Re: Cesium in Deer

[Schoenhofer <schoenho@via.at>]

Having been in Germany a few days I found a lot of mails concerning deer on
my return.

Cs-137 from the nuclear bomb tests is of course still around, due to its
half life. Its presence is not directly linked to contamination of plants,
meet etc. Cs-137 from nuclear bomb fallout has been adsorbed to clay
particles, has migrated down from the surface - maybe a few centimeters.
When it is not available for plants, then of course deer will not ingest it.
The availability depends on factors like initial deposition, potassium
content of the soil (as pointed out already in a mail), pH of soil, chemical
composition of soil, percentage of organic matter in the soil etc. etc. The
contamination of the animal depends on the species - roe deer are higher
contaminated than red deer in the same environment, wild boar exceeding both
by far. 

It was mentioned in one response, that there is a very easy way to determine
whether the Cs-137 contamination is from (old) atmospheric fall out or (new)
emissions from a nuclear power plant. Emissions from NPPs contain Cs-134 as
an activation product, while in bomb fission no Cs-134 is produced. Cs-134
has a half life of approximately 2 years. 

One cannot draw conclusions as to the levels of contamination from different
parts of a country, because even the fallout from nuclear bomb testing was
not evenly distributed. It depended for instance on the amount of
precipitation, because by precipitation the Cs-137 containing aerosols are
washed out and the Cs-137 is deposited in higher quantities than from dry
deposition. 

Cs-137 and Cs-134 have been distributed widely in Europe as one of the
consequences of the Chernobyl accident. Due to the 2 years half life of
Cs-134 the concentrations have declined in many samples below the LLD of the
Germanium system - which does not mean that it is not present. So you can
actually see both radionuclides not only in some places, but everywhere, if
you only bother to lower your LLD for Cs-134 to levels low enough. When
measuring Cs-134 at a 600 km distance from Chernobyl it still originates
from the accident. The forests of Austria, the pastures in Cumbria, the
forests in Sweden, Finland and Norway are far more distant from Chernobyl
than 600 km, but both cesium isotopes are easily measurable. (A 5% HPGe
seems to me not to be state of the art for in situ measurements, but if
Cs-134 is detectable with this detector, then its concentration must be
relatively high.) Radioactive cesium has anyway not become a component of
the natural background after 1986, but Cs-137 is still left over from the
atmospheric nuclear bomb tests worldwide - more in the northern hemisphere,
less in the southern.

The behaviour or radiocesium has been studied more than extensively in
Europe after the Chernobyl accident, but mostly in fields like agriculture
and meet production. Often beef is produced from cattle, living their whole
live indoors and being fed with all kind of products like corn, grain etc.
which is much less contaminated than for instance grass. So beef is less
contaminated than for instance roe deer. In a forest ecosystem radiocesium
is easily available due to the high organic content of soil, low pH and
usually low potassium concentration. Therefore wild animals living in a
forest are higher contaminated than even animals grazing on open spaces,
contaminated to the same extent per m2 than the forest soil. 

These are only some aspects of radiocesium in deer. As mentioned above a
terrible lot of work has been done on such aspects, though the question of
the recycling of radiocesium in forest ecosystems is by far not understood
completely. Work on contamination of wild animals and forest products has
been performed extensivly in the Scandinavian countries, in parts of Germany
and also we have done a lot of work in Austria since one week after the
Chernobyl accident and we still work on it.

For anybody interested in this topic I would recommend to check the
literature - but be careful, you will need a lot of time!

Franz
Schoenhofer
Habichergasse 31/7
A-1160 WIEN
AUSTRIA/EUROPE
Tel./Fax:	+43-1-4955308
Tel.:		+43-664-3380333
e-mail:		schoenho@via.at