Understanding atmospheric peroxyformic acid chemistry: observation, modeling and implication

Abstract

<p><strong>Abstract.</strong> The existence and importance of peroxyformic acid (PFA) in the atmosphere has been under controversy. We present here, for the first time, the observation data for PFA from four field measurements carried out in China. These data provided powerful evidence that PFA can stay in the atmosphere, typically in dozens of pptv level. The relationship between PFA and other detected peroxides was examined. The results showed that PFA had a strong positive correlation with its homolog, peroxyacetic acid, due to their similar sources and sinks. Through an evaluation of PFA production and removal rates, we proposed that the reactions between peroxyformyl radical (HC(O)O<sub>2</sub>) and formaldehyde or the hydroperoxyl radical (HO<sub>2</sub>) were likely to be the major source and degradation into formic acid (FA) was likely to be the major sink for PFA. Based on a box model evaluation, we proposed that the HC(O)O<sub>2</sub> and PFA chemistry was a major source for FA under low NO<sub>x</sub> conditions. Furthermore, it is found that the impact of the HC(O)O<sub>2</sub> and PFA chemistry on radical cycling was dependent on the yield of HC(O)O<sub>2</sub> radical from HC(O) + O<sub>2</sub> reaction. When this yield exceeded 50%, the HC(O)O<sub>2</sub> and PFA chemistry should not be neglected for calculating the radical budget. To make clear the exact importance of HC(O)O<sub>2</sub> and PFA chemistry in the atmosphere, further kinetic, field and modeling studies are required.</p>

The oxidation regime and SOA composition in limonene ozonolysis: roles of different double bonds, radicals, and water

“…However, the similar variation tendency of PFA and PAA yields could provide some evidence for the assumption that they might have similar formation mechanisms. In previous studies, the dominant formation pathway of PAA was considered to be the reaction of CH 3 C(O)OO radicals with HO 2 radicals (Groß et al, 2014;Lightfoot et al, 1992;Winiberg et al, 2016), while the formation pathway of PFA had not been identified yet and was speculated to be the reaction of HC(O)OO radicals with HO 2 radicals (Liang et al, 2015). The rate constant of the RO 2 reaction with HO 2 was investigated in a series of studies and was thought to be unaffected by water (Atkinson et al, 1999;Lightfoot et al, 1992;Tyndall et al, 2001;Wallington et al, 1992).…”

Understanding the oxidants transition and SOA property in limonene ozonolysis: Role of different double bonds, radical chemistry, and water

“…al., 2010), yet there were few reports about PFA existence in the atmosphere (Liang et al, 2015), which might be attributed to the rapid decomposition of PFA or its precursor. The dominant formation pathway of PAA was considered as the reaction of CH3C(O)OO radical with HO2 (Groβ et al, 2014;Lightfoot et al, 1992;Winiberg et al, 2016), while the formation pathway of PFA hadn't been identified yet and was speculated to be the reaction of HC(O)OO radical with HO2 (Liang et al, 2015). In this study the yields of PFA and PAA produced in limonene ozonolysis both showed large discrepancy between the low and high ratio sets of experiments (Fig.…”

To Reviewer #2

“…with HO 2 radicals (Groß et al, 2014;Lightfoot et al, 1992;Winiberg et al, 2016), while the formation pathway of PFA had not been identified yet and was speculated to be the reaction of HC(O)OO radicals with HO 2 radicals (Liang et al, 2015). The rate constant of the RO 2 reaction with HO 2 was investigated in a series of studies and was thought to be unaffected by water (Atkinson et al, 1999;Lightfoot et al, 1992;Tyndall et al, 2001;Wallington et al, 1992). Therefore, the increase of PFA and PAA yields with RH might be attributed to the promoting effect of water on HC(O)OO and CH 3 C(O)OO radical generation.…”