Reactive gas species produced from sulpher, nitrogen and chlorine cycles e.g NOx (NO and NO2 et.c), SO2, reduced sulpher (H2S, DMS) - important in acids precipitation and O3 destruction. SO2 has short (~1-a day) lifetime but easily transported long way.
Aerosols: suspended particles sea salt, mineral dust (esp. silicates), organic matter and smoke.
Particles of d. ~0.1-1 (~0.1) um scatter solar radiation (help condense clouds).
Sulphate aerosols tend to reflect incoming dollar radiation, hence counteract global warming.