Atmospheric polycyclic aromatic hydrocarbons (PAHs) originate mostly from incomplete combustion of carbon-based fuels. Amongst atmospheric contaminants, PAHs account for most (35-82%) of the total mutagenic activity of ambient aerosols. Hence, reduction of air pollution by PAHs is essential for an effective air quality control, which requires reliable source apportionment. Recently developed preparative capillary GC system and microscale 14C analysis made CSRA applicable to environmental samples. The 5730 yr half-life of 14C makes it an ideal tracer for identifying combustion products derived from fossil fuels (14C-free) vs. those from modern biomass (contemporary 14C). In the present study we performed radiocarbon analysis of PAHs in fine particulate aerosols (PM10 and PM1.1) from a residential area in suburb Tokyo, to apportion their origin between fossil and biomass combustion. Acquisition of source information for size segregated aerosols (i.e., PM1.1) from 14C measurement was of special interest as particles with diameter of 1µm or less are known to be able to remain suspended in air for weeks and penetrate into the deepest part of the respiratory system.
Materials and Methods
Using high volume air samplers, aerosol samples were collected in FM Tamakyuryo, FS-Center, Tokyo University of Agriculture and Technology (Hachioji, Tokyo Japan), where direct emissions from either mobile or point sources are negligible. All the samples were extracted for PAHs with toluene/MeOH at 80C using ASE100. Extracts were purified by DMF cleanup and SiO2*10%H2O column chromatography. After quantification of PAHs on GC/MS (SIM), leftover extracts were injected on PCGC. Isolated PAHs rinsed from PCGC traps were combusted to CO2 and then reduced to graphite, which was analyzed for 14C at NIES-TERRA, NIES (Tsukuba, Japan).
Results and Discussion
Total PAHs concentrations (sum of 38 compounds with 3-6 aromatic rings) ranged 0.94-3.25 ng//m3 for PM10 and 0.69-2.68 ng//m3 for PM1.1 samples. Observation of relatively small amount of retene (0.2-0.4% of total PAHs) indicates some contribution from wood (Gymnosperm) combustion. Diagnostic isomer pair ratios of PAHs (i.e., 1,7-/2,6-dimethylphenanthrene, fluoranthene/pyrene and indeno[1,2,3-cd]pyrene/benzo[ghi]perylene) indicated mixed contributions both from petroleum and wood/coal combustion sources. Also the ratios implied that the latter source become relatively important in winter than the rest of the year for both PM10 and PM1.1 samples, which coincides with seasonal trend of retene proportion. The source information obtained from 14C analyses will be compared and discussed against that from diagnostic isomer pair ratios.
See more of Poster Session I
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)