This Collaborative Research Activities in Environmental Molecular Science (CRAEMS) Award to Worcester Polytechnic Institute is supported by the Special Projects Office in the Chemistry Division. Barbara Wyslouzil is supported by this award for the fundamental study of nanoparticle formation in air pollution. Support is also provided to Doug Doren, Murray Johnston, Hai Wang, and Anthony Wexler at the University of Delaware through subawards. An integrated experimental and theoretical program will be carried out to understand, at a molecular level, the processes of nanoparticle formation that are relevant to air pollution. The topics that will be addressed are (1) nucleation in aqueous systems, (2) soot inception, and (3) the interaction between soot and metals during combustion. Water, water/alcohol and water/nitric acid aerosols will be generated in a supersonic nozzle and characterized by small angle neutron scattering and FTIR. Molecular simulation techniques will be applied to calculate nucleation rates and to address important non-equilibrium effects. Soot particles will be generated in a flat flame burner and characterized by sampling with a scanning mobility particle sizer. Size distributions will be compared to those derived from small angle neutron and x-ray scattering experiments. Molecular composition of the particles will be determined by mass spectrometry. The reaction between metals and soot will be studied by generating particles from ethylene-oxygen flames, seeded with ferrocene. Mathematical models will be developed that incorporate molecular mechanisms of metal oxide particle formation and carbon deposition.
Particle nucleation is a key step in many environmental and industrial processes. Refractory particles are formed in combustion and metallurgical processes, while acid-water droplets are produced in stack gases, volcanic plumes and in photochemical reactions in the atmosphere. This research will help define the mechanisms by which they are formed and the role they play in air pollution.
