title: Isotopic constraints on biogeochemical cycling of copper in the ocean.
abstract: Trace elements and their isotopes are being actively studied as powerful tracers in the modern ocean and as proxies for the palaeocean. Although distributions and fractionations have been reported for stable isotopes of dissolved Fe, Cu, Zn and Cd in the ocean, the data remain limited and only preliminary explanations have been given. Copper is of great interest because it is either essential or toxic to organisms and because its distribution reflects both biological recycling and scavenging. Here we present new isotopic composition data for dissolved Cu (δ(65)Cu) in seawater and rainwater. The Cu isotopic composition in surface seawater can be explained by the mixing of rain, river and deep seawater. In deep seawater, δ(65)Cu becomes heavier with oceanic circulation because of preferential scavenging of the lighter isotope ((63)Cu). In addition, we constrain the marine biogeochemical cycling of Cu using a new box model based on Cu concentrations and δ(65)Cu.
authors.affiliation: Institute for Chemical Research, Kyoto University, Kyoto 611-0011, Japan.
authors.forename: Shotaro
authors.initials: S
authors.lastname: Takano
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 200 Monobe Otsu, Nankoku 783-8502, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Tanimizu
authors.affiliation: Laboratory for Planetary Sciences, Division of Earth and Planetary Sciences, Kyoto University, Kitashirakawa Oiwake-cho, Kyoto 606-8502, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Hirata
authors.affiliation: Institute for Chemical Research, Kyoto University, Kyoto 611-0011, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Sohrin
mesh_terms: D003300:Copper / Q000737:chemistry*; D007554:Isotopes / Q000737:chemistry*; D009792:Oceans and Seas; D012623:Seawater / Q000737:chemistry*
chemical_list: D007554:Isotopes; D003300:Copper