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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]

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]

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]

• 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]

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 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]

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]

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]

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]

• 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]

A field experiment was carried out on the silty clay soil of Lack-Lack agricultural research field during two years to select the most suitable fertilization method (fertilizer broadcasting, fertilizer pouring in the furrow, fertilizer banding placement in one side and both sides of seedling) and application rate (30, 60 and 90 kg of net nitrogen from source of urea fertilizer/ha) on corn yield and yield components in Hamedan province in Iran. Corn yield components evaluated were plant height, corn height, percentage of corncob, thousand-kernel mass and net yield. A factorial experiment with 12 treatments (four methods x three levels) was replicated three times in 36 test plots. By analysis of variance and comparison of treatment means using DMRT (Duncan's new Multiple Range Test), application methods had no significant effect on plant height, corn height and percentage of corncob, but net yield and thousand-kernel mass were highly influenced. In addition, effect of fertilizer application rate on plant height, corn height, and percentage of corncob was not significant but was highly significant on net yield and thousand-kernel mass. Interactional effects of method x level on plant height, corn height, percentage of corncob and thousand-kernel mass were not significant but their effects on net yield were very significant. In this study, fertilizer banding on one side of seedling with 60 kg of nitrogen/ha applied 10 cm from the seedling at 5 cm soil depth was selected as the most suitable treatment. [ABSTRACT FROM AUTHOR]

This paper presents the results of geotechnical and mineralogical investigations on lime treated clay soils from Hamedan City, Iran, and effects of pH variations on their shear strength parameters. Initially, lime was added in different percentages and laboratory experiments were conducted after curing times. The results indicate that these soils can be stabilized satisfactorily with the addition of about 7 % lime. Also, investigation of the relationship between lime-treated geotechnical properties and lime percentage and curing time demonstrates high regression coefficients for the proposed relationships. Several laboratory tests were performed on treated and untreated clay soils with lime mixed with pore fluids with different pH values including 3, 5, 7 and 9. The results of shear strength tests indicated that the undrained shear strength parameters for untreated clays increased considerably if the pore fluid had a high pH (pH = 9) or a low pH (pH = 3). It can also be found that for lime-treated soils, maximum cohesion and friction angle values are achieved at pH = 9. [ABSTRACT FROM AUTHOR]

In order to determine the role of topography and drainage condition on soil genesis, a micromorphological study was carried out along a catena in Kohgilouye Province, southwestern Iran. The catena in this study crosses the main physiographical units such as alluvial and colluvial fans, piedmont plain, plateau, river alluvial plain, and lowland. Seven representative soil profiles were described and studied accurately. Thin section observations, scanning electron microscope (SEM), and digital microscope studies were used in this study. The major contributing soil processes can be categorized as calcium carbonate leaching, clay eluviation, and formation of Fe-Mn oxides. Calcite depletion pedofeatures were the most striking aspect of the soil thin sections studied. In pedons that were located on more stable physiographic unit, a higher frequency of micritic calcite nodules was observed. The presence of needle-shaped calcite in aquic and non-aquic conditions throughout the soil profile suggests an appropriate broad range of pedoenvironmental conditions for the formation and stability of this mineral habit. The magnitude of calcite nodules that were impregnated with Fe-Mn oxides was higher in soils formed on more stable geomorphic units. Adjacent formation of needle-shaped calcite and cytomorphic calcite in some horizons may suggest the biogenic source of this mineral. In most thin sections of argillic horizons, clay films were cleared after a mild HCl treatment, suggesting masking of the clay coating by carbonates. [ABSTRACT FROM AUTHOR]

Highlights: [•] Essential oil yield and composition of 21 wild populations of myrtle collected from natural habitats were investigated. [•] Two chemotypes determined for Iranian myrtle populations, including high α-pinene/1,8-cineole, and high limonene/low α-pinene groups. [•] The analyses indicated that populations collected from higher altitudes with loamy and clay soils, had higher amounts of α-pinene and 1,8-cineole, while the populations collected from sandy soils are rich in organic matter that possessed higher contents of limonene. [Copyright &y& Elsevier]

Abstract: In order to contribute to the understanding of carbonate enrichment and clay illuviation in loess-derived soils of subhumid to humid regions, the development of soils was studied along a climate gradient with xeric and udic soil moisture regimes (SMR) and thermic and mesic soil temperature regimes (STR), respectively, in the Golestan Province, Northeastern Iran. Six representative pedons along a climate gradient were investigated. Soils were classified mainly as Hapludalfs and Haploxeralfs. Stability of the geomorphic surface under forest vegetation associated with high leaching conditions has provided appropriate conditions for decalcification followed by clay migration through the profile and formation of argillic horizons in all the studied soils. Clay content of the Bt horizons, soil organic carbon concentration of the A horizons, and depth of the Bk horizons increased significantly with increasing precipitation and decreasing temperature. There was a considerable decrease in silt content with soil development. The main pedofeatures observed in the Bt horizons were clay coatings and decalcified zones. Nodules, coatings and hypocoatings were the main calcitic pedofeatures observed in the Bk horizons. Occurrence and preservation of clay coatings were more pronounced in the udic regions with illite and vermiculite as the dominant clay minerals. Type of clay minerals, shrink/swell properties, and precipitation rate are factors affecting the abundance and preservation of clay coatings. In the strongly developed horizons of the udic SMR, the occurrence of vermiculite clay minerals could reduce the shrink/swell potential and increase the amount of clay coatings. The presence of crystallitic b-fabrics and the high carbonate contents (CaCO3) in the lower horizons (Bk) were mainly related to decalcification processes under descending water flow in the overlying horizons. [Copyright &y& Elsevier]

Abstract: In this study, the influence of cyclic wetting and drying on swelling behavior of polymer-stabilized expansive clays has been investigated. Such a study is required to assess the long-term behavior of these soils in geotechnical applications. Three expansive soils with different plasticity indexes were obtained from a region around Tehran (capital of Iran). These soils were stabilized by different amounts of two polymers, Urea Formaldehyde and Melamine Formaldehyde. The swelling tests have shown that these polymers decreased the swelling potential of the expansive soils. Cyclic swelling and shrinkage potential and cyclic swelling pressure tests were performed on both treated and un-treated expansive clays. In addition, to simulate partial shrinkage, specimens were dried to their initial water contents in each cycle. Variations in grain size distributions and Atterberg limits of both treated and un-treated expansive soils due to cycles of wetting and drying were assessed. The microfabric changes were also studied by scanning electron microscopy (SEM). The results showed that the suppression of swelling in polymer-stabilized specimens was not lost after the first cycle and the swelling potential and pressure of treated specimens were less than those of un-treated specimens during the cyclic wetting and drying; nevertheless, in cyclic swelling and shrinkage, the swelling potential and pressure of all specimens started decreasing after the first cycle. All of the specimens reached equilibrium after the fourth cycle. [ABSTRACT FROM AUTHOR]

There are different approaches to define the soil available water (SAW) for plants. The objectives of this study are to evaluate the SAW values of 12 arable soils from Hamadan province (western Iran) calculated by plant available water (PAW), least limiting water range (LLWR) and integral water capacity (IWC) approaches and to explore their relations with Dexter’s index of soil physical quality (i.e., S-value). Soil water retention and mechanical resistance were determined on the intact samples which were taken from the 5–10 cm layer. For calculation of LLWR and IWC, the van Genuchten-Mualem model was fitted to the observed soil water retention data. Two matric suctions ( h) of 100 and 330 cm were used for the field capacity (FC). There were significant differences ( P < 0.01) between the SAW values calculated by PAW, PAW, LLWR, LLWR and IWC. The highest (i.e., 0.210 cm cm) and the lowest (i.e., 0.129 cm cm) means of SAW were calculated for the IWC and LLWR, respectively. The upper limit of LLWR for all of the soils was h of 330 cm, and that of LLWR (except for one soil that was air-filled porosity of 0.1 cm cm) was h of 100 cm. The lower limit of LLWR and LLWR for five soils was h of 15,000 cm and for seven soils was mechanical resistance of 2 MPa. The IWC values were smaller than those of LLWR for two soils, equal to those of LLWR for three soils and greater than those of LLWR for the rest. There is, therefore, a tendency to predict more SAW using the IWC approach than with the LLWR approach. This is due to the chosen critical soil limits and gradual changes of soil limitations vs. water content in the IWC calculation procedure. Significant relationships of SAW with bulk density or relative bulk density were found but not with the clay and organic matter contents. Linear relations between IWC and LLWR or LLWR were found as: IWC = −0.0514 + 1.4438LLWR, R = 0.83; and IWC = −0.0405 + 2.0465LLWR, R = 0.84, respectively (both significant at P < 0.01). Significant relationships were obtained between the SAW values and S indicating the suitability of the index S to explain the availability of soil water for plants even when complicated approaches like IWC are considered. Overall, the results demonstrate the importance of the choice of the approach to be used and its critical limits in the estimation of the soil available water to plants. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the heavily fertilized soils of northern Iran for their phosphorus (P) fractions and sorption properties for assessing their P availability status in order to minimize P applications and to reduce the danger of P loss to water sources. Different P fractions, namely, total, organic, inorganic, water extractable, and NH4-lactate extractable P varied widely among the studied soils, indicating a wide variability of P supplying capacity of these soils. High values of degree of phosphorus saturation were observed in soils with low amounts of organic carbon (C) and may indicate high P susceptibility to surface runoff and leaching. The maximum P buffering capacity (MPBC) and adsorption isotherm of P were highest in the sandy clay soil from Jamaleddinkola, which also contained high amounts of iron (Fe), aluminium (Al) and clay particles, and lowest in sandy soil from Deseleh, which contained very high initial NH4-lactate extractable P and the lowest content of Fe, Al, silt and clay among all the studied soils. The results suggest the importance of accounting for soil properties (especially soil texture and organic matter) along with soil P adsorption capacity when assessing the efficiency of applied P, P accumulation in soils and subsequently P nutrient management. [ABSTRACT FROM AUTHOR]

It is a current practice to employ composite clay—a mixture of clay and aggregates that float within the clayey matrix—as the core of embankment dams that have classically been constructed from pure clays. Experience has shown that significant pore pressures could build up during cyclic undrained loading in composite clays. This may threaten dam stability during earthquake loading. However, it is difficult to attribute a single value to excess pore pressure in conventional seismic stability analysis because of the random nature of earthquake loading, leading to uncertainty in the evaluation of factor of safety against sliding. This article evaluates the importance of pore pressure build-up in composite clays on the seismic behavior of Karkheh embankment dam in Iran and then documents a quantitative scheme using fuzzy set analysis to evaluate the failure potential of the dam. [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]