 However, one paper on marine sediments for plutonium in marine sediments, atomic bomb fallout is responsible for 66% of the 239Pu and 59% 240Pu found in the English Channel, while nuclear reprocessing is responsible for the majority of the 238Pu and 241Pu present in the Earth's oceans (nuclear weapons testing is only responsible for 6.5 and 16.5% of these isotopes respectively).Richland, Washington was the first city established to support plutonium production at the nearby Hanford nuclear site, to power the American nuclear weapons arsenals.Ozersk, Russia supported plutonium production to power the Soviet nuclear arsenals at the Mayak nuclear plant.