Table 2.

Equivalent emission indices for condensable gases (excluding H₂O), soot and hydroxyl radicals emitted by aircraft engines or formed in the very young exhaust plume (Schumann and Ström, 2001, Eyers et al., 2005).

Species	Emission index ranges (g kg−1)a	Source
Soot	0.025 (0.01–0.1)b	Fuel carbon
H2SO4	0.04 (0.01–0.1)c	Fuel sulphur SO2 + OH, SO2 + O
HNO2d	0.08–0.8	Fuel- and air-nitrogen passed through combustor, NO + OH
HNO3d	0.003–0.3	Fuel- and air-nitrogen passed through combustor, NO2 + OH
OH	0.1–0.5e	Combustion
Low volatility hydrocarbons	≈0.01–0.02f	Fuel carbon
Volatile aerosol particles	0.0065–0.05g	Condensable gases

^aEquivalent emission index.

^bModern engines have a soot emission index of about 0.01 g soot kg⁻¹ fuel.

^cFor a mean fuel sulphur content of 400 μg g⁻¹ and a measured efficiency ɛ = 0.033 for fuel sulphur conversion to H₂SO₄. Commonly used fuel sulphur content values range from 10 to 1000 μg g⁻¹ (upper limit 3000 μg g⁻¹).

^dCondensable only in very cold, lower stratosphere (see text). (T ≤ 200 K).

^eInferred from measurements with chemical plume models.

^fInferred from measurements (see text) and from Kärcher et al. (2000). Very uncertain.

^gTaking 10¹⁶–10¹⁷ volatile particles (diameter 5 nm) and assuming a specific weight of 1 g cm⁻³. Very uncertain.