Recent evolution of the multi-isotopic radioactive content in ice of Livingston Island, Antarctica.

Abstract

The temporal arrangement of the ice layers that are produced in ecosystems with perpetual snows form situations that greatly favour the study of the temporal evolution of the radioactive fallout that occurs in the said zones, whether this fallout is natural or artificial in origin. This allows one to investigate the causes of the fallout and the mechanisms transporting the radionuclides involved from their source point to the study zone, as well as their subsequent behaviour in that zone. There are special difficulties involved in this type of study in Antarctica. Some are of a general character deriving from the conditions of extreme climate and isolation which complicate the processes of extraction and pre-treatment of the samples. Others are directly related to the detection of the temporal evolution of the radionuclides of interest, since these generally possess very low activity levels, so that one has to collect large volumes of samples and use refined techniques of extraction and selective radiochemical concentration prior to assay. In particular, the primordial radionuclides are usually detected in Antarctic ice at lower activity levels than are found for similar latitudes in the northern hemisphere (Nijampurkar and Rao 1993), mainly because of the greater proportion of land to sea in the northern hemisphere. With respect to the deposition of artificial radionuclides, save for those from the re-entry into the atmosphere of the SNAP-9A satellite and from the French atmospheric tests in the Mururoa Atoll between 1966 and 1974, the main events responsible for global artificial radioactive contamination occurred in the northern hemisphere (Kathren 1984), with the resulting observed progressive fall in artificial radioactivity, levels from northern to southern latitudes (Baeza et al. 1996, Holm et al. 1991).