[ RadSafe ] Cesium in Fukushima fish

[Lantzelot]

Maury,

The measured activities in the Baltic Sea may be an interesting 
comparison for "extreme" values.

Anti-nuclear groups often mention the Baltic Sea being the world's most 
radioactive sea, see for instance the following document with Cs-137 
levels in fish from various seas measured during the 1990's: 
http://www.nonuclear.se/files/baltic-radioactive200612.pdf

As you can see from the first graph the activity is of the order of 20 
Bq/kg fish, though near some sediment hot-spots fish with up to 200 
Bq/kg have been found (there are inland fish in Sweden with much higher 
levels). The activity level of Cs-137 in the water is about 45 Bq/m3.
As a side note, the relatively high level is due to 80% from the 
Chernobyl accident. The rest is from atmospherical nuclear tests in the 
1950-60's and from the Sellafield and La Hague processing plants. Only 
0.04% is from the nuclear facilities around the Baltic Sea (something 
that is rarely mentioned by the anti-nuclear groups, it somehow ruins 
their argument).

The activity decreases slowly due to dilution from the rivers that enter 
the Baltic Sea, but in comparison with other waters in the world this is 
a rather slow process due to the closed system with only a narrow exit 
between Sweden and Denmark (see this map that indicates all areas where 
water systems go into the Baltic Sea: 
http://www.grida.no/baltic/related/balans_lc.jpg).
Less than 2.5 Bq/kg is considered to be a "normal" level, and the goal 
is to reach that level within a foreseable future.

Therefore the levels near Fukushima, in an open sea basin of very large 
volume (the Pacific Ocean), is of concern. Please note that the article 
mentions that it is for bottom-dwelling fish. There may be hot-spots in 
the bottom sediments (there are some in the Baltic Sea with rather high 
levels, several 100 kBq/m2) that locally will supply fish with high 
levels for a very long time. So it will have to be investigated closely 
and monitored for a long time. Ironically, a ban on fishing in the area 
may have some positive effects on the local marine life, no risk for 
over-fishing.

Anybody interested in more details about the radioactivity levels in the 
Baltic Sea is recommended to read the Baltic Sea Environment Proceedings 
No. 117 published by HELCOM  (Helsinki Commission - Baltic Marine 
Environment Protection Commission) in 2009.
http://www.helcom.fi/stc/files/Publications/Proceedings/bsep117.pdf

Best wishes for the weekend,
Mattias Lantz

-- 
Mattias Lantz - Researcher
??? ?????
Department of Physics and Astronomy
Division of Applied Nuclear Physics
Uppsala University, Box 516
SE - 751 20, Uppsala, Sweden
email:  mattias.lantz at physics.uu.se




On 10/26/2012 01:14 PM, Maury wrote:
> Thanks, Steve. Does anyone know how much cesium was found in the fish 
> five years ago ... and ten years ago? How much cesium is in fish 
> caught off Newfoundland?
> Best,
> Maury&Dog         [MaurySiskel maurysis at peoplepc.com]
>
> ======================================
> On 10/25/2012 7:31 PM, Steven Dapra wrote:
>> Oct. 25
>>
>>     Small amount of cesium are being found in fish caught near the 
>> Fukushima reactor.  (So says an article in Science reported on at the 
>> below link.)
>>
>> http://news.yahoo.com/cesium-fish-off-fukushima-not-declining-185526202--finance.html 
>>
>>
>> Steven Dapra
>>
>