Total concentrations and fractionation of heavy metals in road-deposited sediments collected from different land use zones in a large city (Nanjing), China

Abstract

In order to investigate heavy metal contamination in an urban environment during urbanization and economic development, 35 road-deposited sediment samples were collected from seven different land-use zones (commercial, residential, traffic, scenic park, educational, industrial and peri-urban) in Nanjing, a large city in P.R. China. The ranges of total metal concentrations found were: 28.7–272 mg kg−1 for Cu; 24.8–268 mg kg−1 for Ni; 37.3–204 mg kg−1 for Pb; 140–798 mg kg−1 for Zn; 0.44–2.19mg kg−1 for Cd; and 60.6–250 mg kg−1 for Cr. Metal fractionation was carried out using a modified three-step European Bureau of References (BCR) sequential extraction procedure. Cadmium and Zn were found predominantly associated with the acid extractable fractions; Ni and Cr were dominant in the residual fraction; Pb was predominantly associated with the residual and reducible fractions; Cu was dominant in the oxidizable and residual metal fractions. Based on the sum of the acid-extractable, reducible, and oxidizable fractions, Cd, Zn and Pb are potentially the most toxic metals in the road-deposited sediment in Nanjing. No significant differences, except for Zn, were found in the metal fractionation pattern for Cu, Ni, Pb, Cd, and Cr in different land use zones.