M. Anoosha; A. Forghani
Abstract
Introduction: Copper and zinc are two of the most important microelements affecting plant growth which can be influenced by many factors. The adsorption processes play a determinative role in solubility of copper and zinc elements in the soil solution and, therefore, their availability to plants. Organic ...
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Introduction: Copper and zinc are two of the most important microelements affecting plant growth which can be influenced by many factors. The adsorption processes play a determinative role in solubility of copper and zinc elements in the soil solution and, therefore, their availability to plants. Organic matter is one of the most important factor that have an significant role on the absorption and desorption of elements in the soil. These materials are divided into humic and non-humic groups. Humic substances are divided into three groups of fulvic acid, humic acid and humic, based on their resistance and solubility in acid and base. Humic acid with a medium molecular weight and color is soluble into base and insoluble into acid, and has a medium resistance against the microbial attack. It forms the most important organic part of the soil and is capable to adsorb metals. The purposes of this study were to extract soil humic acid, study the adsorption of metals on the surface of humic acid and to determine the metals adsorption coefficients using adsorption isotherm models. Materials and Methods: Sampling was done from forest areas of northern Iran. Some physical and chemical properties of the studied soil were determined. Then, the humic acid of the soils was extracted by 0.1 M NaOH and 6 M HCl, and purified by 0.1M HCl+0.3M HF. Functional group, E4/E6 ratio (Optical density or absorption of dilute solutions at wavelengths of 465 and 665 nm), and humification index of the extracted humic acid were measured. Some other properties of the extracted humic acid have also been analyzed. To study the adsorption isotherms of Zn and Cu in the presence of humic acid, solutions with concentrations of 10, 20, 40, 60 and 80 mg/L of ZnCl2 (zinc adsorption testing) and CuSO4 (copper adsorption testing) were prepared, respectively in a 0.01M Ca(NO3)2 background solution, and added to 250 g of humic acid. The samples were shaken for 12 hours (based on the time of equilibrium) at pH=5 and 25 °C in incubator shaker, then the samples were centrifuged and the supernatant was passed through filter paper and measured using atomic adsorption spectrophotometer device. The difference between initial concentration and final concentration identified the amount of adsorbed element. Results and Discussion: The results of the acidic functional groups measurement in the humic acid samples revealed that the most of total acidity (60%) was due to the presence of phenolic groups while the carboxylic groups were responsible for the remaining (40%). Phenolic groups were abundant in the primary stages of the decomposition of humic materials. Since the soil used for extracting humic acid was covered with broad leaf trees and the continuous entry of organic matter into it (the fall of leaves) lasted for many years and due to the low temperature of the soil in part of the year, it can be said that a significant part of the soil organic matter is in the primary or middle stages of humification and the phenolic OH groups/carboxylic groups ratio in the humic acid extracted from them was high. The equilibrium time for adsorption of both metals occured at 12 h to achieve maximum adsorption level in the presence of humic acid. The obtained experimental data were fitted to three models of Langmuir, Freundlich, and Tampkin. The accuracy of mentioned models to fit data were estimated based on the detection coefficient (R2) and the roots of mean square error (RMSE). The results showed that the Freundlich model with higher detection coefficient and lower roots of mean squared error describes the adsorption of copper and zinc elements, well. To better compare the adsorption of the elements by humic acid, Langmuir's b parameter (Expresses maximum adsorption) can be used. The maximum adsorption of copper (23.04 mg/g) by humic acid was higher than zinc adsorption (13.8 mg/g). This trend is consistent with the Irving–Williams series of divalent elements: Mn < Fe < Zn < Co < Ni < Cu. It is generally believed that humic acid is a good complexing agent for many metal ions and its binding to metal ions can improve the adsorption. Significance differences were tested by a parametric 𝑡-test or 𝐹 statistics in ANOVA (analysis of variance). There was a significant correlation between the maximum adsorption of metals (b) and the properties of humic acid at a probability level of 5%.
M. Mosapour; A. Forghani; A. Sabouri
Abstract
Introduction: Potassium is the second essential nutrient for plants. Potassium has a high abundance in the soil, but only a small part of it can be used. The principal forms of potassium in the soil are solution potassium, exchangeable potassium, non-exchangeable potassium, and structural potassium. ...
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Introduction: Potassium is the second essential nutrient for plants. Potassium has a high abundance in the soil, but only a small part of it can be used. The principal forms of potassium in the soil are solution potassium, exchangeable potassium, non-exchangeable potassium, and structural potassium. To evaluate the state of potassium in the soil, three forms of soluble, exchangeable, and non-exchangeable are used. The Q/I curve is used to describe the availability of potassium, due to the competition between calcium, potassium, and magnesium ions by soil exchange sites. This curve represents the supply power of soil potassium. The objective of this study was to investigate soil potassium Q/I curve and relationships between its parameters and soil characteristics in some calcareous soils of Lorestan province.
Materials and Methods: In this study, 16 topsoil samples (0-30 cm) were obtained from the calcareous soils of Lorestan province. The experiment was carried out by a completely randomized design with three replications. To prepare the Q/I curve, six suspensions were prepared from each soil sample containing 1 g of soil and 10 ml of calcium chloride 0.01 M and 10 milliliters of potassium chloride with concentrations of 0.33, 0.66, 1, 1.33, 2 and 2.5 mmol. The solutions were shaken for one hour. They were then left for 20 hours to reach the balance. The samples were centrifuged and the soluble and solid phase were separated and then the soluble potassium solution was read using a potassium flame photometry. Calcium and magnesium concentrations were measured by titration with EDTA. Then, 20 ml of 1 M ammonium acetate (NH4OAC) was added to the solid phase of each sample. Then, the concentration of exchangeable potassium was measured using a flame photometer. Then the Q/I curve was plotted for each sample. In addition, the association analysis was performed using a stepwise multivariable regression method.
Results and Discussion: According to the Q/I curve, ARK0 (potassium activity ratio at equilibrium) ranged from 0.087-0.047 (mmol.L-1). The maximum amount of PBCK (potential buffering capacity) was observed in soil No.11 with value of 45.834 (mmol.kg-1)/(mmol.L-1)0.5 and the lowest value obtained for soil No.13 with value of 23.329 (mmol.kg-1)/(mmol.L-1)0.5. In fact, in soils with PBCK, the soluble potassium activity has a lower oscillation and is better buffered. The low amount of PBCK in soil No.13 indicates low soil power to supply potassium and the necessity of using potassium fertilizers. The lowest and most easily converted easy potassium (ΔK0) were observed for soil No.12 and 4 with a value of 1.269 and 23.243 (mmol.kg-1) respectively. There was a negative correlation between PBCK and ARK, suggesting those high-PBCK soils, lower ARK, are more stable than those with lower PBCK. The KL (available Potassium) with ΔK0 and Kx (Hardly exchangeable K) showed a significant and positive relationship (r=0.70, p<0.01). Therefore, it can be concluded that by increasing each of the two parameters ΔK0 and KX, the amount of potassium (KL) is increased. Also, a positive and significant correlation was found between potassium potential buffering capacity with clay content (r=0.79, p<0/01) and the cation exchange capacity (r=0.73, p<0.01). Therefore, the cation exchange capacity of soils can be used to estimate the buffering capacity of soils and therefore recommend potassium fertilizers. Available potassium (KL) showed a positive and significant correlation with soil organic matter because its organic material is a part of potassium. Also, organic matter can alter the amount of potassium by changing the pH value. Other Q/I curve parameters, such as ARK0, Kx, and ΔK0 did not show any significant correlation with any soil properties. According to regression analysis, it was determined among all soil characteristics the only amount of clay can be used as a proper attribute in order to estimate the potential of potassium in soil according to the following equation: PBCK=17.857+0.482 Clay R2 = 0.631. Also, the amount of organic carbon (O.C) was determined as the proper variable for estimating the KL value according to the following model: KL=14.468+9.017 O.C (R2 = 0.318).
Conclusion: Due to potential buffering capacity (PBCK) in these soils, it seems that soils can be able to provide the absorbable potassium relatively. Therefore, fertilizer recommendation can be performed by considering the amount of determined variables by the Q/I curve.
Samira Abduolrahimi; Nasrin Ghorbanzadeh; Akbar Forghani; Mohammad Bagher Farhangi
Abstract
Introduction: Cadmium is considered to be one of the heavy metals with the highest toxicity, because it has high activity and a relative high dissolution rate in water and in living tissues. In recent years, due to the high volume of natural resources pollution and the inefficiency of conventional physicochemical ...
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Introduction: Cadmium is considered to be one of the heavy metals with the highest toxicity, because it has high activity and a relative high dissolution rate in water and in living tissues. In recent years, due to the high volume of natural resources pollution and the inefficiency of conventional physicochemical methods for refining these resources and the occurrence of environmental crisis, bioremediation process has been at the forefront. Microbially induced calcite precipitation (MICCP) has been considered as a novel solution for these problems, and several bacterial species have been already utilized for MICCP. MICCP based degradation of urea occurs through the ureolytic pathway. Urease (urea amidohydrolase) is an enzyme that hydrolyzes urea into one mole of carbonate and two moles of ammonia per mole of urea. In this aspect, microbial mineral precipitation products such as calcite can strongly adsorb heavy metals on their surfaces and incorporate heavy metal ions into their crystal structure. Some studies have reported MICCP-based sequestration of soluble Cd via coprecipitation with calcite was useful for Cd bioremediation. Several bacterial species have been utilized for MICCP. The endospore forming bacteria Sporosarcina pasteurii have been shown to produce high levels of urease and have therefore been extensively studied. Sporosarcina pasteurii has attracted significant attention for its unique feature of calcium carbonate precipitation, which can be easily controlled. So, In the present study the ability of Sporosarcina pasteurii bacterium has been investigated in the remediation of Cd(II) in Cd-contaminated sandy soil based on MICCP method.
Materials and Methods: Sporosarcina pasteurii (PTCC 1645) was procured from Microbial Bank of Iran (Central Collection of Industrial Fungi and Bacteria, Karaj, Iran). The bacterial strain was inoculated into NB (nutrient broth) media containing 2% urea and 25 mM CaCl2 (NBU media) and then incubated at 37◦C for 6 days. The urease activity was determined at regular time intervals by measuring the amount of ammonia released from urea according to the phenol-hypochlorite assay. Minimum inhibitory concentration (MIC) test was performed to determine the lowest concentration of cadmium chloride, which prevents the growth of bacteria. Sporosarcina pasteuriiwas inoculated into NBU media supplemented with 0.5, 1,2,4,8 and 10 mmol l-1 Cd and incubated at 37◦C, 130 rpm for 50 hours. Control flasks without adding Cd were also incubated. Bacterial growth was determined in terms of optical density (OD) by measuring absorbance at a wavelength of 600 nm at regular time intervals (0, 10, 20, 30, 40 and 50 hours) and colony-forming units (CFU) were also counted. The cadmium removal in 0.5, 1 and 2 mM cadmium solutions (based on MIC) was measured.A sandy soil from a depth of 0 to 30 cm was sampled. The soil was polluted with 10, 20, 40 and 50 mg/kg of cadmium and incubated in room temperature for two weeks. After incubation time, the cadmium remediation studies were performed at 30◦C in the beakers containing 100 g of sterilized dried contaminated soils and 200 mL of overnight grown of Sporosarcina pasteurii (~ to 107cfu ml−1) in NBU media. For each treatment corresponding control were included with the same condition but without bacteria.After 7 days of incubation, urease and dehydrogenase enzymes activity and concentration of cadmium in soluble + exchangeable and carbonate fractions were measured. The concentration of cadmium in iron-manganese oxides, organic matter and residual fractions in concentration of 50 mg/kg cadmium was also determined according to the continual extraction procedure of Tessier et al. (1979).
Results and Discussion: The amount of released ammonia by ureolytic activity of Sporosarcina pasteurii increased up to fourth day and then became almost constant.Optical density in different concentrations of cadmium decreased in comparison to control treatment after 48 hours. The minimum inhibitory concentration of cadmium for bacteria growth was 2 mM as determined by colony counting after 48 hours of incubation. Cadmium removal efficacy from solutions containing 0.5, 1 and 2 mM of cadmium was 99.6, 99.8 and 99.8%, respectively. The amounts of urease and dehydrogenase activities in the presence of bacterium were significantly higher than control treatments (P≤0.05). The results of the fractionation of contaminated soils in the absence of Sporosarcina pasteurii showed the distribution of cadmium as organic matter
H. Sepahvand; A. Forghani
Abstract
Abstract
Zinc (Zn) is an essential plant nutrient. Knowledge about distribution of Zn between its different chemical forms is useful in understanding the chemistry of this element in soil and also in development of soil testing procedures. The present study was conducted to obtain such information about ...
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Abstract
Zinc (Zn) is an essential plant nutrient. Knowledge about distribution of Zn between its different chemical forms is useful in understanding the chemistry of this element in soil and also in development of soil testing procedures. The present study was conducted to obtain such information about distribution of zinc forms in 20 soil samples of Lorestan province by the use of a sequential extraction procedure to extract different zinc forms in these soils and determination of relations between those and some of soil properties. The percentages of distribution of Zn forms with respect to sum of obtained forms were 0.35 for carbonated bound, 0.41 for exchangeable + water soluble, 0.79 for amorphous Fe-oxide bound, 3.03 for organic bound, 3.97 for crystalline Fe-oxide bound and 91.43 for residual (Mnox bound form was not detected and ignored). Correlation coefficient of equivalent carbonate calcium percent was negative with all the Zn forms (with the exception of organic bound) but with exchangeable + water soluble and Fe-oxides bound was significant.The relation between the available P with Fe-oxides bound and residual form obtained significant. The correlation of organic matter percent of soils with organic bound form was negative and significant. The extractable Zn with DTPA also showed significant correlations with Fe-oxides bound and residual Zn forms. There were significant correlations between some of Zn forms and this result probably showed the existence of a dynamic relationship between them in the soils.
Keywords: Zinc fractionation, Calcareous soil, The soils of Lorestan province, Zinc forms, Sequential extraction methods