Importance of Oxidants and Temperature in the Formation of Biogenic Organosulfates and Nitrooxy Organosulfates

Abstract

Biogenic secondary organic aerosol (BSOA) makes up a significant proportion of organic aerosol, and its formation chemistry, composition, and physical properties can be influenced by anthropogenic emissions, especially in urban areas. Organosulfates (OSs) are an important class of tracers for BSOA and have been well-studied over the past decade, although detailed ambient studies of diurnal variations are still lacking. In this study, fine particulate matter samples were collected eight times a day across summer and winter campaigns at an urban site in Guangzhou, China. Guangzhou is heavily influenced by both biogenic and anthropogenic emissions, allowing for biogenic–anthropogenic interactions to be studied. Individual OSs and nitrooxy OSs (NOSs) species derived from monoterpenes and isoprene were analyzed using ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC–MS2) and quantified using three authentic and proxy standards. The observations show strong diurnal variations of monoterpene derived OSs and NOSs, which peaked during the night, with concentrations increasing from the early evening, highlighting the role of NO3-oxidation chemistry. Isoprene derived OSs/NOSs showed strong seasonal profiles, with summer and winter average concentrations of 181.8 and 69.5 ng m–3, respectively, with exponential increases observed at temperatures above 30 °C. Low-NO formation pathways were dominant in the summer, while high-NO pathways became more important in the winter. Isoprene OS formation was strongly dependent on the availability of particulate sulfate (SO4 2–), suggesting an extensive heterogeneous chemistry of oxidized isoprene species. Overall, this study provides further insights into biogenically derived OS and NOS formation within highly anthropogenically influenced environments.

Molecular Characteristics of Organosulfur Compounds in Guangzhou, South China: Heterogeneous Secondary Reactions Drivers the Molecular Distribution

“…Figure 2b shows the annual variations of the sum relative abundance of the above five OSs groups to the total OrgSs abundance, with annual average proportions of 3.8±1.9%, 23±6.7%, 3.6±0.5%, 6.1±1.4% and 27±2.3% for isoprene-derived, monoterpene-derived, other BVOCs-derived, anthropogenic VOCs-derived OSs and multiple-source-derived OSs, respectively. The high contribution of known terpene-derived OSs to the total OrgSs intensity in GZ is consistent with previous observations of the dominance of terpene-derived OSs in GZ (Wang et al, 2017b;He et al, 2014;Bryant et al, 2021). Several acid-catalyzed chemistry of BVOCs-derived oxidation products (Hettiyadura et al, 2019;Bruggemann et al, 2020).…”

“…Moreover, directly assessing relationships between individual compounds and LWC, NO3 − , NH4 + suggested that the increase of their concentrations would promote the formation of CHONS species, as 72%, 65% and 75% of the OrgSs that have positive correlations (p adjust with "fdr") with the LWC, NO3 − , NH4 + , are CHONS species (Table S13), respectively, further supports the OrgSs formation via aqueous-phase chemistry in Guangzhou influenced by LWC, such as NO3-initiated oxidation, acidcatalyzed epoxide pathways (Wang et al, 2020;Xu et al, 2021b). Recently, Bryant et al (2021) reported that oxidants and temperature are important factors that affect OSs formation in Guangzhou, and high-NOx pathways became more important in the winter when usually suffering high anthropogenic emissions, while low-NO formation pathways were dominant in the summer. The observed opposite influence of OH radicals and inorganic species on OrgSs distributions also suggested the existence of OrgSs formation from heterogeneous OH radical oxidation when there was less anthropogenic emission Lam et al, 2019).…”

“…However, the cluster of anthropogenic organic compounds with reactive nitrogen species and LWC probably also suggested the influences of aqueous-phase reactions of fatty acids and other fossil precursors on OrgSs formation, particularly the inorganic nitrogen species related formation of NOSs (Bryant et al, 2021). This is expected because aerosol LWC provide media for aqueous phase reactions (Guo et al, 2016;Liu et al, 2017;Wang et al, 2018), and positive correlations were observed between LWC and secondary inorganic aerosols (r=0.69, p<0.01), particularly the inorganic nitrogen species.…”

“…Additionally, the high emissions of anthropogenic pollutants (e.g., NOx and SO2) and high concentrations of nitrate and sulfate are present in the particle phase, which makes the particles very acidic (He et al, 2014). Although several studies have reported the concentrations and possible formation mechanisms of biogenic VOCs (BVOCs) derived OSs in the Pearl River Delta region (Bryant et al, 2021;He et al, 2014), these OSs only represented a small fraction of organic aerosol mass. Therefore, a better understanding of the chemical composition, source and influencing factors of OrgSs in Guangzhou will be important to know the particulate pollution and decrease the SOA concentration.…”

Biogenic and anthropogenic sources of isoprene and monoterpenes and their secondary organic aerosol in Delhi, India

“…Globally, isoprene is predominately emitted from biogenic sources, but anthropogenic sources become increasingly important in urban areas especially at night (Borbon et al, 2001;Hsieh et al, 2017;Khan et al, 2018a;Mishra and Sinha, 5 al., 2013;Surratt et al, 2008a) were searched for in an afternoon and a night-time filter sample extract analysis using the Xcalibur software. Further details can be found in Bryant et al, 2021 and the SI. Isoprene and monoterpene markers were quantified using the method in Bryant et al, 2021. Overall uncertainties associated with calibrations, proxy standards and matrix effects were estimated.…”