210 Pb concentration in soil in poland and its behaviour in radon rich regions

Radon and thoron and their decay products are the most important sources of radiation exposure to thegeneral public, contributing on average about half of the total effective dose equivalent received fromnatural and man-made radioactivity, such situation is encountered also in Poland. The short-liveddecay products of 222Rn decay to 210Pb with half-life of 22 years contribute to the inhaled effectivedose of man.The estimation of radon risk in Poland is made on the basis of radon concentration in soil gas. Theradon exhalation rate shows significant seasonal and daily fluctuations, therefore the search ofmeasurement methods independent on these factors is still the open question. The first part of thiswork is devoted to measurement of 210Pb concentration in soil and in air as the routine soil and airmonitoring in Poland.The soil sampling is done in 86 places every second year. The soil samples are taken from 5-10 cmdepth according to IAEA rules. The 210Pb concentration in the surface soil (5-10 cm layer) its averagevalue is 24,7 Bq/kg and varies from 7,9 Bq/kg up to 91.2 Bq/kg (Jagielak et all., 1998). The map of210Pb distribution compiled on the basis of such sampling result is presented. The sampling was donein 1996.The average yearly 222Rn concentration in the air in Poland amounts to 4,5 to 8,9 Bq/m3 with averagevalue 6,5 Bq/m3 in 1996. The presence of 210Pb in the air is on average ?430 Bq/m3 bound with dustparticles of air born aerosols. In Poland in 1997 this contamination constituted 98,4% of the totalinhaled dose equal to 11,28 ?Sv (Mys?ek-Laurikainen et all., 1998), due to the presence of 7Be, 40K,226Ra,228Ra, 137Cs and as well 210Pb in atmospheric air.The mapping of the radon risk in Poland was done on the basis of measurements of radonconcentration in soil gas at the depth of 60-80 cm as well as on the basis of in situ gammaspectrometricmeasurements (Strzelecki et all.,1993).Simultaneously with the radon risk mapping the soil sampling was done on the same depth in someregions of Poland (Sudety Mts, Upper Silesian Basin and Lublin vicinity) with high and medium radonpotential (Strzelecki et all.,1998). The distribution of 210Pb concentration was studied also for soilprofiles. A significant decrease of this concentration was observed up to a depth of about 20 cm,below which the concentration becomes constant. For selected localities where radon concentrationmeasurements in soil gas were performed, the 210Pb concentration was studied in soil with samplescollected from the same depth (60-80 cm). 64 such soil samples have been examined and the observedcorrelation between those two parameters is discussed.