Radiological risk assessment of beaches from volcanic oceanic islands: A case study of the Eastern Canary Islands (Spain)

Abstract

This work constitutes the first survey that allows the establishment of baseline levels of environmental radioactivity in beach sands from the volcanic oceanic islands of La Graciosa, Lanzarote, Fuerteventura and Gran Canaria. Activity concentration values of 226Ra, 232Th and 40K were measured by gamma spectroscopy in 108 samples, collected from 39 beaches across the whole study region. The radiological hazard risks associated with these sands were studied. The mean absorbed dose rate in the study region was 20 nGy h−1, which is below the world average value. The mean outdoor annual effective dose for the beaches studied was 0.025 mSv y−1, which is within the internationally accepted safe limit. Additionally, the assessment of the radium equivalent showed that all samples from the Eastern Canary Islands are below the safe limit of 370 Bq kg−1. Despite not posing any radiological risk to the human population, the radiological hazard indices obtained in Gran Canaria were significantly higher than those of other islands. These significant differences seem to be related to the presence of sediments in the beaches of Gran Canaria that have their origin in lithologies with higher activity concentration values of 226Ra, 232Th and 40K that are not present in the rest of the islands.