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Kristin Doering

Kristin Doering

Researcher

Kristin Doering

Dissolved silicon isotope dynamics in large river estuaries

Author

  • Zhouling Zhang
  • Zhimian Cao
  • Patricia Grasse
  • Minhan Dai
  • Lei Gao
  • Henning Kuhnert
  • Martha Gledhill
  • Cristiano M. Chiessi
  • Kristin Doering
  • Martin Frank

Summary, in English

Estuarine systems are of key importance for the riverine input of silicon (Si) to the ocean, which is a limiting factor of diatom productivity in coastal areas. This study presents a field dataset of surface dissolved Si isotopic compositions (δ30SiSi(OH)4) obtained in the estuaries of three of the world's largest rivers, the Amazon (ARE), Yangtze (YRE), and Pearl (PRE), which cover different climate zones. While δ30SiSi(OH)4 behaved conservatively in the YRE and PRE supporting a dominant control by water mass mixing, significantly increased δ30SiSi(OH)4 signatures due to diatom utilization of Si(OH)4 were observed in the ARE and reflected a Si isotopic enrichment factor 30ε of −1.0 ± 0.4‰ (Rayleigh model) or −1.6 ± 0.4‰ (steady state model). In addition, seasonal variability of Si isotope behavior in the YRE was observed by comparison to previous work and most likely resulted from changes in water residence time, temperature, and light level. Based on the 30ε value obtained for the ARE, we estimate that the global average δ30SiSi(OH)4 entering the ocean is 0.2–0.3‰ higher than that of the rivers due to Si retention in estuaries. This systematic modification of riverine Si isotopic compositions during estuarine mixing, as well as the seasonality of Si isotope dynamics in single estuaries, needs to be taken into account for better constraining the role of large river estuaries in the oceanic Si cycle.

Publishing year

2020-03-15

Language

English

Pages

367-382

Publication/Series

Geochimica et Cosmochimica Acta

Volume

273

Document type

Journal article

Publisher

Elsevier

Topic

  • Oceanography, Hydrology, Water Resources

Keywords

  • Biological fractionation
  • Conservative mixing
  • Large river estuaries
  • Riverine Si input
  • Stable Si isotopes

Status

Published

ISBN/ISSN/Other

  • ISSN: 0016-7037