Polycyclic aromatic hydrocarbon emissions from motorcycles

Emissions of polycyclic aromatic hydrocarbons (PAHs, 2-7 ring) and regulated air pollutants (CO, HC, NOx, PM) from 2-stroke carburetor (2-Stk/Cb), 4-stroke carburetor (4-Stk/Cb) and 4-stroke fuel injection (4-Stk/Fl) motorcycles were investigated by testing these vehicles on a chassis dynamometer. Exhaust samplings were carried out on diluted exhausts in a dilution tunnel connected to a constant volume sampling system. Measurements were performed On a standard driving cycle. The results reveal that low molecular weight PAHs (especially naphthalene) dominated in the exhaust gas. The averages of soluble organic fractions were 86.4%. 46.3% and 48.9% for the 2-Stk-/Cb. 4-Stk/Cb and 4-Stk/Fl motorcycles, respectively. PAH emissions are greater from cold-start driving than those from hot-start driving cycle for all these three kinds of motorcycles. Total PAH emission factors were 8320. 5990 and 3390 mug km(-1) for the in-used 2-Stk/Cb, 4-Stk/Cb and 4-Stk/Fl motorcycles, respectively. PAH emission factors were the largest for the 2-Stk/Cb motorcycles. Besides, the 2-Stk/Cb motorcycle had the largest total BaP equivalent emission factor of 10.8 mug km(-1) indicating that the emission exhaust from the 2-Stk/Cb motorcycle was most carcinogenic. HC. PM and PAH emissions were the lowest for the 4-Stk/Fl motorcycles. The correlation coefficient between CO and total PAH emissions for all the test motorcycles was 0.51, indicating that CO and PAH emissions are not highly correlated. (C) 2004 Elsevier Ltd. All rights reserved.