EPA-600/4-76-012
March 1976
Environmental Monitoring Series
MEASUREMENT OF TOTAL RADIUM AND
RADIUM-226 IN ENVIRONMENTAL WATERS
A Tentative Reference Method
Environmental Monitoring and Support laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, Nevada (9114
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical Informa-
tion Service. Springfield, Virginia 22161.
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EPA-600/4-76-012
March 1976
MEASUREMENT OF TOTAL RADIUM AND RADIUM-226 IN ENVIRONMENTAL WATERS
A Tentative Reference Method
by
Quality Assurance Branch
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
ROAP Number 22ACW
Program Element 1HA327
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
LAS VEGAS, NEVADA 89114
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and Support
Laboratory-Las Vegas, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
Effective June 29, 1975, the National Environmental Research Center-Las
Vegas (NERC-LV) was designated the Environmental Monitoring and Support Labo-
ratory-Las Vegas (EMSL-LV). This Laboratory is one of three Environmental
Monitoring and Support Laboratories of the Office of Monitoring and Technical
Support in the U.S. Environmental Protection Agency's Office of Research and
Development.
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CONTENTS
Page
1. Principles and Applicability 1
2. Range and Sensitivity 2
3. Interferences 2
4. Precision and Accuracy 3
5. Apparatus 4
6. Reagents 4
7. Procedure 9
8. Calibration 24
9. Calculations and Reporting 24
References 26
APPENDIX A. Factors for Decay of Radon-222, Growth of
Radon-222 from Radium-226, and Correction of
Radon-222 Activity for Decay During Counting ... 27
APPENDIX B. Error and Statistical Calculations 30
FIGURES
1. Apparatus for Radon Transfer 5
2. Emanation Tube (Bubbler) 6
3. Lucas Scintillation Cell 7
iii
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TENTATIVE REFERENCE METHOD FOR THE MEASUREMENT OF
TOTAL RADIUM AND RADIUM-226 IN ENVIRONMENTAL WATERS
1. Principles and Applicability
1.1 Total radium in water is concentrated and separated from sample
solids by coprecipitation with barium and/or lead sulfate. The
precipitate is purified by washing with nitric acid, dissolving in
alkaline EDTA, and reprecipitating as radium-barium sulfate after ad-
justing the pH to 4.5. This slightly acidic EDTA keeps other naturally
occurring alpha emitters and the lead carrier in solution. The pre-
cipitate is transferred to a counting dish, dried, weighed to determine
chemical yield, and alpha-counted to determine the total disintegration
rate of radium isotopes.
For radium-226, the barium-radium sulfates are solubilized, the
radon-222 daughter allowed to grow in, then radon-222 is de-emanated
from the ingrowth bubbler chamber to a counting cell. The radon-222 is
counted for radium-226 determination.
1.2 This method is applicable for measuring radium in environmental
waters. It is also applicable to sewage and industrial wastes,
provided steps are taken to destroy organic matter and eliminate other
interfering ions. The method may be used for absolute measurements by
calibrating with a suitable alpha emitter or for relative methods by
comparing measurements with each other.
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2. Range and Sensitivity
2.1 The minimum limit of concentration to which this method is appli-
cable will depend on sample size, counter characteristics, back-
ground and counting time. It is recommended that samples be counted
long enough so that samples with activities as low as the detection
limit of the method and counting instrument used, will have a counting
error (± cpm) of no more than the sample net count rate (when counting
error cpm equals sample net cpm, the counting error is 100 percent).
For instance, when a 1-liter water sample is analyzed for total radium
by this method and is counted for 50 minutes in an alpha scintillation
detection system having a background of 0.005 cpm, a counting efficiency
of 45 percent, and gives a gross count rate of 0.09 cpm, the sample will
have a net count rate of 0.085 cpm and a counting error of ± 0.085 cpm
at the 95 percent confidence level. This corresponds to a detection
limit of 0.09 ± 0.09 pCi/liter. Also, when a 1-liter water sample is
analyzed by this method for radium-226 by radon-222 count in a gas
scintillation detector with a background count rate of 0.13 cpm, a
counting time of 30 minutes, a counting efficiency of 76 percent, and
a gross count rate of 0.39 cpm, the sample will have a net count rate
of 0.26 cpm and a counting error of ± 0.26 cpm at the 95 percent confi-
dence level. This corresponds to a detection limit of 0.15 ± 0.15
pCi/liter. Samples having concentrations above the detection limit and
counted for the time indicated above will have correspondingly lower
counting errors. Since radium is separated from the sample, the detec-
tion limit can be improved by analyzing larger samples.
3. Interferences
3.1 If barium is present in the sample it will cause an error in the
barium sulfate yield determination. The error will be proportion-
al to the amount of barium present.
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3.2 The gaseous alpha-emitting radionuclides, radon-219 and -220
(through the alpha-emitting decay products), can interfere with
the test, but can be corrected for if known to be present. Interfer-
ences from these radionuclides would be rare in water not contaminated
by industrial wastes from some type of uranium operation.
4. Precision and Accuracy
Water samples of 1-liter size containing as little as 1 pCi of
radium (as radium-226) can be analyzed for total radium by this method
with a precision of less than ± 25% at the 95 percent confidence level,
when precipitated samples are counted in an alpha scintillation detec-
tion system with a background of 0.12 cpm (blank sample), and counted
for 60 minutes at a counting efficiency of 45 percent. Liter size
samples containing as little as 5 pCi of radium (as radium-226) can be
analyzed with a precision of less than ± 20 percent at the 95 percent
confidence level (same counting time, background, and counting effici-
ency as indicated above).
Water samples of 1-liter size containing as little as 1 pCi of
radium-226 can be analyzed for radium-226 by radon-222 gas-alpha scin-
tillation counting by this method with a precision of less than ± 35
percent at the 95 percent confidence level, when counted for 30 minutes
at 76 percent counting efficiency. Liter size samples containing as
little as 5 pCi can be analyzed with a precision of less than ± 10 per-
cent at the 95 percent confidence level (at 30-minute counting time
and 76 percent counting efficiency).
The overall accuracy is a combination of the accuracy of the
standardised (data furnished by the supplier) and the precision and
accuracy of the method of measurement. Analytical results, using the
"Total Radium by Precipitation" portion of this method, of spiked water
samples prepared with as little as 1 pCi/liter of radium-226, should
show an'accuracy with a deviation from the known of less than ± 10 per-
cent, at the 95 percent confidence level. Analytical results, using
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the "Radium-226 by Radon-222 De-emanation" portion of this method, of
spiked water samples prepared with as little as 1 pCi/liter of
radium-226, should show an accuracy with a deviation from the known of
less than ± 15 percent at the 95 percent confidence level.
5. Apparatus
Counting Systems
For radium-226 by radon-222 emanation: an alpha
scintillation counting system that will accommodate
gas counting cells
For total precipitated radium: an alpha scintillation
counting system or a thin window proportional counting
system
Filter holder for, and 0.45 micrometer pore size membrane
filters (47-mm diameter, cellulose triacetate type)
Filter flask, 2-liter
Suction pump
Four-liter (or one-gallon) polyethylene bottles and labels
Gas de-emanation apparatus (see Figures 1 and 2)
Scintillator-type gas counting cells (see Figure 3)
A cylinder of helium gas provided with a 2-stage regulator
and a needle valve
Vacuum pump
Two-liter beakers and 50-ml centrifuge tube
Centrifuge
Platinumware: 50-75 ml crucibles, 500-ml dish, and platinum-
tipped tongs
6. Reagents. It is implied in this "guideline" that all reagents are
of "reagent-grade" purity whenever such reagents are commercially
available.*
* Reagent Chemicals, "American Chemical Society Specifications,"
American Chemical Society, Washington, DC. For reagents not listed by
the ACS see "Reagent Chemicals and Standards" by Joseph Rosin, D. Van
Nostrand Co., Inc., New York, NY, or the "United States PharmacopeiaV
for purity tests.
4
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To Vacuum
Pump
Scintillation Cell
Open End Manometer
11/2mm I.D.
Capillary T-tube
Thermometer Capillary
Anhydrous Magnesium
Perchlorate
Ascarite
Air From a
Compressed Air Regulator
Radon Bubbler
Figure 1. Apparatus for Radon Transfer
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7mm O.D.
110/30
Coming No. 2
or Equivalent
135
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33
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Liquid ^
Level
mm
17mm
O.D.-""
>
>
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— j
&r>§A9K
\
i
^
J>
035mm-|
.^ Bubble Trap
J 7mm I.D.
Rigidity Brace
7mm Capillary Tubing
iy2mm LD.
Fritted Glass Disc
/ 10-15 micron pores
Volume to be kept
at minimum
Figure 2. Emanation Tube (Bubbler)
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67 mm
90 mm
Phosphor
Coated
Corning No. 2
or Equivalent
Brass Collar
Clear Silica
Window
Kovar Metal*
U (HK? 'HWffll WTOKfffl!
E] 50 mm-
* Cell can be made from 2-inch OD aluminum tubing by 3^-inch long,
to which one end is epoxy-cemented a 2-inch diameter by 1/8-inch thick
aluminum disc with aluminum or brass collar. Stopcock and quartz window
can also be cemented in place by epoxy cement.
Figure 3. Lucas Scintillation Cell
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Ammonium hydroxide, concentrated
Citric acid, 1M, dissolve and dilute 210 g of H3C6H507'H20
with distilled water to 1 liter
Barium carrier solution: dissolve and dilute 3.555 g of
BaCl2-2H20 plus a few drops of concentrated HC1 with
distilled water to 1 liter (1 ml equals 2 mg Ba)
Barium chloride solution: dissolve and dilute 17.79 g
of BaCl2'2H20 plus a few drops of concentrated HC1 with
distilled water to 1 liter (1 ml equals 10 mg Ba)
Lead carrier solution: dissolve and dilute 160 g of
Pb(N03)2 plus a few drops of concentrated HN03 with
distilled water to 1 liter (1 ml equals 100 mg Pb)
Methyl orange indicator solution: dissolve and dilute
0.05 g of methyl orange with distilled water to 100 ml
Phenolphthalein indicator solution: dissolve 0.5 g
of phenolphthalein in 50 ml ethanol and dilute with
50 ml of distilled water
Bromcresol green indicator: dissolve and dilute 0.1 g
bromcresol green sodium salt with distilled water to
100 ml
EDTA solution; dissolve and dilute 93 g of disodium
ethyl enediaminetetraacetate dihydrate with distilled
water to 1 liter
Acetic acid, concentrated (glacial)
Nitric acid, concentrated
Sulfuric acid, 18N, and 0.1N
Hydrochloric acid, concentrated, 6N, IN, and 0.1N
Phosphoric acid, 85%
Ammonium sulfate solution: dissolve and dilute 10 g
of ammonium sulfate with distilled water to 100 ml
Ascarite, 20 mesh (drying agent)
Hydrogen peroxide, 30%
Anhydrous magnesium perchlorate
Sample preservative solution, 6N hydrochloric acid
containing 24 mg barium carrier per 150 ml
8
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Radium-226 solutions:
Solution A: Obtain a National Bureau of Standards
radium-226 standard, 0.1 yg radium-226
in solution (glass ampul). Prepare a barium-HCl
diluting solution containing 7.116 g of BaCl2*2H20
and 40 ml of concentrated HC1 diluted to 2 liters
in a volumetric flask (1 ml = 2 mg Ba). Place the
radium standard, glass ampul, in a 400-ml beaker
containing 200 ml of the barium-HCl diluting solu-
tion. Break the ampul with a glass rod, stir to
mix, then very carefully transfer the solution to
a weighed 1-liter volumetric flask through a funnel
provided with a glass wool mat to collect the broken
ampul pieces. Rinse the beaker three times with
200-ml portions of the barium-HCl diluting solution
and add the washes to the 1-liter volumetric flask.
Dilute to the 1-liter mark with the diluting solu-
tion. Stopper and mix thoroughly. Weigh the flask
plus contents. Solution concentration then is:
r.. _ pg of radium-226 x p.990 pCi/pg
p 1/g ~ g of Solution A
(approximately 100 pCi/g and 2 mg Ba/g)
Solution B: Transfer and accurately weigh approxi-
mately 3 g of Solution A into a weighed
100-ml volumetric flask. Dilute to the mark with
the barium-HCl diluting solution, stopper, and mix
thoroughly. Weigh the flask plus contents. Solution
concentration is:
nri/n - g of Solution A x pCi/g of Solution A
p /g " g of Solution B
(approximately 3 pCi/g and 2 mg Ba/g)
7. Procedure
7.1 Sampling
Sampling may be accomplished as described in "Environmental Radio-
activity Surveillance Guide," published by the U.S. Environmental Pro-
tection Agency as report ORP/SID 72-2. It is recommended that samples
be preserved at the time of collection by the addition of 150 ml of
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6N hydrochloric acid containing 24 mg of barium carrier (from standard
barium carrier solution) per 4 liters (or 1 gallon) of sample collected.
Care should be taken in adding the acid-carrier solution to samples in
the field because the barium carrier is to be accounted for (recovery
to be determined) in the sample analysis. However, if determination is
to be made of the radium content in the separate dissolved and suspended
fractions of the sample, then those fractions must be separated before
the preservative is added, since the preservative may change the distri-
bution of the sample radioactivity. Rather than separating the dis-
solved and suspended solids fractions of samples in the field, samples
can be brought to the laboratory without preservative added. Separation
is then done by filtering out the suspended solids on a tared 0.45-micro-
meter membrane filter. The filter is dried, weighed, and set aside for
further analysis. The preservative solution is then added to the fil-
trate which is then returned to the original sample container and held
there for overnight or longer before analysis is begun.
7.2 Analysis for Radium-226 by Radon-222 De-emanation
7.2.1 Calibration of Gas Scintillation Counting Cells
7.2.1.1 Determine the background of each scintillation counting cell
before using to count standards or samples. In the apparatus
shown in Figure 1, substitute a glass tube adapter provided with stop-
cocks for a bubbler in the apparatus. Evacuate the counting cell and
the apparatus and check for leaks, especially the counting cell, by
closing the vacuum source stopcock and observing the manometer reading.
If there is no change in the manometer reading after 5 minutes the
cell and system can be considered leak-free. With the system and the
cell evacuated, open the stopcock to the carrier-counting gas supply
and fill the cell and system just to atmospheric pressure. Remove the
cell from the apparatus and place it on the phototube in the counting
system. Cover the cell and phototube with a light-tight cover and
10
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after a 15 minute dark-adapting period, count the cell activity for
at least 30 minutes. (The cover should be provided with a high voltage
interlock switch so that there is never high voltage on the phototube
when it is exposed to room light. Exposure to room light when high
voltage is applied will destroy the phototube.)
7.2.1.2 Before adding standard radium-226 to the bubbler, test the
bubbler for flaws in the frit that will cause unwanted larger
bubbles (larger bubbles reduce the de-emanation efficiency). Add about
10 ml of distilled water and 5-10 drops of isopropyl alcohol to the
bubbler and apply about 5-10 psi of helium gas pressure to the gas
inlet of the bubbler. Observe the bubble action. Satisfactory bubble
size is evidenced by a milky appearance in the bubbler solution. Reject
bubblers that do not show a milky appearance under the conditions of
this test (be sure both bubbler stopcocks are open). Remove the test
water from the bubbler.
7.2.1.3 Clean and lubricate bubbler stopcocks with silicone grease,
and close the gas inlet stopcock. Thoroughly degrease the
standard taper joint of each bubbler. Clamp each bubbler to a ring
stand or lattice.
7.2.1.4 Accurately transfer 10.0 ml of the radium-226 Solution B
(3 pCi/ml) to each of three bubblers (triplicate analyses).
Add 0.1N HC1 to fill bubblers to about two-thirds full. Add 5-10 drops
of isopropyl alcohol to each bubbler.
7.2.1.5 Dry the standard taper joint with lint-free cloth or paper.
Heat both parts of the joint with a hot air stream or care-
fully with a blue gas-air flame from a bunsen burner. Apply sealing
wax sparingly to the male part of the joint and join the two parts
with a twisting motion to make a complete seal.
11
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7.2.1.6 Attach the gas inlet of the bubbler to the helium gas
cylinder outlet with Tygon tubing, adjust the outlet pressure
to 5-10 psi, open the bubbler outlet stopcock, open the bubbler inlet
stopcock, and purge the standard radium-226 sample for 20 minutes.
Note the time at the end of the purge as the beginning of the radon-222
ingrowth period. Isolate the bubbler chamber by closing both bubbler
stopcocks. Store the closed bubblers for a measured ingrowth period
(for this standard amount of radium-226 a 24-hour period is sufficient
time, but be sure to record the ingrowth period). See Appendix A for
the decay, ingrowth and decay during counting factors for radon-222.
Since the radon is ingrowing during the de-emanation period, the end
of the de-emanation period should be noted as the end of the ingrowth
period.
7.2.1.7 Place the bubbler in the de-emanation system (Figure 1) with
a clean counting cell whose background count has been meas-
ured. Evacuate the system, including the cell, but only up to the
outlet of the bubbler (inlet and outlet stopcocks of the bubbler should
still be closed).
7.2.1.8 Check the cell and the system for leaks by closing the stop-
cock to the vacuum source and observing the manometer. No
change in the manometer reading for 5 minutes is .sufficient indication
for no leaks.
7.2.1.9 Then with the vacuum stopcock still closed, the de-emanation
of the radon gas to the cell can be started. Open the bubbler
outlet stopcock and allow a minute or so for the system pressure to
equilibriate. Adjust the carrier gas outlet pressure to 5 psi at the
diaphragm valve. Open the bubbler inlet stopcock and the carrier gas
needle valve and allow gas to flow at a rate that produces a froth a
few mm thick until the system pressure just reaches atmospheric pressure.
Then close the counting cell stopcock and the carrier gas needle valve.
12
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Close the bubbler stopcocks and remove the bubbler from the system.
Store the bubbler for future radium-226 (radon-222) calibrations of
the counting cells.
7.2.1.10 Remove the counting cell from the de-emanation system and
after 4 hours of equilibrating time (radon-222 with its
daughters) place the counting cell in the phototube counting system.
Close the counting chamber (to be light-tight), wait 15 minutes, and
then start the count. Count for the length of time needed to give
the desired reliability (see Section 2.1 and Appendix B).
7.2.1.11 Calculate the counting cell counting efficiency using the
ingrowth time (hours), the decay time (between de-emanation
and start of count), and the decay during counting. See Appendix A
for these factors.
Calculations:
RSTD " ^ C
_
pCi of radium-226 AB
where E = counting efficiency, counts per hour/pCi of radium-226
R p = counts per hour from the radium-226 standard
R. = counts per hour background of the cell
A = factor for decay of radon-222, see Appendix A
B = factor for the ingrowth of radon-222 from radium-226,
see Appendix A
C = factor for the decay of radon-222 during counting,
see Appendix A
The error associated with the results of the analysis should also be
reported. See Appendix B for error and statistical calculations.
13
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7.2.1.12 To clean the counting cells for reuse, evacuate with a
10-minute pumping period, then refill with carrier counting
gas (helium preferred). Repeat the evacuation and refill steps at
least twice (more times are necessary if cell has contained high
radon-222 activity).
7.2.1.13 Repeat steps 8-13 for each counting cell. Number each
counting cell and record its counting efficiency.
7.2.2 Water-soluble Radium-226
7.2.2.1 The insoluble or suspended radium-226 fraction should have
been removed by filtration before the HC1-barium carrier
preservative has been added to the sample (see Section 7.1). The in-
soluble or suspended fraction can be analyzed by the method described
in the next section (7.2.3).
7.2.2.2 To 800-ml or 1000-ml fractions (3) of the sample add 20 ml
of concentrated HC1 and 40 ml of barium chloride solution
(10 mg Ba/ml) in a 1- or 2-liter beaker.
7.2.2.3 With each series of samples set up a reagent blank with dis-
tilled water and all of the reagents used with the sample,
including those added at the time of collection.
7.2.2.4 To each sample and blank, with vigorous stirring, add
(cautiously) 20 ml of concentrated H2SOi,. Cover each
beaker and allow the sulfate precipitate to settle overnight.
7.2.2.5 Filter the barium-radium sulfate precipitate onto a membrane
filter using dilute HzSOit solution (0.1N) to make the trans-
fer and wash.
14
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7.2.2.6 Transfer the filter to a platinum dish, add 0.5 ml of concen-
trated HF and 0.2 ml of the ammonium sulfate solution (10%),
and evaporate to dry ness.
7.2.2.7 Burn off the membrane filter in a 600° C muffle furnace or
carefully over a Meker burner.
7.2.2.8 Wet the sulfate precipitate with only 1 ml of 85% H3POi*,
heat the platinum dish on a hot plate at 200° C, slowly in-
creasing the heat to about 400° C, maintaining that temperature for
about 30 minutes.
7.2.2.9 Continue heating the dish over a Meker burner at just below
red heat, swirling to coat the dish walls with the hot melt
to insure the complete removal of S03.
7.2.2.10 Cool the platinum dish and add 6N HC1 to about one half the
dish volume. Heat on a steam bath for ten minutes, then
dilute with distilled water to a few mm from the top of the dish.
Evaporate the solution to just a few ml on the steam bath.
7.2.2.11 Add 5 ml of IN HC1 and 5 ml of distilled water, warm and
swirl carefully to dissolve the BaCl2. Sample is now ready
to transfer to a de-emanation bubbler.
7.2.2.12 Close the gas inlet stopcock of a prepared bubbler (see
calibration section for preparation), wet the frit in the
bubbler with 2-3 drops of distilled water and quantitatively transfer
the sample from the dish to the bubbler using a transfer pipette.
Rinse the dish with 3-4 portions of distilled water, adding the rinses
to the bubbler until it is about three-fourths full.
15
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7.2.2.13 Apply silicone stopcock grease to the bubbler joint and close
the bubbler. Purge the sample solution with helium gas for
20 minutes (see the calibration section, 7.2.1.7). Record the date
and time as the beginning of the ingrowth period. Store the sample
bubbler for radon-222 ingrowth, for 3 weeks for low radium-226 con-
centrations.
7.2.2.14 Place the sample bubbler in the de-emanation system
(Figure 1) with a clean counting cell whose background count
and counting efficiency have been measured and de-emanate the radon-222
from the sample solution to the counting cell and count as described
in the calibration section (7.2.1), steps 8-11.
7.2.2.15 Calculate the radium-226 in the sample and in the reagent
blank and subtract the reagent blank value from the sample.
See Section 9, Calculations and Reporting, step 2.
7.2.2.16 The sample may be stored for a second ingrowth or may be
discarded (so also the reagent blank). When sample and
reagent blank solutions are discarded, the bubblers should be carefully
cleaned for further use. If the sample (or reagent blank) just dis-
carded contained no more than 10 pCi/1 of radium-226, the bubbler may
be cleaned by rinsing with 200 ml of 0.1N HC1. To insure a complete
rinse of the bubbler invert the bubbler, attach a tube from the inlet
to a beaker containing the rinse solution, attach another tube from
the outlet to a suction flask, and by alternately opening and closing
the outlet and inlet stopcocks successively fill the bubbler with the
rinse solution and draw the rinse to the suction flask. Bubblers that
have held samples containing more than 10 pCi/liter should be cleaned
as follows: discard the sample solution; rinse the bubbler with dis-
tilled water; fill with a solution of 10 g of disodium ethylenediamine-
tetraacetate dihydrate (EDTA) plus 10 g of sodium carbonate per liter;
place the bubbler in a hot water bath and heat for 1 hour; discard ^
the cleaning solution; and rinse the bubbler with distilled water,
16
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0.1N HC1, and again with distilled water by the technique described
above. Degrease the stopcocks and the joint fittings of the bubbler
with benzene or toluene and regrease for reuse.
7.2.3 Water Insoluble (Suspended) Radium-226
7.2.3.1 In the analysis of suspended matter for radium-226, organic
and siliceous materials must be eliminated without loss of
radium-226 and this is accomplished in the following steps.
7.2.3.2 Prepare an alkaline flux mixture as follows: to a 500-ml
platinum dish (if only a smaller size dish is available re-
duce the following amounts proportionately) add 30 mg barium sulfate,
65.8 g potassium carbonate, 50.5 g sodium carbonate, and 33.7 g sodium
tetraborate decahydrate. Mix the contents thoroughly, then heat
cautiously to expel water of hydration. Then fuse the mixture by
heating over a Meker burner, carefully swirling to mix the melt. Cool
and grind the fused material in a porcelain mortar to pass through
a 12-mesh screen. Store the flux in an airtight bottle.
7.2.3.3 Place a membrane filter, on which a sample of suspended matter
has been collected, in a tared platinum crucible or dish.
Carefully ignite the filter and residue over a small flame until carbon
is burned off. Cool and weigh the dish to determine the weight of the
residue.
7.2.3.4 Add alkaline flux to the platinum dish, 8 g of flux for each
gram of residue but not less than 2 g of flux. Mix the flux
and residue with a glass stirring rod. Run a reagent blank for
radium-226 determination starting with a blank membrane filter and
all subsequent reagents as is used for the sample.
17
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7.2.3.5 Heat the dish over a Meker burner (carefully to avoid
spattering) until melting begins. Continue heating after
bubbling stops for 20 minutes more, carefully swirling occasionally
to achieve a uniform melt. Remove the dish from the burner and rotate
as the melt cools to form a thin layer on the dish wall and bottom.
7.2.3.6 Place the cooled dish in a beaker containing sufficient
distilled water to fill and cover the dish. Add to the
beaker (cautiously) 20 ml of concentrated H2SOif and 5 ml of diluted
H202 (30% to 3%) proportionately for each 8 g of flux used (increasing
or reducing the H2SOi» and H202 accordingly). Cover the beaker and
swirl it occasionally to aid in dissolution of the fused residue.
Rinse the dish with distilled water into the beaker.
7.2.3.7 Heat the solution on a hot plate to near boiling and add
slowly, with stirring, 10 ml of the 10-mg Ba/ml barium
chloride solution. Cover the beaker and let stand overnight for
precipitation.
7.2.3.8 Continue the analysis as described above for soluble
radium-226, Section 7.2.2, steps 5-16. In the calculation
account for the volume of the water sample represented by suspended
solids fraction used in the analysis and report'"in pCi/liter.
7.2.3.9 The total sample radium-226 content.is, of course, the sum
of the soluble and insoluble fractions and should be normal-
ized to a 1-liter quantity of sample and reported in pCi/liter.
7.2.4 Combined Soluble and Insoluble (Suspended) Radium-226
7.2.4.1 Mix the sample thoroughly by vigorous shaking and immediately
take three 1-liter aliquots and put in separate 2-liter
beakers. Add 20 ml of concentrated HC1 and 10 ml of 10 mg Ba/ml bajrium
18
-------
chloride solution to each beaker. Stir the mixture thoroughly. Proceed
with the analysis in step 3 below.
7.2.4.2 Prepare a reagent blank using one liter of distilled water
and all of the reagents used with the sample. Analyze the
reagent blank the same as with a sample.
7.2.4.3 Slowly and with vigorous stirring add 20 ml of concentrated
H2SOi, to each sample and reagent blank beaker. Cover the
beakers and let stand overnight for precipitation of the barium-radium
sulfate.
7.2.4.4 Filter the barium-radium sulfate precipitate onto a membrane
filter completing the transfer of the precipitate with 0.1N
HaSOij solution.
7.2.4.5 Continue the analysis as described for Insoluble Radium-226,
Section 7.2.3, steps 3-8. Omit the addition of barium
carrier in step 7 (since sufficient carrier is already in these samples),
digest the solution on a hot plate for 1 hour and then immediately
filter, collecting the barium-radium sulfate again on a membrane filter.
After step 7 of 7.2.3 continue the analysis as described for Soluble
Radium-226, Section 7.2.2, steps 5-16.
7.3 Analysis - Total Radium by Precipitation - a screening
analysis for potable water and filtered raw water.
7.3.1 Calibration - determination of a combined counting efficiency,
self-absorption factor.
7.3.1.1 Prepare three standard radium-226 samples and two reagent
blanks as follows: to separate 1500- or 2000-ml beakers add
• %
1 liter of distilled water; add 3.0 ml of the barium carrier solution
(2 mg Ba/ml) to each reagent blank beaker; add 0.25 ml of the standard
19
-------
radium-226 solution, 100 pCi/ml (Solution A), using a 250-yl pipette;
and 2.75 ml of the barium carrier solution (2 mg Ba/ml) to each stand-
ard sample beaker (the barium and radium-226 additions can be done
more accurately by aliquoting from a weighed polyethylene doll bottle
containing the respective solutions (1), a recovery determination is
to be made on the added barium carrier, therefore accuracy of barium
addition is important).
7.3.1.2 To each beaker add 5 ml of 1M citric acid, 2.5 ml of concen-
trated NH^OH, and 2 ml of the lead carrier solution (100 mg
Pb/ml). Heat the solutions to boiling and add 10 drops of methyl
orange indicator. Stir to mix.
7.3.1.3 While stirring the solution, slowly add 18N H2SOi* to obtain
a permanent pink color, then add 0.25 ml excess of the 18N
H2SO^. Boil the solution gently for 5 to 10 minutes then set aside
for 3-4 hours allowing the precipitate to settle.
7.3.1.4 Draw off or decant and discard the clear supernate. Transfer
the precipitate to a 50-ml centrifuge tube, centrifuge at
2000 rpm for ten minutes and discard the supernate.
7.3.1.5 Rinse down the wall of the centrifuge tube and wash the
precipitate three times with 10-ml portions of concentrated
HN03, stirring the precipitate each time with a glass rod, centrifuging
at 2000 rpm for ten minutes, and discarding the wash HN03. (Ultrasonic
agitation of centrifuged precipitates is an excellent way of stirring
up precipitates for washing action without having to transfer a
stirring rod to and from the centrifuge tube, resulting in some chance
of losing sample material).
20
-------
7.3.1.6 To each centrifuge tube add 10 ml of distilled water and
2 drops of phenolphthalein indicator solution. Stir up the
sulfate precipitate and add 5N NH^OH, while stirring, until the solu-
tion shows a definite red color.
7.3.1.7 Add 10 ml of EDTA reagent solution and 3 ml of 5N NH^OH
(fresh solution) to each tube. Heat the tubes in a boiling
water or steam bath for 10 minutes with frequent stirring to dissolve
the sulfate precipitate. If the precipitate does not completely dis-
solve in 10 minutes, add 1 ml more of 5N NH^OH and continue heating
with frequent stirring for 5-10 minutes more. Excessive heating will
drive off anmonia and some sulfate may reprecipitate.
7.3.1.8 In the next step, barium-radium sulfate will be selectively
precipitated out of solution while the Pb-sulfate carrier
is held in solution. This step is very pH dependent, therefore a pH
adjusted color reference should be prepared by which to adjust the
pH of the samples and reagent blanks. To a clean 100-ml beaker add
10 ml of distilled water, 2 drops of phenolphthalein solution, 10 ml
of the EDTA solution, and 4 ml of 5N ItUOH. Stir the solution and
add glacial acetic acid, dropwise, until the alkaline red color dis-
appears. Add 3 drops of bromcresol green indicator solution, stir
the solution with a magnetic stirring bar, mount pH electrodes to dip
into the solution and add glacial acetic acid dropwise until pH is
at 4.5. Transfer this adjusted solution to a clean centrifuge tube.
7.3.1.9 Now add glacial acetic acid to the sample and reagent blank
centrifuge tubes, dropwise, and with stirring until the alka-
line red color disappears. Add 3 drops of bromcresol green indicator
solution to each tube and add glacial acetic acid, dropwise, and with
generous stirring between drops to a color adjustment to the reference
color (aqua green). With this pH adjustment barium-radium sulfate will
precipitate. Note the time and date of this precipitation as zero time
for ingrowth of alpha activity.
21
-------
7.3.1.10 Heat the centrifuge tubes (containing the precipitating
mixture) in a hot water bath for 5-10 minutes, cool, and
centrifuge at 2000 rpm for ten minutes. Decant and discard the super-
nate. Wash the precipitate three times with 10-ml portions of distilled
water, centrifuging at 2000 rpm for ten minutes and discarding the
supernate.
7.3.1.11 Weigh a membrane filter, a counting dish, and an o-ring that
fits snugly in the counting dish (o-ring will serve to mount
the filter flat in the counting dish).
7.3.1.12 Suspend the precipitate in about 20 ml of distilled water and
quantitatively transfer the precipitate to the filter. Trans-
fer the filter to the counting dish and place the o-ring on the filter.
Place the dish in a drying oven and dry for one hour at 110° C. Cool
and weigh the counting dish.
7.3.1.13 Count the standard sample and reagent blank filters in a thin
window proportional counting system or in a phototube counting
system after removing the o-ring, placing a ZnS phosphor mylar film over
the filter (phosphor side facing the filter), and replacing the o-ring.
The phototube counting system has a higher counting efficiency and is
therefore the preferred system.
7.3.1.14 Determine the chemical yield of the barium carrier for the
standard samples and reagent blanks. Subtract instrument
background count from standard samples and reagent blanks. Normalize
the net cpm for the reagent blanks to 100% yield and average the
normalized counts. Normalize the standard samples net cpm to 100%
yield and from those normalized cpm values subtract the average nor-
malized reagent blank cpm. From these corrected net cpm values calcu-
late the combined factor for counting efficiency and sample self-
absorption. *r
22
-------
- _ net cpm
2.22 x pCi radium-226 added
where f is the combined factor for counting efficiency and sample self-
absorption.
7.3.2 Potable Water and Filtered Raw Water Samples.
7.3.2.1 Samples that have been treated (at the time of collection)
with barium-acid preservative whose volumes are not accurately
known, should be measured for volume and the barium carrier concentra-
tion determined (from the known addition). Samples that have not been
treated with barium-acid preservative at the time of collection should
be measured for volume, treated with 20 ml of concentrated HC1 and
3.0 ml of the barium carrier solution (2 mg Ba/ml) for each one liter
of sample, and allowed to stand overnight before aliquots are taken
for total radium analysis.
7.3.2.2 Place aliquots of samples containing 6.0 mg of barium carrier
in 1500 or 2000-ml beakers. Also prepare and analyze at
least one reagent blank using one liter of distilled water, 6.0 mg of
barium carrier, 20 ml of concentrated HC1, and carry through each step
of the analysis. Before proceeding with the following steps neutralize
each sample and blank to the methyl orange end-point (red to orange)
by adding dropwise, with stirring, concentrated NHi»OH (approximately
16 ml will be required).
7.3.2.3 Perform the analysis on all samples and reagent blanks as
described above in the Calibration section (7.3.1) from
step 2 through the corrected net cpm determination of step 14. Calcu-
late the total radium, pCi/liter as described in the following Calcu-
lation section.
23
-------
8. Calibration
See Section 7.3.1 for "Total Radium by Precipitation" and Section
7.2.1 for "Radium-226 by Radon-222 Determination."
9. Calculations and Reporting
9.1 Total Radium
Total Ra, pd/Hter = corrected net com
uT6 X c. * ££
where a = ingrowth factor (daughter products, see table
below)
f = the combined counting efficiency, self-absorption
factor for 6.0 mg of barium carrier, determined
in the Calibration section (7.3.1.14)
e = the sample aliquot volume in liters
corrected
net cpm = the sample cpm normalized to 100% barium carrier
yield and corrected for instrument background and
reagent blank cpm contribution
Radium-226 Alpha Activity Ingrowth
Ingrowth (Hours) Alpha Activity Factor
0 1.00
1 1.02
2 1.04
3 1.06
4 1.08
5 1.10
6 1.12
7 1.14
8 1.16
9 1.18
10 1.20
24 1.49
48 1.90
72 2.25 ^
24
-------
Since the recommended limit for radium-226 in drinking water is
3 pCi/liter (Public Health Service Advisory Committee 1962 Drinking
Water Standards), when a total radium value for a water sample is found
to be 3 pCi/liter or greater, a radium-226 by radon-222 analysis should
be made. A radium isotopic content can be estimated from a total
radium analysis by successive counts of the precipitated radium at
increasing ingrowth ages and solving a set of simultaneous equations
(2,3,4).
9.2 For radium-226 by radon-222, determine the radium-226 for the
sample by the following equation:
Rs " Rb.l „ Ci Rr " Rb.2 C2
Radium-226, pCi =
where Rg = observed counts per hour for the sample radon-222
R = observed counts per hour for reagent blank radon-222
RL = observed counting cell background counts per hour
(Rb i for sample, Rb 2 for reagent blank)
E = counting efficiency of the particular cell, counts
per hour/pCi of radium-226 (Ei for sample, E2 for
reageant blank)
V = volume of sample analyzed, in liters
A = factor for decay of radon-222, see Appendix A
(Ai for sample, A2 for reagent blank)
B = factor for the ingrowth of radon-222 for radium-226,
see Appendix A (Bi for sample, B2 for reagent blank)
C = factor for the decay of radon-222 during counting,
see Appendix A (Ci for sample, C2 for reagent blank)
The error associated with the results of the analysis should also be
reported. See Appendix B for error and statistical calculations.
25
-------
REFERENCES
1. HASL-300, Procedures Manual, 6. H. Harley, 1972, Section G-12-02,
Health and Safety Laboratory, U.S. Atomic Energy Commission,
New York, NY 10014.
2. C. Sill, 1960, Determination of Radium-226, Thorium-230, and
Thorium-232, U.S. Atomic Energy Commission, Rpt. No. TID 7616
(Oct), USAEC, Washington, DC.
3. A. S. Goldin, 1961, Determination of Dissolved Radium, Anal.
Chem., 33:406.
4. N. A. Hallden and J. H. Harley, 1060, An Improved Alpha-Counting
Technique, Anal. Chem. 32:1961.
GENERAL REFERENCES
Standard Methods for the Examination of Water and Wastewater, 13th
Edition, 1971, APHA, AWWA, WPCF, AmerTcarTPuElic Health Association,
1015 Eighteenth Street NW, Washington, DC 20036.
J. B. Hursh, 1954, Radium-226 In Water Supplies of the U.S., JAWWA
46:43.
D. E. Rushing, 1967, Determination of Dissolved Radium-226 In Water,
JAWWA 59:593.
H. F. Lucas, 1957, Improved Low-Level Alpha Scintillation Counter
For Radon, Rev. Sci. Instr. 28:680.
1973 Annual Book of ASTM Standards. Part 23, pp. 551-564, 662-626,
American Society for Testing and Materials, 1916 Race St., Philadelphia,
PA 19103.
26
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APPENDIX A
Factors for Decay of Radon-222, Growth of Radon-222 from Radium-226,
and Correction of Radon-222 Activity for Decay During Counting
Ti **n
Time
0.0
0.2
0.4
0.6
0.8
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Factor for Decay
of Radon-222
A=e-Xt
Hours
1.0000
0.9985
0.9970
0.9955
0.9940
0.9925
0.9850
0.9776
0.9703
0.9630
0.9557
0.9485
0.9414
0.9343
0.9273
0.9203
0.1134
0.9065
0.8997
0.8929
0.8862
0.8795
0.8729
0.8664
0.8598
Days
0.8343
0.6960
0.5807
0.4844
0.4041
0.3372
0.2813
0.2347
0.1958
0.1633
0.1363
0.1137
0.0948
0.0791
0.0660
0.0551
0.0459
0.0383
0.0320
0.0267
Factor for Growth
of Radon-222 from
Radi um-226
B=l-e"Xt
Hours
0.000 00
0.001 51
0.003 01
0.004 52
0.006 02
0.007 52
0.014 99
0.022 40
0.029 75
0.037 05
0.044 29
0.051 48
0.058 61
0.065 69
0.072 72
0.079 69
0.086 62
0.093 49
0.100 31
0.107 07
0.1138
0.1205
0.1271
0.1336
0.1402
Days
0.1657
0.3040
0.4193
0.5156
0.5959
0.6628
0.7187
0.7653
0.8042
0.8367
0.8637
0.8863
0.9052
0.9209
0.9340
0.9449
0.9541
0.9617
0.9680
0.9733
Factor for
Correction of
Radon-222
Activity for
Decay during
Counting
C=Xt/(l-e-Xt)
Hours
1.000
1.001
1.001
1.002
1.003
1.004
1.008
1.011
1.015
1.019
1.023
1.027
1.031
1.034
1.038
1.042
1.046
1.050
1.054
1.058
1.062
1.066
1.069
1.073
1.077
27
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Factors for Decay of Radon-222, Growth of Radon-222 from Radium-226,
and Correction of Radon-222 Activity for Decay During Counting
(continued)
T
-------
Factors for Decay of Radon-222, Growth of Radon-222 from Radium-226,
and Correction of Radon-222 Activity for Decay During Counting
(continued)
T-JmX-,
nme
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Factor for Decay
of Radon-222
A=e-Xt
Hours
0.7066
0.7013
0.6960
0.6908
0.6856
0.6804
0.6753
0.6702
0.6652
0.6602
0.6552
0.6503
0.6454
0.6405
0.6357
Days
0.0002
0.0002
0.0002
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
Factor for Growth
of Radon-222 from
Radium-226
B=l-e~Xt
Hours
0.2934
0.298-7
0.3040
0.3092
0.3144
0.3196
0.3247
0.3298
0.3348
0.3398
0.3448
0.3497
0.3546
0.3595
0.3643
Days
0.9998
0.9998
0.9998
0.9999
0.9999
0.9999
0.9999
0.9999
0.9999
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
Factor for
Correction of
Radon-222
Activity for
Decay during
Counting
C=Xt/(l-e'Xt)
Hours
1.184
1.188
1.192
1.196
1.201
1.205
1.209
1.213
1.218
1.222
1.226
1.231
1.235
1.239
1.244
29
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APPENDIX B. ERROR AND STATISTICAL CALCULATIONS
Because of the random nature of radioactivity disintegrations there
is an error associated with any measured count of these disintegrations.
The variability of any measurement is indicated by the standard devia-
tion. The standard deviation in the counting rate is determined by the
following equation:
(R) =
where R = gross count rate (sample plus reagent) (cph)
ti = counting time for the gross count (hours)
B = reagent blank count rate (cph)
t2 = counting time for the reagent blank (hours)
The counting error for a given sample expressed in pCi/liter and
at the 95% confidence level is shown by:
F _ 1.96a(R)
L ~ eV
where 1.96 = 95% confidence factor
e = efficiency factor, cph/pCi
V = volume of the aliquot analyzed, in liters
The standard deviation associated with the overall random uncer-
tainty may be estimated by performing replicate analyses'on a given
sample and is calculated from the following equation:
S
n
m
£(n, - fi)2/(m -
• ^ I
30
-------
where n = activity (pCi/liter) of a given sample
n = mean activity (pCi/liter of a series of analyses
m = the number replicate analyses
31
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/4-76-012
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
MEASUREMENT OF TOTAL RADIUM AND RADIUM-226 IN ENVIRON-
MENTAL WATERS A Tentative Reference Method
5. REPORT DATE
March 1976
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
Quality Assurance Branch
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas. Nevada 89114
10. PROGRAM ELEMENT NO.
1HA327
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA-ORD, Office of Monitoring
and Technical Support
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A tentative reference method for the measurement of total radium and radium-226 in
environmental water sources is described. Samples are collected, preserved with
acid-barium carrier treatment, and analyzed for total radium and/or radium-226.
For samples analyzed for total radium, the radium is separated from the sample
with barium and lead carriers. The barium and radium are then separated from the
lead carrier, precipitated as the sulfate, filtered, and counted for alpha activity.
For samples analyzed for radium-226, the radium is separated from the sample with
barium carrier, dissolved and transferred to a de-emanation bubbler, the radon-222
daughter allowed to grow in, the ingrown radon-222 de-emanated from the solution
and transferred to a scintillation counting cell, and alpha counted. Recoveries
are determined from the added and found (recovered) barium carrier. Counting
efficiencies are determined with prepared standard reference samples. Results
are reported in pCi/liter.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
radium isotopes
radon isotopes
barium isotopes
reference standards
quality assurance
standards
radiochemistry
water pollution
de-emanation
07B
14B
14D
18B
18. DISTRIBUTION STATEMENT
Release to the public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. Og^PAGES
36
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
690-369-1976
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