Analysis of Volatile-Phase Transport in Soils Using Natural Radon Gas as a Tracer

We have conducted a f~eld study of soil gas transport processes using radon gas as a naturally occurring tracer. T!le experiment monitored soil gas radon activity, soil moisture, and~oih~mperature at depth; barometric pressure, rainfall, and wind speed were monitored at the soil surface. linear and multiple regression analysis under natural environmental conditions are influenced by soil moisture content, bar-ometric pressure variations, soil temperature, and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been observed. RADIOACI"IVE WASTES, pesticides, and other hazard-ous chemicals in both soil and groundwater are se-rious contaminant threats to our living environment. Our ability to contain, control, and treat these contaminants depends on our ability to understand the physical processes involved in their release, transport, and interaction with the subsurface environment. Volatile phase transport is a very important component of contaminant displace-ment and degradation in the unsaturated zone. In recent years, a number of techniques have been applied to the investigation ofthe mechanisms of volatile phase transport of pollutants in the subsurface. Helium has been applied as a tracer gas in groundwater to detect diffusion and adsorption of gas-phase pollutants in the saturated zone (Dikum et al., 1975; Gupta, 1983; Davis et al., 1985; Gupta et al., 1990). Naturally occurring radon has also been recently monitored and modeled to better understand its mode of transport into dwellings where it, and its daughter products, can pose a health regard. Accumulated evidence and analyses also indicate that radon gas can be an effective tracer to investigate gas-phase transport under natural environmental condi