7 Pedosphere

Ugolini, F. C.; Spaltenstein, H.

doi:10.1016/s0074-6142(08)62690-x

Cited by 15 publications

(10 citation statements)

References 54 publications

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“…A metric for defining how these models treat Fe cycling, for instance, is to produce a global ocean Fe residence time by comparing the ocean Fe inventory to total sources in the model (which are set to equal their sinks, so in this case residence time and replacement would be equivalent). However, available global ocean biogeochemistry models produce Fe residence times that range over 2 orders of magnitude, 4 to 560 years (Tagliabue et al, 2016). This highlights the present uncertainty associated with this essential bioactive trace element's biogeochemical cycle.…”

Section: Introductionmentioning

confidence: 99%

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Hayes

Anderson

Cheng

et al. 2018

Global Biogeochemical Cycles

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The measurable supply of 232Th to the ocean can be used to derive the supply of other elements, which is more difficult to quantify directly. The measured inventory of an element divided by the derived supply yields a replacement time estimate, which in special circumstances is related to a residence time. As a proof of concept, Th‐based supply rates imply a range in the replacement times of the rare earth elements in the North Atlantic that is consistent with the chemical reactivity of rare earth elements related to their ionic charge density. Similar estimates of replacement times for the bioactive trace elements (Fe, Mn, Zn, Cd, Cu, and Co), ranging from <5 years to >50,000 years, demonstrate the broad range of elemental reactivity in the ocean. Here we discuss how variations in source composition, fractional solubility ratios, or noncontinental sources, such as hydrothermal vents, lead to uncertainties in Th‐based replacement time estimates. We show that the constraints on oceanic replacement time provided by the Th‐based calculations are broadly applicable in predicting how elements are distributed in the ocean and for some elements, such as Fe, may inform us on how the carbon cycle may be impacted by trace element supply and removal.

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Section: Introductionmentioning

confidence: 99%

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Hayes

Anderson

Cheng

et al. 2018

Global Biogeochemical Cycles

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“…Similarly, Ewing and others (2006) demonstrated a strong shift from accumulation of atmospheric salts in the hyperarid core of the Atacama Desert to in situ mineral weathering and pedogenic carbonate formation on the wetter, arid fringes of the desert. Additional thresholds exist along regional scale ecotones such as transitions from tundra to boreal forest (Ugolini and Spaltenstein 1992).…”

Section: Introductionmentioning

confidence: 99%

Pedogenic Thresholds and Soil Process Domains in Basalt-Derived Soils

2013

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Pedogenic thresholds occur where soil properties change abruptly and/or nonlinearly with a small increment in environmental forcing; soil process domains are the regions between thresholds where soils change much more gradually across a large range of environmental forcing. We evaluated thresholds and domains in basalt-derived soils on two rainfall gradients in Hawaii-one from 260 to 3,540 mm/y precipitation on 150,000-year-old substrate, the other from 600 to 3,760 mm/y on 4,100,000-year-old substrate. We identified thresholds associated with the initiation of biological uplift of nutrients at about 700 mm/y on the younger substrate, the depletion of primary minerals at about 2,100 mm/y on the younger and about 900 mm/y on the older substrate, and the initiation of anoxic conditions and associated Fe mobility at about 2,500 mm/y on the older substrate. These thresholds delineated process domains characterized by pedogenic carbonate accumulation and wind erosion (dry young substrate); by weathering and biological uplift of nutrients (intermediate rainfall young substrate and dry old substrate); by surface Fe enrichment and nutrient depletion (wet young substrate and intermediate rainfall old substrate); and by Fe mobilization and loss (wet old substrate). Soils on the older substrate were more highly weathered, lower in total and available P, and characterized by more crystalline clays than otherwise comparable soils on the younger substrate. Prior to European contact, Hawaiian cultivators developed an intensive rainfed agricultural system in the weathering/biological uplift domain on the younger substrate; we suggest that only this domain could support indigenous agricultural intensification in upland soils.

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“…Strakhov contrasted the soil pro les in these climate zones with progressively more arid climate zones: the savannas, steppes, tundra and hot deserts. An update on this global section has been constructed by Ugolini and Spaltenstein (1992) within a comprehensive review of soils and soil processes. Table 1 is a selection of just four Soil Order descriptions from ten given in their gure 7-4.…”

Section: Factors Of Soil Formationmentioning

confidence: 99%

“…Mineral and organic matter attributes: selected characteristic soil pro les (afterUgolini and Spaltenstein, 1992).…”

mentioning

confidence: 99%

The aqueous geochemistry of metals in the weathering environment: strengths and weaknesses in our understanding of speciation and process

Curtis

2003

Mineral. mag.

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Soil profiles developed in different climates and physical settings are highly variable in structure, in mineralogy, in the local biosphere and in the compositions of the soil gas and water phases. Discussion of metals in 'the weathering environment' needs to acknowledge and address this diversity.The thermochemical methods developed by Pourbaix (1949) and Garrels and Christ (1965) remain useful predictors of metal speciation and solubility but the approach is valid only for processes involving carbonates, sulphides, hydroxides and similar minerals in soils and sediments. Almost no primary silicates are thermodynamically stable: they spontaneously decompose to non-equilibrium solid products with metal release determined by kinetics.Hydrolysis constants for aquo-complexes are useful indicators of metal speciation, mobility and availability. Recent work on soluble soil organic matter confirms that the active ligands are overwhelmingly oxygen based: phenols, carboxylic acids, alcohols. Many of these molecules compete very effectively with aquo-complexes to form strong metal chelates and appear to be responsible for substantial Al and Fe mobilization within and translocation down soil profiles.It is important to note also that strong clay mineral/organic matter associations (clay-organic complex) will fix metals as a consequence of the same chelation reactions (in this case removing them from solution -retardation).

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7 Pedosphere

Cited by 15 publications

References 54 publications

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Pedogenic Thresholds and Soil Process Domains in Basalt-Derived Soils

The aqueous geochemistry of metals in the weathering environment: strengths and weaknesses in our understanding of speciation and process

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