Ozone formation potential

TABLE 13.10 Calculated Ozone Formation Potentials for Some CFC Replacements11... 

Carter, W. P. L. Environmental chamber studies of ozone formation potentials of VOCs. Presented at the NATO EST-ARW Workshop on Environmental Simulation Chambers Application to Atmospheric Chemical Processes, Zakopane, Poland, October 1-4 (2004b). 

In general the updated mechanism, MCMv3.1, shows improved ability to simulate some of the observations from the EXACT EUPHORE datasets and represents our current understanding of aromatic degradation. However, significant discrepancies remain concerning, in particular, ozone formation potential and oxidative capacity of aromatic hydrocarbon systems ... 

Environmental Chamber Studies of Ozone Formation Potentials of Volatile Organic Compounds... 

Although the UCR EPA chamber has only been in operation for a relatively short time, it has already obtained usefiil information concerning the performance of current mechanism in predicting the effects of VOCs and NOx on ozone formation. As discussed here and also in our companion paper (Carter, 2004a), the SAPRC-99 mechanism predicts O3 formation reasonably well in low NOx experiments, and in ambient simulation experiments at the high ROG/NOx levels where maximum ozone formation potentials are achieved. However, die new data indicate problems with the mechanisms that were not previously realized. The SAPRC-99 mechanism consistently under predicts O3 formation in the lower ROG/NOx experiments where O3 formation is most sensitive to VOCs, and the problem is even worse for CB4. Other experiments indicate that there are problems with the formulation wifli die current aromatics photooxidation mechanisms. It is possible that the problems with the under prediction at low ROG/NOx ratios may be caused by problems with the aromatics mechanisms. Experimental and mechanism development work to investigate and hopefully resolve these problems is underway... 

Carter, W. P. L. and I. L. Malkina Development and application of Improved methods for measurement of ozone formation potentials of volatile organic compounds. Final report to California Air Resources Board Contract 97-314, May 22 (2002). Available at http //www.cert.ucr.edu/ carter/absts.htm ftrmethipt. 

In all experiments performed, significant formation of ozone was observed. Table 2 compares for all runs both the ozone formation rates and the values for d([03]-[N0])/dt, which provides a measure for the ozone formation potential, derived from die experimental data 2 h after opening the chamber. Both rates are significantly smaller for the base mixture experiments than for the exhaust runs. 

For the future, detailed measurements of NO, HONO and aldehydes in diesel exhaust for typical motor conditions should be considered. The use of such data as input parameters for the calculation of ozone formation potentials (e.g. incremental reactivities by the method of Carter et al. 1995) can contribute to a better estimation of the influence of diesel exhaust on tropospheric ozone formation. 

Future solvent consumption is expected to decrease on account of worldwide environmental restrictions. There will be a shift from aromatic and aliphatic hydrocarbons to oxygen-containing solvents because the latter have a lower ozone formation potential and better dissolution properties. 

Urban ozone formation potential is expressed relative to ethene. It represents the potential of an organic solvents vapor to form ozone relative to fliat of efliene ((g OJg sol-vent)/(g Os/g ethene)). Several groups of solvents, including alcohols, aldehydes, amines, aliphatic and aromatic hydrocarbons, esters, ethers, and ketones are active in ozone formation. Aldehydes, xylenes, some unsaturated compounds, and some terpenes are the most active among those. 

VOC oxidation under high NOx conditions Mechanisms and ozone formation potentials,... 

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