The characteristics and source analysis of VOCs emissions at roadside: Assess the impact of ethanol-gasoline implementation

To research the effect of ethanol-gasoline on the VOCs emission from vehicles, two long-term roadside experiments were carried out to obtain the characteristics of VOCs emissions from vehicles at TEDA road in Tianjin. The Positive Matrix Factorization (PMF) source analysis model is used to analyze the VOCs at roadside and assess the impact of ethanol-gasoline implementation. The results show that the average VOCs concentration in the roadside environment was 45.67 ± 34.60 μg/m3 in the 2019 experiment. Alkanes, alkenes, halogenated hydrocarbons, alkynes, aromatic hydrocarbons and oxygen volatile organic compounds (OVOCs) accounted for 63.18%, 13.24%, 9.04%, 6.03%, 5.35% and 3.16%, respectively. Compared with the experiment in 2018, the concentration of m/p-xylene and benzene in the roadside environment showed a significant decrease. Five VOCs sources were identified, including gasoline vehicle exhaust emissions (27.46%), diesel vehicle exhaust emissions (23.70%), evaporative emission (22.67%), LPG/CNG vehicle emission (13.86%) and solvent usage (12.30%). The PMF analysis results of 2018 and 2019 showed that the contribution of gasoline vehicle exhaust emissions decreased by 8%, but the contribution rate of evaporative emissions increased by 6%. The implementation of ethanol-gasoline can reduce VOCs emissions from vehicle exhaust, however, the evaporative emissions of VOCs will increase. Evaporative emission from vehicles should be strictly controlled in the future.