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Measures for Air Quality

(1972-1973)

Annual Report-FY 1973

JUN 2 5 1974
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards 1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear

Sciences 2 — Applied Radiation 2 — Quantum Electronics 3 — Electromagnetics 3 — Time

and Frequency * — Laboratory Astrophysics " — Cryogenics "'. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides

advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor

Radiation — Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote

the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of

technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innovation — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety * — Building

Environment ' — Technical Evaluation and Application * — Fire Technology.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus within

the executive branch for the development of Federal standards for automatic data processing

equipment, techniques, and computer languages. The Institute consists of the following

divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and

a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum

accessibility to the scientific information of the world. The Office consists of the following

organizational units: Office of Standard Reference Data — Office of Information Activities — Office of Technical

Publications — Library — Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, DC. 20234.

3 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

* Part of the Center for Building Technology.
Measures for Air Quality (1972-1973)

Annual Report-FY 1973

James R. McNesby

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

1

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued May 1974
National Bureau of Standards Technical Note 828

Nat. Bur. Stand. (U.S.), Tech. Note 828, 143 pages (May 1974) CODEN: NBTNAE

US. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1974

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TABLE OF CONTENTS

IntroductionAIR POLLUTION PROJECTS

1. Effect of Polymeric Structure on the Permeation Rate

of Sulfur Dioxide 7

2. Development of Equipment and Test Materials for the

Evaluation of the Reliability of S0

2

Measurements 11

3. Fluorescence Detection of S0

?

in Air at the Parts

Per Billion Level 16

4. Ultraviolet NO Detector (FY 72 Project) 18

5. Gas Standards for Air Pollution Analysis 20

6. Absolute Coulometric Determination of NO 25

7. Nitrogen Dioxide Permeation Tube 29

8. IR Laser Detector for NO — 32

x

9. Light Scattering Methods for the Determination of

the Properties of Particulate Matter in Air 37

10. Instrumentation for Particle Sizing ___________ 49

11. Fossil Fuel Standards ,__ = _„_____.= ___ 44

12. X-ray Fluorescence Analysis of Air Particulates 51

13. Airborne Quartz Measurement 53

14. Polycyclic Aromatic Hydrocarbons in Air Borne

Particulates 56

15. Particle Dispersion in a Gas 60

16. Urban Particulate Sample ____= 61

17. Project Threshold 62

18. Analytical Reference Standards for Environmental

Analysis 69

19. Characteristics of Exponential Dilution Flasks — 74

20. Calibration Standards by Thermal Decomposition 81

21. Gas Dilution System 89

22. Automotive Exhaust Flowrate Measurement 91
23. Survey of Various Approaches to the Chemical

Analysis of Environmentally Important Materials 94

24. Electron Spectroscopy for Gas Analysis 96

25. Laser Magnetic Resonance Spectroscopy 100

26. Kinetics of Atmospheric Reactions 106

27. Atomic Reaction Kinetics 109

28. Air Pollutant Properties 111

29. Degradation of Polymers 113

WATER POLLUTION PROJECTS

30. Low Velocity Measurements in Water Pollution 115

31. Fate and Effects of Oil in the Seas 119

32. Transformations of Heavy Metals in Aquatic

Environments 121

33. Reactor Effluent and Environmental Radioactivity

Standards 125

34. Noble Gas Radionuclides 132

VI
MEASURES FOR AIR QUALITY (1972-1973)

ANNUAL REPORT-FY 197 3

James R. McNesby

This report is a project-by-project description of the

Measures for Air Quality program covering the fiscal years

1972 and 1973. Participation in the program is bureau-wide

but the program office operates out of the Institute for

Materials Research. Although air pollution measurement

science has formed the major thrust of the program, it has

been extended in FY 73 to include the beginnings of a water

pollution effort to respond to new needs, particularly those

arising out of the requirements of the Federal Water

Pollution Control Act of 1972. A report on the MAQ program

for FY 72 was not issued. However, the project reports

in the current document include progress made during FY

72 for those FY 73 projects which were active in FY 72.

Where a project was terminated at the end of FY 72 its

description is included in the present document with appropriate notation.

In water pollution the situation is much more complex

since there are many more pollutants in more types of water

that will be subject to control under the Federal Water

Pollution Control Act of 1972. When a pollutant is of concern in the discharge permit program, water quality standards,

the toxic pollutant list and in the specimen bank program,

the state of the measurement art is scrutinized at NBS

and the need for development assessed.

Key words: Air pollution; measurement; Standard Reference

Material; water pollution.
Introduction

Although a report on the MAQ program for FY 72 was not

issued, the project reports in the current document include

progress made during FY 72 for those FY 73 projects which

were active in FY 72. Where a project was terminated

at the end of FY 72 its description is included in the

present document with appropriate notation.

The following projects begun in FY 71 (NBS Technical Note

711) were terminated at the end of that fiscal year:

IDENTIFICATION AND STUDY OF CRYSTALLINE COMPONENTS OF

PARTICULATE MATTER IN AIR POLLUTION SAMPLES — This project

stimulated the interest of the National Institute of Occupational Safety and Health in analysis of quartz in industrial atmospheres and forms the basis of a project reported

in the current document. INDOOR AIR POLLUTION — The

continuation of this project was judged not to be of a

high priority. MOLECULAR COMPLEXES OF GASEOUS POLLUTANTS —

The early results failed to turn up sufficiently promising

systems for continued study. FRICTIONAL DEGRADATION OF

RUBBER — The project, completed in FY 72, was a joint

project with EPA. MODULATED INFRARED LASER ABSORPTION

TECHNIQUES FOR ATMOSPHERIC POLLUTANT MEASUREMENTS — This

project was judged not to be of sufficiently high priority

to carry into the experimental phase. ATOMIC EMISSION

DETECTOR — The project was completed. THE ROLE OF THE

LOWEST EXCITED METASTABLE STATE OF S0

2

IN THE PHOTOCHEMICAL

PRODUCTION OF AIR POLLUTANTS The report was terminated

because of the departure of a guest worker. Several "Minor"

MAQ projects described in NBS Technical Note 711 were

dropped for various reasons. Those "Minor" MAQ projects

continued included Calibration Standards Via Purolysis,

2
Fluorescence Detector for S0„ , Nitric Oxide SRM Development.

Fiscal Year 1971 projects supported by the Environmental

Protection Agency and completed in FY 71 included Instrumentation Assistance to the National Air Pollution Control

Administration and Emissions of Rubber from Auto Tires.

The National Bureau of Standards has given its primary

attention to needs for new measurement techniques and

Standard Reference Materials for the six "Criteria Pollutants"

(S0?/ NO , CO, Hydrocarbons, 0- and particulate matter)

in three media ambient air, stack gases and auto exhaust.

The matrix is shown in Figure 1. To find the description

of a project impacting on a particular matrix element,

locate the matrix element in Figure 1 and read off the

number of the project whose title is listed in the table

of contents.

The Measures for Air Quality program was extended in FY 73

to include the beginnings of a water pollution program to

respond to new measurements needs , particularly those

arising out of the requirements of the Federal Water

Pollution Control Act of 1972. In water pollution the

situation is much more complex than in air since there are

many more pollutants in more types of water that will be

subject to control under the Federal Water Pollution Control

Act of 1972. Pollutant discharges are limited for 71

parameters (FR 3_£, No. 199, Page 28757) and EPA has in

draft form restrictions on 162 contaminants in receiving

water including 97 pesticides. Because it is impossible

for NBS to give attention to all of these pollutants, we

must consider other criteria for ordering priorities.

For compliance with section 307 of the Federal Water Pollution Control Act, the EPA presented a list of 9 "Toxic

Pollutants" emitted from point sources and known to be
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damaging to the public health. In this list appear the

metals mercury and cadmium. Also, the Human Studies Laboratory of EPA has named mercury, cadmium, lead, arsenic,

zinc, copper, nickel, vanadium, selenium, berylium, chromium,

and manganese as first priority elements in their projected

National Environmental Specimen Bank. When a pollutant

is of concern in the discharge permit program, water quality

standards, the toxic pollutant list and in the specimen

bank program, the state of the measurement art is scrutinized

at NBS. Among the metals, mercury and cadmium appear to

be of most interest. It is to be noted that analytical

methods are specified usually from one or more of three

sources, 1,2,3.

1. Standard Methods for the Examination of Water and Waste

Water, 13th Edition, 1971 (APHA) . 2. Annual Book of Standards, Part 23, Water Atmospheric Analysis, 1972 (ASTM)

3. Methods for Chemical Analysis of Water and Wastes,

1971, (EPA).

These sources often provide precision and accuracy estimates

For mercury, standard deviations of 40 percent at 0.35ug/l

by atomic absorption and for cadmium standard deviations

of 22-73 percent by atomic absorption have been reported.

Mercury and cadmium will form the initial thrust of our

modest program in water pollution.

Plans include development of Standard Reference Materials

for mercuy in water in the ppb range and for mixtures of

Hg, Cd and other toxic metals in the same concentration

range.

5
Among, the organics, the pollutants of special concern

by the above criteria are PCB and cyanide and the pesticides,

DDE, DDD. DDT, Aldrin, Dieldrin, Endrin, toxaphene. These

pollutants are likely to be high priority items when we

enter the organic phase of the water pollution program.

he manuscript was d and typed by B. Veronica Bowie.

IES R. McNESBY

fanager, Measures for Air Quality

WILLIAM H. KIRCHHOFF HJ

Deputy Manager

Measures for Air Quality
AIR POLLUTION PROJECTS

1. Effect of Polymeric Structure on the Permeation Rate of

Sulfur Dioxide

Project Leader D. H. Reneker, Polymer Division

Other Personnel G. M. Martin and J. D. Barnes

Objective

Standard Reference Materials 1625, 1626 and 1627 are sulfur

dioxide permeation tubes of lengths ten, five and two

centimeters .respectively. These tubes are intended for

standardization of apparatus and procedures used in air

pollution and related chemical analysis. The tubes are

fabricated by sealing liquid S0

2

into a length of tubing

made from tetrafluoroethylene-hexafluoropropylene copolymer.

The equilibrium rate at which sulfur dioxide permeates

the wall of a particular tube has been found to depend

only on the ambient temperature . However, the differences

in permeation rate between tubes made in the same way

from stock fluorcarbon tubing are so large that the extra

work of individual calibration of each tube by a weighing

procedure is necessary. The observed variation in permeation

rate at 25°C for a typical batch of 50 permeation tubes

was about ± 10% from the mean. This variation was much

larger than would be expected if the dimensions of the

tube were reasonably close to the nominal values. In addition, during calibration of a batch of tubes in which

the sequence of the tubes along the stock tubing was record2 ed, it was observed that the permeation rate fluctuated

periodically so that a complete cycle of this variation

occurred in a length of stock tubing corresponding to thirty

Figures that appear as superscript indicate the literature

references at the end of some of the sections.

7
five-centimeter long tubes. The amplitude of this periodic

fluctuation in the permeation rate was also about ± 10%.

Since each SRM tube was calibrated individually, the use

of the tubes was not affected by this variation within

a batch. Therefore, the cause of this observed variation

in permeation rate was not determined before these devices

were issued as SRMs. Periodic variations in the dimensions

of the tube were suspected as a cause for the variation

in permeation rate. There was also concern that other

parameters, mainly morphological, which are not generally

controlled during extrusion processing might cause variations

of the sort observed. Certain parameters that describe

the morphology of crystalline polymers are known to affect

3 the permeation rate through crystalline polymers . The

investigation described here was undertaken to identify

the uncontrolled parameters in the process by which the

permeation tubes were manufactured. Control of all important

variables would allow the tubes to be calibrated on a batch basis and thereby reduce their cost. Also it is

undesirable to have poorly understood and uncontrolled

fluctuations in an SRM, even though individual calibration

eliminates the undesirable effects of the fluctuations.

Approach

This investigation encompasses the tube dimensions, that

is, length, inner and outer diameter, as well as the ellipticity and eccentricity of the inner and outer walls of

the tube. The density of the polymer, which is known to

be a function of the detailed thermal and mechanical history

that the tube experienced during extrusion, was investigated.

Morphological features such as birefringence, per f erred

orientation of the lamellar crystallites and variations

in these features along a radial direction through the

8
wall of the tube were also studied. Other possible sources

of variation such as the presence of hydrocarbon impurities

in the polymer, pinholes and stress cracking were not

included in this investigation. No obvious flaws in the

tubes were seen. Pinholes or leaks around the plugs would

produce a much higher rate of loss, which would be detected

when the tubes were calibrated. This polymer is not likely

4

to be porous or contain pinholes

Progress

An excellent (negative) correlation of permeation rate

with density was observed. Previous observations of the

permeation rate of small molecules through polymers showed

that small variations in density produce much larger variations in permeation rate. The only theoretical estimates

available for the relation between density and permeation

rate are based on an over simplified two phase crystallineamorphous model of morphology. These theories, which have

been successful in fitting data from some polymer systems,

suggest that the variations in density observed here are

not large enough to account entirely for the observed

variation in permeation rate.

The observed variations in physical dimensions were much

too small to account for the observed variations in permeation rate. The observed length variation was not only

too small but uncorrelated with permeation rate. Some

negative correlation with the inner and outer radius was

observed but the observed variation in these dimensions

accounts for only 1/15 of the observed variation in permeation rate. The observed variations in eccentricity and

ellipticity of the inner and outer walls were small and

not correlated with variations in permeation rate. The

weight per unit length of the tube correlated with the

9
permeation rate largely because this parameter involves

the density of the polymer and as noted above the density

is correlated with the rate. The weight per unit length

varies slightly more than the density suggesting some

correlated changes in the radial dimensions. These conclusions are supported by a multiple linear regression analysis

of the more important parameters.

Since the observed variations in density and physical

dimensions of the tube account for only part of the observed

variation in permeation rate, it appears probable that

variations in the morphology of the crystallites of which

the polymer is composed must also be present. This morphology determines the paths available to the permeation

molecule and this affects the permeation. Morphological

observations made on these tubes showed a variation in

orientation of crystallites in different parts of the

tube. Small morphological variations were observed between

different tubes. These variations, which are probably

caused by differences in thermo-mechanical history, can

reasonably be expected to account for a significant part

of the observed variation in permeation rate. However,

quantitative measurements of these morphological features

have not yet been made with sufficient accuracy to prove

this.

REFERENCES

1. NBS Technical Note 545 (December, 1970) pps. 930.

2. Figure 9, p. 29 in reference 1.

3. R. K. Eby, Jour. Appl. Phys . , Vol. 35, No. 9 pages 2720-

24 (1964).

4. Dupont Polychemicals Department Information Bulletin

No. X-90A page 3.

10
2. Development of Equipment and Test Materials for the

Evaluation of the Reliability of S0

2

Measurements

Project Leader John K. Taylor, Analytical Chemistry

Division

Other Personnel Erie R. Deadorff, Ernest E. Hughes,

Rolf A. Paulson

Objective

To develop a system for generation of accurate concentrations of S0

2

in air, that would be useful to evaluate the

performance of analytical methods and monitoring instrumentation; to develop test materials to evaluate the reliability

of measurements of S0

2

in the air, using the EPA reference

method.

Approach

The gas generation system makes use of an NBS-SRM permeation

tube and a means to control the flow of an air stream

to produce S0

2

-air mixtures in a manifold. By selection

of appropriate parameters, S02 concentrations ranging

from 0.02 ppm to 1 ppm may be produced.

The test materials consist of ampoules containing measured

amounts of sodium sulfite. The quantities are chosen

to be equivalent to the amount of S0

2

that would be collected

during a 24-hour sampling period using the reference method

as described in the Federal Register, Vol. 36, No. 158,

Page 15486, August 14, 1971 (PRA method).

Progress

The project has been completed and the details have been

11
described in a Final Report to EPA, dated September 19,

1972. The essential details are given in the following

sections.

GAS GENERATION SYSTEM

The gas generation system was constructed from readily

available sub-units, except for the permeation tube chamber.

A diagramatic sketch of the system is shown in Figure 2.1.

The system was housed in a metal cabinet 15 x 20 x 22,

in. and can be easily carried from one location to another.

It contains its own water bath for controlling the temperature of the permeation tube but requires connection to

a cold water supply if the temperature is to be maintained

at or below ambient.

The flow meters were calibrated to an accuracy of 1 percent

and the temperature can be maintained to at least 0.1°C.

Accordingly, it should be possible to generate an S02

concentration with a reliability consistent with these

measurements

.

The system was performance tested by analysis of the manifold

gas using the PRA method. By use of suitable combinations

of either a 2 cm or 5 cm permeation tube and adjustment

of flow rate, concentrations in the range 0.02 to 1.14

ppm were produced. A least squares fit of predicted concentration with respect to analytical values, showed agreement

within 2 percent which is well within the analytical uncertainty.

SULFUR DIOXIDE REFERENCE MATERIALS

Initial experiments were carried out in an attempt to

develop aqueous solutions containing S0 9 that would

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simulate the composition of a typical absorber. Such

solutions decrease in concentration at the rate of about

1.5 percent per day of storage. Attempts to preserve them

by sealing in ampoules in a nitrogen atmosphere and by

addition of inhibitors such as mannitol were unsuccessful.

The only satisfactory procedure found was low temperature

storage which is not a feasible approach.

The method of R.C. Paule [Anal. Chem. 44_, 1537 (1972)]

consisting of encapsulating S0

2

in precision-bore capillary

tubes was studied. Tubes of this type were prepared and

used to introduce S0

2

into the absorber solution. Excellent

results were obtained but the method was considered to

be too cumbersome for routine quality control purposes

The procedure finally developed consisted of powder samples,

containing small amounts of sodium sulfite in an inert

solid diluent, namely mannitol. A pre-weighed sample containing a definite amount of sulfite can be emptied into

the absorber solution to simulate an atmospheric sample,

which can be analyzed by a laboratory to evaluate its

analytical proficiency.

A total of 800 sets of such samples containing 5 levels

of S0

2 were prepared for EPA for the study. Twenty samples

were selected from the production lot at each level and

analyzed at NBS to ascertain the S0

2 levels, with the results summarized in Table 2.1.

14
Table 2.1

S0

2

Test Samples

yg SO

? /sample (lg)

C.l. s Series Average Average Single

1000 14.3 0.8 1.9

2000 41.8 1.6 3.5

3000 120.4 2.7 5.7

4000 190.4 3.3 7.2

5000 242.1 3.7 7.8

The standard deviations, s, and confidence intervals, c.i.,

include uncertainties due to both analysis and inhomogeneity

of mixing of the material. These samples were sent to

EPA and were used in an extensive quality control evaluation

study. The results of this study were reported in "Survey

of Laboratory Performance — Analysis of Simulated Ambient

S0

2

Bubbler Samples", by S. M. Bromberg, G. K. Akland,

and John C. Puzak, EPA No. 73-154, March, 1973.

Reference materials of this type have definite merit for

quality control purposes. When used as a set, and the

analytical values compared with the certified values, a

slope of 1.00 + 0.03 is expected. Values outside of this

range are cause for quality control measures.

15
3. Fluorescence Detection of S0 2 in Air at the Parts Per

Billion Level

Project Leader - H. Okabe, Physical Chemistry Division

Other Personnel - F. P. Schwarz, IMR, J. K. Whittaker

Objective

To extend the detection limit of the previously developed

S0

2 fluorescence monitor downwards to the parts per billion

level.

1. H. Okabe, P. L. Splitstone and Joseph J. Ball, J. Air

Poll. Control Assn, 23, 514 (1973)

Approach

The principle of detection is based on photon counting

of the S0

2

fluorescence excited by the Zn 213.8 nm line.

Fluctuation of the lamp intensity is accounted for by

measuring the the ratio of the number of fluorescence

photo counts to that of the excitation source.

Progress

At 8.6 ppb, the standard deviation is 29% for a counting

time of about 1 minute. The detector response is linear

from at least 8.6 ppb to 1.8 ppm. The major source of

measurement error at low ppb concentrations is the statistical fluctuation of the low scattered light and signal

counts, whereas at high S0

2 levels it is due to fluctuations

in the sample preparation. The cell design was modified

to reduce the scattered light. The inside of the cell

was coated with a non-water-absorbing black Teflon to

16
reduce possible H

2 0-SO„-wall interactions. With the Zn

lamp as an excitation source the quenching effect of water

vapor on the S0 fluorescence signal previously observed

with Cd 2 2 8.8 nm was found to be negligible. The result

can be reasonably explained by the shorLer life time of

the S0„ fluorescence.

i.

A similar technique has been used to detect N0 9 in air.

In this case, however, the detection limit would be in

the ppm range with a glow discharge light source such as

Kg, because of the efficient quenching of N0~ fluorescence

by air. On the other hand, a detector with a Zn light

source may be used to detect ppb NO in pure N« since it

is known that N 9 even at one atmosphere does not appreciably

2 quench NO A I state produced by absorption of the 213.8

nm line. The sensitivity will be greatly reduced if NO

in air mixtures are tested because is known to be an

2 efficient quencher of NO A Z. Such studies are in progress.

17
4. Ultraviolet NO Detector (FY 1972 Project)

Project Leader W. Braun, Physical Chemistry Division

Other Personnel Prof. H. P. Broida, U. of Calif., Santa

Barbara

Objective

To develop a UV optical detector for NO in air or nitrogen

at levels below 1 ppm and to assess the relative merits

of the various optical methods.

Approach

(A) The light source is an NO lamp. Absorption is measured

in the region of small absorption where the absorbed light

is approximately proportioned to the NO concentration.

(B) Absorption is measured directly by an optoacoustic

detector (C) Measurement of NO fluorescence in which selection of the exciting wavelength is done by means of a

filter or a monochromator.

Progress

1. An NO resonance lamp with maximum output and minimum

reversal was developed. The NO resonance radiation (light

source) was isolated by a monochromator. The detectability

limit for a 3 cm path length was determined to be about

10 ppm (with about 5% absorption) using simple DC detection.

Differential phase sensitive detection would extend this

measurement to ^ 1 ppm. With lOx longer path lengths

0.1 ppm can easily be obtained. This additional complexity

suggests that fluorescence measurement may result in a

simpler and more sensitive device.

18
2. U.V. absorption of NO resonance radiation not isolated

by monochromator: Absorption measurement by means of

acoustic detection (Kreuzer detector) . For this measurement

a non-coherent source appears to present many problems.

The limit of detection is about 100 ppm (with difficulty)

This detection method was abandoned. 3. U.V. absorption of

NO resonance radiation and measurement of NO fluorescence.

The NO (1,0) 215 nm resonance line was isolated by means

of a dielectric filter. Fluorescence was measured at right

angles. Ceveral collimating designs were developed and

checked and an optimum design was developed. Dielectric

filters were evaluated and it was found that, in the u.v.

,

these filters are low (<10%) in transmission. The detection

limit is probably as low as 0.1 ppb for NO in N

2

. A similar

method involves isolating the exciting line (0,0) or (1,0)

at 225 and 215 nm from an emission line at higher wavelengths

by means of a monochromator. Measurement requires developing a high speed monochromator. A preliminary approach

was designed and several bread board experiments were performed. The project was terminated.

19
5. Gas Standards For Air Pollution Analysis

Project Leader Ernest E. Hughes

Other Personnel W. E. Dorko, E. C. Kuehner, W. P. Schedie

R. J. Joseph, J. K. Taylor

Objective

This project is concerned with the development of Standard

Reference Materials for air pollution analysis, to provide

traceability, through NBS, of all pollution related measurements to a common set of analytical standards. Auto exhaust

emission standards formed the focus of this year's activity.

Approach

Research is conducted to provide gas mixtures meeting

the three prime requirements of SRM's: accuracy; stability;

ready availability. Accuracy requires the existence or

development of an absolute method of analysis, or of an

absolute method for preparation of primary standards.

Stability requires that long term data be available on the

particular gas system in the container in which it will

be furnished. Availability requires the development of

specifications for production of the gas in sufficient

quantity to serve the needs of potential users.

Progress

Earlier research has made possible the certification of

the following SRM's: carbon dioxide in nitrogen, SRM 1601-

1602-1603;oxygen in nitrogen, SRM 1606-1607-1608-1609;

hydrocarbon (methane) in air, SRM 1611-1612-1613; S0

2

permeation tube, SRM 1625-2626-1627. Details of the past

20
year's activities are described below.

PROPANE-IN-AIR

Propane standards in the range from 3 to 1000 ppm have

been studied in detail and their stability in terms of

time and total cylinder pressure is excellent. Primary

standards can be prepared by gravimetric techniques with

accuracy of +1 percent at concentrations above 10 ppm.

A gas chromatographic procedure has been developed for

intercomparison of standards with a precision of one part

in a thousand. Specifications for SRM production were

prepared and cylinders of gas were produced by a commercial

supplier. SRM's have been certified as follows:

i Propane-Air SRM's

SRM No. Propane Concentration, ppm

1665 2.8

1666 9.5

1667 48

1668 95

1669 475

l These SRM's were prepared with the special requirements

of automobile emission measurements in mind, but may be

useful for other purposes as well.

CARBON DIOXIDE IN NITROGEN

SRM's of this kind offer no special problems. The stability

is excellent and no problems were encountered in the certification analysis.

21
Carbon dioxide in this Standard Reference Material was

determined by comparison with a secondary standard that

had previously been intercompared with a set of gravimetric

primary standards.

The imprecision of intercomparison is less than 0.3 percent

of the concentration of carbon dioxide. The method of

intercomparison was gas chromatography using thermal conductivity determination of carbon dioxide. The gravimetric

standards against which the secondary standard was analyzed

were prepared at such concentrations and in such numbers

that non-linearity of the thermal conductivity detection

was minimized. The limits of inaccuracy represent the

uncertainty in the concentration of carbon dioxide in the

gravimetric primary standards.

SRM's have been certified as follows:

Carbon Dioxide-in-Nitrogen SRM's

SRM No. CO^Concentration, Mole Percent

1673 0.95

1674 7.2

1675 14.2

CARBON MONOXIDE

The major difficulty associated with these standards is

the tendency for the concentration to decrease with time,

especially at low concentration levels. Storage in stainless steel cylinders is a solution to the problem but this

is not economically feasible for SRM purposes. A simple

treatment of mild steel cylinders, consisting of applying

a thin coating of ceresin wax to the interior surface, is

22
very effective. The wax is applied hot, to a heated

cylinder which is subsquently allowed to drain and cool.

SRM's for issuance in the near future have been prepared by

a commercial supplier, using this technique according to

an NBS specification.

The analytical procedure for measurement of CO after catalytic reduction to methane, has been improved to the

point that intercomparisons precise to a part in a thousand

are easily obtained. The certification analysis will

be done by comparison with gravimetric standards prepared

in stainless steel cylinders, which are adequate for this

purpose.

SRM's containing CO in nitrogen became available in the

fall of 1973.

NITRIC OXIDE

Some progress has been made in preparing SRM's consisting

of nitric oxide in nitrogen but problems of instability

remain. This appears to be due to adsorbtion of NO on

the cylinder walls which is differentially released as

the pressure drops in the cylinder during use. Pre-treatment of the cylinder with high concentration of NO, seems

to minimize the difficulty, so an adequate solution to

the problem appears imminent.

Chemiluminescent measurements of the SRM's with reference

to gravimetric standards will be used for certification

and the results will be correlated with absolute measurements

under development elsewhere within NBS (See project 6)

23
OTHER STANDARDS

Studies are continuing on the stability of SO^-air mixtures

at high concentration. Cylinder pre- treatment and/or allowing sufficient time to equilibrate are solutions to the

stability problem. The production of SRM's awaits clarification of the needs for such materials.

The NBS-developed ozone generator has been shown to be

rugged and stable, and hence can provide an adequate means

to calibrate oxidant measurements. A number of these

generators have been constructed, calibrated, and used

by EPA in their method evaluation studies. Several generators are maintained in continuous calibration in the NBS

laboratory, using the neutral-Kl reference method. A

simple procedure has been developed for comparison of an

uncalibrated generator with respect to these, using the

chemiluminescent method of measurement.

24
6. Absolute Coulometric Determination of NO

Project Leader George Marinenko, Analytical Chemistry

Division

Other Personnel Dale Friend, Ryna Joseph, and W. Dorko

Objective

Accurate determination of NO and NO^ in the parts per million concentration range for the purpose of confirming

the integrity of automotive SRMs.

Approach

The chemical scheme employed in the analysis is as follows

1. 2N0 + 5H

2

CatalyS ^

2NH

3 + 2H

2

2N0

2 + 7H2

CatalyS S 2NH

3 + 4H

2

2. NH

3 + H2

> (NH

4

OH t ) NH

4 +

+ 0H~

The electrochemical measurement scheme is based on the

anodic reaction

3. 2H

2

> 2 + 4H

+ + 4e.

The final stoichometric reaction is

4. H

+ + 0H~ > H

2

i.e. neutralization of ammonium hydroxide with electrogenerated sulfuric acid.

25
Progress

1. Measurement Aspects of Coulometric Determination of

NO. Sampling of Gas - Two different methods of gas sampling

were employed: (1) isolation of known volume of gas and

(2) continuous flow of gas at a known rate.

C

Conversion of NO to NH-. - An accurately measured volume

of unknown gas is injected into a stream of hydrogen flowing

in a specially built glass gas train. The injection of

NO sample is performed under such conditions that the

H 9 /N0 molar ration in the resulting mixture is at least

10 . The mixture passes through the furnace where it

undergoes reduction to NH- on a nichrome surface. Three

different pieces of experimental evidence are offered

as proof of 100% conversion efficiency.

(a) Using N0

2 permeation tubes the coulometrically

determined leak rate is in agreement with the gravimetrically

determined value.

(b) Mass spectrometric analysis of the reaction products after the NO-H? mixture is passed through the furnace,

operated at different temperature also supports the quantitative conversion of NO to NH-.

(c) Assay of "pure" NO coulometrically and the analysis of the same gas for impurities mass spectrometrically

also support the accuracy of conversion and determination

of NO:

Coulometric assay 98.6%

Assay by difference 98.4%

The difference of 0.2% between the two values is well

within the uncertainty of the two measurements.

26
Performance of gas train and coulometric recovery of ammonia.

Pure ammonia was sampled by the (known) volume

isolation method, injected into the gas train by displacement into hydrogen, passed through the gas train, absorbed

in the electrolysis cell by the electrolyte and titrated

coulometrically. The data obtained provide assurance

that the gas system is operating properly, without losses,

absorption of ammonia is efficient and thus the system

can be used for accurate determination of NO and N0

?

.

2. Determination of NO in Gravimetrically Prepared NO-N

2

Mixtures. - All samples in the 100% to 0.1% NO concentration range were analyzed by injection of a known volume

of gas (25 cc) into the H

2

stream and titration of the

absorbed ammonia. Below 0.1% NO, gas samples were continuously injected at a known rate and the flux balance method

of analysis was employed. The results of analysis of

known mixtures are summarized graphically in Figure 6.1.

The data obtained for NO-N? mixtures, covering six orders

of magnitude concentration range, confirm absence of any

systematic measurement error (bias) . The examination

of data clearly shows that significant differences exist

between the measured and the calculated values of NO concentration. Moreover, even for mixtures of nominally the

same NO concentration (e.g. 0.25%) differences between

different preparations exist which are too large to be

ascribed to the measurement error. Work is proceding

in cooperation with the gravimetric preparation group

in an effort to determine the cause of the observed descrepancies.

27
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^ in O &

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o

LUd

LUg

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oe.

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28
7. Nitrogen Dioxide Permeation Tube

Project Leader Ernest E. Hughes, Analytical Chemistry Division

Other Personnel Erie R. Deardorff

Objective

To develop a nitrogen dioxide permeation tube with improved

characteristics of long term stability, increased service

life, and low permeation rate, suitable for certification

as a Standard Reference Material.

Approach

A permeation tube consisting of a small-area permeation

sleeve attached to a larger glass reservior recently developed in this laboratory shows considerable promise. Mechanical improvements will be made, techniques for fabrication

will be developed, and its stability and tolerance to

stress of normal usage will be investigated.

Progress

At present the only practical means of preparing calibration

mixtures of air and nitrogen dioxide at low concentrations

is by means of permeation tubes. The two most serious

objections to early nitrogen dioxide permeation tubes

were that the rate decreased unpredicatably during the

useful life of a tube, and that the rates of permeation

were inconveniently high requiring high air flows to produce

practical low concentrations. The problem of declining

rate has been studied and found to be due to the increase

in water content of the nitrogen dioxide as the total

nitrogen dioxide decreases and is the result of water originally present in the nitrogen dioxide with which the
tube was filled and possibly to water which has permeated

into the tube. A simple solution to the problem was found

which resulted in a stable rate during the lifetime.

This consists of including within the tube a small amount

of phosphorous pentoxide which served to dry the initial

charge and to eliminate the possible effect of permeation

of water vapor into the tubes

An alternative approach is to fill the tubes with anhydrous

N0

2

under conditions to preclude moisture introduction.

Tubes so constructed are under intensive investigation.

The design which appears to be most promising is shown

in Figure 7.1. Tubes of this type have a service life

of more than a year, are mechanically stable, and can survive temperatures above 40 °C although there is some evidence that exposure to elevated temperatures for more than

8 hours may permanently change the characteristics of

the Teflon and consequently the permeation rate. We have

devised a very simple temperature indicator which accompanies the tube at any time when it is not in a controlled

temperature environment. This consists of a crystalline

mixture of Zn (NO.J 2

* 6H

2

and methyl red sealed in a short

length of capillary melting tube. The mixture melts abruptly

at 35°C and the difference between the physical appearance

of a tube which has been exposed even briefly to temperature

above 35 °C and one that has not are quite striking. The

rates of these devices can be controlled to some extent

by adjusting the permeation area during fabrication and

typical rates range from 0.6 to 2.5 mg/minute. Thus the

air flow required to produce a concentration of 1 ppm is

around 1 liter per minute or less.

30
NBS NITROGEN DIOXIDE PERMEATION DEVICE

TEFLON PLUG

PERMEATING AREA STAINLESS STEEL BANDS

GLASS TUBE

5MM O.D.X IMM WALL

TEFLON TUBE

5MM ID. X0.75 WALL

LIQUID NITROGEN DIOXIDE

(NOT TO SCALE)

Figure 7.1 Improved design for a nitrogen dioxide permeation

tube

31
8. IR Laser Detector for NO

x

Project Leader A. Kaldor, Optical Physics Division

Other Personnel A. Maki , S. Freund and W. Lafferty

Objective

Development of a simple, sensitive, specific, accurate

and rapid measurement device to monitor the concentration

of various pollutant molecules in gas samples, particularly

NO and NO,,. This project aims to explore and develop ways

in which molecular spectroscopy, and especially laser

devices, can meet this need.

Approach

We have adopted a two-pronged approach as follows: (1) techniques are being developed to utilize laser devices in measuring air pollutants; (2) spectroscopic measurements are

being made on pollutant molecules to provide back-up data

for our own experimental program as well as experimental

programs outside of NBS.

A. Construction and evaluation of an opto-acoustic detector.

The opto-acoustic detector was built and tested using

C02 as a radiation absorber and a C0

?

laser as a radiation

source. The detector consists of a capacitance microphone.

A number of different microphone configurations have been

constructed. One particular microphone built with 0.0005"

teflon coated with aluminum was most extensively tested.

The microphone has 1/4" I.D. and had 2" active length.

With this detector, using a 2 mm diameter laser beam, linear

sensitivity for C02

from 1 ppm to 10 00 ppm was observed.

Above 1000 ppm rapid departure from linearity was observed.

32
Since this absorption is due to a hot band transition,

rather than a fundamental it is quite weak. For a fundamental transition sensitivity is better by a factor of 100

to 1000. The repeatability of an absolute signal level

from day to day was within 1%. The effect of particulates

on signal fidelity was tested by the introduction of particulates (cigarette or cigar smoke) and was found to

be devastating. Residual gas in the system was also found

to be a serious problem in low concentration studies.

Continuous flow experiments were a complete failure due

to turbulance distorting the capacitor.

Presently the work has moved to the construction of a

bakeable detector and this is now in progress. A number

of materials are being tested. In connection with the

application of this detector to the detection of NO a

sealed CO laser is also under construction. The final

design of this device has been frozen and its construction

should be completed in the near future.

B. Measurement and analysis of high resolution infrared

spectra of NO

?

. In order to provide key information which

was needed to interpret the strong fundamental band v -1 -1

(at 1600 cm ) , the 2v_ band around 3200 cm was measured

and analyzed in detail. This analysis has revealed some

interesting anomalies in the intensity distribution among

the individual absorption lines in this band Such anomalies

can lead to gross errors in estimating the absorption

coefficient of NO~ at a given wavelength from some overall

low resolution intensity measurement. Similar anomalies

also seem to be present in the v, , fundamental band of

N0

2

around 1350 cm . The work on the 2v

2

band is now

completed and is the subject of a paper which is now being

written.

33
After the desired information was extracted from tne 2v~ b

band, it was a simple matter to calculate the spectrum

of the v

3

band. By comparing this calculated spectrum

with the real spectrum measured at the Ohio State University,

it was easy to make a detailed assignment observed spectrum.

As a result of this assignment, a paper on the analysis

of the v_, band of N0

2

is now being prepared in collobration

with Prof. K. N. Rao and Dr. S. C. Hurlock of Ohio State

University.

Since the N0

2 spectrum produced at Ohio State University

was rather inferior by our standards, and since the NBS

high resolution infrared spectrometer was not designed

to operate below 1800 cm , we are now in the process

of collaborating with Prof. A. Cabana at the University

of Sherbrooke on a re-exam

at much better resolution.

of Sherbrooke on a re-examination of the v., band of N02

The bending vibration of N0

2 (v2

at 750 cm ) is also

being analyzed in collaboration with Prof. A. Cabana. The

analysis of this band is more than half completed and

should be finished in the next few months.

C. In order to understand and optimize later Zeeman experiments, a theoretical study of the Zeeman effect in N0

2

was undertaken. That study has been completed, and we

now know in a qualitative sense just what sort of Zeeman

effect to expect. Inititally we had feared that (as was

the case with NO) only a few transitions would show very

large Zeeman effects. We now know that is not the case

although certain transitions will show a greater effect

than others. The final step that remains is to actually

perform some Zeeman modulation experiments and to compare

the sensitivity for N0

2

measurement with that for NO.

34
D. In addition to the usual work on building and improving

lasers, work has progressed on two important new devices,

the spin- flip Raman laser and a Stark-shift and modulation

cell for use in conjuction with any laser source. The

demise of our CO laser tube has delayed work on the spin-flip

laser, but work will resume as soon as a new CO laser

is ready. In the meanwhile absorption measurements on

ozone are being made with a C0

2 laser. That work, however,

has just begun and will be reported at a later date.

Future Plans

The Zeeman modulated N0

2 measuring device will be tested

and the sensitivity and linearity will be determined.

Tests will also be made to determine if the presence of

water vapor has significant effect on the sensitivity.

A Stark modulated absorption cell which is now under

construction will be tested on formaldehyde. A Stark modulation technique may be useful for molecules exhibiting this

effect. The interference from other molecules can be minimized by careful choice of both the d.c. Stark off-set and

the laser frequency. This Stark absorption cell will

initially be used with CO, C02

, or N~0 fixed frequency lasers,

but later it will be used with a tuneable spin-flip laser.

The spin-flip Raman laser is almost completed and should

be operational in a couple of months. Initial work on

the spin-flip laser will probably center around the problems

of frequency measurement and stability.

The work on the analysis of the infrared spectrum of N0

2

, will be continued. In collaboration with the University

of Sherbrooke, the strongest absorption band v_ is being

remeasured and a preliminary analysis of the spectra taken

at Ohio State University will be extended and improved.

35
The remaining fundamental band v. will also be measured

and analyzed as will some important combination bands.

The high resolution spectrum of ozone will be measured

and analyzed. Absolute intensity measurements will be

made on individual rotation-vibration absorption lines

and the variation with rotational quantum numbers will

be determined so thaL remote sensing laser devices can

be more accurately calibrated.

36
9. Light Scattering Methods for the Determination of the

Properties of Particulate Matter in Air

Project Leader C. C. Gravatt, Jr., Polymer Division

Other Personnel Ivo Allegrini guest worker at NBS from

Consiglio Nazionale delle Richerche

Laboratorio sull' Inguinamento Atmosferico

Roma, Italy

Objective

This project involves the study of new light scattering

methods to determine in essentially real time the properties

of particulate matter in air. The properties investigated

are the total number, size distribution, chemical composition (as related to the index of refraction) , and nonspherical character of the particulate matter.

Approach

This project comprises an experimental and theoretical

study of the light scattering properties of particulate

matter with the aim of finding rapid techniques for its

characterization. From simultaneous measurements of light

intensities at several scattering angles as a single

particle passes through a light beam it is possible to

obtain size, shape, and index of refraction information.

Progress

1. Determination of Particle Size Distribution by Intensity

Ratio Method. An instrument has been designed, built,

calibrated and tested which sizes particulates by the intensity ratio technique. The basic concept involves the

37
simultaneous measurement of the intensity of light scattered

by a single particle at two small scattering angles.

The ratio of the two intensities is a direct measure of

the size and is fairly independent of the index of refraction

of the particle. The optical system consists of an argon

ion laser source and an annular iris-fiber optic scattered

light detector. The maximum count rate of the system

is 20,000 particles/sec and the diameter range covered

is 0.2ym to 4ym. The theoretical calculations on the intensity ratio method have been completed and they show that

for the scattering angles of 10° and 5° this technique

can size particles in the 0.2 pro to 4 ym range with an

error no greater than + 15% for all possible materials

in air. In addition, optimum angular ratios and apertures

have been determined for a wide range of size regions.

The conversion of the analog ratio light scattering instrument to a digital instrument with computer data acquisition

and analysis is in progress.

2. Determination of Particle Size in the Range 0.05 ym

to 0.5 ym. As an outgrowth of the theoretical work described

in part 1 above, several methods were developed for the

sizing of particles in the diameter range 0.05 ym to 0.5 ym

with an index of refraction error no greater than + 25%

for all likely materials in air. All of these methods

are based on a measurement of the intensity scattered

at a single angle normalized by the intensity incident

on the particle, and only require minor modification to

the electronic system and no modification of the optical

system.

3. Characterization of Particulates as to their Optical

Absorbing Properties. A very simple method for distinguishing between optically absorbing particles, e.g. carbon

38
and metals, and non-absorbing particles was found from

the theoretical studies. This involves a measurement of

the absolute scattered intensity over the angular range

30= to 70°.

4. Detection of non-Sperical Particles. A preliminary

theoretical study of the depolarized light scattering by

lone rods has been performed. It appears that a measurement

of the ratio I (depolarized) /I polarized would serve as

a way of detecting asbestos particles.

Suggestions for future research: Listed below are several

projects which appear to be attractive on the basis of

what has been learned up to this time about the optical

characterization of particulates. No attempt has been

made to limit these suggestions only to air pollution studies

1. Experimental verification of the detection of particles

in the size range from 0.05 ym to 0.5 ym.

2. Experimental vertif ication of the characterization

of particles as to their optical absorbing character.

3. Possibility of detecting particles smaller than 0.05 ym

by ultra-fast single photon counting methods.

4. Studies of the kinetics and mechanisms of particle growth.

5. Studies of the kinetics and mechanisms of burning by

monitoring the nature of the smoke. A possible result

of this work would be improved smoke detectors.

6. Characterization of particulates and micro-organisms

in liquid systems.

39
10. Instrumentation for Particle Sizing

Project Leader M. L. Greenough, Measurement Engineering

Division

Other Personnel J. Cohen, E. C. Palasky

Objective

Instrumentation is being developed for determining the

size of particles in the 0.1 to 5 micrometer diameter range,

based upon the selective forward scattering of a light

beam across which the particles are caused to flow.

Approach

The general approach follows that proposed and experimentally

verified by Dr. C. C. Gravatt of NBS, Polymer Division.

Specifically the goal is to detect the light scattered

in narrow conical bands located at 5 degrees and at 10

degrees from the beam axis. The ratio of the light levels

in the two bands is to be extracted for individual particles

during transit. These ratio indications are to be summed

in a small computer for periodic printout of numeric distribution according to particle size.

The system planned will be built around an argon ion laser

whose beam is focused as it enters the sample cell. The

air sample being measured will be passed through the

cell, after being extracted from an overall intake manifold.

When particles contained in the air pass through the narrow

laser beam, the small amount of scattered light will be

transmitted through a conical mask assembly called the

director, to two photomultiplier tubes. These tubes will

be the source of analog signal pulses whose relative

40
amplitudes during coincidence are predicted to be dependent

upon size of the particle initiating the scattering. Detection is planned at a conical bands each one degree wide,

at 5 and 10 degrees from the beam axis.

The pulse signals will be fed to an interface unit providing

the interconnection between the optical signals and the

computer. In the interface the 5-degree signal is to be

applied to 32 threshold comparison circuits which have

appropriate voltage dividers. To the other side of the

comparison circuits will be applied the 10-degree signal.

Whenever the 10-degree signal exceeds the threshold fraction

of the 5-degree signal, a digital output is to be created.

The output of the 32 comparison circuits is to be recoded

in a computer word developed on the basis of one eightbit byte for each discrete particle which is detected.

Thus eight bits in the word convey the information regarding

particle size. At the end of the pulse time this word

will be transmitted out of the interface buffer to be accumulated in the computer ' s memory according to bit contends

At periodic intervals, perhaps five minutes or as desired,

the computer will print out a report giving the distribution

of accumulated particle sizes, using the teletype unit

which is to be a part of the computer system.

Physically the system plan calls for the above-mentioned

elements to be mounted in a single rack about 45 inches

high. On the top will be the sensing assembly including

the laser, sample cell and photomultiplier tubes. At

the front of the rack will be the interface, computer,

and power supplies. If air-handling equipment is required,

it will be mounted at the lower rear.

41
Progress

The major activities so far have been in mechanical design

and in procurement of components. The former has been

concentrated on the director and its associated optical

chamber.

In the mechanical design a large part of the effort has

been given to providing flexibility for future options.

Two examples might be the provision for sensing at an

angle of 45 degrees to the beam, and for splitting the

10-degree cone into its polarized components. While these

options are not presently being incorporated, the design

is being carried out insofar as possible in a manner so

as to facilitate their ultimate inclusion. For this reason

we have adopted an alternate approach to the fiber-optic

conduction of light from the director to the photomultiplier

tubes as used in the breadboard design. The planned arrangement involves simple lenses, together with mirrors and

light baffles. An additional benefit should be greater

transmission efficiency. An increase in efficiency at

this point is directly translatable into a requirement

for lower laser power, a feature which is valuable from

the standpoints of economy and safety.

The new director has been designed as a series of baffles,

a mechanically more complex assembly than the original

tapered cones. This was done in an attempt to minimize

possible effects from diffraction and grazing-angle reflections. The specific goal is to take all feasible precautions

to eliminate as many sources of spurious signal as possible

through careful restriction of the effective sensing zone

in the sample cell. Construction of the director has been

completed.

42
Calibration techniques are being studied for the instrument

after installation in the field. Because of anticipated

difficulty in arranging for the passage of a gas of known

quantity and particle size, an alternative technique is

desirable in order to verify or set calibration at frequent

intervals. The currently favored plan for field calibration

is to employ an insertable yoke containing a very fine

tungsten wire. Prior calibration of the wire compared to

known gas composition should then serve to provide the

desired scaling factors.

43
11. Fossil Fuel Standards

Project Leader P. D. LaFieur, Analytical Chemistry Division

Other Personnel The services of many scientists throuyhout

the Analytical Chemistry Division were

employt:d.

Approach

Samples of coal, fly ash, gasoline and fuel oil were acquired

and packaged. The sources and identification of the camples

arc as follows:

Coal and Fly Ash

Sample obtained from the Tennessee Valley Authority, Widow's

Creek Steam Plant, Stevenson, Alabama. One sample of

the coal from Widow's Creek was from the Fabius Mine in

Fabius, Jackson County, Alabama and was washed. The fly

ash sample associated with this coal was obtained from

hoppers beneath centrifugal mechanical collectors. The

other sample of coal was from Fies and Island Mine No.

9, Hopkins and McLean County, Kentucky (Western Kentucky).

The coal was raw. The fly ash sample associated with

this coal was taken from the hopper below an electrostatic

precipitator.

A sample of coal from the Baltimore Gas and Electric Company,

used at the H. A. Wagner Generating Station, was obtained

from Nicholas County, West Virginia, from three separate

mines. The fly ash associated with this sample was obtained

from the hopper below an electrostatic precipitator.

A sample was obtained from the Commonwealth Edison Company

from coal used at their Crawford Station in Chicago. The

44
source of the coal was a mixture of 80% colstrip from

Montana and 20% a blend of colstrip and coal from Southern

Illinois. The fly ash from this sample was also from

an electrostatic precipitator.

The fifth sample of coal was obtained from the Potomac

Flectric Power Company and came from their Potomac River

Station, Alexandria, Virginia. Exact location of the

mines from which it was obtained is essentially impossible

to determine since the coal came from the conveyor into

the burner unit, but essentially all of the coal used

at this Station is from West Virginia and eastern Kentucky.

The fly ash associated with this coal was from an electrostatic precipitator.

The fly ash was sieved and that fraction which passed

a 120 mesh standard sieve (125 ym) was taken for analysis.

The entire sample was mixed in a large double cone mixer.

Homogeneity was demonstrated using X-ray fluorescence

analysis and neutron activation analysis.

The coal was reground (except for the PEPCO sample which

was already fine enough) by Forrest Walker at the U.S.

Bureau of Mines in Pittsburgh, Pennsylvania. The coal

was sieved, and that portion passing through a 170 mesh

(88 ym) standard sieve was taken for analysis. The entire

sample was mixed in a large double cone mixer. Homogeneity

was demonstrated using neutron activation techniques.

Residual Fuel Oil

The fuel oil sample was obtained from the Standard Oil

Company of New Jersey and originated from their refinery

at Aruba, Netherlands Antilles. This material meets all

of the ASTM specifications for a #6 residual fuel. This

45
is the same material (although taken from bulk storage

in a 55 gallon drum) as NBS Standard Reference Material

1622. Homogeneity was demonstrated with neutron activation

analysis and gravimetry.

Gasoline

Gasoline samples were obtained from service station pumps

in the Gaithersburg, Maryland area. Six samples were

obtained from the following stations using metals cans:

American Amoco Premium (lead free)

Shell Shell of the Future (low lead)

Texaco Regular

Gulf Gulftane Low Lead

Citgo Premium

Esso Low Lead

Within 30 minutes of collection, the samples were transferred

to a large polyethylene tank which had been cleaned previously with nitric acid. Homogeneity was demonstrated

using atomic absorption spectrophotometry.

The analytical program, which has commenced, will be accom

plished using the following methods.

46
Coa.L Fly Ash

COL

Fuel

COL

Oil Gasol:

COL

Lne

Be COIi ATA ATA ATA ATA

F DIS DIS N N

V ATA

NAA

or COL ATA

NAA

or COL ATA

NAA

or COL ATA or

NAA

COL

Cr COL

NAA

COL

NAA

COL

NAA

COL

NAA

Mn ATA

NAA

ATA

NAA

ATA

NAA

ATA

NAA

Ni POL

SSM

POL

SSM

POL

SSM

POL

SSM

Zn ATA

NAA

ATA

NAA

ATA

NAA

ATA

NAA

As ATA or COL ATA or COL ATA or COL ATA or COL

NAA NAA NAA NAA

Se SSM

NAA

SSM

NAA

SSM

NAA

SSM

NAA

Cd SSM

POL

or ATA SSM

POL

or ATA SSM

POL

or ATA SSM or

POL

ATA

Hg ATA

NAA

ATA

NAA

ATA

NAA

ATA

NAA

Pb POL

IDM

or ATA POL

IDM

or ATA POL

IDM

or ATA POL or

IDM

ATA

U NAA

IDM

NAA

IDM

N N

s PPT PPT PPT PPT

Key: ATA Atomic Absorption Spectrophotometry

COL Colorimetry

DIS Distillation

IDM Isotope Dilution Mass Spectrometry

NAA Neutron Activation Analysis

POL Polarography

PPT Precipitation

47
SSM Isotope Dilution Spark Source Mass Spectrometry

N Will not be determined

Progress

Results have been received from 32 laboratories who are

participating in the intercomparison exercise on these

samples. The current status of NBS measurements on these

materials is as follows:

Element

FLY ASH

As

Be

Cd

Co

Cr

Cu

Hg

Mn

Ni

Pb

Rb

Se

Sr

Tl

Values -Technique

61.2+2.2 NAA 62+3 PAA

12.4

1.43+0.04 NAA, 1.46+0.05 ATA,

1.45+0.05 IDSSMS

3 8.0+0.6 NAA

131.6 ATA, 131.5 Atomic Flour.

124.5 IDSSMS, 112.1 COLOR

0.145+0.006 NAA

520+10 NAA, 493+10 ATA, 484+20

COLOR

100.8 IDSSMS, 101.8 COLOR,

98+1.5 POL, 96.6 IDMS

70.8+0.1 IDMS, 67.0+1.1 POL

112+1 IDMS

9.1+0.2 NAA, 9.6+0.2 IDSSMS

1379+2 IDMS

4.1+0.1 IDSSMS

Probable Certified

Value or

(Information Value)

yg/g

61+3

(12)

1.45+0.06

(38)

132+5

(120)

(0.15)

495+30

98+3

70+2

(112)

9.3+1.0

(1380)

(4)

48
Element

FLY ASH

Th

U

V

Zn

Values-Technique

24.2+0.1 IDMS

11.6+0.1 IDMS

214+8 NAA, 214 REDOX

195+23 NAA, 216.1+2.4 ATA

Probable Certified

Value or

(Information Value)

yg/g

(24)

(11.6)

214+8

210+20

COAL

As

Cd

Cr

Cu

Hg

Mn

Ni

Pb

Se

Tl

Th

U

V

Zn

5.8+0.3 NAA, 6.1+0.4 PAA 5.9+0.4

0.23+0.02 NAA, 0.24 POL,

0.17+0.05 IDSSMS 0.23+0.03

23.4 COLOR, 20+2 ATA 22+2

18+2 IDSSMS, 18+1 ATA 18+2

0.11+0.01 NAA (0.11)

46.4+0.6 NAA, 49 COLOR 47+3

14.8+0.1 POL, 15 PAA 15+1

14.80+0.05 IDMS

30+9 IDMS, 28.7+0.1 POL 30+9

2.7+0.2 NAA, 2.99+0.2 IDSSMS 2.8+0.2

0.59+0.05 IDSSMS, 0.59+0.01 IDMS 0.59+0.05

3.02+0.01 IDMS (3)

1.39+0.02 IDMS, 1.3+0.1 NTT 1.4+0.1

35.5+1.8 NAA, 33.7 REDOX, 35+4 ATA 35+4

36.0+0.6 NAA 39+5 IDSSMS 37+4

FUEL OIL

As

Fe

Hg

Mn

Ni

0.056+0.004 NAA

12.3+0.5 POL

0.002+0.0002 NAA

0.121+0.001 NAA

38+2 IDMS, 35.2+1.14 POL

(0.06)

(12)

(0.002)

(0.12)

37+3

49
Pb

Se

Th

U

V

Zn

0.041+0.005, IDMS, 0.041+0.005 POL

0.138+0.06 NAA

0.000026+0.000001 IDMS

0.00004+0.00002 IDMS

315+5 NAA

0.17+0.02 NAA

0.041+0.005

(0.14)

(0.00003)

(0.00004)

(315)

(0.2)

Key:

ATA = Atomic absorption

COLOR = Colorimetry

IDMS = Isotope dilution mass spectrometry

IDSSMS = Isotope dilution spark source mass spectrometry

NAA = Neutron activation analysis

PAA = Photon activation analysis

POL = Polarography

REDOX = Redox titrimetry

NTT = Nuclear Track Technique

50
12. X-Ray Fluorescence Analysis of Air Particulates

Project Leader K. F. J. Heinrich, Analytical Chemistry

Division

Other Personnel R. Myklebust, C. E. Fiori, M. M. Darr

Objective

To investigate the use of x-ray fluorescence methods to

obtain accurate and rapid analysis of particulate air pollutants on an economically attractive basis.

Approach

Recent advances in Si (Li) solid-state detectors (energy

dispersive x-ray analysis) have brought their resolution

and sensitivity into the range of practical usefulness

to the analysis of air particulates. These advances provide

an alternative to previously existing x-ray spectrometers,

which accomplish wavelength dispersion by means of crystal

monochromators . The developments in both techniques have

produced uncertainty as to the relative merits of each

arrangement in terms of sensitivity, accuracy and economy.

We are performing experimental work using both techniques

to provide a basis for comparing their characteristics

and relative merits.

Progress

We have encountered problems obtaining well-characterized

air particulates to be used as benchmarks in establishing

the sensitivity, accuracy and efficiency of our methods.

As an interim study, we have made tests using NBS Standard

Reference Material 1571 Orchard Leaves. This powdered

51
material is well characterized for some of the elements

of interest to air pollution studies, such as copper, zinc,

and lead.

The initial tests indicate that the elements lying between

manganese and lead can be detected to lower levels between

1 and 3 ppm when using wavelength dispersion. For energy

dispersive x-ray analysis, similar levels have been reached

when excitation is properly selected.

The arrangement of the equipment for energy dispersion

was constructed at NBS. Experiments with it have pointed

out several possible improvements over the present arrangement in sensitivity and stability. These changes in apparatus are now being made.

Some specimens of air particulates, for which chemical

analyses will be available in September 1973, have been

obtained and qualitatively analyzed. These, along with

other materials that are becoming available, will provide

more relevant standards with which to test x-ray methods.

In spite of the promising results with energy-dispersion

equipment, we do not exclude the possibility that in the

final analysis wavelength-dispersion techniques may be

superior in resolution, sensitivity and cost. Therefore,

we are contemplating an investigation of possible improvement in wavelength-dispersive equipment as well as for

energy dispersion.

52
13. Airborne Quartz Measurement

Project Leader A. Perloff, Inorganic Materials Division

Other Personnel F. A. Mauer, C. Hubbard

Objective

Primarily to establish the detection limits and sensitivity

of the conventional x-ray diffraction technique for the

analysis of quartz in respirable dust samples collected

by personal sampling devices. In addition, investigation

of the feasibility of the energy dispersive technique

as applied to the same samples.

Approach

The possible variables affecting the detection limits and

sensitivity of the conventional x-ray technique are primarily:

1. Filter material.

2. Sample collection techniques.

3. Instrumentation effects.

4. Data measurement techniques.

5. Impurity effects.

Items 1 and 2 have been well established by other investigators and item 5 is a very variable effect dependent

on the source of the sample. It was decided to concentrate

on items 3 and 4 using silver membrane filters and both

air and liquid deposition dust collection procedures to

prepare a series of samples containing a known amount of

pure, respirable sized, quartz dust. The major quartz

peak was measured for these samples on various diffractometers with varying slit sizes and detector systems using

both scanning and peak height techniques. From these

measurements it should be possible to establish a minimum

53
detection limit and determine the sensitivity and reproducibility of a given diffractometer configuration.

After optimization of the energy dispersive equipment

some of the same samples would be measured with this technique to establish its limitations and feasibility as an

analytical tool for quartz dust samples.

Progress

The most recent standard curves indicate that the major

peak of pure quartz is observable at a peak to background

ratio of 2 in a 20 ug sample air deposited on 25 mm Ag

2 membrane filters (surface density 5.3 yg/cm ) utilizing

conventional diffractometer equipment and commonly available

slits. Varying receiving slits has minor influence on

the peak to background ratio. The choice of slits would

be a compromise between lower background rates and sufficient

counts .

The air deposition samples appear to provide a better

uniformity of sample density and a linear calibration curve

through the origin. The wet filtration samples appear

to have greater variation in reproducibility and possibly

a non-linear calibration curve. If the wet filtration

procedure is to become the standard method , further work

on it is indicated.

The comparison of detectors shows that the highest sensitivity (net counts per microgram of quartz) is obtained with

the solid state detector because its energy resolution

permits elimination of the 8 lines without the use of a

filter which normally introduces an attenuation of 50%.

However, this detector is too complex and costly for general

54
use. The scintillation detector is recommended for general

use. The proportional counter appears to have no advantage

that offsets its poor count rate linearity and poor noise

rejection.

Fourier transform theory has been applied to powder diffraction peaks in order to resolve composite peaks. Preliminary

results indicate that the full width at half maxima (FWHM)

of peaks in the conventional pattern is twice the FWHM

of peaks in the resolution-improved spectrum. A composite

of two diffraction peaks with A20=0.024° appears to be

a single peak in the original recorded pattern. The resolution improved pattern clearly reveals the existence of

two peaks. Future extensions of the program will provide

intensity measurements of each component of the spectrum.

We think that the preliminary results of the new deconvolution-of-peaks technique are very encouraging. The method

offers promise of improved analysis accuracy not only

for quartz but for any case of overlapping diffraction

peaks such as asbestos and its associated matrix minerals.

The energy dispersive technique has some attractive features

for bulk samples, but it is not a feasible alternative

for the quantitative analysis of respirable quartz at the

low levels of the present threshold limit value requirements

55
14. Polycyclic Aromatic Hydrocarbons in Air Borne Particulates

Project Leader Charles P. Talley, Analytical Chemistry

Division

Other Personnel Rosalie M. Angeles, Stuart P. Cram

Objective

To make a preliminary investigation of the feasibility

of using high performance liquid chromatography (HPLC)

for the measurement of polycyclic aromatic hydrocarbons

on air-borne particulate matter.

To investigate the potential sample handling and analysis

problems, and suggest future work. Project was limited

to one (1) man-month.

Approach

The aromatic hydrocarbons on air borne particulates have

traditionally been determined as a group by complex, nonselective, and time consuming methods utilizing soxhlet extraction, conventional column chromatography, and absorption

spectrophotometry of isolated fractions. Such a procedure

could require as much as a one man-week effort for each

analysis and at best result in semi-quatitative data.

The advent of HPLC has added a new dimension to the speed,

efficiency, specificity, and accuracy with which cromatographic separations and analyses can be accomplished.

High efficiency chromatographic column materials (<_50ym)

and microvolume ultra-violet detectors sensitive to one

nanogram have increased the sensitivity and selectivity

of analysis and eliminated the cumbersone and macro-level

measurement methods. These methods have been implemented

for the current study and appear to be the method of choice

56
for the analysis of trace amounts of nonvolatile organic

compounds

Progress

The extraction and isolation procedure used followed a

scheme reported in the literature [Closson, A. , Nicotra,

C, Perilhon, and Cornu, A., Pollut. Atmos., 12, 239 (1970)]

which replaced the rigorous 24 hour soxhlet extraction

with a mild one-hour leaching aided by ultrasonic agitation.

This extraction was followed by a series of solvent extractions which separated the polycyclic aromatics from the

other organics which were also leached from a New York

City filter dust sample.

The final extract was subsequently concentrated and

an aliquot equivalent to the extract from 3 mg of air

particulates was subjected to reversed phase chromatography.

The following experimental conditions were used for the

separation:

Column: 2m x 2.1 mm Corasil-C, 8

Mobile Phase: Methanol/Water/Acentonitrile = 3/2/1

Flow Rate: 0.32 ml/min

Detector: 8pl UV cell (b = 1.0 cm) at 254 nm.

Figure 14.1 is a typical chromatogram resulting from this

procedure after optimization of the separation conditions.

More than 15 different peaks are discernible from this

analysis, and six have been tentatively identified by comparison of their retention volumes with those of known

standards. Those identified are labeled as follows:

57
A. Biphenyl

B. Naphthalene

C. Phenanthene

D. Fluoranthrene

E. Pyrene

F. Chrysene

Future Work

The accuracy and precision of the total procedure including

isolation and chromatography as applied to the problem

of aromatics in air particulates must be rigorously established. The identity of all discernible peaks must be

confirmed by fraction collection and measurement utilizing

other techniques such as infra-red spectrophotometry,

mass spectrometry, and nuclear magnetic resonance spectroscopy. Then meaningful measurements at the subpart per

million level can be made.

HPLC with ultrasonic extraction has been shown to be a

potentially rapid, selective, and sensitive method of analysis

for polycyclic aromatic hydrocarbons in air borne particulate

matter.

58
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o

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<0 ** CM

30NV8UOS8V

59
15. Particle Dispersion in a Gas

Project Leader H. J. M. Hanley, Cryogenics Division

Other Personnel S. Jarvis, Jr.

Objective

To conduct a theoretical assessment of the importance of

microscopic molecular diffusion as a mechanism for dispersion

of pollutants in air relative to other mechanisms such

as turbulence and convection.

Approach

The kinetic theory of gases is used to study the dispersion

mechanism. The treatment is sufficiently general that

the results are applicable not only to gaseous mixtures

but also to gas-particle mixtures.

Progress

The dispersion of particles in a gaseous medium has been

studied with respect to the ratio of a mean particle

radius (r) to the mean free path of the gas molecules (A).

A parameter, s, is defined by the relation s=r/10X which

is equivalent to (10 K 7 where K is the Knudsen number.

n n

We indicate that if s<l, the particle dispersion follows

the diffusion laws of kinetic theory. An equation to

determine the dispersion velocity for all values of s is

proposed.

The calculations are related to particle dispersion in

the atmosphere and it is suggested that diffusion can contribute to an overall dispersion mechanism, even if convection is present in the atmosphere.

60
16. Urban Particlate Sample

Project Leader W. H. Kirchhoff, Measures for Air Quality

Other Personnel J. K. Taylor, W. Cassatt

Obiective

Collection of two 50 lb. samples of airborne urban particulates, one from the St. Louis vicinity and one from the

Los Angeles vicinity. This material will ultimately be

used as a Standard Reference Material for urban particulate

analysis.

Approach

The following tasks are delineated:

1. Site selection

2. Provide as collection equipment:

a. Fabric filters with 80% collection efficiency for

particles 0.3-3 micrometers diameter.

b. Prefilter to remove particles of greater than 10

micrometers

c. A 30,000 cubic feet per minute fan.

d. Protection of the collected dust from moisture and

other environmental hazards.

3. Installation of Equipment

4. Collection of Sample

5. Relocation of equipment from St. Louis to Los Angeles

6. Maintenance of equipment

7. Removal of equipment and site restoration

Progress

The contract has been let to the MECH-CON Corporation.

61
17. Project Threshold

Project Leaders Richard H. Johns and John K. Taylor

Objective

Project Threshold is a program of collaborative tests of

ASTM methods for analysis of air contaminants. Begun in

19 70, the project is sponsored by about 100 representatives

of major industry and its trade associations. Target

funding is $2.25 million for the certification of about

thirty-five methods. T The NBS objective is to provide calibration materials and proceedures for ASTM.

Approach

Because of the complexities of sampling and sample storage,

the approach differs considerably from that of the familiar

"round robin" methods evaluation. A group of collaborators,

representing from five to ten participating laboratories

is brought into the field by ASTM to collect and analyze a

number of samples from various point-sources. Statistical

analysis of the resulting data then enables the precision

and accuracy of the method to be assessed. It is the

responsibility of NBS, through an ASTM Research Associateship,

to provide the program with standard reference samples

of the air contaminants being measured. Nine such standards

have been provided to the program during 1971-73 and four

additional ones are under development.

Progress

Typical air contaminants are present in the atmosphere

at levels of 5-500 parts ber billion, and neither samples

nor reference standards in this range are stable to storage.

62
In this program, primary attention has been focused on

systems wherein the reference sample is generated by dilution at the point of use. One example of such a system

is the permeation-tube sample generator diagrammed in Figure

17.1. This technique has reasonably broad applicability

for contaminants which are liquifiable gases and possess

vapor pressures of a few atmospheres at ambient temperature.

Certified (SRM) permeation tubes were employed in the

program for sulfur dioxide, and developmental tubes were

procured from a commercial cource and used for nitrogen

dioxide after calibration. Similar sources may be developed

in the Threshold program for hydrogen sulfide, alkyl mercaptan, and hydrogen fluoride. As indicated in Figure 17.1,

the reference materials are employed in a standard-addition

or "spiking" mode. That is, the distribution manifold

provides the analyst with pairs of atmospheric samples,

one of which has been spiked with a known quantity of the

contaminant undergoing measurement. This procedure, which

is unique to the ASTM program, was conceived from a desire

that the reference be exposed to the same atmospheric

background as the contaminant itself.

The problems associated with simulating airborne particulate

samples are legion, and a substitute procedure of "offstream spiking" was adopted for dusts and airborne lead.

By way of example, certified (SRM) Orchard Leaves was

used as a lead source for spiking collected samples of

airborne particulate lead. For convenience of use, these

spikes were weighed into coded gelatin capsules which

could be added to the collected samples during digestion.

Similar encapsulated standards containing inorganic sulfate

were prepared for spiking a sulfation candle procedure

for total sulfur. Each of the off-stream spiking procedures

was checked thoroughly in the laboratory to assure compatability with its respective method.

63
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64
A second group of ASTM methods is intended for the measure

ment of pollutants in industrial process emissions, and

four of these are currently being evaluated. Several field

sources were chosen which represent major emissions problems:

Electric utilities, a foundry, and a cement plant. Reference materials for these methods represent quite different

tasks from ambient standards, owing to concentration levels

5 which are about 10 times larger than ambient for typical

contaminants. Here again, the program was committed to

a "spiking" or standard-addition mode of reference usage.

The spiking of an industrial facility fueled at rates measured in tons per hour is impractical. Accordingly, field

Tests on such facilities were confined to the determination

of repeatability and reproducibility — the precision

of the methods under test. Accuracy tests, using a spiking

system developed at NBS, were conducted in a small pilot

plant at Battelle Columbus Laboratories. The system is

illustrated in Figure 17.2. A portion of the effluent

from a furnace was piped to an adjoining laboratory via

a branched line whose flow parameters could be measured

accurately. To one of these lines was added a gaseous

spike at a flow rate controlled by calibrated metering

orifices. Previously-analyzed high purity cylinder gases

(nitric oxide and sulfur dioxide) were used for the purpose.

Spiking rates in these cases approached one mole per hour.

Again, each collaborator was provided with sampling ports

from which he could draw spiked and unspiked stack gas

simultaneously. (Figure 17.3).

It is further desired to assess the precision and accuracy

of the analytical procedures apart from the sampling operation. Each collaborator was supplied with triplicate ampouled

samples representing three discrete levels of nitrogen

and sulfur oxides. The resulting data are now being assembled

65
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67
and analyzed to provide evaluation of the methods.

Future Work

A third phase of the program will test methods of ambient

levels of fluoride, hydrogen sulfide, mercaptan and ozone.

Reference materials for this purpose are under development.

Permeation tube technology may provide standards for the

first three of the aforementioned. A commercial ozone

generator has been obtained which is capable of providing

1000 ppm ozone, to the dilution apparatus shown in Figure

17.1. This instrument has been tested for compatability

with the inherent back-pressure of the system and found

to be suitable for use. It will be calibrated by a chemical method at NBS before use in the field.

68
18. Analytical Reference Standards for Environmental Analysis

Project Leaders John K. Taylor, Ernest E. Hughes

Objective

To develop reference materials for evaluation of analytical

methods applicable to industrial hygiene analysis; to

develop gas-generation systems for performance evaluation

of gas detector tubes and industrial atmospheric monitors.

All of the reference materials are to be developed to

provide maximum usefulness to the sponsor, the National

Institute for Occupational Safety and Health.

Analytical test materials will be developed, specifically

designed to evaluate the accuracy and precision of various

optional approaches to industrial hygiene analyses. Modular

gas generation systems will be designed and constructed

to produce gas mixtures of known concentration. Each system

shall consist of both a generator and an analytical unit

to verify generation levels. For all reference standards,

traceability to NBS SRM's shall be possible. In addition,

the test materials shall be developed with their ultimate

production as SRM's as a definite possiblity.

Progress

Generation systems have been developed and constructed

to produce gaseous mixtures of 20 different substances

in the concentration range 0.2 to 5.0 times the Threshold

Limit Value (TLV) . Table 18.1 lists the substances and

the concentrations generated.

In general, the systems provide the gas mixtures at a minimum rate of 2 1/min for extended periods of time. The

69
accuracy of the concentration produced is at least +5

percent and almost any concentration can be obtained, within

the design limits, by adjustment of flow rates. The systems

are housed in instrument cases, approximately 15 x 20

x 22 in. , and are fully portable. Attempts have been made

to make the systems modular, as far as possible. Thus

a GDL system can be used for several purposes, with or

without interchange of analytical systems.

Filter Standards

This includes reference standards for a number of substances which are normally collected in the atmosphere on

filters, usually of the membrame type. Such filters are

attached to a miniature pump, worn by the worker, to monitor

his exposure during actual working conditions.

The analytical reference standards are not produced by

collection of air-borne materials but are typical filters

on which have been placed the substance of interest either

from solution or suspension. While they do not simulate

the collection process, they represent all of the other

analytical problems and hence serve to evaluate analytical

methodology.

A series of 3 filters containing lead, cadmium, zinc,

and tin; a second series containing lead, zinc and manganese,

and a third containing beryllium have been produced.

They stradle the TLV range. The technique has been developed for producing filters on which are placed mixtures

of quartz and clay, and these will be completed in the

near future.

70
Biological Samples

A series of reference samples for clinical examination

of workers has been developed. One of them consists of

urine containing normal and elevated amounts of mercury,

while another consists of blood containing normal and

elevated concentrations of lead. Both of these were prepared

in-vivo by incorporating salts of the elements into animal

f eedings--hogs . The concentrations were determined by

intercompetence trace analysis.

Reference standards of urine containing normal and elevated

levels of selenium, arsenic, copper, nickel and chromium,

and a similar material containing fluoride have been produced by a spiking procedure and are now undergoing analysis.

The samples will consist of freeze-dried specimens and

will again serve to evaluate analytical methods.

Charcoal Tubes

Vapors such as organic solvents can be determined in the

industrial atmosphere by collection on charcoal absorbers

and later eluted and analyzed by gas chromatography.

Techniques have been developed for producing tubes containing

accurately known amounts of these solvents, and a series

of them have been produced for NIOSH for use in method

evaluation. The results are presently being statistically

analyzed. The technique of solid-state sampling appears

to be one of considerable utility, since it eliminates

the need for liquid collection systems which often are

a source of trouble.

Initial work has been done on iodized charcoal as a collection system for mercury vapor. Techniques have been developed

to produce such tubes containing known amounts of mercury,

71
but production awaits a critical study of the analytical

method by others.

72
Table 18.1

Substances and Concentrations Generated

Generation Analytical Concentration Range

Substances System System TLV in PP1" in ppm

Carbon Monoxide GD SRM 50 25 - 250

Carbon Dioxide GD SRM 5,000 2,500 -25 ,000

Ozone uv SP 0. 1 0.05 - 0.5

Sulfur Dioxide PT SRM 5 2.5 - 25

Hydrogen Sulfide PT FP 10 5.0 - 50

Nitrogen Dioxide PT GV 5 2.5 - 25

Carbon Tetrachloride GDL GC 10 5 - 50

Tetrachlorethylene GDL GC 100 50 - 500

Trichloroethylene GDL GC 100 50 - 500

Benzene GDL GC 25 12.5 - 125

Ammonia SGA-•GDL TR 50 25 - 250

Chlorine SGA-GDL TR 1 0.5 - 5.0

Mercury VS-GDL AA 0. 01* 0.005* - 0.5*

Hydrogen Cyanide SGA-GDL ISE 10 5 - 50

Hydrogen Fluoride SGA-GDL ISE 3 1 - 20

Methyl Bromide GDL GC 20 5 - 100

Nitric Oxide GDL SRM 25 12.5 - 125

Methane GDL SRM — 5% LEL - LEL

Arsine SGA-•GDL SP 0. 05 0.02 - 0.25

Acrolein SGA-•GDL GC 0. 1 0.05 - 5

Notes: GD = gas delivery; UV = ultraviolet; PT = permeation tube; GDL = gas dilution; SGA = stock gas analysis; VS = vapor saturation;

LEL = lower explosive limit; TLV = threshold limit value; SRM = Standard Reference Material; SP = spectrophotometry; FP = flame

photometric; GV = gravimetric; GC = gas chromatographic; TR = titrimetric; AA = atomic absorption; ISE = ion selective electrode,

* (mg/m )

73
19. Characteristics of Exponential Dilution Flasks

Project Leader J. J. Ritter, Inorganic Materials Division

Other Personnel N. K. Adams

Objective

Experimental examination of the capabilities and limitations

of the exponential dilution flask as a certifiable device

for rapid calibration of fast-response air pollution monitoring equipment.

Approach

In an ideal exponential dilution flask (EDF) , a given gaseous sample is continuously diluted with a flowing carrier

gas and the change of sample concentration with time is

a simple first-order exponential decay process.

The decay constant (k) is related to measurable parameters

in the system, viz., it is the quotient of the carrier

gas flow rate and the volume of carrier gas contained within

the EDF. The exponential character of this process offers

a method of obtaining concentration-time information over

several orders of magnitude from a single injection of

sample.

The dilution technique will be tested with the EDF connected

to a flame ionization detector using air as a carrier

gas and propane as the sample material. The results of

the exponential dilution calibration technique will be

compared with those from a calibration regime utilizing

a series of certified propane-air mixtures.

74
Progress

Our evaluation of the performance of conventionally designed

EDF's led us to examine the effect of uncertainties in

slope and time measurements upon the concentration values

(c) calculated from the theoretical first-order equation,

-kt

c = c e . These investigations indicated that while

the time (t) could be easily measured to within 0.1 sec.

slope values (k) obtained from a least-square fit of

log signal vs time curves would show a standard deviation

(a) of the order of 0.02k. An evaluation of the effect

of these uncertainties through an error propagation analysis'

showed that variations in k were principally responsible

for uncertainties in c. An example of this error propagation, using typical experimental values is given in table

19.1.

Table 19.1

For k = 0.200 min" , a (k) = 0.02 k

a (t) = ^4—t, the percentage variation (%CV ) anticipated in

the measurement of c is given by: %CV = 2kt.*

t (min

)

c (ppm) %CV

c

300 - 14.9 6.0

0.76 12.0

0.037 18.0

15

30

45

*In general, if a (t) is small relative to a (k) , then %CV = %CVk

(kt)

.

From this analysis it was apparent that the uncertainty

in k should be reduced in order to utilize effectively the

dilution technique in the calibration of air quality

75
monitoring instruments. The most obvious sources of uncertainty in the measured k's are related to:

1. drift in both the signal amplifications and signal

integration components of the detector. (This is estimated

to be in the range 0.2 - 0.4% per hour),

2. non-linearity of detector response,

3. inadequate mixing.

Flame ionization detectors are almost never truly linear.

At a given flow rate, the relationship between the signal

(s) and concentration (c) is given by s = Ic , where I

o is a proportionality constant. If n = 1 the detector

is truly linear. In practice n is usually found in a range

between 0.95 and 0.99.

The effect of non-linearity on a measured k can be found

from the following relationships

s = Ic

-at

c = c e o . Thus s = I (c e ) o

£n s = (An I+n£nc)-nat o

where k=na, (in I + n In c ) is a

, carrier flow rate _, constant and a = :—

= . The expression is mixing volume r of the form y = a + bx, indicating that a plot of in s vs t should yield a straight line with K=a when n=l. Thus

the agreement between k and a is a measure of detector

linearity.

2-7 Design and performance data for EDF ' s are notably sparse.

There are no published critical design guidelines for

EDF construction. Accordingly, as a result of our evalutation of conventional EDF's, we have undertaken to design

and construct a dilution flask based on fluid dynamic

76
principles. (See fig. 19.1).

The results of the evaluation of the NBS prototype EDF

are summarized below:

1. A comparatively more random distribution of residuals

about the fitted lines was noted from the least-square fits.

2. Slope values (k's) obtained from runs made under essentially identical operating conditions were found to be

in agreement with a standard deviation in the range 0.008

k to 0.01 k.

3. The k values, on the average, fell to within +1.5%

of the theoretical values predicted from flow rates and

mixing volume.

These results indicate that the new design approaches ideal

performance more closely, and is certainly more reproducible

than its predecessors. More recent experiments have been

performed by introducing premixed propane-air mixtures

(span gas) of accurately known concentrations and then

diluting the mixtures with pure carrier gas to obtain the

response curve related to all other concentrations below

the span gas level. In this procedure, a change over

was effected from nitrogen to air as a carrier gas which

caused some perturbations in detector performance. Most

of the difficulties have been resolved and# preliminary

indications suggest that EDF performance is comparable

to that observed with the injection technique.

Our initial experiments with the EDF - flame ionization

detector air-propane system indicated that the reduction

of uncertainty of slope measurements to the 1% level

could be readily achieved. A slope uncertainty of this

magnitude will propagate an uncertainty of 4-5% in the

measurement of c at the 1 ppm level under the conditions

77
described in Table 19.1. More recent experiments suggested

that the slope uncertainty could be reduced even further

to a = 0.006 k, when careful adjustments were made of the

detector fuel supply, relative to carrier gas flow rate.

These results suggest that the sources of uncertainty may

be as much for the detector system as for the mixing processes. Further studies oriented towards optimizing detector

parameters are currently under investigation. Concurrently,

an independent survey of detector linearity using Standards

Reference Materials is in progress as well as a study

designed to suggest the best operational technique in using

an EDF to calibrate a flame ionization detector.

78
ZoHO z w

CO

O OS 3 H J O o

I=> Z W z Z O as M Z M X < O O M w §5 s O X ~ Z O M W

<c z s

as

h

as

l-l

H

HX >-i fu

M s w as CO X w "? *i CO w o oicafl as co < OS as c_> <fl o 0* f3-1 s o

.-1 CM CO <t iO

79
References

1. J. Mandel, The Statistical Analysis of Experimental Data/

Interscience Publishers, New York (1964) p. 72

2. J. E. Lovelock, Gas Chromatography / R. P. E. Scott ed.

,

Butterworths , Inc. Wash. D. C. (1960).

3. J. E. Lovelock/ Anal. Chem . 33, 162, (1962).

4. H. P. Williams/ and J.D. Winefordner, J. Gas_Chrom. , 4, 271/

(1966)

.

5. G. Greco Jr., F. Gioia, F. Alfani, La. Chimica EL 1 Industria / 53/ 1133, (1971)

6. Arthur Fontijon, Alberto Isabadell, and Richard J. Ronco,

Anal. Chem. 42, 575/ (1970)

7. J. Krugers, Instrumentation in Gas Chromatography / J. Krugers

ed. , Centrex Pub. Co. Eindhoven, Netherlands (1968) p. 24

8. H. M. McNair and E. J. Bonelli/ Basic Gas Chromatography 5th

ed. / Varian Aerograph Inc. California, (1969), p. 88

80
20. Calibration Standards by Thermal Decomposition

Project Leader Wing Tsang, Physical Chemistry Division

Other Personnel Douglas Cornell, on Leave From FairleighDickenson University

Objective

The aim of this project is to investigate the possibility

of generating dilute, known quantities of pollutant gases

through the thermal decomposition of appropriate "parent"

compounds. Such an in situ procedure provides a simple

solution to the difficult problem of preserving the integrity of dilute samples of pollutant gases prepared in

the usual static manner. Futhermore, through the proper

selection of the parent molecule, such a procedure may

be easily calibrated. That is, for the reaction A (parent) -*B

(pollutant) + C, where C is a more stable and easily calibratable species, then a determination of the concentration

of C will fix the value for B. Finally, by controlling

the concentration of the "parent" molecule and/or the

extent of decomposition, any concentration of pollutant

can be readily produced. Overall, the present procedure

calls for a minimal amount of experimental skill and is

thus ideal for incorporation into test instruments and

routine field usage.

The experimental procedure is to use as the parent compound

a molecule which decomposes into the desired components

via a molecular mechanism. It is particularly important

that there is no possibility of free radical induced decomposition since such systems may not be reproducible.

The selected compound is then pyrolyzed in a gold tube

reactor (flow rate ~20 cc/min, residence time ~ 6 sec)

and the requirements are that only the expected products

81
be produced and in the proper stoichiometric proportions.

The extent of decomposition is varied from <1% to 100%

and is determined by the temperature of the reactor.

Sample introduction is either by liquid injection (dilute

quantities of parent compound in toluene) or by flowing

the helium carrier gas over a sample (liquid or solid)

of the parent compound and thus introducting a mixture

that is related to the vapor pressure of the compound.

The experimental set up is seen in Figure 20.1. By suitable

changes in connections it is also possible to generated

the desired pollutant continuously. Detection may be by

gas chromatography with flame and helium ionization detection. In the case of S0

2

and NO it proved to be necessary

to use the fluorescence detector of Okabe (Project No. 3)

.

During the first half of the present year, a demonstration

of the feasibility of this method as a means of generating

formaldehyde, acetaldehyde and acrolein has been completed.

The relevant reactions are

H

2

C=C-CH

2

CH OH ^isobutene + HCHO

H

2

C=CH-CH

2 CH(OH)CH

3 ^propylene + CH-jCHO

and H^/ J^* Methylene + H

2

C=CHCHO (acrolein)

Quantitative results are summarized in Figures 20.2,20.3, a

and 20.4. The key points to be noted are the equality

(on a mole basis) of the olefins and aldephydes formed,

the great variation in the concentration delivered to the

82
detector and the wide range of temperatures employed (entered

parentheticitly in the figures) . The latter demonstrate

that temperature control is not critical for the present

application. On the basis of these results it is suspected

that the generation of organic acids, alchols, ketones

and hydrogen halides will proceed with equal facility.

A paper on these matters has been prepared and submitted

for publication.

Two substances that appear to behave in the required manner

for generation of S02 and NO are shown in the following

reactions.

CH S0 cyclopropane + S0

I I I

CH

2 - CH2 Propylene

and

CH„l CH-CH CH-r—>2CH„CH0 + 2N0

3 3 "-"3'

1 I NO NO

It has been demonstrated with trimethylenesulfurdiodixe

that proportional amounts of C

3

H

g (cyclopropane plus propylene) and S0

2

are formed over all reaction conditions.

This is also the case for acetaldehyde and NO except at

high extents of decomposition where CH

3

CHO may well be

quenching NO fluorescence. There remains the need of absolute calibration of the S02 and NO fluorescence signals.

This will permit plots similar to those given in Figures

20.2, 20.3, and 20.4.

It should be noted that the trimethylene sulfur dioxide

system has characteristics which make it ideal for present

83
applications. For example, at 0°C it is a solid with

a vapor pressure of the order of 0.03 Pa (0.2 microns).

Thus, with a carrier gas at 1 atm and with complete reactions

(>800°K) one obtains S0

2

at the .3 ppm level. At 70°C

it is a liquid and its vapor pressure is such that with

1 atm of the carrier gas one obtains ~300 ppm samples.

(Note that as long as saturation is maintained the concentration is independent of flowrate.) Futhermore, the extent

of cyclopropane conversion to propylene provides an excellent internal check with regard to the temperature of

the pyrolyzer.

In the coming year we hope to complete our work on the

S0

2 system. This includes calibration with a permeation

tube and the use of a stainless steel pyrolyzer. With

regard to the dinitrite, aside from the absolute calibration

we hope to investigate the pyrolytic properties of several

other dinitrites. The aim is to obtain some internal

standard other than acetaldehyde and also to find parent

substances which have a lower vapor pressure than

the nitrite used here. We also hope to begin work on

a pyrolytic source for CO.

84
<ecCOo<oec:r

CO

CO<

CD I -P

CO

+Je

•HXo

<N

CUup

•H

Em

85
8.5

-9.0 —

CO U

GO

UJ

_JO~ -9.5 —

CD

o

10.0 —

I I (675)L_

(700)./«\

V^(750)

(850)^^(700)

(750J>T(800)

(650)^/

< 575j^(675)

JW5) _

y^(600)

*(570)

(550)-

•(550)

(625)/

/•(575)

| I I I -10.0 -9.5

L0G

1Q

(MOLES HCH0)

9.0 8.5

Figure 20.2 Yield of aldehyde as a function of olefin and

reactor temperature ()

86
CO O

CO

LU

_J

o

CDo

7.5

1 I I

(700)

< 750

J*(775) (72 l^(500)

yH690)

(^690)

—

yY700)

8.0

8.5

(690)j#/T700)

(800)^^(650)

< 670)^750)

(630UM680)

(650U^ < 65 °)

y^(650)

>(690)

9.0 — / —

9.5

(610) /

\ «/(750)

^R750)

(750) | I I 1

9.5 9.0 -8.5 -8.0

L0G

1Q (MOLES CH3CH0)

7.5

Figure 20.3 Yield of aldehyde as a function of olefin and

reactor temperature () K

87
-7 —

-8 —

o

3:

o

DCo

CM o

CO

S -9 -

CO

o

10 -

I I (800)^-

(800)J^800)

—

(850K

(800)-—^

(750)-^*

(725)^(800)

>(800)

P<700)

^700)

^-(875)

(775)

(750)

— >(675) —

>(650)

I J_ i 1 10 -8

LOG (MOLES C„H

J

z 4

Figure 20.4 Yield of aldehyde as a function of olefin and

reactor temperature () K

88
21. Gas Dilution System

Project Leader F. W. Ruegg, Mechanics Division

Other Personnel G. P. Baumgarten

Objective

The project is to provide a prototype gas proportioning

system. The system is to mix a concentrated pollutantin-air with pure air in the necessary proportions to produce

three specific low concentrations by which monitoring

instruments can be checked for errors in analysis. Simplicity and practicality rather than high accuracy are overriding considerations for the Sponsor, EPA.

Approach

The system proposed is composed of two types of metering

devices. A critical flow nozzle is to be used to meter

the pure diluent air and laminar flow devices to meter

the concentrated pollutant. The two flows will be brought

together in a mixing section and delivered to an outlet

connection. Both capillary tubes and porous plugs are

under consideration as the laminar flow devices.

Progress

Six critical flow nozzles have been fabricated and are

being flow tested for reproducibility of construction.

Three sizes of porous plugs and a flame photometric sulfur

dioxide analyzer were loaned to us by EPA to compare

the performance of the porous plugs vs. capillary tubes,

and to evaluate the accuracy of the prototype delivery

system. A small positive displacement prover has been

89
built to measure and calibrate the very low flows needed

from the laminar flow devices. In preliminary use of

the small prover it appears to perform satisfactorily.

90
22. Automotive Exhaust Flowrate Measurement

Project Leader F. W. Ruegg, Mechanics Division

Other Personnel J. E. Potzick

Objective

Develop and evaluate a real-time, essentially non-instrusive,

mass rate-of-flow meter for use in measurement of automotive

pollutant emissions. Measurement uncertainty reduction

to one percent is the goal.

Approach

Survey devices and principles applicable to flowrate measurement of automotive exhaust. Perform trial experiments

toward selection of a method and/or devices for development

which show promise for real-time , non-intrusive mass-rate

of- flow measurement of the unsteady flow of exhaust gas.

Progress (February to June 1973)

A survey of the literature and of commercial instruments

has been made for selection of methods and or devices for

trial. Sonic and ultrasonic methods of flow measurement

appear to offer the most promise for development. Rather

intensive development and application of these principles

is evident in the U.S., but all developments appear directed

to measurement of volume rather than mass-rate-of-flow.

Two approaches toward measurement of mass rate have been

selected for initial experiments hopefully designed to

determine the most promising approach. Method 1 involves

use of sonic pulses, generated by a spark or other means,

91
and determination of the difference in flight time to upstream

and downstream pulse sensors. Method 2 involves use of

high frequency (40 k Hz) continuous sound waves, and determination of their phase difference at sensors upstream

and downstream from the wave source. Phase difference

can be expressed as a time difference At, and both methods

can give the mass- rate- of- flow per unit area, pV as

C

The quantity in [ ] is expected to be little changed by

flowrate and gas composition over the range of use and

hopefully can be determined as a part of the calibration

factor. The quantity n defines the velocity profile in

steady, turbulent flow in round pipe, and must also be

determined by calibration, especially in the situation

of unsteady flow in the auto exhaust tail-pipe.

Pressure p at the auto tail-pipe will not undergo large

excursions and therefore is included in the bracketed term

[ ] . Flowrate information in digital form and as a function

of the time can be secured with method 1. Method 2 probably

cannot follow high frequency changes in flowrate due to

time delays in the electronic apparatus. Some very preliminary trials of method 1 indicate further trials should

be made, and electronic apparatus is being assembled.

Meanwhile other apparatus is being assembled for calibration

of the sonic and ultrasonic meters under development.

This includes both a shock tube for response-time calibrations and a steady flow air system with some heat input

for steady state, but variable density, calibrations.

Further consideration was given to use of a commercial

cooled sensor for mass flow measurement. Consideration

of the fouling problem (frequent calibration requirement)

92
and the difficulty in specifying its performance in rapidly

changing gas temperatures made it appear too unattractive

for investigation at this time.

A commercial ion deflection mass meter has been tested

over the density and flow range of interest. Although

its performance could be adequate with dry air, its sensitivity to fouling and gas composition changes probably precludes its development into an effective exhaust gas meter.

Further tests are planned of its response time and of

its sensitivity to exhaust gas composition changes.

93
23. Survey of Various Approaches to the Chemical Analysis

of Environmentally Important Materials

Project Leaders - B. Griefer and J. K. Taylor, Analytical

Chemistry Division

Other Personnel D. A. Becker, P. J. Paulsen, S. D. Rasberry,

K. F. J. Heinrich, T. C. Rains, R. W. Burke,

D. W. Golightly, E. J. Maienthal, R. A. Durst

Objective

To evaluate various approaches to the chemical analysis

of heavy industry process materials and waste products

for constitutents that may find their way into the environment and be considered pollutants, on a cost-benefit basis.

Approach

A literature survey, together with the experience of analytical experts at NBS was used to assess the capability

and cost of analysis for environmentally important materials.

Progress

A cost-benefit study has been made of a number of analytical

techniques on the basis of the following performance parameters: Instrumentation requirement; detection limit;

accuracy; sample preparation; sample size; manpower skills;

cost per analysis.

The capabilities and costs of nuclear methods, spark source

mass spectrometry, x-ray fluorescence and electron microprobe

spectrometry, atomic absorption spectrometry, absorption

spectrophotometry, atomic emission spectroscopy, voltammetry

(polarography) and potentiometry (ion-selective electrodes)

94
for determining traces (less than 100 parts per million)

of mercury, beryllium, cadmium, arsenic, vanadium, manganese,

nickel, antimony, chromium, zinc, copper, lead, selenium,

boron, fluorine, lithium, silver, tin, iron, strontium,

sodium, potassium, calcium, silicon, magnesium, uranium,

and thorium in such matrices as fly ash, coal, oil, ores,

minerals, metals, alloys, organometallics, incinerator

particulates, slurry streams, and feeds to and from sedimentation processes have been assessed.

A comprehensive report has been prepared with a chapter

devoted to a discussion of each analytical technique.

A general discussion is given of the problem of trace analysis in environmental studies, including material balance

considerations

.

Extensive use is made of tabular formats in the presentation

of the data. The report includes a critically selected

bibliography of the current literature on environmental

trace analysis.

95
24. Electron Spectroscopy For Gas Analysis

Project Leader C. E. Kuyatt, Optical Physics Division

Other Personnel R. Celotta, S. R. Mielczarek

Objective

To determine the applicability of electron energy loss

spectroscopy to gas phase quantitative analysis, to assess

the sensitivity of the procedure and to improve the ultimate

sensitivity and reliability of the method.

Approach

The NBS Model AN electron spectrometer, shown in Fig. 24.1

was the analytical instrument. The electron gun is a

Pierce type diode run in the temperature limited emission

region of its cathode, a Philips dispenser cathode, type

A. A three lens system, containing two sets of four quadrant deflection plates, injects the electrons into a monochromator which is noramlly operated at a center potential

of 11 volts and a E/AE of 1000.

The electrons are then accelerated and deflected by three

more lenses and two more sets of deflectors, until they

pass through a 0.003" entrance aperature to the gas scattering cell with an energy of 100 eV and an energy dispersion

of approximately 25 meV FWHM. Losses in electron energy

occur as a result of interaction of a electrons with molecular species, raising the gas to discrete energy levels

above the ground state.

The electrons leave through a 0.012" aperture, are decelerated to 3 volts and analyzed with a E/AE of 100. The

magnitude of the decelerating voltage determines the value

96
of the energy loss to be observed. Finally, the electrons

are accelerated again and the beam is focused on the

cathode of a multistage electron multiplier.

The path length inside the gas scattering cell is 1.5

mm and the angular acceptance of analyzer injection optics

is limited to a solid angle of 0.02 steradians. Typically,

— 8

an electron current of 10 amp is utlized.

Progress

The following gases and nominal concentrations in helium

were studied: acetone (100 ppm) , n-hexane (100 ppm) , ethanol

(100 ppm) , benzene (10 ppm) and trichloroethylene (10

ppm) . These mixtures were produced by the Matheson Company

and analyzed by Matheson to a stated accuracy of + 5%

by means of gas chromatography. Additionally, a mixture

of all five of the above trace contaminants in helium

had been supplied by Matheson and analyzed to the same

accuracy.

Mixtures of CO in dry air (20%

2

, 79% N

2

, 0.9% Ar, 0.1%

CCO were studied at nominal concentrations of 10, 50

and 200 ppm. This was repeated with water saturated

air. These gases have been prepared and analyzed by

the Analytical Chemistry Division of NBS. The CO concentration

is accurate to + 2%.

Also analyzed were mixtures of N

2 (50 ppm) in N2

and

CH

4 (50 ppm) in2

. These have been prepared by Matheson

and analyzed to a stated accuracy of + 5%.

In the analysis of gaseous mixtures, the spectrum of the

mixture is fit by the method of least squares to the spectra

97
of the separate pure substances. From this least squares

fit, the concentration of each individual component of the

mixture is determined. Comparison of these determined

concentrations with those concentrations provided by the

gas blend supplier indicated that the analysis technique

is working well (although there is as yet some unexplained

difficulty with ethanol.) The fact that there are no

run-to-run variations in the relative intensity across the

spectrum of a particular substance or mixture indicates

that the "up-down" energy sweep procedure leads to the

cancellation of long-term, linear intensity drifts. The

accuracy of the determined concentrations as compared to the

"known" concentration also indicates that square root of

mass correction for differential effusion from the scattering chamber is sufficiently accurate.

Difficulties are still encountered in the determination of

the concentrations of two substances when the concentrations

of these two substances differ by several orders of

magnitude. Small errors in the line shape of the concentrated substance can lead to substantial errors in the

determined concentration of the dilute substance when the

spectra of the two substances overlap.

Work is also planned on providing techniques for adjusting

line shapes at varying energy resolution to correspond to

some standard energy resolution.

Our work with methane in oxygen has pointed out the importance of low, or at least structureless, background signals.

We have completely disassembled and cleaned the instrument

in order to lower the background.

A major problem in the accumulation of data during the

course of these experiments has been the lack of a readout

98
device for observing the data during, or soon after, the

experiment. A problem, such as the existence of a background,

might not be noticed until a few days later. To remedy

this situation we have designed and constructed a cathode

ray tube display system, which, when used with minicomputer, provides a real time display of our data.

An experiment can benefit from more signal and less background noise, and to this end we shall attempt to improve

the electron spectrometer by a careful redesign of the

electron optics. This redesign is facilitated by the use

of a computer optimization procedure for electron lens

design which has recently been developed by Kuyatt and

applied successfully at NBS.

Finally, a great deal of effort was expended during the

past year in developing procedures to accumulate, store,

process and analyze large quantities of data. We were

careful to make these systems flexible and fairly easy

to modify. Now that the ground work has been done, we

plan to test different techniques of data accumulation

and analysis toward the goal of greater sensitivity and

reliability for electron energy loss spectroscopy as an

analytical tool.

99
25. Laser Magnetic Resonance Spectroscopy

Project Leader . K. M. Evenson, Quantum Electronics Division

Other Personnel C. J. Howard, NOAA Aeronomy Laboratory

Objective

Develop Laser Magnetic Resonance Spectroscopy for the purpose of measuring concentrations of free radicals of interest in tropospheric and stratospheric pollution.

Approach

Rotational levels of paramagnetic molecules can be Zeeman

shifted into coincidence with far infrared laser lines

to produce resonance absorption of laser radiation. This

technique, called laser magnetic resonance, was first

12 3 demonstrated with ' ' and has subsequently been success4 fully applied to other stable molecules such as NO and

5 N0 9

. Recently, the Zeeman rotational spectra of the trans6 7 8 9 10 ient free radicals OH ' CH , H0

2

, and HCO have also

been observed.

The laser magnetic resonance (LMR) spectrometer used in

most of these studies is shown schematically in Fig. 25.1.

The laser oscillates in the cavity between mirrors C and

D in a single longitudinal mode. The cavity is divided

into two parts by a dielectric beam splitter; the sample

or absorption region is on the left and the active laser

medium, a dc discharge, is on the right. The beam splitter

serves three purposes: (1) it provides a vacuum seal between

the absorption cell and the laser discharge, (2) it acts

as a reflector to couple a small fraction of laser power

out of the cavity to detectors A and B (for this purpose

100
wP

(CHa

a,a«s

•poe

fO •HO

•HM

f«g

a> xiow

LD

CD3

tn H

101
its angle with respect to the axis of the laser is adjustable near the Brewster angle) , and (3) it restricts the

laser radiation to a single linear polarization which may

be oriented either parallel or perpendicular with respect

to the magnetic field in the absorption cell.

Dectector A is a Golay cell which is normally used for

tuning the laser to the desired wavelength and power level.

The laser can be operated at 78, 79, or 119 ym with H~0

vapor in the discharge tube and at 72, 84, or 108 ym with

D-0. The power level is normally between 1 and 10 yW

at the detectors. Detector B is a liquid helium cooled

Bolometer which is used to detect the modulated absorption

signal during spectroscopic measurements.

A 15 inch magnet with 5.5 inch ring shimmed pole tips and

a 2 inch air gap was used to produce fields up to 23.5

kG in the absorption cell. An adjustable field modulation

of up to 100 G at 270 Hz was used to generate the modulated

absorption signal which was measured using phase sensitive

detection.

Progress

Figure 25.2 shows an HO- spectrum taken with the 79 ym

water vapor laser line. In this case the electric field

of the laser radiation was polarized parallel to the dc

magnetic field.

The high sensitivity and versatility of the laser magnetic

resonance spectrometer has made it desirable to combine

it with a flow reaction system for the study of free-radical

reaction kinetics. Measurements are now being made on

several important reactions, of OH, H0

2

, and CHO. This

is the first time it has been possible to study directly

102
CM

CM

LO

in

U 'O

0) rH

CO CD

nj -h

rH M-) £ U

-P -H

•H -P 5 CDC ^ Cn

CD rt w e

«d rH

U

T3 o

CNCD

ffi x:

+J IW

-p

CD CO c fH •H CD rH rH 3 rH < g (0 CD 3- >-l o en nj TM»—J t> a ^ 1 T3

rH e <u 3 -H

r-l <4-l -Po o

CD -H a n

CO -Pu

(N CD O rH

ffi CI)

(Nin

CN

CDup

tP •H

fa

103
the kinetics and mechanisms of numerous radical reactions

which are necessary for a complete understanding of the

chemistry of discharges , flames and other combustion

processes, and of the atmosphere.

104
References

1. K. M. Evenson, H. P. Broida, J. S. Wells, R. J. Mahler,

and M. Mizushima, Phys. Rev. Letter 21, 1038 (1968)

2. M. Mizushima, J. S. Wells, K. M. Evenson, and William M.

Welch, Phys. Rev. Lett. 29_,831 (1972)

3. K. M. Evenson and M. Mizushima, Phys. Rev. A6, 2197 (1972)

4. M. Mizushima, K. M. Evenson, and J. S. Wells, Phys. Rev.

A5, 2276 (1972).

5. R. F. Curl, Jr., K. M. Evenson, and J. S. Wells, J. Chem.

Phys. 56, 5143 (1972) .

6. K. M. Evenson, J. S. Wells, and H. E. Radford, Phys. Rev.

Lett. 25, 199 (1970)

7. P. Kasuya and K. Shimoda, Japan J. Appl. Phys. 1JL, 1571 (1972)

8. K. M. Evenson, H. E. Radford, and M. M. Moran, Jr., Appl.

Phys. Letter. 13, 426 (1971).

9. H. E. Radford, K. M. Evenson, and C. J. Howard [Paper in

preparation]

10. R. F. Curl, Jr., C. J. Howard, and K. M. Evenson (Paper in

preparation)

105
26. Kinetics of Atmospheric Reactions

Project Leader W. Braun, Physical Chemistry Division

Other Personnel M. J. Kurylo, A. Kaldor

Objective

Measure kinetics of reactions of importance in assessing

the perturbation of stratospheric chemistry by future

SST traffic. The studies are being conducted as part of

the Climatic Impact Assessment Program of the Department

of Transportation.

Approach

The method of flash photolysis resonance fluorescence

is used. The apparatus was designed to permit kinetic investigations of systems containing such reactive species

as N0~ and 0_. In addition, it encompasses a facility

for monitoring such species by light absorption techniques

during the course of a chemical reaction. The working

system was optimized for atom detection and then modified

for the study of OH radical chemical dynamics.

Progress

The all-glass variable temperature cell, which is well

suited for the atomic studies, gave too much light scattering to be suited for OH investigations. Consequently,

the stainless steel outer chamber was Teflon coated and

used for some room temperature OH measurements. A larger

stainless steel variable temperature cell (more accessible

for internal light collimation) is currently being constructed.

106
The reaction OH + NH., •* H_0 + NH 9 was investigated at

14 3 -1 -1

298K. A rate constant of 4.1 x 10 cm molec s was obtained. Through a comparison of a number of OH and

O atom reactions involving NH_, CH., and C

2

H

fi a lower

limit for the rate constant at stratospheric temperature

(225K) was calculated. This calculation indicates that

the reaction of OH with NH~ becomes the rate determining

step in the conversion of NH_. into NO via reaction of

NH

2

with 0- and 0^.

. . . -9

A mixing ratio of 10 for stratospheric NH_ is thereby

capable of introducing as much NO into the stratosphere

as does the reaction of ( D) with N^O. This latter reaction is presently considered as the dominant natural production mechanism for NO in the stratosphere. The possibility

of a larger natural source can minimize the significance

of any artifical input of NO (i.e., SST engine exhaust).

The reaction OH + 0^ -*- HO_ + o , an important step in the

photochemistry of wet ozone, was studied at 298K. The

rate constant of 6.5 x 10 cm molec s confirms

the most recently measured values of other workers. As

such, it tends to indicate the validity of these workers 1 low temperature results, thereby minimizing the importance

of the reaction as a part of the destructive mechanism

for stratospheric ozone.

It is planned to extend the studies of the OH + NH~ and

OH + 0- reactions to conditions of stratospheric importance,

Future OH radical investigations will also include the

OH + S0

2

reaction. The atomic systems to be investigated

will include reactions in the chlorineoxygen system (i.e.

CI +

3

, CI +

2 + M, etc.). Such reactions may bear on

atmospheric perturbations caused by space shuttles.

107
Complementary to our atmospheric kinetics program, an investigation of the influence of laser excitation on chemical

reactivity was begun during the past year. A large number

of atom-molecule and molecule-molecule systems were studied

in a preliminary way. To date, the NO + 0- reaction has

yielded the most promising results. The absorption of

9.6y radiation from a CO,, laser by 0~ has a definite enhancement effect on the reaction rate. The study of this and

other 0- reactions (viz with CI and 0) will be studied

during the coming year. These experiments are being conducted in collaboration with the newly formed Laser Program

at NBS headed by Dr. DesLattes.

108
27. Atomic Reaction Kinetics

Project Leaders J. T. Herron and R. E. Huie, Physical

Chemistry Division

Objective

The objective of this project is the kinetic characterization

of the elementary reactions which may play an important

role in troposperic and stratospheric air pollution chemistry

Specifically, this includes the reactions of atomic oxygen,

singlet molecular oxygen, ozone and hydroxyl radicals

with primary organic pollutants, and with the oxides of

nitrogen and sulfur.

Approach

The approach used is a combination of laboratory studies

with data compilation and evaluation.

The laboratory programs center around the NBS chemical

kinetics mass spectrometer, used for the study of atomic

oxygen, singlet molecular oxygen and ozone chemistry, and

the resonance fluorescence facilities at NBS and at the

University of Maryland used for the study of atomic oxygen

reactions.

In the case of the atomic oxygen reactions, the laboratory

program is designed to complement the data evaluation

program by establishing absolute rate constants for key

reactions to be used in converting the existing large body

of relative rate measurements into absolute rate constants,

and to provide data on important reactions where none

exists or where the existing data are unreliable.

109
Progress

The principal accomplishments in FY 1973 have been in the

measurement and evaluation of atomic oxygen rate constants.

Rate constants for the reactions of atomic oxygen with

0^ and NOp have been measured over a wide range of temperatures. The rate constants are:

k

2 = 6.57 + 0.59 x 10"35 exp(l014 + 46/RT) cm

6 molecule~ 2

s~

1

-12 3 -1 -1

kN0 = 9 * 12 - °* 44 x 10 c molecule s , from 230-339K,

These reactions play a critical role in determining the

ozone profile in the stratosphere. This work was supported

in part by DOT under the CIAP program which attempts

to assess the importance of exhausts from stratospheric

aircraft flights on the concentrations of ozone.

Rate measurements of interest to tropospheric air pollution

have also been carried out. Rate constants for the reactions

of atomic oxygen with ethylene, the butenes, tetramethylethylene and some haloethylenes have been measured. In addition

studies on the oxidation of SO have been initiated from

the point of view of the origin and control of S0

2

in stack

gases.

110
28. Air Pollutant Properties

Project Leaders D. Garvin and R. F. Hampson, Physical

Chemistry Division

Objective

Produce a compilation of data on the properties of air

pollutants.

Approach

Employ the resources of the Data Centers of the Office

of Standard Reference Data to evaluate and compile existing

data on the properties of air pollutants.

Progress

A. Physical properties: A preliminary draft of the tables

on physical properties was prepared during the summer

of 1972. After reviewing this material it was decided to

expand the coverage of properties and to enlist the aid

of various experts at NBS and elsewhere in the compilation

and evaluation of data. At the present time we have received

contributions on electron affinities , dipole moments,

polarizabilities/ PVT properties, microwave spectra and

isotopic composition of molecules. Other contributions

are still being prepared.

B. Chemical Kinetics and Photochemistry: It is our plan

to include in this compilation a set of tables of rate constants for chemical reactions, quantium yields for photolysis

processes and optical absorption coefficients for pollutants

and the normal constituents of air. Data have been evaluated

111
for reactions and photo processes in the /NO /HO /HNO

.A. ^K. ^C ^C system. Selections of rate constants for reactions of

organic species still must be made.

The plan is to complete this work during FY 1974.

The following data evaluations were issued during the year.

Direct distribution of reports is made to about 300 kineticists and atmospheric modellers. Data in these reports

will be used in the proposed handbook.

1. R. F. Hampson, et. al. "Survey of Photochemical and

Rate Data for Twenty-eight Reactions of Interest in Atmospheric Chemistry" J. Phys. Chem. Ref . Data 2_ No. 2 (in

press summer 1972) . This article is a revision of the

data sheets issued earlier as NBS Reports 10692 (Jan 1972)

and 10828 (April 1972)

.

2. David Garvin, editor "Chemical Kinetics Data Survey

V. Sixty-six Contributed Rate and Photochemical Data Evaluations on Ninety-four Reactions" NBSIR 73-206 (May 1973)

.

These are data evaluations made for us by scientists not

at NBS.

3. R. F. Hampson, et. al. "Chemical Kinetics Data Survey

VI. Photochemical and Rate Data for Twelve Gas Phase Reactions

of Interest for Atmospheric Chemistry" NBSIR 73-207 (Summer

1973, now being reviewed).

112
29. Degradation of Polymers

Project Leader R. E. Florin, Polymer Division

Other Personnel L. Dunlap, W. J. Pummer, S. Straus, C. N.

Cascaval (Guest worker) and Roestamsjah

(Guest Worker)

Objective

The objective of this project is to gain as full an understanding as possible of the mechanisms of polymer degradations

of all sorts. Special emphasis is placed on thermal

degradation to volatiles. This is important in its application

to limits on service conditions, to fire hazard, to incineration, and to production of toxic or irritating volatile

products. Application of the knowledge to various situations,

e.g., fires, is also involved.

Approach

Mechanism is most readily deduced from studies of pyrolysis

in vacuum, the curves of rate and of molecular weight

versus conversion to volatiles being the most important

data. For new polymers, products are characterized by

mass spectrometry, gas chromatography, and measurement of

molecular weight, etc. Interpretation is in terms of

the free radical chain theory, often quantitatively developed.

The influence of inert gases and oxygen is is also being

studied.

Progress

Data were acquired for rates of pyrolysis of polyimide

as a function of film thickness and oxygen partial pressure.

113
Initial data of this sort were obtained for polystyrene.

The reduction in decomposition temperatures in going

to an air environment is of the order of 50 to 100°.

Initial data were obtained for oxidative pyrolysis of

polystyrene.

A comprehensive experimental and theoretical study of

the pyrolysis in vacuum of polystyrene was completed and

published. The initiation step is principally at chain

ends with a minor random scission component for thermally

prepared polystyrene. However, for an ionically prepared

polystyrene, initiations is at first exclusively random

scission. Supplementary work with azobis-isobutyronitrile

prepared polystyrene was begun, and pyrolysis of polyalpha

methylstyrene at molecular weights extending to 10 million.

Pyrolysis studies of polyoctafluorostyrene were begun.

Pyrolysis gas chromatography was used to survey decomposition products of many hydrofluoro copolymers and certain

anomalous polystyrenes.

Burning behavior was studied in the limiting oxygen index

apparatus for transition-metal containing ionomers (i.e.,

ethylene-methacrylic acid copolymers) . The same equipment

was used to study the modifications in burning behavior

of polymers caused by gamma ray induced degradation and

crosslinking. Oxygen index increases of a few points

were sometimes found.

114
WATER POLLUTION PROJECTS

30. Low Velocity Measurements in Water Pollution

Project Leader G. Kulin, Mechanics Division

Objective

The objective of this project is to improve the state-ofthe-art of measurement of low velocities of water as practiced in the field by instrument users concerned with

water pollution abatement. For this purpose "low" velocity

is defined as less than approximately 1 foot per second,

but with emphasis on the lower end of the range, down

to 0.1 fps and even lower. These low velocities play major

roles in lake, reservoir and estuary dynamics and have attained

increased importance because of recent intense interest

in water quality control and marine disposal of thermal

discharges and other wastes. The design specifications

for the new NBS water tunnel now under construction anticipated this need and provided for test section velocities

down to 0.1 fps

.

Approach

The approach is two-pronged, consisting of a field contact

program and a laboratory program.

Field Contacts: Special effort is being made to contact

personally people who have the responsibility of making

low-velocity measurements in the field. The purposes of

the contact program are to:

'Observe field work firsthand and identify measurement

problems met on site.

115
Survey present instrumentation capability and identify accuracies attained compared with accuracies required now or

anticipated in the future.

Generally establish or improve communications with instrument users in the field.

The results of the field contacts program hopefully will

help us to identify and plan purposeful experiments to

supplement the NBS low-velocity measurements program and

will foster transfer of NBS measurement capability where

such improved transfer would be benefical in the field.

Laboratory Program: The laboratory program includes three

phases, all of which are subject to adjustments by inputs

from the field contact phase.

•Evaluation of present low-velocity measurement instruments

including calibration methods, near-threshold performance,

and error sources.

•Improvements on existing meters.

•Development and evaluation of new types of velocity measuring instruments.

Progress

During the year contacts were established with 60 organizations. Of these contacts, 16 were personal visits to

field measurement sites and/or offices, and the remainder

were mostly telephone communications with a few letter

communications. The organizations contacted included 30

Government (federal, state and local) agencies, 19 private

companies, 9 university laboratories and 2 trade associations.

This is a continuing effort.

Some of the major preliminary conclusions, which will

be described in more detail together with documentation

116
in a forthcoming internal report are as follows:

Improvements in low-velocity measurements are needed.

Commercially available instruments for measuring very low

velocities are not doing the job under all conditions.

Most of the problems are technological but some appear

to be hydrodynamic in origin.

• Regulatory requirements have created a need for more lowvelocity measurements for environmental impact statements,

etc. , but as yet there are no requirements on accuracy

of specific velocity measurements.

• Many of these measurements are being performed by capable

and experienced people who are specialists in this field.

However, the extent to which this is not true is probably

significant and is still under investigation.

• Velocity measurements for pollution abatement are intimately

related to flowrate measurements for water delivery systems

and industrial and municipal wastewater effluents.

Improved velocity measurements are needed for velocityarea flowrate integarations and for in-place calibrations

of wastewater meters.

• Field practice in wastewater measurements in small industries is often very poor and measurements are made by

inexperienced personnel.

• Regulatory agencies need improved instruments and methods

for monitoring industrial effluent flowrates.

In the laboratory an investigation was started on the

low-velocity near-threshold performance of rotating-bucket

vertical-axis current meters. This is being done in a small towing tank. Results to date suggest that the Price

meter is a better low-velocity performer than it is generally

given credit for.

The survey of field contacts will be continued in order

117
to fill gaps in the information, to delineate better areas

where help is needed and to consider the most effective

methods for transferring measurement capability where

needed.

In the laboratory, the evaluation of rotating-bucket meters

will be continued. Additional work during FY 74 will be

selected from the following, subject to modification by

field contact results and to availability of facilities.

•Evaluation of miniature propeller and other meters for

field use and for suitability for flowrate meter field

calibrations.

•Evaluation of towing tank test procedures for very low

velocities and comparison with calibrations in the existing

open-circuit water tunnel and the new high-performance

tunnel (scheduled to come on line late in FY 1974)

.

118
31. Fate and Effects of Oil in the Seas

Project Leader S. Wasik, Physical Chemistry Division

Other Personnel G. T. Armstrong, R. L. Brown, and J.

I. Minor, Jr.

Objective

Develop a method for indentifying and measuring the solubilities of individual components of oil-water and processed

oil-water extracts.

Approach

A repetitive gas phase extraction technique is used followed

by analysis of the gas phase in a gas-liquid chromatography

column. The physical chemical studies may be divided

into two parts: (1) the determination of solubilities and

partition coefficients of hydrocarbons in sea water and

(2) the development of analytical gas chromatography columns

for the separation of hydrocarbons from their deuterated

analogs.

Progress

A. Hydrocarbon solubility: A method for identifying and

measuring the solubilities of the individual components

of petroleum and processed oil-water extracts has been

developed. A paper describing these results was presented

at the 1973 Conference on Prevention and Control of Oil

Spill meeting held in Washington, D. C. in March 1973.

This aspect of the work is important in that it demonstrates

the strong effect the higher alkanes ( C T9~C 22^ nave on

the solubility of the toxic aromatic hydrocarbons.

119
The higher alkanes form emulsions on shaking which are

stable for long periods of time. The solubilities of the

volatile aromatic hydrocarbons are enhanced by the presence

of these emulsions.

The partition coefficients and solubilities of cyclohexane,

cyclohexene, 1, 4-cyclohexadiene, 1, 3-cyclohexadiene, and

benzene have been measured in fresh and sea water over the

temperature range 0-25°C. The results indicate that the

partition coefficients and solubilities of hydrocarbons

in aqueous solutions increase with the degree of unsaturation of the hydrocarbons.

A paper describing the results of solubility and partition

coefficient measurements on dimethyl mercury in fresh

and sea water is almost completed.

B. Analytical column development: To date, we have been

able to separate the volatile aromatic (benzene, toluene,

and the xylenes) , the olefinic (ethylene, butene, and

pentene) and the aliphatic hydrocarbons (n-octane) from

their deuterated analogs. The first two separations were

obtained using an aqueous silver nitrate column while

the latter separation was achieved on a liquid crystal

column. These columns should prove useful for isotope

dilution analyses of trace amounts of hydrocarbons in sea

water.

120
32. Transformations of Heavy Metals in Aquatic Environments

Project Leaders F. E. Brinckman, Inorganic Materials

Division and W. P. Iverson, Metallurgy

Division

Objective

The principal objective of this project is to characterize

biological and other mechanisms operative in natural water

systems for mobilization and transport of heavy metals.

It is expected that information derived from these studies

can provide keys for the prevention or control of release

of such heavy metals in the highly toxic forms (viz. methyland dimethylmercury) from already established reservoirs

in natural bodies of water (rivers, estuaries, etc.).

Approach

An understanding of the chemical and biological nature

of metals transport in natural waters necessitates a balanced interdisciplinary approach to characterizing key

pathways. The NBS interdivisional team is comprised of

an organometal chemist and a biologist expert in microbial

corrosion. The effort has involved outside sponsorship

and collaboration along the lines depicted in Figure 32.1.

Progress

During the report period, a number of sediment, water,

and plankton samples obtained from the Chesapeake Bay with

Dr. Colwell's group have been analyzed for total mercury

using flameless atomic absorption techniques.

121
<o<o

(Nn

0)upH

Cm

122
A number of mercury tolerant aerobic bacteria isolated

from the Chesapeake Bay by Dr. Colwell's group have been

screened for their ability to produce free mercury or

volatile organomercurials from phenylmercuric acetate.

In parallel with the microbiological investigations, we

have studied non-enzymatic mercury transformations, primarily

organic group transfer reactions between mercury and other

metals in aqueous solution. It has been found by a combination of proton nuclear magnetic resonance and laser-Raman

spectrometry that trimethyllead cation undergoes demethylation reactions in water similar to those as observed

earlier for trimethyltin cation, e.g., rapid methylation

of mercuric ion to methylmercury cation.

Moreover, the process of methylating mercuric ion is sensitive to the presence of certain counterions; for example,

excess cyanide and thiocyanate anions effectively inhibit

the transmethylation process noted above.

The significance of these results is the demonstration

that non-enzmatic reaction pathways can substantially affect

concentrations of organomercury cations in the presence

of inorganic- or organo-cations of other metals in aquatic

environments

.

Project activities to date have resulted in publication

or presentation of several aspects of the work:

1. "Biodegradation of Phenylmercuric Acetate by Mercury

Resistant Bacteria," J. D. Nelson, W. Balir, F. E.

Brinckman, R. R. Colwell, and W. P. Iverson,

Appl. Microbiol. , 2£, 321 (1973)

123
2. "Transmethylation of Heavy Metal Ions in Water," F.

E. Brinckman and K. L. Jewett, 8th Middle Atlantic

Regional Mtg. of the Amer. Chem. Soc, Washington,

D. C. January 1973, Abstracts of Papers , p. 52.

124
33. Reactor Effluent and Environmental Radioactivity Standards

Project Leader W. B. Mann, Applied Radiation Division

Other Personnel B. M. Coursey, J. M. R. Hutchinson,

J. R. Noyce

Objective

The objective is to improve the accuracy of measurements

of radioactivity in the environment and in the effluents

from nuclear facilities. In order to accomplish this,

an immediate goal is to make all such measurements in the

United States either directly or indirectly traceable

to the National Bureau of Standards.

Approach

There are three major elements in our current approach

to these objectives. (1) Traceability: We are working

toward establishing traceability of radioactivity measurements of the major quality control laboratories with NBS.

(2) Standard Reference Materials (SRM's): We are providing

standard sources and test sources through the SRM program

for general use by the nuclear industry and environmental

monitoring laboratories. (3) Reference Laboratory:

We are developing the capability to serve as a "third party"

or referee laboratory to help resolve discrepancies involving

environmental measurements of radioactivity.

Progress

Traceability

Over the past two years, we have engaged in a traceability

125
study with one of the national quality control laboratories.

In connection with this study we have:

a. provided the laboratory with 6 calibration standards,

b. provided 19 test sources and evaluated the laboratory's

results for these sources,

c. sent the project leader to their laboratory to evaluate

their instrumentation and methods of analysis, and

d. provided them a calibrated mixture which they then

distributed as an unknown to laboratories under their

jurisdiction, such as the state radiological health

laboratories

.

This mixture (d) closely simulated a reactor waste water

sample, as it contained the beta-particle emitters hydrogen3 and strontium-90 , as well as three gamma-ray-emitting

radionuclides

.

Standard Reference Materials

The following sources, which are useful for calibrating

instruments used in environmental radioactivity measurements,

have been distributed by this section during the past

two years.

a. Mixed Radionuclide Gamma-Ray Emission-Rate SRM's: The

composition of the four mixtures prepared to date is

given in Table 33.1.

b. Iodine-131: A special distribution of solution standards

of iodine-131 was made to 23 laboratories.

c. Iodine-129 (SRM4949): Solution standards of iodine-129

were prepared. (This work was not supported by the

AEC contract.)

126
Reference Laboratory

During the past two years we have worked to improve our

low- level radioactivity measurements capabilities by:

a. improving our apparatus (A list of major counting systems

developed for this laboratory is given in Table 33.2.)

b. developing our expertise in low-level radiochemistry

techniques/ and

c. engaging in intercomparison studies.

A specific example of the latter two items was our participation in an international intercomparison, sponsored by

the IAEA, Monaco (2) . Twenty-four of the participants

determined the strontium-90 content of lyopholized, homogenized seaweed. The values reported ranged from 2.4

to 15.6 pCi/g. The average value, excluding the outlying

lowest value, was 10.0 pCi/g. The NBS value was 10.1

pCi/g.

Future Plans

Traceability: We will continue and expand traceability

studies with major quality control laboratories, and extend

these studies to include the state laboratories.

SRM Program: The mixed radionuclide SRM's will be reissued

at least annually. Strontium-90 and strontium-89 solution

standards will be distributed soon. A calibrated mixture

of the two will also be made available.

Reference Laboratory: River sediment samples, with environmental levels of radioactivity, are being developed.

Liquid scintillation counting techniques are being developed

127
for low-level measurements of hydrogen-3 and selected

alpha-particle emitters in environmental water samples,

A new anticoincidence shielded Ge(Li) detector system

will be used to assay environmental samples.

128
Table 33.1. NBS Mixed Radionuclide Gamma-Ray Emission-Rate

Standards and Test Sources

(A) List of standards and test sources

SRM No.

Test source

1 Test source

Description

450-ml solution

50-ml solution

Prepared From

Master Solution No,

I

I

4242-B

4243-B

4244-B

450-ml solution

50-ml solution

15-ml solution

II

II

II

4252

4253( 450-ml solution50-ml solution

III

III

4242-C

4243-C

4215

4216

450-ml solution

50-ml solution

point source

point source

IV

IV

IV

IV

a. Four master radionuclide solutions have been prepared.

Sources in several different forms are normally prepared

from the same master solution.

b. These two sources were distributed as unknowns in a "round

robin" intorcomparison (1)

.

c. SRM-4252 and -4253 were first distributed as unknowns,

An SRM certificate was later furnished to each user.

129
(B) Radionuclidic components in the four master solutions

I II III IV

51Cr

543 Mn

58Co

59 Pe

65 Z„

137Cs- 137mBa

54MMn 51Cr 57Co

57Co 54

Mii

60CO

60CO 58Co 85

Sr

88

Y

59Fe

88

y

109Cd 60CO

109Cd

113

Sn113m,.In 65 Zn 113 Sn_113m

In

137Cs- 137mBa 134Cs 137Cs- 137mBa

137„_ 137rrL l-J/nu, 139 ijy_ Cs- Ba Ce

144^ 144 n 203^ Ce- Pr Hg

130
Table 33.2- Major Counting Systems for Reference Laboratory5

For the analysis of gamma-ray emitters:

(1) Anticoincidence shielded Ge(Li) detector system

(2) 8" x 4" - Mtty" - Nal(Tl) scintillation detector

system

(3) 5" dia. - Nal(Tl) scintillation well detector system

The above systems are used in conjunction with two Northern

Scientific MCA's of 1024 and 4096 channel

For the analysis of beta-particle emitters:

(1) Omniguard gas-flow proportional counter

(2) Sharp low-beta counting system

(3) Packard 3320 liquid scintillation counter

For the analysis of alpha-particle emitters:

(1) silicon surface barrier detectors

(2) liquid scintillation counter

The Northern Scientific MCA's may be used with these two

methods.

(3) HASL "b-raters"

The use of a particular manufactured product does not

constitute an endorsement of the product by the National

Bureau of Standards.

131
34. Noble Gas Radionuclides

Project Leader W. B. Mann, Applied Radiation Division

Other Personnel F. J. Schima, M. P. Unterweger

Objective

The objective of this program is to improve the detection

and measurement capabilities for noble gas fission products

by means of the preparation of activity calibrated samples

of various gaseous radionuclides. Further, production

mechanisms and decay characteristics of these radionuclides

will be studied insofar as they might be relevant.

Approach

The gaseous radionuclides are generally calibrated in activity/ gram mole units by means of length compensated gas

proportional counters. These counters are operated very

close to 100% efficiency for decay event detection. A

portion of the gas radionuclide sample is then diluted to

the desired activity level in a gas handling system which

contains very accurate barometers and measured volume chambers. In the related work, the general facilities of the

Radioactivity Section as well as the Center for Radiation

Research are made use of as needed. For example, the isotope

133 separator is used to prepare samples of Xe free from

131mvXe.

Progress

Table 34.1 is a list of the gaseous radionuclide samples

which have been prepared in the last year with some as Stand133 ard Reference Material. Due to short half-lives Xe

132
appears in the list (Table 34.2) of environmental related

organizations which have obtained some of these samples.

The Xe and Xe radionuclides have medical applications,

but without significant environmental impact.

TOO I TC

Additional work includes the measurement of ~ Xe and Xe

production cross-section by the (n , "a) a) reactions on

Ba isotopes.

These results are:

for Ba (n . a) Xe a<21yb;

for 136 Ba(nth a)

133

Xe a Zi 50f20yb.

129 The 8.89+.02d half-life -iteasurement for mXe radionuclide

was published in the last year.

References

1. L. D. Miller and F. J. Schima "The Half-Life of 129mXe",

Int. J. Appl. Rad. Isotopes, 24, 353 (1973).

2. S. B. Garfinkel, W. B. Mann, F. J. Schima and M. P.

Unterweger "Present Status in the Field of Internal Gas

Counting" Nuel. Instr. & Methods (in press)

.

Future Plans

85

It is planned to gas count several of the Kr samples,

in order to determine an activity value with accuracy suffic133 lent for OSRM certification. Related to the current Xe

calibration, ssamples will sent directly to seven state

laboratories, under the AEC program for delegating to the

States responsibility for environmental monitoring of reactor

effluents. 233
Table 34.1

Gas Radionuclides

Nuclide Nominal Activity

(dpm/ml)

OSRM #

If applicable

14.

37Ar

37Ar

85Kr

131m

xe

133,Xe

133Xe

in process

11 ,000

10

100

15 ,000

15 ,000

in process

4300

4301

4305

134
Table 34.2

Gaseous Radionuclide Sample Users

A.E.C. Division of Compliance, HSL Idaho

A.E.C. Nuclear Division, ORNL Oak Ridge, Tenn

E.P.A. Western Environmental Research Laboratory Nevada

N.B.S. Analytical Chemistry, IMR

Smithsonian Institute - Astrophysical Obs. Massachusetts

135

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1. PUBLICATION OR RKPORT NO. NBS TN-828

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MEASURES FOR AIR QUALITY (1972-1973)

ANNUAL REPORT-FY 1973

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James R. McNesby

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