Yañez Cindy C, Bares Ryan, Czimczik Claudia I, Lin John, Zhang Jiachen, Bush Susan, Hopkins Francesca M
Department of Earth System Science, University of California, Irvine, Irvine, California 92697, United States.
Department of Atmospheric Sciences, University of Utah, Salt Lake City, Utah 84112, United States.
Environ Sci Technol. 2025 Jan 21;59(2):1287-1297. doi: 10.1021/acs.est.4c11701. Epub 2025 Jan 8.
Policy interventions and technological advances are mitigating emissions of air pollutants from motor vehicles. As a result, vehicle fleets are expected to progressively combust fuel more efficiently, with a declining ratio of carbon monoxide to carbon dioxide (CO/CO) in their emissions. We assess trends in traffic combustion efficiency in Los Angeles (LA) and Salt Lake City (SLC) by measuring changes in summertime on-road CO/CO between 2013 and 2021 using mobile observations. Our data show a reduction in CO/CO in LA, indicating an improvement in combustion efficiency that likely resulted from stringent regulation of CO emissions. In contrast, we observed an increase in CO/CO values in SLC. While slower progress in SLC compared to LA may be partially due to a later adoption of vehicle emission regulations in Utah compared to California, differing driving conditions and fleet composition may also be playing a role. This is evidenced by increased CO/CO in LA during the COVID-19 pandemic, which led to faster driving speeds and changes to the fleet composition. Our results demonstrate the success of California's CO-reducing policy interventions and illustrate the impacts of traffic characteristics on vehicle combustion efficiency and air pollutant emissions.
政策干预和技术进步正在减少机动车的空气污染物排放。因此，预计车队将逐步更高效地燃烧燃料，其排放物中一氧化碳与二氧化碳的比例（CO/CO₂）将下降。我们通过使用移动观测数据测量2013年至2021年夏季道路上CO/CO₂的变化，来评估洛杉矶（LA）和盐湖城（SLC）的交通燃烧效率趋势。我们的数据显示，洛杉矶的CO/CO₂有所下降，这表明燃烧效率有所提高，这可能是由于对CO排放的严格监管所致。相比之下，我们观察到盐湖城的CO/CO₂值有所增加。虽然与洛杉矶相比，盐湖城的进展较慢可能部分是由于犹他州比加利福尼亚州更晚采用车辆排放法规，但不同的驾驶条件和车队构成也可能起到了作用。这在COVID-19大流行期间洛杉矶的CO/CO₂增加中得到了证明，这导致了更快的驾驶速度和车队构成的变化。我们的结果证明了加利福尼亚州减少CO排放政策干预的成功，并说明了交通特征对车辆燃烧效率和空气污染物排放的影响。
