PERIODICITY ANALYSIS OF GAMMA RADIATION MEASUREMENTS IN THESSALONIKI, NORTHERN GREECE, IN THE PERIOD 1988-2015.

Area of Science:

• Environmental radioactivity monitoring
• Atmospheric physics
• Solar physics

Background:

• Long-term gamma radiation monitoring is crucial for understanding environmental radioactivity.
• The Chernobyl accident significantly impacted environmental 137Cs levels.
• Understanding periodicities in radiation is key to identifying influencing factors.

Purpose of the Study:

• To analyze the time-series of gamma radiation dose rates over 27 years.
• To identify and characterize periodicities in the absorbed dose rate in air.
• To investigate the correlation of these periodicities with meteorological and solar activity.

Main Methods:

• Utilized NaI(Tl)-based Xetex 501A and portable high purity germanium (HPGe) detectors for gamma measurements.
• Collected time-series data from 1988 to 2015.
• Applied time series analysis, including Fourier analysis and Zhao-Atlas-Marks transform.

Main Results:

• The total absorbed dose rate in air shows an exponential decrease over time.
• 137Cs contributed significantly, decreasing with an effective half-life of ~13.5 years.
• Identified three main periodicities (12, 42.3, and 53.2 months), linked to seasonal variations, air temperature, and potentially solar activity.

Conclusions:

• Environmental gamma radiation exhibits complex temporal variations beyond simple decay.
• Meteorological parameters and solar activity appear to influence measured gamma dose rates.
• The study highlights the interplay between anthropogenic and natural factors in environmental radioactivity.