Indoor radon periodicities and their physical constraints: a study in the Coimbra region (Central Portugal) |
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Authors: | L.J.P.F. Neves S.M. Barbosa A.J.S.C. Pereira |
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Affiliation: | aIMAR, Department of Earth Sciences, University of Coimbra, 3000-272 Coimbra, Portugal;bUniversity of Porto, Department of Applied Mathematics, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal |
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Abstract: | Indoor radon activities were measured during a period of 6 months, as well as several physical environmental variables (temperature, pressure, humidity and rainfall). The location was a small room at an administrative building of the University of Coimbra, usually undisturbed by human activities and situated over bedrock of low-uranium Triassic red sandstones. A low average activity of radon was observed (36 Bq m−3), however showing a very well marked daily periodicity (10 ± 5 Bq m−3), with maximum values occurring more frequently between 9 and 10 a.m. Daily variations are shown to have no relation with earth tides, and their amplitudes exhibit a significant correlation with outdoor temperature; no dependence on barometric pressure was found. Rainfall disturbs the observed daily radon cycles through a strong reduction of their amplitude, but has no effect on the long-term variability of the gas concentration. |
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Keywords: | Indoor radon Continuous monitoring Environmental influences Cyclicity Time series analysis |
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