Natural Sandy Soil Research Articles

Influence of Humidity and of the Electric and Magnetic Microwave Radiation Fields on the Remediation of TCE-contaminated Natural Sandy Soils

The influence of moisture content (15% w/w) on the remediation (vaporization) of trichloroethylene (TCE) present in natural sands, chosen as a TCE-polluted model system for soils, was investigated with regard to applied microwave power levels, the depth of the sand sample, and the dielectric factors. The heating process occurring in the sand samples arises through the microwave conduction loss heating and dielectric loss heating mechanisms. The characteristic relevance of the electric and magnetic microwave radiation fields to the heating mechanisms was also examined. Heating by the magnetic microwave radiation field was considerable when magnetite was added to the dry and wet sand samples as the microwave absorber. Optimal microwave conditions are reported for a single-mode microwave applicator. Near-quantitative elimination of the TCE contaminant was achieved for sandy soils within a very short time.

Filter properties of seam material from paved urban soils

Abstract. Depositions of all kinds of urban dirt and dust including anthropogenic organic substances like soot change the filter properties of the seam filling material of pervious pavements and lead to the formation of a new soil substrate called seam material. In this study, the impact of the particular urban form of organic matter (OM) on the seam materials CECpot, the specific surface area (As), the surface charge density (SCD), the adsorption energies (Ea) and the adsorption of Cd and Pb were assessed. The Cd and Pb displacement through the pavement system has been simulated in order to assess the risk of soil and groundwater contamination from infiltration of rainwater in paved urban soils. As, Ea and SCD derived from water vapor adsorption isotherms, CECpot, Pb and Cd adsorption isotherms where analyzed from adsorption experiments. The seam material is characterized by a darker munsell-color and a higher Corg (12 to 48g kg-1) compared to the original seam filling. Although, the increased Corg leads to higher As (16m2g-1) and higher CECpot (0.7 to 4.8cmolckg-1), with 78cmolckg-1C its specific CECpot is low compared to OM of non-urban soils. This can be explained by a low SCD of 1.2×10-6molc m-2 and a low fraction of high adsorption energy sites which is likely caused by the non-polar character of the accumulated urban OM in the seam material. The seam material shows stronger sorption of Pb and Cd compared to the original construction sand. The retardation capacity of seam material for Pb is similar, for Cd it is much smaller compared to natural sandy soils with similar Corg concentrations. The simulated long term displacement scenarios for a street in Berlin do not indicate an acute contamination risk for Pb . For Cd the infiltration from puddles can lead to a breakthrough of Cd through the pavement system during only one decade. Although they contain contaminations itself, the accumulated forms of urban OM lead to improved filter properties of the seam material and may retard contaminations more effectively than the originally used construction sand.

Evaluation of the mechanical properties of class-F fly ash

Coal-burning power plants in the United States (US) generate more than 70 million tons of fly ash as a by-product annually. Recycling large volumes of fly ash in geotechnical applications may offer an attractive alternative to the disposal problem as most of it is currently dumped in ponds or landfills. Class-F fly ash, resulting from burning of bituminous or anthracite coals, is the most common type of fly ash in the US. In the present study, the mechanical characteristics (compaction response, compressibility, and shear strength) of class-F fly ash were investigated by performing various laboratory tests (compaction test, one-dimensional compression test, direct shear test and consolidated-drained triaxial compression test) on fly ash samples collected from three power plants in the state of Indiana (US). Test results have shown that despite some morphological differences, class-F fly ash exhibits mechanical properties that are, in general, comparable to those observed in natural sandy soils.

Retention of pesticides in soil columns modified in situ and ex situ with a cationic surfactant

A study of the effect of a clayey soil modified in situ and ex situ with the cationic surfactant octadecyltrimethylammonium bromide (ODTMA), on the retention of linuron, atrazine and metalaxyl was carried out. Leaching of these compounds was studied in columns of a natural clayey soil and the same clayey soil modified by direct injection of the surfactant in situ, and in columns of a natural sandy soil and the same sandy soil modified by intercalation of a barrier of the clayey soil saturated ex situ with the surfactant. Breakthrough curves indicated the total immobilization of linuron in modified soils and a decrease in the leaching kinetics of atrazine and metalaxyl compared to what was obtained in the natural soil. The results indicate the use of the clayey soil modified in situ or ex situ with the surfactant ODTMA could be of interest in the immobilization of pesticides of different hydrophobicities.

Modification of clay barriers with a cationic surfactant to improve the retention of pesticides in soils

In this work, the efficiency of reactive clay barriers in the immobilisation of organic pesticides in a sandy soil was studied. Reactive barriers were prepared by modification of montmorillonite, kaolinite and palygorskite clay minerals, and of a clayey soil with the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Percolation curves of the pesticides linuron, atrazine and metalaxyl of different hydrophobic character, were obtained in columns packed with a natural sandy soil with these barriers intercalated under saturated flow conditions. The cumulative curves in the unmodified soil indicated a leaching of pesticides greater than 85% of the total amount of compound added. After barrier intercalation, the breakthrough curves (BTC) indicated a dramatic decrease in the amounts of linuron leached in all columns and a significant modification of the leaching kinetics of atrazine and metalaxyl. Retardation factors, R, of the pesticides in the columns were significantly correlated with the organic matter content (OM) derived from the ODTMA of the organo clay/soil barriers ( r 2 ≥ 0.78). Significant correlations were also found between these R factors and the pore volume values corresponding to the maximum peaks of the BTCs ( r 2 = 0.83; p < 0.01) or the total volumes leached ( r 2 = 0.44; p < 0.05) for the pesticides atrazine and metalaxyl. The results obtained point to the interest in the use of reactive clay barriers for almost complete immobilisation of hydrophobic pesticides or for decreasing the leaching of moderately hydrophobic pesticides coming from point-like sources of pollution. These barriers would avoid the generation of elevated concentrations of these compounds in the soils due to their rapid washing.

Pore‐system characteristics of pavement seam materials of urban sites

AbstractThe original light‐brown sandy seam filling of pavements in urban areas turns dark and changes its properties by the time due to various inputs of urban dust. Deposited Corg inputs do mostly not have natural characteristics but are man‐made, e.g., diesel dust. Thus, properties of the seam material are not predictable from experiences with forest or agricultural soils. Semiperviously sealed urban areas are sites of contaminant deposition as well as groundwater recharge. For an assessment of the resulting groundwater‐contamination risk in these areas, the properties of the seam material, which influences transport processes, must be known. The aim of this study was to investigate the pore‐system build‐up, which includes size distribution and fractal character in the seam material of urban sites. The investigated samples were taken from pavements adjacent to roads in Berlin and Warsaw.The micropore parameters (nanometer range) were characterized using water‐vapor desorption isotherms, mesopore parameters (micrometer range) were estimated from mercury‐intrusion porosimetry and macropore parameters (millimeter range) from water‐retention curves. Particle density, dry bulk density, and particle‐size distribution were measured using standard methods. Volumes of micro‐ and mesopores as well as particle densities and dry bulk densities correlated with Ctot contents. However, no such relation was found for macropore volumes. Compared to the original sandy seam filling, the altered seam material shows significantly higher Corg contents and higher amounts of micro‐ and mesopores. Therefore, the available water capacity increases by 0.05–0.11 m3 m–3, as compared to the original sandy seam filling. Compared to natural sandy soils having similar Corg contents, the seam material shows similar macropore volumes, but the volume of mesopores and micropores is a few times smaller. That is mainly because of the particulate character of the organic matter.

Lead (II) Removal from Natural Sandy Soils by Enhanced Electrokinetic Remediation

Lead (II) Removal from Natural Sandy Soils by Enhanced Electrokinetic Remediation

Maximum and Minimum Void Ratio Characteristics of Sands

ABSTRACT Characteristics of the maximum and minimum void ratios of sands and their possible use for material characterization have been investigated in this study. Data of over 300 natural sandy soils including clean sands, sands with fines and sands containing small amount of clay-size particles have been used to examine the influence of fines, grain-size composition and particle shape on emax, emin and void ratio range (emax - emin). A set of empirical correlations are presented which clearly demonstrate the link between these void ratios and material properties of sands. The key advantage of (emax - emin) over-conventional material parameters such as Fc and D50 is that (emax - emin) is indicative of the overall grain-size composition and particle characteristics of a given sand and that it shows off the combined influence of relevant material factors. The void ratio range provides a general basis for comparative evaluation of material properties over the entire range of cohesionless soils. Important issues related to the laboratory procedures used for determination of emax and emin as well as their applicability to fines-containing sands are also addressed. Three distinct linear correlations were found to exist between emax and emin for clean sands, sands with 5-15% fines and sands with 15-30% fines respectively, thus illustrating that the standard JGS procedures for minimum and maximum densities of sands can provide reasonably consistent emax and emin values for sands with fines content of up to 30%. The importance of the grain-size distribution and presence of gaps in the grading of composite soils or mixtures of sands with fines produced in the laboratory is also discussed.

Differential Hypocotyl and Root Development of Arabidopsis Auxin-Insensitive Mutants

, aux1-7, axr1-3 and axr2-1, grown in a natural sandy soil, without sucrose supplementation. The three mutants showed impaired epidermal cell elongation in the hypocotyls of 15-day-old seedlings, with axr2-1 showing the most marked effects. In addition, the roots of axr2-1 elongated faster and presented a more extended meristematic zone than the other genotypes. Unchanged epidermal cell length in the differentiation zone of axr2-1 relative to the wild-type suggested enhancement of cell proliferation. These alterations may have affected the timing and site of emergence of the root hairs, starting later and further from the root tip than in the other genotypes. Similarly to the wild-type, no root hair growth was initiated in axr2-1 drought-induced short roots, although the epidermis was differentiated into trichoblasts and atrichoblasts. On rehydration of the short roots, hair formation occurred from trichoblasts prior to epidermal cell elongation. Therefore, auxin-insensitivity in the axr2-1 mutant did not result in alterations of the hair-forming process itself. The differential development of axr2-1 seedlings, relative to the other auxin-insensitive mutants, suggested that the AXR2 gene has a complex, regulatory function in multiple hormone signaling.

Effect of Particle Shape on Interface Behavior of DEM‐Simulated Granular Materials

This paper presents a detailed computational investigation of the effect of particle shape on the interface shear behavior of granular materials. The discrete element method (DEM) using clusters to model rough particles is used, expanding the procedure introduced in an earlier paper by Jensen et al. [1]. Seven new cluster shapes (i.e., particle configurations) of varying degrees of roughness are presented herein, and numerical experiments simulating ring shear tests are made using these clusters. From these simulations, the effect of particle shape on void ratio (e) and interface angle of friction between soil and structure surface (δ) is reported. Particle shape characteristics include roundness, angularity, and surface roughness. The results of numerical simulations using the newly formed cluster shapes are in very good qualitative agreement with laboratory tests. Simulation results showed that the void ratio of a particle mass increased as the angularity or roughness of the particles increased. They also showed an increase in interface shear strength between perfectly round DEM particles and the more angular cluster shapes, but no systematic correlations with the various definitions of particle shape parameters was found. It may be necessary to use greater accuracy in modeling the size and shape distributions of a natural medium to further investigate the influence of particle shape on interface friction. The simulations also successfully reflected the relationship between interface friction angle and structure surface roughness as demonstrated in recent physical experiments. The simulations comparing initially “dense” media to initially “loose” media demonstrated behavior that is similar to the behavior of a natural sandy soil observed in experiments.

Single and multi‐component adsorption of toluene, xylene and hexane in disturbed soils

An experimental work was conducted to study the adsorption of petrochemicals ‐hexane, toluene and xylene onto natural sandy soils. Adsorption experiments were performed in complete‐mix batch reactors with sandy soils collected from three different locations around Beirut, Lebanon. The results indicated significant difference in potential adsorption of petrochemicals in different soils. The results were discussed and presented in perspective of various physical and chemical attributes of soils and chemicals. Soil properties such as sand equivalency, natural moisture content, particle size distribution and porosity as well as properties of chemicals such as molecular weight, “H/C” atomic ratio and molecular structure appeared to have effect on the adsorption. From the results, an attempt had been made to fit toluene and xylene adsorption data in Langmuir type isotherm model. The isotherm model in its extended form applicable to competitive adsorption was calibrated and subsequently tested for performance reliability. Model adsorption predictability was found to be satisfactory.

Rate-Limited Sorption and Desorption of 1,2-Dichlorobenzene to a Natural Sand Soil Column

The rate of sorption of 1,2-dichlorobenzene (DCB) onto a natural sandy soil in water-saturated soil columns was measured. Desorption rates were also measured after allowing the solute-sorbent system to equilibrate during a no-flow period, ranging from 3 to 49 d. Two-site equilibrium/kinetic and Γ-distributed rate sorption models were then used to determine a single set of sorption parameters that could describe both the uptake and desorption of 1,2-DCB from these columns. Ninety-five percent confidence regions for the mass transfer rates and the two-site parameters were generated. Both the Γ-distribution model and the two-site model could describe uptake and desorption with a single set of parameters, although the Γ-distribution model was better at the 95% confidence level in three of five experiments. There was no statistically significant change in the sorption parameters between 3 and 49 d of no-flow. Allowing the Γ-distributions of rates to differ between uptake and desorption improved the ability to ...

Inoculation with phosphate-solubilizing microorganisms and a vesicular-arbuscular mycorrhizal fungus improves dry matter yield and nutrient uptake by wheat grown in a sandy soil

The effect of inoculating wheat (Triticum aestivum L.) with the PO43–-solubilizing microorganisms (PSM) Bacillus circulans and Cladosporium herbarum and the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus sp. 88 with or without Mussoorie rock phosphate (MRP) amendment in a nutrient-deficient natural sandy soil was studied. In the sandy soil of low fertility root colonization by VAM fungi was low. Inoculation with Glomus sp. 88 improved root colonization. At maturity, grain and straw yields as well as N and P uptake improved significantly following inoculation with PSM or the VAM fungus. These increases were higher on combined inoculation of PSM and the VAM fungus with MRP amendment. In general, a larger population of PSM was maintained in the rhizosphere of wheat in treatments with VAM fungal inoculation and MRP amendment. The results suggest that combined inoculation with PSM and a VAM fungus along with MRP amendment can improve crop yields in nutrient-deficient soils.

Fate of pendimethalin, carbofuran and diazinon under abiotic and biotic conditions

The insecticides carbofuran and diazinon as well as the herbicide pendimethalin were irradiated with UV light of different wavelengths in water or water/soil suspensions under various conditions. As compared to pure distilled water, photodegradation was increased in the presence of titanium dioxide, hydrogen peroxide or ozone, or by using natural river or lake water. In a water/soil suspension, diazinon was converted, besides to other products, to the isomeric isodiazation. When subjected to various direct or indirect photolysis conditions, pendimethalin was transformed to various products resulting from dealkylation and reduction. [14C]Pendimethalin was applied to two natural sandy soils in lysimeters under outdoor conditions. Leachate collected at 1 m depth was analysed for radioactivity for 300 days. Radioactive products were detected from the third week onwards and continued to be leached during the whole experimental period. The radioactive products were neither the parent compound nor carbon dioxide nor carbonate but water-soluble organic conversion products.

Die kohäsion ungesättigter sandböden und deren beeinglussung durch organische substanz

It is well known in soil science, that organic matter contributes considerably to the stability of soil structure. There are also many methods to determine this stabilizing effect of soil organic matter. But as a matter of fact those methods are mostly developed under chemical or colloido-chemical aspects and do only satisfy the demands of special purposes. The physical and mechanical aspects are often neglected. In this work, however, the mechanical parameter “cohesion of soils” c is selected to describe the stabilizing effect of organic matter on soil structure of sandy soils. Organic matter (black peat) was mixed with a fine sand in gravimetric proportions of 0:100, 1:100, 3:100, 5:100, 8:100. The mixtures were then wetted with distilled water and left undisturbed for a few weeks. A natural sandy soil (Haplo-humod) was also taken, part of the sample was treated with H 2O 2 to destroy the organic matter, so the stabilizing effect of organic matter could be evaluated. The cohesion of all the samples was determined with an annular shearing apparatus under a constant soil water suction between 0 and 300 cm H 2O. Results were calculated using the Coulomb equation τ = c + σ n tan ϕ 0, where τ shear strength, c cohesion, σ n normal stress, and ϕ 0 friction angle respectively. The results show, 1. 1. all samples have no cohesion under saturated conditions (water suction = 0 cm H 2O); 2. 2. with all samples the cohesion at first increases with increasing soil water suction, reaches a maximum under a soil water suction of about 40 to 70 cm H 2O, and then decreases with further increasing soil water suction; 3. 3. organic matter enhances the cohesion of both the artificial mixtures of sand and organic matter as well as the natural sandy soil, the increase being the higher, the higher the content of organic matter. 4. 4. no difference between the artificial mixtures of sand and organic matter and the natural sandy soil was found.

The influence of soil characteristics on the toxicity of four chemicals to the earthworm Eisenia fetida andrei (Oligochaeta)

The acute toxicity of Cd (chloride), chloroacetamide, 3,4-dichloroaniline and pentachlorophenol to the earthworm Eisenia fetida andrei was determined using the OECD (1984) artificial soil and contact testing procedures. To investigate the influence of two soil characteristics (pH and organic-matter content), the toxicity of the chemicals was also determined in two natural sandy soils. It is concluded that the filter-paper contact test cannot be recommended to predict earthworm toxicity of these chemicals in soil. Toxicity in soil was influenced by both pH and organic-matter content. Differences between LC50 values in the high-organic-matter artificial soil and in an acid, low-organic-matter sandy soil were, however, not greater than a factor of 3–4. The results of this study therefore support the use of a well-defined artificial soil substrate for standardized earthworm toxicity tests.