Vehicular non-exhaust particulate emissions in Chinese megacities: Source profiles, real-world emission factors, and inventories.

Vehicular non-exhaust emissions account for a significant share of atmospheric particulate matter (PM) pollution, but few studies have successfully quantified the contribution of non-exhaust emissions via real-world measurements. Here, we conduct a comprehensive study combining tunnel measurements, laboratory dynamometer and resuspension experiments, and chemical mass balance modeling to obtain source profiles, real-world emission factors (EFs), and inventories of vehicular non-exhaust PM emissions in Chinese megacities. The average vehicular PM2.5 and PM10 EFs measured in the four tunnels in four megacities (i.e., Beijing, Tianjin, Zhengzhou, and Qingdao) range from 8.8 to 16.0 mg km-1 veh-1 and from 37.4 to 63.9 mg km-1 veh-1, respectively. A two-step source apportionment is performed with the information of key tracers and localized profiles of each exhaust and non-exhaust source. Results show that the reconstructed PM10 emissions embody 51-64% soil and cement dust, 26-40% tailpipe exhaust, 7-9% tire wear, and 1-3% brake wear, while PM2.5 emissions are mainly composed of 59-80% tailpipe exhaust, 11-31% soil and cement dust, 4-10% tire wear, and 1-5% brake wear. Fleet composition, road gradient, and pavement roughness are essential factors in determining on-road non-exhaust emissions. Based on the EFs and the results of source apportionment, we estimate that the road dust, tire wear, and brake wear emit 8.1, 2.5, and 0.8 Gg year-1 PM2.5 in China, respectively. Our study highlights the importance of non-exhaust emissions in China, which is essential to assess their impacts on air quality, human health, and climate and formulating effective controlling measures.

[Air Pollution Characteristics and Jogger Inhalation Exposure in Typical Running Area of Beijing].

To investigate the exposure to major air pollutants of runners while running in Beijing, the concentrations of PM2.5, CO, O3, and NO2 were constantly monitored at typical park running areas (Tiantan Park and Olympic Sports Center), roadside running areas (Qianmen East Street and Yongding Inner Street), and a background area (Dinglin) during April, June, and October of 2016 and in January 2017. The concentration variation characteristics for the pollutants in different areas and at different times were analyzed. Using a numerical model of human respiratory exposure, 102 joggers were studied, as was the temporal-spatial variation of inhalation dose of pollutants. At typical running areas, the concentrations of CO, NO2, and PM2.5 were relatively higher in winter, whereas the concentrations of O3 were higher in spring and summer. The concentrations of CO, NO2, and PM2.5 were lower in the afternoon (16:00-18:00), whereas the concentrations of O3 were lower in the morning (06:00-08:00) and evening (18:00-20:00). There was a linear correlation between concentrations roadside to those in nearby parks, as the concentrations of CO roadside were generally consistent with those in parks (croad/cpark=1.01, R2=0.93), the concentrations of NO2 and PM2.5 roadside were higher than those in parks (croad/cpark were 0.56 and 1.19, respectively), and the concentrations of O3 roadside were lower than those in parks (croad/cpark=0.74, R2=0.97). During moderate or higher pollution conditions, 92% of joggers halted outdoor activities, 62.7% chose to jog in parks, 66.7% chose to jog at night, and 64.7% of joggers had single run mileages of 10-20 km. When people chose to jog in the afternoon and evening, the inhalation of CO, NO2, and PM2.5 were relatively lower, whereas the inhalation of O3 was higher. During spring and summer, night running after 20:00 reduced the O3 inhalation dose. Running roadside led to higher inhalation of CO, NO2, and PM2.5 than that in parks; however, O3 inhalation was lower.