leila tabande; M. R.Bakhshi
Abstract
Introduction
Among essential plant microelements, iron (Fe) exert the highest restriction of crop production in Fars Province. Trace elements in the soil is composed of forms into 5 groups. These are the water-soluble and variable, adsorbed, chelate creating with complex compounds, secondary clay minerals, ...
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Introduction
Among essential plant microelements, iron (Fe) exert the highest restriction of crop production in Fars Province. Trace elements in the soil is composed of forms into 5 groups. These are the water-soluble and variable, adsorbed, chelate creating with complex compounds, secondary clay minerals, forms insoluble metal oxide minerals, and primary minerals. Water-soluble, changeable, adsorbed or form in chelates to be present as balance in the soil is noted and to be important for plants in nutrition.
Materials and Methods
In a greenhouse experiment was done with Soybean planting, the effects of Fe chelate (FeEDDHA) fertilizer levels on William cultivar of soybean (Glycine max L.) growth and chemical composition were studied by using a completely randomized design with 3 replications. Treatments were consisted of 10 soil samples and 3 levels of Fe applications (control, 5 and 10 mg.kg-1 as Fe EDDHA). Beside some physical and chemical soil properties and Extractable iron content with DTPA and EDTA were determined. By sequential extraction methods of Singh & Sposito ( 1982), chemical forms of Iron, exchangeable iron (Exch-Fe), organic bounded iron (OM-Fe), amorph iron oxides bounded iron (AFeOX-Fe), crystal iron oxides bounded iron (CFeOX-Fe) contents of soils were determined. Then, Concentration and uptake of Fe, Mn, Cu and Zn in plant were calculated.
Results and Discussion
carbonate, organically, amorphous oxide, crystalline iron oxide bounded and residual forms of iron were 0.0053, 0.0016, 0.44, 21.1 and 78.6% of the total iron as average, respectively. Therefore, content of carbonate, organically bound iron of soil, represented only a small fraction would not be considered as important as the total iron. In other words, crystalline iron oxide bound iron and residue iron forms constitued an important part of total iron.
Considering the average iron content of the soil related to chemical forms of iron was arrenged such as:
Res-Fe>CFeOX-Fe>AFeOX-Fe>Car-Fe> OM-Fe > Exch.-Fe
Applications of Fe had significant effect on dry matter, concentration, and uptake of Fe, Zn, Cu and Mn, extractable forms via extracting DTPA, EDTA, organic and exchangeable forms in soybean compared to control. Among chemical forms of iron, organic form with the amount of available iron plant (extraction by DTPA) had significant positive correlation. Also, many of the physical and chemical properties of calcareous soils studied, were significantly correlated with some chemical forms and amount of iron uptake by plant. DTPA extractable iron had negative correlation with pH ( R2= 0.514*) and EDTA extractable iron had positive correlation with organic matter (R2= 0.428*).
Conclusions
Application of Fe EDDHA, was leaded to significant increase organic and plant available (DTPA) forms of iron and due to significant regression equation (r=0.435*) between two chemical forms of iron (organic and DTPA extracted), it can be inferred that, the bulk of available iron plant was in form of organically bound. One reason for the positive reaction to the use of Fe EDDHA, subjected to a significant increase absorbable forms of iron in the studied soils.
Keywords: Chemical and Physical properties of soil, DTPA, EDTA, Iron, Sequential extraction
Mohamad Rahmanian; AliReza Hosseinpour; Ebrahim Adhami; Hamidreza Motaghian
Abstract
Introduction: Rhizosphere is commonly defined as the zone where root activity significantly influences the biological and chemical properties of the soil. Biological, physical and chemical characteristics of rhizosphere, especially metal availability and metal chemical forms are different than the bulk ...
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Introduction: Rhizosphere is commonly defined as the zone where root activity significantly influences the biological and chemical properties of the soil. Biological, physical and chemical characteristics of rhizosphere, especially metal availability and metal chemical forms are different than the bulk soil. Plant roots continuously release compounds such as sugars, amino acids, and carboxylic acids. Plant roots have the ability to transform metal fractions for easier uptake through root exudation in the rhizosphere. This study was conducted to investigate change in availability and fractions of Copper in the rhizosphere of sunflower (Helianthus annuus L.) in a sandy contaminated soil treated with chelators (EDTA, citric acid and poultry manure extract (PME)) in greenhouse condition.
Materials and Methods: In this study, EDTA and citric acid were used at concentrations of 0, 0.5 and 1 mmol kg-1 soil and PME was used at concentrations of0, 0.5 and 1 g kg-1 soil. Three seeds of sunflower were planted in the rhizobox. After 10 weeks, plants were harvested and rhizosphere and bulk soils were separated. Dissolved organic carbon (DOC), microbial biomass carbon (MBC), available Cu (by using 7 chemical procedures including DTPA-TEA,AB-DTPA, Mehlich1, Mehlich3, CaCl2 0.01 M, rhizosphere-based method and distilled water) and Cu-fractions were determined in the rhizosphere and bulk soils.
Results and Discussion: Rhizosphere soils properties were different with bulk soils. The results showed that the mean of DOC and MBC in the rhizosphere soils were higher than the bulk soils, but this difference was significant in some treatments. The mean value of pH in the rhizosphere soils was significantly (p
T. Mansouri; A. Golchin; J. Fereidooni
Abstract
Introduction: 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 ...
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Introduction: 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.
Materials and Methods: 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.
Results and Discussion: 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< 0.01). The dry weights of above and below ground parts of radish decreased as the Pb levels of polluted soils increased. By increasing the soil pollution level (1200 mg Pb/kg soil), the total dry weight of plant decreased by %47.3 which was probably due to phytotoxicity of lead and deficiency of several essential nutrients such as phosphorus. When the Pb levels of the polluted soils increased up to 400 mg/kg soil, the concentrations of Pb in above and below ground parts of the plant increased. But when the Pb levels of the polluted soils were higher than 400 mg/kg soil, the Pb concentration in above ground part of the plant decreased but in below ground part of the plant significantly increased. The decrease in Pb concentration in above ground part of radish was probably due to formation of insoluble lead complexes in soil. the use of soil amendments increased the concentrations of Pb in above and below ground parts of radish. The Application of EDTA increased the concentration of Pb in aerial part of radish more than the application of H2SO4. Also, the application of EDTA and H2SO4at low concentrations increased dry weight of plant since, the availability of micro- and macro elements enhanced and plant uptake of nutrients increased. But at the high concentrations of these amendments the increased availability of lead caused the reduced plant growth due to phytotoxicity. But the ability of the low level of sulfuric acid to absorb lead was more than EDTA. An antagonistic effect between phosphorus and lead uptake was also observed.
Conclusion: 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.
seyed sajjad hosseini; Amir Lakzian; Akram Halajnia
Abstract
Introduction: Application of EDTA may increase the heavy metal availability and phytoextraction efficiency in contaminated soils. In spite of that, it might also have some adverse effects on soil biological properties. Metals as freeions are considered to be severely toxic, whereas the complexed form ...
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Introduction: Application of EDTA may increase the heavy metal availability and phytoextraction efficiency in contaminated soils. In spite of that, it might also have some adverse effects on soil biological properties. Metals as freeions are considered to be severely toxic, whereas the complexed form of these metalswith organic compounds or Fe/Mn oxides may be less available to soil microbes. However, apart from this fact, some of these compounds like EDTA and EDTA-metal complexes have low bio- chemo- and photo-degradablity and high solubility in their own characteristics andable to cause toxicity in soil environment. So more attentions have been paid to use of low molecular weight organic acids (LMWOAs) such as Citric acid because of having less unfavorable effects to the environment. Citric acid increases heavy metals solubility in soils and it also improves soil microbial activity indirectly. Soil enzymes activity is a good indicator of soil quality, and it is more suitable for monitoring the soil quality compared to physical or chemical indicators. The aims of this research were to evaluate the changes of dehydrogenase, urease and alkaline phosphomonoesterase activities, substrate-induced respiration (SIR) and Pb availability after EDTA and citric acid addition into a contaminated soil with PbCl2.
Materials and Methods: An experiment was conducted in a completely randomized design with factorial arrangement and three replications in greenhouse condition. The soil samples collected from surface horizon (0-20 cm) of the Typic haplocalsids, located in Mashhad, Iran. Soil samples were artificially contaminated with PbCl2 (500 mg Pb per kg of soil) and incubated for one months in 70 % of water holding capacity at room temperature. The experimental treatments included control, 3 and 5 mmol EDTA (EDTA3 and EDTA5) and Citric acid (CA3 and CA5) per kg of soil. Soil enzymes activity, substrate-induced respiration and Pb availability of soil samples were determined by standard methods after 7, 14, 21 and 28 days of chelates addition.
Results and Discussion: The soil texture was loam and the indigenous Pb content was 25.55 mg kg-1. The soil pH was 7.4 and electrical conductivity of saturated extraction measured 2.5 dS m-1. The soil carbonate calcium was 14% and the content of organic carbon and essential nutrients were low. The results showed that EDTA3 and EDTA5 treatments increased Pb availability by 2.17% and 10% compared to control treatment but CA3 and CA5 treatments decreased it by 3.8% and 15.7% respectively. The Pb availability in control and EDTA5 treatments did not change during the incubation time. The available Pb concentration dropped sharply during the incubation time in EDTA3, CA3 and CA5 treatments. The reduction rates in CA3 and CA5 treatments were more than EDTA3 treatment. This may be due to the high stability and low biodegradability of EDTA than biodegradable chelators and low molecular weight organic acids. The results showed that urease and dehydrogenase activities were significantly reduced in EDTA3 and EDTA5 treatments compared to control treatment. Urease and dehydrogenase activities were decreased with the increase of EDTA concentration. Alkaline phosphomonoesterase activity was not affected by the EDTA3 and EDTA5 treatments. In CA3 and CA5 treatments, dehydrogenase and alkaline phosphomonoesterase activities significantly increased with increasing the concentration of citric acid. CA5 treatment showed a prominent effect on urease activity compare to CA3 treatment. The soil enzyme activities increased with incubation time. It seems that reduction in Pb availability causes an increase of soil enzymes activities. Significant negative relationships were found between soil enzymes activities and available Pb concentration (dehydrogenase activity (r=-0.906, P
E. Babaeian; M. Homaee; R. Rahnemaie
Abstract
Phytoextraction is a remediation technology for contaminated soils with lead (Pb). The application of chelating agents can be resulted in high efficiency in this method. In current study, the effect of synthetic and natural chelates applicationon efficiency of lead phytoextraction from soil by carrot ...
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Phytoextraction is a remediation technology for contaminated soils with lead (Pb). The application of chelating agents can be resulted in high efficiency in this method. In current study, the effect of synthetic and natural chelates applicationon efficiency of lead phytoextraction from soil by carrot was investigated. The experiment factors were 1) six levels of Pb (0, 100, 200, 300, 500 and 800 mg Pb kg-1 soil, added as Pb(NO3 )2, 2) chelates (EDTA, NTA and oxalic acid, and 3) chelate concentration (0, 2.5, 5 and 10 mmol kg-1 soil). The results indicated that EDTA effectively increased the Pb content in soil solution. At the highest applied rate (10 mmol EDTA kg-1), it resulted in 463-fold increase in extractable Pb, compared to the control treatment. Pb content in the shoot and taproot increased with the chelates application rates.The highest Pb content in the shoot (342.2±13.9 mg kg-1) and root (310 ±15.5 mg kg-1) occurred in 10 mmol kg-1 EDTA when Pb level was 800 mg kg-1. Pbphytoextraction potential increased with increasing thechelate and Pb concentration. Maximum Pb extraction from soil (1208±26.6 g ha-1 yr-1) during growth season occurred in 10 mmol kg-1 EDTA, when soil Pb level was 800 mg kg-1. It may be concluded that carrot can take up high amount of Pb and concentrate it in its roots and shoots. Thus, it can be introduced as a lead accumulator to phytoextractPb from contaminated soils.
