Project Description

OBJECTIVES AND METHODS Objectives 1) Determine the contribution of WSOC to hygroscopic growth under sub- and supersaturated conditions. 2) Measure the molecular composition and physical properties of WSOC. 3) Parameterize measured hygroscopic growth of water-soluble ambient aerosol using ?E-Kohler theory and represent the measurements using thermodynamic equilibrium models to determine: a) how well hygroscopic growth and CCN activity of mixed inorganic and organic aerosols can be represented; and b) to what extent structure-based models of the thermodynamics of water uptake can be constrained by the measurements of WSOC composition and compound structure. 4) Add the representations of WSOC properties developed in (3) to the web-based Extended Aerosol Inorganics Model (E-AIM) of Clegg and Wexler (E-AIM, http://www.aim.env.uea.ac.uk/aim/ aim.php) so that they can be used by other researchers and students. The objectives will be met by conducting the following activities: 1: Collect aerosol samples at Storm Peak Laboratory (SPL) and measure total organic carbon (OC) and WSOC concentrations in the laboratory. Separate WSOC from inorganic ions using solid phase absorbents. Conduct hygroscopic growth and CCN activity experiments on aerosols generated from total water-soluble material (WSM) and isolated WSOC. Hygroscopic growth experiments will be conducted in the laboratory using an HTDMA for 10