Spatial distribution of natural radionuclides and radiological hazard assessment in beach sands of the Visakhapatnam coast, Eastern India.

The primordial radionuclides present in beach sands serve as important indicators for understanding the physical and geochemical processes that influence the ocean floor and the marine geological environment. The present research work reports the study on the natural radioactivity present in the beach sands and ambient radiation levels in the beaches of Visakhapatnam, eastern coast of India. The concentrations of primordial radionuclides 238U, 226Ra, 232Th, and 40 K in beach sand samples were measured using the high-purity germanium (HPGe) based gamma spectrometry system. The range of concentrations of 238U, 226Ra, 232Th, and 40 K was 8.9-868, 2.8-1282.8, 6.9-13,691.7, 77.2-1191.1 with mean values 167, 292, 2614 and 449 Bq kg-1, respectively which exceed global average levels. The measured absorbed gamma dose rates on the beaches are comparable to those in monazite-rich high background radiation areas (HBRAs) in India and worldwide. A clear spatial variation was observed, with relatively higher concentrations towards the northern sector of the study area. Spatial distribution maps were generated to visualize the heterogeneity of radionuclide distribution along the coastline. Additionally, variations in radioactivity were observed in samples collected across the width of the beach. The Radiological hazard indices, including radium equivalent activity (Raeq), absorbed gamma dose rate (DR), annual effective dose equivalent (AEDE), gamma level index (Iγ), external and internal hazard indices (Hex & Hin), were evaluated for public risk assessment. Statistical analyses were performed to determine the correlation among the radionuclides. The study provides important baseline data for long-term environmental monitoring and radiological risk assessment in coastal ecosystems.