use of national pm2.5 and speciation network measurements for model evaluation for presentation at...
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Use of National PM2.5 and Speciation Network Measurements
for Model EvaluationFor presentation at
PM Model Performance Workshop February 10-11, 2004: Research Triangle Park, NC
Neil FrankOAQPS/USEPA
Scope
• Networks– FRM– EPA Urban Speciation (aka STN) – IMPROVE– CASTNET
• Measurements– PM2.5 mass– Major Chemical Components– Sulfur and Nitrogen Species
• Data interpretation related to Model Evaluation
National Speciation Networks
IMPROVE filters + HNO3 denuder
EPA spec. filters + HNO3 denuder
CASTNETSimple Filter pack
Main Purpose Visibility PM NAAQS Deposition
Time avg 24-hr 24-hr weekly
Particle size PM2.5 PM2.5 >=PM2.5
Frequency 1 in 3 days 1 in 3 / 1 in 6 complete
No. Sites 110 + 54=164 54 + 186 = 240 87 ?
Sampler types 1 6 1
Reporting Local conditions Local conditions STP (&local)
Sulfates Ambient Ambient Ambient
Ammonium - <=ambient? <= ambient
pNO3 Ambient Ambient <=ambient
HNO3 - - >=ambient
TNO3 - - ~ambient
OC/EC DRI method (TOR) EPA/NIOSH (TOT) -
Crustal Estimated from Al, Si, Ca, Fe, Ti
same -
CASTNET Network
Dense in Ohio Valley and Eastern US
PM2.5 speciation sites (became IMPROVE in 2001 )
FilterPacks
8 Supplementary PM2.5 Speciation Sites (1993-2002)
IMPROVE Network, 200298 Sites with “complete” data, Mar 01-Feb 02
Sulfate
0 - 0.4
0.4 - 0.5
0.5 - 0.7
0.7 - 1
1 - 1.3
1.3 - 1.7
1.7 - 2.2
2.2 - 3.5
3.5 - 4.2
4.2 - 5
Sulfate Variation in Rural Areas
Comparison of CASTNET and IMPROVE Measurements in 2001
IMPROVEMarch 01 – Feb 02
CASTNET2001
Concentrations, STP
Nitrate
0 - 0.1
0.1 - 0.2
0.2 - 0.3
0.3 - 0.4
0.4 - 0.5
0.5 - 0.6
0.6 - 0.7
0.7 - 1
1 - 1.5
1.5 - 2.5
Nitrate Variation in Rural Areas
March 01 – Feb 02
IMPROVEMarch 01 – Feb 02
Better resolution will come from new ( 2002-2003) data
CASTNET2001
Gradient is overstated
Concentrations, STP
CASTNET 2001
HNO3 exhibit different spatial pattern
TNO3 also shows a MidWest to East gradient
HNO3
Concentrations, STP
NO3
2.7 + 2.1 = 4.8 ug/m3
NO3 HNO3 TNO3
0.8 + 2.0 = 2.8 ug/m3
NO3 HNO3 TNO3
CASTNET ComparisonsSulfates and Nitrates
Ames RB, Malm WC (2001) Comparison of sulfate and nitrate particle mass concentrations measured by IMPROVE and the CDN. ATMOSPHERIC ENVIRONMENT 35 (5): 905-916.
Western and Eastern Sites
Sulfate: Comparison of 4-week mean IMPROVE and CASTNET
Great Agreement for Sulfates (after adjustment to LTP)
Particle Nitrate: Comparison of 4-week mean IMPROVE and CASTNET
Relative Bias for particle Nitrates
/DC
PINSEK
BBE
CHAGRB
GLR MOR
ROM PND
LAV MEV
CAN
GRC
YEL
YOS
CAN
SEK
GRC
BBE
YEL
MEV
PIN CHA
GRBYOS
LAVPNDROM
MOR
GLR
-2
0
2
4
6
8
10
12
14
16
18
20
-50 0 50 100 150
DNO3- (%)
DN
O3
- / C
M (
%)
and
Tem
per
atu
re (
oC
)
Nitrate difference as a % of CM
Temperature
From: Rodger B. Ames and William C. Malm Comparison of sulfate and nitrate particle mass concentrations measured by IMPROVE and the CDN
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
BVL filterpak
amm_nitrate (PM2.5)
IMPROVE
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
93
-4
94
-3
95
-2
96
-1
96
-4
97
-3
98
-2
99
-1
99
-4
00
-3
01
-2
CDZ filter pak
ammonium_nitrate
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
93-4
94-2
94-4
95-2
95-5
96-2
96-4
97-2
97-4
98-2
98-4
99-2
99-4
00-2
00-4
01-2
QAK filter pak
ammonium_nitrate
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
MKG filter pak
ammonium_nitrate
IL
KY
OH
NW PA
CASTNET filterpak and PM2.5 nitrates in the Eastern US: better agreement in Midwest and during later years
Hypothesis: Better NH4NO3 retention on teflon with free ambient NH3
Less NO3 Agreement between CASTNET filter pack and PM2.5 nitrate as the sites move to the East
Hypothesis: Poorer NH4NO3 retention on teflon in NH3 limited environments
Note: different than pNO3 loss with FRM measurements for PM2.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
CTH filter pak
ammonium_nitrate
0.0
1.0
2.0
3.0
4.0
5.0
6.0
93
-4
94
-3
95
-2
96
-1
96
-4
97
-3
98
-2
99
-1
99
-4
00
-3
01
-2
ARE filter pak
ammonium_nitrate
CTH, NY
0
1
2
3
0 1 2 3
Bondville, IL
0
2
4
6
8
10
0 2 4 6 8 10
Quarterly Average NO3: CASTNet vs PM2.5 Speciation
Good agreement in rural IL…. Relative Bias at Western NYS
CASTNET NO3, ug/m3
PM
2.5
Spe
cia
tion
3:21:1
Routine Estimates of Ambient Carbon More Uncertain than other measurements
• Carbon – Inter-network differences in Measured C
• IMPROVE and STN use different thermo-optical techniques to measure carbon
• Many studies suggest that IMPROVE EC~=2x STN EC • More recent results reveal more agreement
– Total Carbonaceous Mass is estimated as• TCM = k* OC +EC
– Where k can be 1.2 to > 2.5 (+/- 30% regional uncertainty)
– IMPROVE uses 1.4
• OC is blank corrected for artifacts using network-wide estimates
……but still sufficiently robust for model evaluation
Blank corrections vary by Sampler Can Represent Substantial Portion of Measured Values
• Derived from network average quartz filter field blanks to adjust annual averages
• Varies by 24-hr sampler volume– MetOne (SASS): 9.6 m3
– Anderson (RASS): 10.4 m3
– R&P: 14.4 m3
– URG (MASS): 24 m3
– IMPROVE: 32.8 m3
00.20.40.60.8
11.21.41.6
SASS
RA
AS
R&
P
MA
SS
IMP
RO
VE
OCblank,ug/m3
Preliminary OC Blank Corrections Used by Rao, Frank, et al*
* National Air Quality and Emission Trends Report 2003 Special Studies Edition http://www.epa.gov/oar/aqtrnd03/
Values used by Rao et al.
0.56
0.93 1.28
1.4
Newest Blank Corrections Are Slightly Different
Reference: Analysis of Speciation Network Carbon Blank Data DRAFT REPORT, Flanagan et alRTI International August 30, 2002
Newest Blank Corrections
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
SASS RAAS R&P MASS
OC
co
rrec
tio
n,
ug
/m3
For this analysis
Newest estimates
OC now corrected with Total Carbon value
OC wo Blank adjustment
y = 0.26x + 0.92
0
2
4
6
8
10
0 5 10 15 20 25
OC w Blank Adjustment has smaller intercept
y = 0.23x + 0.12
0
2
4
6
8
10
0 5 10 15 20 25PM2.5 Mass Concentration, ug/m3
OC concentration, ug/m3
Evaluation of OC blank correction for 12-month averages using measured OC vs PM2.5 mass
Total Carbon Mass
0.7 - 1
1 - 1.3
1.3 - 1.5
1.5 - 1.8
1.8 - 2
2 - 2.6
2.6 - 3.3
3.3 - 4.2
4.2 - 5.4
5.4 - 7.0
TCM Variation in Rural Areas
March 01 – Feb 02
TCM=1.8*OC+ECBased on TCM= OC*1.8+EC
13 Selected Urban Sites are Paired with Rural Sites for “Urban PM2.5 Excess” Calculations
Fresno IndyS.L.
Tulsa
Missoula
SLC Bronx
Charlotte
Baltimore
Atlanta
Cleveland
Richmond
Birmingham
16 rural IMPROVE sites
13 urban STN sites
Fre
sno
/PIN
N
Mis
sou
la/M
ON
T
SLC
/GR
BA
Tuls
a/W
IMO
St.
Lou
is/3
Sit
es
Bir
min
gha
m/S
IP
Indy
/LIV
O
Atl
ant
a/2
Sit
es
Cle
vel
and
/MK
GO
Cha
rlot
te/L
IGO
Ric
hm
ond
/JA
RI
Bal
tim
ore
/DO
SO
Bro
nx/B
RIG
0
5
10
15
20
25
30
ug
/m3
Urban Increment Regional Contribution
Gravimetric Mass
Bottom: Regional ContributionTop: Urban Increment
Urban PM2.5 is Higher than Nearby Rural Concentrations
Top: Urban Bottom: Rural
12-month average PM2.5 mass from speciation samplers
- PM2.5 STN mass is affected by high filter blanks prior to ~August 2001
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
Dolly Sods, WV
Rural IMPROVE site
(background)
Baltimore MD
STN urban site
Rural Concentrations Superimposed on Urban
Rural Concentrations Adjusted for Elevation differential
“Urban Excess” = Urban – Rural concentrations
Estimated Annual “Urban Excess” for Baltimore, MD
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
Top bars are urban concentrations
Bottom bars are nearby rural concentration
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
Fresno
Missoula
SLC
Tulsa
Birmingham
Indy
Cleveland
Charlotte
Richm ond
Baltim ore
Bronx
St Louis
Atlanta
Sulfa te :
0 .0 0.4 0.9
Am m onium :
0.0 0.9 1.9
N itra te :
0 .4 3.5 6.5
TC M (k=1.8):
2 .9 8.1 13.2
C rusta l:
0 .0 0.4 0.8
Range of TCM based on “k”= 1.4 to 1.8
(k=1.4)
Ambient Urban Excess Concentrations for 13 example areas
“Urban Excess” = urban concentration – regional background
Carbon is > 50-80% of the Urban Excess
Note: GM excess is higher in part, because of bias in STN mass thru June 2001, and because GM contains water.
0
5
10
15
20
25
Fre
sno/
PIN
N
Mis
soul
a/M
ON
T
SLC
/GR
BA
Tuls
a/W
IMO
St.L
ouis
/3 S
ites
Bir
min
gham
/SIP
S
Indy
/LIV
O
Atla
nta/
2 S
ites
Cle
vela
nd/M
KG
O
Cha
rlotte
/LIG
O
Ric
hmon
d/JA
RI
Bal
timor
e/D
OS
O
Bro
nx/B
RIG
urb
an e
xces
s, u
g/m
3
0%10%20%30%40%50%60%70%80%90%
exce
ss c
arb
on
, %
of
PM
2.5
Gravimetric mass Chemical Components %TCM1.4 of total
With straight inter-network comparison,
We see a large OC increment, but…. OC urban increment is potentially over stated
**
* “k” for OCM in rural areas is likely > 1.4, further reducing urban increment as presented
0
2
46
8
10
12
Fre
sno/
PIN
N
Mis
soul
a/M
ON
T
SLC
/GR
BA
Tuls
a/W
IMO
St.L
ouis
/3 S
ites
Bir
min
gham
/SIP
S
Indy
/LIV
O
Atla
nta/
2 S
ites
Cle
vela
nd/M
KG
O
Cha
rlotte
/LIG
O
Ric
hmon
d/JA
RI
Bal
timor
e/D
OS
O
Bro
nx/B
RIG
Regional Contribution Urban Increment (OCM k=1.4)
Note: Comparisons based on different thermo-optical techniques
With straight inter-network comparison,
we don’t always see a large urban increment for EC
Assuming IMPROVE EC > STN EC, urban increment is potentially understated
0.00.20.40.60.81.01.21.4
Fre
sno/
PIN
N
Mis
soul
a/M
ON
T
SLC
/GR
BA
Tuls
a/W
IMO
St.L
ouis
/3 S
ites
Bir
min
gham
/SIP
S
Indy
/LIV
O
Atla
nta/
2 S
ites
Cle
vela
nd/M
KG
O
Cha
rlotte
/LIG
O
Ric
hmon
d/JA
RI
Bal
timor
e/D
OS
O
Bro
nx/B
RIG
Regional Contribution EC Urban Increment
Note: Comparisons based on different thermo-optical techniques
By accounting for potential relative bias in reported EC The Urban EC Increment Can Be Bounded
Assuming IMPROVE EC > STN EC > ½ IMPROVE EC
0.00.20.40.60.81.01.21.4
Fre
sno/
PIN
N
Mis
soul
a/M
ON
T
SLC
/GR
BA
Tuls
a/W
IMO
St.L
ouis
/3 S
ites
Bir
min
gham
/SIP
S
Indy
/LIV
O
Atla
nta/
2 S
ites
Cle
vela
nd/M
KG
O
Cha
rlotte
/LIG
O
Ric
hmon
d/JA
RI
Bal
timor
e/D
OS
O
Bro
nx/B
RIG
Regional (lower est) Regional or add'l urban incr. EC Urban Increment
Note: Comparisons based on different thermo-optical techniques
Upper Estimate EC urban excess
Other Issues
• Data reporting conventions– STP vs LTP– Using high elevation site data to represent
regional concentrations
• Inter-annual variability
• PM2.5 mass vs. Component species
0
3
6
9
Sulfate Ammonium Nitrate TCM1.8 Crustal
Elevation adjustment is a small technical correction to the “Urban Excess” calculation
Urban excess after
elevation adjustment
Concentration, ug/m3
Estimated Annual “Urban Excess” for Baltimore, MD
Concentration at 1158m (Dolly Sods) is 12% lower than a “sea level” estimate
Sulfate
0 - 0.4
0.4 - 0.5
0.5 - 0.7
0.7 - 1
1 - 1.3
1.3 - 1.7
1.7 - 2.2
2.2 - 3.5
3.5 - 4.2
4.2 - 5
Focus on Dolly Sods, WV Average Sulfate
March 01 – Feb 02
Elevation adjustment increases average DOSO sulfate to 4.8 ug/m3
http://capita.wustl.edu/CAPITA/CapitaReports/LocalPM10/LocalP10.HTML#combpandt
Local Condition Concentrations < High Elevation STP Concentrations
http://capita.wustl.edu/CAPITA/CapitaReports/LocalPM10/LocalP10.HTML#combpandt
Local Condition Concentrations > Cold Area STP Concentrations
http://capita.wustl.edu/CAPITA/CapitaReports/LocalPM10/LocalP10.HTML#combpandt
Local Condition Concentrations vs STP Concentrations
Q1 Average Nitrate
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
1995 1997 1998 1999 2000 2001 2002
Annual Average Nitrates
0.0
0.5
1.0
1.5
2.0
2.5
6 Northern
16 MWest/NE
15 Southeast
Large Inter-annual Variability in NO3, 2000-02
Northern
MidWest/NE
Southeast
Trend sites
CASTNET sites
Expressed as Ammonium Nitrates, 1.29*NO3
Use of PM2.5 MeasurementsUse of PM2.5 Measurements
• FRM Mass not = Ambient PM2.5• Ambient PM2.5 = [Sulfates] + [Nitrates] + [Carbon Mass] +[Crustal] +[Other]• Approximation used by IMPROVE program:
PM2.5= [SULFATE] + [NITRATES] + [OCM] + [LAC] + [fine soil]• NH42SO4 and NH4NO3 estimated from 3*S and NO3• OCM=1.4*OC• Fine soil estimated as 2.2[Al]+2.49[Si]+1.63[Ca]+2.42[Fe]+1.94[Ti]
• FRM mass – does not retain all particle nitrates– Includes particle bound water and “other” (e.g. passive PM2.5)– OCM probably different than 1.4*OC = [Ammoniated Sulfate Mass] + [Retained Nitrate Mass] + [Retained
Carbonaceous Mass] + [Metallic Metal Oxides] + [Other Components]
Summary
• Many issues associated with Air Quality Measurement
• Uncertainties are relatively small for Model Evaluation Purposes
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