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USGS Measures Fallout from Fukushima in US NADP Precipitation Samples

USGS and the National Atmospheric Deposition Program (NADP) networks measured fission-product isotopes in the U.S. from the Fukushima Dai-ichi nuclear power facility atmospheric release incidents, which occurred March 12 and 14, 2011 near Sendai, Japan.  This project added to the body of knowledge about radioactive fallout from the March 12-14, 2011 incident and exhibited the capabilities of the USGS and NADP to respond to an unexpected atmospheric release. 

Following the disaster, radioactive iodine and radioactive cesium were detected in precipitation samples collected in the U.S. at NADP sites. Detectable quantities of Iodine-131, Cesium-137 and Cesium-134 were observed at approximately 20% of the NADP locations where precipitation was sampled between March 15 and April 5, 2011.  Radioactive iodine and cesium are often some of the largest contributors to human radiation doses after an accident at a nuclear reactor.  Fallout amounts measured in precipitation by NADP were similar to amounts measured by other organizations, which were determined to be well below any level of public health concern.

Methods and results of the study are documented in USGS Open-File Report 2011-1277.  The data are interpreted and compared to measurements of others in an article published in Environmental Science and Technology, March 6, 2012.  A list of frequently asked questions (FAQs) pertaining to the study is available via the link provided below.

National Atmospheric Deposition Program (NADP) sites where USGS measured 137Cs in precipitation samples

cesium 137 wet deposition in becquerels per square meter march 15 - april 5, 2011Dot size represents relative deposition amounts. Fallout amounts measured in precipitation by USGS provide a clearer picture of fission-product wet deposition across the USA.

Open-File Report 2011–1277
Fission Products in National Atmospheric Deposition Program Wet Deposition Samples Following the Fukushima Dai-Ichi Nuclear Power Station Incident, March 8 - April 5, 2011. U.S. Geological Survey Open-File Report 2011-1277, 2011, 34p., Gregory A. Wetherbee, Timothy M. Debey, Mark A. Nilles, David A. Gay, and Christopher M.B. Lehmann.

Environmental Science and Technology
Wet Deposition of Fission-Product Isotopes to North America from the Fukushima Dai-ichi Incident, March 2011, Environmental Science and Technology, doi:10.1021/es203217u, March 6, 2012, Gregory A. Wetherbee, David A. Gay, Timothy M. Debey, Christopher M.B. Lehmann, and Mark A. Nilles.

Press Release

Frequenty Asked Questions

Points of Contact:
  Publications Author - Greg Wetherbee, USGS Branch of Quality Systems,, 303-236-1837
  USGS Communications Office - Kara Capelli, USGS Public Affairs,, 703-648-5086

Dai Ichi Power Plant, credit:
The damaged Dai-Ichi Power Plant, 3 minutes after the explosion March 14, 2011. Photo courtesy of Digital-Globe-Imagery (some rights reserved)


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Page Last Modified: 02/17/2012