In order to assess the distribution of heavy metals in the urban environment; concentrations of Cd, Cu, Pb, Mn, Ni and Zn were measured on 21 topsoil samples collected from roadside soils of Chittagong city. The heavy metal concentrations were determined by flame atomic absorption spectrometry after digesting the soils with nitric acid-perchloric acid. Mean Cd, Cu, Pb, Mn, Ni and Zn concentrations of the investigated urban soils are 2. 43, 32.63, 7.33, 160.79, 860.33, 139.30 mg kg -1 respectively. Compared to urban soils of some other cities in the world Cu, Cd, Pb, Mn and Zn concentrations were somewhat similar. Ni concentration largely exceeded the maximum allowable concentration (60 mg kg -1) indicating high contamination. Stepwise multiple regression indicated that soil properties was responsible for 37 to 42% variation in Cd, Cu and Pb content and in case of Ni it was only 16%. The main sources of Ni contamination in Chittagong city can be considered as anthropogenic sources.
Total, 1N NH 4 OAc and 0.1N HCl extractable Cd and Pb were determined in soils of four sites of Chittagong City contaminated by city sewage (Site-I), tannery (Site-II), fertilizer factory (Site-III) and cement factory (Site-IV) and collected on profile basis and distance from the source points. Total Cd contents of soils in different sites ranged from 0 to 2.48 mg kg-1 while the values for Pb varied from 7.14 to 54.31 mg kg-1. Ammonium acetate and 0.1 N HCl extractable Cd in the surface soils were in the range between 0.01 and 0.62 mg kg-1 and between 0.03 and 1.66 mg kg-1 , respectively. Lead contents in surface soils extracted with 1N NH 4 OAc and 0.1N HCl varied from 0.18 to 2.72 mg kg-1 and 2.00 to 50.51 mg kg-1 respectively. A close relationship between the total amounts of Cd and Pb and their extractable amounts with 1N NH 4 OAc and 0.1N HCl was found. The concentrations of total and extractable Cd and Pb were inversely correlated with soil pH. Strong positive correlations were observed for Cd and Pb with CEC and organic matter contents of soil.
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