Assessment of potential health risks of heavy metals due to sewage irrigation of agricultural soils in the south of Sabzevar

Agricultural soils irrigation by urban sewage is a key factor to increase soil pollution and environmental risks. Heavy metals are one of the most important sewage pollutants which may produce different diseases.
The specified locations were selected for surface soil sampling to investigate the effect of sewage irrigation on the soil and vegetation (parsley) composition in the south of Sabzevar area. The heavy metals concentration and trace elements composition of whole samples were determined by ICP-MS. The heavy metals bioavailability was measures by DTPA method. The heavy metals concentration in DTPA extracted solution and parsley samples were defined by FAAS method.
Ni and Cr concentrations in the non-polluted soils are more than standard limits. These high concentrations have been generated by enriched parental materials. In addition to Ni and Cr, polluted soils have potential environmental risk because of high concentration of Ag, Cd, Co and Zn. The DTPA results showed that non-polluted soils, unlike polluted soils, have low bioavailability. The vegetables cultivated on the polluted soils have several times higher heavy metal concentrations than non-polluted samples. These vegetations show higher Cr bioavailable value than FAO/WHO standard.
Heavy metal concentration has been increased by long time sewage irrigation in the southern Sabzevar soils. These heavy metals are environmentally harmful. Nickel content of vegetables cultivated on polluted soils have high HRI (>1) index which indicates high health risk for consumers.