فهرست مطالب

Pollution - Volume:5 Issue:4, 2019
  • Volume:5 Issue:4, 2019
  • تاریخ انتشار: 1398/06/11
  • تعداد عناوین: 18
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  • S.N.B. Ukoh *, M.O. Akinola, K.L. Njoku Pages 687-699
    Soil contamination by heavy metals has increased noticeably within the past years. Unlike organic compounds, metals cannot degrade; therefore effective cleanup is required to reduce its toxicity. This experiment was undertaken to investigate the comparative potential of Panicum maximum and Axonopus compressus to bioremediate zinc polluted soils, the impact of Zn on the antioxidant defense system of the plant, assaying for activities of antioxidants proteins. Zinc salts were mixed with soil at various concentrations 5 mg/kg, 10 mg/kg, 20 mg/kg and 40 mg/kg in triplicates and control was setup. After 4 months, the plants (root, shoot and leaf) and soil were analyzed for morphological, biochemical parameters and Zn concentration. The root length of P. maximum and A. compressus decreased as the concentration of zinc increased. The least shoot length inhibition of A. compressus was 6.16% (5 mg/kg) while the highest shoot length inhibition was 40.14% (40 mg/kg). The least shoot length inhibition of Panicum maximum was 6.16% exposed to 5 mg/kg and the highest shoot length inhibition was 53.13% (40 mg/kg). There was significant reduction of the heavy metals in vegetated soils for P. maximum and A. compressus at the end of the study compared to the heavy metals in the soils at the beginning of the study (p<0.05). P. maximum, is a better removal of Zn than A. compressus, however, it was not significant. Glutathione levels varied significantly (p≤ 0.05) with respect to heavy metals. A. compressus has more effects on Glutathione activities than P. maximum. Zn caused a decrease in metallothionein level in P. maximum while A. compressus metallothionein level increased.
    Keywords: Remediation, Zinc, contaminated soil, enzymes, organic matter
  • M. Khatun *, A. K. M. R. Alam Pages 701-707
    The experiment was performed to evaluate effect of heavy metals on total phytoplankton load (TPL) using water of Turag River adjacent to Ashulia locating on the north-eastern side of Dhaka city, Bangladesh. Total phytoplankton load comprises of Euglena sp., Borodinella sp., Pediastrum biradiatum, Pinnularia sp., Fragillaria sp., Fragillaria crotonensis, Gloeocapsa sp., Navicula sp., Cynedra sp., Crucigenia sp., Chlorella sp., Spirogyra sp., Phacus acuminatus, Phacus circulatus., Nitzschia sp. and Nitzschia clausii. Phytoplankton load showed the abundances Bascillariophyceae (43.75%) > Chlorophyceae (37.50%) > Euglenophyceae (18.75%). The average maximum growth rate (log transformed) of TPL in control culture was -0.25μg/l and treated cultures using 1ppm, 3ppm, 5ppm, 7ppm concentration of heavy metals (Zn and Cu) were 0.03 μg/l, 0.03 μg/l, -0.11 μg/l and -0.26 μg/l, respectively. In treated culture using 1ppm concentration of heavy metals (Zn and Cu) the growth rate of phytoplankton load increased significantly whereas the growth rate decreased at higher concentrations (3ppm, 5ppm and 7ppm) of heavy metals. The implication of this finding can be used to monitor health of riverine ecosystems and management of river pollution.
    Keywords: phytoplankton, biovolume, Zn, Cu, Pollution
  • A. Dejaloud, A. Habibi *, F. Vahabzadeh, E. Akbari Pages 709-719
    The present study focuses on effects of initial pH on dibenzothiophene (DBT) desulfurization via 4S pathway by growing cells of Ralstonia eutropha. For so doing, temporal changes of biomass concentration, glucose as a sole carbon source, pH value, and 2-hydroxybiphenyl (2-HBP) formation have been monitored during the bioprocess. The biomass concentration has been modeled by the logistic equation and results show that the values of maximum specific growth rate (μmax) and maximum cell concentration (Xmax) have increased in line with the rise of initial pH from 6 to 9. This confirms the effect of pH on the energetics of cell growth via altering the proton gradient and manipulating ATP-related metabolic pathways. By considering the Pirt’s maintenance concept, the bioenergetic aspects of DBT desulfurization process are affected by changes in pH, where the maximum specific DBT conversion rate (0.0014 mmol/gcell.h) has been obtained at initial pH of 8. Additionally, the kinetic modeling of the 2-HBP formation through the Luedeking-Piret model indicates that the DBT desulfurization rate is linearly related to the cell growth rate, instead of biomass concentration. The growth associated and non-growth associated 2-HBP formation constants have been obtained 3.82 mg2-HBP/gcell and 0.06 mg2-HBP/gcell.h, respectively at an initial pH of 8.
    Keywords: pH effect, logistic equation, Luedeking-Piret model, Pirt concept
  • C. K. Thakur, M. Chaudhary, S.E.A.T.M. Van Der Zee, M. K. Singh * Pages 721-737
    The transport mechanism of contaminated groundwater has been a problematic issue for many decades, mainly due to the bad impact of the contaminants on the quality of the groundwater system. In this paper, the exact solution of two-dimensional advection-dispersion equation (ADE) is derived for a semi-infinite porous media with spatially dependent initial and uniform/flux boundary conditions. The flow velocity is considered temporally dependent in homogeneous media however, both spatially and temporally dependent is considered in heterogeneous porous media. First-order degradation term is taken into account to obtain a solution using Laplace Transformation Technique (LTT) for both the medium. The solute concentration distribution and breakthrough are depicted graphically. The effect of different transport parameters is studied through proposed analytical investigation. Advection-dispersion theory of contaminant mass transport in porous media is employed. Numerical solution is also obtained using Crank Nicholson method and compared with analytical result. Furthermore, accuracy of the result is discussed with root mean square error (RMSE) for both the medium. This study has developed a transport and prediction 2-D model that allows the early remediation and removal of possible pollutant in both the porous structures. The result may also be used as a preliminary predictive tool for groundwater resource and management.
    Keywords: ADE, Aquifer, Solute, Analytical solution, Numerical Solution
  • P. Pakrooh *, E. Pishbahar Pages 739-747
    The present study aims at developing a forecasting model to predict the next year’s air pollution concentrations in the atmosphere of Iran. In this regard, it proposes the use of ARIMA, SVR, and TSVR, as well as hybrid ARIMA-SVR and ARIMA-TSVR models, which combined the autoregressive part of the autoregressive integrated moving average (ARIMA) model with the support vector regression technique (ARIMA-SVR). The main concept of generating a hybrid model is to combine different forecasting techniques so as to reduce the time-series forecasting errors. The data used in this study are annual CO2, CO, NOx, SO2, SO3, and SPM concentrations in Iran. According to the results, the ARIMA-TSVR Model is preferable over the other models, having the lowest error value among them which account for 0.0000076, 0.0000065, and 0.0001 for CO2; 0.0000043, 0.0000012, and 0.000022 for NOx; 0.00032, 0.00028., and 0.0012 for SO2; 0.000021, 0.000014, and 0.00038 for CO; 0.0000088, 0.0000005, and 0.00019 for SPM; and 0.000021, 0.000019, and 0.0044 for SO3. Furthermore, the accuracy of all models are checked in case of all pollutants, through RMSE, MAE, and MAPE value, with the results showing that the hybrid ARIMA-TSVR model has also been the best. Generally, results confirm that ARIMA-TSVR can be used satisfactorily to forecast air pollution concentration. Hence, the ARIMA-TSVR model could be employed as a new reliable and accurate data intelligent approach for the next 35 years’ forecasting.
    Keywords: Accuracy, ARIMA, Predict, TSVR
  • M. Ruhela, R. Bhutiani, F. Ahamad *, D.R. Khanna Pages 749-760
    The present study aims to identify the impact of polluted aquatic body i.e. River Hindon on two selected riparian flora i.e. Azadirachta indica and Acacia nilotica. During the course of study the average concentration of different metals in river water was found as Iron (Fe) 11.27ppm±3.50, Manganese (Mn) 4.00ppm±1.26, Cadmium (Cd) 0.08ppm±0.07, Nickel (Ni) 0.63ppm±0.17 and Zinc (Zn) 1.46ppm±0.38 respectively. The average concentration of heavy metals in A. indica of sampling site was found as Iron (Fe) 24.76ppm±6.25, Manganese (Mn) 5.04ppm±1.38, Cadmium (Cd) 0.05ppm±0.05, Nickel (Ni) 0.34ppm±0.20 and Zinc (Zn) 53.92ppm±19.29 respectively while in control site plant average concentration was found as Iron (Fe) 17.18ppm±3.96, Manganese (Mn) 3.63ppm±1.63, Cadmium (Cd) 0.02ppm±0.03, Nickel (Ni) 0.16ppm±0.06 and Zinc (Zn) 31.26ppm±12.11 respectively and average concentration in A. nilotica of sampling sites was found as Iron (Fe) 45.78ppm±10.67, Manganese (Mn) 42.08ppm±11.98, Cadmium (Cd) 0.59ppm±0.51, Nickel (Ni) 40.83ppm±12.16 and Zinc (Zn) 144.10ppm±49.94 respectively while average concentration in control site plant was found as Iron (Fe) 27.76ppm±9.49, Manganese (Mn) 22.75ppm±7.09, Cadmium (Cd) 0.42ppm±0.27, Nickel (Ni) 23.53ppm±8.02 and Zinc (Zn) 96.61ppm±24.78 respectively. One way ANOVA shows statistically significant difference between sampling site plant and control site plant for all the studied metals except Cr in A. nilotica F (3, 42) = 0.589, P= 0.626. A big difference was found in the concentration of metals between sampling site plants and control site plant. In case of metal uptake A. nilotica was found more efficient as comparison to A. indica.
    Keywords: Riparian vegetation, terrestrial ecosystems, sluggish flow, A.nilotica, A. indica
  • M.D. Salam *, A. Varma Pages 761-774
    The ever increasing pile-up of electronic waste in dumping sites, especially in developing countries such as China, Pakistan, India and several African countries, might have caused a significant alteration in the microbial community of the contaminated sites. This change in the microbial population may have significant impact to the soil ecology function. The major pollutants of electronic waste are heavy metals like cadmium, lead, nickel, mercury, hexavalent chromium, arsenic and persistent organic pollutants like polychlorinated biphenyls and polybrominated diphenyl ethers. In general, the toxic pollutants reduce the normal soil microbial biota but give rise to increase in the heavy metal resistant and organic pollutants remediating microbes. With the development of culture- independent approach as a tool for studying microbial diversity, the microbial community structures in toxic waste contaminated sites have been revealed gradually. Studies on the microbial community structure of electronic waste contaminated sites show that there are significant differences between the contaminated and the non-contaminated sites. Soil pH in the e-waste contaminated sites of various regions has been reported in a wide range varying from pH 4 to pH 12. However, the predominant phyla so far identified in the electronic waste contaminated sites, based on studies through culture independent approach, are Firmicutes, Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Crenarchaeota and Bacteroidetes accounting for more than 80% of the total sequence reads on an average. The genera like Pseudomonas, Bacillus, Clostridium, Rhodococcus, Achromobacter and many unclassified bacteria are the common types in the contaminated sites.
    Keywords: Electronic waste, Microbial community, Microbial diversity, Heavy metals, Organic pollutants
  • F. Loghmani, N. Mirghaffari *, M. Soleimani Pages 775-788
    Management of solid wastes is considered as an economic and environmental issue in the building stone industry. The current study uses raw and calcined calcareous sludge, generated in the stone cutting factories, in order to remove sulfur dioxide. Sludge characterization has been performed, using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analyses. The removal experiments of sulfur dioxide have conducted under different humid contents and adsorbent doses. The results showed that the higher the adsorbent dosage and humidity content, the greater the SO2 adsorption.. The calcination process at temperatures of 400, 500, 600, and 700℃ revealed that with rising calcination temperature and humidity content, the adsorbent capability is enhanced considerably. This method could be developed for the management of stone sludge produced from the stone cutting industry through its conversion into an effective and low-cost adsorbent for desulfurization process.
    Keywords: Adsorbent, adsorption, Calcination, Air pollution
  • A. Pardakhti *, M. Ebrahimi Qadi Pages 789-801
    The city of Tehran undergoes an increasing growth in population as well as industrial activities, both of which increase the concentration of air pollutants. The current research tries to turn a limited and focused system of air contamination measurement and control to an unlimited and extensive one that examines the concentration of each of the contaminants in any area of Tehran. Accordingly, information from twenty air-pollution measurement stations at certain points of the city helps measuring the concentrations of contaminants like SO2, NO2, CO, O3, PM2.5, and PM10 throughout a year on a daily basis. The index of AQI has also been used as the air quality index to determine the level of pollution in the city. Using ARC-GIS software, the AQI or the air quality index has been zoned and a comprehensive map, designed. Moreover, in order to illustrate this map, a map of the zoning has been drawn up for this purpose on December, 26, 2016, considered an unhealthy day in Tehran, the results of which show that only 27.8% of the city is unhealthy and the rest of the city does not fall in unhealthy area. However, due to the lack of a comprehensive map for determining the AQI in different parts of the city, the whole city closes down, leading in an economic loss of about $ 1 million a day for the city.
    Keywords: Air pollution modeling, Monitoring system, Air pollution management
  • G. Dutta, S. Gupta *, A. Gupta Pages 803-819
    Present study aims to unravel the hydro geochemical interaction of sediment and water of Saheb bandh lake, West Bengal, India with an emphasis on heavy metal assessment. Lake water belongs to Ca2+–HCO3− type hydro geochemical faces and water-rock interaction primarily controls the lake water chemistry. Based on different Hydro chemical characteristics it is suggested that silicate weathering is the major hydro geochemical process operating in Saheb bandh lake water. Regarding point source contribution of pollutants the average value of NO3-N, TP and Hg are much higher in inlet water (7.5 mg/L, 1.29 mg/L and 8.5 μg/L) than the lake water (1.5 mg/L, 0.05 mg/L and 0.42 μg/L). Risk assessment indices suggest advanced decline of the sediment quality. Water-sediment interaction of heavy metals reveals that Cd, As, Pb and Hg metals enter into lake water as a result of not only natural processes but also of direct and indirect activities of humans. This study recommends that continuous monitoring of these metals in water and sediment and other aquatic biota of Saheb bandh should be directed to assess the risk of these vital heavy metals in order to maintain the safe ecology in the vicinity of this lake.
    Keywords: Hydro geochemistry, Heavy metal assessment, Water-rock interaction, Risk assessment, Saheb Bandh Lake
  • H. Hasanlou, A. Torabian, N. Mehrdadi, A. R. Kosari, B. Aminzadeh * Pages 821-838
    Any proper operation could be translated as a constrained optimization problem inside a WWTP, whose nonlinear behavior renders its control problems quite attractive for performance of multivariable optimization–based control technique algorithms, such as NMPC. The main advantage of this control technique lies in its ability to handle model nonlinearity as well as various types of constraints on the actuators and state variables. The current study presents the process of BSM1 building, step by step, proposing appropriate numerical methods are creating the simulation model in MATLAB environment. It also makes a detailed comparison of the proposed NMPC with five recent predictive control schemes, namely LMPC, hierarchical MPC+ff, EMPC, and MPC+fuzzy, along with the default PI. The performance of predictive control schemes is much better than the default PI; however, something of highest importance is the ability to use the proposed control scheme in real systems, for a real application faces several limitations, especially in terms of the equipment. Finally, in order to compare predictive controllers, it is necessary to determine the same conditions so that results from more days can be used, and, if needed, more than 28 days have to be simulated. MOI index can help determine which of the proposed control scheme is really applicable.
    Keywords: Stable Operation, Predictive Control, BSM1, Wastewater Treatment Plant, Unconventional Loading
  • K.C. Kanu *, O.A. Ogbonna, I.C. Mpamah Pages 839-846
    In this study, the lethal toxicity, behavioral responses and hematotoxicity of formulated chlorpyrifos on Clarias gariepinus was evaluated. C. gariepinus fingerlings were exposed to 0.2 mg/L, 0.25 mg/L, 0.3 mg/L, 0.35 mg/L and 0.4 mg/L of the active ingredient chlorpyrifos to determine the lethal concentrations and behavioral effects. C. gariepinus juveniles (38.84±7.67g) were then exposed to 0.0256 mg/L and 0.0128 mg/L for 14 days to study somatic indices and haematological effects. The 24h, 48h, 72h and 96h LC50 were estimated as 0.292 (0.210 – 0.376) mg/L, 0.275 (0.252 – 0.297) mg/L, 0.263 (0.242 – 0.282) mg/L, and 0.256 (0.235 – 0.275) mg/L respectively. Hyper activity, loss of equilibrium, erratic swimming, trembling, respiratory distress and poor startle response were observed in fingerlings in response to acute toxic stress of chlorpyrifos. Liver somatic index (LSI) of exposed juveniles increased significantly (p<0.05) compared with control, while there was no statistically significant difference in all the haematological parameters of the exposed fishes compared with the control (p<0.05). The results indicate that the chlorpyrifos formulation was highly toxic and induced behavioral changes in C gariepinus fingerlings, while sub-lethal concentrations induced inflammation in the liver but had no effect on haematological parameters of Clarias gariepinus juveniles. LSI was sensitive to the sub-lethal concentrations and could serve as indicators or exposure to organophosphate insecticides.
    Keywords: Insecticide, hematology, catfish, liver somatic index
  • A. Saadat, L. Hajiaghababaei *, A. Badiei, M. R. Ganjali, G. Mohammadi Ziarani Pages 847-857
    The present study synthesizes a novel adsorbent by coating Fe3O4 magnetic nanoparticles with amino functionalized mesoporous silica. The FTIR spectrums indicate that silica has been successfully coated on the surface of Fe3O4 and 3-aminopropyl tri methoxysilane compound have been grafted to the surface of silica-coated Fe3O4. The XRD analysis shows the presence of magnetite phase with cubic spinel as a highly crystalline structure, before and after silica coating. The study also investigates the potentials of amino functionalized silica-coated Fe3O4 magnetic nanoparticles for extraction of Pb2+ and Cd2+ cations from aqueous solutions, where it has used flame atomic absorption spectrometry to determine ion concentration in both recovery and sample solutions. The optimum conditions of removal of Pb2+ and Cd2+ ions turn out to be pH= 4-8 with a stirring time of 20 minutes. The minimum amount of 3M nitric acid to strip ions from functionalized magnetic nanoparticles is 10 mL. The experimental data show the adsorption isotherms have been well described by Langmuir isotherm model, with the maximum capacity of the adsorbent being 1000.0 (± 1.4) μg, 454.5 (± 1.6) μg of Pb2+, and Cd2+ per each mg of functionalized magnetic nanoparticles, respectively. Finally, the proposed adsorbent is successfully applied to remove Pb2+ and Cd2+ ions in wastewater samples.
    Keywords: Fe3O4 nanoparticles, silica coated, Amino functionalized, Pb2+, Cd2+
  • A. A. Hussein *, M. J. A. Alatabe Pages 859-869
    The present study aims at investigating the feasibility of using solar energy as a power source to run electro-kinetic remediation in order to clean-up lead from three types of Iraqi soil. In order to do so, it carries out six tests with enhancement conditions, involving pH control and injection wells. Conducted in the city of Baghdad, Iraq, the experiment, is divided into two groups so that the effect of applying continuous and constant voltage from solar panels study, by means of charge control and battery along with non-continuous and non-constant DC voltage from solar panel could be studied. The DC voltage has been generated by two Solar panels, each with a maximum voltage of 17 volts. All experiments have commenced in March 2017, wherein the soil has been contaminated with a concentration of Pb, equal to 1500 mg/kg as well as initial moisture content equal to 30%. The remediation lasts for seven days, with a potential gradient of about 1.2 V/cm. At the end, the experimental results show that the overall removal efficiencies of 90.7%, 63.3%, and 42.8% have been achieved for sandy, sandy loam, and silty loam soils, respectively, when using solar panels with charge control and battery.
    Keywords: Soil pollution, lead removal, Electro-kinetic, solar panel, Soil remediation
  • N. Memarizadeh *, M. Ghadamyari, K. Talebi, E. Torabi, M. Adeli, R. Jalalipour Pages 871-878
    The current study investigates the dissipation kinetics of two imidacloprid (IMI) nanoformulations (entitled: Nano-IMI and Nano-IMI/TiO2) on common bean (Phaseolus vulgaris) seeds under field conditions and compares them with 35% Suspension Concentrate (SC) commercial formulation. To do so, it sprays P. vulgaris plants at 30 and 60 g/ha within green bean stage, sampling them during the 14-day period after the treatment. Following extraction and quantification of IMI residues, dissipation data have been fitted to simple-first order kinetic model (SFOK) and to first-order double-exponential decay (FODED) models, with 50% and 90% dissipation times (DT50 and DT90, respectively) assessed along the pre-harvest interval (PHI). With the exception of Nano-IMI at 60 g/ha, other decline curves are best fitted to the FODED model. In general, dissipation is faster for Nano-IMI (at 30 g/ha: DT50 = 1.09 days, DT90 = 4.30 days, PHI = 1.23 days; at 60 g/ha: DT50 = 1.29 days, DT90 = 4.29 days, PHI = 2.95 days) and Nano-IMI/TiO2 (at 30 g/ha: DT50 = 1.15 days, DT90 = 4.40 days, PHI = 1.08 days; at 60 g/ha: DT50 = 0.86 days, DT90 = 4.92 days, PHI = 3.02 days), compared to 35% SC (at 30 g/ha: DT50 = 1.58, DT90 = 6.45, PHI = 1.93; at 60 g/ha: DT50 = 1.58 days, DT90 = 14.50 days, PHI = 5.37 days). These results suggest the suitability of Nano-IMI and Nano-IMI/TiO2 application at both rates in terms of their residues on P. vulgaris seeds.
    Keywords: Pesticide nanoformulation, imidacloprid, dissipation kinetics, Pre-harvest interval
  • S. E. Alavi, M. A. Abdoli *, F. Khorasheh, A. Bayandori Moghaddam Pages 879-893
    Pyrolysis is an applicable method that has been widely used to recover hydrocarbons from Used Lubricating Oil (ULO). However, large-scale application of this approach has been limited by its noticeably energy and time consuming nature. In the present research, it has been attempted to modify the energy and time requirements of ULO pyrolysis using the catalytic effects of metal oxide nanoparticles (NPs). The impacts of γ-Al2O3, γ-Fe2O3 and ZnO NPs on the kinetic features of ULO pyrolysis were studied using thermogravimetric analysis (TGA). The kinetic parameters of the pyrolysis process were calculated based on Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozava (FWO) models. The activation energy of virgin ULO pyrolysis had been calculated to be 161.505 and 162.087 kJ/mol using KAS and FWO models, respectively. However, in the present work, utilization of γ-Fe2O3 NPs significantly reduced the activation energy of ULO pyrolysis to 133.511 and 138.289 kJ/mol through KAS and FWO models, respectively. The catalytic effect of ZnO NPs was not as noticeable as that of γ-Fe2O3 NPs, resulting in activation energies of 155.568 and 158.501 kJ/mol using KAS and FWO models, respectively. Moreover, based on the results of this study, γ-Al2O3 NPs had no significant impact on the kinetics of ULO pyrolysis.
    Keywords: Lubricating Oil, Recovery, Kinetic study, Catalytic Effect, Nanoparticle
  • A. Tarassoli, A. Esmaili Sari *, N. Bahramifar Pages 895-911
    The present study monitors BTEX concentration in outdoor and indoor air of eight different microenvironments during summer 2017 and winter 2018 at Asaloyeh city, Iran's energy capital. It samples BTEX compounds by charcoal tubes, analyzing the samples by means of a gas chromatograph with a flame ionization detector. According to the obtained results, outdoor concentrations of BTEX have been higher than the indoor ones, for both seasons, with the highest outdoor and indoor BTEX being 21.70 and 18.59 μg/m3, respectively. Toluene has been the most abundant substance, among the investigated BTEX in all sampling points. Based on the MIR scale, m, p-xylene is the most dominant contributor to ozone formation potential among BTEX species. Indoor to outdoor (I/O) ratios of BTEX compounds range from 0.53 to 0.88 and 0.41 to 0.77 in winter and summer, respectively. The cumulative hazard index (HI) is within an acceptable range. The LTCR value of benzene concentration, obtained, exceeds the value of 1.0E-06, recommended by USEPA. Sensitivity analysis shows that benzene concentration, exposure duration, and inhalation rate have a greater impact on health risk assessment.
    Keywords: Air quality, BTEX, Temporal variation, LTCR, Spatial distribution
  • Sh. Motamedimehr *, S. Gitipour Pages 913-922
    Finding an environment-friendly and affordable method to remove contaminated soils from Polycyclic Aromatic Hydrocarbons (PAHs) has now become an attractive field for researchers, with super-critical fluid extraction being an innovative process in the field of contaminated soil treatment. Extraction with super-critical fluid is a simple and rapid extraction process that uses super-critical fluids as solvents. The present study has investigated the extraction of contaminated soil with Polycyclic Aromatic Hydrocarbons (PAHs) by means of batch supercritical water reactor, employing variables like pressure (100–300 bar), temperature (60–140 ◦C), residence time (0.5–3 hours), and base, acidic, and neutral pH values. In order optimize the process parameters, Response Surface Methodology (RSM) has been used. Results show that removal efficiency of PAHs is between 82%-100%, where the highest PAHs removal efficiency (100%) has been observed in Test No. 22, with a pressure of 300 bars, temperature of 500°C, acidic pH equal to 5, and duration of 3 hours. In addition, the lowest removal efficiency of these compounds (82%) has been obtained in Test No. 26, with a pressure of 300 bars, temperature of 350°C, base pH of 9, and duration of half an hour. According to the results from this study, it has become clear that residence time is the most important and most effective parameter for removing PAHs from contaminated soil. Afterwards, temperature and pH are most influential with pressure showing the least effect. Using supercritical water method in appropriate conditions can eliminate more than 99% of aromatic contamination.
    Keywords: Soil treatment, PAHs, Supercritical Fluid, Batch reactor, RSM