Bioavailable iron production in airborne mineral dust: Controls by chemical composition and solar flux

Eshani Hettiarachchi; Richard L. Reynolds; Harland L. Goldstein; Bruce Moskowitz; Gayan Rubasinghege

doi:10.1016/j.atmosenv.2019.02.037

Bioavailable iron production in airborne mineral dust: Controls by chemical composition and solar flux

Eshani Hettiarachchi, Richard L. Reynolds, Harland L. Goldstein, Bruce Moskowitz, Gayan Rubasinghege

Earth and Environmental Sciences-Twin Cities

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

A large part of oceanic biological production is limited by the scarcity of dissolved iron. Mineral dust aerosol, processed under acidic atmospheric conditions, is the primary natural source of bioavailable iron to oceanic life. However, synergistic and antagonistic effects of non-Fe-containing minerals on atmospheric processing of Fe-containing minerals and Fe solubilization are poorly understood. The current study focuses on mineralogical influences of non-Fe-bearing semiconductor minerals, such as titanium dioxide (TiO₂), on the dissolution of iron in selected natural mineral dust aerosols under atmospherically relevant conditions. Further, the role of elevated Ti concentrations in dust is evaluated using magnetite, a proxy for Fe(II) containing minerals, under both dark and light conditions. Our results highlight that relatively higher Ti:Fe ratios, regardless of their total Fe content, enhances the total iron dissolution in mineral dust aerosols as well as in magnetite. Moreover, elevated Ti percentages also yield high Fe(II) fractions in mineral dust systems under dark conditions. Upon irradiation however, dissolved Fe(II) is suppressed by high Ti levels due to the involvement of photochemical redox cycling reactions with hydroxyl radicals (^•OH). These synergistic and antagonistic effects of Ti are further evaluated by altering the chemical composition of natural dusts with artificially added anatase (TiO₂) and synthetic amorphous titania. The current study reveals important mineralogical controls by non-Fe-bearing minerals on dust iron dissolution to better understand global iron mobilization.

Original language	English (US)
Pages (from-to)	90-102
Number of pages	13
Journal	Atmospheric Environment
Volume	205
DOIs	https://doi.org/10.1016/j.atmosenv.2019.02.037
State	Published - May 15 2019

Bibliographical note

Funding Information:
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors thank the Department of Chemistry, New Mexico Institute of Mining and Technology. The Institute for Rock Magnetism (IRM) is supported by the Instruments and Facilities Program of the NSF Division of Earth Science . This is IRM contribution 1803.

Funding Information:
The authors are grateful to Paolo D'Odorico and Abi Bhattachan for providing the Kalahari sample, to Ray Kokaly for determining mineralogy from reflectance spectroscopy, and to Gary Skipp for determining mineralogy from X-ray diffraction. This research was supported in part by the Climate and Land Use Change Program of the U.S. Geological Survey . Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The authors also thank Richard Wanty for his thorough and insightful review which greatly improved this manuscript. All the raw data measurements that we used to plot the graphs illustrated in the figures and provided in tables are in the Supplemental Material.

Publisher Copyright:
© 2019 Elsevier Ltd

Keywords

Bioavailable iron
Iron dissolution
Mineralogy effects
Photochemistry
Redox cycling
Titanium dioxide

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10.1016/j.atmosenv.2019.02.037

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title = "Bioavailable iron production in airborne mineral dust: Controls by chemical composition and solar flux",

abstract = "A large part of oceanic biological production is limited by the scarcity of dissolved iron. Mineral dust aerosol, processed under acidic atmospheric conditions, is the primary natural source of bioavailable iron to oceanic life. However, synergistic and antagonistic effects of non-Fe-containing minerals on atmospheric processing of Fe-containing minerals and Fe solubilization are poorly understood. The current study focuses on mineralogical influences of non-Fe-bearing semiconductor minerals, such as titanium dioxide (TiO2), on the dissolution of iron in selected natural mineral dust aerosols under atmospherically relevant conditions. Further, the role of elevated Ti concentrations in dust is evaluated using magnetite, a proxy for Fe(II) containing minerals, under both dark and light conditions. Our results highlight that relatively higher Ti:Fe ratios, regardless of their total Fe content, enhances the total iron dissolution in mineral dust aerosols as well as in magnetite. Moreover, elevated Ti percentages also yield high Fe(II) fractions in mineral dust systems under dark conditions. Upon irradiation however, dissolved Fe(II) is suppressed by high Ti levels due to the involvement of photochemical redox cycling reactions with hydroxyl radicals (•OH). These synergistic and antagonistic effects of Ti are further evaluated by altering the chemical composition of natural dusts with artificially added anatase (TiO2) and synthetic amorphous titania. The current study reveals important mineralogical controls by non-Fe-bearing minerals on dust iron dissolution to better understand global iron mobilization.",

keywords = "Bioavailable iron, Iron dissolution, Mineralogy effects, Photochemistry, Redox cycling, Titanium dioxide",

author = "Eshani Hettiarachchi and Reynolds, {Richard L.} and Goldstein, {Harland L.} and Bruce Moskowitz and Gayan Rubasinghege",

note = "Funding Information: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors thank the Department of Chemistry, New Mexico Institute of Mining and Technology. The Institute for Rock Magnetism (IRM) is supported by the Instruments and Facilities Program of the NSF Division of Earth Science . This is IRM contribution 1803. Funding Information: The authors are grateful to Paolo D'Odorico and Abi Bhattachan for providing the Kalahari sample, to Ray Kokaly for determining mineralogy from reflectance spectroscopy, and to Gary Skipp for determining mineralogy from X-ray diffraction. This research was supported in part by the Climate and Land Use Change Program of the U.S. Geological Survey . Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The authors also thank Richard Wanty for his thorough and insightful review which greatly improved this manuscript. All the raw data measurements that we used to plot the graphs illustrated in the figures and provided in tables are in the Supplemental Material. Publisher Copyright: {\textcopyright} 2019 Elsevier Ltd",

year = "2019",

month = may,

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doi = "10.1016/j.atmosenv.2019.02.037",

language = "English (US)",

volume = "205",

pages = "90--102",

journal = "Atmospheric Environment",

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T1 - Bioavailable iron production in airborne mineral dust

T2 - Controls by chemical composition and solar flux

AU - Hettiarachchi, Eshani

AU - Reynolds, Richard L.

AU - Goldstein, Harland L.

AU - Moskowitz, Bruce

AU - Rubasinghege, Gayan

N1 - Funding Information: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors thank the Department of Chemistry, New Mexico Institute of Mining and Technology. The Institute for Rock Magnetism (IRM) is supported by the Instruments and Facilities Program of the NSF Division of Earth Science . This is IRM contribution 1803. Funding Information: The authors are grateful to Paolo D'Odorico and Abi Bhattachan for providing the Kalahari sample, to Ray Kokaly for determining mineralogy from reflectance spectroscopy, and to Gary Skipp for determining mineralogy from X-ray diffraction. This research was supported in part by the Climate and Land Use Change Program of the U.S. Geological Survey . Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The authors also thank Richard Wanty for his thorough and insightful review which greatly improved this manuscript. All the raw data measurements that we used to plot the graphs illustrated in the figures and provided in tables are in the Supplemental Material. Publisher Copyright: © 2019 Elsevier Ltd

PY - 2019/5/15

Y1 - 2019/5/15

N2 - A large part of oceanic biological production is limited by the scarcity of dissolved iron. Mineral dust aerosol, processed under acidic atmospheric conditions, is the primary natural source of bioavailable iron to oceanic life. However, synergistic and antagonistic effects of non-Fe-containing minerals on atmospheric processing of Fe-containing minerals and Fe solubilization are poorly understood. The current study focuses on mineralogical influences of non-Fe-bearing semiconductor minerals, such as titanium dioxide (TiO2), on the dissolution of iron in selected natural mineral dust aerosols under atmospherically relevant conditions. Further, the role of elevated Ti concentrations in dust is evaluated using magnetite, a proxy for Fe(II) containing minerals, under both dark and light conditions. Our results highlight that relatively higher Ti:Fe ratios, regardless of their total Fe content, enhances the total iron dissolution in mineral dust aerosols as well as in magnetite. Moreover, elevated Ti percentages also yield high Fe(II) fractions in mineral dust systems under dark conditions. Upon irradiation however, dissolved Fe(II) is suppressed by high Ti levels due to the involvement of photochemical redox cycling reactions with hydroxyl radicals (•OH). These synergistic and antagonistic effects of Ti are further evaluated by altering the chemical composition of natural dusts with artificially added anatase (TiO2) and synthetic amorphous titania. The current study reveals important mineralogical controls by non-Fe-bearing minerals on dust iron dissolution to better understand global iron mobilization.

AB - A large part of oceanic biological production is limited by the scarcity of dissolved iron. Mineral dust aerosol, processed under acidic atmospheric conditions, is the primary natural source of bioavailable iron to oceanic life. However, synergistic and antagonistic effects of non-Fe-containing minerals on atmospheric processing of Fe-containing minerals and Fe solubilization are poorly understood. The current study focuses on mineralogical influences of non-Fe-bearing semiconductor minerals, such as titanium dioxide (TiO2), on the dissolution of iron in selected natural mineral dust aerosols under atmospherically relevant conditions. Further, the role of elevated Ti concentrations in dust is evaluated using magnetite, a proxy for Fe(II) containing minerals, under both dark and light conditions. Our results highlight that relatively higher Ti:Fe ratios, regardless of their total Fe content, enhances the total iron dissolution in mineral dust aerosols as well as in magnetite. Moreover, elevated Ti percentages also yield high Fe(II) fractions in mineral dust systems under dark conditions. Upon irradiation however, dissolved Fe(II) is suppressed by high Ti levels due to the involvement of photochemical redox cycling reactions with hydroxyl radicals (•OH). These synergistic and antagonistic effects of Ti are further evaluated by altering the chemical composition of natural dusts with artificially added anatase (TiO2) and synthetic amorphous titania. The current study reveals important mineralogical controls by non-Fe-bearing minerals on dust iron dissolution to better understand global iron mobilization.

KW - Bioavailable iron

KW - Iron dissolution

KW - Mineralogy effects

KW - Photochemistry

KW - Redox cycling

KW - Titanium dioxide

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VL - 205

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JO - Atmospheric Environment

JF - Atmospheric Environment

ER -

Bioavailable iron production in airborne mineral dust: Controls by chemical composition and solar flux

Abstract

Bibliographical note

Keywords

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