Characterizing emission factors and oxidative potential of motorcycle emissions in a real-world tunnel environment
Yu-Chieh Ting, Po-Kai Chang, Po-Chang Hung, Charles C.‐K. Chou, Kai Hsien, Ta-Chih Hsiao
Abstract
Transportation emissions significantly affect human health, air quality , and climate in urban areas. This study conducted experiments in an urban tunnel in Taipei, Taiwan, to characterize vehicle emissions under real driving conditions, providing emission factors of PM 2.5 , eBC, CO , and CO 2 . By applying multiple linear regression, it derives individual emission factors for heavy-duty vehicles (HDVs), light-duty vehicles (LDVs), and motorcycles (MCs). Additionally, the oxidative potential using dithiothreitol assay (OP DTT ) was established to understand PM 2.5 toxicity. Results showed HDVs dominated PM 2.5 and eBC concentrations, while LDVs and MCs influenced CO and CO 2 levels. The CO emission factor for transportation inside the tunnel was found to be higher than those in previous studies, likely owing to the increased fraction of MCs, which generally emit higher CO levels. Among the three vehicle types, HDVs exhibited the highest PM 2.5 and eBC emission factors, while CO and CO 2 levels were relatively higher for LDVs and MCs. The OP DTTm demonstrated that fresh traffic emissions were less toxic than aged aerosols, but higher OP DTTv indicated the impact on human health cannot be ignored. This study updates emission factors for various vehicle types, aiding in accurate assessment of transportation emissions' effects on air quality and human health, and providing a guideline for formulating mitigation strategies.