Soluble ferrous iron (Fe (II)) enrichment in airborne dust

Abstract

The input of soluble iron in dust delivered to the ocean and lakes is critical to their biogeochemistry and phytoplankton productivity. Most iron in soils and sediment deposits is insoluble, while only a tiny fraction is soluble and therefore suitable to meet the phytoplankton's requirements for photosynthesis and nitrogen assimilation. Aerosol deposition constitutes a major source of soluble iron to oceans and lakes, and in some regions the low phytoplankton productivity has been related to limitations in the supply of soluble iron from terrestrial sources. It is suggested that during atmospheric transport part of the insoluble iron is converted into soluble form. While the understanding of increased bioavailability of iron during atmospheric transport is improving, there are only a limited number of studies that actually quantify the increase in iron bioavailability in dust. In this study we compare the soluble ferrous iron, Fe (II) content in dust collected at deposition sites in the high‐altitude mountains of the Sierra Nevada, Spain, to the source of dust in North Africa. We found that the dust is greatly enriched (on average 15 times) in Fe (II) relative to the fine fraction (<45 µm) of the parent soil collected from North African dust sources.

Deposition rates of viruses and bacteria above the atmospheric boundary layer

“…1e). In addition, light detection and ranging vertical profiles for the same study period and latitude confirmed the presence or absence of Saharan dust intrusions at the altitude of the collector sites [26,36].…”

Iron Mineralogy and Speciation in Clay‐Sized Fractions of Chinese Desert Sediments

“…Resolving how much nonrefractory Fe would ultimately become soluble Fe in the North Pacific Ocean needs additional research. Fe solubility in mineral dust that experiences atmospheric processing depends not only on the fine fraction from the source region but also how it is affected by gravitational settling, mixing with anthropogenic products, acid, cloud, and photoreductive processing (Bhattachan et al, ; Shi et al, ). The carbonate minerals in dust contain minimal Fe (result in section 3.1) but might neutralize the inorganic acids in dust aerosols and thereby substantially limit Fe solubility during the atmospheric processing.…”

Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface

“…Atmospheric models also simulate the secondary formation of soluble Fe in the atmosphere due to the dissolution of Feoxides and Fe-substituted aluminosilicates through proton-promoted, organic ligand-promoted, and photo-reductive mechanisms (Myriokefalitakis et al, 2018). Fe in atmospheric aerosols may be present in different forms, i.e., crystalline and amorphous Fe-(oxy)hydroxides (e.g., hematite, goethite, and ferrihydrite), Fe-substituted into aluminosilicate minerals, Fe-rich nanoparticles, and Fe-organic complexes (Claquin et al, 1999;Nickovic et al, 2013;Shi et al, 2009;Cheize et al, 2012) and either in the Fe(III) or Fe(II) oxidation states (Deguillaume et al, 2005;Bhattachan et al, 2016). Therefore, modelto-model and model-to-surface observation comparisons of soluble Fe remain hardelusive.…”