DOI: 10.1016/j.epsl.2018.06.035
Scopus记录号: 2-s2.0-85049732811
论文题名: Time-dependent feldspar dissolution rates resulting from surface passivation: Experimental evidence and geochemical implications
作者: Daval D. ; Calvaruso C. ; Guyot F. ; Turpault M.-P.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 498 起始页码: 226
结束页码: 236
语种: 英语
英文关键词: chemical weathering
; dissolution kinetics
; fluid/silicate interface
; nanoscale characterizations
Scopus关键词: Dissolution
; Feldspar
; Geochemistry
; High resolution transmission electron microscopy
; Kinetics
; Nanotechnology
; Powders
; Silica
; Silicates
; Transmission electron microscopy
; Weathering
; Chemical weathering
; Dissolution kinetics
; Elevated concentrations
; Experimental evidence
; Interfacial boundary
; Nanoscale characterization
; Near surface regions
; Negative correlation
; Passivation
; chemical weathering
; dissolution
; feldspar
; geochemistry
; labradorite
; reaction kinetics
; silicate
; weathering profile
英文摘要: To which extent does the apparent negative correlation reported between silicate weathering rates and time result from the spontaneous physicochemical evolution of the fluid–mineral interface? To address this question, labradorite powders inserted in nylon bags and buried into two different topsoil horizons for four years were subjected to nanoscale characterization of their near-surface regions using transmission electron microscopy. These characterizations revealed the occurrence of a 30 to 70 nm-thick discontinuous amorphous silica-rich surface layer (ASSL) with a sharp crystalline-amorphous interfacial boundary between labradorite and the layer. Dissolution experiments conducted in mixed-flow reactors at ambient temperature and acidic pH demonstrated that the reactivity of fresh and naturally weathered labradorite powders decreased with time, with the dissolution rate of fresh powders remaining systematically greater than that of naturally weathered powders, all over the duration of the experiments (3 weeks). In addition, the dissolution rate of all labradorite batches was noticeably lower in solutions containing elevated concentrations of SiO2(aq), which we attributed to the passivating effect of the ASSLs. This suggestion was confirmed with a simple passivation model, which enabled to capture (i) the greater reactivity of fresh powders; (ii) the dependence of the dissolution rate on [SiO2(aq)]; (iii) the gradual decline of powder dissolution rate with time and (iv) the discontinuous occurrence of ASSLs. The model further supports that surface passivation could be one of the (non-exclusive) mechanisms that could account for the so-called kinetic “field-lab discrepancy”. The geochemical implications of the recognition of the passivation mechanism are broad, ranging from the need to revisit the kinetic rate laws implemented in geochemical codes to the questioning of the formalism used for determining weathering rates from the study of U-series nuclides in soils and weathering profiles. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109744
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: Laboratoire d'Hydrologie et de Géochimie de Strasbourg, Université de Strasbourg/EOST-CNRS UMR 7517, 1 Rue Blessig, Strasbourg, 67084, France; INRA UR 1138, Biogeochimie des Ecosystèmes Forestiers, Centre de Nancy, Champenoux, 54280, France; Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Universités – CNRS UMR 7590, Muséum National d'Histoire Naturelle, UPMC Univ Paris 06, IRD UMR 206, 61 rue Buffon, Paris, 75005, France
Recommended Citation:
Daval D.,Calvaruso C.,Guyot F.,et al. Time-dependent feldspar dissolution rates resulting from surface passivation: Experimental evidence and geochemical implications[J]. Earth and Planetary Science Letters,2018-01-01,498