SCIENCE
The ocean isn’t the only place radiation is lingering—meet the scientists who pee plutonium.
Teachers, scroll down for a quick list of key resources in our Teachers Toolkit, including today’s simple MapMaker Interactive map.
Photograph courtesy U.S. Navy
Discussion Ideas
- New studies measured “levels of radionuclides in the ocean waters, seafloor and groundwater at Bikini and Enewetak Atolls.” What are radionuclides?
- Radionuclides are unstable isotopes. They are atoms that have an unbalanced number of neutrons in their nuclei—the number of neutrons does not equal the number of protons. It is this imbalance that makes the atom unstable. The radionuclide emits its excess energy through the process of radioactive decay.
- When scientists measure the levels of radionuclides, they’re measuring levels of radioactivity in an area. (Radioactivity associated with the nuclear accidents at Chernobyl and Fukushima, for example, is measured by determining the dispersion and deposition of radionuclides.)
- Why do you think the coastal waters surrounding Enewetak and Bikini Atolls might have higher levels of radionuclides than the surrounding ocean?
- Enewetak and Bikini were the main sites of the Pacific Proving Grounds, where the U.S. conducted 66 nuclear weapons tests between 1946 and 1958. Take a look at those tests with our study guide here.
- How did scientists measure radioactivity at Enewetak and Bikini Atolls?
- Scientists measured the presence of radionuclides of three elements: plutonium, cesium, and radium. They took samples from the ocean, lagoons, seafloor sediments, cisterns, wells, beaches, and other sites in and around the atolls.
- Pu. Although tiny, tiny amounts of plutonium exist in nature, it is, by definition, a “rare earth element.” Most plutonium on Earth is radioactive fallout from nuclear testing. Learn more about plutonium radionuclides here.
- The levels of plutonium are 100 times higher in lagoon waters when compared to the surrounding Pacific Ocean.
- Cs. Cesium is not a rare earth element, but the isotope cesium-137 is the principal source of radioactivity associated with nuclear power plants. (Spent nuclear fuel rods and radioactive waste are contaminated with cs-137, for instance.) The radioactivity associated with both the Fukushima and Chernobyl nuclear disasters is cs-137, but it is not the principal contaminant in nuclear weapons fallout. (That would be plutonium.) Learn more about cs-137 here.
- The levels of cesium are two times higher in lagoon waters when compared to the surrounding Pacific Ocean.
- Ra. Radium is not emitted during nuclear testing, but is a naturally occurring radionuclide. It acts as a “tracer” that helps scientists determine how much and how fast groundwater flows from land into the ocean. Learn more about radioactive tracers here.
- Pu. Although tiny, tiny amounts of plutonium exist in nature, it is, by definition, a “rare earth element.” Most plutonium on Earth is radioactive fallout from nuclear testing. Learn more about plutonium radionuclides here.
- Scientists measured the presence of radionuclides of three elements: plutonium, cesium, and radium. They took samples from the ocean, lagoons, seafloor sediments, cisterns, wells, beaches, and other sites in and around the atolls.
- What is the source of most radioactivity in the Enewetak and Bikini lagoons?
- Seafloor sediments contributed the most plutonium to the ocean. This wasn’t a complete surprise: “Until atmospheric testing was banned in 1963, more than 5 tons of plutonium were dispersed in the atmosphere in the form of small particles blown around the globe by the wind … Most of this plutonium dust fell into the oceans, and approximately 96% of that amount simply sank as sediment onto the ocean floors because plutonium is not readily soluble in seawater. The fact that plutonium dissolves very slowly in water also explains why the plutonium concentration in our oceans is low and will continue to be so.”
Photograph by James P. Blair, National Geographic
- What surprised scientists about the radioactivity in the Enewetak and Bikini atolls?
- In a modestly pleasant surprise, scientists discovered that radioactive groundwater was not leaking into the ocean in large amounts. (This is why that radium tracer was so important!) Scientists were concerned about the possibility of a leak because the bottom of Runit Dome, an enormous concrete lid that covers 111,000 cubic yards of radioactive soil and debris on Enewetak Atoll, is not lined below sea level.
- “The foundations of these island atolls are ancient coral reefs that have the porosity of Swiss cheese, so groundwater and any mobilized radioactive elements can percolate through them quite easily,” said WHOI geochemist Matt Charette. Though that does not seem to be happening now, the scientists advise that the Runit Dome area should be continuously monitored as sea level rises and the dome deteriorates.
- In a modestly pleasant surprise, scientists discovered that radioactive groundwater was not leaking into the ocean in large amounts. (This is why that radium tracer was so important!) Scientists were concerned about the possibility of a leak because the bottom of Runit Dome, an enormous concrete lid that covers 111,000 cubic yards of radioactive soil and debris on Enewetak Atoll, is not lined below sea level.
TEACHERS TOOLKIT
Woods Hole Oceanographic Institute: Radioactivity Lingers from 1946-1958 Nuclear Bomb Tests
Nat Geo: Radioactivity at Enewetak and Bikini Atolls
Nat Geo: The Scientists Who Pee Plutonium
Nat Geo: Bombs Away on YouTube
(extra credit!) Science of the Total Environment: Lingering radioactivity at the Bikini and Enewetak Atolls