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Characterisation of Fe-bearing particles and colloids in the Lena River basin, NE Russia
Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
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Number of Authors: 10
2017 (English)In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 213, 553-573 p.Article in journal (Refereed) Published
Abstract [en]

Rivers are significant contributors of Fe to the ocean. However, the characteristics of chemically reactive Fe remain poorly constrained, especially in large Arctic rivers, which drain landscapes highly susceptible to climate change and carbon cycle alteration. The aim of this study was a detailed characterisation (size, mineralogy, and speciation) of riverine Fe-bearing particles (> 0.22 mu m) and colloids (1 kDa-0.22 mm) and their association with organic carbon (OC), in the Lena River and tributaries, which drain a catchment almost entirely underlain by permafrost. Samples from the main channel and tributaries representing watersheds that span a wide range in topography and lithology were taken after the spring flood in June 2013 and summer baseflow in July 2012. Fe-bearing particles were identified, using Transmission Electron Microscopy, as large (200 nm(-1) mu m) aggregates of smaller (20-30 nm) spherical colloids of chemically-reactive ferrihydrite. In contrast, there were also large (500 nm(-1) mu m) aggregates of clay (illite) particles and smaller (100-200 nm) iron oxide particles (dominantly hematite) that contain poorly reactive Fe. TEM imaging and Scanning Transmission X-ray microscopy (STXM) indicated that the ferrihydrite is present as discrete particles within networks of amorphous particulate organic carbon (POC) and attached to the surface of primary produced organic matter and clay particles. Together, these larger particles act as the main carriers of nanoscale ferrihydrite in the Lena River basin. The chemically reactive ferrihydrite accounts for on average 70 +/- 15% of the total suspended Fe in the Lena River and tributaries. These observations place important constraints on Fe and OC cycling in the Lena River catchment area and Fe-bearing particle transport to the Arctic Ocean.

Place, publisher, year, edition, pages
2017. Vol. 213, 553-573 p.
Keyword [en]
iron particles, Arctic reactivity, Transmission Electron Microscopy, X-ray Absorption Spectroscopy
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-146961DOI: 10.1016/j.gca.2017.07.012ISI: 000407259200031OAI: oai:DiVA.org:su-146961DiVA: diva2:1142406
Available from: 2017-09-19 Created: 2017-09-19 Last updated: 2017-09-19Bibliographically approved

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Hirst, CatherineKutscher, LiselottMörth, Carl-Magnus
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