UNDERSTANDING THE EFFECTIVENESS OF PRECURSOR REDUCTIONS IN by zg0IdEC

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									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: steve@sreynolds.com


                    May 22, 2002               1
             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                     2
                 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                   3
                 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                 4
       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                 5
          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                 6
          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                   7
  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                 8
  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                9
   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                 10
1990 and 1999 Domain-wide Emissions
              Daily NOX Emissions for SARMAP Modeling                                            Daily ROG Emissions for SARMAP Modeling
                               Domain                                                                             Domain

       3000                                                                               4500
                                                                                          4000
       2500
                                                                                          3500
       2000                                                                               3000
tons




                                                                                   tons
                                                                     1990                 2500                                             1990
       1500
                                                                     1999                 2000                                             1999
       1000                                                                               1500
                                                                                          1000
        500
                                                                                           500
          0                                                                                  0
                Aug 3     Aug 4         Aug 5            Aug 6                                     Aug 3     Aug 4         Aug 5   Aug 6
                                  day                                                                                day


                                                   Daily CO Emissions for SARMAP Modeling Domain

                                                 18000
                                                 16000
                                                 14000
                                                 12000
                                                 10000
                                          tons




                                                                                                              1990
                                                  8000                                                        1999
                                                  6000
                                                  4000
                                                  2000
                                                     0
                                                            Aug 3    Aug 4         Aug 5          Aug 6
                                                                             day


                                                                    May 22, 2002                                                             11
Percentage Change in 1999 VOC, NOx, and
  CO Emissions Relative to 1990 Values

Area                     VOC                         NOx                          CO
              Aug3   Aug4 Aug5    Aug6   Aug3   Aug4 Aug5      Aug6   Aug3   Aug4 Aug5     Aug6
               Fri    Sat   Sun   Mon     Fri    Sat    Sun    Mon     Fri    Sat    Sun   Mon
San Jose       -32    -30   -27    -31    -34    -27     -17    -32    -43    -37    -33    -43
Stockton       -25    -20   -14    -22    -32    -27     -20    -33    -37    -33    -31    -37
Fresno         -28    -20   -19    -24    -25    -15      -4    -25    -36    -29    -29    -36
Visalia        -19    -16    -7    -12    -21    -10      7     -22    -31    -26    -23    -31
Bakersfield    -39    -39   -34    -36    -40    -38     -33    -41    -40    -36    -34    -40
Tulare         -19    -25    -4    -11    -20     0       9     -35    -16     -8     -3    -15
Lake




                                         May 22, 2002                                             12
   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                13
   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                  14
   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                  15
                                                        Peak 1-hour Ozone Isopleths (ppb) for San Jose Subregion - 5 August 1999

                                                    0       10      20       30       40      50       60       70        80   90   100
                                              100                                                                                     100



                                               90                                                                                     90



                                               80                                                                                     80
Percent of 1999 Anthropogenic NOx Emissions


                                               70                                                                                     70



                                               60                                                                                     60



                                               50                                                                                     50



                                               40                                                                                     40



                                               30                                                                                     30



                                               20                                                                                     20



                                               10                                                                                     10



                                                0                                                                                     0
                                                    0       10      20       30       40      50       60       70        80   90   100
                                                                         Percentage of 1999 Anthropogenic VOC Emissions




                                                                                  May 22, 2002                                              16
                                                    Peak 8-hour Ozone Isopleths (ppb) for San Jose Subregion - 5 August 1999

                                                    0     10     20       30       40      50       60       70        80   90   100
                                              100                                                                                  100



                                              90                                                                                   90



                                              80                                                                                   80
Percent of 1999 Anthropogenic NOx Emissions


                                              70                                                                                   70



                                              60                                                                                   60



                                              50                                                                                   50



                                              40                                                                                   40



                                              30                                                                                   30



                                              20                                                                                   20



                                              10                                                                                   10



                                               0                                                                                   0
                                                    0     10     20       30       40      50       60       70        80   90   100
                                                                      Percentage of 1999 Anthropogenic VOC Emissions




                                                                               May 22, 2002                                              17
                                                        Peak 1-hour Ozone Isopleths (ppb) for Stockton Subregion - 5 August 1999

                                                    0       10      20       30       40      50       60       70        80   90   100
                                              100                                                                                     100



                                               90                                                                                     90



                                               80                                                                                     80

Percent of 1999 Anthropogenic NOx Emissions
                                               70                                                                                     70



                                               60                                                                                     60



                                               50                                                                                     50



                                               40                                                                                     40



                                               30                                                                                     30



                                               20                                                                                     20



                                               10                                                                                     10



                                               0                                                                                      0
                                                    0       10      20       30       40      50       60       70        80   90   100
                                                                         Percentage of 1999 Anthropogenic VOC Emissions




                                                                                  May 22, 2002                                              18
                                                        Peak 8-hour Ozone Isopleths (ppb) for Stockton Subregion - 5 August 1999

                                                    0       10      20       30       40      50       60       70        80   90   100
                                              100                                                                                     100



                                              90                                                                                      90



                                              80                                                                                      80
Percent of 1999 Anthropogenic NOx Emissions


                                              70                                                                                      70



                                              60                                                                                      60



                                              50                                                                                      50



                                              40                                                                                      40



                                              30                                                                                      30



                                              20                                                                                      20



                                              10                                                                                      10



                                               0                                                                                      0
                                                    0       10      20       30       40      50       60       70        80   90   100
                                                                         Percentage of 1999 Anthropogenic VOC Emissions




                                                                                    May 22, 2002                                            19
                                                        Peak 1-hour Ozone Isopleths (ppb) for Bakersfield Subregion - 5 August 1999

                                                    0       10      20       30       40      50       60       70        80   90   100
                                              100                                                                                     100



                                              90                                                                                      90



                                              80                                                                                      80
Percent of 1999 Anthropogenic NOx Emissions

                                              70                                                                                      70



                                              60                                                                                      60



                                              50                                                                                      50



                                              40                                                                                      40



                                              30                                                                                      30



                                              20                                                                                      20



                                              10                                                                                      10



                                               0                                                                                      0
                                                    0       10      20       30       40      50       60       70        80   90   100
                                                                         Percentage of 1999 Anthropogenic VOC Emissions




                                                                                  May 22, 2002                                              20
                                                        Peak 8-hour Ozone Isopleths (ppb) for Bakersfield Subregion - 5 August 1999

                                                    0       10      20       30       40      50       60       70        80   90   100
                                              100                                                                                     100



                                              90                                                                                      90



                                              80                                                                                      80

Percent of 1999 Anthropogenic NOx Emissions

                                              70                                                                                      70



                                              60                                                                                      60



                                              50                                                                                      50



                                              40                                                                                      40



                                              30                                                                                      30



                                              20                                                                                      20



                                              10                                                                                      10



                                               0                                                                                      0
                                                    0       10      20       30       40      50       60       70        80   90   100
                                                                         Percentage of 1999 Anthropogenic VOC Emissions




                                                                                  May 22, 2002                                              21
          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                    22
Summary of key process analysis results for San Jose - August 5




                          May 22, 2002                            23
  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                 24
Summary of key process analysis results for Stockton - August 5




                         May 22, 2002                             25
  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                26
Summary of key process analysis results for Bakersfield - August 5




                        May 22, 2002                                 27
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                   28
  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                   29
  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                30
    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                   31
    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                32
           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                   33
Trends in annual 4th-highest maximum daily 8-hour ozone concentration, 1980
through 2000. Statistical significance (p<0.01) is indicated.




                              May 22, 2002                               34
Trends in annual maximum daily 1-hour ozone concentration, 1980
through 2000. Statistical significance (p<0.01) is indicated.

                        43 00



                                                                   Sacramento
                        42 50




                                                             Bethel Island
                        42 00                                            Stockton                      1-hour M aximum Tr e nd
                                       San Francisc o
                                                                                                         Sl ope Nega ti ve , Not Si gni ficant
                                                          Livermore              Modesto                 Sl ope Nega ti ve , Si gni ficant
                                                                                                         Sl ope P ositive, Not S ig ni fi ca nt
                        41 50
                                                        San Jose
      UTM n orth (km)




                        41 00


                                                                                                                 Fresno
                                                                                                             Parlier
                        40 50



                                                                                                         Hanford          Visalia
                        40 00




                        39 50
                                                                                                                                 Oildale
                                                                                                                                      Edison
                                                                                                                     Bakersf ield

                        39 00




                        38 50
                                52 5       57 5           62 5           67 5.         72 5           77 5            82 5             87 5
                                                                                     UTM ea st (km)



                                                                             May 22, 2002                                                         35
Diurnal patterns of ozone, NOx and CO at the San Jose 4th Street site




                              May 22, 2002                              36
Diurnal patterns of ozone, NOx and CO at the Stockton site




                         May 22, 2002                        37
Diurnal patterns of ozone, NOx and CO at the Bakersfield sites




                           May 22, 2002                          38
              Mean maximum hourly ozone on Top 21 days:
          Comparable numbers of sites with increases and decreases



20
                                                              Increasing WD O3
15
                 Number of sites with increasing ozone        Decreasing WD O3
10
                                                              Increasing WE O3
 5
                                                              Decreasing WE O3
 0

 -5                                                          Top 21 days
                                                             1998-2000
-10                                                          compared with
             Number of sites with decreasing ozone           1989-91
-15
      Bay area      Sacramento     SVV-north     SJV-south




                                       May 22, 2002                              39
                Mean maximum hourly O3/NOx on Top 21 days:
                 Many more sites with increases than decreases



10
           Number of sites with increasing O3/NOx        Increasing WD O3/NOx
 8
                                                         Decreasing WD O3/NOx
 6
                                                         Increasing WE O3/NOx
 4
                                                         Decreasing WE O3/NOx
 2

 0                                                      Top 21 days
                                                        1998-2000
-2                                                      compared with
           Number of sites with decreasing O3/NOx       1989-91
-4
     Bay area   Sacramento    SVV-north     SJV-south




                                     May 22, 2002                               40
                    Mean maximum hourly O3/CO on Top 21 days:
                    Many more sites with increases than decreases



12
                Number of sites with increasing O3/CO        Increasing WD O3/CO
10
                                                             Decreasing WD O3/CO
 8
                                                             Increasing WE O3/CO
 6
                                                             Decreasing WE O3/CO
 4

 2                                                          Top 21 days
                                                            1998-2000
 0                                                          compared with
     Number of sites with decreasing O3/CO                  1989-91
-2
     Bay area      Sacramento     SVV-north     SJV-south




                                        May 22, 2002                               41
                  Mean maximum hourly CO/NOx on Top 21 days:
                   Many more sites with decreases than increases


             Number of sites with increasing CO/NOx
 2
                                                           Increasing WD CO/NOx
 0
                                                           Decreasing WD CO/NOx
 -2
                                                           Increasing WE CO/NOx
 -4
                                                           Decreasing WE CO/NOx
 -6

 -8                                                       Top 21 days
                                                          1998-2000
-10                                                       compared with
                 Number of sites with decreasing CO/NOx   1989-91
-12
      Bay area    Sacramento    SVV-north     SJV-south




                                       May 22, 2002                               42
 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                   43
 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                44
Consistent increases in:
 > model-predicted NO cycles from 1990 to 1999
 > ambient ozone/NOx ratios, 1989-91 and 1998-00


  4
         Model          Ambient data
3.5
         NO cycles      O3/NOx                1999
  3                                           WE

2.5
                                       1990
  2                                    WE
1.5
                              1999
               1999
  1    1990           1990    WD
                      WD
0.5

  0
                        San Jose




                      May 22, 2002                   45
Consistent increases in:
 > model-predicted NO cycles from 1990 to 1999
 > ambient ozone/NOx ratios, 1989-91 and 1998-00


6
    Model
                              Ambient data
    NO cycles
5                             O3/NOx            1999
                                                WE
4

                                         1990
3
                                         WE

2                                1999
                1999
      1990             1990      WD
1                      WD


0
                         Stockton




                       May 22, 2002                    46
Consistent increases in:
 > model-predicted NO cycles from 1990 to 1999
 > ambient ozone/NOx ratios, 1989-91 and 1998-00

12
     Model
                               Ambient data
     NO cycles
10                             O3/NOx            1999
                                                 WE
 8
                                  1999
                                  WD
 6


 4               1999   1990              1990
       1990             WD                WE
 2


 0
                         Bakersfield




                        May 22, 2002                    47
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.
                                                  Hours w ith ozone 80 to 120 ppbv                                                             Hours w ith ozone greater than 120 ppbv




                                                                                                                                                                                          1



                                                                                                                                                                                                             204


                                                                                                                                                                                                                          117
                                                                                                                                                               805


                                                                                                                                                                               728
                                                                                  686




                                                                                                                 1753




                                                                                                                                             89
                                                     14972




                                                                                                  5022
                                   4527




                                                                  12882
                             100                                                                                                      100
                              90                                                                                                       90
                              80                                                                                                       80
       Frequency (percent)




                              70                                                                                                       70
                              60                                                                                                       60
                              50                                                                                                       50
                              40                                                                                                       40
                              30                                                                                                       30
                              20                                                                                                       20
                              10                                                                                                       10
                               0                                                                                                        0
                                                                  Southern SJV




                                                                                                                                              Northern SJV




                                                                                                                                                                           Southern SJV
                                   Northern SJV




                                                                                                                                                                                          Northern SAC

                                                                                                                                                                                                         Southern SAC
                                                                                 Northern SAC




                                                                                                                                                                                                                        San Francisco
                                                                                                Southern SAC


                                                                                                               San Francisco
                                                    Central SJV




                                                                                                                                                             Central SJV
                                                                                                                               Limiting Pre cursor

                                       All days March - October                                                                     NOx
                                       1994 - 2000
                                                                                                                                    Tran sitional

                                                                                                                                    VOC

                                                                                                                     May 22, 2002                                                                                                       48
Central California            1991-98                  In all areas, frequency of NOx
Texas                         1993-99                  limited hours is greater for hours
Southern California           1994-97
Atlanta                       1994-99                  with ozone>120 ppbv (right)
Northeast and mid-Atlantic    1994-99                  than for hours with ozone
Southern Lake Michigan area   1994-98
                                                       > 80 ppbv (left).

                                        May 22, 2002                                   49
Extent of reaction during 1-hour and 8-hour episode days in 1994-2000 versus
sequence of days within an episode
                                                                      1HOUR                                                                                8 HOUR
                                                    2.0
                                                                                                                                        2.0
                                                    1.8   Livermore
                                                                                                                                       1.75
                                                                                                                                                 Livermore
                                                    1.6




                                                                                                            Exte nt o f Rea ction
                            Exte nt o f Rea ction
                                                    1.4                                                                                 1.5
                                                    1.2                                                                                1.25
                                                    1.0
                                                                                                                                        1.0
                                                    0.8
                                                                                                                                       0.75
                                                    0.6
                                                    0.4                                                                                 0.5
                                                    0.2                                                                                0.25
                                                     0
                                                                                                                                             0
                                                                1           2              3
                                                                                                                                                           1                 2
                                                                     Day of Ep isode
                                                                                                                                                           Da y of Ep isod e
                                                    2.0                                                                                 2.0
                                                    1.8   Stockton                                                                               Stockton
                                                                                                                                       1.75
                                                    1.6




                                                                                                               Exte nt o f Rea ction
                    Exte nt o f Rea ction




                                                    1.4                                                                                 1.5

                                                    1.2                                                                                1.25
                                                    1.0                                                                                 1.0
                                                    0.8
                                                                                                                                       0.75
                                                    0.6
                                                    0.4                                                                                 0.5

                                                    0.2                                                                                0.25

                                                     0                                                                                       0
                                                                                                                                                     1      2       3       4    5
                                                            1              2           3
                                                                                                                                                           Da y of E pi sod e
                                                                    Day of Ep isode

                                                    2.0                                                                                2.0
                                                    1.8   Bakersfield                                                                            Bakersfield
                                                                                                                                       1.75
                                                    1.6
                                                                                                     Exte nt o f Rea ction


                                                                                                                                       1.5
             Exte nt o f Rea ction




                                                    1.4
                                                                                                                                       1.25
                                                    1.2
                                                    1.0                                                                                1.0
                                                    0.8                                                                                0.75
                                                    0.6
                                                                                                                                       0.5
                                                    0.4
                                                                                                                                       0.25
                                                    0.2
                                                     0                                                                                  0
                                                                1     2   3      4   5                                                           1       2 3 4 5 6 7 8 9 10
                                                                     Day of Epis ode                                                                        Day o f Ep isode

                                                                                               May 22, 2002                                                                          50
                  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                   51
                  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                52
   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




                       May 22, 2002                   53

								
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