Acta Facultatis Ecologiae - Technická univerzita vo Zvolene

134the airborne radon is pushed upward and outward.A large amount of precipitation may cause a rise ofthe water level and entrapment of air with an airborneradon by the downward infiltrating water [3].In this paper we present the results of radonconcentration monitoring in water from boreholes.We will compare the interdependence among thevariations of 222 Rn activity concentration in boreholewater and water level changes with precipitationfrom January to July in both years 2006 and2007 of our investigation.METHODSThree boreholes V-1 (10 m), V-2 (40 m) and V-3 (10 m) have been drilled at the area of Astronomicaland Geophysical Observatory of ComeniusUniversity in Modra-Piesok (AGO Modra) in theLittle Carpathian Mts (40 km NE from Bratislava).The inner diameter of those boreholes is 80 mm,they are cased with a PVC pipe with 10 % perforationalong the whole length. All of them have beendrilled in the Lower Triassic quartzites folded inthe granodiorite of the Modra massif [4, 5].Since August 2003 the investigation of radonconcentration in borehole air has been performedin V-2 and V-3 borehole [6]. The continual monitoringof the atmospheric temperature is also performedin Modra AGO from 2003 [6]. Since 2006the study of the 222 Rn activity concentration changesin borehole water has been performed in all threeboreholes [7].The sampling of water from boreholes has beencarried out regularly three times a week by plasticbottle. Simultaneously the state of water level hasbeen measured. The 222 Rn activity concentrationanalyses have been executed at the laboratory ofthe Department of Nuclear Physics and Biophysicsat Faculty of Mathematics, Physics and Informaticsof Comenius University in Bratislava. The scintillationcell of Lucas type DS 401M with volume125 ml have been used for the measurements ofradon concentration in water [8].The precipitation amount and the height ofsnow cover have been regularly measured at theobservatory and which was kindly available for ourinvestigation.RESULTSIn this paper were studied the results obtainedfrom January to July (respectively to Augustin the case of V-1 borehole) for two years of theinvestigation of 222 Rn activity concentration in boreholewater at AGO Modra. This time period wasselected to comparise of the results because sincesummer there is no water in V-1 and V-3 boreholeeach year.It is interesting and very useful, that those twoyears of our research were completely different forthe sake of different atmospheric temperature, precipitationamount and height of snow cover (Fig. 1).Generally, in 2006 the winter temperatures weresignificantly lower than in 2007. Equally the precipitationamount in winter and spring months washigher in comparison with 2007. Since January toMarch the study area was covered by a permanentthick layer of snow in 2006. On the contrary, therewas almost no snow in 2007. Those different conditionsallowed us to compare the courses of radonconcentration in borehole water and the changes ofwater level in diverse situations.Average monthly temperature2520 2006 2007151050-51 2 3 4 5 6 7monthtemperature [ o C]Precipitation amount1501209060300precipitation[mm]2006 20071 2 3 4 5 6 7monthFig. 1 The comparison between the average monthly atmospheric temperature and the precipitation amountat AGO Modra for the years 2006 and 2007