eas 4/8803: experimental methods in aq
DESCRIPTION
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, SO 2 ) Measurement of CO (Exp 5) - PowerPoint PPT PresentationTRANSCRIPT
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