HEAVY METALS AND NATURAL RADIOACTIVITY CONCENTRATION IN SOILS FROM SELECTED MINING AREAS IN BOSSO LOCAL GOVERNMENT, NIGER STATE, NIGERIA

Abstract

Activity concentration of naturally occurring radioactive materials (NORMs) and Heavy Metals (HMs) concentration in the soil samples of two artisanal mining areas in Bosso local government, Niger State, were estimated using gamma spectrometry with NaI(TI) detector and flame atomic absorption spectro-photometry. The mean activity concentration of ⁴⁰K ranged from 250± 7 to 433± 6 Bq kg^-1 in the soil samples. ²²⁶Ra ranged from 12± 0.5 to 25± 2 Bq kg^-1, and ²³²Th ranged from 25± 2 to 11± 1 Bq kg^-1. The Annual effective dose (AED) ranged from 26.02 to 39.54  and the absorbed gamma dose rate ranged from 21 to 32.24 nGy/year. The results suggest that the soil radioactivity in the study area, although enhance by the mining and farming activities, are not significant to cause harm to human health considering that the effective doses estimated were lower than the world average of 70  recommended by UNSCEAR, 2000. The radium equivalent (Ra_eq), internal hazard index (H_in), and external hazard index (H_ex) were estimated and their mean fell within the acceptable limit recommended by ICRP, 2007. The HM concentration of Zn, Pb, Cd, Cu, Ni, and Fe in the soils were evaluated and their associated health risk were estimated. The results, when compared with the Canadian Environmental Quality Guidelines (CEQG) indicated that all the metals were far below the standards and the soil samples from the artisanal mining sites are said to be safe for building and construction.