Bililign gives distinguished lecture at UConn on analysis of organic acids from biomass burning

University of Connecticut logoAround the world, forests and grasslands are being cleared for agriculture. Increasingly, the biomass being produced by this clearing is being burned, adding to the atmosphere carbon dioxide, carbon monoxide, methane and other hydrocarbons, nitric oxide, nitrous oxide, organic acids, inorganic acids and atmospheric particulates and aerosols.  This process may be a significant driver of global atmospheric and climate change.

One especially problematic group among these pollutants is gas-phase organic acids, a significant but poorly understood class of volatile organic compounds.  N.C. A&T physics professor Dr. Solomon Bililign is studying these acids in the atmosphere, and that work was the subject of his address at the University of Connecticut last week when he delivered the Norman Hascoe Distinguished Lecture.

Dr. Bililign’s slides are here.  The abstract of his talk:

Study of Vibrational Overtone Induced Dissociation of Organic Acids From Biomass Burning Using Cavity Ring Down Spectroscopic Techniques
Recent information suggests that on the global scale, biomass burning is much more extensive and widespread than previously thought. Biomass burning refers to the burning of the world’s forests and grasslands and agricultural lands following the harvest for land clearing and land conversion. Combustion products of biomass burning include carbon dioxide, carbon monoxide, methane, nonmethane hydrocarbons, nitric oxide, nitrous oxide, organic acids, inorganic acids and atmospheric particulates and aerosols. One poorly understood, but significant class of volatile organic compounds (VOC) present in biomass burning is gas-phase organic acids and inorganic. These acids are extremely difficult to measure because of their adsorptive nature. Measurements of a variety of organic acids (e.g. acetic acid, peracetic acid, formic acid, pyruvic acid, glycolic acid) and inorganic acids (HNCO, HONO, HCl, HBr, HNO3) were made in Pasadena, California, during May and June 2010 as part of CalNex 2010. Particulates and aerosols produced during biomass burning impact the radiation budget of the Earth and, hence, impact global climate. It is thought that as much as 90% of global biomass burning is human-initiated and that such burning is increasing with time. Hence, biomass burning may be an important driver for global atmospheric and climatic change.

Work in our laboratory uses two methods, Cavity Ring Down Spectroscopy and Mass Spectrometric methods, to characterize some of the properties of the organic acids and aerosols. The following will be presented in this talk.

(a) Use of cavity ring down spectroscopy to measure absorption cross sections for overtone induced photochemistry (vibrational overtone excitation of an O-H bond in organic acid molecules present in the atmosphere). Overtone excitation has been shown to cause dissociation of molecules leading to OH radical production for several species. Results of for acetic acid and peracetic acid will be presented.

(b) Proposed use of cavity ring down CRD technique to determine the optical properties of aerosols composed of mixtures of different absorbing and non-absorbing species and to determine their complex refractive indices and extinction efficiency and progress in this area will be presented.

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