Usoro M. Etesin¹, Aniefiok E. Ite^{1, 2,}, Thomas A. Harry³, Clement E. Bassey³, Edet W. Nsi¹

This study investigates the distribution of cadmium and lead concentrations in the outcrop rock samples collected from Abakaliki anticlinorium in the Southern Benue Trough, Nigeria. The outcrop rock samples from seven sampling locations were air–dried for seventy–two hours, homogenized by grinding and pass through < 63 micron mesh sieve. The ground and homogenized rock samples were pulverized and analyzed for cadmium and lead using X-Ray Fluorescence Spectrometer. The concentrations of heavy metals in the outcrop rock samples ranged from < 0.10 – 7.95 mg kg^–1 for cadmium (Cd) and < 1.00 – 4966.00 mg kg^–1 for lead (Pb). Apart from an anomalous concentration measured in Afikpo Shale (Middle Segment), the results obtained revealed that rock samples from all the sampling locations yielded cadmium concentrations of < 0.10 mg kg^–1 and the measured concentrations were below the average crustal abundance of 0.50 mg kg^–1. Although background concentration of <1.00 ± 0.02 mg kg^–1 was measured in Abakaliki Shale, rock samples from all the sampling locations revealed anomalous lead concentrations above average crustal abundance of 30 mg kg^–1. The results obtained reveal important contributions towards understanding of heavy metal distribution patterns and provide baseline data that can be used for potential identification of areas at risk associated with natural sources of heavy metals contamination in the region. The use of outcrop rocks provides a cost–effective approach for monitoring regional heavy metal contamination associated with dissolution and/or weathering of rocks or parent materials. Evaluation of heavy metals may be effectively used in large scale regional pollution monitoring of soil, groundwater, atmospheric and marine environment. Therefore, monitoring of heavy metal concentrations in soils, groundwater and atmospheric environment is imperative in order to prevent bioaccumulation in various ecological receptors.

cadmium, lead, rock outcrop, mineralization, shale, contamination