1  

A New Porous Membrane Denuder for Measuring

Ammonia Gas: the Validation Test  

   

 

   By  

 CHENG-­‐TUNG  LIU  

 

   

 

     

     

 A  PROJECT  PRESENTED  TO  THE  GRADUATE  SCHOOL  

OF  THE  UNIVERSITY  OF  FLORIDA  IN  PARTIAL  FULFILLMENT  

OF  THE  REQUIREMENTS  FOR  THE  DEGREE  OF  MASTER  OF  ENGINEERING  

 

UNIVERSITY  OF  FLORIDA    

2015  

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© 2015 Cheng-Tung Liu  

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To  my  family.      

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ACKNOWLEDGMENTS

I would like to thank my graduate advisor and committee chair, Dr. Chang-Yu

Wu, for his unending patience and support during my studies. Without his guidance

and hard work, this project would not have been possible. I would also like to thank

my committee members, Dr. Paul Chadik, for his suggestions and support.

Additionally, I’d like to thank my graduate mentor, Chih-Hsiang Chien, for his support

during my studies. His leadership helped inspire me to pursue a graduate degree. I

would like to acknowledge the funding agency for this project— Florida Industrial and

Phosphate Research Institute. I would also like to extend my gratitude to all of my

fellow research team and graduate lab mates who helped throughout this research.

Finally, I’d like to thank my better half, Chun-Yu Shih, for supporting me during the

difficult times during my studies and helping me find the strength to continue striving

towards my goal when I faltered.

 

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Table of Content

ACKNOWLEDGMENTS .................................................................................. 4  

1. INTRODUCTION .......................................................................................... 7  

2. THEORY ......................................................................................................... 8  

3. EXPERIMENT DISCRIPTION ................................................................... 8  

3.1 Experiment setup  ...................................................................................................................................  9  3.2 Denuder preparation and Coating procedure  ................................................................................  10  

3.3 Bubbler preparation  ...........................................................................................................................  10  3.4 Sample analysis  ...................................................................................................................................  11  

4. QUALITY CONTROL AND QUALITY ASSURANCE ......................... 11  

4.1 Mass flow controller calibration  ......................................................................................................  11  

4.2 Input ammonium calibration  ...........................................................................................................  11  4.3 Blank test  .............................................................................................................................................  12  4.4 Mass balance  .......................................................................................................................................  12  

5. RESULT AND DISCUSSION ..................................................................... 13  

5.1 Denuder collection efficiency prediction  ........................................................................................  13  5.2 Denuder configuration  ......................................................................................................................  13  5.3 Ammonia gas collection efficiency  ..................................................................................................  13  

5.4 Future work  .........................................................................................................................................  14  

6. CONCLUSION ............................................................................................. 15  

7. REFERENCE ............................................................................................... 16  

8. Tables and Figures ....................................................................................... 18  

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Abstract of Project Presented to the Graduate School

of the University of Florida in Partial Fulfillment of the

Requirements for the Degree of Master of Engineering

A NEW POROUS DENUDER FOR MEASURING AMMONIA GAS: THE VALIDATION

TEST

By

Cheng-Tung Liu

April 2015

Chair: Chang-Yu Wu

Major: Environmental Engineering Sciences

The sampling performance of porous membrane denuder (PMD) made of cellulose

membrane with an accordion shape configuration and phosphoric acid coating was

investigated. Advantages of the PMD over the traditional annular or honeycomb denuder

include low cost, lightweight, and easy replacement. An experiment was conducted to test its

8-hour ammonia gas collection efficiency by measuring the ratio of downstream to upstream

ammonia concentration with a feed concentration of 10 ppm at 2 L/min and coating chemical

of 6% phosphoric acid. OSHA’s Validation Guidelines for Air Sampling Methods Utilizing

Chromatographic Analysis was followed to determine the downstream concentration. The

results showed that the 30-fold denuders’ analytical recovery was 90% under low relative

humidity (lower than 5%). The collection efficiency of the denuder after 8-hour sampling

was over 99.9%, which meets the requirement of over 95% collection efficiency. The results

demonstrated that the PMD is feasible for low concentration sampling such as stack

emission.

   

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1. INTRODUCTION

The significant role played by ammonia (NH3) in air pollution has been frequently

recognized (Goebes et al., 2003). Ammonia is the most abundant basic gas in the atmosphere

among all reactive nitrogen-bearing species. Ammonia is used to make household cleaners,

refrigeration units, fertilizers, explosives, fuels, and other chemicals and most of them could

cause NH3 emission (Chen et al., 2014). Agricultural emissions such as livestock and

nitrogen fertilizer application are the main sources for atmospheric NH3 (Bouwman et al.,

1997). Biomass burning can also be an important source for ammonia emissions (Akagi et al.,

2011, Bouwman et al., 1997). Accurate prediction of ambient ammonia concentration is

important for several reasons. Ammonia is a precursor to secondary particulate matter when

it reacts with gases such as NOX, SOX and hydrocarbons to form species such as ammonium

nitrate and ammonium sulfate. Some of these chemical compounds are major constituents of

PM2.5, which contributes to human health effect and results in visibility reduction (Bergström

et al., 2006, bouwman et al., 1997). Plus, the deposition of NH3 in the ecosystems may cause

eutrophication and loss of biodiversity (Goebes et al., 2003). However, accurate measurement

of ambient ammonia concentration can be challenging because of the appreciable volatility of

some ammonium chemical species at ambient temperature (Chen et al., 2014).

Several diffusion denuder techniques, which allow select gaseous phase chemicals to

absorb by chemical coating on the denuder, have provided good results for sampling gaseous

pollutants (Brauer et al., 1989, Possanzini et al., 2004). Most commonly used materials for

denuders are glass and stainless steel. Denuders with different shapes and geometries have

been applied to increase collection efficiency such as flat, annular (Sekiguchi et al., 2009, Ye

et al., 1991), parallel plate (Rosman et al., 2001, Eatough et al., 1993) and honeycomb

(Sioutas et al., 1996). Also, different chemical coatings have been applied to improve the

collection performance of gases (Perrino and Gherardi, 1999). The honeycomb denuder made

of glass has been commercialized and integrated into a denuder-filter system, called

“ChembComb Speciation Sampling Cartridge” (Model 3500, Thermo Electron Co., Inc.).

However, this commercial denuder-filter system is quite bulky, heavy and relatively

expensive, rendering it undesirable for personal sampling (Shou et al., 2012).

In this research, a newly designed Porous Membrane Denuder (PMD) was tested for the

performance of ammonia gas absorption. The principle of the PMD is to utilize the porosity

of a membrane to increase the surface area for absorption (Shou et al., 2012). Porous

membrane denuder made from Whatman Grade 42 filter paper to collect SO2 gas had already

been successfully demonstrated in a previous study (Shou et al., 2012). The PMD possesses

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several benefits to the industry of gas sampling. The novel denuder allows accurate

measurement of ammonia gas concentration at the ambient level. Different from traditional

sampling devices, the PMD is a very effective, inexpensive, lightweight and

easy-to-assemble gas collector. The main objectives of this study were to validate that the

PMD could collect 95% of 10 ppm ammonia gas for 8 hours and to confirm the mass

conservation in this sampling procedure.

2. THEORY

Ammonia gas can be captured by PMD though diffusion with chemical bonding

between coated phosphoric acid and the ammonia gas. The stoichiometric reaction between

NH3 and H3PO4 is:

H3PO4 +3NH3→ (NH4 )3PO4 (1)

The theoretical diffusional gas collection efficiency (η) of an annular denuder for a gas can

be determined from the following equation (Gormley and Kennedy, 1949):

η =1− 0.8191exp(−11.489µ)− 0.0975exp(−70.1µ)− 0.0325exp(−179µ) (2)

where

µ =nDLQ (3)

where η is collection efficiency of the denuder; µ is dimensionless deposition parameter; n is

the fold number of the denuder; D is diffusion coefficient of the penetrating gas; Q is the

volume flow rate through the entire denuder; and L is the length of the denuder. This equation

is valid when the denuder is a perfect sink, i.e. when the absorption surface is fresh.

3. EXPERIMENT DISCRIPTION

Sampling for NH3 measurement followed the experiment procedures of Shou et al.

(2012) and OSHA’s sampling and analysis method ID-164 that collects ammonia gas on

denuders and bubbler. A PMD made of cellulose filter with an accordion shape configuration

and phosphoric acid coating was tested for its performance in collecting ammonia gas. The

coating on the denuder was prepared by immersing the membrane in 6% phosphoric acid.

OSHA’s Validation Guidelines for Air Sampling Methods Utilizing Chromatographic

Analysis was followed to determine the downstream concentration.

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3.1 Experimental setup

Figure 1 illustrates the experimental set-up for denuder performance test. A feed

concentration of 10 ppmv was targeted because commercially available NH3 monitors are

capable of measuring NH3 concentration from 1 to 100 ppm in real time but their detection

principle prevents their measurement from low concentration at ambient level. In order to

provide 10 ppm ammonia gas for testing PMD’s performance, 100 ppm ammonia gas

(Certified Standard-SPEC, Airgas) supplied from a standard ammonia gas cylinder, and the

gas was diluted at a glass chamber with compressed air supplied from an air cylinder

(Breathing air grade L, Airgas) at a ratio of 1:9. The total flow rate of the mixed stream, 2

L/min, was controlled by both a mass flow controller (OMEGA, Model FMA 5520) and a

rotameter (AFP) before of the denuders. The mixed air was then introduced into the denuder

section. The denuder section consisted of four cellulose denuders assembled in a denuder

holder cassette made from acrylic; the number of folds for the cellulose denuder varied from

20 to 30 in different sets of experiment. Figure 2 shows the whole denuder section. A bubbler

with 0.02N H2SO4 solution was placed downstream the denuder section to absorb gas that

penetrated the cellulose denuder and it was replaced hourly during 8-hour denuder

performance experiment. After each 8-hour experiment, all the samples from denuders and

bubblers were analyzed by an ion chromatography system (Dionex, ICS-3000). To obtain

hourly denuder performance, preliminary results showed that one bubbler was enough for

one-hour absorption in this experiment since the second bubbler in series detected no

ammonium. The experimental gas collection efficiency Eff of ammonia can be obtained by

measuring the feed concentration (Cu) upstream and exit concentration (Cd) downstream of

the denuders. The exit concentration can be determined by the summing of the mass

concentrations in bubblers, which are the device to capture ammonia from denuders (Fig 1).

Eff at any given time can be calculated by the following equation:

Eff = Cu −Cd

Cu

=1− Cd

Cu (4) The feed NH3

mass was calculated from feed ammonia gas concentration and flow rate.

The downstream NH4+ mass includes NH4

+ mass collected on denuders and bubblers with

0.02 N H2SO4 solution and quantified by ion chromatography system (Dionex, ICS-3000).

The bubblers could increase the pressure drop of the system. Therefore, the pressure drop of

the system was measured every hour. Humidity monitor was used to check relative humidity

and recorded it hourly. The temperature was 22°C, and the relative humidity was below 5%

for the low relative humidity test. High relative humidity (69%) environment will be applied

  10  

to the denuder performance test in the next set of experiment.

3.2 Denuder preparation and Coating procedure

Material strength and low cost are two important factors to be taken into account for

denuder material selection. Whatman Grade 541 cellulose filter paper, which has higher

chemical resistance, was substituted for Whatman Grade 42 used in the previous study for

absorbing SO2 gas since Whatman 541 is strong chemically compatible with the acid coating

solution. Folds number of the denuder was varies from 20 to 30 to determine the optimal for

collection efficiency.

Although citric acid has been widely used to coat the surface of denuders for capturing

ammonia gas, a past study (Perrino and Gherardi, 1999) indicated that using citric acid

coating for ammonia gas collection suffers from insufficient bonding strength between

collected ammonia and the coating layer, which causes a release of the collected ammonia

both towards the remaining active sites of the denuder wall and the air flow. The same study

also showed that phosphoric acid was able to achieve the highest ammonia collection

efficiency among citric acid, oxalic acid and phosphoric acid (Perrino and Gherardi, 1999).

Indeed, phosphoric acid has been used as the coating chemical for collecting ammonia in a

study (Perrino and Gherardi, 1999). In this study, Whatman Grade 541 filter papers were

immersed in 6% phosphoric acid solution in a sonication bath for 30 minutes to accomplish

the coating. The coating solution was prepared by 14.1 mL 85% H3PO4 blended with 20 mL

DI water, and 165.9 mL methanol. Ammonia-free clean gas dried the denuder for 12 hours to

prevent it from the ambient NH3 contamination. Denuders were dried by purging gas instead

of oven baking that could cause damage to denuder material. Figure 3 shows the comparison

of the products by the two drying methods. As shown, filter paper dried by oven baking was

damaged and unusable. Dried denuders were placed in sealed plastic bags (Ziploc) for

storage until test. Also, ammonia scrubbers were placed in the storage bag along with

bubblers and experimental equipment to minimize contamination possibilities. During

method evaluation, test filter papers were also extracted and analyzed by ion chromatography

as blank test.

3.3 Bubbler preparation

OSHA’s Sampling and Analytical Method ID-164 was followed for ammonia analysis

and bubblers with 0.02 N H2SO4 solution were applied to collect ammonia gas that escaped

the denuder. This OSHA method used a known volume of air drawn through a glass midget

bubbler containing approximately 10 mL of 0.1 N H2SO4 to collect 50 ppm ammonia. Since

  11  

in this study 10 ppm ammonia was targeted, the bubbler reagent was 10 mL 0.02 N H2SO4

solution accordingly. Besides, one bubbler was found to be enough for one-hour absorption

in this experiment since the second bubbler in series detected no ammonium in testing.

3.4 Sample analysis

According to the RTI international’s Standard Operating Procedure for Coating and

Extracting Denuders for Capture of Ammonia and Its Measurement (2008), each exposed

denuder was extracted using 50 mL DI water in a sonication bath for 45 minutes. Particles

and solid contaminations in extraction were removed by 17 mm PES filter (0.45 µm, Thermo

Scientific). All samples were quantified to 50 mL by DI water and stored in a refrigerator (5

°C). The denuder extracts and ammonium in bubblers were analyzed by ion chromatography

with a Dionex CS12A separation column and cation self-regenerating suppressor (CSRS);

separations were conducted using 20 mM methanesulfonic acid (MSA) as eluent at a flow

rate of 0.5 mL/min. The ion chromatography was calibrated prior to the analysis by injection

of aqueous standards prepared from analytical-grade solutions.

4. QUALITY CONTROL AND QUALITY ASSURANCE

4.1 Mass flow controller calibration

Out of calibration of the mass flow controller (MFC) was noticed during the experiment.

Therefore, calibration test for the MFC was conducted. Figure 4 shows the calibration set-up.

By using the five-point calibration method that compared five flow rate points in the MFC to

the five actual flow rates measured by a primary flow calibrator (The Gilibrator, PN

D-800268), the calibration curve of the MFC was established to be y=0.936x+13.82. Figure 5

displays the calibration curve of MFC.

4.2 Input ammonium calibration

Out of calibration of Rotameter performance was identified during the 8-hour

experiment. Therefore, calibration test of input ammonium was conducted by directly

providing 10 ppm ammonia gas into the bubbler for one hour. The measured ammonium

concentration was then compared with the calculated input ammonium concentration from

equation 4. The result shows that the actual input ammonium concentration was 88.5% of the

calculated ammonium. By doing the calibration, it can be assured that the analytical recovery

was correct.

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4.3 Blank test

Although several preventive strategies were applied to avoid potential ammonia

contamination, blank test by measuring background ammonium loading of cellulose

membrane paper was conducted to verify the contamination level. Accordingly, the blank test

result was compared with the ammonium concentration obtained from denuder extraction

solution to determine the signal to noise ratio, which was used to measure the detectability of

a flaw and to further calculate the minimum sampling time. The result showed the signal to

noise ratio was 17.9; thus, by applied equation 4, the minimum sampling time for 10 ppm

ammonia gas with 2 L/min was determined to be 51 minutes. The data could be considered

meaningful if the signal to noise ratio is larger than 3 (Barker., 1990).

4.4 Mass balance

A mass balance calculation was carried out to confirm for data quality assurance. The

feed NH4+ mass was only from the cylinder and was controlled by a mass flow controller and

a rotameter. The flow rate, Q (L/min) and sampling time were incorporated into the following

equation to calculate the input ammonium mass:

MNH4

+ =1000CNH3

MWNH3

24.2Q× time1000

"

#$

%

&'1817"

#$

%

&'×R

(4) where C (µg/L) is the feed concentration of NH3 (10 ppm); MW is the molecular weight of

NH3 (17 g/g mole). The volume per mole of an ideal gas has the value 24.2 L/gmol at T=

22°C and 1 atm. R is recovery factor of 88.5%. On the other hand, the output of ammonium

concentration was based on NH4+ mass collected on denuders and bubblers and analyzed by

ion chromatography. The outlet mass concentration was determined by summing the mass

concentrations in all bubblers and denuders. The ratio of input and output ammonium

concentration demonstrates the mass conservation of this experiment.

Table 1 shows the result of 20 folds and 30 folds denuder mass balance under low

relative humidity. Input and output ammonium masses for 20 folds were 5914 µg and 5490

µg, respectively. Input ammonium mass was calculated by equation 4 and output ammonium

mass was the summation mass concentration of denuder and bubblers. Accordingly, the ratio

of input to output ammonium mass was 92.8%. For 30 folds, input and output ammonium

masses were 6246 µg and 5430 µg, respectively and the corresponding ratio was 87%.

Therefore, the denuders’ analytical recovery was 90% under low relative humidity (lower

than 5%). The difference could be the result from unstable input flow rate or uncertainty due

to the analysis. If the input flow rate variation was ± 5%, the difference in recovery could be

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up to ±10%. Therefore, stable input ammonia gas plays an important role in denuder analysis.

5. RESULT AND DISCUSSION

5.1 Denuder collection efficiency prediction

The collection efficiency of the denuder can be predicted by Eq. 1 with a known

diffusion coefficient, 0.227 cm2/s, of ammonia gas (Sekiguchi et al. 2009). The calculation

shows that when the denuder length is 5 cm, the designed length of our denuder, the

collection efficiency of 99% can be achieved with 3 denuder folds. However, this prediction

equation assumes steady-state and the concentration is independent of time. In reality, as the

sampling time increases, the coating chemical on the denuder will be consumed and the

capacity of the denuder will decrease. Accordingly, it is invalid that the assumption in Eq. 1

of coating chemical can be perfectly used for capturing all ammonia gas. Previous research in

our lab indicated that the 20 folds denuder in the same configuration was enough for 95%

collection efficiency. Therefore, folds number of 20 and 30 were applied to determine the

suitable folds for ammonia gas collection.

5.2 Denuder configuration

There are two configurations of denuder in the experiment, well-spread configuration

and condensed configuration (Fig. 6). For a denuder with the condensed configuration, as

shown in Fig. 7, the collection efficiency dropped rapidly. The ammonia gas flowed through

the lateral space outside denuders instead of through the denuder itself due to the lower

pressure drop- leading to the >5% penetration. On the other hand, the well-spread denuder

configuration with evenly distributed grid space in the denuder holder cassette demonstrated

the acceptable and reasonable result in collection efficiency. Penetration of the denuder

stayed stable in the first four hours and gradually decreased after that owing to the reagent

consumption. Consequently, configuration of denuder is important for coating chemical

consumption and gas collection.

5.3 Ammonia gas collection efficiency

The ammonia gas collection efficiency of denuder folds number of 20 and 30 in each

filter holder is shown in Fig. 8. For the 20 folds denuder, when a feed NH3 concentration of

10 ppm was used, analysis of all samples from bubblers indicates that the one-hour average

exhaust gas concentration was below 1 ppm during the first four hours, which means the

ammonia was collected efficiently by the denuders in the first four hours. However, for the

fifth to eighth hours, collection efficiency gradually decreased to 93%, which did not meet

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the requirement of 95% collection efficiency. The main reason for the collection performance

reduction is not only the reagent was consumed with time, but also the product covering the

top layer of the coating. This top layer became a barrier slows down the target gas diffusing

into the unreacted sorbents inside. In this case, ammonia reacts with phosphoric acid to form

ammonium phosphate, which is the substance of the top layer. Consequently, even though

some reagents have not been consumed yet, the collection efficiency decreases with time.

Therefore, the larger surface area offered by increasing folds number should be a good way

to improve the performance. For the 30 folds denuder, Fig. 8 shows that the collection

efficiency of 10 ppm ammonia gas remained 100% for the entire eight hours, which meets

the 95% requirement of performance. A report from National Atmospheric Deposition

Program unveils that the average ambient concentration of NH3 in 2007 to 2012 was 0.32 to

3.42 µg/m3 based on records from different places in the United States and it increased 0.03

to 0.31 ppm every year (Lehmann et al., 2012). Provided the sampling time, 24 hours, the

ambient NH4+ mass amount is 43.2 µg. The 30-folds PMD can sample 5430 µg according to

the obtained results, which is 2 orders higher. Thus, 30 folds PMD is promising for 24-hour

ambient ammonia sampling. However, purity of the denuder could be the challenge of this

technology at the ambient level. Further research should focus on background ammonia

concentration reduction for ambient sampling purpose. Besides, PMD with the characteristic

of lightweight, inexpensive and accurate can also be applied to sampling at low ammonia

concentration level such as stack emission sampling and other stationary emission (Kallinger

et al. 1997).

5.4 Future work

The experiment for 20 and 30 folds denuder under low relative humidity (<5%) were

successfully conducted. However, ambient ammonia sampling could be under high relative

humidity condition. So 30 folds denuder performance test under high relative humidity (70%)

should be investigated in the next set of experiment. Besides, the comparison against the

commercial Honeycomb denuder, which has been extensively used for sampling ammonia,

should be tested to examine method accuracy and precision of the PMD. The purity of the

denuder should also be taken into consideration for ambient sampling application.

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6. CONCLUSION

A new porous membrane denuder has been validated for its capability to measure low

concentration ammonia gas. The bulky, heavy and relatively expensive conventional denuder

can be replaced by PMD with the characteristics of effective, inexpensive, lightweight and

easy-to-assemble. It’s a feasible application for personal sampling at low concentration

ammonia environment. Tested with a flow rate of 2 L/min and a feed NH3 concentration of

10 ppm, PMD with 30 folds showed ammonia gas collection efficiency of nearly 100% for 8

hours. The quality assurance and quality control procedure including calibration and blank

test verified 90% recovery in the mass balance. The difference could be the result from

unstable input flow rate or uncertainty due to the analysis. The application of PMD is

promising for low concentration ammonia sampling.

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7. REFERENCE

! Akagi, S. K., Yokelson, R. J., Wiedinmyer, C., Alvarado, M. J., Reid, J. S., Karl, T., ...

& Wennberg, P. O. (2011). Emission factors for open and domestic biomass burning for

use in atmospheric models. Atmospheric Chemistry and Physics, 11(9), 4039-4072.

! Barker, T.B. (1990). Engineering Quality by Design. Marcel Dekker, New York, 21-35.

! Bergström, A.-K., Jansson, M., 2006. Atmospheric nitrogen deposition has caused

nitrogen enrichment and eutrophication of lakes in the northern hemisphere. Global

Change Biology 12, 635-643.

! Bouwman, A.F., Lee, D.S., Asman, W.A.H., Dentener, F.J., Van Der Hoek, K.W.,

Olivier, J.G.J., 1997. A global high-resolution emission inventory for ammonia. Global

Biogeochemical Cycles 11, 561-587.

! Brauer, M., Koutrakis, P., Wolfson, J. M., & Spengler, J. D. (1989). Evaluation of the

gas collection of an annular denuder system under simulated atmospheric

conditions. Atmospheric Environment (1967), 23(9), 1981-1986.

! Chen, X., Day, D., Schichtel, B., Malm, W., Matzoll, A. K., Mojica, J., ... & Collett, J.

L. (2014). Seasonal ambient ammonia and ammonium concentrations in a pilot

IMPROVE NHx monitoring network in the western United States.Atmospheric

Environment, 91, 118-126.

! Eatough, D. J., Wadsworth, A., Eatough, D. A., Crawford, J. W., Hansen, L. D., &

Lewis, E. A. (1993). A multiple-system, multi-channel diffusion denuder sampler for the

determination of fine-particulate organic material in the atmosphere. Atmospheric

Environment. Part A. General Topics, 27(8), 1213-1219.

! Goebes, Marian Diaz, Ross Strader, and Cliff Davidson. "An ammonia emission

inventory for fertilizer application in the United States." Atmospheric

Environment 37.18 (2003): 2539-2550.

! Gormley, P.G. and Kennedy, M. (1949). Diffusion from a Stream Flowing through a

Cylindrical Tube. Proc. R. Irish Acad. 52: 163–196

! Kallinger, G., & Niessner, R. (1997). Development of an annular denuder sampling

system for the determination of lower aliphatic aldehydes and amines in stack

gas. Journal of Aerosol Science, 28, S613-S614.

! Lehmann, C.; Kerschner, B.; Gartman, N.; Green, L.; Gay, D.; Puchalski, M. The

National Atmospheric Deposition Program/Ammonia Monitoring Network

(NADP/AMoN): Five Years of Trends. 2012 Clean Air Markets Division U.S. EPA,

1200 Pennsylvania Ave. NW Washington, D.C.

  17  

! Lodge Jr, J. P. (1988). Methods of air sampling and analysis. CRC Press.

! Perrino, C., and M. Gherardi. "Optimization of the coating layer for the measurement of

ammonia by diffusion denuders." Atmospheric Environment 33(28) (1999): 4579-4587.

! Possanzini, Massimiliano, et al. "Determination of phase-distributed PAH in Rome

ambient air by denuder/GC-MS method." Atmospheric Environment38.12 (2004):

1727-1734.

! Rosman, K., Shimmo, M., Karlsson, A., Hansson, H. C., Keronen, P., Allen, A., &

Hoenninger, G. (2001). Laboratory and field investigations of a new and simple design

for the parallel plate denuder. Atmospheric Environment, 35(31), 5301-5310.

! Sioutas, C., Wang, P. Y., Ferguson, S. T., Koutrakis, P., & Mulik, J. D. (1996).

Laboratory and field evaluation of an improved glass honeycomb denuder/filter pack

sampler. Atmospheric Environment, 30(6), 885-895.

! Sekiguchi, K., Kim, K. H., Kudo, S., Sakamoto, K., Otani, Y., Seto, T., ... & Kato, T.

(2009). Evaluation of multichannel annular denuders for a newly developed ultrafine

particle sampling system. Aerosol Air Qual. Res, 9, 50-64.

! Shou, L., Theodore, A., Wu, C. Y., Hsu, Y. M., & Birky, B. (2012). Development of a

Novel Porous Membrane Denuder for SO2 Measurement. Aerosol and Air Quality

Research, 12(6), 1116-1124.

! Ye, Y., Tsai, C. J., Pui, D. Y., & Lewis, C. W. (1991). Particle transmission

characteristics of an annular denuder ambient sampling system. Aerosol science and

Technology, 14(1), 102-111.

   

     

   

 

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8. Tables and Figures

Figure 1. Experimental set-up for testing collection efficiency of ammonia gas

 

Figure 2. Denuder holder cassette and Porous Membrane Denuders

  19  

 Figure 3. Comparison of two different dry methods for cellulose filter papers: the left ones

were dried by high temperature baked, and the right ones were dried by clean air purge.

  20  

 

Figure 4. MFC calibration set-up

 

Figure 5. Calibration curve for Mass Flow Controller

Table 1. Mass balance of 20 and 30 folds denuder under low relative humidity

Input (µg) Bubbler (µg) Denuders (µg) Output (µg) Output/Input

20 folds 5914.7 405.9 4805.3 5490.2 93%

30 folds 6246.8 0 5430.4 5430.4 87%

y  =  0.936x  +  13.82  R²  =  0.99952  

0  

100  

200  

300  

400  

500  

600  

0   100   200   300   400   500   600  

Actual  /low

 rate  (mL/min)  

MFC  /low  rate  (mL/min)  

Calibration  curve  

  21  

(a) (b)

Figure 6. (a) Condensed denuder configuration and (b) well-spread denuder configuration

This is cross-sectional view and the air direction is flow into the paper

Figure 7. Collection efficiency for different denuder configurations

70%  

75%  

80%  

85%  

90%  

95%  

100%  

105%  

0   2   4   6   8   10  

Collection  ef/iciency  (%

)

Time  (hr)

Ammonia  collection  ef/iciency  

20  folds  condensed  

40  folds  condensed  

20  folds  well-­‐spread  

  22  

Figure 8. Ammonia collection efficiency

80%  

85%  

90%  

95%  

100%  

105%  

0   2   4   6   8   10  

collection  ef/iciency    

Time  (hour)  

Ammonia  Collection  Ef/iciency  

20  folds  

30  folds