For your information…
The source has a calculated average 2.4 day half life. The half life matches Neptunium 239. Np239 decays into Plutonium 239.
IF WE ARE LUCKY, the source will not be Americium 243 but rather Uranium 239 (in Fukushima); given the 2.4 day half life of Np 239, it is possible that source came directly across the jet-stream as Np-239. The result would be higher levels of Np-239 and Plutonium 239 the further west one went from Saint Louis.
Otherwise, the source would probably be Americium 243 created in the MOX fuel reactor at Fukushima Unit 3.
The video below records raw data being taken from the 1.33 mR/hr radioactive rainfall which fell in Saint Louis, Mo on 9/14/11. This data was taken after shorter half life contamination had mostly burned off.
The data shown is from one hour total count readings taken of the radioactive source, and local background. The raw data from the later part of the video has yet to be fully analyzed.
STAY OUT OF THE RAIN!