Influence of soil organic matter on sulfate retention in two Podzols in Quebec, Canada

1999 ◽  
Vol 79 (1) ◽  
pp. 103-109 ◽  
Author(s):  
F. Courchesne ◽  
J.-F. Laberge ◽  
A. Dufresne
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Ammonium Oxalate ◽  
X Ray Diffraction ◽  
Weighted Mean ◽  
Fine Silt ◽  
Mineral Horizon ◽  
Organic C ◽  
X Ray

The role of soil organic matter (OM) on SO4 retention was investigated by comparing OM content, SO4 retention, and the distribution of Fe, Al and Si compounds in OM-poor (Grands-Jardins, PGJ) and OM-rich (Hermine, HER) Podzols from Québec, Canada. At both sites, four pedons were sampled by horizon; soil pH in H2O, organic C, phosphate-extractable SO4 and, sodium pyrophosphate, acid ammonium oxalate and dithionite-citrate-bicarbonate (DCB) extractable Fe, Al and Si were measured for each mineral horizon. The mineralogy of the clay (<2 µm) and fine silt (2–20 µm) fractions of selected horizons was determined by X-ray diffraction (XRD) and infrared spectroscopy (IR). Weighted mean organic C and pyrophosphate extractable Fe and Al contents were significantly higher in the HER than in the PGJ sola, while the PGJ soils were richer in amorphous inorganic Al. No trends were observed for inorganic Fe compounds. Chemical dissolution and IR allowed the identification of short-range ordered aluminosilicates, probably allophane, in the OM-poor and slightly acidic to neutral PGJ soils. These materials were absent from the OM-rich and acidic HER soils. Phosphate extractions showed that the weighted mean native SO4 content was five times higher in the PGJ than in the HER soil. Finally, native SO4 was strongly related to inorganic Fe, Al and Si (associated with allophane) at PGJ but only to inorganic Fe at HER. These results indicate that OM indirectly affects SO4 sorption through the influence organic substances exerts on the nature and distribution of pedogenic Fe, Al and Si compounds, such as allophane, in Podzolic profiles. Key words: Organic matter, sulfate, imogolite, allophane, silica, Podzol

EFFECT OF SOIL ORGANIC MATTER OXIDATION ON THE COLLAPSE OF VERMICULITE

1985 ◽  
Vol 65 (3) ◽  
pp. 593-597 ◽  
Author(s):  
N. M. MILES ◽  
M. SCHNITZER ◽  
C. R. DE KIMPE
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Key Words ◽  
Mixed Layer ◽  
Ir Spectrum ◽  
X Ray Diffraction ◽  
X Ray ◽  
Organic Matter Oxidation ◽  
Ir Spectrophotometry ◽  
Complete Collapse

Oxidation of organic matter with H2O2 produced substantial amounts of NH3 which was then fixed by vermiculite, causing partial or complete collapse and converting the mineral to a mica-like product. The collapse of the mineral was indicated by shifts in the 001 spacing from 1.476 to 1.030 nm and the appearance of a well-defined band at 1430 cm−1 in the IR spectrum, indicative of the presence of NH4+ in the interlayer positions of the clay. Our data suggest that: (a) the transformation of vermiculite to mica during H2O2 oxidation may result in underestimation of the vermiculite content of soils by XRD, and (b) the wide occurrence of mixed-layer minerals in soils may in part have resulted from the fixation of NH3 liberated from the microbial mineralization of organically bound N. Key words: Ammonia, X-ray diffraction, IR spectrophotometry, mixed-layer minerals, H2O2 pretreatment

scholarly journals Evidence linking calcium to increased organo-mineral association in soils

2021 ◽  
Author(s):  
Mike C. Rowley ◽  
Stephanie Grand ◽  
Jorge E. Spangenberg ◽  
Eric P. Verrecchia
Keyword(s):  
Organic Matter ◽  
Photoelectron Spectroscopy ◽  
Isotope Composition ◽  
Density Fractionation ◽  
Stable Isotope Composition ◽  
Mineral Association ◽  
Organic Matter Quality ◽  
Organic C ◽  
X Ray

AbstractGeochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO3-bearing) or without carbonates (CaCO3-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ13C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ13C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO3-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ13C values. Bulk SOC content was twice as high in the CaCO3-bearing profiles, which also had lower bulk δ13C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ13C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ13C values.

scholarly journals Characterization of Ferrihydrite-Soil Organic Matter Coprecipitates by X-ray Diffraction and Mössbauer Spectroscopy

2008 ◽  
Vol 42 (21) ◽  
pp. 7891-7897 ◽  
Author(s):  
Karin Eusterhues ◽  
Friedrich E. Wagner ◽  
Werner Häusler ◽  
Marianne Hanzlik ◽  
Heike Knicker ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
X Ray Diffraction ◽  
X Ray

Influence of aggregate architecture and minerals on living habitats and soil organic matter

1997 ◽  
Vol 77 (3) ◽  
pp. 367-377 ◽  
Author(s):  
C. M. Monreal ◽  
H. Kodama
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Ammonium Oxalate ◽  
Clay Content ◽  
Integrated Approach ◽  
Soil Particle ◽  
Organic C ◽  
Equivalent Spherical Diameter ◽  
Primary Particles ◽  
Spherical Diameter

We used an integrated approach to determine the effects of soil particle architecture and minerals on living habitats and soil organic matter (SOM). Macroaggregate (> 250 µm), microaggregate 1 (50–250 µm), and microaggregate 2 (< 50 µm) fractions of adjacent forested and cultivated Gleysolic soil were obtained by wet sieving. The forested site was used as a reference to evaluate the effects of cultivation on soil particle architecture. Aggregates and respective clay fractions were characterized using optical, chemical, physical and microbial methods. Microaggregates 1 had primary particles with the largest mean equivalent spherical diameter (ESD) and void volume of all aggregate fractions. These physical characteristics were paralleled by the highest SOM and microbial biomass content, and number of microorganisms. Cultivation increased the weathering of primary particles and SOM loss, and decreased the content of microbial pools, suggesting deteriorated living habitats. Soil organic C content in aggregates correlated significantly with the amount of ammonium oxalate extractable Al, chloritized vermiculite, and vermiculite, and was inversely associated with the total clay content. The mean ESD of primary particles and expandable phyllosilicates of aggregates influenced living habitats by supplying substrates, and providing different void and protective space for soil microorganisms. Key words: Aggregate, mean equivalent spherical diameter, bacteria, fungi, actinomycetes, microbial biomasss, organic carbon, vermiculite, non-crystalline inorganic soil components

Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said
Keyword(s):  
Active Sites ◽  
Isopropyl Alcohol ◽  
Oxide Catalyst ◽  
Flow System ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalyst Composition ◽  
Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

T4-like Phages Reveal the Potential Role of Viruses in Soil Organic Matter Mineralization

2021 ◽  
Author(s):  
Xiaomeng Wei ◽  
Tida Ge ◽  
Chuanfa Wu ◽  
Shuang Wang ◽  
Kyle Mason-Jones ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Potential Role ◽  
Organic Matter Mineralization

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

Soil stripping and replacement for the rehabilitation of bauxite-mined land at Weipa. I. Initial changes to soil organic matter and related parameters

Soil Research ◽  
2000 ◽  
Vol 38 (2) ◽  
pp. 345 ◽  
Author(s):  
G. D. Schwenke ◽  
D. R. Mulligan ◽  
L. C. Bell
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Field Experiments ◽  
Surface Soil ◽  
Soil Disturbance ◽  
Microbial Biomass C ◽  
Low Grade ◽  
Double Pass ◽  
Organic C ◽  
The Difference

At Weipa, in Queensland, Australia, sown tree and shrub species sometimes fail to establish on bauxite-mined land, possibly because surface-soil organic matter declines during soil stripping and replacement. We devised 2 field experiments to investigate the links between soil rehabilitation operations, organic matter decline, and revegetation failure. Experiment 1 compared two routinely practiced operations, dual-strip (DS) and stockpile soil, with double-pass (DP), an alternative method, and subsoil only, an occasional result of the DS operation. Other treatments included variations in stripping-time, ripping-time, fertiliser rate, and cultivation. Dilution of topsoil with subsoil, low-grade bauxite, and ironstone accounted for the 46% decline of surface-soil (0–10 cm) organic C in DS compared with pre-strip soil. In contrast, organic C in the surface-soil (0–10 cm) of DP plots (25.0 t/ha) closely resembled the pre-strip area (28.6 t/ha). However, profile (0–60 cm) organic C did not differ between DS (91.5 t/ha), DP (107 t/ha), and pre-strip soil (89.9 t/ha). Eighteen months after plots were sown with native vegetation, surface-soil (0–10 cm) organic C had declined by an average of 9% across all plots. In Experiment 2, we measured the potential for post-rehabilitation decline of organic matter in hand-stripped and replaced soil columns that simulated the DS operation. Soils were incubated in situ without organic inputs. After 1 year’s incubation, organic C had declined by up to 26% and microbial biomass C by up to 61%. The difference in organic C decline between vegetated replaced soils (Expt 1) and bare replaced soils (Expt 2) showed that organic inputs affect levels of organic matter more than soil disturbance. Where topsoil was replaced at the top of the profile (DP) and not ploughed, inputs from volunteer native grasses balanced oxidation losses and organic C levels did not decline.

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