Preliminary Investigation of Inorganic and Organic Contaminants in Soils within Wukari Metropolis, Taraba State, Nigeria

Abstract

This study aimed at the preliminary investigation of inorganic and organic contaminants in soils within Wukari metropolis and to assess the contamination status and metal bioavailability. Digested soil samples for total metals and fractionation were analyzed for heavy metal concentrations in triplicates using Flame Atomic Absorption Spectrophotometer while 5 Varian Bond Elu SI SPE cartridges was used for solid phase extraction and the soil sample extracts were analyzed by GC-MS. The percentage bioavailability of metals ranged from Fe: 13.81 – 98.85 %, Ni: 65.01 - 80.93 %, Cr: 34.82 – 77.19 %, Pb: 66.93 - 86.59 % and Co: 70.35 - 99.14 % respectively. The bioavailability of Fe, Ni, Pb and Co station ST3 which is an agricultural area were above 50.00%. This indicates that food crops grown in the area may be contaminated by the metals. Irrespective of sampling points, the distribution of metals in the soil samples generally followed the order Fe: residual > carbonate > exchangeable > oxidizable; Ni: exchangeable > carbonate > oxidizable > residual; Pb: exchangeable > residual > carbonate > oxidizable; Co: exchangeable > carbonate > oxidizable > residual. Organic contaminants such as Halo alkanes; bromodichloromethane (molecular weight 162.0 g/mol) and chloroform (molecular weight 118.0 g/mol) were detected in ST1 while, 1, 1, 2 trichloroethane (molecular weight 132.0 g/mol). Another contaminant phenol d5 was recorded in sample ST2, ST3 and ST4 respectively. BTEX compounds were also contaminants present in ST5 (Fuel station near some automobile workshops).