DOI: 10.1016/j.epsl.2018.09.022
Scopus记录号: 2-s2.0-85054446697
论文题名: Ge and Si isotope signatures in rivers: A quantitative multi-proxy approach
作者: Baronas J.J. ; Torres M.A. ; West A.J. ; Rouxel O. ; Georg B. ; Bouchez J. ; Gaillardet J. ; Hammond D.E.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 503 起始页码: 194
结束页码: 215
语种: 英语
英文关键词: fractionation
; germanium
; isotopes
; rivers
; silicon
; weathering
Scopus关键词: Biogeochemistry
; Dissolution
; Earth (planet)
; Fractionation
; Germanium
; Isotopes
; Rivers
; Silicate minerals
; Silicon
; Suspended sediments
; Biogeochemical cycle
; Chemical similarity
; Chemical weathering
; Isotope compositions
; Isotopic composition
; Isotopic fractionations
; Particulate phasis
; Weathering process
; Weathering
英文摘要: Solutes derived from the dissolution of silicate minerals play a key role in Earth's climate via the carbon and other biogeochemical cycles. Silicon (Si) is a unique constituent of silicate minerals and a biologically important nutrient, so tracing its behavior in near-surface environments may provide important insights into weathering processes. However, Si released by weathering is variably incorporated into secondary mineral phases and biota, obscuring signals derived from primary weathering processes. Due to chemical similarities, Germanium (Ge) may help better understand the Si cycle and its relationship to chemical weathering. With this aim, we report new measurements of the concentration and isotopic composition of Ge for both the dissolved and particulate phases of a variety of global rivers. These measurements are combined with analyses of concentration and isotopic ratio of Si on the exact same sample set in order to make direct comparisons of the behavior of these two elements in natural river systems. With this dataset, we develop a new modeling framework describing the full elemental and isotopic systems of these solutes in rivers (i.e., Ge/Si, δ74Ge, and δ30Si). This multi-proxy approach allows us to ascertain the relative importance of biological versus mineral uptake in modulating the fluxes of these elements delivered to the modern ocean. Dissolved δ74Ge composition of rivers studied thus far range from 0.9 to 5.5‰ with a discharge-weighted global average of 2.6 ± 0.5‰. The Ge isotope composition of riverine suspended and bedload sediments is indistinguishable from silicate source rocks, which is consistent with mass balance expectations. The multi-proxy modeling suggests that, among the watersheds studied here, the isotopic fractionation of Si during secondary mineral phase precipitation (Δ30Sisec) ranges from −2.7 to −0.2‰, which removes between 19–79% of the initial dissolved Si, while between 12–54% is incorporated by biota. For Ge, modeling indicates that 79–98% of the dissolved load is incorporated into secondary mineral phases with a Δ74Gesec ranging from −4.9 to −0.3‰. The fractionation induced by biological uptake is calculated to range from −2.6 to −1.3‰ for Δ30Sibio and −0.7 ± 0.7‰ for Δ74Gebio. In addition to improving our understanding of the coupled Ge and Si cycles, our study provides a framework for using multiple isotopic tracers to elucidate the chemical behavior of solutes in natural waters. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109630
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, United States; Institut Français de Recherche pour l'Exploitation de la Mer, Centre de Brest, Technopôle Brest Iroise, Plouzané, 29280, France; Water Quality Centre, Trent University, Peterborough, ON K9L 1Z8, Canada; Institut de Physique du Globe de Paris (IPGP), Sorbonne Paris Cité, University Paris Diderot, CNRS, Paris, 75231, France; Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom; Department of Earth, Environmental and PLanetary Sciences, Rice University, Houston, TX 77005, United States; Agilent Technologies Canada, 6705 Millcreek Dr MississaugaON L5N 5M4, Canada
Recommended Citation:
Baronas J.J.,Torres M.A.,West A.J.,et al. Ge and Si isotope signatures in rivers: A quantitative multi-proxy approach[J]. Earth and Planetary Science Letters,2018-01-01,503