New particle formation in the marine boundary layer

Abstract

Aerosol measurements were made in the marine boundary layer along the coast of Washington State. On April 22 the particle concentration increased to levels much higher than usual for the clean marine boundary layer. The total particulate number concentration greater than 3 nm diameter increased rapidly from about 250 cm-3 to 3200 cm-3, remained near that level for 7 hours, and then decreased over the next 2 hours to less than 400 cm-3. The change could not be attributed to either local or distant contamination. Immediately before the increase particulate surface area concentration dropped from 25μm2 cm-3 to less than 5μm2cm-3. The SO2 concentration increased from about 20 pptv to 40-50 pptv just before the increase in particle concentration. This homogeneous nucleation, as opposed to heterogeneous condensation on existing particles, is strongly and inversely dependent on the concentration of existing particles. -from Authors