Measurements of superoxide radical concentration and decay kinetics in the Gulf of Alaska

Hansard, S. Paul; Vermilyea, A.; Voelker, Bettina M.

doi:10.1016/j.dsr.2010.05.007

Cited by 71 publications

(146 citation statements)

References 44 publications

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“…Pseudo first order decay constants determined here are in excellent agreement with k pseudo values previously obtained in studies using additional precautions to collect trace metal clean samples in the Gulf of Alaska (2-16 × 10 − 3 s − 1 ; Hansard et al, 2010), providing support that metal contamination was not a significant issue in our experiments. Otherwise, k pseudo values determined here are at the lower end of k pseudo values determined from superoxide additions in the Eastern Pacific (18.9-27.6 × 10 − 3 s − 1 ; Rusak et al, 2011), the Southern Ocean (4-74 × 10 −3 s −1 ; Heller and Croot, 2010a), and DTPA amended seawater from the equatorial Atlantic, which solely reflects the CDOM sink (9-34 × 10 −3 s −1 , Heller and Croot, 2010b).…”

Section: Measured a [Osupporting

confidence: 83%

“…Otherwise, we are not aware of any [O 2 − ] ss data in the literature that adequately reflects the photochemical source for superoxide. Hansard et al (2010) measured superoxide concentrations in surface waters of the Gulf of Alaska ranging from 140-540 pM but, as the authors note, the 2-3 min transit time required for the sample to reach the flow cell and react with MCLA greatly underestimates the contribution of photochemical O 2 − production. Based on these reports, and because the irradiance spectra measured under our solar simulator is somewhat higher than natural sunlight in our study region (Fig.…”

Section: Measured a [Omentioning

confidence: 96%

“…Lat those measured in the field (Hansard et al, 2010;Rose et al, 2008b;Shaked et al, 2010). This likely reflects both the short transit time for the sample to reach our detector and the higher and constant photon flux under simulated sunlight relative to natural sunlight with variable cloud cover (Fig.…”

Section: Stationmentioning

confidence: 96%

“…Because SOD can interfere with MCLA autooxidation (i.e. the MCLA − CL reaction with oxygen; Fujimori et al, 1993;Hansard et al, 2010), and lower the FeLume signal below the baseline, pre-irradiation baselines were always subtracted from O 2 − photoproduction data, never those containing SOD.…”

Section: Superoxide Analysismentioning

confidence: 99%

“…A number of studies using chemiluminescent methods have investigated the dominant superoxide decay pathways in seawater Croot, 2010a, 2010b;Voelker et al, 2000;Wuttig et al, 2013). An interesting observation resulting from these recent superoxide studies is evidence for a widespread particle associated source of superoxide (Diaz et ] ss measurements have been made well after samples are removed from UV radiation and do not fully reflect the photochemical source (Hansard et al, 2010;Rose et al, 2008b). Despite the recognition that DOM photolysis in natural waters will produce O 2 − at significant rates (Micinski et al, 1993;Petasne and Zika, 1987;Zafiriou et al, 1990) direct O 2 − photoproduction rates in marine environments are rare.…”

Section: Introductionmentioning

confidence: 96%

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Probing the photochemical reactivity of deep ocean refractory carbon (DORC): Lessons from hydrogen peroxide and superoxide kinetics

et al. 2015

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Most marine DOC is thought to be biologically-recalcitrant, especially that in the deep ocean pool (N 1000 m). In particular, the deep waters of the North Pacific should contain the most recalcitrant DOC because they do not form locally, with deep DOC having survived long isolation from the surface during global-scale thermohaline circulation. One of the proposed removal pathways involves photochemical reactions when refractory DOC circulates through sunlit surface waters (Mopper et al., 1991). Here, we reevaluate the general photoreactivity of refractory DOC by investigating the photochemical production of two reactive oxygen species (ROS), hydrogen peroxide (H 2 O 2 ) and superoxide (O 2 − ), using controlled irradiations at sea and in the laboratory. The photoproduction of these two ROS were compared between deep and surface water samples collected in the Gulf of Alaska. For irradiated samples, initial superoxide steady-state concentrations ([O 2 − ] ss ) and first-order decay constants (k pseudo ) were similar between surface and deep waters, ranging from~1-4 nM and 4-12 × 10 −3 s −1 , respectively. Initial photoproduction rates were comparable between surface and deep waters, ranging from-173 nM h −1 for O 2 − and from 1-8.3 nM h −1 for H 2 O 2 , indicating that a large portion of photoproduced O 2 − does not lead to H 2 O 2 formation. In fact, the photoproduction ratio of O 2 − to H 2 O 2 averaged 4:1 in paired experiments, instead of the 2:1 stoichiometry expected for O 2 − dismutation to form H 2 O 2 . Continued irradiation for up to 48 h showed photoproduced H 2 O 2 to be much lower in deep samples compared to surface samples with accumulation slowing or stopping in deep samples despite both measurable [O 2 −] ss and photon absorbance by colored dissolved organic matter (CDOM). These results are consistent with a loss of source material (i.e. CDOM) for O 2 − photoproduction and a shift to a predominantly oxidative pathway for O 2 − decay. Low photoproduction rates, loss of continued accumulation with extended radiation, and an apparent loss of O 2 − source material argues that the deep refractory DOC pool is less photochemically reactive than previously suggested.

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Section: Measured a [Osupporting

confidence: 83%

Section: Measured a [Omentioning

confidence: 96%

Section: Stationmentioning

confidence: 96%

Section: Superoxide Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Probing the photochemical reactivity of deep ocean refractory carbon (DORC): Lessons from hydrogen peroxide and superoxide kinetics

et al. 2015

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Dynamics of hydrogen peroxide in a coral reef: Sources and sinks

Shaked

Armoza-Zvuloni

2013

JGR Biogeosciences

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[1] The dynamics of hydrogen peroxide (H 2 O 2 ) was studied in the fringing coral reef off the coast of Eilat, Red Sea. Diurnal changes in H 2 O 2 concentrations in the reef lagoon were typical of photochemically produced species. During the daytime H 2 O 2 accumulated in the lagoon at low tide and exceeded open water concentrations by 100-250 nM. Elevated H 2 O 2 decay kinetics (termed hereafter antioxidant activity) were also recorded in the lagoon at low tide. The observed antioxidant activities were high enough to moderate H 2 O 2 accumulation in the lagoon. In pursuit of the antioxidant source, the ability of corals to release antioxidant activity to their surrounding water was examined in both natural and laboratory settings. Water collected in situ from surfaces of individual corals and next to a coral knoll contained high antioxidant activity. Incubation experiments revealed that many Red Sea corals release antioxidant activity to their external milieu. Besides serving a potential antioxidant source to the reef system, the antioxidant activity detected on coral surfaces enabled corals to lower H 2 O 2 concentrations in their vicinity. The ability of corals to offset exogenous H 2 O 2 was validated in incubations with Stylophora pistillata in the absence of mixing. Conversely, corals subjected to mixing in a beaker were found to release H 2 O 2 , implying that corals may act as both a sink and a source for H 2 O 2 in the reef. This newly described ability of corals to change H 2 O 2 dynamics by releasing both H 2 O 2 and antioxidants may bare important implications for coral physiology and interactions with the environment.

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Hydrogen peroxide and superoxide photoproduction in diverse marine waters: A simple proxy for estimating direct CO₂ photochemical fluxes

Powers

Miller

2015

Geophysical Research Letters

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The photoproduction of H 2 O 2 and CO 2 exhibits a well-defined relationship with an average CO 2 : H 2 O 2 molar ratio of 6.6 ± 1.8 as determined in a variety of marine waters ranging from a dark tidal creek to clear offshore stations near the Gulf Stream. Even when corrected for photobleaching, accumulation of both H 2 O 2 and CO 2 was not linear beyond 12 h of constant irradiation, with interval rates indicating that production efficiency for both products decreased with increasing photon dose. Direct measurements of O 2 À photoproduction, together with its dark thermal decay to H 2 O 2 , indicate that O 2 À may be the better proxy for photochemical dissolved organic matter oxidation to CO 2. Given the very short irradiation times needed to determine O 2 À production rates (~2-5 min), determination of O 2 À photoproduction may provide robust estimates for initial CO 2 photoproduction rates even in blue water, allowing greatly improved estimates for the global significance of dissolved organic carbon photooxidation.

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Measurements of superoxide radical concentration and decay kinetics in the Gulf of Alaska

Cited by 71 publications

References 44 publications

Probing the photochemical reactivity of deep ocean refractory carbon (DORC): Lessons from hydrogen peroxide and superoxide kinetics

Probing the photochemical reactivity of deep ocean refractory carbon (DORC): Lessons from hydrogen peroxide and superoxide kinetics

Dynamics of hydrogen peroxide in a coral reef: Sources and sinks

Hydrogen peroxide and superoxide photoproduction in diverse marine waters: A simple proxy for estimating direct CO₂ photochemical fluxes

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Measurements of superoxide radical concentration and decay kinetics in the Gulf of Alaska

Cited by 71 publications

References 44 publications

Probing the photochemical reactivity of deep ocean refractory carbon (DORC): Lessons from hydrogen peroxide and superoxide kinetics

Probing the photochemical reactivity of deep ocean refractory carbon (DORC): Lessons from hydrogen peroxide and superoxide kinetics

Dynamics of hydrogen peroxide in a coral reef: Sources and sinks

Hydrogen peroxide and superoxide photoproduction in diverse marine waters: A simple proxy for estimating direct CO2 photochemical fluxes

Contact Info

Product

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Hydrogen peroxide and superoxide photoproduction in diverse marine waters: A simple proxy for estimating direct CO₂ photochemical fluxes