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© 2015. This work is published under http://creativecommons.org/licenses/by/3.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by palaeoecologists to study environmental changes. Alkaline extractions are typically used to measure BSi in both terrestrial and aquatic environments. The dissolution properties of volcanic glass in tephra deposits and their nanocrystalline weathering products are hypothesized to overlap those of BSi; however, data to support this behaviour are lacking. The potential that Si-bearing fractions dissolve in alkaline media (SiAlk) that do not necessarily correspond to BSi brings the applicability of BSi as a proxy into question. Here, analysis of 15 samples reported as tephra-containing allows us to reject the hypothesis that tephra constituents produce an identical dissolution signal to that of BSi during alkaline extraction. We found that dissolution of volcanic glass shards is incomplete during alkaline dissolution. Simultaneous measurement of Al and Si used here during alkaline dissolution provides an important parameter to enable us to separate glass shard dissolution from dissolution of BSi and other Si-bearing fractions. The contribution from volcanic glass shards (between 0.2 and 4 wt % SiO2), the main constituent of distal tephra, during alkaline dissolution can be substantial depending on the total SiAlk. Hence, soils and lake sediments with low BSi concentrations are highly sensitive to the additional dissolution from tephra constituents and its weathering products. We advise evaluation of the potential for volcanic or other non-biogenic contributions for all types of studies using BSi as an environmental proxy.

Details

Title
The contribution of tephra constituents during biogenic silica determination: implications for soil and palaeoecological studies
Author
Clymans, W 1 ; Barão, L 2 ; Van der Putten, N 1 ; Wastegård, S 3 ; Gísladóttir, G 4 ; Björck, S 1 ; Moine, B 5 ; Struyf, E 2 ; Conley, D J 1   VIAFID ORCID Logo 

 Department of Geology, Lund University, Sölvegatan 12, 22362 Lund, Sweden 
 Department of Biology, Ecosystem Management, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium 
 Department of Physical Geography, Stockholm University, 10691 Stockholm, Sweden 
 Institute of Life and Environmental Sciences, and the Nordic Volcanological Center, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland 
 Université de Lyon, Magmas et Volcans (UBP-UJM-CNRS-IRD), 23 rue Dr. P. Michelon, 42023 Saint-Etienne, France 
Pages
3789-3804
Publication year
2015
Publication date
2015
Publisher
Copernicus GmbH
ISSN
17264170
e-ISSN
17264189
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2414567079
Copyright
© 2015. This work is published under http://creativecommons.org/licenses/by/3.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.