科研之友
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摘要
In view of the lacks of Oxygenated volatile organic compounds (OVOCs) and VOCs emission characteristics from motor vehicles with the latest China VI emission standard. In this study, fleet of light-duty gasoline vehicles spanning emission standards from China I to VI and diesel vehicles with China Ⅲ- China Ⅴ emission standards were selected to carry out the chassis dynamometer test. SUMMA canisters and DNPH cartridges were collectively used for sample analysis to identify the trends of VOCs (including OVOCs) emission characteristics from motor vehicles under different emission standards and to explore the impacts of starting styles on the VOCs emissions. Huge differences in the compositions of gasoline vehicles exhausts were found under different emission standards. With the upgrading of emission standards, the mass fractions of alkanes, alkenes and aromatics gradually reduced and OVOCs increased. Alkanes and aromatics occupied the VOCs emissions from China I-IV gasoline vehicles, while OVOCs were the dominant species in VOCs emissions from China V-VI vehicles, especially China VI vehicles with the OVOCs fraction of 58.0%, in which formaldehyde, acetaldehyde and acetone had the fraction of 47.3%. OVOCs and alkenes were the main components for diesel vehicle exhaust under different emission standards, ranging from 79.0% to 83.0%. Additionally, vehicles had more VOCs emissions during cold start, and the emission factor was much higher than that of hot start. However, the reduction magnitude of VOCs from the starting stage was only around 40%, much lower than that of 77.5% for the entire sampling period with the increasing emission standards. This indicated that the emission contributions from the starting period became much greater with the newer emission standard. This study highlighted the importance of VOCs with the continuous upgrading of emission standards in China. More attention should be paid on OVOCs for light-duty vehicles and alkenes for diesel vehicles when formulating effective control strategies to reduce VOCs emissions from motor vehicles.
