Changes in the atmospheric fluxes of arsenic, antimony, thallium, and bismuth to the Antarctic snow during the past 50 years

초록

Arsenic, Sb, Tl and Bi are highly toxic elements and found in trace amounts in the earth’s crust. Various investigations documented that the atmospheric load and geochemical cycles of these rare elements in the Northern Hemisphere where industrial activities are intensive, have been controlled by changing emissions from various natural and industrial processes in modern times. In order to understand the atmospheric behavior of As, Sb, Tl, and Bi in the most remote areas in the Southern Hemisphere, we have determined these elements in a continuous series of 80 snow samples from a 4-m snow pit, covering 50 years from 1957 to 2007, at Dome Fuji in East Antarctica. They were measured by ultrasensitive inductively coupled sector field mass spectrometry (ICP-SFMS) under a Class 10 ultraclean condition. Concentrations of As, Sb, Tl, and Bi are extremely low, with mean values of 11.3 pg g-1 for As, 0.29 pg g-1 for Sb, 0.07 pg g-1 for Tl, and 0.12 pg g-1 for Bi, respectively. Our snow profiles show that a large fraction of Sb, Tl, and Bi can be attributed to anthropogenic sources, while more than a half of the total Tl originated from natural sources, especially from volcanic emissions including the Mt. Erebus volcano plume in East Antarctica. Our data suggest that Tl is a unique signature for identifying volcanic aerosol from both quiescently degassing and eruptive volcanoes.