DETERMINATION OF MOTOR-VEHICLE PROFILES FOR NONMETHANE ORGANIC-COMPOUNDS IN THE MEXICO-CITY METROPOLITAN-AREA

Non-methane organic compound (NMOC) profiles for on-road motor vehicle emissions were measured in a downtown tunnel and parking garages in M exico City during 1996. Hydrocarbon samples from the tunnel and ambien t air samples (C2-C12) were collected using stainless steel canisters, and carbonyl compounds were collected using 2,4-dinitrophenylhydrazin e (DNPH) impregnated cartridges. Canister samples were analyzed by gas chromatography/flame ionization detection (GC/FID) to ascertain detai led hydrocarbon composition. DNPH samples were analyzed by high perfor mance liquid chromatography (HPLC). NMOC source profiles were quantifi ed for evaporative emissions from refueling, cold start, and hot soak, and on-road operating conditions. The ultimate purpose will be to det ermine the apportionment of ambient NMOC concentrations using the Chem ical Mass Balance (CMB) model. The tunnel profile contained 42.3 ppbC% of alkanes, 20.6 ppbC% of unsaturated compounds, and 22.4 ppbC% of ar omatics. The most abundant species were acetylene with 7.22 ppbC%, fol lowed by ipentane with 5.69 ppbC%, and toluene with 5.42 ppbC%. These results were compared with those from studies in the United States; Th e cold start profile was found to be similar to the tunnel profile, al though there were differences in the content of acetylene, isopentane, and oxygenates. The abundance of saturated NMOC in the hot soak profi le was similar to gasoline head space profiles; it was also much large r than saturated NMOC in the roadway profile.