NO2 Concentrations in the Greater Pittsburgh Area

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Nitrogen Dioxide (NO2) Concentrations in the Greater
Pittsburgh Area
Kristina Marks
Advisor: Dr. Dan Short
Robert Morris University

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Abstract
A comprehensive assessment of levels of the pollutant gas nitrogen dioxide (NO2) in the
atmosphere is required for developing effective strategies for air quality control methods. The
Palmes diffusion tube method is an inexpensive and accurate method of measuring NO2. The
Atmospheric Research Kit (ARK), which utilizes Palmes tubes, was developed as an educational
tool for high school teachers and their students in Allegheny County. The ARK was used to
measure NO2 concentrations at various sites in the Greater Pittsburgh Area for a six month
period. Results from the Palmes method were standardized against the EPA’s approved
chemiluminescence technique. The study recorded daily, weekly, monthly and annual variation
in NO2, via chemiluminescence; with monthly NO2 PDT measurements at all 7 sites having close
correlation with Allegheny Heath Department’s routine monitoring of both an urban and rural
(background) sites. The study also investigated meteorological factors; finding a negative
correlation between temperature and NO2 concentrations, and no correlation with snowfall and
rainfall. The Palmes method average NO2 concentration of 15ppb RMU for the six month period
was ±1 ppb from the chemiluminescence monitor average, indicating the reliability of the PDT
method.

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1. INTRODUCTION
Nitrogen dioxide (NO2) is a reddish-brown gas that belongs to a family of highly reactive
gases called nitrogen oxides (NOX). These gases form primarily when fuel is burned at high
temperatures, and come principally from motor vehicle exhaust and other fuel combustion
sources. NO2 plays major roles in the atmospheric reactions that produce ground-level ozone or
smog and acid rain, which potentially causes human health concerns (Heal, 2002). In order to
assess the potential effect of NO2, as well as develop strategies for effective control of NO2
pollution, monitoring of atmospheric gas pollutants must be accurate and reliable. There are two
methods routinely used for the monitoring of atmospheric NO2; (i) chemiluminescence method,
(ii) Palmes diffusion tube (PDT) method. Nitrogen dioxide is routinely monitored using fixed
location chemiluminescence analyzers which require an on-site power source. Due to those
requirements, extensive ground-based air quality monitoring over wide geographical areas
presents serious difficulty and is no longer widely undertaken.
The Atmospheric Research Kit (ARK) was developed in order to engage school students
(local) in the study of atmospheric pollutant gases, showcasing spectroscopic analysis as an
important scientific technique; and to test the reliability of Palmes diffusion tubes against
chemiluminescence monitors. The project was grant funded and lasted from September to
March. The five other participating schools (West Mifflin, Hopewell, McGuffey, North Hills,
and South Fayette) were involved in training days on June 16 and 17, 2014. The first training
day included instruction of how to properly use an auto pipet and an overview of UV-Visible
spectroscopy. The second training day was an overview of NO2 measurements and introduction
to the Palmes diffusion tube method. The grant was sponsored by the Colcom Foundation, a
local environmental foundation. Colcom provided the funds for the ARK kits and the installation
of a chemiluminescent analyzer at Robert Morris University (RMU). Support is given by RMU
in the form of laboratory space and supplies. The goal of the study was the compare and contrast
measurements of nitrogen dioxide over a wide variety of locations in the Pittsburgh area and to
use the project as a whole to help promote awareness of Pittsburgh’s air quality issues in the
local community.
2. ENVIRONMENTAL IMPACTS OF NITROGEN DIOXIDE
NO2 is a major component in the atmospheric reaction that produces ground-level ozone,
and is also a strong oxidizing agent that reacts in the atmosphere to form nitric acid, a key
component of acid rain/deposition. In addition to these negative effects on our atmosphere, the
amounts of NO2 that are being produced today can have dire consequences on human respiratory
health and so they must be monitored to ensure safe living conditions.
Photochemical smog is a unique type of air pollution which is caused by reactions
between sunlight, nitrogen dioxide and hydrocarbons (HCs). Photochemical smog forms
through a series of chemical reactions among those compounds in the atmosphere. When nitric
oxide (NO), a component of the exhaust from cars and power plants, enters the atmosphere, it
reacts with oxygen to produce NO2. The sun's UV rays then can break nitrogen dioxide down,
which leads to the formation of low-level ozone (O3). Ozone's presence at the ground level is
what poses a serious health risk.
Another problem associated with elevated levels of NO2 in the atmosphere is acid
deposition. Acid deposition is formed primarily from sulfur oxides (SOX) and NOX reacting with

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water in the atmosphere to form sulfuric acid and nitric acid; its two major components. When
the newly acidified precipitation reaches the ground it can have several negative effects on the
local area. Perhaps one of the better known effects is acidification, a condition in which lakes
and streams have a low pH level due to the acid deposition, resulting in the death of a variety of
animal and plant life that cannot survive in the poor conditions. Soils are also affected by acid
deposition, particularly in areas with highly siliceous bedrock (granite, gneisses, quartzite, and
quartz sandstone) that is already partially acidic. When acid deposition occurs on acidic soils,
important cations including potassium, calcium, magnesium, and sodium are readily leached out,
making them unavailable to plants as nutrients. This occurrence, termed soil depletion, reduces
the fertility of the soil. Similarly, in areas with old, highly leached soils, acid deposition depletes
the small amounts of cations present, and the soil soon becomes unable to support plant life.
Elevated levels of NO2 in our atmosphere and environment has led to some major human
health concerns. The health effects associated with breathing ground level ozone caused by
photochemical smog. Studies have shown that O3 can cause negative pulmonary function
responses and alterations in lung function and breathing patterns of otherwise healthy test
subjects. These effects are compounded when suffering from a multitude of other respiratory
issues (i.e., asthma, chronic obstructive pulmonary disease, etc.). Similar health problems exist
when dealing with nitrogen dioxide by itself. For instance, studies have shown that bronchitis
symptoms of children with asthma increase in association with annual NO2 concentration, and
that reduced lung function growth in children is linked to elevated NO2 concentrations within
communities already at current North American and European urban ambient air levels.
Monitoring nitrogen dioxide is vital in understanding exposure patterns and to establish a link
between exposure and health effects (Atkins, 1986).
3. SAMPLING PLAN, QUALITY CONTROL AND
EXPERIMENTS
The Atmospheric Research Kits (ARK) of Palmes diffusion tubes were sent to five
different schools in the Pittsburgh area between May and June of 2014 (table 1).
School Location
Robert Morris University (RMU) Lat: 40˚31’14”N Long: 80˚12’39”W
Colfax Upper Elementary (CUE) Lat: 40˚32’29”N Long: 79˚46’56”W
West Mifflin (WMHS) Lat: 40˚22’40”N Long: 79˚52’80”W
South Fayette (SFHS) Lat:40˚22’33”N Long: 80˚10’14”W
McGuffey (MHS) Lat: 40˚7’4”N Long: 80˚24’37”W
Hopewell (HHS) Lat: 40˚35’18”N Long: 80˚15’11”W
North Hills (NHSHS) Lat: 40˚31’30”N Long: 80˚1’37”W
Table 1: Sampling sites
Since the participants at Colfax Upper Elementary (CUE) were not comfortable acting as
analysts (due to the age of their students) their location was used both as a sampling site and
inter-laboratory quality control. CUE provided tube samples to all six participating site for
comparison. Training in the use of the devices for the schools was undertaken on June 16 and
17, 2014. Beginning in September 2014, the Palmes diffusion tubes were placed at designated
sampling site at RMU along with CUE, North Hills Senior High School (NHHS), West Mifflin

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High School (WMHS), South Fayette High School (SFHS), McGuffey High School (MHS),
Hopewell High School (HHS), Harrison Township (HT), and Lawrenceville. RMU is located in
Moon Township, CUE in Springdale, HHS in Aliquippa, MHS in Claysville, NHHS north of
Pittsburgh, SFHS in McDonald, and WMHS in West Mifflin (figure 1). At the beginning of
September, twenty diffusion tubes were prepared with the three stainless steel screens coated
with TEA solution. Those tubes were sealed and kept in a container away from outdoor air
pollutants. Each month one stability tube was analyzed with the RMU and CUE diffusion tubes
to test how long the prepared diffusion tubes can be used before contamination. The PDT
concentrations were to be compared to two different chemiluminescent analyzers operated by the
Allegheny County Health Department (ACHD) at fixed locations in Lawrenceville (LAW) and
Harrison Township (HT). One location was in LAW for the comparison of the Pittsburgh high
school PDT. A chemiluminescence monitor on the RMU campus was also used to compare the
monthly concentration of the RMU PDT. The RMU PDT average monthly concentration was
compared to the monthly average snowfall, temperature, and rainfall in order to determine the
existence of any correlations.
Figure 1: Sampling locations: crosses denote ARK sites and asterisks denote
chemiluminescent analyzer sites

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Testing Period
The deployment dates for RMU site and CUE were recorded by the inter lab personnel.
RMU CUE
September 8/29/14 – 10/2/14 9/3/14 – 10/3/14
October 10/2/14 – 11/4/14 10/3/14 – 11/3/14
November 11/5/14 – 12/8/14 11/3/14 – 12/3/14
December 12/8/14 – 1/14/15 12/3/14 – 1/6/15
January 1/17/15 – 2/17/15 1/3/15 – 2/3/15
February 2/10/15 – 3/10/15 2/3/15 – 3/3/15
Table 2:RMU deployment dates compared to CUE
4. ANALYTICAL METHODS
The Allegheny County Health Department (ACHD) and the Environmental Protection
Agency (EPA) routinely monitors nitrogen dioxide using chemiluminescence fixed monitors and
Palmes diffusion tubes.
4.1 Palmes Diffusion Tubes
Passive diffusion tubes (figure 2) are an acrylic tube, a removable cap, a fixed cap, and
three stainless steel screens coated with TEA – triethanolamine. Passive diffusion tubes were
originally designed to be on-person samplers with a method developed for industrial
environments (Palmes et al., 1976; and Shooter, 1993).
Figure 2: Palmes Diffusion Tube (PDT)
Over time, passive samplers were created for measuring NO2 in indoor (Spengler et al.,
1983; Hoek et al., 1984; Noij et al., 1986; Colbeck, 1998) and outdoor environments. Atkins et
al. (1986) has shown diffusion tubes used for experimental studies of numerous pollutants
including SO2, CO, O3, and VOCs; as well as in multiple different countries. Passive samplers,
developed by Palmes, Gunnison, DiMattio, and Tomczyk (1976), provide a convenient
alternative for measuring NO2 in a highly inexpensive, accurate, and simple manner. The
method has been thoroughly described by Shooter (1993). NO2 is absorbed onto TEA for a one
month period. After that month, nitrite concentrations is measured by spectroscopy (figure 3)
and converted into an NO2 concentration using Fick’s law of diffusion.

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Figure 3: Diagram of Beer-Lambert
Each individual piece of the Palmes diffusion tubes, along with the stainless steel screens
are all placed in the sonicator. The sonicator is used as a mechanism to loosen up particles
adhering to surfaces, such as the stainless steel and diffusion tubes, in ultrasonic cleaning. The
components of the PDTs and stainless steel screens are placed in the drying oven in order to
control for contamination and speed up the process. All glassware was acid washed to remove
contamination.
The TEA – triethanolamine – solution was prepared with 50% deionized water and 50%
solution to coat the screens for 10 minutes before being placed into each PDT for that particular
month testing period. Once three screens are inserted into each of the three tubes, plus a method
blank, the three samplers are positioned using mounting devices (figure 4). They are placed
vertically at a height of 1.5–4 m from the ground surface (Palmes, 1976). The sample blank is
retained with its cap intact, while the remaining tubes are exposed to the NO2 by removing their
red cap (Aoyama and Yashiro, 1983). After exposure period, which in this experiment was
typically 4 - 5 weeks, all samplers including the field blanks are collected and begin the process
of chemical analysis.
Figure 4: sampling apparatus
Analysis
The ARK kit used in the experiment provides enough materials for the preparation of a single
batch of reagents. These chemicals are stable for six months if stored in a sealed dark container
and refrigerated. Storage containers should be covered with black paper or tape in order to
preserve the light sensitive compounds.

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Standard Preparation
Palmes diffusion tube NO2 concentrations are determined using a set of sodium nitrite
(NaNO2) calibration standards (figure 5). It is very important that the solutions are made up
carefully, and accurately as the standards are used in the concentration calculation. The
following steps were taken to prepare the standards:
STEP 1: A solution of 800 ppm NaNO2 is first prepared by adding 1.200 g of NaNO2 to
1 L of DI water in a volumetric flask. The flask should be capped and mixed thoroughly (50
inversions).
STEP 2: A working standard of 40 ppm NaNO2 is prepared by adding 5 mL of the 800
ppm solution to 100 mL of DI water in a volumetric flask. The flask should be capped and
mixed thoroughly (50 inversions).
STEP 3: Calibration standards of 0, 0.5, 1, 2, and 4 ppm NO2
- are made by adding 0, 1.25,
2.5, 5, and 10 mL of the 40 ppm solution to five 100 mL volumetric flasks. The flasks should be
capped and mixed thoroughly (50 inversions).
Standards were to always be capped and never have a pipet or stirring rod placed in them.
When using standards a sub sample was always removed for use to control external
contamination. All of the above solutions were stored at 4 °C in appropriate containers and
properly labeled with their makers name, contents, date of production and expiration date.
Figure 5: Standard Preparation

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Reagent Preparation
There are four reagents required. Reagents I and II are stable for six months if stored in a
sealed dark container and refrigerated, while reagents III and IV have two week shelf lives.
4.2mL of reagent III is added to each PDT for spectroscopic analysis (figure 6).
REAGENT I: A 2 % solution of sulfanilamide is prepared by adding 20 g of
sulfanilamide into 500 mL beaker, 100 mL DI water is added. 50 mL of 85 % ortho-phosphoric
acid is slowly added. The solution is made up to 1 L with DI water and stored in an amber glass
or dark colored bottle.
(Note: Phosphoric acid is not included in the ARK kit.)
REAGENT II: 0.14 g of N-1-Napthyl-Ethylene-Diamine (NEDD) is added to a 100 mL
volumetric flask. The solution is made up to 100 mL with DI water. Store in an amber glass or
dark colored bottle.
(Note: NEDD is not very soluble. Add approximately 50 mL DI water and shake vigorously to
dissolve before making up to 100 mL.)
REAGENT III: In a 250 mL beaker mix 100 mL DI water, 100 mL of reagent I, and 10
mL of reagent II. Swirl to mix.
REAGENT IV: In a 250 mL beaker mix 100 mL of reagent I and 10 mL of reagent II.
Swirl to mix.
(Note: If reagents III and IV show any signs of a pink coloration they are contaminated and
should be discarded and remade.)
Figure 6: Reagent Preparation

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Chemistry of Reaction
NO2 reacts with TEA to produce nitrosodiethanolamine (NDELA):
Figure 7: Reaction of TEA with NO2
The nitrosoamine is then hydrolyzed in presence of H3PO4 to form nitrite:
(CH2CH2OH)2N.NO + H2O → (CH2CH2OH)2NH +HNO2
Nitrite reacts with sulfanilamide:
Figure 8: Chemistry of nitrite reacting with sulfanilamide
Diazonium salt couples with NEDD to form purple azo dye (chromophore):
Figure 9: Chemistry of NEDD reacting with diazonium salt

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Calculation
The equivalence between absorbed NO2 and nitrite ion is known as the Saltzman factor.
Calibration exercises have confirmed that the factor is effectively 1.0. The rate of absorption is
determined by the rate of diffusion of the gas along the tube. Fick’s law states that the rate of
diffusion of a gas is proportional to the concentration gradient:
F = -D dC mol cm-2 s-1;
dz
Where F is the flux of gas, D is the diffusion coefficient (cm2 s-1), C is the gas
concentration (mol cm-3) and z is the length of diffusion (cm).
The quantity of gas Q (mols) transferred in t seconds for a cylinder radius r is:
Q = F(πr2)t
Thus Q = -D(C – C0) πr2t mol (C0 = 0 with TEA)
z
If r = 0.55 cm, D = 0.154 cm2 s-1, z = 7.1 cm then Q = -0.021Ct. In 1 hr the tube absorbs
74C mol NO2, or the NO2 in 74 cm3 of air (Boleij, 1986).
Spreadsheet Calculations
The calculations and conversions of the absorption from the spectrometer to the
concentration of nitrogen dioxide in ppb are determined through the use of a spreadsheet. The
spreadsheet (table 3) uses the calculated hours of the tubes outside for that month, the volume of
the air, the slope of the linear regression from the monthly standards, and the absorption rate at
540nm.
Calculated
Hours Out Abs.
Corrected
Absorbance NO2
- on TEA NO2 in Air NO2 in Air NO2 in Air
(1 dec. pl.) (ppm) (mg m-3) (ppm) (ppb)
672.0 0.1370.137 0.274 0.0231 0.0120 12.0
Table 3: Example PDT calculation
The calculations are as follows:
Corrected Absorbance: Absorption - Absorption of Blank: 0.137 – 0 = 0.137;
NO2 on TEA: Corrected Absorption/Slope from Standards: 0.137/2 = 0.274;
NO2 in air (mg/m3): (NO2 on TEA*0.0042*1000000)/(Volume of air*hours outside):
0.274*0.0042*1000000 = 1150.8/(74)*(672) = 1150.8/49728 = 0.0231;
NO2 in air (ppm): NO2 in air (mg/m3)*Avog. constant/molar mass of NO2:
0.0231*(6.022x1023)/46.0055 = 24/46.01 = 0.0120; and
NO2 in air (ppb): NO2 in air (ppm)*1000: 0.0120*1000 = 12.0.

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4.2 Chemiluminescence Analyzer
NO2 is measured routinely by state and local agencies. Continuous measurement
requires the use of expensive instrumental techniques such as chemiluminescence. These
are usually located at fixed sites and do not provide spatial coverage.
Chemiluminescence is a chemical technique which measures the intensity of light
emission. NO is a relatively unstable molecule which will oxidize to NO2 (especially) in
the presence of O3. The reaction of NO to NO2 through chemiluminescence is: NO + O3
==> NO2+ O2 + hv. This reaction produces a quantity of light for each NO molecule
which is reacted.
5. RESULTS
Location
Robert Morris University
Time of the Year/Month
Sept 2014 Oct 2014 Nov 2014 Dec 2014 Jan 2015 Feb 2015
RMU 1 0 17 16 12 11 26
RMU 2 10 15 24 18 17 22
RMU 3 1 12 18 13 14 28
Average
NO2
(ppb)
4 15 19 14 14 25
Std.
Dev.
6 3 4 3 3 3
Table 4: RMU monthly NO2 concentration of PDT 1,2 and 3, and averages

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Figure 10 shows the results of each month’s tubes from September 2014 through February 2015.
Figure 10: NO2 measured at RMU by Palmes Diffusion Tube method
Weather
Temperature
RMU NO2 (ppb) Average Temperature (˚F)
Sept 2014 4 65
Oct 2014 15 53
Nov 2014 19 43
Dec 2014 14 34
Jan 2015 14 28
Feb 2015 25 30
Table 5: RMU PDT average NO2 concentration and Moon Township (local weather station)
average monthly temperature
0
5
10
15
20
25
30
NO2Concentration(ppb)
Month
RMU 1
RMU 2
RMU 3
Average

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Figure 11 compares the calculated Moon Township, PA, monthly average temperature with the
Robert Morris University site monthly average nitrogen dioxide concentration (site:
http://www.homefacts.com/weather/Pennsylvania/Allegheny-County/Moon-Township.html).
Figure 11: RMU NO2 concentrations vs average monthly temperature
Snowfall
RMU NO2 (ppb) Average Snowfall (inches)
Sept 2014 4 0
Oct 2014 15 0.5
Nov 2014 19 3.5
Dec 2014 14 8
Jan 2015 14 11.9
Feb 2015 25 8.9
Table 6: RMU PDT NO2 concentration and Moon Township average monthly snowfall
0
10
20
30
40
50
60
70
Month
RMU Average
(ppb)
Average
Temperature (˚F)

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Figure 12 displays the relationship between the monthly average snowfalls in Moon Township,
PA, and the calculated nitrogen dioxide concentration average at the Robert Morris University
site (site: http://www.homefacts.com/weather/Pennsylvania/Allegheny-County/Moon-
Township.html).
Figure 12: RMU NO2 concentrations vs monthly average snowfall
Rainfall
RMU NO2 (ppb) Average Rainfall (inches)
Sept 2014 4 2.81
Oct 2014 15 2.99
Nov 2014 19 2.81
Dec 2014 14 3.99
Jan 2015 14 1.73
Feb 2015 25 2.98
Table 7: RMU PDT NO2 concentration and Moon Township average monthly rainfall
0
5
10
15
20
25
30
Month
RMU Average
(ppb)
Average Snowfall
(inches)

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Figure 13 displays the relationship between the monthly average rainfall in Moon Township, PA,
and the calculated nitrogen dioxide concentration average at the Robert Morris University site
(site: http://www.homefacts.com/weather/Pennsylvania/Allegheny-County/Moon-
Township.html).
Figure 13: RMU NO2 concentrations vs monthly average rainfall
Stability Tube
RMU NO2 Average
(ppb)
4 15 19 14 14 25
Stability tube NO2
(ppb)
0 0 0 0 0 1
Table 8: RMU PDT average concentration vs concentration of RMU stability tube
0
5
10
15
20
25
30
Sept
2014
Oct
2014
Nov
2014
Dec
2014
Jan
2015
Feb
2015
Month
RMU Average (ppb)
Average Rainfall
(inches)

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Figure 14 shows the stability of the Palmes diffusion tubes after preparation over a certain period
of time.
Figure 14: RMU NO2 concentration vs RMU stability tube concentration
High School Comparison
Hopewell West Mifflin McGuffey South Fayette North Hills
Sept 2014 15±9 6±1 17±5
Oct 2014 5±2
Nov 2014 12
Dec 2014 23±25 14±2 15±5
Jan 2015 20±8 11±2 5±1 14±1
Feb 2015 8±1 12±1 13±4
March 2015 13±2
Table 9: Monthly PDT average concentration of Hopewell, West Mifflin, McGuffey, South
Fayette, and North Hills with standard deviation
0
5
10
15
20
25
30
Month
RMU Average
Stability of
sealed tube

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Figure 15 shows the comparison of NO2 PDT monthly concentration between Hopewell, West
Mifflin, McGufey, and South Fayette High School. Not every school gathered sufficient results
each month; therefore, concentrations for few of the months are missing.
Figure 15: HHS, WMHS, MHS, NHSHS and SFHS monthly NO2 concentration
Colfax Upper Elementary
RMU NO2
(ppb)
4 15 19 14 14 25
CUE NO2 (ppb) 7 6 10 15 23 30
Table 10: RMU PDT average vs CUE PDT average
0
5
10
15
20
25
Sept 2014 Oct 2014 Nov 2014 Dec 2014 Jan 2015 Feb 2015 March 2015
NO2concentration(ppb)
Month
Hopewell
West Mifflin
McGuffey
South Fayette
North Hills

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Figure 16 compares the calculated Colfax Upper Elementary site monthly average concentration
with that of the calculated monthly average concentration at the Robert Morris University site.
Figure 16: RMU NO2 average concentration vs CUE NO2 average concentration
RMU - CUE West Mifflin McGuffey
Sept 2014 7 7
Oct 2014 6 12 22
Nov 2014 10 15
Dec 2014 15
Jan 2015 23
Feb 2015 30
Table 11: comparison of CUE NO2 concentration between Hopewell, West Mifflin and
McGuffey, and the inter-laboratory CUE from RMU
Chemiluminescence Monitor
RMU Chemiluminescence
RMU PDT Average 4 15 19 14 14 25
RMU
Chemiluminescence
5.6 5.2 7.5 15.3 59.5 10.5
Table 12: RMU PDT monthly average concentration vs RMU Chemiluminescence monthly
average concentration
0
5
10
15
20
25
30
35
40
Month
RMU Average
CUE Average

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Figure 17 shows the comparison between the chemiluminescence fixed monitor at RMU versus
the use of the Palmes diffusion tubes at RMU.
Figure 17: RMU NO2 PDT average concentration vs RMU NO2 Chemiluminescence average
concentration
Figure 18 shows the correlation between the RMU Chemiluminescence monitor concentrations
to the RMU PDT concentrations. The January 2015 concentrations were removed as outliers due
to the extensive construction work going on at the same time. The R2 value is 0.7 showing a
good correlation.
Figure 18: RMU NO2 PDT average concentration correlated to RMU Chemiluminescence
concentration
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
Month
Chemil. @ RMU
PDT @ RMU
R² = 0.6517
0
2
4
6
8
10
12
0 5 10 15 20 25 30
NO2viaChemiluminescence
(ppb)
NO2 via PDT (ppb)

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Harrison Township & Lawrenceville Chemiluminescence NO2 concentration
Month RMU (ppb) Lawrenceville (ppb) Harrison Twp (ppb)
Feb 2014 9 20 14
Mar 2014 7 14 5
April 2014 6 12 5
May 2014 5 9 4
June 2014 4 8 6
July 2014 4 7 4
Aug 2014 4 7 4
Sept 2014 6 9 5
Oct 2014 5 11 7
Nov 2014 8 14 9
Dec 2014 9 14 5
Jan 2015 60 15 7
Feb 2015 11 15 10
Mar 2015 10 16 7
April 2015 5 11 4
Table 13: Comparison between RMU, Lawrenceville, and Harrison Township monthly
chemiluminescence averages in ppb
Figure 19 shows the comparison between the RMU, Harrison Twp and Lawrenceville
Chemiluminescence NO2 monthly concentrations.
Figure 19: RMU, Harrison Township, and Lawrenceville chemiluminescence monthly average
NO2 Concentrations (ppb).
0
10
20
30
40
50
60
70
Month
RMU
Lawrenceville
Harrison Twp

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Figure 20 shows the correlation between the Lawrenceville location and the RMU
chemiluminescence NO2 average. The January 2015 concentrations were removed as outliers
due to the extensive construction work going on at the same time. The R2 value is 0.8 showing a
significant correlation.
Figure 20: Lawrenceville NO2 concentration vs RMU chemiluminescence NO2
concentration (ppb).
Figure 21 shows the NO2 concentration (ppb) from the RMU chemiluminescence fixed
monitor each day from March 2014 to March 2015.
Figure 21: RMU Chemiluminescence NO2 concentration (ppb) from March 2014 to
March 2015.
R² = 0.7971
0
2
4
6
8
10
12
0 5 10 15 20 25
NO2viaChemiluminescence
(ppb)
NO2 via PDT (ppb)
0
100
200
300
400
500
600
700
800
J-14 M-14 A-14 J-14 J-14 S-14 N-14 D-14 F-15 A-15 M-15
NO2concentration(ppb)
Time

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6. DISCUSSION
The data for the average of the Robert Morris University tubes show a significant leap from
September 2014 to October 2014 with an 11ppb difference. From October 2014 to January 2015
each RMU tube is relatively close with the averages between 14ppb and 19 ppb. The average
then increased up to 25 ppb in February 2015, which compares to the RMU fixed monitor
concentration of 10ppb in February 2015. The average of the RMU chemiluminescence analyzer
was 17 ppb compared to the RMU PDT average of 15 ppb. The RMU chemiluminescence was
typically lower than the monthly average of the RMU PDT until January 2015 when the fixed
monitor had a reading of 60 ppb.
When the monthly temperature in Moon Township was higher, the nitrogen dioxide
concentration was lower, showing a negative correlation. However, in the comparison of
average rainfall and snowfall in Moon Township and the average nitrogen dioxide concentration
on the Robert Morris University campus, no correlation was found.
The results from the stability tube measurements showed that the concentration remained 0
ppb from September through January. As the concentration only rose to 1 ppb in February,
overtime the concentration from the tested tubes could be affected if the prepared tubes are not
placed out in reasonable time.
The average nitrogen dioxide concentration of WMHS over the six month time span was 12
ppb. MHS average concentration was calculated to be 14, with HHS average being 15, and
SFHS slightly lower at 8 ppb. The inter-laboratory site with Colfax Upper Elementary site
averaged to 15 ppb. The average standard deviation of each high school falls higher than the
anticipated standard deviation of ±3 to ±5, which may have been the result of miscalculation
from the ARK high school participants.
Harrison Township and RMU chemiluminescence averages were relatively the same due to
the Harrison Township monitor placed for the comparison of city NO2. The overall Harrison
Township average was 6 ppb, while RMU was 10 ppb and Lawrenceville was 12 ppb. The
Lawrenceville average is higher since the location is a more polluted area, but the RMU average
is higher again due to the 60 ppb January 2015 concentration.
7. CONCLUSION
The differences in the RMU PDT average can be attributed to the beginning of construction
around the location of the tube’s testing site. As stated before, the majority of sources of
nitrogen dioxide are man-made sources such as cars, trucks, heavy machinery, and coal-burning
industries (Shooter, 1993). The monthly fluctuations in the PDT values follow a similar pattern
to changes measured by the chemiluminescence analyzer. The 0.7 R2 value between the RMU
PDT and RMU Chemiluminescence show good correlation, as well as the significant correlation
between the Lawrenceville PDT and RMU Chemiluminescence at 0.8. The chemiluminescence
measurements, however, are less time consuming to analyze, and has been adopted more often
over the PDT method.
Chemical stability is the tendency to resist change due to internal reaction or action of
outside factors, such as air and light. Our results have shown that the time frame of stability of
TEA solution in a Palmes diffusion tube method atmospheric pollution test is roughly five
months without any contamination.
With the fixed monitor average of Pittsburgh being 14 ppb, the averages of the participating
schools show no significant variation with location around the Greater Pittsburgh area with NO2

25
concentration. Pittsburgh’s average at 14 ppb, measured by the RMU chemiluminescence, is
higher than the national average of 9 ppb, but significantly lower than the EPA national
regulation for nitrogen dioxide at 53 ppb (EPA).
Experimental studies by Glasius et al. (1999), Bush et al. (2001), and Hansen et al. (2001)
have shown that over estimation by a passive sampler for NO2 above 15 ppb was less than 10
percent. Shown by Kirby et al. (2001), the accuracy of the passive sampler even for worst
possible conditions is within the accuracy limit recommended by the European Union for
analytical monitoring of ±25 percent.
The chemiluminescence fixed monitor at RMU calculated to have an average concentration
of 16 ppb compared to the RMU PDT average of 15 ppb. With a difference of only 2 ppb and
standard deviations of the participating schools ranging from ±1 to ±25, our current results show
that the diffusion tube method is a reliable method for testing atmospheric gases, specifically
nitrogen dioxide.
Future Research
With the temperature having a strong negative correlation on the nitrogen dioxide
concentration, a comparison of humidity and pollution concentration could be studied. Also, two
different tests could have been completed at the RMU site to compare the effect of the heavy
machinery from construction of a new building. Since construction began next to the testing site
in October-November, a sub-site could have been placed across campus.
The overall involvement of the schools that were in the partnerships was not as
dependable as needed for the study. With all schools, except for RMU and CUE, being
responsible for their own analysis, the study relied on their consistency. MHS only had three
reliable months, SFHS only had two, HHS had one reliable month, and data from NHHS was
sent well after the study was completed. At SFHS, HHS and MHS, students involved either
lacked desire to constantly continue the study for a full six month time span, or were not
supervised and had error in the testing/analysis period. Not receiving data from NHHS until the
report was written, and missing data from MHS, SFHS, and HHS could have a significant effect
on the monthly and overall averages for each location. In future research, participation should be
monitored more closely over the span of the study to ensure accurate and complete data.

26
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Investigation of the Reaction by Trapping of Nitrogen Dioxide in Air Using the
Triethanolamine Method,’ Journal of Chromatography 256, 69–78.
Atkins, D.H.F., Sandalls, J., Law, D.V., Hough, A.M. and Stevenson, K.: 1986, ‘The
Measurement of Nitrogen Dioxide in the Outdoor Environment Using Passive Diffusion
Tube Samplers,’ United Kingdom Atomic Energy Authority Report, AERE R-12133,
Harwell Laboratory, Oxford shire.
Beer, R. (1992) Remote Sensing by Fourier Transform Spectroscopy, in the Chemical Analysis
Series, Vol. 120, John Wiley & Sons, New York.
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diffusion tubes for measuring NO2 in homes. Atmospheric Environment – Part A General
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Glasius, M., Carlsen, M.F., Hansen, T.S. and Lohse, C.: 1999, ‘Measurements of Nitrogen
Dioxide on Funen Using Diffusion Tubes,’ Atmospheric Environment 33, 1177–1185.
Hansen, T.S., Kruse, M., Nissen, H., Glasius, M. and Lohse, C.: 2001, ‘Measurements of
Nitrogen Dioxide in Greenland Using Palmes Diffusion Tubes,’ Journal of
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Concentrations Across an Urban Landscape: Cambridge, UK,’ Environmental
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