Effects Of Soil Mineralogy Research Articles

The Effect of Soil Mineralogy and Particle Breakage on the Impulse Generated from Shallow Buried Charges

Historically, most testing with shallow buried charges has focussed on soils which are predominantly quartz (silica)-based. Particle size, moisture content and density have previously been investigated to ascertain their importance, along with other geotechnical parameters, in governing the magnitude of an impulsive output. This has shown that, in order of importance, moisture content, density and particle size drive the total impulse imparted. The work in this paper presents the results of blast testing carried out with carbonate sands to investigate the difference that particle mineralogy (and hence, propensity for breakage) has on both the localised loading and the total impulse using an array of 17 Hopkinson pressure bars known as the Characterisation of Blast Loading (CoBL) apparatus. Carbonate sands are thought to have more friable particles due to their plate-like morphology, as opposed to the rounded morphology of quartz-based sands. Testing was conducted with low moisture content samples and compared with the well-established Leighton Buzzard uniform sand to isolate the effect of particle mineralogy/morphology on the loadings measured. The results show that, despite attaining a 23% lower bulk density, carbonate soils deliver almost identical total impulses (0.7–3.0% higher) when compared with quartz soils for nominally identical moisture contents.

Effect of soil mineralogy on potassium fixation in soils developed on different parent material

Potassium release from weathering of soil minerals may support the K nutrition of crops for many years. However, when soils become exhausted, the response to K fertilisation may be limited due to its fixation in non-exchangeable forms, reducing the efficacy of K fertilisation. The present study examines the role of soil mineralogical composition on the K fixation characteristics of soils developed under a Mediterranean type of climate. Nine soils derived from different parent materials were collected in several regions of Portugal. Soil properties were determined, and clay, silt and fine-sand fractions were studied by X-ray diffraction. Potassium fixation was determined after the soil samples had been treated with increasing rates of K application. The amount of K fixed was obtained by difference, measuring the amount of K remaining extractable by ammonium acetate.The soils under study showed a relatively high K fixation capacity, varying between 30 and 80% for an application rate equivalent to 800 kg K ha−1. Soils with high K fixation capacity were derived from gabbros, gabbrodiorites and quarzdiorites, and had relevant amounts of vermiculites and/or interstratified mica-vermiculite minerals, either in the clay or in the silt and fine sand fractions.Soils rich in calcium carbonates also fix high amounts of K. These soils contain mica-illite minerals and are rich in some of the above-mentioned minerals in the clay and silt fractions. While K fixation capacity is normally assumed to derive from minerals in the clay fraction, the results of this study show that vermiculites and/or interstratified mica-vermiculites present in the silt and fine sand fractions can contribute a significant proportion of the total K fixation capacity and, thus, these size fractions should also be included in any assessment of K fixation capacity.

Mobility of multiple heavy metalloids in contaminated soil under various redox conditions: Effects of iron sulfide presence and phosphate competition

The mobility of heavy metalloids including As, Sb, Mo, W, and Cr in soil was investigated under both reducing and oxidizing conditions. The effects of soil mineralogy and the presence of competitive anions were studied as important factors affecting the mobility of these contaminants. Batch experiments conducted with the addition of oxidized and fresh FeS exhibited enhanced sorption rates for As and W under oxidizing conditions, and for Mo under reducing conditions. The inhibitory effect of phosphate on the sorption rates was most apparent for As and Mo under both oxidizing and reducing conditions, while only a small phosphate effect was observed for Sb and W. For Sb and W mobility, pH was determined to be the most important controlling factor. The results of long-term batch experiments revealed that differences in the mobility of metalloids, particularly As, were also influenced by microbial activity in the oxidizing and reducing conditions.

Soil microorganisms and enzyme activity at different levels of organic matter stability

Soil biological activity has important implications for soil carbon (C) sequestration. However, very little is known about the environmental factors, particularly the effect of soil mineralogy on availability of C for soil microorganisms. In this study, we have investigated the influences of soil type (clay mineralogy)on C mineralization and its effects on biological activity at different levels of soil organic matter stability. Two soils an allophanic, derived from recent volcanic ash and a kaolinitic, resulting from metamorphic parent materials were physically fractioned in to light(LF, coarse sand 250-2000 µm), intermediate (IF, fine sand53-250 µm) and mineral (MF,silt and clay < 53 µm) fractions. Several biological and biochemical analyses at Ah horizons of mineral soil and physical fractions were conducted: soil respiration, enzymatic activities, carbohydratesand microbial biomass, amongst others soil variables. The results indicated that the bulk soiland physical fractions had a significant impact on cumulative C mineralizedafter 30 days of incubation and soil enzyme activities. More than 76% of total C-CO2 variation was explained by stepwise multiple regression analysis including factors such as soil enzymes (s-glucosidase, dehydrogenase and phosphatase) and inorganic P. Soil ATP extractionwas agood indicator of microbial activity, because of a positive and significant correlation among ATP and i) C-CO2 and ii) metabolic quotient (soil respiration rate divided by microbial biomass). We also found an inverse and significant relationship between Al pyrophosphate (Al bound to SOM) and the C-CO2 in volcanic soil, whereas the same correlation did not occur in kaolinitic soil. Our results confirmed a greater stabilization capacityof MF in allophanicthan in kaolinitic soils due to the amorphous minerals clay materials.

Physical crust formation and steady-state infiltration rate in soils dominated by primary minerals in some South African ecotopes

Physical crust formation is affected by the inherent soil properties such as texture and mineralogy. However, inconsistencies exist in soil mineralogy effects of soil crusting. In addition, investigations of soils dominated by primary minerals such as quartz, especially in South Africa, are scant despite the abundance of such soils. Effects of texture and aggregate size on crust formation and steady-state infiltration rate (SSIR) in soils dominated by primary minerals were investigated. Soil aggregate sizes of <2, 2–3 and 3–5 mm were exposed to ∼60 mm h−1 simulated rainfall. Aggregate size significantly affected crust strength (P < 0.05). Physical crusts ∼0.2 to ∼0.8 mm thick with a surface layer of loose grains formed over a thin plasmic layer. Crusts with strengths between 0.25 and 3.42 × 10−4 kg m−2 developed on the <2 mm aggregates compared with <2.23 × 10−4 kg m−2 in the >2 mm aggregates. The reverse occurred in the Alice Jozini ecotope, which had a relatively low clay content of 120 g kg−1. The SSIR was between 1.24 and 3.60 mm h−1 in ecotopes dominated by primary minerals and clay content between 12% and 26%. In the Amatola Jozini ecotope, which was dominated by kaolinite and higher clay content, SSIR was 15.23 mm h−1. Consequently, physical crust formation decreased but SSIR increased with increase in aggregate size if there was a concomitant increase in the clay fraction, decrease in primary minerals and presence of kaolinite.

Effect of Soil Mineralogy and Pore-Water Chemistry on the Electrical Resistivity of Saturated Soils

The electrical characteristics of soil-water mixtures reflect the soil type, ionic concentration, surface conduction, fluid saturation, porosity, and pore connectivity of the mixtures. Archie’s law commonly is used to analyze the electrical resistivity measurement results of soil-water mixtures. This paper explores the pore-fluid effect on Archie’s law. Experimental tests were performed on sand and clay specimens to measure the variation in their electrical resistivity at different porosities and for different electrical resistivities of the pore fluid. The results demonstrate that the sand specimens (i.e., low specific surface soil) have a unique Archie’s law curve; however, the clay specimens (i.e., high specific surface soil) have an inconsistent Archie’s law curve owing to the surface conduction induced by the double layer of clay particles. In particular, Archie’s law should be applied and analyzed cautiously when high specific surface soils are subjected to pore fluids with high electrical resistivities (i.e., low electrolyte conductivity).

The effect of soil mineralogy and pore fluid chemistry on the suction and swelling behavior of soils

Soil suction is one of the most important parameters for describing the moisture condition and engineering behavior of unsaturated soils. Therefore, changes in suction behavior of soils in the presence of saline waters are important for engineered barriers. The aim of this study was to determine the change in suction and swelling behavior of soils, which were exposed to salt solutions (NaCl, CaCl2, natural seawater) with respect to distilled water. The three soil samples were gathered with different mineralogy and plasticity characteristics and tested for determining matric and total suction values and for obtaining free swelling characteristics in the presence of salt solutions. The bentonitic soil sample had the highest total suction value in the presence of seawater. Kaolinitic and zeolitic soil samples had the highest total suction values in the presence of NaCl solution. The highest modified free swell index value of the samples was obtained in the presence of NaCl solution for all the soil samples. No relationship was found between the total suction, matric suction and the modified free swell index value of the tested soils.

Soil mineralogy and slope effects on infiltration, interrill erosion, and slope factor

Interactions between the effects of soil mineralogy and of slope gradient on seal formation, infiltration rate (IR), runoff, and soil loss were evaluated, and the slope factor (Sf) functions for various soils with differing mineralogy were examined. Three different soils, on slopes of 9, 15, 20, and 25%, were subjected to 80 mm of simulated rainfall. The final IR was ≥20.5 mm h−1 in a clayey kaolinitic soil and ≤15 mm h−1 in smectitic soils. The total runoff, as a percentage of rainfall, ranged from 24 to 18%, 65 to 43%, and 50 to 35% from the kaolinitic, clayey smectitic, and sandy loam smectitic soils, respectively. The total soil loss ranged from 0.32 to 0.45 and from 1.14 to 3.93 kg m−2 for the kaolinitic and smectitic soils, respectively. In all three soils, increasing the slope gradient increased the detachment of coarse particles (&gt;0.1 mm) more sharply than that of small particles (&lt;0.1 mm), especially in the smectitic soils. Combining these results with previous findings for six soils indicated that soils could be divided into two groups according to their Sf values: (1) soils that contained smectite and were therefore dispersive and (2) soils that did not contain smectite and were therefore stable. For the former soils the regression Sf = 0.47exp(7.7 sin ) defined the Sf values significantly, whereas for the latter group a linear regression Sf = 0.81 + 1.77 (sin ) was required. It was suggested that the difference in the Sf functions was mainly due to seal formation enhancement by the smectite.

Soil mineralogy effects on seal formation, runoff and soil loss

Interaction between clay particles is one of the main factors responsible for soil aggregation. Therefore, soil mineralogy, which has substantial effects on clay dispersion, may also influence aggregate stability, seal formation, runoff and soil loss. In spite of this, the effects of soil mineralogy on these phenomena have received much less attention in the literature than those of other soil properties. This paper reviews the effects of soil mineralogy on aggregate stability, seal formation and micromorphology, and on the associated infiltration rate (IR), runoff and soil loss. The paper is focused mainly on the authors' previous studies. In order to determine these effects, various soils with different mineralogy were collected from Israel, South Africa and Kenya. In these soils, the aggregate stability was determined under fast wetting conditions, and the IR and the interrill soil loss were determined using rainfall simulator of a rotating disk type. The micromorphology of the crust, which was developed at the soil surface by the rainstorm, was determined by scanning electron microscope. Clay mineralogy was found to be a dominant factor in controlling aggregate stability, seal formation, soil IR and interrill soil loss. The phyllosilicate soils, which were review in this paper, were divided into two main groups: (i) stable soils with final IR>8.0 mm h −1 and (ii) unstable soils with final IR<4.5 mm h −1. These two soil groups differ in their mineralogy. Kaolinitic and illitic soils that do not contain smectite were stable soils and less susceptible to seal formation. In contrast, kaolinitic and illitic soils that contain some smectite and smectitic soils were unstable. Examination of the susceptibility of 21 phyllosilicate soils to interrill erosion indicated that these soils could be divided into three groups. Soil loss was higher for unstable soils than for stable soils, but the soil loss of the smectitic soils was significantly higher than that of the unstable soils, which contained kaolinite or illite as the dominant clay.

Multiple Linear Regression of Complex Permittivity of a Till at Frequency Range from 200 MHz to 400 MHz

The complex permittivities of 40 compacted natural clayey till specimens at various water content, density and pore fluid salinity as independent variables are analyzed. A multiple linear regression model is constructed and the statistical analyses for the relative permittivity (e') and dielectric loss (e '')-regression equations in the frequency range from 200 to 400MHz are performed. It is concluded that the multiple linear regression model of the complex permittivity is highly significant. The coefficient of determination (R 2) and standard error (SE) of the linear regression equations vary with frequency. At 200MHz for e ' -regression and 300MHz for e '-regression, all three independent soil variables are significant at a probability of 0.95. The complex permittivity regression model with two variables at 250MHz for e 'and 350 for e '-regression equations. Upon further study on the effect of soil mineralogy to the complex permittivity, the results obtained in this study may serves as the principle of the characterization of subsurface and detection of soil and groundwater contamination.

Mid-infrared backscatter characteristics of various benchmark soils

Active mid-infrared laser reflectance characteristics of 18 different benchmark soil samples were measured at different angles of incidence at 9.283, 9.569, 10.247, and 10.633 mu m wavelengths under both copolarized and cross-copolarized conditions. Calibration was performed for each measurement using a Labsphere Infra-fold Diffuse Reflectance Standard of 94% reflectance. One hundred independent samples were averaged for each measurement to yield a mean reflectance value. The soil samples were characterized in terms of the soil taxonomy, mineralogy, geographic location, soil texture, and organic content and represented wide variability in soil properties. The data thus obtained are presented in graphical form, and the effect of soil mineralogy on the spectral features is investigated. A physically based empirical model is also presented to predict the angular dependence of copolarized backscatter. >