Soil Chemistry and Pollution
Alireza Abdollahpour; Mojtaba Barani Motlagh; Amir Bostani; Farshad Kiani; Farhad Khormali; REZA GHORBANINASRABADI
Abstract
Introduction Soil organic carbon (SOC) is the largest source of terrestrial organic carbon and small changes in its components have many effects on global warming and carbon cycle. Soil organic matter (SOM) is considered as the most complex and least known component of soil, because it consists of plant, ...
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Introduction Soil organic carbon (SOC) is the largest source of terrestrial organic carbon and small changes in its components have many effects on global warming and carbon cycle. Soil organic matter (SOM) is considered as the most complex and least known component of soil, because it consists of plant, microbial and animal masses in various stages of decomposition and is a mixture of heterogeneous organic materials that are closely related with mineral components. Soil organic matter has beneficial effects on the chemical (buffering and changes in pH) and biological (precursor and supply of nutrients for microbes) properties of the soil and thus affects the fertility capacity of the soil. The quality and quantity of soil organic matter is the most important criterion for sustainable soil management. Total organic carbon (TOC) consists of labile and non-labile forms of SOC and have different degrees of sensitivity to different types of land use changes and management operations. The purpose of this research is to investigate the effect of changing land use on the chemical components of soil organic carbon and carbon recalcitrant index in Toshan Watershed, Golestan provinceMaterials and Methods For this research, four major and dominant types of land use were considered in the study area, including forest, cropping land, garden and abandoned lands in the Toshan watershed in the northwest of Gorgan city of Golestan province. The soil organic carbon and total C of soils were measured. Furthermore, the soil carbon fractionation was performed by Young's method (using hydrolysis methods with HCl and Labile fraction). In this research, Acid hydrolysis method was used to separate the recalcitrant SOM pool. For this purpose, one gram of SOM sample was treated with 25 ml of 6 M hydrochloric acid solution at 105°C for 18 hours in a Pyrex tube in a hydrolysis package. After cooling, the remaining non-hydrolyzed materials were separated by centrifugation. Then, they were dried in an oven at a temperature of 60 degrees Celsius and considered as a part of resistant organic matter. The resistant part of the soil organic carbon was determined with the CHNS Analyzer device. The Labile fraction consists of water soluble carbon, microbial biomass carbon and mineralizable carbon are measured using the following methods and the labile part of carbon is calculated from their sum. Water-soluble organic carbon is extracted by adding 20 ml of distilled water to 10 grams of wet soil. The mixture will be shaken and centrifuged, filtered. Then they will be quickly analyzed by TOC Analyzer. Microbial biomass carbon will be determined by the chloroform fumigation-extraction method. Mineralizable carbon determined as follow. The amount of CO2 will be measured by titration of NaOH solutions with 0.1 M HCl in the presence of BaCl2. Cumulative amount of CO2-C emitted in 30 days of incubation is called Mineralizable carbon. The data were analyzed based on the factorial test in the form of a completely randomized design (CRD) with two levels of soil depth and four land uses with five replications. Correlation between traits was also estimated. Statistical analyzes were performed using SAS software. Therefore, it can be concluded that depending on the climatic conditions and the condition of the soil, the forest, in terms of natural cover, the correct management of agricultural lands (using modern methods of no-tillage or low-tillage) can be a potential practice. It is to store carbon in the soil as well as various soil components and increase soil formation, which will subsequently reduce the concentration of carbon dioxide in the atmosphere.Results and Discussion The results showed that the first depth of forest use has the highest amount of total carbon and soil organic carbon (6.12% and 3.5% respectively). Also, the highest amount of resistant organic carbon (HCl hydrolysis), water-soluble organic carbon, microbial biomass carbon, and microbial mineralizable carbon were observed in forest land use. The second depth (10-20 cm) of forest land use had the highest and the second depth (10-20 cm) of garden land use had the lowest organic carbon resistance index (82.1% and 50.17%, respectively). In all land uses, except for the forest, the soil organic carbon resistance index decreased with increasing sampling depth. Due to the fact that the carbon management index can be easily calculated, it can be a suitable index for quick assessment of soil quality.Conclusion The results showed that with the change of land use and cultivation, the soil organisms received more oxygen and the speed and intensity of respiration in the soil increased in the short term, which caused more decomposition of organic matter and with the decrease of organic matter in the long term, the quality of soil decreases after a while.
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.
Soil Chemistry and Pollution
Khosro Betyar; Neda Moradi; Abdolamir Moezzi; Shila Khajavi-Shojaei
Abstract
Introduction Phosphorus deficiency is one of the major problems of calcareous soils and a limiting factor for crop production in these soils and excessive use of phosphate fertilizers can cause pollution in soil and water. The use of organic amendments such as compost, biochar or a combination of them ...
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Introduction Phosphorus deficiency is one of the major problems of calcareous soils and a limiting factor for crop production in these soils and excessive use of phosphate fertilizers can cause pollution in soil and water. The use of organic amendments such as compost, biochar or a combination of them can be effective in improving the amount of available phosphorus of the soil. For this purpose, the effect of combined application of compost and biochar of sugarcane bagasse on phosphorus sorption and desorption were investigated.Materials and Methods Sugarcane bagasse and compost were provided from Debal Khozaei agro-industry Company. The oven-dried sugarcane bagasse 105 ºC were pass through 2 mm sieve and slow pyrolysed at 500 ºC using a laboratory muffle furnace with a heating rate of 5 ºC min-1 and presence of N2 flow to provide an anoxic condition. Some physico-chemical properties of samples were determined. The soil sample was collected from 0-30 cm of the campus of Shahid Chamran University of Ahvaz, Ahvaz, Khuzestan province, SW Iran (48° 65′91.12′′E31°30′53.82′′N). The studied soil classified as a Typic Haplocalcids. The air-dried soil samples were sieved (˂ 2 mm) and used for physico-chemical analysis. The incubation experiment was conducted with 7 treatments. The treatments including (1) control (without any amendments), (2) 100% sugarcane bagasse, (3) 100% sugarcane bagasse compost, (4) 100% sugarcane bagasse biochar, (5) 50% compost +50% biochar, (6) 75% compost + 25% biochar, (7) 25% compost + 75% biochar were added as 2% w/w to soil. The 200 g air-dried soil and treatments were mixed and kept in poly-ethylene containers for 120 days. Samples were incubated in 25 2 ºC and soil moisture was adjusted to soil field capacity using distilled water during the incubation time. At the end of incubation time, soil phosphorus sorption isotherm was measured. A 2.5 g of each treatment was transferred to a 50 ml centrifuge tube. Then, a 25 mL of CaCl2 0.01 M containing 0, 10, 20, 40, 60, 80, and 100 mg P L-1 (prepared from KH2PO4) was added to each centrifuge tube. Two drops of chloroform were added to each centrifuge tube to inhibit microbial growth. Samples were equilibrated at 25 1 ºC for 24 h on shaker at 150 rpm, and then centrifuged for 5 min at 3000 rpm and pass through 0.45-μm filter paper. The phosphate desorption was conducted on soil remaining in the filter immediately after sorption experiment. For this purpose, each treatment was resuspended with 25 ml of CaCl2 0.01 M solution without phosphate and shaken for 24 h. after collecting the supernatant, desorbed phosphate was measured. For assessing the adsorbed phosphate, the difference between the initial phosphate concentration and the phosphate concentration at equilibrium was calculated. The Langmuir, Freundlich and temkin isotherm models were used to describe the sorption of phosphate. In addition, some phosphorus buffering indices including maximum buffering capacity (MBC), standard buffering capacity (SBC), equilibrium buffering capacity (EBC) and standard phosphorus requirement (SPR) were obtained from P sorption equations at 0.2 mg P L-1 concentration in soil solution. The experimental data were fitted by Microsoft Excel-SOLVER and graphs were plotted by Microsoft Excel.Results and Discussion The soil was had loam texture, with low SOC content and high pH and calcium carbonate content, also the results of the characteristics of sugarcane bagasse compost and biochar showed that the compost had high salinity and the biochar had high pH and C/N ratio. The amount of phosphorus absorption increased with increasing the initial concentration of phosphorus in the treated soils. The highest and lowest amount of phosphorus absorption were in the control in compost treatments, respectively. In general, different levels of biochar and compost treatments caused a decrease in phosphorus absorption compared to the control treatment. The results showed that P sorption and desorption are described well by the Freundlich and Langmuir equations with a high correlation coefficient; however, the Temkin equation described the P sorption and desorption in the soils poorly. Biochar and compost treatments significantly decreased the Freundlich n parameter. Results showed that the effects of compost and 75% compost + 25% biochar were significantly greater than the effects of other treatments on the n parameter exponential adsorption equation. Application of different treatments of sugarcane bagasse compost and biochar application caused a significant increase in MBC (25.4-70.7%) and EBC (33.1-69.4%). The standard P requirements (SPR) were lower in soils treated than in control soil.Conclusion The results showed that the combined application of biochar-compost of sugarcane bagasse reduced the sorption and increased desorption of phosphorus. The maximum buffering capacity (MBC) and equilibrium buffering capacity (EBC), standard buffering capacity (SBC) and standard phosphorus requirement (SPR) in compost and compost 75% + biochar 25% showed more decrease than the control. In general, the results of this study indicate that the combined application of biochar-compost of sugarcane bagasse reduces phosphorus sorption in soil in calcareous soils, which can increase the availability phosphorus for plants.
Soil Chemistry and Pollution
Mina Hashemi Tazangi; Soheila Ebrahimi; Reza Ghorbani Nasrabadi; Seyed Alireza Movaheddi Naeeni
Abstract
Background and objectives: Hydrocarbons derived from petroleum and gas have gained increased attention as the most important fossil resources of energy as well as crude material for petrochemical industries. However, environmental issues such as pollution due to extraction, exploitation and transportation ...
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Background and objectives: Hydrocarbons derived from petroleum and gas have gained increased attention as the most important fossil resources of energy as well as crude material for petrochemical industries. However, environmental issues such as pollution due to extraction, exploitation and transportation of these materials has raised concerns as an environmental warning. In recent years, utilization of biochar (via biomass burning) has been regarded as a soil refiner to reduce or eliminate pollution, especially in in situ studies. Biochar is a product rich in carbon, which is produced during the pyrolysis of various types of woods, fertilizers, leaves, straws as well as agricultural wastes under abiotic conditions. It seems that biochar can be suggested as a suitable compound to manage biomass wastes as well as to enhance soil fertility. Thus, kinetic behavior of biochar in reduction of gasoil pollution of soil, its changes of this pollutant over time and changes in the microbial activity in this time period were investigated.Materials and methods: The soil polluted with gasoil was collected from the vicinity of the gasoil tanker located in Shiraz refinery. The soil had been polluted for years due to the leakage of gasoil. Then, after the measurement of the initial total petroleum hydrocarbon content and physical and chemical properties (soil texture via hydrometry, electrical conductivity in the saturated paste, available phosphorous using the Olsen method, total nitrogen using the Kjehdahl method, pH of soil in the saturated paste, soil carbon using the Walkey and Black method) of the polluted soil, 700 gram soil samples containing wheat straw biochar at one and two mm sizes and 20, 40, 60, 80 and 100 g kg-1 weight doses were prepared as split-split-plot experiment based on a completely randomized design with three replicates. The samples were then rested in a 50% constant humidity for four weeks at 28 ± 2 °C, and were aerated two times a week. Finally, the results of the changes in the total petroleum hydrocarbon and microbial activity over time were recorded. A three- parameter sigmoidal function was fitted to the data related to the total petroleum hydrocarbon and microbial activity over time. Analysis of variance was carried out using the SAS software v. 9.0. The leas significant difference method (LSD) was used to compare the means. The changes in the total petroleum hydrocarbons and microbial activity were analyzed using the SigmaPlot software v. 12.5. Microsoft Excel v. 2013 and SigmaPlot v. 12.5 were used to draw the figures. Results: According to the results of the present study, the application of biochar had a significant effect on the reduction of gasoil pollution of the soil. The results related to determination of the kinetic model for the reduction of pollution during the biochar application process showed that the kinetic of reduction in total petroleum hydrocarbon was of first order equation; so that in the first 28 days of the experiment, the rate of total petroleum hydrocarbon degradation was increasing, whereas it decreased 35 days after the beginning of the experiment. Biodegradation constant (k) was higher for the soil treated with the refiner and these soils had a lower half-life compared with the polluted control. The rate of reduction in half-life and Biodegradation constant rate increased with increasing refiner weight. On the contrary, half-life increased and Biodegradation constant decreased with increasing refiner size. The results indicated a significant difference in the traits as a result of applying various sizes and weights of refiner. Weekly monitoring of the pollution degradation and bioremediation performance in all refiner sizes and weights showed that the lowest time to 50% pollutant removal was obtained in 100g kg-1 and 1 mm size treatment. Investigation of the respiration under the mentioned conditions showed that the lower sizes and higher weights of biochar led to improved hydrocarbon degradation. Also, according to the results, biological efficiency (E%) of biochar was calculated 40.05 at the end of the 60 day period.Conclusion: According to the present study, biochar refiner has a great potential for utilization as a cheap and relatively new strategy to eradicate or reduce soil hydrocarbon pollution. This method is compatible with the in situ bioremediation in the soils polluted with petroleum and other petroleum derivate compounds, due to being less costly and posing less hydrocarbon threat to the environment. It is also a suitable tool to devise bioremediation strategies.
Soil Chemistry and Pollution
Masoumeh Sadeghi Poor Sheijany; Fatemeh Shariati; Nafiseh Yaghmaeian Mahabadi; Hassan Karimzadegan
Abstract
Introduction One of the most important results of population growth, urbanization, and industrialization is the increase of urban waste. Accumulation of municipal solid waste produces toxic leachate that can transfer contaminants to the soil and alter its quality, especially in vulnerable forest ecosystems. ...
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Introduction One of the most important results of population growth, urbanization, and industrialization is the increase of urban waste. Accumulation of municipal solid waste produces toxic leachate that can transfer contaminants to the soil and alter its quality, especially in vulnerable forest ecosystems. This study was carried out to determine the properties of the soil of the Saravan municipal solid waste disposal site that is located in a part of the Hyrcanian forests, Rasht, Guilan province, which have been affected by the activity of the open dumpsite; Determining the minimum data set (MDS) and evaluating the quality adjacent soil to the dumpsite, the route affected by leachate and downstream lands, through soil quality indices such as simple integrated quality index (IQISA), weighted integrated quality index (IQIW) and Nemoro quality index using total data set (TDS) and MDS, and comparing them with each other.Materials and Methods Based on the distance from the disposal site, slope, height, and the route of leachate, from 32 sampling points with the same vegetation, a total of 32 composite samples were prepared in plots 10×10 from (five sub-samples from four heads and the middle by a polyethylene hand auger) a depth of 0-15 cm in June 2019.The soil properties including pH, clay, silt, sand, available phosphorus (Pava), copper (Cuav), zinc (Znav), and iron (Feav), total nitrogen (N), cation exchange capacity (CEC), electrical conductivity (EC), organic carbon (OC), basal respiration (BR), microbial biomass carbon (MBC), the metabolic quotient (qCO2) and enzymatic activities of Urease (UR) and alkaline phosphatase (ALP) were measured. One-way analysis of variance (ANOVA) and independent comparison tests was used to compare the results of the soil samples in areas exposed to dumpsite activities and control. Six properties were selected as MDS using principal component analysis (PCA). The models of the simple integrated quality index (IQIsa), weighted integrated quality index (IQIW), and the Nemoro index were used to determine soil quality. One-way ANOVA and Duncan’s multiple range tests were used to compare the mean soil quality indices in the areas around the disposal site, leachate-affected route, and downstream lands. The possible relationship between chemical, physical and biological properties was investigated by calculating Pearson’s correlation coefficients.Results and Discussion The results showed that the value of soil properties including Feav, EC, Pav, N, Znav, Cuav, OC, BR, MBC, the enzymatic activities of UR and ALP is significantly different from the control (p < 0.01). The properties of Pav, Cuav, EC, clay, silt and MBC were selected as MDS, which can describe 73% of changes in the soil quality. Evaluation of the soil quality through Nemoro index, using MDS and TDS (IV and III, respectively) at different distances from the dumpsite was the same as the control. The values of IQIsa and IQIw using MDS did not show any significant difference with the control in all routes exposed to the activity of the disposal site, except around the dumpsite. However, the degree of soil quality through the overall average IQIsa and IQIw, using MDS in all areas exposed to the dumpsite was the same as the control. The results of IQIsa and IQIw, using TDS were so different so that the values of IQIsa and IQIw, using TDS in the path of leachate and lands downstream of the disposal site showed a significant difference with the control (p < 0.01). Also, the quality degree through the overall mean value of IQIsa and IQIw, using TDS (III and IV, respectively), around the disposal site and the path of leachate were different from the control (II and III, respectively).The Saravan municipal waste disposal site is located in an area, with a Mediterranean climate, with high relative humidity and rainfall. It has increased the possibility of leachate production. On the other hand, with the leachate flowing along the sloping path of 15%, especially after each rainfall in the area, the soil is contaminated by leachate and transfer downstream. Also, Leachate is discharged from the disposal site downstream, into the river, which is used to irrigate agricultural land downstream of the dumpsite. The results of changes in IQIsa and IQIw by TDS can indicate the possible consequence of the leachate effect from the disposal site on the path to the soil of downstream farms.Conclusion According to the objectives of the research, it seems that soil properties including Feav, Pav, EC, N, BR, MBC, and the enzymatic activities of UR and AIP have been affected by the activity Saravan solid waste disposal site. Investigating the results of the quality indices using MDS and TDS showed that IQIsa and IQIw, using TDS can better represent the effect of waste disposal site activity on soil quality. Significant differences of the IQIsa and IQIw, in the leachate route and downstream agricultural lands with the control can probably be due to the effect of leachate and leaching of soil around the leachate route and its transfer downstream. Considering the same quality results in the area exposed to the activity of the disposal site with the control through the Nemoro index, using MDS, TDS, it can be concluded that Nemoro index does not have the required sensitivity to describe the effect of waste disposal activity on the quality adjacent soil. This study showed that the change of use of the forest area to waste disposal site affected its soil quality in the path of leachate and downstream lands. Therefore, to protect the areas of Hyrcanian forests in the Saravan region and to prevent the reduction of soil quality in the region, taking the necessary measures to separate the municipal solid waste from the origin, to establish leachate collection systems and treatment of leachate before flowing in the forest areas should be carried out.
Soil Chemistry and Pollution
Hasan Bolbol; Majid Fekri; Majid Hejazi-Mehrizi; Naser Bromand
Abstract
Introduction Phosphorus (P) is an essential nutrient for all forms of life on the earth, but in excess concentrations, it can act as a serious water pollutant through eutrophication. Thus, it is very important to remove P from aqueous solutions before their release into natural water resources. Among ...
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Introduction Phosphorus (P) is an essential nutrient for all forms of life on the earth, but in excess concentrations, it can act as a serious water pollutant through eutrophication. Thus, it is very important to remove P from aqueous solutions before their release into natural water resources. Among the various P removal techniques that have been developed, the sorption process is widely accepted to be an effective water treatment technique because of low cost, ease of operation, simplicity of design, and high sorption capacity in dilute solutions. Layered double hydroxides (LDHs) are a type of two-dimensional nanostructure anionic clays with high capacities to sorption of anions. These non-silicate clays consist of positively charged brucite-like octahedral sheets which neutralize by a negatively charged interlayer containing relatively weak bonded anions and water molecules. The positive charges generated by the isomorphous substitution of trivalent cations for divalent cations are balanced by interlayer anions that can be exchanged by other anions making them good anion-exchangers with high selectivity. LDHs have been widely used as environmental sorbents because of their high charge density, large interlayer areas, good thermal stability, and high anion exchange capacities of the interlayer anions. The aim of the present study was to synthesize a Mg-Fe LDH as a sorbent for P removal from aqueous solution. Materials and Methods The Mg-Fe LDH was synthesized using the co-precipitation method. In brief, a mixture solution containing 0.03 mol MgCl2. 6H2O, and 0.01 mol FeCl3. 6H2O was added dropwise into a flask containing 100 ml of 1 M NaOH solution under vigorous stirring at pH=10. The obtained slurry was filtered and washed repeatedly with DW until the filtrate pH reached neutral. Mg-Fe LDH particles were then obtained by drying the filtrate at 70 °C in an oven overnight. The crystallinity of the sample was studied using X-ray diffraction (XRD) analysis. In order to investigate the performance of the synthesized LDH as a P sorbent, batch experiments were carried out in polyethylene centrifuge tubes. The suspensions were shaken for 24 hours at 250 rpm, and the supernatant was then separated by centrifugation at 4000 rpm for 10 minutes and were filtered by Whatman ashless grade 42 filtration papers. Equilibrium P concentration was determined according to the ascorbic acid method using UV-vis spectrophotometer at the wavelength of 880 nm. The effects of pH, initial P concentration, and contact time on P sorption were investigated in the ranges of 2-10, 0-300 mg/L and 0-1440 min, respectively. Results and Discussion The XRD pattern of the LDH sample showed typical structure of hydrotalcite-like compounds with sharp and reflection peaks corresponding to the (003), (006), (012), (015), and (110) crystal planes which are characteristic planes of hydrotalcite-like compounds. The efficiency of LDH to remove P decreased with the increasing of initial P concentration and the maximum removal efficiency of LDH occurred in the range of 5-20 mg/L of initial P concentration. With increasing of initial P concentration from 20 to 300 mg/L, the P removal efficiency of LDH decreased from 98.7 to 24.6 %. The P removal efficiency was increased with time and reached equilibrium at 60 min. The P removal rate of LDH in this time was about 66 % and no significant decrease in residual P concentration was observed after 60 min. The sorption of P on LDH was highly pH dependent, and the maximum P removal was found at pH of 4. The sorption kinetic and isotherm data were well described by pseudo-second-order and Langmuir equations, respectively. According to the Langmuir equation, the maximum P sorption capacity (Qmax) of LDH was obtained as 13.96 mg/g. Conclusion It was found from the results of this study that the mechanisms involved in the P sorption onto LDH included electrostatic attraction, ligand exchange, and surface complex formation. In addition, the results suggested that the synthesized Mg-Fe LDH can be potentially used as an effective sorbent for the removal of P from aqueous solutions. Further research is needed on the regeneration of the LDH after P sorption and the evaluation of desorption behavior of P from LDH under different conditions.
Soil Chemistry and Pollution
Neda Moradi; Mir Hassan Rasouli-Sadaghiani
Abstract
Introduction Recently, due to the enhancement of industrialization, urbanization, and disposal of wastes, fertilizers, and pesticides the concentration of heavy metals in agricultural soil has increased. Heavy metals are a serious threat to the environment due to their hazardous effects. Heavy metal ...
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Introduction Recently, due to the enhancement of industrialization, urbanization, and disposal of wastes, fertilizers, and pesticides the concentration of heavy metals in agricultural soil has increased. Heavy metals are a serious threat to the environment due to their hazardous effects. Heavy metal contamination of the soil is of particular attention due to food security issues and several reported health risks to both human and living organisms. In addition, large areas worldwide are polluted by lead (Pb). One of the major problems in the process of Phytoremediation is the low solubility of heavy metals, such as lead in the contaminated soil. Phytoextraction is a solar-driven remediation technology which greatly reduces the costs and has minimum adverse side effects. Lead (Pb) is among the highly toxic and most common heavy metals at contaminated sites. It originates from various anthropogenic sources and causes a variety of health, environmental, and ecological problems. The weed plant species are usually of the quickly growing nature and have higher biomass under unfavorable environments. Their phytoremediation potential could be more effective in reducing food chain contamination and consequently the risk to human health. Therefore, the objective of this study was to assess the Pb remediation potential of Artemisia (Artemisia absinthium L.) and Xanthium (Xanthium strumarium L.) in contaminated calcareous soil. Materials and Methods This study was carried out under a greenhouse condition as a factorial experiment based on a randomized complete block design with two factors, including Pb concentration in four levels (0, 250, 500, and 1000 mg Pb kg-1 soil) and plant type in two levels of Artemisia (Artemisia absanthium L.) and Xanthium (Xanthium strumarium L.) and in three replications. In this study, the soil was selected and was spiked with 0, 250, 500, and 1000 mg Pb kg−1 soil. Then plants were grown in pots containing the contaminated soil. At the end of the growth period, the dry weight of root and shoot, Pb concentration in the root and shoot of plants, and soil bioavailable Pb were measured. Also, the tolerance index (TI) of root and shoot was calculated by dividing the dry biomass of plant in each treatment by dry biomass in the control treatment at Pb0 mg kg-1 of the soil. Moreover, the stabilized Pb in roots (MS) and extracted Pb by shoots (ME) were calculated. For evaluating the ability of plants on uptake and shoot and root accumulation of Pb, mBCF (Modified bioaccumulation factor) and mBAF (bioconcentration factors) of shoot and root were calculated by dividing the Pb concentration in plant dry matter to bioavailable Pb concentration in soil and dividing the Pb accumulation in the plant fraction bioavailable metal content in the soil. In addition, the modified translocation factor (mTF) was calculated by dividing the Pb concentration in shoot dry matter by Pb concentration in root dry matter. Results and Discussion Results of this study indicated that with increasing soil Pb contamination, the root and shoot dry weight and tolerance index of plants decreased, while shoot and root Pb concentration, stabilized Pb in roots and the extracted Pb from shoots increased. The highest and lowest relative shoot and root dry weight were observed in Pb0 and Pb1000 treatments, respectively. There was no significant difference in the tolerance index (TI) of plants. In this study, roots and shoots mBCF, obtained for both plants and different levels of Pb in soil, were above unity, indicating that the plant is able to take up and accumulate Pb. A. absanthium PGPR had higher mTF than X. strumarium plant at every concentration of soil Pb. The assessment of the phytoremediation performance clearly revealed that the amounts of all phytoextraction indices in A. absanthium were higher than X. strumarium, while all phytostabilization indices in X. strumarium were higher than X. strumarium. In general, maximum Pb accumulation for root was recorded for X. strumarium (average of root mBAF, mBCF, and mTF 1.65 %, 5.48 and 0.97, respectively) and maximum accumulation of Pb in shoot was observed for A. absantium (average of shoot mBAF, mBCF, and mTF 2.79 %, 2.86, and 1.84, respectively). Conclusion It could be concluded that X. strumarium and A. absanthium, with high biomass in native condition, might be effective in phytostabilization and phytoextraction of Pb, respectively, especially in low levels of soil Pb contamination (250 and 500 mg kg-1).
Soil Chemistry and Pollution
Hadi Habiby; Alireza Movahedi; Mojtaba Khoshravesh; Alireza Saberi
Abstract
Introduction Increasing the yield and, consequently, increasing the concentration of macro and micro nutrients in the plant is one of the important aspects of agriculture. The improvement of the quality and quantity of some elements, such as potassium, zinc, and iron in the soil can cause an increase ...
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Introduction Increasing the yield and, consequently, increasing the concentration of macro and micro nutrients in the plant is one of the important aspects of agriculture. The improvement of the quality and quantity of some elements, such as potassium, zinc, and iron in the soil can cause an increase in the yield of the crop and the concentration of these elements in plant tissues. The increase in the concentration of these elements in plants can be effective in the health of livestock and consequently the health of humans. One of the new approaches that can be used in this field is the use of magnetic water. Magnetic water is obtained by passing water from a magnetic field. An externally applied magnetic field causes changes in the atomic, molecular, and electronic structure of the treated water, such as changes to its solidifying and boiling points, viscosity and the dielectric constant, the formation of clustering structures from linear and ring hydrogen-bound chains of molecules, the magnetic interaction between these clustering structures, and increasing the polarization effects of water molecules. The biological effects of magnetic field or electromagnetic field treatments depend on the strength and exposure period of water conditioning, in particular, the ion content, quality, and the volume of water. Materials and Methods For this purpose, a field experiment was conducted in a factorial arrangement with two main treatments, adding and without adding potassium and zinc fertilizers, and five sub-treatments (magnetic field strengths, including a 0.4 Electromagnetic Coil (EC), 0.3 magnet, 0.3 EC, 0.1 EC, and the control treatment) in four replications at Research Station of Goran University of Agricultural and Natural Resources. The size of each experimental plot was 2 m × 2.5 m. Corn was planted in each plot with the distances of 15 cm from each other and rows with distances of 70 cm from each other. An electromagnetic coil and a permanent magnet were used to create a magnetic field. Water was passed from the middle of this magnetic field through a hose and the plots were irrigated with this magnetic water. The irrigation was conducted based on soil moisture content and continued until the harvest and drying of the plants. Soil and plant samples were taken at two flowering and harvesting stages and were transferred to the laboratory for analyzation. Concentrations of Zn and Fe in the soil and plant tissues were measured. Statistical analysis was performed using the SAS software. Results and Discussion The results of this study showed that all the plots that were irrigated by magnetic water had corn plants with greater height and more yield was obtained than the control treatments. This could be due to the ease of absorbing water from the soil. Magnetic water has lower surface tension than untreated water, so the plant needs less force to absorb water from soil particles. Also, the plants that were irrigated by magnetic water had higher concentrations (P <0.01) of elements such as zinc and iron in their cobs. Magnetic water can increase the availability of the elements in the soil. So, more concentration of elements can be absorbed by the roots and transferred to the aerial parts of the plants. Among the magnetic water treatments, 0.4 Tesla strength treatment had the highest effect on the yield and corn height, as well as zinc and iron concentration in cobs (P <0.01). Higher strengths of the magnetic field (0.4 T) had more effect on the availability of elements in the soil and their absorption by the plants. The yield of corn in 0.4 EC, 0.3 M, 0.3 EC, and 0.1 EC treatments that potassium and zinc fertilizers were added to them increased as compared to the control. So, increasing the strength of the magnetic field had more effects on some soil properties. The treatments that K and Zn fertilizers were added to them had more yield than other treatments that these fertilizers were not added to them. This could be attributed to the fact that magnetic water has increased the solubility of K and Zn fertilizers. In fact, magnetic water has been able to increase the uptake of Zn from the soil. Conclusion These results indicate that the magnetization of water can be used as an appropriate approach to increase the quantity and quality of product yield and the concentration of the elements in the crops.
Soil Chemistry and Pollution
Narges sousaraeS; Mojtaba Baranimotlagh; Farhad Khormali; Esmaeil Dordipour
Abstract
Introduction Biochar is a charcoal, pyrolyzed from a wide range of carbon-rich biomass materials, such as crop and wood residues, animal manures and a range of industrial wastes and once added into soil, it can store the soil carbon for a long period, improve the soil structure and increase the crop ...
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Introduction Biochar is a charcoal, pyrolyzed from a wide range of carbon-rich biomass materials, such as crop and wood residues, animal manures and a range of industrial wastes and once added into soil, it can store the soil carbon for a long period, improve the soil structure and increase the crop yield. However, the physical and chemical characteristics of biochars are influenced by the properties of the feedstock and pyrolysis conditions, such as highest temperature treatment and furnace residence time. Considering the large variation in biochar properties, it is not surprising that crop yields vary with different biochars. We investigated the effects of biochars on corn growth in the greenhouse. The specific objectives were (a) to assess whether feedstock properties or pyrolysis temperature are important in preparing of biochar and (b) to quantify the effects of varying biochar characteristics on corn growth and chlorophyll index in a calcareous soil under greenhouse condition. Materials and Methods Biochar was produced from crop residues including rice, cotton and canola. Feedstock was oven-dried before pyrolysis. The pyrolysis process was conducted for 1 h at 10°C min‒1 heating rate to produce biochars at different temperatures of 350 and 700 oC under oxygen-limited conditions. All biochars were ground and passed through a 2-mm sieve before experimentation. Ash content and char yield was calculated and biochar pH and electrical conductivity (EC) were measured using 1:20 solid: solution ratio. The soil used in this experiment was taken from the Research Farm of Gorgan University of Agricultural Sciences and Natural Resources. The soil was air-dried and ground to pass through a 2-mm sieve then analyzed for various soil physico-chemical properties using standard methods. A greenhouse experiment was set up using pots with 5 kg prepared soil. Various treatments comprising of 3 biochars type produced at different pyrolysis temperatures (350 and 700°C) from three crop residues (rice, cotton and canola) at three application rates (0, 2 and 5% w/w). A completely randomized design was used in factorial arrangement and treatments were replicated four times. After the soil had been prepared and biochar added, six seeds of maize were planted approximately 20 mm deep in the center of the pots and thinning to seedlings of four plants pot‒1 was done at plant establishment. Distilled water was used to maintain moisture contents of the soil in all the pots during the experimental period. Plant stem and leaves were harvested 96 days after planting. Washed with distilled water then dried with tissue paper. The leaf and stem samples were air-dried and then oven dried at 65˚C to a constant weight in a forced air driven oven. The studied traits included leaf and stem fresh and dry weight, plant height, number of leaves, time to first flowering, chlorophyll index (SPAD), concentration of chlorophyll a, chlorophyll b and total chlorophyll. The analysis of variance (ANOVA) with the factors biochar type, application rate and pyrolysis temperature were performed using a completely randomized design. Significantly different treatment means were separated using least significant difference (LSD) test at PResults and Discussion The results showed that pyrolysis temperature significantly influenced the measured chemical properties of biochars. EC values were tended to increase with pyrolysis temperature. The pH of the biochars was also influenced by temperature. Biochars pH ranged from 6.8 to 9.6. The pH of the biochars was increased with increasing temperature and highest pH (9.6) was observed at 700°C of rice residues. These increases in pH values are mainly due to separating of alkali salts from organic materials by increased pyrolysis temperature. The results showed that the yield of biochars was reduced by increasing pyrolysis temperature and ranged from 19.4% to 40.1%. This decline in yield content is mainly due to the destruction of some compounds such as cellulose and hemicellulose as well as combustion of organic materials with increased pyrolysis temperature. By contrast to biochar yield, the biochar ash content increased with increasing pyrolysis temperature. The lowest values of leaf and stem fresh and dry weight was observed at 700°C of canola residues. These results suggest that biochar produced at high pyrolysis temperature (especially at 700°C), when applied to the soil, may increase soil salinity and subsequently provide undesirable impacts on the plant growth. It has been reported that the negative impacts of high salinity on the plant growth could be due to the following reasons: (1) the low osmotic potential of the soil solution, resulting in water stress, (2) specific ion effects, resulting in salt stress, and (3) nutrient imbalances. Addition of each three types of biochars caused a significant increase in chlorophyll concentration compared to control. Conclusion The type of feedstock material is an important factor that determines the final application of the biochar and its effect on plant growth papameters. Therefore, there is further need for research focusing on the effects of biochar addition on soil properties and plant growth in order to assess biochar as a valuable resource for agriculture.
Soil Chemistry and Pollution
Vafa Bozar; Nafiseh Rang Zan; Habibollah Nadian Qomsheh
Abstract
Introduction Soil quality is very important because of the direct impact on agricultural production and the nutrition of living creatures. The use of urban and industrial wastewaters (as lower quality water for irrigation of plants to reduce raw water consumption) can lead to a gradual accumulation of ...
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Introduction Soil quality is very important because of the direct impact on agricultural production and the nutrition of living creatures. The use of urban and industrial wastewaters (as lower quality water for irrigation of plants to reduce raw water consumption) can lead to a gradual accumulation of some heavy metals in the soil, which can enter the food chain and menace the health of creatures. Due to the high costs of the physical cleaning up methods, it is sometimes more logical to use methods that reduce the effects of contaminants in the environment. Materials and Methods For this purpose, a pot experiment with lettuce and spinach was conducted to investigate the effect of carbon black and hair waste (as adsorbent) on the concentration of cadmium and lead in plants, as well as fresh and dry weight as affected by contaminated water irrigation. Carbon black with defined properties was prepared by the Iranian Carbon Black Company. After collecting the hair waste, all was washed with raw water, diluted acid, and distilled water properly. Then the waste was air dried and ground as much as possible to make it uniform and increase the specific area to cause more reaction between the waste and soil. The waste was applied to the soil at a rate of 3 percent by weight. The carbon black was applied to the soil at the same rate as the hair waste. After preparing the pots, spinach and lettuce were planted in the pots and irrigated with contaminated water and harvested 60 days after sowing. At the end of the pot experiment, some growth parameters, as well as the uptake of some elements, including micronutrients and heavy metals, was measured by standard methods. The data were analyzed by using SAS and graphs were plotted with the help of Excel program. So, this study was carried out in a completely randomized design with three treatments, including carbon black (two levels of zero and three percent by weight), hair waste (at two levels of zero and three percent by weight), and irrigation water (at two levels of contaminated water and Non-contaminated) with 3 replications. Results and Discussion The results showed that the use of heavy metal contaminated water significantly reduced the growth parameters in both plants, which was significantly limited by the use of adsorbents, which shows the effect of adsorbents in reducing the negative effects of pollutants in the environment. The analysis of data showed that the effect of carbon black, hair waste, and irrigation water on fresh weight of spinach and lettuce was statistically significant (at the level of 1 and 5%). The interaction effect of carbon black and irrigation water on fresh weight of plants showed that the use of carbon black increased the fresh weight of spinach and lettuce from 16.65 to 19.68 and 11.38 to 16.68, respectively. In the case of treatment of 1.5% carbon +1.5% hair waste, the fresh weight of plants decreased significantly as compared to treatments without hair waste, as well as the control treatment. This can be due to the negative effect of hair waste on the physical properties of soil according to the short time of the research work (2 mounts). More or less, the effect of carbon black and irrigation water on iron, zinc, copper, cadmium, and lead content in both experimented plants was statistically significant. In the case of hair waste effect on iron and lead for spinach, iron and copper for lettuce were statistically significant. The irrigation with contaminated water decreased the amount of iron, zinc, and copper in the aboveground part of plants which is indicating the negative effect of heavy metals in irrigation water on root development and nutrient uptake, as well as competing through antagonistic relationships with micronutrients which are necessary for the plant growth. In the treatments containing 3% carbon black, the number of micronutrients in plants increased significantly due to surface absorption of heavy metal on carbon black and the reduction in the negative effect of heavy metals in soil. In the case of cadmium and lead, the reverse trend was observed. In spinach application of 3% carbon black decreased cadmium and lead content at the rate of 76% and 58%. In the case of hair waste, the effect on lead content at the rate of 25% was significant but for cadmium was not significant. In aboveground parts of lettuce, carbon black reduced cadmium and lead content at the rate of 69% and 54%, respectively. Same as spinach, the effect of hair waste on cadmium content was not significant. The results showed that carbon black had the highest amount of metal adsorption capacity and, therefore, can be more effective than hair waste. Conclusion According to the results, carbon black can be used in the agricultural system which requires more research in the case of its ability.
Soil Chemistry and Pollution
Alireza Zarasvandi; Majid Heidari; Ahmadreza Lahijanzadeh; Sedigheh Jalali; Mohsen Rezaei; Madineh Saed; Zahra Fereydouni
Abstract
Introduction Dust storms or sand storms are some of the meteorological phenomena that demonstrate differences with one another terminologically. These kinds of storms usually occur under arid and semiarid areas in circumstances which the blowing speed of a gale is higher than the erosion threshold. In ...
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Introduction Dust storms or sand storms are some of the meteorological phenomena that demonstrate differences with one another terminologically. These kinds of storms usually occur under arid and semiarid areas in circumstances which the blowing speed of a gale is higher than the erosion threshold. In other words, Dust and sand storms are persistent problems in the Middle East Region. The regional dust storms have bad effects on the health of human life which can cause asthma, bronchitis and lung diseases, due to their carrying micro-organisms (such as bacteria, fungi, spores, viruses and pollen) and their sharp edged particles. Several studies researches have shown that microorganisms mobilized into the atmosphere along with desert soils are capable of surviving long-range transport on a global scale. Dust-borne microorganisms in particular can. directly impact human health via pathogenesis,exposure of sensitive individuals to cellular components. The chemical components of dust are affecting the microbial life besides the precipitation, wind direction, time of day, season and atmosphere inversion conditions, all affecting the survival of total bacteria communities associated with dust particles, and the microbes are capable of surviving long distance transport. Dust storms have become a major environmental concern during the last decades in the oil- and gas-rich Khuzestan province in the southwestern Iran. Dust storms frequently occur in Khuzestan mainly during summer, and intense dust storms are particularly associated with easterly-blowing winds. High frequency (10-15%) and health outcomes of local dust storms in Khuzestan province, requires an extensive study on various factors of local storms such as heavy metal geochemistry and its environmental consequences are very important. In this paper, we present an overview of the geochemical and geo-environmental characteristics of dust storms in Khuzestan. Materials and Methods Information about dust storms of source and coverage was obtained from meteorological stations in Khuzestan province. In this study, airborne dust samples were collected to obtain TSP and PM10 by using the high-volume air (HVA) sampler model TCR. The geochemistry of airborne dust samples was analyzed at the Actlabs (Canada). The concentration of V, Co, Ni, As, Cd, Pb and Zn was determined in Actlab, Canada, using ICP-MS method. Results and Discussion The obtained results showed that Pb concentration in TSP samples ranges between 8.11 and 197 ppm with an average and median value of 23.6 and 11.15 ppm, respectively. The zinc content in PM10 samples, ranges between 4670 and 5000 ppm. Also, Ni has high concentration that ranges between 5.8 - 43.2 in PM10 samples. Lowest concentration of Cobalt is present in PM10 samples that ranges between 0.6 and 4.7 ppm. Vanadium has the highest concentration in Ahvaz samples. Also, PM10 samples include higher Arsenic concentration than TSP samples. Finally, Cd has the lowest concentration in all of the studied heavy metals with the mean value of 0.12 ppm. Positive correlation (0.9) between Cu with V, Co and Ni shows probably a similar source for these elements. Investigation of heavy metals concentration in various dust storms confirms that arsenic has a higher concentration in local storms. Seasonal studies show that V, Co and As have high concentrations in warm periods and Pb has the highest frequency in the cold season, in Khuzestan province. Based on the study of Contamination Factor (CF), the mean CF of heavy metals was in the order Pb > Zn > Cd >As > Ni > Co> V. Also, Degree of Contamination (DC) factor of the studied heavy metals in PM10 samples with mean value of 40 ppm is higher than TSP samples with average value of 10 ppm. In relation to the Enrichment Factor (EF) for V, Co, Ni, As, Cd, Pb and Zn, the EF mean of these metals was in the order Cd > Zn > Ni > Pb > As > V > Co. The highest Arsenic enrichment factor can be seen in PM10 samples. Conclusion The obtained results from calculation of Integrated Pollution Index (IPI) in PM10 samples showed that, V, Co, Ni and Pb are non-polluted. Also, Cadmium, Arsenic and Zinc showed a low, medium and high levels of pollution, respectively. Furthermore, based on IPI data in TSP samples, Co, As and V were non-pollution and Pb, Ni, Zn showed low level of contamination. Finally, Cadmium in TSP samples in dicated a high level of Integrated Pollution Index.
Soil Chemistry and Pollution
Somayeh Sefidgar shahkolaie; Mojtaba Baranimotlagh; Farhad Khormali; Esmael Dordipour
Abstract
Introduction At present, contamination of water and soil resources is an important environmental challenge. Therefore, decontamination of such is a prerequirement for using these resources. Cadmium (Cd) and lead (Pb) often coexist in contaminated soils and there is currently no effective means for their ...
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Introduction At present, contamination of water and soil resources is an important environmental challenge. Therefore, decontamination of such is a prerequirement for using these resources. Cadmium (Cd) and lead (Pb) often coexist in contaminated soils and there is currently no effective means for their concurrent removal. Concerns about their mobility and bioavailability have increased because of food safety, potential health risks and its detrimental effects on the ecosystems. The stabilization/solidification is a cost effective remediation method that prevents spreading of heavy metals in soil and water resources. In this process, contaminated soil reacts with amendments such as organic and liming materials to form low soluble or non-soluble stable materials. The objective of this study was to evaluate the effect of several low cost amendments on Cd and Pb stabilization by a sequential extraction method. Materials and Methods In this research, in order to investigate the effect of organic amendments (biochar 640°C, and biochar 420°C) and inorganic amendments (Pumice, Leca, Zeolite, and Bentonite) on Pb and Cd stabilization in a contaminated soil, an incubation experiment was carried out. One kilogram of each amended soil and the control soil were packed into respective pots. Soils were amended in the laboratory using biochar 640 (BI1), biochar 420 (BI2) bentonite (BE), pumice (P), leca (LE), and zeolite (Z). A control treatment (C) without adding amendment was also prepared. The amendment materials were applied at 1 and 5 percent wt. Each treatment was performed in three replicates and the samples were incubated in the dark at 14°C for 6 months. At the end of the incubation time, the potential bioavailability of Cd in non-amended and amended soils was evaluated by extraction with DTPA and ethylenediamine tetraacetic acid (EDTA). Total Cd (CdT) and Pb (PbT) was extracted by aqua regia (HNO3 + HCl) extraction. The chemical fractions of Cd and Pb were determined by a sequential extraction method which is a five-step chemical fractionation based on the work of Tessier et al. (1979). All statistical analyses were performed using SAS software. Means of different treatments were compared using LSD (P ≤0.05) test. Results and Discussion The results indicated that the additions of amendments to soils reduced the concentration of DTPA and EDTA-extracted Pb and Cd. The smallest concentration of Pb-extracted DTPA and EDTA was observed in organic amendments treated soil (biochar 640°C, and biochar 420°C) and treated with 5% biochar 640°C, respectively. The high sorbent capacity of the BI used in this study could be due to its high pH, high content of organic carbon and cation exchange capacity (CEC). The highest decreasing rate of DTPA and EDTA-extractable of Cd was observed in treated with 5% pumice and zeolite, respectively. Application of the amendments (except for 1% LE) decreased exchangeable fraction (F1) of Pb compared to the non-amended soil. Also, the amendments (except for 1% P, Z and BE) decreased exchangeable fraction (F1) of Cd compared to the non-amended soil. Although the biochar 640 (5%) showed the highest decreasing rate of exchangeable fraction (F1) of Pb and Cd, they increased the oxide (F3) and organic (F4) fractions, which might be due to its rich O-containing functional groups and high alkalinity leading to an increase in the binding of Cd and Pb to organic compounds and mineral oxides. Conclusion Results indicated that application of amendments was successful in lowering the potential bioavailability of Pb and Cd soils. The 5% biochar 640 treatment had the greatest decrease in extractable Pb. Also, the 5% zeolite and pumice treatment had the greatest decrease in extractable Cd. Application of BI resulted in a significant decrease in both Pb and Cd exchangeable fraction (F1). This reduction in the exchangeable fraction (F1) of Cd and Pb in the soil was due to an increase in the fraction of heavy metals bound to the soil organic matter (F4) oxides (F3) after BI addition. Enhanced precipitation or co-precipitation and complexation of metals with amendments led to the reduction of the solubility of the metals. The P, LE, BE, and Z altered the exchangeable fraction (F1) of Cd and Pb to the oxide fraction (F3) and the carbonate fraction (F3), respectively. Application of BI amendment causes the highest decreasing rate of solubility Cd and Pb, suggesting this as the suitable amendment for the remediation of Cd and Pb in contaminated soils.
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.
Soil Chemistry and Pollution
M Ayeneh Heydari; M Hejazi Mehrizi; A Jafari; M Yousefifard
Soil Chemistry and Pollution
Roya Zalaghi; Ali Akbar Safari Sinegani
Volume 37, Issue 1 , September 2014, , Pages 49-65
Abstract
Phytoremediation, a relatively new and an environmentally friendly technology, is the use of plants for the removal of pollutants from contaminated soils. A greenhouse pot experiment was conducted to evaluate the heavy metal (lead, zinc and copper) accumulation of Zea mays, Helianthus annuus, Cannabis ...
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Phytoremediation, a relatively new and an environmentally friendly technology, is the use of plants for the removal of pollutants from contaminated soils. A greenhouse pot experiment was conducted to evaluate the heavy metal (lead, zinc and copper) accumulation of Zea mays, Helianthus annuus, Cannabis sativa and Brassica napus. Plants were grown in two soils; one from Ahangaran Lead-Zinc Mine, and the other from an agricultural soil. The shoot and root dry weight, heavy metal concentrations in shoot and root, translocation factor (TF), Enrichment factor (EF) and heavy metal fractions were measured. The distribution of different lead and zinc fractions were revealed the following order: residual > carbonate > organic > exchangeable. However, for copper the order was as residual > organic > carbonate > exchangeable. The minimum lead concentration (25.50 mg kg-1) was observed in Z. mays shoot tissue and the maximum (301.30 mg kg-1) in C. sativa shoot tissue. Lead TF ranged from 0.72 to 0.96 and decreased in the following order: H. annus > C. sativa > B. napus > Z. mays. Zinc TF changed from 0.70 to 0.99 and as H. annus > Z. mays> C. sativa > B. napus, and copper TF turned from 0.49 to 1.83 and as H. annus > C. sativa > B. napus > Z. mays. The EF value of lead varied from 0.24 for Z. mays to 0.48 for C. sativa, from 0.75 for Z. mays to 1.01 for H. annus regarding to zinc, and the copper EF value ranged from 0.39 for C. sativa to 1.42 in H. annus. Although H. annus and C. sativa accumulated lead more than Z. mays and B. napus, none of the plants was hyperaccumulator for lead, zinc or copper.
Soil Chemistry and Pollution
K. Dalvand; A. Eftekhari
Volume 37, Issue 1 , September 2014, , Pages 67-75
Abstract
Cadmium (Cd) is a heavy metal that is uptaken by plants, accumulates in edible parts of plants and negatively impacts human health. This study was conducted to investigate the uptake and accumulation of Cd in different parts of reddish. The experimental design was a factorial with complete block design ...
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Cadmium (Cd) is a heavy metal that is uptaken by plants, accumulates in edible parts of plants and negatively impacts human health. This study was conducted to investigate the uptake and accumulation of Cd in different parts of reddish. The experimental design was a factorial with complete block design using three levels of Cd (0, 30 and 60 mgkg-1) and two dates of harvesting (commercial maturity and one week after commercial maturity, called 1st and 2nd dates of harvesting) with three replications. The experiment was carried out using pots which were inserted at research farm of Shahid Chamran University of Ahwaz. Results indicated Cd accumulation in different parts of reddish as the Cd concentration rates increased. The highest Cd accumulation was in the roots (79.35 mg kg-1) at the 2nd date of harvesting. The maximum Cd accumulated in hypocotyls (36.0 mg kg-1) at the 1st date of harvesting, hypocotyls skin (45.0 mg kg-1) at the 1st date of harvesting, and leaves (95.4 mg kg-1) at the 2nd date of harvesting when 60 mg kg-1 of Cd was applied. The results also showed that Cd treatment maximizes Cd at the 1st date of harvesting and increases over the second time of harvesting in reddish organs. The order of Cd accumulation from the highest to the lowest concentration was leaves, roots, petioles, hypocotyls skin and hypocotyls.
