Abstract
The concentrations of more than 100 VOC species have been measured at three sites in Tokyo to estimate the source apportionment considering chemical loss during the summer high ozone concentration period. The photochemical initial concentrations (PICs), the levels of VOCs from sources before undergoing chemical reactions, have been calculated from the reactivity of the VOCs with OH radicals and the ethylene/1,3-butadiene ratio. When the ethylene/1,3-butadiene ratio is set to 17, the PICs are 1.4 times higher than the observed concentrations indicating a 30% chemical loss of emitted VOCs in the summer daytime. The PIC values depend on the value of the ethylene/1,3-butadiene ratio. Isoprene is the most affected because of its high reactivity. The CMB analysis using PICs have yielded better results, when comparing to the VOCs emission inventories. Diesel vehicle exhaust is the greatest source in the center of Tokyo while the biogenic source of isoprene is the highest in the site close to a mountain area. Gasoline vehicle exhaust, gasoline vapor (refueling loss and diurnal breathing loss), and coating are also important sources. Ethylene, formaldehyde, aromatics and other alkenes provide high contributions as a single substance.
