Volatile organic compounds from the exhaust of light-duty diesel vehicles

Abstract

The exhaust gas constituents of light-duty diesel vehicles (LDDVs), including total hydrocarbon (THC), non-methane hydrocarbon (NMHC), carbon monoxide (CO), nitrogen oxide (NOx), and volatile organic compounds (VOCs) were measured by a dynamometer study following federal test procedure-75 (FTP-75) and highway fuel economy cycle. The average fuel consumption of these LDDVs was 0.126 L km−1 for FTP-75, with about 10% fuel consumption savings for highway driving. The average emission factors of NMHC, CO and NOx for light-duty vehicles were 0.158/0.132 (90% of THC), 1.395/1.138, and 1.735/1.907 g km−1 for FTP-75/Highway, respectively. Styrene, n-propylbenzene, n-undecane, o-ethyltoluene, 1,2,4-trimethylbenzene, toluene, o-xylene, isopropylbenzene, m,p-xylene, and ethylbenzene were the dominant VOCs of LDDV exhaust, and the emission factors were about 10–60 mg kg−1. In addition, formaldehyde, acetaldehyde, acetone, butyraldehyde, and m-tolualdehyde were the major carbonyl species from LDDV exhaust, and the emission factors ranged from 1 to 10 mg km−1. The ozone formation potentials of m,p-xylene, o-ethyltoluene, 1,2,4-trimethylbenzene, o-xylene, n-propylbenzene, styrene, and isoprene were >50 mg-O3 km−1. In addition, formaldehyde, acetaldehyde, and butyraldehyde revealed high ozone formation potential of carbonyl species, with values ranging from 10 to 95 mg-O3 km−1. Based on the exhaust constituents and ozone formation potential observed, diesel vehicles could be an important air pollution source for urban and industrial areas.