| dc.description.abstract | Background and Objective:
The issue of environmental pollution has emerged as a significant global concern in recent years. The process of urbanization, industrialization, and agricultural activities have contributed significantly to environmental contamination, including soil pollution. Heavy metals represent one of the most critical soil pollutants, with the potential to cause significant environmental and health problems. These metals can pose serious risks to human health through direct or indirect exposure, including ingestion, inhalation, and dermal absorption. Therefore, the aim of this study is to assess surface soil contamination with heavy metals in the industrial area west of Tabriz city and evaluate the associated health risks.
Materials and Methods:
This cross-sectional, descriptive-analytical study was conducted to assess heavy metal contamination in surface soils of the western industrial zone of Tabriz in 2023. A total of 48 soil samples were collected from three areas (highway-adjacent, agricultural, and residential) at a depth of 0–10 cm. Key soil properties, including pH, electrical conductivity, texture, and cation exchange capacity, were determined. After initial preparation and acid digestion, total heavy metal concentrations and their bioavailability in plants and humans were assessed using a single-step extraction method with EDTA and glycine, analyzed by ICP-OES. The health risk assessment was performed based on the U.S. Environmental Protection Agency (EPA) guidelines for children (1–17 years) and adults (18+ years). Additionally, the environmental risk of heavy metals was evaluated using the Pollution Index (PI) and the Nemerow Integrated Pollution Index (NIPI) for the three studied areas.
Results:
The results indicated that the concentrations of zinc, nickel, chromium, and copper in the surface soils of the industrial region were 71.47, 64.37, 30.96, and 26.30 mg/kg, respectively. The primary sources of contamination were anthropogenic activities, including industrial wastewater discharge, waste disposal, traffic emissions, and agricultural fertilizers and pesticides. Zinc exhibited the highest bioavailability in plants (4.57 mg/kg) and humans (5.93 mg/kg). The highest concentrations of zinc and copper were found in soils near the highway, while nickel, chromium, lead, and arsenic had elevated levels in agricultural and residential soils. Lead and copper in highway-adjacent soils exhibited 33% and 27% plant bioavailability in agricultural areas, whereas cadmium and lead showed the highest plant uptake (23%) in residential soils. In terms of human bioavailability, arsenic and lead near highways had 33% absorption, while arsenic and cadmium in agricultural (29%) and residential (28%) areas had the highest levels.
The Hazard Quotient (HQ) and Hazard Index (HI) values indicated that non-carcinogenic risks for all metals were below the acceptable limit (<1), but the cumulative non-carcinogenic risk (Total HI) was higher in children than in adults. The Carcinogenic Risk (CR) assessment identified nickel and arsenic as the most hazardous metals, with nickel posing a carcinogenic risk through ingestion 60 times higher than the acceptable limit (CR > 10⁻⁶) in children. The PI values confirmed severe heavy metal pollution in the study area, with zinc having the highest contamination level (4.86) near the highway. Chromium (3.27), zinc (3.25), and nickel (3.12) showed high contamination levels in residential soils. The NIPI index revealed that 67% of highway-adjacent soils and 65% of residential soils were highly polluted.
Conclusion:
Heavy metal contamination in the region’s soils is primarily due to anthropogenic activities, with non-carcinogenic and carcinogenic risks being higher in children than in adults. Nickel and arsenic were identified as the most hazardous metals, and elevated concentrations of zinc, chromium, and nickel were confirmed in highway-adjacent and residential soils. To mitigate the effects of this contamination, stricter regulations on heavy metal emissions should be enforced. Additionally, industries should be encouraged to adopt cleaner technologies, and environmental monitoring should be intensified. Effective soil remediation methods, such as phytoremediation, along with continuous collaboration among governmental agencies, industries, and local communities, are essential steps in addressing this issue.
Keywords: Soil pollution, Heavy metals, Bioavailability, Health risk assessment, Pollution Index | en_US |
