School of Transportation Engineering, Chang'an University, Xi'an, 710064, China; Institute for Transport Studies, University of Leeds, Leeds, LS2 9JT, UK.
Institute for Transport Studies, University of Leeds, Leeds, LS2 9JT, UK.
Chemosphere. 2022 Nov;306:135523. doi: 10.1016/j.chemosphere.2022.135523. Epub 2022 Jun 30.
Switching diesel buses (DBs) to electric buses (EBs) has been a global trend to reduce the use of fossil fuels and improve air quality. However, buses electrification may lead to additional vehicle weight, which may emit more non-exhaust particulate matter (PM) emissions. It remains debatable whether buses' electrification will successfully improve air quality as excepted. To assess the effect of the buses' electrification on the levels of PM emissions, PM emission factors (EFs) were evaluated from EBs and equivalent DBs. In addition, the total mass of PM emissions from EBs and equivalent DBs in 2021 was calculated in Xi'an using the real-world number and mileage of EBs. The non-exhaust PM EFs from EBs were larger than total exhaust and non-exhaust PM EFs from DBs, indicating that the electrification of buses would cause an increase in the level of PM emissions. The total annual mass of PM emissions from EBs was apparently higher than that from DBs. Moreover, a sensitivity analysis showed that tire wear, brake wear, and road wear PM emissions were more reliant on vehicle mileage, whereas resuspension of road dust was more dependent on vehicle weight. This finding can serve as a guideline for policymakers to design mitigation strategies for reducing extra PM emissions due to the electrification of buses by reasonably reducing vehicle weight and annual mileage.
切换柴油公交车 (DB) 为电动公交车 (EB) 已成为减少化石燃料使用和改善空气质量的全球趋势。然而，公交车的电气化可能会导致车辆重量增加，从而可能排放更多的非尾气颗粒物 (PM) 。除了化石燃料，PM 排放主要有两种成因：尾气排放和非尾气排放。除尾气排放外，机动车行驶过程中还会产生大量的非尾气排放，如轮胎磨损、刹车片磨损和道路扬尘等。电动公交车的普及可能会导致非尾气排放的增加，从而对空气质量产生负面影响。然而，电动公交车的使用是否能够成功改善空气质量仍存在争议。为了评估公交车电气化对 PM 排放水平的影响，需要评估 EB 和等效 DB 的 PM 排放因子 (EF) 。此外，还需要使用实际的 EB 数量和里程，计算 2021 年西安的 EB 和等效 DB 的总 PM 排放量。从非尾气 PM EF 来看，电动公交车的非尾气 PM EF 大于等效 DB 的总尾气和非尾气 PM EF ，这表明公交车的电气化会导致 PM 排放水平的增加。电动公交车的年总 PM 排放量明显高于柴油公交车。此外，敏感性分析表明，轮胎磨损、刹车片磨损和道路磨损 PM 排放更依赖于车辆里程，而道路灰尘的再悬浮则更依赖于车辆重量。这一发现可以为政策制定者提供指导，通过合理降低车辆重量和年里程，设计减轻因公交车电气化而导致的额外 PM 排放的缓解策略。
