Soil Material Research Articles

Microbial Biosynthesis of Medium-Chain-Length Polyhydroxyalkanoate (mcl-PHA) from Waste Cooking Oil.

Waste cooking oil is a common byproduct in the culinary industry, often posing disposal challenges. This study explores its conversion into the valuable bioplastic material, medium-chain-length polyhydroxyalkanoate (mcl-PHA), through microbial biosynthesis in controlled bioreactor conditions. Twenty-four bacterial isolates were obtained from oil-contaminated soil and waste materials in Mahd Ad-Dahab, Saudi Arabia. The best PHA-producing isolates were identified via 16S rDNA analysis as Neobacillus niacini and Metabacillus niabensis, with the sequences deposited in GenBank (accession numbers: PP346270 and PP346271). This study evaluated the effects of various carbon and nitrogen sources, as well as environmental factors, such as pH, temperature, and shaking speed, on the PHA production titer. Neobacillus niacini favored waste cooking oil and yeast extract, achieving a PHA production titer of 1.13 g/L, while Metabacillus niabensis preferred waste olive oil and urea, with a PHA production titer of 0.85 g/L. Both strains exhibited optimal growth at a neutral pH of 7, under optimal shaking -flask conditions. The bioreactor performance showed improved PHA production under controlled pH conditions, with a final titer of 9.75 g/L for Neobacillus niacini and 4.78 g/L for Metabacillus niabensis. Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) confirmed the biosynthesized polymer as mcl-PHA. This research not only offers a sustainable method for transforming waste into valuable materials, but also provides insights into the optimal conditions for microbial PHA production, advancing environmental science and materials engineering.

Novel Frame-Type Seismic Surface Wave Barrier with Ultra-Low-Frequency Bandgaps for Rayleigh Waves

Seismic surface waves carry significant energy that poses a major threat to structures and may trigger damage to buildings. To address this issue, the implementation of periodic barriers around structures has proven effective in attenuating seismic waves and minimizing structural dynamic response. This paper introduces a framework for seismic surface wave barriers designed to generate multiple ultra-low-frequency band gaps. The framework employs the finite-element method to compute the frequency band gap of the barrier, enabling a deeper understanding of the generation mechanism of the frequency band gap based on vibrational modes. Subsequently, the transmission rates of elastic waves through a ten-period barrier were evaluated through frequency–domain analysis. The attentional effects of the barriers were investigated by the time history analysis using site seismic waves. Moreover, the influence of the soil damping and material damping are separately discussed, further enhancing the assessment. The results demonstrate the present barrier can generate low-frequency band gaps and effectively attenuate seismic surface waves. These band gaps cover the primary frequencies of seismic surface waves, showing notable attenuation capabilities. In addition, the soil damping significantly contributes to the attenuation of seismic surface waves, resulting in an attenuation rate of 50%. There is promising potential for the application of this novel isolation technology in seismic engineering practice.

Origin and evolution of soil materials of the Paleo-Chadian linear-dune landscape in the Far North Region of Cameroon

The mineralogy and micromorphology of associated red Arenosols and both yellow and grey Gleysols of the Paleo-Chadian linear-dune landscape of the Far North Region of Cameroon were studied in order to obtain information about depositional environments and pedogenic processes. Differences between the red soils and both others include a significant difference in clay content, which is much higher in the grey and yellow soils. The composition of the clay fraction is also different, with kaolinite and illite as main mineral phases in the red soils, whereas smectite is strongly predominant in the grey soils and a major phase in the yellow soils. Mössbauer spectroscopy analysis reveals a predominance of hematite as iron oxide mineral in the red soils, in contrast to goethite-predominance in the yellow soils. Thin section observations reveal poor sorting of the coarse fraction, differences in feldspar content, and an absence of reworked clay aggregates, as well as the presence of pore-related carbonate features in the grey soils and iron oxide nodules in the grey and yellow soils. The obtained results indicate that the red soils are derived from a different parent material than the other soils. The grey soils developed on flood-related fluvial deposits in interdune depressions, whereas the red soils formed on aeolian sands and the yellow soils show a mixed origin. In the interdune depressions, hydromorphic conditions led to iron reduction and pedogenic carbonate enrichment.

Application of the material point method (MPM) to characterise the impact forces of granular landslides on rigid obstacles

This study deploys the Material Point Method (MPM) to investigate the soil pressures exerted on a 3D rigid obstacle partially obstructing a dry granular flow; a configuration not previously addressed in the literature on a numerical modelling basis. A 2D simulation is first developed and validated against a flume experiment that monitors the interaction of dry granular flows with retaining structures under varying flume angles. The model is then extended to 3D, enabling the adjustment of the obstacle's geometry to observe the impact of granular flows on impermeable rigid obstacles partially obstructing the soil material. The trend in the recorded soil forces exhibits an initial peak that occurs simultaneously with the first impact, followed by a steep degradation branch as the soil deposits in front of the structure, thus reducing the flow's dynamics. The numerical simulation is subsequently upscaled to ensure that macroscopic dimensional analysis adequately interprets small-scale numerical observations to mimic prototype conditions using the MPM approach. Simplified factors are finally derived to represent the response characteristics of large-scale simulations based on the original findings.

The emission of CO from tropical rainforest soils

Abstract. Soil carbon monoxide (CO) fluxes represent a net balance between biological soil CO uptake and abiotic soil and (senescent) plant CO production. Studies largely from temperate and boreal forests indicate that soils serve as a net sink for CO, but uncertainty remains about the role of tropical rainforest soils to date. Here we report the first direct measurements of soil CO fluxes in a tropical rainforest and compare them with estimates of net ecosystem CO fluxes derived from accumulation of CO at night under stable atmospheric conditions. Furthermore, we used laboratory experiments to demonstrate the importance of temperature on net soil CO fluxes. Net soil surface CO fluxes ranged from −0.19 to 3.36 nmol m−2 s−1, averaging ∼1 nmol CO m−2 s−1. Fluxes varied with season and topographic location, with the highest fluxes measured in the dry season in a seasonally inundated valley. Ecosystem CO fluxes estimated from nocturnal canopy air profiles, which showed CO mixing ratios that consistently decreased with height, ranged between 0.3 and 2.0 nmol CO m−2 s−1. A canopy layer budget method, using the nocturnal increase in CO, estimated similar flux magnitudes (1.1 to 2.3 nmol CO m−2 s−1). In the wet season, a greater valley ecosystem CO production was observed in comparison to measured soil valley CO fluxes, suggesting a contribution of the valley stream to overall CO emissions. Laboratory incubations demonstrated a clear increase in CO production with temperature that was also observed in field fluxes, though high correlations between soil temperature and moisture limit our ability to interpret the field relationship. At a common temperature (25 °C), expected plateau and valley senescent-leaf CO production was small (0.012 and 0.002 nmol CO m−2 s−1) in comparison to expected soil material CO emissions (∼ 0.9 nmol CO m−2 s−1). Based on our field and laboratory observations, we expect that tropical rainforest ecosystems are a net source of CO, with thermal-degradation-induced soil emissions likely being the main contributor to ecosystem CO emissions. Extrapolating our first observation-based tropical rainforest soil emission estimate of ∼ 1 nmol m−2 s−1, global tropical rainforest soil emissions of ∼ 16.0 Tg CO yr−1 are estimated. Nevertheless, total ecosystem CO emissions might be higher, since valley streams and inundated areas might represent local CO emission hot spots. To further improve tropical forest ecosystem CO emission estimates, more in situ tropical forest soil and ecosystem CO flux measurements are essential.

Lipid biomarkers and stable isotopes uncover paleovegetation changes in extremely species-rich forest-steppe ecosystems, Central Europe

The historical development of the vegetation of semi-dry grasslands in Central Europe is not satisfactorily understood. Long-term continuity of open vegetation or, conversely, deep-past forest phases are considered possible sources of the current extreme species diversity of these ecosystems. We aimed to reveal the trajectory of paleovegetation development in these ecosystems through detailed analysis of terrestrial in-situ soil geoarchives. We measured the bulk soil carbon and nitrogen contents, lipid molecular distribution, and compound-specific stable carbon and hydrogen isotopic signatures of mid- and long-chain n-alkanes extracted from soil and modern plant material tissues (i.e., deciduous and Pinus leaves and grass/herbaceous species).The C23–C33 n-alkane homologues were identified in soils with different abundances. Normally, C27 and C29 n-alkanes were the most abundant homologues in tree-leaf samples, while grass-derived n-alkanes were mostly C31 and C33 homologues. Soils were largely dominated by C29 and C31 n-alkanes. Odd-numbered C27–C33 soil n-alkane δ13C values ranged from −36.2‰ to −23.2‰, whereas their δ2H values showed a wider range of variability that fluctuated from −224‰ to −172‰. Molecular distribution in combination with radiocarbon analysis of soil organic matter (SOM) and δ13C and δ2H values of n-alkanes revealed a large contribution of C3 trees (both deciduous and coniferous trees/pine trees) as the main source of n-alkanes between the late Pleistocene and early Holocene (ca 15,000–8200 calibrated year before present/cal year BP). A clear shift toward more grassy/herbaceous vegetation was observed from the early Holocene (ca 11,700–8200 cal year BP) onwards. Distribution patterns of lipids and soil geochemical parameters showed that plants are the main source of SOM and that biodegradation and kinetic isotope fractionation are not the main reasons for 13C enrichment in soil profiles. Past C3 vegetation shifts as well as paleoclimate changes (i.e., aridity) can have played a role in the observed 13C depth profiles.

Suitability of XRF for Routine Analysis of Multi-Elemental Composition: A Multi-Standard Verification.

This study investigated the suitability of X-ray fluorescence (XRF) analysis for routine multi-elemental composition analysis, checking its analytical capabilities by measuring a wide array of certified reference materials of soil and plant origin. A portable XRF analyzer was used to evaluate 32 soil and 12 plant standard materials, using both the Soil and Geochem mode, with sequential beams, allowing the detection of a wide range of elements. Recovery rates were calculated by comparing XRF measurements with certified values, and their correlations were verified through the Spearman coefficient. The results demonstrated the reliability of XRF measurements for soil samples, with a large number of elements showing a good or very good recovery and strong correlations with certified values. For plant samples, XRF largely overestimated the certified values, but the strong statistically significant correlations for almost all tested elements allowed us to correct this systematic bias, using the reported median value for dividing the value obtained via XRF. The Geochem mode emerged as more reliable for a larger number of elements. It was concluded that XRF may be a suitable alternative to ICP-MS in routine multi-elemental composition analysis.

Pseudo Sliding Plane in Super-Thick Soil Materials Deposit at Ngasinan Deep Landslide Area

Pseudo Sliding Plane in Super-Thick Soil Materials Deposit at Ngasinan Deep Landslide Area

Soil development and ancient Maya land use in the tropical karst landscape: Case of Busiljá, Chiapas, México

AbstractThe soil mantle of the tropical karstic landscapes of Southern Mexico was shaped by specific processes of pedogenesis and long‐term human impacts of ancient Maya agriculture. To understand the interaction between natural and human‐induced soil‐forming processes in the calcareous mountains of Chiapas state, we studied soil toposequences around the Classic Maya site of Budsilhá and related them to the archaeological evidence of settlement and land‐use distribution. Soil chemical analysis, micromorphological observations, and clay mineral identification were carried out in key soil profiles at the main geoforms. Limestone hills are occupied by shallow Rendolls which are usually perceived as incipient soils. However, high content of silicate clay composed of kaolinite and vermiculite and ferruginous clayey soil material observed at macro‐ and microscale backed the hypothesis that these soils were formed from the residues of thick Terra Rossa after their erosion. Swampy lowlands are occupied by thick clayey gleyic soils with clay mineral assemblages similar to those in the upland Rendolls. We suppose that the mineral matrix of the lowland soils is largely derived from the pedosediments of eroded upland Terra Rossa, which lost original ferruginous pigmentation and aggregation due to redoximorphic processes. Some wetland soils contain neoformed gypsum that is atypical for humid tropics; sulfide‐sulfate transformation under fluctuating redox conditions could promote gypsum synthesis. Ancient Maya land use was closely related to soil‐geomorphic conditions: settlements with homegardens occupied calcareous hills, whereas the primary agricultural domain was developed on lowland soils after their drainage by artificial canals.

The Sliding Surface Determination of A Deep-seated Landslide on Cisumdawu Highway, West Java, Based on The Electrical Resistivity Tomography

Sumedang is one of the regencies in West Java Province that usually experiences landslides due to its lithology, slopes, and water level conditions. Previously slow-moving landslides occurred between 2016 and February 2021, affected the new Cileunyi-Sumedang-Dawuan (Cisumdawu) Highway at Section 2, Station 21 in the North Sumedang District. This research aims to identify the causes of these landslides using a combination of geological field observation, subsurface geo-electric resistivity-based survey, and borehole drilling. A total of fourteen boreholes were drilled to collect geotechnical data from the subsurface of the researched area, including the soil material and N-SPT value. The soil hardness and resistivity were measured and compared to establish the relationship between resistivity and engineering properties. The result of the resistivity measurement showed that the percolating water zone in the permeable loose soil was located above the impermeable layer, estimated as a slip surface. The subsurface measurement and borehole data show that the lithology of the sliding surface is a layer of clay with a thickness of 5 - 12 m, the slope of the sliding surface is 20o, and the depth is between 24 - 26 m. The cover layer of the sliding surface is a layer of silty clay and gravelly clay with a thickness of 5 - 10 m. Thus, based on the data presented, installation of bore piles and groundwater level monitoring need to be done as mitigation efforts.

Soil organic matter components and sesquioxides integrally regulate aggregate stability and size distribution under erosion and deposition conditions in southern China

Water erosion considerably affects the stability and particle size distribution of soil aggregates, but the underlying mechanisms of water erosion remain unclear. To this end, we selected four landscape positions (top-, up-, mid-, and toe-slope) with distinct erosion and deposition characteristics on a typical eroded slope in southern China to conduct experiments- aiming to investigate the main drivers of soil aggregate stability during erosion and deposition processes. Soil samples were collected from 12 sites, and 4 size classes (>2, 2–0.25, 0.25–0.053, and <0.053 mm) of soil aggregates were obtained using the wet sieving method. The composition and stability of the soil aggregates, as well as the contents of organic (organic matter components) and inorganic (iron-aluminum oxides) cementing materials of different particle sizes, were determined. The results indicated that erosion significantly reduced the aggregate stability and the >0.25 mm water-stable aggregate content (WR0.25) (P < 0.05). The mean weight diameter (MWD) and geometric mean diameter (GMD) values of the soil aggregates at the eroding site decreased, and the fractal dimension (FD) increased. Furthermore, erosion markedly reduced the humic acid (HA) and fulvic acid (FA) contents in the bulk soils and soil aggregates, while the HA content showed no obvious difference between the eroding and depositional sites. In addition to the presence of complexed iron/alumina oxides (Fep/Alp), erosion markedly reduced the contents of amorphous (Feo/Alo) and free-form (Fed/Ald) iron/alumina oxides in the bulk soils and size fractions. Moreover, Fed/Ald, Fep and Feo/Alo were present in the microaggregates, while Alp was found in the macroaggregates. Additionally, boosted regression tree (BRT) analysis indicated that FA (36.70 %), Feo (19.00 %), and Ald (12.71 %) were the crucial predictors of soil aggregate stability. These findings further confirm that the organic and inorganic cementing materials in red soils collectively contribute to aggregate stabilization under the impact of erosion. This study facilitates a deeper understanding of the mechanisms governing soil aggregate stability in eroded landscapes, and provides a theoretical basis for biogeochemical cycling processes.

Characteristics of pipestems from acid sulfate soils of Finland and Australia

AbstractThis study describes iron (Fe) pipestems formed around and within root channels during the development of a homogeneous unripe sulfidic sediment into a ripe soil where redox‐ or pH‐active elements segregate. Pipestems and adjacent soil material samples were characterised by chemical and mineralogical analyses and scanning electron microscopy (SEM) associated with energy dispersive spectroscopy (EDS). Pipestems occurred at 60–190 cm and at 30–130 cm in a young Finnish soil and a more mature Australian soil, respectively, while sulfidic materials were found below 170–180 cm. The pipestems consisted of mineral grains cemented together by Fe precipitate. There was an up to 24‐fold enrichment of Fe and an up to 13‐fold enrichment of sulfur (S) in the Finnish pipestems compared to the adjacent soil material, whereas the corresponding enrichment in the Australian soil was up to 27‐fold for Fe and up to 8‐fold for S. In the Australian pipestem matrices, the Fe concentration was as high as 40% compared to 14% in the Finnish ones. It was estimated that about 70 ton ha−1 S had been mobilised from the sulfidic material in the Finnish soil at the depth of 50–150 cm. Part of S has leached out but a substantial amount remained in the soil constituting the stock of retained acidity. Almost all pipestems contained a new solid phase precipitated within the former cortex cells of the plant roots. In the Finnish samples, this precipitate consisted of jarosite and schwertmannite. After oxidative exhaustion of sulfidic material in the surrounding soil, these metastable minerals are gradually hydrolysed, associated with leaching of S. In the mature Australian soil, most of these minerals had already been transformed to goethite. Pipestems formed after roots in unripe soil are sites for synthesis and hydrolysis of minerals and serve as routes for atmospheric oxygen into the reduced subsoil and for soluble reaction products to exit the soil. Pipestems have an important role in the ripening of the soil profile.

Comparative study on mechanical performance of silty soil and expansive soil below canal structures in cold regions

Silty soil was widely used as filling soil materials for the replacement of expansive soil in cold regions. This paper presents a straightforward approach for the effects of wetting-drying-freezing-thawing cycles on mechanical behaviors of silty soil and expansive soil by laboratory tests. The results showed that the silty soil and expansive soil after 7th wetting-drying-freezing-thawing cycles presented the decreases of elastic modulus, failure strength, cohesion and angel of internal friction by 8.9 %∼12.0 %, 7.7 %∼9.0 %, 7.9 %, 4.5 % and 17.6 %∼37.0 %, 20.5 %∼29.4 %, 43.2 %, 13.0 %, respectively, indicating that wetting-drying-freezing-thawing cycles had little impact on mechanical property of silty soil and a great influence on that of expansive soil. Among them, the mechanical property attenuation ratio in the first three wetting-drying-freezing-thawing cycles accounted for over 90 % of the total. In the meantime, the micro-structure damage, surface crack characteristics and grain size distribution variations of expansive soil were all more significantly than these of silty soil exposed to wetting-drying-freezing-thawing cycles, which brought insight into the causes of the differences in mechanical properties for silty soil and expansive soil. It is found that the silty soil properties were more stable than expansive soil properties, and the silty soil is very effective for replacing the expansive soil below canal structures in cold regions.

Empirical Model of Unconsolidated Tephra Erosion: Verification and Application on Micro Catchment

Erosion is an important process that shapes the earth's surface. Given the complexity of the process, efforts to understand it are essential. Over the last 50 years, numerous models of soil particle erosion by surface runoff emerged, some of which share similar forms and parameters. The differences lie in the coefficient values of the parameters, attributed to the characteristics of the soil material such as texture, structure, and organic matter content. However, these erosion models tend to underpredict in the case of new volcanic deposit erosion. The erosion model for unconsolidated tephra, proposed by Yunita, was developed through laboratory experiments using volcanic material from Merapi Volcano, Indonesia. Nevertheless, the model has not been implemented for other cases. Therefore, this study aims to verify the erosion model for volcanic material in other cases, explore the possibility of broader implementation, identify the factors that influence its accuracy, and determine the model’s limitations. To verify the model’s potential for broader application, we applied it to micro-scale catchments in St. Hellens (USA), Sakurajima (Japan), and a laboratory scale plot in Merapi (Indonesia). The verification yielded satisfactory results for all three cases, especially for new tephra deposits. In the case of St. Helens, the extrapolation of model coefficients was proven to still be applicable even for thicker tephra layers. However, the erosion prediction was overestimated for tephra layer deposits older than 1 year, as the erosion rate decreases over time due to the compaction and stabilization of the tephra layer. In the Sakurajima, the model was also suitable for predicting long-term erosion amounts (daily and monthly). Meanwhile, in Merapi, the model provided accurate predictions for slopes of 20º and 25º but was less accurate for 30º slopes, where the measured erosion was due to both erosion and slope failure. These verification results demonstrate the potential of applying the empirical erosion model to micro catchments with relatively homogenous slopes and tephra properties. The sensitivity test revealed that slope, runoff, rainfall intensity, and volcanic ash thickness are strongly influence the erosion rate. This study also simplified the volcanic ash erosion model as a function of slope (S0), runoff (q), and rainfall (i) by assuming the value of (1-τc/τ0) is equal to 1. Further study using GIS tools is required for its application on several catchments with heterogeneous characteristics. Doi: 10.28991/CEJ-2024-010-07-02 Full Text: PDF

LABORATORY DETERMINATION OF THE MAXIMUM DENSITY AND OPTIMAL HUMIDITY OF LARGE-BLOCK SOILS

he purpose of our field research was to develop and select a method of work on laying and compacting the material of large-block soils, ensuring the receipt and determination of maximum density and optimal soil moisture. On the basis of these studies, technical conditions for the construction of thrust prisms are further drawn up. This article presents the results of the work performed with a brief methodology of field and laboratory research. The article provides data characterizing the material intended for installation in the body of the dam. The currently existing methods for determining the control parameters of laying large-block soils are contradictory and require experimental work. A number of parameters are taken into account: grain composition, humidity, density. Therefore, the article considers a laboratory method for determining the maximum density and optimal humidity of stone material when laying in the body of the dam. The results of the research carried out on the development of our quarry area, the thickness of the uncompacted layer was determined, the choice of a sealing mechanism, the number of passes along one track, the determination of the density of dry soil in experimental field sites intended for use in filling the body of the dam, graphs of the required densities for full-scale grain composition are presented. The strength properties of the stone material were determined experimentally for the average grain composition and for the upper curve of the accepted “fish”

Estimation of Standard Penetration Test (SPT) Depth Testing Plan on Geoelectrical Resistivity Data Correlation (Ωm)

Abstract— Analysis of soil bearing capacity in receiving loads is an important step in the construction of building structures, namely as a basis for planning types, materials, material quality, and foundation dimensions. This study aims to analyze the minimum resistivity (Ωm) of soil or rock material that is correlated with the Standard Penetration Test (N-SPT) value of ≥ 50. This is done as the basis for estimating the depth of drilling in the Standard Penetration Test (SPT) test. This study applies a geolytic approach to study soil and rock specifications. The research data includes descriptions of soil types, depth and thickness of each soil layer, material resistivity which is interpreted as soil density, minerals, to the presence of water content in the soil layers. The results of the data correlation analysis show that the higher the resistivity value of the soil or rock material (Ωm), the greater the number of collisions (N). The minimum resistivity value of soil material is more than (&gt;) 121.27 Ωm obtained from the number of (N) collisions of the Standard Penetration Test (N-SPT) of more than (≥) 50. Thus, further estimation of the drilling depth can be carried out. The depth of drilling for each location varies, depending on the carrying capacity of the soil, which ultimately determines the amount of drilling costs.

Wykorzystanie metody radaru penetrującego grunt w badaniu gleby zanieczyszczonej węglowodorami w obszarze Navodari - Rumunia

Ground penetrating radar (GPR) is a very useful geophysical method for use in hydrogeologic and near-surface mapping studies. It can be used to study contaminants in groundwater, subsurface faulting, and underground cavities (natural or man-made), all of which pose potentially dangerous geological hazards. The GPR technique is similar in principle to seismic reflection and sonar techniques. The propagation of the radar signal depends on the frequency-dependent electrical properties of the ground.Electrical conductivity of the soil or rock materials along the propagation paths introduces significant absorptive losses which limit the depth of penetration into the earth formations and is primarily dependent upon the moisture content and mineralization present.Reflected signals are amplified, and transformed to the audio-frequency range, recorded, processed, and displayed. From the recorded display, subsurface features such as soil/ soil, soil/rock, and unsaturated/saturated interfaces can be identified. In addition, the presence of floating hydrocarbons on the water table, the geometry of contaminant plumes, and the location of buried cables, pipes, drums, and tanks can be detected. The GPR data are presented as a two-dimensional depth profile along a scanned traverse line in which the vertical axis is two-way travel time measured in nanoseconds. The location of hydrocarbon contamination in the ground using the GPR method is based mainly on information taken from reflected signals. In the cases investigated in Romania contaminated sites (Navodari area), such signals were very rarely recorded. A long time after spillage, contamination takes the form of plumes with different size and distribution, which depends on the geological and hydraulic properties of the ground. The survey discussed in this paper was carried out using the GPR system-Noggin with two antennas (250 and 500mHz) Data collected were processed using software(EKKO_Project™ GPR Data Analysis) to produce 2D radargram in time scale. The presence of contaminant plumes as well as the water table are observed in the GPR sections at depths approximately of 0.5 to 1.5 m. In the GPR section, the oil contaminated layer exhibits discontinuous, subparallel, and chaotic high amplitude reflection patterns. Promising results were also obtained in the GPR survey where three obvious reflection patterns representing the top sand-silt layer, oil-contaminated zone and, the underlying thick soft clay were detected in all 2D radargrams of the GPR traverse lines.

Delineating the Acquired Genetic Diversity and Multidrug Resistance in Alcaligenes from Poultry Farms and Nearby Soil.

Alcaligenes faecalis is one of the most important and clinically significant environmental pathogens, increasing in importance due to its isolation from soil and nosocomial environments. The Gram-negative soil bacterium is associated with skin endocarditis, bacteremia, dysentery, meningitis, endophthalmitis, urinary tract infections, and pneumonia in patients. With emerging antibiotic resistance in A. faecalis, it has become crucial to understand the origin of such resistance genes within thisclinically significant environmental and gut bacterium. In this research, we studied the impact of antibiotic overuse in poultry and its effect on developing resistance in A.faecalis. We sampled soil and faecal materials from five poultry farms, performed whole genome sequencing & analysis and identified four strains of A. faecalis. Furthermore, we characterized the genes in the genomic islands of A. faecalis isolates. We found four multidrug-resistant A. faecalis strains that showed resistance against vancomycin (MIC >1000μg/ml), ceftazidime (50μg/ml), colistin (50μg/ml) and ciprofloxacin (50μg/ml). From whole genome comparative analysis, we found more than 180 resistance genes compared to the reference sequence. Parts of our assembled contigs were found to be similar to different bacteria which included pbp1A and pbp2 imparting resistance to amoxicillin originally a part of Helicobacter and Bordetella pertussis. We also found the Mycobacterial insertion element IS6110 in the genomic islands of all four genomes. This prominent insertion element can be transferred and induce resistance to other bacterial genomes. The results thus are crucial in understanding the transfer of resistance genes in the environment and can help in developing regimes for antibiotic use in the food and poultry industry.

Centrifuge modelling of vegetated soils: A review

Understanding the soil–root mechanical interaction is crucial to advancing the utilisation of vegetation as a nature-based approach to designing more stable slopes and resilient urban forestry against tree windthrown. Although numerical and analytical models for detailed analysis of soil–root interaction exist, these models are seldom validated due to the lack of field data and the significant challenges in quantifying such interactions due to the complex nature of root system. The centrifuge modelling technique is an effective alternative for unravelling the complexities of the hydromechanical behaviour of vegetated soils by recreating prototype stress levels in small-scale physical models and testing them under more controlled conditions. This work presents a critical review on existing centrifuge modelling methods for vegetated soils, paying particular attention on the (i) fundamentals of centrifuge modelling, where principles, scaling laws and applications relevant to modelling vegetated soils are detailed; (ii) methods for modelling soils, including choice of soil material and sample preparation; and (iii) methods for modelling roots by means of natural plants and root analogues, where the replication of root morphology, mechanical properties and capabilities of modelling transpiration effects are discussed. In every topic, the challenges that could further advance the centrifuge modelling of vegetated soils and the possible ways to address them are highlighted. Finally, the prospect for future studies is discussed, highlighting the potential to enhance the understanding of the underlying mechanisms amongst plant roots, soil, water and external loading.

ANALISIS STABILISASI TANAH LEMPUNG MENGGUNAKAN CAMPURAN ABU SEKAM PADI TERHADAP NILAI KUAT GESER TANAH

The main aim of stabilization is to change the technical properties of the soil itself, such as the compressibility and bearing capacity of the soil. Based on the results of testing the physical and mechanical properties of the original soil of Sambirejo Village, Puhpelem, Wonogiri according to the ASSHTO method, the original soil is included in group A-7-6, which is medium to poor clayey soil material. Meanwhile, according to the USCS method, it is included in the CH group, namely organic clay with high plasticity, fat clays. After conducting further research with variations in the rice husk ash mixture of 0%, 5%, 10%, 15%, and 20%, the results showed that the soil physical test showed the values of water content (W), liquid limit (LL), plasticity index (PI ), and the percentage passing filter No. 200 experienced a decrease with increasing percentage of addition of rice husk ash with yield figures on original soil of 53.00%, 52.00%, 15.32%, 62.00% while on original soil with a mixture of 20% rice husk ash obtained results of 50.11%, 41.10%, 1.65%, 51.00 %. Meanwhile, the specific gravity (Gs), plasticity limit (PL), and shrinkage limit (LL) increased with increasing percentage of rice husk ash addition with the yield figures on the original soil being 5.409%, 36.68%, 12.65%, while on the original soil with a mixture of rice husk ash 20% rice obtained yields of 6.071%, 39.45%, 26.89%. Based on the results of the Direct Shear Test, the soil experienced an increase with each addition of rice husk ash. The highest Direct Shear Test value occurred in 20% mixed soil, namely 0.583 kg/cm2 and the lowest Direct Shear Test value occurred in original soil, namely 0.394 kg/cm2.