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

Abstract

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.

Ecological and Human Health Risks Assessment of Potentially Toxic Elements Contamination of Surface Soils in Shushtar and Dezful, Iran

“…A research reported that accumulation of PTEs in the surface soils of Ahvaz was Cu > Pb > Cr > Zn > As > Cd and the high concentrations in addition to a high coefficient of variation indicated the human role for toxic metals. 26 Guan et al investigated the amount of PTEs in an industrial and mining area called Tianjin in China. They found that the highest levels of contamination in the study area were related to Zn, and the contamination of Cu, Cd and Pb was higher than average earth's crust.…”

“…43,44 The average concentrations of arsenic, cadmium, chromium, copper, lead and zinc in the soils of Eghlid city in southern Iran were 45 Many studies have showed that the concentration of heavy metals in topsoil can vary. 10,11,16,26,45 This difference in concentration of heavy metals may be due to human activities such as industry, agriculture and urbanization. However, the geological processes of the region can also affect the concentration of heavy metals in the soil.…”

“…Human-made contaminants enter into soils and aquatic ecosystems which increase the amount of heavy elements in these environments, causing many problems for animals and plants. 26,43 The EF value of Ni, Zn and Cr showed that the amounts of these metals in the soils of the two regions were the result of natural erosion and geological and anthropogenic activities did not play an effective role in the mineralization of these metals. However, very high concentration of Cd in the study areas might be due to industrial, agricultural and urban resources.…”

“…These mines include oil, gas, salt, sulfur, limestone, silica, gypsum and limestone. 10,26 Shushtar and Dezful are two important cities of Khuzestan province in terms of vegetables, summer crops, fruits and vegetables. In the industrial areas of the cities, there are various industries, including food and processing industries.…”

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

“…In the equation, Cn represents the concentration of each element in the sediment, and Co is the average concentration of each element in the shale ( Supplementary Table S1 ) ( 49 , 50 ).…”