The Reston Chlorofluorocarbon Laboratory
SF5CF3 and CFC-13 FAQ
- Where should I use SF5CF3 and CFC-13 dating?
This procedure should be used in aquifers that are contaminated with CFC-11, CFC-12, and CFC-113. The new tracers are useful in dating ground waters that have high concentrations of terrigenic SF6 and/or He and cannot be dated by the SF6 and tritium/helium-3 method. Some environments that appear to have given good results with the new tracers include sandy aquifers (Atlantic and Gulf coastal plain), areas of rapid recharge and lack of mixing with old water (Blue Ridge Mountains of Virginia, some coastal aquifers), and some shallow, urban environments. For more details read the research section then contact Ed Busenberg if you have further questions.
- How do I get sample bottles and equipment for SF5CF3 collection?
- Can I get some one to train me in collection or help with the sampling?
Yes. Contact the CFC lab.
- How should the SF5CF3 and CFC-13 samples be stored after collection?
The dissolved gases present in the ground water are sampled. The gas samples and some of the ground water are collected in bottles. The bottles are stored UPSIDE DOWN with the ground water in contact with the aluminum foil of the cap. The cap MUST be taped with electrical tape to prevent contamination of the extracted gas with air. They should be stored at room temperature. Avoid leaving samples in the sun or hot enclosed spaces (like field vehicles). Storage on ice is not recommended.
- How long can I keep the bottles before shipping?
Although the samples are probably stable for several weeks, it is recommended that they be shipped to the CFC lab within several days of collection. They will be analyzed within approximately 1 month of receipt.
- How do I ship the bottles back to the CFC lab without breaking?
Put the bottles upside down in the original cardboard box, wrap the box with bubble wrap, place it in cooler and ship via FedEx.
- What is required for sampling?
A special stripping apparatus and special training is required for sampling.
- Can I pre-pay for analyses?
- What are the limitations of the new sampling procedure?
One hundred liters or water are required to spray through an equilibration chamber supplied by the CFC Lab. Also see "General Comments and Limitations of the New Procedure" section.