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The stability of Fe-isotope signatures during low salinity mixing in subarctic estuaries


Conrad, S and Wuttig, K and Jansen, N and Rodushkin, I and Ingri, J, The stability of Fe-isotope signatures during low salinity mixing in subarctic estuaries, Aquatic Geochemistry, 25, (5-6) pp. 195-218. ISSN 1380-6165 (2019) [Refereed Article]

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DOI: doi:10.1007/s10498-019-09360-z


We have studied iron (Fe)-isotope signals in particles (> 0.22m) and the dissolved phase (< 0.22m) in two subarctic, boreal rivers, their estuaries and the adjacent sea in northern Sweden. Both rivers, the Rne and the Kalix, are enriched in Fe and organic carbon (up to 29mol/L and up to 730mol/L, respectively). Observed changes in the particulate and dissolved phase during spring flood in May suggest different sources of Fe to the rivers during different seasons. While particles show a positive Fe-isotope signal during winter, during spring flood, the values are negative. Increased discharge due to snowmelt in the boreal region is most times accompanied by flushing of the organic-rich sub-surface layers. These upper podzol soil layers have been shown to be a source for Fe-organic carbon aggregates with a negative Fe-isotope signal. During winter, the rivers are mostly fed by deep groundwater, where Fe occurs as Fe(oxy)hydroxides, with a positive Fe-isotope signal. Flocculation during initial estuarine mixing does not change the Fe-isotope compositions of the two phases. Data indicate that the two groups of Fe aggregates flocculate diversely in the estuaries due to differences in their surface structure. Within the open sea, the particulate phase showed heavier δ56Fe values than in the estuaries. Our data indicate the flocculation of the negative Fe-isotope signal in a low salinity environment, due to changes in the ionic strength and further the increase of pH.

Item Details

Item Type:Refereed Article
Keywords:Fe-isotopes, Fe geochemistry, dissolved and particulate Fe, organically complexed Fe, Fe(oxy)hydroxides, salinity gradient, spring flood
Research Division:Earth Sciences
Research Group:Geochemistry
Research Field:Isotope Geochemistry
Objective Division:Environment
Objective Group:Physical and Chemical Conditions of Water
Objective Field:Physical and Chemical Conditions of Water in Marine Environments
UTAS Author:Wuttig, K (Dr Kathrin Wuttig)
UTAS Author:Jansen, N (Dr Nils Jansen)
ID Code:136992
Year Published:2019
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2020-01-24
Last Modified:2020-02-19

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