A STUDY OF NEW PARTICLE FORMATION AND GROWTH INVOLVING BIOGENIC AND TRACE GAS SPECIES MEASURED DURING ACE-1

Measurements are presented of ambient nanoparticle distributions (2.7 to 10 nm diameter) in regions of high biogenic emissions encountered d uring the First Aerosol Characterization Experiment (ACE 1), November 15 to December 14, 1995. Large numbers of newly formed nanoparticles w ere observed directly downwind of penguin colonies on Macquarie Island (54.5 degrees S, 159.0 degrees W). In these regions, nanoparticle conc entrations were also correlated with sulfuric acid (H2SO4(g)) gas conc entrations. The measurements show that biogenic species, possibly ammo nia (NH3), either by itself or with H2SO4, nucleated to form new parti cles at rates much higher than bimolecular H2SO4/H2O nucleation. Nanop article distributions evolved as air was advected away from the island showing clear evidence of growth of the newly formed particles. Obser ved growth rates were in the range of 2 to 5 nm h(-1) and were about a factor of 4 to 17 limes higher than the growth by condensing H2SO4(g) and associated water. The cause for fast growth of the newly formed p articles is unknown.