Chlorine-39 in rainfall at a temperate latitude (40 degrees N)

Area of Science:

• Environmental radioactivity
• Cosmic ray physics
• Atmospheric chemistry

Background:

• Cosmic rays interact with atmospheric gases, producing radionuclides.
• Chlorine-39 (39Cl) is a radionuclide formed from Argon-40 and muons.
• Radioactive isotope concentrations in precipitation can indicate atmospheric processes and geographic location.

Purpose of the Study:

• To confirm the presence of Chlorine-39 in rainwater.
• To measure the radioactivity of Chlorine-39 in Thessaloniki, Greece.
• To investigate the latitudinal effect on cosmic radiation by comparing results with other locations.

Main Methods:

• Rainwater samples were collected.
• Radioactivity measurements were performed to determine the presence and half-life of radionuclides.
• The half-life of the detected radionuclide was estimated to be between 58 and 63 minutes, averaging 60.4 minutes.
• Disintegration rates were measured in Becquerels per liter (Bq L(-1)) and disintegrations per minute per liter (dpm/L).

Main Results:

• The presence of Chlorine-39 (half-life 56.2 min) was confirmed in rainwater samples.
• The measured half-life of the radionuclide in rainwater averaged 60.4 min.
• The average disintegration rate of the radionuclide was 2.3 Bq L(-1) (140 dpm/L) in Thessaloniki.
• The concentration of 39Cl was lower than reported for southern latitudes, consistent with the latitudinal effect of cosmic radiation.

Conclusions:

• The study confirmed the presence of Chlorine-39 in rainwater at mid-latitudes.
• The measured radioactivity levels align with expected cosmic radiation intensity at Thessaloniki's latitude.
• The findings support the influence of latitude on cosmic ray-induced radionuclide concentrations in the atmosphere.