Estimates of Tracer-Based Piston-Flow Ages of Groundwater from Selected Sites: National Water-Quality Assessment Program, 2006-10.

摘要

Piston-flow age dates were interpreted from measured concentrations of environmental tracers from 812 National Water-Quality Assessment (NAWQA) Program groundwater sites from 27 Study Units across the United States. The tracers of interest include chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis were collected from 2006 to 2010 from groundwater wells in NAWQA studies, including: Land-Use Studies (LUS, shallow wells, usually monitoring wells, located in recharge areas under dominant land-use settings); Major-Aquifer Studies (MAS, wells, usually domestic supply wells, located in principal aquifers and representing the shallow drinking water supply); Flow System Studies (FSS, networks of clustered wells located along a flowpath extending from a recharge zone to a discharge zone, preferably a shallow stream) associated with Land-Use Studies; and Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) also associated with Land-Use Studies.