majid forouhar; Reza Khorassani; Amir Fotovat; Hossein Shariatmadari; Kazem Khavazi
Abstract
Introduction: Global warming is strongly linked to the increase in greenhouse gas emissions to the atmosphere. One of the most efficient ways to reduce the amount of atmospheric CO2 is to produce a lot of biomass and convert the biomass into a biochar. Biochar is an organic carbon-rich solid that can ...
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Introduction: Global warming is strongly linked to the increase in greenhouse gas emissions to the atmosphere. One of the most efficient ways to reduce the amount of atmospheric CO2 is to produce a lot of biomass and convert the biomass into a biochar. Biochar is an organic carbon-rich solid that can be obtained from pyrolysis of various organic materials. In other words, biochar can be produced via thermal degradation of many organic materials such as vegetation biomass, animal waste, sewage sludge, etc. in absence or lack of oxygen. Biochar is more resistant to microbial degradation than its feedstock and has a mean resistance time of several decades. In connection with the use of biochar, the most researches have been done in non-fertile and highly weathered soils. The most significant effects of biochar application, have been also observed in strongly acidic soils. In many arid and semi-arid regions of the world, including Iran, the soil organic matter content is low. The lack of organic resources and their instability in the soil are considered as some of the most important challenges in improving soil fertility and plant growth and yield. To improve soil fertility by using insufficient existing organic resources, stabilizing organic matter by converting it into the biochar can be a fundamental strategy. If this strategy is applied in our country with calcareous soils, it is necessary to study the effects of different biochars on calcareous soils from different aspects .In this regard, in the present study, the effect of three types of biochar in a calcareous soil has been investigated in comparison with their feedstock.
Materials and Methods: The effects of three types of biochar and their feedstock in a calcareous soil were investigated in a 6-months period of incubation. A completely randomized design in the form of split plot experiment, was carried out. The main plots were consisted of Control, Municipal Waste Compost (MWC) and its biochar (BMWC), Sewage Sludge (SS) and its biochar (BSS) and Cow Manure (CM) and its biochar (BCW). The sub plots consisted of five sampling times as 10, 30, 60, 120 and 180 days after the beginning of incubation. Application rate of each treatment per kilogram of soil was calculated based on having the same weight of organic carbon content. So that all treatments contained 2.2 grams of organic carbon. After mixing the treatment with soil and adjusting the humidity to the moisture content of the field capacity (FC), they were transferred to the cans (with 3 holes embedded on their doors) and kept at 25°C in the incubator. During the 6-month incubation period, soil moisture was set at FC levels at intervals of two to three days. Sub samples were taken at five times. After air drying the sub samples, the chemical parameters such as EC of 1:2.5 extract, pH of 1:2.5 suspension, available phosphorus (extracted with sodium bicarbonate 0.5N) and available potassium (extracted with ammonium acetate 1N) were measured. After data collection, statistical analysis was performed using SAS software.
Results and Discussion: The soil texture was sandy loam with 21% of clay, 7% of silt and 72% of sand. Soil CaCO3 content and soil organic carbon content was 16% and 0.23% respectively. Available forms of potassium and phosphorous in soil were 76 and 6.3 mg kg-1, respectively. According to the results, under the influence of each treatment, the variation of soil available P, showed a significant increasing trend with the time. Changes in available potassium and soil pH were not significant over the time. Variation of soil salinity with time although showed an increasing trend but was not significant. Comparison of the effects of treatments showed that both biochars and their feedstock could significantly increase the available phosphorus and potassium in soil. In this regard, the effect of biochars was more pronounced than their feedstock. Among the feedstock, ranking for enhancing effect on available P, was SS > CM > MWC and among the biochars, it was BCM > BSS > BMWC. Ranking for enhancing effect on available K, was CM > MWC > SS and BCM > BMWC > BSS among the feedstock and biochars respectively. The increase in available phosphorus and potassium due to the use of biochars were much higher than that of total phosphorus and total potassium added by biochars. The soil pH decreased as a result of the application of each treatment compared to control. In this regard, the significant difference between biochars and their feedstock were not seen. Probable presence of some amounts of pyrogenic carbon with biochars can be one of the reasons for soil pH reduction. Electrical conductivity of 1:2.5 extract of soil was increased by all treatments compared to the control. Except for BSS, two other biochars significantly increased soil salinity more than their feedstock. This increasing effect on soil salinity can be partially due to the existence of some amount of ash accompanied with biochars.
Conclusions: Application of biochars derived from cow manure, sewage sludge or municipal waste compost in this experimental conditions, led to a significant increase in the amount of available phosphorus and potassium in soil compared to control and their feedstock. Therefore, the use of these biochars can have a high potential for reducing the consumption of some chemical fertilizers. From this point of view, the order of the superiority of the coal was as follows: biochar of cow manure > biochar of municipal waste compost> biochar of sewage sludge. The conversion of any of these feedstock to biochar did not have an effect on their potential for soil pH changes. Except for biochar of sewage sludge, in two other biochar, the potential for increasing soil salinity was higher than the feedstock. Considering that the durability of biochar in soil is much higher than that of its feedstock, it is possible to use suitable biochars such as those examined in this study as a great potential for the sustainable improvement of soil fertility and for reducing the use of chemical fertilizers in our country's agriculture. This requires extensive field researches for other soil properties in different soil and water conditions, with different kinds of biochars and crops.
Ahmadreza Sheikhhosseini; H. Shariatmadari; M. Shirvani
Abstract
Introduction: Pollution of soil and water environment by release of heavy metals is of great concerns of the last decades. Sorption of heavy metals by low cost materials is considered as an inexpensive and efficient method used for removal of heavy metals from soil-water systems. The presence of different ...
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Introduction: Pollution of soil and water environment by release of heavy metals is of great concerns of the last decades. Sorption of heavy metals by low cost materials is considered as an inexpensive and efficient method used for removal of heavy metals from soil-water systems. The presence of different ligands with various complexing abilities can change the sorption properties of heavy metals and their fate in the environment as well. In order to assess the effect of citrate and arginine as natural organic ligands in soil environment, in a batch study we investigated the effects of these ligands on equilibrium sorption of nickel to sepiolite and calcite minerals and also kinetics of Ni sorption by these minerals.
Materials and Methods: Minerals used in this study included sepiolite from Yazd (Iran) and pure calcite (Analytical grade, Merck, Germany). Sepiolite was purified, saturated with Ca using 0.5 M CaCl2, powdered in a mortar and sieved by non-metal 230 mesh standard wire sieve. For equilibrium sorption study, in a 50-mL polyethylene centrifuge tube,0.3 g sample of each mineral was suspended in 30 mL of a 0.01 M CaCl2 solution containing 0, 5, 10, 20, 40, 60, 80 and 100 mg L-1 Ni (NiCl2) and containing zero (as control) or 0.1mmol L-1 citrate or arginine ligands. The applied concentrationsfor each ligand can naturally occur in soils. Preparedtubes were shaken (180±2 rpm, 25±1oC) for 24 h using an orbital shaker and centrifuged (4000×g for 10 min) and the supernatants were analyzed for Ni concentration using an atomic absorption spectrophotometer (AAnalyst 200 Perkin-Elmer) at a wavelength of 232 nm and a detection limit of 0.05 mg L-1. The quantity of Ni retained by each mineral at equilibrium was calculated using equation qe = (Ci - Ce)V/W where qe was the amount of nickel retained by mineral surface at equilibrium. Ci and Ce were the initial and the equilibrium concentrations (mg L-1) of Ni, respectively, V was the volume (L) of the solution, and W was the mass (g) of the sorbent. The Langmuir, Freundlich and linear isotherm models were fitted to sorption data using Graphpad prism 5.0. For kinetic study,30 mL of 0.01 M CaCl2 solution, with or without 0.1 mM citrate or arginine, containing Ni at a concentration corresponding to the maximum sorption capacity of each mineral (estimated from sorption isotherms) were transferred into 50-ml polyethylene centrifuge tubes containing 0.3 g of sepiolite or calcite. The suspensions were shaken (180±2 rpm, 25 °C) continuously and after 0.5, 1.5, 3, 6, 12, 18 and 24 hours, corresponding tubes were centrifuged (4000×g for 10 min) and supernatants were analyzed for Ni concentration by atomic absorption spectrophotometer. Using Graphpad prism 5.0, kinetic data were fitted to Pseudo-first order, pseudo-second order and power function kinetic models.
Results: With or without ligands, the Langmuir model was the best description of Ni sorption to sepiolite while the linear model was the best fit of calcite data showing the physical nature of Ni sorption by this mineral. Kinetics of Ni sorption to sepiolite and calcite were best described by power function model. In the presence of citrate, both capacity and rate of sorption of Ni to sepiolite decreased. There was no considerable change in sorption of Ni to calcite. In the presence of arginine, however, sorption capacity of minerals for Ni increased. Arginine enhanced the rate of Ni sorption on all three minerals. Citrate showed opposing effects on Ni sorption kinetics depending on the studied minerals. Totally, citrate and arginine had opposite effects on sorption of Ni to sepiolite and calcite.
Conclusion: Organic ligands can change sorption characteristics of the minerals. It seems that citrate decreases sorption of Ni to sepiolite but its effect on Ni sorption to calcite is negligible, while arginine increases Ni sorption to both minerals. Our results suggested that presence of citrate and arginine in soil influence Ni sorption by soil minerals. As in warmer seasons of year,microbial activities due to optimum temperature and moisture result in production of citrate and argininewhich facilitate and suppress uptake of Ni by plants respectively. Production of citrate in soil may increase risk of Ni contamination of underground and surface water sources while arginine can decrease soil solution Ni and in turn the risk of water contamination.
Y. Azimzadeh; H. Shariatmadari
Abstract
Phytoremediation is one of the lowest-cost methods for remediation of soils contaminated with heavy metals. This study was conducted to investigate the phytoremediation potential of corn and canola, grown under single and mixed culture systems. Thus, a pot experiment was carried out on a calcareous ...
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Phytoremediation is one of the lowest-cost methods for remediation of soils contaminated with heavy metals. This study was conducted to investigate the phytoremediation potential of corn and canola, grown under single and mixed culture systems. Thus, a pot experiment was carried out on a calcareous soil contaminated by Pb and Zn. Treatments included single culture of corn, single culture of canola and mixed culture of corn and canola. Results showed that bioavailability of metals, lead, zinc, nickel and copper increased with decreasing soil pH and increasing DOC as influenced by root activity. Root uptake of metals; lead, zinc, copper and nickel in mixed culture, was more than that of in canola and lower than that of in corn. Zinc and nickel uptake by shoots of canola and mixed culture, were more than corn. Also, the results concerning the uptake of metals in the total biomass (sum of roots and shoots) showed uptake of copper and nickel in corn was more than mixed culture and it was more than canola while, uptake of lead and zinc in corn and mixed culture was more than canola. Also, the total yield of corn and canola in mixed culture increased. Therefore, it seems use of mixed culture system may extract metals, zinc and nickel more than corn, and copper more than canola, in single culture systems.
M. Hamidpour; M. Kalbasi; M. Afyuni; H. Shariatmadari
Abstract
Abstract
Siderophores are of important factors influencing bioavailability and fate of heavy metals in the arid and semi-arid soils. They are low molecular weight organic ligands excreted by aerobic soil microorganisms and some plants roots to acquire Fe. Siderophores may also complex other metals such ...
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Abstract
Siderophores are of important factors influencing bioavailability and fate of heavy metals in the arid and semi-arid soils. They are low molecular weight organic ligands excreted by aerobic soil microorganisms and some plants roots to acquire Fe. Siderophores may also complex other metals such as Pb .The main objective of this study was to investigate the effects of DFOB-siderophore on sorption of Pb on montmorillonite. The sorption of Pb on montmorillonite was studied as a function of pH (sorption envelopes) and as a function of Pb concentration (sorption isotherms) in the presence of siderophore using a 24–h batch equilibration experiment. The results of sorption envelopes showed that the siderophore increased sorption of Pb onto montmorillonite in all solution pH, specially at pH ≥5. The results of equilibrium test (isotherms) revealed that removal of Pb from solution was not affected by siderophore at pH=4.5, while the siderophore strongly influenced the isotherm shape and increased Pb sorption onto montmorillonite at pH=6.5. The equilibrium data is best described by a Freundlich isotherm, in which the values obtained for the KF constant were 4.8 and 196.5 and for n constant were 0.8 and 2.1 in the absence and presence of the siderophore, respectively. These values are indication of high sorption affinity of Pb on montmorillonite in the presence of the siderophore.
Keywords: Lead, Siderophore, Sorption, Montmorillonite