Heavy Metals Contamination and Risk Assessment of Surface Soils of Babol in Northern Iran

Background: Currently there is much concern in the field of soil contamination with heavy metals due to rapid urbanization. Soil contamination significantly reduces environmental quality and affects human health. Objectives: This study was performed to determine the level of As, Cd, Co, Cr, Ni, Pb, and Zn in the soils of Babol city in Mazandaran province and to evaluate the pollution indices of heavy metals. Methods: Concentrations of heavy metals in 50 samples of surface soils (5 to 15 cm) in urban and rural areas of Babol city were measured using inductively coupled plasma optical emission spectrometry (ICP-OES). In this study, various indices including contamination factor (Cfi), degree of contamination (Cdeg), Nemerow integrated pollution index (NIPI) and the potential ecological risk (ERi) with heavy metals were assessed. Results: Mean content of As, Pb, Cd, Zn, Cr, Ni, and Co in soil samples of different locations were 6.90 +/- 2.60, 31 +/- 5.70, 0.32 +/- 0.1, 82.80 +/- 15, 32.40 +/- 8.30, 34.50 +/- 7.50, and 22.6 +/- 6 mg/kg, respectively. The average content of these metals is ranked in the following descending order: Zn > Cr > Ni > Pb > Co > As > Cd. The order of contribution of the potential ecological risk by metals was Cd (51.91%) > As (23.75) > Pb (7.61%) > Cr (5.57%) > Co (5.24%) > Zn (3.04%) > NI (2.88%). Conclusions: This study indicated that the risk assessments of the soil samples with heavy metals in the studied locations are categorized from low to moderate degree of contamination.