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ANALYSIS OF CHAOTIC BEHAVIOR OF INDOOR RADON ONCENTRATIONS

G. Pausch, P. Bossew, W. Hofmann
Institute of Physics and Biophysics, University of Salzburg, Hellbrunnerstr. 34, A-5020 Salzburg, Austria and F. Steger
Division of Radiation Protection, Austrian Research Center Seibersdorf,
A-2444 Seibersdorf, Austria

Indoor 222 Rn concentrations are influenced by several factores which may change with time,
thereby causing temporal fluctuations of radon concentrations in rooms. Different chaos based
measurements (fractal analyses) were applied to radon time series in three different rooms (kitchen,
working room, radiation laboratory) in Austria to determine the degree of chaotic behavior, to
predict fluctuations in the future, and to investigate correlation's with meteorological parameters.
Our fractal analyses of these indoor radon time series demonstrated that indoor 222 Rn
concentrations do indeed exhibit features which are characteristic of chaotic systems. The
computed fractal dimensions, such as Hurst exponent, Lyapunov exponent, capacity dimension,
embedding dimension and attractor dimension, provided estimates of the degree of chaotic
behavior, such as low dimensional chaos for the kitchen, high dimensional chaos for the working
room and chaos with additive noise for the radiation laboratory. Application of a nonlinear
prediction algorithm revealed that the predictability of radon time series is restricted to
approximately three relative time steps into the future and into the past, e.g. monthly radon
measurements cannot be reliably extrapolated beyond a period of three months. If the similarity of
fractal dimensions between radon concentrations and meteorological parameters is used as a
measure of the degree of correlation, our analyses suggest a strong correlation between radon
concentrations and negative pressure differences.

Key words: radon, indoor, meteorological parameters, fractal analysis, chaotic systems