Abstract
Atmospheric aerosols were collected during several oceanographic cruises in the Atlantic and Pacific Oceans as well as in the continental source regions of soot carbon aerosols. The samples were analyzed for soot carbon by a reflection technique, for light elements by proton elastic scattering (PESA), and for elements heavier than Na by proton induced X-ray emission (PIXE). Significant amounts of soot carbon were observed consistently over the remote tropical Atlantic and occasionally over the remote Pacific. On the basis of the concentrations of other aerosol components, in particular excess fine potassium (the amount of submicron K not related to the seasalt and soil components), we are able to suggest that a substantial fraction of the soot carbon over the remote tropical oceans originates from biomass burning in the tropics.