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Assessment of the stability, sorption, and exchangeability of marine dissolved and colloidal metals

Assessment of the stability, sorption, and exchangeability of marine dissolved and colloidal metals
Assessment of the stability, sorption, and exchangeability of marine dissolved and colloidal metals
The size partitioning of dissolved trace metals is an important factor for determining reactivity and bioavailability of metals in marine environments. This, alongside the advent of more routine shipboard ultrafiltration procedures, has led to increased attention in determining the colloidal phase of metals such as Fe in seawater. While clean and efficient filtration, prompt acidification, and proper storage have long been tenets of trace metal biogeochemistry, few studies aim to quantify the kinetics of colloidal exchange and metal adsorption to bottle walls during storage and acidification. This study evaluates the effect of storage conditions on colloidal size partitioning, the kinetics of colloid exchange over time, and the timescale of bottle wall adsorption and desorption for dissolved Fe, Cu, Ni, Zn, Cd, Pb, Mn and Co. We report that preservation of dissolved size partitioning is possible only for Fe and only under frozen conditions. All metals except Mn and Cd show regeneration of the colloidal phase following its removal in as short as 14 h, validating the importance of prompt ultrafiltration. Adsorption of metals to bottle walls is a well-known sampling artifact often cited for Fe and assumed to be potentially significant for other metals as well. However, only Fe and Co showed significant proclivity to adsorption onto low density polyethylene bottle walls, sorbing a maximum of 91 and 72% over 40 months, respectively. After 20 weeks of acidification neither Fe nor Co desorbed to their original concentrations, leading to an acidified storage recommendation of 30 weeks prior to analyses following storage of unacidified samples for long periods of time. This study provides empirical recommendations for colloidal and dissolved trace metal methodology while also paving the way for much-needed future methods testing.
0304-4203
1-16
Jensen, L.T.
007c25cc-0d92-4528-a012-380134ba5a4a
Wyatt, N.J.
258d214b-9dae-4a5f-acc9-c0a55fb66efd
Landing, W.M.
26eb4b62-d05c-42bb-a757-f840915f6576
Fitzsimmons, J.N.
c361acaf-0553-4e11-84ac-5772a454e9da
Jensen, L.T.
007c25cc-0d92-4528-a012-380134ba5a4a
Wyatt, N.J.
258d214b-9dae-4a5f-acc9-c0a55fb66efd
Landing, W.M.
26eb4b62-d05c-42bb-a757-f840915f6576
Fitzsimmons, J.N.
c361acaf-0553-4e11-84ac-5772a454e9da

Jensen, L.T., Wyatt, N.J., Landing, W.M. and Fitzsimmons, J.N. (2020) Assessment of the stability, sorption, and exchangeability of marine dissolved and colloidal metals. Marine Chemistry, 220, 1-16, [103754]. (doi:10.1016/j.marchem.2020.103754).

Record type: Article

Abstract

The size partitioning of dissolved trace metals is an important factor for determining reactivity and bioavailability of metals in marine environments. This, alongside the advent of more routine shipboard ultrafiltration procedures, has led to increased attention in determining the colloidal phase of metals such as Fe in seawater. While clean and efficient filtration, prompt acidification, and proper storage have long been tenets of trace metal biogeochemistry, few studies aim to quantify the kinetics of colloidal exchange and metal adsorption to bottle walls during storage and acidification. This study evaluates the effect of storage conditions on colloidal size partitioning, the kinetics of colloid exchange over time, and the timescale of bottle wall adsorption and desorption for dissolved Fe, Cu, Ni, Zn, Cd, Pb, Mn and Co. We report that preservation of dissolved size partitioning is possible only for Fe and only under frozen conditions. All metals except Mn and Cd show regeneration of the colloidal phase following its removal in as short as 14 h, validating the importance of prompt ultrafiltration. Adsorption of metals to bottle walls is a well-known sampling artifact often cited for Fe and assumed to be potentially significant for other metals as well. However, only Fe and Co showed significant proclivity to adsorption onto low density polyethylene bottle walls, sorbing a maximum of 91 and 72% over 40 months, respectively. After 20 weeks of acidification neither Fe nor Co desorbed to their original concentrations, leading to an acidified storage recommendation of 30 weeks prior to analyses following storage of unacidified samples for long periods of time. This study provides empirical recommendations for colloidal and dissolved trace metal methodology while also paving the way for much-needed future methods testing.

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Jensen-etal-2020-Unformatted - Accepted Manuscript
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e-pub ahead of print date: 16 January 2020
Published date: 20 March 2020

Identifiers

Local EPrints ID: 440897
URI: http://eprints.soton.ac.uk/id/eprint/440897
ISSN: 0304-4203
PURE UUID: a3c60e42-3f08-4a6c-942d-bb1c53898ad4
ORCID for N.J. Wyatt: ORCID iD orcid.org/0000-0002-1080-7778

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Date deposited: 21 May 2020 16:33
Last modified: 26 Nov 2021 05:56

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Contributors

Author: L.T. Jensen
Author: N.J. Wyatt ORCID iD
Author: W.M. Landing
Author: J.N. Fitzsimmons

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