Occurrence and distribution of heavy metal in arable soils around lead–zinc mining sites of Abakaliki, Southeast Nigeria

Abstract

This study involved the geochemical assessment of the occurrence and distribution of heavy metals in available agricultural soils and stream sediments in the lead–zinc mining areas of Abakaliki, Southeastern Nigeria. A total area of about 794.2 km2 was assessed, with major communities covered including Enyigba, Mkpuma Akpatakpa, Ameka, Amorie, Amanchara and Alibaruhu where active and abandoned mines are located. One hundred and sixteen soil/stream sediments were collected and subjected to geochemical analysis using the atomic absorption spectrophotometric method. The result shows concentration of Cd > Pb > As > Zn > Cu > Ag > Hg > Cr, especially in the areas close to the active mines. The contamination percentage of metal in samples shows Cd (40.51%), Pb (36.20%), As (23.27%), Zn (17.24), Cu (8.62%) and Cr (0%). This implies that arable soils around the mining areas are not suitable for food crop production as biomagnification can occur in the food chain. The consumption of food produce in these areas can lead to potential health risk as they accumulate. However, the Mkpuma Akpatakpa and Ameka areas show higher distribution of these metals than the Enyigba and Amanchara areas. Seasonal analysis shows a decreased concentration of chemical constituents in the rainy season relative to the dry season except for Cd, Cr and Hg.