Source Characterization of Formaldehyde in the Wintertime Eastern US

Formaldehyde is one of the most ubiquitous volatile organic compounds (VOCs) in the atmosphere. Photolysis of formaldehyde is a highly-significant production pathway for HOx, a key radical family in tropospheric ozone production. For much of the year, regional formaldehyde concentrations are determined by the photochemical oxidation of virtually all VOCs. In the winter, however, a rapid decline in biogenic VOC emissions makes direct anthropogenic emissions of formaldehyde more relevant on a regional scale. Few regional measurements of formaldehyde during the winter season exist to permit study of the relative significance of primary and secondary formaldehyde. We will present analysis of the sources of formaldehyde observed in the eastern United States winter during the Wintertime Investigation of Transport, Emission, and Reactivity (WINTER) 2015 campaign. The WINTER 2015 campaign provided a unique dataset of VOC precursors, oxidants, and other trace species, permitting the identification of primary and secondary formaldehyde. We will also discuss the diurnal and regional dependences of wintertime formaldehyde concentrations as well as comparisons with other recent airborne campaigns (e.g. DISCOVER-AQ).