Journal of North Khorasan

Background and objectives: Due to the non-biodegradable and persistent nature, heavy metals are accumulated in vital organs in the human body and lead to serious health disorders. The present study was done to determine the intensity of soil contamination by heavy metals, identify the locations with high contamination levels and assessment of health risk for children (1-5 years old) by soil ingestion.

Material & Methods: Twenty-four surface soil samples were collected from 12 stations. The concentrations of heavy metals in the soil samples and physicochemical properties were determined. In order to evaluation relationship between heavy metals and soil properties, Pearson correlation was used. Daily exposure to heavy metals by soil ingestion was calculated for children aged 1-5 years

Results: The average concentrations for Cu, Zn, Pb and Cd were 18.29  40.54, 63.27  148.06, 9.1020  3.638 and 0.2005  0.1856 mg/kg respectively. The results showed that there is statistically significant relationship between Zn-Cu, Cu-Pb, Cu- Cd, Zn-Pb, Pb-Cd, Zn-Cd, Clay-Silt, Pb-pH, Zn-pH, Zn- Electrical conductivity (EC), Cu- EC, Pb- EC and EC -Cd. The results of the risk assessment indicated that average daily intake of Cu, Zn, Pb and Cd via soil ingestion for children aged 1-5 years are 3.11  10^-4, 11.3  10^-4, 6.98  10^-5 and 1.53  10^-6  mg/kg per day respectively.  

Conclusion: Heavy metals concentration in urban soils of Bojnurd city may be due to traffic emission and industrial activities. Also at present with regard to low daily exposure of metals and compare them with RAIS, they pose no threat to children health.

Key words : Heavy metals, Topsoil, Health Risk, Daily Intake, Bojnourd City