Heavy Metal Pollution in Surface Soils of Ahvaz, Iran, Using Pollution Indicators and Health Risk Assessment

Article Notes: Received: Aug 1, 2020 Received in revised form: Sep 14, 2020 Accepted: Sep 26, 2020 Available Online: Nov 15, 2020 Background & Aims of the Study: Heavy metals are among the most dangerous environmental pollutants entering the air, water, and soil through human and natural activities with the potential of poisoning, pathogenicity, and carcinogenicity to living organisms and humans. The current study aimed to determine the contamination of heavy metals, including lead, zinc, copper, arsenic, chromium, and cadmium, in the surface soils of Ahvaz, Iran, using pollution indicators and health risk assessment. Materials and Methods: Sampling of surface soils in Ahvaz with 227 soil samples was performed in August 2017 based on the regular networks of 1 × 1 km. The measurement of heavy metals was carried out by inductively coupled plasma optical emission spectrometry. Results: The mean concentrations of Pb, Zn, Cu, Cr, Cd, and As in the surface soils of Ahvaz were reported as 180.99, 88.61, 185.13, 101.59, 5.63, and 8.97 mg/kg, respectively. Based on the contamination factor (CF), pollution index (PI), geoaccumulation index (Igeo), and ecological risk, the highest levels of pollution were related to Cd and Pb, and the lowest level was associated with Cr. The enrichment factor (EF) of heavy metals showed moderate contamination of Cr, high contamination levels of Cu, Cd, and As, and very high contamination levels of Pb and Zn. According to the Nemro Integrated Pollution Index (NIPI), 3% and 55% of the surface soils of Ahvaz showed high and low levels of pollution, respectively. The daily absorption of heavy metals through ingestion in children and adults was higher than that through respiration and dermal contact. The highest risk index was related to Cr and As through ingestion for children, and the lowest risk index was associated with Zn through respiration in adults. Conclusion: The levels of As, Cr, and Cd in the surface soil of Ahvaz were higher than the Iran soil standard values; however, the levels of Pb, Zn, and Cu were lower. Based on the CF, PI, Igeo, and ecological risk, the surface soils were highly contaminated with Cd and Pb. According to the EF, Pb and Zn showed the highest levels of contamination. Based on the NIPI, the pollution of heavy metals was reported at low levels. The highest and lowest values of metals carcinogenicity were related to Cr in children and Pb in adults, respectively.