Silty Soil Samples Research Articles

Application of Inductively Coupled Plasma Spectrometric Techniques and Multivariate Statistical Analysis in the Hydrogeochemical Profiling of Caves-Case Study Cloșani, Romania.

The aim of the study was to develop the hydrogeochemical profiling of caves based on the elemental composition of water and silty soil samples and a multivariate statistical analysis. Major and trace elements, including rare earths, were determined in the water and soil samples. The general characteristics of water, anions content, inorganic and organic carbon fractions and nitrogen species (NO3− and NH4+) were also considered. The ANOVA—principal component analysis (PCA) and two-way joining analysis were applied on samples collected from Cloșani Cave, Romania. The ANOVA-PCA revealed that the hydrogeochemical characteristics of Ca2+-HCO3− water facies were described by five factors, the strongest being associated with water-carbonate rock interactions and the occurrence of Ca, Mg and HCO3− (43.4%). Although organic carbon fractions have a lower influence (20.1%) than inorganic ones on water characteristics, they are involved in the chemical processes of nitrogen and of the elements involved in redox processes (Fe, Mn, Cr and Sn). The seasonal variability of water characteristics, especially during the spring, was observed. The variability of silty soil samples was described by four principal components, the strongest influence being attributed to rare earth elements (52.2%). The ANOVA-PCA provided deeper information compared to Gibbs and Piper diagrams and the correlation analysis.

Various textured soil as nitrous oxide emitter and consumer

A b s t r a c t. Changes of NO3, and N2O concentrations during 34 days hypoxic incubation of eleven nitrate amended samples of the Eutric Cambisols developed from sand, silt and loam were studied. It was found that initial generation of nitrous oxide was followed, after a maximum by its subsequent absorption. The absorption rate was correlated with the efflux. Both were negatively correlated with sand content and positively with silt, clay and Corg. The percentage of nitrate reduced equals 35, 97, and 100% for Eutric Cambisols developed from sand, loam and silt, respectively. The highest N2O efflux was observed from silty soils, the lowest one from sandy soils. Total N2O consumption ranged between 3.3 and 66.5 mg N kg -1 , and consisted 32.9, 99.2, and 100% of the produced N2O for the sandy, loamy and silty soil samples, respectively. The tested soils were characterized by various ratio of the N2O emitted to the consumed. Most of sandy samples are characterized by a weak capacity to N2O production and consumption, while loamy and silty soils are characterized by a good or very good capacity to N2O production and consumption. K e y w o r d s: soil, nitrous oxide, emission, consumption, nitrate reducing

Calcium carbonate precipitation catalyzed by soybean urease as an improvement method for fine-grained soil

Although great advances have recently been made in biological soil-improvement methods, the treatments of fine-grained soil using these methods are still challenging. In this study, we tested a new method for the improvement of silty soil. This method adopts the calcium carbonate precipitation process catalyzed by soybean urease. Crude urease is derived simply by collecting the liquid formed by soaking soybean powder in water. The activity of crude urease is linearly related to the amount of soybean powder added to the water, and is high enough to be used for soil treatment. Under batch conditions, the reactions catalyzed by crude urease can be completed, although the reaction rates are slower than those using live bacteria with the same initial activity. In triaxial consolidated undrained tests, the treated silty soil shows more dilative responses in the stress-strain curves and larger peak deviatoric stresses as compared with the untreated soil, indicating significant improvements in the mechanical behaviour. In the results of CaCO3 measurements, it is seen that there are continuous increases in the CaCO3 content of the samples during the treatment process, which implies that the silty soil samples are not clogged when treated by crude urease. Such results indicate that calcium carbonate precipitation catalyzed by soybean urease can be used for the improvement of fine-grained soil.

Impact of Sustainable Granular Materials on the Behavior Sedimentary Silt for Road Application

The current paper aimed to investigate the effect of granular materials addition from construction and demolition waste (CDW) on the engineering properties of sedimentary silty soil for pavement application. An intensive laboratory study of silty soil samples treated with different percentages of sustainable granular materials (sand and gravel) from construction and demolition waste plant (ranged between 40 and 60% by weight) was investigated by a series of Compaction, Swelling, California Bearing Ratio (CBR), Resilient Modulus (Mr), Unconfined Compressive (UCS) and Split Tensile Tests (STS). Further, analysis of several percentages addition of granular materials was examined using pH and water absorption tests. Results demonstrates there was an increase in UCS and STS, whereby both improved with the increase in CDW content being used, reaching a maximum value of 72% for UCS, 92% for STS, and 552% for Mr in relation to initial strength of the soil without the addition of CDW. Furthermore, the addition of 60% CDW provided the most satisfactory result in relation to the parameters of UCS, tensile strength, CBR, swell and resilience modulus. Thus, the use of CDW in the soil was satisfactory since the soil-CDW mixtures can be used as granular layers of flexible pavement.

Relevance of a near infrared spectral index for assessing tillage and fertilization effects on soil water retention

Agricultural practices are expected to have significant effects on soil physical properties, such as soil structure and soil water retention (SWR) properties are among the relevant properties that can be used to assess these effects. Ex-situ measurements are costly and time-consuming. Visible (vis) and near infrared (NIR) spectroscopy has been widely used as a rapid, cost-effective and nondestructive technique to predict many soil properties, including soil water content (SWC). In this study, we explored the ability of vis-NIR to assess the effects of soil tillage and fertilization on SWR. The study was performed on silty soil samples with 10.4 g kg−1 of organic carbon content and a pH of 5-6.5. Undisturbed soil blocks were collected from an experimental station located in Brittany, France. In 2012, the field was designed as two separate experiments, each with a different tillage system (conventional tillage (CT) and shallow tillage (ST)). For each experiment, two fertilizer types were considered (mineral and organic). Six undisturbed soil blocks were sampled at each of two depths (0–15 cm and 15–25 cm) and from each agricultural practice. Soil was sampled on two dates: before starting the treatment (2012) and after 5 years of agricultural practices (2017). From each soil block, four aggregates 3–4 cm wide and 5–6 cm long were collected. The whole aggregates were set at a number of matric potentials, from saturation to the permanent wilting point (pF = 4.2). At a given pressure head, soil samples were scanned in triplicate to acquire reflectance spectra from 400 to 2500 nm using a handheld spectrometer (ASD Fieldspec®). We focused on the absorption band near 1920 nm and used a new NIR spectral index based on the band’s full width at half maximum, called SWSI. Our results showed a linear relation between SWSI and SWC (R² > 0.99). Moreover, the slope and intercept of this linear relation were significantly correlated with water holding capacity (WHC) and soil quality. Using these parameters, we found that SWR and soil physical quality under CT were significantly greater under cattle manure (CTC) than under mineral fertilizer (CTM) or at T0. This significant effect was more pronounced at 15–25 cm. In ST treatments, SWR properties and soil quality were significantly lower than at T0. More importantly, our results show that the slope and intercept of the linear relation offer a way to summarize and assess the effects of agricultural practices on SWR properties and soil structural quality.

Effect of hydraulic and mechanical stresses on cyclic deformation processes of a structured and homogenized silty Luvic Chernozem

The deformation behavior of soils is strongly affected by coupled mechanical and hydraulic stresses especially under cyclic loading. Contrary to static loading tests cyclic loading caused plastic deformation increments with ongoing loading cycles even for stresses in the re-compression range associated with alterations in the hydraulic stress state. The aim of this study was to proof the interference of hydraulic properties on the mechanical deformation behavior (cyclic compressibility) depending on soil structure and cyclic loading time. Cyclic loading tests with changing boundary conditions in terms of initial matric potential, loading time and magnitude on structured and homogenized silty soil samples were performed. Furthermore, pore water pressures during cyclic loading and the air conductivity of soil cores before and after cyclic loading were measured. The results indicated differences in the stress–strain response accompanied by typical hydraulic stress regimes. These were classified into five categories representing a typical development of pore water pressures according to soil structure and loading time. Predominantly at short-time cycles a built-up of pore water pressures with increasing number of cycles occurred resulting in a high cyclic compressibility of the homogenized soil. The loss of soil strength could be linked to the beginning of partial liquefaction processes induced by heavy soil loading of 150kPa and by a higher initial matric potential. In contrast, the less compressible structured soil showed a better internal redistribution of pore water and faster dissipation of stress-induced pore water pressures compared to the homogenized soil. Finally, the influence of soil structure plays an important role in understanding hydro-mechanical relationships, especially since the reversal of pore water pressures back to the hydraulic equilibrium state was restricted by the time between repeated loading events.

세립토 위주의 토석류에 관한 유변학적 모델: 입자크기 효과

This paper presents the applicability of rheological models for describing fine-laden debris flows and analyzes the flow characteristics as a function of grain size. Two types of soil samples were used: (1) clayey soils - Mediterranean Sea clays and (2) silty soils - iron ore tailings from Newfoundland, Canada. Clayey soil samples show a typical shear thinning behavior but silty soil samples exhibit the transition from shear thinning to the Bingham fluid as shear rate is increased. It may be due to the fact that the determination of yield stress and plastic viscosity is strongly dependent upon interstructrual interaction and strength evolution between soil particles. So grain size effect produces different flow curves. For modeling debris flows that are mainly composed of fine-grained sediments (

Phenanthrene Contaminated Soil Biotreatment Using Slurry Phase Bioreactor

Problem Statement: Polycyclic Aromatic Hydrocarbons (PAHs) are suspected toxins that accumulate in soils and sediments due to their inso lubility in water and lack of volatility. Slurry-ph ase biological treatment is one of the innovative techn ologies that involve the controlled treatment of excavated soil in a bioreactor. Due to highly soil contamination from petroleum compounds in crude oil extraction and also oil refinery sites in Iran, this research was designed based on slurry phase biotreatment to find out a solution to decontaminat ion of oil compounds polluted sites. Approach: Soil samples were collected from Tehran oil refiner y site and Bushehr oil zones. Two compositions of soils (clay and silt) were selected for slurry biot reatment experiment. Soil samples were contaminated with three rates of phenanthrene (a 3 ring PAH), 10 0, 500 and 1000 mg kg -1 and mixed with distilled water in solid concentration of 30% by weight after washing out with strong solvent (hexane) and putting in to the oven. Bacterial consortium was re vived in culture medium which consisted of Mineral Salt Medium (MSM) based on phenanthrene concentrations and ratio of C/N/P in the range of 100/10/2. Prepared soil samples were mixed with dis tilled water, nutrient and bacterial consortium together in the 250 mL glass Erlenmeyer and putted in the shaker incubator with 200 rpm revolutions and 25°C for 7 weeks (45 days). Samples were analyzed for residual phenanthrene, bacterial population every week. For statistical analysis, ge neral linear model with repeated measures (type III ) analysis was applied. Results: The concentration of 100 mg L -l of phenanthrene in clayey and silty soils reached to non detectable limit after 5 and 6 weeks, respectively. While concentration of 500 mg L -l of phenanthrene both in clayey and silty soils rea ched to non detectable limit after 6 weeks. But concentration of 1000 mg L -l both in clayey and silty soil samples has not met this limitation after 7 weeks. Due to presence of Pseudomonas strains in clayey soil samples and their ability i n breaking down of benzene rings, the removal efficiency of ph enanthrene in our slurry bioreactor in clayey soil was a little more than silty soil samples over time . There was a significance relationship between ini tial concentrations of phenanthrene and type of soil wit h time of biotreatment (p<0.001). Conclusion: Therefore, this technology may be applied to remedi ation of small foot print oil contaminated sites, e.g., gas station, oil extraction and refinery site s in Iran, in the case of urgency. Thus this study concludes that the remediation of phenanthrene with concentration up to 1000 mg kg -1 in the oil contaminated sites can be removed to the acceptable limits using slurry based system.

Oxygen Diffusion Coefficient of Soils at High Degrees of Saturation

Abstract The oxygen diffusion coefficient is an essential parameter for design of soil covers over mine waste. This study presents a method for measuring the oxygen diffusion coefficient of soils at high degrees of saturation. The method eliminates measurement errors caused by soil microbial activity, high humidity, and stagnant air in laboratory diffusion cells. Results show that microbial activity is an important factor that causes errors in O2 measurements. Sterilization of soil, utilization of a silica gel-membrane system with oxygen sensors, and minimal stirring in the cell headspace greatly reduce the variability in O2 diffusion coefficient measurements. The variations in estimated O2 diffusion coefficients for the same soil at the same degree of saturation were ±31% about the mean for clayey soil samples and ±10% about the mean for silty soil samples.

Magnetic detection of heated soils at paleolithic sites in Japan

We present a methodological approach to detect heated soil on ancient sites, using magnetic measurements. The method is based on changes in magnetic signals of soil by heating. The following three types of soil were used for testing the method: silty soil (SS), weathered volcanic ash (WVA, = loam) and fairly fresh volcanic ash (VA) called Odori tephra. On heating above 250–600°C, the magnetic susceptibility and remanent magnetization intensity increased for the SS and WVA samples, reflecting chemical alteration of magnetic minerals (from goethites to magnetites through hematites). The VA sample showed no susceptibility change suggesting the absence of goethites within it. On heating below 250°C, only the intensities of all the samples increased. This is possibly due to acquisition of thermal remanent magnetization. The largest change of the magnetic signals was identified for the SS sample and the smallest one was seen for the VA sample. Therefore, the in situ susceptibility measurement, which is the nondestructive and indirect method, seems to be effective to detect heated soil for sites of aqueous deposits as the SS. On the other hand, for sites of aeolian deposits as the WVA (loam) and VA, the intensity measurement of collected soils seems to be the most reliable method to detect evidence of heating. The degree of the magnetic stability (coercivity) against progressive alternating-field demagnetization was also an important parameter, indicating whether the investigated soils were heated or unheated. © 1999 John Wiley & Sons, Inc.

Assessment of micro-aggregation using laser diffractometry

In order to evaluate the influence of the measuring technique on the determination of (micro-)aggregation in soil and sediment samples, results of grain size distributions of undispersed silty soil samples obtained by the sieve-pipette method are compared with those obtained using a laser diffraction grain size analyser, the Coulter LS-100. Reduced major axis relationships are calculated which may be used to convert Coulter LS-100 results to those obtained by the sieve-pipette method. The relationships obtained are very similar to the reduced major axis relationships established for dispersed silty soil samples. The results also show that the Coulter LS measurements have a systematic bias compared to the sieve-pipette data. This implies that, if the percentage of (micro-)aggregation is determined, the (interpretation of the) results will be strongly dependent on the measurement technique used. Using the calibration relationships that were established, nomographs can be developed to predict the level of sieve-pipette (micro-) aggregation from Coulter LS-100 data. Copyright © 1999 John Wiley & Sons, Ltd.

Grain-size analysis by laser diffractometry: comparison with the sieve-pipette method

Results of a traditional sedimentation technique for grain-size analysis (the sieve-pipette method) were compared with those of a laser diffraction grain-size analyser, the Coulter LS-100. Milled quartz samples and silty soil samples were used to investigate the effect of particle shape. The reproducibility of the Coulter LS-100 was better than that of the sieve-pipette method, except for the sand fraction. The agreement between the two methods is strongest for the milled quartz samples. The Coulter LS-100 underestimated the clay content of the silty soil samples and generally overestimated the clay content of the milled quartz samples. This indicates the importance of particle morphology. The milled quartz grains are very angular and somewhat elongated whereas the clay minerals in the clay fraction of the silty soil samples usually have a platy shape. Reduced major axis relationships are calculated which may be used to convert Coulter LS-100 results to those of the sieve-pipette method. Correlation is strongest for percentiles size data. The Coulter LS-100 underestimates the clay, but correctly estimates the sand fraction. This results in a weak relationship for the total silt fraction as measured by the two techniques. Therefore, an alternative method is proposed for estimating this fraction. A comparison of our data with published data and relationships suggests that the calibration relationships are quite robust as long as the clay mineralogy of the samples is similar.

The magnetic susceptibility of modern soils in China and its use for paleoclimate reconstruction

Magnetic susceptibility of more than 160 modern silty soil samples in China was measured to assess the relationship between the magnetic susceptibility and modern climatic parameters. Correlation between magnetic susceptibility and mean annual temperature (MAT) or mean annual precipitation (MAP), shows a complex picture and no single function can be found to fit all the data on the national scale. In East China, where East Asian monsoon plays an important role for the climate conditions, magnetic susceptibility increases with the increase of MAT or MAP in temperate semi-arid regions of the Loess Plateau and surrounding areas. This can be attributed to increasing intensity of pedogenesis which would favor the formation of strongly magnetic minerals and/or reduce depositional rate of eolian dust. Magnetic susceptibility tends to decrease with the increase of temperature and precipitation in the tropical and subtropical warm and humid regions of the vast areas south of the Yangtze River. This may be explained by pedogenic transformation of iron-bearing minerals to weakly magnetic minerals. Between these two different correlation patterns, 15°C of MAT and/or 1200 mm of MAP seem to be the thresholds. In West China, the correlation becomes quite complex in the great mountains and vast sedimentary basins in the north-west. This may be due to the prevailing continental climate in this region and topographic contrast within short distance. The correlation for the Qinghai-Xizang (Tibetan) Plateau is not clear because very few samples were collected. Fluctuations of paleo-temperature and paleo-precipitation at Luochuan for the last 130 ka were estimated using the climofunction obtained from this study.

Settlement Response of Soft Soils Reinforced by Compacted Sand Columns

Stone/compacted sand columns is a technique of soil reinforcement that is frequently implemented in soft cohesive soils to increase the bearing capacity of the foundation soil, to reduce the settlement, and to accelerate the consolidation of the surrounding saturated soft soil. The soil‐column interaction depends on several parameters, including the loading process and the loading rate, the replacement factor, the group effect, and the partial consolidation of the soft soil due to radial drainage through the column. This paper presents the results of a laboratory study that was conducted to investigate the effect of these various parameters on the settlement response of a soft foundation soil reinforced by compacted sand columns. Triaxial compression tests under different boundary conditions were performed on composite soil specimens made of annular silty soil samples with a central, compacted river‐sand column. These tests, performed in a specially modified triaxial cell, show that the group effect, the replacement factor, and the consolidation of the soft soil have a significant effect on the vertical stress concentration on the column and on the settlement reduction of the foundation soil.