@article {2996,
	title = {Over a third of groundwater in USA public-supply aquifers is Anthropocene-age and susceptible to surface contamination},
	journal = {Communications Earth \& Environment},
	volume = {3},
	year = {2022},
	month = {07/2022},
	pages = {1 - 9},
	abstract = {The distribution of groundwater age is useful for evaluating the susceptibility and sustainability of groundwater resources. Here, we compute the aquifer-scale cumulative distribution function to characterize the age distribution for 21 Principal Aquifers that account for ~80\% of public-supply pumping in the United States. The aquifer-scale cumulative distribution function for each Principal Aquifer was derived from an ensemble of modeled age distributions (~60 samples per aquifer) based on multiple tracers: tritium, tritiogenic helium-3, sulfur hexafluoride, chlorofluorocarbons, carbon-14, and radiogenic helium-4. Nationally, the groundwater is 38\% Anthropocene (since 1953), 34\% Holocene (75 {\textendash} 11,800 years ago), and 28\% Pleistocene (>11,800 years ago). The Anthropocene fraction ranges from <5 to 100\%, indicating a wide range in susceptibility to land-surface contamination. The Pleistocene fraction of groundwater exceeds 50\% in 7 eastern aquifers that are predominately confined. The Holocene fraction of groundwater exceeds 50\% in 5 western aquifers that are predominately unconfined. The sustainability of pumping from these Principal Aquifers depends on rates of recharge and release of groundwater stored in fine-grained layers.},
	keywords = {Environmental impact, hydrology, Sustainability},
	isbn = {2662-4435},
	doi = {10.1038/s43247-022-00473-y},
	url = {https://www.nature.com/articles/s43247-022-00473-y},
	author = {Jurgens, Bryant C. and Faulkner, Kirsten and McMahon, Peter B. and Hunt, Andrew G. and Casile, Gerolamo and Young, Megan B. and Belitz, Kenneth}
}
