THE EFFECTS OF VEGETATION ON RADON ENTRY INTO A BASEMENT STRUCTURE

Measurements were made to determine if vegetation planted near a basement would increase or decrease radon entry due to changes in the soil. Experiments were performed on two identical structures; one planted with lawn grass while the other served as a bare-ground control. A data acquisition system collected meteorological information as well as continuous measurements of indoor radon concentrations, natural ventilation and radon entry rate. Vegetation significantly reduced soil moisture, increased soil permeability and reduced soil gas radon concentrations in the soil down to 2 m. Reduction of soil gas radon concentrations could be explained by changes in soil moisture content. Both the indoor radon concentration and entry rate were influenced by vegetation. No trends in radon entry rate vs pressure differentials between the basement and atmosphere were identified. Time series analyses indicated an association between radon entry and diurnal changes in barometric pressure but was not shown to be significantly influenced by the sod. Diurnal barometric pumping caused less than 10% of the long term radon entry which was dominated by a DC component previously associated with diffusion.