title: The impact of particle size, relative humidity, and sulfur dioxide on iron solubility in simulated atmospheric marine aerosols.
abstract: Iron is a limiting nutrient in about half of the world's oceans, and its most significant source is atmospheric deposition. To understand the pathways of iron solubilization during atmospheric transport, we exposed size segregated simulated marine aerosols to 5 ppm sulfur dioxide at arid (23 ± 1% relative humidity, RH) and marine (98 ± 1% RH) conditions. Relative iron solubility increased as the particle size decreased for goethite and hematite, while for magnetite, the relative solubility was similar for all of the fine size fractions (2.5-0.25 μm) investigated but higher than the coarse size fraction (10-2.5 μm). Goethite and hematite showed increased solubility at arid RH, but no difference (p > 0.05) was observed between the two humidity levels for magnetite. There was no correlation between iron solubility and exposure to SO2 in any mineral for any size fraction. X-ray absorption near edge structure (XANES) measurements showed no change in iron speciation [Fe(II) and Fe(III)] in any minerals following SO2 exposure. SEM-EDS measurements of SO2-exposed goethite revealed small amounts of sulfur uptake on the samples; however, the incorporated sulfur did not affect iron solubility. Our results show that although sulfur is incorporated into particles via gas-phase processes, changes in iron solubility also depend on other species in the aerosol.
authors.affiliation: †Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208-9020, United States.
authors.forename: Benton T
authors.initials: BT
authors.lastname: Cartledge
authors.affiliation: ‡Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States.
authors.forename: Aurelie R
authors.initials: AR
authors.lastname: Marcotte
authors.affiliation: ‡Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States.
authors.forename: Pierre
authors.initials: P
authors.lastname: Herckes
authors.affiliation: ‡Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States.|§School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, United States.
authors.forename: Ariel D
authors.initials: AD
authors.lastname: Anbar
authors.affiliation: †Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208-9020, United States.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Majestic
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D052203:Ferrosoferric Oxide / Q000737:chemistry; D006813:Humidity; D007501:Iron / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D008903:Minerals / Q000737:chemistry; D010316:Particle Size; D012623:Seawater / Q000737:chemistry*; D012995:Solubility; D013458:Sulfur Dioxide / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000336:Aerosols; D005290:Ferric Compounds; D058085:Iron Compounds; D008903:Minerals; D013458:Sulfur Dioxide; C094886:goethite; C000499:ferric oxide; D007501:Iron; D052203:Ferrosoferric Oxide