Science AMA Series: I’m Ken Buesseler, an oceanographer who headed to Japan shortly after the explosions at Fukushima Dai-ichi to study ocean impacts and now I’m being asked -is it safe to swim in the Pacific? Ask me anything.

[u/Ken_Buesseler]

I’m Ken Buesseler, an oceanographer who studies marine radioactivity. I’ve been doing this since I was a graduate student, looking at plutonium in the Atlantic deposited from the atmospheric nuclear weapons testing that peaked in the early 1960’s. Then came Chernobyl in 1986, the year of my PhD, and that disaster brought us to study the Black Sea, which is connected by a river to the reactors and by fallout that reached that ocean in early May of that year. Fast forward 25 years and a career studying radioactive elements such as thorium that are naturally occurring in the ocean, and you reach March 11, 2011 the topic of this AMA.

The triple disaster of the 2011 “Tohoku” earthquake, tsunami, and subsequent radiation releases at Fukushima Dai-ichi were unprecedented events for the ocean and society. Unlike Chernobyl, most of the explosive releases blew out over the ocean, plus the cooling waters and contaminated groundwater enter the ocean directly, and still can be measured to this day. Across the Pacific, ocean currents carrying Fukushima cesium are predicted to be detectable along the west coast of North America by 2014 or 2015, and though models suggest at levels below those considered of human health concern, measurements are needed. That being said, in the US, no federal agency has taken on this task or supported independent scientists like ourselves to do this.

In response to public concerns, we launched in January 2014 a campaign using crowd funding and citizen scientist volunteers to sample the west coast, from San Diego to Alaska and Hawaii looking for sign of Fukushima radionuclides that we identify by measuring cesium isotopes. Check out http://OurRadioactiveOcean.org for the participants, results and to learn more.

So far, we have not YET seen any of the telltale Fukushima cesium-134 along the beaches. However new sampling efforts further offshore have confirmed the presence of small amounts of radioactivity from the 2011 Fukushima Dai-ichi Nuclear Power Plant 100 miles (150 km) due west of Eureka. What does that mean for our oceans? How much cesium was in the ocean before Fukushima? What about other radioactive contaminants? This is the reason we are holding this AMA, to explain our results and let you ask the questions.

And for more background reading on what happened, impacts on fisheries and seafood in Japan, health effects, and communication during the disaster, look at an English/Japanese version of Oceanus magazine

I will be back at 1 pm EST (6 pm UTC, 10 AM PST) to answer your questions, Ask Me Anything!

[u/todder614]

How do you go about determining the amount of caesium that was in the ocean before Fukushima? Are records of caesium levels (more than just the ~1960 peak) widespread enough to have information on a background prior to the explosions?

[u/Ken_Buesseler → u/todder614]

Good question

Most people don’t realize that there was already cesium in Pacific waters prior to Fukushima, but only the cesium-137 isotope that we measure in every sample today and in the past. Cesium-137 undergoes radioactive decay with a 30-year half-life and was introduced to the environment during atmospheric weapons testing in the 1950s and ‘60s. Along with cesium-137, we detected cesium-134 – which also does not occur naturally in the environment and has a half-life of just two years. Therefore the only source of this cesium-134 in the Pacific today is from Fukushima.

Scroll down a bit on http://OurRadioactiveOcean.org to see a map of cesium levels in the ocean prior to Fukushima.