Helium as a ground-water tracer

Abstract

Laboratory and field experiments were conducted with helium as a ground‐water tracer. Techniques were developed for the addition and extraction of helium from water. A mass spectrometer and a pressure‐volume apparatus were used for helium measurements at concentrations in water ranging from 1.5 to 5.5×10−4 milligrams per liter. In the field investigation, flow was traced through a confined aquifer for a distance of 188 feet. Both laboratory and field experiments showed that helium traveled at a slightly lower velocity than chloride. The advantages of helium as a ground‐water tracer are its safety, low cost, relative ease of analysis, low concentrations required, and chemical inertness. The disadvantages include the relatively large errors in analysis, difficulties of maintaining a constant recharge rate, time required to develop equilibrium conditions in unconfmed aquifers, and possible loss to the atmosphere in unconfined aquifers.

Gas Transport below Artificial Recharge Ponds: Insights from Dissolved Noble Gases and a Dual Gas (SF6 and 3He) Tracer Experiment

“…However, trapped air is only expected above the water table, and hence, for most of the distance, the gas tracers were transported through saturated material where these tracers are not retarded (8,10,18,19). At El Rio #6 where vertical flow dominates, the infiltrating water traveled ∼12 m through the unsaturated zone to the water table (as recorded at the monitoring well and El Rio #7) and then ∼38 m through saturated media to the top of the screen.…”

“…Our experiment, which was conducted at the El Rio spreading grounds, Ventura County, CA was designed to quantify gas transfer from the percolating recharge water to the soil air in a field setting. SF6 and 3 He were chosen as tracers because they are conservative, not retarded in saturated porous media (8,18,19), have Henry's Law coefficients that differ by about 50%, and are sufficiently inexpensive to tag large volumes of water (typically >10 6 m 3 ) as is required when performing tracer experiments at artificial recharge sites.…”

Changes in Entrapped Gas Content and Hydraulic Conductivity with Pressure

“…Reduced hydraulic conductivity due to entrapped air has been proposed as a means to restrict saline water intrusion (Dror et al 2004) and will also affect the transport of solutes (Orlob and Radhakrishna 1958) and microbes ). Finally, because of mass transfer with entrapped gas, dissolved gas concentrations in groundwater may be increased (Fry et al 1995;Williams and Oostrom 2000) or the transport of dissolved gases and volatile contaminants may be retarded (Carter et al 1959;Fry et al 1996;Cirpka and Kitanidis 2001;Geistlinger et al 2005). Finally, because of mass transfer with entrapped gas, dissolved gas concentrations in groundwater may be increased (Fry et al 1995;Williams and Oostrom 2000) or the transport of dissolved gases and volatile contaminants may be retarded (Carter et al 1959;Fry et al 1996;Cirpka and Kitanidis 2001;Geistlinger et al 2005).…”

California GAMA Special Study: A Noble Gas Membrane Inlet Mass Spectrometry (NG-MIMS) system for water and gas samples

“…Noble gases dissolved in groundwater can reveal paleotemperatures (Aeschbach-Hertig et al, 2000;Mazor, 1972;Stute et al, 1995), recharge conditions (Cey et al, 2009;Ingram et al, 2007;Osenbrück et al, 2009), and (as introduced tracers) precise travel times of groundwater (Carter et al, 1959;Clark et al, 2005;Gupta et al, 1994a). Water samples for dissolved noble gases are typically collected in copper tubes, pinched or cold-welded at the ends, to prevent atmospheric contact.…”