Occurrence, Fractionation, and Human Health Risk Assessment of Potentially Toxic Metals in Urban Soils of Different Land use Types

Abstract

In the present study, surface soil samples from Nagpur city, India, were studied for the fractionation of potentially toxic metals using a modified European Community Bureau of Reference sequential extraction procedure (SEP). The results indicated that the metals Cd, Pb, Co, and Zn showed substantial associations with the mobile fraction (F1: soluble + F2: reducible). The mobile fraction of the metals followed the order Cd (73%) > Pb (47%) > Co (29%) > Zn (25%). The metals Cr, Cu, and Ni were predominantly associated with the residual fraction (F4), suggesting their geological origin, whereas Zn and Co were distributed across all fractions, with higher concentrations in the oxidizable and residual fractions (F3). The ecological risk assessment revealed that Cd, Cu, Ni, and Pb posed greater risks in industrial and residential areas, indicating that industrial and anthropogenic activities were the primary sources of heavy metals. The chronic toxic risk to children, i.e., the hazard quotient (HQ) of heavy metals (∑₆HM), exceeded the threshold limit for ingestion and dermal routes in residential and commercial areas, respectively, whereas for adults, the HQ was closer to the threshold limit of 1 (5.13 × 10^–1). The cumulative carcinogenic risk for children and adults was unacceptable (> 1 × 10^–4) and attributed to the relatively high levels of Cd, Cr, and Pb in soils. These findings underscore the need for risk reduction measures to safeguard human health and reduce the ecological impact of heavy metal pollution.