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

Clymans, Wim LU ; Barao, L.; Van der Putten, Nathalie LU ; Wastegard, S.; Gisladottir, G.; Björck, Svante LU ; Moine, B.; Struyf, E. and Conley, Daniel LU (2015) In Biogeosciences 12(12). p.3789-3804
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 (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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biogeosciences
volume
12
issue
12
pages
3789 - 3804
publisher
Copernicus Publications
external identifiers
  • wos:000357119000009
  • scopus:84935031352
ISSN
1726-4189
DOI
10.5194/bg-12-3789-2015
language
English
LU publication?
yes
id
9b90b2ed-75ee-40a7-8e39-3408befad9f4 (old id 7791128)
date added to LUP
2015-09-02 10:00:48
date last changed
2017-01-01 03:06:30
@article{9b90b2ed-75ee-40a7-8e39-3408befad9f4,
  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 (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.},
  author       = {Clymans, Wim and Barao, L. and Van der Putten, Nathalie and Wastegard, S. and Gisladottir, G. and Björck, Svante and Moine, B. and Struyf, E. and Conley, Daniel},
  issn         = {1726-4189},
  language     = {eng},
  number       = {12},
  pages        = {3789--3804},
  publisher    = {Copernicus Publications},
  series       = {Biogeosciences},
  title        = {The contribution of tephra constituents during biogenic silica determination: implications for soil and palaeoecological studies},
  url          = {http://dx.doi.org/10.5194/bg-12-3789-2015},
  volume       = {12},
  year         = {2015},
}