本帖最后由 秋之皓月 于 2011-3-25 19:01 编辑
Home » Forums » Berkeley Radiological Air and Water Monitoring Forum
Fallout effects from Fukushima on the US west coast...
http://www.nuc.berkeley.edu/node/1944
I would be interested in your reaction to:
http://idealist.ws/
http://www.stretchingminds.wordpress.com/
Are they wrong? If you could give a scientific explanation why it might make me feel a little better about this situation...
Here is an excerpt:
[slightly technical] A nuclear engineering academic
department scientist at a university in California has recently made
public the concentrations of radioactive material found in rain water collected
on the roof of a hall on a Berkeley campus. The values reported for March 19 were
measurements of 5.61 Becquerels per Liter for Iodine-131 and 0.26
Becquerels per Liter for Cesium-137 (a sampling run ending on 3/20
found slightly lower levels of Cesium-137 and 7.1 Becquerels per Liter for Iodine-131.)
If our calculations are correct, and
the units convert to 151 picocuries per Liter of water for Iodine-131 for the March 19th values, then each liter of tap
water consumed at these levels will give affected Americans a thyroid dose of
about 1 millirem (or 1,000 microRems). [NRC NUREG 1.109 rev. 1
Oct. '77 gives 0.0139 milliRems thryoid dose per pCi of I-131 for infants; and
0.00195 mRem for adults). We use average of 0.008 milliRems thryoid dose per pCi. ]
If our estimates are correct, each
liter of tap water (March 19th values) with Cesium-137 is 25% of the levels that scared the pants
off Taiwanese officials on March 20 when imports of Japanese beans were measured at '1
becquerel of cesium ...detected in 1 kilogram (about 2 pounds) of fava bean.'
The Berkeley lab's levels are equal
to 7 picoCuries per liter/or kilogram of Cesium-137 in rainwater, which, if
manifested at those levels in grown foods, this would be similar to lower levels
in the U.S. food supply in the 1960s. More maps on that here.
How do foods become contaminated
by rainwater? It is well established that cow milk tends to
reflect a concentration about 1,000 times the levels of radioiodines in the air over a pasture.
This effect, called bioaccumulation, also applies (although to a lesser extent) to cesium-137 and
strontium-90 in milk.
The radioactive
'distilling' effect in the air-grass-cow-milk-human chain is enhanced when it rains because
precipitation is more effective at depositing airborne radioactive debris to the ground
than with 'dry deposition.' Even on dry feed lots, cows drink from puddles of rain
water and are exposed in other ways to their rain-soaked environment.
So, the slightly
radioactive levels in California air - according to recently
released EPA data - that included a high reading of 0.068 picoCuries per cubic meter (March 18, San Francisco, CA) for
iodine-131 means that pasture-fed dairy cow milk measuring 68 picoCuries per
*liter* may have recently been on Bay Area store shelves. Iodine-131 levels in milk could have been even higher than this because the EPA failed to correct for the fact that iodine-131 captured on the San Francisco RADNET filter
decayed during transit to the EPA's lab in the Southeast. Although
public health officials might consider these levels to be of zero concern,
prolonged intakes of contaminated milk might pose a health danger to toddlers, infants or young children. State and federal public
health officials need to determine the impact of sustained and uncertain radioiodine inputs to the thyroid glands
of the young. The daily rate of
exposure is not the issue - it is the cumulative exposure that could lead to
dire problems down the road. |
发表于 2011-3-25 10:15
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