Importance of different types of marine particles for the scavenging of heavy metals in the deep-sea bottom water |
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| Institution: | 1. Department of Earth Sciences – Geochemistry, Utrecht University, PO Box 80021, 3508 TA Utrecht, the Netherlands;2. Department of Estuarine and Delta Systems, NIOZ, Royal Netherlands Institute for Sea Research and Utrecht University, PO Box 140, 4400 AC Yerseke, the Netherlands;1. CEFREM, CNRS, Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860, Perpignan, France;2. LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France;3. IDYST, Université of Lausanne, Switzerland;4. Rutgers, The State University of New Jersey, New Brunswick, NJ, USA;1. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China;2. Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia;3. Géosciences Montpellier, Université de Montpellier, Montpellier 34095, France;4. State Key Laboratory of Isotope Geosciences, Guangzhou Institute of Geochemistry, Guangzhou 510640, China;5. Department of Geology, University of Maryland, College Park, MD 20742, USA;6. Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, DC 20015, USA;7. CAS Center for Excellence in Comparative Planetology, China;1. Massachusetts Institute of Technology, Cambridge, MA, USA;2. Universidad de Zaragoza, Zaragoza, Spain;3. Woods Hole Oceanographic Institution, Woods Hole, MA, USA;4. Rosentiel School of Marine and Atmospheric Science, University of Miami Miami, Coral Gables, FL, USA;5. Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA;1. Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China;3. University of Chinese Academy of Sciences, Beijing, 100049, China;1. Università Politecnica Delle Marche, Dipartimento di Scienze Della Vita e Dell’Ambiente, 60131, Ancona, Italy;2. University of Barcelona, CRG Marine Geosciences, Department of Earth and Ocean Dynamics, 08028, Barcelona, Spain;3. Scienze e Ingegneria Della Materia, Dell’Ambiente Ed Urbanistica, Università Politecnica Delle Marche, 60131, Ancona, Italy;4. Institute of Marine Sciences, National Research Council, ISMAR-CNR, Arsenale, Tesa 104, Castello 2737/F, 30122, Venice, Italy;5. Università Degli Studi di Cagliari, Dipartimento di Scienze Della Vita e Dell''Ambiente, 09126, Cagliari, Italy;6. Stazione Zoologica Anton Dohrn, 80121, Napoli, Italy |
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| Abstract: | In experiments of 7 days duration using voltammetric and radiotracer measurement techniques, the role of different particle types in the sorption of dissolved metal species in a disturbed deep-sea bottom seawater system were investigated. Resuspension of oxic to suboxic surface sediment into the bottom water in the deep sea (either by natural events or industrial activities like Mn nodule mining) has been shown to be followed quickly by scavenging of dissolved heavy metals, e.g. released from interstitial water, on the resuspended particles. Compared to other deep-sea particles (like clay minerals, calcite and apatite), Mn and Fe oxides and oxyhydroxides were found to be by far the most important phases in scavenging many dissolved heavy metals. Only Pb was sorbed strongly on all particles used, with highest affinity to carbonate fluorapatite. Caesium+ was significantly scavenged only by clay minerals like illite. The sorption experiments support a simple electrostatic model: Hydrated cations and labile cationic chloro-complexes in seawater like Mn2+, MnCl+, Co2+, Ni2+, Cu2+, Zn2+, Ba2+, and PbCl+, are preferentially adsorbed or ion-exchanged on the negatively charged surfaces of Mn oxides. In contrast, oxyanions and neutrally or negatively charged complexes like HVO42?, MoO42?, HAsO42?, UO2(CO3)22?, and PbCO30 associate with neutral to slightly positive amphoteric Fe oxyhydroxide particles. Metals forming strong chloro-complexes in seawater like Cd (CdCl20), are less readily sorbed by oxides than others. A comparison of the results of voltammetric and radiotracer techniques revealed that after fast sorption within the first hour, isotopic exchange dominated reactions on MnO2-rich particles in the following days. This was especially pronounced for Mn and Co which are bound to the Mn oxide surface via a redox transformation. |
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