Effect of photooxidation on .DELTA.13C of benzo(a)pyrene and benzo(e)pyrene in the atmosphere.

Abstract

The objective of this study is to clarify the effect of photooxidation on δ 13 C of benzo(a)pyrene (BaP) and benzo(e)pyrene (BeP) in the atmosphere. They are structural isomers but are known to differ significantly in terms of photooxidation rate. The results of literature reviews and measurements revealed that the concentration ratio of BaP and BeP (BaP/BeP) is almost constant independent of the fuel type and emission source (almost constant at 2.1), while δ 13 C values for the two PAHs are almost equal. On the other hand, the results of ultraviolet irradiation experiments indicated that the concentration of BaP was reduced by photooxidation while δ 13 C of the remaining BaP increased due to isotopic fractionation. In contrast, BeP was not photooxidized and there was no change in δ 13 C. These results lead to the expectation that BaP/BeP and the difference in δ 13 C between BaP and BeP (δ 13 C BaP -δ 13 C BeP ) would decrease and increase, respectively, from the corresponding values at the time of emissions (BaP/BeP: ~2.1; δ 13 C BaP -δ 13 C BeP : ~0) with the progress of photooxidation. This anticipated relationship was close to the results observed over Matsue, which is located on the Japan Sea coast, strongly suggesting there is a change in δ 13 C of BaP due to photooxidation. In addition, the observed results revealed that BaP/BeP and δ 13 C BaP -δ 13 C BeP levels during the winter, when photooxidation is less likely to occur compared to the summer, were similar to the levels during the summer. This supports the hypothesis that in winter, BaP emitted in the Asian continent was photooxidized during the long-range transport process before reaching the atmosphere over Matsue.

Long-range transport of particulate polycyclic aromatic hydrocarbons at Cape Hedo remote island site in the East China Sea between 2005 and 2008

“…Tanaka and Sakata (2002) summarized previous laboratory results of the BaP/BeP ratios from various fuels (gasoline, light oil, heavy oil, coal, and wood). They concluded that the BaP/BeP ratio is almost a Original data given in units of nmol m -3 were converted by assuming a molecular weight to be 250 g mol −1 .…”

Isotopic evidence of boron in precipitation originating from coal burning in Asian continent

“…In Japan, it has been reported that various substances, including non-sea-salt sulfate (nss-SO 4 2-), heavy metals and organic compounds, are transported from the Asian continent to Japan during winter and spring when the airflows from the Asian continent are dominant (Mukai et al, 1990(Mukai et al, , 1994Ichikawa et al, 1998;Tanaka and Sakata, 2002;Sakata and Marumoto, 2005;Sakata et al, 2006). Moreover, Tanimoto et al (2005) showed that the spring maximum of surface O 3 over Japan is significantly caused by NO x from sources in China and Korea.…”

“…Tracers of emissions from coal burning are useful for such evaluation. Several tracers have been used for precipitation and aerosol samples, namely, sulfur isotopes in nss-SO 4 2- (Kitamura et al, 1993), lead isotopes (Mukai et al, 1994), carbon isotopes in some polycyclic aromatic hydrocarbons (Tanaka and Sakata, 2002), selenium composition (Se(IV) and Se(VI)) (Kagawa et al, 2003), and concentration ratio of Pb/Zn…”

Evaluation of long-term trend of atmospheric lead pollution in western Japan based on lead isotope ratios and Pb/Zn ratio as indicators of long-range transport of aerosols from the Asian continent

“…Thus, the long-range transport of air pollutants from China has a measurable impact on atmospheric composition in Japan, which is located at the forefront of the eastern regions of the Asian continent. Studies over the past few decades have shown that various gaseous and particulate pollutants, including non-sea-salt sulfate (nss SO 4 2 − ), nitrate, O 3 , heavy metals, PAHs, and black carbon, are transported from the Asian continent to Japan in winter and spring when the airflows from the Asian continent are dominant (Mukai et al, 1990(Mukai et al, , 1994Ichikawa et al, 1998;Tanaka and Sakata, 2002;Matsumoto et al, 2003;Uno et al, 2003;Tanimoto et al, 2005).…”