Soil, particle size distribution

Tyler, S.W., and S.W. Wheatcraft. 1992. Fractal scaling of soil particle size distribution Analysis and limitations. Soil Sci. Soc. Am. J. 56 362—369. 

From the examples given here, it is evident that soil adhesion can be reduced by surface modification through the application of a coating that minimizes adhesion or by forming a layer of water between the contact surfaces. The adhesion depends on the soil moisture content and the soil particle size distribution. By changing the moisture content and by the use of electroosmosis, the adhesion of soil to solid surfaces can be reduced. 

Mechanical analyses determine the particle-size distribution in a soil sample. The distribution of coarse particles is determined by sieving, and particles finer than a 200 or 270-mesh sieve and found by sedimentation. 

FIGURE 14.13 Ranges of soil-washing difficulty, based on the particle size distribution in the soil. 

Infiltration rate Water content Particle size distribution Frozen soil Bulk density Clay mineralogy Macro porosity... 

In the design of granular soil (sand) filter materials, the particle-size distribution of the drainage system and that of the invading (or upstream) soils is required. The filter material should have its... 

The size, and particularly the size distribution of the particles (or PSD, as particle size distribution is often abbreviated), which is closely related to the texture of the soil, is an important characteristic that determines many of the... 

Coarse-sized particles dominate the particle size distribution of arid soils. Some soils are also quite gravelly. The subsurface horizons commonly exhibit accumulation zones of carbonates, gypsum and more soluble salts. Many arid zone soils are shallow and gravelly, some are alkaline. Their structure is weak. From most soils, clay accumulation horizons (argillic horizons) are absent, or are only weakly developed, and so are minerals that indicate an advanced degree of weathering. 

Figure 4.1 Relationship between class name of a soil and its particle size distribution.

Fujitake N, Kusumoto A, Tsukamoto M, Kawahigashi M, Suzuki T, Otsuka H. Properties of soil humic substances in fractions obtained by sequential extraction with pyrophosphate solutions at different pHs I. Yield and particle size distribution. Soil Sci. Plant Nutr. 1998 44 253-260. 

The Analysis of Agricultural Materials, 2nd edn, R.B. 427. HMSO, London, (1979) Method 2, p. 6. Preparation of Samples of soil Method 8, p. 21. Boron, water soluble in soil Method 57, p. 134. Nitrogen in soil Method 62, p. 148. Organic matter in soil Method 63, p. 151. Particle size distribution in soil... 

Knowing the particle size distribution for soils provides information about many of the soil properties, such as how much heat, water, and nutrients the soil will hold, how fast they will move through the soil, and what kind of structure, bulk density, and consistency the soil will have. The texture of the soil, how it feels, is based on the relative amounts of sand, silt, and clay present. Particles larger than 2.0 mm are called stones or gravels and are not considered soil material. Sand varies in size from 2.0 to 0.05 mm. Silt varies from 0.05 to 0.002 mm. Clays are less than 0.002 mm. 

Mishra, S., Parker, J. C., and Singhal, N., 1989a, Estimation of Soil Hydraulic Properties and Their Uncertainty from Particle Size Distribution Data Journal of Hydrology, Vol. 108,... 

Particle size distributions of natural sediments and soils are undoubtedly continuous and do not drop to zero abundance in the region of typical centrifugation or filtration capabilities. Additionally, there is some evidence to indicate that dissolved and particulate organic carbon in natural waters are in dynamic equilibrium, causing new particles or newly dissolved molecules to be formed when others are removed. Experiments with soil columns have shown that natural soils can release large quantities of DOC into percolating fluids [109]. 

Equation (9.46) has a slope of 2.35 instead of 3.0 and implies that there are 0.65 moles of nitrate in the structure of ferrihydrite. The problem with this formulation is, however, that it refers to a salt, not an oxide hydroxide and thus, cannot apply to ferrihydrite. On the other hand, Byrne and Yu (2000) suggest that their Kso = [Fe] [OH] for freshly precipitated ferrihydrite has a non integral value owing to variations in the activity of the solid phase, which as mentioned earlier, is due to the influence of pH (3-7.5) on the particle size distribution of the precipitate. Two fairly similar values of ca. -39 have been reported for soil ferrihydrite (Table 9.4). It is probable that in these soils, ferrihydrite determined the activity of dissolved Fe. 

A number of environmental applications [3] have been performed in order to size characterize colloids collected in rivers (riverbome particles, SPM, and sediments), clay samples and ground limestone (from soils), coal particles, diesel soot particles (from combustion processes), or airborne particles in urban areas (from waste incinerators, vehicles, household-heating systems, and manufacturing). In many of these cases, not only the size but also the particle size distribution was important and thus, in conjunction with the traditional UV detector, specific detectors such as ETAAS, ICP-MS, ICP-AES were used [40] in order to obtain more detailed, more specific compositional information. 

The effectiveness of the BSWS as a volume reduction unit depends largely on the solubility of the lead compounds in the washing medium, the efficiency of density separation for removing discrete lead particles, and the particle size distribution in the feed soil. 

Danesi et al.96 applied SIMS, in addition to X-ray fluorescence imaging, by using a microbeam (p-XRF) and scanning electron microscope equipped with an energy dispersive X-ray fluorescence analyzer (SEM-EDXRF) to characterize soil samples and to identify small DU particles collected in Kosovo locations where depleted uranium (DU) ammunition was employed during the 1999 Balkan conflict. Knowledge of DU particles is needed as a basis for the assessment of the potential environmental and health impacts of military use of DU, since it provides information on possible resuspension and inhalation. The measurements indicated spots where hundreds of thousands of particles may be present in a few mg of contaminated soil. The particle size distribution showed that most of the DU particles were < 5 pm in diameter and more than 50 % of the particles had a diameter of < 1.5 p.m.96... 

In parametric studies using this method, calculation of fission product distribution among the various particle size groups was found to be insensitive to size of the detonation and the quantity of soil picked up. It is, of course, somewhat sensitive to the thermodynamic and kinetic values used, but most of all, it is sensitive to the particle size distribution itself. This result is of considerable interest. 

Decontamination of soils using supercritical fluids is an attractive process compared to extraction with liquid solvents because no toxic residue is left in the remediated soil and, in contrast to thermal desorption, the soils are not burned. In particular, typical industrial wastes such as PAHs, PCBs, and fuels can be removed easily [7 to 21]. The main applications are in preparation for analytical purposes, where supercritical fluid extraction acts as a concentration step which is much faster and cheaper than solvent-extraction. The main parameters for successful extraction are the water content of the soil, the type of soil, and the contaminating substances, the available particle-size distribution, and the content of plant material, which can act as adsorbent material and therefore prolong the extraction time. For industrial regeneration, further the amount of soil to be treated has to taken into account, because there exists, so far, no possibility of continuous input and output of solid material for high pressure extraction plants, so that the process has to be run discontinuously. 

Particle size distribution refers to the distribution of particles in the soil matrix. In general, the three types of soil are sand, clay, and loam. Sand is soil composed of at least 70% sand clay is soil consisting of at least 35% clay and loam soil contains equal weights of sand, clay, and silt. Particular size or soil texture can affect the treatability of contaminated soil in two ways. The potential reaction sites are primarily limited to the surface of particles. The surface-to-volume ratio has a major impact on the nature and rate of reactions between the particle and the contaminant therefore, larger sandsized particles are less reactive than smaller clay-sized particles, particularly if reactions may occur between the sheets of clay minerals. 

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