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)

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

PTR-MS as mounted onboard the NOAA WP-3 aircraft Weight 300 lbs Power 750 W

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

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 ?”

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

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

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

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

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

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

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

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

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

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

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

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