may 22, 20021 understanding the effectiveness of precursor reductions in lowering 8-hour ozone...
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May 22, 2002 1
UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING
8-HOUR OZONE CONCENTRATIONS
Steve Reynolds
Charles Blanchard
Envair
12 Palm Avenue
San Rafael, CA 94901
Telephone/fax: (415) 457-6955
E-mail: [email protected]
May 22, 2002 2
Purpose of the Study
• Develop a better understanding of the physical and chemical mechanisms underlying observed ozone trends
• Assess the technical feasibility of attaining the 8-hour ozone standard
May 22, 2002 3
Key Findings
• Various VOC and NOx emissions reductions effective in reducing peak 1-hour ozone levels
• VOC reductions have modest impact on peak 8-hour ozone concentrations
• Anthropogenic NOx emissions must be reduced by 90 percent to reach the 8-hour ozone standard
May 22, 2002 4
Key Findings
• Anthropogenic VOC reductions ineffective because biogenic VOC, less reactive VOC, and CO continue to produce ozone
• Effectiveness of NOx reductions offset by an increase in ozone produced per NO
• Such NOx reductions may increase ozone levels in some areas
• These results call into question the technical feasibility of attaining the 8-hour ozone standard
May 22, 2002 5
Overview of Study Approach
• Combined application of– analyses of ambient measured ozone data– photochemical modeling with process analysis
• Employ modeling to provide insights into physical and chemical processes associated with ozone formation
May 22, 2002 6
Photochemical Modeling
• Choice of study area based on soundness of existing model application and availability of code with process analysis facilities
• SARMAP domain in central California
• SARMAP Air Quality Model (SAQM) with process analysis
May 22, 2002 7
Photochemical Modeling
• Extensive field measurements during summer of 1990 to support model application and evaluation
• 2-6 August 1990 ozone episode
• MM5 used to develop meteorological inputs
• Recent updates to emissions inventory by CARB
May 22, 2002 8
SAQM Emissions Sensitivity Results
• Array of VOC and NOx sensitivity runs performed by CARB using 1999 emissions
• Anthropogenic VOC and NOx emissions reduced from base case levels in 10 percent increments
• Results used to produce peak 1- and 8-hour EKMA-type isopleth diagrams
May 22, 2002 9
SAQM Emissions Sensitivity Results
• Isopleth diagrams developed using results for– entire study domain– San Jose (24 km x 24 km)– Stockton (36 km x 72 km)– Fresno (60 km x 48 km)– Visalia (36 km x 48 km)– Bakersfield (36 km x 48 km)– Tulare Lake (36 km x 36 km)
May 22, 2002 10
SAQM Runs with Process Analysis
• 1990 and 1999 base case emissions– VOC reductions ranged from 4 to 39 percent– NOx reductions ranged from -7 to 41 percent– CO reductions ranged from 3 to 43 percent
• Additional runs with anthropogenic VOC and NOx reduced to 50 and 25 percent of 1999 base case values
May 22, 2002 11
1990 and 1999 Domain-wide EmissionsDaily NOX Emissions for SARMAP Modeling
Domain
0
500
1000
1500
2000
2500
3000
Aug 3 Aug 4 Aug 5 Aug 6
day
ton
s 1990
1999
Daily ROG Emissions for SARMAP Modeling Domain
0
500
1000
1500
20002500
3000
3500
4000
4500
Aug 3 Aug 4 Aug 5 Aug 6
day
ton
s 1990
1999
Daily CO Emissions for SARMAP Modeling Domain
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
Aug 3 Aug 4 Aug 5 Aug 6
day
ton
s 1990
1999
May 22, 2002 12
Percentage Change in 1999 VOC, NOx, and CO Emissions Relative to 1990 Values
VOC NOx COAug3 Aug4 Aug5 Aug6 Aug3 Aug4 Aug5 Aug6 Aug3 Aug4 Aug5 Aug6
Area
Fri Sat Sun Mon Fri Sat Sun Mon Fri Sat Sun MonSan Jose 32 30 27 31 34 27 17 32 43 37 33 43Stockton 25 20 14 22 32 27 20 33 37 33 31 37Fresno 28 20 19 24 25 15 4 25 36 29 29 36Visalia 19 16 7 12 21 10 7 22 31 26 23 31Bakersfield 39 39 34 36 40 38 33 41 40 36 34 40TulareLake
19 25 4 11 20 0 9 35 16 8 3 15
May 22, 2002 13
Model Predicted Peak Ozone Levels
• Peak 1- and 8-hour ozone isopleth diagrams for 5 and 6 August based on 1999 emissions– domain-wide– San Jose, Stockton, Fresno, Visalia, Bakersfield
and Tulare Lake• Various combinations of VOC and NOx emissions
reductions effective in reducing peak 1-hour ozone
May 22, 2002 14
Model Predicted Peak Ozone Levels
• VOC emissions reductions have modest impact on peak 8-hour ozone concentrations
• Anthropogenic NOx emissions must be reduced by 90 percent to reach level of 8-hour standard over entire domain
May 22, 2002 15
Model Predicted Peak Ozone Levels
• With significant NOx controls, VOC reductions have small additional benefit
• Biogenic VOC emissions with small amount of anthropogenic emissions sufficient to produce peak 8-hour ozone levels at or exceeding the 8-hour standard somewhere in the domain
May 22, 2002 16
0 10 20 30 40 50 60 70 80 90 100
Percentage of 1999 Anthropogenic VO C Em issions
0 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
90
100
Per
cent
of
1999
Ant
hrop
ogen
ic N
Ox
Em
issi
ons
0
10
20
30
40
50
60
70
80
90
100
Peak 1-hour O zone Isop le ths (ppb) for San Jose Subreg ion - 5 August 1999
May 22, 2002 17
0 10 20 30 40 50 60 70 80 90 100
Percentage of 1999 Anthropogenic VO C Em issions
0 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
90
100
Per
cent
of
1999
Ant
hrop
ogen
ic N
Ox
Em
issi
ons
0
10
20
30
40
50
60
70
80
90
100
Peak 8-hour O zone Isople ths (ppb) for San Jose Subreg ion - 5 August 1999
May 22, 2002 18
0 10 20 30 40 50 60 70 80 90 100
Percentage of 1999 Anthropogenic VO C Em issions
0 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
90
100
Per
cent
of
1999
Ant
hrop
ogen
ic N
Ox
Em
issi
ons
0
10
20
30
40
50
60
70
80
90
100
Peak 1-hour O zone Isople ths (ppb) for S tockton Subreg ion - 5 August 1999
May 22, 2002 19
0 10 20 30 40 50 60 70 80 90 100
Percentage of 1999 Anthropogenic VO C Em issions
0 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
90
100
Per
cent
of
1999
Ant
hrop
ogen
ic N
Ox
Em
issi
ons
0
10
20
30
40
50
60
70
80
90
100
Peak 8-hour O zone Isople ths (ppb) for S tockton Subreg ion - 5 August 1999
May 22, 2002 20
0 10 20 30 40 50 60 70 80 90 100
Percentage of 1999 Anthropogenic VO C Em issions
0 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
90
100
Per
cent
of
1999
Ant
hrop
ogen
ic N
Ox
Em
issi
ons
0
10
20
30
40
50
60
70
80
90
100
Peak 1-hour O zone Isople ths (ppb) for Bakersfie ld Subreg ion - 5 August 1999
May 22, 2002 21
0 10 20 30 40 50 60 70 80 90 100
Percentage of 1999 Anthropogenic VO C Em issions
0 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
90
100
Per
cent
of
1999
Ant
hrop
ogen
ic N
Ox
Em
issi
ons
0
10
20
30
40
50
60
70
80
90
100
Peak 8-hour O zone Isople ths (ppb) for Bakersfie ld Subreg ion - 5 August 1999
May 22, 2002 22
Process Analysis Results
• Useful elements of process analysis results– NO cycles (~ ozone produced per NO)– mass of NO reacted– mass of VOC reacted– ozone created
• Ozone production involves– radical initiation, propagation, and termination– NO recreated by photolysis of NO2
May 22, 2002 23
Summary of key process analysis results for San Jose - August 5
May 22, 2002 24
Process Analysis Results for San Jose
• Lower precursor emissions in 1999 produce higher ozone relative to the levels formed in 1990
• Increased ozone forming efficiency in 1999
• 50 percent reduction in NOx emissions coupled with a 250 percent increase in NO cycles yields an increase in the mass of NO reacted…and ozone produced
May 22, 2002 25
Summary of key process analysis results for Stockton - August 5
May 22, 2002 26
Process Analysis Results for Stockton
• Ozone produced in 1999 comparable to 1990– NO cycles increase, NO mass reacted decreases
• 50 percent NOx emissions scenario– 40 percent increase in NO cycles– net decrease in NO reacted
• 25 percent NOx emissions scenario– 100 percent increase in NO cycles– net decrease in NO reacted by 50 percent
May 22, 2002 27
Summary of key process analysis results for Bakersfield - August 5
May 22, 2002 28
Process Analysis Results for Bakersfield
• Ozone in 1999 ~ 10-30 percent lower than 1990– total OH reacted is less in 1999
• 50 percent NOx emissions scenario– increases in NO cycles offset by decreases in
NO reacted in proportions similar to Stockton• 25 percent NOx emissions scenario
– 100 percent increase in NO cycles– net decrease in NO reacted by 50 percent
May 22, 2002 29
Summary of Process Analysis Results
• Reductions in NOx lowered 8-hour ozone concentrations but effectiveness offset by increases in NO cycles
• Substantial NOx emissions reductions required to reach 8-hour standard in Stockton and Bakersfield
• VOC reductions have little effect on either OH or NO cycles or the mass of VOC reacted
May 22, 2002 30
Summary of Process Analysis Results
• Anthropogenic VOC reductions– effective in lowering peak 1-hour ozone levels
in areas where anthropogenic emissions dominate biogenic sources
– effectiveness limited in lowering peak 8-hour ozone due to contributions of biogenic VOC and anthropogenic CO emissions
• CO contribution to ozone produced significant when VOC and NOx emissions at 25 percent level
May 22, 2002 31
Analyses of Ambient Ozone and Precursor Data in Central California
• Characterize trends, explain observed patterns, assess how patterns relate to modeling results
• Trends determined from annual statistics using t-tests of log-transformed data
• 4th highest 8-hour maximum, annual 1-hour maximum, and annual 1- and 8-hour maxima averaged over 21 days per year
May 22, 2002 32
Analyses of Ambient Ozone and Precursor Data in Central California
• Average diurnal concentration profiles for 21 high-ozone days
• Data separated into– weekdays and weekends– 3- and 5-year time periods
May 22, 2002 33
Observed Ozone Trends
• 4th-highest maximum daily 8-hour ozone concentrations declined at most sites in central California– statistically significant (p<0.01) only at some
sites in Bay Area and Stockton
• Annual 1-hour maxima also declined– statistically significant at more sites
May 22, 2002 34
Trends in annual 4th-highest maximum daily 8-hour ozone concentration, 1980 through 2000. Statistical significance (p<0.01) is indicated.
San Jose
San Francisco
Livermore
Sacramento
Fresno
Modesto
Stockton
Bakersfield
Bethel Island
Parlier
Visalia
Oildale
Edison
Slope Positive, Not Significant
Slope Negative, Significant
Slope Negative, Not Significant
8-hour Trend
3850.0
3900.0
3950.0
4000.0
4050.0
4100.0
4150.0
4200.0
4250.0
4300.0
UT
M N
ort
h (
km
)
525.0 575.0 625.0 675.0 725.0 775.0 825.0 875.0UTM East (km)
May 22, 2002 35
San Jose
San Francisco
Livermore
Sacramento
Fresno
Modesto
Stockton
Bakersfield
Bethel Island
Parlier
VisaliaHanford
OildaleEdison
Slope Positive, Not Significant
Slope Negative, Significant
Slope Negative, Not Significant
1-hour Maximum Trend
3850
3900
3950
4000
4050
4100
4150
4200
4250
4300
UTM
nor
th (
km)
525 575 625 675. 725 775 825 875UTM east (km)
Trends in annual maximum daily 1-hour ozone concentration, 1980 through 2000. Statistical significance (p<0.01) is indicated.
May 22, 2002 36
0
20
40
60
80
100
120
140
160
180
200
NO
x (p
pbv
)0 4 8 12 16 20 24
Hour
0
500
1000
1500
2000
2500
3000
3500
4000
CO
(pp
bv)
0 4 8 12 16 20 24Hour
1995 - 1998
1990 - 1994
1985 - 1989
1980 - 1984
0
10
20
30
40
50
60
70
80
90
100
O3
(p
pbv)
0 4 8 12 16 20 24Hour
1995 - 1998
1990 - 1994
1985 - 1989
1980 - 1984
1995 - 1998
1990 - 1994
1985 - 1989
1980 - 1984
San Jose AIRS 060850004 Top 3 per Weekday
San Jose AIRS 060850004 Top 3 per Weekday
San Jose AIRS 060850004 Top 3 per Weekday
Diurnal patterns of ozone, NOx and CO at the San Jose 4th Street site
May 22, 2002 37
0
20
40
60
80
100
120
NO
x (p
pbv
)
0 4 8 12 16 20 24Hour
0
200
400
600
800
1000
1200
1400
1600
1800
CO
(pp
bv)
0 4 8 12 16 20 24Hour
0
10
20
30
40
50
60
70
80
90
100
O3
(p
pbv)
0 4 8 12 16 20 24Hour
1995 - 1998
1990 - 1994
1985 - 1989
1980 - 1984
Stockton - Hazelton AIRS 060771002 Top 3 per Weekday
1995 - 1998
1990 - 1994
1985 - 1989
1980 - 1984
Stockton - Hazelton AIRS 060771002 Top 3 per Weekday
1995 - 1998
1990 - 1994
1985 - 1989
1980 - 1984Stockton - Hazelton AIRS 060771002 Top 3 per Weekday
Diurnal patterns of ozone, NOx and CO at the Stockton site
May 22, 2002 38
0
20
40
60
80
100
120
140
NO
X (
ppb
v)
0 4 8 12 16 20 24Hour
0
500
1000
1500
2000
2500
3000
CO
(pp
bv)
0 4 8 12 16 20 24Hour
0
20
40
60
80
100
120
O3
(p
pbv)
0 4 8 12 16 20 24Hour
1995 - 1998 California Ave.
1990 - 1994 Chester St.
1985 - 1989 Chester St.
1980 - 1984 Chester St.
Bakersfield Airs 060029004 (Chester) Airs 060290014 (California) Top 3 Ozone Days per Weekday
1995 - 1998 California Ave.
1990 - 1994 Chester St.
1985 - 1989 Chester St.
1980 - 1984 Chester St.
Bakersfield Airs 060029004 (Chester) Airs 060290014 (California) Top 3 Ozone Days per Weekday
Bakersfield Airs 060029004 (Chester) Airs 060290014 (California) Top 3 Ozone Days per Weekday
1995 - 1998 California Ave.
1990 - 1994 Chester St.
1985 - 1989 Chester St.
1980 - 1984 Chester St.
Diurnal patterns of ozone, NOx and CO at the Bakersfield sites
May 22, 2002 39
Bay area Sacramento SVV-north SJV-south-15
-10
-5
0
5
10
15
20Increasing WD O3
Decreasing WD O3
Increasing WE O3
Decreasing WE O3
Number of sites with increasing ozone
Number of sites with decreasing ozone
Top 21 days1998-2000compared with1989-91
Mean maximum hourly ozone on Top 21 days:Comparable numbers of sites with increases and decreases
May 22, 2002 40
Mean maximum hourly O3/NOx on Top 21 days:Many more sites with increases than decreases
Bay area Sacramento SVV-north SJV-south-4
-2
0
2
4
6
8
10Increasing WD O3/NOx
Decreasing WD O3/NOx
Increasing WE O3/NOx
Decreasing WE O3/NOx
Number of sites with increasing O3/NOx
Number of sites with decreasing O3/NOx
Top 21 days1998-2000compared with1989-91
May 22, 2002 41
Bay area Sacramento SVV-north SJV-south-2
0
2
4
6
8
10
12Increasing WD O3/CO
Decreasing WD O3/CO
Increasing WE O3/CO
Decreasing WE O3/CO
Number of sites with increasing O3/CO
Number of sites with decreasing O3/CO
Top 21 days1998-2000compared with1989-91
Mean maximum hourly O3/CO on Top 21 days:Many more sites with increases than decreases
May 22, 2002 42
Mean maximum hourly CO/NOx on Top 21 days:Many more sites with decreases than increases
Bay area Sacramento SVV-north SJV-south-12
-10
-8
-6
-4
-2
0
2Increasing WD CO/NOx
Decreasing WD CO/NOx
Increasing WE CO/NOx
Decreasing WE CO/NOx
Number of sites with increasing CO/NOx
Number of sites with decreasing CO/NOx
Top 21 days1998-2000compared with1989-91
May 22, 2002 43
Comparison of Modeling and Ambient Data Analysis Results
• Limitations of modeling results– uncertainties in biogenic emissions estimates– unclear whether ozone response for modeling
period is representative of other days when moderate to relatively high 8-hour ozone concentrations occur
May 22, 2002 44
Comparison of Modeling and Ambient Data Analysis Results
• Consistency of modeling and ambient data analysis results– both indicate modest changes in ozone levels
over the period from 1990 to 1999– observed changes in ambient NOx and CO
corroborate the ~30 percent reduction in NOx and VOC emissions
– both indicate consistent increases in model NO cycles and ambient O3/NOx ratios
May 22, 2002 45
Consistent increases in: > model-predicted NO cycles from 1990 to 1999 > ambient ozone/NOx ratios, 1989-91 and 1998-00
San Jose0
0.5
1
1.5
2
2.5
3
3.5
4
ModelNO cycles
Ambient dataO3/NOx
1990 1990WD
1990WE
19991999WD
1999WE
May 22, 2002 46
Stockton0
1
2
3
4
5
6ModelNO cycles
Ambient dataO3/NOx
1990 1990WD
1990WE
19991999WD
1999WE
Consistent increases in: > model-predicted NO cycles from 1990 to 1999 > ambient ozone/NOx ratios, 1989-91 and 1998-00
May 22, 2002 47
Consistent increases in: > model-predicted NO cycles from 1990 to 1999 > ambient ozone/NOx ratios, 1989-91 and 1998-00
Bakersfield0
2
4
6
8
10
12ModelNO cycles
Ambient dataO3/NOx
19901990WD
1990WE
1999
1999WD
1999WE
May 22, 2002 48
No
rth
ern
SJV
Ce
ntr
al S
JV
So
uth
ern
SJV
No
rth
ern
SA
C
So
uth
ern
SA
C
Sa
n F
ran
cisc
o
0
10
20
30
40
50
60
70
80
90
100
No
rth
ern
SJV
Ce
ntr
al S
JV
So
uth
ern
SJV
No
rth
ern
SA
C
So
uth
ern
SA
C
Sa
n F
ran
cisc
o0
10
20
30
40
50
60
70
80
90
100
VOC
Transitional
NOx
45
27
14
97
2
12
88
2
68
6
50
22
17
53
89
80
5 1
20
4
117
72
8
Fre
qu
en
cy (
pe
rce
nt)
Limiting Precursor
Hours with ozone 80 to 120 ppbv Hours with ozone greater than 120 ppbv
All days March - October 1994 - 2000
Frequency of occurrence (percent of hours) of limiting ozone precursor in central California areas for hours with ozone concentrations of 80-120 ppbv (left panel)
and hours exceeding 120 ppbv (right panel). March through October, 1994-2000.
May 22, 2002 49
VOC-limited (extent<0.6)
Transitional (0.6 to 0.9)
NOx-limited (extent>0.9)
Hours > 80 ppbv Hours > 120 ppbv
FREQUENCY OF VOC-LIMITED, TRANSITIONAL, AND NOx-LIMITED HOURS AT ALL MONITORS
Lo
s A
ng
ele
s
Sa
n F
ran
cisc
o
Sa
n J
oa
qu
in
Ho
ust
on
La
ke M
ich
iga
n
Ne
w Y
ork
Wa
shin
gto
n
No
rth
Ca
rolin
a
Atla
nta
0
10
20
30
40
50
60
70
80
90
100
Pe
rce
nta
ge
Lo
s A
ng
ele
s
Sa
n F
ran
cisc
o
Sa
n J
oa
qu
in
Ho
ust
on
La
ke M
ich
iga
n
Ne
w Y
ork
Wa
shin
gto
n
No
rth
Ca
rolin
a
Atla
nta
0
10
20
30
40
50
60
70
80
90
100
Pe
rce
nta
ge
11,8
26
4
26
9
36
,29
3
29
79
2
27
1
10
71
1
69
2
35
67
3
14
8
58
78
1
84
1
34
7
36
4
95
3
8
38
4
1
24
3
Central California 1991-98Texas 1993-99Southern California 1994-97Atlanta 1994-99Northeast and mid-Atlantic 1994-99Southern Lake Michigan area 1994-98
In all areas, frequency of NOx limited hours is greater for hourswith ozone>120 ppbv (right)than for hours with ozone > 80 ppbv (left).
May 22, 2002 50
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
1 2 3 Day of Episode
Ext
ent
of
Rea
ctio
n
Livermore
1HOUR
1 2 Day of Episode
Livermore
0
0.25
0.5
0.75
1.0
1.25
1.5
1.75
2.0
Ext
ent
of
Rea
ctio
n
8 HOUR
1 2 3 Day of Episode
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Ext
ent
of
Rea
ctio
n
Stockton Stockton
1 2 3 4 5 Day of Episode
0
0.25
0.5
0.75
1.0
1.25
1.5
1.75
2.0
Ext
ent
of
Rea
ctio
n
Ext
ent
of
Rea
ctio
n
Bakersfield
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
1 2 3 4 5 Day of Episode
0
0.25
0.5
0.75
1.0
1.25
1.5
1.75
2.0E
xte
nt o
f R
eact
ion
1 2 3 4 5 6 7 8 9 10 Day of Episode
Bakersfield
Extent of reaction during 1-hour and 8-hour episode days in 1994-2000 versus sequence of days within an episode
May 22, 2002 51
Conclusions
• Various VOC and NOx emissions reductions effective in reducing peak 1-hour ozone levels
• VOC reductions have modest impact on peak 8-hour ozone concentrations
• Anthropogenic NOx emissions must be reduced by 90 percent to reach the 8-hour ozone standard
May 22, 2002 52
Conclusions
• Anthropogenic VOC reductions ineffective because biogenic VOC, less reactive VOC, and CO continue to produce ozone
• Effectiveness of NOx reductions offset by an increase in ozone produced per NO
• Such NOx reductions may increase ozone levels in some areas
• These results call into question the technical feasibility of attaining the 8-hour ozone standard
May 22, 2002 53
Recommendations for Further Study
• Conduct data analyses and modeling in another area to assess consistency of findings with those obtained in central California– northeastern U.S. using CMAQ