Influence of transition metal complexes on atmospheric droplet acidity

Graedel, T. E.; Weschler, Charles J.; Mandich, M. L.

doi:10.1038/317240a0

Cited by 110 publications

(38 citation statements)

References 27 publications

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“…The detachment of the Fe metal center from minerals is the rate limiting step and is promoted by the surrounding ligands and/or protons in the solution (Siffert and Sulzberger 1991). In general, transition metal complexes absorb spectrum significantly in the UV region; however, the photochemistry of Fe in the ambient environment requires special emphasis because some of the Fe(III) complexes can also absorb radiation in the near UV to some portion of visible spectrum which overlaps with the incoming solar radiation (Graedel et al 1985). Figure 1 shows the photoreductive dissolution of Fe(II) from hematite at four different oxalate concentrations.…”

Section: Resultsmentioning

confidence: 99%

Efficiency of organic ligands in adsorptive dissolution and photoreductive dissolution of hematite

Mukherjee

Gao

2016

Int. J. Environ. Sci. Technol.

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Organic ligands, especially oxalate, play an important role in iron dissolution from iron-containing minerals. To study the effects of organic acid ligands on the dissolution of iron-containing minerals, the dissolution kinetics of hematite in the presence of oxalate, acetate, and formate were studied under ultraviolet radiation with varying ligand concentrations (10-3 mM). The results indicate that for adsorption dissolution, oxalate is the dominating ligand for producing soluble iron (III) from hematite; for photoreductive dissolution under ultraviolet radiation and in oxic conditions, the production of iron (II) is highly proportional to the concentrations of oxalate, whereas the effects of varying concentrations of formate and acetate are not significant. At low oxalate concentrations (10-500 lM), the photoreductive dissolution of iron (II) is substantially low, while at high oxalate concentrations (3 mM), oxalate is equally effective as formate and acetate for producing photoreduced iron (II) from hematite. Combining with field data from other works, it is likely that the ratios of oxalate to total iron need to be higher than a threshold range of *1.2-5.5 in order for oxalate to effectively produce photoreduced iron (II) from hematite. This study demonstrates that the iron (II) yield from photoreduction of hematite is significantly lower when the hematite surface is pre-coated with organic ligands versus when it is exposed to ultraviolet radiation instantaneously.

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Section: Resultsmentioning

confidence: 99%

Efficiency of organic ligands in adsorptive dissolution and photoreductive dissolution of hematite

Mukherjee

Gao

2016

Int. J. Environ. Sci. Technol.

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“…As a result of H 2 SO 4 and HNO 3 uptake and within-cloud SO 2 oxidation, which may itself be catalysed by transition metals (Graedel et al, 1985), the cloud and raindrop pH values can be extremely low. Incorporation of acids and seasalt to form internally mixed aerosols (Andreae et al, 1986) during this cloud cycling results in individual aerosol particles with hydration layers which not only are extremely acid (Zhu et al, 1992 calculate pH values to be between 0 and 1) but also have very high ionic strength (Clegg and Brimblecombe, 1990).…”

Section: 6mentioning

confidence: 99%

“…In addition, trace metals are involved in the catalysis of a number of atmospheric reactions including the oxidation of SO 2 and the production of OH radicals (Graedel et al, 1985;Martin et al, 1991;Sedlak and Hoigné, 1993) and such processes again depend on the presence of free metal ions. The complexes found are strong (with conditional stability constants from log KЈ CuL 11.4 to 12.6) and organic complexation reduces the free copper ion concentration by 3-4 orders of magnitude in rainwater .…”

Section: 8mentioning

confidence: 99%

“…Photochemical reduction is postulated to be the dominant mechanism by which this Fe II is produced, with the differing amounts reflecting varying conditions during atmospheric transport. At low pH, photochemical reduction can occur directly through [FeOH(H 2 O) 5 ] 2ϩ (Graedel et al, 1985;Faust and Hoigné, 1990;Zhuang et al, 1992;Zhu et al, 1993) and /or through photoreactive Fe III -oxalate complexes (Zuo and Hoigné, 1992;Grgic et al, 1998). Oxalate complexation extends the absorption band of Fe III into the visible (Zuo 1995) and may enhance the pH range over which Fe II can be photoproduced.…”

Section: Biogeochemical Effects Of Atmospheric Input On the Oceanmentioning

confidence: 99%

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Speciation of Metals in the Atmosphere

Spokes¹,

Jickells²

2002

Chemical Speciation in the Environment

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“…[3] The dark Fenton and related photo-Fenton (includes a photo-assisted Fe(III) to Fe(II) reduction step) and Fenton-like reactions (involving either organic peroxides or transition metals other than Fe), have been widely reported in various atmospheric systems [Graedel et al, 1985;Faust and Hoigné, 1990;Sedlak and Hoigné, 1993;Siefert et al, 1994;Chevallier et al, 2004;Deguillaume et al, 2005]. By virtue of OH radical production, Fenton and photo-Fenton reactions are well known to oxidize many organic compounds, including pesticides, phenols, polynuclear aromatic hydrocarbons, and polychlorinated biphenyls [Fukushima et al, 2000;Vione et al, 2004;Pignatello et al, 2006;Kochany and Lipczynska-Kochany, 2007].…”

Section: Introductionmentioning

confidence: 99%

Atmospheric HULIS enhance pollutant degradation by promoting the dark Fenton reaction

Moonshine¹,

Rudich²,

Katsman³

et al. 2008

Geophysical Research Letters

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[1] Humic-like substances (HULIS) in the atmosphere are ubiquitous macromolecular substances that comprise a major fraction of the organic component of atmospheric aerosols. In this study we report that HULIS extracted from collected wood burning and urban pollution atmospheric particles enhance aqueous phase oxidation of model organic contaminants (pyrene and phenol), by promoting the dark Fenton reaction under atmospherically relevant conditions. The paucity of radical sources at night makes this reaction, which is not accounted for in cloud chemistry models, potentially quite important for understanding and quantifying in-cloud degradation of organic pollutants, and for understanding Fe oxidation state speciation in atmospheric waters. Citation: Moonshine, M., Y. Rudich, S. Katsman, and E. R. Graber (2008), Atmospheric HULIS enhance pollutant degradation by promoting the dark Fenton reaction, Geophys.

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Influence of transition metal complexes on atmospheric droplet acidity

Cited by 110 publications

References 27 publications

Efficiency of organic ligands in adsorptive dissolution and photoreductive dissolution of hematite

Efficiency of organic ligands in adsorptive dissolution and photoreductive dissolution of hematite

Speciation of Metals in the Atmosphere

Atmospheric HULIS enhance pollutant degradation by promoting the dark Fenton reaction

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