Molecular composition and compound-specific stable carbon isotope ratio of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere in suburban areas

Abstract

Molecular and carbon isotopic compositions of atmospheric polycyclic aromatic hydrocarbons (PAHs) were measured in sites at 1 m (S1), 10 m (S2) and approximately 200 m (S3) distant from roads in Tokyo, Japan. Total suspended particles (TSP) concentrations at S1 was approximately three times higher than S2 and S3, while the concentration of atmospheric PAHs was almost the same (76-166 µg g -1 -TSP) at S1, S2 and S3. Compound-specific δ 13 C of atmospheric PAHs ranged from -23.3 to -24.5‰ at S1, from -24.1 to -25.6‰ at S2, and from -25.2 to -27.0‰ at S3. The concentration of some PAHs and the weighted averages of δ 13 C of some selected PAHs differed significantly among the three sites. The PAH concentration ratios indicating automotive contribution were S1 > S2 > S3, while the ratios indicating non-vehicle contribution were S3 > S2 > S1. These differences in molecular and isotopic signatures among the three sites are not caused by photolysis, instead they are possibly due to differences in the sources of PAHs.A quantitative approach to identify compound-specific sources is to use the concentration and δ 13 C of individual PAHs at each site. The estimated average δ 13 C values of individual PAHs derived from automobiles, which was calculated using a mass balance model, ranged from -19.5 to -23.6‰. Taking into account the results of this study and those of previous studies, -26 to -28‰ was adopted as the δ 13 C value of PAHs derived from non-vehicle sources. We estimated that the automotive contribution to the concentration of individual PAHs ranged from 33 to 88% at S1, from 11 to 74% at S2, and from 0 to 52% at S3. We conclude that compound-specific δ 13 C measurement is a powerful and useful tool to identify such compound-specific sources of atmospheric PAHs.

Isotopic characterization of aerosol organic carbon components over the eastern United States

“…However, the depleted δ 13 C values for aromatic OC reported here (Table 2 and Figure 2; −29.6 to −27.8‰) are consistent with those reported for PAHs from European background sites (Table 3; −29.2‰ to −27.7‰ [ Mandalakis et al , 2005]) as opposed to the more enriched values noted from near a roadway in Tokyo (Table 3; −27‰ to −23‰ [ Okuda et al , 2004]) and from urban areas in Washington, DC (Table 3; −24.3‰ to −22.4‰ [ Reddy et al , 2002]) and China (Table 3; −27‰ to −21‰ [ Okuda et al , 2002a]). Okuda et al [2004] estimated the δ 13 C value of PAHs from automotive exhaust in Japan to range from −23.6‰ to −19.5‰, while a separate study revealed PAHs from wood burning to be isotopically lighter (Table 3; −32‰ to −27‰ [ Okuda et al , 2002b]) suggesting that lighter PAH δ 13 C values may also be indicative of biomass sources. Compound or compound‐specific measurements were not possible in the present study due to the limited sample sizes.…”

“…In contrast to aromatic OC in the present study (Table 2 and Figure 2), previously reported aerosol‐derived PAH δ 13 C signatures covered a broad range (Table 3; −32 to −21‰ [ Okuda et al , 2002a, 2002b, 2004; Reddy et al , 2002; Mandalakis et al , 2005; Kumata et al , 2006]) and were not uniformly 13 C‐depleted relative to aerosol TOC [ Reddy et al , 2002]. However, the depleted δ 13 C values for aromatic OC reported here (Table 2 and Figure 2; −29.6 to −27.8‰) are consistent with those reported for PAHs from European background sites (Table 3; −29.2‰ to −27.7‰ [ Mandalakis et al , 2005]) as opposed to the more enriched values noted from near a roadway in Tokyo (Table 3; −27‰ to −23‰ [ Okuda et al , 2004]) and from urban areas in Washington, DC (Table 3; −24.3‰ to −22.4‰ [ Reddy et al , 2002]) and China (Table 3; −27‰ to −21‰ [ Okuda et al , 2002a]). Okuda et al [2004] estimated the δ 13 C value of PAHs from automotive exhaust in Japan to range from −23.6‰ to −19.5‰, while a separate study revealed PAHs from wood burning to be isotopically lighter (Table 3; −32‰ to −27‰ [ Okuda et al , 2002b]) suggesting that lighter PAH δ 13 C values may also be indicative of biomass sources.…”

“… n Data ranges are reported for measurements on selected individual PAHs in these references: Currie et al [1997]‐ fluoranthene, benz[ a ]anthracene, benzofluoranthenes, benzo[ ghi ]perylene; Okuda et al [2002a]‐ fluoranthene, pyrene, benzofluoranthenes, benzopyrenes, indeno(1, 2 ,3‐cd)pyrene, benzo[ ghi ]perylene; Okuda et al [2002b]‐ benzofluoranthenes, benzopyrenes, indeno(1, 2, 3‐cd)pyrene, benzo[ ghi ]perylene, coronene; Reddy et al [2002]‐ phenanthrene, fluoranthene, pyrene, benz[ a ]anthracene, chrysene/triphenylene, benzofluoranthenes, benzo[ghi]perylene; Okuda et al [2004]‐ fluoranthene, pyrene, cyclopenta( cd )pyrene/benzo[ a ]anthracene/chrysene, benzofluoranthenes, benzopyrenes, indeno(1, 2, 3 ‐cd )pyrene, benzo[ ghi ]perylene, coronene; Kumata et al [2006]– values were reported as LMW and HMW PAHs combined, LMW = anthracene, 3‐,2‐methylphenanthrene, 9‐,1‐methylphenanthrene, 2‐phenylnaphthalene, fluoranthene, acephenanthrylene, pyrene, benzo[ghi]fluoranthene, cyclopenta(cd)pyrene/benz[a]anthracene/chrysene/triphenylene. HMW = benzo[ b + j + k ]fluoranthenes, benzo[ e ]pyrene, benzo[ a ]pyrene, indeno(1, 2, 3 ‐cd )pyrene, benzo[ ghi ]perylene, coronene. …”

Analysis of the mixing state of airborne particles using a tandem combination of laser-induced fluorescence and incandescence techniques

“…The contributions of FBAPs to total "FL" and "MIX" particles were only 3% and 2%, respectively, indicating that over 95% of "FL" and "MIX" particles were not categorized as FBAPs. The remaining part might be polycyclic aromatic hydrocarbons (PAHs), considering their ubiquity in ambient particles of the Tokyo region (Okuda et al,2004), or humic-like substances (HULIS) and secondary organic aerosols (SOAs) (Pöhlker et al, 2012). More studies are needed to reliably relate each category to specific compound types.…”

Use of a temperature‐programmable injector coupled to gas chromatography–combustion–isotope ratio mass spectrometry for compound‐specific carbon isotopic analysis of polycyclic aromatic hydrocarbons

“…For example, the isotopic composition of mono‐aromatic hydrocarbons has been used to elucidate the sources of ground water pollution 5. Polycyclic aromatic hydrocarbons have been analysed for source apportionment in marine sediments, soils and aerosols with methods using their isotopic composition 6–13. The molecular stable isotopic composition of hydrocarbons appears to be a powerful tool which can be used in conjunction with molecular concentration data in environmental studies investigating the origin and fate of those compounds in the environment 4…”