Figure 3-3: (a) Emission indices of detectable volatile particles in
number per kg fuel measured in situ in plumes of various subsonic aircraft
and the supersonic Concorde. The aircraft were examined as part of several
missions in Europe and the United States of America; aircraft types are indicated
in the legends. Ultrafine volatile particles with radii greater than 2 to
3 nm were measured at plume ages less than 20 s (ATTAS, B737, DC-8, B757,
T-38, F-16), with radii greater than 4 to 5 nm at ages of 0.25 to 1 h (Concorde),
and with radii greater than 6 nm at ages of 1 to 2 min (B747, DC-10, A340).
Observations involving the same aircraft are connected by lines. Fuel sulfur
content values were determined by chemical analysis of fuel or inferred from
in situ SO2 measurements (for B747 and DC-10). During the observations, a
contrail either did (filled symbols) or did not (open symbols) form. (b) Same
as (a), but for the emission indices of soot particles. Values from Howard
et al. (1996) for a modern jet engine (about 1013/kg) are below the range
of values shown.