Soil science
S. Nikkhosani Gol Tapah; S. Sadeghi; M. Nouraein; S. Zavareh
Abstract
IntroductionThe contamination of agricultural soils with heavy metals is considered as a fundamental problem of industrial and non-industrial societies all over the world, which is increasing significantly with technological advances and is considered a serious threat to the environment, soil and human ...
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IntroductionThe contamination of agricultural soils with heavy metals is considered as a fundamental problem of industrial and non-industrial societies all over the world, which is increasing significantly with technological advances and is considered a serious threat to the environment, soil and human health. One of these heavy metals is cadmium, which has entered the environmental cycle due to various industrial activities such as metal smelting, battery manufacturing, paints, and plastic production. One of the suitable methods for cleaning the soil contaminated with heavy metals is to stabilize the elements by adding a modifier to the soil, which leads to a decrease in their mobility and bioavailability during the processes of absorption, oxidation and reduction, complexation or deposition. The use of iron nanoparticles is a new generation of environmental cleaning technology that can be an economic solution to some problems caused by pollutants, unlike traditional methods. Considering the importance of soil as a plant food holder and its special role in the food chain and the harmful effects of pollutants such as heavy metals in the soil, this research seeks to explore the potential of magnetic iron nanoparticles in remediating cadmium-contaminated soil. The study aims to investigate the effectiveness of these nanoparticles in reducing cadmium levels and their impact on the distribution of cadmium in different soil components. Materials and MethodsThe experiments were carried out in the chemical and biological research laboratory of the Department of Soil Science and Engineering of Maragheh University. To conduct the experiment, a soil sample from Ajabshir city with a geographic location of 54 degrees 46 minutes 51.7 seconds east longitude and 37 degrees 24 minutes 34 seconds north latitude located in East Azarbaijan province with an altitude of 1451 meters above sea level, with this The target of extractable cadmium less than 1.16 mg/kg of dry and textured soil (loam) was selected. This experiment is factorial based on random design with two factors of heavy metal cadmium from cadmium sulfate source including cadmium concentrations at three levels of zero, 6 and 12 mg/kg of soil and the factor of magnetic iron nanoparticles at three levels of zero, 1 and 2% in The time was four weeks after the addition of cadmium treatments and it was implemented in three repetitions. After measuring some physical and chemical properties of soil, cadmium concentrations in different species and ionic fractions were measured according to the method provided by Tisser. Finally, the obtained data were analyzed using SPSS and MSTATC software and the means were compared with Duncan's multiple range test at the level of five and one percent probability and the results were interpreted. Discussion and ConclusionBy increasing the amount of cadmium treatment levels from 6 to 12 mg/kg, the amount of cadmium absorption in the exchange phase decreased. Therefore, the increase in the amount of cadmium levels in different levels of iron nanoparticles reduced the absorption of cadmium in the exchange phase, which in turn reduced the ability of the plant to absorb cadmium and removed cadmium from the plant. By increasing the amount of cadmium in the soil by 1%, nanoparticles increased the amount of cadmium extracted from the carbonate phase. Increasing the amount of cadmium added to the soil at different levels of nanoparticles, the amount of cadmium absorption extracted from the carbonate phase increased, and at the level of 12 mg cadmium/kg, the amount of cadmium extracted from the carbonate phase increased compared to the level of 6 mg cadmium/kg. In cadmium treatments at the level of 12 mg/kg, the amount of cadmium extracted from the phase of iron and manganese oxides were increased compared to cadmium at the level of 6 mg/kg, and in the same treatments at the level of 12 mg/kg, the amount of cadmium extracted was increased with the increase in the amount of nanoparticles. The results showed an increase in the phase of iron and manganese oxides, which may reduce the amount of cadmium available to the plant. In cadmium treatments at the level of 6 mg/kg at the level of 1% of nanoparticles, compared to the other two treatments, an increase in the amount of cadmium extracted from the oxide phase was observed. In the treatment of cadmium at the level of 12 mg/kg, the amount of cadmium extracted from the phase of organic matter increased compared to the treatment of cadmium at the level of 6 mg/kg. Indeed, the research findings reveal an interesting trend in the impact of increasing iron nanoparticles at both cadmium levels of 6 and 12 mg/kg. Specifically, the changes in the amount of cadmium extracted from the organic phase of the soil follow a consistent pattern. Initially, as the iron nanoparticles were introduced, the cadmium extraction from the organic materials decreased. However, at higher levels of nanoparticles, the cadmium extraction started to increase again.This trend suggests that the presence of a higher concentration of nanoparticles may play a role in stabilizing cadmium in the organic matter of the soil. As a result, it may reduce the accessibility of cadmium to plants. In the treatment of cadmium at the level of 12 mg/kg, the amount of cadmium extracted from the residual phase increased compared to cadmium at the level of 6 mg/kg. In the examination of cadmium extracted from the residual phase, it was found that, unlike other phases, the difference between treatments at zero cadmium level and other treatment levels of cadmium in the remaining phase was less compared to other phases, so that the amount of cadmium absorbed in the remaining phase 6 and 12 mg of cadmium per kilograms of soil have the lowest values among different absorption phases. Also, another noteworthy point about this examination was the trend of changes in extracted cadmium according to the levels of nanoparticles in all three levels of cadmium, so that with the increase of nanoparticles from zero to 1% in all levels of cadmium, there was a decreasing trend and with the increase of non-particles to two percent, an increasing trend was observed. ConclusionThe results showed that in general, with increasing the level of iron nanoparticles, treatment of 12 kg of cadmium, the amounts of residual cadmium, carbonate, organic and oxide phases increased. Increasing the level of cadmium in different levels of iron nanoparticles reduced the absorption of cadmium in the exchange phase, which reduces the ability of the plant to absorb cadmium and removes cadmium from the plant, so that in the treatment with cadmium at the level of 12 mg/kg, the amount of cadmium extracted from the exchange phase reduced. Also, in the cadmium treatment at the level of 6 mg/kg with increasing the amount of nanoparticles, the amount of cadmium extracted from the exchange phase first increased and then a slight decrease in the amount of absorbed cadmium was observed, while at the level of 12 mg of cadmium, the amount of cadmium increased, absorption reduced, and thus removing cadmium from the plant.
Soil science
H. Emami; M. Memarzadeh
Abstract
Introduction
Wind Erosion is the natural process of transportation and deposition of soil by wind. It is a common phenomenon occurred mostly in dry, sandy soils or anywhere the soil is loose, dry, and finely granulated. Heavy metals are found in the environment and soils may become contaminated by accumulation ...
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Introduction
Wind Erosion is the natural process of transportation and deposition of soil by wind. It is a common phenomenon occurred mostly in dry, sandy soils or anywhere the soil is loose, dry, and finely granulated. Heavy metals are found in the environment and soils may become contaminated by accumulation of heavy metals through emissions from the rapidly expanding industrial areas, mine tailings, disposal of high metal wastes, leaded gasoline and paints, land application of fertilizers, animal manures, sewage sludge, pesticides, wastewater irrigation, coal combustion residues, spillage of petrochemicals, and atmospheric deposition. Soils are the major sink for heavy metals released into the environment by the aforementioned anthropogenic activities and their total concentration in soils persists for a long time after their introduction. The heavy metal contamination of soil and its potential risks to humans and the ecosystem is a significant concern. Windy deposition, which is the process of heavy metals being transported by erosive winds and deposited onto soil, is one of the sources of heavy metal contamination. Due to the geographical situation and climatic conditions such as arid soil, erosive winds are blown in periods of year in Tabas. Since wind are erosion is severe in this area, huge amounts of wind deposition accompanied with erosive winds entered into this town. Heavy metals through the windy deposition are suspended, translated and finally deposited in residential regions, which can create some problems for human health. Therefore, the knowledge of wind erosion and the human risk of these deposits is essential. The aim of this research was to determine the rate of wind erosion and the concentration of some heavy metals in these deposits.
Materials and Methods
For this purpose, the rate of suspended load was measured monthly from February 2021 to January 2022. Based on previous information from the erosive winds and storms, suspended depositions were gathered in some directions (north, northwest, northeast, west and southwest) of the Tabas entrance. In addition, the suspended load in the city center of Tabas was also measured. The cumulative load of suspended depositions was measured monthly and the concentration of some heavy metals such as manganese (Mn), iron (Fe), cupper (Cu), and zinc (Zn) were measured in these suspended particles. Soil digestion was made by Aqua regia (nitric acid and chloridric acid; ratio of 3:1), and after then atomic absorption was used to measure the total concentration of above heavy metals.
Results and Discussion
The results indicate that Tabas experiences significant wind deposition of suspended loads, with the highest rates entering from the northeast direction and the lowest rates from the southwest direction. This pattern aligns with the wind rose of Tabas, which illustrates the prevailing wind directions in the region. Additionally, substantial suspended loads are observed in the northwest and north directions. The variations in suspended load discharge reveal that the maximum discharge occurs in the city center of Tabas during the months of June and July 2021. This corresponds to the arid climate conditions of these months, where plant growth is limited, soil cohesion is low, and loose soil particles on the surface are susceptible to wind forces. As a result, these loose particles are easily detached by the wind, contributing to the high levels of suspended load. Regarding the spatial variation of heavy metals in suspended particles, the cumulative concentrations of Mn, Fe, Cu, and Zn are found to be higher in the west, northwest, north, and west directions, respectively. This suggests that these heavy metals are transported and deposited in specific areas within Tabas due to the prevailing wind patterns. In terms of temporal variation, the highest concentrations of Mn and Fe in suspended particles are observed in April 2021, predominantly in the northeast and west directions, respectively. On the other hand, the highest concentrations of Cu and Zn are found in May 2021, with the southwest and northeast directions being the primary deposition areas for each metal, respectively. These findings highlight the spatial and temporal dynamics of suspended load and heavy metal deposition in Tabas, emphasizing the influence of wind patterns and climatic conditions on these processes. Understanding these variations is crucial for assessing the potential risks associated with heavy metal contamination and implementing appropriate mitigation measures in the region.
Conclusion
The results of this research showed that most contents of the suspended load are entered from the northeast direction into Tabas. In addition, the spatial variation of heavy metals indicated that the concentrations of studied heavy metals (Mn, Fe, Cu, and Zn) in suspended particles, especially in the western, northwestern, and northern in spring, are very high and they can cause carcinogenic effects on human life. Therefore, the management practices should be mostly made in these directions to control or reduce soil erosion and reduce its damage effects.
Soil science
Reyhaneh Kashtabeh; M. Akbari; Ava Heidari; Aliasghar Najafpour
Abstract
IntroductionOne of the most fundamental global environmental challenges in the past two decades has been the issue of soil pollution and degradation. Soil, as an important environmental element, has played a significant role in food production, human health, and living organisms, but various factors, ...
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IntroductionOne of the most fundamental global environmental challenges in the past two decades has been the issue of soil pollution and degradation. Soil, as an important environmental element, has played a significant role in food production, human health, and living organisms, but various factors, by both human and naturally have destroyed it. The exploitation of natural resources with activities such as mining and quarrying, as an anthropogenic action (caused by human activities), is one of the most important factors of human intervention in nature and also one of the environmental hazards of soil degradation, which has caused the spread of desertification. Sangan iron mines in Khaf city are the largest mines in the northeast of Iran. According to the geomorphological disturbances caused by the activity of Khaf iron ore mines and the geological composition of the region, there is a potential for causing pollution and destroying the soil around the mine. This research was conducted with the aim of evaluating the impact of mining activity on concentration of some heavy metals such as lead, iron, nickel, copper, and arsenic in the soil around the iron ore mine in Sangan area of Khaf city in Khorasan Razavi province. Realizing the polluted hotspots due to the concentration of heavy metals, as one of the important signs of soil pollution and the spread of desertification, is one of the goals of this research, and the results can be effective in making appropriate management decisions to prevent soil pollution and further destruction.Materials and MethodsIn order to conduct this research, 60 soil samples were systematically taken from a depth of 0-20 cm from two areas adjacent to the mine and control. The concentration of aqua regia extracted heavy metals was measured using an inductively coupled plasma-optical emission spectroscopy (ICP-OES). In the first stage, the results were descriptive, and in the second part, after performing tests related to the normality of the data, they were inferential using the parametric independent t-test and Pearson's correlation coefficient in the statistical environment of the SPSS software. In order to quantify the level of soil contamination with heavy metals, geochemical indices including contamination factor, pollution load index, and enrichment factor were used. The pollution load zoning map of the area adjacent to the mine as well as the average enrichment map of lead and arsenic elements were prepared using the inverse distance weighting interpolation method in the ArcGIS environment.Results and DiscussionThe results of this research showed that the average concentrations of arsenic, copper, nickel, lead, and iron elements in the area near the mine were 12.71, 25.54, 34.59, 48.64, and 38860 mg/kg and in the control area were 8.57, 15.97, 32.13, 16.96, 29110 mg/kg, respectively. The comparison of the coefficient of variation (dispersion criterion) of heavy metals showed that the highest coefficient of variation among the metals is related to the lead with a value of 42.8%, as well as the coefficient of variation for other metals in the area adjacent to the mine also has a relatively high dispersion compared to the control area. In addition, it was found in all elements except for nickel (p<0.05), which indicates a significant difference in the average concentrations between the control area and the area adjacent to the mine. The correlation between lead element and nickel, copper and arsenic variables was inverse and there was a positive and very strong correlation between iron and copper and nickel with values of 0.8 and 0.76 respectively and nickel and copper with values of 0.82. The pollution coefficient of the lead elements in the area adjacent to the mine showed moderate to significant pollution levels, which is more polluted than other elements. The pollution load in the area near the mine showed that the value of this index was greater than one in the samples closer to the mining areas, which indicates the high contamination of the surface soil with these elements. Lead and arsenic elements in the area adjacent to the mine showed moderate to relatively intense enrichment. From the examination of all the pollution indicators used in this research, as well as the positive and very strong correlation between copper and nickel, the presence of these two elements in the soil of the study area showed no pollution. The comparison of the results obtained from the analysis of soil samples in the two areas of the control and adjacent to the mine showed an increase in the concentration of heavy metals (iron, lead, and arsenic, copper) in the area adjacent to the mining.ConclusionThe results obtained from the analysis of soil samples and pollution indicators in the two control areas adjacent to the Sangan iron ore mine in Khaf city showed that the presence of iron ore industrial and mining sites in the study area and the spread of its wastes and tailings by seasonal and local winds, as well as the activities of humanity and the spread of these pollutants to other areas, can be one of the main reasons for the increase in the concentration of metal pollutants in the soils of this region.
Soil science
B. Rezaei; A. Amirinejad; M. Ghobadi
Abstract
IntroductionIndustrial development has resulted in higher soils pollution with heavy metals. Plants which are subjected to heavy metals may severely lose their yield capabilities. Applying improving compounds in the soil is a new method to reduce effects of heavy metals on plants growth. Biochar as a ...
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IntroductionIndustrial development has resulted in higher soils pollution with heavy metals. Plants which are subjected to heavy metals may severely lose their yield capabilities. Applying improving compounds in the soil is a new method to reduce effects of heavy metals on plants growth. Biochar as a carbon rich source and salicylic acid as an important plant hormone, are two main compounds to alleviate heavy metals stresses in plants. These are the cost-effective and environmentally friendly substances for increasing the resistance of plants. Lead (Pb), as a common and extremely poisonous element in polluted soils, can be accumulated due to its non-biodegradability nature. When Pb content in plants reaches a toxic level, it can inhibit plant growth by reducing enzyme activities and photosynthesis and changing mineral nutrients balance. However, with regard to the program of expanding the area under cultivation of medicinal plants, including thyme, there is a possibility of contamination of soils in the vicinity of industrial centers and roads with lead. Therefore, the present study was conducted to evaluate the effects of salicylic acid as a plant growth stimulant and biochar made of rapeseed wastes, as a stable organic compound, on alleviation of Pb-induced stress in thyme (Thymus vulgaris L.). Materials and MethodsIn order to investigate the effects of salicylic acid (SA) and biochar (BC) on reducing Pb stress in thyme (Thymus vulgaris L.), a factorial experiment was conducted based on a completely randomized design with three replications in the greenhouse of Razi University. The factors included Pb at three levels (0, 150, and 300 mg/kg as Pb(NO3)2), SA at three levels (0, 150, and 300 μM) and BC at three levels (0, 1 and 3% by weight). To apply the Pb treatments, the soil samples of each pot (8 kg) were sprayed with Pb(NO3)2 solutions, 4 weeks before planting, according to the contamination levels. Then, BC treatments were performed by mixing it with the soil samples. In each pot, four thyme seedlings were planted. At four-leaf stage, SA solutions were sprayed three times on foliage of the thyme plants , until the beginning of flowering. After harvesting, some characteristics of aerial and root parts of thyme, including soluble sugars and proline contents, plant height, dry weights of shoots and roots, root volume and root length were determined. All plant parameters were then averaged for each pot. Also, Pb concentrations in extracts obtained from digestion of leaf tissues, were measured by Varian AA220 atomic absorption spectrophotometer. The analysis of variance (ANOVA) and comparison of means (Duncan's multiple range test) were performed using SPSS-16 software.Results and DiscussionThe results revealed that Pb stress reduced all plant characteristics, such as plant height, root volume and root length, as well as, dry weights of shoots and roots, and elevated leaf Pb concentration, proline content and soluble sugars in thyme. However, BC application resulted in improvements in growth parameters. The positive effect of BC was further enhanced when SA was sprayed onto the foliage of the thyme plants. The interaction effects of SA, BC and Pb treatments on the growth parameters of thyme, i.e, shoot dry weight, root volume, Pb concentration, soluble sugars and proline contents were significant (P < 0.01). In other words, SA and BC treatments moderated the negative effects of Pb on the growth traits. The highest Pb concentration (4.83 mg) and proline content (37.8 μmol/g) were obtained in 300 μg/kg of Pb, and SA and BC controls. Also, the highest concentration of soluble sugars (0.46 mg/kg) was found at 300 mg/kg of Pb, 300 μM SA and BC control.ConclusionOur results indicated the positive effects of SA and BC treatments on the growth parameters, such as; shoot and root dry weights in thyme plants, especially under Pb stress. In other words, Pb stress, while reducing all growth characteristics, increased proline content and soluble sugars in thyme. In general, it seems that under Pb stress, treatment of thyme with SA (as a plant growth regulator) and BC (as an organic matter with high viability in the soil) is a simple and appropriate method in order to increase the plant's resistance and reduce the effects of Pb toxicity on the overall growth of thyme.
Sh. Hassani; Mohammad Babaakbari; M.R. Neyestani; M.A. Delavar
Abstract
Introduction:High concentrations of As in contaminated soils represent a potential risk for groundwater sources and threat the food chain. It has been found that the iron-containing compounds used in remediation of As contaminated soils have distinct effects on the solubility of As and can be used as ...
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Introduction:High concentrations of As in contaminated soils represent a potential risk for groundwater sources and threat the food chain. It has been found that the iron-containing compounds used in remediation of As contaminated soils have distinct effects on the solubility of As and can be used as adsorbents for As removal from aqueous and soil solutions. The objectives of this study were to determine As stabilization in soil, with iron-containing compounds and also to compare the fixation of magnetite nanoparticles, ferrous sulfate, ferrosilicon, magnesium ferrosilicon and iron oxide in fixation of arsenic in contaminated soils. Materials and Methods: A factorial experiment was conducted using a completely randomized design with three replications. The experimental factors were the amendment types and levels. The modifiers used were magnetite nanoparticles, ferrous sulfate, ferrosilicon, magnesium ferrosilicon, Sfordi, and Golgohar iron soil containing 0, 0.1, 0.2 and 0.3% iron. The soil was artificially contaminated with As (20 mg/kg) using Na2HAsO4.7H2O salt and incubated for 1 month. At the end of incubation time, the modifiers were added to the As contaminated soils and after 3 months, the available fractions of arsenic, iron, zinc and copper were extracted using 0.1 M HCl and measured with ICP. Results: The results showed that the type and the amount of the modifiers had a significant effect on the available fraction of arsenic and iron in soil (extractable fraction with 0.1 M hydrochloric acid). The available fraction was reduced due to the addition of all modifiers: Magnetite nanoparticles > iron sulfate > magnesium ferrosilicon > ferrosilicon > Esfordi iron soil and Golgohar iron soil, respectively. The highest decrease in the concentration of available arsenic occurred in the soils treated with 0.3% of modifier. Application of 0.3% levels of magnetite nanoparticles, iron sulfate, ferrosilicon, ferrosilicon magnesium, Golgohar iron soil and Esfordi iron soil stabilized 91, 63, 57, 32 and 48% of arsenic extractable with 0.1 M HCl, respectively. Application of 0.3% of magnetite nanoparticles reduced available arsenic more than other adsorbents. Among the studied modifiers, magnetite nanoparticles showed more efficiency in chemical stabilization of arsenic in soil. The application of magnetite nanoparticles increased the Fe available fraction in soil. Golgohar iron soil, ferrosilicon, Esfordi iron soil, magnesium ferrosilicon, ferrous sulfate and Magnetite nanoparticles, increased the iron extractable with 0.1 M HCl of the soil, respectively. The highest Fe concentrations were observed in 0.3% of Gol Gohar soil, ferrosilicon, Esfordi soil and ferrosilicon. Increasing the modifiers decreased soil copper extractable with 0.1 M hydrochloric acid concentration and increased soil zinc extractable with 0.1 M hydrochloric acid concentration, which was not statistically significant. Conclusion: Application of magnetite nanoparticles reduced arsenic concentration more than other adsorbents and showed more efficiency in chemical stabilization of soil arsenic. Other modifiers have also been able to stabilize the arsenic in the soil, suggesting the possibility of using iron-containing modifiers in arsenic-contaminated soils. The use of modifiers increased the iron concentration in the soil. Due to their reasonable price and availability, iron sulfate and magnesium ferrosilicon are recommended for soil arsenic stabilization. At 0.3% soil level, Gol Gohar and Esfordi iron soil were able to reduce 32% and 48% the arsenic concentration, respectively and are recommended for arsenic stabilization in contaminated soil. Golgohar, ferrosilicon, Esfordi and magnesium iron soils caused the highest increase in soil iron concentration. Due to the concentration of other soil elements and the price of modifiers, the level of 0.2% of iron sulfate, Gol Gohar and Esfordi iron soil, ferrosilicon and magnesium ferrosilicon is recommended for stabilization of arsenic in contaminated soil.
S. Salavati-Nik; S. Saadat; M. Alameh
Abstract
Introduction: Sheshtamad area is located in the western part of Khorasan Razavi province and includes Sheshtamad city and its surrounding villages. A variety of sedimentary and igneous rock units, mainly belonging to the Cretaceous or younger age, are found in the area. A series of orogenic movements, ...
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Introduction: Sheshtamad area is located in the western part of Khorasan Razavi province and includes Sheshtamad city and its surrounding villages. A variety of sedimentary and igneous rock units, mainly belonging to the Cretaceous or younger age, are found in the area. A series of orogenic movements, lithofacies changes and magmatic activities led to the distribution of heavy elements that can cause environmental problems in the area. This study aimed to assess the heavy metal contamination of the soil in the extent of the study area. It has been attempted to investigate the origin of pollution and its impact on the environment using geochemical data.
Materials and Methods: In this study distribution and possibility of contamination from arsenic (As), lead (Pb), zinc (Zn), copper (Cu), chromium (Cr), nickel (Ni), cobalt (Co), antimony (Sb), strontium (Sr) and vanadium (V) were investigated. These variables were determined using chemical analysis of the sediments. For this purpose, network sampling was carried out at 1.5×1.5 km and 3 to 4 samples were taken from each cell. Throughout the study area (geological sheet of 1:100,000 Sheshtamad), 1248 samples of sediments were collected by Jiangxi Company and analyzed by ICP-MS method. The analysis results were summarized in ArcGIS software and elemental concentration zoning was performed by Kriging and Inverse Distance Weighting methods. Some indices have been proposed to evaluate heavy metal contamination in sediments and soils. In order to determine soil contamination with heavy metals, some parameters such as Contamination Factor and Pollution Index were calculated. Multivariate statistical analyses such as correlation analysis have been applied to identify the geochemical behaviors of different geochemical groups.
Results and Discussion: Surface distribution of As with values above 270 mg kg-1 was observed in the drainages of the southern part of the study area. Sr and Sb were measured with values above 2900 mg kg-1 in the drainages from south to eastern part, and above 4 mg kg-1 in south and central drainages, respectively. Surface dispersion of Zn above 210 mg kg-1 was present in the drainages from central, south, southwest and northwestern parts of the region. Cu and Pb were measured with values greater than 240 mg kg-1 in North and Northwestern parts, and greater than 110 mg kg-1 in East, Central and southwest, respectively. Surface distribution of Co element with values above 58 mg kg-1 from drainages in central, north and southwest and V with values higher than 85 mg kg-1 in central and southwest part were also observed. Finally, distribution of Cr element with values above 7400 mg kg-1 in east central and southwestern part and Ni with values higher than 890 mg kg-1 in center and north section were found.
Pb had significant contamination only in a small area of the central part. Cu also showed little pollution only in a small area of the center of the region on the fringes of mining activities. According to the Pollution Index, As had a high pollution in the south and west parts. The central and southwestern parts of the study area show moderate Cr pollution, based on the Contamination Factor. Based on the correlation matrix used to determine the relationship of heavy elements with each other, some elements have a positive correlation with each other, which may indicate their common origin. For example, Co had a positive correlation with Ni and Cr indicating a common origin associated with the distribution of mafic rock units in the region. Pb and Zn have a positive correlation with each other as well as with Co and V, whereas the absence or negative correlation of As with these elements indicates a separate source for this element compared to Pb, Zn, V and Co. The presence of Cu element, despite its limited correlation with zinc, appears to be independent and likely to be more closely related to mineralization processes and mining activities in the region. Sr was negatively or very weakly correlated with most elements. It is chemically similar to calcium and can be present in carbonate sediments with gypsum in addition to substituting for plagioclases. The results of correlation coefficients with elemental zoning maps, geological maps and results of pollution coefficients showed very good agreement. The results of this study indicated that heavy metal contamination in the region was mainly due to the geological characteristics of this area. In other words, that was mainly “lithogenic”.
Conclusion: The results showed that Cr in the central and southwestern parts of the region had moderate contamination and it should be considered by experts and residents of the area to prevent Cr entering the biological cycle of the region in the future. It is one of the most toxic heavy metals and contaminated areas should receive proper attention. Studies were also indicated the presence of As in the stream sediments, especially in the southern parts of the region, and it is necessary to measure the permeability of this element into groundwater and surface waters in addition to the soil. V, Sb, Zn and Co had no significant contamination and specific environmental problems at current concentrations, is unlikely. Anthropogenic contamination, except from limited mining activities, did not play a significant role in the contamination of this region.
M. piri; E. Sepehr; A. samadi; KH. Farhadi; M. Alizadeh khaled abad
Abstract
Introduction: 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 ...
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Introduction: 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).
Materials and Methods: 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, R2 and the model equation was used to predict the optimum value and subsequently to elucidate the interaction between the factors within the specified range.
Results: 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.
Conclusion: 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.
Parvin Kabiri; hamid reza motaghian; Alireza Hosseinpur
Abstract
Introduction: Anthropogenic activities have transformed the global geochemical cycling of heavy metals. Mine tailings are of great concern due to the detrimental effects of toxic inorganic elements causing environmental risks. Zinc (Zn) as an essential element is required in small amounts for various ...
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Introduction: Anthropogenic activities have transformed the global geochemical cycling of heavy metals. Mine tailings are of great concern due to the detrimental effects of toxic inorganic elements causing environmental risks. Zinc (Zn) as an essential element is required in small amounts for various biochemical reactions and physiological functions. However, high concentrations of Zn can induce oxidative stress. Applying an organic amendment is a promising, in situ phytostabilization approach to alleviate the phytotoxic effects of heavy metal in contaminated soils. The application of biochar as an amendment may be a solution to reduce the risk of pollutant diffusion. Biochars is a fine-grained biological residue combusted under low oxygen conditions, resulting in a porous, stable carbon-based material. The potential biochar applications include carbon sequestration, soil fertility improvement, and pollution remediation; therefore, it can reduce pollutants mobility and bioavailability.
Materials and Methods: Results of this research indicated that biochars decreased Zn concentration in maize shoots and roots. They reduced Zn concentration in the shoot/root of maize. Zinc concentration in shoots and roots of maize (Zea mays L.) harvested at 60 days after sowing, decreased with increasing thermochemical temperature and application rate of biochar. In treated soil with 2% (w/w) biochar prepared at 600 °C, Zn concentration in shoots and roots decreased by 21.6 and 33.0 % respectively (p
shahab ahmadi doabi; Majid Afyuni; Mahin Karami
Abstract
Introduction: Atmospheric dust is an important source of heavy metals, particularly in urban environments. Heavy metals can easily attach to dust particles and be distributed in large areas. Therefore, assessing the extent of heavy metals pollution present in nuisance dust is important for establishing ...
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Introduction: Atmospheric dust is an important source of heavy metals, particularly in urban environments. Heavy metals can easily attach to dust particles and be distributed in large areas. Therefore, assessing the extent of heavy metals pollution present in nuisance dust is important for establishing pollution control strategies and evaluating the results of previous measurements. Heavy metals contamination in atmospheric dust of Kermanshah provine has not been previously investigated. The main objective of this initial study was to determine the concentrations of heavy metals in atmospheric dust samples that were collected from Kermanshah province and to assess their contamination level. The results can provide a baseline for use in future environmental impact assessments and to guide pollution mitigation targets.
Materials and Methods: Dust samples were collected from 49 sites across the province, during the summer 2013. Dust sampling sites were selected in different urban (35 site) and suburban (14 site) locations in Kermanshah, Songhor, Gilangharb, Ghasre-Shirin, Sahneh, Sarpolzahab, Kangavar, Paveh and Javanrood cities. Dust collectors were installed on the roof of buildings about 3–4 m above the ground level. Each collection tray consisted of a circular plastic surface (320 mm in diameter, 120 mm depth) that was fixed on holders with 33 cm height and covered with a 2 mm PVC mesh on top to form a rough area for trapping saltant particles. The dust samples were analyzed for their Zn, Cu, Ni, Cr, Mn and Fe concentrations using an Atomic Absorption Spectrophotometer. In the present study, geo-accumulation index (Igeo), enrichment factor (EF), pollution index (PI) and integrated pollution index (IPI) were calculated to assess the heavy metal contamination level in the atmospheric dust.
Results and Discussion: The results showed that except for Fe and Mn, all heavy metal concentrations of atmospheric dust in Kermanshah provine were higher than in the background soils of world, showing that these heavy metals are likely from anthropogenic sources. The order of mean Igeo values was Ni> Zn> Cu> Cr> Mn> Fe, similar to the order of their EFs and PIs, which can also be seen as the decreasing order of their overall contamination degrees in atmospheric dust of Kermanshah province. The mean Igeo for Ni points to moderately to strongly pollution. 59% of calculated Igeo for Ni falls into class 2 (moderately polluted) and 37% into class 3 (moderately to strongly polluted), while according to the Igeo values for Mn (98%) and Fe (100%), they were practically unpolluted (class 0). The maximum EFs of Zn, Cu and Ni were higher than 10, which show that Zn, Cu and Ni in atmospheric dusts mainly originate from anthropogenic sources. It seems that EFs can also be an effective tool to differentiate the natural origins from anthropogenic sources. The mean EF (11.2) and 94% of Ni EFs were in the range of 5–20 indicating that Ni was a main contaminant in studied samples. Mn had 41% EFs less than 2 and 59% EFs in the range of 2–5, with mean EF less than 2, indicating minimal enrichment. The analytical results of heavy metals Igeo are same as the analytical results of EFs. The PIs of Zn, Cu and Ni were in the ranges of 2.1 to 11.3, 1.7 to 18.3 and 3.3 to 13.6, with an average of 3.8, 3.3 and 6.9, respectively. These data indicate that Zn, Cu and Ni may cause serious pollution in atmospheric dust of Kermanshah. The IPIs of atmospheric dust samples vary from 1.9 to 6.2 with mean value of 2.9, indicating that all studied samples were polluted by heavy metals.
Conclusion: The concentrations of heavy metals that were investigated in this study were compared with the reported data of other cities and with the background values of elements in the world soils. The concentrations of Zn, Cu, Ni and Cr in urban dust samples, and Fe and Mn in suburban dust samples were higher than their respective values in the world soils. The results indicate that atmospheric dusts in Kermanshah provin have elevated metal concentrations in general. The calculated values of Igeo and EF of heavy metals revealed the order of Igeo and EF as Ni> Zn> Cu> Cr> Mn> Fe. The high Igeo and EF for Ni, Zn and Cu in atmospheric dusts indicated that there was a considerable Ni, Zn and Cu pollution (Especially nickel), which possibly originate from traffic and industrial activities. The Igeo and EF of Mn and Fe were low. The results of PI also supported Zn, Cu and Ni serious pollution in atmospheric dust. Similarly, IPI results confirmed atmospheric dust samples pollution by heavy metals. These findings indicated that more attention should be paid to heavy metal contamination of atmospheric dusts in Kermanshah, especially in case of Ni.
Anahid Salmanpour; Mohammad hasan Salehi; jahangard mohammadi
Abstract
Introduction: The heavy metal concentration in agricultural lands, due to the toxicity, persistence and their accumulation in the environment has become a major concern. Ophiolitic formations extend in southern part of central Iran and parallel to folds of the Zagros Mountains, is located in the north ...
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Introduction: The heavy metal concentration in agricultural lands, due to the toxicity, persistence and their accumulation in the environment has become a major concern. Ophiolitic formations extend in southern part of central Iran and parallel to folds of the Zagros Mountains, is located in the north of Neyriz town and in the west of Bakhtegan Lake. Rock weathering of these complexes forms sediments and soils with a large amount of Mn, Ni, Cr, Co, Mg and Fe. Laboratory analysis of Neyriz ophiolitic rocks indicates that they are a source of heavy metals as well, and may cause problems for the environment. However, there is no investigation in Neyriz area regarding contamination of the soils. The present study was conducted to assess soils pollution in Ghal-e Bahman area, 20 km from Neyriz which derived from ophiolitic formations of this area.
Materials and Methods: The study area located in the Ghal-e Bahman region, eastern part of Bakhtegan Lake. The soils of this region are affected from Neyriz ophiolite. In this region, three physiographic units including a hill, an alluvial fan and a lowland (playa) were separated. In each unit, some pedons were dug and classified according to American Soil Taxonomy. Soil samples were obtained from each genetic horizon and rock samples were also taken from ophiolitic formation. Then, chemical and physical properties were determined. Heavy metals were also extracted by nitric acid and amount of Cr, Ni, Co and Fe were calculated. Enrichment Factor (EF) and Geo-accumulation indices (Igeo) were also calculated and soils were classified according to their pollution level.
Results and Discussion: In general, soils on different landforms had different horizon properties and different classification. They are varied from a shallow, thin layer on hills to relative deep layer on lowland. These soils were classified in three different subgroups according to American Soil Taxonomy. Soils on ophiolitic hills classified as Lithic Torriothents because of a thin surface layer on a weathered bedrock. Soils developed on alluvial fan landform, with several alluvial subsurface horizons with different rock fragments percentage and size, was classified as Typic Torrifluvents; and the soils on lowland (Bakhtegan playa (was Gypsic Aquisalids because of salt and gypsum concentration in all layers and had redox color (chroma of less than 2) affected by high level of groundwater in the soil surface and subsurface layers.
The results showed that the amount of chromium with the average of 2200 mgkg-1, was 10 to 40 times higher than the Iran and Europe threshold levels (100 and 150 mgkg-1, respectively). The amount of nickel, with the average of 300 mgkg-1,were 10 fold higher than the threshold level and cobalt (19 mgkg-1) was lower than criteria defined by soils standards of Iran and Europe (40 mgkg-1).The amount of studied metals were the highest in ophiolitic hills, and playa soils were in second place in this respect. The amount of metals had a significant decrease in alluvial fan but didn’t drop under threshold level. The lowest amount of heavy metals in alluvial fan was probably because of the high percentage of sand, higher permeability and low soil water retention in all horizons. The negative significant correlation between the elements and sand also confirms this hypothesis. In addition, increasing elements at the depth of 70 cm of the soil in alluvial fan showed that land type (orchards) and long period of irrigation may cause leaching heavy metals from topsoil to the soil depth. However, no significance correlation was observed between the elements and soil organic carbon. The correlation coefficients between three elements revealed that all of them had the similar geologic origin and thus their spatial occurrence in soils can be attributed to the weathering of similar parent material.
Igeo showed an almost constant trend from ophiolitic hill (7.7-7.8) to alluvial fan (7.2-7.7) and a significant decrease in playa (3.9-6.2) for all metals. The variation of EF for nickel had an almost constant trend from ophiolitic hill (with the average of 0.6) to alluvial fan (with the average of 0.7) and a significant decrease in playa (with the average of 0.1). Also, a decreasing trend was observed from ophiolite hill (0.9 and 0.6 for chromium and cobalt, respectively) to alluvial fan (0.5 for both) and playa (0.3 and 0.1 for chromium and cobalt, respectively). A decreasing trend observed for indices can be due to the reduction of sediment transport processes and dilution effect of elements from hill to playa during the deposition and their formation .It seems that the EF index and the Igeo provide more useful information about hydrologic processes during formation of landform and development of soils than absolute values of heavy metals.
Conclusions: The present study showed that the amounts of chromium and nickel were higher than the threshold in studied soil. The soils derived from ophiolitic formation showed the highest values and the soils over alluvial fans had the lowest levels of heavy metals. Useful information was obtained from EF index and Igeo about the prominent geomorphic processes during landforms formation
Future studies should be focused on possible transfer of these elements into the groundwater and also trees of the orchards in Ghal-e Bahman region.
zeinab bigdeli; ahmad golchin; saeid shafiei
Abstract
Introduction: Dynamics of organic carbon and nitrogen are controlled by several factors, including physical, chemical and biological properties of soil. Heavy metals contaminate soils and change soil properties and affect organic carbon and nitrogen dynamics. Since toxicities of heavy metals are different ...
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Introduction: Dynamics of organic carbon and nitrogen are controlled by several factors, including physical, chemical and biological properties of soil. Heavy metals contaminate soils and change soil properties and affect organic carbon and nitrogen dynamics. Since toxicities of heavy metals are different and organic carbon and nitrogen dynamics are affected by available concentrations of these metals, the aims of this experiment were to assess the effects of different levels of soil cadmium on mineralization of organic carbon and nitrogen.
Materials and Methods: To assess the effects of different levels of soil cadmium on mineralization of organic carbon and nitrogen, a factorial pot experiment was conducted using litter bag method. The factors examined were different levels of soil cadmium (0, 10, 20, 40, and 80 mg kg -1soil) and incubation periods (1, 2, 3 and 4 months) that were applied in three replications. Soil samples were artificially contaminated with cadmium to desirable levels using cadmium sulfate and the samples were placed in plastic pots and the pots incubated at constant moisture and temperature for one month. Then litter bags containing 15 g wheat residues were buried in pots and incubated for different periods of time. At the end of incubation periods, the remaining amounts of plant residues were measured and analyzed for organic carbon and nitrogen concentrations using Walkley and Black and Kjeldahl methods respectively. The decomposition rate constants of organic carbon and nitrogen were calculated using Mt = M0 e –kt equation. Organic carbon and nitrogen losses were calculated by subtracting the remaining amounts of organic carbon and nitrogen in one incubation time interval from those of former one.
Results and Discussion: The results showed that the effects of soil cadmium levels and incubation periods were significant on organic carbon and nitrogen mineralization. The losses of organic carbon and nitrogen from wheat residues decreased as the levels of soil cadmium increased. The highest and the lowest organic carbon and nitrogen losses were measured in control and treatments with 80 mg Cd kg -1 soil respectively. Increase in soil cadmium levels decreased the losses of organic carbon and nitrogen from wheat residue. The losses of organic carbon for a period of four months were 37.54, 37.21, 36.11, 35.12 and 33.69 (%) in treatments with soil cadmium levels of 0, 10, 20, 40 and 80 mg kg -1 respectively. The loss of organic carbon in the first month of incubation was (30.78%) and in the other three months of incubation was (9.74%) with a sum of (40.52%) for a period of 4 months. Similarly, the loss of organic nitrogen in the first month of incubation was 23.69% and in the other three months of incubation was 8.56% with a sum of 32.25 (%) for a period of 4 months. The highest losses of organic nitrogen from wheat straw residue were measured in treatment of control cadmium (31.64 percent) and lowest losses of organic nitrogen (23.86percent) related to treatment with 80 mg of cadmium / kg of soil. The losses of organic nitrogen, after 4 months were 31.64, 30.69, 28.68, 26.25, and 23.86 (%) when treatment of cadmium contamination of soil was 0, 10, 20, 40 and 80, respectively. The decomposition rate constants for organic carbon were 0.0076, 0.0075, 0.0073, 0.0070 and 0.0066 day -1 when soil cadmium levels were 0, 10, 20, 40, and 80 mg kg -1 respectively. The rate constants for organic nitrogen at the mentioned soil cadmium levels were also 0.0061, 0.0059, 0.0054, 0.0048 and 0.0044 day -1 respectively.
Conclusions: The results of this research indicate that contamination of soils by heavy metals increases the residence time of organic carbon and nitrogen in soils and slows down the cycling of these elements. The mineralization rate of organic nitrogen was affected by soil cadmium levels more than that of organic carbon. The amounts of organic carbon and nitrogen losses are higher in the first month of incubation than those of other months and decomposition of wheat residue had a fast and a slow stage. The results of this study indicate that due to the adverse effects of heavy metals on soil organisms, mineralization rate of plant residue carbon is slower in polluted soils compared with non polluted soils.
shahrzad karami; mehdi zarei; jafar yasrebi; najafali karimian; s.Ali Akbar Moosavi
Abstract
Introduction: Heavy metals such as cadmium (Cd) are found naturally in soils, but their amount can be changed by human activities. The study of the uptake and accumulation of heavy metals by plants is done in order to prevent their threats on human and animal’s health.Cadmium is a toxic element for ...
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Introduction: Heavy metals such as cadmium (Cd) are found naturally in soils, but their amount can be changed by human activities. The study of the uptake and accumulation of heavy metals by plants is done in order to prevent their threats on human and animal’s health.Cadmium is a toxic element for living organisms. Cadmium competes with many of nutrients to be absorbed by the plant and interferes with their biological roles. Water stress affects the cell structure and the food is diverted from its normal metabolic pathway. It also reduces the availability and uptake of nutrients by the plant. One reason for the reduction of plant growth under drought stress is the accumulation of ethylene in plants. There are ways to mitigate the negative effects of drought stress that one of which is the use of Plant Growth Promoting Rhizobacteria(PGPRs) to increasing the availability of nutrients. Soil beneficial bacteria play an important role in the biological cycles and have been used to increase plant health and soil fertility over the past few decades.The aim of this study was to investigate theeffect of PGPRson the concentration and uptake of macro nutrients by corn in a Cd-contaminated calcareous soil under drought stress.
Materials and Methods: A greenhouse factorial experiment was conducted in a completely randomized design with three replications. The treatments were two levels of bacteria (with and without bacteria), four levels of Cd (5, 10, 20, and 40 mg kg-1), and three levels of drought stress (without stress, 80, and 65% of field capacity). The pots were filled with 3 kg of treated soil. Cd was treated as its sulfate salt in amounts of 5, 10, 20, and 40 mg kg-1. The soil was mixed uniformly with 150 mg N kg-1 as urea, 20 mg P kg-1 as Ca (H2PO4)2, 5 mg Fe kg-1 as Fe-EDDHA and 10, 10 and 2.5 mg Zn, Mn and Cu kg-1, respectively as their sulfate salt in order to meet plant needs for these nutrients. Six seeds of Zea mays (var. HIDO) were planted at each pot. Each seed of maize was inoculated with 2 mL (1×108 colony-forming units (cfu) mL-1) of Micrococcus yunnanensis (a gram positive bacterium with the ability of production of sidrophore and phosphate dissolving characteristic). Each pot was irrigated daily with distilled water to near field capacity by weight, until 15 days after corn planting. Then corn was thinned to 3 plants per pot and irrigation was started with different levels of drought stress (without stress (F.C), 80, and 65% of field capacity) by weight. At harvest (8 weeks after planting), the aerial parts of the plants was cut at the soil surface. The harvested plants were washed with distilled water, dried to a constant weight at 65C. Representative samples were dry-ashed and analyzed for macro nutrients.
Results and Discussion: The results indicated that the inoculation of bacteria increased shoot dry weight (DW) and total uptake of nitrogen (N), phosphorus (P), and potassium (K). Drought stress decreased DW, total uptake of N, P, and K, concentrations of N and K in corn shoots, and concentration of K in the soil. The application of biological fertilizers, such as plant growth promoting rhizobacteria, increase plant growth through increasing microorganism’s activities and population in the soil and so increase macro nutrients uptake by the plant. Phosphate solubilizing rhizobacteria increase plant growth and phosphate availability with production of organic acids and secretion of phosphatase enzymes or protons and conversion of non-soluble phosphates (either organic or inorganic phosphates) to the forms that are more available for the plants and improve their nutrition and increase their growth. Drought stress decreases Dry Matter Weight(DMW) through decreasing relative humidity of the air of plant growth environment and increases evaporation, transpiration, plant temperature and light intensity of the sun. It prevents normal development of roots, water uptake, and plant growth by reducing the moisture content of the soil. It also decreases uptake and availability of Phosphorus in arid soils because plant growth and root activity in arid soils are lower from those of wetlands and as phosphorus is immobile in the soil, its uptake by the plant will decrease. N concentration of plants will increase drought stress conditions through rapid accumulation of amino acids that had not been converted into protein. The combined effects of drought stress and inoculation of bacteria on decomposition of silicates, cause the release of nutrients such as potassium. Increasing levels of cadmium in both cases, with and without bacterial inoculation, decreased DW, N and K uptake by corn because of its toxicity and its competition and interactions with these nutrients.
Conclusion: The inoculation of bacteria mitigated the negative effects of drought stress and cadmium contamination by increasing dry weight of corn and increasing uptake of macronutrients by aerial parts. Drought stress in both cases (with and without bacterial inoculation) reduced shoot dry weight, total uptake of macro nutrients, N and K concentrations in corn shoots and post-harvest potassium concentration in the soil. Cadmium levels decreased shoot dry matter and N and K uptake by the plant. The use of bacteria was more effective at low cadmium and drought stress levels.
Marzieh tavanaei; somayeh bakhtiari; mehran shirvani
Abstract
Introduction: Heavy metals contamination due to natural and anthropogenic sources is a global environmental concern. Lead (Pb) is one of the very toxic heavy metals. Industrial production processes and their emissions, mining operation, smelting, combustion sources and solid waste incinerators are the ...
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Introduction: Heavy metals contamination due to natural and anthropogenic sources is a global environmental concern. Lead (Pb) is one of the very toxic heavy metals. Industrial production processes and their emissions, mining operation, smelting, combustion sources and solid waste incinerators are the primary sources of lead. This heavy metal has aberrant effects on the environment and living organisms. Hence, proper treatment of lead from soil and industrial wastewaters is very important. In order to remove toxic heavy metals from contaminated water systems, conventional methods such as chemical precipitation, coagulation, ion exchange, solvent extraction and filtration, evaporation and membrane methods are being used. These conventional methods generally have high costs and technical problems. Therefore, biosorption processes, in which microorganisms are used as sorbents, have been considered as economical and environmentally friendly options for removal of heavy metals from aqueous solution. Clay minerals are another group of sorbents used in removal of heavy metals from polluted environments. Furthermore, bacterial cells can be attached on clay mineral surfaces and form bacteria-mineral composites. These composites adsorb heavy metals and convert them into forms with low mobility and bioavailability. Pseudomonas putida is a unique microorganism with a high tendency to sorb and/or degrade certain environmental pollutants. Palygorskite and sepiolite are the fibrous clay minerals of arid and semiarid regions; their structures consist of ribbons and channels. These fibrous minerals have various applications in industry and the environment because of its large surface area and high adsorption capacity. The present study was conducted in order to determine the ability of Pseudomonas putida (P168), and its composites with palygorskite and sepiolite in lead sorption.
Materials and Methods: The bacterial strain used in the present study was Pseudomonas putida (P168) grown and maintained on Nutrient Broth (NB). The population of living and non-viable bacteria in suspension was determined by an optical microscope. The minerals used in this study were palygorskite from Florida (the Source Clay Minerals Repository, Purdue University, IN) and sepiolite from Yazd (Iran). The clay samples were ground and passed through 0.05 mm (mesh #270) sieve. The clays were then saturated with calcium chloride (0.5 M) and washed free of salts. Batch experiments were performed to measure Pb sorption by Pseudomonas putida. For this purpose, 10-ml aliquots of bacterial suspension (7.24×107 cells ml-1) were added to10 ml solutions containing Pb with concentration ranged from15-110 mg L-1. The mixtures were gently shaken at 30 ◦C for 24 h and centrifuged at 3000 rpm for 20 min. The concentration of Pb in the supernatants was finally measured by atomic absorption spectrometer. The percentage of sorbed Pb was determined by subtracting the amount of unabsorbed Pb from that initially added. Various hybrids of P. putida and clays were also exposed to solution of 0.5 mM Pb in 0.01 M KNO3 to determine the role of composites in sorption of Pb. Langmuir and Freundlich adsorption isotherms were chosen to describe the biosorption equilibrium data. GraphPad Prism 5.0 was used for determining the isothermal parameters using non-linear regression analysis. Data were analyzed with the Statistical Analysis System (SAS). Experimental design was factorial in form of complete randomized block.
Results and Discussion: Pseudomonas putida showed a considerable capacity to sorb Pb ions. Lead sorption isotherms were sufficiently fitted with the Langmuir and Freundlich models. The Pb sorption isotherms by P. putida were L-type showing a high affinity of P. putida for Pb ions. Lead sorption capacity (qmax) of P. putida was estimated to be 582.4 mg g-1 and its Langmuir constant (KL) was found to be 0.11 mg L-1. The experimental data of lead sorption (7.5-55.5 mg L-1 initial concentration) by P.putida (P168) demonstrated that about 31.5% to 78.4% of the intial concentration of Pb was taken up by these bacteria. Sorption of Pb decreased with the increase of bacteria in the bacteria-clay composites, which may be due to the occupation of adsorption sites on the clay surface by the bacteria. Composites of bacteria-sepiolite were more effective than bacteria-palygorskite in Pb sorption due to the larger channel dimensions, greater surface area, and more functional groups of sepiolite than palygorskite. LSD test showed that there were significant differences between the hybrid sorbents with different ratios and single bacterial cells in Pb sorption.
Conclusion: The results showed that P. putida and its composites with palygorskite and sepiolite clays exhibited a high potential for the removal of Pb from aqueous solutions.
Mohsen Hamidpour; Leila Akbari; Hossein Shirani; Ali akbar Mohammadi
Abstract
Introduction: Soil contamination by heavy metals is a major concern throughout the world, due to persistence of metals in the environment and their toxicity and threat to all living organisms. Several strategies have been used to immobilize heavy metal ions in soils. Immobilization can be achieved by ...
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Introduction: Soil contamination by heavy metals is a major concern throughout the world, due to persistence of metals in the environment and their toxicity and threat to all living organisms. Several strategies have been used to immobilize heavy metal ions in soils. Immobilization can be achieved by adding natural and synthetic amendments such as zeolites and organic materials. Because of large specific surface area, high cation exchange capacity (CEC), low cost and wide spread availability, zeolites are probably the most promising materials interacting with many heavy metal ions in contaminated soils and water. Organic amendments such as vermicompost contains a high proportion of humified organic matter (OM), may decrease the bioavailability of heavy metals in soil by adsorption and by forming stable complexes with surface functional groups, thus permitting the re-establishment of vegetation on contaminated sites. Recent studies showed that the co-application of zeolite and humic acids could be effective in reducing the available fraction of Pb in a garden polluted soil. Fractionation of heavy metals cations in amended polluted-soils is needed to predict elemental mobility in soil and phyto-availability to plants. Therefore, the objective of this study was to investigate the effects of co-application of zeolite and vermicompost on Zn redistribution in a contaminated soil.
Material and Methods: A contaminated soil was collected from the top 20 cm in the vicinity of zinc mine in Zanjan province, western north of Iran. The soil sample was air-dried, passed through 2-mm sieve and stored at room temperature. The soil sample was thoroughly mixed to ensure uniformity. Sub-samples were then digested using the hot-block digestion procedure for total Zn concentration. The experiment was conducted under greenhouse condition. The polluted soil was put in polyethylene pots and mixed well vermicompost and zeolite at the rate of 0, 50 and 100 g kg-1 soil. The treatments were evaluated in a 3 × 3 factorial design and were arranged in a randomized block design with three replications. After incubation for 45 days, five seeds of corn were sown in each pot. After germination the seedlings were thinned to 3 per pot. Plants were grown for 2 months under control conditions. After the corn had been harvested, soil samples were air-dried, and analyzed for pH, cation exchange capacity (CEC), and electrical conductivity (EC). Chemical fractionations of Zn in soils collected after the pot trial were investigated using the procedure of Salbu et al. (1998). This procedure subdivides the heavy-metal distribution into an water-extractable+exchangeable fraction, a form bound to carbonates, a form bound to Fe and Mn oxides, a form bound to organics, and a residual form. An analysis of variance was used to test significance (P≤0.05) of treatment effects and Duncan multiple range test (P≤0.05) was used to compare the means (SAS, 2002).
Results and Discussion: Soil pH gradually decreased with application of both vermicompost and zeolite amendments. This may be due to degradation of organic matter and releasing of organic and inorganic acids such as carbonic, citric and malic acids as well as H+ produced from mineralization of nitrogen in the organic matter. Electrical conductivity (EC) of soils increased with increasing amounts of vermicompost and zeolite applications. The highest EC was observed in pots containing 10% w/w zeolite and 10% w/w vermicompost. Addition of zeolite significantly increased soil CEC. The overall distribution of Zn in different fractions was in the sequence residual (38.6%)> Fe and Mn oxides bound (31.0 %) > carbonated (21.6%)> organic (4.3%)≈exchangeable +water soluble (4.4 %). The application of vermicompost significantly decreased concentration of Zn in water+exchangeable fraction as compared to the control soil. Although singly zeolite amendment had not significant effect on water+exchangeable Zn concentration, this form decreased significantly with co-application of vermicompost and zeolite. This may be due to redistribution of Zn from this form to less available forms (e.g. organic and residual fractions). The addition of vermicompost had not significant effect on the carbonated fraction of Zn, whereas co-application of zeolite and vermicompost significantly decreased concentration of Zn bound in carbonates. Singly zeolite and co-application of amendments decreased the concentration of Zn in Fe and Mn oxides bound. Although singly compost and zeolite amendments increased concentration of Zn bound to organics, this form decreased furthest with co-application of them. Zeolite and vermicompost alone had not significant effect on mobility factor (MF) of Zn over the un-amended soil. Co-application of vermicompost and zeolite to polluted soil resulted in a significant decrease in MF values of Zn compared to control.
Conclusion: Co-application of vermicompost and zeolite to polluted soil resulted in redistribution of Zn from available forms (exchangeable +water soluble) to less available form (e.g. organic), thus may be useful for the immobilization of Zn from polluted sites.
MirHassan Rasouli-Sadaghiani; Habib Khodaverdiloo; Mohsen Barin; Solmaz Kazemalilou
Abstract
Introduction: Heavy metals (HMs) are serious threat for environment due to their dangerous effects. These metals as contaminants that can be accumulated in soil and after absorption by plants, finally will be found in food chains. Cadmium (Cd) is one of the dangerous HMs that threats the health of plants, ...
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Introduction: Heavy metals (HMs) are serious threat for environment due to their dangerous effects. These metals as contaminants that can be accumulated in soil and after absorption by plants, finally will be found in food chains. Cadmium (Cd) is one of the dangerous HMs that threats the health of plants, living organisms and human. Physicochemical remediation methods may cause large changes in different characteristics of soils . Recently environmental-friendly strategies including phytoremediation have been emphasized by researchers. Phytoremediation that refers to the use of plants and their assistance with microorganisms for remediation of contaminated soils is an effective and low cost method for reclamation of heavy metals polluted soils. The most important limitation of phytoremediation is low availability of heavy metals and sensitivity of plants to contamination. There are evidences that soil microbes can help to overcome these limitations through several ways. Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are known to enhance plant growth and survival in heavy metal contaminated soils through different mechanisms including producing promoting metabolites, auxin, siderophore and antibiotics. In this study the role of some strains of PGPR (a mixture of Pseudomonas species including P. putida, P. fluorescens, and P. aeruginosa) and AMF (a mixture of Glomus species including G. intraradices, G. mosseae and G. fasciculatum), on uptake and accumulation of Cd, Fe, Zn and Cu as well as some physiological properties of Onopordon (Onopordon acanthium L) were evaluated.
Materials and Methods:This study was carried out under greenhouse condition as a factorial experiment based on a randomized complete block design with two factors including Cd concentration (four levels) and microbial treatment (three levels) in three replications. Consequently, a soil was selected and spiked uniformly with different concentrations of Cd (0, 10, 30 and 100 mg Cd kg-1 soil) at greenhouse of agricultural college in Urmia University. The contaminated soils were then sterilized and subsequently inoculated with arbuscular mycorrhizal fungi (a mixture of Glomose species including G. intraradices, G. mosseae and G. fasciculatum) and plant growth promoting rhizobacteria (a mixture of Pseudomonas species includeing P. putida, P. fluorescens, and P. aeruginosa). The seeds of Onopordon plants were grown in 2.5 kilogram pots under greenhouse condition. At the end of growing season the shoot dry weight, Cd, Fe, Zn and Cu concentration and element contents and some of physiological parameters of plant as well as microbial properties were analyzed. Furthermore, the effect of soil Pb level on population, activity and efficiency of the inoculated microbes was studied.
Results and Discussion: Significant difference was observed for plants’ dry weights. At different Cd levels, the yield of inoculated plants was higher than that of control plants. Furthermore, at elevated Cd concentration, plant height, biomass, relative yield, chlorophyll a, b, carotenoids, relative water content (RWC) decreased significantly (P < 0.05), however, plants inoculated with plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi showed considerable amount of dry matter, chlorophyll a, b as well as RWC. Mycorrizal and bacterial inoculation and Cd treatment also had significant effect on leaf photosynthetic pigments concentration and plant relative water content. In general, concentrations of photosynthetic pigments and RWC were higher in inoculated plants at every level of soil Cd. The microbial inoculation effectively decreased the inhibitory effects of Cd on plant growth. Shoot yield of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria plants increased by 2.7 and 2.1 times as well as microbial respiration increased by 2.17 and 2.01 times compared to control treatment. The results showed inoculated plant absorbed more Cd than non-inoculated plants. Plant growth promoting rhizobacteria were more effective than arbuscular mycorrhizal fungi inoculation in shoot Cd concentration. Cd contamination reduced soil microbial population and basal respiration. Results showed that with increasing soil Cd concentration shoot Fe, Zn and Cu concentrations significantly decreased. Root colonization rates decreased significantly with 10 mg kg-1 Cd addition for AMF treatments, and drastically with 100 mg kg-1 Cd added. Plant roots in the control and PGPR treatment were not colonized.
Conclusion: It is concluded that plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi inoculation could be sustained and promoted plant growth in phytoremediation processes. Therefore, under Cd contamination it can be use PGPR and AMF as growth promoters and finally enhance phytoremediation efficiency.
Amir Parnian; Mostafa Chorom; Nematolah Jafarzade Haghighy Fard
Abstract
Introduction: With increasing of population and the valuable water resource pollutions, a demand has been felt for new and inexpensive methods in order to remediation and improving of water quality. Cadmium is a trace element. In low concentration, this heavy metal is harmful to life, and considered ...
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Introduction: With increasing of population and the valuable water resource pollutions, a demand has been felt for new and inexpensive methods in order to remediation and improving of water quality. Cadmium is a trace element. In low concentration, this heavy metal is harmful to life, and considered as a dangerous pollutant. Cadmium leads to pollution and reduction of water quality; sometimes even toxicity through contaminated sources such as wastewater (Agricultural, municipal and industrial). Phytoremediation with aquatic macrophytes is an effective and inexpensive method for improving water quality and wastewater. The aim of this study was to investigatethe cadmium phytoremediation by Ceratophyllumdemersum L. as a potential method for remediation of cadmium pollution in aquatic medium.
Materials and Methods: In this study, the remediation of cadmium pollution in aquatic medium monitored, within 14 days cultivation of coontail (Ceratophyllumdemersum L.). At first, for estimating the level of local wastewater cadmium pollutions, five-month cadmium concentration measurement of steel industrial wastewater and urban wastewater set. Then, plants collected from the irrigation channels of ShahidChamran University of Ahvaz. After finding the best pH of nutrient solution for Ceratophyllumdemersum L. growth by cultivating the plants in 2 liters pots filled by the solutions withthree different pH(5.5, 7 and 9.5) within three weeks; 12 grams of plants cultivated in 2 liters of Hoagland nutrient solution contaminated by cadmium(pH = 7). The initial contamination levels were setasfive different concentrations of cadmium (0, 1, 2, 4, and 6 mg l-1) with three replications. The cadmium concentrations of the pots were measured every day and on the last day of cultivation, plants wet weight, plants dry weight and Cd concentration in plants weremeasured. Then,biomass production, Cd bioconcentration factor (BCF), Cd uptake index, and Cd uptake percentage of plants were calculated. Standard deviations calculationand correlation and regression analysis were performed using Microsoft Office Excel2007 and SPSS 16. One-way ANOVA performed to identify significant differences in metal concentrations in the different treatments. Differences considered significant atp < 0.05.
Results and Discussion: Among three pH (5.5, 7 and 9.5) for plants cultivation, C. demersum L.grewbetter in pH = 7. In fact, the average amount of produced biomasses were 46.6 g (pH = 5.5), 79.6 g (pH = 7) and 68.4 g (pH = 9.5). Therefore, to investigate the Cd remediation, the pH of nutrient solution set equal to 7. The final Cd concentrations in nutrient solution for initial Cd concentrations of 1, 2, 4 and 6 mg l-1 were 0.30, 0.36, 2.76 and 3.85 mg l-11respectively. Moreover, the Cd uptake percentage after 14days cultivation of C. demersum L.in nutrient solution for initial Cd concentrations of 1, 2, 4 and 6 mg l-1 were 70.00, 82.01, 31.00 and 35.83 %respectively. Cd uptake percentage of plants for initial concentrations of 4 and 6 mg l-1weresignificantly lesser than those of 1and 2 mg l-1.The decreased uptake efficiency percentage maybe caused by the effect of Cd toxicity on plant cell membrane permeability and efficiency.The average of BCF in plants for initial Cd concentrations of 1, 2, 4 and 6 mg l-1 were 384.4, 707.9, 66.5 and 75.0respectively. High reduction ofBCF amounts with increasing the initial concentration of 2to 4 and 6mg l-1, maybe caused by cadmium physiological adverse effects on plants. The averages of uptake index in plants were 1.26, 2.95, 2.24 and 3.92 mg for initial Cd concentrations of 1, 2, 4 and 6 mg l-1respectively. The results showed a reduction between 2 and 4 mg l-1concentrations that probablycaused by Cd toxicity disruption on plants uptake mechanism and growth. Moreover, the increase of plants uptake index in initial concentration of 6 mg l-1 could be explain by partial losing of the selective permeability of the plants cell membrane. The maximum (3.60 g/day) and minimum (1.62 g/day) of biomass production related to pollutant concentrations of 0 and 6 mg l-1 respectively, and it shows a greatefect of the Cd on C. demersum L.growth.
Conclusion: The plant accumulated cadmium efficiently, and the remediation efficiency was near to 82%. However, the pollutant removal was not complete in a short time.In total, phytoremediation of cadmium and other pollutants from wastewater or other aqueoussolutions by Ceratophyllumdemersum, as a native aquatic plant of most of Iran’s rivers, could be anefficient and appropriatemethod.
M. Taheri; M. Esmaeili Aftabdari; T. Khoshzaman; M. Tokasi; M. Abbasi
Abstract
Introduction: Soil is a hardly renewable natural resource. Although soil degradation, caused by either human activities and natural processes is a relatively slow procedure, but its effects are long lasting and most often, irreversible in the time scale of man's life. Among the most significant soil ...
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Introduction: Soil is a hardly renewable natural resource. Although soil degradation, caused by either human activities and natural processes is a relatively slow procedure, but its effects are long lasting and most often, irreversible in the time scale of man's life. Among the most significant soil contaminants resulting from both natural and human sources, heavy metals are more important due to their long- term toxicity effects. For evaluating soil's enrichment rate by heavy metals, a wide and full study of soils background values, including total and available fractions of heavy metal contents should be done. Zanjan province has some great mines and concentrating industries of lead and zinc especially in Angoran, Mahneshan. Unfortunately produced waste materials of these industries spread over the adjacent areas. Investigations showed that accumulation of some heavy metals in vegetables and crops planted in this region had occurred. Therefore, performing some investigations in these polluted areas and assessing pollution rate and heavy metals distribution in arable lands had prime importance. Our goals were: 1) determining the total and available amounts of Cu, Pb, Zn and Cd in the soils of arable lands in polluted areas of Zanjan city, 2) producing the distribution map for the metals mentioned above and 3) calculating pollution indices in the soils.
Materials and Methods: The study area was in south west of Zanjan city. For soil sampling, a 1 Km by 1 Km grid defined in ArcGIS software on landuse layer and totally 144 points that placed on agricultural lands, due to our goals, were sampled. For sampling, in a 5m radius around the point we collected some subsamples from depth of 0 - 15 cm, and after mixing the subsamples, finally a 1Kg soil sample prepared and sent to the laboratory. Sampled soils were air dried and were passed through a 2mm sieve. Soils organic matter (OM) content and texture were determined by Walkely-Black and Bouyoucos hydrometer methods, respectively. Soils pH were determined by glass/calomel electrode in saturation paste, EC by EC-meter in saturation paste extract, and calcium carbonate equivalent (lime) by reverse titration method. Total and available amounts of Zn, Cu, Cd and Pb were extracted by Aqua- Regia method (wet oxidation by chloridric acid and nitric acid with the 3:1 ratio) and by DTPA extracting solution, respectively. After extracting and filtering liquid samples, metal concentrations were measured by atomic adsorption method using GBC avanta P. Statistical analysis by SPSS and indices calculation by Excel were performed, and distribution maps were prepared by Inverse Distance Weighting method in ArcGIS software. For evaluating pollution rate, Geoaccumulation index, Enrichment factor and Availability Ratio indices were calculated and interpreted.
Results and Discussion: The textures of soil samples were loam, clay loam and sandy loam. The OM contents of almost soils were less than 2 percent. Lime was less than 25 percent and acidity of soils were neutral to slightly alkaline. Soils salinity were less than 2 dS/m except a few samples. Accordingly, these soils were suitable for agriculture and there were no limitation due to evaluated properties. Median values for the total concentrations of Cd, Cu, Pb and Zn (extracted by Aqua Regia) were 0.5, 22.5, 14 and 82.3 mg/Kg of soils, respectively, and for available fraction (extracted by DTPA) were 0.1, 0.9, 1.6 and 3.2 mg/Kg of soils that were much lower than measured total values. According to 90th percentile of geoaccumulation index, at least 10 percent of samples had been polluted with Zn, Pb and Cd. Enrichment factor revealed no long term pollution. Availability ratios of Pb and Zn were relatively high, showing there exists unique and recent pollution source for them. All pollution indices showed positive correlations with OM content of soils (except for availability ratios of Cd, which had negative correlation). Therefore, OM content of soils were respect to control these indices. Geoaccumulation index of Zn, Cd and Pb, and availability ratios of Zn and Pb showed negative correlations with soil pH. Therefore, in some seasons of the year, their availabilities will increase in soil.
Conclusion: The results showed that Cu content in soils were not in the critical limit but Cd, Pb and Zn content in soils were greater than standard levels and reclamation procedures for remedy of these soils must be done. The high values of the heavy metals in available fraction inthe soils increased the risk of bioaccumulation in microbial and biotic tissues. In areas where there are high content of available form of heavy metals in soils, it could be an index of new contamination in soils by heavy metals. According to geoaccumulation index of Cd, Zn and Pb, there are some contaminated points around waste depositition areas near Zanjan city. These points are in the direction that wind could effectively transport the particles of wastes to urban area. Enrichment factor (EF) showed that at least there were a few points polluted by Cd, Zn and Cu, although EF values were generally low. The leaked wastes of Zinc and lead industries had been spread in deposited areas caused difficulties in determining background values for the selected metals.
M.A. Delavar; Y. Safari
Abstract
Introduction: The accumulation of heavy metals (HMs) in the soil is of increasing concern due to food safety issues, potential health risks, and the detrimental effects on soil ecosystems. HMs may be considered as the most important soil pollutants, because they are not biodegradable and their physical ...
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Introduction: The accumulation of heavy metals (HMs) in the soil is of increasing concern due to food safety issues, potential health risks, and the detrimental effects on soil ecosystems. HMs may be considered as the most important soil pollutants, because they are not biodegradable and their physical movement through the soil profile is relatively limited. Therefore, root uptake process may provide a big chance for these pollutants to transfer from the surface soil to natural and cultivated plants, which may eventually steer them to human bodies. The general behavior of HMs in the environment, especially their bioavailability in the soil, is influenced by their origin. Hence, source apportionment of HMs may provide some essential information for better management of polluted soils to restrict the HMs entrance to the human food chain. This paper explores the applicability of multivariate statistical techniques in the identification of probable sources that can control the concentration and distribution of selected HMs in the soils surrounding the Zanjan Zinc Specialized Industrial Town (briefly Zinc Town).
Materials and Methods: The area under investigation has a size of approximately 4000 ha.It is located around the Zinc Town, Zanjan province. A regular grid sampling pattern with an interval of 500 meters was applied to identify the sample location, and 184 topsoil samples (0-10 cm) were collected. The soil samples were air-dried and sieved through a 2 mm polyethylene sieve and then, were digested using HNO3. The total concentrations of zinc (Zn), lead (Pb), cadmium (Cd), Nickel (Ni) and copper (Cu) in the soil solutions were determined via Atomic Absorption Spectroscopy (AAS). Data were statistically analyzed using the SPSS software version 17.0 for Windows. Correlation Matrix (CM), Principal Component Analyses (PCA) and Factor Analyses (FA) techniques were performed in order to identify the probable sources of HMs in the studied soils.
Results and Discussion: Comparing the measured HMs contents with their normal range in uncontaminated soils demonstrated the contamination of soils by Pb, Zn and Cd, with average concentrations of 152.8, 294.2 and 5.6 mg kg-1, respectively,whereas Ni and Cu did not show any pollution risk. The total concentration of Zn, Pb and Cd in the soil showed a great degree of variability, indicated by large coefficients of variation (CV) from 228.5 % of Cd to 354.8 % ofPb. These elevated CVs may indicate that these elements’ distribution in the studied area is influenced by an anthropogenic source. In contrast, the relatively low calculated CVs for Ni and Cu may imply that natural sources are responsible for these elements’ distribution in the studied soils. Correlation matrix (CM) analysis revealed high correlation coefficients between Zn-Cd and Ni-Cu, indicating the influence of the same factors in controlling their distribution. On the other hand, Pb contents showed low correlation with Ni and Cu values, whereas its correlation with Zn and Cd was relatively high. Therefore, it seems that Pb distribution in the studied soils is more influenced by the factor which controls the Zn and Cd distribution, rather than another factor that is responsible for accumulation of Ni and Cu in the studied soils. According to the PCA analysis, two significant components were extracted explaining about 84% of total variance. FA analysis showed that studied variables have a relatively high communality with two extracted principal components, indicating that almost all of the measured total variation can be efficiently explained by the extracted principals. Industrial activities in the Zinc Town seem to be the main factor which caused the high concentrations of Pb, Zn and Cd in the soil environment in this area; whereas Ni and Cu were associated with the natural sources including geology of the studied area (parental material’s factor). The obtained results from this study coincide with the prior studies indicating that multivariate statistics is a powerful technique for identification of probable sources of HMs in the soil.
Conclusions: The studied soils are classified as polluted soils with Zn, Pb and Cd,whereas Ni and Cu did not show any pollution risk. PCA and correlation analyses between HMs indicated that HM pollution in the studied area may originate from natural and anthropogenic factors. It can be concluded that Zinc Town controls the distribution of Zn, Pb and Cd in the surrounding soils, but Ni and Cu distribution in the studied area is mainly influenced by natural factors.Totally, industrial activities related to Zn production caused simultaneous entrance of several HMs to the adjacent soils and led to degradation of the lands in the studied area.
Najme Yazdanpanah
Abstract
Introduction: Water scarcity is an important challenge worldwide, especially in arid and semi-arid regions. In these areas, the excessive exploitation of groundwater for irrigation, inefficient irrigation methods, irrigation with low-quality water and uncontrolled utilization of fertilizers in agricultural ...
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Introduction: Water scarcity is an important challenge worldwide, especially in arid and semi-arid regions. In these areas, the excessive exploitation of groundwater for irrigation, inefficient irrigation methods, irrigation with low-quality water and uncontrolled utilization of fertilizers in agricultural lands in addition to contamination of water resources by domestic and industrial wastewater in urban as well as rural regions, have led to water pollution problems. Furthermore, pollution and transportation of pollutants through wastewater have been considered as an environmental issue. Wastewater is a term that is used to describe waste materials that includes liquid waste and sewage waste. Wastewaters from single houses in the countryside that are not connected to sewers are generally treated on-site by septic tank systems or individual domestic wastewater treatment systems. Study on wastewater quality derived from refining systems in rural areas has been rarely taken into account. This study investigates the efficiency of some refining systems in the reduction of wastewater pollution indices and heavy metal concentrations.
Materials and Methods: This study was done in four rural areas including Dehmilan, Hotkan, Sarbagh and Sekukan which are located around the city of Zarand in the Kerman province. Recently, some refining systems have been established in these areas in order to mitigate the environmental issues. An experiment was done to assess the efficiency of these refining systems and to determine the pollution indices for such small communities. Wastewater sampling was done in 10 replicates each at one week interval from four refineries. Different variables including BOD, COD, TOC, EC, TSS, TDS, DO, TKN, TP, pH, temperature, turbidity (Turb), alkanity (Alk) and also the concentrations of Cd, Zn, Pb, Ni and Mo were measured using standard methods. To quantify the performance of each system, the amount of each variable at the outlet was compared to the value of the same variable at the inlet. Also, the percentage change of wastewater properties at the outlet ratio to the inlet values in the refining systems was calculated. Meanwhile, the efficiency was evaluated using permissible values reported by the Environmental Protection Organization of Iran.
Results and Discussion: The results showed that after purification, the amounts of DO, Cd and Mo were not significantly different among the studied systems, while, the other parameters were found to be similar. In almost all the cases, the amounts of pollutants decreased at the outlets, nevertheless considering the permissible standards, just in few cases the pollution was reduced. Moreover, in comparison to the standard values, the amount of TP increased, while Turbidity decreased. Additionally, the amount of DO was higher than the threshold values. As a result of purification in all the studied systems, the concentrations of Cd and Pb were reduced, whereas the concentration of Ni increased. Also, the concentrations of heavy metals, except Mo were less than the standard values.
Conclusion: It was concluded that the selected refining systems had limited performance in the purification of wastewater in the studied rural areas. However, the amounts of pollutants showed some reductions at the outlets, based on the permissible standards reported by the Environmental Protection Organization of Iran. In just a few cases the pollution indices were reduced. In fact, the septic tank systems could not remove the chemical pollutants from wastewaters, although the best performance was observed for TSS and Turbidity, which were reduced with respect to permissible levels. The amounts of BOD and COD were higher than the standard values, indicating low efficiency of the refining systems in removal of chemical and biological agents. Also, the concentration of TP was found to be higher than the permissible level. The entrance of phosphorous into the surface runoff and water bodies may lead to eutrophication. The results of assessment of heavy metals indicated that the refining system could reduce the concentrations of Cd and Pb, whereas, the concentration of Ni increased. Anyway, the concentrations of heavy metals, except Mo were less than the standard values. The source of Mo seems to be within the wastewater generated by the rural communities, which can lead to serious environmental problems. The main concern arises from the high concentration of Mo, which was 4000 percent greater than the permissible level. Therefore, more studies are needed on the possible source of Mo in the rural study region. Also, a modification in the current systems particularly in removal of chemical agents is necessary.
N. Namazi; M.H. Salehi; jahangard mohammadi
Abstract
Introduction: Heavy metals released from stationaryand mobile origins can be transported in water, air and soil and can be even absorbed by plants, animals and human bodies. Trace elements are currently of great environmental concern. Nowadays, one of the most important environmental problems is pollution ...
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Introduction: Heavy metals released from stationaryand mobile origins can be transported in water, air and soil and can be even absorbed by plants, animals and human bodies. Trace elements are currently of great environmental concern. Nowadays, one of the most important environmental problems is pollution of agricultural soils occurs by heavy metals due to human activities. Atmospheric subsidence is one of the main sources of these elements which can result from industrial activities, fertilizers, sewage sludge, compost and pesticides. Heavy metals mapping of the atmosphere dusts indicates the status of pollution and its intensity in industrial regions. This information can also be used as a guideline for better management and pollution control. This study was performed to investigate the spatial and temporal availability of heavy metals in atmospheric dusts of Lenjanat region, Isfahan where agricultural land is extensively surrounded by industrial activities like steel making factory (Esfahan), cement making factory (Sepahan and Esfahan) and Bamalead mine.
Materials and Methods: Sampling was done from 60 points with the same altitude(three to six meters from the ground)and their location was recorded by GPS. Glass traps (1×1 m2) covered by plastic mesh (2 × 2 cmvents) were used to trap the dusts for four seasons of the year. Collected dust samples were passed through a 200 mm mesh screen size and the total weight of the dusts and the heavy metals content of Cd, Zn, Cu, Ni and Pbwere determined(with HNO3 60%). Data analysis was performed using Statistical 6.0 software. Analysis of spatial data via variogram was calculated and performed using Variowin, 2.2 software packages. After determination of the best fitting model, kriged maps of the total concentration of heavy metals were prepared by Surfer 8 software.
Results and Discussion: The average concentrations of Zn, Pb and Cd in dust in most parts of the study area were much higher than the soil standard values and the maximum value was around the Zn and Pb mines. However, the concentrations of Cu and Ni were higher than the standard values only in some parts of the area. Comparison of the averages for different seasons showed that in most cases there were significant differences between the concentrations of the various elements. A significant correlation was observed among Pb, Zn and Cd concentrations in all seasons indicating similar origin of these elements. The average dust deposition rate in the summer was more than the other seasons. Moreover, in all seasons except the spring and fall, there was a significant difference between the average dust deposition rates. Kriged maps of Zn, Cd, and Pb showed that the maximum concentrations of these elements occurred near the Pb and Zn Bama mine and the concentrations of these elements decreased with increasingthe distance from the mine. The contamination was lower in the spring and higher in the summer. Based on the kriged maps, samplingfrom one seasononly can be used to assess the trend of element contamination but if the objective focuses on absolute heavy metals values, season strongly influences the results and interpretation from one season can be misleading. The determination of the amounts of dust and their heavy metal contents in different wind directions is recommended to identify the source of dusts and heavy metals.
Conclusion: Results showed a significant difference among the mean values of dusts for the different seasons except for the spring and fall. The mean values of Pb and Cd in all seasons and Zn except for the spring were higher than the threshold values reported for the soils. A significant correlation was observed among the concentrations of some elements which may suggest their same origin. Interpretation of kriged maps showed that zinc and lead Bamamine in the region could be the main source of the contamination of Zn, Pb and Cd. According to quantitative calculations, a low accordance was observed for the pattern and the values of each element in different seasons. This can be related to the wind velocity and its direction, intensity of industrial and mining activities and also the amount of humidity of soil and air during the year. Interpretation of atmospheric data based on one season may be considerably misleading.
Keywords: Atmosphericdusts, Heavy metals, Season
A. Afshari; H. Khademi; shamsollah Ayoubi
Abstract
Introduction: Heavy metals are types of elements naturally present in soil or enter into soil as a result of human activities. The most important route of exposure to heavy metals is daily intake of food. Crops grown in contaminated soil (due to mining activities, industrial operations and agriculture) ...
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Introduction: Heavy metals are types of elements naturally present in soil or enter into soil as a result of human activities. The most important route of exposure to heavy metals is daily intake of food. Crops grown in contaminated soil (due to mining activities, industrial operations and agriculture) may contain high concentrations of heavy metals. Also closeness to cities and industrial centers can have a great influence on the accumulation of heavy metals to agricultural products grown in the region. The study aimed to determine the concentration of heavy metals in soil and agricultural products around urban and industrial areas of Zanjan province (North West of Iran) and consumption hazard probability.
Materials and Methods: Soil (75 samples of soil from a depth of 0 to 10 cm) and plant (101 samples) samples, in the summer 2011, were randomly taken from industrial areas as follow: tomatoes (Lycopersicum esculentum M), wheat seed (Triticum vulgare), barley seeds (Hordeum vulgare), alfalfa shoots (Medicago sativa L.), potato tubers (Solanumtuberosum L.), apple fruit, vegetables and fruits such as Dill (Aniethum graveolens L.), leek (Allium porrum L.), Gardencress (Barbara verna L.) and basil (Ocimum basilicum L.). Plant samples were then washed with distilled water, oven dried for48 hours at a temperature of 70 ´C until constant weight was attained and then they digested using 2 M hydrochloric acid (HCl) and nitric acid digestion in 5 M. Concentrations of heavy metals in the soil and crops were determined by atomic absorption spectrometry. DTPA extraction of metals by Lindsay and Norvell (1978) method and sequential extraction method by Tessier et al. (1979) were performed. Statistical analysis was accomplished using the software SPSS 16.0 and the comparison of mean values was done using the Duncan test at the 5% level of significance.
Results and Discussion: The magnitude of variations for total copper was from 11.5 to 352.5 (average 52.4), zinc was from 96.3 to 1353.8 (average 264.8), lead was between 40.0 and 470.0 (average 105.7), nickel ranged from 12.8 to 77.0 (average 46.7) and chromium varied from 10.0 to 49.5 (average 21.7) mg kg-1. DTPA extracted heavy metals for copper varied from 1.50 to 21.23, averaging 4.47, zinc from 0.57 to 76.50 averaging 23.15, lead from 2.43 to 63.38 averaging 16.81 and nickel from 0.28 to 2.32 averaging 1.20 mg kg-1. Chemical changes in the different fractions were as follows: Cu (residual > bounded to organic matter > bounded to Fe-Mn oxides > bounded to carbonate > exchangeable fraction), Zn and Ni (residual > bounded to Fe-Mn oxides > bounded to carbonate > bounded to organic matter > exchangeable fraction,) and Pb (residual > bounded to Fe-Mn oxides > bounded to organic matter > bounded to carbonate > exchangeable fraction). The concentration of heavy metals in plant parts were high with respect to studied location. The highest amounts of Zn (Gardencress), Pb (Dill), Cu (Leek), Ni (Basil) and Cr (Basil), respectively were found to be 150.25, 41.25, 23.13, 6.46 and 3.47 mg kg-1 and the minimum amounts of the metals studied were found in fruits, wheat and barley grains. The total amount of metals in plants were as follow (Zn >> Pb > Cu > Ni > Cr). Bioaccumulation factor (BAF) of metals in plants were as Zn=Cu > Pb >> Cr > Ni. Hazard probability (HQ) in cancerous diseases for each element (except Pb) in both children and adults was less than unit. HQ content of Pb was much higher than the unit and for children and adults 9.07 and 6.94, respectively showing high contribution of Pb contamination of crops that threatens the consumer health in that location. The total amount of risk (THQ) in children was higher than that in adults.
Conclusions: The results obtained in this study indicate that an urgent attention is required for consumer products related to public health, especially vegetables grown in the studied regions. Toxic effects of heavy metals have many deleterious effects which are more pronounced over time. With conventional monitoring of food quality produced in farms and presented in markets, excessive accumulation of heavy metals entering in to the human food chain can be prevented. Also, we can change the risk potential of heavy metals in the region by growing vegetables which accumulate heavy metals.
Keywords: Agriculture products, Biological risk, Heavy metals, Soil, Zanjan province
A. Falahati Marvast; alireza hosseinpuor; Seyed Hassan Tabatabaei
Abstract
The objective of this study was to evaluate the effect of soil salinity on the availability and uptake of cadmium(Cd), lead(Pb), nickel(Ni), zinc(Zn) and copper(Cu) in a soil treated with municipal sewage sludge (MSS). Soil was salinized (2, 4, 8 and 12 dSm-1 soil paste extract) with NaCl + CaCl2 (1:1ratio), ...
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The objective of this study was to evaluate the effect of soil salinity on the availability and uptake of cadmium(Cd), lead(Pb), nickel(Ni), zinc(Zn) and copper(Cu) in a soil treated with municipal sewage sludge (MSS). Soil was salinized (2, 4, 8 and 12 dSm-1 soil paste extract) with NaCl + CaCl2 (1:1ratio), and incubated at soil field capacity (FC) for 1 month. The soil was treated with a 1.5 percent of MSS and incubated again at FC for 1 month. Before planting,soluble and DTPA-TEA extractable of heavy metals and soluble Chloride(Cl-) were determined. Then barley seeds were planted and, plants were harvested 10 weeks after germination. The plant indices (dry weight, heavy metal concentration and heavy metal uptake) were measured. The results showed that all salinity levels significantly increased soluble and availability of Cd, Pb, Ni, Zn and Cu. Soil salinity had a significant effect on concentrations and absorption of Cd and Pb in plant (P
Mohammad Reza Naderi; A. Danesh-Shahraki; F. Raiesi
Abstract
The right selection of an appropriate cultivar, which can be adapted with a particular pollutant and environmental conditions, is a crucial factor for a successful phytoremediation technology. Sunflower might be a suitable plant to remove the toxic metals from soil of polluted sites due to its rapid ...
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The right selection of an appropriate cultivar, which can be adapted with a particular pollutant and environmental conditions, is a crucial factor for a successful phytoremediation technology. Sunflower might be a suitable plant to remove the toxic metals from soil of polluted sites due to its rapid growth and high biomass production. In order to evaluate the efficiency of six sunflower cultivars in lead (Pb) phytoextraction from a contaminated soil, an experiment was carried out using a completely randomized design with three replications in Research Station of Shahrekord University. Sunflower cultivars used in this experiment were Alestar, Serena, Sanburu, Hysun 33, Record and Euroflor. Results showed that there was a significant difference in shoot lead concentration, translocation factor and total lead harvested by shoot among sunflower cultivars at 1% probability level. Generally, due to translocation factor of all cultivars was less than 1, this can be stated that none of cultivars had the proper efficiency for extraction of lead from contaminated soil. However, high root lead concentration and low translocation factor of these cultivars show that efficiency of them for use in phytostabilization technique is more than phytoextraction technique.
Sh. Nosratipoor; M. Nael; Mohsen Sheklabadi; A.A. Sepahi Garo
Abstract
To determine the origin of heavy metals, the effects of parent materials, soil genesis, and human activities on the content and distribution of selected metals in soils near Mofateh Martyr powerhouse, Hamedan, were assessed. Six types of parent materials including shale, schist, limestone, alluvial ...
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To determine the origin of heavy metals, the effects of parent materials, soil genesis, and human activities on the content and distribution of selected metals in soils near Mofateh Martyr powerhouse, Hamedan, were assessed. Six types of parent materials including shale, schist, limestone, alluvial plain, alluvial terraces and fan deposits were identified and soil genesis were studied. Total content of Cd, Cu, Mn, Ni, Zn, Pb, Fe were determined in soil horizons and parent materials. Concentration of the metals in four different chemical phases, including acetic acid extractable, reducible, oxidizable and residual fractions, was determined with four-step sequential extraction procedure. Soil development is limited in the studied region so that the discrepancy between solum and parent material in terms of heavy metal content is not great in general. Calcareous soils and limestone have the lowest amount of copper, manganese, nickel, zinc, lead and iron. Independent of soil types and parent materials, most of the heavy metals, except Mn, were present in the residual fraction. The concentration of Mn in all profiles is highest in reducible fraction. Low degree of soil development and the prevalent presence of metals in residual fraction show the influential role of parent materials in controlling metal concentration and distribution; pedogenic processes have minor effects. The role of human activities is limited for most of the selected metals; however, the tangible presence of Pb and, in some cases, Cd in acetic acid extractable fraction, reflects the impact of human activities on the concentrations of these two metals.
salman naimi marandi; shamsollah Ayoubi; B. Azimzadeh
Abstract
Soil pollution by heavy metals is an important environment issue throughout the world. Heavy metals’ origin, accumulation, and distribution in soil have been the focus of much attention by many researchers. The objective of this study was to recognize the sources of some heavy metals in surface soils ...
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Soil pollution by heavy metals is an important environment issue throughout the world. Heavy metals’ origin, accumulation, and distribution in soil have been the focus of much attention by many researchers. The objective of this study was to recognize the sources of some heavy metals in surface soils in Zob-Ahan industrial district, Isfahan province, using multivariate geostatistical techniques. A total of 202 surface (0–30 cm) soil samples were collected. Total lead (Pb), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co) and chromium (Cr) contents of the samples were determined. A multivariate geostatistical analysis was performed to identify the common source of heavy metals. The results of principal component analysis led to the identification of three components. So, these components were explained 31, 27, and 16 % of total variance of heavy metal concentration, respectively. The distribution of scores of each components were shown that the quantities of Fe, Mn, Pb and Zn were found to be associated with anthropogenic activities, corresponding to the first factor was termed the “anthropogenic component”. The quantities of Co were found to be associated with parent rocks, corresponding to the second factor was termed the “lithologic component”. Also, the third factor was mainly attributed to Cu, Ni and Cr which also comprised the first and third factors, indicating a mixed source both from lithologic and anthropogenic inputs.
