Fission Products in National Atmospheric Deposition Program--Wet Deposition Samples Prior to and Following the Fukushima Dai-Ichi Nuclear Power Plant Incident, March 8-April 5, 2011

Radioactive isotopes I-131, Cs-134, or Cs-137, products of uranium fission, were measured at approximately 20 percent of 167 sampled National Atmospheric Deposition Program monitoring sites in North America (primarily in the contiguous United States and Alaska) after the Fukushima Dai-Ichi Nuclear Power Plant incident on March 12, 2011. Samples from the National Atmospheric Deposition Program were analyzed for the period of March 8-April 5, 2011. Calculated 1- or 2-week radionuclide deposition fluxes at 35 sites from Alaska to Vermont ranged from 0.47 to 5,100 Becquerels per square meter during the sampling period of March 15-April 5, 2011. No fission-product isotopes were measured in National Atmospheric Deposition Program samples obtained during March 8-15, 2011, prior to the arrival of contaminated air in North America. On March 11, 2011, a magnitude 9.0 earthquake centered off the Pacific Coast of Japan triggered a tsunami and a 14-meter (m)-high tidal wave that inundated the Fukushima Dai-Ichi Nuclear Power Plant near Sendai, Japan.