Determination of enhancement ratios of HCOOH relative to CO in biomass burning plumes by the Infrared Atmospheric Sounding Interferometer (IASI)

Abstract

Abstract. Formic acid (HCOOH) concentrations are often underestimated by models, and its chemistry is highly uncertain. HCOOH is, however, among the most abundant atmospheric volatile organic compounds, and it is potentially responsible for rain acidity in remote areas. HCOOH data from the Infrared Atmospheric Sounding Interferometer (IASI) are analyzed from 2008 to 2014 to estimate enhancement ratios from biomass burning emissions over seven regions. Fire-affected HCOOH and CO total columns are defined by combining total columns from IASI, geographic location of the fires from Moderate Resolution Imaging Spectroradiometer (MODIS), and the surface wind speed field from the European Centre for Medium-Range Weather Forecasts (ECMWF). Robust correlations are found between these fire-affected HCOOH and CO total columns over the selected biomass burning regions, allowing the calculation of enhancement ratios equal to 7.30 × 10 −3 ± 0.08 × 10 −3 mol mol −1 over Amazonia (AMA), 11.10 × 10 −3 ± 1.37 × 10 −3 mol mol −1 over Australia (AUS), 6.80 × 10 −3 ± 0.44 × 10 −3 mol mol −1 over India (IND), 5.80 × 10 −3 ± 0.15 × 10 −3 mol mol −1 over Southeast Asia (SEA), 4.00 × 10 −3 ± 0.19 × 10 −3 mol mol −1 over northern Africa (NAF), 5.00 × 10 −3 ± 0.13 × 10 −3 mol mol −1 over southern Africa (SAF), and 4.40 × 10 −3 ± 0.09 × 10 −3 mol mol −1 over Siberia (SIB), in a fair agreement with previous studies. In comparison with referenced emission ratios, it is also shown that the selected agricultural burning plumes captured by IASI over India and Southeast Asia correspond to recent plumes where the chemistry or the sink does not occur. An additional classification of the enhancement ratios by type of fuel burned is also provided, showing a diverse origin of the plumes sampled by IASI, especially over Amazonia and Siberia. The variability in the enhancement ratios by biome over the different regions show that the levels of HCOOH and CO do not only depend on the fuel types.

Spaceborne Measurements of Formic and Acetic Acids: A Global View of the Regional Sources

“…Over the biomass burning areas, the ratios are similarly close to 1, although higher fire emission factors for COOH than for HCOOH are reported in the literature (Akagi et al, ; Andreae, ). While we cannot rule out potential retrieval biases, another explanation is a rapid secondary HCOOH formation, as suggested by space‐based pyrogenic HCOOH enhancement ratios that are significantly higher than expected (Chaliyakunnel et al, ; Pommier et al, ), and which would not be present to the same degree for COOH.…”

IASI-derived NH<sub>3</sub> enhancement ratios relative to CO for the tropical biomass burning regions

“…One main advantage of the ERs compared to the EFs is that ER calculation only requires simultaneous measurements of the studied (NH 3 ) and the reference species (CO), while EF calculation requires fuel information that is not always available or completely reliable (Andreae and Merlet, 2001). In fire plumes, ERs can be estimated following (Goode et al, 2000;R'Honi et al, 2013)…”

“…With a contribution estimated to be about 13 % (Galloway et al, 2004) of the total emissions, biomass burning is believed to be the second most important source of NH 3 after agriculture. From previous studies, it has been shown that biomass burning could significantly affect NH 3 concentrations in the atmosphere, especially in the tropics but also at higher latitudes (e.g., Bouwman et al, 1997;Coheur et al, 2009;Adon et al, 2010;Alvarado et al, 2011;Shephard et al, 2011;Adon et al, 2013;R'Honi et al, 2013;Whitburn et al, , 2016aBenedict et al, 2017;Warner et al, 2017). Excess NH 3 in the environment is of great concern since it is responsible for many environmental is-12240 S. Whitburn et al: ER NH 3 / CO in tropical biomass burning regions sues such as eutrophication of terrestrial and aquatic ecosystems, soil acidification, and loss of plant diversity (Aneja et al, 2001;Erisman et al, 2007).…”

“…A recent study was also dedicated to formic acid (HCOOH) (Pommier et al, 2017). Until now, less attention has been given to NH 3 (Coheur et al, 2009;Alvarado et al, 2011;R'Honi et al, 2013;Luo et al, 2015). In this paper we derive biome-specific NH 3 enhancement ratios (ERs) relative to CO (ER NH 3 / CO , also known as normalized excess mixing ratios) and relate them to EFs (see Sect.…”

IASI-derived NH<sub>3</sub> enhancement ratios relative to CO for the tropical biomass burning regions

“…Today, the focus is principally on CO, nitrogen dioxide (NO 2 ), and aerosols (e.g., Pechony et al, 2013;Castellanos et al, 2014;Ichoku and Ellison, 2014;Mebust and Cohen, 2014;Schreier et al, 2014a, b). A recent study was also dedicated to formic acid (HCOOH) (Pommier et al, 2017). Until now, less attention has been given to NH 3 Alvarado et al, 2011;R'Honi et al, 2013;Luo et al, 2015).…”