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Sepiolite is a fibrous clay mineral, which is mostly associated with a semi-arid to arid climate, with characteristics intermediate between kaolinite and montmorillonite minerals. An experimental study was conducted, with the goal of creating a substantial database of physical, microstructural, and geotechnical characteristics of sepiolite to develop its applications as a natural resource that is explored as the main deposit of Iran. It has been found that sepiolite soils were lightweight, porous, and cohesive with negligible settlement and swelling properties and almost high UCS values. Various analysis were performed to characterise the macroscopic behaviour (Atterberg limit, physical, and compressibility tests), microstructural, chemical, and mineralogical characterisations by chemical analysis, X-Ray diffraction, and Scanning Electron Microscopy. At first glance, sepiolite soils showed high liquid limits with medium to high plastic indices which can result in problems including creation of up and down movements in foundations. After mixing with silt and fine sand to decrease high liquid limit and optimum moisture amounts, sepiolite is suitable candidate for engineering applications (including clay liners, clay cores, etc.) due to its compressibility and strength characteristics. In conclusion, sepiolite soils are strongly recommended for geo-environmental structures due to their adsorption capacity, low permeability coefficient, and suitable strengths. [ABSTRACT FROM AUTHOR]

Some soil characteristics, such as the shear wave velocity, the shear modulus, the Poisson ratio, and the porosity, affect how clay soils behave. The soil design parameters under loading, such as soil liquefaction induced by dynamic earthquake loading, employ the shear wave velocity and shear module with modest stress. In order to understand the pore saturation, the Poisson ratio and seismic velocity ratio are also utilized. Additionally, one of the most crucial physical characteristics for assessing permeability at the base of any engineering structure, resolving consolidation issues that may arise at the foundation of an engineering structure, and influencing the deformation behavior of soils is soil porosity. Predicting the porosity of clay soils is a crucial first step in tackling engineering and environmental issues that may arise in the soil after an earthquake or not. With the use of dynamic soil metrics such as seismic velocities, shear modules, bulk modules, seismic velocity ratios, and Poisson ratios, the current work aims to estimate soil porosity. Seismic refraction was used by various studies in the past to conduct in-situ geophysical research. The lithological characteristics of the soil (such as the grain size, shape, type, compaction, consolidation, and cementation of the grains) and the physical characteristics of the soil (such as porosity, permeability, density, anisotropy, saturation level, liquid–solid transition, pressure, and temperature), as well as the elasticity characteristics of the soil (such as shear modulus (G), bulk modulus (K), Young modulus (E), Poisson ratio (μ) and Lamé constants (λ )) all have an impact on seismic waves passing through a medium. [ABSTRACT FROM AUTHOR]

Mitigation of global climate change by means such as soil carbon (C) sequestration has become an important area of research. Soil organic matter (SOM) that is stabilized with clay minerals is the most persistent in soils. Currently, little is known regarding the C sequestration ability of nanoclay extracted from Vertisols in semi-arid regions. Therefore, the aim of this study was to extract and characterize nanoclay and bulk clay from a Vertisol from Iran, in terms of physicochemical surface properties and resistance of SOM to chemical oxidation. The clay fractions were studied before and after H2O2 treatment by total C analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), pyrolysis gas chromatography mass spectrometry (GC–MS), Fourier transform infrared (FTIR) spectroscopy, specific surface area analysis, and zeta potential. TEM and SEM images showed that the diameter of the extracted nanoclays was 16–46 nm and their morphology was more porous than bulk soil clay. The nanoclay had a much greater specific surface area (111.9 m2 g−1) than the bulk clay (67.9 m2 g−1). According to total C, FTIR, and zeta potential results, the nanoclay was enriched with 1.4 times more C than the bulk clay after peroxide treatment, indicating enhanced soil C stabilization in the nanoclay. About 45% of the peroxide-resistant SOM in the nanoclay was associated with N-containing compounds, indicating that these compounds contribute to SOM stability. The results demonstrate important role of nanoclay in soil C sequestration in Vertisols. [ABSTRACT FROM AUTHOR]

Knowledge about the spatial distribution of the soil physical and mechanical properties is crucial for soil management, water yield, and sustainability at the watershed scale; however, the lack of soil data hinders the application of this tool, thus urging the need to estimate soil properties and consequently, to perform the spatial distribution. This research attempted to examine the proficiency of three machine learning methods (RF: Random Forest; Cubist: Regression Tree; and SVM: Support Vector Machine) to predict soil physical and mechanical properties, saturated hydraulic conductivity (Ks), Cohesion measured by fall-cone at the saturated (Psat) and dry (Pdry) states, hardness index (HI) and dry shear strength (SS) by integrating environmental variables and soil features in the Zayandeh-Rood dam watershed, central Iran. To determine the best combination of input variables, three scenarios were examined as follows: scenario I, terrain attributes derivative from a digital elevation model (DEM) + remotely sensed data; scenario II, covariates of scenario I + selected climatic data and some thematic maps; scenario III, covariates in scenario II + intrinsic soil properties (Clay, Silt, Sand, bulk density (BD), soil organic matter (SOM), calcium carbonate equivalent (CCE), mean weight diameter (MWD) and geometric weight diameter (GWD)). The results showed that for Ks, PsatPdry and SS, the best performance was found by the RF model in the third scenario, with R2= 0.53, 0.32, 0.31 and 0.41, respectively, while for soil hardness index (HI), Cubist model in the third scenario with R2= 0.25 showed the highest performance. For predicting Ks and Psat, soil characteristics (i.e. clay and soil SOM and BD), and land use were the most important variables. For predicting Pdry, HI, and SS, some topographical characteristics (Valley depth, catchment area, mlti-resolution of ridge top flatness index), and some soil characteristics (i.e. clay, SOM and MWD) were the most important input variables. The results of this research present moderate accuracy, however, the methodology employed provides quick and cost-effective information serving as the scientific basis for decision-making goals. [ABSTRACT FROM AUTHOR]

Biocrusts are multifaceted communities including mosses, lichens, and cyanobacteria that are crucial for sustaining soil functions in drylands. Most studies on biocrust functions to date have focused on biocrust cover and development, largely in non‐saline soils, and we know very little about the importance of biocrust diversity for maintaining multifunctionality in saline dryland soils. We assessed the direct and indirect linkages between biocrust richness, soil texture and salinity and soil multifunctionality by measuring 13 variables characterizing soil biological, nutrient and hydrological functions across 32 plots in a salinized dryland in northeastern Iran. We assessed the species richness of biocrust patches and characterized soil functions in bare soils. Overall, biocrust species richness declined with soil clay content and soil salinity, whereas soil salinity increased with soil clay content. Structural equation modeling showed a strong positive association between biocrust species richness and all measured dryland soil functions (soil biological, nutrient, and hydrological functions), but soil hydrological function declined with soil salinity. Overall, dryland soil multifunctionality was positively associated with biocrust species richness but negatively associated with soil clay content. Biocrust species richness likely enhances soil multifunctionality via the distinct roles of species and biocrust functional groups in providing carbon and nutrient inputs, creating favourable microsites, enhancing infiltration, and facilitating soil microbial colonization in saline dryland soils. Overall, our findings highlight a key role for biocrust diversity in facilitating and maintaining soil multifunctionality in drylands affected by soil salinity. [ABSTRACT FROM AUTHOR]

Spatial information on land and soil resources are critical towards addressing land degradation for ensuring sustainable soil and crop management. To address these needs, digital soil mapping techniques have emerged as an efficient and low-cost solution. Although digital soil mapping has typically leveraged geospatial environmental variables (e.g. remote sensing), the application and integration of spectroscopic data with those environmental variables remain limited. Hence, this study combines visible and nearinfrared (Vis-NIR) spectroscopy, remote sensing, and topographic data and applies random forests, hybridized with particle swarm optimization algorithm (RF + PSO), to predict the spatial variability of soil clay content, electrical conductivity (EC), and calcium carbonate equivalent (CCE) for 370km² of agricultural land in western Iran. Using a conditioned Latin hypercube approach, 220 soil samples at the 0–20 cm depth increment were acquired throughout the study area. Three sets of environmental covariates were tested: Scenario A (Vis-NIR spectroscopy data), Scenario B (environmental data), and Scenario C (Vis-NIR spectroscopy þ environmental data). According to the 10-fold crossvalidation procedure with 100 replications, the RF + PSO model showed an acceptable level accuracy for all scenarios, although the accuracy of the RF + PSO model using the Scenario C data was higher than all other scenarios: the Lin’s Concordance Correlation Coefficient values were 0.77, 0.83, and 0.74 for the clay contents, EC, and CCE, respectively. The results demonstrated that the combination of Vis-NIR spectroscopic data and commonly available environmental covariates provided the best input data for the hybridized model and enhanced its performance. [ABSTRACT FROM AUTHOR]

Artemisia sieberi Besser occurs in many parts of the Irano-Turanian floristic region, which is mostly distributed throughout the Iranian plateau, especially in Iran. This study aimed to identify the effect of the soil and topography variables on A. sieberi distribution. We used canopy cover data to fit models using generalized additive models (GAMs). The results showed that the response pattern of A. sieberi along with the gradient of soil clay, soil saturation moisture, soil nitrogen and soil acidity followed the monotonic increase model, and its canopy cover percentage augmented by increasing the values of the factors. Conversely, the A. sieberi canopy cover percentage decreased by increasing the amount of soil sand, bare soil and the geographic aspect. The A. sieberi responses are in contrast to the niche theory. The relationship between the species response pattern and the gradients of soil silt, soil salinity, lime percentage, organic carbon, altitude, land slope, litter, gravel percentage, stone percentage, mean annual precipitation and mean annual temperature followed a unimodal model (consistent with the niche theory). The optimal growth limits for these factors were 32%, 1.75 ds/m, 35%, 1.3%, 2000 m, 43%, 10%, 32%, 250 mm and 15 °C, respectively. Our results highlight that environmental factors, such as soil texture, amount of soil lime, mean annual precipitation, altitude and land slope, had quantifiable effects on the performance of A. sieberi. Our findings could provide useful information for improvement, restoration and conservation programs. However, a further comprehension of the species–environment relationship is needed to predict the effects of climate change on the species habitat. [ABSTRACT FROM AUTHOR]

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Turnip (Brassica rapa var. rapa L.) (syn. B. campestris L. ssp. rapifera Sinsk) is an important crop species belonging to the Brassicaceae family. The 185 accessions belonging to this crop were collected from several areas of Toodshak region in Isfahan province, Iran, and their tubers were cultivated under homogeneous conditions in loamy clay soil. The morphological traits of different organs of those accessions were evaluated. Significant variations were detected among the accessions studied based on the traits recorded. Tuber shape showed high variation and included globose, oblong, ovate, obovate, and fusiform. Also, tuber skin color was highly variable, including white, bicolor white–violet, light violet, and dark violet. Tuber weight ranged from 1.56 to 35.70 g, while total soluble solids (TSS) of tuber flesh ranged from 7.00 to 11.80%. Principal component analysis (PCA) showed that 18 components were extracted by explaining 74.88% of total variance. The dendrogram obtained based on all the characters measured clustered the accessions into two major clusters. Sixteen accessions were placed into the first cluster, while the remaining accessions were placed into the second cluster which was divided into six subclusters. High level of morphological variabilities was observed among the accessions, which is applicable and useful for B. rapa var. rapa breeding programs. Based on the commercial and quality traits, 17 accessions could be selected for direct cultivation. Also, the promising accessions identified here can be utilized directly in breeding programs for genetic enhancement of this crop. [ABSTRACT FROM AUTHOR]

The potential of the soil to hold plant nutrients is governed by the cation-exchange capacity (CEC) of any soil. Estimating soil CEC aids in conventional soil management practices to replenish the soil solution that supports plant growth. In this study, a multiple model integration scheme supervised with a hybrid genetic algorithm-neural network (MM-GANN) was developed and employed to predict the accuracy of soil CEC in Tabriz plain, an arid region of Iran. The standalone models (i.e., artificial neural network (ANN) and extreme learning machine (ELM)) were implemented for incorporation into the MM-GANN. In addition, it was tested to enhance the prediction accuracy of the standalone models. The soil parameters such as clay, silt, pH, carbonate calcium equivalent (CCE), and soil organic matter (OM) were used as model inputs to predict soil CEC. With the use of several evaluation criteria, the results showed that the MM-GANN model involving the predictions of ELM and ANN models calibrated by considering all the soil parameters (e.g., Clay, OM, pH, silt, and CCE) as inputs provided superior soil CEC estimates with a Nash Sutcliffe Efficiency (NSE) = 0.87, Root Mean Square Error (RMSE) = 2.885, Mean Absolute Error (MAE) = 2.249, Mean Absolute Percentage Error (MAPE) = 12.072, and coefficient of determination (R2) = 0.884. The proposed MM-GANN model is a reliable intelligence-based approach for the assessment of soil quality parameters intended for sustainability and management prospects. [ABSTRACT FROM AUTHOR]

This study has been done to see the impact of phosphorus (P) on the concentration of cadmium (Cd) chemical fractions in two sorts of calcareous soils within the Fars province in Iran. Because of these interactions, we looked at the influence of phosphorus on cadmium fractions. Variables were three levels of Cd (0.0, 30.0 and 60.0 mg kg-1 of soil from CdSO4.8H2O), three levels of p (0.0, 50.0 and 100.0mg kg-1 of soil from Ca (H2PO4)2.H2O, three levels Incubation time (2, 4 and 8 weeks) and two sorts of soil (clay and sandy clay loam). The randomized completed block design (RCBD) was used for this research. After 2, 4 and 8 weeks of treatments, the sequential extraction procedure was done to determine cadmium concentration in WsEx (Water Soluble and Exchangeable), Sorb (EDTA extractable), MnOx (Manganese Oxides), Car (Carbonate), OM (Organic matter), AFeOx (Amorphous Iron Oxides), CFeOx (Crystaline Fe oxides) and Res (Residual) fractions. The results showed that 69.0 to 71.0% of the added Cd was removed within the WsEx, Sorb and MnOx fractions. Cadmium concentration in Sorb, OM and Res fraction was higher within clay soil while cadmium concentration within WsEx and Car fractions were higher within sandy clay loam soil. Adding P as monocalcium phosphate reduced cadmium concentration within WsEx and Sorb fractions while increased Car, OM and Res fractions. The presence of phosphorus reduces the concentration of Cd in those forms that are easily released into soil solution (WsEx and Sorb) from where they'll be absorbed by plants and thus decrease cadmium uptake by plants. [ABSTRACT FROM AUTHOR]

The widespread distributions of saline soils in Iran cause a range of problems for road construction projects due to insufficient shear strength, salt solubility potential and swelling. This paper conducts experimental tests using different cement contents and a sort of petrochemical waste with two curing methods to stabilise saline soil samples. Strength, compressibility and chemical tests were conducted, X-ray diffraction analyses were performed, and scanning electron microscope pictures were prepared for basic materials and stabilised saline soil samples in this paper. The results indicate that both petrochemical soda ash waste and cement enhance the shear strength of saline soil, especially after 28 days of curing. However, the combination is more appropriate from the swelling and salt solubility potential viewpoint. The optimum combination of 2% cement and 5% of petrochemical soda ash waste, cured by method 2 for 28 days, results in the most significant shear strength enhancement (127%). Furthermore, a swelling quantity of the optimum combination is reasonably restricted. X-ray diffraction test results and scanning electron microscope pictures demonstrated that despite the presence of ettringite agents, the formation quantity of these minerals is negligible. The salt is well stabilised, and its solubility potential dramatically decreases. [ABSTRACT FROM AUTHOR]

The Zagros forest region in western Iran is facing dieback processes, impacting both the environment and the local economy. Understanding the cause of forest dieback remains a challenge for forest experts due to the wide set of factors usually involved in the dieback phenomenon. To achieve this goal, we measured woody species dieback intensity (DI) using 124 plots distributed in oak forests across a wide range of environmental conditions. On these plots, we measured stand and vegetation factors (e.g. woody species richness, WSR), various soil properties and topographic indices (in particular the SAGA wetness index) and climatic factors. We then modeled dieback intensity using structural equation modeling (SEM) and machine learning (ML). We found a significant positive correlation between WSR and DI (r=0.48), and very low to low but still significant negative correlations with the SAGA wetness index (r=-0.10) and soil clay content (r=-0.16), respectively. Other soil properties and climate factors showed no significant influence on DI. After six rounds of respecification, the SEM fitting gave satisfactory results based on the validation map of DI indices (Goodness-of-fit Index = 0.948 and Comparative fit index =0.958). The DI map was generated using a random forest (RF) machine learning model to achieve an accuracy of 75% and a kappa index of 0.45, and then categorized into four classes. The map showed that the intensity of dieback was contrasting in our area: 41.1% of plots had no dieback, 58.4% had low DI, and less than 1% had moderate or high DI. We also found that soil clay content and woody species richness were crucial factors, explaining around 50% of the variance in DI. In conclusion, combining the methods from SEM and RF models provides an efficient approach to understand and identify key factors in the complex process of dieback. [Display omitted] • Structural equation modelling was used to identify the most influential drivers of dieback intensity (DI). • Woody species richness and soil clay were the most significant factors affecting DI. • Random Forest technique satisfactorily mapped DI in oak forests. • Combining SEM with machine learning techniques is a powerful approach to get further insights in the complex process of dieback. [ABSTRACT FROM AUTHOR]

• Using in-situ measurements, size fractionation from soil to sediment was investigated for numerous calcareous soils. • The 0.2 mm was suggested as the boundary between high and low erodible fractions of calcareous soils. • Size range of 0.063–0.2 mm was found as the most susceptible fraction to wind erosion. • Soil fraction of 0.063–0.1 mm intensified calcareous soil potential for suspension-size sediment generation. • Critical values of various soil PSD criteria for wind erosion rate of calcareous soils were suggested. Soil texture and soil surface aggregate size distribution (ASD) are key factors to study soil erodibility by wind and sediment size distribution (SSD) in arid and semi-arid areas. However, less research has studied the effect of soil fractions on soil erodibility and wind-blown sediment size of calcareous soils. In the present study, we focused on the size fractionation and particle size distribution (PSD) of 60 calcareous soil samples collected from 20 semi-arid and arid areas in Fars province, southern Iran. Extensive in-situ wind tunnel experiments were conducted under controlled high wind speed to measure wind erosion rate (WER) and SSD. The results showed that the calcareous soils had different erodibility based on their PSD. Generally, the most erodible soils to the wind force were those with less than 10 % of clay and higher frequency of the 0.1–0.2 mm size class. However, when the soil clay content exceeds 20 %, ASD got dominated with the fraction of 0.4–0.8 mm and WER of the calcareous soils got limited. Besides, size range of 0.063–0.2 mm was suggested as the most wind erodible fraction of the calcareous soils. Furthermore, the mean weight diameter (MWD) of sediment particles averagely reduced 1.3 times as compared to that of the soil samples and WER got inhibited for regions in which the difference of soil and sediment MWD exceeded 0.05 mm. The SSD was significantly controlled by soil PSD and suspension-size sediments < 0.1 mm (SSS) were negatively proportional to soil clay, MWD, geometric mean diameter of soil particles (GMD), dry stable aggregates > 0.25 mm (DSA), and organic carbon as logarithmic equations. Moreover, the presence of the size fractions > 0.2 mm restricted the potential of calcareous soils to generate SSS, which would be quite beneficial for wind erosion combat and dust control of calcareous soils. [ABSTRACT FROM AUTHOR]

The fifth season of archeological excavation of Konar Sandal Mound Hill in Jiroft (located in southeast of Iran) in 2006 was characterized by discovery of a clay monument on the wall of one of the architectural spaces there. With dimensions of 110 X 95 cm and 18cm thickness, the monument is regarded as the unique and oldest clay relief ever discovered (third millennium BC). On the one hand, historical and artistic values of the unique monument and its location in the site and environmental and human threats causing serious damages to it on the other hand, has made its documentation ever more necessary. The study of constituting materials and building techniques of the monument was done through macroscopic (field and visual study) and microscopic (optical and electron) methods as well as chemical analysis of elements and compounds on the clay foundation and its color layers (FT-IR, XRF, XRD, and SEM-EDS). The results suggest that the clay monument was built in two parts, namely the built-on torso and lower torso (skirt) which was carved out on a cob wall. Then, a delicate finish layer made of clay was put on the colored layer. The finish layer was made by using mineral pigments such as limonite (yellow) for covering the body (i.e. arms, chest and waist scarf), and Ochre hematite (red) and carbon (black) for ornament of embossed skirt. The used clay soil is of montmorillonite type which reacts, expands and contracts significantly due to humidity variation. [ABSTRACT FROM AUTHOR]

Rice grain yields can be affected by several parameters including mostly the climate, cultivars, soil types, and the fertilizer managements. In this study, the performance of two empirical models i.e. AquaCrop and artificial neural network models for simulating the grain yields of two most cultivated varieties including the Shirudi (high-yielding) and Tarom (low-yielding) in three contrasting soil series with different fertilizer managements, were calibrated and validated during 2016 and 2017 rice growing seasons for 459 paddy fields in Mazandaran province, northern Iran. Both models were tested by correlation (R²), normalized root mean square error (nRMSE) and coefficient of residual mass (CRM). Results indicate that the performance of both models were affected by the rice cultivar, soil type and soil fertilizer management for both calibration and validation datasets. The ability of both models proved to be satisfactorily applicable for spatial simulation of rice yields in northern Iran, but AquaCrop model was superior. The higher accuracy was observed in AquaCrop for the Shirudi cultivar (R²=0.89; nRMSE=5.87%; CRM=0.03) compared to the Tarom (R²=0.67; nRMSE=10.41% and CRM=0.04) for 2017 dataset demonstrating that the AquaCrop has more performance for high-yielding cultivar. Two models had lower accuracy in Esmaeilkola soil series with deep clay soil texture. The best accuracy was observed in paddy fields with optimum fertilizer managements for both models. Overall, it is possible to suggest that AquaCrop model could be used to simulate the spatial distribution of rice grain yield with an acceptable accuracy at province-scale and is applicable for local climate change related scenarios. [ABSTRACT FROM AUTHOR]

More has yet to be indicated on the adsorption and degradation processes, determining herbicides recycling in the environment. The sorption and degradation of 2, 4-D, affected by organic carbon (1.92–2.81%), soil clay (20–30%) and pH of the citrus orchards of Mazandaran province, Iran was investigated using HPLC equipped with UV detector for the identification and quantification of soil 2, 4-D. The adsorption (kd) and degradation (Kdeg) coefficients were determined using Freundlich and the first-degree kinetic equations. Gardens C (2.45 mL g−1), and B (0.3 mL g−1), with the highest (8.2 g day−1) and least (2.7 g day−1) degradation coefficients, had the highest and lowest Kd values. Kd variations with pH indicated higher adsorption of 2, 4-D in acidic pH. Due to the high presence of functional groups and soil biological activities, organic carbon affected the adsorption and degradation rates more effectively, which is of economic and environmental significance. [ABSTRACT FROM AUTHOR]

To assess the effect of long-term rice cultivation and aquic conditions on the physicochemical properties and different forms of iron and manganese and also to make a comparison with non-paddy and adjoining uncultivated soils in calcareous soils of southern Iran. The soil samples were taken from the paddy and non-paddy soils with similar parent materials and landforms. The results showed that in the paddy fields, the amounts of available (extracted by DTPA), total (extracted by nitric acid), and poorly crystalline iron and manganese oxides (extracted by ammonium oxalate) were higher than those in the non-paddy soils and show the highest amount in the surface horizons of paddy fields. In general, the paddy land use increases the iron and manganese oxides with poorly crystalline form, Feo/Fed and Mno/Mnd ratios by 1.84, 1.57, 2 and 3.2, respectively. It also reduces the amount of pedogenic iron and manganese oxides and their crystalline forms relative to the adjacent uncultivated soils. Finally, a significant positive relationship was found between the amounts of poorly crystalline iron and manganese oxides and total form and the amount of organic matter and clay in the soils under study. Also, by changing the land use from the non-paddy to paddy field, the amount of smectite increased and, in contrast, the amounts of illite and chlorite decreased. Therefore, it seems that the significant amount of organic matter introduced and their burial caused by the plowing operation and, on the other hand, their slow decomposition due to the inactivation of aerobic activities in the reduction conditions is among the factors affecting the variations of chemical properties in paddy soils and, generally, wet land soils. [ABSTRACT FROM AUTHOR]

Texture is one of the most important soil properties that knowledge of the spatial distribution is essential for land-use planning and other activities related to agriculture and environment protection. So, this study was performed to supply the soil texture spatial distribution using standardized spectral reflectance (ZPC1) index of Landsat 8 satellite images in the northwest of Iran. The soil sampling was performed using a random method in 145 points. Mineral soil particles including clay, silt, and sand were determined, and soil texture was calculated. In this study, Landsat 8 satellite images were used to interpolate the soil texture spatial distribution. In the first step, the principal component analysis (PCA) was obtained. Then, PCA1 was standardized using a z-score (ZPC1), and regression techniques were used to create proper relationships between ZPC1 and the primary soil particles. Then, spatial distribution of soil particles was used to create a spatially distributed map of the soil textural classes. The results showed that the standardization of the first component reduced the standard deviation of PCA1 from 23.6 to 10.8. The results of comparing ZPC1 with soil mineral components showed that with increasing the amounts of soil clay and sand, the ZPC1 value decreases and increases, respectively. The results showed that the ranges of the spatial distribution of clay and sand were similar to the laboratory-measured amounts. The results of texture class prediction using the soil texture triangle showed that the amount of similarity between the measured and predicted classes was 53.79%. [ABSTRACT FROM AUTHOR]

Understanding spatial variations of soil properties is necessary for the management of rangelands vegetation ecosystem. The present study aimed to assess the spatial variations of soil properties in the hillslope of the Taftan semi-active volcanic mountain, Sistan and Baluchestan Province, south-eastern Iran. The locations of 30 sampling points were determined using random - systematic method and soil samples were taken from two depths: 0–30 and 30–60 cm. Spatial distribution of soil properties and relationships between soil properties and covariates were investigated using Random forest method. Model validation was done through 10-fold cross-validation approach. Based on results elevation, channel network base level and vertical distance to channel network, were the most importance environmental variables in predicting of the some soil characteristics such as soil clay, silt, sand, SOC, and EC in two studied depths. The maps produced indicated higher clay at 30–60 depth in the higher elevations. EC amounts were increased in the lower parts of the mountain because of leaching. Furthermore, the highest map accuracy was related to EC map at both depths and clay at 30–60 depth. The prediction maps of other properties of soil had low accuracy. [ABSTRACT FROM AUTHOR]

Soil and desert varnish are powerful records capable of saving invaluable data regarding environmental factors and processes during their formation stages. The present research was carried out to identify the environmental variations and paleoclimate reconstruction in the central deserts of Iran using soil and varnish micromorphological characteristics. Mantled pediment, alluvial fan, and alluvial plain landforms were selected. A minimum of one representative pedon was described and sampled on each geomorphic surface, amounting to a total of eight pedons. Varnished rocks were further collected from all geomorphic surfaces and studied by petrography microscope. Clay (coatings and micro layers), calcite (nodules, coatings, quasicoatings, and infillings), anhydrite (nodules), halite (coatings) pedofeatures, clay coating-calcite infilling, and anhydrite nodule-clay coating compound pedofeatures were investigated in the thin sections of the soil. Lenticular, vermiform, and platy gypsum crystals were identified as nodules and interlocked plates. Desert varnishes (100-600 µm) were different from host rocks as far as color, texture, and formative components are concerned. According to micromorphological evidence, the area probably experienced two different climates. Coatings and infillings of clay in soils and rock crevices were developed in an environment with more available humidity. Evaporite minerals were formed in soils and clay coatings on rock surfaces in the following period with less available moisture. The study results showed that micromorphology could be a necessary and useful tool in pedology and paleopedology investigations. [ABSTRACT FROM AUTHOR]

The effects of specimen disturbance on determining of various soil properties are one of the most challenging issues in geotechnical engineering. Types of disturbance mechanisms were generated in consolidation test. One of the important parameters in computing of consolidation settlement is the compression index (Cc). So that the effects of disturbance in the soil specimen reduced the amount of this parameter and could have a significant effect on the settlement calculations. Main propose of this study is evaluation of disturbance effects on Cc with using shear wave velocity. Study area was Tabriz in located in the northwest of Iran with different silty and type of clayey soils such as yellow, green, and gray marls have a significant consolidation potential. In this research, three boreholes drilled and twenty intacy samples obtained. Also, Shear wave velocity in field and laboratory was determined respectively with performing down hole and bender element (in situ effective confining stress) tests. In continue, the quality of all specimens were evaluated by five recent methods. Then, the correlation between the common specimen evaluation methods new process based on shear wave velocity values with the calculation of statistical coefficients were computed. Results showed that, shear wave velocity values before and after consolidation with in situ effective stress could a new evaluation criterion provide for the definition of sample quality (Q). Also, the compression index as well as pre-consolidation pressure for disturbance effects were corrected by the estimation of the disturbance percent using shear wave velocity. [ABSTRACT FROM AUTHOR]

This study has been performed to determine the impact of zinc (Zn) on cadmium (Cd) fractions in two types of calcareous soils of the Fars province in Iran at the waterlogged condition. High-reduced conditions in soil reduce Cd solubility because of the development of Cd Sulfide. Cadmium and Zn have similar physical-chemical properties; they are maintained in soil's exchangeable sites as a divalent ion. Since such few studies have been conducted in calcareous soils of Iran, we examined the effect of Zn on Cd fractions due to their similar characteristics. Treatments were three levels of Cd (0, 30 and 60 mg kg−1 of soil as CdSO4.8H2O), three levels of Zn (0, 5 and 10 mg kg−1 of soil as ZnSO4.7 H2O), three levels of incubation times (2, 4 and 8 weeks), and two types of soils (clay and sandy clay loam). The randomized completed block design (RCBD) was used for this experiment. After 2, 4, and 8 weeks of treatments, the sequential extraction technique was used to determine the Cd concentration in (WsEx), (Fe-MnOx), (Car), (OM) and (Res.) fractions. The data indicated that based on the soil texture 64% to 70% of the Cd was extracted in the WsEx and Fe-MnOx fractions. The waterlogged condition decreased the Cd concentration in the WsEx fraction and increased the Fe-MnOx, Car and OM fractions. Cd concentration in Res. fraction was higher in the clay soil while WsEx, Car and OM fractions were higher in the sandy clay loam soil. Adding Zn as zinc sulfate reduced the concentration of Cd in Fe-MnOx, Car and OM fractions but had no significant effect on the WsEx and Res. fractions. It can be concluded that the change in the Cd concentration in its chemical fractions caused by Zn addition might be from the competitive transport and adsorption interaction between these two ions. The presence of Zn reduces the concentration of Cd in those forms that are easily released into the soil solution from where they can be absorbed by plants. Abbreviation: WsEx: Water Soluble and Exchangeable; Car: Carbonate; Fe-MnOx: Iron-Manganese Oxides; OM: Organic Matter; Res: Residual [ABSTRACT FROM AUTHOR]

Having knowledge about physical, chemical and mechanical properties of problematic soils is necessary when they are applied in construction projects as borrow materials or foundation, because these soils have potential to create large financial losses. This research deals with characterizing dispersive and swelling soils as problematic soils in southeast of Yazd (center of Iran) with aim of establishing a relationship between dispersivity and expansivity indices. In this regard, after performing a series of physical and chemical tests, the characteristics of the soil samples were determined, and their dispersivity degrees were specified by conducting chemical, pinhole and double hydrometer tests. Also, swelling rates of the soils were estimated using direct method (modified free swell index, MFSI) and indirect methods (different criteria developed for swelling assessment). The results showed that chemical parameters overestimate dispersivity of the soil samples (dispersive to semi-dispersive) in compared to pinhole and double hydrometer tests (slightly non-dispersive to moderately dispersive). Different expansivity degrees were defined using the direct and the indirect methods (ignorable to very high) for the soil samples. Among the empirical criteria used to evaluate the swelling potential, the AASHTO's criterion has the closest results to the MFSI in the both boreholes. Also, it revealed that as depth increases, the degree of soil dispersivity and expansivity decrease in response to the reduction of fine grain content in the samples. Finally, the correlations between dispersivity and expansivity indices, showed that sodium absorption ratio (SAR) can be used as a reasonable index to estimate soil swelling potential. [ABSTRACT FROM AUTHOR]

Lemon (Citrus limon), a species of the genus Citrus, is an economically significant crop and extensively cultivated in Iran, especially in Fars Province. Very little information is currently available on the changes in the different forms of soil potassium under the influence of lemon tree plantations or the associated mineralogical changes. The objective of this study was to investigate the status of different forms of K and the transformation of K-bearing minerals in the rhizosphere in lemon orchards of varying ages. Results demonstrated that the amounts of soluble, available, exchangeable, and nonexchangeable K in the control were higher than those in the lemon orchards of all the age range studied. The highest reduction in the different forms of soil K was measured for the 50-year-old orchard. The nonexchangeable K was significantly lower in the 20- and 50-year-old lemon orchards as compared with the control soil. Soil potassium concentration was observed to decrease with increasing soil depth. Our findings also indicated that vermiculitization of illitic clay minerals occurred due to both root potassium uptake and root activities in the rhizosphere of lemon trees. Shallower soil depths in the orchards were found to contain a higher illite content, while the vermiculite and interstratified I/S content increased with depth, except in the case of the 5-year-old orchard. Our findings also show that soils under lemon orchards of different ages exhibit differences in their K availability and, further, that vermiculitization might take place as a result of long-term cultivation despite the application of potassium fertilizers. [ABSTRACT FROM AUTHOR]

• Digital mapping of soil clay types was performed using easily accessible covariates. • Multiple linear regression and random forest algorithms were compared. • Random forest resulted in higher prediction performance. • Topography and soil properties mainly affected palygorskite and kaolinite variation. • Soil properties were considered responsible for the spatial distribution of illite. Understanding the abundance variability of clay minerals, as fundamental soil components, will help the users to improve land management and address concerns over climate change and soil fertility. Therefore, this investigation aimed to model the abundance and spatial distribution of clay types, including palygorskite, illite, and kaolinite, and identify the most significant variables affecting their variability using a digital soil mapping (DSM) approach in Darab district, southern Iran. Multiple Linear Regression (MLR) and Random Forest (RF) techniques were applied to link clay types and environmental attributes that were obtained from a Landsat-8 operational land imager (OLI) and digital elevation model (DEM). A ten-fold cross-validation approach was applied to calibrate and validate the models, and 50 bootstrap models were used to quantify the prediction uncertainty. The models accuracy was defined by the coefficient of determination (R2), root mean square error (RMSE), and the ratio of performance to the interquartile range (RPIQ). Findings denoted that the RF model better predicts the abundance and variability of clay minerals in the study area (R2 = 0.56, 0.47, and 0.48, RMSE = 5.3, 1.91 and 0.63 % and RPIQ = 2.82, 3.28 and 2.62 for palygorskite, illite and kaolinite, respectively). Based on the feature selection analysis, topographic covariates and soil properties determined palygorskite and kaolinite content variations, while for illite, only soil properties could explain the spatial distribution. Besides, the RF produced a lower uncertainty for palygorskite compared to the other clay types. The present research can provide new insight into the spatial variability of clay minerals in arid and semi-arid regions of Iran that could be extended to other similar environments. Moreover, the results showed that the easily available environmental variables could provide reliable predictions. However, other environmental covariates, such as XRF analysis, Vis-NIR, and MIR spectroscopy, are also recommended as input variables for further studies. [ABSTRACT FROM AUTHOR]

Pressuremeter Test (PMT) and shear wave velocity (Vs) are two important in-situ tests for determining soil deformation characteristics in different strain levels. The PMT is an expensive and time-consuming test that can measure pressuremeter modulus (E PMT) of soil and rock. The Vs is a low-cost test for determining soil deformation through the seismic method. So finding the relationship between PMT and Vs can be useful and cost-saving for cross-checking the parameters obtained by these two methods. In this study, 94 PMT and Vs tests were carried out on silty clay and clay soil from 3 sites in Iran, and the relationship between E PMT and Vs was investigated using regression analysis. Finally, the best statistical model for relationships was proposed according to the highest value of adjusted R2 and Fisher coefficient (F) and a minimum value of significance (Sig.). The results showed that there is a direct relationship between E PMT , Vs, and N 60 with depth then the soils with higher relative density are at the deeper layers. On the other hand, there is a linear significant relationship between E PMT and Vs for each site with R2 > 0.79. When the data for all three sites are considered together, R2 decreased to 0.62 but the overall trend of the data is similar. Due to the similarity of the soil of the three sites in terms of classification, minor differences in plasticity index and water content ranges in the three sites can be a reason to reduce the R2. The comparison between estimated E PMT based on proposed equations in the present study and measured E PMT shows that the normalized consistency ratio is generally close to zero (−0.09 < CR < 0.06) so the equations are valid and reliable. A comparison of the results of the present and a previous study showed that the change rates of E PMT and V S were similar so that the CR values are generally close to zero (−0.09 < CR < 0.09). The minor difference between the E PMT and Vs in each site in the present study and the previous research is due to the soil type and plasticity specifications. • PMT and V S are in-situ tests for determining soil stiffness in different strain levels. • There is a direct relationship between E PMT , Vs, and N 60 with depth. • There is a linear relationship between E PMT and Vs for silty clay soil. • The relationship between E PMT and Vs depends on the plasticity index. [ABSTRACT FROM AUTHOR]

We explore changes in magnetic susceptibility (χ lf), and various forms of Fe and ferrimagnetic minerals after incubation by crude oil in four different textural soils. Four soil classes: clay, sandy, silt loam and sandy loam, were collected in central Iran and incubated with 0, 2.5, 5.0, 7.5 and 10% w /w of crude oil at 80% moisture of field capacity for 1, 3 and 6 months. After each period of incubation, various forms of Fe using extraction techniques, χ lf and total petroleum hydrocarbon (TPH) were measured. In addition selected samples from the four soil types were analyzed by XRD for characterization of ferrimagnetic minerals. The results showed that all forms of iron and magnetic susceptibility increased significantly with increasing concentration of crude oil and incubation time. The highest dithionite extractable iron (Fe d), χ lf , as well as the ratio of Fe d to oxalate extractable iron (Fe o) were obtained for 10% w /w crude oil after 6 months incubation due to formation of ferrimagnetic minerals. The increase in the concertation of ferrimagnetic minerals (magnetite/maghemite) was verified by XRD. Significant positive correlations were obtained among χ lf , Fe d and TPH after 6 months of incubation. The results from this study confirm that magnetic methods can be used as a quick and cost-effective means for evaluation of TPH in polluted soils during the remediation, as compared to the chemical analyses. • χ lf and ferrimagnetic minerals following incubation with crude oil were studied. • Forms of iron showed significant difference among applied treatments. • Magnetic properties of the soil enhanced with increasing crude oil pollution. • Magnetite/maghemite were increased by pollution and incubation time. • Intensity of the peaks with χ lf in four soils showed high positive relationships. [ABSTRACT FROM AUTHOR]

Electro-osmosis is a phenomenon describing the motion of liquid adjacent to a charged surface under the influence of an electric field. Electro-osmosis is considered as an efficient soft soil improvement technique. In this study, series of laboratory tests were performed utilizing graphite and stainless steel electrodes under three levels of voltage gradients for 28 days using the soil from north of Iran to investigate the effect of various parameters on electro-osmotic and geotechnical properties. Moreover, the microstructure and chemical analyses of the soil before and after treatment gave an in-depth perspective to underlying mechanism of this process. Water drainage which has the most important effect on consolidation of soils, terminated after a few days. The termination time for stainless steel is smaller than graphite and the whole drained water volume is larger in case of stainless steel compared to graphite. The strength around the anode is larger than that of the cathode zone and the stainless steel electrode induced larger strength than the graphite electrode. The SEM images exhibited the agglomeration of the soil after electro-osmosis treatment, and some precipitation was also identified, which was attributed to iron based compounds. Chemical analysis illustrated that the concentration of calcium ions decreased around the anode and increased near the cathode while Fe and Al amount did not change significantly, implying the ion exchange and ion migration due to the electro-osmosis process. Additionally, the stainless steel electrode introduced iron and chrome ions to the soil, which affected structure and chemical distribution of the ions. • Electro-osmosis changed the microstructure of the soil and decreased the void volume of the soil. • The Calcium and Magnesium ions were substituted by iron and Aluminum ions and migrated through the soil. • The geotechnical properties of plastic soil improved. • The stainless steel electrode had better performance compared to graphite electrode. [ABSTRACT FROM AUTHOR]

• Invasion of the test soil clogged the space between the inner and outer pipes of the Hydroluis drainpipe in two weeks. • High flow velocity at the soil-envelope interface and low retention capacity caused poor function of the Hydroluis. • Based on Stokes' Law, the design of Hydroluis drainpipe is unsuitable for filtering fine silt particles (0.002 < D < 0.02 mm). • PP450 drainpipe showed good hydraulic and filter functions under the same laboratory conditions. Subsurface drains, when installed in non-cohesive soil, are typically covered with an envelope to tackle problems of clogging and siltation. Selecting a suitable envelope material, however, is complicated and depends primarily on soil characteristics in the area where the drains are to be installed. A new promising drainpipe-envelope concept, Hydroluis, has been developed which the designers claim works in a wide range of soils. The Hydroluis drainpipe consists of a corrugated inner pipe with three rows of perforations at the top and an unperforated outer pipe that covers the top two thirds of the inner pipe. We analysed the hydraulic and filter functions of this new drainpipe in a soil tank laboratory model with a saline-sodic problem soil from south-western Iran and compared Hydroluis performance with that of a locally-manufactured synthetic envelope material (PP450). The silty clay soil used in this study was 40 % clay, with a plasticity index (I P) of 16.9 and an exchangeable sodium percentage (ESP) of 60.4 %. The Hydroluis drainpipe clogged during the first two weeks of the test due to invasion of the test soil into the space between the inner and outer pipes. Of the substantial volume of sediment that entered the Hydroluis inner pipe, 38 % removed from the pipe in the first day. In contrast, the PP450 drainpipe showed good hydraulic and filter functions, entering very little sediment to drainpipe during the entire test period and stabilizing at drainage rate of 28 mm/day and entrance resistance of 55 days/m, at around day 50. Our analyses suggest that the clogging and poor drainage function of the Hydroluis drainpipe was caused by the higher flow velocity (21.5 times higher) at the soil-envelope interface of the drainpipe, in addition to the lower Hydroluis drainpipe's soil retention capacity (18 times lower) compared to the PP450 drainpipe. Assuming Stokes' Law governs filter function, the results of Hydroluis design evaluation also suggest that in stable soils, very fine sand or coarser soil particles (D > 0.05 mm) place no serious limitations for Hydroluis drainpipe application, whereas the current design is unsuitable for filtering fine silt particles (0.002 < D < 0.02 mm). In conclusion, we suppose the Hydroluis drainpipe does not perform well in silty saline-sodic soils, such as those found in south-western Khuzestan Province, Iran. [ABSTRACT FROM AUTHOR]

• Adhesion and clogging tendency of clay-rich soil and rocks were investigated using different test methods. • Correlation of normal adhesion to cohesion and tangential adhesion in various IC were investigated. • It was found that clayey material may encountered on the Tabriz subway lines have medium to high clogging risk. Clogging phenomenon is defined as the excessive adhesion of clayey particles to drilling equipment that adversely affect machine efficiency. This study involves the clogging potential of clayey soil and rock samples collected from Tabriz subway lines that were tested by laboratory experiments. In order to achieve the objectives of this study, a series of analyses were carried out including sieve analysis, hydrometer, Atterberg limit, slake durability, direct shear, modified direct shear test on the soil/steel interface, and piston pullout apparatus. According to USCS, the studied samples are classified as CL and CH. The clay minerals of the samples are mainly montmorillonite and illite. According to the exist diagrams and classifications based on Atterberg limits, consistency index and adhesion stress, samples are classified as medium to high risk for clogging. The maximum clogging occurrence is possible in the moisture content between 20 and 52% (IC < 0.75). The results proved that water content is a key parameter in adhesion stress variation and clogging behavior of clayey materials. The results of the direct shear test on clay/clay and clay/steel interface indicate that with increasing water content, the cohesion of soil decreases and tangential adhesion to the steel surface tends to increase. Based on piston pullout test, the normal adhesion stress of samples increased to a peak value at IC = 0.65 to 0.75. The results obtained in this study indicate a moderate to high risk of clogging in the mechanized excavation of subway lines in the study area while encountering clayey layers. [ABSTRACT FROM AUTHOR]

• Persian gum as a new source of carbohydrate polymer was used to improve soil. • Persian gum has acceptable strength results in comparison to xanthan and guar gums. • Strength achievement of Persian gum treated soil by moisture loss is considerable. • Persian gum is useful for permeability reduction due to its pore filling property. • High thermal stability for Persian gum treated soil was observed. Persian gum as a newly introduced source of carbohydrate polymers obtained from the trunk and branches of wild almond trees of Zagros forests in Iran, has found wide applications in food and pharmaceutical industry owing to its unique structure. However, its behavior in soil environment is still unknown. This paper proposes application of Persian gum to stabilization process of a low plasticity clayey soil. A series of macro and micro scale tests including unconfined compression strength, direct shear test, scanning electron microscopy imaging, Stereo zoom microscopy, Brunauer, Emmett and Teller tests, thermal gravimetric analysis and Particle size analysis were conducted on soil stabilized with different amounts of Persian gum. All defined tests were also conducted on previously studied soil additives, xanthan and guar gums. The results confirm the successful performance of Persian gum in binding soil particles, pore filling, thermal stability, soil fluctuation and formation of large particles in comparison to common hydrocolloids. [ABSTRACT FROM AUTHOR]

Nickel bearing soils derived from serpentinized ultramafic rocks are widely exposed as two parallel zones in Bavanat region along the Sedimentary Zagros Orogenic (SZO) and Metamorphic Sanandaj-Sirjan (MSS) belts. These laterites in the Mazayejan area of the Northern zone are divided into two groups; the in situ soils found mainly in the east, and the transported soils which are common in the west of the study area. The maximum Ni concentration of the studied soils is 1787 μg g−1. The main vegetation types of the area include open shrub lands and semi-desert steppes. Many soil characteristics in the study area are quite variable, such as Mg/Ca ratio, exchangeable metal fraction, extraction efficiency (EF), pH, organic content (OM), texture, and cation exchange capacity (CEC) as well as seasonal variation of Ni availability and metal transfer to plants. This study indicated that low Mg/Ca ratio (0.1–2.3 μg g−1), high carbonate content (up to 42.8 wt%) and very low exchangeable Ni fraction (0.01–0.34 μg g−1) result in low uptake of nickel by plants. Low EF, but high pH and OM result in Ni fixation in the soils, and consequently low Ni transfer factor to plants. Clay textured soils with high CEC (10.5 wt%) are characterized by the lowest transfer coefficient of Ni from soil to plant, due to the stronger adsorption of Ni in the soils. Ni concentration in living tissues change with the season, the leaves of the same plants investigated in autumn contain more Ni than in spring. As a result, plant sampling in autumn should be preferred for nickel exploration when using biogeochemical and other methods such as Ni phytoextraction, by selected plants. Unlabelled Image • Laterites in Bavanat are divided into in situ and transported Ni-bearing soils. • Soil properties and sampling seasons affect Ni availability and transfer to plants. • Low Mg/Ca ratio, EF and exchangeable Ni fraction result in low uptake of nickel by plants. • High pH, CEC, OM values and clay texture lead to low transfer coefficient of Ni to plants. • Plant sampling in autumn is preferred in mineral exploration. [ABSTRACT FROM AUTHOR]

This study investigates the correlation between shear wave velocity ( V S ) and standard penetration test blow counts (SPT-N value) in all soil types, gravelly soil, sandy soil and clayey soil for Mashhad city in the north eastern region of Iran. The V S data used were measured through downhole method in 84 construction projects (in 88 boreholes). From among collected data, 424 pairs of V S -SPT recorded in one depth were used for regression analysis. The obtained results showed that the N-value had a critical role in estimating V S and soil type was less effective in this regard. These findings are in line with the findings of the previous studies. Regression equations obtained in this study were compared with correlations from previous studies. There was a relative similarity between the previously published and the new regression equations for Iranian soils. Although almost all correlations follow a similar trend, there are significant differences between new equations and correlations reported for other countries. The regression coefficients of the new equations show the acceptable capability of the suggested correlations in estimating V S through SPT-N value. Therefore, these equations can be used to estimate V S for the soils of the current study area and for other similar areas. Moreover, V S 30 was used for site classification of the study area as per National Earthquake Hazard Reduction Program (NEHRP) guidelines and it was shown that a major portion of the city comes under site class C and other locations are categorised as site class D. [ABSTRACT FROM AUTHOR]