RADIOANALYTICAL AND HYDROGEOCHEMICAL ASSAYS FOR ENVIRONMENTAL AND HEALTH IMPACT ASSESSMENTS OF CEMENT INDUSTRIES IN NIGERIA

Abstract

Radiological and geochemical health and environmental impact assessments of cement production in Nigeria has been carried out in this study. Radioanalytical assays were carried out through gamma spectrometric detectors to analyze different sample groups which include cement dusts, cement raw materials, soil, water, foodstuff and grass in the vicinity of cement production plants. In addition, geochemical analyses of the ground and surface waters were carried out to ascertain some of their physico-chemical properties, major-ions concentrations, and heavy metals composition. Relevant radiological parameters and hazard indices were estimated in order to underscore the health detriments. The activity concentrations of 238U, 232Th and 40K in the cement samples ranged 18.22±0.40 - 91.12±2.10, 15.61±0.75 - 66.85±0.40 and 28.27±8.43 - 451.84±25.00 Bq kg-1 respectively with resulting indoor absorbed dose rates (Din) within the range of national averages of 20 - 200 nGy h-1. The mean annual indoor effective dose and annual gonadal dose equivalent for all the cement samples are approximately equal to the global averages of 0.4 and 0.3 mSv y-1. The activity concentrations of the aforementioned radionuclides in the raw and process materials ranged 5.32±0.85 - 580.02±24.30, 1.87±0.15 - 73.74±3.05, 3.10±0.75 - 75.56±5.62 Bq kg-1 respectively. The average annual outdoor effective dose for all the raw and process materials was approximately equal to the global average of 0.07 mSv y-1 as reported by the United Nations Scientific Committee on the Effects of Atomic Radiation. The mean activity concentration of 238U, 232Th and 40K in the soil samples were found to be 53.17±0.69, 44.66±0.39 and 383.42±4.32 Bq kg-1 respectively. Only 40K was detected in food and grass samples and activity concentrations were found to be within the natural values. The 238U activity concentrations in some ground and surface water make them unsafe for drinking especially to infants and children. Disequilibria in 238U and 232Th decay series were observed in the cement, raw materials and soil 3 samples resulting to activity concentration ratios of 0.45 – 1.02 and 0.13 – 2.53 for 228Ra to 232Th and 226Ra to 238U respectively. All the physico-chemical parameters showed that the cement industries have significant effects on water quality in the vicinity of the production plants. Among the major ions and heavy metals that were measured, F-, PO43-, SO42-, Al, As and Ba occur in some of the surface water and groundwater in concentrations that are above their recommended limits by the World Health Organization. The metal index and metal pollution index have ranges of 0.25 - 6.72 and 3.49 - 57.35 respectively. The results of this study reveal that the cement production process results to radiological and geochemical health hazards to occupational and public exposure groups. It also caused disruptions in the terrestrial and aquatic environments in the host communities of cement plants.