Comparison of Surface Organic Compound Mass Spectrum Patterns by LD-TOFMS for Megalopolis Atmospheric Particles and Diesel Exhaust Particles (DEP)

PM sub(2.5) and PM sub(10) samples for megalopolis atmospheric particles were collected at Shinjuku, Tokyo in December 1998-January 1999 and August 1999, for two weeks both in winter and summer, with a 24 hr sampling interval. Sampling of PM sub(2.5) and PM sub(10) in diesel exhaust particles (DEP) was carried out using an automobile exhaust testing system, with a diesel truck placed on a chassis dynamometer. Sampling conditions included idling, constant speed of 40 km hr super(-1), M-15 test pattern and 60%-revolution/40%-load of maximum power. Mass spectrums of organic compounds adhering to the surface of the PM sub(2.5) and PM sub(10) samples were analyzed by laser desorption time-of-flight mass spectrometry (LD-TOFMS, analytical mass range: m/z 1-m/z 380 000). LD-TOFMS analysis of those samples revealed consistently the detection of low-mass organic compounds up to m/z 800. For the megalopolis atmospheric particles, the mass spectrum pattern of wintertime samples was almost the same as that of the summertime samples for both PM sub(2.5) and PM sub(10). The major peak was m/z 177, and the minor peaks were m/z 84, 94, 101,163, 189 and 235. The mass spectrum pattern of DEP was the same for all samples under all test conditions. The major peak was m/z 101, and other detected peaks were small.