The Gas-Migration-Simulator (GAMS) - A new device for the simulation of soil gas migration processes

Abstract

Since natural soil conditions are hardly ever homogeneous, soil gas migration processes are difficult to investigate. The power of model calculations for describing or predicting soil gas migration processes is often limited. The Gas-Migration-Simu- lator (GAMS) has been developed to cope with this problem. The GAMS takes the form of a cylindrical box which can be homogeneously filled with a soil volume of 1.7 m3. The design allows a solely diffusive input of a gas phase into the base of the soil column. At the same time it allows determination of the gas exhalation rate. By providing a gas-tight crawling space immedi- ately above the soil column and by adjusting a certain air pressure in this space the GAMS also permits the simulation of atmo- spheric high or low pressure fields, enabling the investigation of their influence on soil gas exhalation rate and soil gas migration. Quantitative irrigation of the soil surface and simulation of an adjustable groundwater table are also possible. To record time series of the relevant parameters, the GAMS is equipped with six layers of exchangeable probes at different depths. Recent research focuses on the migration of radon through the ground and its dependence on meteorological parameters. Special “Clipperton” probes have been used to record continuous time series of radon concentration of soil gas together with the temperature and the soil moisture content.