Assessment Of Ambient Gamma Radiation In The Imphal Valley, Manipur: A Geospatial Analysis And Correlation With Geogenic Factors

Abstract

A comprehensive assessment of outdoor ambient gamma radiation levels was conducted across the Imphal East and Imphal West districts of Manipur, India. This study, covering a broader area and more sampling sites than previous investigations, aimed to establish an updated geospatial dataset of terrestrial absorbed dose rates using a portable survey meter. Measurements were taken at 200 selected sites, representing diverse residential, agricultural, and institutional areas. The recorded absorbed dose rates in air ranged from 0.701 to 1.781 milligray per year (mGy/y), with a mean value of approximately 1.25mGy/y. These values, when converted, correspond to an average annual effective dose of approximately 1.0 mSv, which is notably higher than the nationwide average for India but remains well within the global average values recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Spatial variations were observed, which are attributed to the unique geogenic factors of the region, including the underlying Disang and Barail Group formations and the fluvio-lacustrine alluvial soils known to be enriched in naturally occurring radioactive materials, particularly primordial radionuclides. This dataset serves as a valuable supplement to existing soil radioactivity studies, providing a critical baseline for future radiological monitoring, health risk assessments, and environmental safety studies in this geologically distinct region of Northeast India.