Iranian Journal of

Background and Objective: Heavy metal contamination of surface soils has become a serious concern. The aim of this study was to evaluate the potential risk of heavy metal (loid) pollution on human health in the surface soils of Arak industrial areas, the capital of Markazi province in western Iran.
Materials and Methods: 235 surface soil samples were collected from a depth of 0-5 cm. Concentrations of lead, cadmium, nickel, zinc, copper and arsenic were determined by digestion with nitric acid (4 N). The level of soil pollution in the region was measured using geo- accumulation index (Igeo) and enrichment factor (EF). The model proposed by the U.S Environmental Protection Agency (USEPA) was used to assess the health risks of heavy metals.
Results: The Mean concentrations of Pb, Cd, As, Cu, Ni, and Zn were 37.88, 1.17, 151.78, 13.48, 92.98 and 104.04 mg/kg, respectively. The calculated enrichment factor values ​​for soil samples varied from deficiency to significant enrichment. The mean geo-accumulation index (Igeo) for Pb, Cd, Cu, Ni, Zn and arsenic were 0.37, 1.59, -2.53, -0.48, -0.63 and 2.9, respectively. The results of the health risk assessment showed that hazard quotient (HQ) for children and adults through the ingestion route was higher than dermal contact and inhalation pathway. The Hazard index values for all studied metals were lower than the safe level of 1 except for As. Arsenic showed the highest risk of carcinogenicity (CR) for children (2.37 x 10^-4) through ingestion.
Conclusion: The carcinogenic risk (CR) of As in children and adults is higher than the safe limit of 1 × 10^-4, which indicates an unacceptable risk.

Background and Objective: Contamination of roadside soils with heavy metals is a serious threat to soil ecosystems and organisms and human health. Therefore, the purpose of this study was to determine the concentration of heavy metals in the roadside soils of the Rasht-Qazvin old road.
Materials and Methods: 10 out-of-town sampling sites were selected via the field observation of the entire area. surface soil sampling with three replicates was performed around the Rasht-Qazvin old road.  Heavy metals concentrations were measured using ICP-OES following samples preparation and acid digestion. The pollution level of heavy metals was assessed using geoaccumulation index (I_geo) and potential ecological risk index (PERI).
Results: The results showed that the average concentrations of Zn, Cu, Ni and Pb in the roadside soils were 58.07, 19.96, 20.26 and 23.21 mg/kg, respectively. The findings showed that concentration of Zn and Ni were higher than background values and the amount of Zn exceeded WHO standard limit. The potential ecological risk index (PERI) with an average value of 86.24, indicated low level of pollution for all of the studied metals. The results of geoaccumulation index (I_geo) revealed moderately contamination level of Ni.
Conclusion: Old roads are generally known as one of the sources of pollution for the surrounding lands. Although the concentration of pollutants around the road is expected to be very high, we did not detect elevated levels of heavy metals. This fact can be explained by the current road repairs and widening, agricultural activities on marginal lands and wind blows in mountainous regions which leads to the dispersion of the soil pollutants.

Background and Objective: Landfills as municipal solid waste are considered as the source of pollution. The present study aimed to assess the ecological risk of heavy metals in Tehran landfill soil and the adjacent residential area.
Materials and Methods: Having consulted with the specialists and considered the waste processing facilities, 12 sampling points were selected and sampled in four seasons. Soil samples were digested using HNO₃: HClO₄: HCl: HF. The levels of metals were measured using ICP-OES which further applied for the calculation of ecological risk. Kolmogorov-Smirnov, Kruskal-Wallis, and Pearson correlation coefficient analyses were run to determine the significant differences between metals concentrations in various seasons and sampling points. 
Results: Metal concentration showed to follow theorder: Al > Fe > Mn > Zn > Cr > Pb > Cu >Ni > Co > As > Cd. Kruskal-Wallis results and pairwise comparison showed a statistically significant difference between metal concentrations across sampling points and seasons, especially in rainy seasons. Pearson correlation coefficient displayed a strong relationship between the mean concentrations of Cu - Pb, Cu - Zn, and Pb - Zn with obtained values of 0.932, 0.874, and 0.883, respectively. Cu exhibited the highest contamination factor at the compost and fermentation sites (13.2 and 9.89, respectively). The geo-accumulation index proved the anthropogenic sources of pollution. The potential ecological risk index (ERI) for the sampling sites ranged from 67.3 to 154, with the order of Cd > Cu > Pb > Ni > As > Cr > Zn > Co > Mn. 
Conclusion: Due to the obtained moderate to severe ecological risk and exceeded background concentrations of heavy metals, it can be concluded that metal changes and soil pollution are both affected by landfill activities.

Background and Objective: Application of chemical fertilizers in agricultural industry is known as one of the methods of crop enhancement. However, chemical fertilizers application can lead to an increased risk of chemical pollutants entering the human food cycle.  The aim of current research was feasibility study and evaluation of nickel from paddy soils in Lorestan province.
Materials and Methods: Sampling was done from 15 stations and randomly from rice cultivation areas in Silakhor plain of Lorestan province. Then, electrokinetic modification method was carried out in three reactors with lengths of 5, 10 and 15cm. After sample preparation, the initial and final concentration of nickel were measured and calculated using inductively coupled plasma - optical emission spectrometry (ICP-OES).
Results: The results showed that electrokinetic modification method was effective in reducing the concentration of heavy metals in agricultural soil samples and reduced the amount of nickel in soil to the permissible limits of the Iranian soil national standards (50 mg/kg). The initial values of nickel in paddy soil of composite samples were 108 mg/kg. Nickel maximum removal efficiency of 90.84% and 93.75% were observed in cathode and anode regions, respectively.
Conclusion: The health and quality of agricultural products depend on the use of safe soil within the limits of environmental standards. The results of this study showed that the EKR process is able to remove nickel from soil. As a result of the present process, nickel concentration has reached the permissible amount and even lower than the soil quality standard set by the Iranian Environmental Protection Agency.

Background and Objective: Among the emerging contaminants, microplastics threaten public health. This study aimed to determine microplastic and mesoplastics in soil of residential areas adjacent to Tehran Landfill and assess its ecological risk.
Materials and Methods: The present descriptive cross-sectional study was conducted on 20 shallow and deep soil samples from residential areas near the Tehran landfill in July 2021. The microplastics were floated in NaCl and ZnCl₂ solutions, and the mesoplastics were separated manually. The identification of physical and chemical properties of polymers was performed by stereomicroscope and FTIR analysis, respectively.
Results: The average amount of micro-plastics in shallow and deep soils estimated 76±34.98 and 24.7±19.79 particles/kg_soil, respectively. The average amount of mesoplastics obtained 5.25±2.91 and 3.55±1.09 particles/kg_soil, in shallow and deep soils, respectively. Paired-samples T-test showed significant differences between shallow and deep soil in terms of plastic particles (p<0.001). The most abundant microplastic particles were the fragment-shaped with the particle size of 0.1-0.5 mm and LDPE polymer types with the percentage of 37.75, 44.64, and 46.15, respectively. Mesoplastic particles, the 0.5-1 cm film-shaped particles and LDPE polymer types with the percentage of 62.76, 61.46, and 50.7 were found as the most prevalent. Microplastics and mesoplastics' potential ecological risks value in all sampling points was less than 150, indicating low ecological risk.
Conclusion: Despite the low PERI of microplastics and soil mesoplastics in residential areas, the E_rⁱ index for LDPE was high. Thus, Ecological risk is probable if control measures are not taken against plastic pollution.
 

Background and Objective: Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants produced by anthropogenic activities that contaminate all environmental matrices, including soils, and can enter the food chains. Therefore, this study was conducted for the analysis of PAHs compounds content in agricultural soils of Hamedan city, west of Iran, in 2021.
Materials and Methods: a total of 36 surface soil specimens were collected from 12 sampling sites in agricultural soils and after extraction of analytes based on the soxhlet method, the gas chromatography/mass spectrometry (GC–MS) method was used for the determination of PAHs compounds in the samples. Furthermore, soil samples were further analuzed for the amounts of pH, electrical conductivity (EC), and total organic carbon (TOC). Statistical analysis was performed using SPSS software.
Results: Results showed that 16 PAHs (∑16PAHs) total concentrations ranged from 435 to 3292 µg/kg with an average value of 1806 µg/kg. PAHs with higher molecular weight (≥ 4 rings) were dominant in PAHs profiles accounting for 78%. Based on the results, the mean concentrations of all 16 PAHs were lower than MPC established by MHWaS. Furthermore, the mean concentrations of Pyr, B(a)A, Chy, B(b)F, B(k)F­, B(a)P, and B(ghi)P were higher than the MPC established by the Iranian Department of Environment.
Conclusion: Based on the results obtained, as the mean contents of some PAHs were higher than the MPC, therefore, periodic monitoring of soil contamination with PAHs is recommended for the environmental and human health aspects.
 

Background and Objective: The high concentration of petroleum hydrocarbons, along with some other parameters such as aromatics, paraffin, naphthene, and heavy metals, has led to the sludge of oil sludge listed as hazardous materials with a specific source by the US Environmental Protection Agency. Therefore, the purpose of this study is to investigate the potential of oil-contaminated soil in changing the biodegradability indices of oil sludge.
Materials and Methods: Moisture, pH, total organic carbon, total nitrogen, total phosphorus, elemental analysis, and amount and type of TPH of oil sludge samples were identified. The microbial consortium was isolated from contaminated oil soil around the oil refinery and poultry manure. Finally, biodegradability indices of oil sludge were examined.
Results: The results showed that the amount of organic carbon and nitrogen in oil sludge samples were 32.65 and 0.21%, respectively. Also, iron, calcium, and potassium with 5862, 2921, and 524 mg/kg, respectively, were the most elemental components in petroleum sludge. According to the SARA analysis, the highest TPH compounds in oil sludge samples included saturated compounds, aromatics, resins, and asphaltene with 70.45%, 15.2%, 10.9%, and 3.45%, respectively.
Conclusion: According to the results of biodegradability indicators of oil sludge, it can be concluded that the isolated consortium can be proposed as a suitable tool for the treatment of petroleum sludge at the bottom of crude oil storage tanks.
 

Background and Objective: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants with teratogenic, mutagenic and carcinogenic potential, which can pose potential risks to the environment and human health. Therefore, this study was conducted for the analysis of PAHs compounds content in surface soil samples of the disposal site of the wastes resulting from the activity of oil refining units (Nuruddin Abad, Garmsar) in 2022.
Materials and Methods: In this research, surface soil samples were collected from 8 sampling sites in the study area. After the extraction of analytes based on the soxhlet method, the gas chromatography/flame ionization detector (GC-FID) method was used for the determination of PAHs compounds in the samples. Statistical analysis was performed using SPSS software.
Results: The results showed that the concentrations of Naphthalene (Nap), Acenaphthene (Ace), Benzo[b]fluoranthene (BbF), Dibenz[a,h]anthracen (DBA), Benzo[g,h,i]perylene (BP) and Indeno[1,2,3‐c,d]pyren (Ind) were less than the quantification limit of the measurement method <0.01 mg/kg. total concentrations of 16 PAHs compounds ranged from 56.55 to 92.06 mg/kg.
Conclusion: The results showed that the concentrations of Acenaphthylene (Acy), Fluorene (Flu), Phenanthrene (Phen), Anthracene (Ant), Fluoranthene (Flt), Pyrene (Pyr), Chrysene (Chr), Benz[a]anthracene (BaA), Benzo[k]fluoranthene (BkF), Benzo[a]pyrene (BaP) were higher than MPC established by the Iranian Department of Environment. Also, the concentrations of Acy, Flu, Phen, Ant, Pyr, Chr, BaA, BkF, and BaP were higher than MPC established by MHWS. As the mean contents of some PAHs were higher than the MPC, therefore, periodic monitoring of soil contamination with PAHs is recommended for the environmental and human health aspects.
 

Background and Objective: Soil contamination with heavy metals is the most important challenge and common environmental, economic, and public health issue in the world. Therefore, this research was conducted to evaluate the contamination and source identification of Fe, Zn, Cd, and Cr in the surface soils of Khorramabad county, west of Iran in 2020.
Materials and Methods: In this descriptive study, after dividing the study area into 11 homogeneous units, a total of 65 surface soil samples were collected. After preparing the samples, the content of the elements was determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Also, enrichment factor (EF), pollution factor (CF), and Nemrow integrated pollution index (NIPI) were calculated. Statistical analyses of the data were performed using SPSS statistical software.
Results: The results showed that the average content of Fe, Zn, Cd, and Cr (mg/kg) in soil samples were 3.14, 1.13, 0.021, and 0.529, respectively. The EF values showed that the enrichment of Zn, Cd, and Cr was "extremely severe" and the average values of EF for the elements followed the descending order of Cd > Cr > Zn. The average values of CF and NIPI varied from 3.30×10^-5 to 0.182 and 0.043-0.136, respectively, indicating the level of "low pollution" and quality conditions of "no pollution" in all the studied stations. Based on the results of multivariate statistical analysis (PCC, PCA and HCA), Fe has a geological origin; while, Zn, Cd, and Cr mainly originated from a combination of geological processes and anthropogenic activities.
Conclusion: Although the average values of CF and NIPI showed that the study area has an acceptable soil quality, the values of EF indicated the impact of anthropogenic activities on soil contamination. Therefore, regular and periodic monitoring of soil samples as well as management and control of pollutant emission sources is recommended for maintaining environmental and human health.

Background and Objective: The purpose of this study is to identify and comprehensively evaluate international studies related to bioaugmentation and biostimulation methods for the remediation of soils contaminated with petroleum compounds.
Materials and Methods: This systematic review study was conducted in April 2022. The present systematic review study was conducted to address two main questions: 1) Is biostimulation an effective process in the bioremediation of soils contaminated with petroleum hydrocarbons; and 2) Is bioaugmentation an effective process for bioremediation of soils contaminated with petroleum hydrocarbons? Global electronic databases (PubMed, Web of Science, and Scopus) were used to identify relevant studies. After a comprehensive review of studies, 123 studies consistent with the purpose were selected.
Results: The results showed that biostimulation methods can have profound changes in bacterial, Archaebacteria, and soil fungal communities in terms of activity, frequency, and composition. In general, the nutrients and electron receptors added in the biostimulation process improve soil microbial activity, increasing the overall abundance of bacteria, and fungi and promoting selective replication of bacterial, archival, and fungal polyaromatic hydrocarbons (PHC) destroyers. The use of bioaugmentation technology in an environment contaminated with petroleum hydrocarbons has a positive effect on the refining process. However, it is necessary to precisely select the appropriate microbial strains. The most important factor in the removal of hydrocarbons in the soil is the selection of oil-decomposing microorganisms that can survive in high concentrations of pollutants.
Conclusion: Therefore, the result indicated that biostimulation and bioaugmentation can efficiently improve the THP removal efficiency in contaminated soil by considering the environmental conditions.
 

Background and Objective: Agricultural lands around Tehran may become contaminated due to their proximity to pollution sources and such pollution should be investigated. Therefore, the main objectives of this study were to determine the pollution levels of some trace elements in the agricultural soils around Tehran and to assess the attributed health risks.
Materials and Methods: In this study, 43 soil samples were collected from agricultural lands around Tehran. The soil samples were prepared and acid-digested and the concentrations of Vanadium (V), Lithium (Li), Lanthanum (La), Molybdenum (Mo), and Antimony (Sb) were measured by ICP-OES. Based on the concentrations of the elements in soil, the pollution indices and non-carcinogenic risk (based on Monte Carlo simulation) were assessed.
Results: Among the studied elements, V had the highest concentration (131 mg/kg) followed by La > Li > Sb > Mo. The values of the geoaccumulation index (I_geo) and enrichment factor (EF) were in the ranges of -1.9 to 0.8 and 0.5 to 3.1, respectively. The Nemerow integrated pollution index (NIPI) values were in the range of 1.3 to 2.0. The values of non-carcinogenic risk for Li, Mo, Sb, and V were negligible, but it exceeded the threshold limit for La.
Conclusion: This study showed that the agricultural lands around Tehran are contaminated with studied trace elements to a low to moderate extent. However, an unacceptable non-carcinogenic risk attributed to La was estimated. Therefore, it is essential to pay special attention to the La pollution of agricultural soils around Tehran.
 

Background and Objective: Mining is one of the important economic activities all over the world. It causes the release of various emissions, especially heavy metals in the soil, due to the weak exploitation and improper disposal of mineral wastes. Different techniques are used for soil remediation and heavy metal extraction; including the electrokinetic method (so effective in fine-grained soils). In this research, the electrokinetic process was used to extract copper from the waste of the mine in Birjand.
Materials and Methods: In this research, a 24 cm long PVC reactor was used. The retention time was 2, 4, and 6 days and the voltage gradient was 1 V/cm. Graphite electrodes and electrolyte solutions of nitric acid and citric acid were investigated for copper extraction. The electrode polarity was alternately changed in order to pH control and improve the extraction process.
Results: According to the results, the highest removal efficiency (54%) was obtained after 6 days using 0.1 M citric acid and distilled water in the anode and cathode reservoir, respectively. Further, by 24-hour polarity reversing, the copper removal efficiency increased to about 60%.
Conclusion: The use of citric acid in anode was more effective than nitric acid, leading to more copper removal. In addition, by periodically polarity change and keeping the soil pH in the neutral range, further dissolution of the metal and reducing its sedimentation in the soil occurred. As a result, the rate of its transfer outside the treatment area and removal efficiency increased.
 

Background and Objective: The emergence of nanotechnology and the use of nanoscale materials has made it possible to take advantage of the potential and novel applications of this technology in various fields of agriculture. Therefore, this research aims to make fertilizer for high-consumption nutrients such as nitrogen, phosphorus, and potassium (NPK) by hydrogels based on the sepiolite (Sep) clay nanostructure and starch (S).
Materials and Methods: In this study, the physical inhibition method was used to control the release of high-consumption nutrient elements of fertilizer. For this purpose, appropriate amounts of NPK salt were inserted in the structure of Sep-S hydrogels. Then, the release level of nutrients was investigated by the column elution and measuring the conductivity of the outlet solution of the column.
Results: The elution profile of the NPK fertilizer shows that the salts quickly leave the end of the column so that the conductivity of the solution at the end of the column in the first washing after consumption of 250 mL of water reaches about 12000 µS/cm. On the other hand, the elution profile of the slow-release fertilizer containing NPK salts shows that the release profile of the fertilizer in 4 times of washing with the same volume is almost similar (range 1400 µS/cm to 2300 µS/cm). Results show that the placement of fertilizer salt inside the proposed hydrogels leads to the slow release of highly consumed nutrients.
Conclusion: The release of nutrients from the structure of slow-release fertilizer based on Sep-S hydrogels has a delay, which is vital to prevent the excessive release of nutrients, and minimize negative environmental effects and excessive consumption of chemical fertilizers. Also, the materials used to make the slow-release fertilizer have a relatively low cost.
 

Background and Objective: Heavy metals are dangerous pollutants in the environment that accumulate in food. This research was conducted with the aim of evaluating the health risks and contamination of some heavy metals in lettuce and cabbage in the cities of Hamidieh, Dezful and Ramhormoz in Khuzestan province.
Materials and Methods: The sampling was completely random, with three repetitions, and 15 samples of each of the lettuce and cabbage vegetables grown in each region were prepared. Heavy metals were measured using the Perkin Elmer 4100 atomic absorption device. Heavy metal risk assessment was conducted using soil pollution indicators and health risk assessment method.
Results: The highest amount of metal in cabbage is related to zinc (5.84±0.15 mg/kg), while the lowest amounts of chromium metal in lettuce (0.11±0.005 mg/kg) was achieved. Based on the daily absorption of heavy metals in lettuce and cabbage products, the results showed that the highest hazard index (HQ) values, ​​related to lead metal in cabbage for children and adults, were 3.9376 and 3.4253, respectively, compared to other heavy metals. The highest value of the carcinogenicity index in children was 0.0133 for cabbage consumption. The carcinogenic index of chromium metal in lettuce and cabbage products had the lowest values (0.0003 and 0.0004). Regarding the metal enrichment factor, lead, chromium, copper and cobalt were higher in the agricultural soils of Ramhormoz compared to other regions, while nickel and zinc were higher in the soils of Hamidiyeh than in Dezful and Ramhormoz. The soil index of accumulation of chromium, zinc and copper in the soil of Dezful agricultural fields was higher, whereas lead and cobalt were higher in Hamidiyeh soils than in Dezful and Ramhormoz. Additionally, nickel was higher in Ramhormoz agricultural fields.
Conclusion: According to the soil pollution indicators, cobalt metal played an important role in the soil pollution in Dezful, Hamidiyeh and Ramhormoz, while the metals lead, nickel, chromium, copper and zinc showed minimal pollution levels in the soil of the studied areas. The health risk assessment of soil heavy metals showed that the risk index for lead, nickel, chromium, copper, zinc and cobalt was lower than 1. Additionally, the carcinogenicity index of heavy metals for both adults and children was less than 10^-4. The health risk assessment of heavy metals and their risk index showed that the consumption of lettuce and cabbage in these areas can lead to various health problems in people.
 

Background and Objective: Heavy metals are regarded as serious contaminants due to their toxicity, persistence in natural conditions, and ability to enter and accumulate (bioaccumulation and biomagnification) in food chains. The aim of this study was to investigate the concentrations of the heavy metals Pb, Cd, Cu, Zn, Cr, Fe and Ni in surface agricultural soils of the Miandoab landfill area.
Materials and Methods: In this study, 57 soil samples were collected from a depth of 0-20 cm. After preparing and digesting in the laboratory, the samples were analyzed using a inductively coupled plasma spectrometer (ICP-OES). The Ecological Risk Potential Index (EPRI), Earth Accumulation Index (Igeo), Principal Components Test (PCA) Pearson's Correlation, Cluster Analysis, and One-T-test were utilized. Statistical processing was conducted using SPSS software.
Results: According to the results of the single T-test, the average concentrations of Pb, Cd, Cu, Zn, Cr, Ni did not significantly differ from their background concentration in the soil (p≥0.05). A significant difference was pbserved only for Fe (p<0.05), indicating a geological origin for this element. The EPRI was within the low-risk range, with an average value of 46.95. PCA revealed that the first factor was positively associated with Cr, Pb and Fe; the second factor with Zn and Cu; and the third factor with Cd. Cluster analysis showed that Fe was predominantly influenced by natural resources. According to the land accumulation index, all metals, except Cu, were classified non-polluted or slightly polluted at stations 2 and 4.
Conclusion: The origin of elements is related to both natural and human factors. Specifically, Cr, Pb and Cd are more likely to originate from man-made sources, while Fe primarily comes from natural sources. The decrease in the concentration of metals can be attributed to continuous and annual ploughing, inactivity of the landfill, biological absorption by crops, soil leaching and transporting to lower depths.