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Effect of Relative Humidity and Cloud Processing on Biogenic and Anthropogenically-Influenced Organic Aerosols - A Combined Laboratory and Modeling Approach

EMSL Project ID


Recent advances in understanding aerosol chemistry strongly suggest that atmospheric water vapor and liquid water have strong influence of the composition and properties of biogenic and anthropogenic secondary organic aerosols (SOA). The currently on-going Green Ocean Amazon (GOAmazon) campaign has been designed to test how aerosol and cloud life cycles are influenced by the air pollutant outflow from a tropical megacity Manaus in Brazilian rainforest. The main goal of this proposal is to investigate the effects of relative humidity and cloud-processing on the molecular level composition of isoprene-dominated organic aerosols collected during the GOAmazon campaign, using a combination of state-of-the art mass spectrometric experiments and atmospheric chemistry modeling. Recent laboratory studies have demonstrated that evaporation of water from mixtures of biogenic secondary organic aerosols (SOA) with anthropogenic ammonium sulfate leads to an efficient formation of nitrogen organic compounds (NOC), sulfur organic compounds (SOC), and oligomeric compounds. Closely-related processes have also been observed in evaporation of (methyl)glyoxal/ammonium sulfate droplets. This type of chemistry is dramatically accelerated by the water evaporation. The NOC, SOC and oligomeric compounds may sensitively affect the climate-relevant properties of aerosols, such as their optical absorption coefficients, viscosity and hygroscopicity, but the current models do not account for the formation of NOC, SOC, and oligomeric compounds in evaporative processes. We propose to examine particulate matter samples collected during the GOAmazon campaign for evidence of this evaporation driven chemistry, and construct a modeling framework for inclusion of these processes in atmospheric models. The first objective of this proposal is to use unique tools of high-resolution mass-spectrometry, which were recently developed by our DOE PNNL collaborators, Drs. Alexander Laskin and Julia Laskin, to measure the molecular level composition of organic aerosols produced in the Amazon (the samples are being collected as part of GOAmazon by Dr. A. Laskin) from biogenic organics under different humidity scenarios. The second objective is to carry out a set of smog chamber experiments on photooxidation of isoprene and other SOA precursors aimed at reproducing molecular composition of organic aerosol sampled at the GoAmazon campaign, and analyze the resulting SOA composition with methods of high-resolution mass spectrometry and nuclear magnetic resonance. The third objective is to assess the impact of these processes on the aerosol composition using the PNNL's Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) developed by Dr. Rahul Zaveri and the University of California, Irvine (UCI)–California Institute of Technology (CIT) airshed model developed by Prof. Donald Dabdub.

Project Details

Project type
Large-Scale EMSL Research
Start Date
End Date


Principal Investigator

Sergey Nizkorodov
University of California, Irvine


Mary Gilles
Lawrence Berkeley National Laboratory

Team Members

Swarup China
Environmental Molecular Sciences Laboratory

Peng Lin
Environmental Molecular Sciences Laboratory

Lauren Fleming
University of California, Irvine

Donald Dabdub
University of California, Irvine

Rahul Zaveri
Pacific Northwest National Laboratory

Related Publications

Alexandra L. Klodt, Julia Laskin, Alexander Laskin, Peng Lin, Sergey A. Nizkorodov, Dian E. Romonosky. 2019. "Aqueous Photochemistry of Secondary Organic Aerosol of α-Pinene and α-Humulene in the Presence of Hydrogen Peroxide or Inorganic Salts." ACS Earth and Space Chemistry 3 (12):2736-2746. 10.1021/acsearthspacechem.9b00222
Lin P, PK Aiona, Y Li, M Shiraiwa, J Laskin, S Nizkorodov, and A Laskin. 2016. "Molecular Characterization of Brown Carbon in Biomass Burning Aerosol Particles." Environmental Science & Technology 50(21):11815-11824. doi:10.1021/acs.est.6b03024