The role of atmospheric conditions in driving air movement along a deep borehole using radon and CO₂ mutual relation

Understanding and quantifying the air exchange rate at boreholes and wells and subsequently their potential role as a source for greenhouse gases (GHGs) or volatile organic contaminant (VOCs) emissions to the atmosphere is important. Here, we investigate the effect of atmospheric conditions (atmospheric pressure and temperature) on air transport inside a deep dry borehole (88-m deep and 0.9-m wide) using radon, CO₂and absolute humidity measurements. Temperature, relative humidity, CO₂and radon (alpha detector) sensors were placed along the cased borehole, and a standard meteorological station was located a few km from the borehole. All borehole data were logged at high 1-min resolution. Current results show that climatic driving forces have a similar effect on the CO₂ and radon trends within the borehole. In addition, we can distinguish between the diurnal and semi-diurnal periodical effect of the ambient temperature and pressure on both CO₂ and radon concentrations.