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Funding: CMU Startup NSF EPA Send comments to nmd@andrew.cmu.edu Last updated: 26 Feb 2006 by nmd |
Research in the group addresses a number of fundamental questions, combining theoretical, experimental, and observational work in a series of project aereas. Here we dissect the research along several axes. Major Project AreasGas-phase reactive intermediatesShort-lived intermediates are often control branching at rate-limiting steps of oxidation mechanisms. Many are generated with excess energy in exothermic reactions, and collisional energy transfer can dominate their behavior, making the chemistry pressure and size dependent. We seek to observe these intermediates spectroscopically in a flow reactor and model the chemistry with computational quantum chemistry and statistical reaction dynamics in order to develop general models of organic oxidation.low-temperature ozone-alkene oxidation on surfacesThe initial reactive intermediate in ozone-alkene reactions is a primary ozonide (POZ). This POZ can be stabilized and isolated on cold surfaces. We are using cold, IR-transparent surfaces to trap primary ozonides and to use temperature programmed decomposition monitored by real-time FTIR to measure the decomposition kinetics of the ozonides.Secondary organic aerosol behaviorEPA-funded project to improve mechanisms for organic oxidation leading to organic particulate matter. The primary method is to measure aerosol size distributions in our smog chamber for different precursors under different oxidation conditions (temperature, odd-nitrogen levels, etc). The primary result will be resolution of product yields into a number of different volatilities and corresponding constraints on efficient aerosol formation mechanisms used in regional air quality models. A major policy question is whether SOA are formed primarily from industrial or biogenic emissions.Oxidation kinetics of organic aerosolProject to measure the `aging' of organic aerosol, combining field data (results from the Pittsburgh Air Quality Study, PAQS) with chamber oxidation experiments to determine both absolute `uptake' coefficients for oxidants as well as relative rate constants for various condensed-phase organics, using carefully prepared mixtures of a few model compounds and real emissions. The relative rate constants will control which compounds are oxidized in complex organic mixtures characteristic of real emissions.Air toxics in Allegheny CountyProject to measure organics in Pittsburgh, including both gas-phase and condensed-phase compounds, using two gas-chromatograph / mass spectrometer instruments. Engineering objectives include resolution of multiple sources (ie, Neville Island) using high time resolution data for source `fingerprinting' as well as development of an automated instrument for measurement of condensed-phase organics. |
