AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Linking Barbados Mineral Dust Aerosols to North African Sources Using Elemental Composition and Radiogenic Sr, Nd, and Pb Isotope Signatures
AYSE BOZLAKER, Joseph M. Prospero, Jim Price, Shankar Chellam, Texas A&M University
Abstract Number: 99 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Arid and semi-arid regions of North Africa are the largest source of mineral material to the global atmosphere. Large quantities of dust uplifted from the Sahara-Sahel region are carried across the Atlantic to the Caribbean Basin and southern United States where it plays an important role in the biogeochemistry of soils and waters and in air quality. The elemental and isotopic composition of this dust was comprehensively characterized in Barbados during the summers of 2013 and 2014, the season of maximum dust transport. Total suspended particulates (TSP) mass concentrations during high-dust days (HDD) averaged 22.6±9.9µg/m3 in 2013, ~4 times the low-dust days (LDD) value (5.4±3.1µg/m3). Although HDD concentrations approximately doubled in 2014 (40.8±25.1µg/m3) compared to 2013, the abundances (µg element/g TSP) of 50 elements were similar. Predictably, mineral and marine aerosol tracers such as Na, Mg, Al, Si, K, Ca, Ti, and Fe were the most abundant constituents of Barbados aerosols. Aerosols in HDD and LDD were regularly enriched in Na, Cu, Zn, As, Se, Mo, Cd, Sn, Sb, and W relative to the upper continental crust. Enrichment of these elements, many of which are anthropogenically emitted, was significantly reduced during HDD attributed to mixing and dilution with desert dust over source regions. Generally, Ti/Al, Si/Al, Ca/Al, Ti/Fe, Si/Fe, and Ca/Fe ratios in HDD differed from their respective values in North African source regions. Ca/Al, K/Al, Ca/Fe, and K/Fe ratios were also significantly different between LDD and HDD. Nd isotope composition expressed as ɛNd was relatively invariant for LDD and HDD periods. In contrast, HDD-aerosols were more radiogenic with higher 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios compared to LDD periods. Our results demonstrate that summertime Barbados aerosols, both during and between large dust events, are dominated by a mixture of particles originating from different Sahara-Sahel regions.