Iron (Fe) acts as a vital nutrient that can influence the productivity in marine ecosystems. Iron can also participate in aqueous-phase chemical reactions, including the oxidation of S(IV). Atmospheric iron results from both anthropogenic and natural sources, but little is known about the mixing state of iron within atmospheric aerosols. The distribution of iron is critical to understanding connections to sources and determining whether it is available to facilitate sulfate formation. Using an aerosol time-of-flight mass spectrometer (ATOFMS), we determined and compared the size and chemical composition of individual Fe-containing atmospheric aerosols measured in two different Arctic field campaigns. One study measured the ambient particles during the summertime in an Arctic oil field (Oliktok Point, Alaska), and the other during the wintertime near the remote town of Utqiagvik (formerly known as Barrow), Alaska. By analyzing the single-particle mass spectra, which act as chemical fingerprints, the sources of particles containing Fe were determined. Fe-containing particles were found to be internally mixed within particles from several different sources, <i>e.g., </i>natural dust, combustion, and sea spray aerosol. In this work, we evaluate the relative contributions of these different sources to the aerosol population. Some Fe-rich particles were also found to contain secondary species, including sulfate, indicative of atmospheric processes, possibly during long-range transport. The increase in secondary species through chemical processing potentially increases aerosol Fe bioavailability, which has relevant climate implications.

Investigation of iron-rich Alaskan aerosol particles using aerosol time-of-flight mass spectrometry

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