Effect of Ultrasonic Treatment on Radon Exhalation from Porous Media: An Experimental Case Study

Abstract

Radon is internationally recognized as one of the seven seismic precursors. A self-assembly ultrasonic generator and experimental apparatus for radon measurement were utilized to explore the radon exhalation regularities of water-bearing porous media under different ultrasonic intensities. The experimental results showed that there was a coupling relationship among radon exhalation rate, moisture content, and ultrasonic frequency. With the increase of the frequency of the ultrasonic wave, its effect on the promotion of radon exhalation rate was found to be a more obviously positive linear correlation. The radon exhalation rate, which could climb to a maximum value of 0.179 Bq·m−2·s−1 in a naturally air-dried sample, increased at first and then decreased along with increased moisture content. Moreover, this study found that the ultrasonic wave had the most remarkable promoting effects on the radon exhalation rate of porous media with high moisture content, and there is a positive linear correlation between the growth rate of the radon exhalation rate and moisture content. The experimental results could provide a beneficial reference for the continual monitoring of radon in a seismically active belt and an explanation of radon anomalies; however, the proposed experimental model was simplified, so further insights are strictly required for a reliable correlation with the real monitoring of radon in a seismically active belt.