Originally Posted by
underfire
When engines are at reduced thrust in the landing cycle (below 3000 feet), this is when the most pollution occurs, with lower temp and incomplete burn. The primary issue here is Nitrogen Oxides.
NOx is produced at high pressures and burn temperatures (when oxygen reacts with nitrogen) , which coincide with high thrust settings. Low thrust settings result in incomplete combustion and results in things like hydrocarbons and carbon monoxide.
I think the research you quote is on how much concentration of only N2O there is, not all NxOx compounds. Also it is per kg fuel (fuel flow at idle is much lower). Plus they used DC-8 era engines...