Study and update on the characteristic composition of urban emission sources of ozone precursor VOCs in Taiwan

Over the past three decades, the daily maximum eight-hour and annual average concentrations of ozone in Taiwan have not significantly improved with the reduction of its precursors, volatile organic compounds (VOCs) and nitrogen oxides (NOx). High ozone in the lower troposphere may be attributed to a variety of factors, mainly from localized photochemical formation and regional transport as well as minor stratospheric intrusions. Even though the total emissions of precursor VOCs have been significantly reduced in recent years, the reaction potential of different VOCs to ozone formation can vary by dozens of times, as well as their potential to generate SOA and their toxicity to organisms. The composition and quantity of many emission data are old and no longer meet the current conditions under today's new industrial equipment, process methods, new vehicles, engines, catalytic technologies, new lifestyle products and new emission regulations, showing the necessity of updating the emission composition of each major VOCs emission source. The long-term goal of this study is to gradually increase and update the VOC emission characteristics of various major types of emission sources (point sources, line sources, area sources, and biological sources) in the city. The first phase will focus on "mobile source" traffic emissions in urban areas. The composition analysis would be conducted based on vehicle exhaust, indoor parking lots, tunnel vehicle arrays and other sources. Furthermore, the traffic emission indicator, methyl tertiary butyl ether (MTBE), and complete combustion product, CO2, would be exploited to evaluate the VOC composition characteristics and emission factors of various emission sources.