Using Multi-Modal Micro-Spectroscopy Techniques to Determine the Impact of Aerosolized Organic Material on Biogeochemical Cycles of Fe and P in the Amazon Basin
EMSL Project ID
50816
Abstract
Aerosols transported from Africa are thought to critically impact the biogeochemical cycling of iron (Fe) and phosphorus (P) in the Amazon and relieve nutrient limitations in this ecosystem. Spectroscopy and microscopy will be used to compare the Fe and P content of two key sources of aerosols that are transported from Africa and deposited to the Amazon Basin: Saharan dust and biomass burning emissions from Africa. We will focus our analyses on Fe and P associated with organic material in dust and biomass burning particles, which have been under-explored compared to Fe and P associated with inorganic minerals found in dust. We will test the hypothesis that biomass burning emissions from Africa provide an under-appreciated supply of bioavailable Fe and P to the Amazon. Aerosol samples collected on filters at a site in Cayenne, French Guiana that receives African dust and African biomass burning products and is located at the northern entrance to the Amazon Basin will be used to test our hypothesis using EMSL resources. Computer-controlled scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (CCSEM/EDX) will be used to determine the size, Fe and P content, and source of individual particles transported to the Amazon, two forms of secondary ion mass spectrometry (e.g., Nano-SIMS and TOF-SIMS) will be used to probe associations between organic compounds with Fe and P. The oxidation state and phase of Fe-containing minerals will be probed in bulk samples using Mossbauer spectroscopy and at the single-particle level using transmission electron microscopy combined with electron energy loss spectroscopy (TEM/EELS). The use of state-of-the-art EMSL instrumentation and resources are critical for testing our hypothesis and for the overall success of this project. The CCSEM/EDX needed to distinguish different sources of aerosols, TOF-SIMS and Nano-SIMS needed to probe organic material associated with Fe and P and to explore how mineral-organic matter interactions affect the bioavailability of Fe and P, and Mossbauer spectroscopy and TEM/EELS needed to differentiate the mineral phases of Fe present in our samples are only possible through a collaboration with EMSL. Results from this work will improve our understanding of how transported aerosols regulate biogeochemical cycles of Fe and P that are vital for stimulating primary production in the Amazon Basin, which impacts the global carbon cycle through the uptake of carbon dioxide into the biosphere. For example, measurements with Mossbauer spectroscopy and TEM/EELS are critical for understanding the potential sources and biological availability of Fe transported to the Amazon. Additionally, data obtained from CCSEM/EDX can be scaled to particle mass concentrations and combined with deposition models to estimate the deposition of Fe and P from biomass burning aerosol and dust particles within the Amazon Basin. As such, this proposal will fill several critical gaps in our knowledge regarding the supply of bioavailable forms of Fe and P to the Amazon from organic material associated with aerosols, which aligns with DOE's interest in and resources focused on the Amazon region.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2019-10-01
End Date
2021-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
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Anne E Barkley, Ali Pourmand, Arash Sharifi, Amanda Oehlert, Colleen Brown, Ravi Kukkadapu, Mark Bowden, Kathy Panechou, Joseph M Prospero, Andrew Ault, Cassandra Gaston. 2021. Determining the source of African dust transported to the Tropical Atlantic Ocean and its associated Fe mineralogy. Goldschmidt2021• Virtual• 4-9 July
Barkley, A., Sharifi, A., Oehlert, A.M., Pourmand, A., Prospero, J.M., Kukkadapu, R.K., Bowden, M.E., Panechou, K., Ault, A.P. and Gaston, C., 2020, December. Determining the source location of African dust transported to the Amazon and its associated Fe speciation. In AGU Fall Meeting Abstracts (Vol. 2020, pp. A019-02).
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