Unexpected high volatile organic compounds emission from vehicles on the Tibetan Plateau

Abstract. Vehicle emissions significantly affect atmospheric composition, but their behavior in high-altitude environments is still poorly understood. In this paper, we conducted a comprehensive survey of vehicle emissions from ten tunnels in the Qinghai-Tibet plateau, covering an altitude change of nearly 3,000 meters. The results show that the total emission factor of volatile organic compounds (VOCs) increases with elevation, mainly due to a significant increase in evaporation emissions. Source analysis shows that evaporation emissions account for 67 % of VOC and are significantly higher than 24 % of exhaust emissions. This model differs from observed patterns at low elevations, where exhaust emissions are predominant. We believe that low pressure is a key factor in enhancing the release of evaporative VOCs at high altitudes. The study provides important new insights into vehicle emission mechanisms in the highlands and highlights the need to consider specific environmental conditions and fuel evaporation when developing emission control strategies at high altitudes. The promotion of electric vehicles (EVs) at high elevations such as Tibet is a win-win solution for reducing emissions and making use of the abundance of renewable energy sources in Tibet.