1. PTR-MS Measurements of Atmospheric VOCs
Carsten Warneke & Joost de Gouw
NOAA Earth System Research Laboratory
and
CIRES, University of Colorado
Boulder, Colorado
Outline:
PTR-MS and PIT-MS measurements
GC-PTR-MS for identification
Evolution of VOCs in fire plumes (airborne measurements)

2. Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) (de Gouw and Warneke, 2007)
1. Ionization of organic compounds R by:
H3O+ + R  RH+ + H2O
2. Detection of RH+ with mass spectrometer
H3O++R reaction is exothermic and fast for:
alkenes alcohols ketones
aromatics aldehydes acids etc.
H3O++R reaction is endothermic for:
N2 CO CH4 alkanes
O2 CO2 N2O ozone
Can be detected with fast response time (1s)
Are not detected

3. PTR-MS as mounted
onboard the NOAA WP-3 aircraft
Weight lbs
Power W

4. PIT-MS
Proton Transfer
Ion
Trap -
Mass
Spectrometry
PIT-MS uses ion trap mass spectrometer
+ faster time response
+ Identification with CID (collision induced dissociation)
less sensitive

5. Key Problems with PTR-MS
“You only determine the mass. How can you be sure that the signal at a certain mass is due to one particular VOC ?”

6. GC-PTR-MS setup
VOCs are separated by retention time and detected by PTR-MS

7. GC-PTR-MS Analyses of Urban Air Samples
Methanol, acetonitrile, acetaldehyde and acetone are
mostly detected without significant interference

8. GC-PTR-MS Analyses of Urban Air Samples
Benzene, toluene and styrene are uniquely detected
PTR-MS determines the sum of C8- and C9-benzenes

9. 2004 Forest Fire Season in North America
Satellite image
Fires late June and early July
Andreas Stohl, using data from MODIS & Center for International Disaster Information

10. Observation of Smoke Plumes over the U.S.
On July 20 and 21 the
WP-3 sampled the smoke here
Smoke plume at sunset on July 19
GOES-EAST visible imagery at 1 km resolution
Courtesy of Owen Cooper

11. Acetonitrile is a Tracer for the Smoke Plumes
Smoke intercepted over Pennsylvania on July 20
Smoke intercepted over Cape Cod on July 21

12. Acetonitrile is a Tracer for the Smoke Plumes
Large acetonitrile enhancements in forest fire plumes

13. Acetonitrile is a Tracer for the Smoke Plumes
Small acetonitrile enhancements in urban plumes (New York City and Boston)

14. FLEXPART Reproduces Observations Very Well
0-10 km injection in many cases the best description

15. Forest Fire Plumes were not well Processed
Long transport times, but still some very reactive VOCs 
OH low in the plumes?
No production of OVOCs
We need to know the emission ratios

16. PTR-MS Measurements from BB Experiments
Holzinger et al., 1999:
Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide

17. PTR-MS Measurements from BB Experiments
MPI Mainz
Holzinger et al., 1999:
Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide
Fire Lab. Missoula
Christian et al., 2003
Comprehensive laboratory measurements of biomass-burning emissions: 1. Emissions from Indonesian, African, and other fuels
Christian et al., 2004:
Comprehensive laboratory measurements of biomass-burning emissions: 2. Intercomparison of open-path FTIR, PTR-MS, and GC- MS/FID/ECD