, wastewater treatment plant). Absolute bimolecular reaction rate constants for the reaction of hydroxyl radicals (*OH) with DOM (k*(OH), DOM) were determined. k*(OH, DOM) values are expressed as moles of carbon. Based on direct measurement of transient DOM radicals (DOM*) and competition kinetic techniques, both using pulse radiolysis, the k*(OH, DOM) value for a standard fulvic acid from the Suwannee River purchased from the International Humic Substances Society was (1.60 +/- 0.24) x 10(8) M(-1) s(-1). Both pulse radiolysis methods yielded comparable k*(OH, DOM) values. The k*(OH, DOM) values for the seven DOM isolates from different sources ranged from 1.39 x 10(8) M(-1) s(-1) to 4.53 x 10(8) M(-1) s(-1), and averaged 2.23 x 108 M(-1) s(-1) (equivalent to 1.9 x 10(4) (mgC/L)(-1) s(-1)). These values represent the first direct measurements of k*(OH, DOM,) and they compare well with literature values obtained via competition kinetic techniques during ozone or ultraviolet irradiation experiments. More polar, lower-molecular-weight DOM isolates from wastewater have higher k*(OH, DOM) values. In addition, the formation (microsecond time scale) and decay (millisecond time scale) of DOM* transients were observed for the first time. DOM* from hydrophobic acids exhibited broader absorbance spectra than transphilic acids, while wastewater DOM isolates had narrower DOM* spectra more skewed toward shorter wavelengths than did DOM* spectra for hydrophobic acids.

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    • "Dissolved organic matter (DOM) is defined as the organic materials below 0.45 μm or 0.22 μm. In the aquatic environment, DOM has a significant effect on the biogeochemical processes, particle stability and transport, metal complexation in the aquatic systems [1] [2]. Therefore, it is often utilized as a control parameter in design of the water treatment process as well as others such as water treatment efficiency and the formation of disinfection byproducts (DBPs) [3] [4]. "
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    Desalination 08/2014; 346:38–45. DOI:10.1016/j.desal.2014.04.031 · 3.76 Impact Factor
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    • ". Limited information is available on the reaction rate constant of natural organic matter (NOM) with SO 4 @BULLET− . However, its reactivity is expected to be at least one order of magnitude lower than k HO • /NOM [24] [25]. Besides, under UV-254 nm irradiation, S 2 O 8 2− has a much higher radical quantum yield than H 2 O 2 , as shown in Eqs. "
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    • ">6 Â 10 6 versus 2 . 23 Â 10 8 L ( mol C ) À1 s À1 ) ( Gara et al . , 2009 ; Westerhoff et al . , 2007"
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