Measurement report: Photochemical production and loss rates of formaldehyde and ozone across Europe

Abstract

Abstract. Various atmospheric sources and sinks regulate the abundance of tropospheric formaldehyde (HCHO), which is an important trace gas impacting the HOx (≡ HO2 + OH) budget and the concentration of ozone (O3). In this study, we present the formation and destruction terms of ambient HCHO and O3 calculated from in situ observations of various atmospheric trace gases measured at three different sites across Europe during summertime. These include a coastal site in Cyprus, in the scope of the Cyprus Photochemistry Experiment (CYPHEX) in 2014, a mountain site in southern Germany, as part of the Hohenpeißenberg Photochemistry Experiment (HOPE) in 2012, and a forested site in Finland, where measurements were performed during the Hyytiälä United Measurements of Photochemistry and Particles (HUMPPA) campaign in 2010. We show that, at all three sites, formaldehyde production from the OH oxidation of methane (CH4), acetaldehyde (CH3CHO), isoprene (C5H8) and methanol (CH3OH) can almost completely balance the observed loss via photolysis, OH oxidation and dry deposition. Ozone chemistry is clearly controlled by nitrogen oxides (NOx ≡ NO + NO2) that include O3 production from NO2 photolysis and O3 loss via the reaction with NO. Finally, we use the HCHO budget calculations to determine whether net ozone production is limited by the availability of VOCs (volatile organic compounds; VOC-limited regime) or NOx (NOx-limited regime). At the mountain site in Germany, O3 production is VOC limited, whereas it is NOx limited at the coastal site in Cyprus. The forested site in Finland is in the transition regime.

Atmospheric Formaldehyde Monitored by TROPOMI Satellite Instrument throughout 2020 over São Paulo State, Brazil

“…However, the emission of anthropogenic precursors in highly industrialized and polluted urban areas causes the occurrence of centers of a high concentration of HCHO [11], increasing the frequency of its adverse effects on the environment and human health [12,13]. Acetaldehyde and methanol are notable anthropogenic precursors [14]. The main biogenic VOC is isoprene, a highly reactive hydrocarbon with a lifetime of less than one hour, which makes it also the main precursor of formaldehyde in forest regions [15,16].…”

Formaldehyde and hydroperoxide distribution around the Arabian Peninsula – evaluation of EMAC model results with ship-based measurements

“…during the photochemical oxidation of methane (CH4) (R5, R6), or by reactions of acetyl peroxy radicals (CH3C(O)O2) with HO2 and NO, which can dominate the production of CH3O2 (Crowley et al 2018). Note that the production of MHP competes with the production of formaldehyde (HCHO, R7) from the methylperoxy radical (Nussbaumer et al, 2021b). Besides the photochemical pathways, H2O2 and MHP have also been observed to be directly released from biomass burning (Lee et al, 1997).…”

“…It can be emitted directly from a variety of both biogenic and anthropogenic sources and is an intermediate during the oxidation of a large number of VOCs, making budget assessments highly complex. Previous studies designed to dustinguish between secondary production and direct emissions of HCHO vary widely in their estimates and highlight the importance of local phenomena (Dienhart et al, 2021;Nussbaumer et al, 2021b, Luecken et al, 2018Anderson et al, 2017;Wolfe et al, 2016;Stickler et al, 2006;Lee et al, 1997).…”

“…HCHO measurements are currently used as HCHO / NOx ratios for O3 sensitivity studies (i.e., NOx or VOC limitation) and global mapping of OH variability in remote air (Nussbaumer et al, 2021a;Nussbaumer et al, 2022;Tadic et al, 2020;Wolfe et al, 2019;Schroeder et al, 2017;Wolfe et al, 2016). In very clean conditions like the remote MBL or the free troposphere, HCHO production is dominated by the photo-oxidation of methane (R5), with the bimolecular self-reaction of methyl peroxy radicals the rate limiting factor (R11) (Nussbaumer et al, 2021b;Wagner et al, 2001). The methoxy radical product (CH3O) reacts quasi-instantaneously with oxygen to form HCHO and HO2 (R12).…”

“…The methoxy radical product (CH3O) reacts quasi-instantaneously with oxygen to form HCHO and HO2 (R12). In continentally influenced air masses (NO ≥ 100 pptv) R11 is suppressed, as methyl peroxy radicals rapidly oxidize NO, which accelerates HCHO and simultaneously limits MHP formation (Nussbaumer et al, 2021b;Klippel et al, 2011;Lee et al, 2000).…”