This award will support collaborative research between Dr. Mark Rood, University of Illinois at Urbana-Champaign and Dr. Hans Christen Hansson, Lund Institute of Technology, Sweden. The primary objective for this proposed research project is to develop an instrument that can be used to measure simultaneously the hygroscopic, chemical, and thermal characteristics of aerosol particles under in-situ conditions and with a short time response. Information about the aerosol particles hygroscopicity, composition, and thermal volatility will be obtained by this instrument as a function of particle size. Professors Rood and Hansson will utilize their individual expertise to develop components of the instrument and then they will integrate the individual components to assemble a complete aerosol sampling system. No instrument exists that can simultaneously study the hygroscopic and thermal properties of an aerosol as a function of particle size. Such instrument can be used to perform atmospheric chemistry, atmospheric physics, and air pollution control technology related experiments.