Evaluation of Heavy Metals Pollution of Soils around the Derelict Enyigba Mines and Their Sources

The concepts of pollution indices (PI) and enrichment index (EI) were used to evaluate the heavy metals pollution status of soils in areas around the derelict Enyigba Mines. Further to this the possible sources of metals in soils is discussed. The enrichment index of Cu is generally low and is only higher than 1 in Ameka. Cu toxicity in the area is not significant. It can be suggested that there is Cu deficiency in soils in most other areas where the P.I. lies between 0.12 and 0.08. The enrichment index of Pb is high in all sampled soils. This ranges from 12.2 to 155.1 in Enyigba, 1.15 to 1.26 in Ameka. The enrichment index of Zn in the area is generally below 1 except in few samples from Ameka where it ranges from 1.56 to 6.20. The enrichment index of Cd is higher than 1 in over 90% of the soil samples. P.I. for soils in the area is critical in Ameka (1.3 – 18.7), Enyigba (2.68 – 6.38). These show that most of the soils around the derelict Enyigba mines are polluted by heavy metals especially by Pb, Zn, and Cd. Intensive agriculture and manufacturing industry is not developed in the area. The source of metal enrichment in soils in the area is earth materials. These include the Asu River Shales, the mineralised veins and mine tailings. These as the sources of metal in soil is further demonstrated by the proximity of the anomalies to areas of known mineralisation and the trends of the anomalies which show strong relationship to established trend of geologic structures.