Water‐soluble organic compounds in PM_2.5 and size‐segregated aerosols over Mount Tai in North China Plain

Abstract

[1] Daytime and nighttime PM 2.5 samples were collected at the summit of Mount Tai (1534 m) located in North China Plain during a week in 2006 summer. Size-segregated aerosol particles were also collected using an eight-stage impactor during the same period. Samples were analyzed for various water-soluble organic compounds using GC/FID and GC/MS techniques. Among the species identified in PM 2.5 samples, dicarboxylic acids (C 2 -C 11 ) were found as the most abundant compound class, followed by ketocarboxylic acids, saccharides, polyols and polyacids, and dicarbonyls. Daytime concentrations of most compounds were found to be 2-3 times higher than in nighttime. Such a diurnal variation was first interpreted by the depressed transport of pollutants in nighttime from the lowlands to the mountaintop owing to the decreased heights of planetary boundary layer, and second by the photochemical production in daytime. The diurnal variation trends of secondary organic aerosols (SOA) such as diacids at the mountain site are the same as those on lowlands, but the diurnal patterns of primary organic aerosols (POA) on the mountaintop are in contrast to those on lowlands, where POA such as saccharides and polyols are usually higher in nighttime owing to the accumulation within inversion layer developed. The eight-stage impactor samples showed bimodal distributions of diacids and related compounds peaking at size ranges of 0.70-1.1 mm and 5.8-9.0 mm. In the present study, water-soluble organics in the fine mode are largely originated from biomass burning and/or photooxidation of gaseous precursors and the subsequent adsorption on the preexisting particles, whereas those in the coarse mode are mainly derived from suspended soil particles and pollens and in part via the hygroscopic growth of fine particles and formation of cloud/fog droplets.

Impact of Gobi desert dust on aerosol chemistry of Xi'an, inland China during spring 2009: differences in composition and size distribution between the urban ground surface and the mountain atmosphere

“…The small peak of coarse mode of WSOC can be explained by a nature source such as pollen and soil (Fig. 9a), because water-soluble organic compounds like glucose (Graham et al, 2002;Wang et al, 2006bWang et al, , 2009Wang et al, , 2011a and humic acid (Brooks et al, 2004;Dinar et al, 2006;Havers et al, 1998) are enriched in these sources, in addition to deposition of anthropogenic pollutants onto dust. During the dust storm period WSOC still displayed a bimodal pattern, but the fine mode significantly decreased while the coarse mode sharply increased as a dominant peak.…”

Characterization of Organic Aerosol Particles Observed during Asian Dust Events in Spring 2010

“…Oxalate is typically the most abundant dicarboxylic acid in atmospheric aerosols and another important class of WSOC in the atmosphere (Narukawa et al, 2003). Secondary products are considered to be an important source of oxalate (Kawamura and Yasui, 2005;Wang et al, 2009). In addition to the secondary production, oxalate is emitted from vehicle exhausts (Kawamura and Kaplan, 1987), biomass burning (Narukawa et al, 1999) and biogenic activity (Kawamura et al, 1996).…”

Concentrations and stable carbon isotope compositions of oxalic acid and related SOA in Beijing before, during, and after the 2014 APEC

“…For example, Surratt et al (2007Surratt et al ( , 2010 found that aerosol acidity can promote the formation of biogenic SOA (BSOA) derived from isoprene oxidation, such as 2-methylglyceric acid, Gly and mGly. These BSOA precursors can be further oxidized into C 2 (Meng et al, 2014;Wang et al, 2009). …”