Movement of some heavy metals in poorly drained fadama soils in the Southern Guinea savannah zone of Nigeria

Author: I. Adekunle Amoo ^1*, C. Ikechukwu Ogbonnaya ² and Jeremiah Ojediran ³

Received 13 December 2003, accepted 22 March 2004.

Abstract

The movement of heavy metals (Pb, Fe, Cu, and As) down the soil profile was studied on two fadama crop lands under rice and sugar cane cultivation in Minna, Niger State of Nigeria. Soil type in the experimental fields was loamy sand or sandy clay loam, clay content 13-34%, pH(H2O) 7.04-7.68. In the rice farm organic matter content (1.5-2.0%) and CEC (7.2–22.8 mol kg-¹) were higher than in the sugar cane farm (1.1-1.5%; 6.32–9.45 mol kg-¹). The ranges of heavy metals (mg kg-¹) were for rice farm Pb 0.04–0.16, Fe 0.04–0.08, Cu 0.07–0.2, As 0.12–0.22 and for sugar cane farm Pb 0.04–0.15, Fe 0.05–0.11, Cu 0.06-0.13, As 0.10–0.26. Significant proportions of these heavy metals were accumulated in the top soil. The relatively high organic matter content in the top soil appeared to bind the metals in non-leachable forms thereby reducing their mobility. It was evident that all the heavy metals in the soil depths examined exceeded the acceptable standards for table water and therefore, there is possibility of contamination of ground water.