Due to the extreme climate, the polar ecology is most sensitive to environmental changes, especially to the human-made pollution. Antarctica is considered the least polluted continent due to limited human activity there. However, human pollution might be transported in large scale to Antarctica through atmospheric and marine circulation. Investigating levels, sources, and pathways of human-made pollutants in Antarctica is therefore crucial for better understanding the response interms of spatial and temporal scales and thereby protection of the environment in polar regions.
129I is a naturally generated isotope, but anthropogenic releases are the dominated source of 129I in the present environment. Unlike most of the anthropogenic radionuclides, radioiodine released to the atmosphere is mainly in the gaseous form, which disperses in the atmosphere mainly in the gaseous form, with a small fraction (<30%) possibly converted into particulate form during transport, causing a longer residence time and larger dispersion of radioiodine in the atmosphere. Dispersion of radioiodine in the atmosphere has been investigated through analysis of aerosol, precipitation, and ice core, but mostly focusing on the Northern Hemisphere, the data of radioiodine in the Southern Hemisphere, especially in the Antarctic are very sparse.
The 129I research group in the Institute of Earth Environment, Chinese Academy of Sciences (IEECAS) determined 129I and 127I concentrations in snow and seawater samples collected in Bellingshausen, Amundsen, and Ross Seas in Antarctica in Jan. 2011 during the cruise of a Swedish-American Antarctic Expedition, using accelerator mass spectrometry (AMS). It was observed that 129I/127I atomic ratios in the Antarctic surface seawater ((6.1−13) × 10−12) are about 2 orders of magnitude lower than those in the Antarctic snow ((6.8−9.5) ×10−10), but 4−6 times higher than the prenuclear level (1.5 × 10−12), indicating a predominantly anthropogenic source of 129I in the Antarctic environment. The 129I level in snow in Antarctica is 2−4 orders of magnitude lower than that in the Northern Hemisphere, but is not significantly higher than that observed in other sites in the Southern Hemisphere. This feature indicates that 129I in Antarctic snow mainly originates from atmospheric nuclear weapons testing from 1945 to 1980; resuspension and re-emission of the fallout 129I in the Southern Hemisphere maintains the 129I level in the Antarctic atmosphere. 129I directly released to the atmosphere and re-emitted marine discharged 129I from reprocessing plants in Europe might not significantly disperse to Antarctica.