Major element geochemistry of European agricultural soil: weathering processes of silicate parent materials

2021 ◽  
Author(s):  
Philippe Negrel ◽  
Anna Ladenberger ◽  
Clemens Reimann ◽  
Alecos Demetriades ◽  
Manfred Birke ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Agricultural Soil ◽  
Chemical Weathering ◽  
Large Scale ◽  
Secondary Products ◽  
Transfer Coefficients ◽  
Parent Materials ◽  
Weathering Processes ◽  
Continental Scale ◽  
Weathering Indices

<p>Collection of agricultural soil samples in Europe (0–20 cm, 33 countries, 5.6 million km<sup>2</sup>) during the GEMAS (GEochemical Mapping of Agricultural and grazing land Soil) continental-scale project allowed the study of geochemical behaviour of major elements during weathering (SiO<sub>2</sub>, TiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub>, MgO, CaO, Na<sub>2</sub>O, K<sub>2</sub>O, P<sub>2</sub>O<sub>5</sub>) using their total concentrations (XRF data). The chemical composition of soil represents to a large extent the primary mineralogy of the source bedrock, the effects of pre- and post-depositional weathering and element mobility, either by leaching or mineral sorting with the addition of formation of secondary products such as clays.</p><p>Bulk geochemistry is used to calculate a set of weathering indices such as chemical index of alteration CIA, reductive and oxidative mafic index of alteration MIA, the change in mass balance t (calculation relative to immobile Nb) for soil derived from silicate parent materials defined as granite, gneiss and schist at the European continental-scale. Silicate minerals of soil parent materials can be either very resistant to weathering or very soluble and export of elements in dissolved form and precipitation of secondary phases can occur at a large scale. Either way, they leave a strong chemical signature in derived soil, which can be quantified and classified with help of geochemical indices that are useful tools to evaluate chemical weathering trends. Weathering indices and gain-loss mass transfer coefficients were applied to agricultural soil to provide an insight into the weathering processes affecting three silicate parent rocks and their impact on soil development at the European scale. Distinct chemical composition and weathering patterns has been evidenced in silicate derived soil. The interpretation of geographical distribution of soil types with silicate substrate allows better understanding of soil nutritional status, metal enrichments, degradation mechanisms under various climate conditions.</p>

GEMAS: Adaptation of weathering indices for European agricultural soil derived from carbonate parent materials

2021 ◽  
pp. geochem2021-059
Author(s):  
Philippe Négrel ◽  
Anna Ladenberger ◽  
Clemens Reimann ◽  
Alecos Demetriades ◽  
Manfred Birke ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
Large Scale ◽  
Parent Material ◽  
Chemical Compositions ◽  
Secondary Phases ◽  
Good Tool ◽  
Continental Scale ◽  
Rock Types ◽  
Special Adaptation ◽  
Weathering Indices

Carbonate rocks are very soluble and export elements in dissolved form, and precipitation of secondary phases can occur at a large scale. They leave a strong chemical signature in soil that can be quantified and classified by geochemical indices, which are useful for evaluating chemical weathering trends (e.g., the Chemical Index of Alteration CIA or the Mafic Index of Alteration MIA). Due to contrasting chemical compositions and high Ca content, a special adaptation of classical weathering indices is necessary to interpret weathering trends in carbonate-derived soil. In fact, this adaptation seems to be a good tool for distinguishing weathering grades of source rock types at the continental-scale, and allows a more robust interpretation of soil parent material weathering grade and its impact on the current chemical composition of soil. Increasing degree of weathering results in Al enrichment and Mg loss in addition to Fe loss and Si enrichment, leaching of mobile cations such as Ca and Na and precipitation of Fe-oxides and hydroxides. Relation between soil weathering status and its spatial distribution in Europe provides important information on the role played by climate and terrain. Geographical distribution of soil chemistry contributes to a better understanding of soil nutritional status, element enrichment, degradation mechanisms, desertification, soil erosion and contamination.

Clay mineralogy in southern Africa river muds

Clay Minerals ◽  
2014 ◽  
Vol 49 (5) ◽  
pp. 717-733 ◽  
Author(s):  
M. Setti ◽  
A. Lόpez-Galindo ◽  
M. Padoan ◽  
E. Garzanti
Keyword(s):  
Chemical Composition ◽  
Southern Africa ◽  
Chemical Weathering ◽  
Volcanic Rocks ◽  
Clay Mineralogy ◽  
Climatic Conditions ◽  
Continental Scale ◽  
Transmission Electron ◽  
Mineral Associations ◽  
Physical And Chemical

AbstractThe composition, morphology and crystal order of clay minerals in silt-sized sediments carried in suspensions from 25 major rivers across tropical southern Africa have been studied by X-ray diffractometry and scanning and transmission electron microscopy. Our goal was to determine the spatial variability of clay-mineral associations in diverse geological settings, and in climatic conditions ranging from humid Angola and Zambia to hyperarid Namibia and the Kalahari. Specific attention was paid to the micromorphology and chemical composition of smectite particles. The relative abundance of smectites, illite/mica, kaolinite and chlorite enabled identification of regions characterized by different physical and chemical processes: (1) negligible chemical weathering is documented in Namibia, where river muds mostly contain illite/mica or smectite derived from Damara metasedimentary or Etendeka volcanic rocks; (2) kaolinite documenting intense weathering, reaches a maximum in the Okavango, Kwando and Upper Zambezi, sourced in subequatorial Angola and Zambia; (3) suspended-load muds in the Limpopo and middle Zambezi catchments display intermediate features, with varied assemblages and smectite compositions reflecting diverse parent lithologies. Clay mineralogy and chemical composition are confirmed as a most effective tool to unravel present and past climatic conditions on a continental scale.

Trace Metal Cycling

2006 ◽  
Author(s):  
Thomas S. Bianchi
Keyword(s):  
Trace Elements ◽  
Trace Metals ◽  
Chemical Weathering ◽  
Large Scale ◽  
Biological Effects ◽  
Plant Root ◽  
Chemical Properties ◽  
Igneous Rocks ◽  
Weathering Processes ◽  
Anthropogenic Loading

Like many other elements, natural background levels of trace elements exist in crustal rocks, such as shales, sandstones, and metamorphic and igneous rocks (Benjamin and Honeyman, 2000). In particular, the majority of trace metals are derived from igneous rocks, simply based on the relative fraction of igneous rocks in comparison with sedimentary and metamorphic rocks in the Earth’s crust. The release of trace metals from crustal sources is largely controlled by the natural forces of physical and chemical weathering of rocks, notwithstanding large-scale anthropogenic disturbances such as mining, construction, and coal burning (release of fly ash). As discussed later in the chapter, adjustments can be made for anthropogenic loading to different ecosystems based on an enrichment factor which compares metal concentrations in the ecosphere to average crustal composition. Biological effects of weathering, such as plant root growth and organic acid release associated with respiration also contribute to these weathering processes. As some trace metals are more volatile than others, release due to volcanic activity represents another source of metals with such properties (e.g., Pb, Cd, As, and Hg). Just as Goldschmidt (1954) grouped elements (e.g., siderophiles, chalcophiles, lithophiles, andatomophiles) based on similarities in geochemical properties, trace metals also represent a group of elements with similar chemical properties. One particularly important distinguishing feature of these elements is their ability to bond reversibly to a broad spectrum of compounds (Benjamin and Honeyman, 2000). Thus, the major inputs of trace metals to estuaries are derived from riverine, atmospheric, and anthropogenic sources. Although trace elements typically occur at concentrations of less than 1 ppb (part per billion) (or μg L−1, also reported in molar units), these elements are important in estuaries because of their toxic effects, as well as their importance as micronutrients for many organisms. The fate and transport of trace elements in estuaries are controlled by a variety of factors ranging from redox, ionic strength, abundance of adsorbing surfaces, and pH, just to name a few (Wen et al., 1999).

scholarly journals The Cyclops Ophiolite as a Source of High-Cr Spinels from Marine Sediments on the Jayapura Regency Coast (New Guinea, Indonesia)

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 735
Author(s):  
Karol Zglinicki ◽  
Krzysztof Szamałek ◽  
Irena Górska
Keyword(s):  
Chemical Composition ◽  
Marine Sediments ◽  
Chemical Weathering ◽  
New Guinea ◽  
Heavy Minerals ◽  
Average Content ◽  
Weathering Processes ◽  
Geochemical Parameters ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

The first detailed mineralogy, geochemistry and origin of heavy minerals in marine sediments along the Jayapura Regency coast on the Indonesian part of New Guinea Island are reported as part of a larger set of investigations conducted since 2009. In these sediments, the following heavy minerals were identified: high-Al and high-Cr spinels, chromian andradite, Mg-olivine, magnetite, mixture of iron (III) oxyhydroxides (limonite) and minerals from serpentine-group minerals (lizardite, antigorite). The heavy mineral fraction of marine sediments contains increased concentrations of metals, including W (up to 257.72 ppm) and Ag (up to 1330.29 ppb) as well as minor amounts of Ni (7.1–3560.9 ppm) and Cr (68.0–5816.0 ppm). The present state of geological knowledge suggests that there are no known prospects for rich Ti, Ni, Co, Cr, Au deposits along the examined part of the Jayapura coast. However, the average content of Ag and W is high enough to provide an impulse for suggested further deposit research. The source of marine sediments is Cyclops ophiolite, which contains a typical ophiolite sequence. Cyclops Mountain rocks have undergone intense chemical weathering processes and the resulting eroded material has been deposited on the narrow continental shelf. The chemical composition of chromian spinels indicates that their source is depleted peridotites from the SSZ (supra-subduction zone) environment of the Cyclops ophiolite. A detailed geochemical examination indicates that the evolution of parental melt of these rocks evolved towards magma with geochemical parameters similar to mid-ocean ridge basalt (MORB).

Coupled modeling of biospheric and chemical weathering processes at the continental scale

2010 ◽  
Vol 24 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. Roelandt ◽  
Y. Goddéris ◽  
M.-P. Bonnet ◽  
F. Sondag
Keyword(s):  
Chemical Weathering ◽  
Coupled Modeling ◽  
Weathering Processes ◽  
Continental Scale

scholarly journals Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 847-857 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
R. A. Graziani ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

scholarly journals Analog Downscaling of Seasonal Rainfall Forecasts in the Murray Darling Basin

2013 ◽  
Vol 141 (3) ◽  
pp. 1099-1117 ◽  
Author(s):  
Andrew Charles ◽  
Bertrand Timbal ◽  
Elodie Fernandez ◽  
Harry Hendon
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Seasonal Prediction ◽  
General Circulation Models ◽  
Meridional Wind ◽  
Seasonal Forecasts ◽  
Local Climate ◽  
Continental Scale ◽  
Predictive Skill ◽  
Murray Darling Basin

Abstract Seasonal predictions based on coupled atmosphere–ocean general circulation models (GCMs) provide useful predictions of large-scale circulation but lack the conditioning on topography required for locally relevant prediction. In this study a statistical downscaling model based on meteorological analogs was applied to continental-scale GCM-based seasonal forecasts and high quality historical site observations to generate a set of downscaled precipitation hindcasts at 160 sites in the South Murray Darling Basin region of Australia. Large-scale fields from the Predictive Ocean–Atmosphere Model for Australia (POAMA) 1.5b GCM-based seasonal prediction system are used for analog selection. Correlation analysis indicates modest levels of predictability in the target region for the selected predictor fields. A single best-match analog was found using model sea level pressure, meridional wind, and rainfall fields, with the procedure applied to 3-month-long reforecasts, initialized on the first day of each month from 1980 to 2006, for each model day of 10 ensemble members. Assessment of the total accumulated rainfall and number of rainy days in the 3-month reforecasts shows that the downscaling procedure corrects the local climate variability with no mean effect on predictive skill, resulting in a smaller magnitude error. The amount of total rainfall and number of rain days in the downscaled output is significantly improved over the direct GCM output as measured by the difference in median and tercile thresholds between station observations and downscaled rainfall. Confidence in the downscaled output is enhanced by strong consistency between the large-scale mean of the downscaled and direct GCM precipitation.

Dating of chemical weathering processes by in situ measurement of U-series disequilibria in supergene Fe-oxy/hydroxides using LA-MC-ICPMS

2006 ◽  
Vol 235 (1-2) ◽  
pp. 76-94 ◽  
Author(s):  
J.P. Bernal ◽  
S.M. Eggins ◽  
M.T. McCulloch ◽  
R. Grün ◽  
R.A. Eggleton
Keyword(s):  
Chemical Weathering ◽  
In Situ Measurement ◽  
Weathering Processes

scholarly journals Ocean deoxygenation, the global phosphorus cycle and the possibility of human-caused large-scale ocean anoxia

2017 ◽  
Vol 375 (2102) ◽  
pp. 20160318 ◽  
Author(s):  
Andrew J. Watson ◽  
Timothy M. Lenton ◽  
Benjamin J. W. Mills
Keyword(s):  
Chemical Weathering ◽  
Large Scale ◽  
Oxygen Demand ◽  
Subsurface Water ◽  
Phosphorus Cycle ◽  
Low Oxygen ◽  
Positive Feedbacks ◽  
Future Possibility ◽  
Warming World ◽  
Ocean Deoxygenation

The major biogeochemical cycles that keep the present-day Earth habitable are linked by a network of feedbacks, which has led to a broadly stable chemical composition of the oceans and atmosphere over hundreds of millions of years. This includes the processes that control both the atmospheric and oceanic concentrations of oxygen. However, one notable exception to the generally well-behaved dynamics of this system is the propensity for episodes of ocean anoxia to occur and to persist for 10 5 –10 6 years, these ocean anoxic events (OAEs) being particularly associated with warm ‘greenhouse’ climates. A powerful mechanism responsible for past OAEs was an increase in phosphorus supply to the oceans, leading to higher ocean productivity and oxygen demand in subsurface water. This can be amplified by positive feedbacks on the nutrient content of the ocean, with low oxygen promoting further release of phosphorus from ocean sediments, leading to a potentially self-sustaining condition of deoxygenation. We use a simple model for phosphorus in the ocean to explore this feedback, and to evaluate the potential for humans to bring on global-scale anoxia by enhancing P supply to the oceans. While this is not an immediate global change concern, it is a future possibility on millennial and longer time scales, when considering both phosphate rock mining and increased chemical weathering due to climate change. Ocean deoxygenation, once begun, may be self-sustaining and eventually could result in long-lasting and unpleasant consequences for the Earth's biosphere. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’.

scholarly journals Carbothermic Reduction of Zinc Containing Industrial Wastes: A Kinetic Model

2021 ◽  
Author(s):  
M. Leuchtenmueller ◽  
C. Legerer ◽  
U. Brandner ◽  
J. Antrekowitsch
Keyword(s):  
Mass Transfer ◽  
Zinc Oxide ◽  
Kinetic Model ◽  
Large Scale ◽  
Industrial Wastes ◽  
Oxide Reduction ◽  
Transfer Coefficients ◽  
Metallothermic Reduction ◽  
Metal Bath ◽  
Zinc Recovery

AbstractEffective recycling of zinc-containing industrial wastes, most importantly electric arc furnace dust, is of tremendous importance for the circular economy of the steel and zinc industry. Herein, we propose a comprehensive kinetic model of the combined carbothermic and metallothermic reduction of zinc oxide in a metal bath process. Pyro-metallurgical, large-scale lab experiments of a carbon-saturated iron melt as reduction agent for a molten zinc oxide slag were performed to determine reaction constants and accurately predict mass transfer coefficients of the proposed kinetic model. An experimentally determined kinetic model demonstrates that various reactions run simultaneously during the reduction of zinc oxide and iron oxide. For the investigated slag composition, the temperature-dependent contribution of the metallothermic zinc oxide reduction was between 25 and 50 pct of the overall reaction mechanism. The mass transfer coefficient of the zinc oxide reduction quadrupled from 1400 °C to 1500 °C. The zinc recovery rate was > 99.9 pct in all experiments.

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