1. Total Non-Methane Organic Carbon Christophe Maris, Myeong Chung, Udo Krischke, Richard Meller and Suzanne Paulson Department of Atmospheric Sciences University of California at Los Angeles Funding Provided by California Air Resources Board UC Campus-Laboratory Collaboration California Space Institute

2. Motivation  The goal of this work is to 1. Measure total non- methane organic compounds (TNMOC), and  2. Determine the relationship between TNMOC and the sum of the speciated volatile organic compounds (VOC’s) measured by standard techniques.  VOC’s are one of the key determinants of air quality and control strategies.  Standard measurement methods are known to detect hydrocarbons and their oxidation products incompletely.

3. Possible Sources of Excess TNMOC compared to the Sum of Speciated VOC’s (Standard VOC Measurement)  Compounds that are lost in the inlet or column (polars, semi-volatiles).  Compounds that are obscured in the GC baseline (hydrocarbons).  Heteroatom compounds that have a reduced response in an FID.

4. Method 1.Trap VOC’s from 2 ambient air samples simultaneously in a cryogenically cooled trap. Allow CO, CO 2, and CH 4 to pass through. 2.Desorb both VOC samples. Speciated VOC’s: analyze directly with DB-1 Column, GC/FID. = Standard Measurement TNMOC: oxidize CO 2, analyze as methane w/ GC/FID. = True total of VOC’s 3. Compare TNMOC with the standard measurement of VOC’s.

5. Flow Schematic

7.  of Speciated VOC’s = 450 ppbC TNMOC = 620 ppbC

8. Trapping Efficiency

9. Chamber Oxidation of m-Xylene

10. TNMOC/  of Speciated VOC’s Location/DateAverage RatioSite Description Azusa 9-10/97 1.3 (  0.3) Downwind Site UCLA 8/99 1.4 (  0.4) Upwind, Elevated Burbank 9/99 1.1 (  0.2) Heavily Source Influenced UCLA 9-10/00 2.0 (  0.7) Upwind, Elevated UCLA 12/00 1.2 (  0.15) Upwind, Elevated

11. Weekend/Weekday UCLA 2000 SeasonDay of Week/ Weather Average TNMOC (ppbC) Average TNMOC/Sum of Speciated VOC’s Sept-OctWeekday Sunny 444  3301.56  0.41 (stdev-mean=0.04) Weekend Sunny 328  1502.03  0.76 (stdev-mean=0.1) Weekday Cloudy 280  1272.3  0.54 (stdev-mean=0.07) Weekend Cloudy 157  582.16  0.68 (stdev-mean=0.08) Nov-DecWeekday 350  1501.18  0.14 (stdev-mean=0.02) Weekend 175  1201.26  0.3 (stdev-mean=0.05)

12. Weekend/Weekday UCLA 2000 Season Day of Week/ Weather Average TNMOC (ppbC) Average TNMOC/Sum of Speciated VOC’s TNMOC-Sum of Sp. VOC’s (ppbC) Sept-OctWeekday Sunny 444  3301.56  0.41 (stdev-mean=0.04) 142  117 Weekend Sunny 328  1502.03  0.76 (stdev-mean=0.1) 134  50 Weekday Cloudy 280  1272.3  0.54 (stdev-mean=0.07) 148  55 Weekend Cloudy 157  582.16  0.68 (stdev-mean=0.08) 81  45 Nov-DecWeekday 350  1501.18  0.14 (stdev-mean=0.02) 45  31 Weekend 175  1201.26  0.3 (stdev-mean=0.05) 27  22

13. Excess VOC’s and O 3 at West LA

14. 9/15/00 Friday

15. UCLA Summer, All Data

16. Weekday vs. Weekend

17. Sunny vs. Cloudy Days

18. UCLA Winter

19. Excess VOC’s vs. VOC Concentration

20. UCLA Weekday Summer 2000 R=0.5 R=0.3

21. 9/13/00 Wednesday, 9/17/00 Sunday

22. Conclusions  Standard VOC measurement underestimates VOC level typically by 10-60%, total can be up to 5x higher than the sum of speciated VOC’s.  Ratio of TNMOC/  of speciated VOC’s is often inversely related to the VOC and NOx concentrations.  Excess may be associated with photochemical activity, and possibly with mixing from aloft.  Excess varies strongly with location, day of week and meteorology.  Chemical identity and source of excess VOC’s is still to be determined.