Progress 05/15/01 to 04/30/04
Outputs
Our contribution to this project was to serve as an analytical laboratory for the lead investigator, Dr. Joe McConnell, at the Desert Research Institute. We developed a method for determining trifluoroacetate (TFA) in polar ice. TFA is a transformation product of the new freon substitutes, particularly HFC 134A. In the atmosphere, hydroxyl radical oxidizes HFC 134A, followed by hydrolysis to TFA. This molecule is very stable, and due to the global existence of this compound, it can serve as an indicator of age of snow. Dr. McConnell gathered a series of snow and ice samples in polar regions, melted the snow and submitted the resulting samples to us for TFA determination. The analytical method used required extensive development time. It utilized a very sensitive head space gas chromatograph, with an electron capture detector. The primary challenge was to eliminate contamination from the procedure, since TFA is distributed widely. Briefly, the procedure (adapted from a
method by Cahill and Seiber) contained the following steps. A small amount of base was added to the samples in a 20 mL head space vials, which were then evaporated in a vacuum oven. Methanol and sulfuric acid were then added to the samples, they were capped and placed on the head space gas chromatograph auto sampler. Quantitation was completed using external standards. The results indicated that TFA was detected in polar snows above the detection limit. Although further samples need to be analyzed, it appears probable that the results can be used to distinguish general age of the snow and ice. However, some redistribution is apparent and the data have not yet been analyzed completely to assess usefulness of this method.
Impacts
While the data are not yet completely analyzed, it appears that this method may be able to allow an estimation of the age of polar snow and ice, as well as be used to better understand mixing and redistribution reactions and processes in the snow.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
This project is determining the concentration of trifluoracetic acid (TFA) in samples from the South Pole, and is being conducted with Dr. Joe McConnell from DRI. TFA is a very stable transformation product of freon substitutes and can be used as a tracer in groundwater, as well as snow and ice. Out portion of this project is to serve as an analytical laboratory for TFA. We receive melted ice samples from Dr. McConnell and analyze these samples for TFA. We use a method developed by a previous graduate student, utilizing head-space gas chromatography of methylated TFA and electron capture detection. During the previous year, we re-established the utility of the method and analyzed approximately 100 samples. The results indicate that TFA can be determined reliably to about 20 ng/L. However, in recent months we have noted a degradation of the reproducibility of the method and have been required to determine the cause. This has largely been accomplished and we expect to
resume analysis of South Pole samples in the next weeks.
Impacts
Trifluoroacetic acid is potentially an excellent tracer of anthropogenic contamination of the environment. This study, conducted on pristine snow samples from the South Pole, can be used to assess how extensively humans have contaminated the polar regions. The results to date are encouraging.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
This project will measure trifluoracetic acid in ice and snow. We have not yet initiated work on this project, but expect to determine TFA in approximately 50 collected samples over the next three months.
Impacts
This project will help to determine if TFA can be a tracer for deposition of anthropogenic in polar snow and ice.
Publications
- No publications reported this period
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