FINAL REPORT
May 8, 1970 through May 8, 1972
FIELD EVALUATION OF NEW AIR POLLUTION MONITORING SYSTEMS
C. E. Decker
T. M. Royal
J. B. Tommerdahl
Environmental Protection Agency
Contract No. CPA 70-101
RESEARCH TRIANGLE PARK.NORTHCAROLINA
27709
-------
FOREWORD
This final report describes the results of a field evaluation qf
ambient air analyzers conducted by the Research Triangle Institute
for the Environmental Protection Agency under Contract CPA 70-101
during the period May 8, 1970 to May 8, 1972.
During this study,
a mobile laboratory was located in Los Angeles for three months and
in St. Louis for six months.
Interim reports describing the three phases
of this instrument evaluation program have been prepared and are available
from the Environmental Protection Agency.
The work on this project was performed by the Instrumentation,
Measurements and Device Research Department, Engineering Division,
Research Triangle Institute for the Field Methods Development Section,
Division of Chemistry and Physics, Environmental Protec~ipn Agency.
Mr. R. K. Stevens, EPA, WaS Project Monitor.
Mr. C. E. Decker and
Dr. L. F. Ballard served as Project Leaders.
Mr.. J. B. Tornmerdaql,
Mr. T. M. Royal, Mr. R. W. Murdoch, and Mrs. L. K. Matus participated
in the field evaluation program.
The Research Triangle Institute wants to acknowledge the cooperation
and assistance provided throughout the evaluation program by Messrs.
Stevens, O'Keeffe, Hodgeson, Clark, and others of the Field Methods
Development Section, Division of Chemistry and Physics, Environmental
Protection Agency.
Appreciation is also expressed to the Los Angeles County Air
Pollution Control District and the St. Louis County Air Pollution Control
Office for providing the respective sites for the evaluation program.
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Section
1.0
2.0
3.0
4.0
5.0
6.0
8.0
9.0
10.0
11.0
TABLE OF CONTENTS
INTRODUCTION
1.1
1.2
Obj ectives
Experimental ,Approach and Description of Facilities
GAS ANALYZERS
CALIBRATION AND SAMPLING SYSTEM
3.1
3.2
Calibration Procedures
tmbient Air Sampling System
METEOROLOGICAL SENSORS
DATA ACQUISITION
7.0
5.1
5.2
General System Description
Automatic Calibrat~on Technique
COMPUTER PROCESSING OF FIELD DATA
6.1
6.2
General Data Processing Pro~rams
Data Output
INSTRUMENT EVALUATION
7.1
7.2
7.3
7.4
7.5
Performance Characteristics
Calibration Stability
Operational Summary
Comparison of N02 Measurements
Comparison of S02 Measurements
to Standard Method
to Standard Method
AIR POLLUTION SUMMARY
8.1
8.2
8.3
Los Angeles Study
St. Louis Study:
St. Louis Study:
Phase I
Phase II
SUMMARY OF FINDINGS
RECOMMENDATIONS
REFERENCES
Page
1
1
3
7
10
10
10
18
20
20
20
27
27
27
31
31
~l
32
36
39
40
40
41
43
45
50
51
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1.0
INTRODUCTION
1.1
Objectives
The purpose of this program was to conduct a full scale field
evaluation of ambient air analyzers in different geographical areas to
determine the effects of typical combinations of urban environment
pollutants on the instrument performance level.
The aim was to establish
on both an absolute and comparative basis the degree to which the iqstruments
evaluated meet the needs of control agencie~ for reliable and accurate
measurements.
This study was also intended to determine if newly
developed instrumentation can adequately measure pollutant
concentrations in ambient air and to compare them to the reference
methods.
As a result of the tremendous growth in pollution monitoring instru-
mentation, it was also very important that techniques for rapidly evalu-
ating the performance level of a large number of instr~ents under iden-
tical field conditions be conceived and implemented.
Automatic calibration
techniques and electronic data acquisition and analysis were considered to
be necessary ingredients for this accomplishment in terms of accuracy, time,
and economy.
As a pioneer program in combining all these features, the
procedures that have been used may serve as guidelines for broader
application.
The instrument evaluation program conducted over the past two
years was divided into three separate studies.
The ftrst study was
conducted in Los Angeles [1], where the major source of pollution is
th~ internal combustion engine, during the period September 4 to
-------
December 1, 1970.
St. Louis was selected for the additional tests
because of its varied industrial activities, which are typical of many
urban environments in the United States and which introduce a large
number of organic an~ inorganic pollutants into the atmosphere.
Phase
I [2] in St.. Louis was conducted during the period May 13 to August 17,
1971.
Phase II [3] in St. Louis was conducted during the period October
.7 ,to December 20, 197L
In each of the three studies the performance
of classical measurement principles for ambient air pollutants were
compared with new analytical techniques.
Gas analyzers were included in the instrument evaluation program
for measuring S02' 03' Ox' NO, N02' H2S, THC,'CH4' CO, and non-methane
hydrocarbons.
Meteorological instruments were included for supporting
meaSurements of wind speed and direction, temperature, solar radiation,
anq dewpoint.
...'
Several of the ambient air analyzers evaluated during these studies
were prototype instruments based on newly-developed measurement techniques
or first production models.
Mechanical and electrical problems were
. frequently encountered with these systems which hindered their performance.
An important. aspect of this evaluation program was to identify weaknesses
in the monitoring principle and design and to make appropriate adjustment
where possible.
2
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1.2
Experimental Approach and Description of Facilities
An environmentally controlled mobile laboratory was considered
to be the most realistic vehicle to both transport and house the instru-
ments, data acquisition system, and supporting laboratory equipment.
Figure 1.1 shows two internal views of the mobile laboratory on location
adjacent to the St. Louis County air monitoring station at 55 Hunter Road,
Clayton, Missouri.
Figure 1.2 is a diagram of the mobile laboratory
showing the location of the monitoring instruments evaluated during Pijas~ II
in St. Louis, the data acquisition system, and gas sampling manifold.
During the Los Angeles Study (Sept. 4-Dec. 1, 1970), the trailer was
located adjacent to the Los Angeles County Air Pollution Control
District's research facility on San Pedro Street in downtown L08 Angeles.
The gas analyzers evaluated during each study are listed in Section
2.0.
Instrument descriptions and operation summaries for each evaluation
period are presented in three Interim Reports [1,~,3] and are not
duplicated here.
The calibration schedule consisted of a zero air and
span calibration every two (2) days and a multi-point calibration on
alternating weekends.
Calibration procedures used during this study are
given in Section 3.0.
Meteorological sensors are described in Section 4.0 and the data
acquisition system in Section 5.0.
In addition to the data storage
function, the overall system was designed to automate the communication
between the laboratory operator and the data processing and analysis
facili ty.
The data handling programs used to process all data are given in
Section 6.0.
These programs provide a~r quality data, cross correlation
3
-------
.t:-
FIGURE 1.1.
Mobile Field Laboratory
-------
Wind
System
~
~solar Radiometer
Sample
Inlet ~
Climet Temperature
Aspirator
>.
~
o
+J
cu
~
.0
.c
cu
,.:j
't:J
~
aJ
.~
r.:.
aJ
~
.,..j
.c
o
::E:
t-
35 it 8 m
Air Samp.le
Manifola
-1
Blower
St. Louis County
Monitoring Station
t
14
.
~
~
II
II
------
- - -
- - -
~
1:1
~
H
fz<
1 Tracor S02' H2S 8 Thermo Electron NO, NO
2 Melpar SOO 9 Aerochem NO x
3 Philips S 10 Beckman N02
4 Pollution ~on. S02 11 Beckman - THC, Cll , CO
5 Bendix 03 12 Power Design Paci1ic THC
6 Technicon ° 13 MSA NDIR CO
7 Mast 0 x 14 Data Acquisition System
x
FIGURE 1.2 Diagram of Air Sampling System and
Location of Continuous Ambient Air Analyzers in the Mobile Laboratory
5
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between various instruments and statistical data on the stability and
overall performance of each instrument.
Summaries of these results are
given in Section 7.0 and 8.0.
6
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2.0
GAS ANALYZERS
The instrumentation and measurement methods evaluated in the field
program in Los Angeles and St. Louis (Phase I and Phase II) are summarized
in Tables 2.1, 2.2, and 2.3.
The principle of operation of these instruments
and measurement methods have previously been described in the literature.
For further information refer to the three interim reports [1,Z,3] or the
additional references provided.
TABLE Z.l INSTRUMENTATION AND MEASUREMENT METHODS
EVALUATED IN THE LOS ANGELES STUDY
Pollutant
Ozone
Oxidant
Nitrogen Dioxide
Sulfur Dioxide
Hydrogen Sulfide
Analyzer or Method Principle of Operation References
RTI 03 Chemiluminescent 4
EPA 03 (Prototype) Chemiluminescent 5
Mast 0 Coulometric 6
x
Technicon 0 Colorimetric 7
x
Technicon N02 Colorimetric 8,9
Melpar S02 Flame Photometric 10,11
Philips SOZ Coulometric 3
L&N S02 Conductometric 2
Tracor GC-S02 GC-Flame Photometric 12
Technicon S02 Colorimetric 1
Tracor GC-HZS GC-Flame Photometric 12
Technicon HZS Colorimetric 13
7
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TABLE 2.2 INSTRUMENTATION lU~D MEASUREMENT METHODS
EVALUATED IN THE ST. LOUIS STUDY: PHASE I
Pollutant
Ozone
Oxidant
Nitrogen Dioxide
Nitric Oxide
Sulfur Dioxide
Hydrogen Sulfide
Carbon Monoxide
Total Hydrocarbons
Non-Methane
Hydrocarbons
Analyzer or Method
RTI 03
Principle of Operation
Chemiluminescent
Bendix Environmental 03 Chemiluminescent
Dasibi 03
Mast 0
x
Beckman 908 0
x
Technicon IV 0
x
Beckman 910 N02
Beckman 909 NO
Aerochem NO
Melpar S02
Philips S02
Beckman 906A S02
L&N S02
Tracor GC-S02
Pollution Monitors S02
Tracor GC-H2S
MSA CO
Beckman 6800 CO
Power Design Pacific
Beckman 6800
Beckman 6800
8
UV-Absorption
Coulometric
Coulometric
Colorimetric
Coulometric
Coulometric
Chemiluminescent
Flame Photometric
Coulometric
Coulometric
Conductometric
GC-Flame Photometric
Colorimetric
GC-Flame Photometric
NDIR
GC-FID
FID
GC-FID
GC-FID
References
4
5
2
6
2
7
2
2
14
10,11
3
2
2
12
2
12
2
15,16
2
15,16
15,16
-------
TABLE 2.3 INSTRUMENTATION AND MEASUREMENT METHODS
EVALUATED IN THE ST. LOUIS STUDY: PHASE II
Pollutant
Ozone
Oxidant
Nitrogen Dioxide
Nitric Oxide
Sulfur Dioxide
Hydrogen Sulfide
Carbon Monoxide
Total Hydrocarbons
Non-Methane
Hydrocarbons
Analyzer or Method
Bendix Process 03
Mast 0
x
Technicon IV 0
x
Beckman 910 N02
Thermo Electron N02*
Technicon NOZ
Jacobs-Hochheiser
Aerochem NO
Thermo Electron NO
Melpar S02
Tracor GC-SOZ
Philips S02
Pararosaniline
Tracor GC-HZS
Beckman 6800 CO
MSA CO
Beckman 6800
Power Design Pacific
Beckman 6800
*Modified to measure both NO and NO
x.
9
Principle of Operation
Chemiluminescent
Coulometric
Colorimetric
Coulometric
Chemiluminescent
Colorimetric
Manual-Colorimetric
Chemiluminescent
Chemiluminescent
Flame Photometric
GC-Flame Photometric
Coulometric
Manual-Colorimetric
GC-Flame Photometric
GC-FID
NDIR
GC-FID
FID
GC- FID
References
3
6
7
2
17
8,9
18
14
17
10,11
12
3
19
12
15,16
z
15,16
2
15,16
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3.0
CALIBRATION PROCEDURES
3.1
Calibration Techniques
Dynamic calibration techniques were used to calibrate the
monitoring systems evaluated during these studies and are outlined
in Table 3.1.
Multipoint calibrations were performed bi-weekly with
zero and span checks every two days.
These data were used to provide
updated transfer equations for input into the computer for data
reduction.
For additional information regarding calibration procedures,
refer to the three interim reports [1,2,3] or the references cited.
Diagrams of these calibration systems are included in Figures 3.1,
3.2, and 3.3.
TABLE 3.1
CALIBRATION TECHNIQUES
Pollutant
Calibration Technique
References
Ozone/Oxidant
UV-Ozone generator referenced
to Manual KI
20
Nitrogen Dioxide
Permeation Tube & NO-N02
Conversion System
21,22
Nitric Oxide
Cylinder-dilution
22
Sulfur Dioxide
Permeation Tube
21,23
Hydrogen Sulfide
Permeation Tube
3
Carbon Monoxide
Cylinder
3
Total Hydrocarbons
Cylinder
3
Non-Methane Hydrocarbons
Cylinder
3
3.2
Ambient Air Sampling System
In order to avoid eddy currents and street pollution, the
sample inlet was located five feet above the trailer.
A 1" 1. D . TFE
10
-------
Rotameter
Filter and
Dryer
Compressed
Air
Figure 3.1
Ozone
Generator
5/8"
Quartz
Tube
Penray
Hercury Vapor
Lamp
Ozone Calibration System
11
To Calibration
Manifold
-l
I
I
o
I
I
I
I
!
To
Regulated
AC Voltage
-------
"
COMPRESSED AIR
Figure 3.2
PERMEATION TUBE
EQUILIBRATION COIL
-
lLVE
iNIFOLD
CONSTANT-TEMPERATURE
WATER BATH
THERMISTOR TEMPERATURE MONITOR
Permeation Tube Calibration System
12
-------
Ozone
Generator
Conversion
Chamber
Rotameter
Compressed
Air
Mixing
Chamber
To
Calibration
Manifold
48.6 ppm
NO in
Nitrogen
Figure
3.3
Nitric Oxide and Nitrogen Dioxide Calibration System.
13
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teflon tube extended from the sample holder located on the meteorological
tower to the trailer where it connected to a 1" a.D. pyrex glass manifold
which extended behind the air monitoring systems.
This arrangement is
shown in Figures 3.4, 3.5, and 3.6.
A glass flower pot protected the sample
inlet and prevented moisture and settleable particulates from entering the
sample line.
Sample air was aspirated via a blower through the teflon line
and glass manifold at a rate of 3 CFM.
Sampling ports made of 12/5 ball
and socket joints were used for easy hook-up of instrument sample inlet
lines.
14
-------
35 ft. 8 in.
SOLAR
RADIOMETER
SAMPLE INLET.......
CLiMET - [:::::::=
TEMPERATURE
ASPIRATOR
10 ft
l-in.-I.D. TFE- 1
TEFLON TUBE
SIGNAL CABLE
:::I:
..
L.A.C.A.P.C.D. .
HEADQUARTERS
BUILDING
90fL
:r
:r
ANALYZER DESIGNATION
(1) TECHNICON CSM6 (Ox. SOZ. NOZ' HZS)
,(2) MAST Ox
(3) REGENER 03
(4) NEDERBRAGT 03
(5) LEEDS & NORTHRUP SOZ
(6) PHILIPS SOZ
(7) MELOY SOZ
(8) TRACOR GC- FPD SOZ
o
MOBILE VAN
Figure 3.4
Diagram of Air Sampling System and Sulfur Dioxide and
Ozone Monitors in Mobile Laboratory
15
-------
Wind
System
~
Samp Ie
Inlet
~Solar Radiometer
Climet Temperature
Aspirator
I-
35 it 8 m
Air Samp.le
Manifola
-1
Blower
+
St. Louis County
Monitoring Station
19
II
II
------
- - -
1
2
3
4
5
6
7
8
9
10
Tracor S02' H2S
Melpar S02
Beckman S02
L & N SO
Philips So
Pollution ~on.SO
Solid Phase 03 (Tul-B)
Bendix 03
Technicon 0
Mas t 0 x
x
11 Dasibi 03
12 Beckman 0
13 Be ckman N~
14 Aerochem Nt)
15 Beckman NO
16 Beckman - THC
17 FID THC
18 NDIR CO
19 Data Acquisition
System
FIGURE 3.5 Diagram of Air Sampling System and
Location of Continuous Ambient Air Analyzers in the Mobile Laboratory
16
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Wind
System
~
Sample
Inlet
Climet Temperature
Aspirator
tc 35 £t8m Air Samp'le -1
Blm...er Man if ala
t St. Louis County
Monitoring Station
14
'I II ~ up rm
. .. .. .~- ~CW 1 I
nlr: u
- - - - - - - - -
1 Tracor S02' H2S 8 Thermo Electron NO, NO
2 Melpar SOb 9 Aerochem NO x
3 Philips S 10 Beckman N02
4 Pollution ~on. S02 11 Beckman - THC, CH , CO
5 Bendix 0 12 Power Design Paciiic THC
6 Technico5 0 13 HSA NDIR CO
7 Mast ° x 14 Data Acquisition System
x
FIGURE 3.6 Diagram of Air Sampling System and
Location of Continuous Ambient Air Analyzers in the Mobile Laboratory
17
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4.0
METEOROLOGICAL SENSORS
The following meteorological parameters were monitored throughout
the duration of the field evaluation program:
wind speed and direction,
ambient air temperature, relative humidity and solar radiation.
Sensors
for monitoring these parameters were mounted on a small tower which
was attached to the top of the mobile van.
The tower as assembled
for checkout is shown in Figure 4.1.
The instrumentation used to
monitor these meteorological parameters is outlined in Table 4.1.
TABLE 4.1
METEOROLOGICAL INSTRUMENTATION
Parameter
Instrument or Method
Reference
Wind Speed & Direction
Modified Bendix Aerovane
3
Temperature
Thermistor in Aspirated
Temperature Shield
3
Dewpoint
Foxboro Dewcell
3
Solar Radiation
Kipp & Zonen Solarimeter
3
18
-------
Wind Speed &
Direction Sensor:
Air Sampling
Tube Bracket
Dewpoint Sensor
Bracket
~
.. ~
.. ~';.;..'"'7' ..."1... Solar radiation
Sensor
;,' "
".
!
Air Temperature
Sensor
Figure 4.1
Meteorological Sensor Tower
19
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5.0 . DATA ACQUISITION SYSTEM
5.1
General System Description
The basic purpose of the data acquisition system was to
automatically acquire and record in digital form the output signals
derived from the air monitoring instruments, meteorological sensors
and manual data.
The data acquisition system consists basically of
the signal conditioning circuitry, on-line digital and analog
recording systems and power supply units.
The off-line data processing
was an important consideration in nearly all aspects of the design of
the data acquisition system.
A block diagram illustrating the functional relationships between
the various subsystems which comprise the data acquisition system and a
photo of the data acquisition system are shown in Figures 5.1 and 5.2.
The system was so designed that data channels could be added or deleted
without disturbing the digital recording system.
The data was sampled
in sequence once every 5 minutes and required approximately 12 seconds
for a complete scan.
Manual data such as instrument mode or status were introduced into
the system via the manual data entry channels.
By utilizing codes the
status or operational mode information was placed in the respective
channels and utilized in the data processing phase to indicate the
status of the respective sensors for each scan.
5.2
Automatic Calibration Technique
When evaluating a large number of air monitoring analyzers
simultaneously, it is highly desirable to employ an automatic calibration
system.
The manual data entry modes shown in Table 5.1 were used to
20
-------
[-- -- --
N
t-'
GAS SENSORS
SENSOR SENSOR
MODE OUTPUT-
Ll}-- -.
([L---- ---- --- - ---- - .
:---.
I
I
1
I I I
I i
ID---Q)~-- -.:
CALIBRATION
MANIFOLD
MODE
lJJ
[4J
SENSOR
COUPLER
~
,
lID
~
_O_UU_=:::=--: I
I
..!
i
i
---~I
I
I
IJ}---------
SYSTEM
STATE
(])
-----
ANALOG SIGNALS
DIGITAL SIGNALS
-_._.__.~. --- -
_.__._..-.-.....~
MODE SWITCHES
DATA INPUTS FIGURE 5.1
I
--..--...
CONTROL
DIGITAL
CLOCK
--=-~-I
-.--
.
.
.
---- -----
~-'---'---
-_..._-- -
SCANNER
AID
CONVERTER I
I
FORMAT -
CONTROL
t-
DATA
STORAGE
DIG IT AL
INCREMENTAL
MAGNET! C
TAPE
RECORDER
DIGITAL
PRI NTER
--
ANALOG
RECORDER
._~
FUNCTIONAL DIAGRAM OF DATA ACQUISITION SYSTEM
.--'- OFF-LINE
0.' DATA
PROCESSING
-------
Di gita 1
Clock
AID
Converter
Scanner
Tape Format
Control
Magnetic
Tape Unit
Power Monitor
Manual Data Entry
Unit for Sys tern
State and Calibratior
Manifold Data
Signal Conditioner
Unit
-DC Power Supplies
---Battery-Back-up
Unit
Figure 5.2 Data Acquisition System
22
-------
indicate the different phases of calibration such as stabilizing, zero
averaging and multi-point averaging.
The concentration levels were set
to the appropriate calibration values and simultaneously placed in the
respective calibration channels and utilized in data processing to
determine a best fit calibration curve for both linear and non-linear
instrument response.
TABLE 5.1
INSTRUMENT OPERATIONAL MODES
Output
Symbol
Mode
Switch
Setting
Operating Condition
o
Measure - -- Valid Ambient Data
C
1
Calibration - Stabilizing
A
2
Calibration - Zero Averaging
B
3
Calibration - Multi-point Averaging
T
4
Routine Test Procedures
x
5
Offline - - - Not Set-up or Available
Q
6
Awaiting Repair
R
7
Repair
L
8
Awaiting Maintenance
M
9
Maintenance
99999
Data Not Available
23
-------
A typical stripchart recording of the calibration technique is
shown in Figure 5.3 and can be used to demonstrate the calibration
procedure.
Looking at the bottom of the stripchart recording the
calibration is begun by changing the operational mode switch from
"0" position to "1" position and introducing zero air into the ozone
calibration manifold.
Mode 1 is maintained while the instrument
response is reaching equilibrium.
The mode switch is now set to
Mode 2 to indicate that the data is valid for determining V , the
o
instrument output voltage for zero air.
The instrument is returned
to Mode 1 completing the zero calibration.
In the meantime, an ozone
concentration of 0.055 ppm has been introduced into the calibration
manifold.
The voltage of the manual data entry channel for ozone is
adjusted to read 0.055 volts using a 10-turn potentiometer and a
digital voltmeter.
After the analyzer reaches equilibrium the mode
switch is set to "3" to indicate that the data is valid for determining
VI in the transfer function described in Section 6.1 corresponding to
Yl = 0.055 ppm.
After several scans at this concentration level the
mode switch is returned to position "1".
These valves establish one
calibration point.
The same procedure is repeated for concentrations
of 0.097, 0.130, and 0.170 ppm of ozone and the analyzer is returned
to the ambient air manifold.
During the data processing this portion
of the raw data was used to establish a new transfer function and to
eliminate zero and span adjustments to fit B given voltage versus
concentration response curve.
Analyzer zero and span adjustments were
made if the intercept (zero-level) or a slope of the transfer function
changed by approximately 20 percent from the original transfer function.
A computer printout demonstrating the automatic calibration procedure is
shown in Figure 5.4.
24
-------
Recorder Scale
o
1
2
3
4
5
6
7
8
o
r-l==~- ----------- - - - _A:.'1B_I~N!_A..I~ -- J
3
~- - - - ----- --~~~ ~- --- _~'17.9_P!~-_.J
------------
3
-1- -- - - - - -- -=-:. -=-- -=-- - - - - - - - - - - - - ~. ':3_0 -P!:: - - J
---------
3
_1= = = = -=: :: -::_-- - - - - - - - - - - - - - - - - - - - ~. ~~7 _P!~ - - J
3
-1-= ~ ~ ~ - - - -- - - - - - - - - - - - - - - -- - -- - - Q.. Q~ - P.!".! -- J
2
1
----
- - -' - - - - - - - - - - - - - - - - - - - - - - - - - - ~E~Q. ~I_R - - - j
t TIME
CHART SPEED 2 IN/HR
o
MODE SWITCH
SETTING
AMBIENT AIR
FIGURE 5.3.
Automatic Calibration Procedure Showing Mode Switch Settings
25
9
10
t
-------
PAGe: 1 t1:JP i Lt 'IAN L:cCA 01 0"1 '::"'. LOUIS 12 DEC 1971
*.ODO~O*O*t~*aoau OZOI\i: (PPM) ut~aooa*noabaoG~oo '"' a (", ~~. ,,. '" .::. ,. ".:"; ,:. !",,.w Ux I UAtH (PPM) 0*0*00000000'00*
TIM;: (ADJ) (ADJ)
(C5;) CHEMI COLQR COULl AVG COLOR COULl
lOGO .JOOC I Stabilizing .003C .OOOC 99.999 99.999 99.999
1005 -.000<: .003C O.OOOC 99.999 99.999 9 .013 .018 99.999 99.999
1115 .01< .021 .013 .017 99.999 99.999
1120 .01;; .020 .017 .016 99.999 99.999
1125 .U07 .019 .011 .015 99.999 99.999
113~ .007 .017 .009 .013 99.999 99.999
1135 .001> .017 .010 .014 99.999 99.999
1140 .007 .017 .011 .014 99.999 99.999
1145 .007 .018 .011 .014 99.999 99.999
1150 .009 .018 .012 .015 99.999 99.999
1155 .01U .0;:>3 .013 .018 99.999 99.999
N
0-
(oUeti;. 'lJITROGEN UIOXIDE UU,i-i;' 0 OXIDES or NITROGEN 0 *,"-" * '1', 0 .:;.**** 0* it 0 NITRIC OXIDE 0000000000000000
TIME (PPM) (f'PM) (PPM)
(CST> COUL iJV AVG NOX NOX-NO UV CHEMl CHEM2 CHEM3 AVG
1000 .025 99.999X .U;>5 .037 .022 99.990x .010 .015 99.999X .013
1005 .027 99.999X .027 .039 .025 9'J.9<;9x .010 .014 99.999X .012
1010 .028 99.999X .078 .044 .037 99.999X .004 .012 99.999X .008
1015 .030 99.999X .030 .048 .02!! 99.9<;
-------
6.0
COMPUTER PROCESSING OF FIELD DATA
6.1
General Data Processing Programs
Field data can be processed by computer either by real time
monitoring of the instrument output or by the method of temporarily
storing the data on magnetic tape and later processing the tapes.
In
this program, data stored on magnetic tapes were received weekly from
the mobile laboratory in the form of digital voltages.
The flow diagram
in Figure 6.1 describes the treatment of the data from the time they were
received on magnetic tape reels until they were printed in the various
useful forms.
The calibration data for each instrument were programmed as a
n
transfer equation [y = M(V-V ) or y = M(V-V ) ] to convert the voltages
o 0
to appropriate physical units.
The current calibration curves are
automatically updated in this program when the calibration modes are
switched by the operator.
The five-minute data with respective manual
entry operational modes and hourly averages are printed out with two
hours of data per page.
6.2
Data Output
Average values, frequency distributions, and maximum hourly
averages per day are calculated for all data output from Program 6.6.
The diurnal averages and standard deviations for each analyzer were
calculated from the S-minute data output.
These diurnal averages for
each sensor were plotted against time with the standard deviation and
case count included on each plot.
27
-------
Raw voi-;~~~' [voi~~~es- --
Dump ,---~ / by channell
P:~?-~~i-~ ._~J L-.!!intout-
'VI
VOlta~
Pari ty
Errors
Deleted
Card
Input
~->
j
>
Copy
Program
6.2
,
Card >l Edit
Input Program <
6.3
I
I
\V .~
/Card Input
I Calibration
Parameters
I
I
\J!
~ I Tr-~~~-~-~; .--
~1 Equat1.on
I Program 6.4
---- ---\F ------1
I
I
..h._"- .~---- ,-.- --.
.,"
r/ Card
Input
( -~)
\ '
.----."
FIGURE 6.1 (a).
C~~:ut J
5-min.
Data in
Physical
Units
Printout
»
Card Output
Calibration
Parameters
L----.-----
I . ----------------.---- 'I
I 5-IIlJ.n. Lagged I
~ I Data and Hourly I
I Averages Pr1.ntout .
-.... .._.~_.. ---.-----....-.----.-----..--J
.-.
( B \\
. I
" /
"--- -- /
Data Processing Flow Chart
\V
..~~---- ---"-1
i Lag Time i
I I Correction ~
I I.. ~-~~;111_--~_.6!
~- --~
. . 5-min." Hourly
Lagged Averages -
Data ~
28
C:)
-------
~
~\
\. A )
Diurnal
Averaging
Program 6.10
Plots of
Diurnal
Averages
}1axi mum
Hourly Averages
Program 6.11
Card
Input
Printout of
Maximum Aver- j
ages per day
Averaging Program
and Frequency Dis-
tribution Subroutine
Program 6.8
~
3-hour Avg.
and Freq.
Dist. Print-
out
Card
Input
W
j6-hour Avg.
and Freq.
Dist. Print-
. out
12-hour Avg.
and Freq.
Dist. Print-
out
~
Diurnal Averages
of Events S02
£ Ozone
Program 6.12
P lots of
Diurnal
Averages
t
~
.._--.-.".-~. '.-.r.
24-hour Avg.
and Freq.
Dist. Print-
out
Correlation
of Instruments
Program 6.13
Slope, Intercept
Correlation
Coefficient by
Pairs of Instruments
Printouts
~
Statistical
Summary of Cali-
bration Parameter
Program 6.14
,Statistical
[Summary
LPrintout (M)
--.--.--
./
Card
Input
! Statistical
I Summary
Printout (B)
Slope, Intercept,
Correlation
Coefficient by
Instrument
FIGURE 6.1 (b).
Data Processing Flow Chart
29
t
Regression Analysis
of Instrument
Calibration Data
Program 6.15
Calibration
Curve Plots
with Confidence
Limits
-------
Correlation of instruments measuring the same pollutants were
performed using the output of Program 6.8 for all hours in which
sensor pairs had valia data.
In addition to the ambient air data
analysis and regression analysis, a statistical summary of all
instrument calibration data was performed.
The mean, standard
deviations, average drift per day, standard deviation of drift,
and confidence limits were calculated using the output from
Program 6.4.
30
-------
7.0
INSTRUMENT EVALUATION
7.1
Performance Characteristics
A general set of performance criteria was established in the
earlier report of the Los Angeles Study [1].
These criteria were based
on instrument characteristics that are independent of the type of instru-
ment being evaluated or the application in which it was to be used.
Following this philosophy the evaluation program used performance data
of one or more instruments operating under realistic field conditions
to assess the level of performance in each of the important performance
areas.
Instrument performance characteristics fall into four major groups.
These are physical characteristics, measured responses to standard test
procedures, field data quality, and functional capacity.
Physical
characteristics are usually obvious and worthy of only minimum analysis.
Response times of the instruments measured using standard test procedures
pose no significant problems in determination of values for comparison
with suggested performance specifications [19].
However, lengthy response
times require substantial time to obtain good multi-point calibrations.
Field data quality was concerned with calibration requirements, stability,
accuracy, and limits of detection.
Performance in the area of functional
capability was concerned primarily with instrument failure.
The most
obvious negative functional characteristics are instrument downtime and
maintenance costs.
7.2
Calibration Stability
A summary of calibration data for a few selected performance
factors is shown in Table 7.1
The selected data are typical for each
31
-------
instrument during its best 90 day period of performance during the
evaluation study.
The minimum detectable concentration is estimated
from the standard deviations of the intercept values of the calibration
curve (transfer function).
The standard deviation about the higher
concentrations is equal to the minimum detectable change at the point
of measurement on a long-term basis (approximately 65% confidence).
On
a short-term basis the variability would be expected to be much less and
therefore a smaller minimum detectable change for an equivalent confidence
level.
This broadening effect with time is typical of stability estimates.
Factors that are used to assess the minimum detectable change can thus be
seen to depend upon the testing conditions.
Calibration data for the selected period were used to determine a
single linear regression estimate of the transfer function and correlation
coefficient for each instrument in Table 7.1.
A higher correlation
coefficient is indicative of greater long term stability of the analyzer.
Many performance factors such as response time, interferences, maintenance
time and physical parameters were described in earlier reports [1,2,3] and
are worthy of analysis in choosing the proper instrument.
7.3
Operational Summary
Operational data are summarized in Table 7.2 for each analyzer
evaluated during this program.
The operational time is divided into the
following categories:
(1) ambient monitoring time, (2) calibration time,
and (3) downtime.
The ambient monitoring time category includes the
percent of time that the instrument was available for monitoring.
The
calibration period includes only the percentage of time required for
32
-------
calibrating the analyzer.
The downtime data include repair, routine
maintenance, awaiting maintenance, and awaiting repair.
The ozone/oxidant and sulfur dioxide analyzers group includes
8 instruments that were operational better than 93% of the evaluation
period.
Approximately one-half of the analyzers were operational 85%
of the total time tested.
33
-------
TABLE 7.1 Sunnnary of Long Term Calibration Data
Minimum
Number of Detectable Average Average ,
Calibration Concentration Zero Drift Span Drift CorreIa tij
Instrument Pollutant Points (ppm) (ppm/day) (%/day) Coefficie
,
Bendix Env. Sci. 03 23 0.0066 0.0001 0.072 0.882
Bendix Process 03 105 0.0003 -0.0000 -0.128 0.998
RTI (Solid Phase) 03 52 0.0004 0.0000 -0.074 0.992
Dasibi 03 21 0.0011 -0.0001 -1. 749 0.967
Beckman 0 67 0.0122 -0.0001 0.592 0.963
x
Mast 0 103 0.0003 0.0000 -0.129 0.993
x
Technicon 0 74 0.0118 -0.0004 -0.552 0.947
x
Beckman N02 74 0.0131 0.0000 0.518 0.978
Technicon N02 6 0.0192 0.993
Thermo Electron N02 49 0.0101 0.0000 0.505 0.995
Aerochem NO 83 0.0042 -0.0001 0.083 0.998
Bedanan NO 38 0.1303 -0.0015 -0.066 0.824
Thermo Electron NO 73 0.0075 0.0000 0.565 0.990
Beckman S02 65 0.0108 0.0003 0.128 0.990
Leeds & Northrup S02 60 0.0114 -0.0002 0.269 0.957
Me1par S02 20 0.0047 -0.0006 0.398 0.969
Philips S02 46 0.0039 -0.0000 -0.050 0.994
Pollution Monitor S02 14 0.0244 0.0009 -0.781 0.988
Technicon S02 23 0.0084 -0.0001 -1. 620 0.983
Tracor S02 26 0.0097 0.0003 0.003 0.805
Technicon H2S 11 0.0047 0.0003 -2.320
Tracor H2S 16 0.0033 0.0007 0.000 0.958
'Beckman THC 35 0.1357 0.0067 -0.006 0.999
Power Design THC 15 0.1318 -0.0000 -0.043 0.999
Beckman CO 36 0.1275 0.0098 -0.045 0.999
Mine Safety Appliances CO 26 0.786 -0.0124 3.033 0.852
Beckman CH4 35 0.0077 0.0004 0.126 0.998
34
-------
Bendix Env. Sci. 03
Bendix Process 03
RTI (Sclid Phase) 03
Dasibi 03
Mast 0
x
Technicon °
~, .~.,X-
. -'"'7 .
". -- ~ ~,"
Beckman °
': X
Beckman N02 -.-- -,
Techn~c.on N02
Thermo Elect~on N02
Aerochem NO
. "_."
Beckman NO
Thermo Electron NO
Be ck..'!lan S 02
Leeds & Northr~I>:.,S02--
Melpar S02
Philips S02
Pollution Moni.~?t: :S02~
Technico? S0:2: .
Tracor S02 '
Technicon H2S
Tracor H2S
Beckman THC
Power Design THC
Beckman CO
Mine Safety Appliances CO
Beckman CH4
TABLE 7. 2
Operational Summary
NUtllber of
Days Tested
Ambient
Monitoring
Time (%)
94 94.7
74>.:,_~ ~', 94.3:.; :'-'::c::-,:;'
185 94..1.
32;, ' 9:8.5 ,..
.., . .. -- , ,
::-:2:56 - '- -,"- '- 94'.2
256 ... 87;5 '
65 90.:0.
154 81..1.
90 78.4
65 82.1
146 82.8-
84 41.:5.
65 "- 83.6
95 94.9-
184 93.5
260 ' 93.5 :
260 86.0,,' , '
124 57.3
90 74.4
205 67.0
90 47.3
199 67.0
148 72.0
139 85.0
148 72.0
124 82.5
148 72.0
35
Calibration
Time (%)
2.9
~~'2";'4 '-=:;
2.7
i~4"":"Y:
,. ~ '\
'J
3.3
4. s: - '
5.5'
5.9-' '
3.6
6.4:'
2.9;c
33.9": J
6.9:;')
3.6":'
2.6':
3. 0 'd~
2. 4C":'. .
2.8 ,. . C
4.0
2.7
1.9
2.7
2.1
1.0
2.1
3.7
2.1
Downtime
(%)
2.4
3.3
3.2
O.L
2.5
8.0
4.5
13.0-
18.0
12.5-- .
14.3'
24.6" -
9.5 .
1. 5 .
3. 9 ~ .
3.5 -
11. 6--'
39.9
21.6
30.3
49.2
30.3
25.9
14.0
25.9
13.8
25.9
-------
7.4
Comparison of NOZ Measurements by Chemiluminescent, Coulometric,
Saltzman, and Jacobs-Hochheiser Methods
During the latter part of Phase II of the St. Louis Study, a
study was conducted to compare the classical colorimetric procedures to
measure NOZ with chemiluminescent and coulometric N02 instruments.
Included in this study was Beckman's coulometric N02 analyzer, Technicon's
colorimetric analyzer, Thermo Electron's chemiluminescent NOZ analyzer
(NOx-NO), and the Jacobs-Hochheiser 24-hour integrated method.
This study
is the first to compare the chemiluminescent and coulometric methods with
the Jacobs-Hochheiser reference method.
Eighteen 24-hr Jacobs-Hochheiser samples were collected at 3-day
intervals during the period October 14, 1971 to December 17, 1971.
Table 7.11 includes the 24-hr average data for the instruments on the
days when the reference method (Jacobs-Hochheiser) was run.
Table 7.12
shows the correlation coefficients between the instruments and the Jacobs-
Hochheiser reference method.
The average of the absolute values for each
instrument is also shown.
The average concentration of NOZ as measured by the Jacobs-Hochheiser
procedure for eight days when Jacobs-Hochheiser, chemiluminescent, coulometric,
and colorimetric data were available, was 0.051 ppm.
Average values obtained
with the chemiluminescent, coulometric, and colorimetric (Saltzman) monitors
were 0.046, 0.033, and 0.047 ppm, respectively.
An agreement of better
than 90% of absolute concentration of N02 was obtained among the Jacobs-
Hochheiser, Saltzman, and chemiluminescent methods at this sampling site,
when the mean concentration of N02 for a 24-hr period was below 0.1 ppm.
36
-------
DATE
10-14-71A
10-18- 71 A
10-21-71 A
10-25-71A
10-28-71A
1i-1-71A
11-4-71 A
11-9-71
11-12-71
11-16-71
11-19-71
11-23-71
11-26-71
11-30-71
12- 3- 71
12-7-71
12-10-71
12-14-71
12-17-71
TABLE 7.11.
Nitrogen Dioxide Method Comparison Study
BECKHAN
N02
(PPH)
J-H*
METHOD
(PPM)
TECHNICON
SALTZ:r-fAL'1**
(PPM)
THERMO-ELECTRON
NOx -NO
(PPM)
0.056
0.021
0.060
0.038
0.055
0.052
0.036
0.023B
0.061 B
0.035
0.041
0.055
0.021
0.031B
0.023
0.066
0.059
0.012
0.047
0.046
0.023
0.052B
0.052
0.036
0.055
0.042
0.082
0.079
0.031
0.064
0.040
0.038
0.068
0.069
0.034
0.048
0.038
0.085
0.090
0.006
0.040
0.018
0.026B
0.023
0.021
0.027
0.021
0.027
0.020
0.032B
0.050
0.044
0.054
0.034
0.032
0.039
0.022
0.030
0.058
0.023
0.047
0.031
*
Jacobs-Hochheiser Method
**
Technicon Saltzman from St. Louis County Hunter Road Station
A24-hour period from 0900 hours on date given to 0900 hours next day
and all other data 0000-2400 hours on given date.
BSensor data available for more than 12 hours, but less than 24 hours.
37
-------
TABLE 7. 12. Correlation Coefficients and Average N02 Values
Correlation Average N02 Case
Coefficients (PPM) Count
Thermo Electron (NO -NO) (CHEM 2) 0.041
x
Beckman N02 (COUL) 0.945 0.038 9
Beckman N02 (COUL) 0.032
J-H* Method (COLOR) 0.911 0.047 14
Thermo Electron (NO -NO) (CHEM 2) 0.043
. x
Saltzman (COLOR) 0.894 0.047 9
Thermo Electron (NO -NO) (CHEM 2) 0.040
x
J-H* Method (COLOR) 0.849 0.049 11
. * (COLOR) 0.053
J-H Method
Saltzman (COLOR) 0.823 0.045 11
Beckman N02 (COUL) 0.038
Saltzman (COLOR) 0.699 0 . 046 9
*J-H is Jacobs-Hochheiser Method
38
-------
7.5
Comparison of 802 Measurements by Coulometry, Flame
Photometry, and Hodified West-Gaeke Procedure
Twenty-four hour integrated bubblers were run at 3-day intervals
and analyzed using the Modified West-Gaeke reference procedure during
the period October 14, 1971 to December 17, 1971.
These measurements were
compared with measurements obtained with the Philips coulometric and
Melpar flame photometric analyzers.
Table 7.13 is a tabulation of the
correlation coefficients of the 802 monitors with the 24-hour West-Gaeke
method.
The average value of the 24-hour measurements for each analyzer
is also included.
The coulometric analyzer had the best correlation
with the West Gaeke procedure with a value of 0.933.
The average concen-
tration of 802 as measured by the West-Gaeke procedure was 0.026 ppm,
while values obtained with the coulometric and flame photometric analyzers
were 0.016 and 0.006 ppm, respectively.
TABLE 7.13.
Correlation Coefficients and Average Values
for 802 Principles Tested
Correlation
Coefficient
Average 802
(PPH)
Instrument
Melpar 802 (FPD)
Philips 802 (Coul)
Melpar 802 (FPD)
W-G* (Color)
0.830
0.006
0.016
0.874
0.007
0.026
Philips 802 (Coul)
W-G* (Color)
0.933
0.016
0.026
W-G* (Color) III
W-G* (Color) //2
0.978
0.029
0.029
*West-Gaeke Procedure
39
-------
8.0
AIR POLLUTION SUMMARY
8.1
Los Angeles Study [September 4 to December 1, 1970]
The ambient air monitoring that was performed at the Los
Angeles site in the course of evaluating each instrument's performance
indicated several characteristics of this environment.
Diurnal averages,
frequency distributions, and other pertinent data for each parameter
are presented in the Interim Report for the Los Angeles Study [1].
A. Ozone
The ozone concentration was relatively high during the
daylight hours averaging 0.033 ppm from 0600 to 1800 with maximum
hourly averages above 0.1 ppm between 1200 and 1500 hours.
Occasionally,
nighttime ozone was observed.
The ozone standard of 0.08 ppm maximum
hourly average was exceeded 151 times during the 90 day evaluation period.
B.
Oxidant
The primary oxidant was ozone.
On many occasions ozone concentrations
were actually higher than indicated oxidant values, due to S02 interference
with oxidant readings.
c.
Nitrogen Dioxide
Sustained levels of N02 were observed with hourly averages above
0.1 ppm about 33% of the time.
The twenty-four hour average for N02 exceeded
0.05 ppm fifty days during the 90 day evaluation period.
D.
Sulfur Dioxide
Sulfur dioxide levels were relatively low with a daylight
average of 0.011 ppm.
Hourly averages frequently rose above 0.030 ppm
and on four occasions, real time peaks were between 0.1 and 0.15 ppm.
Other sulfur compounds such as H2S and mercaptans were generally below
the minimum detectable level of the instrument.
40
-------
8.2
St. Louis Study:
Phase I (May 13 to August 17, 1971)
The availability of more than one instrument measuring the
same environment provides the option of selectively screening the
data in a manner that is designed to improve the estimate of air
quality.
Data on air quality determined during the period of time
May 13 to August 17, 1971 are summarized here.
Diurnal averages,
frequency distributions, plots of air pollution events, and other
pertinent information are included in the Interim Report for the
St. Louis Study:
Phase I [2].
A.
Ozone
Ozone concentrations are normally about 0.01 ppm at night
and rise to approximately 0.06 ppm in the early afternoon.
The
average daily ozone concentration was approximately 0.030 ppm.
During the daylight hours the ozone standard of 0.08 ppm maximum
hourly average was exceeded approximately 15 percent of the time.
B.
Oxidant/Nitrogen Dioxide
The primary oxidant in the St. Louis atmosphere was ozone,
although atmospheric gases such as oxides of nitrogen contribute
to the response of the oxidant instruments.
The average daily
concentration of NO was 0.010 ppm with N02 being 0.018 ppm.
c.
Sulfur Dioxide
The average S02 level for the evaluation period was 0.010
ppm with peak hourly average concentration frequently in excess of
0.05 ppm.
An inverse relationship between S02 and 03 was observed.
41
-------
D.
Carbon Monoxide
Data on CO were considered to be less reliable than those for
502 and 03.
The average daily concentration was approximately 1 ppm.
E.
Hydrocarbons
Total hydrocarbon concentration averaged 2 ppm during this
period of time with the average methane concentration being 1.7.
Non-
methane concentration averaged approximately 0.3 ppm.
42
-------
8.3
St. Louis Study:
Phase II (October 7 to December 20, 1971)
Data regarding the air quality at the evaluation site during
this period of time are summarized.
Diurnal averages, frequency distri-
but ions , plots of air pollution events, and other pertinent information
are included in the Interim Report for the St. Louis Study:
Phase
II [3].
A.
Ozone/Oxidant
Typical ozone levels observed at the evaluation site during
the afternoon were 0.04, 0.03, and 0.01 ppm for the months of October,
November, and December, respectively.
The nighttime ozone average
for this period was 0.005 ppm.
Overall average was approximately 0.01
ppm and constituted approximately 50% of total oxidant.
The remaining
50% of total oxidant can not be attributed to oxides of nitrogen
interference, since oxidant data were corrected for these interferences.
B.
Nitric Oxide
Hourly averages of NO above 0.25 ppm occur almost every day
and values of 0.50 ppm are frequent.
The average for this period was
0.05 ppm.
c.
Nitrogen Dioxide
Hourly averages of N02 above 0.05 ppm occur almost every day
and concentrations of 0.08 ppm are frequent.
The average for this
period was 0.032 ppm.
D.
Sulfur Dioxide
Typical S02 levels observed at the evaluation site at mid-
day were 0.02, 0.03, and 0.042 ppm for the months of October, November,
43
-------
and December, respectively.
Overall average for the period was approxi-
mately 0.01 ppm.
No measureable concentration of H2S was observed during
this period.
E.
Carbon Monoxide
Hourly averages of CO above 4 ppm occur alreost every day and
values of 5-6 ppm are frequent.
The average for this period was 1 ppm.
F.
Hydrocarbons
Total hydrocarbons and methane averages for this period were'
2.2 and 1.7 ppm.
The daily average concentration was approximately
0.45 ppm.
The average non-methane hydrocarbon concentration between
0600-0900 hours was 0.80 ppm.
44
-------
9.0
SUMMARY OF FINDINGS
This field evaluation program has provided valuable information
on instrument evaluation procedures, instrument performance, the effects
of interferences, and the characteristics of the local environment.
It
has shown that the use of an environmentally controlled mobile laboratory,
with automatic data acquisition and mode switch inputs that describe the
operational status of each instrument and magnetic tape storage of data
calibration information in computer compatible format, is a rapid and
economical approach to a large scale instrument evaluation program.
Note-
worthy observations from each of the three studies are presented in the
following paragraphs:
A)
Los Angeles Study
1.
Coulometric and conductimetric 802 measurements were
generally higher than values obtained with the colorimetric
West-Gaeke, flame photometric, and gas chromatographic-
flame photometric analyzers.
2.
In the oxidant category, the gas and solid phase
chemiluminescent and the coulometric instruments exhibited
excellent long term stability with a standard deviation
near zero of about 0.001 ppm and a standard deviation about
a single average calibration curve of less than 8 percent.
3.
The following instruments were operational better than
96% of the time:
gas phase 03' solid phase 03' flame
photometric S02' and gas chromatographic-flame photo-
metric S02.
45
-------
B)
St. Louis:
Phase I
1.
The Philips and Beckman Cou1ometric S02 instruments
exhibited excellent long term zero and span stability
with a standard deviation near zero of about 0.010 ppm
and had a standard deviation about a single calibration
curve of less than 5%.
2.
Electronic and flow problems experienced during this
study seriously impaired the Melpar flame photometric
and Tracor gas chromatographic-flame photometric
instruments.
3.
The following ozone-oxidant instruments exhibited
excellent long term zero and span stability with a
standard deviation near zero of less than 0.010 ppm
and a standard deviation about a single average
calibration curve of less than 8 percent; Bendix gas
phase 03' RTI solid phase 03' and Mast cou1ometric Ox.
4.
Specific ozone measurements techniques are more reliable
than adjusted ozone values obtained from non-specific
total oxidants measurments that have been corrected for
oxide of nitrogen and other interferences.
5.
The Aerochem chemiluminescent instrument exhibited
excellent long term zero and span stability with a standard
deviation near zero of 0.011 ppm and a standard deviation
about a single average calibration curve of 5 percent.
The
chemiluminescent technique is a major improvement in the
measurement of nitric oxide.
46
-------
C)
6.
The Beckman gas chromatographic-flame ionization
analyzer required several field modifications before
an acceptable level of performance was attained near
the end of the study.
7.
The following instruments were operational 99.5 percent
of the time:
Aerochem (NO), RTI (03)' Melpar (502)' and
Mast (0 ).
x
Calibration during this study accounted for
approximately 4 percent of this time.
5t. Louis:
Phase II
1.
The coulometric 502 instrument exhibited excellent long
term zero and span stability with a standard deviation
of zero level of less than 0.005 ppm and a standard
deviation about a single average calibration curve of
less than 3 percent.
2.
For this study 502 measurements obtained with a coulometric,
a flame photometric, and a gas chromatographic-flame
photometric analyzer were compared with measurements
made with the reference method (modified West-Gaeke
procedure).
In general these analyzers displayed similar
diurnal patterns; however, only the coulometric analyzer
has a correlation coefficient with the West-Gaeke
procedure of better than 0.933.
3.
The following ozone-oxidant instruments exhibited good
long term stability during the 75-day period with a
standard deviation of zero level of less than 0.002 ppm
47
-------
and a standard deviation of less than 7 percent about
a single average calibration curve:
(1) chemiluminescent
03 and (Z) coulometric Ox.
4.
The chemiluminescent method is a major improvement in
measuring nitric oxide.
Good long term zero and span
stability and excellent correlation were observed for
NO measurements with both chemiluminescent analyzers.
5.
Good correlation was obtained between the chemiluminescent
and coulometric NOZ measurements.
The coulometric analyzer,
however, recorded concentrations of NOZ approximately 30
percent lower than the chemiluminescent analyzer.
6.
This study was the first to compare chemiluminescent,
colorimetric, and coulometric NOZ analyzers with the
reference method for measuring NOZ (Jacobs-Hochheiser
Method).
The average concentration of NOZ for eight sets
of data as measured by the Jacobs-Hochheiser procedure
was 0.051 ppm, while values obtained with the chemiluminescent,
coulometric and colorimetric (Saltzman) monitors were 0.046,
0.033, and 0.047 ppm, respectively.
An agreement of better
than 90% of absolute concentration of NOZ was obtained among
the Jacobs-Hochheiser, Saltzman colorimetric, and chemiluminescent
methods, at this monitoring site.
7.
The average non-methane hydrocarbon concentration between
0600-0900 hours was 0.8 ppm.
The standard for non-methane
hydrocarbons is 0.Z4 ppm and was exceeded 75% of the time.
48
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8.
Acceptable measurements for carbon monoxide, methane,
and total hydrocarbons can be obtained with the gas
chromatographic-flame ionization analyzer, provided
the proper purity of combustion and calibration gases
can be maintained.
9.
The following instruments were operational 98 percent
(1) chemiluminescent 03' (2) coulometric
Ox' and (3) coulometric 502.
of the time:
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10.0
RECOMMENDATIONS
During the three phases of the evaluation program covering almost
two years in time and about nine months of actual field testing,
instrumentation based on new concepts in air pollution monitoring became
commercially available and their performance was evaluated under field
conditions.
Most noteworthy of the new instruments were the chemiluminescent
analyzers for measuring 03' NO, NOZ' and NOx'
technique for measuring THC, CH4' and CO and the gas chromatographic-
In addition, the GC-FID
flame photometric technique for measuring HZS and 802 appear to be
satisfactory; however, improvements are needed to decrease maintenance
requirements.
Recommendations for future instrument evaluation programs are as
follows:
1.
Standardized test protocol should be developed for determining
performance characteristics, such as drift, accuracy, inter-
ference equivalent, etc.
2.
Evaluation studies should include more than one model of any
instrument for a more accurate assessment of its performance.
3.
The duration of the evaluation period should be of sufficient
length to identify weaknesses in the monitoring principle or
design and to make appropriate adjustment.
4.
On-line data processing would facilitate early identification
of degradation in instrument performance.
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11.0
REFERENCES
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