Reload Index (ZRiChK UMCS)

 

 

MONITORING OF RADON CONCENTRATION IN THE OLD TOWN OF SANDOMIERZ

 

STANISŁAW CHIBOWSKI, ANDRZEJ KOMOSA

DEPARTMENT OF RADIOCHEMISTRY AND COLLOID CHEMISTRY

 

 

Gaseous radon appears in the environment as a result of decaying of radium, the progeny of uranium. The sources of radium isotopes are various uranium and thorium bearing minerals, which are common in the upper layer of the Earth’s crust. The most important radon isotope is 222Rn, which decays by alpha emission with a half-life of 3.8 days, forming the charged particles of short-living radon daughters. They attach rapidly to atmospheric aerosols and can enter into a human body. Therefore, the presence of radon and its progeny in the environment causes a significant hazard to human health. About a half of annual equivalent dose obtained by inhabitant of Poland is a result of radon and and its decay products intake.

The importance of radon monitoring is supported in 1996 by the Directive of European Communities, which suggests the necessity of paying greater attention on the natural isotope impact on the people [1].

The radon monitoring methods are being developed in our Department for few years. As a result of our study a concentration of radon and its decay products were determined in dwellings of several old towns in Lublin region. Particular attention was paid to tourist underground facilities being in use (Chełm and Sandomierz towns) or in construction (Lublin) [2]. This study is concerned with radon determination in basements and first floors of buildings in Sandomierz old town, and also in underground tourist route. Two different methods were used: a passive one (which allows to determine average gaseous radon concentration in 48 hour exposition) and active one (to measure a momentary concentration of short-living radon progeny, what can be recalculated to radon concentration). Comparison of the results obtained by these two methods allows calculating the radioactive equilibrium factor. The results of measurements are summarized in Table 1.

The values of radon concentration follow a lognormal distribution; thus geometric mean better describes the average value of radon radioactivity. According to Polish regulations radon concentration in new buildings should not exceed 200 Bq/m3, and in old ones - 400 Bq/m3. Taking into account these limits it can be seen that 65% of the results does not exceed the first limit, and only 23% are laying above the second limit values. It is worth of notice that values of radon concentration exceeding the limit appeared only in closed basement rooms, without any ventilation. On the other hand radon concentration in the underground tourist route is very low, what is a result of efficient ventilation.

 

 

 

 

Table 1. Summary results of 222Rn determination in Sandomierz old town buildings.

 

Underground tourist route

All results

222Rn [Bq/m3]

passive method

222Rn [Bq/m3]

radon progeny measurement

No. of measurements

15

6

108

Arithmetic mean [Bq/m3]

43,4

540,1

433,4

Geometric mean [Bq/m3]

38,2

31,9

115,6

Median [Bq/m3]

39,8

50,2

111,1

Std. deviation

(1s)

22,5

839,5

861,4


Min. value

20,1

1,4

1,4

Max. value

86,4

1983

5101,9

 

Figure 1. Probability distribution of the results of radon measurement in Sandomierz old town.

 

References:

[1] Directive 96/29 Euratom, Official Journal, European Communities, L 159 (1996).

[2] St. Chibowski, A. Komosa, J. Radioanal. Nucl. Chem. 247 (2001).