Geochemical variation and contamination level of potentially toxic elements in land-uses urban soils

Urban soils pollution by potentially toxic elements (PTEs) due to natural and anthropogenic factors arouses a growing interest in Bangladesh. In this study, nine PTEs (Cr, Ni, Cu, As, Cd, Pb, Fe, Mn and Zn) in five different land-uses urban soils were analysed by inductively coupled plasma mass spectrometry (ICP-MS) to assess the geochemical speciation of PTEs in soils. The values of pH, electrical conductivity and organic carbon were ranged from 5.2 to 6.9, 36.3 to 124.4 mu S/cm and 0.55% to 1.32%, respectively. The mean concentration of PTEs in soils were followed the decreasing order of Fe (1097) > Zn (91.82) > Mn (55.52) > Cu (41.99) > Cr (35.11) > Ni (33.32) > Pb (32.10) > As (15.88) > Cd (3.14). The speciation analysis indicated that Cr, Ni, Fe, Mn and Zn were predominantly associated with the residual fraction where Cu, As, Cd and Pb were associated with the exchangeable and carbonate-bound fractions. The contamination factor (C-f(i)) values of As ranged from 0.69 to 2.66 and Cd ranged from 8.22 to 14.74 revealing that the land uses urban soils were strongly impacted by As and Cd. Contamination factors and ecological risk index suggest that land-use urban soils have considerable to very high ecological risk due to major contribution of As and Cd contamination in soil. Therefore, it is essential to develop functional concepts of urban land-uses soils adapted to the high level of contamination which shall improve human well-being in Dhaka City, Bangladesh.