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UNCERTAINTIES AND RESEARCH NEEDS IN QUANTIFYING VOC REACTIVITY FOR STATIONARY SOURCE EMISSION CONTROLS WILLIAM P L CARTER STATEWIDE AIR POLLUTION RESEARCH CENTER and COLLEGE OF ENGINEERING CENTER FOR ENVIRONMENTAL RESEARCH AND TECHNOLOGY UNIVERSITY OF CALIFORNIA RIVERSIDE CA 92521 PRESENTED AT THE CHEMICAL MANAFACTURERS ASSOCIATION FEBRUARY 8 1996 THE PHOTOCHEMICAL OZONE PROBLEM PHOTOCHEMICAL SMOG IS CHARACTERIZED BY THE FORMATION OF OZONE AND OTHER OXIDANTS IN SUNLIGHT EXCESSIVE GROUND LEVEL OZONE IS AN AIR QUALITY PROBLEM BECAUSE IT CAUSES ADVERSE HEALTH EFFECTS AND DAMAGE TO MATERIALS SOUTHERN CALIFORNIA HAS THE WORST OZONE PROBLEM IN THE UNITED STATES BUT MANY OTHER URBAN AREAS ALSO EXCEED OZONE AIR QUALITY STANDARDS OZONE IS NOT EMITTED DIRECTLY IT IS FORMED WHEN SUNLIGHT REACTS WITH EMITTED OXIDES OF NITROGEN NOx AND VOLATILE ORGANICS COMPOUNDS VOCs OZONE IS NOT THE ONLY POLLUTANT OF CONCERN IN PHOTOCHEMICAL SMOG BUT IT IS THE FOCUS OF MOST CONTROL REGULATIONS FOR VOCs OTHER THAN TOXICS OZONE CONTROL THE ONLY WAY TO REDUCE OZONE FORMATION IS TO REDUCE EMISSIONS OF ITS VOC AND NOx PRECURSORS BUT ALL THE EASY CONTROLS HAVE BEEN IMPLEMENTED ADDITIONAL CONTROLS WILL BE COSTLY AND DISRUPTIVE VOC AND NOx CONTROL ARE NOT EQUALLY EFFECTIVE IN REDUCING OZONE DIFFERENT TYPES OF VOCs HAVE DIFFERENT OZONE IMPACTS REACTIVITIES AN UNDERSTANDING OF THE PROCESS OF OZONE FORMATION NECESSARY TO DETERMINE THE MOST COST EFFECTIVE OZONE CONTROL STRATEGY CHEMISTRY OF O3 IN PHOTOCHEMICAL SMOG THE ONLY SIGNIFICANT CHEMICAL REACTION WHICH FORMS OZONE IN THE TROPOSPHERE IS THE PHOTOLYSIS OF NO2 k1 NO2 h NO O OR OVERALL NO 2 h M O O2 O3 NO O 3 BUT THIS IS REVERSED BY THE RAPID REACTION OF O3 WITH NO k2 NO O3 NO2 O2 THESE PROCESSES RESULT IN A PHOTOSTATIONARY STATE BEING ESTABLISHED WHERE O3 IS PROPORTIONAL TO THE NO2 TO NO RATIO k1 O3 k2 NO2 NO IF OTHER REACTANTS ARE NOT PRESENT TO CONVERT NO TO NO2 ONLY VERY LOW LEVELS OF OZONE ARE FORMED ROLE OF VOCs IN OZONE FORMATION WHEN VOLATILE



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