[ RadSafe ] RE : Chernobyl Exclusion Zone Radioactive Longer ThanExpected

[Dan W McCarn]

Hello Group:

In my last posting, I implicitly discussed "mechanisms of reconcentration"
of cesium and strontium.  Basically, because of the high cation-exchange
selectivity of cesium / strontium, there is a mechanism that RECONCENTRATES
Cs & Sr in zones of high cation-exchange capacity.  Geologists are always
aware of these type of mechanisms because they emplace ore deposits, cause
caliche buildup in certain soil types and constantly changes a "uniform"
environment into a very heterogeneous one. If one were to look at an active
roll-front uranium deposit, one would remark that through time, the
concentration increases! That's because it really is trapping uranium very
efficiently from groundwater and precipitating it into the roll-front.

Mechanisms in plants will likely redistribute Cs in a way similar to
potassium (K) or for Franz, Kalium.  In some fungi such as mushrooms, the Cs
is hyper-accumulated.  In fact, they do it so well that one French research
group studied the possibility of using mushrooms to clean-up soils of Cs &
Sr.

One must look at mechanisms that mobilize and redistribute R/Ns and weight
the importance of each one.

Another mechanism: around the Chernobyl plant, deep-plowing was used to
turn-over the top meter of soil to reduce the effects on people working
there. Perhaps the cesium is being pulled closer to the soil surface over
the intervening 23 years (evapotranspirative pumping?) and is being
reconcentrated closer to the upper soil profile. Plants are thirsty
critters, and they produce a flow upwards into the capillary fringe zone of
the soil. Perhaps this active transport mechanism is also leaching the Cs &
Sr from the deep-plowed zone and depositing the material in the upper soil
zone.

As I mentioned earlier, there is still significant redistribution of cesium
during wildfires.  Not only the trees are burned, but the upper soil zone,
quite rich in cesium & strontium in the humus, is also lofted and aerially
dispersed. Back in the 90s, this would raise the background radiation in
Minsk 10 fold when there was significant smoke from the zone in the air. The
area around Las Alamos experienced a similar phenomenon some years back
following the forest fire there. 

In mass-balance terms, a forest fire that burns the top 10-15 cm of forest
floor would loft a significant amount of cesium and strontium in that area
skyward in the ash.  The ash that remained and was not lofted, would also be
significantly more radioactive per gram of material.  The lofted material
would then be re-deposited elsewhere downwind. The ash that remained would
simply increase the surface radioactivity because of the reconcentration of
Cs, Sr, & K in the ash.  The ash, as every farmer knows, is easily
leachable.  That is why "pot ash" is used for garden fertilizer.

Just my very late-night thoughts!

Dan ii

--
Dan W McCarn, Geologist
2867 A Fuego Sagrado
Santa Fe, NM 87505
+1-505-310-3922 (Mobile - New Mexico)
HotGreenChile at gmail.com (Private email)

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf
Of Bailey, Pete
Sent: Wednesday, December 16, 2009 08:56
To: safe rad (radsafe at radlab.nl)
Subject: [ RadSafe ] RE : Chernobyl Exclusion Zone Radioactive Longer
ThanExpected

>Cesium 137's half-life - the time it takes for half of a given amount

of material to decay - is 30 years, but the amount of cesium in soil near

>Chernobyl isn't decreasing nearly that fast. And scientists don't know
>why

Not withstanding the discussion about plant 'recycle'; there must be an
'unknown'  source of Cs-137 to allow the measured concentrations to exceed
the values based on the physical half-life.
This 'unknown' source could be such things as poor (underestimated)  time=0
values or an underground (soils,clay etc)
deposit of Cs that is feeding the 'assumed' fallout only Cs concentration
profile.

I also believe, from my own continuing experience with Rad Env Monitoring,
the Cs fallout still occurs; sample results I see in vegetation does not
truly follow 30 yr
....but that is very tied to "when is T=0"   . . .  late 50's when 'we'
stopped' ?  how about the Chinese weapons tests in the 60's, etc.

Interesting note, however, Gross Beta in Air did follow a nice Rad Decay
curve....
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