Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

The purpose of this study is to investigate the day-to-day and seasonal variations of soil-gas radon concentrations. The monitoring holes were drilled in the vicinity of a laboratory(Seoul National University) on the residual soil profiles that overlie Jurassic granite bedrock. The soil-gas radon level and other meteorologic factors have been measured for 6 months from November, 2000 to April, 2001. The results of long-term study of soil-gas radon concentration in soil revealed that interactions of meteorologic factors (rainfall, snowfall and temperature changes) and soil characteristics govern the radon concentration both on a daily scale and seasonal time scale. Seasonal variation of soil-gas radon concentration was greater than day-to-day fluctuation. The highest radon concentration of 5,131 pCi/L was measured during winter season and the lowest radon concentration of 107 pCi/L was measured during spring season. Time-series analysis showed that seasonal variation patterns fitted well to AutoRegressive Integrated Moving Average, ARIMA(2,1,1) model. The compositions of trend variances and irregular variances from ARIMA(2,1,1) were also calculated by decomposition method. Trend composition showed that soil-gas radon concentrations increased during winter season due to capping effect by surface freezing and decreased during late winter-early spring season due to radon exhalation to ground surface. The variances of irregular compositions were highly governed by the dramatic changes of meteorologic factors such as strong snowfall and rainfall.