Contribution from biogenic organic compounds to particle growth during the 2010 BEACHON-ROCS campaign in a Colorado temperate needle leaf forest.

New particle formation (NPF) is an important atmospheric phenomenon. During a NPF event, molecular clusters first form by nucleation and then grow further by condensation of vapors. The growth step is crucial because it controls the number of particles that can become cloud condensation nuclei. In order to better understand the influence of biogenic emissions on particle growth, we carried out modeling studies of NPF events during the BEACHON-ROCS campaign at Manitou Experimental Forest Observatory in Colorado, USA. The site is representative of the semi-arid Western US. The implemented chemistry scheme with the latest Criegee intermediates reaction rates under estimates sulfuric acid concentration by 50%, suggesting missing atmospheric sulfuric acid sources. The results emphasize the contribution from biogenic volatile organic compound emissions to particle growth by demonstrating the effects of the oxidation products of monoterpenes and 2-Methyl-3-buten-2-ol (MBO). Monoterpene oxidation products are shown to influence the nighttime particle loadings significantly while their concentrations are insufficient to grow the particles during the day. The growth of ultrafine particles in daytime appears to be closely related to the OH oxidation products of MBO. [ABSTRACT FROM AUTHOR]