United Slates
Environmental Protection
Agency
Oilico ol Research and
Development
Washington, DC 20460
Novambar 1992
&EPA Determination of the
Strong Acidity of
Atmospheric Fine-
Particles (<2.5 urn)
Using Annular Denuder
Technology
Standard Method
Enhanced Method
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TECHNICAL REPORT DATA
1. REPORT NO.
EPA/600/R-93/037
2.
3 PB93- 1 7823«4
4. TITLE AND SUBTITLE
Determination of the Strong Acidity of Atmospheric
Fine Particles (-<2.5 fm) Using Annular Denuder
Technology
5.REPORT DATE
November 1992
6.PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Larry J. Purdue
6. PERFORMING ORGANIZATION REPORT
NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Atmospheric Research and Exposure Assessment
Laboratory
Human Exposure and Field Research Division (MD 55)
Research Triangle Park, NC 27711
10.PROGRAM ELEMENT NO.
A101/C/A/66 j
11. CONTRACT/GRANT NO.
68-DO-0123, WA 1-49
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Research and Development
Atmospheric Research and Exposure Assessment
Laboratory
Research Triangle Park, NC 27711
13.TYPE OF REPORT AND PERIOD COVERED
Methods Manual
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY notes
16. ABSTRACT
This report is a standardized methodology description for the determination of
strong acidity of fine particles {less than 2.5 microns) in ambient air using
annular denuder technology. This methodology description includes two
parts: Part A - Standard Method and Part 8 - Enhanced Method. The unique features
of the annular denuder method which separates it from other established monitoring
methods are elimination of sampling artifacts due to interaction between the
collected gases and particles, and preservation of the samples for subsequent
analysis. The Standard Method utilizes a denuder for removing ammonia and a filter
assembly for determination of atmospheric strong acidity fine particle aerosols in
ambient air, but does not account for potential interferences from nitric acid,
ammonium nitrate aerosol or other ammonium salts which might bias the acidity
measurement. The Enhanced Method adds an additional denuder upstream of the filter
assembly to selectively remove acid gases (nitric acid vapors, nitrous acid and
sulfur dioxide) from the gas stream prior to filtration. In addition, backup nylon
and citric acid impregnated filters are used to correct for biases due to the
dissociation of ammonium nitrate aerosol. The techniques, procedures, equipment,
and other specifications comprising this method are derived and composited from
those actually used by the contributing research organizations and thereby known to
be serviceable and effective. At this Btage, this method is a unified, consensus,
tentative method intended for further application and testing. The method is
presented in document control format to facilitate appropriate changes as
experience is gained with its use.
3 7. KEY WORDS AND DOCUMENT ANALYSIS
i DESCRIPTORS
b. IDENTIFIERS/ OPEN ENDED
TERMS
c.COSATI
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
21.NO. OF PAGES
134
20. SECURITY CLASS (This Page)
22. PRICE
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EPA/600/R-93/037
November 1992
DETERMINATION OF THE STRONG
ACIDITY OF ATMOSPHERIC FINE-PARTICLES
(<2.5 fjm) USING ANNULAR
DENUDER TECHNOLOGY
• STANDARD METHOD
~ ENHANCED METHOD
Ł n \
\ S2E2J
%>¦ an
PRO^
EPA Project Manager
Larry J. Purdue
Atmospheric Research and Exposure Assessment Laboratory
Office of Research, and Development
TJ. S. Environmental Protection Agency
Research Triangle Park, NC 2771 1
Revision 0
November 1992
-------
DISCLAIMER
The information in this document has been funded wholly or in
part by the U.S. Environmental Protection Agency under Contract 68-
DO-0123 to Midwest Research Institute. It has been subjected to
the Agency's peer and administrative review, and has been approved
for publication as an EPA document. It is being distributed solely
for evaluation of its technical content and accuracy. Mention of
trade names or commercial products does not constitute endorsement
or recommendation for use.
ACKNOWLEDGEMENT
This manual was prepared for the U.S. Environmental Protection
Agency by Midwest Research Institute (MRI) Cary, North Carolina.
Mr. William T. "Jerry" Winberry, Jr. was the principle author for
MRI. Mr. Larry J. Purdue, USEPA, Atmospheric Research and Exposure
Assessment Laboratory (AREAL) served as EPA Project Manager. Mr.
Tom Ellestad and Mr. Frank McElroy, USEPA, AREAL, served as project
advisors.
Acknowledgement is given to Dr. Ivo Alligrini, Director and
the initial developer of this methodology at the Laboratory for
Atmospheric Pollution of C.N.R., Rome, Italy. We also acknowledge
the contributions of R.K. Stevens of USEPA, Dr. P. Koutrakis of
Harvard School of Public Health, Dr. J. Waldman of Robert Wood
Johnson Medical School and Dr. Joe Sickles of Research Triangle
Institute, for their insights and contributions to the development
of an improved version of the annular denuder system.
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FOREWORD
The Atmospheric Research and Exposure Assessment Laboratory (AREAL) in
Research Triangle Park, Ncrth Carolina, is one of three laboratories in the Office of
Modeling, Monitoring Systems, and Quality Assurance (OMMSQA). It conducts research
programs in the chemical, physical, and biological sciences designed to (I) characterize,
monitor, arid quantify the current status of ambient air quality and air pollutant exposure to
humans and ecosystems through both direct and indirect pathways, (2) develop and apply
mathematical models over broad spatial and temporal domains to interpolate between
measured environmental parameters and the transport and transformation of air pollutants and
to predict future changes, (3) report on trends, (4) determine scurce-receptor relationships,
(5) provide research support to program offices, (6) carry out long term multidisciplinary
research programs, and (7) collect, analyze and interpret (both numerically and visually) air
quality and other environmental and human exposure related data.
Recently, AREAL lias been given the responsibility by the Clean Air Scientific
Advisory Committee (CASAC) of obtaining information needed for scientific assessment of
the possible need for a fine particle standard for acid aerosols to protect human health. To
tills end, AREAL conducted a workshop in 1989 to determine and exchange views on the
various methods that have been and are being used to measure aerosol acidity. Based upon
the recommendations from that workshop, AREAL sponsored an Intercomparison Study at
EPA's RTP facility to quantify Ike performance of methods currently used in characterizing
aerosol acidity in epidemiology, studies to ensure comparability of measurements by different
groups. The participating groups were:
• Harvard School of Public Health,
• Robert Wood Johnson (RWJ) Medical School, and
• Research Triangle Institute
All three research teams used, variations of the annular denuder system (ADS) to
determine fine-particle strong acidity.
Based upon the findings of the Intercomparison Study, AREAL has developed this
standard methodology for determination of fme-paiticle strong acidity and to promote the
accurate determination and assessment of human exposure to strong acid aerosol acidity.
Gary J. Foley
Director
Atmospheric Research and Exposure Assessment Laboratory
Research Triangle Park, NC 27711
iii
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INTRODUCTION
Acid aerosols are found in the atmosphere as a result of atmospheric reaction of
emissions from a variety of fossil fuel combustion sources including power plants, industrial
and commercial facilities, hazardous waste storage and treatment facilities, etc. Awareness
of the effects of concentrations of acid aerosols on human health and property has been
documented over the past several years. The Clean Air Act Amendments of 1970 required
the U. S. Environmental Protection Agency (U. S. EPA) to develop uniform national
ambient air quality standards (NAAQS) for pollutants which were recognized as widespread
(emitted by numerous mobile and stationary sources) and which endangered public health and
welfare. Further, Section 109 of the Clean Air Act, as amended, requires EPA to
periodically review the NAAQS as well as the scientific information and data on which they
are based. New pollutants are identified for NAAQS development if the Administrator
concludes that they may reasonably be anticipated to endanger the public health and welfare.
To assist the Administrator in evaluating the need for new or revised NAAQS, the
Clean Air Act created the Clean Air Scientific Advisory Committee (CASAC). This
committee's mandate is to provide the Administrator with scientific advice and research
recommendations on critical areas of knowledge on new or revised NAAQSs. The Acid
Aerosol Subcommittee of CASAC identified a need for a coordinated acid aerosol research
program to assist the Agency in making recommendations on a new acid aerosol NAAQS.
The Subcommittee recommended a research program involving characterization and exposure
assessment, animal toxicity, human exposure research, and epidemiology. As documented in
the CASAC Report to the Administrator, the foundation for any research program and
potential air quality standard development is "...a measurement method, not only because the
standard itself must specify the method, but equally important, because before establishing a
standard the contaminant must be fully characterized and exposure measurements made to
correlate with health outcomes." The Atmospheric Research and Exposure Assessment
Laboratory (AREAL) was directed by CASAC of obtaining information needed for scientific
assessment of a possible fine particle standard for acid aerosols to protect human health.
In 1989, AREAL conducted a workshop to determine and exchange views on the
various methods that have been and are being used to measure aerosol acidity. It was held in
response to recommendations by CASAC to identify issues associated with the
characterization of aerosol acidity and acid aerosol measurement methods. The workshop
was structured to accomplish two principal objectives. The first was to identify appropriate
indicators and methodology for characterizing aerosol acidity. The second was to develop
ideas and recommendations for the evaluation of acid aerosol methods currently in use. The
workshop participants identified the development of an accurate, reliable, and interference-
free method as an important initial research objective.
They concluded that the most appropriate indicator of aerosol acidity is the fine
particle, strong acidity, i.e. the amount of strong acidity available in the fine particle
component of the atmospheric aerosol. The available hydrogen ion is measured, either by
titration or by pH, after extracting the aerosol in the size range below 2.5 /xm with an
iv
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aqueous solution of perchloric acid at a pH of approximately 4.00 (to prevent dissociation of
weak acids). This definition includes free hydrogen ion and hydrogen ion available from
either undissociated of weak ion available from either undissociated sulfuric acid or from
uncissociatec bisulfate ioc. Available hydrogen icn may be reported either as nanomcles of
hydrogen icn per cubic meter of air (nmcies/m-*) or as equivalent sulfuric acid in micrograms
per cubic meter of air (/xg/irP). It is recognized that ir. salts of partially neutralized sulfuric
acid or in concentrated sulfuric acid droplets some hydrogen ion may be tied up in the
bisulfate ion. However, it is assumed that this hydrogen ion would be available for reaction
after the particle impacted the surface of the lung.
In addition, the workshop participants considered procedures to evduate current acid
aerosol measurement methods and concluded that audit standards must be developed and
distributed to establish analytical accuracy and precision, and that laboratory and field tests
should be conducted to evaluate and compare acic aerosol sampling and analysis systems.
The primary objective for both laboratory and field evaluations should be to quantify the
performance of methods currently used in epidemiology studies to ensure comparability of
measurements by different groups.
In December 1989 and February 1990, Intercomparison Studies were held at the
AREAL facility in Research Triangle Park, NC to quantify the performance of methods
currently used in measuring aerosol acidity in epidemiology studies to ensure comparability
of measurements by different groups. The criterion for selecting the three participants for
the initial Pilot Intercomparison Study was that they represented denuder systems being used
in epidemiological field studies currently in progress or had developed a prototype sampler
under contract to EPA that the agency wanted evaluated. The three invited research groups,
Harvard School of Public Health, Robert Wood Johnson (RWJ) Medical School and Research
Triangle Institute (RTI), used variations of the annular denuder system (ADS) to determine
fine-particle strong acidity.
Based upon the findings of the Pilot Intercomparison Study, AHEAL has developed
this methodology entitled: "Determination of the Strong Acidity of Atmospheric Fine-
Particles (<2.5 nm) Using Annular Denuder Technology." This standard methodology
represents a composite of the most viable features of the three research methods utilized in
the Pilot Intercomparison Study. This methodology includes two parts:
* Part A-Standard Method, and
* Part B-Enhanced Method.
The unique features of the annular denuder which separates it from ether established
monitoring methods are elimination of sampling artifacts due to interaction between the
collected gases and particles, and the preservation of the samples for subsequent analysis.
The Standard Method utilizes a denuder for removing ammonia and a filter assembly for
determination of atmospheric strong acidity fine particle aerosols in ambient air, but does not
account for potential interferences from nitric acid, ammonium nitrate aerosol (NH4NO3) or
other ammonium salts which might bias the acidity measurement. The Enhanced Method
v
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adds an additional denuder upstream of the filter assembly to selectively remove acid gases
(nitric acid vapor, nitrous acid and SO2) from the gas stream prior to filtration. In addition,
to correct for biases due to the dissociation of ammonium nitrate aerosol captured on the
Teflon® filter, a backup nylon filter has been incorporated to capture the dissociated HNO3
from NH4NO3, followed by a glass-fiber filter impregnated with citric acid to retain the
dissociated NH
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DETERMINATION OF THE STRONG
acidity of atmospheric fine-paiiticles
(<2.5 fim) USING ANNULAR
DENUDER TECHNOLOGY
STANDARD METHOD
TABLE OF CONTENTS
Topic Page
1. Scope A-l
2. Applicable Documents A-2
3. Summary of Method A-2
4. Significance A-3
5. Definitions A-4
6. Apparatus A-5
7. Reagents and Materials A-10
8. Preparation of Impactor- Frit and Denuder Coating A-11
9. Impactor Frit Installation A-il
10. Filter Preparation and Assembly A-12
11. Annular Denuder System Preparation A-13
11.1 Coating Procedure A-13
11.2 Drying Procedure A-14
11.3 Denuder System Assembly A-14
11.4 Laboratory Leak-Check of ADS A-15
ix
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TABLE OF CONTENTS (continued)
Topic Page
12. Sampling A-16
12.1 Placement of Denuder System A-16
12.2 Start-up A-17
12.3 Sample Shutdown A-19
12.4 Corrective Action for Leak Test Failure A-19
13. ADS Disassembly A-20
14. Extraction Procedure A-21
15. pH Analysis A-22
15.1 Standard and Reagent Preparation A-22
15.2 Calibration of pH Meter A-26
15.3 Pre-analysis Calibration A-26
15.4 pH Test of HC104 Solutions A-27
15.5 Analysis of Working Standard A-27
15.6 Analysis of Filter Extracts A-28
16. Assumption of Annual Denuder System A-29
17. Atmospheric Species Concentration Calculations A-29
17.1 Calculations Using Results from pH Measurement A-29
17.2 Calculation of Air Volume Sampled, Corrected to
Standard Conditions A-31
17.3 Calculation of Strong Acidity Aerosol Concentration A-32
18. Variations of the Acid Aerosol Denuder System A-32
19. Method Safety A-33
20. Performance Criteria and Quality Assurance (QA) A-33
20.1 Standard Operating Procedures (SOPs) A-33
20.2 Quality Assurance Program A-34
21. References A-35
x
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PART A
DETERMINATION OF THE STRONG
ACIDITY OF ATMOSPHERIC FINE-PARTICLES
{<2,5 //ni) USING ANNULAR
DENUDER TECHNOLOGY
(STANDARD METHOD)
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Date 11/92
Page 1 of 51
DETERMINATION OF THE STRONG
ACIDITY OF ATMOSPHERIC FINE-PARTICLES
(<2.5 //in) USING ANNULAR
DFNUDER TECHNOLOGY
STANDARD METHOD
1, SGQpQ
1.1 This document describes the protocol for llie quantitative determination of
equivalent strong-acid (H^SO^) acidity of f:ne-particle (<2.5 atmospheric
aerosol as hydrogen ion by pH.
1.2 The methodology detailed in this document is a composite of methodologies
developed by U.S. Environmental Protection Agency (USEPA), University of -
Kansas, Robert Johnson Medical School, New York State University, Harvard
University and the CNR Laboratories. It is currently employed in a number of air
pollution studies in Italy, U.S.A., Canada, Mexico, Germany, Austria, and Spain,
and in such institutions as public health services and epidemiology and
environmental research centers.
The techniques, procedures, equipment, and other specifications comprising tliis
method are derived and composited from those actually used by the contributing
research organizations and thereby known to be serviceable and effective. At this
stage, this method is a unified, consensus, tentative, draft method intended for
further application and testing. Users should be advised that the method has not
yet been adequately tested, optimized, or standardized. Many of the specifications
have been initially established by tecfmical judgment and have not been subjected
to mggedness testing. In some cases alternative techniques, equipment, or
specifications may be acceptable or superior. In applying the method, users are
encouraged to consider alternatives, with the understanding that they should test
any such alternatives to determine their adequacy and to confirm and document
their possible advantages. Information and comments are solicited on
improvements, alternative equipment, techniques, or specifications, performance,
or any other aspect of the method. All such information should be sent to the
EPA Project Manager identified on the cover page and will be considered for
incorporation in future revisions of the method.
1.3 The equipment described herein can be modified to measure acidity of
atmospheric gases and particulate matter contained in both indoor and outdoor
atmospheres. Modification to this methodology were developed for monitoring
regional-scale acidic and basic gases and particulate matter in support of U.S.
EPA field programs involving the Integrated Air Cancer Research Program and
Acid Aerosol
Part A
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Page 2 of 51
the Acid Deposition Network. Similarly, the methodology has been used to
characterize urban haze in Denver, Houston, Boston and Los Angeles.
2. Applicable Documents
2.1 ASTM Standards
D1356 Definitions of Terms Related to Atmospheric Sampling and Analysis
2.2 Other Documents
Ambient Air Studies (1-23)
U.S. EPA Technical Assistance Document (24)
3. Summary of Method
3.1 The annular denuder system (ADS) consists of an inlet with an impactor or
cyclone preseparator designed to remove all particles with a DP50 of 2.5 nm or
greater, an annular denuder to remove ammonia, and a filter for collecting the
aerosol. In operation, air is drawn through a cyclone or a elutriator-accelerator
jet assembly followed by an impactor frit and coupler assembly, through the
denuder to remove ammonia, then into a single-stage filter assembly. The single-
stage filter assembly contains a 47-mm Teflon® filter supported by a stainless steel
screen. The filter is a 2 ^m pore-size Teflon® membrane filter, Zefluor (Gelman
Sciences). The Teflon® filter collects the fine aerosol. A pump unit maintains a
flow of 10 Lpm, and a timer allows programmed start and end times.
Figure la illustrates the ADS with a cyclone assembly, while Figure lb illustrates
the ADS with an impactor assembly. Figure 2 shows the field sampling box with
the pump-timer system.
3.2 Following each run, the ADS assembly is removed from its field housing, its ends
capped, and it is brought back to the laboratory. In the laboratory, the assembly
pieces are uncoupled and capped. The denuder tube is not extracted. The
Teflon® filter is unloaded from the filter assembly in an ammonia free atmosphere
and either immediately extracted or stored in a ammonia free container for later
extraction. A glove-box, lined with citric-acid soaked paper, is used to maintain
an ammonia-free atmosphere.
To extract the Teflon® filter, it is placed in an extraction vessel, particle-laden
side down. The filter is wetted with 200 fiL of methanol, then extracted with 6.0
mL of extraction solution (ES). The extraction vessel is put in an ultrasonic bath
for 20 minutes. The extraction solution is then decanted into a container.
Acid Aerosol
Part A
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3.3 Acicity determination is made using pH measurements of 1 mL aliquot of the
extracted filter solution. Filter acidity is calculated based on standards made with
sulfuric acid. The standards range from 0 to 160 equivalent of strong acid
aerosol. A pH meter is used to measure the pH of the filter extract. For each
batch of filter extracts, a calibration curve is calculated using the mean pH of each
standard.
4. Significance
4.1 Acid aerosols are found in the atmosphere as a result of atmospheric reactions of
emissions from a variety of fossil fuel combustion sources including power plants,
industrial and commercial facilities, hazardous waste storage and treatment
facilities, etc. Awareness of the effects of concentrations of acid aerosols on
human health and property has been documented over the past several years. The
Clean Air Act Amendments of 1970 required the U.S. Environmental Protection
Agency (U.S. EPA) to develop uniform national ambient air quality standards
(NAAQS) for criteria pollutants because of the interstate nature of certain air
pollutants. NAAQS's were established for those pollutants which were recognized
as widespread (emitted by numerous mobile and stationary sources) and wltich
endangered public health and welfare. Further, Section 109 of the Clean Air Act
as amended, requires EPA to periodically review the NAAQS as well as the
scientific information and data on wliich they are based. New pollutants are to be
identified for NAAQS development if the Administrator concludes that they may
reasonably be anticipated to endanger the public health and welfare.
To assist the Administrator in evaluating the need for new cr revised NAAQSs,
the Clean Air Act created the Clean Air Scientific Advisory Committee (CASAC).
This committee's mandate is to provide the Administrator with scientific advice
and research recommendations on critical areas of knowledge on new or revised
NAAQSs. Hie Acid Aerosol Subcommittee of CASAC identified a need for a
coordinated acid aerosol research program io assist the Agency in making
recommendations on a new acid aerosol NAAQS. The Subcommittee
recommended a research program involving characterization and exposure
assessment, animal toxicity, human exposure research, and epidemiology. The
foundation for any research program and potential air quality standard
development is "...a measurement method, not only because the standard itself
must specify the method, but equally important, because before establishing a
standard the contaminant must be fully characterized and exposure measurements
made to correlate with health outcomes."
4.2 The unique features of the annular denuder which separates it from other
established monitoring methods are elimination of sampling artifacts due to
interaction between the collected gases and particles and the preservation of the
samples for subsequent analysis. These features are accomplished by removing
Acid Aerosol
Part A
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Date 11/92
Page 4 of 51
NHg in the gas stream with the citric acid-coated denuder to reduce the
probability of the acid aerosol captured by the Teflon® filter in the filter pack
being neutralized to ammonium sulfate [(NH^SO^J.
5. Definitions
Definitions used in this document and any user-prepared Standard Operating Procedures
(SOP's) should be consistent with ASTM D1356. All abbreviations and symbols are defined
within this document at the point of first use.
5.1 Secondary particles (or secondary aerosols) - Aerosols that form in the
atmosphere as a result of chemical reactions, often involving gases. A typical
example is sulfate ions produced by photochemical oxidation of SC>2.
5.2 Aerosol - A dispersion of solid or liquid particle in a gas-phase medium and a
solid or liquid disperse phase. Aerosols are formed by (1) the suspension of
particles due to grinding or atomization, or (2) condensation of supersaturated
vapors.
5.3 Coarse and fine particles - These two fractions are usually defined in terms of
the separation diameter of a sampler. Coarse particles are those with diameters
(aerodynamic) greater than 2.5 pan and are removed by the sampler's inlet; the
fine particles are those with diameters (aerodynamic) less than 2.5 pm that are
collected on the Teflon® filter.
5.4 Annular - Of, rotating to, or forming a ring. In the annular denuder sampler, the
annular refers to the annulus between two concentric tubes. Chemical coating
applied to the interior surfaces removes gaseous pollutants which diffuse to the
surface.
5.5 Denuder - The denuder refers to the sections in which interfering gases are
removed from the sample stream prior to filtration in determining fine particle
(2.5 nm) strong acidity.
5.6 Equivalent weight - The combining weight, or the equivalent weight, of a
compound or ion is its formula weight divided by the number of replaceable
hydrogen atoms.
5.7 Normal solution - A normal (N) solution is one that contains a gram-equivalent
weight of solute in a liter of solution.
Acid Aerosol
Part A
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6, Apparatus
Note: The following descriptions relate to Figure 2. Most of these parts are available
commercially from University Research Glassware, 118 E. Main Street, Carrboro,
North Carolina, 27510, 919-942-2753. However, these items can be made by any
qualified vendor. Therefore, it is not necessary that these specific items are obtained
and utilized.
6,1 Sampling
6.1.1 Elutriator and acceleration jet (inlet) assembly - Under normal sampling
conditions, the elutriator or entry tube is made of either Teflon® coated
glass or aluminum, as illustrated in Figure 3. When using glass, the
accelerator jet assembly, which directs the air flow towards an impactor
plate, is fixed onto die elutriator and the internal surfaces of the entire
assembly are coated with Teflon® [Figure 3(a)]. When aluminum is used,
the accelerator jet assembly is removable. The jet is made of Teflon18' or
polyethylene and the jet support is made of aluminum [Figure 3(b)].
Again, ail internal surfaces are coated with Teflon®.
6.1.2 Teflon® irnpactor support pin and impactor frit support tools (see
Figure 4) - Made of either Teflon® or polyethylene and are used to aid in
assembling, removing, coating and cleaning the impactor frit.
6.1.3 Impactor frit and coupler assembly (see Figure 5) - The impactor frit is
10 mm x 3 mm and is available with a porosity range of 10-20 pm. The
frits should be made of porous ceramic material or fritted stainless steel.
Before use, the impactor frit surface is coated with a Dow Coming 660 oil
and toluene solution and sits in a Teflon4, seat support fixed within the
coupler. The coupler is made of thermoplastic and has Teflon'6 clad
sealing "0"-rings which are located on both sides of the seat support inside
the coupler.
Note: In situations when there are substantial high concentrations of
coarse particles (>2.5 pm), it is recommended that a Tefio#-coated
aluminum cyclone be used in place of the acceleration jet and impactor
assembly, as illustrated m Figure 2. Figure 2 illustrates the location of
the cyclone with respect to the denuder, heated enclosure and meter box
assembly.
6.1.4 Annular denuder - The denuder consists of two or more concentric glass
tubes (see Figure 6) with an outer aluminum shell. The tubes create a
1 mm annular spacing which allows the air sample to pass through. Flow
in the annular space is maintained in die laminar range and allows fine
Acid Aerosol
Part A
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Page 6 of 51
particles with diameters less than 2.5 pm to pass through with negligible
removal. The inner tube is inset 25 mm from one end of the outer tube;
this end is called the flow straightener end. The other end of the inner
tube is flush with the end of the outer tube. Both ends of the inner tube
are sealed. In this configuration, the flow straightener end is etched to
provide greater surface area for the coating. The inner glass tubes are
inset 25 mm from one end of the outer Teflon®-coated aluminum tube to
serve as the flow straightener end. All denuder types should be equipped
with thermoplastic (Bakelite) or polyethylene caps when purchased.
6.1.5 Caps for annular denuder - Caps are made of either polyethylene
(Caplugs, Protective Enclosure, Inc.) or thermoplastic (Bakelite) and are
used in the coating and drying processes, for storage and for shipment.
The thermoplastic caps include a removable Teflon® seal plate when
purchased.
Note: Recent evaluation of the caps for the denuder system have
indicated that the thermoplastic (Bakelite) screen caps and the polyethylene
screw caps are useful to seal the ends of the denuders when they are dry.
However, during coating and extracting, the Caplugs (Protective
Enclosures, Inc.) provided a better seal, preventing contamination that
would occur from the Teflon® liner of the thermoplastic screw caps or
direct contact with the unprotected thermoplastic screw caps. It is
therefore suggested that the user use Caplugs during coating and extraction
operations.
6.1.6 Annular denuder couplers - The couplers should be made of thermoplastic
and equipped with Teflon® "0"-rings which sandwich a silicone rubber
ring on three sides. This provides elasticity for better sealing under
extremely cold temperature conditions in which Teflon® does not give.
The couplers are equipped with permanent seal rings which provide more
even threading and a better seal when coupled. The couplers are used to
couple the annular denuders together when used in series (enhanced
method) and for coupling the last denuder with the filter assembly.
Caution: When utilizing the couplers, do not overtighten when applying a
glass denuder. Overtightening might "chip" the ends of the denuder,
preventing a tight seal.
6.1.7 Drying manifold assembly - The manifold is made of glass and is
available to accommodate as many as four drying denuders. The denuders
are attached to the manifold with back-to-back Bakelite bored caps, as
illustrated in Figure 7. Air is pushed through an air dryer/cleaner bottle
made of 2 1/2 inch heavy wall glass which contains silica gel. The
Acid Aerosol
Part A
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Teflon® tubing which connects the dryer/cleaner bottle to the drying
manifold should be secured at each cap with either Teflon® washers cr
Teflon® washers coupled with Teflon® hose barbs. The air stream then
passes through a fine particle filter to remove fines. Alternatively, dry
compressed air from a cylinder may be used in place cf the dryer/cleaner
bottle assembly.
6.1.8 Filter assembly - The denuder is followed by a single-stage filter assembly
containing the Teflon® membrane filter, as illustrated in Figure 8. The
filter is supported by a stainless steel porous screen sandwiched between
two Viton® O-rings for sealing and housed in a polyethylene filter ring
housing. The filter housing outlet component is aluminum and
accommodates a polyethylene screw sleeve which seals the filter assembly.
Note: Over time and repeated compression, the Viton® O-rings may
wear, causing poor leak checks due to inadequate sealing. The user is
encouraged to replace these rings after fifteen (15) sampling events or
when the filter pack assembly does not pass an adequate leak check.
Other users have utilized high density polyethylene (HDFE) to prolong the
life of the ring.
6.1.9 Vacuum tubing - Low density polyethylene tubing, 3/8 inch diameter for
distances of less than 50 ft., 1/2 inch diameter for distances greater than
50 ft. [Fisher-Scientific, 711 Forbes Ave., Pittsburgh, PA, 15219
(412-787-6322)]
6.1.10 Tube fitting - Compression fittings (Swagelok®, Gyrolok® or equivalent)
to connect vacuum tubing (above) to an NPT female connector or filter
holder and connect vacuum tubing to fitting on differential flow controller.
The fittings may be constructed of any material since they are downstream
of the sampler. [Fisher-Scientific, 711 Forbes Ave., Pittsburgh, PA,
15219 (412-787-6322)]
6.1.11 Annular denuder system (ADS) sampling box - The housing box is made
of a nhigh-impact;' plastic and is thermally insulated. It is 2 feet long by
6 inches wide and 6 inches deep. The box contains a heater unit, a fan,
and an air outlet located in the lid of the housing. The elutriator end of
the ADS protrudes through one end of the box, while the denuder is
supported in the box by a chrome plated spring clip. If the Teflon's-
ccated aluminum cyclone is used to remove coarse particles, it is also
housed in the heated sampling box, with the elutriator end protruding
through the sampling box, as illustrated in Figure 2.
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Note: Recent studies by the Harvard School of Public Health based on a
comparison of utilizing a sampling box with and without heated enclosure
indicated no difference in sampled species from winter samples. It is
therefore the discretion of the user to determine whether a heated
sampling box is required.
6.1.12 Annular denuder transport case - The transport case is made of formica
backed with plywood and insulated. The corners are reinforced with
metal. It is made to withstand shipping by truck, UPS and Federal
Express. Each case is stackable and lockable and has a carrying handle.
Seven total annular denuder systems can be packed in the case.
6.1.13 Pump/timer unit - The pump/timer unit draws air through the ADS at a
fixed rate of 10 L/min with a precision of ±5 percent over the range of
25 to 250 mm Hg vacuum. A mass flow controller or a differential flow
controller can be used. Typically, the flow rate is monitored with an
exhaust flow rotameter. The unit includes a mechanical 7-day timer and
an elapsed-time counter. A dry gas meter, when available, is placed after
the pump to give a direct readout of total volume of air sampled.
Otherwise, flow rate is manually measured (using a rotameter) before and
after each run to calculate the air volume sampled.
6.1.14 Dry gas meter (DGM) - The DGM should have a capacity of 10 L of gas
per revolution. [NuTech Corp., 4022 Stirnip Creek Road, Suite 325,
Durham, NC 27703, 919-544-8535)]
6.1.15 Electronic mass flow controller - Capable of maintaining a constant rate of
10 L/min (±5 percent) over a sampling period of up to 24 hours and
under conditions of changing temperature (5° to 43 °C) and humidity.
[Tylan General, Flow Division, 19220 S. Normandie Ave., Torrance,
CA, 90502, 213-212-5533, Model FC-262, or equivalent]
6.2 Analysis
6.2.1 pH meter - A pH or pH/ion meter with "integral" automatic temperature
compensation, temperature probe, 2 and 4 mL analytical vials, and
calibrated with standard buffers (pH 4 and 7). The Ross semi-micro glass
electrode from Orion has been used by the Harvard School of Public
Health and found to adequately address the requirements of this protocol.
[Orion Research Inc., The Schraffet Center, 529 Main Street, Boston, MA
02129, 617-242-3900]
6.2.2 Polyethylene bottles with polyethylene screw caps - 100 mL, used for
storage of coating solution; and 1L, used for storing the KC1 solution.
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6.2.3 Erlenmeyer flasks - 250 mL and 2 L borosilicate glass or polyethylene
flasks for calibration, best source.
6.2.4 Graduated cylinders - 5 mL, 1C mL, . 00 rnL, 250 mL ard 1L borosilicate
glass or polyethylene cylinders, best source.
6.2.5 Pipets - Class A 5 mL and 10 rnL borosilicate glass pipettes or automatic
pipettes. Calibrated "to deliver," best source.
6.2.6 Pipet bulb - Made of natural rubber. Recommended to meet OSHA
requirements, best source.
6.2.7 Micropipettes - 25 p.L, 50 ^L, and 100 /xL, calibrated ' to contain,"
borosilicate glass micropipette, best source.
6.2.8 Forceps - Recommended dressing forceps made of stainless steel or
chrome-plated steel and without serrations. Used for handling filter.
6.2.9 Stopwatch - Used for measuring flow rate of gas stream through DGM,
best source.
6.2.10 Ultrasonic cleaner - Used for filter extractions and parts cleaning. The
ultrasonic cleaner should have temperature control capability.
[Cole-Palmer Instrument Co., 7425 N. Oak Park Ave., Chicago, IL,
60648 (800-323-4340)]
6.2.11 Clean air hood (optional) - Closed air hood with ammonia free air
circulation. Used for Teflon® filter extraction for pH analysis, best
source.
6.2.12 Glove-box - Used for handling exposed filter, which is lined with citric
acid impregnated paper sheets to maintain an ammcnia-free atmosphere.
The glove-box works best with a slight positive pressure.
6.2.13 Refrigerator (approximately 5°C) is required for sample storage.
6.2.14 Polyethylene-stoppered volumetric flasks - 25 mL, used for making
sulfuric acid standards.
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7. Reagents and Materials
7.1 Teflon® filter - Zefluoi® (PTFE) membrane filter, 47 mm diameter, with a 2 pim
pore size. The Teflon® filter has a coarse mesh Teflon® side and a fine pore
membrane side. The fine pore membrane side should face the air stream.
[Gelman Sciences, 600 S. Wagner Rd., Ann Arbor, MI, 48106, Part
No. P5PJ047, (800-521-1520)].
7.2 Teflo® membrane filter, 47 mm diameter, with a 2 fim pore size. This filter has a
thin Teflon® membrane stretched across a plastic ring. [Gelman Sciences, 600 S.
Wagner Rd., Ann Arbor, MI, 48106, Part No. R2PJ047, (800-521-1520)].
7.3 Filter extract storage vials - 100 mL polyethylene vials (Nalgene or equivalent).
7.4 Labels - Adhesive, for sample vials, best source.
7.5 Parafilm - Used for covering flasks and pH cups during pH analysis, best source.
7.6 Kimwipes® and Kay-dry towels - Used for cleaning sampling apparatus and
analysis equipment, best source.
7.7 Stoppers - Polyethylene, best source.
7.8 Sodium carbonate (Na2CO
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7.17 Zero air - A supply of compressed clean air, free from particles and ammonia.
The supply may be either from a commercial cylinder or generated on site, best
source.
7.18 BRU-35 - Composed of 0.1 percent of BRIJ-35 in DI water. Tisher Scientific,
711 Forbes Ave., Pittsburgh, PA, 15129, 412-787-6322]
7.19 Perchloric Acid (HCIO4) - 60 to 62 percent, in water, best source.
7.20 Toluene (CyHg) - ACS reagent grade, best source.
7.21 Potassium Chloride (KC1) - ACS reagent grade, best source.
7.22 Acetone (C^HgO) - ACS reagent grade, best source.
8. Preparation of Impactor Frit and Denudnr Coating
5.1 Impactor frit coating solution preparation - Weigh 1 g of silicone oil (Dow
Corning high temperature 660 oil) and place in a 100 inL polyethylene storage
vial. Add 100 niL of toluene. Mix thoroughly, close container, and store at
room temperature. (WARNING - FLAMMABLE LIQUID).
8.2 Annular denuder citric acid coating solution - Clean a 100 rnL polyethylene
storage vial and let dry at room temperature. Measure 50 aiL of methanol
(WARNING - TOXIC, FLAMMABLE LIQUID) with a graduated cylinder and
pour into viai. Weigh 0.5 g of citric acid and add to vial. Mix thoroughly; store,
covered at room temperature.
9. Impactor Frit Installation
9.1 Impactor frit installation - The impactor-coupler assembly shown in Figure 4 is
comprised of two parts: the replaceable impactor frit and the coupler-impactor
housing seat. The impactor surface is a porous ceramic or porous stainless steel
frit, 10 mm x 3 mm. This frit is inserted into the coupler-impactor housing using
the tools illustrated in Figure 4. The impactor frit is pressed gently, but firmly,
into the seat of the impactor housing with a clean gloved finger. The impactor
should fit into the housing so that it does not protrude above the seat. During
sampling, particles accumulate on the impactor's plate surface. After each
sampling event, the assembly must be cleaned to prevent the build-up of
contaminants which may lead to loss of key acidic species being collected by the
AJDS. Cleaning involves immersing the elutriator, coupler-impactor, and frit in
0.1 percent BRU-35 cleaning solution and ultrasonieating for about 5 minutes.
Rinse thoroughly with DDW for additional 5 minutes. Rinse and dry with zero
air or in dust-fee environment and store with ends plugged and capped.
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9.2 Impactor frit coating - With the impactor frit in the impactor seat of either the
coupler (see Figure 5) or the Teflon® impactor seat support pin which fits into the
first denuder, pipette 50 (about two drops) of the toluene-660 oil coating
solution onto the impactor frit surface and allow to dry in dust free environment at
room temperature. Cap both sides of the coupler impactor or denuder-impactor
until use.
Note: It is important to have only the minimum amount of oil on the frit because
any excess will be blown off during sampling and will contaminate the surfaces of
the first denuder.
10. Filter Preparation and Assembly
Note: A clean and dedicated indoor work space is required for the daily preparation,
assembly and disassembly of the denuder and filter assembly. Approximately 2-3 m of
bench space is adequate, with additional space for storing supplies.
Note: All loading and unloading of the filter assembly must be performed in an
ammonia free glove-box. Generally, it is most convenient to reload the filter assembly
after cleaning, at the same time as unloading.
10.1 With clean gloves, disassemble the filter assembly (see Figure 8) by unscrewing
the large outer Delrin® collar (sleeve) from the aluminum filter housing outlet
component.
Note: It is necessary to remove the polyethylene cap first. Lay the pieces out
on clean Kimwipes®. Insert black viton "0"-rings (see Figure 8).
10.2 Lay a clean Teflon® filter ring housing, with its large opening face-up, on a
clean Kimwipe®. Place a clean stainless steel screen in the filter ring housing.
10.3 Using clean filter forceps, place a Teflon® filter on the screen.
Note: If a Zefluoi® Teflon® filter is used, be sure to place the membrane
coated side, not the coarse side, toward the air stream. By observing the filter
in the light, one can differentiate between the coarse and membrane side.
10.4 Place the Teflon® filter housing inlet component (see Figure 8) on top of the
Teflon® filter. This forms a "sandwich" with the Teflon® filter held between
the second filter ring housing and the housing inlet component. The housing
inlet component connects the filter assembly to the annular denuder through a
thermoplastic coupler. Be careful not to twist the filter assembly components,
or damage will occur to the filter.
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10.5 Lay the aluminum filter housing outlet component, with its Large opening face-
up, on a clean Kimwipe®. Insert a black viton nO"-rmg in the aluminum filter
base.
10.6 Insert the filter ring sandwich with the filter housing inlet component extending
upward, on the black viton "0"-ring in the aluminum filter base. Place the
larger outer Delrin® sleeve over the filter sandwich and screw onto the
aluminum filter base. DO NOT 0VKRTIGHTEN! Then install the second
black viton ,:0''-ring on top of the filter sandwich support.
10.7 Install the "quick-release" plug into the filter outlet component. Tighten the
housing outlet to the Detrin® screw sleeve. DO NOT OVERTIGHTEN!
10.S Install the polyethylene cap onto the filter inlet component and the orange dust
cover onto the quick release plug. The filter assembly should he sealed tight
before it is removed from the glove-box.
10.9 As an option, the filter assembly is leak-checked according to Section 12.4.
11. Annular Ptmudar System Preparation
All new annular denuder parts obtained from suppliers should be cleaned by placing
them in a dilute BR1J-35 solution in an ultrasonic cleaner for about 30 minutes. The parts
should then be thoroughly rinsed in DDW, then rinsed with acetone, and allowed to dry to
room temperature. Store with end caps in place.
11,1 Coating Procedure
11.1.1 Cap one end of a denuder using Caplugs (which has the inner tube flush
to the outer tube) and set the denuder upright on the capped end. For
the denuder with flow-straighteners at both ends, either end may be
capped. Measure 10 mL of the citric acid solution and pour into the
denuder.
11.1.2 Cap the open end of the denuder and, holding it horizontally, rotate the
denuder to distribute the coating solution evenly, wetting all surfaces.
11.1.3 Remove cap and decant excess coating solution into a 100 mL
polyethylene bottle.
11.1.4 For the impactor denuder, the coaling is performed without the
impaclor pin in place.
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11.2 Drying Procedure
Note: As denuders dry, they change from translucent to a frosted appearance.
Denuders are dry when they become uniformly frosted.
Note: A supply of zero air is needed to dry the annular denuder tubes after
applying the coating solutions. This air should be free of ammonia, moisture
and particles. Ether a tank of pure air or an air purifier assembly can be used.
11.2.1 Assemble the drying train and manifold as illustrated in Figure 7.
Drying train and manifold clean air flow should be adjusted to 2 to 3
L/min through each denuder. Close toggle valve controlling clean air
flow through manifold before attaching denuders.
11.2.2 Attach the flow-straightener end of the denuder to the drying manifold
port (see Figure 7).
11.2.3 Open toggle valve and allow clean air to flow through the denuder tube
for 5 minutes.
Caution: Excess air flow will cause uneven coating to the tube walls.
11.2.4 Close toggle valve, and reverse ends of the denuder attached to the
manifold. Start clean air flow again.
11.2.5 When an even frosted appearance is achieved, remove denuder from
manifold, cap both ends with clean caps and store until ready for use.
Turn off air to drying manifold. Affix label indicating coating date on
denuder.
11.3 Denuder System Assembly
Note: Described herein is an annular denuder system consisting of one
denuder. Extreme care should be exercised in handling and assembling of the
ADS if the denuder is made of glass. The coupling of components must be
effective to prevent leaks but, at the same time, not stress the glassware. Only
patience and practice with the ADS will enable the operators to obtain optimum
performance from the system with minimum breakage.
The annular denuder system (ADS) assembly consists of:
• an inlet nozzle/impactor or cyclone assembly;
• 1 glass annular denuder tube; and
• a 1-stage filter assembly.
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The following procedure involves an inlet nozzle/impactor assembly.
11.3.1 Lay the ADS pieces on a clean surface (i.e., Kim wipes®).
11.3.2 Remove the end caps from the citric acid coated denuder. Gently insert
the impactor support pin and coated frit assembly into the denuder-pin
support.
11.3.3 Attach a thermoplastic coupler to the opposite denuder end. Place a
Teflon® clad ,,0"-ring inside the coupler, if needed.
11.3.4 Tlie filter assembly has been previously loaded with a Teflon® filter.
The components are assembled with plastic couplers.
11.3.5 Attach the filter assembly inlet to the denuder coupler assembly.
11.3.6 Attach the elutriator-acceleration jet assembly to the other end of the
denuder. Tighten very gently - DO NOT OVERTIGHTEN or breakage
will result.
11.3.7 Tighten the remaining couplers very gently.
11.3.8 Cap elutriator with orange dust cover until used. Attach "quick-
release" tube to outlet of filter assembly.
11.4 Laboratory Leak-Check of ADS
l
Caution: Do not subject the system to sudden pressure changes or filter
may tear.
11.4.1 Remove the orange dust cap from the impactor opening. Attach the
"quick-release" outlet of the filter assembly to a pump module. Turn
on the pump. Be certain that flow through the ADS occurs by checking
the rotameter.
11.4.2 Briefly cap the elutriator with, the orange dust cap. The flow, as
indicated on the rotameter, should drop to zero if no leaks exist.
11.4.3 Disconnect the pump from the ADS at the "quick-release" plug. Cap
the "quick-release" plug with an orange dust cover. Turn off the pump.
REMEMBER - Never overtighten joints or breakage will result. If the
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joints can not be sealed with gentle tightening, then the Teflon®
"0"-rings are worn or defective and must be replaced.
11.4.4 Place the assembled sampler in its field-to-lab carrying case for
transport to the field.
Note: It is recommended that the ADS joints be loosened slightly when
extreme temperature changes are incurred during transportation. This
will prevent unnecessary breakage or distortion of the ADS
components. Remember to allow the system to adjust to the outdoor air
temperature before tightening the joints and checking for leaks.
11.4.5 Before proceeding to the field, review the following checklist:
• Run IDs on the Field Test Data Sheet should match labels affixed to
the ADS components and filter assembly;
• Recessed ends of the denuder should face the inlet;
• ADS ends are capped; and
• Transport case is secured firmly containing the ADS along with
chain-of-custody and Field Test Data Sheet.
12. Sampling
12.1 Placement of Denuder System
12.1.1 The placement of the fine particle strong acidity aerosol monitor must
conform to a consistent set of criteria and guidance to ensure data
comparability and compatibility. A detailed set of monitor siting
criteria for ambient air monitoring and meteorological programs is
given in the following EPA document:
• U.S. EPA, May 1987. Ambient Monitoring Guidelines for
Prevention of Significant Deterioration (PSD), EPA-450/4-87-007,
Office of Air Quality Planning and Standards, Research Triangle
Park, N.C. 27711.
The site must be away from localized sources of ammonia such as
composting and livestocking operations, landfills, sewage treatment
plants, fertilizer plants and storage facilities, and recently plowed
fertilized fields because aerosol acidity is subject to rapid neutralization
by ambient bases.
12.1.2 A summary of key factors that should be considered as part of the
placement of an air quality monitoring station containing an ADS are:
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* Vertical placement above ground;
* Horizontal spacing from obstructions and obstacles;
* Unrestricted air flow; and
* Spacing from roads.
The ADS sampler is mounted on a supported mast pole or tripod. The
ADS inlet should be located 2-3 m above ground level. Placing the
inlet closer to ground level should be considered only if the surface is
flat and man-made (i.e., not unpaved dirt).
12.1.3 A summary of key criteria associated with these siting factors for sir
monitoring stations is included in Table 1.0. The information included
in the table should be used to the extent possible as pari of the
monitoring network design to ensure that the monitoring program
provides representative and unbiased data. However, site-specific
constraints could make it very difficult to meet all criteria. For
example, the occurrence of wooded areas around a site would make the
siting very difficult. The use of the information in Table 1.0, coupled
with a balanced evaluation by an experienced air quality and
meteorology specialist, is highly recommended.
12.1.4 In general, for a site with no major obstruction and obstacles, the air
sampler intake should be about 2-3 meters aboveground. For a site
with nearby roadways, however, intake placement should take into
account the effects of road dust re-entiaimneut and vehicular emissions.
Iff fact, a linear relationship should be established between the
horizontal, distance of the sampler intake from the roadway and the
aboveground elevation of that intake. For any roadway accommodating
more than 3000 vehicles per day, the intake should be between 5 and
25 meters from the edge of the nearest traffic lane. It should also be
15 meters aboveground for a distance of 5 meters from the nearest
traffic lane and 2 meters aboveground for a distance of 25 meters from
the nearest lane. For a roadway supporting less than 3000 vehicles per
day, the intake should be placed at a distance greater than 5 meters
from the edge of the nearest traffic lane and at a height of 2-15 meters
aboveground.
12.2 Start-up
12.2.1 Remove the ADS from its field-to-lab carrying case and load into the
field sampling box. Place the assembly in the box with the impactor
extended outside the case. The ADS field sampling box is insulated
and configured to hold the ADS without allowing movement. Chrome
plated spring cEps holds the denuder in place. Automatic and manual
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control switches allow the sampling box to control the temperature of
the ADS. The automatic switch should be used when the ADS is not in
use and when the ADS is sampling for extended periods of time without
constant supervision to prevent low temperature or sudden pressure
change exposure of the ADS (these types of exposure can cause leaks to
occur, condensation, or the filter to tear). When sampling, the ADS
should be kept 1 °C above the outdoor temperature to prevent
condensation.
12.2.2 Allow the pump to warm up for ~ 5 minutes prior to testing.
12.2.3 To check the Heat/Cool cycles, flip one switch from "AUTO" to
"MANUAL" and the other between "COOL" and "HEAT." Check to
insure that the fan and heater (i.e., light bulb) work, respectively.
12.2.4 With the elutriator still capped, turn on the pump with the switch on the
timer. The rotameter should indicate zero flow. Run leak check for
5-10 seconds, then turn off pump and remove elutriator cap. Record
leak rate on Field Test Data Sheet (see Figure 9). If there is a flow,
refer to Section 13.4 for corrective action for leak test failure. The
Field Test Data Sheet is used to keep track of the denuder tube, filter
and impactors, as to when and by whom they are prepared, assembled,
extracted and data input as well as to record the installation data and
time, run date, sampling period, pump flow rates, start and end times,
and other data relevant to each run.
12.2.5 Attach a DGM output to the inlet of the annular denuder system. Turn
on pump. Record start time on Field Test Data Sheet. Using a
stopwatch, record the time for 20.0 L to pass through the DGM.
Record the DGM temperature and the absolute pressure of the DGM.
12.2.6 Calculate the flow rate as follows:
Qstd = (V/T)
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Pjj = barometric pressure, mm Hg
Pstcj = standard barometric pressure, 760 mm Hg
Tgt(j = standard temperature, 298°K
Tm = temperature of dry gas meter, °K(= °C + 273)
Fc = dry gas meter correction factcr, dimensionless
12.2.7 If the calculated flow rate is not between 9.5 and 10.5 L/oiia, then
readjust the flow rate until the rate is in the above range. Stop the
pump.
12.2.8 Record the flow rate on Field Test Data Sheet.
12.2.9 Remove DGM connection tubing from elutriatcr inlet. With all
information correctly on the Field Test Data Sheet, start the pump and
begin sampling.
12.3 Sample Shutdown
12.3.1 Attach DGM connection tubing to the elutriator inlet with pump still
running. Measure flow rate. Record calculated flow rate, temperature,
and pressure on Field Test Data Sheet.
12.3.2 Turn off the pump. Record time and elapsed time meter reading on
Field Test Data Sheet. Remove DGM connection tubing from elutriator
inlet. Remove ADS from the sampling box, cap the ends, and place the
ADS in field-to-lab carrying case for transport to lab. Secure the
latches on the transport case. Be careful not to stress the ADS during
the transfer or breakage will result.
Camion: When the ADS is brought from a cold field sampling location
to a warn laboratory, it is necessary to loosen the denuder couplings to
prevent thermal expmision from breaking the denuder.
12.4 Corrective Action for Leak Test Failure
Note: These steps should be followed when failure occurs during testing at the
laboratory before transport to the field and in the field before sampling.
12.4.1 Sampler leaks - Note the problem on the Field Test Data Sheet. Check
assembly of ADS components. Replace gaskets. Check for proper
seating of denuder surfaces. Replace any defective parts.
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12.4.2 Cracked or chipped denuder or elutriator assembly - Note problem on
Field Test Data Sheet. Discard defective pieces. Do not try to extract
cracked pieces.
Warning: Use caution when disassembling cracked glassware. Pieces
may shatter and cause severe cuts. Wear protective clothing.
12.4.3 Flow rate disagreement - Note problem on Field Test Data Sheet.
Check vacuum gauge on flow module. If a high vacuum exists then the
sampler has become blocked. This may be due to dust or smoke
particles clogging the filter or to obstructions in the system or tubing.
Check flow module. Repair as needed.
12.4.4 Inadequate flow rate - Note problem on Field Test Data Sheet. Check
rotameter on flow controller. If adequate flow is shown here, then a
leak exists between the controller and the DGM. If no flow is shown
on rotameter, then check vacuum gauge on controller. If no vacuum
exists, then pump needs repair. If a high vacuum is shown, then an
obstruction exists in the system. Check to see that the paper filter
dividers were not accidentally installed with the filter in the filter
assembly. Check tubing for kinks.
13. ADS Disassembly
13.1 In the laboratory, remove the ADS from the field-to-lab carrying case using
both hands. To prevent stress, hold the ADS by its ends.
Caution: Do not stress the ADS while removing it from the case.
13.2 Decouple the elutriator-jet assembly from the first denuder-impactor-coupler
assembly.
13.3 The impactor assembly and the denuders will not be extracted. However, each
run should begin with a clean impactor and charged denuder.
13.4 The handling of the exposed Teflon® filter requires protection from
contamination with NHj, which would rapidly neutralize aerosol acidity on the
filter and bias the sample results. In order to ensure ammonia-free air occupies
the glove-box, a positive pressure is maintained by blowing air through a PVC
tube (4 inch O.D.) filled with glass-wool dosed with citric acid before entering
the manifold which enables uniform distribution of air from top of the glove-
box. Flow the ammonia-free air for five minutes before retrieving the filter. A
citric acid soaked filter paper is also placed on the bottom to deplete ammonia
while unused. Disassemble the filter assembly in the clean, ammonia-free
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glovs-box. Clean ail glove-box surfaces and utensils with methanol. Wearing
clean gloves and using clean filter forceps, remove the filter and place in die
100 mL bottle, with the exposed fdter surface facing downward. Label the
bottle with appropriate information.
14, Extraction Procedure
14.1 Samples should be analyzed as scon after collection as possible. It is
imperative that the solutions and extraction procedures are prepared and
performed on the day of pH analysis. Keep samples in a refrigerator until
extracted and analyzed.
14.2 Samples should not be extracted until the day of analysis; however, if samples
are extracted and then it is not possible to analyze them that day, they should be
refrigerated. Allow the samples to return to room temperature before analysis.
14.3 It is imperative that the same extract solution (ES) be used for the samples to be
analyzed, the working standards, and the EA solution. Also, the same batch of
alcohol must be used to prepare the EA solution, the working standards, and in
extracting the Teflon® filters.
14.4 Handling and extraction must take place in an ammonia-free glove box.
Note: Teflon® is not wetted by water, therefore, the filter will float on top of
an aqueous solution. The use of alcohol aids wetting. Also, ail types of
Teflon® curl to some extent. It is tlie analyst's responsibility to ensure the
extraction solution makes complete contact with the particle deposit on the
Teflon® fdter during extraction. It may be necessaiy to use a clean plastic
(Teflon® or polyethylene) rod or tubing stub to hold the filter in better contact
with the fluid during extraction.
14.5 Teflon® filter extraction
14.5.1 Allow the glove-box to be flushed with ammonia-free air for at least
5 minutes before proceeding.
14.5.2 Process the filters in the same order in wliich they will be analyzed.
14.5.3 Open the sample vial and pipet 0.2 mL methanol onto the filter.
14.5.4 As soon as tlie methanol lias wet the entire surface of the filter, deliver
6.00 mL of ES solution into the vial. Cap tlie vial.
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14.5.5 Put a batch of vials into the ultrasonic bath and sonicate for a total of
20 minutes, rotating the position of the vials 90° every 5 minutes.
14.6 Aliquot preparation
14.6.1 Using a 1 mL automatic pipet, transfer 1 mL of the sample extract into
each of two labeled 2 mL vials, one labeled A and the other
labeled Al.
Subsequent samples will be labeled B and Bl, C and CI, etc.
14.6.2 Recap each vial after its aliquots are drawn. Store the original sample
vials in a refrigerator for possible repeat analysis or for analysis of
other components.
14.6.3 Proceed immediately with pH analysis.
15. oH Analysis
15.1 Standard and Reagent Preparation
15.1.1 Standard H2SO4 Solution, 1.000 N
Note: Each of the standard H2SO4 stock solutions must be prepared
fresh the day of pH analysis.
15.1.1.1 Label seven 25 mL polyethylene stoppered volumetric flasks.
Also, label each flask with the volume of 1.000 N H2SO4
solution.
15.1.1.2 Use the 25 fiL automatic pipet to add the 1 N stock H2SO4
solution to flasks 2 and 3. Use the 100 piL pipet to add
1.000 N stock H2SO4 solution to flasks 4 through 7. Dilute
all flasks to the 25 mL marie with methanol. Cap with
stoppers or parafilm and mix well. Proper dilution ratios are
indicated in the following table:
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Standard
h2so4
flask
Volume of
1,000 N H2S04
added to each
flask, QiL)
Working standard
concentration, 10~%T
H7SQa
Equivalent
strong acid mass
collected on
filter (CRl), /*ga
Approximate pH
1
0
0
n
v>
4.09
L
25
1
4.90
4.01
3
50
2
9.80
3.95
4
100
4
19.60
3.84
5
200
8
39.20
3.68
6
400
16
78.40
3.48
7
800
32
156.8
3.23
aBased on 3.1 mL extraction volume.
15.1.2 2 M Potassium Chloride (KCi) Solution
15.1.2.1 Weigh 149.2 ± 0.1 g of KCI. Add the KCI to a 2 L flask.
15.1.2.2 Add about 700 mL of DDW water to the flask. Swirl the
solution until the KCI is completely dissolved.
15.1.2.3 Pour tills mixture into a 1 L graduated cylinder. Rinse the
flask with a small amount of DDW water and transfer the
rinse into the cylinder. Fill the cylinder to the 1 L mark.
15.1.2.4 Pour the solution from the cylinder into the 1 L polyethylene
bottle. Cap and shake the bottle to mix well. Mark the
bottle with date of preparation.
15.1.3 0.100 N Perchloric Acid (HClO^j) Solution
15.1.3.1 Fill a 1 L graduated cylinder about half full with DDW.
Transfer 10 ± 0.1 mL of 60-62 percent HCIO^ into the 1 L
cylinder with a 10 mL pipet.
15.1.3.2 Fill the cylinder to the 1 L mark. Pour the solution into the
i L polyethylene bottle.
IS. 1.3.3 Cap and shake the bottle to mix well. Mark the date of
preparation on the bottle.
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15.1.4 0.010 N HC104 Solution
15.1.4.1 Fill a 1 L graduated cylinder about 1/2 full with DDW.
15.1.4.2 Measure 100 mL of the 0.1 N HCIO4 solution with the
100 mL graduated cylinder. Add this to the 1 L cylinder.
15.1.4.3 Fill the 1 L cylinder with DDW to the 1 L mark. Pour the
solution into the 1 L polyethylene bottle.
15.1.4.4 Cap and shake the bottle to mix well. Mark the date of
preparation on the bottle.
15.1.5 Extraction Solution (ES)
Note: This solution must be prepared fresh on the day of pH analysis.
15.1.5.1 Measure 20 ± 0.5 mL of 2 M KC1 into 2 L erlenmeyer
flask.
15.1.5.2 Using a 5 mL calibrated automatic pipet, add 10 ± 0.1 mL
of 0.01 N perchloric acid (HCIO4), to the flask. Add
980 ± 10 mL of DDW to the flask.
15.1.5.3 Mix well and cover with parafilm until ready for use.
15.1.6 Extraction Solution with methanol (EA Solution)
15.1.6.1 Measure 150 ± 2 mL of ES (prepared in Section 15.1.5) into
a 250 mL graduated cylinder. Transfer to a 250 mL
erlenmeyer flask.
15.1.6.2 Using a 5 mL graduated cylinder, add 5 ± 0.1 mL of
methanol (this must be from the same fresh bottle of methanol
that was used to prepare the standards in Section 15.1.1) to
the flask.
15.1.6.3 Mix well and cover with parafilm until ready for use.
15.1.6.4 pH of the EA solution should be 4.09 ± 0.04. If not, the
solution must be reprepared.
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15,1.7 Working Standard Test Solutions
15.1.7.1 Place fourteen-4 mL polystyrene sample vials (as used with
Technicon Auto-Analyzer if system) labeled 1A, IB, 2A
2B...7A, 7B into support racks. Using the calibrated
dispensing pipet bottle, add 3 niL of ES solution to each
4 rnL vial.
15.1.7.2 Using the displacement pipet, add 50 jtL of methanol to each
vial. Pour about 3 mL of Standard Flask #1 standard
(see Section 15.1.1) into a labeled 4 mL vial.
15.1.7.3 Immediately pipet 50 /iL of this standard into the 4 mL vials
labeled 1A and IB containing the ES solution and methanol.
Note: This transfer must be done without delay to prevent
the standard concentration from increasing significantly cue to
evaporation of the methanol solvent.
15.1.7.4 Repeat the procedure for each of the other 6 standards. If
there is a delay of more than 5 minutes between the
preparation of these mixtures and the next step, put caps on
the 4 mL vials.
Note: There should be fourteen vials, each containing 3 mL
of ES solution, 50 p-L of methanol, and. 50 fiL of Standard
H2SO4 solution (see Section 16.1.1). Two aliquots from
each vial (1A, IB, 2A, 2B, 3A, 3B,...7A, 7B) will be
analyzed.
15.1.7.5 Place vial 1A in a rack. In a second rack place two-2 mL
vials labeled 1A1 and 1A2. Use the 1 mL automatic pipet to
mix the contents of vial 1A by drawing I mL into the pipet
tip and then dispensing it back into the vial three times. Then
use the same pipet to transfer 1 mL of the contents of vial 1A
to each of the two labeled (IA1,1A2) 2 niL vials. Place caps
on the vials. After transferring the two aliquots, rinse the
automatic pipet tip in a flask of DDW. Repeat the transfer
procedure for each of the other working standard pairs. (IB
aliquot into vials IB1 and 1B2, 2A aliquot into vials 2A1 and
2A2, etc.). These are the working standards.
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15.2 Calibration of pH Meter
The pH meter requires temperature calibration whenever a new electrode is
used. Use the manufacturer's procedure in the instrument manual. This
calibration should be repeated every three months while not in use. The pH
meter is left with the power cord plugged into the AC outlet, the mode control
knob is left in the standby position, and the combination electrode is immersed
in a 4 M KC1 solution (a slit nibber stopper seals the bottle with the electrode
in it). Keep a record of the temperature calibrations in a lab notebook.
15.3 Pre-analysis Calibration
Note: Figure 10 outlines the steps for proper calibration and set-up for analysis
of the Teflon® filter sample for pH determination. Analysis should be
performed at room temperature.
15.3.1 Use a pH Analytical Laboratoiy Log Form (see Figure 11) to record all
data.
15.3.2 Fill three 4 mL vials with pH 7 buffer. Withdraw the electrode from
the 4 M KC1 bottle and wipe the tip gently with a Kimwipe® to remove
the bulk of the solution. Rinse the electrode with one vial of pH 7
buffer. Do not test pH of the first vial.
15.3.3 Immerse the electrode in the second vial of the pH 7 buffer. Use a
small bottle or other support to hold the vial up to the electrode while
waiting for the meter reading to equilibrate.
15.3.4 Test the pH by turning to the pH mode of the meter. Allow the reading
to stabilize for at least 30 seconds. Record the result on the Analytical
Laboratory Log Form for pH 7, entry 2.
15.3.5 Turn to standby mode, and then test the last vial of pH 7 buffer.
Record the results on the log form for pH 7, entry 3. If the pH value
for the 2nd cup is not 7.00 ± 0.01, adjust the "calib." knob to obtain a
reading of 7.00. Note this adjustment on the log foim.
15.3.6 Fill three 4 mL vials with pH 4 buffer. With the meter in the standby
mode, remove the cup containing pH 7 buffer, wipe the tip of the
electrode gently with a Kimwipe®, and then rinse the electrode with the
first vial of pH 4 buffer. Do not record pH.
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15.3.7 Test the next two yials of pH 4 buffer as above, recording the results
on the log form. If the pH value for the third vial is not 4.00 ± 0.01,
adjust the "slope" knob to get a reading of 4.00. If the value for the
second vial was not 4.00 ± 0.01, the calibrations at pH 7 and at pH 4
must both be repeated.
15.4 pH Test of HCIO^ Solutions
Note: The 0.01 N HCIO^ solution is used to prepare the ES solution which, in
turn, is used to prepare the EA solution. It is imperative that the pH value for
the EA solution be 4.09 ± 0.04. If this pH value is not achieved, then one or
more of the HCIO^ solutions must be reprepared.
15.4.1 Finish the calibration of the pH meter with pH 4 buffer.
15.4.2 Rinse the pH electrode with DDW. Wipe the tip of the electrode with
a Kimwipe®.
15.4.3 Fill three 4 mL vials with EA solution. Measure the pH of the test EA
solution in similar fashion to the buffer solutions. The values must be
4.09 ± 0.04.
15.4.4 If the above pH values axe not achieved, follow Section 15.1.6 to
rsprepare the solutions. Test the pH of the new solutions. Repeat as
necessary to obtain an average pH of 4.09 ± 0.04.
15.4.5 Leave the electrode immersed in the "3rd vial" with the meter in the
standby mode until ready to start analysis of the working standards.
15.5 Analysis of Working Standard
Note: Immediately following the EA analysis, start testing the working
standards.
15.5.1 With the pH meter still in the standby mode, remove the last vial from
the electrode, gently wipe the tip with a Kimwipe®, and then immerse
the electrode into the working standard vial 1A1.
Note: Only two yials are available for each working standard (also for
filter extracts). Thus, pH measurement is made for both of the two
vials for each sample. Also, the electrode tip is not wiped, between the
1st and 2nd vials of each sample.
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15.5.2 After testing the pH of vial 1A1, test vial 1A2. Record the results of
both on the Analytical Laboratory Log Form.
15.5.3 With the meter in the stand-by mode, remove vial 1A2, wipe the
electrode with a Kimwipe® and test one 2 mL vial of EA solution.
15.5.4 Test a 2nd vial of EA solution; record the results on the log form.
Discard the 1st vial of EA, but retain the 2nd vial to be used as the 1st
vial for the next EA test.
15.5.5 Mean pH value for the EA solutions should be 4.09 ± 0.04. If the
above pH values are not achieved, follow Section 15.1.6 to reprepare
the EA solution. Retest. If still outside range, investigate problem
with probe, have Laboratory Manager review previous recorded pH
data for samples and EA solutions to determine validity of
measurements.
15.5.6 Continue testing the remainder of the working standards, 1B1, 1B2,
2A1, 2A2, 2B1, 2B2. . .7B1, 7B2. Remember that the electrode tip is
wiped both before and after each pair of test solutions, but not in
between two vials of the same sample.
Note: If there is trouble in obtaining constant pH values, it may be
necessary to use a magnetic stirrer to keep the contents to be measured
uniform. If employed, ensure that the sample vials are insulated from
any temperature increase of the stirring platfoim which may occur
during extended use.
15.5.7 Use the mode control knob in the "temp." position to measure the
temperature of the test solutions every 5-10 samples and record the
results on the Analytical Laboratory Log Sheet Form.
15.6 Analysis of Filter Extracts
Following measurement of the pH of the working standards, measure the pH of
the filter extract and record on the Analytical Laboratory Log Form. After ten
filter extracts have been tested, make an additional test with the EA solution
and record temperature. At the end make a final test of pH 4 buffer. If not
4.00 ± 0.04, then perform a new calibration; the laboratory manager must then
decide (and document) how to reduce the unknowns based on pre- and post-
calibrations. Criteria and corrective action should be met according to
Section 15.5.5. Follow manufacturer's directions for shut-down of pH meter.
Immerse the electrode tip in the bottle of 4 M KC1.
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16. Assumption of Annual Denuder System
16.1 The measurement of acid aerosol requires that ammonia be eliminated from the
sample stream to prevent inaccurate measurement of the acid aerosol, thus
biasing the results. To address this issue, a citric acid coated denuder to
remove (denuder) ammonia from the gas stream is positioned in front of the
filter assembly where strong acid aerosols are. collected. The efficiency of the
citric acid denuder to remove NH3 is assumed to be 100 percent.
16.2 The efficiency of the impactor collection system decreases with Increased
particulate loading. The average operational time before such loading occurs
has not been determined. Likewise, the removal efficiency of the denuders
have cot been fully explored. Thus, both the impactor and denuders are
removed after each sampling event and replaced with new components.
16.3 Other assumptions which are made associated with the performance of the
annular denuder system for validity of the calculations presented in Section 17
are:
• All alkaline particles (> 2.5 /xm) are removed at the sampler inlet;
• The cyclone or elutriator/impactor assembly have DP50 cut size of 2.5 /*m;
• The citric acid coated-denuder removes 100% of ammonia from the gas
sample stream;
• Fine (<2.5 pm) acid (H2SO4) aerosol losses in the denuder are less than 1%;
• The Teflon0 filter is 100% efficient in collecting fine acid aerosols; and
• The molar ratio of NH4NO3 to is assumed to be less than 1C%.
However, if NH4NO3 is captured on the Teflon® filter, its dissociation during
sampling may occur, thus affecting acidity measurements. To address these
concerns, the user is encouraged to consider the "Enhanced Method", as
outlined in Part B of this document.
17, Atmospheric Srmcm.s Coinientrntlon Calculations
17,1 Calculations Using Results from pH Measurement
17.1.1 A convenient method of expressing concentration of the hydrogen ion
was first proposed by Sorensen in 1909 and has been widely adopted by
chemists.
pH = - log [H+]
[H+] = 10-?H
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17.1.2 For each working standard on a given analytical day, calculate the
"apparent net strong acid concentration" as follows:
Cj = 10'P^^^i - lO-P11^
where:
Cj = apparent net strong acid concentration, molar,
pHWSj = measured mean pH of a working standard, and
pHEA = measured mean pH of the EA solution.
17.1.3 For each analytical day, utilizing a particular set of freshly prepared
daily working standards, develop a standard curve by calculating the
linear regression of Cj vs. Cgg, as documented in Section 15.1.1.1.
Calculate slope and intercept of the standard curve.
17.1.4 Calculate the corresponding "apparent net strong acid concentration"
from the sample pH utilizing the following equation:
r = 10"PHS - lO-P111^
where:
Cs = apparent net strong acid concentration for unknown sample,
molar,
pHS = measured pH of the sample (S), and
pHEA = measured pH of the EA solution.
17.1.5 Utilizing the slope and intercept of the standard curve, calculate
equivalent mass of strong acid:
Cf = [Intercept] + [Cs] [Slope]
where:
Cf = apparent net strong acid mass, fig, as calculated from
standard curve,
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Intercept = calculated relationship from linear regression analysis
of vs. Cgq, and
Slope = calculated relationship from linear regression analysis
of q vs. Cgq.
17.2 Calculation of Air Volume Sampled, Corrected to Standard Conditions
17.2.1 The actual sample air value, V, for each sample is calculated using the
data from the Field Test Data Sheet. These data include the initial and
final elapsed times, the initial rotameter reading, and the rotameter I.D.
No. Use the calibration curve for the given rotameter to calculate the
flow for the sample, in LPM, if applicable. Calculate the value of V as
fellows:
V = [F] IT)
where:
F = flow from the calibration curve, L per minute,
T = net elapsed time, min, and
V = total sample volume, L
17.2.2 Convert L to nr* by:
Vs = V x (10-3)
where:
Vs = total sampling volume, m3, and
1C~3 = conversion factor, m3/L.
17.2.3 Calculate the air volume sampled, corrected to EPA-reference conditions:
v = v
vsstd
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VSstd = volume of sample at EPA-reference conditions, m ,
Vs = volume of gas sample through the dry gas meter, or
calculated volume sampled as indicated by rotameter
(see Section 17.2.1), m3,
^std = absolute EPA-reference temperature, 298 °K,
Tm = average flowmeter or dry gas meter temperature, °K,
^bar = barometric pressure of flow or volume measurement
condition, mm Hg,
Pst(j = EPA-reference barometric pressure, 760 mm Hg, and
Y = dry gas meter calibration factor (if applicable),
dimensionless.
17.3 Calculation of Strong Acidity Aerosol Concentration
17.3.1 Calculate the final concentration of apparent net fine particle (<2.5 nm)
strong acidity (as H2SO4):
cH+=cf/vSstd
where:
CH+ = apparent net fine particle strong acidity concentration,
Mg/m3,
Cf = apparent net strong acid, fig, as calculated from
standard curve, and
Vg = volume of sampled gas at EPA-reference conditions
(see Section 17.2.3), m3.
18. Variations of the Acid Aerosol Denuder System
One modification of the fine particle strong acidic aerosol denuder system involves
adding additional denuders to selectively quantitate other gaseous and particulate
species in the atmosphere, and is illustrated in Figures 12 and 13. This system was
developed to measure reactive acidic and basic gases and particulate matter which are
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contained in ambient air. The chemical species which can be measured utilizing this
system are gaseous SC^, HNO2, HNO3, NII3, and particulate SO^—, NO"^, and
H+. Other similar chemical species can be successfully collected by the system with
modifications (i.e., changing the denuder coating solutions, the denuder sequence, and
the filter types and sequence). Once collected, the pollutant concentrations are
quantified by ion chromatography (IC) analysis and/cr Technicon colorimeter autc-
anaiysis. A full description of this methodology can be found in "Compendium of
Methods for the Determination of Air Pollutants in Indoor Air," U.S. Environmental
Protection Agency, Atmospheric Research and Exposure Assessment Laboratory,
Research Triangle Park, N.C. 27711, HPA-600/4-90-010.
19, Msthod Safety
This procedure may involve hazardous materials, operations, and equipment. This
method does not purport to address all cf the safety problems associated with its use.
It is the user's responsibility to establish appropriate safely and health practices and
determine the applicability of regulatory limitations prior to the implementation of this
procedure. This should be part of the user's SOP manual
20, Performance Criteria and Quality Assurance (OA)
Required quality assurance measures and guidance concerning performance criteria that
should be achieved within, each laboratory are summarized and provided in the
following section.
20.1 Standard Operating Procedures (SOPs)
20.1.1 SOPs should be generated by the users to describe and document the
following activities in their laboratory: I) assembly, calibration, leak
check, and operation of the specific sampling system and equipment
used; 2) preparation, storage, shipment, and handling of the sampler
system; 3) purchase, certification, and transport of standard reference
materials; and 4) all aspects of data recording and processing, including
lists of computer hardware and software used.
20.1.2 Specific stepwise instructions should be provided in the SOPs and should
be readily available to and understood by the personnel conducting the
monitoring work.
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20.2 Quality Assurance Program
The user should develop, implement, and maintain a quality assurance program
to ensure that the sampling system is operating properly and collecting accurate
data. Established calibration, operation, and maintenance procedures should be
conducted on a regularly scheduled basis and should be part of the quality
assurance program. Additional QA measures (e.g., trouble shooting) as well as
further guidance in maintaining the sampling system are provided by the
manufacturer. For detailed guidance in setting up a quality assurance program,
the user is referred to the Code of Federal Regulations (see Section 21,
Citation 11) and the EPA Handbook on Quality Assurance (see Section 21,
Citation 12).
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21. References
1. Waldman, J. M., Operations Manual fcr the Annular Denuder System Used ill the
USEFA/RIVM Atmospheric Acidity Study, UMPNJ - Robert Wocc Johnson Medical
School, Piscataway, NJ, August 28, 1987.
2. American Chemical Society Subcommittee on Environmental Chemistry, "Guidelines
for Data Acquisition and Data Quality Evaluation in Environmental Chemistry,"
Analyt. Chem., 52:2242-2249, 1980.
3. Sickles, n, J. E., "Sampling and Analytical Methods Development for Dry Deposition
Monitoring," Research Triangle Institute Report No. RH/2823/00-15F, Research
Triangle Institute, Research Triangle Park, NC, July 1987.
4. Forrest, J., and L. Newman, "Sampling and Analysis of Atmospheric Sulfur
Compounds for Isotopic Ratio Studies," Atmos. Environ., 7:562-573, 1973.
5. Stevens, R. K., et al., Abstract for ACGIH Symposium: on Aciran COS in Air
Sampling, "Inlets, Denuders and Filter Packs to Measure Acidic Inorganic Pollutants
in the Atmosohere," Asilcmar Conference Center, Pacific Grove, CA, February 16,
1986.
6. Appel B. R., Povard V.s and Kothney E. L., "Loss of nitric acid within inlet devices
for Atmospheric Sampling,' Paper presented at 1987 EPA/APCA Symposium:
Measurement of Toxic and Related Air Pollutants, Research Triangle Park, NC, 3-6
May 1987.
7. B ram an R. S., Shelley T. J., and McCienny W. A., "Tungstic Acid for
Preconcentraticn and Determination of Gaseous and Particulate Ammonia and Nitric
Acid in Ambient Air,,: Analyt. Chem., 54:358-364, 1983.
8. Fern, M., "Concentration Measurements and Equilibrium Studies of Ammonium,
Nitrate and Sulphur Species in Air and Precipitation," Doctoral Thesis, Department of
Inorganic Chemistry, Goteborg University, Goteborg, Sweden, 1986.
9. Ferm, M., and Sjodm A., "A Sodium Carbonate Coated Denuder fcr Determination of
Nitrous Acid in the Atmosphere,1' Atmos. Environ., 19:979-985, 1985.
10. Stevens, R. K., and Rickman, E., Jr., "Research Protocol/Method for Ambient Air
Sampling with Annular Denuder Systems," prepared for U.S. Environmental Protection
Agency, Atmospheric Chemistry and Physics Division, Office of Research and
Development, Research Triangle Park, NC, ASRL-ACPD-RPM 003, January 1988.
11. 40 CFR Part 58, Appendix A, 3.
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12. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume n -
Ambient Air Specific Methods, EPA 600/4-77-0272, May, 1972.
13. Bolleter, C.J., Bushwan, and Tidwell, P.W. (1961), "Spectrophotometric
Determination of Ammonia as Indophenol," Anal. Chem. 21, 592-594.
14. Harwood, J.E. and Kuhn, A.L. (1970), "A Colorimetric Method for Ammonia in
Natural Water," Water Res. 4, 8055-811.
15. Koutrakis, P., Wolfson, J.M., Slater, J.L., Brauer, M., Spengler, J.D., Stevens, R.K.,
and Stone, C.L., "Evaluation of an Annular Denuder/Filter Pack System to Collect
Acidic Aerosols and Gases," Environ. Sci. & Tech. 22, 1463-1468, 1988.
16. Mann, L.T., Jr., "Spectrophotometric Determination of Nitrogen in Total Micro-
kjedahl Digests," Anal. Chem. 35, 2179-2182, 1963.
17. Possanzini, M., Febo, A., and Liberti, A., "New Design of a High-performance
Denuder for the Sampling of Atmospheric Pollutants," Atmos. Environ. 17,
2605-2610, 1983.
18. Stevens, R.K., and Rickman, E.E., Research Protocol/Method for Ambient Air
Sampling with Annular Denuder Systems. Report ASRL-ACPD-RPM 003, U.S. EPA,
Research Triangle Park, N.C., January 1988.
19. Koutrakis, P., Wolfson, J.M., and Spengler, J.D., "An Improved Method for
Measuring Aerosol Strong Acidity: Results from a Nine-Month Study in St. Louis,
Missouri and Kingston, Tennessee," Atmospheric Environment, 22:157-162, 1988.
20. Brauer, M., Koutrakis, P., Wolfson, J.M., and Spengler, J.D., "Evaluation of the Gas
Collection of an Annular Denuder System Under Simulated Atmospheric Conditions,"
Atmosperhic Environment, 23:1981-1986, 1989.
21. Koutrakis, P., Wolfson, J.M., Brauer, M., and Spengler, J.D., "Design of a Glass
Impactor For an Annual Denuder/Filter Pack System," Aeros. Sci., and Techn.,
12:607-612, 1990.
22. Sjodin A. and Ferm, M., "Measurements of Nitrous Acid In An Urban Area,"
Atmospheric Environment 19, 985-992, 1985.
23. Vossler, T.L., Stevens, R.K., Paur, R.J., Baumgardner, R.E., and Bell, J.P.,
"Evaluation of Improved Inlets and Annular Denuder Systems to Measure Inorganic
Air Pollutants,H Atmos. Environ. 22, 1729-1736, 1988.
24. Technical Assistance Document for Sampling and Analysis of Toxic Organic
Compounds in Ambient Air, EPA-600/8-90-005, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1990.
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Table 1.0. Summary of Key Probe Siting Criteria for
Acid Aerosol Monitoring Stations
Factor
Criteria
Vertical spacing above ground
• Representative of the breathing zone and avoiding effects
of obstruction, obstacles, and roadway traffic. Height of
probe intake above ground in general, 2-3 m above ground
and 2-15 m above ground in the case of nearby roadways.
* About 1 m or more above the structure where the sampler
is located.
Horizontal spacing from
obstruction and obstacles
• Minimum horizontal separation from obstructions such as
trees is >20 m from the dripline and 10 m from the
dripline when the trees act as an obstruction.
* Distance from sampler inlet to an obstacle such as a
building must be at least twice the height the obstacle
protrudes above 'iie sampler.
* If a sampler is located on a roof or other structures, there
must be a minimum of 2 m separation from walls,
parapets, penthouses, etc.
• There must be sufficient separation between the sampler
and a furnace or incinerator flue. The separation distance
depends on the height and the nature of the emissions
involved.
Unrestricted, airflow
Spacing from roads
• Unrestricted airflow must exist in an arc of at least 27C
degrees around the sampler, and the predominant wind
direction for the monitoring period must be included in the
270 degree arc.
• A sufficient separation must exist between the sampler and
nearby roadways to avoid the effect of dust re-entrainment
and vehicular emissions on the measured air
concentrations.
• Sampler should be placed at a distance of 5-25 m from the
edge of the nearest traffic lane on the roadway depending
on the vertical placement of the sampler inlet which could
be 2-15 ni above ground.
Acid Aerosol
Part A
-------
TO PUMP
AND FLOW CONTROLLER
FILTER ASSEMBLY
COUPLER
ANNULAR DCNUDCH
COUPLHI
TEFLON
Flllan
NHg removal
I
CYCLONt
Revision No. 0
Date 11/92
Page 38 of 51
AEROSOL(H *)
COLLECTED
Figure la. Annular Denuder System (ADS) with Cyclone
TO PUMP
AND FLOW CONTROLLER
FILTER ASSEMBLY
COUPLER
ANNULAR DENUDER
COUPLER-IIPACTOft
ELlTTMATOft
wf AoMlaraUon M
TEFLON
Fllttfi
T
AEROSOL (H +)
COLLECTED
t
NH. REMOVAL
La
Figure lb. Annular Denuder System with Impactor Assembly
Acid Aerosol
Part A
-------
Revision No, C
Date 11/92
Page 39 of 51
TFMR OONT.
AIR OUTLET "fSMP-
QWITOHES
i2v r
M
8W>
MM |
HEATIh
cyefe Tfrnff
FILTER PACK
COUPLER
ANNULAR DENUDER
WTTH CITRIC ACID
COATfNO
DCOtftpif
Oaamsttf
' gS3 ©
taMssJTlmif
O Ma»
-------
Revision No. 0
Date 11/92
Page 40 of 51
ACCELERATION JET
ELUTRIATOR
ALUMINUM
(a) GLASS ASSEMBLY
AIR
t
AIR
TEFLON
ACCELERATION
JET
t
ELUTRIATOR
ACCELERATION JET REMOVAL TOOL
(b) ALUMINUM AND TEFLON ASSEMBLY
Figure 3. Available Elutriator and Acceleration Jet Assemblies
Acid Aerosol
Part A
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Revision No. 0
Date 11/92
Page 41 of 51
s??:cS:.c^
PIN REMOVAL TOOL
iMPACTOfl SUPPORT PiN
AND FRIT
VITON "0" RING
#30 THREADS
COUPLER / IMPACTOR
HOUSING SEAT
ANNULAR DENUDER/
IMPACTOR <242 mm LONG)
— #30 THREADS
GAP
Figure 4. Glass Annular Denuder with Inset Impactor Assembly
Acid Aerosol Pari A
-------
Revision No. 0
Date 11/92
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VIEW A
TEFLON SEAT SUPPORT
Acid Aerosol
Figure 5. Side View Impactor/Coupler Assembly
Part A
-------
Revision No. 0
Date 11/92
Page 43 of 51
INTERNAL SURFACE
TEFLON COATED
CROSS-SECTIONAL VIEW
Figure 6. Internal Schematic of Annular Denuder
Acid Aerosol
Part A
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Revision No. 0
Date 11/92
Page 44 of 51
WALL
CLAMP
DRYER/
CLEANER
BOTTLE —
FRIT
THERMOPLASTIC CAPS
WI TEFLON ® SEAL RINGS
AND HOSE BARBS
TEFLON®
TUBING
BACK-TO-BACK
CONNECTORS
DENUDERS
DENUDER
CAPS
MANIFOLD
AIR
Figure 7. Drying Train and Manifold
Acid Aerosol
Part A
-------
Revision No. 0
Date 11/92
Page 45 of 51
wm. ¦ REUAftV
PUW
AUWMCW WLTER
SK3y3IH9 OUTLET
VIHYON *er B1N0
WfTON *0* ftlHO
ALTER HOUWtt
WtlT
Df.LflfM
SCRfWSvftVt
Figure 8. Acid Aerosol Filter Assembly
Acid Aerosol Part A
-------
Revision No. 0
Date 11/92
Page 46 of 51
DETERMINATION OF THE STRONG ACIDITY OF
ATMOSPHERIC FINE-PARTICLES (<2.5^)
GENERAL
Project: Date:
Site: Location of Sampler:
Location:
Operator:
Sample Code:
EQUIPMENT
Mass Flow
Controller No.:
Lab Calibration Date:
Flow Rate Set Point:
Calibrated By:
Rotameter No.:
DGM No.:
Sampler
Citric Acid Denuder No.:
Filter Assembly Na_:
SAMPLING DATA
Time
Stop
Time:
Flow Rate: —
Temperature:
Pressure:
Avg. Flow Rate: —
Leak Check (Before):
(After):
Total Sample Vol.:
Flow Maintained Rate:
(±5%)
Time
Flow
Rate (Q),
L/min
Ambient
Temperature,
°C
Barometric
Pressure,
mm Hg
Relative
Humidity,
%
Comments
Figure 9. Annular Denuder Field Test Data Sheet
Acid Aerosol
Part A
-------
Revision No. 0
Date 21/92
Page 47 of 51
pH 7 Buffer
pH 4 Buffer
EA Solution
working Standards
EA Solution
DONE?
DONE?
NO
EA Solution
Analysis of up
to 10 Filter Extracts
Temperamre
NO
pH A B uffer
Figure 10. Calibration and Analysis Step for pH Determination
Acid Aerosol
Part A
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Revision No. 0
Date 11/92
Page 48 of 51
Determination of the Strong Acidity of
Atmospheric Fine-Particles (<2.5 fim)
Name: Sample I.D.:
Date: Location:
LAB:
Constituent
RUN NUMBER
1
2
3
4
5
6
7
pH 7 Buffer
1
2
3
pH 4 Buffer
1
2
3
EA Solution
1
2
3
Working Standards
1A1
1A2
EA
1B1
1B2
EA
2A1
2A2
Temp.
EA
2B1
2B2
EA
3A1
3A2
EA
Temp.
3B1
3B2
EA
Figure 11. pH Analytical Laboratory Log Form
Acid Aerosol
Part A
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Revision No. 0
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Page 49 of 51
1
Constituent
4AI
4A2
EA
4B1
4B2
Temp.
EA
5AI
5A2
EA
5B1
5B2
EA
6AI
6A2
Temp.
EA
6B1
6B2
EA
EA
7A1
7A2
EA
7B1
7B2
TemD.
RU
N NUMB
ER
1
2
3
4
5
6
7
i
Sample Extracts
A
i Ai
B
61
C
CI
D
PI
E
El
EA
Terno.
ur- U) yj » »J t yf | .' !
j
1
EA Solution
1
2
3
. -
pH4 Buffer
1
2
3
Figure 11. pH Analytical Laboratory Leg Form (cont.)
Acid Aerosol
Pari A
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Revision No. 0
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FILTER PACK
NYLON
TEFLON
COUPLER( TYPICAL)
*
—- no-
— nh4 ~ sa-
4,
a
*
*
I
NH.
1
HCI, KN02
HNO3 , SO2
CYCLONE
Figure 12. Schematic View of Annular Denuder with Cyclone
Adaptor for Measurement of Reactive Acidic and
Basic Gases and Particulate Matter (<2.5 pm) in Ambient Air
Acid Aerosol
Part A
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Revision No. 0
Date 11/92
Page 51 of 51
TEMP. CONT,
AIR OUTLET TFMP1. CONT.
SWITCHES
J,
NYLON
. TEFLON
CITRIC ACID
COATING
y, N*2C03 COATING
#f
rooSooFI
i B'T®"
Man Motof
1 Fu§*
l~ŁMP. CONT. FAN
INLET
TOTAL
FLOW
CYCLONE
Figure 13. Annular Demider System with Cyclone in Heated Sampling Case
for Measurement of Reactive Acidic and Basic
Gases aod Particulate Matter (< 2.5 pm) in Ambient Air
Acid Aerosol
Part A
-------
PART B
DETERMINATION OF THE STRONG
ACIDITY OF ATMOSPHERIC FINE-PARTICLES
{<2.5 //m} USING ANNULAR
DENUDER TECHNOLOGY
ENHANCED METHOD
-------
DETERMINATION OF THE STRONG
ACIDITY OF ATMOSPHERIC FINE-PARTICLES
(<2,5 fim) USING ANNULAR
DENUDER TECHNOLOGY
ENHANCED METHOD
TABLE OF CONTENTS
Tonic Page
1. Scope ............. ............. B-1
2. Applicable Documents 0-2
3. Summary of Msthod B-2
4. Significance B-4
5. Definitions 3-5
6. Apparatus ............. 3-5
6.1 Sampling B-6
6.2- Analysis 3-9
7. Reagents and Materials B-li
E. Preparation of Impactor Frit and Denucier Coating B-13
9. Impactor Frit installation . B-13
10. Filter Preparation and Assembly B-14
10.1 Citric Acid Coaled Filter B-14
10.2. Filter Pack Assembly .B-14
11. Annular Denuder System Preparation B-16
11.1 Coaling Procedure .B-16
11.2 Drying Procedure B-16
11.3 Denuder System Assembly . B-17
11.4 Laboratory Leak-Check of ADS B-18
i
-------
TABLE OF CONTENTS (continued)
Topic Page
12. Sampling B-19
12.1 Placement of Denuder System B-19
12.2 Start-up B-21
12.3 Sample Shutdown B-22
12.4 Corrective Action for Leak Test Failure B-23
13. ADS Disassembly B-24
14. Extraction Procedure B-24
15. pH Analysis B-27
15.1 Standard and Reagent Preparation B-27
15.2 Calibration of pH Meter B-30
15.3 Pre-analysis Calibration B-30
15.4 pH Test of HCIO4 Solutions B-31
15.5 Analysis of Working Standard B-32
15.6 Analysis of Filter Extracts B-33
16. Ion Chromatography Analysis B-33
16.1 Standard Preparation B-33
16.2 Reagent Preparation B-34
16.3 Sample Preparation B-35
16.4 Basic System Operations B-36
16.5 Basic Troubleshooting B-40
17. Ammonia Analysis by Technicon Auto-analysis B-42
17.1 Standards and Stock Solutions Preparation B-42
17.2 Reagent Preparation B-45
17.3 Procedure for Auto-analyzer Set-up B-45
17.4 Procedure for Sample Run B-46
18. Assumption of Annual Denuder System B-47
19. Atmospheric Species Concentration Calculations B-48
19.1 Calculations Using Results from pH Measurement B-48
19.2 Calculation Using Results from IC Analysis B-51
19.3 Calculation Using Results from Auto-analyzer B-51
ii
-------
TABLE OF CONTENTS (continued)
IsRk Bags.
20. Variations of the Acid Aerosol Denuder System . B-51
21. Method Safety . .3-52
22. Performance Criteria and Quality Assurance (QA) B-52
22.1 Standard Operating Procedures (SOPs) B-52
22.2 Quality Assurar.ee Program B-53
23. References B-54
iii
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Page 1 of 72
DETERMINATION OF THE STRONG
ACIDITY OF ATMOSPHERIC FINE-PAR f lCLLS
{<2.5 fjm) USING ANNULAR
PLNUDf.R TECHNOLOGY
ENHANCED METHOD
1. Scope
1.1 This document describes the protocol for the quantitative determination of
equivalent strong acidity of atmospheric fine-particle (<2.5 ^m) in ambient air as
hydrogen ion by pH.
1.2 The methodology detailed in the ''enhanced method" is a composite of
methodologies developed by U.S. Environmental Protection Agency (USEPA),
University cf Kansas, Robert Jolinson Medical School, New York State
University, Harvard University and the CNR Laboratories. It is currently
employed in a number of air pollution studies ir_ Italy, U.S.A., Canada, Mexico,
Germany, Austria, and Spain, and in such institutions as public health services
and epidemiology and environmental-research centers.
While the "standard method" utilizes a denuder and filter assembly for
determination of the strong acidity atmospheric fine-particles, it does not account
for potential interferences from nitric acid (HNO^) and nitrate aerosol (NH4NO3)
which might bias the acidity measurement. The "enhanced method" adds an
additional denuder upstream cf the filter assembly to selectively remove nitric acid
from the gas stream prior to filtration. In addition, to correct for biases due to
the dissociation of nitrate aerosol captured on the Teflon® filter, thus affecting
acidity measurements, a backup nylon filter has been incorporated to capture
volatile HNO3 followed by a glass-fiber filter impregnated with citric acid to
retain the dissociated NH3 from NH4NO3. The ammonia concentration is
subtracted from the nitrate value, then combined with the acidity measurement of
the Teflon® filter to give an unbiased measurement of the atmospheric fine particle
strong acidity aerosol found on the Teflon® filter.
The techniques, procedures, equipment, ana other specifications comprising this
method are derived and composited from those actually used by the contributing
research organizations and thereby known to be serviceable and effective. At this
stage, this method is a unified, consensus, tentative, draft method intended for
further application and testing. Users should be advised that the method has not
yet been adequately tested, optimized, or standardized. Many of the specifications
have been initially established by technical judgment and have not been subjected
to ruggedness testing. In some cases alternative techniques, equipment, or
Acid Aerosol
Par! B
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Revision No. 0
Date 11/92
Page 2 of 72
specifications may be acceptable or superior. In applying the method, users are
encouraged to consider alternatives, with the understanding that they should test
any such alternatives to determine their adequacy and to confirm and document
their possible advantages. Information and comments are solicited on
improvements, alternative equipment, techniques, or specifications, performance,
or any other aspect of the method. All such information should be sent to the
EPA Project Manager identified on the cover page and will be considered for
incorporation in future revisions of the method.
1.3 The equipment described herein can be modified to measure acidity of
atmospheric gases and particulate matter contained in both indoor and outdoor
atmospheres. Modification to this methodology were developed for monitoring
regional-scale acidic and basic gases and particulate matter in support of U.S.
EPA field programs involving the Integrated Air Cancer Research Program and
the Acid Deposition Network. Similarly, the methodology has been used to
characterize urban haze in Denver, Houston, Boston and Los Angeles.
2. Applicable Documents
2.1 ASTM Standards
D1356 Definitions of Terms Related to Atmospheric Sampling and Analysis
2.2 Other Documents
Ambient Air Studies (1-23)
U.S. EPA Technical Assistance Document (24)
3. Summary off Method
3.1 The annular denuder system (ADS) consists of an inlet with an impactor or
cyclone preseparator designed to eliminate all particles with a DP50 of 2.5 or
greater, annular demiders, and a three-stage filter assembly. In operation, air is
drawn through the elutriator-accelerator jet assembly, an impactor frit and coupler
assembly, past two demiders to remove nitric acid and ammonia, then into a three-
stage filter pack assembly. The three-stage filter pack contains 47-mm filters
supported by stainless steel screens and separated by polyethylene spacer rings.
The-first filter is a 2 pm pore-size Teflon® membrane filter, Zefluor (Gelman
Sciences), followed by a 1 pm pore-size nylon membrane filter, Nylasort)®
(Gelman Sciences), and then a citric acid-impregnated, glass-fiber filter, and a
prefilter-pad, type AP filter (Millipore). The glass fiber is impregnated with
1.0 mL of 2 percent (w/v) citric acid solution in ethanol. The Teflon® filter
collects fine acidic particles. The nylon second filter traps nitric acid arising from
the dissociation of ammonium nitrate or nitric acid collected on the Teflon® filter.
Acid Aerosol
Part B
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Page 3 of 72
The citric acid-impregnated glass fiber filler retains ammonia also arising from the
disassociation of ammonium nitrate collected on the Teflon® filter. The three
filters together give an unbiased measure of atmospheric acidity. A pump unit
maintains a flow of 10 Lprr., anc. a 7-day tinier allows programmed start and end
times. ADS samples may be run for 8, 12, or 24-hour durations or in cycled
operation (e.g., 10 minutes on/50 minutes off for 7-day periods). Figure 1
illustrates a two-stage annular denuder system assembled, ready for testing.
Figure 2 shows the field sampling box with the two-stage annular denuder and
pump-timer system.
3.2 Following each run, the ADS assembly is removed from its field housing, its ends
capped, and brought back to the laboratory. In the laboratory, the assembly
pieces are uncoupled and capped. The denuder tubes are not extracted. Filters
are unloaded from the filter pack in an ammonia free atmosphere and either
directly extracted or stored in a petri-dish for later extraction. A glove-box, lined
with citric-acid soaked paper, is used to maintain an ammonia-free atmosphere.
As illustrated in Figure 3, the Teflon® filter is extracted and analyzed for
hydrogen ion, or strong acidity, by pH determination. Nitrates, captured by the
Nylon® filter are analyzed by ion chromatography. Ammonium ion collected on
the citric acid-impregnated glass fiber filter is analyzed by the indophenol method
using an auto-analyzer.
To extract the Teflon® filter, it is placed in an extraction vessel, membrane side
down. The filter is wetted with 100 of methanol, then extracted with 3.0 mL
of extraction solution (IS). The extraction vessel is put in an ultrasonic bath for
20 minutes. The extraction solution is then decanted into a container.
3.3 Acidity determinations are made using pH measurements of 1 mL of the extracted
filter solution in polystyrene vials. Filter acidities are calculated from standards
made with sulfuric acid. The standards range from 0 to 150 fig equivalent of
strong acid aerosol concentration. A pH meter is used to measure the pH of the
filter extract. For each batch of filter extracts, a calibration curve is calculated
using the mean pH of each standard reading taken before and after the batch.
Loss of volatile nitrate species from the Teflon® filter may occur. These
volatilized components (NH3, NH^NO^, and HNO3) are collected on the
following nylon and citric acid-impregnated backup glass fiber filters. The blank
corrected nitrate concentration on the nylon filter is due to nitric acid, from the
dissociation of ammonium nitrate from the Teflon® filter. The blank corrected
ammonium concentration on the citric acid impregnated glass fiber filter is due to
ammonia liberated from the Teflon® filter. The final acidity correction is
calculated as the difference cf nylon filter nitrate less glass fiber filter ammonium.
Acid Aerosol
Part B
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Page 4 of 72
4. Significance
4.1 Acid aerosols are found in the atmosphere as a result of atmospheric reactions of
emissions from a variety of fossil fuel combustion sources including power plants,
industrial and commercial facilities, hazardous waste storage and treatment
facilities, etc. Awareness of the effects of concentrations of acid aerosols on
human health and property has been documented over the past several years. The
Clean Air Act Amendments of 1970 required the U.S. Environmental Protection
Agency (U.S. EPA) to develop uniform national ambient air quality standards
(NAAQS) for pollutants which were recognized as widespread (emitted by
numerous mobile and stationary sources) and which endangered public health and
welfare. Further, Section 109 of the Clean Air Act as amended, requires EPA to
periodically review the NAAQS as well as the scientific information and data on
which they are based. New pollutants are identified for NAAQS development if
the Administrator concludes that they may reasonably be anticipated to endanger
the public health and welfare.
To assist the Administrator in evaluating the need for new or revised NAAQSs,
the Clean Air Act created the Clean Air Scientific Advisory Committee (CASAC).
This committee's mandate is to provide the Administrator with scientific advice
and research recommendations on critical areas of knowledge on new or revised
NAAQSs. The Acid Aerosol Subcommittee of CASAC identified a need for a
coordinated acid aerosol research program to assist the Agency in making
recommendations on a new acid aerosol NAAQS. The Subcommittee
recommended a research program involving characterization and exposure
assessment, animal toxicity, human exposure research, and epidemiology. The
foundation for any research program and potential air quality standard
development is "...a measurement method, not only because the standard itself
must specify the method, but equally important, because before establishing a
standard the contaminant must be fully characterized and exposure measurements
made to correlate with health outcomes."
4.2 The unique features of the annular denuder which separates it from other
established monitoring methods are elimination of sampling artifacts due to
interaction between the collected gases and particles and the preservation of the
samples for subsequent analysis. These features are accomplished by removing
NH3 in the gas stream with the citric acid-coated denuder to reduce the
probability of the acid aerosol captured by the Teflon® filter in the filter pack
being neutralized to ammonium sulfate [(NH^SO^].
Acid Aerosol
Part B
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Date 11/92
Page 5 of 72
5. Definitions
Definitions used in this document and any user-prepared Standard Operating Procedures
(SOP's) should be consistent with ASTM D1356. AC abbreviations and symbols are defined
within this document at the point of first use.
5.1 Secondary particles (or secondary aerosols) - Aerosols that form in the
atmosphere as a result of chemical reactions, often involving gases. A typical
example is sulfate ions produced by photochemical oxidation of SO2.
5.2 Aerosol - A dispersion of solid or liquid particle in a gas-phase medium and a
solid or liquid disperse phase. Aerosols are formed by (i) the suspension of
particles due to grinding or atomization, or (2) condensation of supersaturated
vapors.
,5.3 Coarse and fine particles - These two fractions are usually defined in terms of
the separation diameter of a sampler. Coarse particles are those with diameters
(aerodynamic) greater than 2.5 jim and are removed by the sampler's inlet; the
fine particles are those with diameters (aerodynamic) less than 2.5 ;xm that are
collected on the Teflon® filter.
5.4 Annular - Of, rotating to, or forming a ring. In the annular deruder sampler, the
annular refers to the annulus between two concentric tubes. Chemical coating
applied to the interior surfaces removes gaseous pollutants which diffuse to die
surface.
5.5 Bemider - The denude? refers to the sections in which interfering gases are
removed from the sample stream prior to filtration in determining fine particle
(2.5 //.en) strong acidity.
5.6 Equivalent weight - The combining weight, or the equivalent weight, of a
compound or ion is its formula weight divided by the number of replaceable
hydrogen atoms.
5.7 Normal solution - A normal (N) solution is one that contains a gram-equivalent
weight of solute in a liter of solution.
Note: The following descriptions relate to Figure 2. Most of these parts are available
commercially from University Research Glassware, 118 E. Main Street, Carrbcro,
North Carolina, 27510, 919-942-2753. However, these items can be made by any
qualified vendor. Therefore, it is not necessary that these specific items are obtained
and utilized.
Acid Aerosol
Part B
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Date 11/92
Page 6 of 72
6.1 Sampling
6.1.1 Elutriator and acceleration jet (inlet) assembly - Under normal sampling
conditions, the elutriator or entry tube is made of either Teflon® coated
glass or aluminum, as illustrated in Figure 4. When using glass, the
accelerator jet assembly, which directs the air flow towards an impactor
plate, is fixed onto the elutriator and the internal surfaces of the entire
assembly are coated with Teflon® [Figure 4(a)]. When aluminum is used,
the accelerator jet assembly is removable. The jet is made of Teflon® or
polyethylene and the jet support is made of aluminum [Figure 4(b)].
Again, all internal surfaces are coated with Teflon®.
6.1.2 Teflon® impactor support pin and impactor frit support tools (see
Figure 5) - Made of either Teflon® or polyethylene and are used to aid in
assembling, removing, coating and cleaning the impactor frit.
6.1.3 Impactor frit and coupler assembly (see Figure 6) - The impactor frit is
10 mm x 3 mm and is available with a porosity range of 10-20 pm. The
frits should be made of porous ceramic material or fritted stainless steel.
Before use, the impactor frit surface is coated with a Dow Corning 660 oil
and toluene solution and sits in a Teflon® seat support fixed within the
coupler. The coupler is made of thermoplastic and has Teflon® clad
sealing "0"-rings which are located on both sides of the seat support inside
the coupler.
Note: In situations when there are substantial high concentrations of
coarse particles (>2.5 fim), it is recommended that a Teflon®-coated
aluminum cyclone be used in place of the acceleration jet and impactor
assembly, as illustrated in Figure 2. Figure 2 illustrates the location of
the cyclone with respect to the denuder, heated enclosure and meter box
assembly.
6.1.4 Annular denuder - The denuder consists of two or more concentric glass
tubes (see Figure 7) with an outer aluminum shell. The tubes create a
1 mm annular spacing which allows the air sample to pass through. Flow
in the annular space is maintained in the laminar range and allows fine
particles with diameters less than 2.5 ^im to pass through with negligible
removal. The inner tube is inset 25 mm from one end of the outer tube;
this end is called the flow straightener end. The other end of the inner
tube is flush with the end of the outer tube. Both ends of the inner tube
are sealed. In this configuration, the flow straightener end is etched to
provide greater surface area for the coating. The inner glass tubes are
inset 25 mm from one end of the outer Teflon®-coated aluminum tube to
Acid Aerosol
Part B
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Revision No. 0
Dale 11/92
Page 7 of 72
serve as the flow straightener end. All denuder types should be equipped
with thermoplastic (B&kelite) or polyethylene caps when purchased.
6.1.5 Caps for annular denuder - Caps are made of either polyethylene
(Caplugs, Protective Enclosure, Inc.) or thermoplastic (Bakelite) and are
used in the coating and drying processes, for storage and for shipment.
The thermoplastic caps include a removable Teflon® seal plate when
purchased.
Note: Recent evaluation of the caps for the denuder system have
indicated that the thermoplastic (Bakelite} screen caps and the polyethylene
screw caps are useful to seal the ends of the rienuders when they are dry.
However, during coating and extracting, Lie Caplugs (Protective
Enclosures, Inc.) provided a better seal, preventing contamination that
would occur from the Teflon® liner of the thermoplastic screw caps or
direct contact with the unprotected thermoplastic screw caps. It is
therefore suggested that the user use Caplugs during coating and extraction
operations.
6.1.6 Annular denuder couplers - The couplers should be made of thermoplastic
and equipped with Teflon® "0"-rmgs which sandwich a silicone rubber
ring on tliree sides. This provides elasticity for better sealing under
extremely cold temperature conditions in which Teflon® does not give.
The couplers are equipped with permanent seal rings which provide more
even threading and a better seal when coupled. The couplers are used to
couple the annular demiders together when used in series (enhanced
method) and for coupling the last denuder with the filter assembly.
Caution: When utilizing the couplers, do not overtighten when applying a
glass denuder. Overtightening might "chip" the ends of the denuder,
preventing a tight seal.
6.1.7 Drying manifold assembly - The manifold is made of glass and is
available to accommodate as many as four drying demiders. The denuders
are attached to the manifold with back-to-back Bakelite bored caps, as
illustrated in Figure 8. Air is pushed through ail air dryer/cleaner bottle
made of 2 1/2 inch heavy wall glass which contains silica gel. The
Teflon® tubing which connects the dryer/cleaner bottle to the drying
manifold should be secured at each cap with either Teflon® washers or
Teflon® washers coupled with Teflon® hose barbs. The air stream then
passes through a fine particle filter to remove fines. Alternatively, dry
compressed air from a cylinder may be used in place of the dryer/cleaner
bottle assembly.
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6.1.8 Filter pack assembly - The denuders are followed by a three-stage filter
pack assembly containing a Teflon® membrane filter, a nylon membrane
filter and a citric acid-impregnated glass fiber filter, as illustrated in
Figure 9. The filters are supported by stainless steel porous screens and
are housed in a polyethylene filter ring housing. The Teflon® filter ring
housing directly follows the Teflon® filter housing inlet component. The
nylon filter ring housing follows the Teflon® ring housing and sits on a
Teflon® "0"-ring which seals the filter ring housing components to the
filter housing outlet component. The Teflon® filter retains all the strong
acidic particulate aerosols. Under certain conditions, nitric acid (HNO3)
and/or nitrate aerosol (NH4NO3) on the Teflon® filter can dissociate. The
nylon back-up filter captures the volatile HNO3, while the glass-fiber
filter impregnated with citric acid, retains the NH3. The three filters
together give unbiased measures of strong acidic of atmospheric fine-
particles (<2.5 /zm). The filter housing outlet component is aluminum
and accommodates a polyethylene screw sleeve which seals the filter pack
assembly.
Note: Over time and repeated compression, the Viton® O-rings may
wear, causing poor leak checks due to inadequate sealing. The user is
encouraged to replace these rings after fifteen (15) sampling events or
when the filter pack assembly does not pass an adequate leak check.
Other users have utilized high density polyethylene (HDPE) to prolong the
life of the ring.
6.1.9 Teflon® tubing - 3/8 inch diameter for distances of less than 50 ft.,
1/2 inch diameter for distances greater than 50 ft. [Fisher-Scientific,
711 Forbes Ave., Pittsburgh, PA, 15219 (412-787-6322)]
6.1.10 Tube fitting - Compression fittings (Swagelok®, Gyrolok® or equivalent)
to connect vacuum tubing (above) to an NPT female connector or filter
holder and connect vacuum tubing to fitting on differential flow controller.
The fittings may be constructed of any material since they are downstream
of the sampler. [Fisher-Scientific, 711 Forbes Ave., Pittsburgh, PA,
15219 (412-787-6322)]
6.1.11 Annular denuder system (ADS) sampling box - The housing box is made
of a "high-impact" plastic and is thermally insulated. It is 4 feet long by
6 inches wide and 6 inches deep. The box contains a heater unit, a fan,
and an air outlet located in the lid of the housing. The elutriator end of
the ADS protrudes through one end of the box, while the denuders are
supported in the box by chrome plated spring clips. If the Teflon®-coated
aluminum cyclone is used to remove coarse particles, it is also housed in
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the heated sampling box, with the elutriator end protruding through the
sampling box, as illustrated in Figure 2.
Note: Recent studies by the Harvard School of Public Health based on a
comparison of utilizing a sampling box with and without heated enclosure
indicated no difference in sampled species from winter samples. It is
therefore the discretion of the user to determine whether a heated
sampling box is required.
6.1.12 Annular denuder transport case - The transport case is made cf formica
backed with plywood and insulated. The comers are reinforced with
metal. It is made to withstand shipping by truck, UPS and Federal
Express. Each case is stackable and lockable and has a carrying handle.
Seven total annular denuder systems can be packed in the case.
6.1.13 Pump/diner unit - The pump/timer unit draws air through the ADS at a
fixed rate of 10 L/rrJn with a precision of ±5 percent over the range of
25 to 250 mm Hg vacuum. A mass flew controller or a differential flow
controller can be used. Typically, the flow rate is monitored with an
exhaust flow rotameter. The unit includes a mechanical 7-day timer and
an elapsed-time counter. A dry gas meter, when available, is placed after
the pump to give a direct readout of total volume of air sampled.
Otherwise, flow rate is manually measured (using a rotameter) before and
after each run to calculate the air volume sampled.
6.1.14 Dry gas meter (DGM) - The DGM should have a capacity of 10 L of gas
per revolution. [NuTech Corp., 4C22 Stirrup Creak Road, Suite 325,
Durham, NC 27703, 919-544-8535)]
6.1.15 Electronic mass flow controller - Capable of maintaining a constant rate of
10 L/min (±5 percent) over a sampling period of up to 24 hours and
under conditions cf changing temperature (5° to 43°C) and humidity.
[Tylan General, Flow Division, 19220 S. Ncrmandie Ave., Torrance,
CA, 90502, 213-212-5533, Model FC-262, or equivalent]
6.2 Analysis
6.2.1 pH meter - A pH or pH/icn meter with "integral" automatic temperature
compensation, temperature probe, 2 and 4 irtL analytical vials, and
calibrated with standard buffers (pH 4 and 7). The Ross semi-micro glass
electrode from Orion has been used by the Harvard School of Public
Health and found to adequately address the requirements of this protocol.
[Orion Research Inc., The Schraffet Center, 529 Main Street, Boston, MA
02129, 617-242-3900]
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6.2.2 Ion chromatograph - A chromatograph equipped with the appropriate
anion exchange resin filled separator and suppressor columns and
conductivity detector for measuring NO3 ~~ ion in solution (i.e., nylon
filter extract). [Dionex Coip., 1228 Titan Way, Sunnyvale, CA 94086,
(408-737-0700)]
6.2.3 Technicon colorimeter auto-analyzer - Colorimetric analyzer able to detect
specific ions of interest in aqueous extracts. [Technicon Industrial
Systems Coip., 511 Benedict Ave., Tanytown, NY, 10591-5097, (800-
431-1970)]
6.2.4 Polyethylene bottles with polyethylene screw caps - 100 mL, used for
storage of coating solution; and 1L, used for storing the KC1 solution.
6.2.5 Erlenmeyer flasks - 250 mL and 2 L borosilicate glass or polyethylene
flasks for calibration, best source.
6.2.6 Graduated cylinders - 5 mL, 10 mL, 100 mL, 250 mL and 1L borosilicate
glass or polyethylene cylinders, best source.
6.2.7 Pipets - Class A 5 mL and 10 mL borosilicate glass pipettes or automatic
pipettes. Calibrated "to deliver," best source.
6.2.8 Pipet bulb - Made of natural rubber. Recommended to meet OSHA
requirements, best source.
6.2.9 Micropipettes - 25 pL, 50 fiL, and 100 jiL, calibrated "to contain,"
borosilicate glass micropipette, best source.
6.2.10 Forceps - Recommended dressing forceps made of stainless steel or
chrome-plated steel and without serrations. Used for handling filter.
6.2.11 Stopwatch - Used for measuring flow rate of gas stream through DGM,
best source.
6.2.12 Ultrasonic cleaner - Used for filter extractions and parts cleaning. The
ultrasonic cleaner should have temperature control capability.
[Cole-Palmer Instrument Co., 7425 N. Oak Park Ave., Chicago, IL,
60648 (800-323-4340)]
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6.2.13 Clean air hood (optional) - Closed air hood with ammonia free air
circulation. Used for Teflon® filter extraction for pH analysis, best
source.
6.2.14 Glove-box - Used for handling exposed filter, which is lined with citric
acid impregnated paper sheets to maintain an ammonia-free atmosphere.
The glove-box works best with a slight positive pressure.
6.2.15 Refrigerator (approximately 5°C) is required for sample storage.
6.2.16 Polyethylene-stoppered volumetric flasks - 25 r.iL, used for making
sulfuric acid standards.
7. Reagents and Materials
7.1 Teflon® filter - Zefluor® (FI FE) membrane filter, 47 mm diameter, with a 2 pm
pore size. The Teflon® filter has a coarse mesh Teflon® side and a fine pore
membrane side. The fine pore membrane side should face the air stream.
[Gelman Sciences, 600 S. Wagner Rd., Ann Arbor, MI, 48106, Part
No. P5PJ047, (800-321-1520)].
7.2 Teflo® membrane filter, 47 mm diameter, with a 2 pore size. This filter has a
thin Teflon® membrane stretched across a plastic ring. [Gelman Sciences, 600 S.
Wagner Rd., Am Arbor, MI, 48106, Part No. R2PJ047, (800-521-1520)].
7.3 Nylasorb® fillers - Membrane filter, 47 mm diameter, with a \ fim pore size.
These filters are specially prepared and batch analyzed for low NO3 ~ background
levels. If other brands of nylon membrane filters are used, they should be batch
analyzed tc ensure low and replicable levels of NO3-. [Gelman Sciences, 600 S.
Wagner Rd., Ann Axbor, MI, 48106, Part No. P5PJC47, (800-521-1520)]
7.4 Glass fiber filter - Glass fiber filter, 47 mm diameter, with a 2 pm pore size.
["AP,: filters by Millipore, Part No. AP4004705] or Whatman 41, 47 mm ashless
filter paper [Whatman Part No. 1441047EA]
7.5 Filter extract storage vials - 100 mL polyethylene vials (Nalgene or equivalent).
7.6 Labels - Adhesive, for sample vials, best source.
7.7 Parafilm - Used for covering flasks and pH cups during pH analysis, best source.
7.8 Kim wipes® and Kay-dry towels - Used for cleaning sampling apparatus and
analysis equipment, best source.
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7.9 Stoppers - Polyethylene, best source.
7.10 Sodium carbonate (Na2CC>3) - ACS reagent grade, best source.
7.11 Citric acid [monohydrate - HOC (CH2CO) OH^COOH : H2O) - ACS reagent
grade, best source.
7.12 Methanol (CH3OH) - ACS reagent grade, best source.
7.13 Sulfuric acid (H2SO4) - ACS reagent grade, 1.000 N solution, best source.
7.14 Distilled deionized water (DDW) - ASTM Type I water.
7.15 pH buffers - Standard buffers, 4.00 and 7.00, for internal calibration of pH meter,
best source.
7.16 Silica gel - ACS reagent grade (indicating type), best source.
7.17 Gloves - Polyethylene disposable. Used for impactor frit assembly and filter
assembly, best source.
7.18 Dow Coming high temperature vacuum oil - Dow Coming 660 oil used for
impactor frit coating solution, best source.
7.19 Zero air - A supply of compressed clean air, free from panicles and ammonia.
The supply may be either from a commercial cylinder or generated on site, best
source.
7.20 BRD-35 - Composed of 0.1 percent of BRU-35 in DI water. [Fisher Scientific,
711 Forbes Ave., Pittsburgh, PA, 15129, 412-787-6322]
7.21 IC eluent solution - For extracting filters. This should be the same eluent as used
for the ion chromatographic analysis of the filters. If the filter analysis is not to be
performed by ion chromatography, then a slightly basic solution (e.g., 0.003 N
NaOH or sodium carbonate/bicarbonate) should be used to extract the Nylasorb®
filter, while the Teflon® filter should be extracted with DDW.
7.22 Perchloric Acid (HCIO4) - 60 to 62 percent, in water, best source.
7.23 Toluene ^Hg) - ACS reagent grade, best source.
7.24 Potassium Chloride (KC1) - ACS reagent grade, best source.
7.25 Acetone (C^HgO) - ACS reagent grade, best source.
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8. Preparation of Impactor Frit and Denuder Coating
8.1 Impactor frit coaling solution preparation - Weigh 1 g of silicone oil (Dow
Coming high temperature 660 oil) ard place in a 100 mL polyethylene storage
vial. Add 100 mL of toluene. Mix thoroughly, close container, and store at
room temperature. (WARNING - FLAMMABLE LIQUID).
8.2 Annular demider citric acid coating solution - Clean a 100 mL polyethylene
storage vial and let dry at room temperature. Measure 50 mL of methanol
(WARNING - TOXIC, FLAMMABLE LIQUID) with a graduated cylinder and
pour into vial. Weigh 0.5 g of citric acid and add to vial. Mix thoroughly; store,
covered at room temperature.
8.3 Annular denuder Na2C03 coating solution - Clean a 100 mL polyethylene storage
vial and let dry at room temperature. Measure 50 mL of methanol (WARNING -
TOXIC, FLAMMABLE LIQUID) with a graduated cylinder and pour into vial.
Measure 50 mL of DDW with a graduated cylinder and add to vial. Weigh 1 g of
glycerol and add to the DDW. Weigh 1 g of Na2CG3 and add to the vial. Mix
thoroughly, solution may fizz; wait for fizzing to step before sealing vial. Store
at room temperature.
8.4 Impactor frit extraction solution preparation - Add 100 elL of IC eluent to a clean
polyethylene storage container. Pipette 5 mL of methanol into container. Mix
thoroughly. Store, covered at room temperature.
9. Impactor Frit Installation
9.1 Impactor frit installation - The impactor-coupler assembly shown in Figure 4 is
comprised of two parts: the replaceable impactor frit and the coupler-impactor
housing seat. The impactor surface is a porous ceramic oi porous stainless steel
frit, 10 mm x 3 mm. This frit is inserted into the coupler-impactor housing using
the tools illustrated in Figure 5. The impactor frit is pressed gently, but firmly,
into the seat of the impactor housing with a clean gloved finger. The impactor
should fit into the housing so that it does not protrude above the seat. During
sampling, particles accumulate on the impactor's plate surface. After each
sampling event, the assembly must be cleaned to prevent the build-up of
contaminants which may lead to loss of key acidic species being collected by the
ADS. Cleaning involves immersing the elutriator, coupler-impactor, and frit in
0.1 percent BRD-35 cleaning solution and ultrasonicating for about 5 minutes.
Rinse thoroughly with DDW for additional 5 minutes. Rinse and dry with zero
air or in dust-fee environment and store with ends plugged and capped.
9.2 Impactor frit coating - With the Teflon® impactor seat support pin which fits into
the first denuder (see Figure 5) or the impactor frit in the impactor seat coupler
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(see Figure 6), pipette 50 pL (about two drops) of the toluene-660 oil coating
solution onto the impactor frit surface and allow to dry in dust free environment at
room temperature. Cap both sides of the coupler impactor or denuder-impactor
until use.
Note: It is important to have only the minimum amount of oil on the frit because
any excess will be blown off during sampling and will contaminate the surfaces of
the first denuder.
10. Filter Preparation and Assembly
Note: A clean and dedicated indoor work space is required for the daily preparation,
assembly and disassembly of the denuder and filter assembly. Approximately 2-3 m of
bench space is adequate, with additional space for storing supplies.
10.1 Citric Acid Coated Filter
Mix 2 percent (w/v) citric acid in ethanol.
Load the glass-fiber filter into half a petri-dish. Pipet 1.0 mL of the
citric acid solution onto the filter. Dry under vacuum in a desiccator.
Cap the petri-dish and seal with parafilm. Store in NH^-free glove-box
or chamber.
For Whatman 41, 47 mm, ashless filter paper, wash filters with 1 L of
10 percent HC1 followed by 1 L of distilled deionized water. Dry
under vacuum in a desiccator. Coat filters with 0.5 mL of 0.02 M
citric acid in a glycerol/methanol (1/100) solution and dry in a vacuum
desiccator. After coating the filter, store in an acid-wash petri-dish.
Keep in NHj-free glove-box until use.
10.2 Filter Pack Assembly
Note: All loading and unloading of the filter pack must be performed in the
Nl^-free glove-box. Generally, it is most convenient to reload the filter pack
at the same time as unloading.
10.2.1 With clean gloves, disassemble the filter pack (see Figure 9) by
unscrewing the large outer Teflon® collar (sleeve) from the aluminum
filter housing outlet component.
10.1.1
10.1.2
10.1.3
10.1.4
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Note: It is necessary to remove the polyethylene cap first. Lay the
pieces out on clean Kimwipes®. Insert black viton "0"-rings (see
Figure 9).
10.2.2 Lay a clean Teflon® filter ring housing, with its large opening face-up,
on a clean Kiinwipe®. Place a clean stainless steel screen in the filter
ring housing.
10.2.3 Using a clear (wipe with clean Kimw:pe® filters) forceps, load the
citric acic-impregoatec glass-fiber or Whatman 41 filter onto the screen
of the lowest stage.
10.2.4 Place a second stainless steel screen in the filter housing.
10.2.5 Using clean filter forceps, place a Nylasorb® nylon filter on the screen.
Insert a second filter ring housing on top of the nylon filter with its
large opening face-up. This forms a "sandwich" with the nylon filter
held between the two filter ring housing.
10.2.6 Place another clean screen on the second filter ring housing. Using
clean filter forceps, place a Teflon® filter on the screen.
Note: If a Zefluoi4* Teflon® filter Is used, be sum to place the
membrane side, not the coarse side, toward the air stream. By
observing the filter in the light, one can differentiate between the coarse
and membrane side.
10.2.7 Place the Teflon® filter housing inlet component (see Figure 9) on top
of the Teflon® filter. This forms another "sandwich" with the Teflon®
filter held between the second filter ling housing and the housing inlet
component. The housing inlet component connects the filter pack
assembly to the annular denudsr through a thermoplastic coupler. Be
careful not to twist the filler pack components, or damage will occur to
the filters.
t0.2.8 Lay the aluminum filter housing outlet component, with its large
opening face-up, on a clean Kimwipe^. Insert a black viton "Q"-ring in
the aluminum filter base.
10.2.9 Insert the filter ring sandwiches with the filter housing inlet component
extending upward, on the viton "O '-ring in the aluminum filter base.
Place the larger outer Teflon® sleeve over the filter sandwich and screw
onto the aluminum filter base. DO NOT OVERTIGHTEN!
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10.2.10 Install the "quick-release" plug into the filter outlet component. DO
NOT OVERTIGHTEN!
10.2.11 Install the polyethylene cap onto the filter inlet component and the
orange dust cover onto the quick release plug ready to attach denuder.
The filter pack should be sealed tight before it is removed from the
glove-box.
11. Annular Denuder System Preparation
All new annular denuder parts obtained from suppliers should be cleaned by placing
them in a dilute BRD-35 solution in an ultrasonic cleaner for about 30 minutes. The parts
should then be thoroughly rinsed in DDW, then rinsed with acetone, and allowed to dry to
room temperature. Store with end caps in place.
11.1 Coating Procedure
11.1.1 Cap one end of a denuder using Caplugs (which has the inner tube flush
to the outer tube) and set the denuder upright on the capped end. For
the denuder with flow-straighteners at both ends, either end may be
capped. Measure 10 mL of the citric acid solution and pour into one of
the denuders. Then add sodium carbonate coating solution to the other
capped denuder.
11.1.2 Cap the open end of the denuders and, holding them horizontally, rotate
the denuders to distribute the coating solution evenly, wetting all
surfaces.
11.1.3 Remove cap and decant excess coating solution into separate 100 mL
polyethylene bottle.
11.1.4 For the impactor denuder, the coating is performed without the
impactor pin in place.
11.2 Drying Procedure
Note: As denuders dry, they change from translucent to a frosted appearance.
Denuders are dry when they become uniformly frosted.
Note: A supply of zero air is needed to dry the annular denuder tubes after
applying the coating solutions. This air should be free of ammonia, moisture
and particles. Either a tank of pure air or an air purifier assembly can be used.
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11.2.1 Assemble the drying train and manifold as illustrated in Figure 8.
Drying train and manifold clean air flow should be adjusted to 2 to 3
L/min through each denuder. Close toggle valve controlling clean air
flew through manifold before attaching denuders.
11.2.2 Attach the flow-straightener end of the denuders to the drying manifold
ports (see Figure 8).
11.2.3 Open toggle valve and allow clean air to flow through the denuder tubes
for 5 minutes.
Caution: Excess air flow will cause uneven coating to the tube walls.
11.2.4 Close toggle valve, and reverse ends of the denuders attached to the
manifold. Start ciean air flow again.
11.2.5 When an even frosted appearance is achieved, remove denuders from
manifold, cap both ends with clean caps and store until ready for use.
Turn off air to drying manifold. Affix label indicating coating date on
denuders.
11.3 Denuder System Assembly
Note: Described herein is an annular denuder system consisting of two
denuders. Extreme care should be exercised in handling and assembling of the
ADS if the denuders are made of glass. The coupling of components mast be
effective to prevent leaks but, at the same time, not stress the glassware. Only
patience and practice with the ADS will enable the operators to obtain optimum
performance from the system with minimum breakage.
The annular denuder system (ADS) assembly consists of:
* an inlet nozzle/impactor or cyclone assembly;
* two glass annular denuder tubes; and
* a 3-stage filter assembly.
The following procedure involves an inlet nozzle/impactor assembly.
11.3.1 Lay the ADS pieces on a clean surface (i.e., Kimwipes®).
11.3.2 Remove the sod caps from the denuders. Denuder i is coated with
Na2C03 and may or may not hold the impactor frit pin support. If the
first denuder is equipped with the impacted frit pin support, gently
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insert the impactor support pin and coated frit assembly into the
denuder-pin support.
Note: DO NOT TIGHTEN!
11.3.3 Attach a thermoplastic coupler to the opposite denuder end. Place a
Teflon® clad "0"-ring inside the coupler, if needed.
11.3.4 Remove the end caps of the second denuder (citric acid coated). Attach
the end with the flow-straightener section to the first denuder-coupler
assembly.
11.3.5 Attach a thermoplastic coupler to the opposite denuder end. Place a
Teflon® clad "0"-ring inside the coupler, if needed.
11.3.6 The filter pack has been previously loaded with (a) a Teflon® filter,
(b) a nylon filter, and (c) a glass-fiber filter (previously impregnated
with citric acid) or Whatman 41 filter coated with citric acid in
glycerol/methanol solution. The components are assembled with plastic
couplers.
11.3.7 Attach the filter pack inlet to the denuder coupler assembly.
11.3.8 When using the first denuder equipped with the impactor frit-pin
support, a thermoplastic coupler with a Teflon® clad "0"-ring is used to
attach the inlet assembly. ATTACH, BUT DO NOT TIGHTEN!
11.3.9 Attach the elutriator-acceleration jet assembly to the first denuder-
qoupler assembly. Tighten very gently - DO NOT OVERTIGHTEN or
breakage will result.
11.3.10 Tighten the remaining couplers very gently - do not overtighten or
breakage will result.
11.3.11 Cap elutriator with orange dust cover until used. Attach "quick-
release" tube to outlet of filter pack assembly.
11.4 Laboratory Leak-Check of ADS
Caution: Do not subject the system to sudden pressure changes or filter
may tear.
11.4.1 Remove the orange dust cap from the impactor opening. Attach the
"quick-release" outlet of the filter assembly to a pump module. Turn
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oil the pump. Be certain that flow through the ADS occurs by checking
the rotameter.
11.4.2 Briefly cap the elutriator with the orange dust cap. The flew, as
indicated on the rotameter, should drop to zero if no leaks exist.
11.4.3 Disconnect the pump from the ADS at the "quick-release" plug. Cap
the "quick-release" plug with an orange dust cover. Turn off the pump.
REMEMBER - Never overtighten joints or breakage will result. If Lh's
joints can not be sealed with gentle tightening, then the Teflon®
"O"-rings are worn or defective and must be replaced.
11.4.4 Place the assembled sampler in its field-to-lab carrying case for
transport to the Held.
Note: It is recommended that the ADS joints bs loosened slightly when
extreme temperature changes are incurred during transportation. This
will prevent unnecessary breakage or distortion of the ADS
components. Remember to allow the system to adjust to the outdoor air
temperature before tightening the joints and checking for leaks.
11.4.5 Before proceeding to the field, review the following checklist:
* Run IDs on the Field Test Data Sheet (sec Figure 10} should match
labels affixed to the ADS components and filter assembly;
* Recessed ends of the demider should face the inlet;
* ADS ends are capped; and
* Transport case is secured firmly containing the ADS along with
chain-of-custody and Field Test Data Sheet.
12. Sampling
12.1 Placement of Denuder System
12.1.1 The placement of the denuder system must conform to a consistent set
of criteria and guidance to ensure data comparability and compatibility.
A detailed set of monitor siting criteria for ambient air monitoring and
. meteorological programs is given in the following EPA document:
* U.S. EPA, May 19E7. Ambient Monitoring Guidelines for
Prevention of Significant Deterioration (PSD), EPA-450/4-87-007,
Office of Air Quality Planning and Standards, Research Triangle
Park, N.C. 27711.
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The site must be away from localized sources of ammonia sucb as
composting and livestocking operations, landfills, sewage treatment
plants, fertilizer plants and storage facilities, and recently plowed
fertilized fields because aerosol acidity is subject to rapid neutralization
by ambient bases.
12.1.2 A summary of key factors that should be considered as part of the
placement of an air quality monitoring station containing an ADS are:
• Vertical placement above ground;
• Horizontal spacing from obstructions and obstacles;
• Unrestricted air flow; and
• Spacing from roads.
The ADS sampler is mounted on a supported mast pole or tripod. The
ADS inlet should be located 2-3 m above ground level. Placing the
inlet closer to ground level should be considered only if the surface is
flat and man-made (i.e., not unpaved dirt).
12.1.3 A summary of key criteria associated with these siting factors for air
monitoring stations is included in Table 1.0. The information included
in the table should be used to the extent possible as part of the
monitoring network design to ensure that the monitoring program
provides representative and unbiased data. However, site-specific
constraints could make it very difficult to meet all criteria. For
example, the occurrence of wooded areas around a site would make the
siting very difficult. The use of the information in Table 1.0, coupled
with a balanced evaluation by an experienced air quality and
meteorology specialist, is highly recommended.
12.1.4 In general, for a site with no major obstruction and obstacles, the air
sampler intake should be about 2-3 meters aboveground. For a site
with nearby roadways, however, intake placement should take into
account the effects of road dust re-entrainment and vehicular emissions.
In fact, a linear relationship should be established between the
horizontal distance of the sampler intake from the roadway and the
aboveground elevation of that intake. For any roadway accommodating
more than 3000 vehicles per day, the intake should be between 5 and
25 meters from the edge of the nearest traffic lane. It should also be
15 meters aboveground for a distance of 5 meters from the nearest
traffic lane and 2 meters aboveground for a distance of 25 meters from
the nearest lane. For a roadway supporting less than 3000 vehicles per
day, the intake should be placed at a distance greater than 5 meters
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from the edge of the nearest traffic lane and at a height of 2-15 meters
aboveground.
12,2 Start-up
12.2.1 Remove the ADS from its field-to-lab carrying case and load into the
field sampling box. Place the assembly in the box with the impactor
extended outside the case. The ADS field sampling box is insulated
and configured to hold the ADS without allowing movement. Chrome
plated spring clips holds the denuders in place. Automatic and manual
control switches allow the sampling box to control the temperature of
the ADS. The automatic switch should be used when the ADS is not in
use and when the ADS is sampling for extended periods of time without
constant supervision to prevent lew temperature or sudden pressure
change exposure of the ADS (these types of exposure can cause leaks to
occur, condensation, or the filter to tear). When sampling, the ADS
should be kept 1 °C above the outdoor temperature to prevent
condensation.
12.2.2 Allow the pump to warm up for -5 minutes prior to testing.
'12.2.3 To check the Heat/Cool cycles, flip one switch from "A.UTO': to
"MANUAL11 and the other between "COOL" and "HEAT." Check to
insure that the fan and heater (i.e., light bulb) work, respectively.
12.2.4 With the elutriator still capped, turn on the pump with the switch on the
timer. The rotameter should indicate zero flow. Run leak check for
5-10 seconds, then tarn off pump and remove elutriator cap. Record
leak rate on Field Test Data Sheet (sne Figure 10). If there is a flow,
refer to Section 12.4 for corrective action for leak test failure. The
Field Test Data Sheet is used to keep track of the denuder tube, filter
and impactors, as to when and by whom they are prepared, assembled,
extracted and data input as well as to record the installation data and
time, inn date, sampling period, pump flow rates, start and end times,
and other data relevant to each run.
12.2.5 Attach a DGM output to the inlet of the annular denuder system. Turn
on pump. Record start time on Field Test Data Sheet. Using a
stopwatch, record the time for 20.0 L to pass through the DGM.
Record the DGM temperature and the absolute pressure of the DGM.
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12.2.6 Calculate the flow rate as follows:
Qstd = (V/T)(Pb/Pstd)(Tstd/Tm)(Fc)
where:
Qstd = flow rate corrected to standard conditions, 25 °C and
760 mm Hg, L/min
V = volume of gas pulled through denuder system, 20 L
T = time required to pull 20 L of gas through denuder
system, minutes
P^ = barometric pressure, mm Hg
Pst(j = standard barometric pressure, 760 mm Hg
Tstd = standard temperature, 298°K
Tm = temperature of dry gas meter, °K(= °C + 273)
Fc = dry gas meter correction factor, dimensionless
12.2.7 If the calculated flow rate is not between 9.5 and 10.5 L/min, then
readjust the flow rate until the rate is in the above range. Stop the
pump.
12.2.8 Record the flow rate on Field Test Data Sheet.
12.2.9 Remove DGM connection tubing from elutriator inlet. With all
information correctly on the Field Test Data Sheet, start the pump and
begin sampling.
12.2.10 Sample for pre-set period.
12.3 Sample Shutdown
12.3.1 Attach DGM connection tubing to the elutriator inlet with pump still
running. Measure flow rate. Record calculated flow rate, temperature,
and pressure on Field Test Data Sheet.
12.3.2 Turn off the pump. Record time and elapsed time meter reading on
Field Test Data Sheet. Remove DGM connection tubing from elutriator
inlet. Remove ADS from the sampling box, cap the ends, and place the
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ADS in field-to-lad carrying case for transport to lab. Secure the
latches on the transport case. Be careful not to stress the ADS during
the transfer or breakage will result.
Caution: When the ADS is brought from a cold field sampling location
to a warm laboratory, it is necessary to loosen the denuder couplings to
prevent thermal expansion from breaking the denuder.
12.3.3 Each test run generates three samples for determination. These are
analyzed by methods appropriate for the chemical species under
quantifications: (a) ion chroma tog rapli for NOj-, (b) indophenol
method using an auto-analyzer for NH^+, and (c) pH determination for
strong acidity or "H+".
12.4 Corrective Action for Leak Test Failure
Note: These steps should be followed when failure occurs during testing at the
laboratory before transport to the field and in the field before sampling.
12.4.1 Sampler leaks - Note the problem on the Field Test Data Sheet. Check
assembly of ADS components. Replace gaskets. Check for proper
seating of denuder surfaces. Replace any defective parts.
12.4.2 Cracked or clupped denuder or elutriator assembly - Note problem on
Field Test Data Sheet. Discard defective pieces. Do not try to extract
cracked pieces.
Warning: Use caution when disassembling cracked glassware. Pieces
may shatter and cause severe cuts. Wear protective clothing.
12.4.3 Flow rate disagreement - Note problem on Field Test Data Sheet.
Check vacuum gauge on flow module. If a high vacuum exists then the
sampler has become blocked. This may be due to dust or smoke
particles clogging the fdter or to obstructions in the system or tubing.
Check flow module. Repair as needed.
12.4.4 Inadequate flow rate - Note problem on Field Test Data Sheet. Check
rotameter on flow controller. If adequate flow is shown here, then a
leak exists between the controller and the DGM. If no flow is shown
on rotameter, then check vacuum gauge on controller. If no vacuum
exists, then pump needs repair. If a high vacuum is shown, then an
obstruction exists in the system. Check to see that the paper filter
dividers were not accidentally installed with the filter in the filter
assembly. Check tubing for kinks.
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13. ADS Disassembly
13.1 In the laboratory, remove the ADS from the field-to-lab carrying case using
both hands. To prevent stress, hold the ADS by its ends.
Caution: Do not stress the ADS while removing it from the case.
13.2 Decouple the elutriator-jet assembly from the first denuder-impactor-coupler
assembly.
13.3 The impactor assembly and the denuders will not be extracted. However, each
run should begin with a clean impactor and charged denuder.
13.4 Label three (3) separate clean 100 mL polyethylene bottle (extraction vials) with
the sampler ID number and filter type (i.e., Teflon® or Nylasorb®, as
appropriate) for each of the filters.
13.5 The handling of the exposed Teflon® filter requires protection from
contamination with NH^, which would rapidly neutralize aerosol acidity on the
filter and bias the sample results. In order to ensure ammonia-free air occupies
the glove-box, a positive pressure is maintained by blowing air through a PVC
tube (4 inch O.D.) filled with glass-wool dosed with citric acid before entering
the manifold which enables uniform distribution of air from top of the glove-
box. Flow the ammonia-free air for five minutes before retrieving the filter. A
citric acid soaked filter paper is also placed on the bottom to deplete ammonia
while unused. Disassemble the filter assembly in the clean, ammonia-free
glove-box. Clean all glove-box surfaces and utensils with methanol. Wearing
clean gloves and using clean filter forceps, remove the filters and place each in
100 mL bottles (extraction vials) separately, with the exposed filter surface
facing downward. Label the bottles with appropriate information.
Note: Be careful to place the filters in the properly labeled bottles.
14. Extraction Procedure
14.1 Samples should be analyzed as soon after collection as possible. It is
imperative that the solutions and extraction procedures are prepared and
performed on the day of pH analysis. Keep samples in a refrigerator until
extracted and analyzed.
14.2 Samples should not be extracted until the day of analysis; however, if samples
are extracted and then it is not possible to analyze them that day, they should be
refrigerated. Allow the samples to return to room temperature before analysis.
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14.3 It is imperative that the same extract solution (ES) be used for the samples to be
analyzed, the working standards, and the EA solution. Also, the same batch of
alcohol must be used to prepare the EA solution, the working standards, and in
extracting the Teflon® filters.
14.4 Handling and extraction must take place in an ammonia-free glove box. The
extracts must be processed in the order in which they will be analyzed, so that
each sample will have a similar time interval between extraction and analysis.
Filters should be stored in the refrigerator until just prior to analysis. Samples
stored longer than 30 days tend to degrade due to bacteria growth and/or losses
to the walls of the extraction vessel.
14.5 Teflon® filter extraction
Note: Teflon® is not wetted by water, therefore, the filter will float on top of
an aqueous solution. The use of alcohol aids wetting. Also, all types of
Teflon® curl to some extent. It is the analyst's responsibility to ensure the
extraction solution makes complete contact witli the particles deposited on
the Teflon® filter during extraction. It may be necessary to use a clean
plastic (Teflon® or polyethylene) rod or tubing stub to hold the filter in better
contact with the fluid during extraction.
14.5.1 Allow the glove-box to be flushed with ammonia-free air for at least
5 minutes before proceeding. All of the hood surfaces and extraction
utensils must be cleaned with a Kimwipe® moistened with ethacol.
14.5.2 Process the filters in the same order in which they will be analyzed.
14.5.3 Remove the extraction vial from the refrigerator. Allow the contents to
reach room temperature before proceeding. Using forceps and gloved
hands, lift the filter from the extraction vial. Holding the filter over the
extraction vial, and using an automatic pipet, apply 200 ± 5 /
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14.6 Nylon filter extraction
14.6.1 Transfer the nylon filter (sampled surface facing up) into a sample vial.
Pipet 10 mL of IC eluent into the appropriately labeled filter vial or
bottle with caps.
Note: Be sure that the filter lies flat on the bottom of the bottle and that
all of the filter is covered by the extraction solution.
14.6.2 Replace the bottle's cap and put in an ultrasonic bath for 30 minutes.
14.6.3 Store the bottle in a clean (i.e., pollutant free) refrigerator at 5°C in the
dark until analysis.
14.7 Glass-fiber Filter Extraction
14.7.1 Transfer glass-fiber filter (sampled surface facing up) into a sample
vial.
14.7.2 Pipet 10 mL of DDW into the appropriately labeled filter vial or bottle
with caps.
Note: Be sure that the filter lies flat on the bottom of the bottle and that
all of the filter is covered by the extraction solution.
14.7.3 Replace the bottle's cap and put in an ultrasonic bath for 30 minutes.
14.7.4 Store the bottle in a clean (i.e., pollution free) refrigerator at 5°C in the
dark until analysis.
14.8 Aliquot preparation
14.8.1 When ready for pH analysis, the extracts are prepared in the order of
pH measurement. Inside the glove-box, remove the caps from
extraction vials. Wipe off any drops which may leak onto the outside
of the vial.
14.8.2 Using gloved bands and a 1 mL automatic pipet, transfer 1 mL of the
sample extract to each of two correspondingly labeled 2 mL vials, one
vial labeled A and the other vial labeled Al.
Note: The first 2 mL vial for each extract has the same letter (i.e., A,
B, C etc.) as the second mL vial, except a one is added (Al, Bl, CI
etc.). This is the same system used with the working standards.
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14.8.3 After transferring the extracts to the 2 oiL vials, recap the 4 niL extract
vial. Store at 5 °C in a refrigerator for future analysis, if applicable.
14.8.4 Proceed immediately with pH analysis.
15. pH Analysis
15.1 Standard and Reagent Preparation
15.1.1 Standard H2SQ4 Solution, 1.C00 N
Note: Each of the standard stock solutions must be prepared
fresh the day of pH analysis.
15.1.1.1 Label seven 25 mL polyethylene stoppered volumetric flasks.
Also, label each flask with the volume of 1.000 N f-^SO^
solution indicated in the following table:
Volume of
Equivalent
Standard
1.000 N %SO A
Working standard
strong acid mass
h2so4
added to each f concentration, lO'^N
collected on
flask
flask, (^L)
%S04
filter (CF/1), /ig*
Approximate pH
1
0
0
0
4.09
2
25
1
4.90
4.01
3
50
2
9.80
3.95
4
100
4
19.60
3.84
5
200
8
39.20
3.68
6
400
16
78.40
3.48
7
800
32
156.8
3.23
aBased on 3.1 mL extraction volume.
15.1.1.2 Use the 25 automatic pipet to add the I. N stock H^SO^
solution to flasks 2 and 3. Use the 100 fiL pipet to add
1.000 N stock H2SO4 solution to flasks 4 through 7. Dilute
ail flasks to the 25 mL mark with methanol. Cap with
stoppers or paiafilm and mix well.
15.1.2 2 M Potassium Chloride (KC1) Solution
15.1.2.1 Weigh 149.2 ± 0.1 g of KC1. Add the KG to a 2 L flask.
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15.1.2.2 Add about 700 mL of DDW water to the flask. Swirl the
solution until the KC1 is completely dissolved.
15.1.2.3 Pour this mixture into a 1 L graduated cylinder. Rinse the
flask with a small amount of DDW water and transfer the
rinse into the cylinder. Fill the cylinder to the 1 L mark.
15.1.2.4 Pour the solution from the cylinder into the 1 L polyethylene
bottle. Cap and shake the bottle to mix well. Mark the
bottle with date of preparation.
15.1.3 0.100 N Perchloric Acid (HCIO4) Solution
15.1.3.1 Fill a 1 L graduated cylinder about half full with DDW.
Transfer 10 ± 0.1 mL of 60-62 percent HCIO4 into the 1 L
cylinder with a 10 mL pipet.
15.1.3.2 Fill the cylinder to the 1 L mark. Pour the solution into the
1 L polyethylene bottle.
15.1.3.3 Cap and shake the bottle to mix well. Mark the date of
preparation on the bottle.
15.1.4 0.010 N HCIO4 Solution
15.1.4.1 Fill a 1 L graduated cylinder about 1/2 full with DDW.
15.1.4.2 Measure 100 mL of the 0.1 N HCIO4 solution with the
100 mL graduated cylinder. Add this to the 1 L cylinder.
15.1.4.3 Fill the 1 L cylinder with DDW to the 1 L mark. Pour the
solution into the 1 L polyethylene bottle.
15.1.4.4 Cap and shake the bottle to mix well. Mark the date of
preparation on the bottle.
15.1.5 Extraction Solution (ES)
Note: This solution must be prepared fresh on the day of pH analysis.
15.1.5.1 Measure 20 ± 0.5 mL of 2 M KC1 into 2 L erlenmeyer
flask.
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15.1.5.2 Using a 5 mL calibrated automatic pipet, add 10 ± 0.1 mL
of 0.0! N perchloric acid (HCIO^, to the flask. Add
980 ±10 mL of DDW to the flask.
15.1.5.3 Mix well and cover with parafilm until ready for use.
15.1.6 Extraction Solution with methanol (EA Solution)
15.1.6.1 Measure 150 ± 2 mL of ES (prepared in Section 15.1.5) into
a 250 mL graduated cylinder. Transfer to a 250 mL
erleruneyer flask.
15.1.6.2 Using a 5 mL graduated cylinder, add 5 ± 0.1 mL of
methanol (this must be from the same fresh bottle of methanol
that was used to prepare the standards in Section 15.1.1) to
the flask.
15.1.6.3 Mix well and cover with parafilm until ready for use.
15.1.6.4 pH of the EA solution should be 4.09 ± 0.04. If not, the
solution must be reprepared.
15.1.7 Working Standard Test Solutions
15.1.7.1 Place fourteen-4 mL polystyrene sample vials (as used with
Technicon Auto-analyzer n system) labeled 1A, IB, 2A
2B...7A, 7B into support racks. Using the calibrated
dispensing pipet bottle, add 3 mL of ES solution to each
4 mL vial.
15.1.7.2 Using the displacement pipet, add 50 //L of methanol to each
vial. Pour about 3 mL of Standard Flask #1 standard
(see Section 16.1.1) into a labeled 4 mL vial.
15.1.7.3 Immediately pipet 50 ,«L of this standard into the 4 mL vials
labeled 1A and IB containing the ES solution and methanol.
Note: This transfer must be done without delay to prevent
the standard concentration from increasing significantly due to
evaporation cf the methanol solvent.
15.1.7.4 Repeat the procedure for each of the other 6 standards. If
there is a delay of more than 5 minutes between the
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preparation of these mixtures and the next step, put caps on
the 4 mL vials.
Note: There should be fourteen vials, each containing 3 mL
of ES solution, 50 fiL of methanol, and 50 /iL of Standard
H2SO4 solution (see Section 16.1.1). Two aliquots from
each vial (1A, IB, 2A, 2B, 3A, 3B,...7A, 7B) will be
analyzed.
15.1.7.5 Place vial 1A in a rack. In a second rack place two-2 mL
vials labeled 1A1 and 1A2. Use the 1 mL automatic pipet to
mix the contents of vial 1A by drawing 1 mL into the pipet
tip and then dispensing it back into the vial three times. Then
use the same pipet to transfer 1 mL of the contents of vial 1A
to each of the two labeled (1A1,1A2) 2 mL vials. Place caps
on the vials. After transferring the two aliquots, rinse the
automatic pipet tip in a flask of DDW. Repeat the transfer
procedure for each of the other working standard pairs. (IB
aliquot into vials 1B1 and 1B2, 2A aliquot into vials 2A1 and
2A2, etc.). These are the working standards.
15.2 Calibration of pH Meter
The pH meter requires temperature calibration whenever a new electrode is
used. Use the manufacturer's procedure in the instrument manual. This
calibration should be repeated every three months while not in use. The pH
meter is left with the power cord plugged into the AC outlet, the mode control
knob is left in the standby position, and the combination electrode is immersed
in a 4 M KC1 solution (a slit rubber stopper seals the bottle with the electrode
in it). Keep a record of the temperature calibrations in a lab notebook.
15.3 Pre-analysis Calibration
Note: Figure 11 outlines the steps for proper calibration and set-up for analysis
of the Teflon® filter sample for pH determination. Analysis should be
performed at room temperature.
15.3.1 Use a pH Analytical Laboratory Log Form (see Figure 12) to record all
data.
15.3.2 Fill three 4 mL vials with pH 7 buffer. Withdraw the electrode from
the 4 M KC1 bottle and wipe the tip gently with a Kimwipe® to remove
the bulk of the solution. Rinse the electrode with one vial of pH 7
buffer. Do not test pH of the first vial.
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15.3.3 Immerse the electrode in the second vial of the pH 7 buffer. Use a
small bottle or other support to hold the vial up to the electrode while
waiting for the meter reading to equilibrate.
15.3.4 Test the pH by turning to the pH mode of the meter. Allow the reading
to stabilize for at least 30 seconds. Record the result on the Analytical
Laboratory Log Form for pH 7, entry 2.
15.3.5 Turn to standby mode, and then test the last vial of pH 7 buffer.
Record the results on the log fonn for pH 7, entry 3. If the pH value
for the 2nd cup is not 7.CO ± 0.01, adjust the "calib." knob to obtain a
reading of 7.00. Note this adjustment on the leg form.
IS.3.(3 Fill three 4 mL vials with pH 4 buffer. With the meter in the standby
mode, remove the cup containing pH 7 buffer, wipe the tip of the
electrode gently with a Kimwipe®, and then rinse the electrode with the
first vial of pH 4 buffer. Dc not record pH.
15,3.7 Test the next two vials of pH 4 buffer as above, recording the results
on the log form. If the pH value for the third vial is not 4.00 ± 0.01,
adjust the "slope" knob to get a reading of 4.00. If the value for the
second vial was not 4.00 ± 0.01, the calibrations at pH 7 and at pH 4
must both be repeated.
15.4 pH Test of HCIO^ Solutions
Note: The 0.01 N HCIO4 solution is used to prepare the ES solution which, in
turn, is used to prepare the EA solution. It is imperative that the pH value for
the EA solution be 4.09 ± 0.04. If this pH value is not achieved, then one or
more of the HCIO4 solutions must be reprepared.
15,4.1 Finish the calibration of the pH meter with pH 4 buffer.
1-5.4.2 Rinse the pH electrode with DDW. Wipe the tip of the electrode with
a Kimwipe®.
15.4.3 Fill, three 4 mL vials with EA solution. Measure the pH of the test EA.
solution in similar fashion to the buffer solutions. The values must be
4.09 ± 0.04.
15.4.4 If the above pH values are net achieved, follow Section 15.1.6 to
reprepare the solutions. Test the pH of the new solutions. Repeat as
necessary to obtain an average pH of 4.09 ± 0.04.
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15.4.5 Leave the electrode immersed in the "3rd vial" with the meter in the
standby mode until ready to start analysis of the working standards.
15.5 Analysis of Working Standard
Note: Immediately following the EA analysis, start testing the working
standards.
15.5.1 With the pH meter still in the standby mode, remove the last vial from
the electrode, gently wipe the tip with a Kimwipe®, and then immerse
the electrode into the working standard vial 1A1.
Note: Only two vials are available for each working standard (also for
filter extracts). Thus, pH measurement is made for both of the two
vials for each sample. Also, the electrode tip is not wiped between the
1st and 2nd vials of each sample.
15.5.2 After testing the pH of vial 1A1, test vial 1A2. Record the results of -
both on the Analytical Laboratory Log Form.
15.5.3 With the meter in the stand-by mode, remove vial 1A2, wipe the
electrode with a Kimwipe9 and test one 2 mL vial of EA solution.
15.5.4 Test a 2nd vial of EA solution; record the results on the log form.
Discard the 1st vial of EA, but retain the 2nd vial to be used as the 1st
vial for the next EA test.
15.5.5 Mean pH value for the EA solutions should be 4.09 ± 0.04. If the
above pH values are not achieved, follow Section 15.1.6 to reprepare
the EA solution. Retest. If still outside range, investigate problem
with probe, have Laboratory Manager review previous recorded pH
data for samples and EA solutions to determine validity of
measurements.
15.5.6 Continue testing the remainder of the working standards, 1B1, 1B2,
2A1, 2A2, 2B1, 2B2. . .7B1, 7B2. Remember that the electrode tip is
wiped both before and after each pair of test solutions, but not in
between two vials of the same sample.
Note: If there is trouble in obtaining constant pH values, it may be
necessary to use a magnetic stirrer to keep the contents to be measured
uniform. If employed, ensure that the sample vials are insulated from
any temperature increase of the stirring platform which may occur
during extended use.
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15.5.7 Use the mode control knob in the "temp." position to measure the
temperature of the test solutions every 5-10 samples and record the
results on the Analytical Laboratory Log Sheet Form.
IS,6 Analysis of Filter Extracts
Following measurement of the pH of the worldng standards, measure the pH of
the filter extract and record on the Analytical Laboratory Log Form. After ten
filter extracts have been tested, make an additional test with the EA solution
ar.d record temperature. At the end make a final test of pH 4 buffer. If not
4,00 ± G.04, then perform a new calibration; the laboratory manager must thee
decide (and document) how to reduce the unknowns based on pre- and post-
calibrations. Criteria and corrective action should be met according to
Section 15.5.5. Follow manufacturer's directions for shut-down of pH meter.
Immerse the electrode tip in the bottle of 4 M KCl..
16. Ion Chromatography Analysis
Ion Chromatography is a method used to determine anion concentrations (NO3 ~)
employing liquid chromatography with conductivity or UV absorbance detection.
16.1 Standard Preparation
Special Precaution: Storage of these solutions should be no longer than I week.
All of the working standard solutions are used to calibrate the IC and are made
from reagent grade stock. The crystals are dried overnight in covered petri
dishes at 1.05 DC in a vacuum oven prior to preparing the standard solutions.
Any yellowish discoloration of the dried crystals indicated decomposition and
crystals should be discarded.
16.1.1 Potassium Nitrate Stock Solution
16.1.1.1 Dry KMO3 crystals at 105°C for 2 hours.
16.1.1.2 In a clean, calibrated, 1 L flask, add 500 mL of DDW.
16.1.1.3 On a weighing paper, weight out 0.8158 g of the dried
KNO3.
16.1.1.4 Add the dried crystals to the 500 mL of DDW. Dilute to
mark with DDW.
16.1.1.5 This stock solution contains 1 mg/mL of NO3 ~.
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16.1.2 Nitrate Working Standards
16.1.2.1 Make the standard series in 100 mL volumetric flask.
16.1.2.2 Add the following amount of stock solution and fill to the
mark with DDW, as illustrated in the following table.
Stock
no3"
Solution
Concentration,
Flask ID
Added, mL
pg/mL,
F1
0.25
2.5
F2
0.50
5.0
F3
1.00
10.0
F4
2.00
20.0
F5
5.00
50.0
F6
10.00
100.0
16.1.3 Storage Life
16.1.3.1 The stock solution (5 x 10—^ equiv./L of NO^-) should be
kept in an amber bottle in the refrigerator and may be stored
up to 6 months.
16.1.3.2 The nitrate working standards must be made fresh within 2
weeks of its use.
16.2 Reagent Preparation
Note; Storage of these reagents should be no longer than one week.
16.2.1 Anion eluent - The anion eluent is a solution of 1.8 nM Na2C03 and
1.7 pM NaHCOj. A concentration solution can be prepared and
diluted as needed.
Note: See Anion storage solution.
16.2.1.1 Concentrated Na2C03 solution (0.36 M) - Weigh out
38.156 g of Na2C03 (MW = 105.99). Dissolve into 1 L of
DDW. Store in refrigerator until ready to dilute.
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16.2.1.2 Concentrated NaHCOj solution (0.34 M) - Weight cut
28.564 g cf NaHCOj (MW = 84.01). Dissolve into 1 of
DDW. Store in refrigerator until ready to dilute.
16.2.1.3 Dilution of stock solutions - Bring both solutions to room
temperature. Accurately pipet 10 mL of each solution into a
2000 mL volumetric flask which lias been partially filled with
DDW. Bring to the mark with DDW (1:200 dilution).
16.2.2 Anion regenerant - The regenera.it is a C.025 N solution.
VERY CAREFULLY dispense 2.8 mL of concentrated Ultrex sulfuric
acid (36 N) into a graduated cylinder. Partially fill the regenerant
reservoir with DDW (3L). Slowly add the acid to the regenerant
reservoir. Bring to the mark with DDW (4 L).
Note: Protective clothing and eye protection should be utilized.
16.2.3 Anion storage solution - Since the anion columns contain carbonates
from the eluent, protection must be taken against microorganisms that
will live on this food source and clog up the columns. If the columns
are not being used for long periods of time (>2 weeks), a storage
solution of 0.1 M NaOIi should be pumped into them.
16.3 Sample Preparation
16.3.1 Mark the auto sampler vials with the appropriate identification numbers.
Place the vials in an (IC) autosampler tray.
16.3.2 Using clean, calibrated 0.5 mL pipets transfer the remainder of the
nylon filter extract from the extraction vial to a clean disposable 0.5
mL (IC) autosampler (polyethylene) vial. Fill the autosampler vial up
to the line on the side.
Note: If refrigerated, the contents cf the 4 mL extraction vial must be
vortex-mixed prior to transfer to the autosampler vials.
16.3.3 Place black filter cap on top cf the vial. Use the tool provided to push
the cap into the vial until it is flush with the top. (See the IC manual
for more detailed instructions).
16.3.4 Wipe away any excess fluid from the top of the vial to avoid
contamination from other samples.
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16.3.5 After all of the trays are filled, place them into the left side of the
autosampler. The white dot on the tray indicates the first sample.
Press the button labeled RUN/HOLD to the RUN position. The trays
should move until the first sample is under the sampling head. The
front panel should indicate a READY message. Press local/remove
switch to remove.
16.4 Basic System Operations - Staxt-up and Shut-down
16.4.1 Start-up Procedure for Ion Chromatograph
16.4.1.1 Turn helium and nitrogen tanks on by opening the valve on
top of each tank (pressure in either tank should not be less
than 500 psi. Replace if necessary). Open valves at the
outlet end of both regulators. Pressure on the nitrogen
regulator is adjusted to 100 psi. Pressure on the helium
regulator is adjusted to 14 psi.
16.4.1.2 Check the level of eluents and regenerating solutions. Turn
the chromatography (CMA) values for the anion channel
switch ON. Verify that the pressure reading on the face of
the degassing unit is 7 psi. Adjust by turning dial next to
pressure gauge. Turn the degas switch to HIGH.
16.4.1.3 Turn the eluent reservoir switches, corresponding to the
eluents to be degassed, to the ON position. Let the eluents
degas on HIGH for 3-5 minutes, then turn degas switch to
LOW.
16.4.1.4 Select the appropriate program on the gradient pump module
using the PROGRAM switch. (Programs are recalled from
memory by first pressing the PROGRAM switch, then the
single digit reference number corresponding to the appropriate
program).
16.4.1.5 Priming the eluent lines.
Note: All of the eluent lines used during analysis must be
primed to remove any air bubbles that may be present. The
selected program identifies which lines are used.
• Open the gradient pump drawer. Turn the pump to the
START position for 10 seconds, or until a CLICK is heard,
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then turn the pump OFF. This step opens the valve to the
eluent line displayed on the front panel.
• Attach a 10 rnL syringe to the priming block ok the face of
the gradient pump module. Willi the pruning block valve
closed, pull the syringe plunger out to the end of the syringe.
• Open the priming block valve. The syringe will quickly fill
with eluent. Close the valve on the priming block when the
syringe is almost full. Remove syringe from block and
discard collected eluant.
• This priming procedure can bs repeated if necessary. All of
the eluent lines that are to be used during a day of analysis
should be primed at this time.
16.4.1.6 Open the door of the Advanced Chromatography Module.
On the back of the door, at the bottom, is the conductivity
detector. There are four labeled lines (anion, cation, waste,
and cell) located next tc the cell. Hie plumbing must be
configured according to the type of analysis to be performed.
The ANION line must be attached to the CELL line, and the
CATION line must be attached to the WASTE line. The line
coming from the pump must be attached to the correct port on
the advanced chromatography module. SYSTEM 1 on the
left is for anions, SYSTEM 2 on the right is for cations.
Note: If switching from one system to the other, the pump and the
lines coming from the pump must be purged of the original eluent.
This is done by disconnecting the pump line from the
chromatograph module, turning the pump on and running the new
eluent into a waste beaker for 2-3 minutes.
16.4.1.7 Select the columns to be used by pressing the blue button
located below the labels. To verify that the correct columns
are being used, the switch should be pressed at least once,
and then set to the appropriate position. This is done in case
the indicator light is reflecting a "default" setting, regardless
cf the actual position of the switch.
16.4.1.8 Turn the power switch on the autosampler ON (switch is
located on the back of the unit, on the right). The default
settings will be displayed on the front panel. Attach the
SAMPLE OUT line from the autosampler to the advanced
chromatography module. The connection should be made to
the port marked SAMPLE of the appropriate system. Turn
the pump to START.
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16.4.1.9 Turn the conductivity cell ON. Switch is located on the
gradient pump module. Turn the REGEN switch for the
appropriate system ON. Verify that regenerant is flowing by
inspecting the regenerant waste line which empties into the
sink. Open the advanced chromatography module door and
inspect for leaks at columns, fittings, etc. Shut pump off if
leaks are found.
16.4.1.10 Turn stripchart recorder ON. Baseline should stabilize in
less than 20 minutes. If baseline is not stable, see
troubleshooting Section 16.5 for assistance.
16.4.2 Data acquisition start-up - The following is a description of the current
data acquisition program used by the U.S. EPA. The program is
available (U.S. EPA, Atmospheric Research and Exposure Assessment
Laboratory (AREAL), Office of Research and Development, Research
Triangle Park, NC) and is for IBM or IBM compatible computers.
Other appropriately designed programs may be used to compile the data
collected for any given sampling network. It is not necessary to use a
computer programmed integrator for the computation of data, however,
for large sampling networks, it is recommended.
16.4.2.1 Turn on the IBM XT computer. From the C: >prompt, type:
cd/chart, then type: cchart. This loads the Chromatochart
software. Turn switch on relay box to ENABLE, indicator
light could go on.
16.4.2.2 Press F2 to enter the methods development module. Select
option number 1 - "select channel # and load method file."
"Select channel # <0>" type 0 or press ENTER to select the
default choice shown in the brackets (in this case 0). "Load
method file named" type the name of the appropriate method,
then press ENTER. A directory of all of the current methods
in memory can be obtained by pressing the F2 function key.
16.4.2.3 Press F3 to enter the Data Acquisition module. At this point
you will be asked to save the method file. If there has not
been any changes to the methods file, it does not need to be
saved. Select option #4 - "Collect Data." Press ENTER to
deactivate the method queue. "Load Run Queue named,"
type the name of the run queue if one has been created. Type
ENTER to deactivate the run queue.
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16,4,2.4 "Total // runs for method < i >type how many times the
method is to be repeated (total number of samples). "Auto-
analyze Data" type Y. "Autosave data to disc" type Y.
"Data file name (xxxxx) change?", type data file name.
"Press ENTER to begin methods." Press ENTER only after
the samples have been loaded into the autcsampler and the
baseline has stabilized.
16.4.3 Calibration of IC - The instrument should be brought to normal
conditions with a warm-up time of at least thirty minutes.
16.4.3.1 With the "Reading" light on, check tc ensure the flow rate is
1.5 irLs/minute, the fluid pressure is 600 psi ± 103 psi and
the conductivity is constant as measured by offset difference.
16.4.3.2 Fill the IC vials with the prepared standard solutions.
16.4.3.3 Load the four viols into the sample vial holder, and place the
holder in the automated sampler tray.
16.4.3.4 The tray is controlled by a Spectra-Physics SP4200 or SP4270
Computer Integrator. Use the integrators operation manual to
begin calibrating. (A typical program in Basic for integrators
which illustrates integrator capability is shown in the
Appendix of this procedure). By using the RUN command
the analysis and data treatment phases of the calibration are
set in motion. Four calibration standards are run, the
chromatograms and peak areas displayed for each run, and
the run results for the nitrate anion are fitted to a quadratic
curve by a least squares regression calculation. The curve is
plotted and the correlation coefficient is calculated. The
value of the coefficient is normally greater than 0.999, where
1.000 indicates a perfect fit. Values of less than 0.S9 indicate
the calibration procedure should be repeated.
Note: Recalibration should be carried out whenever standard
concentrations show consistently high or low results relative
to the calibration curve is compared to the calibration curve
from the old standards. Comparability of points should be
within ±0.1 ppm or ±10 percent. For standard
concentrations of greater than 1 ppm, comparability will
normally be within 5 percent or better. Old standards are
assumed correct since they are referenced to the entire
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historical series of previous standard solutions all of which
are comparable.
16.4.4 System Shut-down
16.4.4.1 Shut off the pump. Turn the REGEN switch and the
conductivity cell to the OFF position.
16.4.4.2 Switch the eluent degas switch to HIGH.
16.4.4.3 Turn the strip chart recorder FOF, cap the pen. Press the
F10 function key on the computer. Select option 3, to exit to
DOS. Shut off the printer and the computer.
16.4.4.4 Shut the eluent degas system and reservoir switches and the
autosampler to the OFF position. Close the valves on both
gas cylinders. Then close the regulator valves.
16.4.5 NO3" Concentration Calculations
16.4.5.1 Develop a calibration curve of conductivity versus
concentration (jtg/mL).
16.4.5.2 Perform a linear regression of the tabulated values.
16.4.53 Utilize the slope and intercept of the curve, calculate the
concentration of unknown filters by the following equation:
CNO3 = [Intercept] + [Conductivity] [Slope]
16.5 Basic Troubleshooting
Before proceeding with the troubleshooting guide, make sure that the reagents
used were prepared correctly, and are not "old."
16.5.1 Unstable Baselines
16.5.1.1 Wavy baseline - The most common reason for a wavy
baseline is an air bubble in the gradient pump. This is
diagnosed by observing the pump head indicator lights on the
gradient pump module front panel. If the baseline is pulsing
in phases with pump pistons, it usually indicates a bubble.
Other possibilities include a dirty or stuck check valve, piston
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seal or "C"-rhg, as well as an air bubble in the conductivity
cell.
16.5.1.2 Drifting baseline - Steadily increasing or decreasing baselines
usually indicate that the suppressor column is not performing
as it should. Parameters to change include the regenerate and
eluen'. concentrations and flow rates. Check temperature
routinely as chaEges in temperature can cause drifting.
Balancing these should stabilize the baseline, if the suppressor
is functioning correctly. The Dionex manual describes clean-
up procedures if the suppressor is believed tc be
contaminated.
16.5.1.3 High baselines - As with drifting baselines, the parameters to
change are eluent and regenerant concentrations and flow
rates. A high baseline usually indicates that there is not
enough baseline suppression, tliis can be controlled by
increasing the regenerant flow rate.
16.5.1.4 Low baselines - Low baselines usually indicate that there is
too much suppression. Oversuppressicn can be controlled by
decreasing the flow of the regenerant.
16.5,2 Backpressure - Variations in system backpressure are common and
should not raise concern UNLESS the pressure change is greater than
200 psi.
16.5.2.1 High backpressure - The system is protected from pressure
related damage through the high and low pressure alarm
settings on the front panel of the gradient pump module. If
the high pressure setting is correctly selected (200 psi above
normal operating range), the pump will automatically shut-off
if this value is exceeded. The reason for high backpressure is
that there is some kind of blockage in the system.
Possibilities include: loading against a closed valve; a plugged
line; contaminated columns; etc. Diagnosis of the problem is
done by removing one component of the system and
observing how the pressure changes.
16.5.2.2 Low pressure - Low pressure readings usually indicate a leak
somewhere in the system. Carefully check all fittings for
leaks, tighten if necessary.
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16.5.3 Flow
16.5.3.1 Regenerant lines - If there is no flow at the waste outlet end
of the regenerant line, check the following:
• Make sure that the correct regenerant switch is turned on
• Verily that the reservoir is not empty
• Make sure the nitrogen tank is turned on
• Check that the regulator is correctly set
16.5.3.2 Eluent lines - If there is no flow at the outlet end of the
eluent lines check the following:
• Check that the pump is on
• Check that the eluent lines are connected to the correct port
17. Ammonia Analysis by Technicon Auto-analvsis
Presented in Sections 17.1 and 17.2 are the recipes for the standards and reagents
required for the analysis of the ammonium ion [NH^+ - or ammonia (NHj)] by
Technicon Auto-analysis. Figure 13 illustrates how the sample is carried through the
Technicon Auto-analyzer. The samples, along with all standards, are taken from the
auto-advance sampler tray by the use of a proportioning pump. Air and EDTA are
first added to the samples and are mixed in the first set of coils. After mixing,
phenoiate is added and mixed in the next set of coils. Nitroprusside is then added and
mixed, followed by the addition and mixing of hypochlorite. At this stage, the sample
should be a bright blue color. The color formation depends on having a system that
allows for adequate reaction time and provides a sufficiently basic pH (pH > 11) for
the reaction to occur. Color formation is enhanced by the presence of a metal catalyst.
After the last mixing stage, the sample is sent through a heated bath, followed by
another mixing staje. Finally the sample is sent through a colorimeter where the
results are recorded on a digital printer and stored in a computer file for further
manipulation.
17.1 Standards and Stock Solutions Preparation
Note: Before discarding the old solution, it should be checked against the fresh
solution by comparing calibration curves on the working solutions prepared
from them. Slopes and intercepts are calculated for each set of standards. The
old slope and intercept are used to calculate concentration values from readings
for the new standards. This determines if the old solution has deteriorated or if
an error has been made in preparing the new solution.
17.1.1 Ammonium solution standard (1000 /ig/mL) - Dry ammonium chloride
in an oven for one hour at 50 to 60 °C and desiccate over silica gel for
one hour. Weigh 2.9470 g ammonium chloride and dissolve in 800 mL
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DDW. Dilute to one liter with DDW and mix thoroughly. This
solution is stable for one year.
17.1.2 Intermediate ammonium standards (100 /xg/mL)- To make a 100 /ig/mL
ammonium standard, pipet 10 mL of ammonium stock standard Into a
100 mL volumetric flask. Dilute to volume with DDW and mix
thoroughly. Keep refrigerated. This solution remains stable for one
month. To make a 10 pg/mL ammonium standard, pipet 1.0. mL of
ammonium stock standard into a 100 mL volumetric flask. Dilute to
volume with DDW and mix thoroughly. This solution remains stable
for one week.
17.1.3 Working ammonium standards in DDW - Pipet aliqucts of the 100
/xg/mL and 10 fig/mL ammonium intermediate standards into 100 mL
volumetric flasks according to the table below. Dilute to volume with
DDW. Prepare fresh daily.
Standard
Stock or
Intermediate
Standard,
jig/mL
Aliquot,
mL
t i
1
Final !
Concentration, !
fig/mL
A
100
40.0
40.0 ;
B
100
4.0
4.0
C
100
3.0
3.0
D
100
2.0
2.0
E
100
1.0
1.0
F
100
0.5
0.5
G
10
2.0
0.2
I-I
10
1.0
0.1
17.1.4 Sodium citrate stock solution - Dissolve 294.1 g of sodium citrate in
800 mL DDW. Dilute to 1 liter and mix thoroughly. Store at room
temperature.
17.1.5 20 percent citric acid/5 percent glycerol stock solution - Dissolve 25 g
citric acid in 80 mL DDW. Add 5 mL glycerol and dilute to 100 mL
with DDW. Mix thoroughly and store at room temperature.
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17.1.6 Sodium citrate/citric acid/glycerol working solution - Put 100 mL
sodium citrate stock solution into a 1000 mL volumetric flask. Add 20
mL of the 10 percent citric acid/5 percent glycerol stock solution and
dilute to volume with DDW. Mix thoroughly and store at room
temperature.
Note: This solution will be used to make up ammonium working
standards for citric acid/glycerol-impregnated filter extract analyses.
17.1.7 Working ammonium standards in sodium citrate/ citric acid/glycerol
working solution - Pipet aliquots of the 100 jtg/mL into appropriate
volumetric flasks according to the table outlined in Section 17.1.3.
17.1.8 Potassium chloride stock solution - Dissolve 74.6 g potassium chloride
in 800 mL DDW. Dilute to one liter with DDW and mix thoroughly.
Store at room temperature.
17.1.9 Potassium chloride working solution - Put 100 mL of the potassium
chloride stock solution into a 1000 mL volumetric flask. Dilute to
volume with DDW.
17.1.10 Working ammonium standards in potassium chloride working solution-
Pipet aliquots of the 100 ng/mL ammonium stock standard or
intermediate standards into 100 mL volumetric flasks according to the
table below. Dilute to volume with potassium chloride working
solution and mix thoroughly. Prepare fresh daily.
Ammonium
Standard
Stock or
Intermediate
Standard,
pg/mL
Aliquot,
mL
Ammonium
Concentration,
ng/mL
A
1000
40.0
40.0
B
100
4.0
4.0
C
100
3.0
3.0
D
100
2.0
2.0
E
100
1.0
1.0
F
100
0.5
0.5
G
10
1.0
0.1
H
10
0.5
0.005
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17.2 Reagent Preparation
Note: When reagents are prepared, label the container with the contents,
concentration, date prepared, and the preparer's initials.
17.2.1 Alkaline phenol - To 800 mL DDW in a one liter volumetric flask, add
83.0 g loose crystallized phenol. Keeping the flask in an ice bath or
under tap water, slowly add 96.0 mL 50 percent sodium hydroxide
solution. Shake the flask while adding the sodium hydroxide. Cool to
room temperature, dilute to one liter with DDW and mix thoroughly.
Store in ail amber glass container. This solution remains stab's for
three months, if kept out of direct light.
17.2.2 Sodium hypochlorite solution - The amount of sodium hypochlorite
solution varies from batch to batch of sodium hypochlorite (5 percent
commercial grade). Therefore, for each new batch, a base and gain
experiment must be run to adjust the amount of sodium hypochlorite
required to obtain the existing base and gain values. In a 150 mL
volumetric flask, dilute 86 mL of 5 percent sodium hypochlorite
solution to 100 mL with DDW and mix thoroughly. Check base and
gain values. Reduce or increase the amount of sodium hypochlorite to
obtain the same base and gain values as the previous sodium
hypcclilorite batch. This solution remains stable for one day.
17.2.3 Sodium nitroprusside solution - Dissolve 1.1 g of sodium nitroprusside
in about 600 mL of DDW, dilute to 1 liter with DDW and mix
thoroughly. Store in an amber container, and keep in refrigerator.
This solution remains stable for one month, if kept out of direct light.
17.2.4 Disodiuni EDTA solution - Dissolve 1.0 mL of 50 percent w/w sodium
hydroxide and 41.0 g of disodium EDTA mix thoroughly. Add 3.0 mL
of BRTJ-35 and mix. Store in plastic container. This solution remains
stable for six months.
17.3 Procedure for Auto-analyzer Set-up
17.3.1 Proportioning pump - Marked tubing lines should be positioned across
rollers. When proportioning pump is not in use, plane press should be
unlocked.
17.3.2 Manifold - The air tube feeds bubbles into the sample tube, breaking
the sample flow into separate sample aliquots. The EDTA solution is
added and this mixture goes through a double mixing coil (20 turns).
Phenolate and nitroprusside are added and the solution goes through
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another double mixing coil (10 turns). Bleach is added, and the
mixture goes through a single mixing coil (5 turns). Then, the mixture
passes through a heat bath (37°C), and a delay coil (for about
10 minutes). A debubbler diverts a fraction of the flow to waste to
ensure a smooth, bubble-free flow to the colorimeter. The solution
passes through single channel colorimeter (set at 630 nm) and finally to
a waste stream.
17.3.3 Reagent and Sample Volumes - Typically flow rates for the auto-
analyzer are listed in the following table:
Item
Flow Rate
Air
0.32 mL/min
Sample Aliquot
1.00 mL/min
Complex Solution
0.23 mL/min
Alkaline Phenol
0.60 mL/min
Bleach
0.42 mL/min
Total liquid
2.25 mL/min
Volume to waste
1.05 mL/min
Colorimetric return
1.20 mL/min
Needle washing
1.60 mL/min
17.4 Procedure for Sample Run
17.4.1 Allow colorimeter and recorder to wann up for 30 minutes.
17.4.2 Start the proportioning pump, with all reagent lines in a
beaker of DDW.
17.4.3 One at a time, place the reagent lines into the respective reagent bottles.
Make sure that the air bubbles are being fed into the sample line at a
constant interval. Obtain a baseline reading on the recorder.
17.4.4 Take samples from the refrigerator and set-up the sample tray. Put the
cover on sample tray to avoid evaporation.
17.4.5 Run system. Standard should be run first to calibrate recorder output.
Run standard levels low-to-high. Standard should be run every 10
samples for verification.
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17.4.6 Once a week cr prior to extended, period cf non-use, run a solution of
0.01 percent BRXJ-35 through all reagent lines.
17.'(.7 Record peak height for all standards and samples as determined.
17.4.S A calibration curve is derived from the values of ammonia standards
(fjig/mL) versus peak height.
17.4.9 Perform a linear regression of the tabulated value.
17.4.10 Utilizing the slope and intercept of the curve, calculate the
concentration of NH^+ on the unknown filter by the
following equation:
CNH4+ = [Intercept] 4- [Peak Height] [Slope]
18. Assumption of Annual Denuder System
IS J. The measurement cf acid aerosol requires that ammonia be eliminated from the
sample stream to prevent inaccurate measurement of the acid aerosol, thus
biasing the results. To address this issue, a citric acid coated denuder to
remove (denuder) ammonia from the gas stream is positioned in front of the
filter assembly where strong acid aerosols are collected. The efficiency of the
citric acid denuder to remove NH3 is assumed to be 100 percent.
18.2 The efficiency of the impactor collection system decreases with increased
particulate loading. The average operational time before such loading occurs
has not been determined. Likewise, the removal efficiency of the denuders
have not been fully explored. Thus, both the impactor and denuders are
removed after each sampling event and replaced with new components.
18.3 Other assumptions which are made associated with the performance of the
annular denuder system for validity of the calculations presented in Section 19
are:
* All alkaline particles (>2.5 /xm) are removed at the sampler inlet;
* The cyclone or elutriator/impactor assembly have DP5Q cut size of 2.5 /iin;
* The citric acid coated-denuder removes 100 % cf ammonia frcm the gas
sample stream;
* Fine (<2.5 urn) acid (H^SO^) aerosol losses in the denuder are less than 1 %;
* The Na2C03 coated denuder collects 100 percent of the nitric acid, while the
following citric acid coated denuder collects 100 percent of the ammonia.
Particle losses are less than 1 percent in each denuder.
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• The Teflon® filter is 100 percent efficient for collection of fine acid aerosols.
If ammonium nitrate (NH4NO3) was collected on the Teflon® filter, its
probability of evaporation is high. Therefore, a citric acid-impregnated filter
downstream would collect some of the dissociation products from the Teflon®
filter. Also, interaction of ammonia and sulfuric acid neutralizes the sample
and causes the acidic measurement to be biased.
• The nylon filter collects any nitrate that dissociates from the Teflon® filter.
• The citric acid impregnated retains all the ammonia arising from the
dissociation of NH4NO3 collected on the Teflon® filter.
19. Atmospheric Species Concentration Calculations
19.1 Calculations Using Results from pH Measurement
19.1.1 A convenient method of expressing concentration of the hydrogen ion
was first proposed by Sorensen in 1909 and has been widely adopted by
chemists.
pH = - log [H+]
[H+] = 10-PH
19.1.2 For each working standard on a given analytical day, calculate the
"apparent net strong acid concentration" as follows:
C- = iQ-pffWSj. jQ-pHEA
where:
Cj = apparent net strong acid concentration, molar,
pHWSj = measured mean pH of a working standard, and
pHEA = measured mean pH of the EA solution.
19.1.3 For each analytical day, utilizing a particular set of freshly prepared
daily working standards, develop a standard curve by calculating the
linear regression of Cj vs. C™ as documented in Section 15.1.1.1.
Calculate slope and intercept of the standard curve.
19.1.4 Calculate the corresponding "apparent net strong acid concentration"
from the sample pH utilizing the following equation:
cs = io_PHS - io-p11^
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where:
Cs = apparent net strong acid concentration for unknown sample,
molar,
pHS = measured pH of the sample (S), and
pHEA = measured pH of the EA solution.
19.1,5 Utilizing the slope and intercept of the standard curve, calculate
equivalent mass of strong acid:
Cc = [Intercept] + [Cg] [Slope]
where:
Cf = apparent net Strang acid mass, ^g, as calculated from
standard curve,
Intercept = calculated relationship from linear regression analysis
of vs. Cgq, and
Slope = calculated relationship from linear regression analysis
cf q vs. cEq.
19.1.6 The actual sample air value, V, for each sample is calculated using the
data from the Field Test Data Sheet. These data include the initial and
final elapsed times, the initial rotameter reading, and the rotameter I.D.
No. Use the calibration curve for the given rotameter to calculate the
flow for the sample, in LPM, if applicable. Calculate the value of V as
follows:
V = [F][T]
where:
F = flow from the calibration curve, L per minute,
T = net elapsed time, min, and
V = total sample volume, L
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-l
Convert L to mJ by:
V„ = V x (10"3)
where:
Vs =total sampling volume, m3, and
10~3 =conversion factor, m3/L.
19.1.7 Calculate the air volume sampled, corrected to EPA-reference conditions:
v. . = vsY(l!^)(Z^Ł)
Sstd 5 Tra Pstd'
where:
Vsstd = volume sample at EPA-reference conditions, m3,
V$ = volume of gas sample through the dry gas meter, or
calculated volume sampled as indicated by rotameter
(see Section 12.2.6), m3,
^std = absolute EPA-reference temperature, 298°K,
Tm = average flowmeter or dry gas meter temperature, °K,
**bar = barometric pressure of flow or volume measurement
condition, mm Hg,
Pst(j = EPA-reference barometric pressure, 760 mm Hg, and
Y = dry gas meter calibration factor (if applicable),
dimensionless.
19.1.8 Calculate the final concentration of apparent net fine particle (<2.5 jtm)
strong acidity (as H2SO4):
CH+ = Cf / VSs[d
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where:
Cj[+ = apparent net fine particle strong acidity concentration,
Cr = apparent net strong acid, /tg, as calculated from
standard curve, and
Vs . = volume of sampled gas at EPA-reference conditions
st (sec Section 19.1.7}, nP.
19.2 Calculations Using Results from IC Analysis
These assumptions lead directly to equations for computing atmospheric
concentrations from denuder measurements.
19.2.1 Analytical results are given at NO3- in ptg/mL.
1,9.2.2 The extraction volume was 10 mL (i.e., 0.010L).
19.2.3 Nitrate concentration converted to equivalent sulfuric acid:
CNO3- = - NO3-blank][10 inL][98/62]
19.3 Calculations Using Results from Auto-analyzer
19.3.1 Analytical results are given in NH^+ in ^cg/niL.
19.3.2 The extraction volume was 1.0 mL,
19.3.3 Ammonium concentration converted to equivalent sulfuric acid:
CNH4+ = [NH4+sample-NH4+blaEl,][10][98/18]
20. Variations of Ww Acid Aerosol Denuder System
One modification of the fine particle strong acidic aerosol denuder system involves
adding additional denuders to selectively quantitate other gaseous and particulate
species in the atmosphere, and is illustrated in Figures 14 and 15. This system was
developed to measure reactive acidic and basic gases and particulate matter which are
contained in ambient air. The chemical species which can be measured utilizing tills
system are gaseous SO2, HNO2, HNO3, NH3, and particulate SO^-, NO'j, and
H+. Other similar chemical species can be successfully collected by the system with
Acid Aerosol
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modifications (i.e., changing the denuder coating solutions, the denuder sequence, and
the filter types and sequence). Once collected, the pollutant concentrations are
quantified by ion chromatography (IC) analysis and/or Technicon colorimeter auto-
analysis. A full description of this methodology can be found in "Compendium of
Methods for the Determination of Air Pollutants in Indoor Air, "U.S. Environmental
Protection Agency, Atmospheric Research and Exposure Assessment Laboratory,
Research Triangle Park, N.C. 27711, EPA-600/4-90-010.
21. Method Safety
This procedure may involve hazardous materials, operations, and equipment. This
method does not purport to address all of the safety problems associated with its use.
It is the user's responsibility to establish appropriate safety and health practices and
determine the applicability of regulatory limitations prior to the implementation of this
procedure. This should be part of the user's SOP manual.
22. Performance Criteria and Quality Assurance (QA)
Required quality assurance measures and guidance concerning performance criteria that
should be achieved within each laboratory are summarized and provided in the
following section.
22.1 Standard Operating Procedures (SOPs)
22.1.1 SOPs should be generated by the users to describe and document the
following activities in their laboratory: 1) assembly, calibration, leak
check, and operation of the specific sampling system and equipment
used; 2) preparation, storage, shipment, and handling of the sampler
system; 3) purchase, certification, and transport of standard reference
materials; and 4) all aspects of data recording and processing, including
lists of computer hardware and software used.
22.1.2 Specific stepwise instructions should be provided in the SOPs and should
be readily available to and understood by the personnel conducting the
monitoring work.
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22.2 Quality Assurance Program
The user should develop, implement, and maintain a quality assurance program
to ensure that the sampling system is operating properly and collecting accurate
data. Established calibration, operation, and maintenance procedures should be
conducted on a regularly scheduled basis and should be part cf the quality
assurance program. Additional QA measures (e.g., trouble shooting) as well as
further guidance in maintaining '.he sampling system are provided by the
manufacturer. For detailed guidance in setting up a quality assurance program,
the user is referred to the Code cf Federal Regulations (see Section 23,
Citation li) and the EPA Handbook on Quality Assurance (see Section 23,
Citation 12).
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23. References
1. Waldman, J. M., Operations Manual for the Annular Denuder System Used in the
USHPA/RTVM Atmospheric Acidity Study, UMPNJ - Robert Wood Johnson Medical
School, Piscataway, NJ, August 28, 1987.
2. American Chemical Society Subcommittee on Environmental Chemistry, "Guidelines
for Data Acquisition and Data Quality Evaluation in Environmental Chemistry,"
Analyt. Chem., 52:2242-2249, 1980.
3. Sickles, n, J. E., "Sampling and Analytical Methods Development for Dry Deposition
Monitoring," Research Triangle Institute Report No. RTI/2823/00-15F, Research
Triangle Institute, Research Triangle Paris, NC, July 1987.
4. Forrest, J., and L. Newman, "Sampling and Analysis of Atmospheric Sulfur
Compounds for Isotopic Ratio Studies," Atmos. Environ., 7:562-573, 1973.
5. Stevens, R. K., et al., Abstract for ACGIH Symposium: on Adran COS in Air
Sampling, "Inlets, Denuders and Filter Packs to Measure Acidic Inorganic Pollutants
in the Atmosphere," Asilomar Conference Center, Pacific Grove, CA, February 16,
1986.
6. Appel B. R., Povard V., and Kothney E. L., "Loss of nitric acid within inlet devices
for Atmospheric Sampling," Paper presented at 1987 EPA/APCA Symposium:
Measurement of Toxic and Related Air Pollutants, Research Triangle Park, NC, 3-6
May 1987.
7. Braman R. S., Shelley T. J., and McClenny W. A., "Tungstic Acid for
Preconcentration and Determination of Gaseous and Particulate Ammonia and Nitric
Acid in Ambient Air," Analyt. Chem., 54:358-364, 1983.
8. Ferm, M., "Concentration Measurements and Equilibrium Studies of Ammonium,
Nitrate and Sulphur Species in Air and Precipitation," Doctoral Thesis, Department of
Inorganic Chemistry, Goteborg University, Goteborg, Sweden, 1986.
9. Ferm, M., and Sjodin A., "A Sodium Carbonate Coated Denuder for Determination of
Nitrous Acid in the Atmosphere," Atmos. Environ., 19:979-985, 1985.
10. Stevens, R. K., and Rickman, E., Jr., "Research Protocol/Method for Ambient Air
Sampling with Annular Denuder Systems," prepared for U.S. Environmental Protection
Agency, Atmospheric Chemistry and Physics Division, Office of Research and
Development, Research Triangle Park, NC, ASRL-ACPD-RPM 003, January 1988.
11. 40 CFR Part 58, Appendix A, B.
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12. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume n -
Ambient Air Specific Methods, EPA 600/4-77-0272, May, 1972.
13. Bolleter, C.J., Bushwan, and Tidwell, P.W. (1961), " Spectrophotometry
Determination of Ammonia as Indcphenol," Anal. Chem. 32, 592-594.
14. Harwood, J.E. and Kuhn, A.L. (1970), "A Colorimetric Method for Ammonia in
Natural Water," Water Res. 4, 8055-811.
15. Koutrakis, P., Wolfson, J.M., Slater, J.L., Brauer, M., Spengler, J.D., Stevens, R.K.,
and Stone, C.L., "Evaluation of an Annular Denuder/Filter Pack System to Collect
Acidic Aerosols and Gases," Environ. Sci. & Tech. 22, 1463-1468, 1988.
16. Mann, L.T., Jr., "Spectrophotometric Determination of Nitrogen in Total Micro-
kjedahl Digests," Anal. Chem. 21, 2179-2182, 1963.
17. Possanzini, M., Febo, A., and Libeiti, A., ,:New Design of a High-performance
Denuder for the Sampling of Atmospheric Pollutants," Annas. Environ. 17,
2605-2610, 1983.
18. Stevens, R.K., and Rickman, E.E., Research Protocol/Method for Ambient Air
Sampling with Annular Denuder Systems. Report ASRL-ACFD-RPM 003, U.S. EPA,
Research TriangLe Park, N.C., January 1988.
19. Koutrakis, P., Wolfson, J.M., and Spengler, J.D., "An Improved Method for
Measuring Aerosol Strong Acidity: Results from a Nine-Month Study in St. Louis,
Missouri and Kingston, Tennessee,'' Atmospheric Environment, 22:157-162, 1988.
20. Brauer, M., Koutrakis, P., Wolfson, J.M., and Spengler, J.D., "Evaluation of the Gas
Collection of an Annular Denuder System Under Simulated Atmospheric Conditions,"
Atmospheric Environment, 23:1981-1986, 1989.
21. Koutrakis, P., Wolfson, J.M., Brauer, M., and Spengler, J.D., "Design of a Glass
Impactor For an Annual Denuder/Filter Pack System," A eras. Sci., and Techn.,
12:607-612, 1990.
22. Sjodin A. and Ferm, M., "Measurements of Nitrous Acid In An Urban Area,"
Atmospheric Environment 19, 985-992, 1985.
23. Vcsslsr, T.L., Stevens, R.K., Paur, R.J., Baumgardner, R.E., and Bell, J.P.,
"Evaluation of Improved Inlets and Annular Denuder Systems to Measure Inorganic
Air Pollutants," Annas. Environ. 22, 1729-1736, 1988.
24. Technical Assistance Document for Sampling and Analysis of Toxic Organic
Compounds in Ambient Air, EPA-600/8-90-005, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1990.
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Table 1.0. Summary of Key Probe Siting Criteria for
Acid Aerosol Monitoring Stations
Factor
Criteria
Vertical spacing above ground
• Representative of the breathing zone and avoiding effects
of obstruction, obstacles, and roadway traffic. Height of
probe intake above ground in general, 2-3 m above ground
and 2-15 m above ground in the case of nearby roadways.
• About 1 m or more above the structure where the sampler
is located.
Horizontal spacing from
obstruction and obstacles
• Minimum horizontal separation from obstructions such as
trees is >20 m from the dripline and 10 m from the
dripline when the trees act as an obstruction.
• Distance from sampler inlet to an obstacle such as a
building must be at least twice the height the obstacle
protrudes above the sampler.
• If a sampler is located on a roof or other structures, there
must be a minimum of 2 m separation from walls,
parapets, penthouses, etc.
• There must be sufficient separation between the sampler
and a furnace or incinerator flue. The separation distance
depends on the height and the nature of die emissions
involved.
Unrestricted airflow
Spacing from roads
• Unrestricted airflow must exist in an arc of at least 270
degrees around the sampler, and the predominant wind
direction for the monitoring period must be included in the
270 degree arc.
• A sufficient separation must exist between the sampler and
nearby roadways to avoid the effect of dust re-entrainment
and vehicular emissions on the measured air
concentrations.
• Sampler should be placed at a distance of 5-25 m from the
edge of the nearest traffic lane on the roadway depending
on the vertical placement of the sampler inlet which could
be 2-15 m above ground.
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TO PUMP
and row controller
FILTCa PACK
ANNULAR
DEMUOEft#2
ANNULAR
DENUOER #1
COUPLER / iMPACTOR
iNLtr
ANALYTS
COATING DETERMINED
7
H *,NO- .NH4 *
KH*
1
UNO 3
_i_
Figure i. Annular Denucisr System (ADS) with Coupler/Impactor Assembly
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TEMP. CONT.
AIR OUTLET TEMP- CONT.
SWITCHES
NYLON
12V [
Is*
vN
? / V
igpil
ifeir
^ v
§«il8
lilll
\ ''i- .VV..'
¦>
HEATER
TEFLON
CITRIC ACID
COATING
Na2C03 COATING
FLOW
CONTROL
OL
DC Output
E3 ©
tMedunw
\i/
7\"
Vacuum
¦•I'Mitti
Auto DrfGm
Fum
TEMP. CONT. FAN
INLET
TOTAL
FLOW
CYCLONE
Figure 2. Annular Denuder System in Field Sampling Box
With Pump-Timer System
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Teflon
ft
Figure 3 . Acidity Determination of the Teflon® Filter
with Correction For Volatilized Nitrate Species
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ACCELERATION JET
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PIN UrMOVAL TOOL
IMP ACTOR SUPPORT PIN
AND FRIT
ViTON "O" RING
mo THREADS
COUPLER /1MPACT0R
HOUSING SEAT
ANNULAR DENUDER'
IMPACTOR (242 mm LONG)
#30 THREADS
V
CAP
Figure 5. Glass Annular Denuder with In set Impactor Assembly
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VIEW A
TEFLON SEAT SUPPORT
Figure 6. Side View Impactor/Coupler Assembly
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1mm ANNULAR SPACE
INTERNAL SURFACE
TEFLON COATED
\'
CROSS-SECTIONAL VIEW
Figure 7. Internal Schematic of Annular Denuder
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WALL
CLAMP
DRYER/
CLEANER
BOTTLE
FRIT
THERMOPLASTIC CAPS
W / TEFLON ® SEAL RINGS
AND HOSE BARBS
TEFLON©
TUBING
BACK-TO-BACK
CONNECTORS
DENUDERS
DENUDER
CAPS
MANIFOLD
Figure 8. Drying Train and Manifold
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STMNUOf
flTCBl
POftOW
SCfiW
K
w~:
mm < ncLfAsi
PLWO
ALUMINUM FILTCR
H0USIN3 CUTLET
vw6N '«r wwa
niffwi
f'ULftW
VWroM-flTBIHa
Fll TFSNOOSJNO
tNlff
OCLRIM
Figure 9. Acid Aerosol Filter Pack Assembly
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DETERMINATION OF THE STRONG ACIDITY OF
ATMOSPHERIC FINE-PARTICLES (< 2.5/xjii)
GENERAL
Project: Date:
Site: Location of Sampler:
Location:
Operator:
Sample Code:
EQUIPMENT Sampler
Mass Flow Citric Acid Denuder No.:
Controller No.: Filter Assembly Na_:
Lab Calibration Date:
Flow Rate Set Point:
Calibrated By:
Rotameter No.:
DGM No.:
SAMPLING DATA
Time Stop
Time: ;
Flow Rate:
Temperature:
Pressure:
Avg. Flow Rate:
Leak Check (Before):
(After):—
Total Sample Vol.:
Flow Maintained Rate: (±5%)
Time
Flow
Rate
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pH 7 Buffer
ir
pH 4 Buffer
—T~
EA Solution
Working Standards
HO
DONE?
YES
NO
DONE?
YES
EA Solution
Analysis of up
to 10 Filter Extracts
pH 4 Buffer
Figure 11. Calibration and Analysis Step for pH Detemiinatioii
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Determination of the Strong Acidity of
Atmospheric Fine-Particles (<2.5 nm)
Name: Sample I.D.:
Date: Location:
LAB:
Constituent
RUN NUMBER
1
2
3
4
5
6
7
pH 7 Buffer
1
2
3
pH 4 Buffer
I
2
3
EA Solution
1
2
3
Working Standards
1A1
1A2
EA
1B1
1B2
EA
2A1
2A2
Temp.
EA
2B1
2B2
EA
3A1
3A2
EA
Temp.
3B1
3B2
EA
Figure 12. pH Analytical Laboratory Log Form
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Constituent
4A1
4A2
EA
4B1
4B2
Temp.
EA
5A1
5A2
EA
5BI.
5B2
HA
6A1
6A2
Temp.
EA
6B1
632 .
EA
EA
7A1
7A2
EA
731
732
Temo.
RU1
Sf NUMB
ER
1
2
3
4
j
6
7
Sample Extracts
A
A1
B
B1
C
! CI
D
D1
E
El
EA
Temn.
:
4
i
111111
- ¦—
sis
— .
>
EA Solution
1
2
i 3
• —- -
pH4 Buffer
2
- -
: , -
Figure 12. pH Analytical Laboratory Log Form (coat.)
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Proportioning
Pump
Wash Water
Wash Water
To Sampler
Air
nnnnn nnnnn ooooo nnnnn
Sample
EDTA
Phenolate
Nltropmsslde
Heating
Bath
37®C
Hypochlorite
Water
Waste
O
O
o
o
o
Digital
Printer
Recorder
~
Colorimeter
Sampler
Figure 13. Technicon Auto-Analyzer Flow Diagram for Ammonia Analysis
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FiLTFn PACK
NYLON
TBFION
d2
d1
COUPLER { TYPICAL}—
r
NH„/ S
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|