1. Basics of Reactivity March 1, 2001 Dongmin Luo Research Division California Air Resources Board

2. Ozone Problem l Ozone is an ambient ground level pollutant of health concern l Significant reductions have been achieved in ambient ozone levels l However, many urban areas in CA still exceed ozone air quality standards l Additional control strategies are needed

3. Ozone Formation l Ozone is formed from reactions of VOCs and NOx in sunlight l Very low levels of ozone are formed if VOCs are absent l No ozone is formed if NOx is absent l Many types of VOCs promote ozone formation

4. Ozone Control l NOx control l VOC control Mass-based Reactivity-based

5. VOC Reactivity l Thousands of VOCs present in the atmosphere l VOCs differ in their effects on ozone formation e.g., 1 g ethane = 0.31 g ozone 1 g ethylene = 9.1 g ozone alkenes > aromatics > alkanes l Reactivity-based control strategy recognizes the differing reactivities

6. Measures of Reactivity l Ozone formation rate l NO2 formation rate l VOC loss rate l K OH rate constant

7. Ozone Reactivity l Incremental Reactivity Maximum Incremental Reactivity (MIR) Maximum Ozone Incremental Reactivity (MOIR) Equal Benefit Incremental Reactivity (EBIR) l Relative Reactivity

8. Incremental Reactivity l MIR is the most appropriate for regulatory purpose l MIR in California regulation LEV/CF regulation Aerosol coatings regulation