Multiple seasonality in soil radon time series

Area of Science:

• Environmental Science
• Geophysics
• Atmospheric Science

Background:

• Radon dynamics are complex, influenced by numerous environmental factors.
• Understanding temporal variations in radon concentration is crucial for environmental and health studies.
• The Italian Radon mOnitoring Network (IRON) provides extensive data for analyzing radon behavior.

Purpose of the Study:

• To characterize temporal variations in radon measurements across multiple monitoring sites in Italy.
• To investigate the relationship between radon concentration, temperature, and other environmental factors.
• To identify common periodicities and site-specific influences on radon dynamics.

Main Methods:

• Continuous wavelet transformation for time-frequency spectral analysis.
• Analysis of 2-hourly and daily radon measurements from the IRON network.
• Comparison of frequency content and synchronicity between radon and local temperature time series.

Main Results:

• Persistent sub-daily, daily, and yearly periodicities were observed across all monitoring stations.
• Structural seasonal breaks occurred with consistent frequency but at different times across sites.
• Radon time series showed marked 1-day and 365-day cycles, with less evident 0.5-day and 180-day cycles.
• Phase differences in 365-day cycles between radon and temperature were site-location dependent, indicating local factor control.

Conclusions:

• Environmental-climatic factors, including temperature, pressure, and rainfall, significantly influence radon concentration cycles.
• Short-period radon cycles are linked to temperature and pressure variations.
• Long-period radon cycles are influenced by seasonal rainfall patterns.
• Observed variations in radon-temperature phase differences can explain discrepancies in previous research.