Radiometric and petrographic characterization of sediment samples collected from Jhelum, Neelum and Kunhar Rivers of Muzaffarabad, Azad Kashmir

In the present study, we present results of radiometric and petrographic analyses of sediment samples collected from the river banks of Jhelum, Neelum, and Kunhar confluencing in the district Muzaffarabad. Gamma activity concentrations due to ²²⁶Ra, ²³²Th, and ⁴⁰K were determined using high-purity germanium detector (HPGe). For a total of thirty sediment samples collected from three rivers, the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K varied from 03.32 ± 0.40 to 100.45 ± 2.08 Bq Kg⁻¹, 02.17 ± 1.35 to 298.42 ± 4.50 Bq Kg⁻¹ and 37.88 ± 11.66 to 1386.32 ± 30.17 Bq Kg⁻¹ with mean values of 36.91 ± 1.12, 61.57 ± 2.81 and 557.33 ± 19.81 Bq Kg⁻¹, respectively. The overall value of Ra_eq for all the investigated sediment samples was found to be in the range from 9.34 ± 3.23 to 633.53 ± 10.14 Bq Kg⁻¹ with mean value of 167.88 ± 6.66 Bq Kg⁻¹. The values estimated for hazard indices, viz., external hazard index (H_ex), internal hazard index (H_in), representative index (I_r), gamma index (I) and alpha index (I_α) for all sediment samples were found to be in the range from 0.02 ± 0.008 to 1.71 ± 0.03, 0.034 ± 0.009 to 1.98 ± 0.03, 0.07 ± 0.02 to 4.57 ± 0.07, 0.03 ± 0.01 to 2.29 ± 0.03 and 0.02 ± 0.002 to 0.50 ± 0.010 with mean values of 0.45 ± 0.02, 0.55 ± 0.02, 1.23 ± 0.04, 0.62 ± 0.02 and 0.18 ± 0.010, respectively. The activity concentrations were subsequently used to estimate the terrestrial gamma ray absorbed dose rate in air at 1 m above the ground and annual effective dose. For all the samples, the values of gamma absorbed dose rate and annual effective dose ranged from 4.42 ± 1.49 to 284.24 ± 4.64 nGyh⁻¹ and 0.027 ± 0.009 to 1.74 ± 0.03 mSv year⁻¹ with mean values of 77.49 ± 3.04 nGyh⁻¹ and 0.48 ± 0.02 mSv year⁻¹, respectively. Mean gamma absorbed dose rate computed in the present study is higher than that reported for world average (59 nGy h⁻¹) and it also exceeds the UNSCEAR proposed safe limit of 55 nGyh⁻¹. The resulting annual effective dose is also higher than the worldwide average value of 0.07 mSv year⁻¹, however, it is less than the safe limit of 1 mSv year⁻¹. From the present study, it is concluded that there is a possibility of high radiation risk from the sediments of the surveyed rivers due to elevated activity concentrations and doses when used as building materials. The building codes need to be revisited taking into account the effects of radiation exposure and absorbed dose on the inhabitants.