THALLIUM AND CADMIUM IN RECENT SNOW AND FIRN LAYERS IN THE CANADIAN ARCTIC BY ATOMIC FLUORESCENCE AND ABSORPTION SPECTROMETRIES

Compared to the Antarctic and Greenland, the Canadian Arctic has seen extremely few trace metal studies on snow and ice. Surface, subsurface and depth samples of snow and firns were collected from the Agassiz I ce Cap, Ellesmere Island, Canada using clean room practices. Results f or Tl (directly determined by LEAFS) and Cd (determined by GFAAS) are reported. To our knowledge, the thallium depth profile presented here is the first one so far reported for both polar systems, Greenland or other places. Tl concentrations peak in the winter-spring periods, whe n the Arctic atmosphere is loaded with foreign pollutants and suspende d particulates which sometime severely reduce the visibility, creating a phenomenon commonly known as the Arctic haze. These results are in general accordance with the historical Arctic air pollution and acidit y/conductivity data on ice cores. Surface concentrations of Tl range f rom 0.3 to 0.9 pg/g, which is a few times higher than those found in A ntarctica. Cadmium shows seasonal characteristics similar to Tl althou gh there is not a definite correlation between the two. However, there could be two predominant origins of metals which were deposited in th e snow: Eurasian origin in January-April corresponding to high level m etals (main deposition), and a less definite origin in May-December co rresponding to low level metals.