In this study, a compound method using modified Boeing Fuel Flow Method 2 (BFFM2) and an updated First Order Approximation V3.0 (FOA3.0) method deploying the ICAO Time-in-Mode (TIM) was used to produce a more reliable aircraft emission inventory for the Guangdong–Hong Kong–Macao Greater Bay Area (GBA). The results show that compared with the International Standard Atmosphere (ISA) conditions, the total emission of nitrogen oxides(NOx) decreased by 17.7%, while carbon monoxide(CO) and hydrocarbons(HC) emissions increased by 11.2%. We confirmed that taxiing is the phase in which an aircraft emits the most pollutants. These pollutant emissions will decrease by 0.3% to 3.9% if the taxiing time is reduced by 1 minute. Furthermore, the impact of reducing taxi-out time on emissions is more significant than that of reducing the taxi-in time. Taking the total aircraft emission factors as the main performance indicators, Hong Kong International Airport (VHHH) contributes the most to the total emissions of the GBA, while the Zhuhai airport(ZGSD) contributes the least. The contribution of an individual airport to the total emissions of the GBA is mainly determined by the proportion of Boeing B77L, B77W, and B744.

Cabin air quality and thermal conditions have a direct impact on passenger and flight crew’s health and comfort. In this study, in-cabin thermal environment and particulate matter (PM) exposures were investigated in four China domestic flights. The mean and standard deviation of the in-cabin carbon dioxide (CO₂) concentrations in two tested flights are 1440 ± 111 ppm. The measured maximum in-cabin carbon monoxide (CO) concentration is 1.2 ppm, which is under the US Occupational Safety and Health Administration (OSHA) permissible exposure limit of 10 ppm. The tested relative humidity ranges from 13.8% to 67.0% with an average of 31.7%. The cabin pressure change rates at the end of the climbing stages and the beginning of the descending stages are close to 10 hPa·min⁻¹, which might induce the uncomfortable feeling of passengers and crew members. PM mass concentrations were measured on four flights. The results show that PM concentrations decreased after the aircraft cabin door closed and were affected by severe turbulences. The highest in-cabin PM concentrations were observed in the oldest aircraft with an age of 13.2 years, and the waiting phase in this aircraft generated the highest exposures.

The COVID-19 pandemic has affected air quality due to extreme changes in human behavior. We assessed the air quality response to different emergency levels during different COVID-19 periods and the naught period in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). We obtained the following conclusions: (1) The measures implemented to prevent and control of COVID-19 directly impacted ambient air pollutants. The air quality index and the concentrations of NO2, PM2.5, PM10, and CO in the GBA for 1–19 January 2020 declined 19.4%, 16.7%, 27.5%, 15.8%, and 25.7%, respectively, compared to the same time period in 2016–2019. (2) The reduction in air pollution was strongly associated with the first-level emergency response during this pandemic. The AQI, NO2, PM2.5, PM10, O3, and CO in the GBA decreased by 37.4%, 47.0%, 40.5%, 44.8%, 6.7%, and 24.1%, respectively. We found no statistically significant difference in the concentrations of different pollutants, except for NO2, during the second- and third-level responses. (3) The higher the emergency response level, the greater the NO2 pollutants reduction. The NO2 concentration was reduced by 47.0%, 25.5%, and 12.1% at emergency response levels 1, 2, and 3, respectively. The results highlight the importance of understanding the role of emergency response in air quality, and provide reference for authorities to formulate more scientific and reasonable emergency responses to epidemic prevention and control.

Passengers carrying the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a commercial aircraft cabin may infect other passengers and the cabin crew. In this study, a cabin model of the seven-row Airbus A320 aircraft is constructed and meshed for simulating the SARS-CoV-2 spread in the cabin with a virus carrier using the Computational Fluid Dynamics (CFD) modeling tool. The passengers’ infection risk is also quantified with the susceptible exposure index (SEI) method. The results show that the virus spreads to the ceiling of the cabin within 50 s of the virus carrier’s normal breathing. Coughing makes the virus spread to the front three rows with a higher mass fraction. While the high mass fraction areas always stay on the same side of the aisle as the virus carrier, the adjacent passengers and the passengers in the back two rows are affected more than the others when the virus carrier breathes normally. Spread patterns under the carrier’s two breath conditions, normal breath and cough, were numerically simulated.

Serious traffic-related pollution and high population density during the spring festival (Chinese new year) travel rush (SFTR) increases the travelers’ exposure risk to pollutants and biohazards. This study investigates personal exposure to particulate matter (PM) mass concentration when commuting in five transportation modes during and after the 2020 SFTR: China railway high-speed train (CRH train), subway, bus, car, and walking. The routes are selected between Nanjing and Xuzhou, two major transportation hubs in the Yangtze Delta. The results indicate that personal exposure levels to PM on the CRH train are the lowest and relatively stable, and so it is recommended to take the CRH train back home during the SFTR to reduce the personal PM exposure. The exposure level to PM_2.5 during SFTR is twice as high as the average level of Asia, and it is higher than the WHO air quality guideline (AQG).

During the Spring Festival Travel Rush (SFTR) in China, many people travel and public vehicles are always full. This research studies the air pollutant exposure of commuters under five transportation modes: China railway high-speed train (CRH train), subway, bus, car, and walk. The routes are selected between Nanjing and Xuzhou. The volatile organic compounds (VOCs), carbon dioxide (CO₂), and formaldehyde (HCHO) levels are compared in five different transportation modes. The results indicate that personal exposure level to VOC and HCHO in CRH train is the lowest and relatively stable. So taking the CRH train during the SFTR may be the best choice. During the Corona Virus Disease 2019 (COVID-19) outbreak, spraying 70% alcohol for disinfection in public spaces significantly increased the personal exposure level to VOCs.