Molecular distribution and stable carbon isotopic compositions of dicarboxylic acids and related SOA from biogenic sources in the summertime atmosphere of Mt. Tai in the North China Plain

Abstract

Abstract. Molecular distributions and stable carbon isotopic (δ13C values) compositions of dicarboxylic acids and related secondary organic aerosols (SOA) in PM2.5 aerosols collected on a day/night basis at the summit of Mt. Tai (1534 m a.s.l.) in the summer of 2016 were analyzed to investigate the sources and photochemical aging process of organic aerosols in the forested highland region of the North China Plain. The molecular distributions of dicarboxylic acids and related SOA are characterized by the dominance of oxalic acid (C2), followed by malonic (C3), succinic (C4) and azelaic (C9) acids. The concentration ratios of C2 ∕ C4, diacid-C ∕ OC and C2 ∕ total diacids are larger in the daytime than in the nighttime, suggesting that the daytime aerosols are more photochemically aged than those in the nighttime due to the higher temperature and stronger solar radiation. Both ratios of C2 ∕ C4 (R2>0.5) and C3 ∕ C4 (R2>0.5) correlated strongly with the ambient temperatures, indicating that SOA in the mountaintop atmosphere are mainly derived from the photochemical oxidation of local emissions rather than long-range transport. The mass ratios of azelaic acid to adipic acid (C9 ∕ C6), azelaic acid to phthalic aid (C9 ∕ Ph) and glyoxal to methylglyoxal (Gly ∕ mGly) and the strong linear correlations of major dicarboxylic acids and related SOA (i.e., C2, C3, C4, ωC2, Pyr, Gly and mGly) with biogenic precursors (SOA tracers derived from isoprene, α/β-pinene and β-caryophyllene) further suggest that aerosols in this region are mainly originated from biogenic sources (i.e., tree emissions). C2 concentrations correlated well with aerosol pH, indicating that particle acidity favors the organic acid formation. The stable carbon isotopic compositions (δ13C) of the dicarboxylic acids are higher in the daytime than in the nighttime, with the highest value (-16.5±1.9 ‰) found for C2 and the lowest value (-25.2±2.7 ‰) found for C9. An increase in δ13C values of C2 along with increases in C2 ∕ Gly and C2 ∕ mGly ratios was observed, largely due to the isotopic fractionation effect during the precursor oxidation process.

Multiphase MCM–CAPRAM modeling of the formation and processing of secondary aerosol constituents observed during the Mt. Tai summer campaign in 2014

“…Additionally, the multiphase chemistry mechanism is also constrained by the initial concentrations of key species at the corresponding originated areas. The initial chemical data include gas-phase concentrations of inorganic gases (NO, NO 2 , O 3 , SO 2 , HNO 3 , NH 3 , H 2 O 2 ), VOCs (including alkanes, alkenes, aromatics, aldehydes, alcohols and ketones) (Barletta et al, 2005;Duan et al, 2008;Liu et al, 2009;Ianniello et al, 2011;Meng et al, 2011;Li et al, 2011;Liu et al, 2012b;Y. H. Wang et al, 2014;Rao, et al, 2016; and particle-phase data (Hu et al, 2015;Sun et al, , 2015Liu et al, 2014).…”

Molecular Compositions and Sources of Organic Aerosols from Urban Atmosphere in the North China Plain during the Wintertime of 2017

“…Organic aerosol (OA) accounts for a substantial fraction (20-90%) of the global submicron aerosol loading (Kroll and Seinfeld, 2008;Hallquist et al, 2009). Asubstantial fraction (up to 80%) of OA is water-soluble (Verma et al, 2017), and thus it has a crucial impact on radiative forcing of aerosols by altering the cloud condensation nuclei (CCN) (Zhang et al, 2015;Wang et al, 2016;Meng et al, 2018). Moreover, a large quantity of OA (e.g., polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and n-alkanes) is cytotoxic, mutagenic, and carcinogenic for humans (Zhang et al, 2009;Yang et al, 2017a;Huang et al, 2018), resulting in an increasing concern about its source, formation mechanism, and emission control (Kong et al, 2015a, b;Nirmalkar et al, 2015a;Zhao et al, 2018).…”

“…In January 2017, an extremely severe haze occurred in eastern and central China with a record daily PM 2.5 concentration of over 450 µg m -3 observed in Beijing, the largest city in the North China Plain, attracting worldwide attention. Liaocheng is an inland city located in the center of the North China Plain, one of the regions with the worst air pollution in the world (Meng et al, 2018), which suffering from serious air pollution and was listed as Jing-Jin-Ji air pollution transmission channel city ("Air pollution prevention and control plan for Jing-Jin-Ji and surrounding areas in 2017"). To our knowledge, this is the first time to fill the knowledge gap in the compositions and sources of organic aerosols in Liaocheng, which in turn may inform policy for local and regional pollution control strategies in the North China Plain.…”

An IBBCEAS system for atmospheric measurements of glyoxal and methylglyoxal in the presence of high NO<sub>2</sub> concentrations

“…Atmospheric sinks of GLY and MGLY include photolysis and reactions with OH radicals (Volkamer et al, 2005a;Fu et al, 2008), which play an important role in the formation of both O 3 and peroxyacetyl nitrate (PAN) (Müller et al, 2016). Furthermore, the contribution of GLY and MGLY to the formation of secondary organic aerosol (SOA) has drawn widespread attention in the past few years (Washenfelder et al, 2011;Nakao et al, 2012;Meng et al, 2018). Although GLY and MGLY have relatively low molecular weights, they can form oligomers and participate in SOA formation in aqueous particles (Yu et al, 2011;Hamilton et al, 2013).…”