Soil science
B. Abolfazli Behrooz; S. Oustan; H. Mirseyed Hosseini; H. Etesami
Abstract
IntroductionCadmium (Cd) contamination has been a widespread concern in paddy soils because of its subsequent transfer to the food chain. Biochar amendment is proposed to stabilize Cd in the contaminated soils. However, the pristine biochar shows limited functionality towards Cd sorption in practice. ...
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IntroductionCadmium (Cd) contamination has been a widespread concern in paddy soils because of its subsequent transfer to the food chain. Biochar amendment is proposed to stabilize Cd in the contaminated soils. However, the pristine biochar shows limited functionality towards Cd sorption in practice. Recently, Mg-modified biochars have attracted much attention for their low toxicity. These biochars are coated by MgO or Mg(OH)2 precipitates during the pyrolysis process. Magnesium chloride (MgCl2)-modified biochars have been used widely in the removal of heavy metals from the aqueous solutions. However, there is little literature about their performance in soils. The present study therefore was conducted to investigate the effects of application of unmodified and MgCl2-modified rice husk biochars on the kinetics and isotherms of Cd sorption in a calyey paddy soil. Materials and MethodsThe unmodified and MgCl2-modified biochars were produced from rice husk at 600°C. Some relevant characteristics of the produced biochars (including elemental composition, pzc, pH1:10, ash content and BET surface area) were determined. Moreover, the studied soil was taken from a paddy field (0-20 cm) in the Qaemshahr region of Mazandaran province. The biochars (< 0.5 mm) were added to the soil samples at three levels (0, 3, and 5% w/w) and the amended soils were incubated at 25°C for 45 days. Then, the kinetic experiments of Cd sorption at a concentration of 375 mg Cd/L at times of 0.25, 0.5, 1, 2, 4, 8, 16, 24 and 48 hours and the isothermal experiments of Cd sorption at concentrations of 50, 100, 150, 200, 300, 350, 400, 600 and 800 mg Cd/L were performed. In both kinetic and isotherm experiments, a 0.01 M KCl solution was used as the background electrolyte. Finally, the relevant kinetic and isotherm models were fitted to the sorption data and their parameters were calculated. Results and DiscussionBiochar characterization indicated that modification with MgCl2 resulted in an increase of the O/C ratio (from 0.27 to 0.48) and pH (from 7.67 to 8.60). This modification also increased the H/C ratio (from 0.032 to 0.071) and the specific surface area (from 195.6 to 231.2 m2/g). As a result, the MgCl2-modified biochar was more hydrophilic and less carbonized than the unmodified one. Moreover, the characteristic peaks of the MgCl2-modified biochar (3700, 1428 and 500 cm-1) were present in its FTIR spectrum. The results revealed that about 74 to 89% of the Cd sorption by the soils occurred in times less than 2 hours. With MgCl2-modification, the sorption equilibration time was reduced from 48 hours to 24 hours. In contrast, the unmodified biochar had no considerable effect on the Cd sorption kinetics. Among the kinetic models, the Elovich model with lower SEE was the best to fit the Cd sorption kinetic data. The intra-particle diffusion model was not satisfactory for Cd sorption on the biochars. Freundlich model with lower SEE well described the Cd sorption isotherms. Application of 3% and 5% MgCl2-modified biochar increased the Freundlich KF parameter by 2.4 and 2.8 times as compared to the control. Moreover, the aforementioned treatments increased the heterogeneity parameter of the Freundlich model (n) from 3.48 to 6.08. The Temkin model could not reasonable fit the sorption data. In contrast, the unmodified biochar did not show any considerable effect on the Cd sorption capacity of the clayey soil used in this research. This finding means that the unmodified biochar could not improve the sorption performance of negatively charged soil clay particles. ConclusionAccording to the results obtained, it could be concluded that the Cd sorption behavior of the soil treated with unmodified rice husk biochar was similar to that of the untreated soil. Whereas, the MgCl2-modification improved both sorption rate and sorption capacity of the soil for Cd. Application of MgCl2-modified biochar improved the Cd sorption properties of a clayey soil with high intrinsic sorption ability. Thus, this may be a promising approach in remediation of Cd-contaminated paddy soils with the aim of reducing Cd mobility and availability. However, there is need to do more research to create awareness about the importance of biomass nature as well as pyrolysis temperature, the ratio of MgCl2 to biomass, the mechanism of Cd stabilization and the desorption of Cd from soils treated with MgCl2-modified biochars.
S. Bagheri; hossein mirseyed hosseini
Abstract
Zinc is an essential element for plant growth which its high concentrations can cause pollution and toxicity in plant. In this study, the effects of sorghum cultivation on some indicators of microbial activity and its association with increased zinc concentrations in two soils with relatively similar ...
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Zinc is an essential element for plant growth which its high concentrations can cause pollution and toxicity in plant. In this study, the effects of sorghum cultivation on some indicators of microbial activity and its association with increased zinc concentrations in two soils with relatively similar physical and chemical properties, but different in concentration of heavy metals were investigated. In both soils zinc levels were added to obtain 250, 375 and 500 mg kg-1 (based on the initial nitric acid extractable) content. Using plastic boxes containing 8 kg of soil, growth boxes (Rhizobox) were prepared. The box interior was divided into three sections S1 (the rhizosphere), S2 (adjacent to the rhizosphere) and S3 (bulk soil) using nylon net plates. The results showed that at all levels of zinc in both soil types, BCF were bigger than units, so using this indicator, sorghum can be considered as a plant for accumulation of zinc. Microbial respiration and dehydrogenase activity was reduced in all sections adjacent to root in the polluted soil. It is generally understood that substrates and inhibitors (heavy metals) compete in the formation of substrate-enzyme and inhibitor-enzyme complexes, but the effects of sorghum cultivation in increasing biological and enzyme activity indexes in soil 1 (non-polluted) was higher than soil 2 (polluted), perhaps due to improvements in microbial activity in the vicinity of the roots, even in concentration higher than stress condition levels for zinc in soil.
A. Golestani Fard; H. Mirseyed Hosseini; Gholam Reza Savaghebi; Gh.R. Savaghebi
Abstract
In this research chemical forms of lead and zinc in bulk and rhizosphere soil of different cultivars of maize and canola were determined by sequential and single step extraction methods. Some factors affecting chemical transformation of the two elements such as pH, dissolved organic carbon (DOC), their ...
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In this research chemical forms of lead and zinc in bulk and rhizosphere soil of different cultivars of maize and canola were determined by sequential and single step extraction methods. Some factors affecting chemical transformation of the two elements such as pH, dissolved organic carbon (DOC), their uptake by plant and also cation exchange capacity in the rhizosphere and bulk soil were also assessed. Rhizosphere was obtained with gentle shaking and separating the soil around plant roots. Results showed that zinc uptake was more than lead in both plant cultivars. Zinc and lead accumulation in all cultivars roots were also more than shoots. Translocation index (The ratio of element concentration in shoot to root) in the corn cultivars was higher than canola cultivars (significant correlation= 1%) while the ratio was higher for lead in canola cultivars. Metal concentration in shoots to total metal concentrations in soil (Accumulation factor) showed a similar trend like the translocation index. In total, the corn ability in zinc and lead absorption and extraction in soil was higher compared to canola. There weren’t any significant changes in rhizosphere pH compared to bulk soil. Dissolved organic carbon in the rhizosphere of different cultivars was more than bulk soil and the amount of it in canola was significantly more than corn cultivars. Among each plant cultivars, the absorption rate increased with increasing root exudates. The results of sequential and single step extraction methods showed that the general trend and the soil system tendency (Root-Soil interface) is toward zinc availability in the rhizosphere. The amount of lead in rhizosphere showed no significant changes to bulk soil with none of the extractants in single step extraction method but with regards to the results of sequential extraction method, rhizosphere processes tend to reduce the availability of this element in both plant cultivars.
A. Mohseni; H. Mirseyed Hosseini; F. Abbasi
Abstract
Fertilizing method plays an important role in fertilizer and water use efficiency and plant yield and losses fertilizer. A field experiment was carried out at 16 treatments with factorial a complete randomized block design during 2010 for free drainage furrows. First factor was four levels of water (60, ...
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Fertilizing method plays an important role in fertilizer and water use efficiency and plant yield and losses fertilizer. A field experiment was carried out at 16 treatments with factorial a complete randomized block design during 2010 for free drainage furrows. First factor was four levels of water (60, 80, 100 and 120% of full irrigation) and second factor was four levels of fertilizer (0, 60, 80 and 100% of required fertilizer) for fertigation method. The 16 treatments mentioned above, were compared with common fertilizing method. Nitrogen requirement was applied in four stages of the growth: before cultivation, in seven leaves, shooting and earring stages, the first portion (before cultivation) was applied by manual distribution and others by fertigation. In conventional treatment, the whole of required fertilizer was used in two split applications (before planting and in seven leaves). Results showed, the highest yield, yield component and use efficiency of corn was obtained on 100% irrigation and 100% fertilizer treatments. While the highest amount percolation of nitrate into soil was related to conventional treatment.
Z. Farzanegan; Gh. Savaghebi; H. Mirseyed Hosseini
Abstract
Abstract
The use of plants to remove contaminants from the environment and concentrate them in above-ground plant tissue is known as phytoextraction. This study was conducted to investigate the potential of phytoextraction of Pb and Cd metals canola (Brassica napus) and sorghum (Sorghum bicolor) which ...
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Abstract
The use of plants to remove contaminants from the environment and concentrate them in above-ground plant tissue is known as phytoextraction. This study was conducted to investigate the potential of phytoextraction of Pb and Cd metals canola (Brassica napus) and sorghum (Sorghum bicolor) which are high Biomass Crop and the effect of amendments on the efficiency of phytoextraction. The soil sample for the experiment was collected from an area adjacent to a Zinc Concentrate factory in west of Zanjan, Iran. Five treatments compared included powdered sulfur, sulfur plus thiobaccilus inucolum (S+I) at 8g kg -1 rate, citric acid at two levels of 1g kg-1 (CA1) and 3g kg-1 (CA2) and the control (C). The experiment was conducted in two stages. In the first stage of study, the treated soil with the above material were incubated for 8 weeks at field capacity and 25˚C temperature. In the incubation period the subsamples were collected at 0, 4 and 8 weeks to determine the amount of plant available Pb and Cd using DTPA extraction. In the second stage, a greenhouse experiment was conducted using the same soil and treatments. Sorghum and canola were planted and grown for 60 days and then the above ground parts and roots were harvested. Plant samples were analyzed for Cd and Pb content and the amount of DTPA exractable Pb and Cd were measured in soils before and after planting. Both experiments were conducted in the factorial experiment with randomized complete design with 5 treatments (including control) and 4 replications. The statistical Analysis was done using SAS and MSTATC Softwares. The resulst indicated that effect of sulfur plus thiobaccilus and citric acid at 1g.kg-1 treatments on Cd and Pb availability were highest and lowest, respectively. The pot experiment showed that the best of amendment in transfer of metal from root to shoot for two plant species was powdered sulfur plus thiobaccilus inucolum. The results of greenhouse experiment indicated that canola has higher potential for remediation of Cd and Pb from contaminated soil in comparison with sorghum.
Keywords: Lead, Cadmium, Sorghum, Canola, Phytoextraction, Amendment
F. Vahabbi; H. Mirseyed Hosseini; M. Shorafa; S. Hatami
Abstract
Abstract
Spent mushroom compost (SMC) is a by-product of the mushroom industries. It is made from straw, manure, gypsum and horse-bedded straw, hay and poultry manure. SMC has been used as a soil amendment, particularly for intensive horticultural production. In this study the effects of various SMC's ...
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Abstract
Spent mushroom compost (SMC) is a by-product of the mushroom industries. It is made from straw, manure, gypsum and horse-bedded straw, hay and poultry manure. SMC has been used as a soil amendment, particularly for intensive horticultural production. In this study the effects of various SMC's types (fresh, one year old, two years old) on changes of chemical characteristics of a loamy soil was studied for 12 weeks in a laboratory column incubation under controlled conditions. Different rates of each SMC (0, 15, 30, 60 t ha-1) were mixed with a loamy soil. The columns were leached with deionized water every week. Leachates were collected and analyzed for EC, pH, soluble cations (Sodium, Potassium, Calcium, and Magnesium), and anions (Chloride, Bicarbonate, Nitrate) content. Similar data collection was conducted on the soil samples at the beginning and at the end of the test. The results showed that EC and concentration of nutrients was the lowest in two years old SMC. It is probably due to the amount of salts leached out during the weathering of SMC. The leachate contained a higher amount of Calcium and Magnesium over the 12 week period. Two years old SMC had less Cl and Na and had less effect on soil salinity and sodification. Since the slow inorganic-N release rate from SMC-amended soil is predominantly the result of the slow mineralization of recalcitrant organic-N in SMC, therefore, nitrate content in two years old SMC can provide the primary requirements of plants. Comparison of different levels of SMC showed that using 30 t ha -1 is more favorable as compared with other levels. The 60 t ha -1 level caused higher EC and salinity in the soil. As a general rule if SMC with proper aging is used at an appropriate level it can affect the chemical and physical characteristics of the soil and can be used as a soil amendment.
Key words: Spent Mushroom Compost (SMC), wastage mushroom, Composting, Soil amendment, Columns leaching
