Academic Journal
Ge and Si Isotope Behavior During Intense Tropical Weathering and Ecosystem Cycling
| العنوان: | Ge and Si Isotope Behavior During Intense Tropical Weathering and Ecosystem Cycling |
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| المؤلفون: | Baronas, J. Jotautas, West, A. Joshua, Burton, Kevin W., Hammond, Douglas E., Opfergelt, Sophie, Pogge von Strandmann, Philip A. E., James, Rachael H., Rouxel, Olivier J. |
| المساهمون: | UCL - SST/ELI/ELIE - Environmental Sciences |
| المصدر: | Global Biogeochemical Cycles, Vol. 34, no. 8 (2020), p. e2019GB006522 (1-25) (2020) |
| بيانات النشر: | American Geophysical Union (AGU) |
| سنة النشر: | 2020 |
| المجموعة: | DIAL@USL-B (Université Saint-Louis, Bruxelles) |
| مصطلحات موضوعية: | Atmospheric Science, Global and Planetary Change, General Environmental Science, Environmental Chemistry, Si Cycling, volcanic soils, Ge Si, Isotopes, bulk soils, weathering, chemical weathering |
| الوصف: | Chemical weathering of volcanic rocks in warm and humid climates contributes disproportionately to global solute fluxes. Geochemical signatures of solutes and solids formed during this process can help quantify and reconstruct weathering intensity in the past. Here, we measured silicon (Si) and germanium (Ge) isotope ratios of the soils, clays, and fluids from a tropical lowland rainforest in Costa Rica. The bulk topsoil is intensely weathered and isotopically light (mean±1σ: δ 30Si = –2.1 ± 0.3‰, δ 74Ge = –0.13 ± 0.12‰) compared to the parent rock (δ 30Si = –0.11 ± 0.05‰, δ 74Ge = 0.59 ± 0.07‰). Neoforming clays have even lower values (δ 30Si = –2.5 ± 0.2‰, δ 74Ge = –0.16 ± 0.09‰), demonstrating a whole-system isotopic shift in extremely weathered systems. The lowland streams represent mixing of dilute local fluids (δ 30Si = 0.2 – 0.6‰, δ 74Ge = 2.2 – 2.6‰) with solute-rich interbasin groundwater (δ 30Si = 1.0±0.2‰, δ 74Ge = 4.0‰). Using a Ge-Si isotope mass balance model, we calculate that 91 ± 9% of Ge released via weathering of lowland soils is sequestered by neoforming clays, 9 ± 9% by vegetation, and only 0.2 ± 0.2% remains dissolved. Vegetation plays an important role in the Si cycle, directly sequestering 39 ± 14% of released Si and enhancing clay neoformation in surface soils via the addition of amorphous phytolith silica. Globally, volcanic soil δ 74Ge closely tracks the depletion of Ge by chemical weathering (Ï„Ge), whereas δ 30Si and Ge/Si both reflect the loss of Si (Ï„Si). Because of the different chemical mobilities of Ge and Si, a δ 74Ge-δ 30Si multi-proxy system is sensitive to a wider range of weathering intensities than each isotopic system in isolation. |
| نوع الوثيقة: | article in journal/newspaper |
| اللغة: | English |
| تدمد: | 0886-6236 1944-9224 |
| Relation: | boreal:232716; http://hdl.handle.net/2078.1/232716; urn:ISSN:0886-6236; urn:EISSN:1944-9224 |
| DOI: | 10.1029/2019gb006522 |
| الاتاحة: | http://hdl.handle.net/2078.1/232716 https://doi.org/10.1029/2019gb006522 |
| Rights: | info:eu-repo/semantics/openAccess |
| رقم الانضمام: | edsbas.57A25AB4 |
| قاعدة البيانات: | BASE |
| تدمد: | 08866236 19449224 |
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| DOI: | 10.1029/2019gb006522 |