Imaging VOC distribution in cities and tracing VOC emission sources with a novel mobile proton transfer reaction mass spectrometer*

Volatile organic compounds (VOCs) are important precursors of ozone (O3) and secondary organicaerosols (SOAs). Tracing VOC pollution sources is important for controlling VOC emissions and reducingO3 and SOAs. We built a novel mobile proton transfer reaction mass spectrometry (M-PTR-MS) instrument to image the distribution of VOCs and trace their emission sources in cities and industrial parks.The M-PTR-MS is composed of a vibration-resistant proton transfer reaction mass spectrometry (PTRMS) with a global positioning system receiver, modifified box vehicle, and geographic information system(GIS) software. The PTR-MS, mounted on a vehicle, sends VOC data and vehicle position information tothe GIS software. These data are used to image the space distribution of VOCs in real time while thevehicle platform is in motion and the VOC sources are precisely traced using the GIS. The spatial dataresolution of the M-PTR-MS is typically 0.8 m. The limits of detection, sensitivity, and repeatability of theM-PTR-MS are 43.5 ppt, 347 counts ppb 1 , and 2.4% (RSD, n ¼ 5), respectively. The intensity of reagentions is stable over 8 h (RSD¼ 0.45%). Compared with commercial PTR-MS equipment, the M-PTR-MSdemonstrated high consistency, with a correlation coeffificient of 92.665%. Several fifield experiments wereconducted in China using the M-PTR-MS. In one fifield experiment, the VOC distribution along threedifferent routes was surveyed; the navigation monitoring lasted 1.8 h over a distance of 26.7 km at anaverage speed of 15 km h 1 . The VOC sources in an industrial park were identifified by analyzing thecomponents near different factories. The main species from a VOC source in an underground garage wasrelated to paint. The M-PTR-MS instrument can be used by environmental protection agencies to traceVOC pollution sources in real time, and by researchers to survey VOC emissions in regions of concern.© 2020 Elsevier Ltd. All rights reserved.