Gamma emitters in atmospheric precipitation in Krakow (Southern Poland) during the years 2005-2015

The results of the sum of dry and wet activity deposition for naturally occurring ⁷Be, ²¹⁰Pb, ⁴⁰K, ²²Na and anthropogenic ¹³⁷Cs radionuclides in Krakow (Southern Poland) for the samples collected over 10 years (from August 2005 to July 2015) are presented and discussed. The radionuclides were determined using low background gamma spectrometry with HPGe detectors. Additionally, in this paper there are shown the results of activity concentrations in water from air precipitation for ⁷Be, ²¹⁰Pb, ²²Na, ⁴⁰K and ¹³⁷Cs radioisotopes from the period of 7 years (from August 2008 to July 2015). For all these series the statistical analysis including Spearman correlations, effects of seasonal variation and multiple regression models were conducted. After excluding two months from 2011 affected by the Fukushima accident, high Spearman correlation factors (R > 0.5) for activity deposition were noticed for the pair of the cosmogenic radionuclides ⁷Be and ²²Na (R = 0.508) and between ²¹⁰Pb and ⁷Be (R = 0.570). High correlation was noted between activity deposition and amount of precipitation for ⁷Be (R = 0.677). The seasonal correlations between ⁷Be-²²Na, ⁴⁰K-¹³⁷Cs, ²¹⁰Pb-¹³⁷Cs and ⁷Be-²¹⁰Pb were investigated and the highest correlation coefficient R = 0.731 for the ⁴⁰K-¹³⁷Cs pair was in the spring season. High correlations were observed also between ²¹⁰Pb and ⁷Be for autumn (R = 0.594), ⁴⁰K-¹³⁷Cs in summer (R = 0.582), ⁷Be-²²Na in spring (R = 0.635) and ²¹⁰Pb-¹³⁷Cs in autumn (R = 0.672). The multiple regression approach showed the interesting difference in scavenging mechanisms of cosmogenic and terrestrial radionuclides. According to that model, the deposition of cosmogenic nuclides was noticeably related to the amount of precipitation, while the deposition of terrestrial radionuclides did not show such dependence.