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Paired dissolved and particulate phase Cu isotope distributions in the South Atlantic

Paired dissolved and particulate phase Cu isotope distributions in the South Atlantic
Paired dissolved and particulate phase Cu isotope distributions in the South Atlantic

Copper (Cu) is both an essential micronutrient and toxic to photosynthesizing microorganisms at low concentrations. Its dissolved vertical distribution in the oceans is unusual, being neither a nutrient-type nor scavenged-type element. This distribution is attributed to biological uptake in the surface ocean with remineralisation at depth, combined with strong organic complexation by dissolved ligands, scavenging onto particles, and benthic sedimentary input. We present coupled dissolved and particulate phase Cu isotope data along the UK-GEOTRACES South Atlantic section, alongside higher resolution dissolved and particulate phase Cu concentration measurements. Our dissolved phase isotope data contribute to an emerging picture of homogeneous deep ocean δ65Cu, at about +0.65‰ (relative to NIST SRM 976). We identify two pools of Cu in the particulate phase: a refractory, lithogenic pool, at about 0‰, and a labile pool accessed via a weak acidic leach, at about +0.4‰. These two pools are comparable to those previously observed in sediments. We observe deviations towards lighter δ65Cu values in the dissolved phase associated with local enrichments in particulate Cu concentrations along the continental slopes, and in the surface ocean. Copper isotopes are thus a sensitive indicator of localised particle-associated benthic or estuarine Cu inputs. The measurement of Cu isotopes in seawater is analytically challenging, and we call for an intercalibration exercise to better evaluate the potential impacts of UV-irradiation, storage time, and different analytical procedures.

Copper isotopes, Dissolved, GEOTRACES, Particulate, South Atlantic
0009-2541
29-43
Little, Susan H.
e85f87f2-ac3f-461c-bcc7-034a684b93b9
Archer, Corey
df45dced-b5fc-4f2d-ba90-e047cdcc1dc1
Milne, Angela
39b44fbd-8f5e-40ea-80c9-244c20998020
Schlosser, Christian
93df4206-5ae4-48a3-80b9-d6f4fc2d4b0a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Vance, Derek
9c0575d3-caf4-4d57-b08b-b7a81f6c107c
Little, Susan H.
e85f87f2-ac3f-461c-bcc7-034a684b93b9
Archer, Corey
df45dced-b5fc-4f2d-ba90-e047cdcc1dc1
Milne, Angela
39b44fbd-8f5e-40ea-80c9-244c20998020
Schlosser, Christian
93df4206-5ae4-48a3-80b9-d6f4fc2d4b0a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Vance, Derek
9c0575d3-caf4-4d57-b08b-b7a81f6c107c

Little, Susan H., Archer, Corey, Milne, Angela, Schlosser, Christian, Achterberg, Eric P., Lohan, Maeve C. and Vance, Derek (2018) Paired dissolved and particulate phase Cu isotope distributions in the South Atlantic. Chemical Geology, 502, 29-43. (doi:10.1016/j.chemgeo.2018.07.022).

Record type: Article

Abstract

Copper (Cu) is both an essential micronutrient and toxic to photosynthesizing microorganisms at low concentrations. Its dissolved vertical distribution in the oceans is unusual, being neither a nutrient-type nor scavenged-type element. This distribution is attributed to biological uptake in the surface ocean with remineralisation at depth, combined with strong organic complexation by dissolved ligands, scavenging onto particles, and benthic sedimentary input. We present coupled dissolved and particulate phase Cu isotope data along the UK-GEOTRACES South Atlantic section, alongside higher resolution dissolved and particulate phase Cu concentration measurements. Our dissolved phase isotope data contribute to an emerging picture of homogeneous deep ocean δ65Cu, at about +0.65‰ (relative to NIST SRM 976). We identify two pools of Cu in the particulate phase: a refractory, lithogenic pool, at about 0‰, and a labile pool accessed via a weak acidic leach, at about +0.4‰. These two pools are comparable to those previously observed in sediments. We observe deviations towards lighter δ65Cu values in the dissolved phase associated with local enrichments in particulate Cu concentrations along the continental slopes, and in the surface ocean. Copper isotopes are thus a sensitive indicator of localised particle-associated benthic or estuarine Cu inputs. The measurement of Cu isotopes in seawater is analytically challenging, and we call for an intercalibration exercise to better evaluate the potential impacts of UV-irradiation, storage time, and different analytical procedures.

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Accepted/In Press date: 17 July 2018
e-pub ahead of print date: 21 July 2018
Keywords: Copper isotopes, Dissolved, GEOTRACES, Particulate, South Atlantic

Identifiers

Local EPrints ID: 424465
URI: https://eprints.soton.ac.uk/id/eprint/424465
ISSN: 0009-2541
PURE UUID: 8efa0b27-b918-40f6-8f3f-c2febb088386

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Date deposited: 05 Oct 2018 11:37
Last modified: 14 Aug 2019 16:44

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