Seasonal variations of radon activity concentration in mofettes from Harghita and Covasna Counties, Romania

Abstract

In Harghita and Covasna County (Romania) are many mofettes. The mofette is mainly CO₂ composed low temperature volcanic gas emanation. The mofettes can contain important quantities of radon. In these regions of Romania, the mofettes have long been used on curative purposes. We proposed monitoring the seasonal variation of radon activity concentration (RAC) in 10 frequented mofettes. Measurements in mofettes have shown radon concentrations ranging from a few hundred to several thousand becquerels per cubic meter (Bq/m³). The same trend can be observed for most mofettes. In the spring and summer months, the radon activity concentration values are higher than in the autumn and winter period. We found that a moderate negative relationship can be observed between the RAC and atmospheric pressure variations. From the average RAC values measured above the gas level in the indoor air of the mofettes, the annual effective dose received by the patients during a treatment session and by the mofette workers (if any) was calculated. The annual effective dose of inhaled radon received by patients during a treatment session does not exceed the annual dose limit for the population (1 mSv), but in mofettes with staff, the effective dose they receive can be significant, which already requires attention.

Keywords: CO(2) dry bath; Effective dose; Mofette; Radon; Radon seasonal variation; Volcanic gas.