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United States
Environmental Protection
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Atmospheric Sciences Research C"
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Research Triangle Park NC 27711 ~s,
Research and Development
EPA/600/S3-86/010 Mar. 1986
4>EPA Project Summary
Feasibility of Using Radioactive
Sulfur in Long-Range Transport
Experiments
Paul Michael
An evaluation has been made of the
feasibility of the use of radioactive 3SS
as a tracer in long-range transport
experiments. This report discusses a
conceptual experiment that places quite
stringent restraints upon the use of the
material. On the basis of the background
concentrations of 35S, the amount of
material required to be released for
detection at 1000 km., public health
considerations as prescribed in Federal
regulations, the capability of current
technology to produce the required
material, and the availability of sampling
and detection techniques, it is conclud-
ed that the use of 35S is technically
feasible. On the other hand, it appears
that the use of stable isotopes of sulfur
would be severely constrained because
of the magnitude and variability of the
occurrence of these isotopes in the
sulfur already being emitted by anthro-
pogenic sources.
This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
An important objective of the National
Acid Deposition Assessment Program is
to determine how much deposition in a
sensitive region is attributable to anthro-
pogenic sources in other regions of the
cou ntry. A key experi mental toot would be
the use of tracers. In the past, nonreactive
tracers have been used to define air
motion on the subcontinental scale, how-
ever, since removal processes such as dry
deposition, clear air chemical transfor-
mations, and wet scavenging depend
upon the chemical nature of the trans-
ported material, the use of tracers that
mimic the pollutant of interest would
provide a great step forward. Because
radioactive 35S has a very low natural
occurrence and, indeed, would undergo
the same transformations as the sulfur
emitted from sources, it would be an ideal
tracer. An examination has been made to
determine the feasibility of using this
substance in long-range transport exper-
iments.
Conclusions
A conceptual experiment consisting of
continual releases of 3SS over a one-year
time period was specified in order to h'ave
conditions as stringent as possible. A
simple transport model estimate of the
release rate that would be required for
detection at 1000 km was approximately
180 Ci per week. The results obtained by
using a wind rose Gaussian plume model
indicated that the air concentrations near
the release point would be below the
levels that have been set by Federal
regulations to protect public safety. Pro-
duction of the radioactive material by the
exposure of 35CI to neutrons in a nuclear
reactor is within existing capability; the
costs of material for the extreme con-
ceptual experiment would be substantial
(on the order of one million dollars), but
are considered not so great as to be
disqualifying. The sampling and detection
techniques would require the use of
state-of-the-art technology and an invest-
ment of about one half of that needed for
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the tracer material. The general conclu-
sion was that the use of 35S was tech-
nically feasible. However, the study did
not include consideration of the public
perception of the use of radioactive
material on this scale. It is likely that a
reasonable public education effort would
be required before approval for such
experiments could be obtained.
The use of stable sulfur isotopes, 34S
and 38S, was considered briefly. The
natural occurrence of these isotopes is so
large, and so variable, that very large
release rates would be required (on the
order of 3 tonnes of 34S per hour); it was
concluded that the use of stable isotopes
would require the development of new
technology at very great expense. Until
new production techniques are proven,
the use of these isotopes as tracers was
considered not feasible.
Paul Michael is with Brookhaven National Laboratory, Upton, NY 11973.
Francis Binkowski is the EPA Project Officer (see below).
The complete report, entitled "Feasibility of Using Radioactive Sulfur in Long-
Range Transport Experiments," (Order No. PB 86-160 280/AS; Cost: $9.95,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-86/010
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