Speciated VOCs emissions and ozone formation potential from on-road vehicles in North China Plain based on detailed and localized source profiles

One of China's most heavily ozone (O3) contaminated regions is the North China Plain (NCP). On-road vehicles are major contributors to volatile organic compound (VOC) emissions. We established localized speciated VOC emission inventories for 153 sub-sources using detailed and comprehensive source profiles based on local measurements. The survival ratio of the cars was used to perform a more accurate investigation of vehicle populations. The O3 formation potential (OFP) was calculated based on the speciated VOCs emissions, and key reactive species and sources were identified. Total VOC emissions and OFPs from the on-road vehicles in the NCP were 319.49 kt and 1480 kt, respectively. The emissions of alkanes, alkenes, alkynes, aromatics, halohydrocarbons, and oxygenated VOCs (OVOCs) were 130.53, 50.60, 14.21, 63.07, 3.42, and 57.67 kt, respectively. Formaldehyde, isopentane, and acetylene dominated emissions. Alkenes contributed the most to the OFPs, accounting for 34.47%, followed by aromatics and OVOCs. Formaldehyde, ethylene, and propene were the most common contributors to the OFPs. The emissions and OFPs varied by city, vehicle type, fuel type, and emission standards. Beijing and Xuzhou had the highest emissions, primarily because of their high vehicle populations, while Beijing and Tianjin had the highest OFPs. In addition, high emissions and OFP were detected in Jiangsu, Anhui, Shandong, and Henan (JASH) border areas, as well as in cities with developed industries such as Zhengzhou, Baoding, and Shijiazhuang. For both VOCs emissions and OFP, passenger car was the dominant source among the different vehicle types; petrol vehicle was the dominant source among various fuel types; vehicle under China 3 standard was the dominant source among different standards. The primary contributors to VOC emissions were 4-stroke petrol motorcycle (4-stroke < 250 cm3) under China 0 while the major sources to O3 pollution were heavy-duty diesel trucks with rigidities of 40–50 t under China 3 standard.