[ RadSafe ] Multiple Source, Radon-222 Plumes

Dan W McCarn hotgreenchile at gmail.com
Thu Sep 10 12:23:16 CDT 2009

Dear Mike:

Ha! Indeed! "If you find funding for that, let me know, because I have a
couple of neat projects in mind, too."  I will, I will... pot of gold...

Dilution / vertical diffusion / mixing would reduce the concentration
significantly, I agree. One of the features that perhaps makes it more
easily modeled is that the entire area is spectacularly FLAT! I've done
quite a bit of modeling for groundwater (and plumes), and as long as the
conditions do not "break" the model, GW / hydrologic modeling is pretty

But empirical data works best! I agree that measurements trump models
always, that is if the measurements can be made effectively.

What about the other alpha activity... How much of that would fall as dust
and be incorporated into the upper soil zone?

Dan ii

Dan W McCarn, Geologist
7 Likely Place
Santa Fe, NM 87508-5938
+33.(0). (Mobile - France)
+33.(0). (Skype - France)
+1-505-240-6872 (Skype - New Mexico) 
HotGreenChile at gmail.com (Private email)

-----Original Message-----
From: Brennan, Mike (DOH) [mailto:Mike.Brennan at DOH.WA.GOV] 
Sent: Thursday, September 10, 2009 11:06
To: Dan W McCarn
Subject: RE: [ RadSafe ] Multiple Source, Radon-222 Plumes

All of this is "gut reaction", so I could be wrong.

One of the most insightful items I picked up in grad school was, "All
models are wrong, and some are useful."

I am suspicious of using models for doing plume prediction, because I've
seen so many really, really bad ones.  I remember one exercise where a
plume from a city on the west side of the Puget Sound supposedly reached
Wenatchee, because the model didn't take into account the Cascade
Mountain Range.  Given the complexity of the situation you describe, I
doubt any model will do it justice, and any decisions based on the model
will be worse than guesses, because policy makers will have more
confidence in results from a model than in a guess.  Just the effect of
the irrigated circles on local wind patterns would be almost impossible
to model.  Even if you have a model you will need to sample to verify
the predictions it makes.    

I think it would be very interesting to find out what the radon levels
are, and how they respond to weather conditions, season, etc., but I
think that the only way is going to be to actually gather data.  At a
guess, I'd think to do a good job you would need a couple hundred
continuous radon monitors and a dozen or so automatic met stations, and
a way of gathering data on when irrigation is going on, how much water
is being used, and the radon concentrations at that moment.  And of
course, the staff and computers to run it.  A year or two of data should
suffice.  If you find funding for that, let me know, because I have a
couple of neat projects in mind, too.  

I agree with your math, and I agree that almost all of the radon is
being released from the water.  On the bright side, there is no reason
to believe the radon from the irrigation is concentrating in buildings.
While you are talking about a lot of radon, the dilution factor is
pretty big.  

Should be interesting.

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Dan W McCarn
Sent: Thursday, September 10, 2009 7:31 AM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Multiple Source, Radon-222 Plumes

Dear Group:


Does anyone have a Gauss-Plume code or other suggestion (meteorological
model) to calculate the air concentrations and dose from multiple point
sources of radon?  I've been considering writing a code using multiple
sources and a typical wind rose to estimate the concentration / dose.
The ground surface is extremely flat in every direction over the entire


Actually, the number of points may be as large as 7,500 from
central-pivot, spray-type irrigation systems and the release "point" is
actually the center of a large central-pivot irrigation system.  The
average concentration of
Ra-222 in the groundwater is about 2-4,000 picoCuries / L and the annual
water use is on the close order of 1.2x10^12 L based on the historical
record of consumptive water demand for the produced crops.


Lowest concentration is about 2,000 pCi/L and the highest may be perhaps
0.1-0.5 million pCi/L, since there is a uranium feature involved (based
on other, similar uranium deposits) - a regional redox controlled,
roll-front about 60 km long.  Based on data from a similar "control"
deposit, total alpha activity in water could be up to 1 million pCi/L in
the roll-front.


I am assuming that the fine, misting spray will cause the release of
most of the radon. The area involved is about 180,000 Hectares with
several modest sized towns.


That's about 1 million acre feet of water per annum..


1.2x10^12 L * 3000 pCi/L = about 3600 Ci annual release, if I've done my
math correctly.


Dan W McCarn, Geologist
7 Likely Place

Santa Fe, NM 87508-5938

+33.(0). (Mobile - France)

+33.(0). (Skype - France)
+1-505-240-6872 (Skype - New Mexico)
 <mailto:HotGreenChile at gmail.com>  <mailto:HotGreenChile at gmail.com>
HotGreenChile at gmail.com (Private email)


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