Assessment of Natural Radioactivity Level of Shallow Aquifers in Enugu Metropolis, Nigeria

Thirteen samples from shallow aquifer in Enugu were assessed for Natural Radioactivity Level using High Purity Germanium (HPGe) Analyser. The radionuclides identified in the water samples are 238U, 232Th, 226Ra and 40K. The activity concentration values of 238U range from below detection level to 0.49 ± 0.04Bql–1 , with an average of 0.19 ± 0.03Bql-1 ; 226Ra range from below detection level to 10.26 ± 0.72Bql–1 , with an average of 5.18 ± 0.42Bql–1 ; 232Th range from below detection level to 1.26 ± 0.11Bq l–1 , with an average of 0.63 ± 0.07Bql–1 ; 40K range from 9.67 ± 0.55Bql–1 to 16.52 ± 0.88Bql–1 , with an average of 14.44 ± 0.79Bql–1 . Comparing the result with the available standards, 226Ra in the groundwater is above the guidance level. The seasonal variation in concentration of 238U, 226Ra, 232Th and 40K in groundwater are 0.28 ± 0.03, 8.45 ± 0.72, 0.96 ± 0.12 and 20.01 ± 1.08Bql–1 respectively. The annual effective dose due to ingestion of 238U, 226Ra, 232Th and 40K in groundwater received by adult in the study area ranges from 0.073mSvy-1 to 4.33mSvy-1 with an average value of 1.28mSvy-1 while that of the children ranged from 0.16 to 4.80mSvy-1with an average of 1.37mSvy-1 . These exceeds WHO, and UNSCEAR recommended limit of 0.1mSvy-1 , 1.0mSvy-1 and 0.29mSvy-1 .