Periodic behaviour in ground-level environmental radioactivity: fingerprints of solar activity?

Abstract

Long-term data on ground-level environmental radioactivity are analysed, these referring to daily records of the total β activity in air and absorbed dose rate between 1976 and 2016 in Zagreb, Croatia. A Fourier analysis of these two datasets reveals a periodic behaviour with numerous periods ranging from approximately four months to roughly 21 years. Ninety per cent of the periods agree remarkably well with known periodicities in solar activity throughout solar cycles 21–24, which suggests that the observed modulations were most probably caused by variations in the cosmogenic radionuclide production in the upper atmosphere. Hence, one can extract the fine structure of solar activity from environmental radioactivity monitoring data, which implies that it could be possible to supplement the existing information on the exposure of Earth to cosmic rays by analysing results from radioactivity monitoring stations all over the world. These datasets cover Earth densely due to the existence of a global radioecological network and are complementary to those resulting from dedicated cosmic ray detection experiments. Because of that, such analyses might possibly lead to new findings.

Mosses in the Kopački Rit Nature Park, Croatia, as bioindicators of a potential radioactive contamination of the middle Danube River basin

“…Regarding naturally occurring radionuclides, mosses have been used mostly in studies on 7 Be 18 , 28 and 210 Pb 9 , 18 , 22 , 23 , 28 due to their abundance in the air. From the radioecological point of view, however, 7 Be is of no particular interest, because it is just one of cosmogenic radionuclides—the production of which depends solely on the influx of cosmic rays on Earth 41 and not on any human activity. On the other hand, the impact of 210 Pb is important in radioecology.…”

The role of physics in radioecology and radiotoxicology

“…Tc, 123 I, 111 In, 201 Tl, and 67 Ga are used in single-photon emission tomography, while positron emission tomography is based on the use of 18 F, 11 C, 15 O, 13 N, and 64 Cu (21). Medical and technological procedures employing radioactive sources continue to develop.…”