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LL
The most tmp i tent bebect rant ef delayed lle
All groups stucying Strontiu-90 falloutagree on two pointss
first, that most of 1t comes dow in precipitation and second, that
the Strontiw:-90 is probably soluble in water. The Canadfans end
_ Eritish state that about 65% comes dow in rain, Libby has pointed
out that Antofagasta in Chile, a location with essentially no precipitation has a lower Strontius-90 soil content by a factor of
perhaps 50 than any other place on earth that has been sempled.
To understand hew one computes the total Strontiuc-90 deposition
per year, it is nocessary to review the sampling cevices in the
light of the importance ef precipitation.
First, is the soil itself.
Use of the soil ss a method of integrating the world-wide Gelayed
fallout has the following shortcomings:
1.
The soil contains fallout from all tines} it is a cumlative
rather than a differential sampling device,
However, successive
sampling from the sams locale may overcome this difficulty.
2.
The-sgree-of leeching of Strontiun-90 is assumed to be
szall, since the upper ssveral inches are-sseunet—te containsall
that hes fallen out.
3.
There ara water losses during moderate and heavy reins or
malting of snow packs dus to runoff.
h. Removal by impaction on vertical surfaces is not reassured.
S. Sampling over the oceans and other water bodies is inpossible.
This is serious only if spray, vave action or some other ocean
phenomena causes a systematic bias of the results caocpared vith land.
:
6,
Radiocherical enalysis is difficult so that only lirited
numbers of geographical areas have been sampled.
Ths gecond most relisble sampling technique is collection of
precipitation saxples by a pot or funnel. Thess devices collect
éry fallout as well as rain crops.
It is evident thet the pot or
funnel 4s a cifferential sampler, suffers no leeching or runoff
losses, could ba used over oceans, and the reciochemical analysis
is sixpler then for soil.
On the other hand, it probably is very