Development of New Tracers for Determining Travel Time Near MAR Operations
Research Impact
Water quality studies near MAR operations have shown that subsurface residence time is one of the most important parameters for potential contaminant removal. Current SWRCB DDW regulations require underground retention times of 6 to 24 months from infiltration to extraction for potable use. The development of new tracer methods that require minimal field and laboratory work, and that can resolve subsurface travel times on timescales of <1 year, is paramount for protecting public and environmental health. Study objectives were to assess three alternative tracers to replace sulfur hexafluoride (SF6), a synthetic gas and the principle deliberate tracer for work near MAR sites. SF6 is a strong greenhouse gas and its emission is being regulated in California. Two natural (intrinsic) tracers were evaluated: heat (with recharging water ~10° C warmer than native groundwater) and radio-sulfur (35S). Also evaluated were the added (deliberate) tracers10B, as 10B-enriched boric acid, and conservative bromide (Br-).
Originally funded as WERF project Reuse-09-11.
