Soil Chemistry and Pollution
Zahra Albozahar; Neda Moradi; ُSaeid Hojati
Abstract
Introduction: Today, water consumption has increased dramatically as a result of technological advancement, extraordinary industrial development and urbanization, which has caused the production of large amounts of toxic waste. Zinc (Zn) is an essential element for plants and humans, however, excessive ...
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Introduction: Today, water consumption has increased dramatically as a result of technological advancement, extraordinary industrial development and urbanization, which has caused the production of large amounts of toxic waste. Zinc (Zn) is an essential element for plants and humans, however, excessive concentrations of zinc can cause problems for humans such as abdominal pain, nausea and vomiting. Zinc is the most toxic pollutant that enters the aquatic system through industrial wastewater. World health organization (WHO) has recommended limit concentration of zinc in drinking water of 5.0 mg L-1. Adsorption is one of the most efficient ways to remove heavy metals from the environment. Clay minerals are one of the good adsorbents for the adsorption of heavy metals due to their large surface areas, high ion exchange capacity and layered structure. Some factors such as temperature, pH, size of adsorbent, type of adsorbent and amount of adsorbent are considered as important factors in controlling the behavior of heavy metals in aqueous solution. The temperature of the solution can increase or decrease the adsorption of elements, which indicates the exothermic or exothermic nature of the surface adsorption reaction. Therefore, this research was carried out with the aim of investigating the effect of temperature on the kinetics and thermodynamics of Zn removal using sepiolite and kaolinite minerals.Materials and Methods: In this research, two clay minerals (kaolinite and sepiolite) in a size of 25-53 µm were used as zinc metal adsorbents. Sepiolite mineral was collected from mines in Fariman region of Razavi Khorasan province and kaolinite was collected from Lalejin in Hamadan province. The kinetics and thermodynamics of Zn absorption from aqueous solutions by sepiolite and kaolinite were investigated. For kinetic studies, 0.1 g of sepiolite and kaolinite adsorbent was poured into a centrifuge tube and 20 ml of Zn solution with a concentration of 50 mg L-1 of zinc nitrate background solution was added to it and at different times (5, 10, 15, 20, 30, 60, 120, 240, 480, 720, 1440 and 2880 minutes) was stirred. The experiment of adsorption kinetics was performed at pH 5 and at a temperature of 25 ± 1 °C. The thermodynamics of zinc adsorption was investigated at temperatures of 25, 35 and 45 ℃. The adsorption behavior of zinc metal by sepiolite and kaolinite minerals was evaluated at different times with pseudo-first-order, pseudo-second-order, Ilovich and intraparticle diffusion kinetic models through non-linear regression and using Solver software. Then, the thermodynamic parameters of adsorption process including: the activation energy (Ea), gibbs free energy (ΔG), entropy (ΔS) and enthalpy (ΔH) were determined.Results and Discussion: The results of this research showed that by increasing the contact time and decreasing the temperature of the solution from 45 to 25 ℃, the amount of Zn adsorption by both minerals increased. Also, the equilibrium time was determined to be 720 minutes. The results showed that the adsorption efficiency decreases with increasing temperature and the highest removal percentage was observed at 25 ℃. Based on the results obtained from the fitting of kinetic models with experimental data, the pseudo-second order model with the highest explanatory coefficient (R2=0.99) was selected as the best model. Adsorption capacity (qe) of Zn estimated from the pseudo-second order model for sepiolite and kaolinite at 25℃ compared to 45℃ decreased by 44.30 and 38.19%, respectively. Also, the amount of Zn adsorption capacity for sepiolite mineral was higher than kaolinite. The activation energy (-9.79 to -23.81 kJ mol-1) revealed the physical adsorption of Zn by sepiolite and kaolinite. The activation energy of Zn adsorption onto the sepiolite (-23.81 kJ mol-1) and Kaolinite (-9.79 kJ mol-1) indicated that Zn was more strongly sorbed by sepiolite than kaolinite. Conclusion: the results obtained showed that sepiolite and kaolinite can be used an adsorbed to remove Zn from aqueous solution with good efficiency and low cost, while sepiolite had higher Zn adsorption capacity compared to kaolinite. Adsorption of Zn decreased with increasing temperature. The optimal temperature in this study for maximum adsorption of Zn by sepiolite and kaolinite was 40℃. Thermodynamic parameters including changes in Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) showed that zinc adsorption process by the studied minerals is an exothermic and spontaneous reaction. As a conclusion, sepiolite has a high potential for remove of Zn from wastewater.
Seyedh Sanaz Mousavi; ُSaeid Hojati; Ahmad Landi
Abstract
Introduction Soils at the earth crust could be considered as the result of interaction among five soil-forming factors. The strength and weakness of each of these factors causes formation of different soils with different properties and horizons. Previous studies have reported that Iranian agricultural ...
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Introduction Soils at the earth crust could be considered as the result of interaction among five soil-forming factors. The strength and weakness of each of these factors causes formation of different soils with different properties and horizons. Previous studies have reported that Iranian agricultural soils show different levels of zinc deficiency. Although the literature review confirms many studies in this regard, the number of studies compared the distribution of the chemical forms of micronutrients and especially zinc after the application of chemical fertilizers in the soils of Khuzestan especially in the common diagnostic horizons of these soils, is limited. Therefore, the purposes of this study were two-fold: (1) to measure and determine the chemical forms of zinc in selected diagnostic horizons (Mollic, Calcic and Salic) of Khuzestan Province, (2) to identify the contribution of some physical and chemical properties of these soils on availability of zinc.Materials and Methods In order to carry out this research, Mollic and Calcic diagnostic horizons were collected from the Karun 3 watershed in the east of Khuzestan province, with thermic and mesic temperature and xeric moisture regimes. However, Salic diagnostic horizon was sampled from the route between Ahvaz to Abadan in the southwest of the province, with hyperthermic temperature regime and an aridic moisture regime. After being transferred to the laboratory, the samples were first air-dried, and after passing through a 2-mm sieve and before carrying out the fractionation and speciation experiments, their physical and chemical characteristics including electrical conductivity (EC), pH, particle size distribution, organic C content, calcium carbonate equivalent, cation exchange capacity (CEC), specific surface area (SSA), and total and DTPA extractable Zn were determined employing common standard procedures (Table 2). Different forms of zinc in the solid phase of the Mollic, Calcic, and Salic soils were extracted using the method described by Tessier et al. (1979). In brief, 5 components including water soluble, exchangeable, carbonates, iron and manganese oxide, organic and residual forms were determined. The concentration of zinc in the extracts obtained from different stages of successive soil extraction was determined using an atomic absorption device. In order to estimate the accuracy of the extraction method described above, the recovery percentage was calculated. To do this, one gram of a certified soil from the state of Montana (ANIST 2711A) was used and the recovery percentage of zinc in our study was 94.5%. In order to determine the chemical forms of zinc in the solution phase of the soils, 100 g of each soil sample was saturated with double distilled water, and then extracted using a vacuum pump and Buchner funnel. The extracts were passed through filter paper and centrifuged at 2500 rpm for 8 minutes, then the values of pH, electrical conductivity, dissolved organic carbon, and dissolved cations and were determined using common laboratory methods described earlier (Table 1). These parameters were considered as input in Visual MINTEQ software to predict zinc species in soil solution (all free and complexed organic and mineral species). The data analysis was conducted considering a factorial design based on a completely randomized design through SAS software (v9.1). The comparison of means was also done using the Tukey’s test at the 5% probability level. Graphs were also drawn using Origin software (v2018).Results and Discussion Considering the critical level of zinc deficiency in the soil (1 mg/kg), all the soils are deficient in terms of available zinc. The studied soils are among alkaline and calcareous soils, but they did not show any differences from each other in terms of soil texture. It is noteworthy that the mollic horizon has a greater cation exchange capacity and specific surface area than the other two soils due to the higher amount of organic matter and the greater abundance of clay contents. The results of zinc fractionation in the studied soils showed that organic, carbonate and oxide forms in the Mollic and Calcic horizons, and carbonate, oxide and exchangable forms in the Salic horizon were the dominant forms of Zn which affects its supply to the plants. The results also showed that Zn2+, Zn(OH)2(aq), Zn-DOM (aq), and Zn (OH)+ species were the dominant species of Zn in soil solution of all diagnostic horizons. The result of Zn mobility factor calculations with the addition of 10 mg/kg Zn(SO4)2 showed lower values of mobility factor in the mollic diagnostic horizon than those of the calcic and salic.
ُSaeid Hojati
Abstract
Introduction Khuzestan province in southwestern Iran is one of the most critical areas affected by dust storms due to the arid climate and the abundance of desert areas in its western and southern parts. Dust storms in these areas are among the most critical environmental issues. Air pollution, the development ...
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Introduction Khuzestan province in southwestern Iran is one of the most critical areas affected by dust storms due to the arid climate and the abundance of desert areas in its western and southern parts. Dust storms in these areas are among the most critical environmental issues. Air pollution, the development or increase of respiratory diseases, reduced soil fertility, damage to crops, and reduced solar radiation are among the most critical consequences of dust storms. Dust particles can absorb significant amounts of heavy metals, which facilitate their transport on a large scale due to their fine particle size distribution. Street dust is considered the major source of pollutants from a wide range of traffic, industrial emissions, pesticides, and mining activities. Although many studies have been conducted to identify the origin and pollution status of dust particles in the country, the assessment of pollution and source of street dust particles during dust storms, especially in Ahvaz city, has received less attention. .Thus, this study was conducted to: (1) identify the source of street dust in Ahvaz city, and (2): determine the level of contamination to Pb, Zn, and Cu.Materials and Methods Dust and soil samples were collected respectively at 69 and 23 points from streets and the surface soil (0-5 cm) in Ahvaz city in February 2015. To determine the particle size distribution pattern in the dust samples, they were first dispersed in 1 M sodium hydroxide and 10% sodium hexaphosphate solutions for 2 hours. Then, they were analyzed using A Malvern Hydro 2000g laser diffraction device. The ionic compositions of the dust and soil samples were also determined after extraction from 1 (dust/soil): 5 (water) suspension with an advanced Meterohm 861 model ion chromatography apparatus. The heavy metal contents of soil and dust particles were determined using inductively coupled plasma (ICP) spectroscopy. To determine the Pb, Fe, Cu, and Zn contents, 0.5 g of the dust or soil samples were digested with 60% nitric acid, and after 24 hours, the samples were heated for 0.5 hours at a temperature of 80 ° C. Then, they were filtered with Whatman 42 paper and finally were examined using an Agilent 7000 inductively coupled plasma (ICP) spectrometer. To assess the degree of street dust pollution in Ahvaz city, various indicators, including the single element pollution index and Nemerow integrated pollution index, were calculated. A pollution index is expressed as the ratio of the concentration of an element in soil or dust samples to the same component's baseline value in soil or dust sample. If this index is greater than 1, it indicates different levels of pollution.Results and Discussion The particle size distribution in the studied samples showed a bimodal pattern with more abundance of particles in the size of silt and fine sand. Accordingly, 57 to 89% of the particles were in the silt size, and 5 to 16% were in the size of fine sand. The results also indicated that the abundance of sodium, calcium, chloride, and sulfate ions was comparably higher than the local soils. Similarly, the average concentration of each heavy metal was higher than those of the local soils and the upper earth crust, which followed the order Zn> Cu> Pb. Accordingly, The average Pb, Cu, and Zn concentrations were 5.23, 6.37, and 6.89 times more than their corresponding values in the earth's upper crust. Accordingly, and based on the values obtained from the pollution index (PI), all the studied elements in the street dust of Ahvaz city could be categorized as highly polluted. The average of Nemrow integrated pollution index was found 7.26, which shows a high pollution level for street dust in Ahvaz cityConclusion It seems that dust particles collected from streets and sidewalks of the Ahvaz city are mainly originated from regional focal points in eastern and southeastern parts of the city. When Pb, Cu, and Zn concentrations in the street dust of Ahvaz city and those reported from different cities in Iran and other countries are compared, it is concluded that dust particles deposited over the streets and sidewalks in Ahvaz county have a higher degree of pollution. Therefore, Prompt actions are needed to lower the risk of these elements for the environment.
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.
N. Mehrab; M. Chorom; S. Hojati
Volume 37, Issue 1 , September 2014, , Pages 1-11
Abstract
To evaluate the effect of two types of soil textures and zeolite enriched with ammonium on growth characteristics of wheat and water use efficiency, a factorial experiment based on a completely randomized design with three replications in greenhouse condition was conducted at Shaid Chamran University ...
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To evaluate the effect of two types of soil textures and zeolite enriched with ammonium on growth characteristics of wheat and water use efficiency, a factorial experiment based on a completely randomized design with three replications in greenhouse condition was conducted at Shaid Chamran University in the autumn of 2011. Treatments were 5% and 10% of the raw zeolite, 5% and 10% zeolite enriched with ammonium, fertilizer treatment (100 kg ha-1) and soil textures were clay loam and sandy loam. The results showed that the soil texture significantly affected the growth characteristics of wheat and water use efficiency (P<0.01). The plant nitrogen percentage, 1000-seed weight and seed yield were higher in sandy loam soil than in clay loam. Water use efficiency in sandy loam, was more than clay loam. None of the zeolite treatments had a significant effect on water use efficiency. The highest percentage of plant nitrogen fertilizer plants treated with ammonium-rich zeolite and 10%, respectively. The highest percentage of plant nitrogen was observed in chemical fertilizer treatment and 10% NH4+-zeolite and the highest seed yield was obtained in 10% NH4+-zeolite treatment. The highest C/N ratio was measured in treated with 10% raw zeolite in a sandy loam soil. Therefore, the application of ammonium zeolite enriched can be improved wheat growth characteristics and using less chemical fertilizer and thereby also saving on fertilizers helped to reduce environmental pollution.
Saeid Hojati; Ahmad Landi; Heyam Alekasiri
Volume 36, Issue 1 , September 2013, , Pages 13-22
Abstract
Wastewaters from different industries contain great amounts of heavy metals which can contaminate the ground water after entering the soil. Few studies have been conducted on the application of clay minerals such as sepiolite in preventing the leaching of these elements. This study was conducted to evaluate ...
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Wastewaters from different industries contain great amounts of heavy metals which can contaminate the ground water after entering the soil. Few studies have been conducted on the application of clay minerals such as sepiolite in preventing the leaching of these elements. This study was conducted to evaluate sepiolite as a strong and inexpensive adsorbent in preventing the leaching of lead and zinc from sandy soil columns under laboratory conditions. Therefore, 400 ml of solutions containing lead and zinc with a concentration of 75 mg/l, were passed through pre-saturated soil columns with different amounts of sepiolite (2, 4, 6 and 8 weight percent) in two sizes, < 2 and 20- 50 microns, under a flow rate of 1.2 liter h-1. The concentration of lead and zinc in the successive 20 ml leachate was then measured using atomic absorption spectrophotometer. Results showed that application of sepiolite in soil columns decreased leached amount of Pb and Zn as compared to control treatments. Also, with increasing sepiolite application rate, and decreasing its particle size, leaching of zinc and lead from the soils was reduced. However, the amount of lead leached was less than that of zinc. It seems that sepiolite mineral could be utilized as suitable materials to reduce the leaching of lead and zinc from soil to ground waters.
