Dispersed clay and organic matter in soil: their nature and associations

Soil Research ◽  
1999 ◽  
Vol 37 (2) ◽  
pp. 289 ◽  
Author(s):  
P. N. Nelson ◽  
. A. Baldock ◽  
J. M. Oades ◽  
G. J. Churchman ◽  
P. Clarke
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
High Surface ◽  
High Surface Area ◽  
Clay Fraction ◽  
Sodic Soils ◽  
Organic C ◽  
Clay Dispersion ◽  
13C Nuclear Magnetic Resonance ◽  
Colloidal Materials

Clay dispersion in soil results in structural instability and management problems. The aim of this study was to determine whether or not the easily dispersed colloidal materials differ in their properties from colloidal materials that do not disperse easily. Soil samples from the topsoil of sodic and non-sodic variants of an Alfisol under irrigated pasture (Kyabram, Victoria, Australia), and from the topsoil and subsoil of a sodic Alfisol under cultivation (Two Wells, South Australia) were fractionated into easily dispersed, moderately dispersed, and difficult to disperse clay, and silt, sand, and light fractions. As a proportion of total clay, easily dispersed clay content was greatest in the subsoil, and least in the Kyabram topsoils. In the topsoils, easily dispersed clay had larger particle size and lower cation exchange capacity than difficult to disperse clay, suggesting that high surface area and charge lead to increased inter-particle interactions and lower dispersibility. Easily dispersed clay had lower organic C contents than difficult to disperse clay. Organic matter was examined by 13C nuclear magnetic resonance, and the spectra were interpreted using major groups of biomolecules as model components. In all soils, organic matter in the easily dispersed clay fraction contained a high proportion of amino acids, suggesting that amino acids or proteins acted as dispersants. Difficult to disperse clay contained a high proportion of aliphatic materials in the topsoils, and carbohydrate in the subsoil, suggesting that these materials acted as water-stable glues. Selectivity for Na (KG) was negatively correlated with organic C content in the clay fractions. In the Kyabram soils, KG was greater in easily dispersed clay than in difficult to disperse clay. In Two Wells soil, clay with high KG appeared to have already moved out of the topsoil, into the subsoil. This work showed that variability in the nature of organic matter and clay particles has an important influence on clay dispersion in sodic and non-sodic soils.

Effect of crop rotations and fertilization on soil organic matter and some biochemical properties of a thick Black Chernozem

1991 ◽  
Vol 71 (3) ◽  
pp. 377-387 ◽  
Author(s):  
C. A. Campbell ◽  
R. P. Zentner ◽  
K. E. Bowren ◽  
L. Townley-Smith ◽  
M. Schnitzer
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Crop Residues ◽  
Cultural Practices ◽  
Organic Matter Content ◽  
Biochemical Properties ◽  
Matter Content ◽  
Organic C ◽  
Cropping Frequency

The effects of crop rotation and various cultural practices on soil organic matter and some biochemical characteristics of a heavy-textured, Orthic Black Chernozem with a thick A horizon were determined after 31 yr at Melfort, Saskatchewan. Treatments investigated included: fertilization, cropping frequency, green manuring, and inclusion of grass-legume hay crops in predominantly spring wheat (Triticum aestivum L.) systems. The results showed that neither soil organic C nor N in the top 15 cm of soil, nor hydrolyzable amino acids, nor C mineralized in 14 d at 20 °C were influenced by fertilization. However, the relative molar distribution (RMD) of the amino acids reflected the influence of fertilization and the phase (Rot-yr) of the legume green manure rotation sampled. Some characteristics assessed increased marginally with increasing cropping frequency but differences were less marked than results obtained earlier in a heavy-textured Black Chernozem with a thin A horizon at Indian Head, Saskatchewan. The relationship between soil organic matter or C mineralization versus estimated crop residues, residue C, or residue N returned to the land over the 31-yr period, were not significant in the Melfort soil. This contrasts with our findings for the thin Black soil. We speculate that the lack of soil organic matter response in the Melfort soil was due to its very high organic matter content (about 64 t ha−1C and 6.5 t ha−1N in the top 15 cm). We also hypothesized that the amino acid RMD results, which differed from most of those reported in the literature, may be reflecting the more recent cropping history of the soil. This aspect requires further research into the composition and distribution of the humic materials in this soil. Key words: Amino acids, relative molar distribution, C respiration, green manures, fertilization

scholarly journals Extraction and Transport of Amino Acids Using Kryptofix 5 as Carrier through Liquid Membrane

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Pankaj Raizada ◽  
Uma Sharma
Keyword(s):  
Amino Acids ◽  
Liquid Membrane ◽  
High Surface ◽  
High Surface Area ◽  
Membrane System ◽  
Extraction Process ◽  
Bulk Liquid ◽  
Bulk Liquid Membrane ◽  
Aromatic Donor ◽  
Egg Shell

The present work explores membrane-mediated extraction and transport studies of amino acids through artificial bulk liquid membrane system with kryptofix 5 as a carrier. The various reaction parameters such as amino acid concentration, carrier concentration, time, pH, and stirring effect were studied to optimize reaction conditions. The stirring of source and receiving phases increased the efficiency of extraction process. Noncyclic receptor kryptofix 5 with five oxyethylene units and terminal aromatic donor end groups governs its transport and extraction efficiency. The extraction and transport efficiency followed the following trend: valine > alanine > glycine > threonine. Supported liquid membrane (SLM) studies were performed using cellulose nitrate, PTFE, eggshell, and onion membranes. The egg shell membrane support proved to be most efficient due to intricate network of water insoluble proteins fibers with very high surface area and homogeneity.

NITROGEN DISTRIBUTION IN ILLUVIAL ORGANIC MATTER

1967 ◽  
Vol 47 (2) ◽  
pp. 111-116 ◽  
Author(s):  
F. J. Sowden ◽  
M. Schnitzer
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Fulvic Acid ◽  
Fulvic Acids ◽  
Organic N ◽  
Insoluble Residue ◽  
Amino Sugars ◽  
Humic And Fulvic Acids ◽  
Organic C ◽  
Soil Amino Acids

Organic matter (O.M.) was extracted with 0.5 N NaOH under N2, from samples of the Bh horizon of a Podzol soil. The NaOH-soluble O.M. from one sample was partitioned into "classical" humic and fulvic acids. The O.M. extracted from other samples was passed over an H-resin and purified fulvic acid" was prepared from the eluate. The O.M. retained on the resin was eluted with base. After hydrolysis a sample of the original soil the NaOH-insoluble residue and the various O.M. preparations were analyzed for amino acids, amino sugars and ammonia.Eighty percent of the amino acids in the original soil were accounted for in the NaOH-insoluble residue plus the purified fulvic acid and the NH4OH eluate. Most of the soil amino acids were recovered in the NaOH-insoluble residue plus classical humic plus classical fulvic acid fractions. Qualitatively, the amino acid distribution in all fractions was similar to the distribution or amino acids in an "average" protein. Amounts of amino sugars were small consisting of two-thirds glucosamine and one-third galactosamine. Recoveries of amino sugars were low, possibly due to the effect of alkali.Slightly more than 50% of the soil-N was accounted for as amino acids plus NH3 plus amino sugars. The behavior of the fraction on the exchange resin suggested that the organic C- organic N-system extracted from the soil was not uniform, and that at least portions of the ammo acids and amino sugars were either adsorbed on or physically mixed with organic matter.

Sorption of anthropogenic organic compounds by soil organic matter: a mechanistic consideration

2001 ◽  
Vol 81 (3) ◽  
pp. 317-323 ◽  
Author(s):  
Baoshan Xing
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Compounds ◽  
High Surface ◽  
High Surface Area ◽  
Fate And Transport ◽  
Dual Mode ◽  
Subsurface Environments ◽  
Desorption Hysteresis ◽  
Sorption Mechanisms

Sorption experiments with apolar organic compounds (naphthalene and 1,2-dichorobenzene) were conducted to evaluate sorption mechanisms in soil organic matter (SOM). All isotherms were nonlinear and competition between solutes was observed. Nonlinearity and competition increased in an order of peat humic acid (HA) < peat < peat humin. Isotherms of Al-saturated HA (Al-HA) were more nonlinear than untreated HA and Ca-HA, and sorption/desorption hysteresis occurred only in Al-HA. These results are not consistent with partitioning theory or the presence of high-surface-area carbonaceous materials (HSACM) in soil. But the results are consistent with dual-mode sorption, where SOM is postulated to have both condensed (rigid) and expanded (flexible) domains, and adsorption takes place only in the condensed domains and partitioning in both domains. These non-ideal sorptive behaviors need to be incorporated into predictive models to more accurately describe the fate and transport of organics in soil and subsurface environments. Key words: sorption, organic compounds, organic matter, dual-mode, partition, mechanisms

scholarly journals Diagenetic alterations of amino acids and organic matter in the upper Pearl River Estuary surface sediments

2012 ◽  
Vol 9 (1) ◽  
pp. 555-564 ◽  
Author(s):  
J. Zhang ◽  
R. Zhang ◽  
Q. Wu ◽  
N. Xu
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
C:N Ratio ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Total N ◽  
Organic C ◽  
Diagenetic Alteration ◽  
C And N

Abstract. The objective of this study was to investigate the diagenetic alteration of sediment organic matter (OM) in the upper Pearl River Estuary. Sediment analyses were conducted for three size fractions of OM, including coarse particulate OM (CPOM), fine particulate OM (FPOM), and ultrafiltered dissolved OM (UDOM). Results showed that the highest and lowest carbon (C): nitrogen (N) ratios were in CPOM and UDOM, respectively, indicating that CPOM was relatively enriched in organic C. The highest average total N content in the FPOM fraction showed that FPOM was enriched in N-containing molecules. Our study showed that the "size-reactivity continuum" model was applicable to sediment particulate and dissolved OM. Distributions of amino acids and their D-isomers among the sediment fractions indicated that the amino acid-based diagenetic index, C:N ratio, and percentage of total N represented by total hydrolysable amino acids could be used as diagenetic indicators. Furthermore, the diagenetic state of sediment OM could also be characterized by C- and N-normalized yields of total D-amino acids, and C- and N-normalized yields of D-alanine, D-glutamic acid, and D-serine.

scholarly journals Diagenetic alterations of amino acids and organic matter in the upper Pearl River Estuary surface sediments

2011 ◽  
Vol 8 (2) ◽  
pp. 3323-3352
Author(s):  
J. Zhang ◽  
R. Zhang ◽  
Q. Wu ◽  
N. Xu
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Vascular Plant ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Total N ◽  
Organic C ◽  
Estuary Sediment ◽  
C And N

Abstract. The objective of this study was to investigate the sources, diagenetic alterations of, and bacterial contributions to sediment organic matter (OM) in the upper Pearl River Estuary. Sediment analyses were conducted for three size fractions of OM, including coarse particulate OM (CPOM), fine particulate OM (FPOM), and ultrafiltered dissolved OM (UDOM). Results showed that the highest and lowest carbon (C): nitrogen (N) ratios were in CPOM and UDOM, respectively, indicating CPOM was relatively enriched in organic C, whereas FPOM was enriched in N-containing molecules. Distributions of amino acids and their D-isomers among the sediment fractions indicated that the percentage of total N represented by total hydrolysable amino acids, C- and N-normalized yields of total D-amino acids, and C- and N-normalized yields of D-alanine, D-glutamic acid, D-serine could be used as diagenetic indicators of sediment OM. Correlations between the N yields in total D-amino acids and total hydrolysable amino acids, and total N yields suggested that the bacterial N in general reflected the bulk N changes in CPOM, FPOM, and UDOM. Our results demonstrate the crucial role of bacteria as a N source in the terrestrial (soil and vascular plant debris) OM transported by the river.

Possible role of aluminum in stabilizing organic matter in particle size fractions of Chernozemic and solonetizic soils

2002 ◽  
Vol 82 (2) ◽  
pp. 265-268 ◽  
Author(s):  
D. Curtin
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Specific Surface ◽  
Clay Fraction ◽  
Organic Matter Content ◽  
Ultrasonic Dispersion ◽  
Organic C ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Organic Matter Stabilization

Although phyllosilicate clays, with their large surface areas, are often considered to play the leading role in stabilizing soil organic matter against microbial attack, several studies have suggested recently that oxides of Al and Fe may stabilize organic matter in some soils. The distribution of organic C and oxides in clay (< 0.2 and 0.2–2 mm) and silt fractions (2–5, 5–20, and 20–50 mm) of four Saskatchewan soils (organic C ranged from 21 to 46 g kg-1) was examined to differentiate the contributions of oxides and specific surface to organic matter retention. Carbon concentrations in the particle size fractions (separated following ultrasonic dispersion of the soils) tended to be highest in the fine silt and coarse clay fractions, not in the fine clay as would be expected if specific surface was the sole factor governing organic matter content. When data for the four soils were pooled there was a strong relationship between organic C (y) in the size fractions and Al (x) extracted by dithionite-citrate-bicarbonate [y = 33.9 x0,5 - 7.3; R2 = 0.90***], suggesting a role for A1 in determining the C storage capacity of the size fractions. The C: A1 ratio increased from an average of 12:1 in clay-sized material to 28:1 in coarse silt. Because it had less A1 per unit mass of C, organic matter in the silt separates may be more weakly bonded to mineral material than is clay-associated organic matter. This may imply that organic matter bound to silt is less stable, and thus susceptible to mineralization, than is organic matter residing in the clay fraction. Key words: Organic matter stabilization, particle size separates, extractable A1 and Fe

scholarly journals DISTRIBUTION OF ORGANIC CARBON IN DIFFERENT SOIL FRACTIONS IN ECOSYSTEMS OF CENTRAL AMAZONIA

2015 ◽  
Vol 39 (1) ◽  
pp. 232-242 ◽  
Author(s):  
Jean Dalmo de Oliveira Marques ◽  
Flávio Jesus Luizão ◽  
Wenceslau Geraldes Teixeira ◽  
Max Sarrazin ◽  
Sávio José Filgueira Ferreira ◽  
...  
Keyword(s):  
Organic Matter ◽  
Clay Fraction ◽  
Particle Size Analysis ◽  
Light Fraction ◽  
Size Analysis ◽  
Primary Forest ◽  
Organic C ◽  
Soil C ◽  
Soil Fractions ◽  
C Stocks

Organic matter plays an important role in many soil properties, and for that reason it is necessary to identify management systems which maintain or increase its concentrations. The aim of the present study was to determine the quality and quantity of organic C in different compartments of the soil fraction in different Amazonian ecosystems. The soil organic matter (FSOM) was fractionated and soil C stocks were estimated in primary forest (PF), pasture (P), secondary succession (SS) and an agroforestry system (AFS). Samples were collected at the depths 0-5, 5-10, 10-20, 20-40, 40-60, 60-80, 80-100, 100-160, and 160-200 cm. Densimetric and particle size analysis methods were used for FSOM, obtaining the following fractions: FLF (free light fraction), IALF (intra-aggregate light fraction), F-sand (sand fraction), F-clay (clay fraction) and F-silt (silt fraction). The 0-5 cm layer contains 60 % of soil C, which is associated with the FLF. The F-clay was responsible for 70 % of C retained in the 0-200 cm depth. There was a 12.7 g kg-1 C gain in the FLF from PF to SS, and a 4.4 g kg-1 C gain from PF to AFS, showing that SS and AFS areas recover soil organic C, constituting feasible C-recovery alternatives for degraded and intensively farmed soils in Amazonia. The greatest total stocks of carbon in soil fractions were, in decreasing order: (101.3 Mg ha-1 of C - AFS) > (98.4 Mg ha-1 of C - FP) > (92.9 Mg ha-1 of C - SS) > (64.0 Mg ha-1 of C - P). The forms of land use in the Amazon influence C distribution in soil fractions, resulting in short- or long-term changes.

Krasnozems - organic-matter

Soil Research ◽  
1995 ◽  
Vol 33 (1) ◽  
pp. 43 ◽  
Author(s):  
JM Oades
Keyword(s):  
Organic Matter ◽  
Exchange Capacity ◽  
Annual Rainfall ◽  
Mean Annual Temperature ◽  
High Fertility ◽  
Organic C ◽  
Deep Well ◽  
13C Nuclear Magnetic Resonance ◽  
C And N ◽  
Natural Isotopes

Virgin krasnozems contain about 6% C from 0-15 cm and, while the C content is less at depth, the total C reserves may exceed 200 t ha(-1) to about Im depth. Highest organic matter contents occur where the annual rainfall is 1500 � 200 mm. At higher rainfalls, the C contents are less. There is a negative correlation between organic C and N content and mean annual temperature. Krasnozems contain more C than other soils in the same climate and are comparatively more fertile. Correlations of C contents with clay contents are confounded by the contents of free iron oxides. While data are fragmented, it is evident that the clearing of rainforests and replacement by pastures or other agricultural and horticultural pursuits have led to losses of up to 50% of the organic C over several decades. A simple model illustrates that this is caused by lower inputs of C to the soil in most situations except perhaps long term productive pastures where inputs may be greater than under rainforests. Studies using natural isotopes of C have shown the persistence of some C in krasnozems for hundreds of years. Some of this is particulate organic matter occluded in aggregates but most of it appears to be associated with clays, particularly at depth. The chemistry of organic matter in krasnozems appears similar to that of other soils, although solid state 13C nuclear magnetic resonance has shown more aliphatic materials in krasnozems than other soils, but the reason for this is not clear. There is little information on biota in krasnozems. The deep well structured soils are a good habitat for organisms and their high fertility guarantees a good supply of substrate for fauna and flora. It is important to maintain the organic matter contents of krasnozems to maintain cation exchange capacity, mineralization of N and other elements, to decrease phosphate sorption and to stabilize larger aggregates and thus macro porosity.

In Situ microscopy of the anodic etching of silicon

1995 ◽  
Vol 53 ◽  
pp. 232-233
Author(s):  
Frances M. Ross ◽  
Peter C. Searson
Keyword(s):  
Composite Structures ◽  
High Surface ◽  
High Surface Area ◽  
Chemical Properties ◽  
Selective Etching ◽  
Silicon On Insulator ◽  
Second Phase ◽  
Porous Layers ◽  
New Class ◽  
Porous Semiconductors

Porous semiconductors represent a relatively new class of materials formed by the selective etching of a single or polycrystalline substrate. Although porous silicon has received considerable attention due to its novel optical properties1, porous layers can be formed in other semiconductors such as GaAs and GaP. These materials are characterised by very high surface area and by electrical, optical and chemical properties that may differ considerably from bulk. The properties depend on the pore morphology, which can be controlled by adjusting the processing conditions and the dopant concentration. A number of novel structures can be fabricated using selective etching. For example, self-supporting membranes can be made by growing pores through a wafer, films with modulated pore structure can be fabricated by varying the applied potential during growth, composite structures can be prepared by depositing a second phase into the pores and silicon-on-insulator structures can be formed by oxidising a buried porous layer. In all these applications the ability to grow nanostructures controllably is critical.

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