Radon progeny in hydrometeors at the earth's surface

Abstract

During atmospheric thermal inversions, dew and hoarfrost concentrate gamma emitting radionuclides of the short-lived (222)Rn progeny ((214)Pb and (214)Bi), causing an increase in the total natural gamma background from the ground. To highlight this phenomenon, a volcanic zone of high (222)Rn flux was studied during the winter season 2010-11. High-specific short-lived radon progeny activities up to 122 Bq g(-1) were detected in hydrometeors forming at the earth's surface (ESHs), corresponding to a mean increase of up to 17 % of the normal gamma background value. A theoretical model, depending on radon flux from soil and predicting the radon progeny concentrations in hydrometeors forming at the ESHs is presented. The comparison between model and field data shows a good correspondence. Around nuclear power plants or in nuclear facilities that use automatic NaI or CsI total gamma spectroscopy systems for monitoring radioactive contamination, hydrometeors forming at the ESHs in sites with a high radon flux could represent a relevant source of false alarms of radioactive contamination.

214Bi/214Pb radioactivity ratio three-year monitoring in rainwater in Prague

“…It is worth pointing out that the high values of 214 Bi/ 214 Pb ratio in the raw signal, greater than or equal to 0.7, seem to be associated with the simultaneous occurrence of low wind speed and high relative humidity (Fig. 2), most likely due to atmospheric water vapour condensation [11,12].…”

“…The cross-correlation between the two studied raw time series has also been calculated: the average value of 84 ± 2% was obtained. From this statistical analysis, the progeny of radon is the main reason for the overall ambient dose equivalent rate [11,12,22].…”

“…Such monitoring can be carried out in different ways and the most common ways are gamma-ray spectrometry and gamma dose rate measurements [1,[6][7][8][9]. In this framework, the continuous monitoring of radioactivity ratio of 214 Bi/ 214 Pb as tracers in rainwater was carried out by several works [9][10][11][12]. During atmospheric thermal inversions, there is an increase in the concentration of natural gamma-emitting radionuclides of the short-lived 222 Rn progeny ( 214 Pb and 214 Bi with half-lives of 26.9 min and 19.9 min, respectively) that causes an increase in the total natural gamma background.…”

“…In the atmospheric mixing of the overall variability in ambient gamma dose, radon variability attributable to diurnal changes contributes less than radon variability during precipitation periods [9,10]. Therefore, any information about radon progeny concentrations could be useful for modelling the variation of the natural gamma background depending on the 222 Rn fl ux and the variable atmospheric conditions [11,12]. Moreover, the variations of radon and its short-lived progeny in air have been studied for a long time as indicators of 214 Bi/ 214 Pb radioactivity ratio three-year monitoring in rainwater in Prague height fl uctuations of the mixed layer and potential air pollution conditions [3,6,12].…”

212Pb as tracer for PM deposition on urban vegetation

“…Blanc, one of the discoverers of 228 Th, was used as internal reference material for 212 Pb activity. Reference samples for 214 Pb were prepared by fully dissolving a 226 Ra-enriched potassium soluble salt (Cesano aphtitalite) in water (Voltaggio, 2012). A sample of this salt is commonly used as internal standard material for 226 Ra at the Environmental Geochemistry and Isotope Laboratory of CNR-IGAG (Rome) having a well-constrained 226 Ra specific activity of 0.880 ± 0.009 Bq·g −1 .…”