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210 Pb CONCENTRATION IN SOIL IN POLAND AND ITS BEHAVIOUR IN RADON RICH REGIONS

B. MYS £ EK-LAURIKAINEN 1 , S. WO £ KOWICZ 2 ,
R. STRZELECKI 2 , M. BIERNACKA 3 , M. MATUL 1
1 The Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Πwierk, Poland 2 Polish Geological Institute, 4 Rakowiecka, 00-975 Warsaw, Poland 3 Central Laboratory for Radiological Protection, 7 Konwaliowa, 03-194 Warsaw, Poland

Radon and thoron and their decay products are the most important sources of radiation exposure to the
general public, contributing on average about half of the total effective dose equivalent received from
natural and man-made radioactivity, such situation is encountered also in Poland. The short-lived
decay products of 222 Rn decay to 210 Pb with half-life of 22 years contribute to the inhaled effective
dose of man.
The estimation of radon risk in Poland is made on the basis of radon concentration in soil gas. The
radon exhalation rate shows significant seasonal and daily fluctuations, therefore the search of
measurement methods independent on these factors is still the open question. The first part of this
work is devoted to measurement of 210 Pb concentration in soil and in air as the routine soil and air
monitoring in Poland.
The soil sampling is done in 86 places every second year. The soil samples are taken from 5-10 cm
depth according to IAEA rules. The 210 Pb concentration in the surface soil (5-10 cm layer) its average
value is 24,7 Bq/kg and varies from 7,9 Bq/kg up to 91.2 Bq/kg (Jagielak et all., 1998). The map of 210 Pb distribution compiled on the basis of such sampling result is presented. The sampling was done
in 1996.
The average yearly 222 Rn concentration in the air in Poland amounts to 4,5 to 8,9 Bq/m 3 with average
value 6,5 Bq/m 3 in 1996. The presence of 210 Pb in the air is on average µ430 Bq/m 3 bound with dust
particles of air born aerosols. In Poland in 1997 this contamination constituted 98,4% of the total
inhaled dose equal to 11,28 µSv (Mys ³ ek-Laurikainen et all., 1998), due to the presence of 7 Be, 40 K, 226 Ra,228 Ra, 137 Cs and as well 210 Pb in atmospheric air.
The mapping of the radon risk in Poland was done on the basis of measurements of radon
concentration in soil gas at the depth of 60-80 cm as well as on the basis of in situ gamma-spectrometric
measurements (Strzelecki et all.,1993).
Simultaneously with the radon risk mapping the soil sampling was done on the same depth in some
regions of Poland (Sudety Mts, Upper Silesian Basin and Lublin vicinity) with high and medium radon
potential (Strzelecki et all.,1998). The distribution of 210 Pb concentration was studied also for soil
profiles. 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 concentration
measurements in soil gas were performed, the 210 Pb concentration was studied in soil with samples
collected from the same depth (60-80 cm). 64 such soil samples have been examined and the observed
correlation between those two parameters is discussed.
Key words: radon potential, gamma spectrometry, emanometry, 210 Pb, 226 Ra, soil sampling