14C measurement for size-fractionated airborne particulate matters

A methodology to measure C-14/C-12 of the size-fractionated airborne particulate matter (APM) collected on large quartz substrates in a cascade impactor was established to elucidate the size-fractionated source-receptor relationship of the urban APM in Tokyo. The graphite for the C-14 measurement by the accelerator mass spectrometry was successfully produced from the resultant gas when the APM sample was combusted with increased amounts of 5.0 g copper (II) oxide, 2.5 g copper metal and 0.1 g silver foil in a specially designed large volume combustion tube. In our preliminary field investigation, the percent modern carbon (pMC) values of the size-fractionated APM samples ranged from 37.7 to 65.1 and decreased with particle size, indicating the importance of fossil fuel origins for finer particles. Approximately 40 pMC for the APM of d < 1.1 mum was, however, appreciably higher than our prior expectation. This indicated biomass carbons also contributed significantly to the fine particles in Tokyo. (C) 2004 Elsevier Ltd. All rights reserved.