福島太平洋海輻射污染的地圖 10年 圖像
By the nuclear catastrophe at Fukushima, large quantities of radioactive material were released. A major part of it came through the atmosphere, but partly also by direct discharge into the Pacific Ocean, including long-lived isotopes, such as the highly soluble in seawater cesium-137. Using detailed computer simulations, researchers at the GEOMAR | Helmholtz Centre for Ocean Research Kiel investigates the long-term expansion. "In our models, we have placed great emphasis on a realistic representation of finer details of the flows," said team leader, Prof. Claus Böning, "because the material spread not only through the main current, the Kuroshio, but mainly by intense and highly variable eddy dominated. "
"May have been through this strong turbulence, the radioactive water spreads already has nearly half the North Pacific According to our model calculations," said graduate oceanographer Erik Behrens, lead author of the international scientific journal "Environmental Research Letters" published study. "In addition, winter storms have mixed the water to depths of 500 meters." The attendant dilution in the model bill provides for a rapid decrease of cesium concentration.
The effect of the wide ocean mixing is particularly evident when comparing the model simulated the time course of radiation levels in the Pacific with the situation in the Baltic Sea. "That was in March and April 2011 in the Pacific flowed amount of radioactivity at least three times as large as the one registered in 1986 as a result of the Chernobyl disaster in the Baltic Sea," said Boening. "Nevertheless, we simulated the radiation levels in the Pacific are already lower than the values that we have today, 26 years after Chernobyl, in the Baltic Sea will."
After the simulation model should spur of the first strip about contaminated water in the fall of 2013, the Hawaiian Islands, reaching two to three years later the North American coast. Unlike at the sea surface floating debris, which are also distributed by the wind, the radioactive water is transported solely by the currents beneath the ocean surface. The other concomitant dilution is slow now, but clearly, as the oceanic eddy in the eastern Pacific is much weaker than in the Kuroshio region. Therefore, even for years, the radiation levels in the North Pacific, significantly higher than those before the disaster.
Would be very interested Claus Böning us his team on a direct comparison measurements. "Then we could immediately see whether we are right even if the absolute values of the concentrations," says Prof. Böning. Such data are currently available for the Kiel scientists but not available.