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]

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Page 1: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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]

Page 2: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 3: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 4: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 5: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 6: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 7: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 8: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 9: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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)

Page 10: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 11: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 12: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 13: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 14: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 15: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 16: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 17: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 18: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 19: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 20: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 21: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 22: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 23: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

May 22, 2002 23

Summary of key process analysis results for San Jose - August 5

Page 24: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 25: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

May 22, 2002 25

Summary of key process analysis results for Stockton - August 5

Page 26: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 27: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

May 22, 2002 27

Summary of key process analysis results for Bakersfield - August 5

Page 28: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 29: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 30: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 31: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 32: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 33: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 34: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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)

Page 35: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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.

Page 36: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 37: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 38: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 39: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 40: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 41: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 42: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 43: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 44: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 45: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 46: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 47: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 48: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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.

Page 49: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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).

Page 50: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 51: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 52: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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

Page 53: May 22, 20021 UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN LOWERING 8-HOUR OZONE CONCENTRATIONS Steve Reynolds Charles Blanchard Envair 12

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