جستجوی مقالات مرتبط با کلیدواژه « heavy metal » در نشریات گروه « محیط زیست »

The chemical precipitation using lime, caustic soda and soda ash was investigated for the simultaneous removal of Cu and Zn from copper mine industrial wastewater by conducting jar tests in the present study. Jar experiments were performed with a set of polyethylene beakers (500 ml) in order to investigate the effect of two reaction parameters (precipitant doses and initial pH) on the removal of heavy metals. X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) equipped with X-Ray Energy Diffraction Spectroscopy (EDX) were used to identify the important chemical compounds and to study the surface morphology, chemical composition and particle size of the sludge samples. An increase in the removal of Cu and Zn was observed by increasing the precipitant dose (10-400 mg/L) for each reagent used. Removal efficiency of 90% were obtained for both heavy metal ions. The chemical precipitation efficiency was affected by pH. At high final pH levels (8<pH<10), Cu had higher removal efficiency than Zn by all precipitating agents. In the sludge produced, Zn and Cu were precipitated as amorphous hydroxides including Zn(OH)2 and Cu(OH)2. SEM images showed that the produced sludges have small size and compact structure. EDX analysis determined that in all sludge samples, the content of Cu was higher than Zn. Effluent treatment with soda ash resulted in the sludge production with lower volume and larger particle size. As a result, the use of this precipitating agent can be less expensive for sludge drying steps.

The use of nanoparticles in various industries has led to the release of very large amounts of these materials in the environment, and therefore, its spread in nature has increased the likelihood of their impact on organisms. In this study, the simultaneous and separate effects of mercury ions with/without silver nitrate and silver nanoparticles on Artemia salina were investigated. For this purpose, A. salina was grown in vitro and A. salina nauplius was exposed to different concentrations of silver nanoparticles and mercury ions and its mortality rate was evaluated after 24 and 48 hours. The effects of these contaminants on the fatty acid profile of A. salina were also evaluated. A. salina losses were reduced by simultaneous exposure of mercury and silver nitrate and simultaneous exposure of mercury and silver nanoparticles due to the mercury uptake by silver nitrate and silver nanoparticles, and the effect of mercury toxicity was reduced and mercury caused fewer losses in simultaneous exposure. Also, in the study of A. salina fatty acid profile in comparison with separate mercury treatment, a decrease in SFA fatty acids in the simultaneous exposure of mercury and silver nitrate to the amount of this type of fatty acids in the control was observed. In addition, the amount of MUFA fatty acids in the simultaneous exposure of mercury and silver nitrate was significantly higher than the control (P˂0.05). In conclusion, toxicity effects of mercury on the artemia was reduced in simultaneous exposure to silver ions and nanoparticles compared with the separate exposure, indicating the necessity of paying more attention to the contaminants interactions in aquatic ecosystems and the effects of this interaction on the contaminants bioavailability and toxicity.

In this paper, the preparation of nano zeolite was carried out at different grinding times using a dry planetary ball mill. Sodium Hexa Meta Phosphate (SHMP) was introduced as the dispersant in the milling of natural zeolite adsorbent. In the next step, to remove and adsorb heavy metal ions such as nickel, copper, and cadmium, the application of nano zeolite was studied in batch mode.

In this paper, zeolite nanoparticles were produced using planetary and ball mills. Adsorption experiments were conducted to investigate the adsorption of nickel, copper, and cadmium using new nano zeolite adsorbent. 

The effect of Sodium Hexa Meta Phosphate (SHMP) on grinding and adsorption of ion metals by nano zeolite was investigated and results showed that the application of SHMP led to lower energy consumption in grinding and had a positive effect on nickel and cadmium removal from aqueous solution by nano zeolite particles.

The effect of sodium hexametaphosphate on the absorption of nickel, cadmium, and copper metals showed that this reagent had a positive effect on the absorption of nickel and cadmium ions on nanozeolite particles, but it did not affect the absorption of copper ions. Nano-zeolites have a larger external surface area and a shorter diffusion path length due to having nano-sized particles, so their absorption capacity is very high.

Industrial plating wastewater contains various types of detrimental heavy metals in high concentrations. One of this toxic metal is Nickel that its discharge into the surface waters and soil is considered as an environmental problem. Hence removing of this metal from wastewaters is crucial and vital for protecting the environment and human health. Applying of nanotechnology in elimination of environmental contaminants is one of the methods which attracted a great deal of attention in recent years. In present research, nanographite was utilized as efficient adsorbent in order to remove Ni ions.

In order to investigate the adsorption process, nanographite with a purity of 99.9% and a specific surface area of ​​18-24 m2/g and a plate morphology was prepared from Pishgaman Iranian Nanomaterials Company and used as an adsorbent. Also, the wastewater used in the experiments was prepared from one of the plating workshops in Tehran, which contained 765 mg/L of nickel and a pH of about 1. The parameters of pH, time and amount of adsorbent were evaluated. In each experiment, one of the parameters was considered variable and the other two parameters were considered constant. The amount of nickel was determined before and after each test.

In this study, the parameters including pH, adsorption time and adsorbent dosage were investigated as effective factors on Ni adsorption process. In order to analyze the adsorption mechanism, the obtained results were examined by the Langmuir and Fruendlich isotherm models. In addition, pseudo-first-order and pseudo-second-order models were studied to investigate adsorption kinetics. According to the results, the Ni uptake by nanographite was enhanced significantly with increasing of the pH value from 5 to 7. Thus the pH of 7 was determined as optimum pH for Ni removal. Investigations also showed that increasing the time up to the first 80 minutes had a relatively good effect on nickel adsorption by the nanoparticle, and after that the adsorption almost reached equilibrium. Finally, it was observed that in a constant time, increasing the amount of adsorbent led to an increase in adsorption, and to achieve the maximum adsorption of nickel, the amount of 2g was chosen for the adsorbent. Based on the obtained results, 97.52% primary nickel was adsorbed by nanographite. Results also revealed that the data were best fitted to the Fruendlich models. After determining the amount of nickel adsorption at different times, the resulting data were analyzed by the kinetic model.Kinetic studies also indicated that the adsorption data were described well by pseudo-second-order model.

Examining the results showed that pH plays an important role in the adsorption process and the adsorption rate increases with increasing time until the equilibrium time is reached. One of the effective factors is the amount of adsorbent, which has a direct effect on adsorption. Following the Freundlich isotherm in this research indicates that the adsorption sites in the adsorbent have different energies. Also, the pseudo-second-order model in adsorption kinetics refers to the process of chemical adsorption in addition to physical adsorption.

With the increase in population and the expansion of cities and their transformation into the heterogeneous population and social centers, various types of environmental pollution have been created, causing damage to the city and the excessive growth of cities. Therefore, with the increase in human activities along with the rapid expansion of urbanization in the past few decades, scientific monitoring of important industries is highly needed. When there are several pollutants in the air together, they stimulate each other's effect and have a more aggravating effect and finally multiply the damage caused to living beings, especially plants. In general, one pollutant may create the conditions for the impact of another pollutant, and in this situation, the organisms or the plant as a defenseless organism will be stressed, but which pollutant has the most significant impact on the organisms cannot be easily determined. Pollution in each of the water and soil sources is one of the serious problems that is inseparable from daily and modern civilization. According to international standards, heavy metals are known as the most dangerous group of contaminants created by humans due to their high toxicity and lethality, as well as their high persistence in the environment. Based on this, industries have a high pollution load, especially the release of suspended particles and heavy metals into the surrounding environment, which should be considered with special care in terms of their establishment and exploitation in order to avoid any risks and adverse effects on humans and other organisms. Therefore, the aim of this study was to investigate the environmental effects of the important industries of Shazand city on the surrounding environment.

Shazand city is very important due to the presence of major industries such as gasoline refinery, petrochemical, and thermal power plant, being located on the west and south transit routes, and the national north-south railway line of the country. Therefore, this research was conducted with the aim of creating environmental concerns in the field of pollution caused by metals (including Cu, Zn, Mg, Fe, Cd, Pb, Cr, and Co) in the soil and plants within a five-kilometer radius of important industries in Shazand city. For this purpose, soil samples from a depth of 0-30 cm and plant samples from green areas (pine trees), fruit orchards (leaves and fruits of walnuts and almonds), wheat fields (including samples of roots, stems, leaves, and seeds), pastures (mountain rye (Secale montanum. L) and Euphorbia (Euphorbia helioscopia. L)) were prepared. From each of the tested ranges, 10 samples were selected and tested. A sampling of plants, soil, and water was done based on a random systematic method and the study area was divided into 5×5 km square grids. By examining the area, the areas where the intensity of land use was high or low, grid spacing of 2.5×2.5 square kilometers was selected for sampling. Extraction to determine the concentration of heavy metals in the soil was also done by HCl and HNO2 digestion methods. The concentration of heavy elements was measured using an atomic absorption device and a graphite furnace.

The test results showed that the concentration of Cd, Pb, Co, and Cr in all the studied soils was higher than the permissible limit. Also, the concentration of Fe, Cu and Cr, Cd, and Co in all plant samples of green spaces, gardens, and pastures was beyond the allowed concentration. Although the concentration of Cr and Co in wheat grain exceeded the permissible limit, they were not in the critical range. From the analysis of the concentration of elements in the soil of each vegetation cover, it was found that the highest values of the transfer coefficient were observed in the soil of wheat fields, pastures, orchards, and green spaces, respectively. The concentration of elements in the soil of each vegetation cover was determined, and the highest ecological risk index was obtained in the soil of pastures, orchards, wheat fields, and green spaces, respectively. However, in all the sampled soils, the index value was calculated to be less than 150, which indicates the low ecological risk of the measured elements in the sampled soil. Based on the results, the transfer factor of manganese and cadmium was measured more than once, and these results indicate the bioaccumulation of these metals from soil to plants, and for the rest of the measured metals, this amount was calculated to be less than one. Based on this, it was reported that the transfer factor in gardens and pasture plants was higher than in wheat in the investigated area. The reason for this was the permanent presence of these plants in the region. Another noteworthy point was the accumulation of these elements in the seeds or fruits of plants, which was observed more than in other plant organs.

Due to the increasing importance of food, in recent years, the attention of the public and regulatory organizations in the food sector, especially the World Trade Organization, has been seriously focused on food safety and quality assurance. Based on the results obtained:In pine leaves, the concentration of Cu, Co, Cd, Mg, and Cr elements exceeded the permissible limit, and only the concentration of Cu, Mg, and Cr elements was in the critical concentration range. In walnut leaves, the concentration of Cu and Cr elements exceeded the permissible limit and was in the critical concentration range, but the concentration of Cd and Co exceeded the normal limit. In almond leaves, the concentration of Cr and Co was higher than normal.In almond fruit, the concentration of Cr, Co and Cd elements was higher than normal, but it was not in the critical concentration range. In the investigation of the concentration of elements in wheat grain, it was found that the concentration of Cr and Co elements exceeded the permissible limit, but it was not in the critical range.The concentration of Cu, Co, Cd, and Cr elements in mountain rye and Euphorbia plants exceeded the permissible limits and were in the critical range. However, in mountain rye, the concentration of Cr element was higher than its normal level in plants and was in the critical range. The values of transfer factor were observed in the soil of wheat fields and pastures respectively higher than garden soil and green space. Also, the risk assessment index was obtained in the soil of pastures and orchards higher than wheat lands and green spaces, respectively.

This study was carried out to investigate the concentration of heavy metals of Ni, Cd, Pb, As, Fe, Cr in municipal sewage discharge, urban wastewater and industrial effluent are pumped to the Tembi River. Sampling carried from 10 water and wastewater and 10 sediments. The results of ICP-MMS analysis showed the mean concentration (in ppm) for water sample for As 1/23, Zn 17/71, Cr 0/8, Ni 1.11, Cd 0.09, Pb 6/35, Fe 132/50 and mean concentration of heavy metals in sediment sample for As 0.91, Zn 23/96, Cr 91/50, Ni 56/10, Cd 0/16, Pb 10/40, Fe 14950. Based on the results obtained from the index of enrichment factor, Ni and Cr concentration showed the medium to high pollution level. Based on the molar accumulation land index, Ni and Zn concentration were in the range of moderate to high levels of pollution, and is highly contaminated in all areas with high Fe concentrations. Based on the pollution load factor sediment, It is contaminated with Ni, Cd, Fe and Cr. Based on contamination coefficient at point SA-02 the concentration of Pb and Zn in the sediment is high and As is also contaminated in site C and Ni, Cd, Fe and Cr concentration is high and the sediment is contaminated but there is no heavy metal contamination elsewhere. Tembi River receives untreated municipal and industrial wastewater. According to the results obtained, the Tembi River is in a danger and unsafe area for fishing and swimming purposes.

Heavy metal pollutants in water source sediments are a serious environmental concern in aquatic ecosystems. Sediments collect different amounts of metals and are both a source and a reservoir of heavy metals in aquatic ecosystems. In this study, four heavy metals, including nickel, lead, mercury, and cadmium, were collected and examined from the surface sediments of Bandar Imam (Ghanam Estuary, Zangi Estuary, Petrochemical Estuary, and Ahmadi Estuary). Increased industrial and petrochemical activities in Mahshahr and Imam Khomeini ports have led to an increase in pollutants, most of which enter the waters of the Persian Gulf. The amount of sediment contamination to metals was compared with international standards. Then, the amount of sediment contamination was compared between different estuaries in the region. Surface sediment sampling was performed using the Vane Veen grab method. All four heavy metals were identified in all sampling sites with concentrations higher than the standard value based on correlation analysis and principal component analysis. The results show that the concentration of some metals in sediments is higher than the limits set by the standards. Their mean concentrations decreased by Ni>Pb>Cb>Hg. Contamination in Khor Petrochemicals seems to be more serious, probably due to the contamination source's proximity to a point where there is a very high ecological risk and must be carefully surveyed and corrected. The data analysis showed that lead and cadmium originate mainly from human activities (industrial effluents). Due to their location, the waters of the Mahshahr and Khor Musa regions, which are the location of many petrochemical plants, are directly and indirectly exposed to organic and mineral pollutants. Organic matter and particle size are the main factors influencing the distribution of heavy metals in the sediment. More organic matter and smaller particle sizes result in settlement of heavy metals in the sediment.

Caspian forest of Iran with an area of approximately 1.8 million hectares with more than 80 species of trees and 50 species of shrubs have been identified as the oldest forests in the world which belong to the third geological period. Increasing growth of human population and the development of industries to response of its demands, cause to production of various types of waste. Select landfill without regard to environmental issues poses many threats to the environment, choosing the right place and location for landfill is essential. Accumulation of waste in the forest increases heavy metals such as lead, cadmium, nickel and chromium. Some trees are very sensitive to leachate from sewage and dry out quickly. Hyrcanian forests are one of important reserve habitat in our country. There are many various natural and human threats on it that cause many problems in its ecosystem. One of these threats is landfill forest. Also, the lack of effective studies to determine the negative effects of landfills on forest ecosystems, the purpose of the present study identifies the negative effects of landfills in forest areas in Zarandin region of Neka city.

The purpose of this study is to investigate the effect of landfills in forest lands on heavy metals (lead, cadmium, nickel and chromium) and tree species in Zarandin region. The study area is a forest ecosystem around Zarandin landfill with an area of about 26 hectares located 9 km southeast of Neka city. The important tree species and shrubs of the area can considered to Zelkova carpinifolia (Pall.) k.koch, Parrotia persica C.A.Mey , Quercus castaneifolia C.A.Mey, Carpinus betulus L., Acer velutinum Boiss, Alnus subcordata C.A.Mey ,(Acer cappadocicum Gled ,Diospyros lotus L., Mespilus germanica L, Crataegus microphylla k.koch , Prunus divaricate Ledeb. Along the leachate channel, 10 sampling stations were selected up to a distance of 1000 meters from the landfill. Stations were chosen at intervals of 100 meters along the channel. each sampling station includes of two points; one point at the edge of the channel and the second point at a distance of 20 meters from the channel. Soil samples were taken with three replications. A forest area adjacent to the landfill with similar environmental and floristic characteristics but far from the direct impact of the landfill was selected as a control area. in the control section 10 samples were taken. At each station, soil samples were prepared for laboratory operations. Vegetation inventory were also performed in all plots. The selected plots were similar in terms of slope, general direction and height to minimize the impact of environmental conditions and topography on the comparisons. Plots 20 × 20 m were used to study tree and shrub species and plots 1 *1 m were used to analysis of tree species generation and grass coverage.Determination of heavy metal concentrationsSoil samples were tested to determine the concentrations of the heavy metals lead, nickel, cadmium and chromium. For chemical analysis, the concentration of heavy metals in the soil is weighed 1 gram of each sample dried by a digital scale and poured into Erlenmeyer containers. Then 10 cc of concentrated nitric acid is added to it and placed on a digester (Hot block digester) and placed at a low temperature of 130 ° C for 1 hour and then 400 cc of hydrogen peroxide is added to it. Samples are filtered with S&S filter paper in 50cc c-balloons and the filtered solution is reduced to 50cc using deionized water and poured into plastic containers (Heinrichs et al., 1986).Enrichment factorIn order to investigate and evaluate soil contamination in the study area, the results of heavy metal analysis with NFSI index (Utermann et al., 2019) were compared and the enrichment factor of all samples was calculated.The concentration of elements compared to the normal concentration was measured using the enrichment factor. The following equation was used to calculate this factor.EF = Se / ReEF is the enrichment factor, Se is the concentration of elements in the soil and Re is the concentration of elements in the reference material. The classification of enrichment factor values in determining the degree of contamination is given in the table below (enrichment factor value classification table) (Bhuiyana et al., 2010).Table 1: Classification of enrichment factor valuesFactor amount Pollution degreeNo pollution 0No pollution to moderate pollution 1moderate pollution 2Medium to strong pollution 3strong pollution 4strong pollution to Very strong pollution 5Very strong pollution 6The results showed that the pH and EC in the soil of the contaminated area increased and the concentration of all studied metals in the contaminated area compared to the control area showed a significant difference (P <0.05). The density of Parrotia persica, Carpinus betulus and Zelkova carpinifolia in the infected plot was lower than the control plot. Quecus castanifolia did not show a significant difference but the number of Acer sp in the infected area showed a significant increase. Also, reproduction of Carpinus betulus, Quecus castanifolia and Zelkova carpinifolia in the infected area, a significant decrease and Parrotia persica and Acer regeneration in the infected plot showed a significant increase.

Finally, the results of this study showed that the acidity, concentration of lead, nickel, chromium, cadmium in the soil of the landfill and its margin was significantly higher than the soil of the control area. Soil factors such as pH and EC was high in soil samples in infected area. Also, the results of density of tree and shrub showed that the difference in species density between infected and control plots was significant in all species except Quecus castanifolia. The number of Parrotia persica and Carpinus betulus and Zelkova carpinifolia tree stocks showed a significant decrease in the infected area.Finally, the results of this study showed that municipal waste landfilling has significant effects on the chemical properties of forest soil, so providing the necessary facilities for waste management such as waste incinerators and compost factories in these areas is necessary. It is also necessary to conduct more extensive studies in order to obtain comprehensive information for optimal forest management and reduction of pollution and its spread in forest areas.