scholarly journals Stability-energy relationships and their application to aggregation studies

1992 ◽  
Vol 72 (4) ◽  
pp. 453-466 ◽  
Author(s):  
L.G. Fuller ◽  
Tee Boon Goh
Keyword(s):  
Soil Aggregates ◽  
Energy Levels ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Order Rate Constant ◽  
Ultrasonic Dispersion ◽  
First Order ◽  
Energy Relationships ◽  
Stability Energy ◽  
Gray Luvisol

The objective of this study was to develop a method to describe aggregate stability-energy relationships using ultrasonic dispersion and to examine the role played by carbohydrate in soil aggregation. Aggregate size fractions (ASF) from three soils were sonified, and dispersed clay and solubilized carbohydrate measured at energy levels ranging from 0 to 1000 kJ L−1. Study soils included an Orthic Black, Orthic Dark Gray, and Orthic Gray Luvisol, representing the change from a prairie ecosystem to an aspen-forest ecosystem. Ultrasonic dispersion of aggregated clay resulted in characteristic "stability curves" for each ASF which obeyed a first-order decay curve and provided two parameters describing the release of clay from soil aggregates with increasing levels of applied energy: the "stability constant" k and the E1/2 value, which are analogous to a first-order rate constant and half-life, respectively. E1/2 values ranged from 51 to 502 kJ L−1.These values were smallest for the Ae horizon of the Orthic Gray Luvisol and greatest for the macroaggregates of the Ahe horizon of the Orthic Dark Gray. Carbohydrates solubilized upon aggregate destruction generally constituted a minor proportion (10%) of the total ASF carbohydrate, indicating that most of the carbohydrate was strongly adsorbed to surfaces. The development of a stability-energy relationship for aggregates provides a means to study the role of binding agents, such as carbohydrate, in the aggregation process. Key words: Aggregates, ultrasonic dispersion, clay, carbohydrate

Aggregate size distribution and stability of an oxisol under legume-based and pure grass pastures in the eastern Colombian savannas

Soil Research ◽  
1995 ◽  
Vol 33 (1) ◽  
pp. 153 ◽  
Author(s):  
AJ Gijsman ◽  
RJ Thomas
Keyword(s):  
Size Distribution ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Hot Water ◽  
Aggregate Size Distribution ◽  
Carbohydrate Concentration ◽  
Stability Measurement ◽  
Water Extractable

This study evaluated soil aggregate size distribution and stability of an Oxisol under improved grass-only or grass-legume pastures, established in previously native savanna. Three grass-legume combinations were included at various stocking rates. In all treatments and soil layers, soils were well aggregated, having more than 90% of their weight in macroaggregates (>250 �m). The addition of legumes to pastures did not affect the soil aggregate size distribution, although aggregates showed somewhat more stability against slaking. An increase in stocking rate negatively affected both average aggregate size and aggregate stability. Aggregates showed little or no dispersion of clay particles in any treatment. A positive correlation was found between wet aggregate stability and hot-water extractable carbohydrate concentration, supporting the hypothesis that these carbohydrates equate with plant-derived or microbial polysaccharides which glue soil aggregates together. It is suggested that determination of hot-water extractable carbohydrates may serve as a useful indicator of small differences in aggregate stability, even when these differences are not evident in the stability measurement itself.

Stabilization of Soil Aggregates in Relation to Soil Redistribution by Intensive Tillage on a Steep Hillslope

2014 ◽  
Vol 955-959 ◽  
pp. 3566-3571 ◽  
Author(s):  
Yong Wang ◽  
Zhuang Xiong ◽  
Wu Xian Yan ◽  
Yue Qun Qiu
Keyword(s):  
Soil Aggregates ◽  
Geometric Mean ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Soil Aggregate Stability ◽  
Mean Weight Diameter ◽  
Tillage Operation ◽  
Sloping Land ◽  
The Impact

The objective of this study was to investigate soil aggregate stability within landscape on hillslopes by intensive tillage. Traditional tillage by consecutive hoeing was performed 5 and 20 times on steeply sloping land of the Sichuan Basin, China, by using the methods of simulated tillage to analyze the impact of long-term tillage on soil aggregates at different slope positions. The dry-sieved method was used to determine distribution of aggregate size in the different landscape positions, and mean weight diameter (MWD) and geometric mean diameter (GMD) as indices of soil aggregate stability. The different times of tillage resulted in different soil aggregate distributions. The results showed that the MWD and GMD values of aggregates were significantly decreased (p< 0.05) after 20-tillage operation, compared with pre-tillage operation. The differences in distributions of MWD and GMD demonstrate that the choice of the tillage times can be an important factor in changing soil aggregate stability and productivity in steeply sloping fields.

scholarly journals Potential Benefits of Polymers in Soil Erosion Control for Agronomical Plans: A Laboratory Experiment

Agronomy ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 276 ◽  
Author(s):  
Tugrul Yakupoglu ◽  
Jesús Rodrigo-Comino ◽  
Artemi Cerdà
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Extreme Rainfall ◽  
Rainfall Simulation ◽  
Water Losses ◽  
Total Runoff ◽  
Runoff Sediment

New management and techniques to reduce soil and water losses are necessary to achieve goals related to sustainability and develop useful agronomical plans. Among the strategies to reduce soil losses, the use of polymers has been studied but little is known about the effect of them on soil aggregates under extreme rainfall conditions. The main aim of this study was to compare the effects of polyacrylamide (PAM) and polyvinyl alcohol (PVA) on initial soil erosion process activation. We applied both products on soils and soil aggregate stability was measured on polymer treated and control plots. Laboratory erosion plots (pans) were placed on 15% slope, and sequential simulated rainfalls (under dry and wet conditions) with 360 mm h−1 intensity were applied for 12 min. Time to runoff, total runoff, runoff sediment yield, and splash sediment yield were determined. The results show that polymers do not delay runoff initiation; however, they reduced total runoff, sediment yield, and soil transported by the splash. PVA was not effective in reducing the total runoff during the first rainfall being PAM more effective in this way. However, under the sequential rainfall, both polymers obtained positive results, showing PAM some improvements in comparison to PVA. The effect of the polymer to reduce soil transported by splash after performing the second rainfall simulation was clearly demonstrated, meanwhile the effects during the first simulation were not significant. The effectiveness of the polymers on soil aggregates increased with increasing aggregate size. The application of polymers reached the highest efficiency on aggregates of 6.4 mm in diameter.

scholarly journals The stability of soil aggregates in tilled fallow areas in Hyderabad district, Pakistan

2015 ◽  
Vol 27 (1) ◽  
pp. 51-60
Author(s):  
Ahmed Tagar ◽  
Jan Adamowski
Keyword(s):  
Soil Erosion ◽  
Size Distribution ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Indus River ◽  
Aggregate Size Distribution ◽  
Sieve Size ◽  
The Stability ◽  
The Village

Abstract Arid areas are particularly susceptible to soil erosion due to long dry periods and sudden heavy downpours. This study investigates the aggregate size distribution and aggregate stability of twelve tilled fallow areas of Hyderabad district, Sindh, Pakistan. This study determined aggregate size distribution by dry sieving to evaluate the seedbed condition and aggregate stability using wet sieving to assess the susceptibility of tilled fallow areas to soil erosion. The aggregate size distribution of the soils of the selected areas was highly variable. Gulistan-e-Sarmast had the largest number of clods (51.0%) followed by Kohsar (49.0%), Latifabad # 10 (41.10%) and Daman-e-Kohsar (39.0%). Fazal Sun City, the left side of the Indus River, the Village Nooral Detha and the left side of the Abdullah Sports city had a greater number of large (>8.0 mm) and small aggregates (<0.5 mm). The optimum aggregate size distribution was found in the left side of the channel, which had the largest number of aggregates (50.50%) in the 0.5–8.0 mm sieve size range. Maximum aggregate stability (AS) was found in Gulistan-e-Sarmast (46%), Kohsar (42%) and Latifabad # 10 (34%), while all other soils had minimum aggregate stability (<14%). The minimum aggregate stabilities demonstrate that the tilled fallow areas of Hyderabad district are highly susceptible to erosion. Therefore, the present study suggests investigating potential ways to enhance the aggregate stabilities of soils.

Evaluation of selected factors influencing aggregate fragmentation using fractal theory

1992 ◽  
Vol 72 (2) ◽  
pp. 97-106 ◽  
Author(s):  
V. Rasiah ◽  
B. D. Kay ◽  
E. Perfect
Keyword(s):  
Fractal Dimension ◽  
Probability Model ◽  
Soil Aggregates ◽  
Fractal Theory ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Red Clover ◽  
Probability Of Failure ◽  
Continuous Corn ◽  
Wet Sieving

Two fractal parameters, probability of failure (P) and fractal dimension (D), were used to evaluate the influence of cropping and wetting treatments, and aggregate size on fragmentation of soil aggregates during wet sieving. Five different sizes of aggregates (4–10, 2–4, 1–2, 0.5–1 and 0.25–0.5 mm) from five cropping treatments [conventionally cultivated continuous corn (CCC), CCC underseeded to red clover (CCR), minimally tilled continuous corn underseeded to red clover (CCRM), alfalfa (AL), and bromegrass (BR)] were subjected to two wetting treatments (rapid and slow) before being wet sieved. P increased nonlinearly with increasing aggregate size. The P of the slowly wetted agggregates was always less than that of the rapidly wetted aggregates. The P of larger aggregates, 2–4 and 4–10 mm, increased in the following order of cropping: BR = AL < CCRM < CCR = CCC. The D for the size distribution of 4- to 10-mm aggregates increased in the same order of cropping as that given previously. The D for the rapidly wetted aggregates was higher than that of the slowly wetted aggregates for all cropping treatments except CCC. The values of P predicted from a fractal probability model correlated well with the observed values. The results show that P and D of soil aggregates are strongly influenced by cropping and wetting treatments and aggregate size. Key words: Probability of failure, fractal dimension, wet sieving, wet aggregate stability, prewetting

Development of Sustained Release Multi-Component Microparticulate System of Diclofenac Sodium and Tizanidine Hydrochloride

1970 ◽  
Vol 1 (1) ◽  
pp. 97-105
Author(s):  
Kamlesh Dashora ◽  
Shailendra Saraf ◽  
Swarnalata Saraf
Keyword(s):  
Particle Size ◽  
Sustained Release ◽  
Cellulose Acetate ◽  
Rate Constant ◽  
Diclofenac Sodium ◽  
Order Rate Constant ◽  
Anomalous Transport ◽  
First Order ◽  
Sem Study ◽  
Transport Type

Sustained released tablets of diclofenac sodium (DIC) and tizanidine hydrochloride (TIZ) were prepared by using different proportions of cellulose acetate (CA) as the retardant material. Nine formulations of tablets having different proportion of microparticles developed by varied proportions of polymer: drug ratio ‘’i.e.’’; 1:9 -1:3 for DIC and 1:1 – 3:1 for TIZ. Each tablet contained equivalent to 100 mg of DIC and 6mg of TIZ. The prepared microparticles were white, free flowing and spherical in shape (SEM study), with  the particle size varying from 78.8±1.94 to 103.33±1.28 µm and 175.92± 9.82 to 194.94±14.28µm for DIC  and TIZ, respectively.  The first order rate constant K1 of formulations were found to be in the range of  K1 = 0.117-0.272 and 0.083- 0.189 %hr-1for DIC and TIZ, respectively. The value of exponent coefficient (n) was found to be in the range of 0.6328-0.9412  and 0.8589-1.1954 for DIC and TIZ respectively indicates anomalous  to  non anomalous transport type of diffusions among different formulations

scholarly journals Dynamics of Soil Organic Carbon and Labile Carbon Fractions in Soil Aggregates Affected by Different Tillage Managements

2021 ◽  
Vol 13 (3) ◽  
pp. 1541
Author(s):  
Xiaolin Shen ◽  
Lili Wang ◽  
Qichen Yang ◽  
Weiming Xiu ◽  
Gang Li ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Soil Aggregate ◽  
No Tillage ◽  
Labile Carbon ◽  
Carbon Fractions ◽  
Soil Aggregate Stability ◽  
Positive Effects

Our study aimed to provide a scientific basis for an appropriate tillage management of wheat-maize rotation system, which is beneficial to the sustainable development of agriculture in the fluvo-aquic soil areas in China. Four tillage treatments were investigated after maize harvest, including rotary tillage with straw returning (RT), deep ploughing with straw returning (DP), subsoiling with straw returning (SS), and no tillage with straw mulching (NT). We evaluated soil organic carbon (SOC), dissolved organic carbon (DOC), permanganate oxidizable carbon (POXC), microbial biomass carbon (MBC), and particulate organic carbon (POC) in bulk soil and soil aggregates with five particle sizes (>5 mm, 5–2 mm, 2–1 mm, 1–0.25 mm, and <0.25 mm) under different tillage managements. Results showed that compared with RT treatment, NT treatment not only increased soil aggregate stability, but also enhanced SOC, DOC, and POC contents, especially those in large size macroaggregates. DP treatment also showed positive effects on soil aggregate stability and labile carbon fractions (DOC and POXC). Consequently, we suggest that no tillage or deep ploughing, rather than rotary tillage, could be better tillage management considering carbon storage. Meanwhile, we implied that mass fractal dimension (Dm) and POXC could be effective indicators of soil quality, as affected by tillage managements.

scholarly journals The Use of MgO Obtained from Serpentinite in the Synthesis of a Magnesium Potassium Phosphate Matrix for Radioactive Waste Immobilization

2020 ◽  
Vol 11 (1) ◽  
pp. 220
Author(s):  
Svetlana A. Kulikova ◽  
Sergey E. Vinokurov ◽  
Ruslan K. Khamizov ◽  
Natal’ya S. Vlasovskikh ◽  
Kseniya Y. Belova ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Hydrolytic Stability ◽  
Potassium Phosphate ◽  
Aggregate Size ◽  
Particle Morphology ◽  
Average Crystallite Size ◽  
Cost Effective ◽  
Binding Agent ◽  
Ultrasonic Dispersion ◽  
Radioactive Waste Immobilization

Magnesium oxide is a necessary binding agent for the synthesis of a magnesium potassium phosphate (MPP) matrix based on MgKPO4 × 6H2O, which is promising for the solidification of radioactive waste (RW) on an industrial scale. The performed research is devoted to finding a cost-effective approach to the synthesis of MPP matrix by using MgO with an optimal ratio of the quality of the binding agent and the cost of its production. A method for obtaining MgO from the widely available natural mineral serpentinite was proposed. The phase composition, particle morphology, and granulometric composition of MgO were studied. It was found that the obtained MgO sample, in addition to the target periclase phase, also contains impurities of brucite and hydromagnesite; however, after calcining at 1300 °C for 3 h, MgO transforms into a monophase state with a periclase structure with an average crystallite size of 62 nm. The aggregate size of the calcined MgO powder in an aqueous medium was about 55 μm (about 30 μm after ultrasonic dispersion), and the specific surface area was 5.4 m2/g. This powder was used to prepare samples of the MPP matrix, the compressive strength of which was about 6 MPa. The high hydrolytic stability of the MPP matrix was shown: the differential leaching rate of magnesium, potassium, and phosphorus from the sample on the 91st day of its contact with water does not exceed 1.6 × 10−5, 4.7 × 10−4 и 8.9 × 10−5 g/(cm2·day), respectively. Thus, it was confirmed that the obtained MPP matrix possesses the necessary quality indicators for RW immobilization.

SORPTION OF CARBON AND PHOSPHORUS FROM LIQUID POULTRY MANURE BY SOIL AGGREGATES OF DIFFERING SIZE

1985 ◽  
Vol 65 (3) ◽  
pp. 467-473 ◽  
Author(s):  
V. K. BHATNAGAR ◽  
M. H. MILLER
Keyword(s):  
Soil Aggregates ◽  
Poultry Manure ◽  
Aggregate Size ◽  
Liquid Manure ◽  
Inorganic P ◽  
Supernatant Liquid ◽  
Extractable P ◽  
P Content ◽  
Manure Slurry ◽  
Total P

A series of laboratory experiments was conducted to determine the mechanism(s) responsible for a previously reported observation that addition of liquid manure to soil increased the NaHCO3-extractable P (Ext-P) of large aggregates (> 2 mm) more than that of smaller aggregates whereas addition of an inorganic P solution did not. Application of liquid poultry manure increased the total P, Ext-P and total C concentrations in large aggregates (> 2 mm) much more (> 2.5 ×) than that in small aggregates (< 1 mm). Addition of inorganic P solution or of supernatant liquid from a centrifuged manure slurry increased the P content of the large aggregates only slightly (1.2 ×). A greater increase in Ext-P in large aggregates was observed even when the smaller aggregates were purposely layered on top of the larger ones prior to addition of the liquid manure. A similar but less pronounced effect of aggregate size on increase in P or C concentration was observed when different sized aggregates were left in contact with an effectively infinite source of liquid manure for 24 h. It is concluded that the larger aggregates absorbed more of the bulk manure slurry than smaller aggregates. A partial sealing of small aggregates by particulates is suggested as a possible mechanism. Key words: Carbon, phosphorus, liquid manure, soil aggregates

Kinetics of bioactive compounds in functional spice Jiangpo during thermal processing

2012 ◽  
Vol 8 (3) ◽  
Author(s):  
Xiaoyan Dai ◽  
Chenhuan Yu ◽  
Qiaofeng Wu
Keyword(s):  
Kinetic Parameters ◽  
Bioactive Compounds ◽  
Thermal Processing ◽  
Order Rate Constant ◽  
Heat Processing ◽  
Order Kinetic ◽  
Time Intervals ◽  
First Order ◽  
Order Kinetic Model ◽  
Kinetics Of

Abstract Jiangpo is an increasingly popular East Asian spice which is made from Mangnolia officinalis bark and ginger juice. Since it induces bioactive compounds decomposition and has influence on final flavor and fragrance, cooking is regarded as the key operation in preparation of Jiangpo. To evaluate the bioactive compounds content changes of Jiangpo during thermal processing, kinetic parameters including reaction order, rate constant, T1/2 and activation energy of bioactive markers namely honokiol, magnolol and curcumin were determined. Cooking was set at temperatures 60, 90 and 120 °C for selected time intervals. Results displayed the thermal kinetic characteristics of the three compounds. Thermal degradation of Honokiol and magnolol both followed first order kinetic model and the loss of curcumin fitted second order. A mathematical model based on the obtained kinetic parameters has also been developed to predict the degradation of honokiol, magnolol and curcumin in non-isothermal state. All the information in this paper could contribute necessary information for optimizing the existing heat processing of Jiangpo.

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