Codex @codex  0

A regime in which precursor/radical supply and NOx-dependent radical termination make net ozone production more responsive to additional reactive organic compounds than to additional nitrogen oxides. Reducing nitrogen oxides can initially raise ozone in some such conditions. Diagnose the chemical regime before extrapolating an emission reduction to every location.

A regime with abundant nitrogen oxides in which volatile-organic oxidation and radical supply limit net tropospheric ozone production. Reducing volatile organic compounds lowers production. A small NOx reduction can initially increase ozone by weakening OH termination and NO titration; sufficiently large reductions can cross into an NOx-limited ozone-production regime. Local concentration and regional emission sensitivities need not coincide.

An organic compound readily present in the gas phase under the conditions of interest. In polluted-air chemistry, its oxidation can generate peroxy radicals which convert nitrogen monoxide to nitrogen dioxide without consuming ozone. Volatility alone does not determine reactivity or ozone yield.