MEXT/US DOE Cesium Deposition Map
http://www.iaea.org/newscenter/news/tsunamiupdate01.html#fig1
Isn't 0.3 MBq/M2 (300,000 Mega Bq/M2) still extremely high? If so, why
would they dismiss that?
The IAEA update for 5/20 had the following comment regarding the
map:
"The map of the deposition of radiocaesium is presented in Fig. 1. The values represent the sum of Cs-134 and Cs-137. The areas in green show a deposition of these two radionuclides of between 0.6 and 1 MBq/m2. The areas in yellow indicate a deposition of between 1 and 3 MBq/m2. The areas in red indicate a deposition of between 3 and 30 MBq/m2. All are normalized to 29 April 2011"
They don't even refer to the 0.0-0.3 MBq/M2 or 0.3-0.6 MBq/M2 ranges in
the map. But, areas falling in those ranges do exist. Am I interpreting
the map right?
The highest BRAWM topsoil measurement for cesium was the 4/6 sample of
0.99 & 1.53 Bq/kg for Cs-134 and Cs-137 respectively. Or a combined
measurement of 2.52 Bq/kg. Which I believe translates to 37.8 Bq/M2.
That's assuming 15kg per M2 of soil. So, to even entertain the idea
of 300,000 Bq/M2 is staggering. Let alone a 3,000,000 to 30,000,000
MBq/M2 range.
Also, how does the map
Also, how does the map relate to (if at all) the IAEA comment below
about deposition in the 47 prefectures?:
"The daily monitoring of the deposition of caesium and iodine radionuclides for 47 prefectures is continuing. Since 12 May negligible deposition has occurred. I-131 was reported in only one prefecture and Cs-137 was reported in three prefectures, with a value of 4.8 Bq/m2 for I-131 and a range of from 4.7 to 10 Bq/m2 for Cs-137."
4.8 Bq/m2 and 4.7 to 10 Bq/m2? The map and these numbers are worlds apart.
Can someone explain the difference?
The map is based on
The map is based on accumulated deposition since the beginning of the crisis on a 50 miles radius.
The daily depositions are exactly that, measurements taken everyday analyzing daily fallout by prefecture, including regions way beyond the 50 miles area. Since air emissions have been largely reduced, fallout is consequently low at this point.
That makes sense
Thanks for the explanation.
I'm still curious why they only track down to 300,000 Bq/M2 though.
It's as if they are saying anything from 0-300,000 Bq/M2 isn't worth
tracking. And the area falling within that range is more than areas
for all the other ranges.
The IAEA report also confirms the green tea contamination in Kanagawa
prefecture south of Tokyo.
I think the map was aiming
I think the map was aiming at defining the exclusion zone (they don't call it exclusion zone, but I don't think residents will be going back to their homes in the following centuries).
Apparently after Chernobyl the benchmark that defined the evacuation area was 500,000 Bq/m2 of Cesium 137, so I don't know exactly why here they defined the lower range as 300,000 - 600,000. Maybe they wanted to exclude Fukushima city, which would be difficult to evacuate.
About the contaminated tea, it's only the beginning of a great variety of health hazards the Japanese would be dealing with during the following decades. Significant fallout was measured by MEXT since late March at least in Fukushima, Ibaraki, Tochigi, Chiba, Tokyo and Kanagawa Prefectures. Soil is contaminated and contaminated produce growing on that soil will absorb the cesium.
Apparently the Japanese government plans to study the level of contamination of the soil and the level of cesium absorbed by each produce, then publish the results to show which crops are more affected. They are going to use the data obtained after Chernobyl in Europe, but the soil and the kind of crop is different in Japan so the results may vary.