Assessment of some heavy metals distribution and their possible human health risks: A case study of parts of Langtang south area, middle Benue trough, Nigeria

Abstract

An investigation on the distribution of heavy metals in some parts of Langtang South area located within the middle Benue Trough of Nigeria was carried out with the aim of determining their concentration levels for principally environmental assessment and for future mineral exploration studies. The area is characterized by four (4) lithologic formations; Asu River Group, Awe formation, Keana formation and Lafia formation. The area is endowed with abundant Pb-ZnS and BaSO4 mineralizations. Geochemical analysis of soil samples collected from the area revealed the following heavy metal concentrations; Co = 0.022 - 30.09ppm; Cr = up to 21.64ppm; Ni = 0.02 - 50.67ppm; Cu = 0.39 - 63.77ppm; Zn = 0.04 - 3468ppm; As = up to 465.7ppm; Pb = 0.012 - 9322ppm, Cd = up to 17.74ppm. It is also observed that Co, Cr, Zn, As, Cd, Ni and Cu have relatively low spatial distribution pattern in Agri and Bolya villages as well as its surroundings while high spatial distribution pattern of these elements are observed in Jigawa ba da Goshi. However, Pb is observed to have high spatial distribution pattern in almost all northern parts of the mapped area including Agri, Jigawa ba da Goshi and Bolya villages. The concentrations of heavy metals in water samples decreases in the order Cu(223μg/l) > As(75.3μg/l) > Co(28μg/l) > Ni(27.8μg/l) > Pb(14.3μg/l) > Cr(6.8μg/l) > Zn(2.008μg/l ) > Cd(1μg/l) and these are greater than the recommended no-effect values in water. The calculated daily intake of metal showed that the heavy metals portent potential human health risks in decreasing order of Cu> As >Cd. Health risk index found for these heavy metals was less than one suggesting that the consumption of such waters is safe and therefore pose no human health risks. However, the cumulative intake of such heavy metals over a long period of time may cause serious human health problems.