Seasonal Be-7 behavior in urban PM2.5 and associated inhalation dose in Bangkok

Beryllium-7 (Be-7), a cosmogenic radionuclide produced by cosmic ray spallation in the upper atmosphere, serves as a tracer for atmospheric circulation and aerosol dynamics. This study establishes the first baseline dataset of Be-7 activity concentrations in PM2.5 aerosols across winter, summer, and rainy seasons in Bangkok, Thailand. Nineteen weekly samples were collected from December 6, 2022, to July 25, 2023, using a high-volume air sampler placed 30 m above ground level. Be-7 concentrations were quantified using high-purity germanium (HPGe) gamma spectrometry with ISO-compliant uncertainty analysis. Seasonal variability was observed, with lower concentrations during the rainy season due to precipitation scavenging. The corresponding annual inhalation doses were estimated to be 2.19 × 10^-8 mSv for adult males and 1.89 × 10^-8 mSv for females-orders of magnitude below the 1 mSv/year public dose limit recommended by the International Commission on Radiological Protection (ICRP). These findings indicate minimal radiological health risk from Be-7 inhalation in urban PM2.5 and provide critical input for environmental radiation surveillance and radiation protection strategies in tropical megacities.