Formation of nighttime sulfuric acid from the ozonolysis of alkenes in Beijing

Abstract

Abstract. Gaseous sulfuric acid (SA) has received a lot of attention for its crucial role in atmospheric new particle formation (NPF). And for this reason, studies until now have mainly focused on daytime SA when most NPF events occur. While daytime SA production is driven by SO2 oxidation of OH radicals of photochemical origin, the formation of SA during nighttime and its potential influence on particle formation remains poorly understood. Here we present evidence for significant nighttime SA production in urban Beijing during winter, yielding concentrations between 1.0 and 3.0 × 106 cm−3. We found a high frequency (∼ 30 %) of nighttime SA events, which are defined by the appearance of a distinct SA peak observed between 20:00 and 04:00 local time, with the maximum concentration exceeding 1.0 × 106 cm−3. These events mostly occurred during unpolluted nights with a low vapor condensation sink. Furthermore, we found that under very clean conditions (visibility > 16.0 km) with abundant ozone (concentration > 2.0 × 1011 cm−3, ∼ 7 ppb), the overall sink of SA was strongly correlated with the products of O3, alkenes and SO2 concentrations, suggesting that the ozonolysis of alkenes played a major role in nighttime SA formation under such conditions. This is in light of previous studies showing that the ozonolysis of alkenes can form OH radicals and stabilized Criegee intermediates (SCIs), both of which are able to oxidize SO2 and thus lead to SA formation. However, we also need to point out that there exist additional sources of SA under more polluted conditions, which are not investigated in this study. Moreover, there was a strong correlation between SA concentration and the number concentration of sub-3 nm particles on both clean and polluted nights. Different from forest environments, where oxidized biogenic vapors are the main driver of nighttime clustering, our study demonstrates that the formation of nighttime cluster mode particles in urban environments is mainly driven by nighttime SA production.

Toward Building a Physical Proxy for Gas-Phase Sulfuric Acid Concentration Based on Its Budget Analysis in Polluted Yangtze River Delta, East China

“…Given a very short lifetime, the budget of H 2 SO 4 can be described by the following equation During the daytime, the H 2 SO 4 formation is dominated by the oxidation of SO 2 by OH, which is extremely difficult to be measured but has been demonstrated to be well reproduced by J (O 1 D) . During the nighttime, SO 2 oxidation by sCI and OH, produced from the ozonolysis of alkenes, is believed to control the formation of H 2 SO 4 . In polluted urban areas, alkenes have complex species, and it is generally impractical to make long-term, full-spectrum measurements.…”

“…Gaseous H 2 SO 4 was long believed to be formed only from the reaction between SO 2 and OH. More recently, stabilized Criegee intermediates (sCI), formed in the ozonolysis of alkenes, were demonstrated to be able to oxidize SO 2 and contribute to gaseous H 2 SO 4 . , This was found to be particularly important for the nighttime H 2 SO 4 formation . In the coastal marine atmosphere, SO 2 oxidation by small Criegee intermediates (CI), produced possibly in photochemical reactions, and SO 3 formed from dimethyl sulfide (DMS) oxidation reaction with water might be non-negligible sources of H 2 SO 4 . ,, Recently, Olin et al indicated a potential source of H 2 SO 4 from traffic emissions in urban Helsinki based on the observed positive correlation between H 2 SO 4 and NO x concentrations.…”

Formation of condensable organic vapors from anthropogenic and biogenic VOCs is strongly perturbed by NO<sub>x</sub> in eastern China

“…is a very reliable proxy for SA during the day (Lu et al, 2019). The ozonolysis of alkenes can form stabilized Criegee intermediates (SCIs) in addition to OH, and SCIs can also oxidize SO2 to form SA (Mauldin Iii et al, 2012;Guo et al, 2021). A previous study on SA proxy in this site has revealed that the reactions of SO2 with products from the ozonolysis of alkenes generate a moderate amount of nighttime sulfuric acid, with little effect on daytime sulfuric acid (Yang et al, 2021).…”

Formation of condensable organic vapors from anthropogenic and biogenic volatile organic compounds (VOCs) is strongly perturbed by NO<sub><i>x</i></sub> in eastern China

“…Secondary organic aerosols (SOAs), as an important and complex component of submicron particles (Zhang et al, 2007;Jimenez et al, 2009;Huang et al, 2014), are fully involved in affecting climate (IPCC, 2013) and causing health risks (Nel, 2005;Lim et al, 2012). Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and are recognized as the main precursors of SOAs (Hallquist et al, 2009;Ziemann and Atkinson, 2012). However, the missing intermediate processes from VOCs to SOAs are yet to be elucidated (Hallquist et al, 2009;Ehn et al, 2014).…”

“…Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and are recognized as the main precursors of SOAs (Hallquist et al, 2009;Ziemann and Atkinson, 2012). However, the missing intermediate processes from VOCs to SOAs are yet to be elucidated (Hallquist et al, 2009;Ehn et al, 2014).…”