جستجوی مقالات مرتبط با کلیدواژه « فلز سنگین » در نشریات گروه « آب و خاک »

The rapid growth of technology, industry, and development of cities has led to an increase in heavy metal pollution in freshwater sources and greywater across the world. The use of different adsorbents in order to remove some heavy metals from aquatic environments is a topic that has been addressed many times in different studies. However, the use of inexpensive absorbents with high adsorption capacity and high efficiency is the priority of many researchers especially when they are discussing the removal of heavy metals from the aquatic environment. Nanomaterials by having exceptional properties such as high efficiency of adsorption, high specific surface area, and fast adsorption can be used to remove metal pollutants from aquatic environments. Carbon dot (CD), among various nanomaterials (carbon-based nanomaterials (CNM), including carbon nanotubes (CNTs), graphene) are suitable adsorbents for heavy metals removal due to their specific surface area and many binding sites. Carbon dots are nanoparticles that lack a specific dimension and fall under the category of carbon nanomaterials, measuring over 10 nm in size. They possess various qualities, including being environmentally friendly, simple to create, highly compatible with living organisms, stable, and capable of switching emission on and off based on the excitation wavelength. Additionally, they can be customized for specific uses due to their high carbon content, which can reach up to 99.9%. These characteristics have generated significant interest among researchers in various fields. In this study, the influence of the fungal carbon dots on the adsorption capacity and kinetics, isotherms, and thermodynamics of lead was investigated.

Alternaria alternata provided by the Department of Plant Protection at Ferdowsi university of Mashhad. It was recultured and fungal exopolysaccharide was extracted and then was converted into carbon dot using the hydrothermal method. Fungal exopolysaccharide autoclaved in a Teflon container at a temperature of 200 °C. Lead adsorption of synthesized fungal carbon dots was investigated. Lead adsorption tests by fungal carbon dots were performed in laboratory conditions. Lead concentrations (100, 200, 300, 400, 500, 750 and 1000 mg L-1), contact time (5, 10, 15, 20, 25, 30 and 60 minutes), pH (2, 4, 6, 7, 8, 9, 10 and 11), amount of carbon dots (nanosorbent) (50, 100, 200, 300, 400, 500, 750 and 1000 mg), ionic strength of the solution (0.1, 0.01 and 0.001 M potassium chloride) and solution temperature (25, 30, 35, 40 and 45 °C) was considered for kinetic tests. The data obtained from the kinetic tests were fitted using non-linear regression analysis using Statistica 7.0 software with the kinetic models of intraparticle diffusion, Lagergren (pseudo-first order) and pseudo-second-order. Thermodynamic results were calculated from the data of lead adsorption isotherms at temperatures of 25, 35 and 45 °C. Thermodynamic parameters to analyze the effect of temperature on metal adsorption, such as free energy change, enthalpy change and entropy change, were estimated using thermodynamic equations.

The initial lead concentration had a great effect on the adsorption rate it by carbon dot, and the highest and lowest percentage of lead adsorption with values of 90.65 and 44.2% were observed in two concentrations of 300 and 1000 mg L-1 of lead, respectively. With the increase of pH up to 8, the amount of lead adsorption by fungal carbon dot increased significantly. However, with further increase in pH, this trend was reversed and the amount of adsorption decreased. The results showed that lead adsorption by carbon dot increased with the decrease of potassium chloride molarity. By increasing the amount of carbon dot in the solution, the amount of lead adsorption increased, and the highest adsorption was observed at the concentration of 300 mg L-1 of carbon dot. The results of the experiment also showed that with increase in temperature, the adsorption rate increased at first and then decreased. Based on these results, as the contact time between the absorbent and lead increased, the amount of adsorption by the carbon dots also increased. The maximum adsorption was observed at 25 minutes, which was considered the equilibrium time. As shown in the results, the pseudo-second-order model shows the kinetics of Pb adsorption better than the two pseudo-first-order models and intraparticle diffusion. In this model, R2 values are between 0.9989 and 0.9994, and Qe is almost equal to the equilibrium value. According to these results, the decrease of values DG° with the increase in temperature means that the adsorption of lead increases with the increase in temperature, which shows that the adsorption process is more favorable with the increase in temperature, or in other words, it is a spontaneous reaction. Also, the positivity of the reaction enthalpy value (DH°) shows the endothermic nature of the adsorption process. The positivity of the entropy value (DS°) indicates the increase of disorder of the system between the adsorbent material and the solution during the process of lead adsorption by the carbon dot.

In total, the results showed that the carbon dot is a very good absorbent for removing lead from the water environment. In the experimental condition when the initial concentration of lead was 300 mg L-1, temperature was 25 °C, adsorbent concentration was 0.3 g L-1, reaction time was 25 minutes, and pH 8, the amount of lead adsorption increased significantly. It seems that fungal carbon dot is a safe and relatively cheap adsorbent and suitable for removing lead metal from the solution environment.

Due to the toxicity of metals, their side effects may cause serious damage to soil organisms, plants and living organisms. Many conventional methods for cleaning pollution from soil have problems and limitations. The electro kinetic method is a relatively new method for remediating soils contaminated with heavy metals, which has a high efficiency in removing heavy metals from the soil compared to other existing methods.

In this research, the removal of chromium (VI) from nitrate-containing soil has been investigated. At first, the soil was artificially contaminated with potassium dichromate at a concentration of 250 mg/kg, and then in order to investigate the effect of nitrate on the removal of chromium. The soil was also impregnated with calcium nitrate.

By conducting electrokinetic experiments, it was found that with the increase of the electric current introduced into the soil, the electric gradient passing between the electrodes increased, as a result of which the transfer of ions also increased under the influence of the phenomenon of ion migration and electroosmosis. The percentage gives 98.28%. Also, the use of EDTA complexing agent compared to distilled water increases the efficiency of the method from 95.57% to 97.80%. As a result, the use of EDTA electrolyte and increasing the voltage increases the removal efficiency.

Results revealed experiments showed that the use of the electrokinetic method has a negligible effect on the removal of chromium (VI) from soil containing nitrate.

Phosphorus (P) is one of the most important components and a limiting factor for the growth of plants due to its low mobility and availability in soil. Application of organic materials such as biochar is one of the main choices to increase the availability of P in soil. Biochar is a carbon-rich material derived from pyrolysis of organic feedstocks under limited or no oxygen conditions. Biochar can influence the availability of P by improving the physicochemical, biological, and enzymatic conditions of soil, in addition to directly increasing the concentration of nutritional elements, particularly P. Soil pollution by heavy metals such as Cadmium (Cd) has been one of the environmental concerns in the last several decades. Cadmium alters the activity and diversity of soil microbial communities, and it also lessens soil function by decreasing the activity of enzymes related to nutrient cycling. Application of organic materials such as biochar in contaminated soil can reduce the availability of heavy metals in the soil, and as a result, increase the biological properties. It is hypothesized that application of biochar in heavy metal-contaminated soil influences the availability of P not only directly but also indirectly by improving microbial and enzymatic activity. This issue depends on the type of biochar and soil. Therefore, this study was conducted to investigate the interaction effect of biochar (cow manure and wheat straw) and Cd on microbial respiration, acid and alkaline phosphatase activity and available P in two soils with different physicochemical characteristics. A factorial experiment was conducted using a completely randomized design with three replicates. The experimental factors included 4 levels of Cd contamination (0, 5, 10 and 20 mg kg-1), 3 levels of biochar (control, wheat straw and cattle manure biochar) and 2 types of soil (corck sofla and research center). Two types of soil contaminated with different amounts of Cd from CdCl2, were amended with 2.5% of the biochar, then were incubated for 14 and 90 days at laboratory temperature and 70% field capacity. At the end of each incubation time, available Cd and P, basal respiration and acid and alkaline phosphatase activity were measured. The application of cattle manure and wheat straw biochar in soil reduced the available Cd by 70-86% and 61-85%, respectively. At all levels of Cd contamination, the amount of available Cd in the research center soil with sandy loam texture was higher than that of the Kark Sefala soil with clay texture. Higher concentrations of Cd also reduced the microbial respiration and the enzyme activities in the research center (31-46%) more than in the corck sofla (21.5-35.5%) soil. The decrease in microbial respiration and enzyme activities due to Cd contamination in the soil without biochar (10-41.5%) was more than the soil amended with wheat straw (5-39.8%) and cow manure (0.8-37.9%) biochar. The results also showed that available P increased with biochar addition and decreased with increasing Cd concentration in soil, so that the highest amount of available P was observed in the soil amended with cow manure biochar and without Cd contamination. Positive and significant correlation between available P with microbial respiration (r=0.385-0.604), alkaline (r=0.764-0.879) and acid (r=0.761-0.883) phosphatase activity was obtained, indicating that microbial activity and the enzymes involved in P cycling, play a significant role in the availability of P in the soil. These findings indicated that the application of biochar in Cd-contaminated soils can increase the bioavailability of P in the soil by decreasing the availaility of Cd and increasing microbial activity and alkaline and acid phosphatase activity. This issue was affected by the biochar and soil type.

The accumulation of heavy metals in the soil is a serious environmental problem. One of the heavy metals remediation methods from contaminated soils is the use of chelating agents, particularly organic acids. The aim of this study was to evaluate the potential of citric acid, and tartaric acid for the Cd, Zn, Cu, Pb, Ni mobility and distribution in the contaminated soils. Accordingly, soil samples were collected from contaminated soils of Charmshar Industrial Park located in Varamin city. Six samples were collected from surface (0-15 cm) in 2019. Contaminated soils were washed using 0.05M citric acid and tartaric acid using a soil: liquid ratio of 1:25. In order to understand the distribution of Zn, Pb, Cu, Ni, and Cd in soils before and after washing, a sequential extraction procedure was applied. Accordingly, five chemical fractions of the studied heavy metals were defined: exchangeable (F1), carbonate (F2), organic (F3), Fe-Mn oxide (F4) and residual (F5). Residual forms were the most important for the retention of all heavy metals. Zn and Cu had the same distribution and fractionation pattern. Cd and Pb had a strong affinity for the Fe-Mn oxide fraction. The washing efficiency varied in the order: Citric Acid˃Tartaric Acid. Citric acid removed 45.55% Zn, 31.04% Pb, 35.64% Ni, 48.7% Cu and 37.2%. Tartaric acid showed extraction efficiency of 3.42% Zn, 16.15% Pb, 26.34% Ni, 28.93% Cu and 18.76% Cd. The Cu, Cd and Ni mobility factor were observed higher than 10 %. The mobility factor for five heavy metals calculated less than 10 %, after washing by citric acid and tartaric acid. The results of this study showed that citric acid and tartaric acid have a deleterious role in the release of heavy metals, and using theses acids is recommended to contaminated soil remediation.

Chitosan is a natural and destructive polymer that consists of glucosamine units, which, due to reactive groups, can reduce the availability of heavy metals and change soil enzyme activities which is an indicator of soil quality. However, little information is available on simultaneous effect of chitosan and heavy metals on soil enzymes activities. In this study, the interaction of chitosan at three levels of control, low molecular weight (LMC), and high molecular weight (HMC) with Pb at three levels of 0, 50 and 500 mg/kg on available soil lead (Pb) investigated on activity of acid and alkaline phosphatase, L-glutaminase and fluorcine diacetate hydrolysis enzymes in two different soils, Lavark and Langroud. The results were statistically compared. Both chitosan types significantly reduced available Pb concentration in two soils, but HMC was more effective. In Lavark soil, LMC and HMC application to Pb treatments significantly increased the activity of acid and alkaline phosphatase, L-glutaminease and fluorcine diacetate hydrolysis compared to control treatments. In Langroud soil, LMC application to Pb treatments significantly increased L-glutaminease activity, but did not affect the activity of other enzymes. The HMC application in Langroud soil also did not significantly affect activity of any enzymes compared to control. Level of 50 mg/kg Pb in the presence of chitosan significantly decreased acid phosphatase activity in Lavark soil and hydrolysis of fluorcine diacetate hydrolysis in Langroud soil compared to control, but had a positive effect on the activity of other enzymes. Level of 500 mg/kg Pb in the presence of chitosan also reduced acid and alkaline phosphatase activity in Lavark soil and hydrolysis of fluorcine diacetate in Langroud soil, but significantly increased the activity of other enzymes. Generally, increasing or decreasing enzyme activity due to the simultaneous presence of chitosan and Pb depended on soil, enzyme, Pb concentration, and chitosan type.

The aim of this study was to investigate the possibility of using lead contaminated water in surface irrigation and subirrigation and its effect on silage maize yield. In this regard, lysimeter experiments were conducted in the College of Agriculture and Natural Resources, University of Tehran in 2017 in the form of a completely randomized factorial project with six treatments in three replications and a total of 18 experimental plots. Treatments included: Surface irrigation with lead-contaminated water (SP), Surface irrigation with fresh water as control treatment (SC), Subirrigation with lead-contaminated water and water table depth of 50 cm (50P), Subirrigation with fresh water and water table depth of 50 cm (50C), Subirrigation with lead-contaminated water and water table depth of 75 cm (75P), and finally, Subirrigation with fresh water and water table depth of 75 cm (75C). The results showed that the effect of irrigation management on plant height, plant dry weight and maize silage yield at 1% probability level, wet plant weight and maize wet weight at 5% level was significant and it had no effect on maize dry weight. Also, pollution had no effect on growth and yield and components of maize yield. The results also showed there was a 2.25 mg of lead per one kg of maize dry matter in the SP treatment, which this amount is in the group of low pollution according to the World Health Organization (WHO), No lead was observed in the plant samples of the 50P and 75P treatments. On the other hand, the highest maize yield was recorded in the 75P treatment with 49.65 t/ha and then in the 50P treatment with 47.04 t/ha. Crop yield increased by 36% and 29% in the 75P and 50P treatments compared to the control treatment, respectively. It is noteworthy that the amount of lead metal stabilized and rised in the subirrigation treatment was out of reach of the plant and there was no problem in terms of pollution and maize yeild.

The accumulation of heavy metals in water, sediments, and soils has led to serious environmental problems. In recent years, several processes have been developed with the aim of reducing or recovering heavy metals from contaminated environments. Physical and chemical approaches are capable of removing a broad spectrum of contaminants, but the main disadvantages of these methods lie in the increased energy consumption and the need for additional chemicals. In recent years, the processes such as bioleaching, biosorption, bioremediation, phytoremediation, and bio precipitation are all based on the use of microorganisms that have the ability to solubilize, adsorb, or precipitate heavy metals. Therefore, it is necessary to find some solutions to reduce the negative effects of heavy metals in soil. A factorial experiment was conducted in the greenhouse of the Faculty of Agriculture, the University of Zanjan, using a completely randomized design with three replications. In this experiment, the effects of different levels of soil cadmium (0, 5, 10, 25, and 50 mg/Kg) and soil inoculation (without inoculation and inoculation with Glomus mosseae, Glomus intraradices, Glomus mosseae + Rhizobium trifolii, Glomus intraradices + Rhizobium trifolii bacterium, Rhizobium trifolii, Glomus mosseae + Glomus intraradices and Glomus mosseae + Glomus intraradices + Rhizobium trifolii) on growth of berseem clover were assessed. The results of this study showed that the soil cadmium levels has a significant effect (p < 0.05 and p < 0.01) on fresh weights of aerial parts and roots, height, number of the plant in the pot, Fe, Zn and Cd concentrations in aerial parts and roots of berseem clover. The fresh weights of aerial parts and roots, height, number of the plant in the pot, Fe and Zn concentrations in aerial parts and roots of berseem clover decreased as the levels of soil cadmium increased. The lowest concentrations of iron and zinc were measured in treatment with 100 mg Cd/Kg. Also, Cd concentration in aerial parts and roots increased as the level of soil cadmium increased. The results of this experiment showed that soil inoculation with mycorrhizal fungi and Rihzobium trifolii had a significant effect (p < 0.05 and p < 0.01) on fresh weights of aerial parts and roots, height, number of plant per pot, Fe, Zn and Cd concentrations in aerial parts and roots of berseem clover. The inoculation of soil with mycorrhizal fungi and Rhizobium trifolii increased the fresh weights of aerial parts and roots, height and No. of plant per pot. The highest fresh weights of aerial parts and roots of berseem clover, height, and number of plant per pot were obtained in treatments co-inoculated with Glomus mosseae and Rhizobium trifolii. The highest and lowest concentrations of iron and zinc in aerial parts and roots of berseem clover were measured, respectively, for the treatment co-inoculated by Glomus mosseae and Rhizobium trifolii and control treatment (without inoculation). However, the opposite trends were found in Cd concentrations in the plant. The highest and lowest Cd concentrations in aerial parts and roots were measured in control treatment (without inoculation) and treatment co-inoculated by Glomus mosseae and Rhizobium trifolii (MT), respectively. Bioremediation and phytoremediation are considered as two very safe and necessary technologies which naturally occur in the soil by microbes and plants and pose no hazard to the environment and the people life. The procedure of bioremediation and phytoremediation can be simply carried out on site without initiating a major disruption of normal actions and threating the human life and the environment during transportation. Bioremediation and phytoremediation are used less than other technologies for cleaning-up the wastes and contaminated soils. Microorganisms and plants possess inherent biological mechanisms that enable them to survive under heavy metal stress and remove the metals from the environment. These microbes use various processes such as precipitation, biosorption, enzymatic transformation of metals, complexation and phytoremediation techniques of which phytoextraction and phytostabilization have been very effective. However, environmental conditions need to be adequate for effective bioremediation. The use of hyperaccumulator plants to remediate contaminated sites depends on the quantity of metal at that site and the type of soil. The results of this experiment showed that the Rhizobium trifolii and Glomus mosseae could be used to reduce the soil cadmium contamination. Also, the berseem clover is a hyperaccumulator plant for phytoremediation of cadmium in soils. According to the results of this study, co-inoculation of mycorrhizal fungus Glomus mosseae and Rhizobium trifolii can be recommended to improve the yield and uptake of micronutrients such as iron and zinc in cadmium contaminated soils.

Contamination of soil and water by heavy metals have accelerated since the beginning of the industrial revolution. So cleaning up and removing of the contaminants is one of the major challenges of human societies. There are different methods for remediation of contaminated environments and adsorption and immobilization of heavy metals by the adsorbents is one of them. In addition to being effective and fast, the immobilization technique is simple, inexpensive, and environmentally safe. In recent years, the use of polymeric composites, among the various adsorbents of heavy metals, has attracted the attention of many researchers due to their higher efficiency in comparison of pure adsorbents. Chitosan composites are among those polymeric composites that, due to their properties, can have a high ability to absorb heavy metals in contaminated environments. Chitosan composites have often been used to remove heavy metals from industrial wastewater, however, the efficiency of these composites in immobilization of heavy metals in soils has not been studied. Due to the great variety and environmental safety of these composites, this study aimed to investigate the efficiency of pure and chitosan coated adsorbents in immobilization of soil cadmium.

For this purpose, a pot factorial experiment was conducted in greenhouse conditions using a completely randomized design and three replications. Factors studied were soil cadmium levels (0, 8, 25 and 75 mg/kg soil) and types of adsorbent including pure chitosan, biochar, zeolite and nanomagnetite and composites of chitosan- biochar, chitosan- zeolite and chitosan- magnetite and control (without adsorbents). Each adsorbent was applied to soil at the rate of 0.5% W/W. Uncontaminated soil samples were spiked with different amounts of cadmium sulfate and incubated for two months to achieve relative equilibrium. After two months the samples were treated with different adsorbents and incubated for another two months. Then the amounts of DTPA extractable cadmium and its different chemical forms were determined.

The results showed that the application of adsorbents to soil decreased the concentrations of DTPA extractable cadmium. The results also showed that chitosan composites had higher ability for immobilization of cadmium in the soil than the pure chitosan, biochar, zeolite and nanomagnetite and the highest cadmium immobilization ability was observed for the composite of chitosan- magnetite. Reductions in DTPA- extractable cadmium for pure chitosan, biochar, nanomagnetite, and zeolite were 26.11, 19.38, 18.00 and 7.71% and for composites of chitosan- magnetite, chitosan- biochar and chitosan- zeolite were 34.02, 32.04 and 30.56% respectively when compared to the control treatment. Sequential extraction at the contamination level of 75 mg Cd/kg soil also showed that the use of adsorbents significantly reduced the soluble + exchangeable and carbonate forms of cadmium compared to the control treatment and increased its more stable forms including iron and manganese oxide, organic matter and residue fractions.

According to the results, it can be concluded that coating the pure adsorbents with chitosan by creating more adsorption sites reduces the cadmium mobility in the soils and increased the efficiency of pure adsorbents in the immobilization of cadmium. It was also observed that among the composites that used in this experiment, the highest ability to reduce the cadmium concentration was related to the chitosan-magnetite composite.

Due to the problems of salinity and heavy metals in agricultural soils, this study was designed to reduce the adverse effect of salinity and cadmium stresses when wheat inoculated with pseudomonas. The experiment was designed as a factorial arrangement with three factors including salinity levels (3 and 10 dS m-1), cadmium concentration (0, 25, and 50 mg kg-1), and Pseudomonas inoculation (inoculated and non-inoculated) in a completely randomized design with three replications. After harvesting, some soil biological properties (soil respiration and soil microbial biomass) and some plant growth were measured. The results showed that basal respiration (14.6 mg CO2 100g-1 day-1), substrate-induced respiration (93.2 mg CO2 100g-1 day-1), soil microbial biomass (13.4 mg 100g-1), dry weights of shoot and root (7.65 and 2.30 mg pot-1 respectively), Ca concentration of shoot and root (3.12 and 5.92 mg kg-1 respectively), and Mg concentration of shoot and root (3.16 and 6.75 mg kg-1 respectively) decreased with increasing the salinity and cadmium concentrations. Inoculation of Pseudomonas encouraged those parameters compared to non-inoculated treatments. Cd concentration of shoot and root (1.63 and 7.13 mg kg-1, respectively) increased with increasing the salinity and cadmium stress but inoculation of Pseudomonas lessened the Cd concentration of shoot and root. Therefore, the negatives effect of saline and Cd stress might be condensed if wheat is inoculated by Pseudomonas.

The present study was designed to investigate the effect of Nano hydroxyapatite (nHAP) on some soil bioindicators and availability of cadmium in a polluted calcareous soil. This research was carried out in a factorial arrangement based on completely randomized design with three replications. Treatments included two levels of Cd (0 and 40 mg kg-1 soil), two levels of nHAP (0 and 1%) and two incubation times (14 and 28 days). The cadmium chloride solution was uniformly sprayed on the soil surface and equilibrated for a month, then nHAP was added to the soil at 0 and 1 w/w %. The activity of urease, dehydrogenase, and alkaline phosphatase enzymes, basal respiration and bioavilable Cd were measured after 14 and 28 days. Bioavilable Cd was extracted by DTPA. The results showed that the addition of nHAP in the Cd contaminated soil decreased bioavailable Cd by 2.3%, increased the activity of urease enzyme by 98% while had no effect on the activity of phosphatase, dehydrogenase and basal respiration. Investigation of changes of bioindicators in 14 and 28 days incubation in Cd contaminated soil showed that the activity of urease and dehydrogenase enzyme had a declining trend but the activity of phosphatase enzyme and basal respiration did not significantly change. It was also found that bioavailable Cd decreased with incubation time by 10.7%. In general, it may be concluded that nHAP influenced biological index in the calcareous soil differently, but it caused reduction effect on bioavailable cadmium in soil, although this reduction was not considerable.

Some of the heavy metals such as cadmium (Cd) and lead (Pb) are toxic and represent hazardous pollutants due to their persistence in the environment. These metals have adverse effects on human health, which include growth retardation, cancer, damage to the nervous and heart system. Heavy metals can cause malfunctioning of the cellular processes via the displacement of essential metals from their respective sites. Mainly heavy metals discharge into the environment from industrial and urban sewage. There are different methods to reduce water pollution and the removal of heavy metals from water that one of them is sorption by using organic and inorganic adsorbents such as sepiolite. The low cost of sepiolite along with the high specific surface area, chemical and mechanical stability, and layered structure have made these clay minerals as excellent adsorbent materials for the removal of heavy metals from wastewaters. This study aims to investigate the sorption of Cd and Pb by sepiolite as an inorganic absorbent and optimize process variables (initial concentration, pH and ionic strength) using Response Surface Methodology (RSM) and Box–Behnken design (BBD).
 

Response Surface Methodology (RSM) is a statistical method that uses quantitative data from appropriate experiments to determine regression model equations and operating conditions. RSM is a collection of mathematical and statistical techniques for modeling and analysis of problems in which a response of interest is influenced by several variables. A standard RSM design called Box-Behnken Design (BBD) was applied in this work to study the variables for sorption of Cd and Pb by sepiolite from aqueous solution using a batch process. BBD for three variables (initial Cd and Pb concentrations, pH and ionic strength), each with two levels (the minimum and maximum), was used as an experimental design model. Sepiolite sample used in this study was taken from a mine in Fariman region, northeastern Iran. In the experimental design model, initial concentration (0-200 mg L-1), pH (3-6) and ionic strength (0.01-0.06 mol L-1) were taken as input variables. Design-Expert program was used for regression and graphical analysis of the data obtained. The optimum values of the selected variables were obtained by solving the regression equation and by analyzing the response surface contour plots. The variability independent variables were explained by the multiple coefficients of determination, R 2 and the model equation was used to predict the optimum value and subsequently to elucidate the interaction between the factors within the specified range.

The results showed that the sorption of Cd and Pb intensified by increasing initial concentration and pH but ionic strength had an inverse effect. The sorption of Pb and Cd ions onto the sepiolite minerals were lowest at pH =3 and IS=0.06 but increased with an increase in pH and initial concentration of the solution. High value for R2 (0.99) and adjusted R2 (0.99) showed that the removal of Cd and Pb can be described by the response surface method. One-way ANOVA showed (p< 0.0001) that the quadratic model is the best model for determining the interaction variables. According to optimization results, the sorption of Cd and Pb are maximized when pH: 6, concentration: 200 mg.L-1 and ionic strength: 0.02 mol.L-1. The predicted adsorption at these settings for Pb and Cd are 44.4 and 34.28 mg.g-1, respectively. It was found that the initial concentration is the most effective parameter in the sorption of Cd and Pb by sepiolite. Sepiolite adsorbed more lead ions than cadmium ions from aqueous solution.

Response surface methodology using BBD, proved a very effective and time-saving model for studying the influence of process parameters (pH, initial concentration and ionic strength) on response factor (sorb). This model significantly reduces the number of experiments and hence facilitating the optimum conditions. The experimental values and the predicted values are in perfect match with an R2 value of 0.99. The high correlation coefficient between the model and experimental data (R2=0.99) showed that the model was able to predict the removal of Cd and Pb from aqueous solution by using sepiolite. The model revealed that concentration, metal type and pH were the most effective parameters on the response yield (adsorption by sepiolite), respectively. According to the results, sepiolite showed a greater efficiency for sorption of Cd and Pb from aqueous solution, also usage of sepiolite as an inorganic absorbent due to its low cost and abundance can be economically justified.

Water has been known as an important limiting factor for plant growth and agricultural yields in arid and semi-arid regions. It is a significant input to agricultural production and also an essential requirement for domestic, industrial and municipal activities. Increasing population and standards of living are contributing to a steep rise in demand for fresh water. By using proper irrigation management practices in farmlands, it is possible to utilize water, soil and fertilizer to produce high yield and quality products. Drip irrigation is considered as one of the most efficient irrigation methods. One of its major advantages is the ability to apply water to the soil as often as desired and in smaller quantity than the other irrigation methods. Two systems of drip irrigation including surface and subsurface drip irrigation methods have been widely used in arid and semiarid regions to reduce the water deficiency impact. Subsurface drip irrigation has been used for many years because of its effectiveness in reducing soil surface evaporation. It has been widely used in horticultural crops under both greenhouse and outdoor field conditions. However, the surface drip irrigation system can be used easier than the subsurface drip irrigation system. In addition, deficit irrigation is one of the strategies for efficient use of water and increasing water use efficiency in agricultural district. Deficit irrigation is a suitable solution to gain acceptable and economic performance by using minimum amount of water. The aim of this study was to evaluate the yield and yield components of sunflower affected by different levels of soil matric potential in combination with two contrasting drip irrigation method i.e. surface and subsurface. In addition, water use efficiency as an important criterion of yield was used to achieve the best and more suitable irrigation method under water scarcity conditions.

In order to investigate the irrigation management of sunflower, a field experiment was carried out during 2016 growing season at an experimental farm in Jiroft city. The treatments were laid out in split strip plots based on randomized complete block design with three replications. The treatments were comprised of three soil matric potentials of 40, 55, and 70 centibar for initiation of irrigation in the main plot and sub plots consisted of two drip irrigation systems (surface and subsurface). In  the surface systems, drip lines were placed on the soil surface at a distance of 15 cm from the plant and in the subsurface systems, drip lines were placed at a depth of 30 cm. The irrigation time was determined based on the readings of metal tensiometers. These tensiometers were installed in three depths of 15, 30 and 50 cm of soil and at a distance of 20 cm from the plant. In this regard, in both irrigation systems, the mounted tensiometer at a depth of 15 cm of soil was used in the early growth and development, and mounted Tensiometers at depths of 30 and 50 cm soil were used in the middle and final stages of growth. In order to carry out irrigation at the potential point of view, the tensiometers were fully controlled and when the calibrated tensiometer screen showed the desired potential point, irrigation was carried out and the irrigation process continued until the soil moisture reached the crop capacity level. Yield, yield components such as number of seeds per head, along with water use efficiency were measured. Data were statistically analyzed using SAS Statistical software. Treatment means were compared using LSD test.

The results showed that the water usage parsimony of 153.6 mm (21.5 percent) between the 40 and 55 c-bar tensions caused that the yield, number of seeds per head and height of plant decreased by 12.5%, 12.8% and 11%, respectively, but water use efficiency increased 10.3%. Compared with 55 c-bar tention, 70 c-bar also decreased the yield, number of seeds per head and height of plant by 33.4%, 22.9% and 22.5%, respectively but increased water use efficiency by 4.7%. Moreover, the yield in subsurface drip irrigation increased by 499 kg/ha compared with surface irrigation. In addition, parsimony of water usage was 10% and water use efficiency increased by 21.5%. Number of seeds per head and the height of plant increased by 8.2% and 8.7%, respectively in subsurface drip irrigation.

According to the results of this study conducted on sunflower in Jirot area, it was concluded that the application of soil matric potential of 55 centibar in subsurface drip irrigation system is the best approach to increase water use efficiency during periods of drought.

Cadmium is a very mobile element in soil that is absorbed by plant roots and translocation of cadmium from root to shoot deteriorates crop quality. It enters the food chains of humans and animals easily and is a potential threat to human health. The increase of contaminated areas in the country and the existence of farms under cultivation of various forages and the use of these forage products in the animal feed led to this study was carried out with the aim of investigating the effects of arbuscular mycorrhizal fungi and Rhizobium leguminosarum bv. trifolii on the yield of berseem clover (Trifolium alexandrium) under cadmium stress.

A factorial experiment was conducted in the greenhouse of Faculty of Agriculture, University of Zanjan, using a completely randomized design with three replications. In this experiment, the effects of different levels of soil cadmium (0, 5, 10, 25 and 50 mg/kg) and soil inoculation (without inoculation and inoculation with Funneliformis mosseae, Rhizophagus irregularis, Funneliformis mosseae + Rhizobium leguminosarum bv. trifolii, Rhizophagus irregularis + Rhizobium leguminosarum bv. trifolii, Rhizobium leguminosarum bv. trifolii, Funneliformis mosseae + Rhizophagus irregularis and Funneliformis mosseae + Rhizophagus irregularis + Rhizobium leguminosarum bv. trifolii) on growth of berseem clover (Trifolium alexandrium) were assessed.

The results of this study showed a significant effect (1% and 5% probability level) due to soil cadmium levels on dry weights and N, P, K and Cd concentrations of aerial parts and roots of berseem clover. The dry weights and N, P and K concentrations of aerial parts and roots of berseem clover decreased as the levels of soil Cd increased. The highest dry weights of aerial parts and roots, N, P and K concentrations were measured in treatment co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii and without Cadmium. Also, the lowest dry weights of aerial parts and roots and macronutrient concentrations were observed in treatment 100 mg Cd/kg and without inoculation with microorganism. Soil contamination with Cd decreased the dry weight of aerial parts and roots by 66.49 and 71.11%, respectively. the highest Cd concentrations in aerial parts and roots were measured 11.25 and 17.80 mg/kg in treatment 100 mg Cd/kg and without inoculation with microorganism and the lowest Cd concentrations in aerial parts and roots were 0.0012 and 0.0046 mg/kg in treatment co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii and without Cadmium. The results of the mean comparison of data showed that the Cd concentration in the roots was higher than the aerial parts, and in treatment 100 mg Cd/kg without inoculation with microorganism, Cd concentration of roots was 36.8% higher than the Cd concentration in aerial parts.

Based on the results obtained from this study with the increase in Cd levels of soil, the dry weights and N, P and K concentrations of aerial parts and roots of berseem clover decreased. Soil inoculation with mixture of fungi and bacteria reduced the effect of Cd stress on the growth of clover. Also, the separate inoculation with arbuscular mycorrhizal fungi also reduced the concentration of Cd in the aerial parts and roots. According to the results of this study, in contaminated soils can be used co-inoculated with Funneliformis mosseae and Rhizobium leguminosarum bv. Trifolii to reduce the Cd concentration and increase the yield of plants.

Success of the phytoremediation technique depends not only on plant species, but also largely on the interactions of plant roots with the rhizosphere microorganisms. These microorganisms, especially bacteria with plant growth promoting traits, can improve efficiency of phytoremediation by helping to proper plant establishment, increasing root system growth and, consequently, increasing plant growth and enhancing heavy metal uptake. Considering the important role of soil microbial community in increasing the remediation of polluted soil with plants, this research was conducted with the aim of isolating, screening, investigating the traits of cadmium and lead-resistant bacteria and introducing superior isolates. Soil samples were taken from Cd and Pb contaminated soils of the Shahid Tondguyan oil refinery and after measuring some physical and chemical properties, heavy metals resistant microorganisms were isolated from them. Resistance to cadmium and lead was determined in the isolates, and then the ability of the superior isolates to produce phytohormones of auxin, secretion of growth inhibitor metabolites and solubilization of insoluble inorganic phosphate were evaluated. In this study, thirty microorganisms were isolated from contaminated soils. After examining the appearance of the colony, its color and margin, as well as the growth rate, at the end, 20 different isolates were selected. 70% of the studied isolates showed a very good growth in culture medium up to a concentration of 8 mM l-1 of lead and cadmium. The results of evaluation of plant growth promoting traits in the top 10 isolates in terms of resistance to heavy metals of lead and cadmium showed that all of these isolates had the ability to produce auxins and dissolve insoluble inorganic phosphates. The highest (10.20 mg l-1) and the lowest (0.64 mg l-1) auxin production were observed for C4 and C2 isolates, respectively. The average solubility of tricalcium phosphate by isolates was 106.91 mg l-1. 80% of isolates had the same ability to produce siderophore. The highest rate of production of this metabolite was observed in the isolate C1 with a halo to colony ratio of 23.3. Among 10 studied isolates, three isolates, K2, K5 and C8, were able to produce hydrogen cyanide, protease and cellulase enzymes.

Among wide variety of soil pollutants including heavy metals, acidic precipitation and other toxicants, the importance of heavy metals due to their pollution capacity has received growing attention in recent years. These metals enters into soil through municipal and industrial sewage as well as direct application of fertilizer and pesticides. High cadmium and lead concentration in soil lead to severe environmental pollution. Such pollution not only has a destructive effect on crop yield but also endangers human being and other creatures’ health after entering in their food chain. Several physical, chemical and biological methods used to reduce the adverse effect of high concentration of heavy metals in soil. In spite of the hight cost, these methods are not always suitable for reclamation of small area and mostly have side effect on physico-chemical and biological characters of soil, after application. Biochar produced by thermal decomposition of biomass in the absence or presence of low oxygen. These material due to their high spacific surface area and high cation exchange capacity may have great ability to absorb charged material including heavy metals. Therefore in this study attempt is made to evaluate the effect of sugarcane bagasse –derived biochar in improving maize plant growth in cadmium and lead contaminated soils.
Material and This study was carried out during the year 2014 in two separate experiments in Shahid Chamran university. The treatments in each case consisted of two levels of sugarcane bagasse made biochar (0 and 4 percent by weight) in combination with each soil, properly contaminated with 50 and 100 mg cadmium per kg soil in first experiment and 500 and 1000 mg lead per kg soil in the second. The treated soils were applied to pot and arranged in a complete randomized block designe and replicated 3 times. Prior to introduction of soil to pots, the heavy metal contaminated soils with moisture content around 70 percent of F.C. were incubated for 30 days. During incubation period sugarcane bagasse was dried, milled, sieved, compacted and subjected to traditional furnace at 550 oc for 3 hours on low pyrolysis. The furnace temperature was controlled manually using lesser thermometer. The furnace cooled down and the collected sugarcane bagasse made biochar sieved again. The incubated soil mixed with proper amount of sugarcane bagasse made biochar and incubated under previous condition for 45 days. The treated soils were poured to the labeled pots and 3 maize seeds were sown in each pot and two weeks after emergence thinned to one plant per pot. Nineteen days after sowing, the height of the plants and chlorophyll index were recorded and plants were harvested and leaf area of each plant was recorded, maize root content of each pot were carefully separated from soil and along with shoot property washed, dried, weighed and after milling subjected to chemical analysis. Prior to sowing maize seeds some of physic- chemical properties of untreated soil were estimated. Furthermore few charactoristics of sugarcane bagasse made biochar including pH and EC in 1 : 10 solution of biochar to water recorded. N, C, H, O concentration were estimated by elementary analyzer. Cation exchange capacity of sugarcane bagasse made biochar was measured by ammonium acetate method. Moreover its functional group determined by FT-IR method. Specific surface area estimated as per Branuar Emmet Teller (BET) method. Sugarcane bagasse made biochar image was obtained from scanning electron microscope. Cadmium and lead concentration in root and shoots were estimated by atomic absorption spectrometer after wet digestion. SAS software was used for statistical analysis data which fallowed by Duncan test to compare the mean values.
The results showed that implementation of cadmium and lead led to decrease in chlorophyll index, leaf area, height of plant and root and shoot dry weight significantly. But the sharp decline in the concentration of cadmium and lead in root and shoot after sugarcane bagasse made biochar application improved chlorophyll index, leaf area, height of plant, root and shoot dry weight. Application of 4% Sugarcane bagasse made biochar, decreased transfer factor (TF) and bioaccumulation factor (BF) of these elements compared to control. The results showed high capability of sugarcane bagasse made biochar to absorb cadmuim and lead and reduce their availability to plant respectively. In fact application of sugarcane bagasse made biochar dwindled cadmium and lead absorption as well as their transfer factor and bioaccumulation factor, and hence improved plant growth.
The results obtained after sugarcane bagasse made biochar application mainly initiated due to high cation exchange capacity of which eventually was created by large number of functional groups in its high specific surface area (table 2) to stabilize cadmium and lead and render them unavailable to plant and hence improve its growth.

Introduction Some methods of contaminated soils remediation reduces the mobile fraction of trace elements, which could contaminate groundwater or be taken up by soil organisms. Cadmium (Cd) as a heavy metal has received much attention in the past few decades due to its potential toxic impact on soil organism activity and compositions. Cadmium is a soil pollutant of no known essential biological functions, and may pose threats to soil-dwelling organisms and human health. Soil contamination with Cd usually originates from mining and smelting activities, atmospheric deposition from metallurgical industries, incineration of plastics and batteries, land application of sewage sludge, and burning of fossil fuels. Heavy metal immobilization using amendments is a simple and rapid method for the reduction of heavy metal pollution. One way of the assessment of contaminated soils is sequential extraction procedure. Sequential extraction of heavy metals in soils is an appropriate way to determine soil metal forms including soluble, exchangeable, carbonate, oxides of iron and manganese, and the residual. Its results are valuable in prediction of bioavailability, leaching rate and elements transformation in contaminated agricultural soils.
Materials and Methods The objective of this study was to synthesize magnetite nanoparticles (Fe3O4) stabilized with sodium dodecyl sulfate (SDS) and to investigate the effect of its different percentages (0, 1, 2.5, 5, and 10%) on the different fractions of cadmium in soil by sequential extraction method. The nanoparticles were synthesized following the protocol described by Si et al. (19). The investigations were carried out with a loamy sand topsoil. Before use, the soil was air-dried, homogenized and sieved (

In recent years, use of sewage sludge as a fertilizer has become prevalent in agricultural lands, because of being cheap. Sewage sludge is a source of nutritional elements, however, it contains some heavy metals. A study was conducted to evaluate the effect of incubation time, sewage sludge, and Thiobacillus bacteria on the distribution of cadmium in a calcareous soil. For this purpose, an experiment with three levels of sewage sludge (0 , 50, and 100 t ha-1), two levels of bacteria (with and without), three incubation times (0 , 30, and 60 days) was carried out. The experiment was conducted in three replications in controlled conditions using factorial arrangement with a completely randomized design. The samples were incubated for two months at temperature of 25±2 °C and soil moisture condition close to field capacity. Distribution of Cd in fractions including soluble exchangeable, organically bound, carbonate-bound, and residual fractions was determined by a sequential extraction method. The results illustrated that residual and carbonate form of Cd were dominant and showed a significant change with sewage sludge treatment and time. Sewage sludge application increased the amount of fractions of cadmium significantly in the calcareous soil. The proportion of residual and carbonat-bound Cd was higher in soil with and without bacteria. In soil withThiobacillus thiooxidans bacteria, the percentage of Cd in the carbonate and organic fractions decreased and the percentage of Cd increased in other fractions. Carbonate fraction of Cd was significantly higher in 60 days than 0 and 30 days. The organic forms of Cd decreased significantly in the course of time. In general, based on the results, it may be concluded that sewage sludge, Thiobacillus thiooxidans bacteria, and time treatment play a key role in the distribution of Cd in different fractions of soils.

Vegetables are among the major sources of cadmium entering the human food chain, which can be a serious threat for human health. So, in order to evaluate effects of organic manure, chemical fertilizers, and their combination on cadmium accumulation and growth of purslane, a factorial experiment was conducted in completely randomized block design with three replications, in 2012. Fertilizer treatments included urea fertilizer (60 and 120 mg N kg-1 soil), cattle manure (60 and 120 mg N kg-1 soil) , combined fertilizer (60, 45, 30 mg N kg-1 soil as urea fertilizer and cattle manure), and the control (no N amended). These were evaluated undertwo cadmium levels (no cadmium and 10 mg kg-1soil). Results indicated that concentration and uptake of cadmium in plant, decreased with increasing N rate, especially of cattle manure, and the lowest cadmium concentration was observed in 120 mg kg-1 in the form of cattle manure. Increase in nitrogen application from any source increased concentration and uptake of nitrogen. The greatest yield was obtained in 120 mg N kg-1 as cattle manure. There was no significant difference between 120 and 90 mg N kg-1 in the form of urea and the combined (1:1) fertilizer. In general, it can be concluded that use of cattle manure in vegetables production prevents movement of soil cadmium into vegetables and it is an effective method for protecting food chain from Cadmium contamination.

Soils contaminated with heavy metals such as cadmium (Cd), mainly are poor in nutrients and microbial population. Water deficit stress can deteriorate the situation for healthy plant growth. Application of plant growth promoting rhizobacterium as bio-fertilizer can influence the availability of nutrients and improve the plant growth and health. For this reason, a greenhouse factorial experiment was conducted in a completely randomized design with three replications. Treatments consisted of two levels of Micrococcus yunnanensis bacterium (with and without bacterium), four levels of Cd (5, 10, 20, and 40 mg kg-1), and three levels of soil moisture regimes (100, 80, and 65% of field capacity). Results showed that increasing soil Cd contamination, resulted in reduction of shoots dry weight and total manganese (Mn) and zinc (Zn) uptake, while the soil inoculation with bacterium moderated the negative effects of Cd on the plant by increasing shoots dry weight and total Zn uptake. The main effect of water deficit stress on the shoot dry weight, and the uptake of iron (Fe), Mn, Zn, and copper (Cu) were significant and reduced these traits while the soil inoculation with bacterium increased shoot dry weight and uptake of Fe and Zn and mitigated negative effects of water deficit stress.

Soil contamination by heavy metals is one of the most important environmental concerns in many parts of the world. The remediation of soil contaminated with heavy metals is necessary to prevent the entry of these metals into the human food chain. Phyto-extraction is an effective, cheap and environmental friendly method which uses plants for cleaning contaminated soils. The plants are used for phytoremediation should have high potential for heavy metals uptake and produce enormous amount of biomass. A major problem facing phyto-extraction method is the immobility of heavy metals in soils. Chemical phyto-extraction is a method in which different acids and chelating substances are used to enhance the mobility of heavy metals in soil and their uptake by plants. The aims of this study were: (a) to determine the potential of radish to extract Pb from contaminated soils and (b) to assess the effects of different soil amendment (EDTA and H2SO4) to enhance plant uptake of the heavy metal and (c) to study the effects of different levels of soil Pb on radish growth and Pb concentrations of above and below ground parts of this plant.
Soil samples were air dried and passed through a 2 mm sieve and analysed for some physico-chemical properties and then artificially contaminated with seven levels of lead (0, 200, 400, 600, 800 and 1000 mg/kg) using Pb(NO3)2 salt and then planted radish. During the growth period of radish and after the initiation of root growth, the plants were treated with three levels of sulfuric acid (0, 750 and 1500 mg/kg) or three levels of EDTA (0, 10 and 20 mg/kg) through irrigation water. At the end of growth period, the above and below ground parts of the plants were harvested, washed, dried and digested using a mixture of HNO3, HCl, and H2O2. The concentrations of Pb, N, P and K in plant extracts were measured. Statistical analysis of data was performed using MSTATC software and comparison of means was carried out using duncan's multiple range test.
The results showed that the effects of the type and rate of soil amendment and Pb levels of polluted soils were significant on dry weight and Pb concentrations of above and below ground parts of radish (p The results of the experiment showed that the Radish plant had the ability to absorb and accumulate the high concentration of lead in its tissues and so can be used for the phytoremediation of lead-contaminated soils. The EDTA application had higher potential for enhancing lead mobility and phytoavailability than H2SO4, But the ability of the low level of sulfuric acid to absorb lead was more than EDTA. The rate of amendment also had a significant effect on phyto-extraction process and the process was adversely affected by high concentrations of the amendments.