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Studying Trifluoroacetate in Antarctic Snow and Ice
Investigators:Joseph McConnell - Desert Research Institute, Reno, NV
Glenn Miller - University of Nevada, Reno, NV
Chlorofluorocarbons (CFCs) are man-made synthetic substances used for refrigeration as well as a number of industrial and manufacturing processes. CFCs did not exist before about 65 years ago. Because they are very stable, these substances remain in the atmosphere for a long time. Winds continually mix Earth's atmosphere so these long-lived CFCs eventually reach the upper atmosphere (called the stratosphere) where they have been found to destroy ozone and forming an "ozone hole" over Antarctica each spring. The ozone layer in the upper atmosphere protects life on Earth by absorbing ultra-violet radiation that is constantly bombarding our planet. Without this protective shield, most of life on Earth would be harmed or destroyed. When this hole in the ozone layer was discovered in the 1980s, and CFCs were identified as the major cause of ozone destruction, governments from around the world signed an agreement called the Montreal Protocol. In this landmark agreement, governments agreed to limit and eventually eliminate the production and use of CFCs in their countries. However, new chemical compounds were needed to replace CFCs.
New man-made synthetic chemical compounds, called hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), were developed as replacements for CFCs. These new compounds were designed to break down more quickly in the atmosphere with the breakdown products returning to Earth's surface mainly in rain and snow. In this way, the HCFCs and HFCs would never reach the upper atmosphere and so would not contribute to ozone destruction there. However, some of these new compounds, including one called HFC-134a that is now widely used in refrigerators and air conditioners, form a synthetic compound called trifluoroacetate (TFA) when they break down in the atmosphere. Although the amount of TFA in rain and snow at present is very low and does not pose an immediate toxicity threat, several scientists are concerned that this very stable molecule can accumulate in certain places in the environment and become a problem in the years ahead. Algae appear to be the most sensitive to TFA and increasing concentrations of TFA could affect how algae contribute to the food chain. In addition, it is not clear how much TFA, if any, existed in the environment before human activities began to change the chemistry of both air and of rain and snow.
The purpose of our project is to 1) measure how much TFA is currently being deposited in the snow in Antarctica (both at South Pole and along the ITASE traverse routes in West Antarctica) and 2) to measure how much the deposition of TFA has changed in the past. That is, how much has the recent development and widespread use of HCFCs and HFCs changed the concentration of TFA in snow falling and accumulating on the Antarctic Ice Sheet. On ITASE, we measure concentrations of TFA in samples of snow collected in snow pits along the ITASE routes. We also use measurements of TFA concentration in the ice cores collected during ITASE to determine how much TFA was deposited in the snow more than 200 years ago.
