analysis of voc to nox ratios in the south coast air basin

Analysis of VOC to Analysis of VOC to NOx Ratios in the NOx Ratios in the South Coast Air South Coast Air

BasinBasin

Eileen McCauleyResearch Division

Air Resources Board

California Environmental Protection Agency

MethodologyMethodology

TNMOC from PAMS used for VOC concentration– 3 hour canister samples– C2 - C10 hydrocarbons

NOx concentrations are averages of 3 one hour average

AzusaAzusa

Azusa 1995-1998All VOC/NOx data

0

5

10

15

20

25

0:00 4:00 8:00 12:00 16:00 20:00 0:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

BanningBanning

Banning 1997-1998All VOC/NOx data

0

5

10

15

20

25

4:00 8:00 12:00 16:00 20:00 0:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

8:00 Weekday value of 33

BurbankBurbank

Burbank 1998 (+ 9 days in 1997)All VOC/NOx data

0

5

10

15

20

25

4:00 8:00 12:00 16:00 20:00 0:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

HawthorneHawthorne

Hawthorne 1997-1998All VOC/NOx data

0

5

10

15

20

25

4:00 8:00 12:00 16:00 20:00 0:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

17:00 Weekday values of 28 and 36

LA North MainLA North Main

LA N. Main 1995-1998All VOC/NOx data

0

5

10

15

20

25

0:00 4:00 8:00 12:00 16:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

UplandUpland

Upland 1995, 1997, 1998All VOC/NOx data

0

5

10

15

20

25

0:00 4:00 8:00 12:00 16:00 20:00 0:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

Azusa Average Azusa Average VOC/NOxVOC/NOx

Azusa 1995-1998Average VOC/NOx

0.00

2.00

4.00

6.00

8.00

10.00

12.00

0:00

2:00

3:00

5:00

6:00

8:00

9:00

11:00

12:00

14:00

15:00

17:00

18:00

20:00

21:00

23:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

Banning Average Banning Average VOC/NOxVOC/NOx

Banning 1997-1998Average VOC/NOx

0.0

2.0

4.0

6.0

8.0

10.0

12.0

2:00 5:00 8:00 11:00 14:00 17:00 20:00 23:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

Burbank Average Burbank Average VOC/NOxVOC/NOx

Burbank 1998 (+ 9 days in 1997)Average VOC/NOx

0.00

2.00

4.00

6.00

8.00

10.00

12.00

2:00 5:00 8:00 11:00 14:00 17:00 20:00 23:00

Start Timefor 3 hr sample

ppbC

/ppb

Weekday Weekend

Hawthorne Average Hawthorne Average VOC/NOxVOC/NOx

Hawthorne 1997-1998Average VOC/NOx

0.00

2.00

4.00

6.00

8.00

10.00

12.00

2:00 5:00 8:00 11:00 14:00 17:00 20:00 23:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

LA North Main LA North Main Average VOC/NOxAverage VOC/NOx

LA N. Main 1995-1998Average VOC/NOx

0.00

2.00

4.00

6.00

8.00

10.00

12.00

5:00 12:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

Upland Average Upland Average VOC/NOxVOC/NOx

Upland 1995, 1997, 1998Average VOC/NOx

0.00

2.00

4.00

6.00

8.00

10.00

12.00

0:00

2:00

3:00

5:00

6:00

8:00

9:00

11:00

12:00

14:00

15:00

17:00

18:00

20:00

21:00

23:00

Start Time for 3 hr sample

ppbC

/ppb

Weekday Weekend

Percent Weekend Percent Weekend IncreaseIncrease

Percent Increase in Weekend VOC/NOx

-40

-30

-20

-10

0

10

20

30

40

50

60

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00

Start Time for 3 hr Samples

% In

crea

se

Azusa Banning Burbank Hawthorne N Main Upland

THC vs PAMSTHC vs PAMS

Time Az Bn Bb Hw NM Up5:00 1.30 1.54 1.08 1.34 1.28 1.486:00 1.51 1.358:00 1.40 1.06 1.33 1.00 1.389:00 1.45 1.06

11:00 1.41 2.02 1.20 1.11 1.3612:00 1.39 1.23 1.29

Weekday TNMOC/Weekend TNMOC

Both the 8202 and Beckman THC instruments observed approx.10 - 20% weekend decrease.

Is there a change in VOC inventoryon the weekend?

Recommendations:Recommendations:

Calculate VOC/NOx ratios with carbonyls data and/or correction to total

18 months of hourly total VOC measurements at several sites in SOCAB

Investigate possible differences in weekday / weekend data of THC and PAMS