Measurements of submicron particles by Fourier transform infrared spectroscopy in 14 campaigns in North America, Asia, South America, and Europe were used to identify characteristic organic functional group compositions of fuel combustion, terrestrial vegetation, and ocean bubble bursting sources, each of which often accounts for more than a third o

Organic aerosol particles are ubiquitous in the atmosphere. In forests, such particles can occur in solid form — a finding that will lead to a re-evaluation of how they are formed, and their properties and effects.