New RadWatch Website!

Formerly BRAWM, we have updated our website to become RadWatch. Read more about our previous activities and ongoing measurements!

RadWatch Realtime Air Monitoring


The Radwatch Air Monitoring team has put together a unique system that serves high-resolution gamma-ray data hourly to monitor naturally occurring, airborne radioactivity. Weather data are also served to provide insight to correlations that exist in the transport of these radionuclides. Read about our current activities and future goals!

Seaweed Measurements (2013)

These seaweed samples were provided to our group by a seaweed harvesting company located in Northern California as a continuation of a study beginning in spring 2011. As in previous years, we tested the samples using a high purity germanium (HPGe) detector in Etcheverry Hall, UC Berkeley. HPGe detectors have very high spectral resolution, meaning they are able to distinguish the gamma-ray lines coming from different radioactive isotopes. For seaweed this is especially important because there is typically a large amount of the naturally occurring isotope potassium-40 (K-40).

No isotopes due to Fukushima have been found in these or any previous samples we have tested.




Species Location Date Harvested K-40 [Bq/kg] Cs-134 [Bq/kg] Cs-137 [Bq/kg]
Alaria Marginata Greenwood Cove 04/28/2013 1050 ± 100 N.D. (<0.20) N.D. (<0.20)
Porphyra Lanceolata McKerricken 06/11/2013 360 ± 36 N.D. (<0.085) N.D. (<0.14)
Postelsia Palmaeformis Medocino Coast 07/10/2013 870 ± 90 N.D. (<0.068) N.D. (<0.11)
Laminaria Setchellii McKerricken 07/22/2013 810 ± 80 N.D. (<0.12) N.D. (<0.13)

Results of Red Salmon from Alaska caught in 2011, 2012, and 2013


Three samples of Red Salmon from Alaska have been tested. The salmon was caught at the same location (the Kenai River) in July for each of the last three years-- 2011, 2012, 2013! A small amount of Fukushima-sourced radio-cesium was found in the July 2011 sample, likely from the initial airborne releases of radioactivity in Spring of 2011. No Fukushima-related radioisotopes were found in the 2012 and 2013 samples. In all samples, naturally radioactive potassium dominated the gamma spectrum. Bi-214 and Pb-210 are also naturally occurring radio-isotopes. Most of the Cs-137 originates from releases before Spring 2011.

Half Moon Bay Measurements

Surfer’s beach near Half Moon Bay has been in the news a lot in the past several weeks over a youtube video featuring a Geiger counter making measurements in the area. We made measurements there and decided that it would be good to share this information with the public. Read on to see our results!

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