Seasonal and Diurnal Dynamics of Atmospheric Radon, Carbon Dioxide, Methane, δ 13 C-CO 2 and δ 13 C-CH 4 in a Proposed Australian Coal Seam Gas Field Douglas R. Tait & Damien T. Maher & Isaac R. Santos Received: 3 March 2015 /Accepted: 2 September 2015 # Springer International Publishing Switzerland 2015 Abstract The expected growth of the coal seam gas industry in Australia requires baseline information for determining any potential long-term impacts of the in- dustry. As such, a 1-year atmospheric time series mea- suring radon ( 222 Rn), methane (CH 4 ), carbon dioxide (CO 2 ), δ 13 C-CO 2 and δ 13 C-CH 4 was conducted in an area where coal seam gas (CSG; also referred to as coal bed methane) extraction is proposed (Casino, New South Wales, Australia). We hypothesise that 222 Rn can be used as a tracer of soil-atmosphere CH 4 and CO 2 exchange, and that carbon stable isotope values of atmospheric CH 4 and CO 2 can be used to identify the source of greenhouse gases. Radon, CO 2 and CH 4 followed a diurnal pattern related to increased concen- trations during the formation of a nighttime inversion layer. The study found a significant inverse linear rela- tionship between 222 Rn concentrations and both rainfall (r 2 =0.43, p <0.01) and temperature (r 2 =0.13, p <0.01), while atmospheric pressure, wind speed and wind direc- tion affected concentrations to a lesser degree over seasonal time scales. 222 Rn had a significant, but weak positive correlation with both seasonal CO 2 (r 2 =0.15, p <0.01) and CH 4 (r 2 =0.11, p <0.01) concentrations. The uncoupling between 222 Rn and CO 2 and CH 4 was likely due to biogenic sources and sinks of CO 2 and CH 4 . δ 13 C values of CO 2 and CH 4 indicated variability in the source and sinks of the gases that seems to be linked to different seasonal, soil and spatial sources. This study provides baseline data from a proposed coal seam gas field from which future comparisons can be made. Keywords Coal bed methane . Unconventional gas . Fugitive emissions . Greenhouse gas . Carbon dioxide . Stable isotopes 1 Introduction Substantial growth of the coal seam gas (CSG) industry is predicted in Australia. Newly developed mining methods have made CSG extraction economically viable in previ- ously non-economically viable coal reserves. Thus far, government and community concerns have focused on how CSG activities will influence groundwater resources (NSW Government 2013). However, it remains unclear how CSG will impact atmospheric chemistry. CSG extraction relies on two main processes to fa- cilitate gas extraction: (1) the opening of fractures in the coal seam either through drilling or hydraulic fracturing and (2) the dewatering of the coal seam to reduce the hydrostatic pressure holding the gas in place. There is the potential for both of these processes to release point source and diffuse emissions of soil gases into the atmosphere (Tait et al. 2013). Of particular concern is the release of methane (CH 4 ), the primary gas in CSG mining, which has a sustained-flux global warming Water Air Soil Pollut (2015) 226:350 DOI 10.1007/s11270-015-2597-x D. R. Tait (*) : D. T. Maher : I. R. Santos School of Environment, Science and Engineering, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia e-mail: douglas.tait@scu.edu.au D. R. Tait : I. R. Santos National Marine Science Centre, Southern Cross University, PO Box 4321, Coffs Harbour, NSW 2450, Australia