In-situ Radiometric Assessment of UNESCO World Heritage Sites in Kathmandu Valley of Nepal Using Gamma Ray Spectrometry

Abstract

The paper presents the results of rapid in-situ radiometric assessment of the seven UNESCO Cultural World Heritage Sites of the Kathmandu Valley in Nepal. The geological condition of the valley and NORM present in the building materials of Heritage Sites can increase gamma exposure and, therefore, be hazardous to the public and the environment. The objective of the study is to provide baseline data of annual effective dose (AED) and to assess associated health risks in the surrounding area of World Heritage Sites. The average absorbed dose rates in air and mass concentrations of radioelement ⁴⁰K, ²³⁸U, and ²³²Th are measured in the range 120.907±11.121 to 152.320±15.072 nGy/h, 2.785±0.734 to 3.458±0.802%, 6.599±2.965 to 8.778±3.379 ppm and 17.744±+5.897 to 25.137±6.959 ppm, respectively. The dose rates contributed by the particular gamma radionuclides are also calculated. The statistical analysis shows that the distribution of dose rates is asymmetric with positive skewness. The dose rates have a high and positive correlation with the mass concentrations of radioelements. From the average measured absorbed dose rate, the AED and excess lifetime cancer risk (ELCR) are estimated. Despite the dose rate being higher than the global average value, it does not pose any radiological health risks to visitors or the public living in the vicinity (<1 mSv/y).