GAS-PHASE AND PARTICLE-PHASE ORGANIC-COMPOUNDS EMITTED FROM MOTOR-VEHICLE TRAFFIC IN A LOS-ANGELES ROADWAY TUNNEL

The emission rates for 221 vapor-phase, semivolatile, and particle-pha se organic compounds from motor vehicles plus fine particulate matter mass and some inorganic particle-phase species are calculated based on measurements made inside and outside a Los Angeles roadway tunnel in 1993. These emission rates are calculated based on fuel consumption to remove any uncertainties based on tunnel dilution rates or air circul ation. The results show carbon monoxide emissions rates of 130 g L-1 o f gasoline-equivalent fuel burned and volatile organic compound (VOC) emissions of 9.1 g L-1. These values are higher than predicted.by the baseline version of California's EMFAC 7G emissions inventory program but are within the coemission rate range of 108 +/- 25 g L-1 reported: by roadside remote sensing studies in Los Angeles [Singer, B. C.; Harl ey, R. A. J. Air Waste Manage. Assoc. 1996, 46, 581-593]. When the VOC emissions composition in the tunnel is compared td that of tailpipe e missions source test data and to the composition of additional unburne d. whole gasoline, the tunnel atmosphere is found to be consistent wit h a linear combination of these major contributors over a fairly broad range of about 74-97% vehicle exhaust depending on the tailpipe profi les used. Fine particulate emissions within the tunnel consist largely of carbonaceous material accompanied by a significant amount of ammon ium nitrate apparently formed by gas-to-particle conversion processes within the tunnel atmosphere. Certain gas-phase and particulate organi c compounds traditionally thought to be the Secondary products of atmo spheric chemical reactions are enriched inside the tunnel, and from th is enrichment, the primary emission rates of aromatic alcohols, alipha tic dicarboxylic acids, and aromatic polycarboxylic acids are calculat ed. Data on petroleum biomarkers emissions rates in the tunnel can he used in the future to estimate primary vehicle exhaust fine particulat e matter concentrations in the urban atmosphere.