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https://doi.org/10.5194/bg-2019-183
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-183
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 17 May 2019

Research article | 17 May 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

The Trace Element Composition of Size Fractionated Suspended Particulate Matter Samples from the Qatari EEZ of the Arabian Gulf: The Role of Atmospheric Dust

Oguz Yigiterhan1, Ebrahim Mohd Al-Ansari1, Alex Nelson2, Mohamed Alaa Abdel-Moati3, Jesse Turner2, Hamood Abdulla Alsaadi1, Barbara Paul2, Ibrahim Abdullatif Al-Maslamani4, Mehsin Abdulla Al-Ansi Al-Yafei5, and James Wray Murray2 Oguz Yigiterhan et al.
  • 1Environmental Science Center, Qatar University, P.O. Box 2713, Doha, State of Qatar
  • 2School of Oceanography, University of Washington, Seattle WA, 98195-5351, USA
  • 3Environmental Assessment Department, Ministry of Municipality and Environment, P.O.Box 39320, Doha, State of Qatar
  • 4Office of Vice President for Research and Graduate Studies, Qatar University, P.O. Box 2713, Doha, State of Qatar
  • 5Department of Biological and Environmental Sciences, Qatar University, P.O. Box 2713, Doha, State of Qatar

Abstract. We analyzed net-tow samples of natural assemblages of plankton, and associated particulate matter, from the Exclusive Economic Zone (EEZ) of Qatar in the Arabian Gulf. Size fractioned suspended particles were collected using net-tows with mesh sizes of 50 μm (phytoplankton) and 200 μm (zooplankton) to examine the composition of plankton populations. Samples were collected in two different years (October 2012; April and October 2014) from 11 sites to examine temporal and spatial variabilities. We calculated the excess metal concentrations by correcting the bulk composition for inputs from atmospheric dust using aluminum (Al) as a lithogenic tracer and the metal / Al ratios for average Qatari dust. Atmospheric dust in Qatar is depleted in Al and enriched in calcium (Ca) relative to global average Upper Continental Crust (UCC) due to the geology of the outcropping sedimentary rocks and topsoil deposits in the source areas of the dust. To evaluate the fate of this carbonate fraction when dust particles enter seawater is uncertain, we leached a sub-set of dust samples using an acetic acid-hydroxylamine hydrochloride (HAc-HyHCl) procedure that should solubilize CaCO3 minerals and associated elements. We found that Ca was removed and that the metal/aluminum (Me / Al) ratios for most elements increased after leaching because the change in sample mass resulting from the leach was more important than the loss of metals solubilized by the leach. Because surface seawater is supersaturated with respect to CaCO3 and acid soluble Ca is abundant in the particulate matter, we only used unleached dust for the lithogenic correction. The concentrations of some elements in net-tow plankton samples appear to be mostly of lithogenic (dust) origin. These include Al, Fe, Cr, Co, Mn, Ni, Pb and Li. Several elements are mostly biogenic/anthropogenic origin. These include as Cd, Cu, Mo, Zn and Ca. The excess concentrations, relative to average dust, for most elements (except Cd) decreased with distance from shore, which may be due to differences in biology, currents, proximity to the coast or interannual processes.

Oguz Yigiterhan et al.
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Short summary
We analyzed net-tow samples of plankton, and associated particulate matter, from the Exclusive Economic Zone of Qatar in the Arabian Gulf, using net-tows with mesh sizes of 50 and 200 μm to examine the composition of plankton populations. We also focuses on the role and composition of the atmospheric dust, representative of terrigenous material, deposited in the Gulf. We concluded Al, Fe, Cr, Co, Mn, Ni, Pb, Li are of Dust origin and As, Cd, Cu, Mo, Zn, Ca are of Anthropogenic/Biogenic origin.
We analyzed net-tow samples of plankton, and associated particulate matter, from the Exclusive...
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