Spatial distribution and risk profiling of natural radionuclides in Ravi River sediment

Radiation from Naturally occurring radionuclides can be harmful to the humans and ecology if above the threshold level. This study was designed to assess the natural radionuclides in the sediment of the Ravi River near Lahore city. Sediment samples were assessed for natural radioactivity using a High Purity Germanium detector (HPGe). The mean Ra-226, Th-232 and K-40 activities are 19.64 ± 4.33, 24.55 ± 0.87 and 469.22 ± 83.47 Bq kg −1 respectively. The activities of Ra-226 and Th-232 were below the world average and of K-40 exceeded the world average. Spatial distribution of the radionuclides was done using Inverse distance weighting interpolation. Downstream sediments have higher activity as compared to the upstream sediment samples. The health hazards were assessed by computing Radium equivalent (Ra eq ), External and internal hazard indices (H ex and H in ). Internal and external absorbed (D in and D ex ) and effective doses (E out and E in ) and lifetime cancer risk (LCR out and LCR in ). The average values of Ra eq , H ex , H in , D ex (nGy h −1 ), D in (nGy h −1 ), E out (mSv y −1 ), E in (mSv y −1 ), LCR out × 10 −3 and LCR in × 10 −3 are 91.79 ± 17.5, 0.25 ± 0.05, 0.30 ± 0.06, 43.79 ± 8.38, 83.16 ± 15.9, 0.05 ± 0.01, 0.13 ± 0.03, 0.19 ± 0.04 and 1.43 ± 0.27. Internal exposure to the radionuclides posed a higher risk as compared to the external exposure but the health hazards are below the threshold. Overall, this study concludes that the radionuclide activity in the sediments of Ravi River near Lahore is low and the sediments are safe to use as a construction material, but constant monitoring is recommended.