Radiological impact of the Tajogaite eruption (2021, La Palma, Canary Islands)

It is well known that volcanic eruptions represent an important source of natural radionuclide emissions into the environment; however, there are not many studies evaluating their radiological impact. The recent eruption of Tajogaite volcano, that took place in La Palma Island (Canary Islands, Spain) between September and December 2021, offers the opportunity to monitor its radiological impact on both the environment and the nearby population.
The eruption, located on the western site of Cumbre Vieja rift zone, lasted 85 days and large amounts of lavas and pyroclastic materials, along with fine lapilli and ash, were emitted. More than 1200 ha were covered by lava flows, destroying buildings and thousands of kilometres of roads, in addition to few hundred hectares of crop and farmland. The lava flows descended the western part of the island and finally reached the sea creating extensive lava deltas and platforms. As for the ashes, due to western winds, they also impacted the eastern side of the island. Moreover, emissions of radon gas were also detected. Although it is less known than other volcanic gases, its emission is significant due to its radioactive properties and potential health impact if it accumulates in enclosed spaces. In this work, the radioisotopic characterization of the products of the volcanic eruption is carried out, besides studying the possible radiological impact on the surrounding habitable areas. Activity concentrations of the main radionuclides of 238U, 235U and 232Th series, as well as 40K, have been determined from 40 samples of lava, xenopumices and ashes, by gamma and alpha spectrometry. These results have been analysed and compared with those previously obtained from the lavas of the underwater eruption on El Hierro Island in 2011, the Tagoro volcano. Furthermore, the radiological impact on the surrounding environment is also analysed from both measurements of terrestrial gamma radiation and the determination of the radioisotopic composition of soil samples. A total of 80 soil samples were collected and more than 150 measurements of terrestrial gamma radiation were taken during a campaign carried out in July 2023 around the entire island. Interpolation maps have been drawn using the ArcGIS Desktop 10.8.2 to represent the results obtained. The analysis of these maps identifies the areas near the eruption as areas of maximum activity concentration of 226Ra, as well as terrestrial gamma radiation. This trend significantly differs from results published in work prior to the eruption.