Activity concentration of Cs-137 in undisturbed attic dust collected from Salgotarjan and Ozd (northern Hungary)

Due to the Chernobyl nuclear power plant accident, contaminated air masses, containing Cs-137, were widely propagated across all of Europe. Cesium-137 is easily adsorbed on aerosol particles as it returns to the litho-sphere/pedosphere/via wet and dry deposition in the form of a radioactive fallout component. Following the nuclear accident, primary attention was paid to agricultural areas and less to urban environments. Our Cs-137 activity study using undisturbed attic dust samples has been carried out from two residential areas (city of Salgotarjan and Ozd) in northern Hungary, approx. 1000 km away from Chernobyl. A total of 61 attic dust samples were collected in 2016 and 2018 from houses (> 30 years) functioning as family house, kindergarten, blockhouse and church. Activity concentration of Cs-137 was determined for 1-2 g homogenized (< 125 mu m) attic dust samples in a low background iron chamber with a well-type HPGe detector. The mean Cs-137 activity con-centrations in attic dust samples are 88.5 +/- 5.1 Bq kg(-1) and 87.8 +/- 4.5 Bq kg(-1) in Salgotarjan and Ozd, respectively. The dependence between Cs-137 activities and the age of the houses was found to be significant (p=0.02), which could be explained by Chernobyl nuclear accident-causing elevated activity concentrations in location built prior to the accident. Three outliers in Ozd (> 223 Bq kg(-1)), are probably related to the first rainfall event after the Chernobyl accident. Isotopic landscapes (isoscapes) of Cs-137 were derived for both cities by means of kriging interpolation. In Salgotarjan the Cs-137 activity concentrations were higher than in Ozd which might have been due to redistribution loadings and local topographical features. We concluded that components of attic dust are highly useful indicators of home exposure to pollution events and remain detectable after several decades.