Physicochemical profile studies of soil along the banks of Ubu river in Ekwusigo and Nnewi local government areas of Anambra State of Nigeria

A physicochemical profile study on the soil along the banks of the Ubu river that runs across Ekwusigo and Nnewi Local Government Areas (LGA) of Anambra State of Nigeria was investigated for possible evidence of industrial waste disposal by the various large to medium scale industrial activities taking place within the two LGAs. When compared with soil samples from Uzoakwa Ihiala (pH 5.44) with little or no industrial activities, the soil along the banks of the course of the river were found to be more acidic with mean pH values that are lower than 4.7. Similarity in mean sulphate (7.01 mg/kg), phosphate (12.95 mg/kg) and chloride (242 mg/kg) contents was observed between the soils from the banks at Nnewi with those of the Uzoakwa Ihiala that was used as control. This was attributed to contributions from domestic sources rather than from industrial sources, and partly to the similarity of their soil chemistry that may be indigenous to both areas. Electrical conductivity values (55 -74 microS/cm) show that the ionic content of the soil is lower than those of the control (129 microS/cm). This may have been explained by the higher extractible Ca (175.73 mg/kg), K (34.32 mg/kg), and Mg (1.94 mg/kg) recorded for the control. The abundance of the metals extractible from the soils of the river banks follow the sequence Ca>K>Na>Fe. Results for the digested soil samples show that Fe is the most abundant metal in the soil with mean values that are close to 13,000 mg/kg, but is much lower than the mean value of 39,210 mg/kg recorded for the control. Both bank and control samples can be characterized as ferrous. The relative abundance of metal ions observed in the digested soil samples from the river banks follow the sequence Fe>Al>Ca>Na>K>Zn>Cr. Values of 4,565 mg/kg and 300 mg/kg were recorded for total hydrocarbon content and lead respectively for soils around Cento Group, indicating that there were industrial waste disposal or spillages on soil around the area, which was not observed in other areas.