Girault, Frédéric Perrier, Frédéric Przylibski, Tadeusz A. Radon-222 and radium-226 occurrence in water: a review The database is available as a table. radium -226 occurrence;review;Radon -222;Geology 2016-11-24
    https://geolsoc.figshare.com/articles/dataset/Radon-222_and_radium-226_occurrence_in_water_a_review/4253423
10.6084/m9.figshare.4253423.v1