| Abstract: |
The overall goal of the proposed research concerns the chemical evolution of secondary-organic-aerosol (SOA) particles and how this evolution alters their cloud-nucleating properties. Laboratory studies using the Harvard Environmental Chamber (HEC) are proposed. Data analysis and interpretation will include model development in the framework of modified Köhler theory.
• The first objective is to determine the cloud-condensation-nuclei (CCN) activity of SOA particles for different NOx concentrations, light intensities, precursor chemistries, and mixed inorganic species, such as sulfate and nitrate.
• The second objective is to quantify and mechanistically understand how the CCN activity evolves. Reactions with OH, O3, or NO3 lead to SOA aging, defined as changes in composition and properties. Condensation of sulfate and nitrate is also important. Additional aging processes include photochemistry and reactive uptake of organic molecules, such as of aldehydes.
• The third objective is model development that simplifies the computationally expensive general Köhler equation while still representing the laboratory observations, thereby facilitating the implementation of the new laboratory knowledge within the cloud modules of integrated models.
The research product of the proposed work, which is the simplified Köhler equation described above, will be in a form suitable for on-line use in climate and chemical transport models to describe SOA aging and changes in cloud-nucleating properties. |
