Soil radionuclide concentrations and radiological assessment in and around a refining and petrochemical company in Warri, Niger Delta, Nigeria

摘要

Radioactivity measurements have been carried out using gamma-ray spectroscopy to determine the radionuclide concentrations in soil samples in the premises of the Warri Refining and Petrochemical Company located in the Niger Delta region of Nigeria and also in communities around it. The radionuclide contents of the crude oil and petroleum additives were also similarly determined. Results indicate that on the premises used by the company, the ranges of activity concentrations of K-40, Ra-226 and Th-228 in the soil samples were 261.3-932.3 Bq kg(-1), < 4.2-23.0 Bq kg(-1) and < 5.1-10.2 Bq kg(-1), respectively. For the 13 villages studied, activity concentrations ranged from < 17.2-766.3 Bq kg(-1), < 4.2-104.7 Bq kg(-1) and < 5.1-13.7 Bq kg(-1), respectively, for 40K, 226Ra and 228Th. The lowest radionuclide concentrations were found in the crude oil relative to the petroleum additives. The highest outdoor effective dose rate obtained in the study was 47.5 mu Sv y(-1) for the villages and 35.2 mu Sv y(-1) within the company premises. These values are less than the world average outdoor value of 70 mu Sv y(-1) given by UNSCEAR. Overall, it can be concluded that the long duration of refining activities does not seem to have affected radionuclide concentrations in the environment. Measurements also showed that the observed radiation dose rates did not vary significantly from the previously determined Warri City outdoor gamma radiation dose rates, for which the probability of occurrence of any health effects of radiation was judged low. The measurements, therefore, are interpreted to represent baseline radiometric data for future reference and research in the area.