HR: 1340h
AN: A23B-1262    [Abstracts]
TI: Observations of hygroscopic and optical properties of biogenic secondary organic aerosol generated using a simple continuous flow reaction chamber
AU: * Petters, M D
EM: petters@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523- 1371, United States
AU: Wex, H
EM: wex@tropos.de
AF: Institute for Tropospheric Research, Permoserstr. 15, Leipzig, 04318, Germany
AU: Massling, A
EM: massling@tropos.de
AF: Institute for Tropospheric Research, Permoserstr. 15, Leipzig, 04318, Germany
AU: McMeeking, G R
EM: grm@lamar.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523- 1371, United States
AU: Kreidenweis, S M
EM: sonia@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523- 1371, United States
AU: Stratmann, F
EM: straddi@tropos.de
AF: Institute for Tropospheric Research, Permoserstr. 15, Leipzig, 04318, Germany
AU: Hallbauer, E
EM: eva.hallbau@tropos.de
AF: Institute for Tropospheric Research, Permoserstr. 15, Leipzig, 04318, Germany
AU: Lee, T
EM: thlee@atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523- 1371, United States
AU: Carrico, C M
EM: carrico@lamar.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523- 1371, United States
AU: Collett, J L
EM: collett@lamar.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Fort Collins, CO 80523- 1371, United States
AU: Ziemann, P J
EM: pziemann@ucr.edu
AF: University of California, Riverside, Air Pollution Research Center, Riverside, CA 92521, United States
AB: Biogenic secondary organic aerosols (BSOA) are a major component of atmospheric particles that impact air quality and climate via radiative and hygroscopic processes. Direct measurements of BSOA properties in the atmosphere are usually complicated by the presence of other aerosol species. Here we examine BSOA properties using a simple continuous flow reaction chamber. We present measurements of the optical and hygroscopic properties of BSOA generated through the reaction of alpha-pinene and ozone at two controlled relative humidity values (<5 and 90%) and selected concentrations and ratios of alpha-pinene to ozone. We measured aerosol size distributions using a differential mobility analyzer and optical particle counter sizing system. Based on optical and mobility size we retrieved a refractive index, n ~ 1.55, which is within the range of values assumed by models, and similar to values retrieved previously using the same method for other oxygenated carbonaceous aerosols. BSOA hygroscopicity was determined using a humidified tandem differential mobility analyzer (60 < RH < 90%) and a cloud condensation nuclei (CCN) counter (0.3 < s < 1.0%). The results are interpreted using the hygroscopicity parameter kappa, which compares the two measurements on a common scale. Hygroscopicity inferred from growth factor data (0.008 < kappa < 0.045) was considerably lower than required to explain CCN activity (0.08 < kappa < 0.16), consistent with previous studies of BSOA generated in smog chambers. To test various proposed hypotheses that may explain this discrepancy we will present water uptake data measured at high RH (80 < RH < 100%) using the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and using a high humidity tandem differential mobility analyzer (HH- TDMA).
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 3311 Clouds and aerosols
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting