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Die Strahlenlast im Pazifischen Ozean nach dem Fukushimaunfall

veröffentlicht um 06.04.2012, 20:16 von Martin Walter   [ aktualisiert: 06.04.2012, 20:22 ]
Abstract pnas.1120794109 www.pnas.org/cgi/doi/10.1073/pnas.1120794109

The Tohoku earthquake and tsunami of March 11, 2011, resulted in
unprecedented radioactivity releases from the Fukushima Dai-ichi
nuclear power plants to the Northwest Pacifc Ocean. Results are
presented here from an international study of radionuclide con-
taminants in surface and subsurface waters, as well as in zooplank-
ton and fish, off Japan in June 2011. A major finding is detection of
Fukushima-derived 134Cs and 137Cs throughout waters 30–600 km
offshore, with the highest activities associated with near-shore
eddies and the Kuroshio Current acting as a southern boundary
for transport. Fukushima-derived Cs isotopes were also detected
in zooplankton and mesopelagic fish, and unique to this study we
also find 110mAg in zooplankton. Vertical profiles are used to cal-
culate a total inventory of ~2 PBq 137Cs in an ocean area of 150,000 km2.
Our results can only be understood in the context of our
drifter data and an oceanographic model that shows rapid advec-
tion of contaminants further out in the Pacific. Importantly, our
data are consistent with higher estimates of the magnitude of
Fukushima fallout and direct releases [Stohl et al. (2011) Atmos
Chem Phys Discuss 11:28319–28394; Bailly du Bois et al. (2011) 
J Environ Radioact, 10.1016/j.jenvrad.2011.11.015]. We address risks
to public health and marine biota by showing that though Cs iso-
topes are elevated 10–1,000× over prior levels in waters off Japan,
radiation risks due to these radionuclides are below those gener-
ally considered harmful to marine animals and human consumers,
and even below those from naturally occurring radionuclides.