Evidence of titanium mobility in soil profiles, Manaus, central Amazonia

Cornu, Sophie; Lucas, Yves; Lebon, Éric; Ambrosi, Jean-Paul; Luizão, Flávio J.; Rouiller, J.; Bonnay, M; Neal, Colin

doi:10.1016/s0016-7061(99)00007-5

Cited by 173 publications

(103 citation statements)

References 31 publications

Supporting

Mentioning

100

Contrasting

Unclassified

Order By: Relevance

“…We considered Zr (see Section 2.1) as the immobile element since Ti can be mobilized through complexation with organic compounds (e.g., Cornu et al, 1999;Righi et al, 1997;Dumon and Vigneaux, 1979). The material from which the podzolization developed was taken as a reference.…”

Section: Mass Balance Calculationsmentioning

confidence: 99%

Can Fe isotope fractionations trace the pedogenetic mechanisms involved in podzolization?

et al. 2017

View full text Add to dashboard Cite

a b s t r a c t a r t i c l e i n f oStable Fe isotopes have shown the potential for tracing pedogenetic processes. Large isotopic fractionations were especially observed in Podzols. Nevertheless, a clear link between isotopic fractionation and elementary processes still needs to be established. To spatially distinguish the mechanisms successively involved in pedogenesis, we studied a podzolic chronosequence from Vancouver Island (British Columbia, Canada). We analyzed depth variations in soil properties (pH, particle size fractions, organic carbon, Si/Al ratio, Zr, Ti), Fe concentrations in different Fe pools, and Fe isotopic compositions. The Si/Al ratio, Zr, and Ti demonstrated that the Cox Bay Podzols developed from the same parental material, satisfying the requirements of a chronosequence. We showed that acidification, to a pH of 4.7, was a prerequisite for the start of podzolization. This first phase took place after 270 years. Furthermore, we observed that once the required pH was reached (4.7), podzolization occurred rapidly over 50 years. We found that Fe isotope fractionation in the A/E horizon was linked to mineral dissolution, while in the podzolic B horizons this fractionation was clearly associated with the accumulation of Fe-organic complexes and poorly crystalline Fe oxyhydroxides.

show abstract

Section: Mass Balance Calculationsmentioning

confidence: 99%

Can Fe isotope fractionations trace the pedogenetic mechanisms involved in podzolization?

et al. 2017

View full text Add to dashboard Cite

show abstract

“…This deviation suggests either addition of Ti and Nb to the regolith profile, or loss of Zr, or a combination of both. At Hakgala, Ti might be enriched in topsoil due to external inputs (see section 4.3) followed by translocation downward into the saprolite because of the mobility of fine-grained minerals in weathering horizons (Cornu et al, 1999). Alternatively, Zr might be solubilised from zircons under extreme weathering conditions (Delattre et al, 2007).…”

Section: Chemical Composition Of Bedrock and Choice Of The Immobile Ementioning

confidence: 99%

Slow advance of the weathering front during deep, supply-limited saprolite formation in the tropical Highlands of Sri Lanka

Hewawasam

Blanckenburg

Bouchez

et al. 2013

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

Silicate weathering -initiated by major mineralogical transformations at the base of ten meters of clayrich saprolite -generates the exceptionally low weathering flux found in streams draining the crystalline rocks of the mountainous and humid tropical Highlands of Sri Lanka. This conclusion is reached from a thorough investigation of the mineralogical, chemical, and Sr isotope compositions of samples within a regolith profile extending >10 m from surface soil through the weathering front in charnockite bedrock (a high-grade metamorphic rock), corestones formed at the weathering front, as well as from the chemical composition of the dissolved loads in nearby streams. Weatherable minerals and soluble elements are fully depleted at the top of the profile, showing that the system is supply-limited, such that weathering fluxes are controlled directly by the supply of fresh minerals. We determine the weathering rates using two independent means: (1) in situ-produced cosmogenic nuclides in surface soil and creek sediments in the close vicinity of the regolith combined with immobile element mass balance across the regolith and (2) river dissolved loads. Silicate weathering rates determined from both approaches range from 16 to 36 t km -2 y -1 , corresponding to a weathering front advance rate of 6 to 14 mm ky -1 . These rates agree across the 10 1 to 10 4 y time scales over which our rate metrics integrate, suggesting that the weathering system operates at steady state. Within error these rates are furthermore compatible with those obtained by modeling the advance rate of the weathering front from chemical gradients and mineral dissolution rates. The silicate weathering flux out of the weathering profile, measured on small creeks, amounts to 84% of the profile's export flux; the remaining 16% is contributed by non-silicate, atmospheric-derived input. The silicate weathering flux, as measured by dissolved loads in large catchments, amounts to ca. 50% of the total dissolved flux; the remainder being contributed by dust, rain, and weathering of local marble bands. Spheroidal weathering is the key processes of converting the fresh bedrock into saprolite at the weathering front. The mineralogical composition of weathering rinds shows that the sequence of mineral decomposition is: pyroxene; plagioclase; biotite; K-feldspar. Observable biotite alteration does not appear to initiate spheroidal weathering within corestones; therefore, we infer that other processes than biotite oxidation, like pyroxene oxidation, clay formation from pyroxene and plagioclase decomposition, the development of secondary porosity by plagioclase dissolution, or even microbiologic processes at depth enable the coupling between slow advance of the weathering front and slow erosion at the surface. The comparison to tectonically more active tropical landscapes lets us conclude that the combination of hard rock with tightly interlocked mineral grains and slow erosion in the absence of tectonically-induced landscape rejuvenation lead to these excep...

show abstract

“…The high field strength (HFS) elements Zr, Ti, and Nb are favored as index elements, because their low solubility is equated with low mobility. However, numerous studies have revealed that the HFS elements actually display some degree of mobility (Sudom and St. Arnaud, 1971;Colin et al, 1993;Cornu et al, 1999;Kurtz et al, 2000;Taboada et al, 2006;Jin et al, 2010). Such mobility may stem from redistribution of the clay and colloidal size-fractions through a matrix of larger particles (Sudom and St. Arnaud, 1971;Thompson et al, 2006) or complexation by mobile organic matter (Viers et al, 2000).…”

mentioning

confidence: 99%

Quantification of colloidal and aqueous element transfer in soils: The dual-phase mass balance model

Bern

Thompson

Chadwick

2015

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

Mass balance models have become standard tools for characterizing element gains and losses and volumetric change during weathering and soil development. However, they rely on the assumption of complete immobility for an index element such as Ti or Zr. Here we describe a dual-phase mass balance model that eliminates the need for an assumption of immobility and in the process quantifies the contribution of aqueous versus colloidal element transfer. In the model, the high field strength elements Ti and Zr are assumed to be mobile only as suspended solids (colloids) and can therefore be used to distinguish elemental redistribution via colloids from redistribution via dissolved aqueous solutes. Calculations are based upon element concentrations in soil, parent material, and colloids dispersed from soil in the laboratory. We illustrate the utility of this model using a catena in South Africa. Traditional mass balance models systematically distort elemental gains and losses and changes in soil volume in this catena due to significant redistribution of Zr-bearing colloids. Applying the dual-phase model accounts for this colloidal redistribution and we find that the process accounts for a substantial portion of the major element (e.g., Al, Fe and Si) loss from eluvial soil. In addition, we find that in illuvial soils along this catena, gains of colloidal material significantly offset aqueous elemental loss. In other settings, processes such as accumulation of exogenous dust can mimic the geochemical effects of colloid redistribution and we suggest strategies for distinguishing between the two. The movement of clays and colloidal material is a major process in weathering and pedogenesis; the mass balance model presented here is a tool for quantifying effects of that process over time scales of soil development. Published by Elsevier Ltd.

show abstract

Evidence of titanium mobility in soil profiles, Manaus, central Amazonia

Cited by 173 publications

References 31 publications

Can Fe isotope fractionations trace the pedogenetic mechanisms involved in podzolization?

Can Fe isotope fractionations trace the pedogenetic mechanisms involved in podzolization?

Slow advance of the weathering front during deep, supply-limited saprolite formation in the tropical Highlands of Sri Lanka

Quantification of colloidal and aqueous element transfer in soils: The dual-phase mass balance model

Contact Info

Product

Resources

About