Effect of Land Use on the Distribution of Heavy Metals in Abeokuta, Southwestern Nigeria

To prevent risks of metal pollution and secure public health, the assessment of the pollutant load of different land use is germane in emerging cities. The study investigated the distribution of water, EDTA and HCl extractable Cd, Pb, Zn, Cu, Cr, Ni and Mn in soils of different land uses in Abeokuta, southwestern Nigeria. It was hypothesized that land use pattern has an effect on the depth distribution of heavy metals. Profile pits were sunk and sampled systematically at 0-20, 20-40 and 40-60 cm in agroforestry arboretum, oil palm plantation, plantain plantation, fadama farm, degraded land and cassava farm. Samples collected were analyzed by standard laboratory procedures and data collected were analyzed statistically. Results indicated that water is a poor extractant for metals. Nickel was less than 0.002 mg kg- in the soils irrespective of the extractants used. The metals were more concentrated in the degraded soil followed by soils of plantain plantation, agroforestry, oil palm, cassava and least in fadama. Zinc and Mn are concentrated in 0-20 cm, Pb in 20-60 cm, Cr in 40-60cm. The efficiency of metal extraction was in the order: EDTA > HCl > water. Soil lead, Zn, Cr and Mn are positively correlated.