AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Rapid Modification of Cloud-Nucleating Ability of Aerosols by Biogenic Emissions
SARAH D. BROOKS, Yan Ma, German Vidaurre, Alexei F. Khalizov, Lin Wang, Jun Zheng, Renyi Zhang, Texas A&M University
Abstract Number: 485 Working Group: Aerosol Chemistry
Abstract Emissions of biogenic volatile organic compounds (VOCs) lead to formation of secondary organic aerosol, contributing to a major fraction of the global tropospheric aerosol loading. The extent to which VOC oxidation products condense onto preexisting primary aerosols and modify their cloud-nucleating properties, however, remain highly uncertain. In chamber studies we show that water-soluble organic acids produced from the reaction between alpha-pinene and ozone rapidly accumulate onto preexisting soot particles. In less than 30 minutes, initially hydrophobic aerosols are converted to aerosols containing a mass fraction of 80-90% organics which activate efficiently as cloud condensation nuclei under representative atmospheric conditions. Our results imply that the microphysical properties of aerosols present in continental air masses are largely controlled by the composition and thickness of coatings (approximately 30 nm in 30 minutes) formed during aerosol aging processes, rather than by the size or composition of original primary particles. Current atmospheric models may considerably underestimate the indirect climate forcing from biogenic emissions.