title: Evidence of molybdenum association with particulate organic matter under sulfidic conditions.
abstract: The geochemical behavior of molybdenum (Mo) in the oceans is closely linked to the presence of sulfide species in anoxic environments, where Fe availability may play a key role in the Mo scavenging. Here, we show that Mo(VI) is reduced in the presence of particulate organic matter (represented by sulfate-reducing bacteria). Molybdenum was immobilized at the surface of both living cells and dead/lysed cells, but not in cell-free control experiments. Experiments were carried out at four different Mo concentrations (0.1 to 2 mm) to yield cell-associated Mo precipitates with little or no Fe, consisting of mainly Mo(IV)-sulfide compounds with molecular structures similar to Mo enzymes and to those found in natural euxinic sediments. Therefore, we propose that Mo removal in natural sulfidic waters can proceed via a non-Fe-assisted pathway that requires particulate organic matter (dead or living sulfate-reducing bacteria). This pathway has implications for global marine Mo cycling and the current use of Mo-based proxies for paleo-environmental investigations.
authors.affiliation: Nordic Center for Earth Evolution and University of Southern Denmark, Odense M, Denmark.
authors.forename: T W
authors.initials: TW
authors.lastname: Dahl
authors.affiliation: Department of Earth and Atmospheric Sciences, Central Michigan University, Mount Pleasant, MI, USA.
authors.forename: A
authors.initials: A
authors.lastname: Chappaz
authors.affiliation: Nordic Center for Earth Evolution and University of Southern Denmark, Odense M, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Hoek
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark.
authors.forename: C J
authors.initials: CJ
authors.lastname: McKenzie
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Svane
authors.affiliation: Nordic Center for Earth Evolution and University of Southern Denmark, Odense M, Denmark.
authors.forename: D E
authors.initials: DE
authors.lastname: Canfield
mesh_terms: D001419:Bacteria / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry*; D008982:Molybdenum / Q000032:analysis*; D052638:Particulate Matter / Q000737:chemistry*
chemical_list: D052638:Particulate Matter; D008982:Molybdenum