Concentrations of Selected Heavy Metals in Soil in the Vicinities of Two Major Municipal Dumpsites in Minna, Nigeria

Abstract

This study assesses the concentrations of lead, cadmium, nickel, copper and zinc, as well as some physico-chemical properties of surface soils in the vicinity of Gurusu and Kuyi dumpsites in Minna City, Nigeria, using standard analytical methods. The soil is generally sandy with a pH ranging from 5.20 (slightly acidic) to 8.67 (slightly alkaline). Organic matter content of the soil ranged from 1.0 to 12% while the Cation Exchange Capacity (CEC) ranged from 12 to 120meq/g. The range of mean concentrations (mg/kg) of heavy metals in the Gurusu dumpsite were: Pb(0.71 - 19.51), Cd(2.22 - 2.80), Ni(23.55 - 45.39), Cu(16.74 - 50.37) and Zn(9.52 - 55.73), while that of Kuyi dumpsite were: Pb(37.35 - 54.29), Cd(4.19 - 4.67), Ni(2.83 -10.52), Cu(25.13 - 40.78) and Zn(1.05 - 22.42). The low clay contents, low organic matter and high Cation Exchange Capacity are capable of enhancing metal mobility. Generally, the concentrations of heavy metals in soil decrease with distance from the dump heap in both dumpsites and are higher in the dumpsites than the control sites. This showed that the dumpsites were major contributors to the heavy metal build-up in their vicinities and that the dumpsites were appreciably contaminated by these metals. The concentrations of the heavy metals Pb and Cd in soil samples of both dumpsites were found to be generally higher than the WHO permissive limit for agricultural soils. This calls for concern as these metals are highly toxic and of no known biochemical importance.