Journal articles on the topic 'Aggregate breakdown'
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1
Field, Damien J., Budiman Minasny, and Michael Gaggin. "Modelling aggregate liberation and dispersion of three soil types exposed to ultrasonic agitation." Soil Research 44, no. 5 (2006): 497. http://dx.doi.org/10.1071/sr05127.
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This paper reports on a study involving the application of ultrasonic agitation to 3 soil types to assess soil aggregate disruption and subsequent dispersion. The measurement of various particle size fractions resulting after the application of ultrasonic agitation for different time periods made it possible to describe the resulting aggregate disruption using the established aggregate liberation and dispersion curve (ALDC) model. Originally this model had been used to assess only the 2–20 µm fraction liberated from Vertosols. This work has shown that the model can be applied to a variety of size fractions between 2 and 100 µm in diameter and soil types, namely Chromosols and Ferrosols. By estimating the critical energy (Ecrit) required to initiate dispersion of liberated aggregates for each fraction, it is implied that the linkage between aggregates is weaker than the linkages between the materials composing the aggregates. Further, the ratio between the rate constants in the ALDC model can be used to establish if there is a stepwise breakdown of larger aggregates, a criterion required to establish the presence of an aggregate hierarchy. Finally, by assessing the aggregate distribution on a continuous scale, it is possible to recognise unique pathways of aggregate liberation and dispersion for each soil type rather than assuming that aggregates breakdown into predefined discrete size fractions.
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Arjmand Sajjadi, S., and M. Mahmoodabadi. "Aggregate breakdown and surface seal development influenced by rain intensity, slope gradient and soil particle size." Solid Earth Discussions 6, no. 2 (December 16, 2014): 3303–31. http://dx.doi.org/10.5194/sed-6-3303-2014.
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Abstract. Aggregate breakdown is an important process which controls infiltration rate (IR) and the availability of fine materials necessary for structural sealing under rainfall. The purpose of this study was to investigate the effects of different slope gradients, rain intensities and particle size distributions on aggregate breakdown and IR to describe the formation of surface sealing. To address this issue, 60 experiments were carried out in a 35 cm x 30 cm x 10 cm detachment tray using a rainfall simulator. By sieving a sandy loam soil, two sub-samples with different maximum aggregate sizes of 2 mm (Dmax 2 mm) and 4.75 mm (Dmax4.75 mm) were prepared. The soils were exposed to two different rain intensities (57 and 80 mm h-1) on several slopes (0.5, 2.5, 5, 10, and 20%) each at three replications. The result showed that the most fraction percentages in soils Dmax 2 mm and Dmax 4.75 mm were in the finest size classes of 0.02 and 0.043 mm, respectively for all slope gradients and rain intensities. The soil containing finer aggregates exhibited higher transportability of pre-detached material than the soil containing larger aggregates. Also, IR increased with increasing slope gradient, rain intensity and aggregate size under unsteady state conditions because of less development of surface seal. But under steady state conditions, no significant relationship was found between slope and IR. The finding of this study revealed the importance of rain intensity, slope steepness and soil aggregate size on aggregate breakdown and seal formation, which can control infiltration rate and the consequent runoff and erosion rates.
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Arjmand Sajjadi, S., and M. Mahmoodabadi. "Aggregate breakdown and surface seal development influenced by rain intensity, slope gradient and soil particle size." Solid Earth 6, no. 1 (March 5, 2015): 311–21. http://dx.doi.org/10.5194/se-6-311-2015.
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Abstract. Aggregate breakdown is an important process which controls infiltration rate (IR) and the availability of fine materials necessary for structural sealing under rainfall. The purpose of this study was to investigate the effects of different slope gradients, rain intensities and particle size distributions on aggregate breakdown and IR to describe the formation of surface seal. To address this issue, 60 experiments were carried out in a 35 × 30 × 10 cm detachment tray using a rainfall simulator. By sieving a sandy loam soil, two sub-samples with different maximum aggregate sizes of 2 mm (Dmax2 mm) and 4.75 mm (Dmax4.75 mm) were prepared. The soils were exposed to two different rain intensities (57 and 80 mm h−1) on several slopes (0.5, 2.5, 5, 10 and 20%) each at three replicates. The result showed that for all slope gradients and rain intensities, the most fraction percentages in soils Dmax2 and Dmax4.75 mm were in the finest size classes of 0.02 and 0.043 mm, respectively. The soil containing finer aggregates exhibited higher transportability of pre-detached material than the soil containing larger aggregates. Also, IR increased with increasing slope gradient, rain intensity and aggregate size under unsteady state conditions because of less development of surface seal. However, under steady state conditions, no significant relationship was found between slope and IR. The findings of this study revealed the importance of rain intensity, slope steepness and soil aggregate size on aggregate breakdown and seal formation, which can control infiltration rate and the consequent runoff and erosion rates.
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Herd, Charles R., Gerard C. McDonald, Randolph E. Smith, and William M. Hess. "The Use of Skeletonization for the Shape Classification of Carbon-Black Aggregates." Rubber Chemistry and Technology 66, no. 4 (September 1, 1993): 491–509. http://dx.doi.org/10.5254/1.3538323.
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Abstract A specialized image analysis erosion technique, termed skeletonization, has been used for the first quantitative and direct measurement of branching in carbon-black aggregates. Twenty different carbon-black grades were analyzed using transmission-electron-microscopy/automated-image analysis (TEM/AIA). The skeletonization data were used in a discrimination analysis program for detailed shape classification of carbon-black aggregates into four different shape categories that included spheroidal (Type 1), ellipsoidal (Type 2), linear (Type 3) and branched (Type 4). These data were used to examine differences in the aggregate shape distributions between and within grades. Skeletonization and conventional TEM/AIA analyses were also conducted to examine aggregate breakdown as a result of high-shear mixing in rubber (SBR) and cellulose acetate butyrate (CAB) paint chip compounds. It was found that the number of aggregate branches decreased by as much as 50% in rubber and 70% in CAB compounds, and the distributions became narrower. Aggregate breakdown increases in the direction of the larger particle size carbon blacks which contain more linear (Type 3) aggregates. In rubber, an N650 (131 DBPA) and N330 (102 DBPA) carbon blacks were found to be similar in overall aggregate shape properties. Therefore, the significantly higher vulcanizate modulus for N650 appears to be related to a higher level of carbon-black—polymer interaction, as opposed to high amounts of polymer occluded and immobilized within the aggregate structure.
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Xiao, L., Y. Hu, P. Greenwood, and N. J. Kuhn. "The use of a raindrop aggregate destruction device to evaluate sediment and soil organic carbon transport." Geographica Helvetica 70, no. 2 (June 15, 2015): 167–74. http://dx.doi.org/10.5194/gh-70-167-2015.
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Abstract. Raindrop impact and subsequent aggregate breakdown can potentially change the movement behaviour of soil fractions and thus alter their transport distances when compared against non-impacted aggregates. In a given water layer, the transport distances of eroded soil fractions, and thus that of the associated substances across landscapes, such as soil organic carbon (SOC) and phosphorous, are determined by the settling velocities of the eroded soil fractions. However, using mineral size distribution to represent the settling velocities of soil fractions, as often applied in current erosion models, would ignore the potential influence of aggregation on the settling behaviour of soil fractions. The destructive effects of raindrops impacting onto aggregates are also often neglected in current soil erosion models. Therefore, the objective of this study is to develop a proxy method to effectively simulate aggregate breakdown under raindrop impact, and further identify the settling velocity of eroded sediment and the associated SOC. Two agricultural soils with different sandy and silty loam textures were subjected to rainfall using a raindrop aggregate destruction device (RADD). The aggregates sustained after raindrop impact were fractionated by a settling tube into six different classes according to their respective settling velocities. The same mass amount of bulk soil of each soil type was also dispersed and sieved into the same six classes, to form a comparison in size distribution. The SOC content was measured for each settled and dispersed class. Our results show the following: (1) for an aggregated soil, applying dispersed mineral grain size distribution, rather than its actual aggregate distribution, to soil erosion models would lead to a biased estimation on the redistribution of eroded sediment and SOC; (2) the RADD designed in this study effectively captures the effects of raindrop impact on aggregate destruction and is thus able to simulate the quasi-natural sediment spatial redistribution; (3) further RADD tests with more soils under standard rainfall combined with local rainfalls are required to optimize the method.
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Hurley, Graham C., and Brian D. Prowell. "Refinement of the Hot-Mix Asphalt Ignition Method for High-Loss Aggregates." Transportation Research Record: Journal of the Transportation Research Board 1907, no. 1 (January 2005): 128–34. http://dx.doi.org/10.1177/0361198105190700115.
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Four methodologies for determining the asphalt content of mixtures containing high-loss aggregates in the ignition furnace were evaluated: the standard method using the Thermolyne furnace (control), the Troxler NTO infrared furnace, the Ontario method, and a Tempyrox glass-cleaning oven. Six aggregate sources with high ignition furnace aggregate corrections were obtained from around the country: four dolomites, a basalt, and a serpentine/chlorite. Calibration factors were determined for each method at optimum asphalt content. Additional samples were then tested at optimum plus 0.5% asphalt content, and the measured asphalt content was calculated by using the correction factor determined for that method and aggregate source. The Tempyrox Pyro-Clean furnace, commonly used for cleaning laboratory glassware, produced the lowest aggregate correction factors. The standard method and the Ontario method, both using the Thermolyne ignition furnace, produced the smallest bias or error in measured asphalt content. The standard deviation of the corrected asphalt contents for these high-loss sources was higher than the within-laboratory standard deviation reported for AASHTO T308. The only exception was the Alabama source using the standard method. The Ontario method and Tempyrox oven generally reduced the variability of asphalt content measurements for high-loss aggregates. None of the methods evaluated statistically reduced aggregate breakdown on the nominal maximum aggregate size and 4.75-mm sieves. The Ontario method significantly reduced, but did not eliminate, aggregate breakdown on the 0.075-mm sieve. The Ontario method is the best method for immediate implementation for determining the asphalt content by the ignition method for high-loss aggregates.
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Schomakers, Jasmin, Franz Zehetner, Axel Mentler, Franz Ottner, and Herwig Mayer. "Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation." International Agrophysics 29, no. 4 (October 1, 2015): 501–8. http://dx.doi.org/10.1515/intag-2015-0057.
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Abstract It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested highaccuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm-3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (< 10 J cm-3), which previous studies have largely neglected. This shows that low ultrasonic energies are required to capture the full range of aggregate stability and release of soil organic matter upon aggregate breakdown.
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Guo, Zhonglu, Lichao Zhang, Wei Yang, Li Hua, and Chongfa Cai. "Aggregate Stability under Long-Term Fertilization Practices: The Case of Eroded Ultisols of South-Central China." Sustainability 11, no. 4 (February 22, 2019): 1169. http://dx.doi.org/10.3390/su11041169.
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Soil aggregate stability is an important aspect of soil function and health. Fertilization could potentially alter soil properties and thereby affect aggregate stability. To determine which fertilizer is useful for improving soil fertility and stabilizing soil aggregates and thereby reducing soil erodibility, we examined three types of fertilizer, and measured how soil organic carbon, carbohydrates, and related soil properties influenced aggregate stability in eroded Ultisols. Treatments included control (CK), mineral fertilizer nitrogen (N), phosphorus (P), potassium (K) (NPK), fertilizer NPK plus straw (NPKS), and farmyard manure (FYM). Aggregate stability was tested according to Le Bissonnais method, involving three disruptive tests: fast wetting (FW), slow wetting (SW), and mechanical breakdown (WS). Total organic carbon, particulate organic carbon, mineral-associated carbon, and cold-water-soluble carbohydrate, hot-water-soluble carbohydrate, and dilute acid hydrolysable carbohydrate were measured, as well as soil intrinsic properties (including pH, bulk density, iron and aluminum oxides). The 12-year fertilization had a larger effect on aggregate stability and related soil properties in a 0–15 cm soil layer, whereas no effect was evident at a soil depth of 15–40 cm. MWD (mean weight diameter) under the three tests decreased with increasing soil depth. Fertilization, especially farmyard manure evidently improved MWDFW and MWDWS at a depth of 0–15 cm. Slaking was the main mechanism of aggregate breakdown in Ultisols studied, followed by mechanical breakdown. Correlation analysis showed that MWDFW and MWDWS at a depth of 0–15 cm increased with the increase of particulate organic carbon, total organic carbon, hot-water-soluble carbohydrate and pH. Furthermore, their interaction with amorphous iron oxides enhanced aggregate stability against slaking or, with amorphous aluminum oxides, modified aggregate stability against mechanical breakdown. Consequently, particulate organic carbon was the dominant cementing agent for aggregation in Ultisols studied, and its combination with pH, amorphous aluminum oxides, amorphous iron oxides, and free aluminum oxides play a synergetic role in stabilizing soil aggregate. Accordingly, farmyard manure or fertilizer NPK plus straw improved soil fertility and the ability to resist slaking.
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Legout, C., S. Leguedois, and Y. Le Bissonnais. "Aggregate breakdown dynamics under rainfall compared with aggregate stability measurements." European Journal of Soil Science 56, no. 2 (April 2005): 225–38. http://dx.doi.org/10.1111/j.1365-2389.2004.00663.x.
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Rohošková, M., and M. Valla. "Comparison of two methods for aggregate stability measurement – a review." Plant, Soil and Environment 50, No. 8 (December 10, 2011): 379–82. http://dx.doi.org/10.17221/4047-pse.
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Soil structure is a very important soil property, which influences many processes in the soil. There are many methods for aggregate stability measurement varying in the energy applied in the treatment. The aim of this paper is to compare two aggregate stability measurement methods on a set of reclaimed dumpsite soils. Method proposed by Le Bissonnias (1996) is composed of three tests, which allow distinguishing the particular aggregate breakdown mechanisms. Results can be expressed by a coefficient of vulnerability (Kv). Results of the second method, assessment of water stable aggregates, can be expressed by WSA index. WSA indexes mainly correspond to the results of the first test, which qualify the aggregate breakdown during the fast wetting. A strong statistically significant relationship was found between WSA and Kv for each test. Correlation coefficients were –0.767, –0.806, and –0.741 for linear models. Our conclusion is that results of both methods are comparable.
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Cao, Gang, Bokun Chang, Zhiying Zhou, Liang Hu, Wei Du, and Jialong Lv. "Soil Aggregate Breakdown with Colloidal Particles Release and Transport in Soil: A Perspective from Column Experiments." Agriculture 12, no. 12 (December 14, 2022): 2155. http://dx.doi.org/10.3390/agriculture12122155.
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The strongest fortresses often disintegrate from the inside. Likewise, soil internal forces play a critical role in the initial breakdown process of soil aggregate, thus accelerating soil erosion and the release of soil colloid particles. To date, research on the effect of soil internal forces, especially separating the electrostatic force, and on the process of soil aggregate breakdown with particle release and transport in soil is largely inadequate. Therefore, column experiments were used to investigate the properties of transport and soil particles released from the disintegration of model soil aggregates caused by different levels of electrostatic forces. We found that the increase of electrostatic repulsive pressure was the immediate cause of soil aggregate breakdown, that the highest concentration of released soil particles could reach 808.36 mg L−1, and that the mean particle sizes of the released soil ranged from 100 nm to 300 nm. The particle size distributions and clay mineral composition of the released soil particles were not dominated by the electrostatic force. In practice, the change of external conditions of agricultural soil would lead to the change of soil internal forces, then affect soil aggregate stability. This study aims to provide a micro perspective to understand the release of fine particles from soil matrix and its implication for agricultural soil.
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Zhao, Yikai, Han Wang, Xiangwei Chen, and Yu Fu. "Effect of Rainfall on Soil Aggregate Breakdown and Transportation on Cultivated Land in the Black Soil Region of Northeast China." Sustainability 14, no. 17 (September 3, 2022): 11028. http://dx.doi.org/10.3390/su141711028.
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To clarify the characteristics of soil aggregate breakdown and transportation by rainfall, the cultivated land (0–10 cm) of the black soil region of Northeast China was taken as the research object, with rainfall intensities of 78 and 127 mm·h−1 (RI78, RI127), to analyze the differences in the mass transported, fraction size distribution, mean weight diameter (MWD) and enrichment rate of aggregates before and after runoff generation. Before runoff generation, the total mass of transported aggregates, the total mass percentage of the aggregate fraction size < 1 mm and the MWD of the transported aggregates were not significantly different at rainfall intensities of 78 and 127 mm·h−1. After runoff generation, the mass of transported aggregates was greater than that before runoff generation, and the mass of transported aggregates under RI78 was significantly higher than that under RI127, by 15.6%. The mass percentage of the aggregate fraction size < 0.053 mm after runoff generation was significantly reduced by 8.4% and 19.4% compared to that before runoff generation. After runoff generation, compared with before runoff generation, the MWD of the transported aggregates was significantly reduced by 50.9% and 50.3% under RI78 and RI127, respectively. Compared with before runoff generation, the mass percentage of small macroaggregates increased gradually with the increase in the transport distance. The aggregate fraction size > 0.25 mm was lost, and the fraction size < 0.25 mm was enriched, before and after runoff generation. A comparative study on the characteristics of black soil aggregate breakdown and transportation before and after runoff generation can provide a theoretical basis for the mechanism of soil erosion and the transportation of cultivated soil in the black soil region of Northeast China.
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Li, Zhaoxia, Wei Yang, Chongfa Cai, and Junguang Wang. "Aggregate Mechanical Stability and Relationship With Aggregate Breakdown Under Simulated Rainfall." Soil Science 178, no. 7 (July 2013): 369–77. http://dx.doi.org/10.1097/ss.0b013e3182a74255.
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BLACK, J. M. W., F. A. BARAGAR, and D. S. CHANASYK. "A MATHEMATICAL MODEL TO ESTIMATE AGGREGATE BREAKDOWN DURING SOIL SIEVING IN A MODIFIED RAPD3 ROTARY SIEVE." Canadian Journal of Soil Science 69, no. 4 (November 1, 1989): 817–24. http://dx.doi.org/10.4141/cjss89-082.
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The percentage of soil material > 0.84 mm obtained by dry sieving is commonly used as an index of the wind erodibility of soils. Present sieving procedures do not account for the breakdown of friable aggregates during sieving so that results do not necessarily represent aggregation in the original sample. An equation was fitted to soil sieving data from a modified rapid rotary sieve. It successfully evaluated aggregate attrition during sieving for 397 out of 404 samples representing a wide variety of textures. Good reproducibility of results using the methodology was obtained for 45 paired soil samples. Results obtained employing the new method will relate more closely to field conditions allowing a better estimate of soil erodibility. Key words: Wind erosion, aggregate breakdown, sieving, soil erodibility, modified rapid rotary sieve
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Zanini, E., E. Bonifacio, J. D. Albertson, and D. R. Nielsen. "TOPSOIL AGGREGATE BREAKDOWN UNDER WATER-SATURATED CONDITIONS." Soil Science 163, no. 4 (April 1998): 288–98. http://dx.doi.org/10.1097/00010694-199804000-00004.
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WUSTAMIDIN and L. A. DOUGLAS. "AGGREGATE BREAKDOWN IN RELATION TO RAINDROP ENERGY." Soil Science 139, no. 3 (March 1985): 239–42. http://dx.doi.org/10.1097/00010694-198503000-00008.
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Loch, RJ, and JL Foley. "Measurement of aggregate breakdown under rain - Comparison with tests of water stability and relationships with field measurements of infiltration." Soil Research 32, no. 4 (1994): 701. http://dx.doi.org/10.1071/sr9940701.
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This paper reports comparisons between aggregate breakdown on wetting by rainfall with breakdown measured by a range of alternative methods. It also reports correlations between measured breakdown and steady infiltration rates of simulated rain of high and low energy, and hydraulic conductivities of surface seal layers formed under high energy rain. A wide range of soils in eastern Australia were studied. Highly significant correlations were found between measurements of aggregate breakdown to < 125 �m caused by rainfall wetting and both steady infiltration rates and hydraulic conductivities. Significant, but poorer correlations were found between steady infiltration rates and breakdown resulting from immersion wetting. Deletion of swelling soils from the data set greatly improved correlations between steady infiltration rates of high energy rain and breakdown measured by both immersion and tension wetting, showing that these methods of wetting ace particularly inappropriate for swelling soils. No correlation was found between infiltration rates and measured clay dispersion. Different relationships between the proportion of particles (%) < 125 �m at the soil surface (P125) and steady infiltration rates of low and high energy rain indicated that compaction of the soil surface layer, rather than increased aggregate breakdown, is a major cause of surface sealing by raindrop impacts. Measurements of fall cone penetration confirmed that drop impacts had compacted the surface layer. Suctions across the surface seal were related to P125 in that layer, and the relationship obtained was used in calculating hydraulic conductivities. The results confirm that measurement of aggregate breakdown under rainfall wetting produces results of much greater relevance to soil behaviour under field conditions than do tests based on immersion and tension wetting.
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Edwards, Linnell M. "The effects of soil freeze–thaw on soil aggregate breakdown and concomitant sediment flow in Prince Edward Island: A review." Canadian Journal of Soil Science 93, no. 4 (September 2013): 459–72. http://dx.doi.org/10.4141/cjss2012-059.
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Edwards, L. M. 2013. The effects of soil freeze–thaw on soil aggregate breakdown and concomitant sediment flow in Prince Edward Island: A review. Can. J. Soil Sci. 93: 459–472. The importance of aggregate size and integrity in soil productivity and crop production is paramount, and aggregate size reduction or increase invariably becomes a primary concern in such soil management practices as tillage and organic matter manipulation. In this regard, therefore, the present review looks particularly at the consequence of freeze–thaw cycling (FTC) on agricultural lands in Prince Edward Island (PEI) where an annual average of 40 cycles induce measurable aggregate breakdown with mixed consequences. On the one extreme, the consequences are manifest in increased soil erosion. On the other extreme, reduced (or reversed) soil compaction and improved seedbed conditions are welcomed consequences where temperature alternation breaks up hard pans or soil clods, or where the predominance of smaller aggregates can be an asset in seedbed environments, favouring improved crop emergence and early-spring establishment. In the PEI soils studied, the greatest changes in aggregate size distribution with FTC occurred in the largest and smallest size fractions wherein fractions <0.5 mm showed a 33% average increase while, simultaneously, the 4.75–9.5 mm fractions showed a 28% average decrease. This breakdown is reflected most contrastingly where FTCs to maximum (asymptotic) breakdown averaged up to 3.5 times for a loam as it did for a sandy loam or a fine sandy loam soil. This review also examines FTC in a broader agricultural and environmental context where it can potentially impact agro-sustainability. Where FTC effects on a fine sandy loam were measured in terms of erosion, there was a sediment mass increase of about 90% in interrill flow and about 25% in rill flow. Further, this review emphasizes methodology that has proven to be workable under the circumstances of PEI's dominant agricultural soils and the FTC research objectives that they helped to shape. It was considered important in this review, also, to highlight the need for expanded research (commencing with regional cooperation), particularly on frost depth, to feed into moisture-availability modelling towards improved clarity for end-user benefit.
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Budianta, Wawan, Monika Aprianti Popang, Widyawanto Prastistho, and Jiro Takemura. "Geo-mechanics and Hydraulic Conductivity Study of Claystone in Boyolali, Central Java, Indonesia." Journal of Applied Geology 4, no. 1 (August 14, 2019): 20. http://dx.doi.org/10.22146/jag.48738.
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Claystone middle Miocene age were found in Wonosegoro sub-district, Boyolali region, Central Java, Indonesia. The purpose of the paper is to examine and discuss the geology and typical behavor of this claystone and its micro-level mechanism. The hydraulic conductivity was assessed using consilidated apparatuses; 150 mm diameter column mound using aggregated sample and 60 mm oedometer mould using slurry sample as a reference. Claystone materials used were treated under various conditions. In long term test under constand vertical stress and hydraulic gradient, the hydraulic conductvity decreases with time although the volume of void volume of the sample increased by swelling. Water contens of the individul aggregated increased by swelling, by which strength of particles decreases with and aggregate breakdown was enchanced. As a result, large void created by large particles could be redused in its size, leading the reduction of hydraulic conductuvity. The hydralic conductivities (K values) obtained from the aggregated sample varied in a broad range compared with those from slurry sample. In the test using the higher percentage of gravel-sized aggregate (up until couarse gravel-sized; retained in 26.5 mm sieve), K values changed from 10-5 to 10-7 m/s under vertical stresses from 5 up to 245 kPa. The test was repeated using smaller percentage of gravel-sized aggregate (up until fine gravel-sized, retained in 4.75 mm sieve) and the observed K values changed from 10-5 to 10-10 m/s. While the K values obtained in the specimen made from surry under same vertical stresses was 10-9 to 10-11 m/s. All of the extruded aggregate samples had higher water content than the initial ones, which suggest the alteration mechanism of soled consolidation phase to more deformable plastic phase, whice enables thesample to decrease the void size. These results conclude that using coarse gravel-sized aggregated, which is a reasonable scenario of a practically feasible aggregate size in a field, may noy produce the aimed hydraulic conductivity by the regulated standard. Therefore, breakdown of the aggrgate size and enchament of swelling are crucial factors for the application of the clay stones as a barrier material.
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Raymond, Gerald P., and Richard J. Bathurst. "Repeated-load response of aggregates in relation to track quality index." Canadian Geotechnical Journal 31, no. 4 (August 1, 1994): 547–54. http://dx.doi.org/10.1139/t94-063.
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Track quality rating systems are briefly introduced as a background for undertaking a study of the repeated-load response of ballast aggregates. The results from a number of different laboratory investigations are reviewed and this data interpreted in terms of track quality behaviour. The paper reviews selected results from repeated-load triaxial tests used to investigate the repeated-loading response of different granular railway ballasts at stress levels comparable with those below North America heavy freight axle loads. These results are used to establish an aggregate index to predict deformation and breakdown of ballast under repeated loading. Large-scale test programs are reviewed that relate aggregate quality to simulated ballasted track formation response using a 0.9 m long by 250 mm wide tie to represent a typical loaded rail seat. The large-scale testing was restricted to one aggregate that was subjected to a range of load levels and artificial subgrade stiffness. Similar related work on coarse, single-sized aggregates recommended for drainage layers in highway pavements is reviewed to illustrate the trade-offs between support compressibility and quality of aggregate defined by the aggregate index value. The laboratory tests and model performance are compared with published data to establish a laboratory performance rating in the form of an aggregate index for prediction of those track quality indices that relate to deformation as a function of aggregate type. Key words : ballast, aggregate, hardness, toughness, railway, track quality.
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ALVAROFUENTES, J., J. ARRUE, C. CANTEROMARTINEZ, and M. LOPEZ. "Aggregate breakdown during tillage in a Mediterranean loamy soil." Soil and Tillage Research 101, no. 1-2 (September 2008): 62–68. http://dx.doi.org/10.1016/j.still.2008.06.004.
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Hu, Feinan, Jingfang Liu, Chenyang Xu, Zilong Wang, Gang Liu, Hang Li, and Shiwei Zhao. "Soil internal forces initiate aggregate breakdown and splash erosion." Geoderma 320 (June 2018): 43–51. http://dx.doi.org/10.1016/j.geoderma.2018.01.019.
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Li, Guanglu, Yu Fu, Baiqiao Li, Tenghui Zheng, Faqi Wu, Guanyun Peng, and Tiqiao Xiao. "Micro-characteristics of soil aggregate breakdown under raindrop action." CATENA 162 (March 2018): 354–59. http://dx.doi.org/10.1016/j.catena.2017.10.027.
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Ackermand, Dietrich, Brian F. Windley, and Andriantefison H. Razafiniparany. "Kornerupine breakdown reactions in paragneisses from southern Madagascar." Mineralogical Magazine 55, no. 378 (March 1991): 71–80. http://dx.doi.org/10.1180/minmag.1991.055.378.06.
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AbstractKornerupine-rich layers up to several centimetres thick with minor sillimanite, spinel, Fe oxide and ilmenite occur in a diopsidite in sillimanite-cordierite gneiss south of Beraketa (24°27′S, 46°48′E), southern Madagascar. Kornerupine, sillimanite, spinel and hematite grains up to 1 mm across have mutual polygonal boundaries indicating textural equilibrium at their crystallisation. Kornerupine has XMg 0.67–0.80 and 0.9 to 2.6 wt.% B2O3. Sillimanite contains up to 2.0 wt.% Fe2O3. Spinel is essentially (Mg,Fe2+) Al2O4 with an XMg range of 0.29–0.40 and exsolution lamellae of Fe oxide. Textural relations demonstrate two limited reactions, each confined to areas less than 500 µm across: (1) Kornerupine and spinel reacted along grain contacts to form very fine-grained tourmaline, corundum and chlorite. The replacing phases are symmetrically zoned with a central tourmaline and hematite, bordered by an aggregate of chlorite, tourmaline and corundum, followed outwards by a rim of chlorite against the kornerupine and spinel. (2) Within kornerupine grains, zoned, round aggregates consist of very fine-grained chlorite, tourmaline and corundum of different composition than in (1). They define the terminal reaction of kornerupine breakdown.Geothermobarometry indicates that the early kornerupine-bearing assemblage was stable at 7.0 kbar and 700 °C. This P-T point lies close to the retrograde, nearly isothermal trajectory defined independently by nearby sapphirine-bearing assemblages. The fine-grained aggregates formed most likely during further cooling, or by increasing water fugacity.
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Zhu, ZhaoLong, Damien J. Field, and Budiman Minasny. "Measuring and modelling the actual energy involved in aggregate breakdown." CATENA 82, no. 1 (July 2010): 53–60. http://dx.doi.org/10.1016/j.catena.2010.04.009.
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Doetterl, S., J. T. Cornelis, J. Six, S. Bodé, S. Opfergelt, P. Boeckx, and K. Van Oost. "Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape." Biogeosciences 12, no. 5 (March 4, 2015): 1357–71. http://dx.doi.org/10.5194/bg-12-1357-2015.
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Abstract. The role of eroding landscapes in organic carbon stabilization operating as C sinks or sources has been frequently discussed, but the underlying mechanisms are not fully understood. Our analysis aims to clarify the effects of soil redistribution on physical and biogeochemical soil organic carbon (SOC) stabilization mechanisms along a hillslope transect. The observed mineralogical differences seem partly responsible for the effectiveness of geochemical and physical SOC stabilization mechanisms as the mineral environment along the transect is highly variable and dynamic. The abundance of primary and secondary minerals and the weathering status of the investigated soils differ drastically along this transect. Extractable iron and aluminum components are generally abundant in aggregates, but show no strong correlation to SOC, indicating their importance for aggregate stability but not for SOC retention. We further show that pyrophosphate extractable soil components, especially manganese, play a role in stabilizing SOC within non-aggregated mineral fractions. The abundance of microbial residues and measured 14C ages for aggregated and non-aggregated SOC fractions demonstrate the importance of the combined effect of geochemical and physical protection to stabilize SOC after burial at the depositional site. Mineral alteration and the breakdown of aggregates limit the protection of C by minerals and within aggregates temporally. The 14C ages of buried soil indicate that C in aggregated fractions seems to be preserved more efficiently while C in non-aggregated fractions is released, allowing a re-sequestration of younger C with this fraction. Old 14C ages and at the same time high contents of microbial residues in aggregates suggest either that microorganisms feed on old carbon to build up microbial biomass or that these environments consisting of considerable amounts of old C are proper habitats for microorganisms and preserve their residues. Due to continuous soil weathering and, hence, weakening of protection mechanisms, a potential C sink through soil burial is finally temporally limited.
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Doetterl, S., J. T. Cornelis, J. Six, S. Bodé, S. Opfergelt, P. Boeckx, and K. Van Oost. "Soil redistribution and weathering controlling the fate of geochemical and physical carbon stabilization mechanisms in soils of an eroding landscape." Biogeosciences Discussions 11, no. 11 (November 26, 2014): 16227–68. http://dx.doi.org/10.5194/bgd-11-16227-2014.
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Abstract. It has been suggested that eroding landscapes can form C sinks or sources, but the underlying mechanisms are not fully understood. Our analysis aims to clarify the effects of soil redistribution on physical and biogeochemical soil organic carbon (SOC) stabilization mechanisms along a hillslope transect. The observed mineralogical differences seem partly responsible for the effectiveness of geochemical and physical SOC stabilization mechanisms as the mineral environment along the transect is highly variable and dynamic. The abundance of primary and secondary minerals and the weathering status of the investigated soils differ drastically along this transect. Extractable iron and aluminum components are largely abundant in aggregates, but show no strong correlation to SOC, indicating their importance for aggregate stability but not for SOC retention. We further show that pyrophosphate extractable soil components, especially manganese, play a role in stabilizing SOC within non-aggregated mineral fractions. The abundance of microbial residues and measured 14C ages for aggregated and non-aggregated SOC fractions demonstrate the importance of the combined effect of geochemical and physical protection to stabilize SOC after burial at the depositional site. Mineral alteration and the breakdown of aggregates limit the protection of C by minerals and within aggregates temporally. The 14C ages of buried soil indicate that C in aggregated fractions seem to be preserved more efficiently while C in non-aggregated fractions is released, allowing a re-sequestration of younger C with this fraction. Old 14C ages and at the same time high contents of microbial residues in aggregates suggest that microorganisms either feed on old carbon to build up microbial biomass, or that these environments consisting of considerable amounts of old C are proper habitats for microorganisms and preserve their residues. Due to continuous soil weathering and, hence, weakening of protection mechanisms, a potential C sink through soil burial is finally temporally limited.
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Miller, J. J., E. Bremer, B. W. Beasley, C. F. Drury, B. J. Zebarth, and F. J. Larney. "Long-term effect of fresh and composted cattle manure on the size and nutrient composition of dry-sieved soil aggregates." Canadian Journal of Soil Science 92, no. 4 (May 2012): 673–83. http://dx.doi.org/10.4141/cjss2011-056.
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Miller, J. J., Bremer, E., Beasley, B. W., Drury, C. F., Zebarth, B. J. and Larney, F. J. 2012. Long-term effect of fresh and composted cattle manure on the size and nutrient composition of dry-sieved soil aggregates. Can. J. Soil Sci. 92: 673–683. Application of feedlot manure to cropland may impact the size distribution and nutrient content of soil aggregates. The objective of this study was to determine the effects of fresh or composted feedlot manure containing straw or wood-chip bedding on dry-sieved aggregate size distribution and nutrient contents. Surface (0–15 cm) soil samples were obtained from a long-term field experiment where treatments were fresh (FM) or composted manure (CM) containing straw or wood-chips applied annually at 0 (control) or 77 Mg ha−1yr−1for 11 yr. Air-dried soil samples were separated using a rotary sieve into six aggregate size fractions ranging from <0.47 mm to >12.7 mm. Total C, total N, C:N ratio, soil mineralizable N (41-d incubation), total P, soil test P, and P saturation index were determined on the six aggregate fractions. The amendments significantly (P≤0.05) increased the proportion of smaller (<0.47 mm) aggregates and decreased the proportion of the larger (>12.7 mm) aggregates relative to the unamended control. The geometric mean diameter (GMD) was also lower and wind erodible fraction (WEF) was greater for the amended treatments than unamended control. We attributed this manure effect to increased organic matter content in the soil making the aggregates more friable and susceptible to breakdown by tillage. Carbon, N, and P concentrations were not shifted to smaller aggregate sizes where root growth and nutrient uptake are generally greater. The exception was mineralizable N, which tended to be greater in the finer<0.47 mm fraction. Mineralizable soil N in all aggregate sizes ≥0.47 mm was reduced for wood-chip compared with straw bedding, and resulted in net N immobilization in aggregate sizes ≥1.2 mm. Phosphorus sorption was lower in soil amended with wood-chips compared with straw bedding for aggregates ≥0.47 mm. Long-term manure application may shift soil aggregates from larger to finer fractions because of greater friability and suggests that these soils should be managed to avoid the greater risk of wind erosion.
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Zhang, Jie, Yaojun Liu, Taihui Zheng, Xiaomin Zhao, Hongguang Liu, and Yongfen Zhang. "Nutrient and Stoichiometric Characteristics of Aggregates in a Sloping Farmland Area under Different Tillage Practices." Sustainability 13, no. 2 (January 17, 2021): 890. http://dx.doi.org/10.3390/su13020890.
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Sloping farmland is prevalent in hilly red soil areas of South China. Improper tillage patterns induce decreased soil organic matter, soil aggregate breakdown, and nutrient imbalance, thereby restricting crop production. However, the stoichiometric characteristics could reflect the nutrient availability which was mostly studied on bulk soil. The stoichiometric characteristics of soil aggregates with multiple functions in farmlands has rarely been studied. The study was to reveal the impact of tillage patterns on the size distribution, nutrient levels, and stoichiometric ratios of soil aggregates after 20 years’ cultivation. Soil samples of 0–20 cm and 20–40 cm from five tillage patterns, bare-land control (BL), longitudinal-ridge tillage (LR), conventional tillage + straw mulching (CS), cross-ridge tillage (CR), and longitudinal-ridge tillage + hedgerows (LH) were collected. The elemental content (C, N and P) and soil aggregate size distribution were determined, and the stoichiometric ratios were subsequently calculated. Through our analysis and study, it was found that the nutrient content of >2 mm soil aggregates in all plots was the highest. In the hedgerow plots, >2 mm water-stable soil aggregate content was increased. Therefore, LH plots have the highest content of organic matter and nutrients. After 20 years of cultivation, stoichiometric ratio of each plot showed different changes on soil aggregates at different levels. the C:N, C:P, and N:P ratios are lower than the national average of cultivated land. Among of them, the stoichiometric ratio in the LH plot is closer to the mean and showed better water-stable aggregate enhancement. Therefore, longitudinal-ridge tillage + hedgerows can be recommended as a cultivation measure. This study provides a reference for determining appropriate tillage measures, balancing nutrient ratios, and implementing rational fertilization.
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BLACK, J. M. W., and D. S. CHANASYK. "EVALUATION OF A MODIFIED RAPID ROTARY SIEVE." Canadian Journal of Soil Science 69, no. 4 (November 1, 1989): 813–16. http://dx.doi.org/10.4141/cjss89-081.
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Sieve loading in a modified rapid rotary sieve (MRRS) was investigated and data from the MRRS and a rotary sieve were compared; 1.5–2 kg sieve loadings gave the best precision. Correlation between the rotary sieve and the MRRS was 0.63; it improved to 0.79 when aggregate comminution in the MRRS was considered. Key words: Wind erosion, aggregate breakdown, sieving, modified rapid rotary sieve
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Silva, Érika Andressa, Micael Stolben Mallmann, Monike Andrade Pereira, Sarah Severo Pons, Felipe Dalla –Zen Bertol, Dalvan José Reinert, and José Miguel Reichert. "MACROAGGREGATION OF A PALEUDALF AFFECTED BY CAVITATION INTENSITY AND MANAGEMENT SYSTEMS WITH COVER PLANTS." Revista Brasileira de Engenharia de Biossistemas 15, no. 2 (October 5, 2021): 283–302. http://dx.doi.org/10.18011/bioeng2021v15n2p283-302.
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Ultrasonic-based techniques allow the prediction of the energy required to break the aggregate and have been more commonly used to measure the stability of aggregates. Although they result in the same applied energy, certain combinations of time and power might correspond to different intensities of cavitation. Consequently, different responses in aggregation indexes can be obtained with different configurations of ultrasound techniques. Thus, this work was carried out to evaluate the effects of cavitation intensity in the distribution of aggregates of a Paleudalf under management systems with cover plants and to compare aggregate stability determination methods (ultrasound versus wet sieving). Aggregate samples of the BS (bare soil), OT (black oat + forage turnips) and OV (black oat + hairy vetch) treatments were exposed to ultrasonic irradiation in different combinations of potency and time: (U1) 74.5 W/4 s; (U2) 49.7 W/6 s; (U3) 74.5 W/10 s and (U4) 49.7 W/15 s. After each sonification, the samples were passed in the same set of sieves used in the standard method of wet sieving -WS (8.00 - 4.76, 4.76 - 2.00, 2.00 - 1.00, 1.00 - 0.25 and < 0.25 mm) and the geometric mean diameter (GMD) and mass-weighted mean diameter (WMD) were calculated. The amplitude of vibration exerted a greater influence on soil breakdown than the total energy applied. Compared to the ultrasound method, in the WS method observed higher percentage of retained aggregates in the size class 8-4.76 mm and, consequently, greater aggregation indexes GMD and WMD.
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Glanville, SF, and GD Smith. "Aggregate breakdown in clay soils under simulated rain and effects on infiltration." Soil Research 26, no. 1 (1988): 111. http://dx.doi.org/10.1071/sr9880111.
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Wet sieving was used to separate aggregate-size distributions of four clay soils after pre-treatments of simulated rainfall, tension wetting and immersion wetting. Infiltration rates of columns of the soils were also measured under simulated rainfall. During rainfall, samples for wet sieving and the infiltrating columns were either bare or covered with a cloth mesh designed to absorb raindrop impact without affecting rates of wetting. Two swelling clay soils, one non-swelling clay soil and one clay soil dominated by sesquioxides, were used. For the first three soils, rate of wetting was the major factor governing aggregate breakdown. Significant changes in Mean Weight Diameter (MWD) occurred during the first few minutes of rainfall whether the samples were covered or not. As the rain continued, further breakdown was detected only in the uncovered samples. MWD of the sesquioxide soil decreased slightly during immersion, but most aggregate breakdown resulted from the impact of raindrops. Infiltration into the soil columns was virtually unrestricted if the soils were covered. Slaking without drop impact did not interfere with water entry. On bare soils, positive correlations were found between cumulative rainfall and the per cent of soil particles <0.12 mm diameter. An inverse relationship was found between this particle size range and infiltration rates. It is suggested that 25% of the <0.12 mm fraction must be present before infiltration rates decline.
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Raine, S. R., and H. B. So. "An investigation of the relationships between dispersion, power, and mechanical energy using the end-over-end shaking and ultrasonic methods of aggregate stability assessment." Soil Research 35, no. 1 (1997): 41. http://dx.doi.org/10.1071/s96063.
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The dispersion and energies applied by the end-over-end shaking and ultrasonic methods of assessing aggregate stability were compared. The simple calculation of the kinetic energy of the falling water within the shaking cylinder (0·72 W) was found to underestimate the total energy associated with dispersion, which was estimated as the equivalent energy during the initial period of shaking, as 1·92±0·18 W. A range of mechanical energies up to 24·95 W was applied to suspensions of 2 Vertisols with contrasting stability using the ultrasonic and the end-over-end shaking techniques. Both power and total energy applied was found to affect significantly (P < 0·05) the dispersion of material sized <20 and <2 µm. The results confirmed the presence of aggregate hierarchy, with the end-over-end shaking treatment being unable to disperse completely the <2 µm material for either soil. An increase in the power applied by the ultrasonic probe increased the rate of aggregate breakdown for the stable soil but produced no effect on rate of breakdown in the unstable soil.
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Yang, Jiangang, Wenjie Tao, Jie Gao, Di Yu, Jian Zhou, Liang He, and Yuquan Yao. "Measurement of particle agglomeration and aggregate breakdown of reclaimed asphalt pavement." Construction and Building Materials 296 (August 2021): 123681. http://dx.doi.org/10.1016/j.conbuildmat.2021.123681.
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Ribeiro, Bruno Teixeira, José Maria de Lima, Nilton Curi, and Geraldo César de Oliveira. "Aggregate breakdown and dispersion of soil samples amended with sugarcane vinasse." Scientia Agricola 70, no. 6 (December 2013): 435–41. http://dx.doi.org/10.1590/s0103-90162013000600009.
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Truman, C. C., J. M. Bradford, and J. E. Ferris. "Antecedent Water Content and Rainfall Energy Influence on Soil Aggregate Breakdown." Soil Science Society of America Journal 54, no. 5 (September 1990): 1385–92. http://dx.doi.org/10.2136/sssaj1990.03615995005400050030x.
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Le Bissonnais, Ives. "Abstract: Analysis of aggregate breakdown mechanisms and particle mobilization under rainfall." Soil Technology 2, no. 3 (September 1989): 330. http://dx.doi.org/10.1016/0933-3630(89)90024-x.
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Pourbozorgi Langroudi, Pakdad, Gesa Kapteina, and Marcus Illguth. "Automated Distinction between Cement Paste and Aggregates of Concrete Using Laser-Induced Breakdown Spectroscopy." Materials 14, no. 16 (August 17, 2021): 4624. http://dx.doi.org/10.3390/ma14164624.
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Laser-induced breakdown spectroscopy (LIBS) is a technique which enables the analysis of material components with precision and spatial resolution. Furthermore, the investigation method is comparatively fast which enables illustrating the distribution of elements within the examined material. This opens new possibilities for the investigation of very heterogeneous materials, such as concrete. Concrete consists of cement, water, and aggregates. As most of the transport processes take place exclusively in the hardened cement paste, relevant limit values linked to harmful element contents are specified in relation to the cement mass. When a concrete sample from an existing structure is examined, information on the concrete composition is usually not available. Therefore, assumptions have to be made to convert the element content analyzed in the sample based on the cement content in the sample. This inevitably leads to inaccuracies. Therefore, a method for distinction between cement paste and aggregates is required. Cement and aggregate components are chemically very close to each other and therefore, complex for classification. This is why the consideration of a single distinguishing feature is not sufficient. In this paper, a machine learning method is described and has been used to automate the distinction of the cement paste and aggregates of the LIBS data to receive reliable information of this technique. The presented approach could potentially be employed for many heterogeneous materials with the same complexity to quantify the arbitrary substances.
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KACHANOSKI, R. G., R. P. VORONEY, and E. G. GREGORICH. "ULTRASONIC DISPERSION OF AGGREGATES: DISTRIBUTION OF ORGANIC MATTER IN SIZE FRACTIONS." Canadian Journal of Soil Science 68, no. 2 (May 1, 1988): 395–403. http://dx.doi.org/10.4141/cjss88-036.
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Aggregates (1–2 mm) from a soil under continuous corn management were subjected to a mild shaking treatment and ultrasonic energy levels ranging from 100 to 1500 J mL−1 water to determine the degree of aggregate disruption and dispersion. More clay- and fewer sand-size particles were recovered with greater amounts of applied energy indicating greater aggregate disruption and dispersion with higher energy levels. Most of the breakdown of sand-size aggregates occurred between energy levels of 300 and 500 J mL−1. Ultrasonic energy levels of 500 J mL−1 or greater were more effective than using 20% hydrogen peroxide plus 16 h of shaking in dispersing sand-size microaggregates. Surface area measurements of the clay indicated no severe fragmentation or alteration of primary particles had occurred. With increased applied ultrasonic energy and more complete dispersion, the amount of organic C recovered increased in the clay- and decreased in the sand-size fractions. At complete dispersion, there was no evidence of redistribution of organic matter by ultrasonification and the sand-, silt- and clay-size fractions contained 5, 30 and 60% of the soil organic C. Results of this study suggest that ultrasonic dispersion techniques can be used as a physical method to separate microaggregates from soil and thereby study the nature of organic matter within them. Key words: Ultrasonic dispersion methodology, aggregates, organic matter distribution, particle size fractions
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Hilário, Ronderson Queiroz, and Gilberto Fernandes. "Use of dynamic ballast testing equipment for analysis of rail aggregate breakdown." REM - International Engineering Journal 74, no. 2 (June 2021): 155–63. http://dx.doi.org/10.1590/0370-44672020740076.
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Bender, Tom, Ilka Lewrenz, Sebastian Franken, Catherina Baitzel, and Wolfgang Voos. "Mitochondrial enzymes are protected from stress-induced aggregation by mitochondrial chaperones and the Pim1/LON protease." Molecular Biology of the Cell 22, no. 5 (March 2011): 541–54. http://dx.doi.org/10.1091/mbc.e10-08-0718.
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Proteins in a natural environment are constantly challenged by stress conditions, causing their destabilization, unfolding, and, ultimately, aggregation. Protein aggregation has been associated with a wide variety of pathological conditions, especially neurodegenerative disorders, stressing the importance of adequate cellular protein quality control measures to counteract aggregate formation. To secure protein homeostasis, mitochondria contain an elaborate protein quality control system, consisting of chaperones and ATP-dependent proteases. To determine the effects of protein aggregation on the functional integrity of mitochondria, we set out to identify aggregation-prone endogenous mitochondrial proteins. We could show that major metabolic pathways in mitochondria were affected by the aggregation of key enzyme components, which were largely inactivated after heat stress. Furthermore, treatment with elevated levels of reactive oxygen species strongly influenced the aggregation behavior, in particular in combination with elevated temperatures. Using specific chaperone mutant strains, we showed a protective effect of the mitochondrial Hsp70 and Hsp60 chaperone systems. Moreover, accumulation of aggregated polypeptides was strongly decreased by the AAA-protease Pim1/LON. We therefore propose that the proteolytic breakdown of aggregation-prone polypeptides represents a major protective strategy to prevent the in vivo formation of aggregates in mitochondria.
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Ewane, Ewane Basil, and Heon-Ho Lee. "Effects of vegetation cover on sediment particle size distribution and transport processes in natural rainfall conditions on post-fire hillslope plots in South Korea." Soil Research 54, no. 8 (2016): 937. http://dx.doi.org/10.1071/sr16117.
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Sediments were collected from four slow vegetation recovery plots, six fast vegetation recovery plots and five unburned plots at a post-fire site on a rainfall event basis and sorted for size distribution. The aim was to evaluate the effects of vegetation cover, soil aggregate stability, slope and rainfall intensity on sediment size distribution, transport selectivity and erosion processes between the burned and unburned treatment plots. Sediment detachment and transport mechanisms and the particle size transport selectivity of the eroded sediment were assessed based on enrichment ratios (ER) and mean weighted diameter (MWD) methods. The most eroded particle size class in all treatment plots was the 125–250μm class and, generally, the percentage of eroded particle sizes did not increase with slope and rainfall intensity. Higher MWD of the eroded sediment was related to a higher percentage of bare soil exposed and gravel content associated with high soil burn severity and soil disaggregation in the slow vegetation recovery plots. The enrichment of finer clay silt particle sizes increased with varying maximum 30-min rainfall intensity (I30) in the slow vegetation recovery plots, and reflected increased aggregate breakdown and transport selectivity, whereas no good relationship was found in the fast vegetation recovery and unburned plots with varying I30. A minimum I30 of <3.56mmh–1 and a maximum of 10.9mmh–1 were found to be the threshold rainfall intensity values necessary for aggregate breakdown and transport of finer particles by both rainsplash and rainflow in the slow vegetation recovery plots, whereas the response was weak in the fast vegetation recovery and unburned plots following varying I30 dominated only by rainsplash transport closer to the plot sediment collector. The results show that higher vegetation cover in the fast vegetation recovery and unburned plots reduces erosive rainfall energy by 5.6- and 17.7-fold respectively, and runoff energy by 6.3- and 21.3-fold respectively, limiting aggregate breakdown and transport selectivity of finer particles compared with the slow vegetation recovery plots.
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Vandana Kumari, Ranjan Laik, Shishpal Poonia, and Debabrata Nath. "Regulation of soil organic carbon stock with physical properties in alluvial soils of Bihar." Environment Conservation Journal 23, no. 1&2 (April 17, 2022): 309–14. http://dx.doi.org/10.36953/ecj.021791-2110.
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Soil temperature and water content govern the breakdown of soil organic matter (SOM), which has a large impact on SOC storage. Apparently soil organic carbon is an excellent indicator of soil health. In this experiment, the association between several soil health indices such as soil organic carbon (SOC), soil texture, and wet aggregate stability was investigated (WAS). It was discovered that there is a substantial positive relationship between wet aggregate stability and soil organic carbon storage. Soil carbon store in East Champaran soils ranged from 5.27 to 19.60 mg/ha, with an average of 12.98 mg/ha. The wet aggregate stability ranged from 3.82 to 36.43 %, with a mean of 16.11 %. Wet aggregate stability was shown to increase as the organic carbon storage in the soil increased. This experiment also indicated that clay (%) and silt (%) had a direct impact on wet aggregate stability and, as a result, soil organic carbon storage. As a result, wet aggregate stability and soil texture have a direct and favourable influence on soil organic carbon storage in East Champaran, Bihar soils
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Bullock, Murray S., Francis J. Larney, Sean M. McGinn, and R. César Izaurralde. "Freeze-drying processes and wind erodibility of a clay loam soil in southern Alberta." Canadian Journal of Soil Science 79, no. 1 (February 1, 1999): 127–35. http://dx.doi.org/10.4141/s98-027.
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Freeze-drying has been implicated as a factor causing soil aggregate breakdown on the Canadian Prairies and northern Great Plains. Aggregates of a Dark Brown Chernozemic clay loam soil sampled in October 1993 and January and April 1994 were subjected to repeated cycles of wetting (to 0.1, 0.2 and 0.3 kg kg−1 water contents) freezing, and freeze-drying under laboratory conditions. The October 1993 samples showed less disruption when initially exposed to freeze-drying cycles compared to samples taken in January and April 1994. Using regression analysis, we predicted that 31 freeze-dry cycles were required for the 0.1 kg kg−1 water content aggregates to reach 60% erodible fraction (EF, % aggregates <0.86 mm), 9 cycles for the 0.2 kg kg−1 aggregates and 2 for 0.3 kg kg−1 aggregates. In a field study, conducted over the 1994–1995 winter on a similar clay loam soil, we estimated the number of freeze-drying cycles using large vapour pressure (VPL) and small vapour pressure (VPS) gradients between the soil surface (which had a mean winter water content of ~0.1 kg kg−1) and the atmosphere. With solar energy adjustments, we predicted that the number of freeze-dry cycles required for the soil to reach 60% EF was 60 for VPL and 37 for VPS conditions. The latter number was similar to the 31 cycles predicted in the laboratory study of aggregates at 0.1 water content. Our results demonstrate that freeze-drying is an important overwinter process in the breakdown of soil aggregates and hence wind erosion risk in the Canadian prairie region. Key words: Freeze-drying, wind erosion, erodible fraction
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Tareq, Abdulrahman Marwan, and Abdulhaq Hadi Abedali. "Predicted Affinity Ratio between Asphalt Binder and Aggregate." Journal of Engineering 25, no. 7 (July 1, 2019): 134–44. http://dx.doi.org/10.31026/j.eng.2019.07.08.
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Affinity is a term used to describe the amount of the adhesion bond between asphalt binder and aggregate. Adhesion force may be used as indicator to the amount of energy or work required to breakdown the adhesive bond between asphalt binder and aggregate. In order to study affinity between asphalt binder and aggregate, a modified device is manufacture locally similar to Rolling Bottle Test (RBT) to Predicted the degree of affinity between asphalt binder and aggregate; taking into consideration mineral composition with physical properties of asphalt binder to measure required force to separate asphalt binder from aggregate surface. In this study, suggest new parameters to represent the stripping or affinity phenomena (affinity and stripping ratio) and the time required to make balance between them. From the experimental work result, the affinity ratio of aggregate brought from Dohuk region was 52 % after 24hr of rolling time period which is less than other type because of its mineral composition (high percent of calcite and dolomite which increase ability to resist stripping), pore size and stiffness of aggregate particle. In other hand, the stripping ratio of aggregate brought from al-Taji quarry was 80% after 24hr of rolling time which represent worse case in affinity of aggregate-asphalt binder system due to increased percent of quartz in mineral composition (greater than 80%) and so reduced ability of aggregate to resist stripping
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Bischoff, Norbert, Robert Mikutta, Olga Shibistova, Alexander Puzanov, Marina Silanteva, Anna Grebennikova, Roland Fuß, and Georg Guggenberger. "Limited protection of macro-aggregate-occluded organic carbon in Siberian steppe soils." Biogeosciences 14, no. 10 (May 24, 2017): 2627–40. http://dx.doi.org/10.5194/bg-14-2627-2017.
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Abstract. Macro-aggregates especially in agricultural steppe soils are supposed to play a vital role for soil organic carbon (OC) stabilization at a decadal timescale. While most research on soil OC stabilization in steppes focused on North American prairie soils of the Great Plains with information mainly provided by short-term incubation experiments, little is known about the agricultural steppes in southwestern Siberia, though they belong to the greatest conversion areas in the world and occupy an area larger than that in the Great Plains. To quantify the proportion of macro-aggregate-protected OC under different land use as function of land use intensity and time since land use change (LUC) from pasture to arable land in Siberian steppe soils, we determined OC mineralization rates of intact (250–2000 µm) and crushed (< 250 µm) macro-aggregates in long-term incubations over 401 days (20 °C; 60 % water holding capacity) along two agricultural chronosequences in the Siberian Kulunda steppe. Additionally, we incubated bulk soil (< 2000 µm) to determine the effect of LUC and subsequent agricultural use on a fast and a slow soil OC pool (labile vs. more stable OC), as derived from fitting exponential-decay models to incubation data. We hypothesized that (i) macro-aggregate crushing leads to increased OC mineralization due to an increasing microbial accessibility of a previously occluded labile macro-aggregate OC fraction, and (ii) bulk soil OC mineralization rates and the size of the fast OC pool are higher in pasture than in arable soils with decreasing bulk soil OC mineralization rates and size of the fast OC pool as land use intensity and time since LUC increase. Against our hypothesis, OC mineralization rates of crushed macro-aggregates were similar to those of intact macro-aggregates under all land use regimes. Macro-aggregate-protected OC was almost absent and accounted for < 1 % of the total macro-aggregate OC content and to a maximum of 8 ± 4 % of mineralized OC. In accordance to our second hypothesis, highest bulk soil OC mineralization rates and sizes of the fast OC pool were determined under pasture, but mineralization rates and pool sizes were unaffected by land use intensity and time since LUC. However, at one chronosequence mean residence times of the fast and slow OC pool tended to decrease with increasing time since establishment of arable use. We conclude that the tillage-induced breakdown of macro-aggregates has not reduced the OC contents in the soils under study. The decline of OC after LUC is probably attributed to the faster soil OC turnover under arable land as compared to pasture at a reduced plant residue input.
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García-Corona, R., E. Benito, E. de Blas, and M. E. Varela. "Effects of heating on some soil physical properties related to its hydrological behaviour in two north-western Spanish soils." International Journal of Wildland Fire 13, no. 2 (2004): 195. http://dx.doi.org/10.1071/wf03068.
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Two forest soils rich in organic matter but differing in texture (sandy loam and silty loam) were heated under controlled laboratory conditions in order to examine the consequences of the heating effect that accompanies the passage of a fire on the physical properties of soil. Three samples of both soils were heated for 30 min in a muffle furnace at temperatures of 25, 170, 220, 380 and 460°C. At each temperature, the following parameters were determined: dry aggregate size distribution, water aggregate stability, total porosity, pore size distribution, water repellency and hydraulic conductivity. Heating the soils at 170 and 220°C caused no significant changes in aggregate size distribution or total porosity but increased water aggregate stability and the volume of pores 0.2–30 μm. Also, increased water repellency and strongly decreased the hydraulic conductivity. All parameters underwent much more dramatic changes at 380 and 460°C that can be ascribed to the combustion of organic matter. At such temperatures, water repellency was destroyed and the low hydraulic conductivity can be attributed to the aggregate breakdown observed under dry and wet conditions.
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Chen, Pei-Chin, Chiun-Chieh Yu, Yueh-Sheng Chen, Cheng-Hsien Lu, Shan-Ho Chan, Kun-Hsien Chou, Mei-Hsiu Chen, Meng-Hsiang Chen, and Wei-Che Lin. "The Potential Effects of Oxidative Stress-Related Plasma Abnormal Protein Aggregate Levels on Brain Volume and Its Neuropsychiatric Consequences in Parkinson’s Disease." Oxidative Medicine and Cellular Longevity 2021 (August 14, 2021): 1–10. http://dx.doi.org/10.1155/2021/3666327.
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Background. Oxidative stress has been implicated in the pathogenesis of many diseases, including Parkinson’s disease. Large protein aggregates may be produced after the breakdown of the proteostasis network due to overt oxidative stress. Meanwhile, brain volume loss and neuropsychiatric deficits are common comorbidities in Parkinson’s disease patients. In this study, we applied a mediation model to determine the potential influences of oxidative stress-related plasma abnormal protein aggregate levels on brain volume and neuropsychiatric consequences in Parkinson’s disease. Method. 31 patients with PD and 24 healthy controls participated in this study. The PD patients were further grouped according to the presentation of cognitive decline or not. All participants received complete examinations to determine plasma abnormal protein aggregates levels, brain volume, and neuropsychiatric performance. The results were collected and analyzed in a single-level three-variable mediation model. Results. Patients with PD cognitive decline exhibited higher plasma NfL levels, decreased regional brain volume, and poor neuropsychiatric subtest results compared with PD patients with normal cognition, with several correlations among these clinical presentations. The mediation model showed that the superior temporal gyrus completely mediated the effects of elevated plasma NfL levels due to the poor psychiatric performance of picture completion and digit span. Conclusion. This study provides insight into the effects of oxidative stress-related plasma abnormal protein aggregate levels on regional brain volume and neuropsychiatric consequences in Parkinson’s disease patients.
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Thomaz, Edivaldo L., Cezar F. Araujo-Junior, Pedro R. S. Vendrame, and Thadeu R. de Melo. "Mechanisms of aggregate breakdown in (sub) tropical soils: Effects of the hierarchical resistance." CATENA 216 (September 2022): 106377. http://dx.doi.org/10.1016/j.catena.2022.106377.
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Parker, Nathaniel, Wim M. Cornelis, Kwame Agyei Frimpong, Eric Oppong Danso, Enoch Bessah, and Emmanuel Arthur. "Short-term effects of rice straw biochar on hydraulic properties and aggregate stability of an Acrisol." Soil Research 59, no. 8 (2021): 854. http://dx.doi.org/10.1071/sr20250.
Full textAbstract:
Biochar application to a structurally poor tropical soil could potentially alter the soil’s aggregate strength and hydraulic properties. However, very few field studies have investigated the impact of biochar on the aggregate strength and hydraulic properties of tropical soils. A field experiment was therefore conducted to investigate the short-term effects of rice straw biochar on soil hydraulic properties and aggregate stability of an Acrisol in Ghana. The biochar was broadcast at rates of 10tha−1 and 20tha−1 as single applications that were incorporated into the top 20cm of the soil using a spade and then the soil was levelled using a rake. Field saturated hydraulic conductivity and laboratory-measured soil water retention, aggregate stability and water-repellency were determined 10 months after the biochar application. Biochar increased aggregate stability against fast wetting by up to 33% compared to the control. This implies that biochar might improve the stability of aggregate of an Acrisol against slaking and erosivity of heavy rainfall. However, aggregate stability against slow wetting and mechanical breakdown after pre-wetting were unaffected by the biochar. Biochar did not affect field saturated hydraulic conductivity, water retention characteristics and water-repellency. Further field studies on weathered tropical soils with low native soil organic matter is recommended to elucidate the effect of repeated biochar addition on soil hydraulic and aggregate characteristics.