Radioactivity in the Ocean: Diluted, But Far from Harmless


by Christina MacPherson 

Environment 360 7 April 2011 

With contaminated water from Japan’s crippled Fukushima nuclear complex continuing to pour into the Pacific, scientists are concerned about how that radioactivity might affect marine life. Although the ocean’s capacity to dilute radiation is huge, signs are that nuclear isotopes are already moving up the local food chain. by Elizabeth Grossman Over the past half-century, the world has seen its share of incidents in which radioactive material has been dumped or discharged into the oceans. A British nuclear fuels plant has repeatedly released radioactive waste into the Irish Sea, a French nuclear reprocessing plant has discharged similar waste into the English Channel, and for decades the Soviets dumped large quantities of radioactive material into the Arctic Ocean, Kara Sea, and Barents Sea. That radioactive material included reactors from at least 16 Soviet nuclear-powered submarines and icebreakers, and large amounts of liquid and solid nuclear waste from USSR military bases and weapons plants.

Still, the world has never quite seen an event like the one unfolding now off the coast of eastern Japan, in which thousands of tons of radioactively contaminated water from the damaged Fukushima Daiichi nuclear power plant are pouring directly into the ocean. And though the vastness of the ocean has the capacity to dilute nuclear contamination, signs of spreading radioactive material are being found off Japan, including the discovery of elevated concentrations of radioactive cesium and iodine in small fish several dozen miles south of Fukushima, and high levels of radioactivity in seawater 25 miles offshore.

How this continuing contamination will affect marine life, or humans, is still unclear. But scientists agree that the governments of Japan, the United States, and other nations on the Pacific Rim need to ramp up studies of how far this contamination might spread and in what concentrations.

“Given that the Fukushima nuclear power plant is on the ocean, and with leaks and runoff directly to the ocean, the impacts on the ocean will exceed those of Chernobyl, which was hundreds of miles from any sea,” said Ken Buesseler, senior scientist in marine chemistry at the Woods Hole Oceanographic Institution in Massachusetts. “My biggest concern is the lack of information. We still don’t know the whole range of radioactive compounds that have been released into the ocean, nor do we know their distribution. We have a few data points from the Japanese — all close to the coast — but to understand the full impact, including for fisheries, we need broader surveys and scientific study of the area.”

Buessler and other experts say this much is clear: Both short-lived radioactive elements, such as iodine-131, and longer-lived elements — such as cesium-137, with a half-life of 30 years — can be absorbed by phytoplankton, zooplankton, kelp, and other marine life and then be transmitted up the food chain, to fish, marine mammals, and humans. Other radioactive elements — including plutonium, which has been detected outside the Fukushima plant — also pose a threat to marine life. A key question is how concentrated will the radioactive contamination be. Japanese officials hope that a temporary fishing ban off the northeastern Japanese coast will be enough to avert any danger to human health until the flow of radioactive water into the sea can be stopped…….

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