Dioxins and furans are believed to be among the most toxic chemicals known to man. The presence of these compounds in the emission gases of municipal solid waste incinerators and other combustion sources has raised debate over the location and the ultimate utility of incineration as an approach to waste management. Current methods used to measure dioxins and furans in combustion source emissions do not provide the real-time monitoring necessary to track average incinerator performance or upset emission levels. A study to design and develop a laser-induced fluorescence/continuous emission monitoring system to detect and quantify these compounds is being conducted. This paper reports the results of the study to date. Vapor-phase ultraviolet absorption spectra, absorption cross sections, and laser-induced fluorescence profiles are presented for three dioxins and two furans. These spectral data are needed for initial design and evaluation of the laser-induced fluorescence/continuous emission monitoring system approach.

Removal rate constants for CH3Q by 02 were measured over the temperature range 298-973 K by using a laser photolysis/laser-induced fluorescence technique. The removal rate constant shows a distinct non-Arrhenius behavior suggesting that other removal processes, in addition to reaction, are important at higher temperatures.

Direct measurements of the rate constant for the bimolecular reaction OH + H2 -H + H20 have been completed in the temperature range 800-1550 K. In these experiments, small amounts of water vapor were photolyzed with an excimer laser to 'instantaneously" create OH radicals and H atoms. The subsequent time history of the OH radicals was monitored by using laser-induced fluorescence. Analysis of the OH removal rate as a function of added hydrogen yielded the rate constant for the above reaction. The temperature range of our measurements bridges the gap between the recent shock tube data (1246-2581 K) of Michael and Sutherland; Frank and Just; Davidson, Chang, and Hanson and the quartz cell flash photolysis data (250-1050 K) of Tully, Ravishankara, and co-workers. Our data are in very good agreement with these previous data sets in the overlap region. By combining our data with these four data sets, we derive a new rate constant expression, k = (3.56 X 10-16)T1,52 exp[-l736/7'l cm3 molecule-' s-I, that is applicable in the temperature range 250-2581 K.

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