Physicochemical characteristics and heavy metal levels in soil samples obtained from selected anthropogenic sites in Abeokuta, Nigeria

Abstract

This study assessed the effect of heavy metals introduced into the soils through human activities which can bio-accumulate in plants and passed to man via the food chain that can pose health risk. Topsoil samples were collected from selected anthropogenic and control sites (dumpsites, mechanical workshops, abattoirs, fuel filling stations and hospital incinerators) in Abeokuta, Nigeria at the depths 0-5cm, 5-10cm and 10-15cm. Physicochemical parameters such as pH, moisture content, bulk density, organic matter, organic carbon, particle size distribution and Mn, Zn, Pb, and Cd were analyzed in soils using standard methods. Soil pH values ranged from 5.17 - 8.28, moisture content ranged from 3.50 - 28.55 %, bulk density ranged from 0.78 - 2.29 gcm^-3, organic matter ranged from 0.09 - 16.01 %, organic carbon ranged from 0.02 % - 8.48 %. Mean concentrations of heavy metals (mgkg^-1) ranged from 182.69 ± 61.95 - 697.06 ± 85.62; 122.69 ± 30.04 - 632.94 ± 508.79; 19.38 ± 6.72 - 158.50 ± 71.41; 0.25 ± 0.00 - 1.63 ± 1.38 for Mn, Zn, Pb and Cd respectively. Distribution pattern of heavy metals in petrol stations, abattoirs, mechanic workshops and hospital incinerator sites were Mn > Zn > Pb > Cd, while for dumpsites Zn > Mn > Pb > Cd. Pollution index indicated that soil qualities varied between slightly contaminated to severely polluted status. This showed that the heavy metal contamination of the soils does not call for any alarm; proactive measures must be taken to minimize accumulation of these metals.

Keywords: Heavy metals, dumpsites, pollution, physicochemical parameters,  abattoirs and soils