An assessment of the environmental radiation risk from the petrologic units of north-eastern Nigeria; an insight from aero-radiometric data interpretation

Information regarding the radiation risk posed by radioactive emissions from the petrologic units in North eastern Nigeria is extremely limited. Consequently, there has been little research conducted on the environmental impact of radiation exposure from different petrologic units in this region. Hence, the 13 petrologic components of the area that comprises of the migmatites-gneiss (MG), banded gneiss (BG), biotite-hornblende granites (OGe), porphyritic biotite-hornblende granites (OGp), charnockytes (Ch), ignimbrites (JYG), basalts (bb), Keri-Keri Formation (KK), Gombe Sandstones (GS), Pindiga Formation (PS), Yolde Formation (YL), Bima Sandstones (BS), and alluvium (AL) deposits were assessed using aero-radiometric data (equivalent uranium, equivalent thorium, and percentage potassium radio-elements) acquired by Nigerian geological survey agency (NGSA) in 2009. The objective of this study is to compute the amount of radiation across the various rock units of the study area, and examine their radiation risk parameters. The results of this study showed variable levels of radiation across the various rock units examined. The average total activity concentration values recorded ranges from 261.67 ± 447.12 Bq/Kg across KK rock unit to 1482.02 ± 447.12 Bq/Kg across OGp/OGe rock types of the study area. Moreover, the average radium equivalent (Rn _eq), absorbed dose rates (<i>D</i>) estimated ranges from 113.83±461.3₃ Bq/Kg to 305.19 ± 58.51 Bq/Kg, and 51.88 ± 29.65 nGyh^-1 to 144.94 ± 29.65 nGyh^-1 along KK Formation, OGp, and same KK Formation, and OGp respectively. The average environmental radiation hazard parameters of the annual effective dose rate (AEDE), activity utilization index (AUI), respiratory dysfunction parameters (RH _in, RH _out), annual gonad dose equivalent (AGDE), and excess life cancer risk (ELCR) measured across all rock units were found to be within or above their respective acceptable limits of 1 mSv/y, 300 μSv/y, and 0.29 × 10^-3. Additionally, based on the conspicuously higher hazardous radiation (<i>D</i>, Rn _eq, AEDE AGDE, RH _in, RH _out, and ELCR) emissions estimated from the OGp, OGe, MG, BG, and Ch petrologic units, the inhabitants of these localities should therefore limit themselves from excessive exposure to these rocks. Therefore, periodic monitoring of these areas is recommended.