Linking Laboratory and Field Observations of Carbon Dioxide Transport at the Nevada National Security Site.

Subsurface gas transport is critical for containment performance following underground nuclear detonations or high-explosive tests. Such gases can provide fingerprinting needed to identify whether detected seismic signals have a nuclear or chemical source, provided that their subsurface transport can be accurately interpreted. In this study, we examine carbon dioxide (CO2) diffusion through dry core samples taken from representative lithologies at the Nevada National Security Site (NNSS) and compare laboratory-measured transport with field observations after a subsurface high-explosive experiment. Controlled laboratory breakthrough tests quantified CO2 migration across lithologies with varying zeolite content. Results show pronounced lithologic dependence, with zeolite-rich samples exhibiting marked retardation of CO2 attributed to adsorption within the zeolite frameworks. Field measurements of post-detonation gas composition and concentration gradients similarly revealed delayed CO2 migration within more zeolitized horizons, which were distinct from dissolution into pore water. This corresponding behavior across laboratory and field scales indicates that zeolite content exerts a dominant control on CO2 subsurface mobility and retention at the NNSS. These findings highlight the need to account for mineralogically controlled sorptive processes when modeling gas transport in zeolitized formations and underscore the value of linking laboratory diffusion data with field-scale observations to improve predictions of post-detonation gas behavior at the NNSS and similar sites.