Catalytic oxidation of dimethyl ether

Abstract

The total count number concentration of particles from 10 to 1000 nm, particle size distribution, and PM2.5 (aerodynamic diameter ≤ 2.5 μm) mass concentration were measured on a parking apron next to the runway at Tianjin International Airport in China. The data were collected 250, 270, 300, 350, and 400 m from the runway. Wind direction and wind speed played important roles in determining the characteristics of the atmospheric particles. An inverted U-shaped relationship was observed between the measured particle number concentration and wind speed, with an average peak concentration of 2.2 × 105 particles/cm3 at wind speeds of approximately 4–5 m/s. The atmospheric particle number concentration was affected mainly by aircraft takeoffs and landings, and the PM2.5 mass concentration was affected mainly by the relative humidity (RH) of the atmosphere. Ultrafine particles (UFPs, diameter < 100 nm), with the highest number concentration at a particle size of approximately 16 nm, dominated the measured particle size distributions. The calculated particle emission index values for aircraft takeoff and landing were nearly the same, with mean values of 7.5 × 1015 particles/(kg fuel) and 7.6 × 1015 particles/(kg fuel), respectively. The particle emission rate for one aircraft during takeoff is two orders of magnitude higher than for all gasoline-powered passenger vehicles in Tianjin combined. The particle number concentrations remained much higher than the background concentrations even beyond 400 m from the runway.