Baseline measurements of atmospheric mercury concentrations from Scott Base/Arrival Heights

The southern hemisphere is not as well characterized as that of the northern hemisphere for atmospheric mercury measurements. Very little data exists for baseline atmospheric mercury data in Antarctica. Sampling was initiated in the 1985/86 season at Lake Vanda, Wright Valley. Atmospheric sampling was conducted with samples collected for the determination of aerosol and volatile lead. In the 1986/87 season mercury concentrations were measured in and around Scott Base during a three week period (a total of 34 samples collected) to verify low concentrations observed at Lake Vanda and to determine the best sampling site in the vicinity of Scott Base for the positioning of a photoacoustic mercury analyser. The analyser was erected and left over the winter to obtain a unique over-winter data set and to determine baseline atmospheric mercury levels in Antarctica. Air was sampled for 24 or 48 hours twice weekly from mid February until early October (1987 winter). Concentrations of mercury in the atmosphere are thought to be temperature dependent and therefore the analyser provided a time series at Scott Base to elucidate seasonal variations in atmospheric mercury. 'Clean air' was sampled at the transmitter site at the western end of the base and at a site on the ice shelf on the eastern boundary of the whiteout zone of Williams field. In the 1987/88 season, samples were again collected from around Scott Base in duplicate. Data was received from the photoacoustic mercury analyser and left in place for another winter season of mercury measurements. Clean air samples were collected around Scott Base. All mercury samples over all seasons were collected using a tandem sampler which differentiates between inorganic (including elemental mercury) and organic forms of mercury.