STUDY OF THE INFLUENCE OF SOIL MOISTURE AND GRAIN SIZE ON RADON EMANATION FROM SOIL USING AN ADVANCED MULTIGRAIN MODEL.

Among the most important factors that influence radon emanation from soil particles is the soil moisture and grain size. Both components, in its own way, modify the length of a trajectory that radon atom pass through in a volume of the soil pores. To better understand their impact on an emanation, we have developed our own computer program that can simulate the 222Rn emanation process in the soil environment, using an idea of a multigrain model. In our case, the central, radium-bearing soil grain is surrounded by 1330 adjacent grains of the same size forming a cubic structure and the moisture in a space of the soil pores is differently distributed. The simulation process is based on a two different distribution of 226Ra in soil grains (homogenous and heterogenous), while several variants of the thickness of an escape layer are analyzed for grains of different sizes and moisture contents.

EMANATION OF RADON-222 FROM DIFFERENT SOIL TYPES AND SOIL GROUPS.

In this paper, we deal with measurement of 222Rn emanation coefficient (Ke) of soils using an accumulation method. We created a database of Ke values of dried soils for various soil types and soil groups, classified by the size of soil particles. For 18 different soil samples we obtained the Ke values in range 0.083-0.234. The analysis of radon emanation dependence on moisture for seven of these samples shows two different trends which were related to soil texture (clays or sands). Soils with predominant sandy particles prove weak dependence on moisture and Ke values from minimum value (at zero moisture) do not increase much (max 15% increase on every 5% of moisture), for soils with majority of clayey particles the moisture can affect the Ke more significantly (increase up to 60%).

RADON ACTIVITY CONCENTRATION IN WATERS OF SPRINGS IN SELECTED AREAS OF WESTERN SLOVAKIA.

This paper presents the results of measurements of radon activity concentration (RAC) in spring waters and natural wells in three mountains of Slovakia (Strázov Mountains, Povazský Inovec and Little Carpathians). These mountains provide drinking water for inhabitants of surrounding towns and villages. Little Carpathians is the most seismically active area in Slovakia. Povazský Inovec, where 2 out of 11 uranium deposits of Slovakia are located, is interesting due to increased uranium mineralization. We have collected samples from more than 170 natural water sources, many of which exceed the guide value of 100 Bq l-1, with a maximum value of 274 Bq l-1. The median of these data (15 Bq l-1) is also higher than the national median in groundwater (11.6 Bq l-1). From the obtained data, we have created maps representing RAC of groundwaters for the whole territory. These maps were also compared with the geological maps.

DEVELOPMENT AND TESTING OF DEVICES FOR CONTINUOUS MONITORING OF RADON ACTIVITY CONCENTRATION IN WATERS.

Continuous radon measurement in waters is an appropriate tool for the study of its variations as well as for the clarification and understanding of the factors that cause these changes. In addition, sudden changes in radon activity concentration (RAC) in groundwater can be used to identify geodynamic activities and earthquake predictions. In this paper, two measuring systems for continuous monitoring of RAC in waters are presented and tested. One of them was designed for water sources with a high yield; the second one operates with a constant volume of a sample using a different method of 222Rn release from water. We present our first laboratory tests of continuous measurement of RAC in tap waters as well as the variations of RAC observed during a week.