Iron isotope systematics in Arctic rivers

Type Article
Date 2015-11
Language English
Author(s) Escoube Raphaelle1, 2, 9, Rouxel OlivierORCID2, 3, Pokrovsky Oleg S.4, 5, 6, Schroth Andrew7, Holmes Robert Max8, Donard Olivier F. X.1
Affiliation(s) 1 : Univ Pau & Pays Adour, CNRS, LCABIE, UMR 525, F-64053 Pau, France.
2 : Woods Hole Oceanog Inst, Dept Marine Chem & Geochem, Woods Hole, MA 02543 USA.
3 : Ctr Brest, REM GM, IFREMER, Plouzane, France.
4 : Univ Toulouse 3, CNRS, Georesources & Environm Toulouse GET, UMR 5563, F-31400 Toulouse, France.
5 : Ural Branch RAS, Inst Ecol Problems North, Arkhangelsk, Russia.
6 : Tomsk State Univ, BIO GEO CLIM Lab, Tomsk 634050, Russia.
7 : Univ Vermont, Dept Geol, Burlington, VT 05405 USA.
8 : Woods Hole Res Ctr, Falmouth, MA 02540 USA.
9 : Univ Cologne, Inst Geol & Mineral, D-50674 Cologne, Germany.
Source Comptes Rendus Geoscience (1631-0713) (Elsevier France-editions Scientifiques Medicales Elsevier), 2015-11 , Vol. 347 , N. 7-8 , P. 377-385
DOI 10.1016/j.crte.2015.04.005
WOS© Times Cited 31
Keyword(s) Iron isotope, Colloids, River, Weathering, Arctic, Iron speciation
Abstract The input of iron to the Arctic Ocean plays a critical role in the productivity of aquatic ecosystems and is potentially impacted by climate change. We examine Fe isotope systematics of dissolved and colloidal Fe from several Arctic and sub-Arctic rivers in northern Eurasia and Alaska. We demonstrate that the Fe isotopic (δ56Fe) composition of large rivers, such as the Ob’ and Lena, has a restricted range of δ56Fe values ca.–0.11 ± 0.13‰, with minimal seasonal variability, in stark contrast to smaller organic-rich rivers with an overall δ56Fe range from–1.7 to + 1.6‰. The preferential enrichment with heavy Fe isotopes observed in low molecular weight colloidal fraction and during the high-flow period is consistent with the role of organic complexation of Fe. The light Fe isotope signatures of smaller rivers and meltwater reflect active redox cycling. Data synthesis reveals that small organic-rich rivers and meltwater in Arctic environments may contribute disproportionately to the input of labile Fe in the Arctic Ocean, while bearing contrasting Fe isotope compositions compared to larger rivers.
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