|Fig. 1: Fukushima Nuclear Power Plant. (Source: Wikimedia Commons)|
The northern hemisphere is much more contaminated with radioactive pollution than the south. The reasoning behind this is simple, approximately 90% of all nuclear weapons testing was done in the northern hemisphere, and some of the most notable nuclear power-plant disasters all occurred in the northern hemisphere.  Nuclear weapons testing in the atmosphere accounted for considerable amounts of radioactive materials to be released directly into the environment. This environment includes not only the atmosphere but the ocean as well. The ocean was extremely contaminated by the Fukushima Nuclear disaster (see Fig. 1).
There are three possible origins of the radioactive pollution: liquid radioactive releases from the damaged site, atmospheric fall-out onto the surface of the sea, and the transport of radioactive pollution by leaching through contaminated soil.  The direct release into the sea close to the damaged reactors comes from water that was used to cool the reactors. Next, comes the pollution from the atmospheric fall-out onto the surface of the sea. After the Fukushima disaster, it is estimated that 1016 Bq of Cs-137 was deposited on the surface of the sea up to 30 km out to sea.  Additionally, radioactive pollution was transported to the marine environment through leaching of contaminated soil. Rain water created run-off which carried the radioactive pollution from the ground to the ocean, adding even more radioactive deposits from the disaster to the sea.
The Japanese sand-eel is the most commonly caught fish in the Port of Iwaki (near Fukushima); after the nuclear disaster data was collected to determine the level of radioactive pollution in these species. The highest recorded level came on April 13th and reached a level of 6300 Bq/kg of Cs-137.  These levels come from not only contaminated water, but food as well. These fish will be the best long-term indicators of caesium contamination in the area because of the direct exposure these species have.
What can be gathered from this information is the extremely negative effects that radioactive pollution can have on all forms of life. It is crucial to consider where some items are on the food chain and the fact that radioactive pollution will make its way up the food chain in time. Even if precautions are put in place radioactive pollution will continue to spread through various forms of contamination.
© Michael Humphrey. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 R. Prāvālie, "Nuclear Weapons Tests and Environmental Consequences: A Global Perspective," Ambio 43, 729 (2014). ref
 "Impact on the Marine Environment of Radioactive Releases Following the Nuclear Accident at Fukushima Daiichi," Institut de Radioprotection et de Sûreté Nucléaire, 13 May 11.