Sr and Nd isotopes as tracers in pedogenic studies: Evidence for Saharan dust contribution to the soils of Muravera (Sardinia, Italy)

Castorina, Francesca; Masi, Umberto

doi:10.1016/j.chemer.2015.04.003

Cited by 6 publications

(1 citation statement)

References 48 publications

(77 reference statements)

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“…Furthermore, the elevated Ca mass transfer coefficient (Figure 4 and Figure S4 in Supporting Information S1) is far higher than that produced by any reasonable modeled mineral assemblage. A plausible explanation for these observations is an exogenous dust input to the watershed, likely derived from sections of the Saharan desert (Goudie & Middleton, 2001;Israelevich et al, 2012), which commonly contains Journal of Geophysical Research: Earth Surface 10.1029/2023JF007359 carbonate (Krueger et al, 2004) and has been shown to influence weathering profiles across the European continent (e.g., Angelisi & Gaudichet, 1991;Castorina & Masi, 2015;Menéndez et al, 2007). Taking an average Li composition for Saharan dust (Li/Na = 65 μM/mM and δ 7 Li = +0.7‰; Clergue et al, 2015) and a typical marine aerosol composition, the precipitation signature measured at Sapine suggests the observed rainwater signal (Li/Na = 1.2 μM/mM) is composed of 96% dust input based on a mixing expression for Li/Na (Golla et al, 2022, their equations S3 and S4).…”

Section: Influence Of Atmospheric Depositionmentioning

confidence: 99%

Weathering Incongruence in Mountainous Mediterranean Climates Recorded by Stream Lithium Isotope Ratios

Golla,

Bouchez,

Kuessner

et al. 2024

JGR Earth Surface

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Lithium isotope ratios (δ7Li) of rivers are increasingly serving as a diagnostic of the balance between chemical and physical weathering contributions to overall landscape denudation rates. Here, we show that intermediate weathering intensities and highly enriched stream δ7Li values typically associated with lowland floodplains can also describe small upland watersheds subject to cool, wet climates. This behavior is revealed by stream δ7Li between +22.4 and +23.5‰ within a Critical Zone observatory located in the Cévennes region of southern France, where dilute stream solute concentrations and significant atmospheric deposition otherwise mask evidence of incongruence. The water‐rock reaction pathways underlying this behavior are quantified through a multicomponent, isotope‐enabled reactive transport model. Using geochemical characterization of soil profiles, bedrock, and long‐term stream samples as constraints, we evolve the simulation from an initially unweathered granite to a steady state weathering profile which reflects the balance between (a) fluid infiltration and drainage and (b) bedrock uplift and soil erosion. Enriched stream δ7Li occurs because Li is strongly incorporated into actively precipitating secondary clay phases beyond what prior laboratory experiments have suggested. Chemical weathering incongruence is maintained despite relatively slow reaction rates and moderate clay accumulation due to a combination of two factors. First, reactive primary mineral phases persist across the weathering profile and effectively “shield” the secondary clays from resolubilization due to their greater solubility. Second, the clays accumulating in the near‐surface profile are relatively mature weathering byproducts. These factors promote characteristically low total dissolved solute export from the catchment despite significant input of exogenous dust.

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