Size-distributions of <i>n</i>-alkanes, PAHs and hopanes and their sources in the urban, mountain and marine atmospheres over East Asia

Abstract

Abstract. Size-segregated (9 stages) n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and hopanes in the urban (Baoji city in inland China), mountain (Mt. Tai in east coastal China) and marine (Okinawa Island, Japan) atmospheres over East Asia were studied using a GC/MS technique. Ambient concentrations of n-alkanes (1698±568 ng m −3 in winter and 487±145 ng m −3 in spring), PAHs (536±80 and 161±39 ng m −3 ), and hopanes (65±24 and 20±2.4 ng m −3 ) in the urban air are 1-2 orders of magnitude higher than those in the mountain aerosols and 2-3 orders of magnitude higher than those in the marine samples. Mass ratios of nalkanes, PAHs and hopanes clearly demonstrate coal-burning emissions as their major source. Size distributions of fossil fuel derived n-alkane, PAHs and hopanes were found to be unimodal in most cases, peaking at 0.7-1.1 µm size. In contrast, plant wax derived n-alkanes presented a bimodal distribution with two peaks at the sizes of 0.7-1.1 µm and >4.7 µm in the summer mountain and spring marine samples. Among the three types of samples, geometric mean diameter (GMD) of the organics in fine mode (<2.1 µm) was found to be smallest (av. 0.63 µm in spring) for the urban samples and largest (1.01 µm) for the marine samples, whereas the GMD in coarse mode (≥2.1 µm) was found to be smallest (3.48 µm) for the marine aerosols and largest (4.04 µm) for the urban aerosols. The fine mode GMDs of Correspondence to: G. Wang (wanggh@ieecas.cn) the urban and mountain samples were larger in winter than in spring and summer. Moreover, GMDs of 3-and 4-ring PAHs were larger than those of 5-and 6-ring PAHs in the three types of atmospheres. Such differences in GMDs can be interpreted by the repartitioning of organic compounds and the coagulation and hygroscopic growth of particles during a long-range transport from the inland continent to the marine area, as well as the difference in their sources among the three regions.

Molecular distribution and seasonal variation of hydrocarbons in PM2.5 from Beijing during 2006

“…3, the most abundant nalkanes were C 19 to C 25 compounds. This finding is quite different from what has been observed in some mountainous areas where heavier (C 29 to C 31 ) n-alkanes were found to dominate (Li et al, 2012;Wang, Kawamura, Xie, et al, 2009). Simoneit et al (2004) found that n-alkanes from fossil fuel combustion were mostly low molecular-weight (LMW, carbon number <25) species while those derived from plant waxes were heavier; these authors also noted that plant waxes had preferentially odd carbon numbers.…”

“…The ratio of BaP/BeP has used an indicator of aerosol aging because BaP is more susceptible to photochemical degradation than its isomer BeP (Wang, Kawamura, Xie, et al, 2009;Wang, Kawamura, & Lee, 2009). The lowest BaP/BeP values in our study occurred in spring (Table 3) and that may have been due to the large quantities of aerosols delivered to the region by long-range transport.…”

“…It is well known that many organic species can be used as makers for source identification. For example, diagnostic ratios of normal alkanes (n-alkanes) and polycyclic aromatic hydrocarbons (PAHs) can indicate whether these compounds were produced from the combustion of fossil fuels or from the release of epicuticular waxes from higher plants (Li et al, 2012;Wang, Kawamura, Xie, et al, 2009). Another characteristic of organic aerosols that has led to increased concern over their sources and loadings is their toxicity; PAHs for instance, are mutagenic and carcinogenic for humans (Wang, Jariyasopit, et al, 2011;Xie et al, 2009).…”

Observation of atmospheric aerosols at Mt. Hua and Mt. Tai in central and east China during spring 2009 – Part 1: EC, OC and inorganic ions

“…Numerous studies on changes in the chemical properties of Asian dust particles during long-range transport have been documented (Kanayama et al, 2002;Parrington et al, 1983;Zhang et al, 2003), but most of them were performed in urban (Huang et al, 2010b;Sun et al, 2004;Wang et al, 2002bWang et al, , 2003Yuan et al, 2008;Zhang et al, 2009), rural and marine areas (Decesari et al, 2005;Geng et al, 2009;Kanayama et al, 2002;Wang et al, 2009a) . In contrast, only a limited number of observations on aerosol chemistry were conducted at alpine sites, most of which are situated in the eastern part of China Wang et al, 2009bWang et al, , 2009c. Atmospheric environment in mountain area is unique because of lower temperature, higher relative humidity (RH), and stronger solar radiation.…”

Size distributions of polycyclic aromatic hydrocarbons in urban atmosphere: sorption mechanism and source contributions to respiratory deposition

“…Over the past decade, numerous measurements of PAH size distribution have been repeatedly carried out in various areas around the world, such as Seoul (Korea; Lee et al, 2008); Saitama and Okinawa (Japan; Kawanaka et al, 2004;Wang et al, 2009); Mumbai and Delhi (India; Venkataraman et al, 1999;Gupta et al, 2011); Barcelona (Spain; Mesquita et al, 2014); Dresden (Germany; Gnauk et al, 2011);Birmingham (England;Delgado-Saborit et al, 2013); Lisbon (Portugal; Oliveira et al, 2011); Algiers (Algeria; Ladji et al, 2014); Beauharnois (Canada; Sanderson and Farant, 2005); Los Angeles, Massachusetts, Chicago, and Claremont (USA; Allen et al, 1996;Offenberg and Baker, 1999;Miguel et al, 2004); and Tianjing, Beijing, and Guangzhou (China; Wu et al, 2006;Zhou et al, 2008;Yu and Yu, 2012). These studies, conducted in various countries and cities showed that most PAHs existed on small particles and had a similar modal distribution as isomers.…”