African Dust Transported to Barbados in the Wintertime Lacks Indicators of Chemical Aging
CASSANDRA GASTON, Haley Royer, Michael Sheridan, Hope Elliott, Edmund Blades, Nurun Nahar Lata, Zezhen Cheng, Swarup China, Zihua Zhu, Andrew P. Ault, University of Miami
Abstract Number: 207
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
African dust is transported across the Atlantic Ocean to the Caribbean and south and southeastern US in summer and parts of the Caribbean and South America in the winter and spring. During transport, African dust has the potential to undergo chemical “aging” by reacting with acidic gases that could transform its biogeochemical, radiative, and air quality impacts. However, whether African dust undergoes chemical aging is open for debate. We present evidence that dust collected on the easternmost Caribbean island of Barbados lacks indicators of chemical aging. Samples were collected during the ATOMIC/EUREC4A campaign, which occurred during the wintertime when dust is transported at lower altitudes and, therefore, could undergo more extensive aging than in the summertime. Traditional bulk chemical indicators of chemical aging such as dust, non-sea salt sulfate, and nitrate mass concentrations show strong temporal correlations suggestive of dust chemical aging. However, single-particle evidence from computer controlled-scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (CCSEM/EDX), elemental mapping, and time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals that aging is associated with sea spray and co-transported smoke rather than dust. Our work has implications for understanding dust impacts on clouds, nutrient deposition, direct radiative forcing and further underscores the importance of single particle methods to unambiguously elucidate chemical aging mechanisms.