Distribution and Risk of Metals in Soils of Refuse Dumpsites in Some Urban Towns in Delta State, Nigeria

Refuse dumpsites often contain materials capable of polluting surrounding soils. In this study, the spatial distribution of metals in soils of refuse dumpsites in three urban towns (Ughelli, Sapele, Orhuwhorun) in Delta State, Nigeria were examined. Soil samples were collected from three dumpsites in the aforementioned towns at depths 0-15 cm, 15-30 cm and 30-45 cm, respectively. Some physicochemical properties of the soil profiles such as pH, Electrical Conductivity (EC) and Total Organic Carbon (TOC) were determined using standard methods, while metals concentration were determined using atomic absorption spectrometry after digestion with aqua regia. The results for all sites and depths ranged as follows: 
pH: 4.64 to 7.85; EC (μʃ cm-1): 60.8 to 451; and TOC (%): 0.06 to 1.49 %. Metals concentration (mg kg-1) ranged as follows: 0.05 to 4.5 for Cd, 9.0 to 149 for Pb, 4.20 to 15.4 for Cr, 1.0 to 14.5 for Ni, 1.0 to 124 for Cu, 20 to 510 for Zn, 
and 1650 to 11865 for Fe. The potential ecological risk of the metals is in the order of Cd > Pb > Cu > Zn > Cr > Ni. The study indicates that the metals studied except Cd do not pose environmental risk considering their relatively low concentrations.