The Reston Groundwater Dating Laboratory

Dissolved Gas N2 / Ar and 4He Sampling

Sampling Air or Unsaturated Zone Gas

The bottles and stoppers used for collection of dissolved gas N2 / Ar and 4He are supplied by the USGS. Septum Bottle Picture The equipment and bottle request form can be filled out from within the USGS network by returning to the main lab home page. If you are outside the USGS, please email or call 703-648-5847 or 5347 to request bottles.

Sampling Instructions:

  1. Insert a needle into the stopper until the tip slightly exits through the stopper. (See illustrations below) and Picture Here.
  2. Fill a 2-4 liter plastic or metal beaker with raw unfiltered sample water. Sample flow rate can be between 500 ml and 2 L per minute.
  3. Place the water discharge tubing at the bottom of the 150 mL sample bottle. The tubing can be C-flex, tygon, copper, Teflon, etc. After it is filled place the bottle in the water filled beaker. The water should be flowing into the bottle when it is put in the beaker. Do not filter the sample, use raw sample.
  4. Make sure that no bubbles are adhering to the sides of the bottle. Shake the bottle or jiggle the tubing to dislodge bubbles if present. Place the stopper / needle combination under water and purge the needle of air either by flicking it until all bubbles stop appearing or by directing the discharge from the tubing into the needle until no more air appears.
  5. After at least 500 mL total have flushed through the bottle, withdraw the tubing and insert the stopper in the bottle while the bottle is submerged in the water. Make sure that you push the stopper all the way down. Take duplicates of all samples, two for N2/Ar and two for 4He.
  6. Remove the needle from the stopper while the bottle is still submerged. Properly dispose of all needles.
  7. Take duplicates of all samples, two for N2/Ar and/or two for 4He.
  8. Record the (a) sample name, (b) water temperature and (c) estimated recharge altitude (elevation of the well can be substituted) on the label attached to the foam sleeve. Do not put a label on the bottle. The bottle with stopper is pre-weighed. Do not switch stoppers from bottle to bottle.
  9. Store samples on ice / refrigerated or at least as cool as the temperature of the sampled water. This will keep the stoppers from popping up as sample warms up. Store sample bottles upside down or on their side to keep any bubble that forms away from the stopper. A bubble may form in the sample while stored. This is normal.
  10. Ship samples on ice overnight to:
    USGS Groundwater Dating Lab
    12201 Sunrise Valley Dr. ms432 rm 5B-353
    Reston, VA 20192
    Phone: 703-648-5347, 5847
    Do Not ship samples on a Friday or before a federal holiday. The samples will not be delivered here until the next business day and may heat up in storage.
  11. Include a prepaid return label if you desire to have your cooler / container return shipped.