Abstract:Hourly and daily variations of ground-level ozone have been analyzed in relation to meteorological parameters, UVB radiation and radon near the Baltic Sea in Lithuania. An atypical situation with respect to wind domination was observed during the experiment: the wind from the continent was twice as frequent as the wind from the sea. The close correlation between ground-level ozone concentration and UVB radiation intensity was established. The vertical migration directions of ozone and radon were opposite and the negative correlation between these pollutants was observed. The diurnal course of ozone and radon and the influence of meteorological parameters (temperature, relative air humidity, wind speed and direction) on variation of these pollutants have been estimated. It was established that the wind direction domination during the experiment had a significant influence on the variation of ozone and radon concentrations.

In the territory of Vilnius city radioisotopic composition of different soils was experimentally determined and radon exhalation rate from the soil was evaluated using these data. Specific activitys of natural radionuclides 226Ra, 232Th and 40K were measured. From identified natural radionuclides the biggest quantities were for 40K (263 Bq/kg), the smallest values ‐ for 232Th (5 Bq/kg), average 226Ra values reached 13 Bq/kg. Radon exhalation rate from the soil in Vilnius city was calculated and evaluated. Distribution of radon exhalation rate values in the whole territory of the city is stated. The received values vary from 15 Bq/m2·h (in clay loam) to 23 Bq/m2·h (in sand). It is assessed that of the most important parameters, which determine radon exhalation rate from the soil, are the quantity of radium and the porosity of the soil. It is observed that radon exhalation rate from the soil is bigger than that from building materials. This difference is determined by a bigger porosity of the soil.

The changes of radon and its short-lived decay products were investigated in accommodations under natural living conditions and in tobacco smoke-filled premises. The measured radon and its short-lived decay products volumetric activities, aerosol particle concentration in the air, radioactive equilibrium factor, unattached fraction factor values are presented. It was identified that the increase of aerosol particles concentration in the air (in smoke-filled premises) determines the increase of the unattached nuclides of radon short-lived decay products attached to aerosol particles (the average values of radioactive equilibrium factor varied from 0.35 to 0.72). In this case, larger volumetric activity of the alpha particles is registered. Therefore larger amount of radon progeny is inhaled in smoke-filled premises and there is an increased possibility of damaging the organism. Positive correlation (r 00.9) between the radioactive equilibrium factor and aerosol particle concentration in the air of accommodation, as well as negative correlation (r 0 (0.64) between the radioactive equilibrium factor and unattached fraction factor have been determined. Seasonal changes of the radioactive equilibrium factor are presented.

The change of natural ionizing radiation and the radon exhalation rates from typical building materials in underground parking lots are presented in the article. The activity concentration of natural radionuclides 232Th, 226Ra, and 40K in six important types of construction materials, which are mostly used in Lithuania, were analyzed using high-resolution gamma spectroscopy. The highest values were found in concrete and ferroconcrete samples: 226Ra 44 and 90 Bq kg−1; 232Th 29 and 34 Bq kg−1; 40K 581 and 603 Bq kg−1. A strong positive correlation (0.88) was observed between radium activity concentration and radon concentration. The activity indexes (Iα and Iγ) and radium equivalent activity (Req) evaluating the suitability of materials for such constructions from the view of radiation safety were determined. The average values of the calculated absorbed dose rate in samples ranged from 18.24 nGy h−1 in the sand to 87.26 nGy h−1 in ferroconcrete. The calculated annual effective dose was below the limit of 1.0 mSv y−1. The values of the external and internal hazards index (Hex and Hin) were all below unity, and the values of Iγ and Iα were below the recommended levels of 0.5 and 1. Dosimetric analysis of underground parking lots was carried out. It was determined that the external equivalent dose rate caused by the 222Rn progeny radiation in the underground car parking lots varies from 17 to 30% of the total equivalent dose rate.

Our paper presents data on the annual course of the temperatures of surface sediments in deep bottom areas of a lake that has been assigned a "moderately-warm" designation. It is shown that the highest temperatures of those sediments are reached in autumn when near-bottom waters are involved with the processes of the gravitational mixing of the water column. Mixing conditions of the water column were estimated using additional information on the vertical profiles of standard water variables (pH, oxygen concentration, and conductivity). It is shown that depending on the amount of heat stored in the sediments of the deep bottom areas and the thermodynamic processes of its redistribution, the lake may be designated "super-warm" or "moderately-warm. " This implies that existing thermal classification of lakes is too formal and does not account for the complexity of thermodynamic processes of heat redistribution. Measurement data is evidence of the implication of the inflows from the bottom-feeding sources in the formation of the highly mineralized near-bottom water layer in those bottom areas.