جستجوی مقالات مرتبط با کلیدواژه « Clay mineralogy » در نشریات گروه « آب و خاک »

 Soil classification is the systematic categorization of soils based on distinguishing soil characteristics, aiding in the comprehension of soil properties through soil surveys, and establishing suitable strategies for effective soil utilization and management. One of the main reasons for creating soil classification systems is to identify the differences in important soil characteristics for management purposes. Globally, Soil Taxonomy (ST) and the World Reference Base for soil resources (WRB) are widely used for soil classification. However, these two classification systems have varying criteria which can pose difficulties when exchanging classification results. After years of intensive worldwide testing and data collection, new versions of the ST and WRB systems have been released. In its current state, ST has a strong hierarchy with six categorical levels: order, suborder, great group, subgroup, family, and series (Soil Survey Staff, 2022), while the WRB has a flat hierarchy with only two categorical levels: reference soil groups and soil units (IUSS Working Group WRB, 2022). Several scientists have endeavored to evaluate the merits and demerits of these soil classification systems and offer recommendations for their enhancement. The arid and semi-arid regions located in the western and southwestern parts of Kohgiluyeh and Boyerahmad Province, distinguished by their considerable diversity in parent materials, topography, climate, and land use, present an excellent opportunity for scrutinizing and contrasting the effectiveness of soil classification systems. Remarkably, no prior research has delved into this subject in this specific geographical area. Consequently, this research aims to compare the effectiveness of the ST and WRB systems in characterizing soil attributes. Furthermore, it seeks to analyze the alterations that these two systems have undergone during an eight-year period, spanning from 2014 to 2022.

This study was conducted in the western and southwestern regions of Kohgiluyeh and Boyerahmad Province, specifically in the divisions of Gachsaran, Basht, Choram and Kohgiluyeh. A total of 26 soil profiles were excavated, described, and sampled based on aerial photos, satellite images, topographical and geological maps, as well as field observations. These profiles were selected following the soil description guide provided by the Department of Soil Conservation of the US Department of Agriculture. Subsequently, after reviewing the preliminary results and aligning with the research objectives, 12 representative soil profiles were chosen for further analysis. Soil samples were collected from all genetic horizons and transferred to the laboratory. After air-drying, the samples were passed through a two-millimeter sieve and the routine physical and chemical analyses were conducted, including soil texture, pH, electrical conductivity (EC), calcium carbonate equivalent (CCE), organic carbon, cation exchange capacity (CEC), and gypsum analyses. For mineralogical studies, soil clay minerals were separated and identified using standard methods. Additionally, soil thin sections were prepared from intact soil samples of selected soil horizons and examined under a polarizing microscope. Finally, the soil profiles were classified based on the criteria outlined in Soil Taxonomy (2022) and WRB (2022).

Soil Taxonomy and WRB, as the two most popular classification systems, aim to encompass as manysoil characteristics as possible. According to the ST classification, the soils were classified into four orders: Entisols, Inceptisols, Alfisols, and Mollisols. In the WRB system, they were grouped into seven reference soil groups: Regosols, Flovisols, Luvisols, Cambisols, Kastanosems, Gypsysols and Glysols. The results revealed that WRB was significantly more effective in describing the characteristics of the studied soils. One of the key advantages of this two-level system is its flexibility, allowing for the inclusion of additional principal and supplementary qualifiers to cover all essential soil characteristics. Moreover, in many cases, WRB exhibits better prioritization compared to ST. For example, the presence of gypsic, combic, calcic horizons, as well as fluvic and gley properties, can allocate the soil to the reference groups of Gypsisols, Cambisols, Calsisols, Fluvisols, and Gleysols, respectively. However, a limitation of the WRB system is the absence of mineralogical information in soil classification. Enhancing this classification system's quality and making it more appealing to planners could be achieved by incorporating suitable mineralogical attributes for the reference groups or criteria that express soil fertility conditions with relatively straightforward measurements. In addition, it is proposed to add three subgroups to ST: Gypsic Haplustalfs, Fluventic Gypsiustepts and Cambic Haplustolls. Similarly, following the WRB model, it is recommended to introduce a qualifier in ST to indicate the presence of lithological discontinuity. Regarding the WRB system, suggestions include adding qualifiers such as "Cutanic" to gypsisols with clay films, "hypercalcic" to reference groups of Kastanozems and Luvisols with a calcic horizon comprising more than 50% of calcium carbonate, and "aridic" for better expression of soil characteristics with Aridic-Ustic moisture regimes.

The results of this research demonstrated that WRB is more effective in describing the conditions and characteristics of the studied soils. The WRB system, through its diverse set of qualifiers, is capable of representing field conditions more efficiently. However, it is suggested that the surveyors have the freedom to select an appropriate qualifier from the list provided by WRB without limitation, which can enhance its success in practical applications. Furthermore, it is recommended that both classification systems be used to categorize soils, not only to evaluate their efficiency for the soils in other regions but also to gain a comprehensive understanding of their suitability for different contexts.

Climate and topography are two important soil-forming factors that affect the genesis, evolution, and classification of soils. Topography may influence soil evolution through attributes such as the direction, shape, and percentage of the slope, the amount of precipitation, penetration, and runoff, the rate of erosion, as well as the difference in the drainage conditions. On the other hand, organic carbon, the amount and type of clay, soil color, calcium carbonate, base saturation, leaching depth, and solubility of salts in the soil are closely related to the climate. Hence, this study aimed to investigate the effect of climate and topography on changing physicochemical, mineralogical, and micromorphological properties of soil.

This research focused on two regions including, Sardooeyeh and Bam. The Sardooeyeh region, with the soil moisture-temperature regime of xeric-mesic, is about 3500m above sea level. However, the mean elevation in the Bam region, with the aridic-thermic regime, is 900m. Eight representative pedons on the extrusive igneous parent material with an intermediate composition were selected, sampled, and described. Physicochemical, mineralogical, and micromorphological analyses performed on the soil samples, and the soils were classified using Soil Taxonomy and World Reference Base for Soil Resources (WRB). Soil pH, particle size distribution, electrical conductivity, equivalent calcium carbonate, cation exchangeable capacity, and gypsum were measured, then eight samples were selected for clay mineralogy investigations. A Bruker Dh8 Advance X-ray diffractometer at 30 mA and 40 kW was used to analyze the samples. Scanning electron microscopy was performed. The undisturbed soil samples from horizons were selected for micromorphological observations.

The results revealed the increase in the clay percentage, cation-exchange capacity, organic carbon, and equivalent calcium carbonate in the elevations with the xeric regime. On the other hand, an increase in the amount of electrical conductivity and gypsum percentage in the aridic regime was determined. Thus, changes in soil properties caused different soils, including a range of Mollisols and Alfisols (xeric regime) to Aridisols (aridic regime) in the Soil Taxonomy and the Chernozems, Luvisols, and Calcisols (xeric regime) to Solonchaks, Gypsisols and Cambisols (aridic regime) in the WRB system to be classified. One of the strengths of the WRB system compared to the Soil Taxonomy is the classification of buried soils and the use of the "Raptic" qualifier to indicate the lithologic discontinuity within the pedon. The results of clay mineralogy elucidate the presence of illite, palygorskite, chlorite, smectite, kaolinite, vermiculite, smectite-vermiculite interstratified minerals, and quartz. In the xeric regime, the illite mineral decreased, and vermiculite and smectite increased. However, the amount of illite increased in the aridic climate. Furthermore, the simultaneous presence of palygorskite and smectite-vermiculite interstratified minerals can be the result of the presence of polygenetic soils in this region. Calcite infilling, nodule, and calcite internal hypo-coating, with clay coatings, clay bridges, and link clay capping were among the dominant micromorphological pedofeatures observed in the xeric moisture. On the other hand, the simultaneous presence of calcite and clay coatings and infillings together with gypsum infillings and the interlocked gypsum plates prove the role of paleoclimate in soil formation.

Results of this study showed that the current climate, the paleoclimate prevailing in the region, and topography have key roles on the intensity of weathering, the amount of clay minerals, and the type of pedofeatures in the region. Besides, due to the lack of carbonate in the parent material, it seems that the increase of weathering in the xeric regime part of the area significantly influenced on the alteration of plagioclase mineral which in turn, increased secondary calcium carbonate.

Accurate knowledge of soils and their classification plays a decisive role in the application of various management systems. The purpose of this study is to summarize some of the results of studies in the form of dissertations and articles extracted from them on the factors and processes of soil formation in different climates of Iran during the two last decades performed in different climates of the country in the Department of Soil Science and Engineering, University of Tehran. Variety of soil-forming factors including climate, parent materials, topography, vegetation, and time have led to the emergence of various characteristics and classes based on the Soil Taxonomy system. The predominant morphological traits in the studied soils in each study area, including the existing limitations and advantages, have been determined. In addition to soil classes, morphological, micromorphological, physical, chemical, clay mineralogy, organic and inorganic carbon storage, and geochemistry of formed soils are described in detail. Of the 12 soil categories in the American Classification System, at least 7 categories, and of the 32 reference groups of the WRB System, there are at least 16 reference groups in the study areas. The micromorphological results proved the effect of aeolian sediments on the soils formed on the basalt. Illite and chlorite in the clay mineralogy of many soils of the studied areas indicate that the studied soils are young. Smectite was found in slightly more developed soils (Vertisols and Aridisols). The formation of allophanes from pyroclastic materials is also a proof of the predominance of aluminum over silicon in the early stages of their aeration. Almost all soil-forming processes in this research were studied and discussed, and from an educational and research point of view, a clear view of the country's soils was shown.

Spatial variability of the soil properties is related to the environmental factors such as climate, topography, parent material and vegetation. Topography causes significant differences in soil properties through the three factors of elevation, natural drainage and slope. This research was carried out to investigate the effect of elevation on some physical and chemical characteristics, type and content of the clay minerals, and finally on the evolution of soils of an elevation profile in Talesh Mountain in Ardabil province. Following excavation and description of five profiles on non-eroded surfaces, physical, chemical and clay mineralogy experiments were performed on the samples. The results showed that weathering intensity and type of pedological processes were different and hada significant effect on some soil characteristics such as clay content, different forms of iron, minerals and soil classification at the different surfaces of elevation. With decreasing the altitude, the amount of illite minerals was reduced but the amount of smectite minerals has increased, which is a reason for the improved weathering and evolution of the soils. The results show that toeslope lands have evolved soils of Vertisols and Mollisols, but highlands have Inceptisols with low degree of evolution. Addition, in the studied elevation profile, as the altitude decreases, the climate becomes warmer and consequently the intensity of pedogenic processes increases.The increase in the amount of crystalline iron (Fed-Feo), as an indicator of soil evolution, from 2303.9 mg kg-1 at the topslope to 7558 mg kg-1 at the toeslope of the mountain illustrates this evolutionary trend.

Surveying of soils along a toposequence is a primary key for identification of the spatial variability and development of soils that have been performed continuously at a certain direction. The main objective of this study is to assess both clay mineralogy and Sorensen similarity index to describe the genesis and development of soils in Fasarood region. In this context, three major physiographical units were recognized in this area (i.e., Colluvial fan, Piedmont plain and Flood plain). Moreover, nine presentative pedons were digged according to physiographical map units in the direction of NW to SE. Typic Endoaquepts and Oxyaquic Haplustepts are identified as dominant soils in the flood plain in which the redoximorphic and gleyzation processes have been occurred. Fluventic Haplustepts and Typic Calciustepts were recognized in the piedmont plain along with an irregular decrease in organic-carbon content as well as calcic horizon, caused by erosion and sedimentation, respectively. Typic Ustorthents is the major soil of Colluvial fan that have more than 60% coarse fragment in subsurface horizon. The results revealed that smectite, illite, cholorite, palygorskite and kaolinite were dominating minerals in colluvial fan, piedmont plain and flood plain. According to the similarity index, 0.5, 0.54, 0.55, 0.74 and 0.74 were achieved for order, suborder, great group, sub group, and family levels, respectively. Generally, similarity index could better describe soil variation in different slope position than clay mineralogy due to its quantity approach.

In sustainable agriculture, it is essential to know soil various characteristics for increasing the soil productivity. The relationship between soil and geomorphology in arid and semi-arid regions has been considered by many researchers. Faryab plain is located in arid region of Kerman Province and has diversity in geomorphic positions and parent materials. No previous study has been conducted in this region. Therefore, the objectives of the present research were 1) to study the genesis and development of soils related to different geomorphic surfaces in Faryab region, 2) to study the physicochemical properties, clay mineralogy and micromorphology of soils, and 3) to classify the soils according to Soil Taxonomy (ST) (2014) and World Reference Base (WRB) (2015) systems and compare them. Faryab region with a mean elevation of 630 m above sea level is located in Kerman province, south-eastern of Iran. Mean annual rainfall and temperature of the area are 160 mm and 23.8 oC, respectively. Soil temperature and moisture regimes of the area are thermic and aridic, respectively. From geological point of view, the studied area is a part of west and south west zones and Flysch zone of east of Iran. Ten representative pedons on different geomorphic units including hill, alluvil-colluvial fan, alluvial plain, and lowland were selected, sampled, and described. Routine physicochemical analyses, clay mineralogy, and micromorphological observations performed on soil samples. Soil pH, texture, electrical conductivity, calcium carbonate, Na, Ca, Mg, cation exchangeable capacity and gypsum were identified. Eight samples were selected for clay mineralogy investigations. Four slides including Mg saturated, Mg saturated treated with ethylene glycol, K saturated, and K saturated heated up to 550 oC were analyzed. A Brucker X-Ray diffractometer at 40 kV and 30 mA was used for XRD analyses. Undisturbed soil samples from some representative pedons were selected for micromorphological observations. A vestapol resin with stearic acid and cobalt as hardener was used for soil impregnation. A Lite petrographic microscope was used for micromorphology investigations. The results of the present study indicated that the soils with more evolution were located on the geomorphic surfaces of the lowland and alluvial plain and the soils with lower development on the hill and alluvil-colluvial fan. The most important pedogenic processes of the soils were the eluviation of salt, gypsum, calcium carbonate as well as clay, and the formation of calcic, gypsic, petrogypsic and natric horizons. The soils of the region were classified using ST as Aridisols with three suborders of Argids, Calcids and Gypsids and classified according to the WRB as three soil reference groups of Solonetz, Gypsisols and Calcisolos. A new subgroup of Calcic Natrigypsids is suggested for inclusion to ST for the soils with aridic soil moisture regime and three horizons of gypsic, calcic and natric. The WRB system, due to its flexibility in the use of principle and supplementary qualifiers, prepare a better qualification than ST for the soils of the region. According to mineralogical results, the observed minerals consisted of illite, palygorskite, chlorite, smectite, kaolinite, vermiculite and quartz. The highest amount of palygorskite was observed in the gypsic horizons of hill and alluvil-colluvial fan. By moving to the central part of the plain (lowland), the amount of palygorskite was greatly reduced and the amount of smectite was increased. Two origins of inheritance and transformation (illite and palygorskite) are suggested for the occurrence of smectite in the soils. Due to the lack of the conditions for the formation of kaolinite, illite and chlorite, these minerals are inherited from parent materials. SEM observations suggested a pedogenic pathway for the occurrence of large amounts of palygorskite in the soils of the region. Calcareous and gypsiferous media seems to prepare a favorite environment for the pedogenic formation and stabilizing of this mineral in the studied soils. Coating and infilling of gypsum and calcite crystals in voids and channels, clay coating along chanels as well as Fe and Mn oxide nodules were among the common pedofeatures observed in the thin sections of the studied soils. Occurrence of variable habits of gypsum crystals in different geomorphic surfaces suggested a dynamic soil environment. Larger lenticular gypsum crystals were found in the soils with lighter texture located on more stable geomorphic surfaces. Different geomorphic situations in the region affected the development and evolution, physicochemical properties, clay mineralogy, micromorphology and soil classification and caused the differences in these characteristics in the Faryab region.

The soils developed in the context of the landforms and they evolve under influence of similar factors. Therefore, the identification of soil-landform relationship is the first step for the soil survey, pedology and paleopedology and geomorphology researches. Afghanistan is located between arid environments of Iran and cold and humid highlands of Himalaya. Due to special social and political conditions, little information existed on the soils of Afghanistan. Alluvial fans are the common land forms in arid environments which usually are archive of soil formation and sedimentation periods in the past. Landform assemblage in southern Herat (alluvial fans to piedmont plan and flood plain), could provide suitable information on the soil landform relationship in arid areas of Afghanistan. This study was the first pedology research in Afganistan. The objectives of this research was to identify the soils along a transect from alluvial fan to flood plain of Hariroud River, determine the clay mineralogy and micromorphological features of the soils and finally determine the soil evolution in the study area.
Material and The study area located in southern Herat between longitudes of 34° 20’ 21” to 34° 25’ 33” E and latitudes of 43° 20’ 21” to 43° 25’ 33” N. The mean annual precipitation and temperature of the study area are 250 mm and 16. 1 ºC. A transect from an alluvial fan from Sefidkouh Mountain to flood plain of Hariroud River were selected. The geomorphic surfaces along the studied transect were alluvial fan, alluvial fan-piedmont plain transition, saline and non-saline piedmont plain and flood plain. Five representative soil profiles along a transect of Alluvial fan, intermediate Alluvial fan– piedmont plain (lowland), piedmont plain and flood plain were described and sampled. Undisturbed samples were taken for thin section analysis and recognizing pedofeatures. The mineralogy of the clay fraction was determined using X-ray diffraction method. Calcic-argillic (Btk) horizon was the most developed horizon which occurred in alluvial fan. Alternation of paleosol (Btk horizon) and undeveloped coarse-alluvial layers indicated alternation of soil formation and sedimentation periods in the past. Regarding the argillic horizon development conditions, the Btk is the relict features from a wetter climate in the past. Similar soils were observed in arid regions of Iran. The gleization and few secondary carbonates and salt accumulation was the pedogenic processes in other landforms. Bw horizon was common horizon in other studied soils. In Alluvial fan – piedmont plain transition geomorphic surface, due to depression in the landform, salt accumulated in the surface soil and electrical conductivity reached to 40 dS/m. However, salic horizon because of limited thickness was not identified. In non-saline piedmont plain and floodplain geomorphic surfaces, soils showed oxidizing and reducing conditions and consequently gleyic color pattern. Maximum EC (49 dS/m) was occurred in saline piedmont plain surface. The results showed that electrical conductivity values increased from alluvial fan toward lowland positions. Besides, fine soil textures were found in downward positions. The Soil Taxonomy classification of the soils were Typic Calciargids in alluvial fan, Aquic Haplocombids in alluvial fan-piedmont plain transition, non-saline piedmont plain and flood plain as well as Typic Haplocambids in saline piedmont plain. Chlorite, illite, palygorskite, smectite, and kaolinite were the main clay minerals. Chlorite and illite were inherited from parent materials. Micromorphological observations proved clay coating on carbonate nodules and coarse fractions in Btk horizon. The alternation of secondary carbonates on clay coating is the evidence of polygenetic soils and change of from wetter to drier climate. Also, iron oxides nodules in Btk horizon indicated suitable weathering conditions during clay accumulation. Lenticular gypsum was observed in the soil in saline piedmont plain geomorphic surface. Coating and hypocoating of iron oxides identified in flood plain soil. Results of this research showed the role of geomorphic processes and climate change in the soil evolution in the area. The results of this study indicated the progressive and regressive processes which are preserved in the soil of alluvial fan. The Btk horizon in alluvial fan represent wetter condition than today. The morphological, mineralogical and micromorphological features of the soil in the alluvial fan were similar to correspondence soil in arid environments of Iran. Continuous sedimentation in the piedmont plain and flood plain prevent the soil development in these landforms.

The aim of this study was to evaluate the physico-chemical properties and clay mineralogy in paddy soils of Doroud region in Lorestan province. Seven profiles were sampled and described and all soil profiles were classified in Inceptisols and Entisols orders. According to the results, clay content of soils due to waterlogging was high. Due to the reduction Conditions, pH of all soil samples was nearly neutral. Due to the flooding and accumulation of oxides of bivalent iron and manganese in the upper horizons of soils, the electrical conductivity (EC) was higher compared to the lower horizons. With increasing depth and getting closer to native materials, lime percentage was increased too. In most profiles due to the higher percentage of organic matter in the surface horizons, cation exchange capacity in the surface horizons was more than the lower horizons. The amount of organic matter was high in the surface horizons because of the less oxidation of plant residues in anaerobic conditions. The most clay minerals were chlorite, smectite, vermiculite, and illite respectively. Palygorskite, kaolinite and mixed minerals had very low content. Chlorite, illite, kaolinite and palygorskite often were inherited. The source of smectite can be also transformation of illite or palygorskite, under waterlogging condition. The puddling condition increased the amount of chlorite in paddy soils. The results showed that the type of clay minerals didnt vary in paddy soils and their relative percentage varied. The waterlogging provid conditions for sustainable of vermiculite in paddy soils. The long term waterlogging condition affected soil quality in this area, and however cultivation rotation suggested.

The optimum and sustainable use of soil is possible only with correct and complete understanding of its properties. The objectives of the this study were to enhance understanding of soils available in an area located on 35 km of Chelgerd region in Chaharmahal –va- Bakhtiari province through the study of the Soil morphological, physico-chemical, mineralogical and micromorphological characteristics to check the formation and classification of these soils according to USDA Soil Taxonomy (2014) and WRB (2014) systems.
Mean annual rainfall and soil temperature of the selected location are 1389.6 mm and 9.5 ℃ respectively and Soil temperature and moisture regimes of this region are mesic and xeric, respectively. Eight pedons located on one transect along slope direction were excavated and sampled. Routine physico-chemical analysis such as soil reaction, texture, COLE content, electrical conductivity, calcium carbonate equivalent, cation exchange capacity, organic carbon and clay mineralogy and micromorphology investigations were performed on selected soil samples. Then, based on description card of each profile and laboratory results, soils were classified to phamily level and to second level based on Taxonomy and WRB systems, respectively.
the results showed that the category of the soils of the area according Taxonomy system, are Inceptisols and Vertisols, while in WRB system, named Calcisols, Cambisols and Vertisols. The results showed that, because of higher organic matter content and finer texture of soils of lower slope positions, cation exchange capacity was maximum in this position. The results also revealed that, with increasing soil depth, organic carbon content and cation exchange capacity decreased, whereas clay and lime content had a reverse trend and increased with increasing the soil depth. Coefficient of linear extensibility (COLE) values as well as clay content increased from back slope to foot slope and with increasing soil depth. They are constituted mainly by smectites associated to some amount of illite, chlorite, kaolinite, quartz and illite- smectite as mixed minerals. According to this results, the origin of the clay minerals in different slope positions are mostly inheritance from parent material. Study of thin section revealed the presence of clay coating in the Bt and Btk horizons, that, this clay coatings in the soil are evidence of transmission clay from upper horizons to lower horizons as a result of water penetration. Also, calcite accumulation with various forms such as calcite coating, calcite infilling and calcite needle and calcite nodule in the Bk and Btk were observed, which, confirms the secondary nature of lime and causing calcitic crystalitic b-fabric. Also, the cause is the accumulation of calcite needle in the top of the slope due to highlands area, presence of enough moisture in the soil, the low salinity of soil and presence of biodegradable organic matter.
the result of this study showed the role of topography on variability of soil properties and soil classification in the studied area.

Playa is one of the most important landscapes in arid regions which covers about 1% of the world's total land area. Study of playas is important from different points of view especially pedology, sedimentology, mineralogy, environmental geology, groundwater and surface water chemistry. More than 60 playas have been identified in Iran. Considering the fact that playas and surrounding landforms are important archive of landscape evolution and paleoenvironmental variations, it seems that less attention has been paid to them so far. Soils are known as indicators of the landscapes evolution. Previous studies in arid regions of Iran imply different periods of deposition and soil formation in playa and alluvial fans or pediments. Bajestan playa is one of the known playa in northeastern Iran, and the largest clay flat exists in this playa. There is no information on the soils and their evolution in Bajestan playa. The objective of this study were to 1) identify the soils in different landforms along a transect from alluvial fan to clay in Bajestan playa 2) determine the morphological, micromorphological and mineralogical characteristics of these soils 3) determine the periods of soil and landform evolution and 4) comparison of soils evolution of the study area to other arid regions of Iran.
Material and The study area of approximately 20000 hectares is located in southeastern of KhorasanRazavi province. The climate of the study area is hot and dry with mean annual temperature and rainfall of 17.3 °C and 193 mm, respectively. Soil moisture regime is aridic with subdivisions of weak aridic and soil temperature regime is thermic. Firstly, landforms and geomorphic surfaces of the study area were recognized based on Google Earth images interpretations and field observations. Four main landforms were recognized in the study area. The landforms from north to the south of the study area were alluvial fan, intermediate alluvial fan- clay flat, pediment and clay flat. Considering the diversity of geomorphic units, 11 soil profiles were described and diffrenet soil layers and horizons were sampled. Undisturbed soil samples were taken micromorphological studies. Some horizons were selected for clay mineralogy analysis. The mineralogy of clay fraction was determined using X-ray diffraction method.
Results and discution: All studied soils except the profiles in the pediment were classified in the Aridisols order. There were two geomorphic surfaces in alluvial fans. In the first geomorphic surface a soil with the Bk horizon buried a soil with red Btk horizon. In the second geomorphic surface, it seems that the erosion has been removed the overlying soil. The Bk horizon showed the maximum soil development in the clay flat and intermediate alluvial fan-clay flat landforms. Clay coating on sand in thin section was the evidence of clay illuviation in Btk horizon. Carbonate nodules associated with clay coating are the compound pedofeature in Btk horizon. These evidences reflect polygenetic nature of the soils and different period of climate change and soil formation. Smectite, mica, chlorite and palygorskite are the clay minerals in the studied soils. Similar to soils in arid regions of Iran, palygorskite was found in Bk, Bt and Bz horizons. The existence of Bk horizon in overlying soils, buried Btk horizon, removal of surface horizon in alluvial fan are the evidences of regressive and progressive of pedogenic processes in the study area. Btk horizon represents a warm and wetter and Bk horizon indicates a relatively wetter period in comparison to present time.
Btk was the most developed horizon in the study area that occurred as buried paleosol in alluvial fan. Bk, Bw, By and Bz were the common horizon in other landforms. Clay coating and red color of Btk horizon might seem as indicators of hot and humid conditions in the past, during the argillic horizon formation. Covered carbonate nodules with clay coating can also be mentioned as sign of a hot and wet period which is suitable for clay illuviation and weathering after a period of carbonate accumulation. The buried Btk horizon under alluvial layers in the alluvial fan indicates that after apedogenic period, alluvial processes have been responsible in burying this horizon. Bk horizon in overlying soil of all landforms represents a less intense period of soil formation. The dominant clay minerals in the study area were Illiite, cholorite, kaolinite, and palygorskite. The sequence of Bk and Btk horizons in this research and the occurrence of these soils in central, eastern and northeastern Iran imply the similar pedogenetic conditions in arid regions of Iran.

Potassium (K) fixation in soils creates hysteresis phenomenon between sorption and desorption branches of the isotherm. Therefore, the hysteresis index having highest correlation with K fixation might be introduced as the most proper index for this phenomenon. For this purpose, 12 soil samples with different clay mineralogy were selected from around Dasht-e-Tabriz and Marand regions. At first, K fixation of the soils was measured by addition of 250 and 2500 mg K/kg soil. Then, K sorption isotherms at 10 initial concentrations (5-250 mg K/L) and K desorption isotherms from the point corresponding to an initial concentration of 250 mg K/L were obtained using background solution (0.01 M CaCl2) in 10 desorption cycles. The results showed that the amount of K fixation sharply decreased with increasing the saturation extract K concentration as well as the exchangeable K content. Moreover, the data obtained from both sorption and desorption branches were best fitted to the Freundlich equation. All hysteresis indices showed significant correlations with percentage of K fixed per one percent of clay. Aside from soils with high hysteresis indices, significant correlations were found between values of hysteresis indices and percentages of K fixed. The highest correlation was observed for the hysteresis index based on β exponent of the Freundlich equation.

Salinization and solonization are of common processes in the soils of arid and semiarid regions and are serious problem in agricultural development and sustainable use and management of soil and water resources. Now a day, these processes are extremely active in lands around Urmia Lake and the most of agricultural and horticultural lands around Urmia Lake have been destructed due to these processes and as a result excluded from crop production cycle. In this study physical, chemical and mineralogical properties and classification of six soil profiles in the lands affects by Urmia Lake and two profiles in the lands which unaffected by Urmia Lake were investigated.
The study area has been located at the east of Urmia. Mean annual precipitation and mean annual temperature of this area are 345 mm and 10.83 ºC respectively and the soil moisture and soil temperature regims of this area are Dry Xeric and Mesic respectively. In order to perform this investigation, the position of six soil profiles in saline-sodic soils in the west of Urmia Lake were determined in which include nearly all of saline-sodic soils of this area. In order to control the effect of management and land use, all of soil profiles were dug in non agricultural lands. Additionally, two soil profiles in nonsaline-nonsodic soils which had the same conditions as saline-sodic soils were studied as representative profiles. Soil sampling was done from all of characteristic horizons and the physic-chemical properties of soils were determined using standard methods and soils were classified according to the last version of soil taxonomy. In order to mineralogical studies, pure clay samples were studied using SHIMADUZ XRD 600 diffractometer with 0.4 second time delay in 2θ angels between 2-30 degree, using beam source of Cukα with 30kv voltage and 30 mili ampere.
The results of this study revealed that the soils around Urmia Lake have been extremely salinized and alkalized and their physico-chemical and mineralogical properties were greatly different in comparison with the soils that have not been affected (or less affected) by Urmia Lake. According to the results, saline- sodic soils had more clay content, electrical conductivity, cation exchange capacity, exchangeable sodium and soil evolution, whereas, the content of organic carbon and calcium carbonate equivalent were higher in nonsaline-nonsodic soils. Clay mineralogical investigations revealed that the clay minerals in both groups of saline-sodic and nonsaline-nonsodic soils were mainly smectite, illite, kaolinite, chlorite, vermiculite, hydroxy interlayered vermiculite, mixed layered minerals and quartz. The origin of illite, kaolinite, chlorite, and hydroxy interlayered vermiculite were related to inheritance from parent material, the origin of vermiculite were related to transformation of illite, and smectites have been formed under inheritance from parent material, illite transformation and neoformation from soil solution. It seems that the neoformation is the main mechanism for the formation of smectites in saline-sodic soils. The saline-sodic soils contain more smectite than nonsaline-nonsodic soils and it might that the formation of smectite via neoformation is the main cause of high amounts of smectite in studied saline-sodic soils.
Accordingly, salinization and solonization which have been resulted from Urmia Lake, have caused mineralogical changes in soils around Urmia Lake and presence of more smectite in saline-sodic soils. Differences in morphological and physico-chemical properties of studied soils have been lead to extreme variety in their classification, in which these soils were classified in three orders, three suborders, four great groups and four subgroups.

nano-clays and clays are the most important components constructing soil ecosystems. Which The soil physical and chemical properties depend on their types and amounts. Therefore, they have a key role in soil quality. Most clays particles have nano size at least in one dimention. This characteristic of clay enriches some soil capabilities such as the heavy metals retention processes in soil. Clays separated from volcanic ash like Andisol, in clay size particles there are different structures of nano particles such as alominosilicats with nanoball and nanotube constriction. These particles play an important role in the physical and chemical properties of volcanic soils, stored organic matter, phosphorus stabilization, heavy metals retention, water and biogeochemical processes. Release of heavy metal onto the water and soil as a result of agricultural and industrial activities may pose a serious threat to the environment. In this study, the adsorption of Pb2, Cd2 has been studied in order to compare the ability of Nano-Clays And Clays separated from Different Soils in Retention of Some Heavy Metals.
Twelve samples taken from 5 pedons with different clay mineralogy in three regions around the city of Karaj were measured. After the removing organic material, the soluble salts, carbonates and iron oxides from the soils, pure clays were treated by x-ray diffractive device and diffractions were interpreted. clays and nano-clays were purified and measured retention of cadmium and lead in solutions with different concentrations, 0, 1.6, 8.3, 16.6 and 33.3 ppm, at constant pH. The aim of this research is to evaluation of the effect of soil components particularly clay and nano Clay on the absorption of heavy metal at constant pH. Therefore, we studied absorption amount of lead and cadmium by the clay and natural nanoclay soils after removing cement and seprating using standard methods, at pH 6.
The soils were classified in two groups of Aridisol and Andisol. The current study showed that the bulk of soil mineralogy consist of combination of ilitic, cloritic, smectite and hydroxy inter layer minerals. Also the results showed that the heavy metals retention of soils depend on the different types of element. In all Andic and non-Andic samples, the retention capability showed significant enrichment with increasing heavy metals concentrations. But the trends of retention in nano-clays showed a steeper slope in comparison with clays.
Cadmium absorption of the samples(nano-clays and clays) stopped at 8/3 mg/lit, but lead absorotion. But lead absorption at studied cincentration was increased by increasing trend. The results indicated that in the most samples derived from non-Andic soils their absorption trend was as (Pb> Cd) and in the Andic soils it was (Pb> Cd).

This research is conducted to evaluate the quality of organic matter and clay type in the soils which are located at different positions of the slope of a catena in Deilaman region of Guilan province. To do this, the catena was firstly divided into five transverse sections including summit, shoulder, back slope, foot slope and toe slope. Then each section was longitudinally divided into three parts as three replications and composite soil samples were collected from each sections at the depths of 0-20, 20-40 and 40-60cm and some characteristics of soils and clay minerals of the samples were determined. Results showed that the maximum organic matter and carbohydrate contents were found in the soils located on the lower positions of the catena (representing foot slope and toe slope). Carbon-nitrogen ratio decreased by reducing the slope, indicating the more decay of organic matter in the positions of foot slope and toe slope. Soil microbial respiration amounts also more increased with reducing of the slope. Clay mineralogy of soils located on the catena confirmed the presence of kaolinite, illite, hydroxy interlayer vermiculite and little amounts of chlorite in the soils. The type of clay minerals was the same but their frequency was varied at the different slope positions and soil depths. The results of present study revealed that soil properties were affected by topography in this region.

Effect of land use type on soil functioning within an ecosystem can be assessed by soil quality indices. Such studies that are carried out to improve land resources quality, lead to control the land degradation and help us to identify the sustainable management. In order to study the effect of land use change from pasture to agriculture on soil quality and clay mineralogy, Valarude region of Zanjan province was selected. Composite soil samples were taken from 0 – 30 and 30 – 60 cm depths of both land uses with three replicates and totally 60 soil samples were prepared. Important soil quality indicators such as bulk density, weighted mean diameter of aggregates, quantities of organic carbon, and total nitrogen, soil microbial respiration rate, amount of microbial biomass C and urease and alkaline phosphatase activities were measured. Results revealed that the land use change from pasture to agriculture, led to a significant reduction in the amounts of organic carbon (62%), total nitrogen (70%), mean weight diameter of aggregates (32%), microbial respiration rate 75%) and microbial biomass C quantity (47%). The assay of enzyme activities showed that alkaline phosphatase activity did not change significantly but urease activity decreased in agriculture land (87%). Mineralogical studies showed that the both land uses had illite, kaolinite; chlorite, smectite and mixed layer minerals and change of land use did not have a significant effect on soil clay minerals. Overall, it can be concluded that a change in land use from pasture to agriculture with widespread agricultural practices, especially intensive tillage activities, may lead to decrease soil quality.

Quaternary sediments have occupied most of the agricultural and natural resources of urmia region. Recognition of physicochemical and mineralogical properties of these soils is essential to optimum and stable use of these lands. In this study, eight soils profiles excavated on Quaternary sediments of Urmia region were investigated. The results showed that little thickness and evolution of studied soil was possibly due to the sequential soil erosion and sedimentation processes.Consecutive erosion-deposition processes at different periods led to the formation of calcic horizons and sedimentary layers in lower depths indicating climatic fluctuation, along with dissolution and translocation of carbonate in wetter periods as well as its deposition and accumulation in drier periodsClay mineralogical results revealed smectite, kaolinite, illite, chlorite and vermiculite as dominant clay minerals in the study area. Illite, cholorite and kaolinite mainly considered as inheritance fromthe parent materials while pedogenic formation explain the presence of vermiculite. Moreover, smectites was found to have three origins of inheritance, neoformation and transformation and its abundance was increased with depth. The origin of smectite in the buried horizons was attributed to the illite transformation. According to the heavy moisture demand on illite weathering, the occurrence of this process can be associated with more humid condition during the past climate. So the achieved results of present study can be a clue to recognize the climatic changes in the study area.

Knowledge of the chemical forms of heavy metal pollution in soil, plants and groundwater is important. This study was done to investigate the effect of leonardite in changing the chemical forms of heavy metals in soils derived from different parent materials including Syenite, Schist, Gabbro and Calcite. Analyses of the physico-chemical properties and clay mineralogy of soils were carried out. Chemical forms of the lead (Pb) and cadmium (Cd) in presence of the leonardite (0, 2, and 5%) were evaluated using sequential extraction method. The results showed that the quality and quantity of the clay minerals were different and the smectite mineral was dominant at different ratios of the leonardite. However, the vermiculite (42%) and hydroxy interlayer vermiculite (HIV) (82%) minerals were observed in the schist and calcite-derived soils, respectively. Leonardite application decreased the pH value in the derived soils from Syenite. The result showed that the chemical form of heavy metals in different soils was significantly affected by the leonardite levels. Pb and Cd chemical species were different in each soil type. The maximum amounts of the exchangeable Pb and Cd were observed in the syenite and gabbro, and the syenite soil, respectively. Leonardite decreased the elements related to the oxides Fe- and Mn, whereas the organic carbon based section was significantly increased by the leonardite application. Also leonardite reduced the amounts of the residual fraction of heavy metal in soil. Accordingly, leonardite behavior varied in different soils and its application should be based on the physico-chemical properties of soil.

Lithology and soil forming conditions play a very important role in controlling the properties of residual soils. To assess the role of these factors on the composition of clay minerals, residual soils developed on three parent materials including peridotite (Pe), tonalite (To) and limestone (Li) were studied in forest ecosystems of Fuman-Masoule region. Parent rock mineralogy, clay mineralogy of saprolite and soil genetic horizons were determined. In Pe pedon, saprolite and soil genetic horizons have different clay mineralogy. Kaolinite and vermiculite are the major clay minerals present in C2 horizon, whereas smectite, illite, illitevermiculite, illite-smectite and kaolinite are present in upper horizons. Smectite and kaolinte might have formed from pyroxene, olivine, biotite and vermiculite via autogenic and transformation pathways. The presence of illite in pedogenic horizons of Pe pedon is in line with the vertical distribution of total K concentration of clay fraction and could be due to accumulation of K and formation of secondary illite in topsoil. In the saprolite of Li pedon, illite and smectite are present in clay fraction. However, illite is replaced by kaolinite in genetic horizons. Pyrite oxidation in parent material seems to enhance the pedogenic formation of smectite and kaolinite. Clay mineral composition of saprolite layers, especially in Pe and Li pedons, is highly influenced by parent materials and is different from genetic horizons. Although the mineralogical composition of genetic horizons developed on different parent materials is not substantially different, the relative content of given clay minerals might be different in various soils.

To study the effects of land use change and climate on micromorphological properties and clay minerals distribution in loess derived soils of Golestan Province, 12 soil profiles in summit geomorphic position consisting of aridic, xeric and udic moisture regimes with cultivated, pasture and forest land uses were studied. The results showed that in aridic moisture regimes weakly developed Entisols, in the xeric soils moisture regime, Inceptisols, Mollisols were dominant, and in udic moisture regime, the most developed Hapludalfs were formed. Micromorphological studies revealed that there was a good positive correlation between soil development and climate index (evapotranspiration ratio). Environmental conditions such as land use and climate consequently affected micromorphological properties such as voids, microstructure, b- fabric, and pedofeatures. In the udic moisture regime, thick clay coatings were observed in speckled b- fabric matrix. However, in the soil with aridic moisture regimes, massive microstructure, and crystallitic b- fabric can be seen. Microscopic observations showed granular microstructure in forest surface horizons has been transformed to massive microstructure in cultivated land use. Results obtained from mineralogical studies showed that there were differences in type and distribution of clay minerals in different climate. Illite was found as the main clay mineral of loess parent materials and soils of the three land uses. The origin of illite, kaolinite and chlorite clay minerals are mainly inheritance while smectite and vermiculite are pedogenic. With increasing precipitation and weathering intensity from xeric zones toward udic zone, illite and chlorite have transformed to smectite and vermiculite. Amount of smectite and vermiculite are mainly affected by climate. It can be concluded that conversion of natural land resources into croplands causes serious soil degradation in loess derived soils in Golestan province.

One of the main objectives of soil classification systems is to identify the differences of soil properties for management purposes. In this study, the efficiency of American and WRB soil classification systems were compared in order to describe some of soil physical, chemical and mineralogical properties in arid and semiarid regions of central Iran. Khatoon-Abad and Mobarekeh plains as arid regions and Koohrang and Shahrekord plains as semiarid regions were selected. Then, representative pedons of each plain were chosen from 16 excavated pedons and soil samples were taken from the genetic horizons to determine soil classification. Results showed that soil orders of both Koohrang and Khatoon-Abad plains are vertisols according to American soil classification system whereas based on WRB system, these soils are classified as cambisols and calcisols, respectively. On the other hand, both Mobarekeh and Shahrekord soils are classified as calcisols in WRB system whereas these soils are classified as aridisols and inceptisols, respectively, according to American soil taxonomy. None of soil classification systems could show the existence of gypsum in horizons lower than 100 cm of the soil surface for Mobarekeh soil. Clay mineralogy indicates that smectite is the dominant clay mineral in Koohrang soil as explains well at the family level of American soil classification system. Results suggest that WRB has somewhat higher efficiency rather than American soil classification system for the studied soils.