690
SESSION HIB DISCUSSION
VAN MIDDLESWORTH: When measuringthe total beta concentration, what is the contribution from the natural radioactivity in the soil,
i,e., SOil swept up by the winds as dust. Has there been any evaluation
of the radium content of this dust? Would the contribution from this
source be large or small?
HUFF: You are touching on a point that I mentioned that the relatively large concentration at the beginning of the storm period may
very well be related to entrainment of low-levelor surface particulates
into the storm. As I said, we have some indirect evidence that is dis-
cussed in one of our progress reports. We cannot quantitatively state
that 10 or 20 or 50% of the beta concentration on the leading edge of
the storm is coming from this source. I wish we had measurements
that would allow us to do this. In relation to the radon problem, we
store the samples for several days before we use them to try to reduce
the radioactivity from this source in our analyses. I would be glad to
discuss this with you in more detail later.
STOUT: Mr. Gatz, do you have cases where there were two consecutive rain showers with little or no break in the rain and youstill
found a high pollen content during the second shower period?
GATZ: We have such a case but not in any of the rains reported
here. The rain of May 9, 1964, which we sampled near Chickasha,
Okla., had two rather intense rainfall-rate peaks. The peaks occurred
13 min apart and were separated by a short period of relatively light
rain. The data on pollen concentrations are not yet available, but the
radionuclides showed the usual temporal variations in both bursts.
That is, the concentration was high at the beginning of the rain burst
and then fell rapidly. It will be extremely interesting to see if a
Similar pattern occurred with the pollen concentrations.
REITER: It seems to me that not only the pollen is “sticky” but
the whole problem is because now we have three points of view here.
Your impression seems to be that the low-level air carries most of
the radioactivity because of the agreement with pollen concentrations
early in the storm. There also seems to be some evidence that quite
a number of storms may have high concentrations of contaminants due
to the tapping of the stratosphere by cloud tops. From the one case
which we analyzed, we are convinced that some low tropospheric intrusion of stratospheric air got tapped by precipitation.
SHLEIEN: Have you considered the possibility of material originally deposited on the ground being whipped up by winds and redeposited in rainfall?
GATZ: We haven’t made any calculations, but this may very well
be the source of a part of the contaminants in the low-levelair.