First gaseous ion composition measurements in the exhaust plume of a jet aircraft in flight: Implications for gaseous sulfuric acid, aerosols, and chemiions

Abstract

indicates that the ions observed in the plume were entrained ambient atmospheric ions. By contrast no indications for negative chemiions (with masses < 1100 amu) produced by the airbus engines were found in the plume. Furthermore our measurements indicate a modest decrease of the total concentration of entrained negative ions in the plume compared to the ambient atmosphere outside the plume. This decrease may be due to ion-removal by ion-attachment to aerosol-particles and/or ion-recombination with positive chemiions. We propose that the observed entrained ions can serve as probes for important plume components including gaseous sulfuric acid, aerosol particles and chemiions. Making use of this analytical potential we infer upper limits for the gaseous sulfuric acid concentration, total aerosol surface area density, and positive chemiion concentration. We conclude that initially formed gaseous sulfuric acid must have experienced rapid gas-to-particle conversion already in the very early plume at plume ages < 1.6 s.

Ion recombination in aircraft exhaust plumes

“…At the same time, ion concentrations larger than 10 9 cm -3 are needed, in a model based on the dominant role of ions in ultrafine particles formation (Yu and Turco, 1998), in order to obtain a satisfactory comparison with the available measurements. Very recently, in-flight measurements have been reported (Arnold et al, 1998b(Arnold et al, , 1999, but for plume ages larger than 0.3 s. Unfortunately, at such plume ages the data are more difficult to analyse due to the complexity of ionremoval processes.…”

A Fourier transform infrared study of the adsorption of SO2 on n‐hexane soot from −130° to −40°C

“…However, recent measurements of particulates in the exhaust plume of aircraft indicate that the known mechanisms for sulfur dioxide oxidation are not rapid enough to explain sulfuric acid aerosol formation in combustion exhaust [Fahey et al, 1995; Toon amt Miake-Lye, 1998, and references therein]. One possible explanation is that ions formed during combustion [Yu and Turco, 1997] or entrained from ambient air [Arnold et al, 1998] may enhance particle formation. A second possibility is that soot particles catalyze the oxidation of sulfur dioxide to sulfuric acid, resulting in much higher conversion rates compared to gas-phase oxidation of SO 2 [Schumann, et al, 1996;Fahey et al, 1995;Novakov, 1982].…”

Ultrafine particle size distributions measured in aircraft exhaust plumes

“…A second, neutral mode of particles formed by classical homogeneous nucleation and controlled in number by the FSC is •so believed to be present in the exhaust plume, but may be too small to be detectable at typical FSCs. The presence of chemi-ions in aircraft engine exhaust has been been documented; however, measurements of chemi-ion concentrations and properties both on the ground and in flight are very sparse and represent lower limits [Arnold et al, 1998a[Arnold et al, , 1998b[Arnold et al, , 1999.…”