Trace Organic Gas Analyzer Time-of-Flight mass spectrometer (TOGA-TOF) system for airborne observations of formaldehyde
Year: 2026
Type: article
Abstract: . Formaldehyde (HCHO) is a ubiquitous atmospheric constituent, originating from primary emissions (natural and anthropogenic) and secondary production via the oxidation of volatile organic compounds (VOCs). In addition to being a regulated pollutant, HCHO is a key species used as a tracer of recent photochemical activity due to its short atmospheric lifetime and its role as a source of HOx radicals. Given its diverse sources and high spatial variability, HCHO is challenging to represent accurately in chemical transport models, often resulting in significant discrepancies with observations. Airborne in-situ measurements of HCHO, especially when combined with VOC precursor data, offer valuable insights into its atmospheric distributions for evaluating models. Here, we present HCHO observations from the NSF NCAR Trace Organic Gas Analyzer with Time-of-Flight mass spectrometer (TOGA-TOF), deployed during the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign. While most HCHO instruments target at most a few selected species for measurement, the TOGA-TOF employs a rapid gas chromatography-mass spectrometry (GC/MS) technique and provides discrete VOC measurements—including >100 C1–C10 species—at a time resolution of less than 2 minutes. We compare TOGA-TOF HCHO data to measurements from three 1-Hz instruments aboard the NASA DC-8: the Compact Atmospheric Multi-species Spectrometer (CAMS), the In Situ Airborne Formaldehyde (ISAF) instrument, and a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS). The wide dynamic range of observed HCHO concentrations (from < 100 ppt to ~100 ppb) during FIREX-AQ enabled a robust intercomparison. TOGA-TOF HCHO agreed well with CAMS (slope = 1.1), with similar agreement with the PTR-ToF-MS, while larger discrepancies were observed with ISAF (slope = 1.5), likely due to differences in calibrations. Normalized excess mixing ratios (NEMRs) of HCHO relative to CO in wildfire plumes exhibited consistent trends with plume age across instruments. These findings highlight the TOGA-TOF’s capability for highly sensitive and accurate airborne HCHO measurements.
Authors: Daun Jeong, Rebecca S. Hornbrook, Alan J. Hills, Glenn Diskin, Hannah S. Halliday, Joshua P. DiGangi, Alan Fried, Dirk Richter, James Walega, Petter Weibring, Thomas F. Hanisco, Glenn M. Wolfe, Jason St. Clair, Jeff Peischl, Armin Wisthaler, Tomas Mikoviny, John B. Nowak, Felix Piel, Laura Tomsche, Christopher D. Holmes, Amber Soja, Emily Gargulinski, James H. Crawford, Jack Dibb, Carsten Warneke, Joshua Schwarz, Eric C. Apel
Institution: NSF National Center for Atmospheric Research
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,585
Awards: G2282039835, The Management and Operation of the National Center for Atmoshperic Research (NCAR), IN SUPPORT OF THE SCIENCE GOALS OF THE SUMMER 2019 NASA FIRECHEM MISSION WE PROPOSE TO DEPLOY THE TRACE ORGANIC GAS ANALYZER (TOGA) COUPLED TO A HIGH RESOLUTION (HR) TOFWERK TIME-OF-FLIGHT (TOF) MASS SPECTROMETER (FAST GAS CHROMATOGRAPH/MASS SPECTROMETER; GC/MS) ON THE NASA DC-8 TO PROVIDE CONTINUOUS ACCURATE AND SENSITIVE MEASUREMENTS OF A LARGE SUBSET OF NONMETHANE ORGANIC COMPOUNDS (NMOC) INCLUDING MANY CAMPAIGN PRIORITY LEVEL 1 AND 2 SPECIES. BY PROVIDING A FULL HIGH-RESOLUTION MASS SPECTRUM CONTINUOUSLY AT 50 HZ RATE OR BETTER THE TOF MS OFFERS MANY ADVANTAGES OVER OUR PREVIOUSLY-DEPLOYED QUADRUPOLE MS THAT RELIED ON SCANNING A SINGLE ION MASS FRAGMENT FOR EACH COMPOUND OF INTEREST. THE TOF MS ENSURES THAT: (1) NO CHEMICAL INFORMATION IS LOST BY ELIMINATING THE NEED TO PRE-SELECT TARGET IONS PRIOR TO COLLECTING DATA; (2) FULL MASS SPECTRA ARE AVAILABLE FOR ADVANCED COMPOUND IDENTIFICATION EVEN AFTER THE FACT VIA ESTABLISHED MASS SPECTRA LIBRARIES; (3) FAR MORE SPECIES CAN BE QUANTIFIED; (4) NARROW CHROMATOGRAPHIC PEAKS LESS THAN 0.6 S FULL WIDTH AT HALF MAXIMUM (FWHM) DO NOT PRESENT AN ANALYTICAL LIMITATION THAT IS PRESENT IN THE QUADRUPOLE SYSTEM (DUE TO SLOWER SCANNING RATES); (5) HIGH MASS RESOLUTION ALLOWS FOR THE SEPARATION OF ISOBARS A LIMITATION EVEN WITH GC SEPARATION BUT ESPECIALLY WHEN USING FAST GC METHODS; AND (6) GOOD MASS ACCURACY ALLOWS FOR UNAMBIGUOUS IDENTIFICATION OF PEAKS AND CLEAN SEPARATION OF CO-ELUTING SPECIES. THE DETECTION QUALIFICATIONS WILL ENCOMPASS SPECIES WITH MELTING POINTS>-190 C AND BOILING POINTS BETWEEN -45 C AND 220 C. THIS WILL COVER COMPOUNDS IN THE RANGE OF C3-C10 NON-METHANE HYDROCARBONS (INCLUDING ISOPRENE AND SPECIATED MONOTERPENES) C1-C7 OXYGENATED VOLATILE ORGANIC COMPOUNDS INCLUDING ALCOHOLS ALDEHYDES AND KETONES BUT NOT ACIDS C1-C2 HALOCARBONS C1-C4 ALKYL NITRATES HCN CH3CN AND DIMETHYL SULFIDE. WITH THE EXCEPTION OF THE UPGRADED TOF DETECTOR THE TOGA WE WILL PROPOSE TO DEPLOY HAS BEEN USED IN SEVEN PREVIOUS AIRBORNE MISSIONS WITH EXCELLENT PERFORMANCE AND DATA COVERAGE AND IS CURRENTLY A PART OF THE NASA ATMOSPHERIC TOMOGRAPHY (ATOM) PROJECT ON THE NASA DC-8. DURING THESE DEPLOYMENTS A 35-S INTEGRATED SAMPLE WAS COLLECTED AND ANALYZED EVERY 2 MINUTES. USING THE TOF WILL ENABLE FASTER CHROMATOGRAPHY AS IT WILL ALLOW FOR NARROWER PEAKS WHICH WILL HELP US REDUCE OUR DUTY CYCLE TO 1.5 MINUTES. LIMITS OF DETECTION (LODS) FOR THE QUADRUPOLE VERSION ARE LESS THAN OR EQUAL TO ~1 PPTV FOR MOST SPECIES THESE ARE EXPECTED TO BE SIMILAR FOR THE TOF. FURTHERMORE WE ARE DEPLOYING THE TOGA-TOF ON THE NSF/NCAR FOR THE WE-CAN CAMPAIGN IN SUMMER 2018. WE ALSO PROPOSE TO DEPLOY A CANISTER SAMPLING SYSTEM AS AN ADD-ON TO THE TOGA-TOF USING THE RECENTLY DEVELOPED ENTECH SILONITE MINICANS . THIS WILL ALLOW US TO COLLECT WHOLE AIR SAMPLES IN 1 SECOND WHILE SAMPLING THE CENTER OF FIRE PLUMES. THE MINICANS WILL BE ANALYZED WITH THE TOGA-TOF DURING POST-FLIGHT OR ON MAINTENANCE DAYS. WE HAVE BEEN WORKING WITH AERODYNE RESEARCH INC. TO OPTIMIZE OUR DATA ANALYSIS AND PROCESSING. AN AUTOMATED DATA ANALYSIS TOOL WILL ALLOW IN-FLIGHT PROCESSING SO THAT MIXING RATIOS OF KEY SPECIES WILL BE AVAILABLE TO THE MISSION SCIENTIST IN REAL-TIME. THE INSTRUMENT PACKAGE WILL BE FITTED INTO 1.5 GV RACKS AND WILL CONSUME LESS THAN 2000 W OF POWER. BECAUSE THERE IS STILL MUCH TO BE DISCOVERED WITH QUANTIFYING FIRE EMISSIONS THE POWERFUL TOGA-TOF INSTRUMENT IS IDEAL FOR THE FIRECHEM EXPERIMENT AS IT IS CAPABLE OF IDENTIFYING AND QUANTIFYING BOTH KNOWN (TARGETED) AND UNKNOWN (UNTARGETED) SPECIES IN THE CRITICALLY IMPORTANT QUALIFIED RANGE OF VOCS DETECTABLE BY THIS TECHNIQUE. THE TOGA-TOF WILL BE HIGHLY COMPLEMENTARY TO OTHER POTENTIAL ON-BOARD NMOC MEASUREMENTS SUCH AS THE PTR-TOF-MS WHOLE AIR SAMPLE (WAS) CANISTERS AND CIMS INSTRUMENTS., G7198630863
OpenAlex ID: W4415148759
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