Over a third of groundwater in USA public-supply aquifers is Anthropocene-age and susceptible to surface contamination

Abstract The distribution of groundwater age is useful for evaluating the susceptibility and sustainability resources. Here, we compute aquifer-scale cumulative function to characterize 21 Principal Aquifers that account ~80% public-supply pumping in United States. each Aquifer was derived from an ensemble modeled distributions (~60 samples per aquifer) based on multiple tracers: tritium, tritiogenic helium-3, sulfur hexafluoride, chlorofluorocarbons, carbon-14, radiogenic helium-4. Nationally, 38% Anthropocene (since 1953), 34% Holocene (75 – 11,800 years ago), 28% Pleistocene (>11,800 ago). fraction ranges <5 100%, indicating a wide range land-surface contamination. exceeds 50% 7 eastern aquifers are predominately confined. 5 western unconfined. these depends rates recharge release stored fine-grained layers.