Identification of tidal and climatic influences within domestic radon time-series from Northamptonshire, UK

Analysis of data from extended radon concentration time-series obtained from domestic and public-sector premises in the vicinity of Northampton, UK, and elsewhere, confirms that, in addition to the generally recognised climatic influences, ‘Earth Tides’ and ‘Ocean Tidal Loading’ drive periodic radon liberation via geophysically driven groundwater level variations. Regression and cross-correlation with environmental parameters showed some degree of association between radon concentration and mean temperature and rainfall. Fourier analysis of radon time-series identified periodicities of the order of 23.9 h (luni-solar diurnal, K1), 24.0 h (solar day, S1), 168 h (1 week) and 661.3 h (lunar month, Mm), while cross-correlation with tidal strength demonstrated periodicity of the order of 14 days (lunar–solar fortnight, Mf). These results suggest that astronomical influences, including tides, play a part in controlling radon release from the soil.