Contents lists available at ScienceDirect Aeolian Research journal homepage: www.elsevier.com/locate/aeolia North African mineral dust across the tropical Atlantic Ocean: Insights from dust particle size, radiogenic Sr-Nd-Hf isotopes and rare earth elements (REE) Michèlle van der Does a, ⁎ , Ali Pourmand b , Arash Sharifi b , Jan-Berend W. Stuut a a NIOZ – Royal Netherlands Institute for Sea Research, Department of Ocean Systems, and Utrecht University, Texel, The Netherlands b Neptune Isotope Laboratory, Department of Marine Geosciences, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA ARTICLE INFO Keywords: Mineral dust Sahara Atlantic Ocean Sr-Nd-Hf isotopes Rare earth elements ABSTRACT Large amounts of mineral dust are exported from North Africa across the Atlantic Ocean, impacting the atmo- sphere and ocean during transport and after deposition through biogeochemical processes. In order to char- acterize the isotopic signature of dust from different seasons and years, in relation to their bulk particle size, and to obtain a general idea of its provenance, Saharan dust was collected using subsurface sediment traps moored in the tropical North Atlantic Ocean in 2012–2013, and by shipboard aerosol collection during three trans-Atlantic research cruises in 2005, 2012 and 2015. The samples were analysed for radiogenic Strontium (Sr), Neodymium (Nd), and Hafnium (Hf) isotopes, rare earth element (REE; La-Lu) abundances and particle size. In addition, soil sediments from Mauritania, a potential source area, were analysed and compared to the Atlantic dust samples. The results indicate no relation between Sr and Nd isotopic compositions and dust particle size. In contrast, Hf isotopic compositions show a strong relation with particle size, associated to the so-called zircon effect. We explored alternative sources of lithogenic particles to the sediment traps such as Amazon River sediments. Our results reveal that the sediment-trap samples bear distinctly different geochemical signatures from sediments from the Amazon Basin and Amazon River tributaries, and confirm that the primary source of lithogenic particles is northern Africa. The collected dust samples show close relations to African dust aerosols collected at Barbados and samples from the Bodélé Depression, although differences between seasons are observed, which we relate to differences in source areas. 1. Introduction The Sahara Desert in northern Africa is the world’s largest dust source (Muhs, 2013), contributing up to 70% of all global annual dust emissions (Maher et al., 2010; Huneeus et al., 2011). In particular, the Bodélé Depression, located in the region of the Lake Chad Basin, is currently the largest single dust source, with the biggest dust export in the world (Koren et al., 2006; Washington et al., 2006), and appears to have been active for at least several hundred to thousands of years (Prospero et al., 2002; Armitage et al., 2015). Nevertheless, the con- tribution from the Bodélé Depression aerosols transported over the Atlantic basin arriving at Barbados in the Caribbean appears to be small (Pourmand et al., 2014; Bozlaker et al., 2018; Kumar et al., 2018). Most dust emitted from North African sources is transported westward across the Atlantic Ocean, with an estimated amount of 182 Tg between 30 °N and 10 °S every year (Yu et al., 2015). The emitted dust impacts both the atmosphere and the ocean, from affecting the atmospheric radiation budget (Ryder et al., 2013) and acting as cloud condensation nuclei and ice nuclei (Wilcox et al., 2010; Atkinson et al., 2013), to the enhance- ment of the ocean’s carbon cycle by delivering nutrients stimulating phytoplankton growth (Martin and Fitzwater, 1988), and by mineral ballasting of organic particles in the ocean (Armstrong et al., 2002; Bressac et al., 2014; Van der Jagt et al., 2018). Saharan dust can also transport viable spores, pathogens and microbes over great distances (Griffin, 2007), which can impact marine and terrestrial ecosystems (De Deckker et al., 2008), and be harmful to human health and increase mortality rates (Morman and Plumlee, 2014; Schweitzer et al., 2018). Dust particle size and composition vary seasonally, and with the distance over which the dust is transported. Particle sizes decrease downwind as a result of more rapid gravitational settling of coarse- grained particles (Bagnold, 1941; Van der Does et al., 2016), while the mineralogical and isotopic composition of the deposited dust changes downwind by the preferential settling of heavier quartz and zircon particles closer to Africa (Pourmand et al., 2014; Korte et al., 2017). At https://doi.org/10.1016/j.aeolia.2018.06.001 Received 8 March 2018; Received in revised form 5 June 2018; Accepted 5 June 2018 ⁎ Corresponding author. E-mail address: mdoes@nioz.nl (M. van der Does). Aeolian Research 33 (2018) 106–116 1875-9637/ © 2018 Elsevier B.V. All rights reserved. T