“…Disequilibrium occurs when 234 U enters waters preferentially due to processes linked to the energetic alphadecay of parent 238 U, such as the ejection of 234 U into pore space during alpha-recoil or accelerated diffusion via alpha-recoil tracks (Rosholt et al, 1963;Cherdyntsev, 1971;Kigoshi, 1971;Osmond and Cowart, 1976;Osmond and Ivanovich, 1992;Stirling et al, 2007). The degree of disequilibrium is a function of numerous hydrogeologic parameters, including but not limited to, groundwater source, recharge amount and frequency, water-rock interactions, and flow rate (e.g., Osmond and Cowart, 1976;Andrews and Kay, 1982;Ivanovich et al, 1991;Kronfeld et al, 1994;Toulhoat et al, 1996;Johannesson et al, 1997;Roback et al, 2001;Paces et al, 2002;Neymark et al, 2005;Maher et al, 2006;Bushman et al, 2010;Paces et al, 2013;Paces and Wurster, 2014;Priestley et al, 2018). Thus, studying changes in AMGFS groundwater 234 U-238 U disequilibrium over long timescales provides valuable insight into the long-term hydro logical variability of this region.…”