Diesel vehicle emissions: Dissecting the multi-factorial effect on variations of VOC-component concentrations

As emission standards tighten, addressing Volatile Organic Compounds (VOCs) has become more urgent. The VOC emissions from diesel vehicles are underestimated in transportation, emphasizing the need to reexamine their emission characteristics. Our study analyzed four diesel vehicles and found that aromatics and alkanes were the dominant categories of VOCs, which accounted for approximately 24 % and 19 %, respectively. Tetrahydrofuran, acetone, and toluene were identified as the main components of VOCs, accounting for 78 % of the total emissions. Specifically, the implementation of tighter emission standards for diesel vehicles resulted in a reduction in the contribution of alkanes to VOC emissions, while that of aromatics increased notably. As the driving speed increased, emissions of aromatics and Volatile Halogenated Hydrocarbons (VHCs) experienced a decreasing trend. In addition, Selective Catalytic Reduction (SCR) has the significant impact on aromatics and VHCs, while cold and hot starts phases affect aromatic emissions mostly, as confirmed by Criteria Importance Through Intercriteria Correlation (CRITIC) analysis.