[ RadSafe ] RE : Chernobyl Exclusion Zone Radioactive Longer ThanExpected

[Maury Siskel]

In addition to wishing all a fulfilling year-end holiday season, my 
thanks to Dan and others for this discussion of reconcentration amd 
redistribution mechanisms of various chemicals in plants and soils...  
more samples of the remarkable world around us. This thread has invaded 
successfully one more area of my ignorance -- these descriptions really 
have been interesting as well as instructive and I appreciate your efforts.
Best,
Maury&Dog  (MaurySiskel  maurysis at peoplepc.com)

====================
Dan W McCarn wrote:

>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....
>  
>