Ali Afshari; H. Khademi; shamsollah Ayoubi
Abstract
Introduction: Heavy metals are found to be one of the major environmental hazardous contaminants, for human health, animal life, air quality and other components of environment. They can affect geochemical cycles and accumulate in animal tissues since physical processes are not able to remove them, so ...
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Introduction: Heavy metals are found to be one of the major environmental hazardous contaminants, for human health, animal life, air quality and other components of environment. They can affect geochemical cycles and accumulate in animal tissues since physical processes are not able to remove them, so they are consistent in long term. The analysis of the total concentration of heavy metals in soil may provide information about soils enrichment but in general, it is widely used to determine the potential mobility of heavy metals in environmental behavior under chemical forms of metals in soils. Heavy metals existat several phases including water-soluble, exchangeable, bounded to organic matter, bounded to carbonates, bounded to Fe-Mn oxides, secondary clay minerals and residual fraction within primary minerals network. There is a dynamic equilibrium between different fractions of elements in soil. The main objectives of the present study were a) The analysis of the total concentration of heavy metals such as Fe, Mn, Ni, Cr, Co, Pb, Zn, Cd and Cu and b) The fractionations of heavy metals and identification of controlling factors to distribution and behavior of heavy metals in soils at different land uses.
Materials and Methods: The study was performed at central area of Zanjan province (Iran). The study area was over 2000 km2 in coordinates 20´ 36° to 41´ 36° E and 19´ 48° to 53´ 48° N. The average altitudes were over 1500 meters above sea level. The major land uses of the study area included agriculture (AG), rangeland (RA) and urban (UR). Sample collection was done based on the random grid method in August 2011. Surface soil samples (0-10 cm depth) were taken from grid centers included 137, 77 and 27 samples from AG, RA and UR land uses, respectively. The samples were digested in Nitric acid 5 normal (Sposito et al., 1982) and total concentration of Pb, Zn, Ni, Mn, Cu, Cr, Fe and Co were measured by Perkin-Elmer: AA 200 atomic absorption instrument and cadmium was measured by atomic absorption equipped with Rayleigh: WF-1E graphite furnace. 75 soil samples were selected, DTPA-extraction and sequential extraction were performed and physiochemical characteristics of these samples analyzed. To extract the metals by DTPA, the method developed by Lindsay and Norvell, (1978) was used and sequential extraction was done by Tessier et al., (1979) method. All statistical parameters were calculated using SPSS 16.0 software, and mean comparison (mean separation) was carried out using Duncan test at probability level of 5%.
Results and Discussion: The results indicated that heavy metals concentrations and patterns were evidently affected by different land uses. Co concentration was between 17.0 – 35.7 mg/kg and had the lowest total coefficient of variation (14%). The maximum total Cr and Ni values were measured in AG land use (26.1 and 52.6 mg/kg, respectively) and lowest was in UR land use (17.0 and 37.2 mg/kg, respectively). The highest total average value of Mn was found in RA (698.9 mg/kg) and the lowest in UR (629.1mg/kg) land use. The highest Fe concentrations were measured in AG and RA land uses (17.2 and 17.0 g/kg, respectively) and the lowest in UR land use (14.0 g/kg). The maximum Concentration of total Cd was observed in UR land use (2.47 mg/kg) and its minimum values were found in RA and AG (0.83 and 0.75 mg/kg, respectively) in the study area. In UR land use, Cu and Zn were more significant than AG and RA land uses. Pb variation was the same as Zn so that its increased concentration was found in urban land use (90.2 to 1357.5 on average 220.1 mg/kg). The highest Pb values were measured in UR land use (220 mg/kg) while the lowest concentrations were found in RA and AG land uses (80.6 and 69.0 mg/kg, respectively).
Different elements showed various fractional distribution in different land uses. The highest Co percentage was related to residual fraction at all land uses, with values up to 48.4%, 54.0% and 48.1% in AG, RA and UR land uses, respectively. Ni fractionation had approximately the same pattern with Co in all factions and land uses, except exchangeable fraction of Ni that showed the lowest percentage in all land uses. The dominant fraction of Cu was residual fraction with the amounts of 73.3% 76.0% and 61.9% in AG, RA and UR land uses, respectively. The second dominant fraction in UR and AG land uses was related to that was bounded to OM, with 16.5% and 10.1%, respectively. Zn distribution in the AG and RA land uses had the same trend: Residual>bounded to Fe-Mn oxides>bounded to OM>bounded to carbonate>exchangeable fraction. Whereas, Zn distribution showed different trend in UR land use as bounded to Fe-Mn oxides>residual>bounded to carbonate>bounded to OM>exchangeable fraction. Pb distribution was different in each land use. Pb showed similar distribution to Zn in UR. In AG and RA land uses residual fraction of Pb was measured as highest value while other fractions of Pb had these distributions: Pb bounded to carbonate>bounded to Fe-Mn oxides>exchangeable >bounded to OM fraction in AG land use and Pb bounded to Fe-Mn oxides>bounded to OM>bounded to carbonate>exchangeable fraction in RA land use.
Conclusion: Based on the results of this study, Cr, Co, Ni, Mn and Fe magnitudes are uneven in soils. The total heavy metal concentrations fractionation can provide information on the contaminant metals sources. High levels of exchangeable fractions, acid soluble and easily reducible perhaps indicates anthropogenic activities. Naturally, Chemicals are associated to resistant soil fractions such as oxy hydroxides, organic matter and sulfides. In soil fractionation, the contribution of each fraction in soil was a function of metal type and land uses. Those metals were affected by anthropogenic activities such as lead, zinc, and partly copper, showed the highest percentage in the fraction that influenced by external input sources. Those were characterized by lithogenic origin (cobalt and nickel) was mainly found to be highest in residual fraction. However, in all metals, those fractions affected by anthropogenic activities (non-resistant fractions) were much more in urban land use than agriculture and rangeland ones.
A. Afshari; H. Khademi; P. Alamdari
Abstract
Introduction: Soil forms a thin layer over the surface of the earth that performs many essential life processes . Soil has always been important to humans and their health, providing a resource that can be used for shelter and food production. Higher heavy metals concentration within soils has beenshown ...
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Introduction: Soil forms a thin layer over the surface of the earth that performs many essential life processes . Soil has always been important to humans and their health, providing a resource that can be used for shelter and food production. Higher heavy metals concentration within soils has beenshown to be toxic for human bodies, since they might be broken out easily via dust or direct contact through trophic levels. In addition long term heavy metals recalcitrance in soil results in low potential of soil productivity . Heavy metals interact complicatedly in soil. The present study was conducted in large scale by analyzing elements Mn, Co, Ni, Zn, Pb, Cd and Cu in soils in central lands of Zanjan province. The main objectives of present research were to investigate heavy metals diffusion and total contamination status in soil and determination of their possible origin using multivariate analysis.
Materials and Methods: This research was conducted in central lands located in Zanjan province (northwest of Iran). In terms of the main land uses, study area may involve farmlands, rangelands, urbanized and industrial lands. Study sites are totally covered 2000 km2 in coordinates of 36.20 to 36.41 N latitude and 48.19 to 48.53 E longitude. Sampling was conducted based on gridding method in randomized manner in August 2011. Urban lands affected by much anthropogenic activities and farm and rangelands together were placed in grids of 1.5×x 1.5 and 3×3 km2 respectively. Totally number of 241 soil samples (0-10 cm depth) was taken. Soil specimen's digestions were conducted using nitric acid 5 normal. Total elements concentration of Pb, Zn, Ni, Mn, Cu, Cr, Fe and Co were measured using Atomic adsorption device Perkin-Elmer: AA 200 and Cd concentration was determined by Atomic adsorption device equipped with graphic furnace model Rayleigh: WF-1E. Mean separation analysis of parameters (Pearson and spearman) was conducted using Duncan test in probability level of 5%. Principle component analysis (PCA) and hierarchical cluster analysis (HCA) were used to classify metals group. Achieving a simple structure and better results interpretation, data rotation in varimax type was conducted in PCA algorithm. Before cluster analysis, data were standardized and subsequently exposed to cluster analysis and plotting dendrogram, Euclidean approach was applied.
Results and Discussion Multivariate analysis (PCA, CA and CM) have been shown as an efficient tool to identify heavy metals origins, helping us in better data comprehension and interpretation. Results obtained on multivariate analysis approaches might are promising to distinguish polluted area and heavy metals potential origin, in turns indicating soil environmental quality.
PCA is known as an efficient method to determine anthropogenic impacts on a spatial scale and it may be essential to specify heavy metals contamination degree in respect to anthropogenic and litogenic contribution. As it illustrated, heavy metals are categorized in three-component model framework, accounting for 67% of total data variations. In rotated component matrix the first PC (PC1, 30% of variance) involves Ni, Cr, Co, Mn and Fe, while the second PC (PC2, 19% of variance) involves Zn and Pb and eventually the third one (PC3, 18% of variance) covers Cu and Cd among others. PC1 can be introduced as geological component because of its less coefficient of variations than others, skewedness less than 1 and normalized data status. It denotes lithogenic distribution of these metals in area. Furthermore,as above mentioned, the average heavy metalconcentrations werefound to be less than calculated background threshold. Because of their increased concentration in soil, high coefficient of variations and very high concentration than background threshold level as well as positive skewedness in heavy metals, PC2 and PC3 can be defined to antropogenical components. Atmospheric precipitation (deposition) serves as one of the main anthropogenic source of heavy metals pollution in the soil samples near theintense transportation traffic roads, accumulation site of factories solidwaters, energy generation process, metal melting, construction and traffic breaking out in whole area. Our results are in line with enormous findings on farming operations as the main factor that cause changes in Cd concentration in soils. although Pb, Cu, Zn and Cd have been shown to have anthropogenic origin inputs, however in respect to PCA analysis, the main origins for Lead and Zn may be municipal and industrial operations specially Pb processing factory as well as industrial complexes. At the same time, Cu and Cd stems from farming operations as well as municipal activities. The main municipal input origins for elements Pb, Cu and Cd include all components used in automobile industry, batteries, engines oils, fossil fuels and construction materials (like cement).
Cluster analysis is used to classifying those samples having common and similar characteristics as well as evaluating information obtained from PCA analysis. Cluster analysis gave the same groups. So two majororigins can be identified. First (CI) involves prior interpreted lithogenic elements (Cr, Co, Mn and Fe), while two later clusters (C2, C3) contain anthropogenic elements (Pb, Cu, Zn and Cd). Many researchers believed that Mn, Cr, Ni and Fe are controlled by parent material. In contrast, they attributed any increases of Pb, Cu, Cd and Zn accumulation to anthropogenical operations. Cluster analysis gives the same results as derived from PCA, enabling us to identify two major origins on which heavy metals break out hence, multivariate analysis results confirms the presence of two different heavy metals origins within soils.
Conclusion: The aim of this research was to provide some preliminary information on heavy metals (Pb,Zn,Cd,Cu,Ni,Co,Cr,FeandMn) contamination status in soils in Zanjan province. Metal contamination cannot be assessed by common metal concentration test, hence useful and promising tools were applied to evaluate heavy metals pollution. The highest level of heavy metals pollution and accumulation was related to Cd, Pb and followed by then Cu. Multivariate analysis showed that Fe, Mn, Cr, Co and Ni are controlled by parent materials, while Pb, Cu and Zn originate from anthropogenic sources. In the second class, anthropogenic activity did not seem to significantly affect their accumulation which is strongly supported the lithogenicaly origin of these heavy metals in this study.
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
