Wintertime Formaldehyde: Airborne Observations and Source Apportionment Over the Eastern United States. Issue 5 (25th February 2021)

• Record Type: Journal Article
• Authors: Green, Jaime R.; Fiddler, Marc N.; Fibiger, Dorothy L.; McDuffie, Erin E.; Aquino, Janine; Campos, Teresa; Shah, Viral; Jaeglé, Lyatt; Thornton, Joel A.; DiGangi, Joshua P.; Wolfe, Glenn M.; Bililign, Solomon; Brown, Steven S.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 5(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-25
• Subjects: Airborne observations -- formaldehyde -- primary production -- secondary production -- urban emissions -- WINTER; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2020JD033518
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Formaldehyde (HCHO) is generated from direct urban emission sources and secondary production from the photochemical reactions of urban smog. HCHO is linked to tropospheric ozone formation, and contributes to the photochemical reactions of other components of urban smog. In this study, pollution plume intercepts during the Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign were used to investigate and characterize the formation of HCHO in relation to several anthropogenic tracers. Analysis of aircraft intercepts combined with detailed chemical box modeling downwind of several cities suggests that the most important contribution to observed HCHO was primary emission. A box model analysis of a single plume suggested that secondary sources contribute to 21 ± 10% of the observed HCHO. Ratios of HCHO/CO observed in the northeast US, from Ohio to New York, ranging from 0.2% to 0.6%, are consistent with direct emissions combined with at most modest photochemical production. Analysis of the nocturnal boundary layer and residual layer from repeated vertical profiling over urban influenced areas indicate a direct HCHO emission flux of 1.3 × 10 14 molecules cm −2 h −1 . In a case study in Atlanta, GA, nighttime HCHO exhibited a ratio to CO (0.6%–1.8%) and was anti‐correlated with O3 . Observations were consistent with mixing between direct HCHO emissions in urban air masses with those influenced by more rapid HCHO photochemical production. The HCHO/CO emissions ratios determined from the measured data are 2.3–15 times greater than the NEI 2017 emissions database. The largest observed HCHO/CO was 1.7%–1.8%, located near co‐generating power stations. Key Points: Primary emissions dominate the wintertime formaldehyde (HCHO) budget in the northeastern US, though secondary production impacts HCHO formation downwind of urban areas Observed HCHO/CO emissions ratios are 2.3–15 times greater than the regionally integrated National Emission Inventory (NEI) 2017 database Point source HCHO emissions may be underestimated by a factor of 17–23, depending on the fuel type