The contribution of tephra constituents during biogenic silica determination: implications for soil and palaeoecological studies

Autor: G. Gisladottir, Svante Björck, Eric Struyf, Bertrand Moine, N. Van der Putten, Sefan Wastegård, Lúcia Barão, Daniel J. Conley, Wim Clymans
Přispěvatelé: Lund University [Lund], Department of Physical Geography and Quaternary Geology, Stockholm University, Department of Quaternary Geology, Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Antwerp (UA), Geobiosphere Centre, Department of Geology, Jouhannel, Sylvaine, Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)
Jazyk: angličtina
Rok vydání: 2015
Předmět:
Zdroj: Biogeosciences, Vol 12, Iss 12, Pp 3789-3804 (2015)
Biogeosciences Discussions
Biogeosciences Discussions, European Geosciences Union, 2015, 12, pp.3505-3545
Biogeosciences Discussions, 2015, 12, pp.3505-3545
Biogeosciences
ISSN: 1726-4189
1726-4170
1810-6277
1810-6285
Popis: Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by paleoecologists 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 nano-crystalline weathering products are hypothesized to overlap those of BSi, however, data to support this behavior are lacking. The understanding that the Si-bearing fractions that dissolve in alkaline media (SiAlk) do not necessarily correspond to BSi, question the applicability of BSi as a proxy. 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 shard (between 0.2–4 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.
Databáze: OpenAIRE
Externí odkaz: