Pyruvic acid in the boreal forest: gas-phase mixing ratios and impact on radical chemistry

Abstract

Abstract. Pyruvic acid (CH3C(O)C(O)OH, 2-oxopropanoic acid) is an organic acid of biogenic origin that plays a crucial role in plant metabolism, is present in tropospheric air in both gas-phase and aerosol-phase, and is implicated in the formation of secondary organic aerosols (SOAs). Up to now, only a few field studies have reported mixing ratios of gas-phase pyruvic acid, and its tropospheric sources and sinks are poorly constrained. We present the first measurements of gas-phase pyruvic acid in the boreal forest as part of the IBAIRN (Influence of Biosphere–Atmosphere Interactions on the Reactive Nitrogen budget) field campaign in Hyytiälä, Finland, in September 2016. The mean pyruvic acid mixing ratio during IBAIRN was 96 pptv, with a maximum value of 327 pptv. From our measurements we estimated the overall pyruvic acid source strength and quantified the contributions of isoprene oxidation and direct emissions from vegetation in this monoterpene-dominated forested environment. Further, we discuss the relevance of gas-phase pyruvic acid for atmospheric chemistry by investigating the impact of its photolysis on acetaldehyde and peroxy radical production rates. Our results show that, based on our present understanding of its photochemistry, pyruvic acid is an important source of acetaldehyde in the boreal environment, exceeding ethane and propane oxidation by factors of ∼10 and ∼20.

Measurements of carbonyl compounds around the Arabian Peninsula: overview and model comparison

“…The working principle of PTR-MS has been described in detail in previous studies (Lindinger et al, 1998;Ellis and Mayhew, 2013;Yuan et al, 2017). In brief, H 3 O + primary ions are generated in the ion source and then drawn into the drift tube where they interact with sampled ambient air.…”

Modelling the impact of gas-phase pyruvic acid on acetaldehyde and peroxy radical formation in the boreal forest

“…The IBAIRN campaign (Influence of Biosphere-Atmosphere Interactions on the Reactive Nitrogen budget) took place in September 2016, during the summer-autumn transition, and was characterised by frequent temperature inversions near ground level during night-time (Liebmann et al, 2018), which led to the accumulation of nocturnally emitted trace gases from vegetation. A detailed description of the campaign and the instrumental setup can be found elsewhere (Liebmann et al, 2018;Eger et al, 2020). Briefly, pyruvic acid was measured by a chemical ionisation quadrupole mass spectrometer with a detection limit (LOD) (10 s, 2σ) of 15 pptv (Eger et al, 2020).…”

“…A detailed description of the campaign and the instrumental setup can be found elsewhere (Liebmann et al, 2018;Eger et al, 2020). Briefly, pyruvic acid was measured by a chemical ionisation quadrupole mass spectrometer with a detection limit (LOD) (10 s, 2σ) of 15 pptv (Eger et al, 2020). The sum of monoterpenes (henceforth referred to as MT) was measured by a PTR-ToF-MS and single monoterpenes were monitored by a GC-AED, described in detail by Liebmann et al (2018).…”

“…boreal forest, rural areas with temperate forest, and regions influenced by urban outflow. A recent overview of existing measurements of gas-phase pyruvic acid is given by Eger et al (2020).…”

“…Further potential sources are the photolysis of methylglyoxal (Raber and Moortgat, 1995), the gas-phase photo-oxidation of aromatics in the presence of NOx (Grosjean, 1984;Praplan et al, 2014), the aqueous-phase oxidation of methylglyoxal (Stefan and Bolton, 1999) and reactions taking place within biomass burning plumes (Andreae et al, 1987;Helas et al, 1992). In addition, pyruvic acid has been reported to be directly emitted from vegetation (Talbot et al, 1990;Jardine et al, 2010a;Jardine et al, 2010b;Eger et al, 2020). Compared to acetic acid, the presence of a second (non-acidic) carbonyl group imparts on pyruvic acid an absorption spectrum that extends from ultraviolet to visible wavelengths (see Fig.…”