Pollution status of arable soils and stream sediments in mining areas of Abakaliki, Lower Benue Trough, Nigeria

Abstract

Geochemical assessment to determine the pollution status of arable soils and stream sediments of the lead–zinc mining areas of Abakaliki, Lower Benue Trough, was carried out. Major communities covered include Enyigba, Mkpuma Akpatakpa, Ameka, Amorie, Amanchara and Alibaruhu where active and abandoned mines are located, covering a total area of about 794.2 km2. One hundred and sixteen soil/stream sediments were collected in two seasons and analysed using Atomic Absorption Spectrophotometric method, and pedologic safety analytical tools including effect range low, effect range median, Multiple contamination, geoaccumulation index (Igeo), contamination factor (Cf), pollution load index and contamination degree were used to assess the impact level of mining activities in soils and sediments. Geological mapping and studies of rock types show that the area is underlain by shales, mudstone and thin beds of sandstone and limestone. Geochemical assessment shows high concentration of Cd, As, Pd, Cu and Zn especially in the mining sites, while pollution indices showed high pollution status for Ag < As < Pb < Hg < Cd in the area. Assessment of contamination degree shows a higher contamination degree for the Mkpuma Akpatakpa and Ameka areas than the for Enyigba and Amanchara areas. Arable soils around the mine sites and stream sediments of rivers which serve as disposal channels are not suitable for food crop production as biomagnification can occur in the food chain.