Quantification and Speciation of Lead, Cadmium and Chromium in Dandora Dumpsite Soils

Abstract

Open dumpsites are one of the main sources of heavy metals and as a result, lots of research has been undertaken on the pseudo-total content of heavy metals in dumpsite soils, but little research on the forms in which they exist. The current research was carried out to determine levels of chromium, lead and cadmium in the various fractions of Dandora dumpsite soil and how they are fractionated in the topsoil and subsoil horizons. Samples were obtained from eight sites with depths of (0-30 cm) and (30-60 cm) for topsoil and bottom soils respectively. The modified Community Bureau of Reference (BCR) sequential extraction procedure was used and metal analysis performed using flame atomic absorption spectrophotometry. The metals (lead, chromium and cadmium) total concentration (µg/g) in the upper soil profile ranged from 42.22 to 1096.21, 38.26 to 180.60 and 11.23 to 44.22 while the lower soil profiles were 54.19 to 239.28, 30.56 to 76.48 and 9.47 to 22.56, respectively. The concentration of lead in various fractions of the upper soil profile followed the order; reducible > oxidisable > residual > exchangeable, while that of chromium was residual > oxidisable > reducible > exchangeable. Cadmium followed the order exchangeable > residual > reducible > oxidisable. The percentage of the metals in non-residual fraction were Pb (78%), Cr (58.7%) and Cd (70%). Their mobility factors were (Pb) 39.7 (Cr) 7.75 and (Cd) 5.02 in the upper soil profiles. Thus, the results suggest that Dandora dumpsite is highly polluted with the selected heavy metals.