Elucidating the Extent of Dust Aging at Miami and Barbados

HALEY ROYER, Michael Sheridan, Hope Elliott, Zihua Zhu, Andrew Ault, Nurun Nahar Lata, Zezhen Cheng, Swarup China, Cassandra Gaston, University of Miami

     Abstract Number: 231
     Working Group: Aerosol Sources and Constituents of Emerging Importance and Their Impacts across Spatial Scales

Abstract
Reactions between dust particles and acids in the atmosphere (dust aging) can influence the radiative forcing of dust, cloud droplet formation, and biogeochemical cycles. In biogeochemical cycles, dust aging can enhance the often-poor solubility, and thus bioavailability, of essential nutrients like iron (Fe) and phosphorus (P) that can limit productivity, especially in oligotrophic waters like the tropical Atlantic. Dust aging also potentially increases carbon dioxide (CO₂) drawdown as the addition of bioavailable nutrients can enhance primary productivity. Though previous research shows that dust aging can take place, it isn’t clear how prevalent this process is, particularly within the Saharan Air Layer (SAL) – the primary dust transport mechanism in the tropical Atlantic. In this work, we complement bulk aerosol chemical data from ion chromatography (IC) analysis with single-particle chemical techniques, including computer-controlled scanning electron microscopy with energy dispersive x-ray spectroscopy (CCSEM/EDX), single-particle aerosol mass spectrometry (SPAMS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) to elucidate the extent of aging at two dust receptor sites in the tropical Atlantic: Ragged Point, which is exposed to minimal anthropogenic influence, and Miami, which is influenced by high levels of anthropogenic activity. Results of bulk IC analysis show signs of aging as ions indicative of inorganic acids nitrate and sulfate, as well as organic acids like oxalate and formate, increase upon the arrival of dust to Barbados, suggesting aging may occur. However, CCSEM/EDX analysis reveals the presence of co-transported smoke particles with dust that may contribute to increased sulfate on dust particles. In Miami, signs of aging are present through high levels of nitrate found in bulk IC analysis and SPAMS analysis. These findings highlight the importance of using single-particle techniques for understanding the process of dust aging and provide insight into the extent of dust aging in the atmosphere.