Usgs groundwater age dating


USGS staff collecting groundwater samples in copper tubes for 3He/4He and/or noble gases have access to training at the Field Methods for the Collection of Water Quality Samples courses at the UGGS Office of Employee Development in Denver.Training is also available by request from the USGS Noble Gas Lab in Denver or the USGS Ground Water Dating Lab in Reston.Clear plastic tubing (Tygon) is preferred because one can visually observe whether air bubbles are present in the water line.It is recommended that connections be secured with stainless steel hose clamps, again being careful not to damage the end of the copper tube.Back pressure of approximately 1 atmosphere, 14 psi, is normally sufficient to prevent gas bubble formation in a ground-water sample.

usgs groundwater age dating-73usgs groundwater age dating-20usgs groundwater age dating-60

Any trapped air or formation of gas bubbles in the copper tube water sample will cause erroneous results.By reconstructing the amount of chlorofluorocarbons (CFCs or Freon) in the atmosphere, USGS had developed a method that was able to use CFC concentrations to date recent ground water, but a ban on their use in industrialized countries has led to their decrease in the atmosphere.USGS has now developed a dating method that is based on determining the concentration of sulfur hexafluoride (SFThis method has been used successfully to date shallow ground water (e.g., the Atlantic coastal plain sand aquifers and springs near the top of the Blue Ridge Mountains of Virginia).photo Hewlett Packard 7890B GC with a TCD and FID (FID not used) for the analysis of He and Hewlett Packard GC-Mass Spectrometer (GC-MS) with Mass Selective Detector 5973, for the analysis of organic compounds dissolved in ground water.If glass bottles are used, a headspace of several cc's should be left in the bottle to prevent breakage on warming due to expansion.

You must have an account to comment. Please register or login here!