Iron Redox Cycling in Surface Waters:  Effects of Humic Substances and Light

Voelker, Bettina M.; Morel, François M. M.; Sulzberger, Barbara

doi:10.1021/es9604018

Cited by 374 publications

(335 citation statements)

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“…The mechanism proposed for the oxidation of Fe II in seawater by King et al (1995) has been widely accepted for studies of iron speciation and redox cycling in natural systems (Emmenegger et al, 1998;King, 1998;King and Farlow, 2000;Rose and Waite, 2002;Voelker et al, 1997).…”

Section: Redox Cycling Of Iron In Seawatermentioning

confidence: 99%

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

et al. 2005

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Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. concentrations increased at the depth of the chlorophyll maximum when iron concentrations returned to pre-infusion concentrations (b80 pM) possibly due to biological production related to iron reductase activity.In this work, Fe(II) and dissolved iron were used as tracers themselves for subsequent iron infusions when no further SF 6 was added. EisenEx was subject to periods of weak and strong mixing. Slow mixing after the second infusion allowed significant concentrations of Fe(II) and Fe to exist for several days. During this time, dissolved and total iron in the infusion plume behaved almost conservatively as it was trapped between a relict mixed layer and a new rain-induced mixed layer. Using dissolved iron, a value for the vertical diffusion coefficient K z =6.7F0.7 cm 2 s À1 was obtained for this 2-day period. During a subsequent surface survey of the iron-enriched patch, elevated levels of Fe(II) were found in surface waters presumably from Fe(II) dissolved in the rainwater that was falling at this time.Model results suggest that the reaction between uncomplexed Fe(III) and O 2 À was a significant source of Fe(II) during EisenEx and helped to maintain high levels of Fe(II) in the water column. This phenomenon may occur in iron enrichment experiments when two conditions are met: (i) When Fe is added to a system already saturated with regard to organic complexation and (ii) when mixing processes are slow, thereby reducing the dispersion of iron into under-saturated waters. D

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Section: Redox Cycling Of Iron In Seawatermentioning

confidence: 99%

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

et al. 2005

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“…Therefore, in irradiated systems, the enhanced Fe(II) production in nanorods can also be a result of the (021) surface planes with higher density of surface O-H groups. Recent field and laboratory studies have shown that, in marine surface waters and in acidic surface waters, light-induced reduction of Fe(III) to Fe(II) is a key process and serves to increase the solubility of marine aerosol Fe (22,23). As such, any processes that enhance production of soluble Fe(II) are important and increase total iron dissolution.…”

mentioning

confidence: 99%

Simulated atmospheric processing of iron oxyhydroxide minerals at low pH: Roles of particle size and acid anion in iron dissolution

Rubasinghege¹,

Lentz²,

Scherer

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

121

146

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A number of recent studies have shown that iron dissolution in Fe-containing dust aerosol can be linked to source material (mineral or anthropogenic), mineralogy, and iron speciation. All of these factors need to be incorporated into atmospheric chemistry models if these models are to accurately predict the impact of Fe-containing dusts into open ocean waters. In this report, we combine dissolution measurements along with spectroscopy and microscopy to focus on nanoscale size effects in the dissolution of Fe-containing minerals in low-pH environments and the importance of acid type, including HNO 3 , H 2 SO 4 , and HCl, on dissolution. All of these acids are present in the atmosphere, and dust particles have been shown to be associated with nitrate, sulfate, and/or chloride. These measurements are done under light and dark conditions so as to simulate and distinguish between daytime and nighttime atmospheric chemical processing. Both size (nano-versus micron-sized particles) and anion (nitrate, sulfate, and chloride) are found to play significant roles in the dissolution of α-FeOOH under both light and dark conditions. The current study highlights these important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol.mineral dust aerosol | iron-containing dust | nanoscale iron oxides | acid dissolution | photoinduced dissolution

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“…This leads to an increased • OH-radicai production [15,45]. The experiments [46,47] to Fenton/Photo-Fenton reactions. Fig.…”

Section: Basic Considerations On Photo-fenton Mediated Reactions Actimentioning

confidence: 97%

Accelerated methylene blue (MB) degradation by Fenton reagent exposed to UV or VUV/UV light in an innovative micro photo-reactor

Qiang

Pulgarín

et al. 2016

Applied Catalysis B: Environmental

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a b s t r a c tThis study presents the accelerated discoloration/degradation of methylene blue (MB) in solution by Fenton reagent under exposure to ultraviolet (UV) or Vacuum-UV/UV (VUV/UV) light in an innovative micro photo-reactor. The MB degradation was kinetically faster when using VUV/UV light at 254/185 nm compared to UV-irradiation at 254 nm. Oxidative radicals produced by the photo-Fenton process were identified with appropriate scavengers. The addition of benzoquinone (BQ) at millimolar (mM) concentrations to MB solutions precluded completely the MB photo-induced bleaching, while tert-butanol hindered to a lesser extent the MB degradation suggesting that HO 2 • was the predominant intermediate leading to MB degradation. The VUV/UV micro photo-reactor comprised mercury resonance lines at 185 and 254 nm. The photon percentages absorbed by water were estimated to be 16.8% at 254 nm and 78.3% at 185 nm by water, while those absorbed by H 2 O 2 were 0.9% and 2.2%, correspondingly. The solution parameters affecting the features of MB degradation, such as MB, Fe, and H 2 O 2 concentrations, were explored and reaction mechanism was proposed. The lifetimes of • OH and HO 2 • were estimated to be 2 ns and 0.38 s under an optimized solution with 0.016 mM MB, 0.147 mM H 2 O 2 and 0.05 mM Fe 3+ . Moreover, an estimation of the mean free paths of these radicals in solution provided the evidence that it was the radical lifetimes and mean-free paths, not their oxidation potentials that controlled the MB degradation kinetics. This study shows the potential of this VUV/UV assistant photo-Fenton process for the degradation of diluted organic compounds in aqueous solution.

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Iron Redox Cycling in Surface Waters: Effects of Humic Substances and Light

Cited by 374 publications

References 100 publications

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

Simulated atmospheric processing of iron oxyhydroxide minerals at low pH: Roles of particle size and acid anion in iron dissolution

Accelerated methylene blue (MB) degradation by Fenton reagent exposed to UV or VUV/UV light in an innovative micro photo-reactor

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