The March 2011 earthquake-tsunami-nuclear disaster in Fukushima, Japan, raised lots of questions—about the politics of nuclear energy, about the safety of nuclear power plants on fault lines (like nearby Diablo Canyon), and about the spread of radioactive isotopes in the Pacific Ocean.
One U.S. expert can probably speak to the science of that last question better than anyone: Ken Buesseler, a marine chemist at Woods Hole Oceanographic Institution.
Buesseler's statements about potential radioactivity in seafood (like tuna) have pretty much freaked out half of Facebook. What doesn't get as much mileage: His clarification that only certain fish off the Fukushima coast are unsafe to eat, and that seafood from the U.S. West Coast is virtually unaffected.
But he wanted more data. So he and colleague Colleen Durkin launched a website, Our Radioactive Ocean, to track the spread of Fukushima radiation across the Pacific Ocean.
Over the next six months, they set up more than 30 ocean-water sampling sites from La Jolla, Calif., to Alaska and Hawaii. One of the sites is in Monterey County, at Granite Canyon in Big Sur.
Last week, Buesseler and Durkin sent out an email blast with their findings.
One radioactive isotope that showed up in most water samples: Cesium-137. That's no surprise—cesium-137, released in 1960s nuclear weapons testing, has a 30-year half-life and decays slowly. The average level was 1.5 Bq/m3 (bequerels per cubic meter of water), a really trace amount compared with the EPA's drinking water limit of 7,400 Bq/m3. The levels off Fukushima after the accident, by contrast, were in the millions of Bq/m3—definitely dangerous.
The meltdown also spilled cesium-134. That isotope only has a half-life of two years, so any detected in the sea would point to Fukushima. "Though we do detect this isotope in abundance off Japan, cesium-134 is not YET present in any of the sample[s] collected by citizen scientists along the North American West Coast and Hawaii," the email states. "Our instruments are capable of detecting as little as 0.2 Bq/m3, so the concentration of cesium-134 is below this level."
Cesium-134 might still show up in their samples, the scientists add, depending on the complex mixing of ocean currents. "While those models predict increasing levels of both cesium isotopes for the next 2-3 years, the highest published prediction is for 20-30 Bq/m3, or well below what is thought to be of human health or fisheries concern," they write.
Results from the February 2014 Granite Canyon sample:
Cs137: 1.7 ± 0.1Bq/m3
Cs134: below detection
The beach sampling, however, has limitations, and Buesseler and Durkin are asking for donations to fund offshore seawater sampling "to resolve what levels are in the oceans and how quickly they will end up along the coast line."
They hope to tap a research vessel from Moss Landing Marine Labs. Point Sur is traveling from Dutch Harbor, Alaska, to Eureka, California, taking about 50 samples of both surface and deeper ocean water.
"Even though we were not funded to participate, it was too good an opportunity to pass up," the email states. "Now we’ll need to raise enough funds through OurRadioactiveOcean.org to get these samples analyzed so we can resolve that critical offshore to onshore gradient in cesium isotopes."