A019-02
Determining the source location of African dust transported to the Amazon and its associated Fe speciation

Monday, 7 December 2020: 10:34
Virtual
Anne Barkley, University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, FL, United States, Arash Sharifi, University of Miami, 1- Neptune Isotope Laboratory (NIL), Department of Marine Geosciences, , Rosenstiel School of Marine and Atmospheric Science, Miami, FL, United States, Amanda M Oehlert, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Department of Marine Geosciences, Miami, FL, United States, Ali Pourmand, Neptune Isotope Laboratory (NIL), Rosenstiel School of Marine and Atmospheric Science, University of Miami, Department of Marine Geosciences, Miami, FL, United States, Joseph M Prospero, University of Miami, Miami, FL, United States, Ravi K Kukkadapu, Pacific Northwest National Lab, Richland, WA, United States, Mark E Bowden, Pacific Northwest National Laboratory, William R. Wiley Environmental and Molecular Sciences Laboratory, Richland, WA, United States, Kathy Panechou, ATMO Guyane, Cayenne, French Guiana, Andrew P Ault, University of Michigan Ann Arbor, Department of Chemistry, Ann Arbor, MI, United States and Cassandra Gaston, University of Miami, Department of Atmospheric Sciences, Miami, FL, United States
Recorded Presentation
Abstract:
The Amazon and Tropical Atlantic Ocean (TAO) are both nutrient-depleted ecosystems where primary productivity is controlled in part by the atmospheric deposition aerosols. The primary nutrient-laden aerosol is African dust, which is transported in boreal winter and spring, and an important source of iron (Fe) to the Amazon and TAO. Determining the source location of transported dust would provide key insights into the mineralogy and nutrient content of transported dust. Additionally, Fe mineralogy and speciation associated with this dust have not well characterized despite being important predictors of Fe bioavailability. Using strontium, neodymium, and lead isotopes as well as elemental analysis, we characterized two years of transported African aerosols collected in Cayenne, French Guiana, which is located adjacent to the Amazon and western TAO. Our isotopic analysis revealed no evidence of transport from the El-Djouf region. Instead, our results show that the majority of the dust originates from present day southern Algeria and northern Niger. We also confirm with isotopic evidence that the Amazon and western TAO are impacted by the deposition of biomass burning aerosols in the boreal summer and fall when dust transport is low. Further investigation of mineralogy and Fe oxidation state of transported Saharan dust showed the presence of hematite, goethite, and small amounts of Fe(II), which is the most soluble form of Fe and immediately usable by biota. These results integrate source location, mineralogy, and Fe speciation, which yield a more complete view of how African dust impacts marine and terrestrial ecosystems.
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