[ RadSafe ] Uranium contamination

Thu Mar 25 10:20:57 CDT 2010

Wow!  Dan's note triggered "fond" memories of my 10 years on the Uranium Mill Tailings Remedial Action (UMTRA) Project.  Dan's correct,  "heavy metals"  and a host of other "contaminants" co-exist in the ore.  In fact, it works both ways!  Uranium was not even recognized as a valuable metal until the Manhattan Project.  It "happened" to be found in ores that were otherwise being processed for lead, vanadium, molybdenum, etc.  In fact, many former mineral extraction mill sites tailings were "re-processed" after uranium was recognized as a recoverable metal.  This occurred (at a minimum) at the Durango, CO (lead) and Rifle, CO (vanadium) mill sites.  The North Dakota (Belfield & Bowman) UMTRA sites were actually coal bodies that had unusually high uranium content.  The coal was burned (wasted) on site.  The ash (with the uranium in it, that which didn't escape out the stack when the coal was burned) was shipped to the Rifle, CO mill site, where the uranium was extracted.

Post-mill-operation remediation involved MUCH more than cleanup of radiological contaminants.  You name it, and the project encountered it (often as a surprise), during the course of the work.  There were (to name just a few) issues with residual molybdenum, vanadium, arsenic, lead, Th-234 (daughter of U-234, part of the U-238 decay series in the ore, that ended up in the tailings and the raffinate) and more.

As Dan will attest, geology is nothing if not fascinating!

From: Dan W McCarn [mailto:hotgreenchile at gmail.com]
Sent: Thursday, March 25, 2010 1:42 AM
To: radsafe at health.phys.iit.edu
Cc: blreider at aol.com; Miller, Mark L; radsafe at health.phys.iit.edu
Subject: RE: [ RadSafe ] Fw: Uranium contamination

Dear Barbara:

 1.  The Natural Reactors were at OKLO, in Gabon, in Archean or Early Proterozoic rocks (1.7 - 2 billion years ago).  The concentration of U235 was significantly higher than today - about 3%.  The moderator was natural water and the ore concentration quite high. These "natural reactors" make a good model for waste repositories. The same geologic / geochemical mechanisms that emplaced the ore also made it a good repository of radionuclides. The plutonium produced did not travel more than 3 meters or so.  There is a good IAEA publication on Oklo.
 2.  "Uranium, like most heavy metals has a high chemical toxicity."... Well, I'd place quite a few other metals above uranium in toxicity.  In fact, looking at mill-worker data, they were pretty healthy in spite of relatively high serum concentrations of uranium. Arsenic, for instance, is not only a heavy metal poison at high concentrations but also a carcinogen, mutagen, etc. Arsenic and uranium have about the same crustal abundance. Gold, platinum, silver, copper (all heavy metals) are commonly used "safe" metals. Years ago, I was involved as an expert witness in a case involving arsenic contamination in Georgia. The contaminated pond contained almost 0.5 % Arsenic and was caused by a chicken hatchery using NaOH - based cleaners emptying into a septic-tank leach-field (pH = 12). The fluids hydrolyzed - leached -  the arsenic from the arsenopyrite in the limestone. In that case, every foal exposed to arsenic was either auto aborted or died shortly after birth.
 3.  The Redding Prong does indeed contain high levels of uranium (radon).
 4.  Which heavy metal deposits?  Gold / arsenic association is known worldwide, and cancer related to arsenic can be epidemiologically correlated to gold mining districts. Nevada, for instance, has pretty high levels of arsenic in drinking water. Looking at comparative risk, if reducing the arsenic in Albuquerque's drinking water by 10 ug/l to meet federal standards means also reducing the water hardness (magnesium & calcium) by 10%, then the increased risk of cardiovascular disease most probably far outweighs the reduction in risk from arsenic.
 5.  When heavy metals bio-accumulate in plants, they can cause significant problems.  Selenium poisoning in cattle is one example; another is the hyper-accumulation of Cs & Sr in mushroom caps.  Eating mushrooms around Chernobyl can result in a high internal dose.  Lack of selenium in cattle (a much more likely issue) results in white muscle disease and has a much larger area associated with it.  Selenium poisoning frequently occurs is in soils associated with marine black shales and equivalents. Uranium is associated with these shales but has never caused a toxicity problem because it doesn't tend to bio-accumulate like selenium.
 6.  Uranium has a number of pathfinder elements including arsenic, selenium, molybdenum, rhenium, fluorine, phosphorous, scandium, & rare earths.  Deposits that are redox controlled will concentrate some metals that are redox sensitive.  Other minerals e.g. calcite, though not redox sensitive, are mobilized and reconcentrated via bacterially mediated reactions with Fe+2/Fe+3  with thiobacillus ferrooxidans. The pH drops to around 3 and the bacteria seem quite happy to live in diluted sulfuric acid.  This same mechanism drives acid-sensitive metals forward as well, or at least increases the kinetics of the reactions. Those metals that have lower solubility in reduced environments will concentrate in a manner spatially correlated with uranium, that is if the source for those metals is present.
 7.  Massive sulfide, coal, and other deposits that contain significant pyrite will cause acid leach and remobilization of metals.  However, uranium does not tend to be associated with massive sulfide deposits except possibly at the margins of these deposits.
 8.  Almost all deep mines have, to some degree or another, issues with radon, the Cornish Tin Mines being an example. This is commonly attributed to uranium mines, but it is not an exclusive issue. Note EPS's concern for radon accumulation in basements!
 9.  "Some of the areas in Pennsylvania have been mined for zinc"  are contaminated.  Yes, and we had a project in Leoben, Austria to examine the extent of environmental contamination caused by BRONZE AGE miners and foundries. The principle contaminant was arsenic which was concentrated in the hillsides about the same level as the thermal inversions.  Stated again, the smoke from the foundry would rise to the level of the inversion and the soils on the hillsides at that level would receive a significant amount of arsenic.  I suspect that it was not the mine in Pennsylvania that caused the problem so much as the foundry practices.  But Zinc occurs as part of the gangue minerals which will inevitably include (sulfides of Fe, As, Zn, Pb, Cu)  pyrite, arsenopyrite, sphalerite, galena, chalcocite, chalcopyrite, etc.
Since this last subject was principally on Bronze-Age Austrian mining issues, let me close with the traditional miner's saying:
Glückauf!
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<mailto:HotGreenChile at gmail.com> (Private email)
________________________________
From: blreider at aol.com [mailto:blreider at aol.com]
Sent: Wednesday, March 24, 2010 23:38
To: hotgreenchile at gmail.com; radsafe at health.phys.iit.edu
Cc: mmiller at sandia.gov
Subject: Re: [ RadSafe ] Fw: Uranium contamination

Dan,

Not sure about toxic levels of U in the US, there are so many .orgs dedicated to this you cannot find data.  So perhaps you, as a geologist know more.

I am only going on ancient memories but what about the Redding prong area in PA and western regions mined for heavy metals having levels of U that pose toxicity problems?   Some of the areas in Pennsylvania have been mined for zinc etc. and the USACE says whole towns are highly contaminated with everything under the sun.  Also, mined areas that have been turned acidic I believe sometimes have elevated levels of U and other heavy metals in groundwater.  Uranium, like most heavy metals has a high chemical chemical toxicity.  The question as posed didn't  specify radiological danger.  When I did a search online I found quite a few articles about arsenic from U-mines being toxic, so perhaps the U is not as toxic as other metals used in mining.

And where is that natural plutonium reaction area in Africa I read of years ago.  If true, it had to at one time have large concentrations of U-235 and Unat.  http://www.ead.anl.gov/pub/doc/Plutonium.pdf

Barbara Reider, CHP

-----Original Message-----
From: Dan W McCarn <hotgreenchile at gmail.com>
To: radsafe at health.phys.iit.edu
Cc: 'Miller, Mark L' <mmiller at sandia.gov>
Sent: Wed, Mar 24, 2010 5:39 pm
Subject: Re: [ RadSafe ] Fw: Uranium contamination

Dear Group:

OK, I'll step in on this one!  About 1/4 of the US is directly underlain

with uranium-bearing soils and rock, specifically those underlain by the

Chattanooga Shale, Pierre Shale or Mancos Shale.  Typical concentrations of

uranium in these marine black shales are 80-120 ppm or about 0.01% U.

Phosphorites also contain significant uranium at about the same

concentration.  Florida has abundant occurrences / deposits of uraniferous

marine phosphorites.

That being said, the uranium in these rocks are fairly tightly bound

organically.  Uranium which might occur in other rock types would tend to

lose uranium fairly quickly on exposure to meteoric conditions except under

certain conditions (availability of vanadium).

We had a discussion about this subject two or three years ago including

calculations for the "English Garden".  I did a recalculation for

Chattanooga shale soils about that time.

There are other modes of reconcentration in soils including pedogenic

calcretes which tend to concentrate U by evaporative pumping in the desert

SW. Also called hardpan, duricrusts, pedocretes and caliche, they can be

formed from silica (silcretes), calcium carbonate (calcretes), or gypsum

(gypcretes).  The Ogallala Fm from Texas to the Dakotas contains uraniferous

pedogenic silcretes.

That doesn't answer your question, but perhaps covers some of the ranges of

soil concentrations associated with a common rock type.

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 health.phys.iit.edu

[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jerry Cohen

Sent: Wednesday, March 24, 2010 15:06

To: Miller, Mark L; radsafe at health.phys.iit.edu

Subject: Re: [ RadSafe ] Fw: Uranium contamination

Can anyone suggest any reasonable set of conditions where soil contamination

with uranium might constitute a credible threat to health and safety ?

Jerry Cohen

PS: It is now springtime, or as Al Gore suggests,  "Proof of global warming"

________________________________

From: "Miller, Mark L" <mmiller at sandia.gov>

To: Jerry Cohen <jjcohen at prodigy.net>

Sent: Wed, March 24, 2010 10:16:53 AM

Subject: RE: [ RadSafe ] Fw:  Uranium  contamination

As with everything, the answer is, "It depends."  A pathway analysis (like

RESRAD) can tell you if a problem exists, it's magnitude and the most likely

pathway(s) of exposure.  The devil's in the dose.  Armed with that, you can

THEN ask, "Now what"?  The "what" might be "no action" or appropriately

targeted action.

-----Original Message-----

From: Jerry Cohen [mailto:jjc105 at yahoo.com]

Sent: Tuesday, March 23, 2010 4:24 PM

To: radsafe at health.phys.iit.edu

Subject: [ RadSafe ] Fw: Uranium contamination

Does the existence of Uranium contamination in soil constitute a credible

threat to heath and safety, or is this just another costly federal

"feel-good" program? If such uranium contamination is really a problem, what

should be done with the millions of tons of uranium in the oceanic coastal

waters. We even are allowing children to swim in it.

Jerry Cohen

________________________________

From: Cary Renquist <cary.renquist at ezag.com>

To: radsafe at health.phys.iit.edu

Sent: Fri, March 19, 2010 6:10:01 PM

Subject: [ RadSafe ] Argonne scientists seek natural remediation for

uranium-rich sites

They are looking to understand and optimize the conditions under which

bacteria can

transform U(IV) <soluble> to U(VI) <insoluble>

Argonne scientists seek natural remediation for uranium-rich sites

Link  http://j.mp/b3AHAh

Cary

--

Cary.renquist at ezag.com

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