Aerosol water soluble organic matter characteristics over the North Atlantic Ocean: Implications for iron-binding ligands and iron solubility Andrew S. Wozniak a, ⁎, Rachel U. Shelley b,1 , Stephanie D. McElhenie a , William M. Landing b , Patrick G. Hatcher a a Department of Chemistry & Biochemistry, Old Dominion University, Norfolk, VA 23529, USA b Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA abstract article info Article history: Received 3 June 2014 Received in revised form 29 October 2014 Accepted 4 November 2014 Available online xxxx Keywords: Aerosols Marine aerosols Organic matter Water soluble organic matter Iron solubility NMR spectroscopy Iron Iron-binding ligands GEOTRACES SCOR North Atlantic Ocean Aerosol water soluble organic carbon (WSOC) and iron (Fe) loadings were examined in aerosols collected during the 2011 US GEOTRACES cruise in the North Atlantic Ocean to explore the feasibility of a role for water soluble organic matter (WSOM) organic complexation in determining the higher fractional solubility of Fe (%Fe S ) observed in North American-influenced relative to North African-influenced aerosols. Proton nuclear magnetic resonance spectroscopy ( 1 H NMR) was employed to characterize the WSOM, and principal component analysis was then applied to differentiate North American-influenced from North African-influenced aerosol WSOM and provide clues to the molecular identities of organic ligands. As has been found in previous studies, North African- influenced samples had orders of magnitude higher total Fe (Fe T ) loadings (8.9–101 nmol Fe m -3 air) and orders of magnitude lower %Fe S (0.12–0.29%) than those found in North American-influenced (Fe T : 0.03– 1.4 nmol Fe m -3 air; %Fe S : 0.67–3.62%) and Marine (minimal recent continental influence; Fe T : 0.02– 0.25 nmol Fe m -3 air; %Fe S : 1.1–10.7%) samples. Aerosol %Fe S values were positively correlated with WSOC/ Fe T ratios with North American combustion-influenced (39–540) and Marine (30–850) aerosol samples having orders of magnitude more moles of WSOC per mole of Fe T than North African (0.42–3.8) aerosol samples. The high WSOC/Fe T ratios in the North American combustion-influenced samples suggest a realistic role for organic ligands binding with Fe and accounting for some portion of the higher aerosol %Fe S also observed for these samples. Principal component analyses of 1 H NMR spectra show North American-influenced aerosol WSOM to have higher contributions from hydrogens in aliphatic carbon chains attached to heteroatomic functional groups such as those in nitrate, amine, ether, ester, and carboxylate compounds compared to North African mineral dust- influenced aerosol WSOM. These multifunctional aliphatic WSOM compounds are suggested as candidate Fe binding ligands to be explored with future work. © 2014 Elsevier B.V. All rights reserved. 1. Introduction More than two decades of research has established the role of iron (Fe) as a limiting micronutrient in high nutrient low chlorophyll regions of the ocean (e.g., Behrenfeld and Kolber, 1999; Coale et al., 1996, 2004; Martin and Fitzwater, 1988), and research focused on understanding what controls iron delivery and bioavailability continues to be a focus of the oceanographic community. The primary mechanism for the deliv- ery of new Fe to the oceans is atmospheric transport from continental regions (Mahowald et al., 2009). These regions are known to vary in the quantities and qualities of iron they export depending on land-use and landmass type. For example, it is now well established that mineral dusts from Saharan desert sources deliver loads of Fe that are orders of magnitude higher than those from combustion-influenced continental air masses, but the Fe in those combustion-influenced continental air masses show aerosol Fe fractional solubilities (%Fe S ) that are 1–2 orders of magnitude higher than Saharan desert sources (e.g., Buck et al., 2010; Sedwick et al., 2007; Sholkovitz et al., 2009, 2012 and references there- in). Soluble Fe is most readily available for use by primary producers (e.g., Hassler et al., 2011; Shaked and Lis, 2012) so these combustion- influenced sources may be important for stimulating primary produc- tivity, and therefore atmospheric carbon dioxide drawdown, in certain oceanic regions. The source and chemical composition of aerosols control the solubil- ity (and therefore, the initial bioavailability) of aerosol Fe in the surface ocean. While the higher fractional solubility for Fe from combustion- influenced sources is well established, the relative importance of the potential mechanism(s) leading to the higher fractional solubility remains unclear. Explanations for the higher fractional solubility include Marine Chemistry xxx (2014) xxx–xxx ⁎ Corresponding author. Tel.: +1 757 683 3996. E-mail addresses: awozniak@odu.edu (A.S. Wozniak), rachel.shelley@univ-brest.fr (R.U. Shelley), smcelhen@odu.edu (S.D. McElhenie), wlanding@fsu.edu (W.M. Landing), phatcher@odu.edu (P.G. Hatcher). 1 Current address: Laboratoire des Sciences de l'Environnement Marin, Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, Place Nicolas Copernic, 29280 Plouzané, France. MARCHE-03176; No of Pages 11 http://dx.doi.org/10.1016/j.marchem.2014.11.002 0304-4203/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Marine Chemistry journal homepage: www.elsevier.com/locate/marchem Please cite this article as: Wozniak, A.S., et al., Aerosol water soluble organic matter characteristics over the North Atlantic Ocean: Implications for iron-binding ligands and iron..., Mar. Chem. (2014), http://dx.doi.org/10.1016/j.marchem.2014.11.002