Profiling of formaldehyde, glyoxal, methylglyoxal, and CO over the Amazon: normalized excess mixing ratios and related emission factors in biomass burning plumes

Abstract

Abstract. We report on airborne measurements of tropospheric mixing ratios and vertical profiles of formaldehyde (CH2O), glyoxal (C2H2O2), methylglyoxal and higher carbonyls (C3H4O2*) (see below), and carbon monoxide (CO) over the Amazon Basin during the ACRIDICON-CHUVA campaign from the German High Altitude and Long-range research aircraft (HALO) in autumn 2014. The joint observation of in situ CO and remotely measured CH2O, C2H2O2, and C3H4O2*, together with visible imagery and air mass back-trajectory modelling using NOAA HYSPLIT (National Oceanic Atmospheric Administration, HYbrid Single-Particle Lagrangian Integrated Trajectory), allows us to discriminate between the probing of background tropical air, in which the concentration of the measured species results from the oxidation of biogenically emitted volatile organic compounds (VOCs, mostly isoprene), and measurements of moderately to strongly polluted air masses affected by biomass burning emissions or the city plume of Manaus. For 12 near-surface measurements of fresh biomass burning plumes, normalized excess mixing ratios of C2H2O2 and C3H4O2* with respect to CH2O are inferred and compared to recent studies. The mean glyoxal-to-formaldehyde ratio RGF=0.07 (range 0.02–0.11) is in good agreement with recent reports which suggest RGF to be significantly lower than previously assumed in global chemical transport models (CTMs). The mean methylglyoxal-to-formaldehyde ratio RMF=0.98 (range 0.09–1.50) varies significantly during the different observational settings but overall appears to be much larger (up to a factor of 5) than previous reports suggest even when applying a correction factor of 2.0±0.5 to account for the additional dicarbonyls included in the C3H4O2* measurements. Using recently reported emission factors of CH2O for tropical forests, our observations suggest emission factors of EFG=0.25 (range 0.11 to 0.52) g kg−1 for C2H2O2 and EFM = 4.7 (range 0.5 to 8.64) g kg−1 for C3H4O2*. While EFG agrees well with recent reports, EFM is (like RMF) slightly larger than reported in other studies, presumably due to the different plume ages or fuels studied. Our observations of these critical carbonyls and intermediate oxidation products may support future photochemical modelling of air pollution over tropical vegetation, as well as validate past and present space-borne observations of the respective species.

New photolytic converter for improving aircraft measurements of NO<sub>2</sub> via chemiluminescence

“…with a detection limit of about 5 pptv and an uncertainty depending on the altitude and cloud cover of typically 40 pptv (Hüneke et al, 2017;Kluge et al, 2020). Water vapor was measured via direct absorption by the tunable diode laser system SHARC (Sophisticated Hygrometer for Atmospheric ResearCh) (accuracy of 5 %, detection limit typically in the range of 2 -3 ppmv) (Kaufmann et al, 2018).…”

Organic and inorganic bromine measurements around the extratropical tropopause and lowermost stratosphere: insights into the transport pathways and total bromine

“…The α X j of the target gas and α P j of the scaling gas are wavelength-dependent, and therefore the target and scaling gas should have similar or largely overlapping wavelength fit windows (Table 1). However, for a given wavelength the α factor ratio is insensitive to scattering by aerosols and clouds due to the equivalence theorem (Irvine, 1964) as shown in simulations performed by Knecht (2015) or in the Supplement of Hüneke et al (2017). The SCD X and SCD P are the total slant column densities of the target gas (BrO or NO 2 ) and scaling gas (O 3 ), respectively, evaluated from the mini-DOAS data.…”

Measurement report: Observation-based formaldehyde production rates and their relation to OH reactivity around the Arabian Peninsula

“…Formaldehyde (HCHO) is a ubiquitous trace gas that can help provide insight into the dynamical and chemical processes controlling atmospheric composition as an important source of hydroperoxyl radicals (HO 2 ) (Volkamer et al, 2010;Whalley et al, 2010;Anderson et al, 2017). The global atmospheric distribution of HCHO is dominated by in situ production during the oxidation of volatile organic compounds (VOCs) (Fortems-Cheiney et al, 2012;Anderson et al, 2017), although primary emissions from biomass burning (Akagi et al, 2011;Coggon et al, 2019;Kluge et al, 2020), vegetation (DiGangi et al, 2011, the industry sector (Parrish et al, 2012), shipping (Marbach et al, 2009;Celik et al, 2020) and agriculture (Kaiser et al, 2015) can contribute significantly to the local HCHO abundance. HCHO is the most abundant aldehyde in the atmosphere and one of the few oxygenated volatile organic compounds (OVOCs) that can be measured directly from satellites (De Smedt et al, 2008Marbach et al, 2009;Zhu et al, 2020).…”

“…In most of the free troposphere and the remote marine boundary layer (MBL), HCHO mixing ratios are determined by methane (CH 4 ) oxidation (Ayers et al, 1997;Weller et al, 2000;Wagner et al, 2002;Anderson et al, 2017) and degradation of the oxidation products methanol (CH 3 OH), methylhydroperoxide (CH 3 OOH) and other ubiquitous OVOCs like acetone (Kormann et al, 2003;Reeves and Penkett 2003;Stickler et al, 2006;Anderson et al, 2017). In polluted areas, the oxidation of a large variety of biogenic and anthropogenic precursors contributes to HCHO production (Liu et al, 2007;DiGangi et al, 2012;Wolfe et al, 2016;Wennberg et al, 2018;Kluge et al, 2020). HCHO/NO 2 ratios have been used to differentiate between nitrogen oxide (NO x = NO + NO 2 ) and VOC-limited ozone production (Martin et al, 2004;Duncan et al, 2010;Schroeder et al, 2017;Tadic et al, 2020) and to infer global hydroxyl radical (OH) concentrations (Wolfe et al, 2019).…”