A41A-0021
An Improved, Automated Whole-Air Sampler and VOC Analysis System: Results from SONGNEX 2015

Thursday, 17 December 2015
Poster Hall (Moscone South)
Brian M Lerner1, Jessica Gilman2,3, Travis Wade Tokarek4, Jeff Peischl2,3, Abigail Koss2,3, Bin Yuan2,3, Carsten Warneke2,3, Gabriel A Isaacman-VanWertz5, Donna Sueper6,7 and Joost A De Gouw2,3, (1)NOAA Boulder, Boulder, CO, United States, (2)Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, United States, (3)NOAA ESRL Chemical Sciences Division, Boulder, CO, United States, (4)University of Calgary, Chemistry, Calgary, AB, Canada, (5)Massachusetts Institute of Technology, Cambridge, MA, United States, (6)Aerodyne Research Inc., Billerica, MA, United States, (7)University of Colorado at Boulder, Boulder, CO, United States
Abstract:
Accurate measurement of volatile organic compounds (VOCs) in the troposphere is critical for the understanding of emissions and physical and chemical processes that can impact both air quality and climate. Airborne VOC measurements have proven challenging due to the requirements of short sample collection times (=10 s) to maximize spatial resolution and sampling frequency and high sensitivity (pptv) to chemically diverse hydrocarbons, halocarbons, oxygen- and nitrogen-containing VOCs. NOAA ESRL CSD has built an improved whole air sampler (iWAS) which collects compressed ambient air samples in electropolished stainless steel canisters, based on the NCAR HAIS Advanced Whole Air Sampler [Atlas and Blake]. Post-flight chemical analysis is performed with a custom-built gas chromatograph-mass spectrometer system that pre-concentrates analyte cryostatically via a Stirling cooler, an electromechanical chiller which precludes the need for liquid nitrogen to reach trapping temperatures.

For the 2015 Shale Oil and Natural Gas Nexus Study (SONGNEX), CSD conducted iWAS measurements on 19 flights aboard the NOAA WP-3D aircraft between March 19th and April 27th. Nine oil and natural gas production regions were surveyed during SONGNEX and more than 1500 air samples were collected and analyzed. For the first time, we employed real-time mapping of sample collection combined with live data from fast time-response measurements (e.g. ethane) for more uniform surveying and improved target plume sampling. Automated sample handling allowed for more than 90% of iWAS canisters to be analyzed within 96 hours of collection – for the second half of the campaign improved efficiencies reduced the median sample age at analysis to 36 hours. A new chromatography peak-fitting software package was developed to minimize data reduction time by an order of magnitude without a loss of precision or accuracy.

Here we report mixing ratios for aliphatic and aromatic hydrocarbons (C2-C8) along with select oxygenated species (alcohols and ketones) and cycloalkanes. We present an intercomparison of the GC-MS analysis system and iWAS samples from SONGNEX with a new H3O+ CIMS-TOF and a spectroscopic ethane measurement that also flew aboard the NOAA WP-3D aircraft during SONGNEX. We also consider the effect of sample age on observed mixing ratio.

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