Solid‐phase organization and shrinkage properties of some growing media constituents according to particle size

An expanded description of particle morphology and the analysis of its relationships with physical properties may help to optimize the selection of raw materials and particle size fractions used as growing media constituents. Previous works have described the outlines of these relations based mostly on sieving procedures to characterize particle size distribution. They have shown limited and sometimes contradictory results due to the different methods used, size fractions selected, and physical properties measured. Also, sieve analysis, which separates particles based on their width, is less accurate for non‐spherical particles, which is the case for most growing media constituents. Recent works have promoted the use of dynamic image analysis (DIA) to precisely analyze both particle length and width. Five raw materials were chosen (white and black peats, coir, pine bark, and wood fiber) and sieved to obtain various particle size fractions. For each particle size fraction and the raw materials, the mean weight diameter (MWD), derived from sieving, was calculated, whereas mean particle length and width were determined using a DIA tool, the QicPic device. Also, physical properties were assessed from water retention curves established using Hyprop systems. The statement that the larger the particle size, the higher the air‐filled porosity (AFP), the lower the water holding capacity (WHC) was more precisely redefined. Large variations in WHC and AFP mainly occurred for finest particle size fractions, whereas changes were conversely very small or non‐existent for larger particle sizes. From data obtained for each particle size fractions, regression models were established to relate mean particle length and width (both determined using DIA) and MWD (determined from sieving) with WHC and AFP. Mean particle length was identified as the most relevant parameter for predicting WHC and AFP of the raw materials tested.

Growing media constituents have heterogeneous particle size and shape, and their physical properties are partly related to them. Particle size distribution is usually analyzed through sieving process, segregating the particles by their width. However, sieving techniques are best describing more granular shapes and are not as reliable for materials exhibiting large varieties of shapes, like growing media constituents. A dynamic image analysis has been conducted for a multidimensional characterization of particle size distribution of several growing media constituents (white and black peats, pine bark, coir, wood fiber, and perlite), from particles that were segregated and dispersed in water. Diameters describing individual particle width and length were analyzed, then compared to particle size distribution obtained by dry and wet sieving methods. This work suggests the relevance of two parameters, Feret MAX and Chord MIN diameters for assessing particle length and width, respectively. They largely varied among the growing media constituents, confirming their non‐spherical (i.e., elongated) shapes, demonstrating the advantages of using dynamic image analysis tools over traditional sieving methods. Furthermore, large differences in particle size distribution were also observed between dynamic image analysis and sieving procedures, with a finer distribution for dynamic image analysis. The discrepancies observed between methodologies were discussed (particle segregation, distribution weighing, etc.), while describing in details methodological limitations of dynamic image analysis.

Elemental composition and solution 13C NMR spectra for six humic acid fractions with different particle sizes (i.e. 3K, 10K, 30K, l00K, 300K, and 500K) which were prepared from a humic acid in an Umbric Andosol by successive gel permeation chromatography were determined. Elemental composition of the particle size fractions clearly differed from one another. Contents of nitrogen and hydrogen increased with the increase of the particle size. Small and middle particle size fractions (3K to l00K) showed low contents of hydrogen and nitrogen corresponding to those in typical Andosol humic acids, while the contents in the large fractions (300K and 500K) were distributed in the ranges of those in the other humic acids. As the particle size increased, the HIC ratio increased whereas the O/H decreased. In the HIC versus OIC diagram, the large particle size fractions (300K and 500K) were observed in the area around humic acids with a low humification degree. Variation of the chemical structural properties with particle size differences was assumed, based on the analysis of the HIC versus OIH and HIC versus OIC diagrams. The changes of the carbon species with particle size differences were examined based on the 13C NMR spectra. As the particle size increased, the aliphatic C content increased whereas the carboxylic and aromatic C content decreased and, therefore, the aromaticity decreased. In addition, a negative correlation (r= -0.977) was found to be significant at 0.1% level between the HIC ratios and aromaticity. The peak strength around 30 ppm assigned to chains of methylene group increased remarkably with the increase of the particle size. It was suggested that the changes of the content of the aliphatic carbon with the decrease of the particle size may depend on the changes of the aliphatic chain length. In conclusion, these findings suggest that the Andosol humic acid molecule may be composed of humic acid components with long chains of aliphatic groups for the larger particle size fractions, and of their homologous series through the reduction of the length of the aliphatic long chain for the smaller particle size fractions. These assumptions were compatible with those made in a series of studies previously reported.

ABSTRACTWe evaluated the effect and magnitude of flour particle size on sponge cake (SC) baking quality. Two different sets of wheat flours, including flours of reduced particle size obtained by regrinding and flour fractions of different particle size separated by sieving, were tested for batter properties and SC baking quality. The proportion of small particles (<55 μm) of flour was increased by 11.6–26.9% by regrinding. Despite the increased sodium carbonate solvent retention capacity, which was probably a result of the increased starch damage and particle size reduction, reground flour exhibited little change in density and viscosity of flour‐water batter and produced SC of improved volume by 0.8–15.0%. The volume of SC baked from flour fractions of small (<55 μm), intermediate (55–88 μm), and large (>88 μm) particles of soft and club wheat was in the range of 1,353–1,450, 1,040–1,195, and 955–1,130 mL, respectively. Even with comparable or higher protein content, flour fractions of intermediate particle size produced larger volume of SC than flour fractions of large particle size. The flour fractions of small particle size in soft white and club wheat exhibited lower flour‐water batter density (102.6–105.9 g/100 mL) than did those of large and intermediate particle fractions (105.2–108.2 g/100 mL). The viscosity of flour‐water batter was lowest in flour fractions of small particle size, higher in intermediate particles, and highest in large particles. Flour particle size exerted a considerable influence on batter density and viscosity and subsequently on SC volume and crumb structure. Fine particle size of flour overpowered the negative effects of elevated starch damage, water absorption, and protein content in SC baking.

Control (crops grown in natural conditions) and Fusarium head blight (FHB) damaged (crops inoculated with Fusarium culmorum conidia) grain of four wheat cultivars was ground and sieved into three fractions of different particle size. A series of blended samples differing in content of damaged material were prepared within fractions and cultivars, and diffuse reflectance spectra recorded within the 200–2500 nm wavelength range. Partial least-squares (PLS) models for the percentage of damaged material in blended samples were built for each of twelve series within different spectral ranges, and the root-mean-squared error of cross-validation (RMSECV) was used for the assessment of model performance. Errors using the models were lowest for the finest fraction independent of spectral range; however, their values depended on the cultivar. RMSECV for the finest fraction averaged over cultivars ranged from a little below 3.0 (when the ultraviolet light sub-range was used or participated with another one) to 8.1% (when only the near infrared (NIR) sub-range was used). For the medium and coarse fractions, averaged errors showed the same tendency of dependence on the sub-range(s); however, with higher values that increased with an increase in particle size. In conclusion, within the different fractions of particle size and spectral ranges, the most sensitive to the presence of damaged material were models developed for the finest fraction and when the ultraviolet light sub-range was used in modelling.

Impact of flour particle size on nutrient and phenolic acid composition of commercial wheat varieties

The objective of the current study was to evaluate the effect of unrepresentative sampling of digesta particulate matter entering the omasal canal on the accuracy of fiber flow measurements. The experimental design comprised one period, one diet, and three cows as experimental units. Within each cow, the physical and chemical composition of digesta particulate matter was assessed at seven sites within the digestive tract. Three Finnish Ayshire dairy cows, equipped with ruminal and simple-T duodenal cannulas, in extended lactation were offered grass silage twice daily on an ad libitum basis. Digesta samples were collected from the rumen (dorsal and ventral sac), reticulum, omasal canal, omasum, duodenum, and rectum to determine particle size distribution in digesta, chemical composition of various particle size fractions, and distribution of two flow markers (Cr-labeled straw and indigestible NDF [INDF]) among particle size fractions. Digesta samples were wet-sieved using sieves of 2.50, 1.25, 0.630, 0.315, 0.160, and 0.080 mm. Particulate matter was analyzed for OM, NDF, and Cr concentrations, and INDF concentration was determined based on 12-d ruminal incubation. The particle size of digesta entering the omasal canal was larger compared with the omasum or the duodenum, suggesting that omasal canal samples were not representative of particle size distribution truly escaping the rumen. The concentration of potentially digestible NDF (PDNDF) decreased with decreasing particle size. The PDNDF concentration of particulate matter retained on all sieves was greatest in the rumen and gradually decreased along the digestive tract. From the reticulorumen to the omasum, the decrease was associated with decreased particle size, reflecting selective passage of particulate matter. In contrast, from the omasum to the duodenum and rectum, the PDNDF concentration decreased within each particle size fraction without effect on particle size, indicating a nonselective passage of particulate matter between these sites. Variation between particle size fractions was slightly greater for Cr concentration than for INDF concentration, indicating that unrepresentative sampling of particulate matter had a greater effect on Cr concentration compared with that of INDF. Owing to unrepresentative sampling, NDF entering the omasal canal was overestimated by 5% using INDF and underestimated by 7% using Cr as a particle phase marker. Of total NDF digestibility, proportionally 0.90, 0.07, and 0.03 occurred in the reticulorumen, omasum, and intestines, respectively. The current results indicate that, despite unrepresentative sampling of digesta particulate matter entering the omasal canal, the errors in determined NDF flow were small. The omasum may have a greater role in postruminal NDF digestion than the intestines.

Anisotropy, cracking, and shrinkage of vertisol samples Experimental study and shrinkage modeling

Particle size fractionation as a method for characterizing the nutrient content of municipal green waste used for composting

The permeability of carbonate reservoir rocks is related to interparticle porosity and particle (grain or crystal) size in the absence of touching-vug porosity. Total porosity is normally composed of interparticle and separate-vug porosity and can usually be measured by neutron and density logs. Measuring particle size and separate-vug porosity from wireline log response is difficult, and two methods have been investigated. A shoaling-upward sequence from fossiliferous wackestone to ooid grainstone is present in the Wolfcampian of the Palo Duro basin, Texas. Both the total porosity and the separate-vug porosity increase vertically. A crossplot of acoustic transit time and porosity has been calibrated for separate-vug porosity. Since the interval is 100% water bearing, the lithologic factor (m) can be calculated from resistivity logs using the Archie equation. The lithologic factor has been related to separate-vug porosity through the ratio of vuggy porosity to total porosity. Permeabilities calculated by both methods match core data reasonably well. Shallowing-upward tidal flat cycles are common in the San Andres/Grayburg of west Texas. In the Dune field, vuggy porosity is not abundant and the principal control on permeability is particle size and interparticle porosity. Although particle size tends to increase vertically through the subtidal-intertidal sequence, themore » upper grainstones are generally cemented. Plots of resistivity versus porosity show that oil saturation above the water level is controlled by particle size and interparticle porosity as is the permeability. The permeability profiles which result from this relationship show excellent agreement with core permeability profiles.« less

Changes in microbial community structure and function within particle size fractions of a paddy soil under different long-term fertilization treatments from the Tai Lake region, China

Impact of soil particle size and bioaccessibility on children and adult lead exposure in peri-urban contaminated soils

In recent years, the migration and transformation of heavy metals (HMs) in soil has become a hot issue. Soil particle size has an important effect on the environmental behavior of HMs in soil. The distribution of HMs in soil is strongly affected by the size of a soil aggregate. In this study, paddy samples in both cultivated and uncultivated soils were collected from Anhui Province, China. The soils were sieved into six particle size fractions (diameters of >4000, 4000–2000, 2000–1000, 1000–250, 250–53, and <53 μm) and the wet digestion method was used to determine the concentrations of Cd, Cr, Pb, and As in the soil aggregates. The results showed that the surface soils were characterized by the largest proportion of coarsest aggregates of >4000 μm particles. Moreover, the concentrations of Cd, Cr, Pb, and As were elevated in cultivated paddy soils compared to uncultivated soils. The accumulation of HMs in all paddy soils increased with decreasing particle size. Although the smallest particle size fractions accounted for only 5.65–17.28%, they provided the highest distribution factor (DF) of Cr (1.35), As (1.25), Cd (1.28), and Pb (1.38). The highest contributions of HMs came from the coarser fractions (>2000 μm); however, for Cr, Pb, Cd, and As, the mass loading of <53 μm particles was up to 15.90%, 14.41%, 15.21%, and 15.70%, respectively. The highest content of HMs was found in the finest aggregate, with a pattern of decreasing with increasing aggregate size. In addition, the leachability behaviors of different HMs in different particle size aggregates were different. The leachability behaviors of Cr and Pb in the coarse particle size fractions were the highest, while the leachability behaviors of As and Cd in the less than 250 μm particle size fractions were 10–100 times higher than those of Cr and Pb. A correlation analysis showed that the particle distributions of Fe, TOC, and Mn had significant influences on the distributions of Pb, Cd, As, and Cr. This study provides a theoretical basis for the prevention, treatment, and remediation of HMs pollution in soil.

The dynamics of total N in particle-size and density fractions of six major soils which have been used for cereal cropping for 20-70 years were studied in order to identify the labile organic matter fractions in soil. For virgin soils, no single particle-size was consistently enriched in N as compared with the whole soil. The clay fraction contained the largest proportion (53% overall) of total N. Silt-size and sand-size N fractions accounted for 26% and 21% of total N, respectively. Upon cultivation, the sand-size fraction lost most of its N (as much as 89% in Langlands-Logie soil). However, N losses also occurred from silt-size and clay-size fractions in most soils. Changes in C : N ratios of different particle-size fractions upon cultivation were not consistent in all soils, possibly because of the transfer of organic C and N among these fractions. Therefore, the separation of labile organic matter fractions from the whole soil based upon particle-size may not be successful in all soils. On the other hand, the density fractionation of soil into a light fraction (<2 Mg m-3) containing relatively labile organic matter (76-96% lost upon cultivation) and a heavy fraction (>2 Mg m-3) containing less labile organic matter appears to be more successful in most soils. It is suggested that the cultural practices that enhance the amount of light fraction would increase the rate of nutrient cycling through microbial biomass and may increase the overall availability of nutrients in soil.

The residence time distribution (RTD) in a pilot plant spray dryer was characterised for two kinds of air distributors (centrifugal and parallel flow) and for different atomizing air pressures. To determine the RTD - and the RTD of different particle size fractions - the particle concentration and size at the dryer outlet was measured continuously using a particle counter. Results were modelled using the Bodenstein number and the CSTR in series model. An increasing nozzle pressure leads to a decrease in mean residence time and a more narrow distribution. The influence of nozzle pressure is more pronounced than of air distributor and particle size fraction. Keywords: Residence time distribution; Particle size; Bodenstein number modelling; Nozzle influence; Mechanism of air distribution