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Daniel Conley

Daniel Conley

Professor

Daniel Conley

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

Författare

  • Wim Clymans
  • L. Barao
  • Nathalie Van der Putten
  • S. Wastegard
  • G. Gisladottir
  • Svante Björck
  • B. Moine
  • E. Struyf
  • Daniel Conley

Summary, in English

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 (Si-Alk) 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 Si-Alk. 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.

Avdelning/ar

  • Kvartärgeologi
  • BECC: Biodiversity and Ecosystem services in a Changing Climate

Publiceringsår

2015

Språk

Engelska

Sidor

3789-3804

Publikation/Tidskrift/Serie

Biogeosciences

Volym

12

Issue

12

Dokumenttyp

Artikel i tidskrift

Förlag

Copernicus GmbH

Ämne

  • Earth and Related Environmental Sciences

Aktiv

Published

ISBN/ISSN/Övrigt

  • ISSN: 1726-4189