Plutonium From Nuclear Tests Still High In The Air, But Volcanos Could Bring It Closer To Earth, Study Says
At the height of the Cold War, the United States was feverishly testing its latest nuclear bombs. They detonated the warheads all over the place: underwater, underground, above ground, and high in the air. Today, new research shows that the radioactive effects of that testing still linger high in the atmosphere, with bits of plutonium attached to aerosol particles in the stratosphere.
The research also demonstrates that volcanos, and in particular the one in Iceland that spawned the infamous "ash cloud" of 2010, could help to bring that radioactive matter closer to earth. A study published Tuesday in the journal Nature Communications examined volacano debris as a previously unknown method for transporting "anthropogenic radionuclides" (science code for man-made radioactive particles) through layers of atmosphere.
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"Our results ... reveal that strong volcanic eruptions like [Iceland's] Eyjafjallajökull in 2010 have an important role in redistributing anthropogenic radionuclides from the stratosphere to the troposphere," the researchers, lead by José Corcho Alvarado of Lausanne University Hospital, wrote in the paper.
To understand what Corcho Alvarado and his team found, you need to understand that the sky isn't just a swirling globe of mixing air particles, though it might look that way. It's actually made up of five layers. From closest to farthest from earth: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Each layer is seperated by a stiff boundary which keeps particles separated; the tropopause is the boundary between the stratosphere and the troposphere.
The researchers say the amount of plutonium wafting into our layer, the troposphere, is not nearly enough to cause anybody harm. But they did find that the plutonium concentration in the stratosphere was higher than in the troposphere.
According to Smithsonian magazine, Corcho Alvarado and his colleagues became intrigued by some findings after Eyjafjallajökull's eruption when scientists began testing high levels of plutonium in the troposphere and found them to be out of the ordinary. Usually, weather patterns disperse plutonium and keep the levels virtually nil, but in this case, researchers were getting some readings. So Corcho Alvarado figured something must have been bringing the radiation lower.
In addition to nuclear testing, there was a plutonium-fueled satellite that disintegrated on re-entry and scattered radiation in 1964. Much of that plutonium has dispersed over the years, but some of it has been trapped in the stratosphere because of the tropopause. But Corcho Alvarado discovered that steam-lifted ash and sulfure dioxide particles had probably latched onto plutonium and yanked them along when they fell back to earth.
"The levels of plutonium and (caesium) currently found in the stratosphere are low, and comparable to the levels measured at ground-level air (troposphere) at the end of the '60s and in the '70s," Corcho Alvarado told AFP by email. "Although I'm not a health specialist, I would say that the current levels of plutonium found in the stratosphere do not represent a risk for the population."
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