A comprehensive study on emission of volatile organic compounds for light duty gasoline passenger vehicles in China: Illustration of impact factors and renewal emissions of major compounds.

ABSTRACT

BACKGROUND: Many volatile organic compounds (VOCs) are efficient precursors for both ozone and secondary organic aerosol (SOA) which are problematic to environmental controls in many global cities. Vehicle emission is one of the most important anthropogenic sources for VOCs. In between, light duty gasoline passenger vehicles (LDGPVs) contributed more than half of the on-road vehicles in China, demonstrating unique emission characteristics and also significant contributions in emission inventory. OBJECTIVES: To illustrate the variation of VOCs emissions from LDGPVs under different conditions, evaluate the sensitivity of the potential influencing factors, such as emission standards, displacement, cumulative mileage, and driving mode, on the VOCs emissions profiles, and to update the emission inventory by taking into account of the most influential factor. METHODS: In this study, seventy-four in-used LDGPVs were examined by the chassis dynamometer. A total of 25 VOCs in the emissions was quantified using an online time of flight mass spectrometer (TOF-MS). Fuel-based emission factors (EF) were calculated. RESULTS: The results showed that the maximum ΣEF (260.4 ± 241.1 mg/L) was seen for LDGPVs at a high acceleration rate (0.9 m/s2). From the technical control emission standard aspect, the total emission factor of VOCs (expressed as ∑EF) was declined for China IV LDGPVs relative to China III vehicles, with the decreasing extent determined as 24.8%. Among LDGPVs with engine capacity of <1.5 L, 1.5-2.5 L and >2.5 L, it is for 1.5-2.5 L that the lowest ∑EF (101.2 ± 70.1 mg/L) was determined. Along with the increasing of cumulative mileage, the EF values of VOCs were uplift, and the ∑VOCs increased almost linearity, while the increasing trend became steady for ∑EF when the cumulative mileage more than 8 × 104 km. As for different driving conditions, the sequence of EFs from high to low are presented as acceleration (239.3 ± 203.5 mg/L) >idle (226.1 ± 195.6 mg/L) >deceleration (218.5 ± 193.1 mg/L)>uniform (218.2 ± 182.5 mg/L)>slide (176.1 ± 165.2 mg/L). While the cruising speeds increased between 15 and 50 km/h, the linearity between ΣEF declined; however, an opposite trend was seen when the acceleration rates increased. In the chemical speciation, the reactive aromatics contributed the largest fraction of the VOCs (>40%). The ratio of benzene to toluene (B/T) was loaded in high interval (0.94-1.33) in this paper. Larger fluctuation of coefficient of variation (CV) was found among different cumulative mileage and displacement. By taking into account the deterioration effect related to cumulative mileage, emissions of butene, pentene, benzene and toluene were 42.9 Gg, 49.7 Gg, 109.6 Gg and 51.9 Gg in respect for LDGPVs that composed of China III and China IV. CONCLUSIONS: Our results demonstrated the necessaries in upgrading the emission control technology. Cumulative mileages and displacements are the two most dominated factors that impacted on the EFs and chemical profiles of VOCs. The higher emission of benzene estimated demonstrated the possible elevation of VOCs in comparison with previous studies.