Abstract
Unusually high concentrations of americium and plutonium have been observed in a sediment core collected from the eastern Lombok Basin between Sumba and Sumbawa Islands in the Indonesian Archipelago. Gamma spectrometry and accelerator mass spectrometry data together with radiometric dating of the core provide a high-resolution record of ongoing deposition of anthropogenic radionuclides. A plutonium signature characteristic of the Pacific Proving Grounds (PPG) dominates in the first two decades after the start of the high yield atmospheric tests in 1950’s. Approximately 40–70% of plutonium at this site in the post 1970 period originates from the PPG. This sediment record of transuranic isotopes deposition over the last 55 years provides evidence for the continuous long-distance transport of particle-reactive radionuclides from the Pacific Ocean towards the Indian Ocean.
Highlights
Plutonium isotopes present in today’s oceans originate from various sources[1,2,3]
The significance of any Pacific Proving Grounds (PPG) derived plutonium in ITF sediments is not presently known, high 241Am concentrations were recently reported in ITF sediments from the Lombok Basin off Sumba Island, Indonesia[17]
1. determine, if high 241Am concentrations at the Lombok Basin site are correlated with high concentrations of plutonium isotopes, providing definitive evidence of transport of the transuranic radioisotopes through the ITF, 2. ascertain the fraction of PPG derived plutonium based on known end-members from the PPG and global weapons fallout, and
Summary
Plutonium isotopes present in today’s oceans originate from various sources[1,2,3]. The major portion can be attributed to nuclear weapons testing in the atmosphere between 1952 and 1980. In the 1950’s a series of nuclear tests was performed by the United States in the Marshall Islands, namely at the Bikini and Enewetak Atolls, an area known as the Pacific Proving Grounds (PPG). These tests released substantial quantities of radioactive material into the environment. The distinct 240Pu/239Pu atom ratio provides a fingerprint of PPG-derived material[5], and ratios in the sediments of the Northwest Pacific indicate a notable contribution from the PPG6,7 To this day significant amounts of plutonium continue to be released from the PPG into the surrounding waters. 1. determine, if high 241Am concentrations at the Lombok Basin site are correlated with high concentrations of plutonium isotopes, providing definitive evidence of transport of the transuranic radioisotopes through the ITF, 2. ascertain the fraction of PPG derived plutonium based on known end-members from the PPG and global weapons fallout, and
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