Abstract
The contributions from fuel and engine oil to automotive exhaust emissions of polynyclear aromatic hydrocarbons (PAH) were studied. Only about 1 to 2% of PAH originally in gasoline survived the combustion process and was recovered from the exhaust, under the 10-mode operating condition. The amounts of PAH produced from one liter of ordinary gasoline in the engine were estimated as about follows: BaP 1 μg, BaA 5 μg, chrysene 5 μg, and pyrene 24 μg. PAH accumulation in engine oil was directly related to fuel PAH and oil mileage, and influenced the exhaust emissions of PAH. An increase in oil consumption caused an increase in PAH emission.
In comparatively new cars, the contributions from fuel and engine oil to exhaust PAH emission were comparable. As car mileage increased, PAH emission level increased and the contribution of PAH produced from pyrolysis of consumed oil became to occupy the larger part of the exhaust PAH emission.
The contribution from pyrolysis of consumed oil was, on the average, the most predominant factor of the emissions of BaP, BaA and chrysene from cars in ordinary city service, accounting for 76, 68 and 62% of their total emissions, respectively; the contributions from other factors decreased in the following order: gasoline PAH (11, 16 and 22% for BaP, BaA and chrysene, respectively), pyrolysis of gasoline (7, 13 an) (11%) and oil PAH (6, 3 and 5%). For emission of pyrene from these cars, on the average, original amount present in gasoline was the most predominant factor, with the contribution ratio of 46%; the contributions from other factors decreased in the order of pyrolysis of consumed oil (31%), pyrene in oil (12%) and pyrolysis of gasoline (11%).
