2011 年 27 巻 1 号 p. 62-70
We intensively monitored gas and aerosol compositions near a national road, Route 463, in Saitama, Japan in March 2010. Submicron aerosol composition was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a multi-angle absorption photometer (MAAP). Gas-phase measurements were performed with a typical chemiluminescence instrument for detecting NOX and a proton transfer reaction mass spectrometer (PTR-MS) for volatile organic compounds (VOCs). NOX concentrations were highly correlated with black carbon (BC) concentrations (r=0.919, n=223, p<0.01) near the road; in contrast, NOX were poorly correlated with organic aerosol (OA) concentrations (r=0.439, n=184, p<0.1). HR-ToF-AMS measurements facilitated the determination of organic-mass-to-carbon ratio (average 1.36, range 1.25-1.50) and oxygen-to-carbon (O/C) ratio (average 0.18, range 0.08-0.29). This study also demonstrates the utility of chemical mass balance (CMB) analysis with SOA and POA mass spectra as source data to determine the apportionment of secondary OA (SOA) and primary OA (POA) within OA and the source contributions. Positive matrix factorization (PMF) analysis apportioned oxygenated OA (OOA) and hydrocarbon-like OA (HOA) within the OA samples. The SOA/OA and OOA/OA ratios obtained by these two models were 34% and 43%, respectively. These results indicate that not only traffic-related sources but also SOA, including aged OA, contributed substantially to OA concentrations observed at the roadside.