Chemical and Radiological Risk Assessment of Uranium in Surface and Groundwater in Ogoni Land, Rivers State, Nigeria

The chemical and radiological risks associated with uranium in the well, tap/borehole and river/creek waters within three communities that host Ogoniland oilfields was here assessed and measured with gamma ray spectroscopy. The results obtained were used to evaluate chemical and radiological risk over lifetime ingestion by the inhabitants in the area. The activity concentrations of uranium in the water supply sources were found to range from 2.42±0.45 to 12.77±1.12Bq/l. The uranium mass concentration was found to range from 97.52±18.13 to 514.71±45.14µg/l. These uranium mass concentration values of the three water supply sources was found to be over 5 times higher than the recommended international permissible limits. The radiological risks for cancer mortality and morbidity risks were found to be lower than permissible standard which respectively ranged from 9.08x10-5 to 4.79x10-4 and 1.39x10-4 to 7.34x10-4. However, the chemical toxicity which was estimated using lifetime average daily dose (LADD) and hazard quotient (HQ) was found to vary respectively from 2.67 to 14.09µg/kg/day and 4.45 to 23.48. The LADD values exceeded the acceptable reference dose level of 0.6µg/kg/day and the international threshold daily intake value of 1.0µg/kg/day. The HQ was greater than unity implying significant potential risk of uranium in water due to chemical toxicity. Human risk arising from ingestion of uranium in water was therefore attributed to the chemical toxicity of uranium as heavy metal rather than radiological risks. Ion-exchange pre-treatment and reverse osmosis treatment technique should therefore be adopted to the three water supply sources in order to reduce and remove uranium as heavy metal before consumption.