Assessment of the quality of soil profiles in the vicinity of abandoned barite mines in parts of Oban Massif and Ikom-Mamfe embayment, Southeastern Nigeria
Soil samples were collected at depth intervals of 0-15, 15-30, 30-45 and 45-60 cm subsurface around selected abandoned barite mine dump sites in Oban massif and Ikom-Mamfe Embayment, south eastern Nigeria in order to assess the impact of barite mining activities on soil quality. The soils were characterized by lower clay fraction (<20%), pH range of 4.4-6.2, <4% organic matter content, cation exchange capacity of <12meq/100g, and elevated elemental levels relative to background concentration values. Physico-chemical parameters varied widely both within and among the dump. They decreased with depth in a given soil profiles except for Al, As, Co, Ni and Zn that showed random distribution with depth at some sites. Pollution of the soil profiles by metals were generally restricted to depths of 0-45cm except for As and Zn, Co, Cu, Pb and Ni which extended to 45-60 cm in the subsurface. These mobile metals pose potential contamination danger to aquifers. The absence of significant correlation (p<0.05) between the elements and the physical parameters of surface soils within mine dump sites is indicative of human influence due to barite mining. The significant correlations (p<0.05) among some heavy metals and between some metals with Al, Fe and Mn are suggestive of common sources and controls by hydrous oxides of Al, Fe and Mn respectively. The aluminum normalized enrichment factor and contamination/pollution index indicated different levels of enrichment and pollution. Cd, Cr, Ni, Fe and Mn show minimal enrichment and slight pollution at most sites. While Co, Pb and Zn display moderate enrichment and moderate pollution, Ba, Co and Cu show significant to very high enrichment and severe pollution and as very high enrichment and excessive pollution. These sites require remedial action before any development can proceed and nearby aquifers need to be monitored for heavy metal pollution.
Key words:Soil quality, Soil profile, Barite mines, Enrichment factor, Pollution index