EAS 4/8803: Experimental Methods in AQ

March 22, 2004 EAS 4/8803 1

EAS 4/8803: Experimental Methods in AQ

Week 11:

Air Quality Management (AQM)Clean Air Act (History, Objectives, NAAQS)

Emissions and Atmospheric Trends (Links)

Principal Measurement Techniques (NOx, CO, SO2)

Measurement of CO (Exp 5)NDIR Method (Interferences, Stability, DL, Precision, Accuracy)

Controlling O3 and PM2.5

Principal Measurement Techniques (O3, PM)

Photochemical Processes (NOx vs VOC sensitivities, SOA)

Ambient Measurements and Trends (World, USA, GA)

Measurement of O3 (Exp 6)

UV Absorption (Interferences, Stability, DL, Precision, Accuracy)

March 22, 2004 EAS 4/8803 2

Review CO Lab Experiment

Vent out during calibration

400CMnO2

NV set so that ΔP(Tee-NO) in Sample mode = ΔP(Tee-NC) in Zero modeTee

IR A-Cell

NO

NC

CZT

Manual connect during calibration

COMFM

1425 ppmv in N2

10 sccm

MFC

10 slm

Zero Air

CO Analyzer Calibration

March 22, 2004 EAS 4/8803 3

Review CO Lab Experiment

insulation

T

Thermo-electrically cooled PbSe

4.7 m

30 Hz

360 Hz modulation

16 m

I = I0 e- c l

CO Method: IR-Absorption

March 22, 2004 EAS 4/8803 4

Review CO Lab Experiment

March 22, 2004 EAS 4/8803 5

Review CO Lab Experiment

Time (minutes)

COspan4,0COspan1,0

COspan1

COZA COZA

COspan2

COspan3

COspan4

CO

Ana

lyze

r S

igna

l (

V)

Zero-air/Zero-mode = baseline

Zero-air

CO0

CO0

COnom]1

5 V

COnom]2

COnom]3

COnom]4

zero-mode zero-mode

COsensi (ppb/V) = [COnomi] / COspani

ZTeffi = (COspani – COspani,0) / (COspani – CO0)

If ZTeff < 0.9, correct CO0

CO0* (V) = CO0 / ZTeff – COipol * (1/ZTeff-1)

COnet (V) = COraw – CO0*ipol

CO (ppb) = COnet * COsens

DL (ppb) = t * STD(CO0*) * COsens

P (%) = t * STD(COsens) / AVG(COsens) *100

A1 (%) = (slope{[COnomi] / COspani} -1000) *100

A2 (%) = {[((Xj))2 (COsens/Xj)2]}1/2

…from error propagation analysis.

CO Analyzer Calibration and Zero-Trap Efficiency

March 22, 2004 EAS 4/8803 6

Emissions/AQ Trends: O3

old 1h NAAQS

Secondary Product !!

Potential Risks and Effects• Acute health (respiration, asthma)

• Chronic health (obstructive pulmonary)

• Vegetation damage (chlorophyll)• Agriculture (crop & forest yields)

• Materials deterioration

new 8h NAAQS

March 22, 2004 EAS 4/8803 7

O3 Method: Chemiluminescence

Ambient sample from inlet

Excess NO or C2H4

C

NC NO Chemi-lumi-

nescence600-3200

max 1200 nm

Reaction Vessel

Ze

ro V

olu

me

Trap

PMT

HVPMT

Hz

NO + O3 NO2* + O2

NO + O3 NO2 + O2

NO2* NO2 + hv (front edge max 630nm)

NO2* + M NO2 + M (collisional quenching)

Chemiluminescence of NO2*

C2H4 + O3 2 HCHO* + O2

C2H4 + O3 2 HCHO + O2

HCHO* HCHO + hv (broadband max 440nm)

HCHO* + M HCHO + M (collisional quenching)

Chemiluminescence of HCHO*

Disadvantage: Need of Process Gases

March 22, 2004 EAS 4/8803 8

O3 Method: UV Absorption

I = I0 e- c l

= 308 cm-1 (@STP: 0oC, 760Torr)

l = 38 cm

254 nm

March 22, 2004 EAS 4/8803 9

O3 Method: ECC

Electro-Chemical Cell used in balloon sondes

Advantage: size (8x8x14 cm) and weight (< 300 g)

Two Teflon chambers linked by ion bridge

Cathode: 0.06 mol/l (1% KI)

Anode: 8.0 mol/l (saturated KI)

Redox reaction of ambient O3 in cathode:

2 KI + O3 + H2O I2 + O2 + 2 KOH

I2 + 2 e- + Pt 2 I-   (cathode reaction)

Release of 2 e- at anode Pt mesh electrode:

2 I- + Pt I2 + 2 e-   (anode reaction)

Overall: 2 e- per O3 titrated.

March 22, 2004 EAS 4/8803 10

Emissions/AQ Trends: PM2.5

AQ

Emissions

PrimarySources (2001)

Potential Risks and Effects• Heart (arrhythmias, attacks)

• Respiratory (asthma, bronchitis)

• Among elderly and young• Vegetation (ecosystem)

• Buildings, Materials• VisibilityAQ influenced by

Primary + Secondary PM

March 22, 2004 EAS 4/8803 11

Sources and Mechanisms of Atmospheric PM

Meng et al., Science, 1997

March 22, 2004 EAS 4/8803 12

Secondary organic aerosol (SOA):Organic compounds, some highly oxygenated, residing in the aerosol phase as a function of atmospheric reactions that occur in either gas or particle phases.

SOA formation depends on:Precursorsaromatics (BTX, aldehydes, carbonyls)terpenes (mono-, sesqui-)other biogenics (aldehydes, alcohols)Presence ofO3, OH, NO3, sunlight, acid catalysts

Mechanisms (with few hr yields):Gas-to-particle conversion/partitioninge.g. terpene oxidationHeterogeneous reactionsaldehydes via hydration, polymerization, forming hemiacetal/acetal in presence of alcoholsParticle-phase reactionsacetal formation catalytically accelerated by Meng et al., Science, 1997

particle sulfuric acid (Jang and Kamens, ES&T, 2001)

March 22, 2004 EAS 4/8803 13

Other (Inorganic) Secondary PM2.5 Formation

Secondary formation is a function of many factors including: concentrations of precursors, other gaseous reactive species (e.g., O3, OH), atmospheric conditions, and cloud or fog droplet interactions. BUT: Most secondary products remain semi-volatile and can evaporate back into the gas-phase!

Gas-to-particle conversion (oxidation)

SO2(g) HOSO3 H2SO4 + 2NH3 (NH4)2SO4

NOx(g) HNO3 + NH3 NH4NO3

Heterogeneous reactions

(R7)

R6)(

R5)(

)4R()(

2422

123

233

322

2222

SOOSO

SOHHSO

HSOHOHSO

OHSOOHgSO

March 22, 2004 EAS 4/8803 14

Partitioning of Semi-Volatile Species

Ambient PM2.5 is composed of primary and secondary components of particle-phase species. A large fraction of secondary PM in the atmosphere is in a fragile balance (equilibrium) between its gas-phase precursors and particle-phase products, meeting individual species’ vapor pressures and physical-chemical micro-environments at given ambient conditions. The gas-particle partitioning of these semi-volatile species can easily be altered during sample collection and analysis!

PM2.5 Measurement Challenge

March 22, 2004 EAS 4/8803 15

Separating PM2.5 at Sample Inlet

Classical Cyclone

Sharp Cut Cyclone

Well Impactor Ninety-Six

March 22, 2004 EAS 4/8803 16

Potential Gas/Particle Interactions at a Filter Surface

P

March 22, 2004 EAS 4/8803 17

Discrete PM2.5 Sampling Method, e.g. FRM

Ambient sample air containing PM2.5 (aerosol) passes through a filter, which collects the “particle phase” then through an adsorber, which traps the“gas phase” compounds.

This method suffers from potential positive and mostly negative artifacts !!

air

Filter

Adsorber

March 22, 2004 EAS 4/8803 18

Air passes through an annular diffusion tube (gas phase) then through a filter (particle phase) then through an adsorber to trap the compounds released from the surface of the particles.The denuder is coated with a material that will trap the gas phase molecules. Each sampling medium is extracted separately for direct quantification of:

NH3, HONO, HNO3, SO2, Formic, Acetic, Oxalic;

Na+, NH4+, Cl-, NO2

-, NO3-, SO4

=,Formate, Acetate, Oxalate;

EC, OC, and “SVOC”

Denuder (Diffusion Tube) Application

air

Denuder

Filter

Adsorber

Particle phase

gasphase

March 22, 2004 EAS 4/8803 19

Air passes through an annular diffusion tube (gas phase) then through a filter (particle phase) then through an adsorber to trap the compounds released from the surface of the particles.The denuder is coated with a material that will trap the gas phase molecules. Indirect determination ofgas phase concentrations fromPM-difference.

Denuder Difference Method

Denuder

air

Filter

Adsorber

Particle phase

gasphase

TotalGas &Particle

March 22, 2004 EAS 4/8803 20

Utilizing Fast Gas Diffusion to Walls

Denuder Fluid Dynamics and Efficiency(for annulus)

)53.22exp(82.0 aoC

C

where

oC C

12

21

4 dd

dd

F

DLa

…and making gas molecules stick!

March 22, 2004 EAS 4/8803 21

Diffusion Coefficients Gas vs PM

Particleswith

diameter (m)

D (cm2/s)

NH3 0.24HONO 0.17HNO3 0.15NO2 0.14SO2 0.13HCOOH 0.18CH3COOH 0.15(COOH)2 0.130.01 5.20E-40.05 2.33E-50.1 6.71E-60.5 6.24E-71.0 2.72E-71.6 1.61E-7

Reactivegases

March 22, 2004 EAS 4/8803 22

Providing Large Wall Surface for Gas Adsorption Possible Denuder Configurations

Tubular

Annular Gundel et al. IOVPS Kamens et al. IOVPS

ETSSmog chamber studies

Multi-channel annular

Possanzini et al. Lane et al. GAP sampler Lane and Gundel IOGAPS

TheoreticalAmbient airAmbient air

Capillary bundle Hites et al. Ambient airHuman exposure

Parallel plate Eatough et al. BOSS,Big BOSS, RAMS

Ambient Air - interest inparticles only

Honeycomb Koutrakis et al. Harvard Ambient airHuman exposure

March 22, 2004 EAS 4/8803 23

Making Gases Stick: Scanning electron photomicrograph of an uncoated sandblasted glass denuder fragment

March 22, 2004 EAS 4/8803 24

Making Gases Stick: Scanning electron photomicrograph of a denuder fragment coated with ground XAD-4 adsorbent

March 22, 2004 EAS 4/8803 25

Particle Loss in a Denuder

= 1 - 0.910exp(-7.54) - 0.0531exp(-85.7) - 0.0153exp(-249)

for situations where = D(d)LW/(Qh) >0.003

D(d) = diffusion coefficient of the particle of diameter dL = the channel width in the direction of flowW for an annular denuder = (d1+d2)/2

d1 is the inner diameter of the annulusd2 is the outer diameter of the annulus

h for an annular denuder = (d2-d1)/2Q = Flow rate

March 22, 2004 EAS 4/8803 26

Assessing Particle Loss in a Denuder

Pump

OpticalParticleCounter

Denuder Cyclone inlet

Isokinetic sampling probe

Ambient

Aerosol

or PSL

March 22, 2004 EAS 4/8803 27

Particle Composition Monitor (PCM) “KB”

Channel 1:

NH3

Na+, K+, NH4+, Ca+2

Channel 2:

HF, HCl, HONO, HNO3, SO2,

HCOOH, CH3COOH,

(COOH)2

F-, Cl-, NO3-, SO4

=,

HCOO-, CH3COO-, C2O4=

Channel 3:

EC, OC, “SVOC”

March 22, 2004 EAS 4/8803 28

PM2.5 Mass from Teflon Filter Gravimetry

Equilibration of Teflon filter samples in Class 1000 Clean Room

[PM] < 1000/scf, T = 21 +-0.5 oC, RH = 33 +-3 %

Mettler Toledo MT5 Electronic Micro-Balance

Exp. DL = 1.2 +-0.02 g; P = +- 0.4 % @ 1 g; A = +-0.001 % {1-500 mg}

March 22, 2004 EAS 4/8803 29

Effects of Water Vapor on PM2.5 Mass

y = 0.934x + 6.826

R2 = 0.985

0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

First Weigh (g)

Fin

al W

eig

h A

fte

r D

es

icc

ati

on

(

g)

Dehydration of denuded Teflon filter samples (ch1), Griffin Jan-Jul 2002

March 22, 2004 EAS 4/8803 30

EPA’s FRM Samplers

OC/EC,SO4

2-, NO3-,NH4

+

Size SelectiveInlet (PM10)

Pump

WINSImpactor

Quartz Filter

Mass,Elements by XRF

Size SelectiveInlet (PM10)

Pump

WINSImpactor

Teflon Filter

Air

Flo

w

16.7

Lpm

SamplerHousing

March 22, 2004 EAS 4/8803 31

Andersen RAAS SamplerA

ir F

low

Teflon Filter Teflon Filter Nylon Filter

PM2.5 CycloneFractionator

Pump

OC/EC Mass,Elements by XRF

SO42-, NO3

-, NH4

+

Fine ParticleNitrate

PM10 Inlet

Quartz Filter

7.3

Lpm

16.7

Lpm

16.7

Lpm

7.3

Lpm

MgO

De

nude

r

1 32 4

PM2.5 Cyclone Fractionator

Manifold Manifold

SamplerHousing

XA

D-4

Den

uder

March 22, 2004 EAS 4/8803 32

Met-One SASS SamplerSampler Housing

Pump

Flo

w m

eter

Mass,Elements by XRF

SO42-, NO3

-,NH4

+

Fine ParticleNitrate

OC/EC Replicate OC/EC

EmptyMgO

Denuder

Air

Flo

w

6.7

Lp

m

6.7

Lp

m

6.7

Lp

m

6.7

Lp

m

6.7

Lp

m

1 432 5

Flo

w m

eter

Flo

w m

eter

Flo

w m

eter

Flo

w m

eter

EmptyTeflon Filter Nylon Filter

EmptyQuartz FilterQuartz Filter

Quartz FilterQuartz FilterEmpty

Teflon Filter

Empty

Spiral Impactor

Empty

Spiral Impactor Spiral Impactor Spiral Impactor

Empty

Spiral Impactor

March 22, 2004 EAS 4/8803 33

URG MASS Sampler

Size selectiveInlet (PM10)

Sodium CarbonateDenuder

Nylasorb Filter

Mass, Elements by XRF

Volatilized Nitrate

Pump

HNO3

WINSImpactor

OC/EC, SO4

2-, NO3-,

NH4+

Teflon Filter

Size selectiveInlet (PM10)

Quartz Filter

Pump

Air

Flo

w

16.7

Lpm

WINSImpactor

SamplerHousing

MASS 400 MASS 450

March 22, 2004 EAS 4/8803 34

R&P Speciation Sampler

Teflon Filter Quartz Filter

Quartz Filter

Nylon Filter

Pump

Impactor Impactor

Na2CO3 Denuder

Mass, Elements

SO42-, NO3

-, NH4

-, OC, EC

NO3-

10 Lpm 10 Lpm

10 Lpm

Impactor

Air

Flo

w

SamplerHousing

March 22, 2004 EAS 4/8803 35

URG VAPS Sampler

VI = Virtual Impactor

Quartz Filter

Size SelectiveInlet

Teflon Filter

XA

D-4

De

nu

de

r

VI

Air

Flo

w

Pump Pump Pump

A. Mass, Elements by XRF

B. NO3-

Coarse Particle Mass

A. SVOCs B. OC/EC,

SO42-, NO3

-,NH4+

Teflon Filter

15 L

pm

33 Lpm

3 Lp

m

15 L

pm

Na

2CO

3De

nu

de

r

Nylon Filter

A

B SamplerHousingA

B

March 22, 2004 EAS 4/8803 36

SEARCH/ARIES-PCM “EE”

Na2CO3 Denuder

Citric Acid

Denuder

PM10 Cyclone

3-Stage Filter PackTeflonNylon

Citric Acid Impregnated

1-StageNylon

PM2.5 ImpactorFlow Splitter

CIF Denuder

2-Stage Filter Pack

Quart-Fiber Filter

PM2.5 Impactor

Mass, Elements,

SO42-, NO3

-, NH4-,

Volatilized NO3-, NH4

-,

OC, EC

Solenoid Valves

16.7 Lpm

1 2 3

Flow Control & Pump

SO42-, NO3

-, NH4-

PM10 Cyclone PM10 Cyclone

Figure 3

March 22, 2004 EAS 4/8803 37

Atlanta Super-Site Experiment Aug’99

Wind Profiler

Single Particle & Continuous Samplers

LIDAR

DelawareMaryland

SEARCH/ARIES

Miami

Integrated Samplers

Georgia Power Facilities; Jefferson Street

GIT

March 22, 2004 EAS 4/8803 38

PM2.5 Mass Concentrations Comparison of Different Filter Samplers During ASSE 99

MaxMin

Mean+SDMean-SD

Mean

0

10

20

30

40

50

60

70

RE

L_

RE

F

FR

M-A

FR

M-R

oo

f

ME

T

UR

G

RP

S

RP

D

KB

PC

B(T

VA

)

PC

B (

BY

U)

EE

Co

nce

ntr

atio

n,

g/m

3

FR

M-B

AN

D

March 22, 2004 EAS 4/8803 39

PM2.5 Mass Concentrations Comparison of Different Filter Samplers During ASSE 99

Species

Rel. Ref.

FRM-A

FRM-B

AND

MET

URG

RPS

RPD

EE

(12-hr)

VAPS

KB

PCB

(TVA)

PCB

(BYU)

µg/m3 0

Mass

31.3

30.9

30.2

30.3

32.9

36.5

35.4

34.8

26.0

*

33.3

23.2

25.8

SO4

10.6

10.7

*

10.7

10.8

11.1

10.3

*

10.1

9.8

10.8

9.0

11.0

NO3

0.51

0.22

*

0.58

0.61

0.50

0.62

*

0.08

0.71

0.62

0.33

0.35

NH4

3.6

3.4

*

3.5

3.7

3.9

3.6

*

3.6

3.3

3.7

3.0

*

OC

7.8

8.5

*

9.2

9.3

8.1

10.5

*

6.0

6.3

7.6

5.3

5.1

EC

1.0

0.7

*

0.9

0.9

0.8

0.9

*

2.0

0.8

0.8

1.5

2.6

REL_REF

FRM_A

FRM_B

AND

MET

URG

RPS

RPD

VAPS

KB

EE_12HR

PCB_TVA

PCB_BYU

MASS

1.00

0.97

0.99

0.99

0.97

0.93

0.86

0.99

0.96

0.93

0.68

0.90

SO4

1.00

1.00

1.00

1.00

0.98

0.99

0.99

1.00

0.96

0.88

0.96

NO3

1.00

0.24

0.85

0.86

0.72

0.87

0.67

0.71

-0.33

-0.10

0.26

NH4

1.00

1.00

0.99

0.99

0.97

0.99

0.99

0.98

0.94

0.88

OC

1.00

0.95

0.93

0.94

0.97

0.99

0.97

0.88

0.91

0.88

0.70

EC

1.00

0.60

0.56

0.64

0.59

0.89

0.52

0.76

0.48

0.56

0.70

Pearson Correlation Coefficients (r) for Test Samplers vs Relative Reference

Period Averages for Mass and Chemical Components for Time-Integrated Samplers

Solomon et al., JGR, 2003

March 22, 2004 EAS 4/8803 40

KBPCB(TVA) PCB(BYU) Relative Ref. EE

0

10

20

30

40

50

60

70

8/3/

99

8/5/

99

8/7/

99

8/9/

99

8/11

/99

8/13

/99

8/15

/99

8/17

/99

8/19

/99

8/21

/99

8/23

/99

8/25

/99

8/27

/99

8/29

/99

8/31

/99

g/m

3

FRM-A FRM-B AND METURG RPS RPD

ASSE 99 – PM2.5 Mass

March 22, 2004 EAS 4/8803 41

0

2

4

6

8

10

12

14

16

18

20

8/3/

99

8/5/

99

8/7/

99

8/9/

99

8/11

/99

8/13

/99

8/15

/99

8/17

/99

8/19

/99

8/21

/99

8/23

/99

8/25

/99

8/27

/99

8/29

/99

8/31

/99

g/m

3

FRM-A AND MET URG

RPS VAPS KB PCB(TVA)

PCB(BYU) MOUDI Relative Ref. EE

ASSE 99 – PM2.5 Sulfate

March 22, 2004 EAS 4/8803 42

0

1

2

3

4

5

6

7

8/3/

99

8/5/

99

8/7/

99

8/9/

99

8/11

/99

8/13

/99

8/15

/99

8/17

/99

8/19

/99

8/21

/99

8/23

/99

8/25

/99

8/27

/99

8/29

/99

8/31

/99

g/m

3

FRM-A AND MET URGRPS VAPS KP PCB(TVA)MOUDI Relative Ref. EE

ASSE 99 – PM2.5 Ammonium

March 22, 2004 EAS 4/8803 43

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

8/3/

99

8/5/

99

8/7/

99

8/9/

99

8/11

/99

8/13

/99

8/15

/99

8/17

/99

8/19

/99

8/21

/99

8/23

/99

8/25

/99

8/27

/99

8/29

/99

8/31

/99

g/m

3

FRM-A AND MET URGRPS VAPS KP PCB(TVA)PCB(BYU) MOUDI Relative Ref. EE

ASSE 99 – PM2.5 Nitrate

March 22, 2004 EAS 4/8803 44

Why Nitrate Scatter?

Three Potential Artifact Reactions

2 NO2 + H2O HNO3 + HONO Surface mediated hydrolytic reaction, disproportionating N(IV) to N(III) + N(V)

NO2 + Salkaline NO2-surface

Reductive surface conversion of NO2 to nitrite

NO2-surface + O3 NO3

-surface + O2

Secondary surface oxidation of nitrite to nitrate

Plus volatility

HNO3 + NH3 NH4NO3

March 22, 2004 EAS 4/8803 45

0

3

6

9

12

15

18

8/3/

99

8/5/

99

8/7/

99

8/9/

99

8/11

/99

8/13

/99

8/15

/99

8/17

/99

8/19

/99

8/21

/99

8/23

/99

8/25

/99

8/27

/99

8/29

/99

8/31

/99

g/m

3

FRM-A AND MET URGRPS VAPS KB PCB(TVA)PCB(BYU) MOUDI (w/o AF) MOUDI (w/AF) Relative Ref.EE

ASSE 99 – PM2.5 Organic Carbon

March 22, 2004 EAS 4/8803 46

0

1

2

3

4

5

6

7

8/3/

99

8/5/

99

8/7/

99

8/9/

99

8/11

/99

8/13

/99

8/15

/99

8/17

/99

8/19

/99

8/21

/99

8/23

/99

8/25

/99

8/27

/99

8/29

/99

8/31

/99

g/m

3

FRM-A AND MET URG

RPS VAPS KB PCB(TVA)

PCB(BYU) MOUDI Relative Ref. EE

ASSE 99 – PM2.5 Elemental Carbon