Ecological and health risk assessment of radionuclides and heavy metals of surface and ground water of Ishiagu–Ezillo quarry sites of Ebonyi, Southeast Nigeria

Abstract

Exposure to heavy metals and natural radionuclides via water sources disposes mankind to deterioration of health. Radionuclides (238U, 232Th, 40K) and heavy metals (Pb, Cr, Cd, As) in surface and borehole waters close to granite quarry sites and the extent of metal contamination for evaluating health risk for individual populations were studied. Mean values of 238U, 232Th, and 40K in surface water (11.56, 8.84 and 35.66 Bq/l) and borehole water (2.68, 10.81 and 18.66 Bq/l) were determined. Total estimated annual effective doses for ingestion of radionuclides via surface and borehole water samples were: children (1.139; 1.058 mSv/y) and adults (2.377; 2.231 mSv/y), adults are more vulnerable to radiation risk. Average heavy metals in both water sources are in order, As >Cr > Pb> Cd. Radionuclides and heavy metals exceeded WHO standards for potable water. Contamination factor, pollution load index, geo-accumulation index, ecological risk and potential ecological risk indices (PERI) showed that surface water contamination is higher than the borehole water within the study areas. Multivariate statistical analysis accounted for 86.30% of the total variance indicating strong correlation between As, Cr, Pb and PERI which was traced to geogenic and anthropogenic sources of the metals that contributed to high potential ecological risk in surface water. Hazard quotient (HQ) and hazard index (HI) (non-carcinogenic) and carcinogenic risk assessment values were within USEPA HQ and HI ≤ 1 and 1 × 10−6 – 1 × 10−4 which portrays little or no significant health effect from the use of studied water sources. Therefore, surface and borehole water within 5 km radius from granite quarry locations should be pretreated before use to avoid long-term effect of pollutants accumulation.