The Formation and Transformation of Atmospheric Soluble Iron

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Quality".

Deadline for manuscript submissions: closed (1 November 2020) | Viewed by 14632

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Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, USA
Interests: dust; PAH; iron; air pollution; atmospheric chemistry
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Dear Colleagues,

Iron is the most abundant transition element in the atmosphere, existing as multiple oxidation states and acting as a catalyst for red-ox reactions. Therefore, iron is associated with the production of reactive oxygen species both in environmental and biological systems and plays an important role in many geochemical cycles, including that of carbon and sulfur. With iron solubility largely controlled by its oxidation state and its chemical reactivity largely controlled by solubility, the theme of this Special Issue focuses on how iron speciation, oxidation state, and atmospheric transformations affect iron solubility and reactivity. As iron solubility is key to atmosperic iron’s chemistry, this Special Issue focuses on understanding the origins of atmospheric iron solubility, both from the standpoint of emission sources and transformations during atmospheric transport. Although not restricted to these issues, topics related to the following are of interest:

  • Iron speciation, oxidation state, and solubility measurements in both ambient atmospheres and from specific sources;
  • Laboratory experiments modeling iron behavior and chemistry under relevant atmospheric conditions;
  • Atmospherically relevant chemical reactions between iron and organic compounds.

By bringing these topics together, we hope to integrate the current state of knowledge of both iron emissions and iron transformations, painting a more complete picture of how iron contributes to atmospheric chemistry.

Dr. Brian Majestic
Guest Editor

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Keywords

  • Iron
  • Photochemistry
  • Iron–organic interactions
  • Cloud chemistry
  • Solubility
  • Iron sources

Published Papers (4 papers)

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Research

14 pages, 478 KiB  
Article
Iron Speciation in Different Saharan Dust Advections and Effect of the Procedural Blank on the Results From X-ray Absorption Spectroscopy and Selective Leaching Experiments
by Chiara Petroselli, Beatrice Moroni, Stefano Crocchianti, Roberta Selvaggi, Francesco Soggia, Marco Grotti, Francesco d’Acapito and David Cappelletti
Atmosphere 2020, 11(7), 735; https://doi.org/10.3390/atmos11070735 - 10 Jul 2020
Cited by 1 | Viewed by 2050
Abstract
In this work, we applied X-ray Absorption Spectroscopy (XAS) and selective leaching experiments for investigating iron speciation in different dust advections collected on different unwashed quartz fiber filters. XAS analysis evidenced a predominance of Fe(III) in 6-fold coordination for Saharan dust and a [...] Read more.
In this work, we applied X-ray Absorption Spectroscopy (XAS) and selective leaching experiments for investigating iron speciation in different dust advections collected on different unwashed quartz fiber filters. XAS analysis evidenced a predominance of Fe(III) in 6-fold coordination for Saharan dust and a trend towards Fe(II) and 4-fold coordination in the order: Saharan dust, mixed Saharan, and non-Saharan aerosol samples. The role of the sampling substrate was evaluated explicitly, including in the analysis a set of blank filters. We were able to pinpoint the possible contribution to the overall XAS spectrum of the residual Fe on quartz as the concentration decrease towards the blank value. In particular, the filter substrate showed a negligible effect on the structural trend mentioned above. Furthermore, selective leaching experiments evidenced a predominance of the residual fraction on Fe speciation and indicated the lowest Fe concentrations for which the blank contribution is <20% are 1 μ g for the first three steps of the procedure (releasing the acid-labile, reducible and oxidizable phases, respectively) and 10 μ g for the last step (dissolving the insoluble residuals). Full article
(This article belongs to the Special Issue The Formation and Transformation of Atmospheric Soluble Iron)
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12 pages, 2559 KiB  
Article
Mineral Dust and Iron Solubility: Effects of Composition, Particle Size, and Surface Area
by Aurelie R. Marcotte, Ariel D. Anbar, Brian J. Majestic and Pierre Herckes
Atmosphere 2020, 11(5), 533; https://doi.org/10.3390/atmos11050533 - 21 May 2020
Cited by 26 | Viewed by 4403
Abstract
There is significant iron deposition in the oceans, approximately 14–16 Tg annually from mineral dust aerosols, but only a small percentage (approx. 3%) of it is soluble and, thus, bioavailable. In this work, we examine the effect of mineralogy, particle size, and surface [...] Read more.
There is significant iron deposition in the oceans, approximately 14–16 Tg annually from mineral dust aerosols, but only a small percentage (approx. 3%) of it is soluble and, thus, bioavailable. In this work, we examine the effect of mineralogy, particle size, and surface area on iron solubility in pure mineral phases to simulate atmospheric processing of mineral dust aerosols during transport. Pure iron-bearing minerals common to Saharan dust were partitioned into four size fractions (10–2.5, 2.5–1, 1–0.5, and 0.5–0.25 µm) and extracted into moderately acidic (pH 4.3) and acidic (pH 1.7) leaching media to simulate mineral processing during atmospheric transport. Results show that, in general, pure iron-bearing clay materials present an iron solubility (% dissolved Fe/total Fe in the mineral) an order of magnitude higher than pure iron oxide minerals. The relative solubility of iron in clay particles does not depend on particle size for the ranges examined (0.25–10 μm), while iron in hematite and magnetite shows a trend of increasing solubility with decreasing particle size in the acidic leaching medium. Our results indicate that while mineralogy and aerosol pH have an effect on the solubilization of iron from simulated mineral dust particles, surface processes of the aerosol might also have a role in iron solubilization during transport. The surface area of clay minerals does not change significantly as a function of particle size (10–0.25 µm), while the surface area of iron oxides is strongly size dependent. Overall, these results show how mineralogy and particle size can influence iron solubility in atmospheric dust. Full article
(This article belongs to the Special Issue The Formation and Transformation of Atmospheric Soluble Iron)
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27 pages, 5481 KiB  
Article
Atmospheric Trace Metal Deposition from Natural and Anthropogenic Sources in Western Australia
by Michal Strzelec, Bernadette C. Proemse, Leon A. Barmuta, Melanie Gault-Ringold, Maximilien Desservettaz, Philip W. Boyd, Morgane M. G. Perron, Robyn Schofield and Andrew R. Bowie
Atmosphere 2020, 11(5), 474; https://doi.org/10.3390/atmos11050474 - 07 May 2020
Cited by 10 | Viewed by 3536
Abstract
Aerosols from Western Australia supply micronutrient trace elements including Fe into the western shelf of Australia and further afield into the Southern and Indian Oceans. However, regional observations of atmospheric trace metal deposition are limited. Here, we applied a series of leaching experiments [...] Read more.
Aerosols from Western Australia supply micronutrient trace elements including Fe into the western shelf of Australia and further afield into the Southern and Indian Oceans. However, regional observations of atmospheric trace metal deposition are limited. Here, we applied a series of leaching experiments followed by total analysis of bulk aerosol samples to a unique time-series of aerosol samples collected in Western Australia to determine atmospheric concentrations and solubilities of Fe and V, Mn, Co, Zn, and Pb. Positive matrix factorisation analysis indicated that mineral dust, biomass burning particulates, sea salt, and industrial emissions were the major types of aerosols. Overall, natural sources dominated Fe deposition. Higher atmospheric concentrations of mineral dust (sixfold) and biomass burning emissions were observed in warmer compared to cooler months. The fraction of labile Fe (0.6–6.0%) was lower than that reported for other regions of Australia. Bushfire emissions are a temporary source of labile Fe and may cause a peak in the delivery of its more easily available forms to the ocean. Increased labile Fe deposition may result in higher ocean productivity in regions where Fe is limiting, and the effect of aerosol deposition on ocean productivity in this region requires further study. Full article
(This article belongs to the Special Issue The Formation and Transformation of Atmospheric Soluble Iron)
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24 pages, 6809 KiB  
Article
Atmospheric Trace Metal Deposition near the Great Barrier Reef, Australia
by Michal Strzelec, Bernadette C. Proemse, Melanie Gault-Ringold, Philip W. Boyd, Morgane M. G. Perron, Robyn Schofield, Robert G. Ryan, Zoran D. Ristovski, Joel Alroe, Ruhi S. Humphries, Melita D. Keywood, Jason Ward and Andrew R. Bowie
Atmosphere 2020, 11(4), 390; https://doi.org/10.3390/atmos11040390 - 15 Apr 2020
Cited by 12 | Viewed by 4030
Abstract
Aerosols deposited into the Great Barrier Reef (GBR) contain iron (Fe) and other trace metals, which may act as micronutrients or as toxins to this sensitive marine ecosystem. In this paper, we quantified the atmospheric deposition of Fe and investigated aerosol sources in [...] Read more.
Aerosols deposited into the Great Barrier Reef (GBR) contain iron (Fe) and other trace metals, which may act as micronutrients or as toxins to this sensitive marine ecosystem. In this paper, we quantified the atmospheric deposition of Fe and investigated aerosol sources in Mission Beach (Queensland) next to the GBR. Leaching experiments were applied to distinguish pools of Fe with regard to its solubility. The labile Fe concentration in aerosols was 2.3–10.6 ng m−3, which is equivalent to 4.9%–11.4% of total Fe and was linked to combustion and biomass burning processes, while total Fe was dominated by crustal sources. A one-day precipitation event provided more soluble iron than the average dry deposition flux, 0.165 and 0.143 μmol m−2 day−1, respectively. Scanning Electron Microscopy indicated that alumina-silicates were the main carriers of total Fe and samples affected by combustion emissions were accompanied by regular round-shaped carbonaceous particulates. Collected aerosols contained significant amounts of Cd, Co, Cu, Mo, Mn, Pb, V, and Zn, which were mostly (47.5%–96.7%) in the labile form. In this study, we provide the first field data on the atmospheric delivery of Fe and other trace metals to the GBR and propose that this is an important delivery mechanism to this region. Full article
(This article belongs to the Special Issue The Formation and Transformation of Atmospheric Soluble Iron)
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