Chemical speciation and Distribution of heavy metals in soil of waste dump sites at various automobile mechanic workshops of South-south, Nigeria

Abstract

Distribution and determination of chemical form of heavy metals in soil of automobile mechanic waste dump sites of South-South, Nigeria were investigated. Sequential extraction was use to fractionate heavy metals from the samples into five operationally defined groups; exchangeable fraction, fraction bound to carbonate, Fe/Mn oxide bound fraction, fraction bound to organic matter and residual fraction. Analysis of the metals was carried out by UNICAM SOLAAR 32 atomic absorption spectrophotometer. Zn (2.661; 1.831; 1.035 µg/g) was predominantly associated with Fe/Mn oxide for the Sites A, B and C respectively. The carbonate fraction of Pb represents more than 25% of the total Pb found in the soils. A major portion of Cu (1.716, 0.280, 0.082 µg/g) was associated with organic fractions for the three sites respectively, whereas Cd (0.293, 0.335, 0.305 µg/g) was associated with exchangeable for the three sites respectively. The results were interpreted in terms of the environmental mobility and bioavailability of the metals. However, Pb (96.658, 98.691 and 100 %) was more mobile and bioavailable compared to the other metals studied.