This study provides new data on the properties of aerosol iron (Fe) over the Antarctic Peninsula, one of the fastest warming regions on Earth in recent decades. Atmospheric deposition delivers Fe, a limiting micronutrient, to the Southern Ocean, and aerosol particle size influences the air‐to‐sea deposition rate and fractional solubility of aerosol Fe. Size‐segregated aerosols were collected at Palmer Station on the West Antarctic Peninsula during austral summer 2016–2017. Results show single‐mode size distribution of aerosol Fe, peaking at 4.4 μm diameter. The average concentration of total aerosol Fe was 1.3 (±0.40) ng m−3(range 0.74–1.8 ng m−3). High concentrations of total aerosol Fe occurred in January, implying increased Fe source strength then. Total labile Fe varied between 0.019 and 0.095 ng m−3, and labile Fe (II) accounted for ~90% of the total labile Fe. The average fractional solubility for total Fe was 3.8% (±1.5%) (range 2.5–7.3%). Estimated dry deposition fluxes for the study period were 3.2 μg m−2 year−1for total labile Fe and 83 μg m−2 year−1for total Fe in aerosols. We speculate that local and regional dust sources in Antarctica contributed to the observed aerosol Fe in austral summer and that warming on the Antarctic Peninsula during the past half century may have increased the formation of dust sources in this region. The potential biogeochemical impact of atmospheric Fe input to the West Antarctic Peninsula shelf waters and adjacent pelagic surface waters of the Southern Ocean may need to be re‐evaluated.
Atmospheric iron solubility varies depending on whether the particles are collected in rural or urban areas, with urban areas showing increased iron solubility. In this study, we investigate if the iron species present in different environments affects its ultimate solubility. Field data are presented from the Platte River Air Pollution and Photochemistry Experiment (PRAPPE), aimed at understanding the interactions between organic carbon and trace elements in atmospheric particulate matter (PM). 24‐hr PM2.5samples were collected during the summer and winter (2016–2017), at three different sites on the Eastern Colorado plains: an urban, agricultural, and a mixed site. Downtown Denver had an average total and water‐soluble iron air concentration of 181.2 and 7.7 ng m−3, respectively. Platteville, the mixed site, had an average of total iron of 76.1 ng m−3, with average water‐soluble iron concentration of 9.1 ng m−3. Jackson State Park (rural/agricultural) had the lowest total iron average of 31.5 ng m−3and the lowest water‐soluble iron average, 1.3 ng m−3. The iron oxidation state and chemical speciation of 97 samples across all sites and seasons was probed by X‐ray absorption near edge structure (XANES) spectroscopy. The most common iron phases observed were almandine (Fe₃Al₂Si₃O₁₂) (Denver 21%, Platteville 16%, Jackson 24%), magnetite (Fe3O4) (Denver 9%, Platteville 4%, Jackson 5%) and Fe (III)dextran (Denver 5%, Platteville 13%, Jackson 5%), a surrogate for Fe‐organic complexes. Additionally, native iron [Fe(0)] was found in significant amounts at all sites. No correlation was observed between iron solubility and iron oxidation state or chemical speciation.
more » « less- PAR ID:
- 10369534
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Earth and Space Science
- Volume:
- 7
- Issue:
- 10
- ISSN:
- 2333-5084
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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