Sandy Soil Samples Research Articles

Experimental Study on Tensile Strength of Undisturbed and Disturbed Sandy Soil Samples from Aguascalientes Valley, Mexico

This investigation presents the results of a comparative experimental analysis on the tensile strength obtained from soil samples in both conditions undisturbed and disturbed. For undisturbed soil samples, the tensile strength was obtained from an own-designed testing apparatus of direct tension. In this condition, the geometry of the samples during the carving process was designed to generate a failure plane in a predisposed area of the sample. For disturbed soil samples, a mold was built based on the used by Kim and Hwang (Eng Geol 69:233–244, 2003). Five types of stiff sandy soils from the Aguascalientes Valley, Mexico, were used as testing materials. For the analysis, the tensile strength obtained from undisturbed soil samples was compared with that of disturbed compacted samples within the mold, and at a dry density similar to that of their natural conditions. Three testing processes in disturbed samples were separately performed to obtain and analyze tensile strength. These include: (a) varying the molding water content; (b) completely saturating the samples and allowing them to dry at natural climatic conditions, until the water content was similar to the measured conditions in undisturbed soil samples; and (c) observing the variation in tensile strength on one type of soil when the water content was increased from 9.2%, which is the water content that corresponds to undisturbed samples at the moment of their testing. The results obtained from disturbed soil samples after a drying process were numerically more similar to the results of undisturbed soil samples, in large part because the drying process allowed the carbonated cementing substances of the soil to maintain the cohesion of the particles.

Effect of modified coconut shell biochar on availability of heavy metals and biochemical characteristics of soil in multiple heavy metals contaminated soil

On account of the potential in immobilizing metals and improving soil environment, various biochar materials have been extensively applied in environmental remediation. The purpose of this experiment was to evaluate the effect of modified coconut shell biochar (MCSB) on the availability of metals and soil biological activity in multi-metals (cadmium (Cd), nickel (Ni) and zinc (Zn)) contaminated soil. MCSB was obtained from coconut shell biochar (CSB) by hydrochloric acid pickling and ultrasonication, which has significantly improved its surface functional groups and microcosmic pore structure. Sandy soil samples were incubated at 25 °C amended with MCSB or CSB by 0%, 2.5% and 5% addition for 63 days, respectively. The results showed that the acid soluble Cd, Ni and Zn decreased by 30.1%, 57.2% and 12.7%, respectively, in groups with 5% MCSB addition, which indicated MCSB had a better effect on immobilizing metals compared with CSB. In addition, higher soil biological activities were detected in different treatments compared with control (CK). Especially, the maximum bacterial number was found in 5% MCSB treatment, which increased by 149.43% compared with CK. Accordingly, our results suggested that MCSB could be used as an ameliorant to immobilize heavy metals in contaminated soils and improve soil physicochemical and biological properties.

EFFECT OF SAMPLE RE-SATURATION ON SOIL-WATER CHARACTERISTIC CURVE

ABSTRACT Soil-water characteristic curve (SWCC) is an important tool for water management in irrigated agriculture. However, factors such as texture and structure of soils influence SWCC behavior. According to the literature, wetting and drying cycles alter SWCC. A similar process of re-saturation and drying occurs during SWCC obtainment under laboratory conditions. Based on the hypothesis that re-saturation process alters SWCC due to clay loss in the sample, this study aimed to obtain the SWCC, S index, and pore size distribution from samples submitted to re-saturation cycles, as well as from not re-saturated samples but under higher matric potentials (-2, -4, -6, -8, and -10 kPa). For this, disturbed and undisturbed soil samples, collected from the A (sandy texture) and Btg (sandy clay loam texture) horizons of a Argissolo Acizentado, were used. After obtaining SWCC, each air-dried soil sample was submitted to particle size and clay dispersed in water analyses to verify whether the soil lost clay. The experimental design was a completely randomized design with two methods of SWCC constructing (with and without re-saturation) and eight replications. The re-saturation process generates a loss of clay in the sample, not causing significant changes in SWCC considering the assessed textural soil classes. In addition, sandy soil samples are more sensitive to changes in pore size distribution when submitted to re-saturation.

The role of autophagy in the midgut epithelium of Parachela (Tardigrada)

The process of cell death has been detected in the midgut epithelium of four tardigrade species which belong to Parachela: Macrobiotus diversus, Macrobiotus polonicus, Hypsibius dujardini and Xerobiotus pseudohufelandi. They originated from different environments so they have been affected by different stressors: M. polonicus was extracted from a moss sample collected from a railway embankment; M. diversus was extracted from a moss sample collected from a petrol station; X. pseudohufelandi originated from sandy and dry soil samples collected from a pine forest; H. dujardini was obtained commercially but it lives in a freshwater or even in wet terrestrial environment. Autophagy is caused in the digestive cells of the midgut epithelium by different factors. However, a distinct crosstalk between autophagy and necrosis in tardigrades’ digestive system has been described at the ultrastructural level. Apoptosis has not been detected in the midgut epithelium of analyzed species. We also determined that necrosis is the major process that is responsible for the degeneration of the midgut epithelium of tardigrades, and “apoptosis–necrosis continuum” which is the relationship between these two processes, is disrupted.

Quantification of transformation products of rocket fuel unsymmetrical dimethylhydrazine in soils using SPME and GC-MS

Determination of transformation products (TPs) of rocket fuel unsymmetrical dimethylhydrazine (UDMH) in soil is highly important for environmental impact assessment of the launches of heavy space rockets from Kazakhstan, Russia, China and India. The method based on headspace solid-phase microextraction (HS SPME) and gas chromatography-mass spectrometry is advantageous over other known methods due to greater simplicity and cost efficiency. However, accurate quantification of these analytes using HS SPME is limited by the matrix effect. In this research, we proposed using internal standard and standard addition calibrations to achieve proper combination of accuracies of the quantification of key TPs of UDMH and cost efficiency. 1-Trideuteromethyl-1H-1,2,4-triazole (MTA-d3) was used as the internal standard. Internal standard calibration allowed controlling matrix effects during quantification of 1-methyl-1H-1,2,4-triazole (MTA), N,N-dimethylformamide (DMF), and N-nitrosodimethylamine (NDMA) in soils with humus content < 1%. Using SPME at 60 °C for 15 min by 65 µm Carboxen/polydimethylsiloxane fiber, recoveries of MTA, DMF and NDMA for sandy and loamy soil samples were 91–117, 85–123 and 64–132%, respectively. For improving the method accuracy and widening the range of analytes, standard addition and its combination with internal standard calibration were tested and compared on real soil samples. The combined calibration approach provided greatest accuracies for NDMA, DMF, N-methylformamide, formamide, 1H-pyrazole, 3-methyl-1H-pyrazole and 1H-pyrazole. For determination of 1-formyl-2,2-dimethylhydrazine, 3,5-dimethylpyrazole, 2-ethyl-1H-imidazole, 1H-imidazole, 1H-1,2,4-triazole, pyrazines and pyridines, standard addition calibration is more suitable. However, the proposed approach and collected data allow using both approaches simultaneously.

EFFECT OF BIOCHAR AND COMPOST APPLICATIONS ON MACRONUTRIENTS LOSS FROM SANDY SOIL

Columns experiment was conducted at the laboratory of Soil Sci. Dept., Fac. of Agric., Menoufia Univ., Shebin Elkom, Egypt to study impact of two organic amendments (biochar and compost derived from rice straw) application to sandy soil samples collected from Gabal Quisna, Minoufia governorate (30° 31ꞌ 37.63ꞌꞌ N, 31° 10ꞌ 7.52ꞌꞌ E) on its EC, pH and content of soluble NH4, NO3, P and K. This study was carried out using columns of polyethylene and prior to packing the columns. The prepared soil samples were mixed and thoroughly homogenized with 0.00, 0.75, 1.50 and 3.00% compost (RSC) and/or 0.00, 0.75, 1.50 and 3.00% biochar (RSB). All soil columns were supplied by nutrient solution (Hewitt and smith, 1975), moistened to field capacity level and incubated at the room temperature for 25 days. At the end of incubation period, all soil columns were leached by water to 180% WHC of the studied soil for 3 times with a ten-day interval. The obtained results indicated that, increasing biochar rates led to an increase of pH, EC and soluble content of K and a decrease of soluble NH4+, NO3- and P in the leachate. The compost applications conduced to an increase of EC, soluble NH4+, NO3-, P and K and a decrease of pH in the leachate.

Prediction of soil organic carbon at the country scale: stratification strategies for near‐infrared data

SummaryResearch has shown that the application of near‐infrared (NIR) spectroscopy can be used to predict soil attributes, in particular for regional to continental scales. However, there are challenges when NIR is used at the regional scale because of the considerable spatial variation. This study has predicted SOC at the country scale (German agricultural soil inventory) with different stratification strategies for NIR data: (i) calibration with memory‐based learning (MBL) algorithms that use spectral similarity and (ii) simple stratification based on soil properties (depth, pH and soil texture) and land use. To optimize calibration models, this study aimed to predict soil organic carbon (SOC) determined by these three strategies for 1410 soil profiles selected from the German agricultural soil inventory. The profiles covered a wide range of soil types and characteristics. The calibration procedures were based on complete soil profile data of two‐thirds of the dataset and one‐third of the dataset was used for independent validation (prediction); the profiles were selected randomly. Available soil properties for stratifying the datasets were: soil depth (topsoil 0–30 cm and subsoil 31–100 cm), pH and texture class (silty, clayey, sandy and loamy). The profiles were also stratified by land use (cropland and grassland) and with the MBL method. The calibrations were carried out by partial least‐squares regression (PLSR), and each stratification model was compared with the global model. The root mean square error of cross‐validation (RMSECV) for the global model was 4.2 g SOC kg−1. Stratification according to soil depth reduced the error by 10% (RMSECV 3.8 g kg−1). The best stratification by soil texture was when sandy soil samples were separated from the other samples, which reduced the RMSECV by 14%. Calibration with MBL provided the most accurate predictions of SOC, with an error reduction of 25% (RMSECV 3.2 g kg−1). Thus, calibrations with NIR of country‐scale datasets can be improved easily by stratification or application of the MBL algorithm.Highlights Large country‐scale soil dataset of near‐infrared with &gt; 1400 soil profiles was used. Stratification of NIR data by soil properties increased the accuracy of SOC calibration at country scale. The best stratification design involved calibrating sandy soil separately from other texture classes. A decrease of 25% in calibration error and 22% in prediction error with the MBL model compared with global model.

Microstructure characteristics of cement-stabilized sandy soil using nanosilica

An experimental program was conducted to explore the impact of nanosilica on the microstructure and mechanical characteristics of cemented sandy soil. Cement agent included Portland cement type II. Cement content was 6% by weight of the sandy soil. Nanosilica was added in percentages of 0%, 4%, 8% and 12% by weight of cement. Cylindrical samples were prepared with relative density of 80% and optimum water content and cured for 7 d, 28 d and 90 d. Microstructure characteristics of cement-nanosilica-sand mixtures after 90 d of curing have been explored using atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests. Effects of curing time on microstructure properties of cemented sandy soil samples with 0% and 8% nanosilica have been investigated using SEM test. Unconfined compression test (for all curing times) and compaction test were also performed. The SEM and AFM tests results showed that nanosilica contributes to enhancement of cemented sandy soil through yielding denser, more uniform structure. The XRD test demonstrated that the inclusion of nanosilica in the cemented soil increases the intensity of the calcium silicate hydrate (CSH) peak and decreases the intensity of the calcium hydroxide (CH) peak. The results showed that adding optimum percentages of nanosilica to cement-stabilized sandy soil enhances its mechanical and microstructure properties.

The Hybrid Strategy of Thermoactinospora rubra YIM 77501T for Utilizing Cellulose as a Carbon Source at Different Temperatures.

Thermoactinospora rubra YIM 77501T is an aerobic, Gram-positive, spore-forming and cellulose degrading thermophilic actinomycete isolated from a sandy soil sample of a volcano. Its growth temperature range is 28–60°C. The genomic sequence of this strain revealed that there are 27 cellulase genes belonging to six glycoside hydrolase families. To understand the strategy that this strain uses to utilize carbon sources such as cellulose at different temperatures, comparative transcriptomics analysis of T. rubra YIM 77501T was performed by growing it with cellulose (CMC) and without cellulose (replaced with glucose) at 30, 40, and 50°C, respectively. Transcriptomic analyses showed four cellulase genes (TrBG2, TrBG3, TrBG4, and ThrCel6B) were up-regulated at 30, 40, and 50°C. The rate of gene expression of TrBG2, TrBG3, TrBG4, and ThrCel6B were 50°C > 30°C > 40°C. One cellulase gene (TrBG1) and two cellulase genes (TrBG5 and ThrCel6A) were up-regulated only at 30 and 50°C, respectively. These up-regulated cellulase genes were cloned and expressed in Escherichia coli. The enzymatic properties of up-regulated cellulases showed a variety of responses to temperature. Special up-regulated cellulases TrBG1 and ThrCel6A displayed temperature acclimation for each growth condition. These expression patterns revealed that a hybrid strategy was used by T. rubra to utilize carbon sources at different temperatures. This study provides genomic, transcriptomics, and experimental data useful for understanding how microorganisms respond to environmental changes and their application in enhancing cellulose hydrolysis for animal feed and bioenergy production.

Remediation of Sandy Soil Contaminated with Industrial Wastewater

The present study focuses on measuring the effects of industrial wastewater disposed from thermal electricity power plant as by-product on the geotechnical properties of sandy soil and applying washing process to remediate the contaminated soil samples and measure the efficiency of washing technique. The disturbed sandy soil samples were obtained from Al-Kufa City located to the southwest of Iraq and the industrial wastewater obtained from Al-Musayib thermal electricity power plant. The intact sandy soil was contaminated in the laboratory with four percentages of industrial wastewater (10, 20, 40 and 100%) calculated according to the weight of dry soil. The industrial wastewater is mixed with distilled water to constitute the solution used in the contamination process of soil through soaking the soil by this solution for 30 days. The study results showed that with increasing the percentages of the contaminant, there was a slight increase in both the liquid limit and particle size, while there was a significant increase in the optimum water content. Nevertheless, a slight decrease was observed in the specific gravity, maximum dry unit weight, and void ratio, while, a considerable decrease was noticed in the angle of the internal friction and coefficient of permeability of soil. The proposed remediation technique “soil washing” is efficient, economical, and time saving when used to remediate sandy soils. After remediation, the results showed an increase in the cohesion, angle of internal friction and maximum dry unit weight. Also, a slight increase was observed in the specific gravity, void ratio and permeability coefficient of remediated soil samples when compared with that of contaminated samples. The removal efficiencies of contaminant from soil were (97.63, 96.79, 96.58, and 93.87%) for the soil samples contaminated with industrial wastewater by (10, 20, 40 and 100%), respectively.

Quartz OSL and K-feldspar post-IR IRSL dating of sand accumulation in the Lower Liao Plain (Liaoning, NE China)

The timing of the formation of extensively distributed sand dunes in the Bohai coastal area and its forcing factors are poorly understood. In this study, the chronology of a well-preserved sand dune located in Panjin Forest Park (PJ) in the Lower Liao Plain (LLP) is investigated using quartz optically stimulated luminescence (OSL) and K-feldspar postinfrared (IR) infrared stimulated luminescence (IRSL) (pIRIR) dating. For the pIRIR measurements, the combination of preheating at 180°C and pIRIR stimulation at 150°C (pIRIR&lt;sub&gt;150&lt;/sub&gt;) is exploited. The quartz results show that the sand dune accumulated from &lt;i&gt;c&lt;/i&gt;. 120 a (1890 AD) to c. 70 a (1940 AD) before present, and the underlying sandy soil sediments deposited from &lt;i&gt;c&lt;/i&gt;. 5.0 ka to &lt;i&gt;c&lt;/i&gt;. 0.13 ka as marsh sediment after the sea level highstand since the mid-Holocene. From the evidence in historical coastline records, the PJ sand dune is an inland sand dune and not a coastal sand dune. Based on further information of climate and temperature change after the Little Ice Age (LIA) and human activity in northeastern China, we conclude that the PJ sand dune accumulation was very likely impacted by the immigrants and land reclamation at the end of Qing dynasty. The fading corrected IR&lt;sub&gt;50&lt;/sub&gt; ages, the apparent and fading corrected pIRIR&lt;sub&gt;150&lt;/sub&gt; ages are consistent with quartz ages for two sandy soil samples but overestimate those for six sand samples. The overestimation of the feldspar ages is derived from the residual signal which has not been bleached before burial. The offset obtained from the difference between the quartz OSL and the feldspar pIRIR&lt;sub&gt;150&lt;/sub&gt; ages are ~20–160 a (predicted residual dose: ~0.08–0.60 Gy), whereas the measured residual dose after bleaching 4 h in a solar simulator yielded age overestimation of ~10–40 a (~0.05–0.16 Gy). The age discrepancy calculated from the predicted residual was larger than those obtained from the laboratory measured residuals. We conclude that the pIRIR&lt;sub&gt;150&lt;/sub&gt; of aeolian sediment is applicable for samples older than ~1000 years where the effect of the residual dose become negligible.

The influence of atmospheric conditions on the migration of diesel fuel spilled in soil

Abstract The most common chemical’s spills in typical transportation accidents are those with petroleum products such as diesel fuel, the consequence of which is an extensive pollution of the soil. In order to plan properly fuel recovery from the soil, it is important to gain information about the soil depth which may be affected by pollutant and to predict the pollutant concentration in different soil layers. This study deals with the impact of basic atmospheric conditions, i.e. air temperature and humidity on the diesel fuel migration through the soil. The diesel fuel was spilled into columns (L = 30 cm; D = 4.6 cm) filled with sandy and clay soil samples, and its concentrations at various depths were measured after 11 days under various air temperature (20 and 40°C) and relative humidity (30–100%) conditions. The effects observed were explained by understanding physical processes, such as fuel evaporation, diffusion and adsorption on soil grains. The increase in temperature results in higher fuel evaporation loss and its faster vertical migration. The relative humidity effect is less pronounced but more complex, and it depends much on the soil type.

Analysis of Manganese in Soil Using Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been applied to measure spectral characteristics and to perform quantitative analysis of the concentration of manganese in soil, an issue of great concern for precision agriculture. For the analysis, soil samples were compressed into pellets and a pulsed Nd:YAG laser was employed to produce the plasma in air at atmospheric pressure. Using this approach, we analyzed the time evolution of spectral characteristics and their dependence on the laser pulse energy. A calibration curve was constructed using reference sandy soil samples collected from a farm. An internal standard curve was used to improve the accuracy of the LIBS metrology for soil analyses. The results of this analysis demonstrated the usefulness of this method for analyzing the concentration of manganese in soil.

Incubation of solid state C60 fullerene under UV irradiation mimicking environmentally relevant conditions

Carbon-based nanomaterials, such as C60 fullerenes, are expected to accumulate in soil due to direct release and deposition from the atmosphere. However, little is known about the environmental fate of these nanoparticles which may be susceptible to photochemical and microbial degradation. In the present work, C60 was incubated for a period of 28 days and irradiated with UVA light. Three experiments were carried out where the fullerenes were either spiked onto a glass surface or added to quartz sand or sandy soil samples. At specific time intervals the samples were extracted and analysed by liquid chromatography coupled to UV or high resolution mass spectrometric (HRMS) detection. The fullerenes were degraded in all the treatments and the decay followed a pseudo-first-order rate law. In absence of a solid matrix, the half-life (t1⁄2) of the C60 was 13.1 days, with an overall degradation of 45.1% that was accompanied by the formation of functionalized C60-like structures. Furthermore, mass spectrometric analysis highlighted the presence of a large number of transformation products that were not directly related to the irradiation and presented opened cage and oxidized structures. When C60 was spiked into solid matrices the degradation occurred at a faster rate (t1⁄2 of 4.5 and 0.8 days for quartz sand and sandy soil, respectively). Minor but consistent losses were found in the non-irradiated samples, presumably due to biotic or chemical processes occurring in these samples. The results of this study suggest that light-mediated transformation of the fullerenes will occur in the environment.

Evaluation of Kinetic Approach in Describing Potassium Bioavailability

The objective of this study was to determine the potassium (K) release kinetics of sandy soil sample representative soil of Egyptian new reclaimed areas as affected by treatments of different rates of compost and chemical fertilizers applied individually or mixture of both type sand the effect of two irrigation regimes i.e. 80 and 60% of water requirements IR. Four mathematical models (power function, Elovich, parabolic diffusion and first-order) were used to fitted the data describe K desorption reactions involving 168-hr cumulative reaction time. Comparison of the models using the coefficient of determination (r²) and the standard error of the estimate (SE) indicated that the Elovich and the power function equations overall displayed the best fitted ones. The first-order rate and for less extent, parabolic diffusion equation were less fitted to describe the kinetic data. The constants of the best fitted models represent the rate of K release indicated that all treatments applied to soil gave high and significant increase in rate of K release compared to the control (untreated soil). According to the same constants values, the organic fertilizer applied was the lowest one, meanwhile the chemical one was the highest values, the mixture treatments values, however, were in between the chemical and organic treatments. In addition, the 80% of IR gave the best water management in having both high K adsorption from used soil and significant K uptake by corn plant.

An investigation of pore water pressure and consolidation phenomenon in the unfrozen zone during soil freezing

Accurate modeling of soil deformation depends on the consideration of both frost heave deformation in the frozen zone and consolidation deformation in the unfrozen zone. Pore water pressure investigations are important for revealing these two deformation behaviors. Herein, we aim to reveal the consolidation process by measuring and analyzing changes in pore water pressure in the unfrozen zone. Using a custom-made pore water pressure gauge, we performed a series of real-time pore water pressure measurements in the unfrozen zone of silty clay and sandy soil samples that were exposed to closed and open freezing systems. The results show that the pore water pressure in the unfrozen zone generally increases at first and then decreases. The temperature changes in the unfrozen zone have no significant influence on the changes in pore water pressure, and the variations of the pore water pressure are mainly controlled by the stress and hydraulic boundary (changes in pore water pressure) conditions at the freezing front. Furthermore, changes in the pore water pressure are affected by several parameters, including soil type, water supply condition, initial moisture content, measured soil layer depth, and hydraulic conductivity. Soil consolidation is mainly caused by change in effective stress, which results from increase in total stress or decrease in pore pressure. Based on the observed pore water pressure variations and its numerical simulations, we propose that consolidation in the unfrozen zone during soil freezing includes compression-induced consolidation, which results from an increase in frost heaving stress, and vacuum-induced consolidation, which results from a decrease in pore water pressure. Each consolidation pattern plays an important role in the different stages of soil freezing. Compression-induced consolidation primarily occurs during the early stage of soil freezing, while vacuum-induced consolidation mainly occurs during the later stage of soil freezing.

The relation between liquefaction resistance and shear wave velocity for new and old deposits

Multiple series of cyclic triaxial tests were performed on undisturbed and reconstituted samples of sandy soils obtained from areas of known liquefaction at the time of the 2011 East Japan Earthquake. In this test scheme, the shear wave velocity was firstly measured and then cyclic loads were applied to determine the cyclic shear strength. The undisturbed samples were classified into two groups, namely, one from old alluvial (Pleistocene) deep deposits and the other from near-surface shallow depths which had apparently been disturbed by the liquefaction in the 2011 event. The data thus obtained were plotted in terms of the cyclic strength versus the shear wave velocity, and two curved lines were drawn through average points in the plot for the two groups of soils, that is, one for the undisturbed soils and the other for the liquefaction-disturbed soils. It was found that for a given cyclic strength, the shear wave velocity does have the propensity to become larger for the undisturbed samples from the old deposits in comparison to the undisturbed samples from the seemingly liquefaction-disturbed samples. Similar sets of laboratory tests were also performed on several sand samples reconstituted to a completely disturbed state. The plots of the test results for these reconstituted samples also showed a tendency in the relation between the cyclic strength and the shear wave velocity which is similar to that for the liquefaction-disturbed samples recovered from the in-situ deposits. In order to understand the outcome of the above observations, the ratio between the cyclic strength and the shear modulus from the shear wave velocity was taken as a parameter to distinguish the two different relations as mentioned above. This ratio, which might be called the “reference strain” of the “yield strain”, is used to provide an interpretation of the difference in correlation between the cyclic strength and the shear wave velocity.

MICROSCOPIC ALGAE OF BENTHOS OF THE KHADZHIBEY ESTUARY (ODESA, UKRAINE)

The results of studies (2001-2015) of the species composition of microscopic algae of benthos of the Khadzhibey estuary are presented. The aim of this work was to study the taxonomic composition of microscopic algae of benthos of the Khadzhibey estuary. 44 samples of periphyton macrophytes, silt and sandy soils were collected and processed. 100 species of algae, which belong to 69 genera, 37 families, 20 orders, 9 classes and 6 divisions, were identified. For the first time 35 new species were found for the waters of the studied reservoir, 2 species (Mallomonas apochromatica Conrad, Distigma striato-granulata Skuja) are given as new for the territory of Ukraine. In the microphytobenthos in the Khadzhibey estuary benthic forms (65 species) dominated over planktonic ones (35). With respect to water salinity freshwater forms (67 species) dominated. Brackish-water species (26) were much less numerous. Marine forms constituted 7 taxa. In accordance with the biogeographic distribution of algae, cosmopolitans (63 species) were the dominant group. The boreal group, which accounted 37 species, was considerably less numerous.

Atmospheric pressure dielectric barrier discharge for the remediation of soil contaminated by organic pollutants

The remediation of soil, contaminated by organic pollutants, in a cylinder-to-plane dielectric barrier discharge reactor at atmospheric air pressure was reported. Two model organic pollutants were selected; a solid pollutant (2,6-dichloropyridine) and a liquid pollutant (n-dodecane). The effects of the contaminant’s initial concentration and state, the energy consumption, and the soil type on the pollutant removal efficiency were investigated. To that scope, various contaminated samples of both quartz sand and loamy sandy soil were treated by plasma for various treatment times and initial 2,6-dichloropyridine/n-dodecane concentrations. The results revealed that (1) the removal efficiency of 2,6-dichloropyridine was higher compared to that of n-dodecane at a given plasma treatment time and (2) the removal efficiency increased with the energy density increasing, but decreased as the soil heterogeneity, organic matter and pollutant concentration were enhanced. The main removal mechanism proposed is the evaporation of pollutant molecules coupled with their oxidation by plasma species in the gas and solid/liquid phase.

Estimating Nonaqueous‐Phase Liquid Content in Variably Saturated Soils Using Time Domain Reflectometry

Core Ideas A TDR waveform interpretation method for NAPL content in soils was developed. Correlations between the dielectric response and the NAPL content were determined. The α dielectric mixing model for predicting NAPL presence in soils was expanded. This methodology can be used to obtain predictions of volumetric NAPL content. In recent years, several studies have been conducted in the detection and observation of nonaqueous‐phase liquids (NAPLs) in contaminated soils. Successful remediation of an NAPL‐contaminated site requires appropriate characterization of both the plume extent and the soil volumetric NAPL content (θNAPL). Noninvasive geophysical techniques, such as time domain reflectometry (TDR), may be used to discriminate between θNAPL and soil volumetric water content (θw). Accordingly, the main aim of this work was to develop a TDR waveform interpretation method based on soil dielectric permittivity measurement and observation of the change in the reflected TDR signal amplitude at relatively long times from the waveform source. We demonstrated that the asymptotic value of the reflection signal coefficient can be univocally related with θNAPL in an unsaturated soil. In the procedure adopted, a new formulation of a dielectric mixing model was also derived, introducing a fourth phase that takes the NAPL presence into account. Multiple samples of sandy, silt loam, and loamy soils, at predetermined different θw and θNAPL, were tested, each test consisting in emitting a TDR signal to the soil sample and receiving and analyzing the reflected electromagnetic wave. An empirical dielectric mixing model was calibrated and implemented to estimate the θNAPL. Equipment calibration, measurement accuracy, and error sources, related both to the experimental procedure setup and to the sample preparation conditions, are discussed. The results show that the suggested methodology can be used to obtain predictions of volumetric NAPL content (θNAPL) with acceptable accuracy (R2 = 0.95).