Introduction to Ozone

1. Introduction to Ozone Nate Herbst Southern Ute Indian Tribe

2. Introduction • What is ozone? • Where does it come from? • Why is it bad? • How do we monitor for it? All animation in today’s presentation is provided courtesy of the NASA Goddard Space Flight Center Scientific Visualization Studio.

3. Basic Chemistry • Nature= basic building blocks called elements • Ozone = molecule with 3 oxygen atoms

4. Basic Chemistry (cont.) • Elements in periodic table shown in atomic forms • Atoms can combine to form molecules • Atoms and molecules make up the universe around us

5. Atoms and Molecules • Most elements don’t exist as atoms • Most elements need more electrons than they actually have • To get electrons they need, most atoms take electrons from, or share electrons with, other atoms to form ions and molecules

6. Drawing Molecules • Spheres representing nuclei • Lines beside them representing electrons

7. An Oxygen Atom • Atomic oxygen consists of 1 oxygen atom • The oxygen atom has 3 electron pairs (needs 4) • Unstable, needs more electrons

8. An Oxygen Atom (cont.) • To get 4th electron pair, oxygen atoms can share with other atoms • Results in stable molecules

9. Most common form of oxygen is diatomic (2- atom) molecule This is what we breathe Notice each oxygen atom in molecule has 4 electron pairs Very stable The Oxygen Molecule

10. The Ozone Molecule • Ozone is a tri-atomic oxygen molecule, consists of 3 oxygen atoms • Only 1 of these atoms has 4 electron pairs • Very unstable

11. Ozone Is Very Reactive • Ozone is unstable, will react with anything it can to get 4 electron pairs • Ozone reactivity has positive and negative qualities • Ozone absorbs UV rays • Can react very strongly with body tissues and many other things, such as plants Ozone casts a shadow in U.V radiation (it absorbs some of the radiation). Photo courtesy of University of Wisconsin General Chemistry Class.

12. Two Types of Ozone • Stratospheric ozone- protects our planet by absorbing UV radiation • Tropospheric (ground-level) ozone-harmful, designated as criteria pollutant Ozone absorbing UV radiation. Animation by NASA. Ozone reactivity. Animation by NASA.

13. Ground-Level Ozone • This class focuses on ground-level ozone • “Ozone” refers to ground-level ozone • Corrosive air pollutant • Dangerous at high concentrations • EPA requires ozone monitoring to ensure NAAQS isn’t surpassed

14. Health Effects of Ground-Level Ozone • Respiratory problems, irritates asthma, decreases lung function • Affects • Children, elderly • Those with asthma,other lung problems • People who spend significant time outdoors and exercising • Others…

15. Other effects • Main precursor of smog • Dangerous to animals • Damages vegetation • Damages materials • Others…

16. Ozone standard • 8-hour standard for Ozone: 0.080 ppm • Ozone level must be kept below this standard • More about this later

17. Ozone Formation Is Very Complex • Ozone is not directly emitted • Ozone forms from precursor molecules • anthropogenic, biogenic and pyrogenic sources • Meteorological conditions are also important in ozone formation

18. NOx and VOCs  Ozone • Nitrogen Oxides (NOx) and Volatile Organic Compounds (VOCs) required to form ozone • Can be locally emitted or transported • NOx consists of Nitric oxide (NO) and Nitrogen dioxide (NO2) • Many types of VOCs

19. Majpr sources of NOx and VOCs • Industrial facilities • Mobile source exhaust • Utility companies • Chemical solvents

20. Ozone Precursor Conditions • Most important precursor condition is sunlight • Ozone formation requires sunlight • Other meteorological conditions are also important • Temperature, wind, precipitation, relative humidity, others

21. O3 Dependence on Meteorology

22. Ozone Formation Chemistry • NO + VOCs  NO2 + O2 • NO2 + hv (sunlight)  O + NO • O + O2  O3 • If not enough VOCs, ozone will replace and no net ozone will result Animation shows NO  NO2 and NO2  O+NO. Animation by NASA. Animation shows atmospheric ozone formation but the net process (O+O2O3) is the same. Animation by NASA.

23. Ozone Formation Reaction (Cont.) Net reaction Oxygen atom [ 3 electron pairs] Oxygen molecule [4 electron pairs each] Ozone molecule [4, 5 and 3 electron pairs, respectively] Animation shows atmospheric ozone formation but the net process (O+O2O3) is the same. Animation by NASA.

24. More about NOx, VOC’s and O3 • NOx (NO and NO2) and VOC’s react to form ozone • NO can form and “scavenge” ozone (depends on VOC’s) • Control strategies must address both NOx and VOC’s

25. Ozone Scavenging

26. Good Control Strategies Work EPA 2003 trends report – 4th max 8hr ozone averages are dropping nationwide, due to effective control strategies!

27. Hypothetical Graph (Xs of VOCs)

28. Hypothetical Graph (Few VOCs)

29. Actual Graph (6/1/02)

30. Ozone-Formation Movies • Ozone formation associated with NOx and VOCs (from pyrogenic sources) - temperature also important here (Indonesia 1997) • Global ozone formation (May 1997 – May 1998) Ozone in Indonesia ’97. Animation by NASA. Global ozone ’97-’98. Animation by NASA.

31. Ozone Analysis • Ozone analysis performed using EPA reference method • Ozone absorbs 240nm U.V radiation • By determining UV absorbance, ozone concentration can be known • We’ll discuss this later

32. U. V. Photometric Absorption Quick schematic of ozone U.V absorption analysis Photo courtesy of University of Wisconsin General Chemistry Class. Ozone absorbing U.V radiation. Animation by NASA. The amount of U.V light leaving cell #1 corresponds to [O3] The amount of U.V light leaving cell #2 provides your blank. U.V. Lamp Zero air Ambient air Detector

33. Summary • Ground level ozone is a dangerous pollutant • Must be maintained below standard • Ozone formation is complex, involves different precursor molecules and conditions • Ozone monitoring is important • Ozone monitoring should be included in any air quality program