H.R. Rafiei; A. Jafari; A. Heidari; Mohammad Hady Farpoor; A. Abbasnejad
Abstract
Introduction: Soil carbon (C) sequestration is recognized as a potentially significant option to off-set the elevation of global atmospheric carbon dioxide (CO2) concentrations. Soils are the main sink/source of carbon and also, an important component of the global C cycle. Total soil carbon (C) comprises ...
Read More
Introduction: Soil carbon (C) sequestration is recognized as a potentially significant option to off-set the elevation of global atmospheric carbon dioxide (CO2) concentrations. Soils are the main sink/source of carbon and also, an important component of the global C cycle. Total soil carbon (C) comprises of the soil organic C (SOC) and the soil inorganic C (SIC) components. The soil inorganic C (SIC) stock mainly consists of carbonates and bicarbonates. Processes governing the dynamics of the soil carbon stock differ among ecoregions and strongly interact with soil properties. Understanding the distribution of organic and inorganic carbon stocks in soil profiles is essential for assessing carbon storage at the regional and global scale. Although global estimates provide a general view of carbon stock levels, accurate local estimates and factors affecting soil carbon dynamics are very important. As a result, there is an essential requirement for accurately estimating the distribution of carbon reserves and their differences with regard to soil properties. Materials and Methods: The study area is located in the Sardooeyeh region, South of Kerman, under semiarid conditions. A total of 5 soil profiles were excavated. Percentage of coarse fragments (> 2 mm) using a 2 mm sieve, total organic C by the K2Cr2O7-H2SO4 oxidation method of Walkley-Black, soil inorganic carbon using the Gravimetric carbonate meter method were determined. Bulk density was measured by drying core samples in an oven overnight and dividing the weight of dry soil by the volume of the core occupied by the soil after correction for coarse fragments. Results and Discussion: Organic carbon in the surface horizons of all profiles is maximum due to vegetation and decreases with increasing soil depth. As the altitude increased, the amount of organic carbon increased in the surface horizons. Lower temperature and higher humidity at higher altitudes lead to the lower organic matter decomposition and consequently higher organic carbon content of the soil. Although the upper soil layers had the maximum soil organic C content, the maximum soil inorganic C content was observed in the sub-surface layers. The soil organic carbon storage was between 5.52 to 9.48 kg m-2 and the storage of soil inorganic carbon in profiles was between 14.41 and 91.34 kg m-2. The total soil carbon storage in the profiles varied between 19.92 to 100.83 kg m-2 and the average was 42.66 kg m-2. The average of soil organic carbon storage in 0-25, 25-60, 60-120 cm depths were 2.6, 1.97 and 1.26 kg m-2, respectively. The amount of soil inorganic carbon storage in 0 -25, 25-60 and 60-120 cm depths were equal to 2.7, 10.40 and 8.26 kg m-2, respectively. Therefore, it seems that more than 50% of the total soil inorganic carbon storage is stored at a depth of 25-60 cm from the soil surface. The portion of inorganic carbon storage of total soil carbon was 77.5%, and about 89% of it was stored in sub-surface horizons (below 25 cm). The portion of organic carbon storage of total soil carbon was 22.4%. It seems that an increase in the partial pressure of CO2 in soils leads to some dissolution of the pedogenic carbonate in the top soil. Dissolved pedogenic carbonate transfers to the deep soil and then re-crystallizes under relatively dry conditions and low CO2. Conclusion: The results showed that soil organic carbon storage was mostly higher in surface horizons, and soil inorganic carbon storage was higher in sub-surface horizons. On average, the ratio of soil inorganic carbon storage to soil organic carbon storage was 4.27. The high percentage of soil inorganic carbon storage in total soil carbon, shows that inorganic carbon plays a very important role in semi-arid regions. Almost 89% of the soil inorganic carbon content and about 80% of the total soil carbon were accumulated in the sub-surface horizon of soil (below 25 cm), indicating the importance of sub-surface soil for storing carbon in semi-arid regions.
Mohammad Ali Monajjem; Ahmad Heisari; Gholam Bagheri Marandi
Abstract
Introduction: Nanoclays, due to their high specific surface area (SSA) chemical and mechanical stabilities, and a variety of surface and structural properties are widely applied. Some of their applications are using them as nano composite polymers, heavy metal ions absorbents, catalysts, photochemical ...
Read More
Introduction: Nanoclays, due to their high specific surface area (SSA) chemical and mechanical stabilities, and a variety of surface and structural properties are widely applied. Some of their applications are using them as nano composite polymers, heavy metal ions absorbents, catalysts, photochemical reaction fields, ceramics, paper fillings and coatings, sensors and biosensors. Nano clays and Clays are the most important components constructing soil ecosystems. The physical and chemical properties of soils are mainly depending on the type and amount their clay fraction pertaining to considerable nanoclays. Nano clays have been frequently used to eliminate environmental contaminants from soil and water. Nano clays have also an effective role in the phosphate sorption and desorption from soil solution. Phosphate retention is highly affected by the chemical bonds of the materials, cristalographic properties and pH. In clay size particles there are different structures of nano particles such as alominosilicates with nano ball and nano tube construction. Soils with andic properties have amorphous clay minerals such as allophone. Allophane has a diameter of 3 to 5 nano meter under a transmission electron microscope (TEM) and its atomic Si/Al ratio ranges between 0.5 and 1. Allophane shows variable charge characteristics and high selectivity for divalent cations, and is highly reactive with phosphate.
Materials and Methods: The objective of this research was to inspect the effect of soil components particularly clay and nanoclay on the sorption of phosphate. To achieve this goal, we studied the amount of phosphate sorption by the natural nanoclays. Samples with andic and vitric properties which were previously formed on volcanic ash in Karaj were chosen in 5 pedons as two Andic ( > 5 percent volcanic glass, > 25 percent P retention, pH NaF > 8.6 and Alo +½ Feo > 0.4) and non Andic soils.. After removal of organic materials, soluble salts, carbonates and iron oxides from the soil, clay fraction was prepared for X-ray diffraction analyses. The nanoclay fraction was extracted using the method described by Li and Hu (2003). The specific surface area were determined using EGME method. Different forms of extractable aluminum, including pyrophosphate (Alp) and ammonium oxalate (Alo) extractable forms, as well as silica extractable by ammonium oxalate (Sio) were measured. Routine chemical analyses for organic carbon (OC), cation exchange capacity (CEC) were determined by standard methods. Particle size distribution was determined by the hydrometer method (after ultrasound dispersion). Allophane percentage was calculated using the formula provided in the soils under study by Mizota and Van Reeuwijk (1989). Nano particles were inspected using scanning electron microscope (SEM).
Results and Discussion: The studied soils were classified as Entisols, Andisols and Inceptisols. The results showed that the bulk of soil mineralogy was consisted of combination of illitic, chloritic, smectite and hydroxy interlayer minerals. In addition to sesquioxides, the crystallization degree of soil minerals was also important in phosphate retention. Results of SEM studies of Andisols implied the existence of different types of aluminosilicate nano particles as nano ball (Allophane), nano tubes (imogolite) and smectitic minerals. Hollow spherical structure was proposed for allophane. According to the SEM results, nano particles extracted from non andic soils were dominated by layered silicates (probably montmorillonite). Among physical properties which are effective on phosphate retention, the shape, size and porosity of the particles can be mentioned, all of which have impacts on the specific surface area of the particles. Soils with higher amounts of Alp and Sio were comprised more nanoclay (25,8 g per kg) and higher phosphate retention (%55). Various mechanisms were suggested by soil scientists for phosphate sorption on allophane (Nanoclays). Some of are ligand interchange, silicate replacing by phosphate in high phosphate concentration, and replacing phosphate by weak silicon bonds. There was a positive and significant relation between Sio and Alo amounts (R2= 0,976). The ratio of Alp/Alo in andic soils increased by increasing organic material (at least 0,02 and at most 0,11).
Conclusions: Phosphate retention in the studied soils had a significant relation with Alo (R2 = 0,991).The more percentage of nanoclay showed higher phosphate retention thus the highest amount of phosphate retention was determined in the sample containing highest nanoclays. Nanoclay shows high performance in removal of phosphate from solutions. Little amounts of nanoclays can remove great amounts of phosphate from solution.
pari asadi alasvand; Ahmad Heidari
Abstract
Introduction: Soil and ground water pollution with organic matter and toxic materials is an ordinary environmental problem. In this case, oil compounds are among the most important environmental pollutants. Tehran oil refinery is one of the largest and oldest refineries in Iran located south of Tehran ...
Read More
Introduction: Soil and ground water pollution with organic matter and toxic materials is an ordinary environmental problem. In this case, oil compounds are among the most important environmental pollutants. Tehran oil refinery is one of the largest and oldest refineries in Iran located south of Tehran city. Since the beginning of its activity in 1968, its waste materials (solid, semisolid and liquid) have been disposed in large lagoons next to the refinery site. During this long period, considerable changes in soil properties have occurred, which are of great research interests for soil and environmental scientists.
Materials and Methods: The studied area (about 60 ha) was located in the south of Tehran (latitude: 35°30.299' to 35°30.814' N and longitude: 51°25.682' to 51°26.296' E). Six pedons, including four Technosols developed on the oil refinery waste materials (pedons no. 1, 3, 4 and 6) and two reference pedons (pedons no. 2 and 5) were fully described and sampled. Particle size distribution (PSD) of gypsiferous samples was determined by the specific method for gypsiferous soils (Hesse, 1976). PSD of non-gypsiferous samples were determined according to the standard hydrometer method (Gee and Bauder, 1986), but the oil-polluted samples were analyzed according to the standard ultrasound method (Sawhny, 1996). Organic carbon content was determined by Walkley and Black (1934). pH and EC were measured in soil saturation extracts using EC and pH meter (Jenway). Gypsum and CaCO3 contents were determined using acetone (Sparks, 1996), and calcimetery methods, respectively. Mineralogical analysis was done by Decarreau (1990). Micromorphological descriptions were carried out using the terminology of Stoops (2003). Diagnostic horizons were identified and finally the studied pedons were classified according to the Keys to Soil Taxonomy (Soil Survey Staff, 2014) and the World Reference Base (FAO, 2014).
Results and Discussion: Horizons of both polluted and unpolluted soils were mostly gypseous and/or calcareous especially in the middle parts. Considering the surface and subsurface diagnostic horizons and the aridic-thermic soil moisture and temperature regimes, the studied soils were classified as Gypsids, Calcids or Cambids (Soil Survey Staff, 2014). However, due to the added oil waste compounds and presence of impermeable geomembrane in some of the polluted pedons, they were classified as Technosols in the WRB system (FAO, 2014). Noticeable effects of Pollutants in the soil were decreasing pH and increasing OM and EC. The surface horizons of the unpolluted soils contained less than 2 percent organic matter which regularly decreased by depth. However, In some horizons of the polluted soils, soil organic matter exceeded 12 percent. pH decreased by increasing organic matter (oil waste compounds) possibly due to H+ dissociation from the oil compounds (Laurent et al., 2012). Electrical conductivity throughout the polluted soil horizons showed more limited variability than the unpolluted ones, probably due to their higher capability in water and liquid dynamics. Liquid limit and plasticity limit in polluted soils are higher than unpolluted soils . Plasticity index in polluted soils decreased with increasing the amount of pollutants. The results of mineralogical studies corroborated that dominant clay mineral in this soils is Smectite. Smectites have high swelling and shrinking capacity.So, the pollutants can intercalate between soil mineral layers and then increase d-spacing of clay minerals. The micromorphology of the polluted soils showed that low dielectric constant of petroleum caused flocculation and formation granular aggregates in soil. Studied soils are inactive in terms of activity of clay.
Conclusion: As observed in the studied soils, their physico-chemical properties such as pH and electrical conductivity (EC) of saturated paste extract, organic matter content, mineralogical and micro-morphological properties were severely affected by the oil wastes. These results show these soils have been limited and in use of these soils, considering these properties is required. In polluted soils, due to small differences between plasticity limit and liquid limit, it is possible to their sliding faster than unpolluted soils and then construction should be avoided.
S. chakherloo; Sh. Manafi; A. Heidari
Abstract
In order to comparision of the micromorphic properties of saline-sodic and nonsaline-nonsodic soils in the west of Urmia Lake, four soil profiles (2profile in saline-sodic soils and 2profiles in nonsaline-nonsodic soils) were investigated. These profiles were described and sampled using standard methods. ...
Read More
In order to comparision of the micromorphic properties of saline-sodic and nonsaline-nonsodic soils in the west of Urmia Lake, four soil profiles (2profile in saline-sodic soils and 2profiles in nonsaline-nonsodic soils) were investigated. These profiles were described and sampled using standard methods. soil samples were used for physico chemical analysis and undisturbed and oriented samples were used for thin section preparation. Thin sections were studied using polarizing microscope in PPL and XPL lights. Thin sections studies showed that saline-sodic soils are structure less (apedal), and their voids are mostly vughs and channel and as a result, their, nonsaline-nonsodic soils are pedal with compound packing voids, vughs and planar voids and as a result, The b.fabric in these to group of soils is crystallitic. In saline sodic soils pedofeatures are illuvial clay coatings, salt accumulations including coatings and infillings of halite in channel and vughs. These pedofeatures were not seen in nonsaline-nonsodic soils. Organic coatings were seen as black colored films on peds and in some cases mixed with groundmass of saline-sodic soils.Calcium carbonate accumulations as nodules and coatings and nodules and coatings of iron and Mn oxides were seen in both saline-sodic and nonsaline-nonsodic soils.
kamal nabiollahi; ahmad haidari; rohollah taghizade mehrjardi
Abstract
Soil texture is an important soil physical property that governs most physical, chemical, biological, and hydrological processes in soils. Detailed information on soil texture variability is crucial for proper crop and land management and environmental studies. Therefore, at present research, 103 soil ...
Read More
Soil texture is an important soil physical property that governs most physical, chemical, biological, and hydrological processes in soils. Detailed information on soil texture variability is crucial for proper crop and land management and environmental studies. Therefore, at present research, 103 soil profiles were dogged and then sampled in order to prepare digital map of soil texture in Bijar, Kurdistan. Auxiliary data used in this study to represent predictive soil forming factors were terrain attributes, Landsat 7 ETM+ data and a geomorphologic surfaces map. To make a relationship between the soil data set (i.e. Clay, sand and silt) and auxiliary data, regression tree (RT) and artificial neural network (ANN) were applied. Results showed that the RT had the higher accuracy than ANN for spatial prediction of three parameters. For the clay fraction, determination of coefficient (R2) and root mean square root (RMSE) calculated for two models were 0.46, 0.81 and 17.10, 12.50, based on validation data set (20%). Our results showed some auxiliary variables had more influence on predictive soil class model which included: geomorphology map, wetness index, multi-resolution index of valley bottom flatness, elevation, slope length, and B3. In general, results showed that decision tree models had higher accuracy than ANN models and also their results are more convenient for interpretation. Therefore, it is suggested using of decision tree models for spatial prediction of soil properties in future studies.
