Soil Chemistry and Pollution
Samira Alvani; ُSaeid Hojati; Ahmad Landi
Abstract
Introduction Pollution of the environment to heavy metals is one of the major problems of today's world. Following the development of industries, as well as increasing agriculture in response to the growing population, the overuse of chemical fertilizers, mining activities, the production and disposal ...
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Introduction Pollution of the environment to heavy metals is one of the major problems of today's world. Following the development of industries, as well as increasing agriculture in response to the growing population, the overuse of chemical fertilizers, mining activities, the production and disposal of waste waters and sewage sludge, etc., the entry and accumulation of heavy metals in the environment has increased. There are several methods for removing heavy metals from wastewaters. Among the common methods for removal of heavy metals, adsorption, in particular using inexpensive natural adsorbents, due to the ease of implementation and high efficiency is a cost-effective and economical technique. Palygorskite is a fibrous mineral common in clay fractions of soils of arid and semi-arid regions of the world. Although there are several studies applying palygorskite as a suitable mineral for cleaning of wastewaters, however, few studies have been carried out to evaluate the ability of nanosized particles of such clay minerals for removal of heavy metals from the environment. Therefore, this study was conducted to measure the ability of palygorskite nano- and micro-sized particles to adsorb lead and copper from aqueous solutions. Materials and Methods: Kinetic experiments were carried out at 11 different contact times (5, 10, 20, 30, 60, 120, 240, 480, 720, 1440, and 2880 min) using solutions containing 150 mg / l of lead and copper elements at pH=5. Palygorskite used in this study was purchased from Tulsa Co., Spain Then, micron (Results and Discussion The results illustrated that in the so-called samples as nanosized palygorskite, about 50% of the particles in the sample was found smaller than 100 nm in size, and in this case no samples of particle size of 100 nm and smaller were observed in those so-called palygorskite microparticles. The results indicated that by increasing the contact time and reducing the mineral particle sizes from micron to nanoscale, more amounts of lead and copper heavy elements adsorbed onto the mineral. This is due to an increase in the exposure of active sites on the adsorbent surfaces by the pollutant. When the data were fitted with the pseudo first order, pseudo second order and intraparticle diffusion kinetic models, it was revealed that the pseudo second-order kinetic model with a determination coefficient (R2) of 0.99 was the best model describing kinetics of study. Besides, the lower values of the chi-square (ᵡ2) in fit with the pseudo-second-order kinetic model as compared to those in the pseudo first-order model show a greater similarity between the pseudo-second-order kinetic model and the experimental data. The isotherm of Pb and Cu adsorption was also studied using Langmuir and Freundlich adsorption models. It was observed that the data had a better coordination with the Langmuir model with a determination coefficient of 0.99. By increasing the initial concentration of the lead and copper in the solution, their distribution coefficient (Kd) decreases. This suggests that although with increasing initial concentration of lead and copper, their adsorption increased by palygorskite mineral, however, by increasing the initial concentration of heavy metals, the remaining concentration of these elements also increased. The results also illustrated that both micro- and nanoparticles of palygorskite show more affinity to adsorb lean than copper from solutions. Conclusion: In general, it can be concluded from this study that adsorption of lead and copper by palygorskite nanoparticles depends on the contact time and the adsorbent size. Besides, the use of this mineral could be considered as a suitable, feasible and environmentally friendly way to remove lead and copper from aqueous solutions.
Plant Nutrition, Soil Fertility and Fertilizers
Faranak Ghasemi; ُSaeid Hojati; Ahmad Landi; Roya Zalaghi
Abstract
Introduction Clay minerals are considered as the main source of ion exchange and storage of nutrients in the soil. Knowledge of change and transformation of minerals, in relation to plant nutrition, fixation and release of elements is important. Sepiolite and palygorskite are fibrous clay minerals widely ...
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Introduction Clay minerals are considered as the main source of ion exchange and storage of nutrients in the soil. Knowledge of change and transformation of minerals, in relation to plant nutrition, fixation and release of elements is important. Sepiolite and palygorskite are fibrous clay minerals widely distributed in arid and semi-arid soils. Both minerals are rich in Mg and therefore, their weathering can significantly affect the chemistry of Mg in soil. Biological weathering which is carried out by living organisms (i.e. plant roots, soil fungi and bacteria) plays an important role in providing nutrients to plants. Hence, the use of microorganisms such as mycorrhizal fungi in the rhizosphere of agricultural crops has become more widespread. In recent years several studies have been conducted in relation to the weathering of minerals in the rhizosphere soil. However, few studies in terms of mycorhizal symbiosis with plant roots were carried out on release of Mg from sepiolite and palygorskite. Therefore, a pot experiment with a factorial arrangement through a completely randomized design was conducted to identify how symbiosis of sorghum roots with Glomus mosae mycorhizae affects release of Mg from sepiolite and palygorskite. Materials and Methods Pots containing sterile quartz sand and sepiolite or palygorskite (25-53 µm) were prepared and fungal treatments including presence or absence of fungus Glomus mosae were applied to the pots and then sorghum seeds were sown. Johnson nutrient solutions containing magnesium and without magnesium were used to feed plants during 70 days of experiment. After harvesting, the chlorophyll content, plants height and stem diameter were measured by SPAD, tape measure and caliper, respectively. Afterwards, the roots and shoots were separated and plants biomass and the percentage of roots colonization determined. Then, plants were oven-dried, ground, and the magnesium contents of them after extraction with 1M hydrochloric acid were determined using Agilent 7000 ICP analyzer. The chemical composition of palygorskite, sepiolite, and quartz sand was determined using X-ray fluorescence (XRF) and their mineralogical composition was determined using X-ray diffraction (XRD) approach. Results and Discussion Analysis of variance for the main effect of treatments on plant height, stem diameter, shoot dry weight and root dry weight showed that the effect of different sources of magnesium on plant height, stem diameter and shoot dry weight was significant (P < 0.01). The highest and lowest height, stem diameter, root and shoot dry matter were found in treatments fed with complete Johnson solutions and the palygorskite, respectively. The results also illustrated that application of Glomus mosae symbiotic mycorhizae significantly increased plant height, stem diameter, and root and shoot dry matter compared with non-mycorhizal treatments. This could be attributed to the fact that Mycorrhizal fungi (Glomus mosae) absorb more water and nutrients through increased photosynthesis and plant growth, consequently leading to improved plant characteristics when compared with non-mycorhizal crops. The results also showed the highest percentage of root colonization in palygorskite treatments and the lowest one in control. In general, a symbiotic relationship is created to improve low nutrition of elements that the amount of them in the soilwith a little mobility. Therefore, anything that exacerbates this deficiency, leads to an increase in symbiosis between plants and fungi. On the other hand, When plant is faced with more nutrient deficiencies, the demand for a symbiothic fungusGlomus mosae increases. Besides, the greatest magnesium concentration and chlorophyll contents were found in control, sepiolite and palygorskite treatments, respectively. In all treatments, magnesium intake was sufficient to grow sorghum, but as the results show, the amount of magnesium in the control and that of sepiolite was much more than palygorskite. These results clearly show that sepiolite mineral is able to release more Mg than palygorskite. The results also showed that the presence of the fungus Glomus mosae has significantly affected the release of Mg from both minerals. Conclusion In both sepiolite and palygorskite treatments, magnesium and chlorophyll content increased in symbiosis with fungi. This shows the positive effect of Glomus mosae fungus on release of Mg from these two minerals, especially sepiolite. Although, both sepiolite and palygorskite were able to provide enough amounts of Mg for sorghum plants, however, it seems that in long-term Mg released from sepiolite can more easily meet the need of plants when compared with palygorskite.
M. A. Delavar; A. Naderi
Abstract
Introduction Generally, formation and development of sodic soils often appear as almost large in flat plains capable of cultivation, especially in arid and semi-arid regions. Due to their unsuitable characteristics, Slickspots leave bad effects on plants growth and finally on human health. High levels ...
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Introduction Generally, formation and development of sodic soils often appear as almost large in flat plains capable of cultivation, especially in arid and semi-arid regions. Due to their unsuitable characteristics, Slickspots leave bad effects on plants growth and finally on human health. High levels of soluble and exchangeable sodium ions and colloidal material are the main marks of sodic soils. Different surface areas of Slickspot are spread over the flat and arable plains in Iran. The aim of this study was to evaluate the different properties of sodic soils and related soil formation factors in the semi-arid soils of Abyek plain. Materials and Methods The study area, with the coordinates 35° 47′ - 35° 53′ N and 50° 31′ - 50° 33′ E, was located in the southeastern of Abyek city, Ghazvin providence. Piedmont plain was the main physiography of the area and altitudes were divided in three topographic zones: 1190-1180, 1170-1160, 1150-1140 meters above sea level that the zones were classified into upper, middle and flat parts, respectively. Based on topography and site properties, 13 soil profiles were excavated in the topographic zones and all profiles were described based on USDA Standard Soil Description Manual Results and Discussion The results showed that soil acidity measured in saturated extraction ranged from 8.6 to 9.1, 9.8 to 9.7 and 9.1 to 10.1 for upper, middle and flat areas, respectively. Field observation studies of upper parts revealed that gravelly and subangular blocky soil structures were found in surface and subsurface horizons, respectively, while the subangular blocky and massive structures were found in subsurface horizons of middle parts profiles. The subangular blocky and columnar structures were demonstrated structures in profiles of the flat areas. Despite the low topography difference, 5 to 10 m in upper lands, exchangeable sodium content and electrical conductivity were low, and saline or sodic soils were not observed. These soils were classified as Xeric Haplocambids. In the middle part with 2 to 5 m difference in elevation, soils were classified as Sodic Xeric Haplocambids and Sodic Xeric Haplocalcids. The white spots observed in the sodic soils were classified as Xeric and Vertic Natrargids. Compare with the adjacent areas, the concentration of carbonate and bicarbonate anions were relatively high in soils of the flat areas that led to considerable increase in soil acidity. This can shows the accumulation of sodium carbonate salts in the soils. The presence of carbonate and bicarbonate anions in middle areas, probably was due to the development of Sodicization in the soils. The XRD diffractometers showed illite, montmorilonite, chlorite and palygorskite as the clay minerals in soil heorizons. Illite was found in all soil horizons of flat areas with deep decline. This decline was along with increasing of smectite clay minerals in Natric horizons that had poor drainage conditions. The clay coatings in the natric horizons were confirmed by micromorphology and scanning electron microscopy techniques. The cumulative clays on external surfaces of soil aggregates and wall pores, in flat areas, revealed the clay eluviation process. Because of the high soluble and exchangeable sodium cations, the conditions were favorable for transfer of clay in the soils, even in the presence of lime. Conclusion Consequently, the main soil formation factors in sodic soils can be presented as different in soil positions on piedmont physiography, the local relief, lateral and vertical movement of water and soluble salts from neighboring areas into the downstream lands and also salt and sodium containing minerals deposited by wind. The Slickspots and related soils were one of the major terrestrial phenomena in the plain Abyek. The Sodic soils in the plain were formed in the absence of high ground water table. Other environmental factors such as micro reliefs, position on the Landform, lateral movement of water and soluble salts and windborne sediments, played and essential role in the formation of sodic soils. The results of the experiments indicated that Sodicization process is developing towards the adjacent land and the absence of gypsum accelerated this development in these areas. Also, mineralogical studies indicate the presence of smectite mineral clay in Natric horizon where the drainage condition was poor and gave the possibility of neoformation of smectite, and that clay movement evidence from upper parts of profile was confirmed by micromorphological studies.