Decoding an unexpected mystery at the Montebello Islands
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Date
2022-11-30
Journal Title
Journal ISSN
Volume Title
Publisher
South Pacific Environmental Radioactivity Association
Abstract
During the 1950’s three nuclear tests were conducted in the Montebello Islands in Western Australia by the UK government. The tests introduced a radioactive legacy into the surrounding marine environment but were investigated minimally immediately after and in the decades that followed. Work is currently underway to quantify the persistence and migration of anthropogenic radionuclides within the island archipelago’s marine sediments. Activity concentrations of studied radionuclides (137Cs, 238Pu, 239&240Pu and 241Am) in surface sediments so far have concentrated within a 5 km radius of the three ground zero locations and in the north-west of the islands inline with the original fallout plume trajectories. However, one sampling location does not fit within this originally hypothesised pattern of distribution. This single site, called the Lowendal Islands site, was 26 km south of the detonation ground zero locations and originally sampled as an environmental background. Activity concentrations of studied radionuclides were the second highest of all surface sediments collected (1.6 Bq kg-1, 80 Bq kg-1, 402 Bq kg-1 and 28 Bq kg-1 respectively). Four initial theories are proposed to explain this mystery: currents, air movement, rafting or human involvement. Current analysis indicates that either rafting or human involvement are most likely, based on reviews of historical data, knowledge of regional water movement and 241Am/240Pu/239Pu ratios.
Description
Keywords
Nuclear test sites, Western Australia, Islands, Aquatic ecosystems, Plutonium 238, Plutonium 239, Plutonium 240, Caesium 137, Americium 241, Fallout
Citation
Williams-Hoffman., M., Johansen, M. P., Lavery, P. L., Thirovoth, S., Serrano, O., & Masqué, O. (2022). Decoding an unexpected mystery at the Montebello Islands. Poster presented to SPERA 2022 - Connecting People, developing solutions for a Changing Environment, 28-30 November 2022, Chrischurch, New Zealand, (pp. 52). Retrieved from: https://au-admin.eventscloud.com/file_uploads/baa6bb17538b457fbd436f1552075bea_SPERA2022e-handbook.pdf