Level of heavy metals and environmental pollution index in Ahvaz, Southwest Iran.

This study was designed to evaluate the concentration of heavy metals (HMs) in the north of Ahvaz, southwest Iran. The soil samples were collected from the agricultural farm and riverside in Karun, for the investigation of the environmental impacts of the selected HMs in the soil of the Weiss and Arab Assad regions. For soil sampling in a period, nine farms were selected from each region, and 10 samples were taken from each agricultural farm. Zoning was done using GIS. The highest of Contamination Factor, Enrichment factor and geo-accumulation index of HMs for Cd (7.84, 73.92 and 2.38), and the lowest value of this index for Cr (0.21, 1.98 and - 2.82), respectively. Furthermore of the farm soil showed that the most toxic effect is related to Cd. The HMs contamination indices of the soil samples showed that the studied HMs had contaminated the agricultural fields. Moreover, the zoning maps of the Co, Cu, Pb and Cr showed that they had not contaminated the soil of wheat fields, but Cd and Zn revealed high contamination levels. The zoning of Ni concentration distribution showed that this metal contamination came from both anthropogenic aspects and geological activities in the region. According to our findings, the EF illustrated high levels of pollution for Cd, Cu, Cr, Pb, Ni, Fe, Mn, Co, and Zn, which seems to be in accordance with the accumulation of agricultural fertilizers (phosphate and nitrate), industrial and human activities in the region.

Potential ecological risk assessment of heavy metals (trace elements) in coastal soils of southwest Iran.

Heavy metal pollution has become one of the most important threats that can endanger the health of animals, the environment, and humans. The present study was performed to investigate the potential ecological risk (PER) of heavy metals [zinc (Zn), copper (Cu), cobalt (Co), molybdenum (Mo), manganese (Mn), and selenium (Se)] in the coastal soils of southwest Iran in 2019. The samples were collected from six soil sites and three depth intervals (0-15, 15-30, and 30-45 cm) among bare and vegetated coastal soils. The soil samples to study the soil properties (soil grain size, pH, EC, and soil organic carbon) and metal contamination were taken from soil (36 samples), water (6 samples), and plants (24 samples). The soil ecological risk (ER), the pollution load index (PLI), contamination degree (Cdeg), modified contamination degree (mCdeg) for heavy metal contamination in the soil, and enrichment factor (EF index) indicate the origin of metals entering the environment, and hence these parameters were investigated. The results of this study showed that the levels of Zn, Cu, Co, Mn, Se, and Mo were in the range of low-risk contaminants in this region. According to the results of the study, the risk index (RI) for metals was in the range of 1.296-3.845, which is much lower than 150, and therefore the ecological risk potential calculated in this study was in the low-risk category for toxic elements. Based on the results, it was found that agricultural, industrial, and human activities played an effective role in the accumulation of Zn, Cu, Co, Se, and Mo in the soil. In addition, the main source of Mn metal is believed to be natural due to geological activities in the region.

Status, source, human health risk assessment of potential toxic elements (PTEs), and Pb isotope characteristics in urban surface soil, case study: Arak city, Iran.

The current study was conducted to assess the level of potentially toxic elements (PTEs) contamination (Cu, Pb, Zn, Cr, As, Cd, and Ni) in surface soils from Arak city. Arak, which is an industrial city, is a prominent center of chemicals, metal/electric, manufacturing factories, and other industries. Forty-three surface soil samples were collected from 0-20 cm after removing the visible surface contamination in the dry season in June 2017. Metal concentrations were found highly variable, ranging from 174-3950 mg/kg for Cu, 181-3740 mg/kg for Pb, 48-186 mg/kg for Zn, 105-1721 mg/kg for Ni, 0.8-0.9 mg/kg for As, 114-1624 mg/kg for Cr, and 3.45-12.36 mg/kg for Cd. The results of geochemical fraction indicated that the main components of Pb, Cr, and Zn at most of the sampling sites are Fe-Mn bound/reducible. Meanwhile, the residual fraction is the dominant fraction of sequence extraction for Ni, Cu, and Cd. Higher values of reducible bound for Pb, Cr, and Zn, as well as a considerable percentage of Ni, Cu, and Cd, imply that the main source of the studied PTEs (except As) in the study area is both anthropogenic and geogenic inputs. The results of principal component analysis (PCA), correlation analysis, enrichment factor (EF), enrichment index (EI), and top enrichment factor (TEF) confirm that Pb, Ni, Cu, Cr, Cd, and Zn had a similar anthropogenic source which is confirmed by geochemical fractionation analysis. Carcinogenic risks (CR) of studied PTEs were estimated to be higher than the target limit of 1.0E-06, for adults and children except for Cr with values of 5.91E-04, and 3.81E-04 for children and adults, respectively. Higher CR values of Cr compared to other PTEs in Arak surface soil demonstrate that living target populations, including children and adults, particularly children, are more at risk of carcinogenic risks of PTEs. 206Pb/207Pb ratios of the collected samples indicated that Pb in Arak surface sample was derived from industrial inputs and deposition, as well as re-suspension vehicle exhaust emission from previously leaded gasoline. The findings concerning the applied end-member contribution of geogenic and industrial and vehicle emission represented that the contribution could vary from 68.0% to 15% (mean: 39.3) for industrial emission, 65% to 19% for vehicle exhaust (mean: 39), and 46% to 10% (mean: 21.6) for geogenic sources.

Assessment of the potential ecological and human health risks of heavy metals in Ahvaz oil field, Iran.

The potential hazard to human health from exposure to heavy metals in surface soil was assessed using 66 soil samples collected from Ahvaz oil field. To this end, the contents of heavy metals were measured by the inductively coupled plasma spectroscopy (ICP-OES). Mean levels of As, Cd, Co, Cr, Cu, Ni, Pb, V, and Zn were 5.9, 0.4, 7.1, 36.5, 41.2, 39.8, 67.4, 31.5, and 77.6 mg/kg, respectively. Contents of all studied heavy metals, with the exception of Co, Cr, and V, were several times higher than that of baselines. Correlation coefficients and principal component analysis (PCA) identified two main groups as sources of heavy metals in the surface soil of Ahvaz oil-field. Metals such as Co, Cr, and V were observed to originate from natural sources and As, Cd, Cu, Ni, Pb, and Zn originated from anthropogenic sources such as petroleum leakage and the pollution caused by drilling mud from oil wells. Pb and Zn were of significantly high EF mean enrichment value, and Co, Cu, Cd, and As had high enrichment in surface soil. Pb, Cr, V, Zn, Co, Cu, Ni, and As had a low potential ecological risk (PER) whereas Cd had a moderate PER. The risk of carcinogenic and non-carcinogenic diseases was detected to be higher in children than in adults. The carcinogenic risk (Cr) calculation was more than 1 × 10-6 for children and adults. Additionally, the CR of Cr for both children and adults indicated risk under control conditions.

Application of exploratory and Spatial Data Analysis (SDA), singularity matrix analysis, and fractal models to delineate background of potentially toxic elements: A case study of Ahvaz, SW Iran.

It is essential to study spatial distribution of Potentially Toxic Elements (PTEs) in surface soil, and separate PTEs geochemical background from their human sources, and also determine their correlation with other environmental factors in order to assess their impacts on humans, provide realistic environmental geochemical maps, and carry out soil management. For this purpose, this study was designed to investigate the surface soil in Ahvaz, Southwest of Iran. The applied methods were exploratory data analysis (EDA), including boxplot, Q-Q plot, probability plot (PP), concentration-area (C-A), number-size (N-S) fractal model, and singularity index (SI) model. The obtained results revealed that the fractal models led to a more realistic distinction among the geochemical population compared to the EDA methods such as probability plot. Furthermore, the C-A model was found to be more effective on the separation of subpopulation compared to the N-S and PP models. The studied elements exhibited a similar pattern implying that pollution is a function of geochemical dispersion regarding the surface soil in Ahvaz (Zn â‰« Pb > Cu > As). The studied metals-major elements plot also indicated that there was no meaningful relationship between Pb, Zn, Cu, and major elements in the study area. Plots of association of Pb, Zn, Cu, and As distinctly showed two general geogenic and anthropogenic populations. Moreover, the results of SI revealed that the highly contaminated area was consistent with the main defined hotspots and anthropogenic sources of elements as well as places affected by the contaminated area that have not been reported in previous studies. Furthermore, a combination of geochemical and geographical model comprising different statistical models was developed to more effectively separate geogenic from anthropogenic sources. Also, the geochemical background for the studied elements (Pb 180 mg/kg; Cu 200 mg/kg; Zn 90 mg/kg; As 65 mg/kg) was shown to be higher than the Iranian soil quality guideline with Pb, Zn, Cu, and As of 100, 80, 200, and 18 mg/kg, respectively.