1. METO 637 LESSON 18

2. Schematic of ozone production from VOC

3. SMOG NEEDS Hydrocarbons and nitrogen oxides Strong sunlight to start reactions Warm temperatures to maintain reactions – the higher the temperature the faster the rate. Peak ozone will be close to peak temperature – afternoon

4. Standards Ozone: 1-hour 125 ppbv*, 8-hour 85 ppbv –The 8-hour standard is much more stringent, and encompasses many areas where transport is the only issue (e.g Shenandoah National Park) PM 2.5 : daily 65  g/m 3, yearly 15  g/m 3 –Most areas will have trouble only with the annual standard Visibility: a 60+ year glide path back to “natural conditions” *parts per billion by volume

5. Ozone isopleths (NMHC vs NO x )

6. Ozone vs NO x for NHMC=0.6 ppmc

7. Daily Ozone Cycle SunriseSunset Time of day Ozone Concentration Ozone production follows a daily cycle with maximum concentrations typically observed in the late afternoon. This cycle is a signature of the dynamic processes of atmospheric air pollution

8. Comparison of ozone data at Fort Meade for August 2 and 8 2002

9. Overplot of 2 and 8 Aug 2002 and the difference between the two days

10. Difference 2 Aug minus 8 Aug*1.2

11. Back Trajectories, Hysplit AUG 2, 2002AUG 8, 2002

12. Comparison of Aug 2 and 8, 2002 Ozone data for August 8 is typical for local pollution on a clear warm day. The NO x and VOC are emitted early in the morning and the ozone amount slowly increases as the temperature increases. The peak production is at about 3-4 in the afternoon when the temperature at the ground is a maximum. The back trajectory shows fast upper level winds, which start at a high altitude and then subside to boundary levels at Baltimore. Small probability of upper air being polluted.

13. Comparison of Aug 2 and 8, 2002 On the 2nd of August the back trajectories show that the air is moving slowly at the boundary layer, and the probability of this air being polluted is high. The nocturnal inversion typically breaks down at about 10-11 in the morning. Hence the peak in ozone at this time must come from downward transport. The overall shape of the ozone data on Aug 2 is a combination of locally produced ozone peaking at about 3 pm and a downward movement of ozone from above at about 10.00 am. This ozone above the boundary layer is yesterday’s ozone The winds above the boundary layer are usually high. Hence the ozone has been transported some distance

14. Natural levels of Acidity in Rain Carbon dioxide dissolves in the rain drop CO 2 (g) + H 2 O(aq) ↔ H 2 CO 3 (aq) Henry’s Law states that [H 2 CO 3 ] = K H P(CO 2 ) K H = 3.4E-2 M ATM -1 In the liquid some of the H 2 CO 3 ionizes H 2 CO 3 (aq) ↔ H + (aq) + HCO 3 - (aq) This reaction has an equilibrium constant of 4.2E-7 M -3 For the overall reaction CO 2 (g) + H 2 O(aq) ↔ H + (aq) + HCO 3 (aq) The equilibrium constant K c is 1.43E-8 M 2.ATM -1

15. Natural levels of Acidity in Rain in a liquid [H + ] = [HCO 3 - ] hence [H + ] 2 = K c P[CO 2 ] given that CO 2 has a mixing ratio of 320 ppm we get [H + ] = 2.14E-6 and a pH of 5.67

17. Dispersion of acid rain

18. pH of precipitation over the US

19. Acid rain Acid rain over the Eastern States is the highest – most of the sulfur containing coal occurs in this region Shaded areas in the figure show where granite is found. If the soil/rocks are carbonates (chalk, limestone) then the acid rain can be neutralized, and does not change the pH of the streams and lakes If the soil/rocks are granite then acid rain is not neutralized, and can also leach out the heavy metals. Thus the pH of the lakes and streams can be lowered, and the heavy metal concentration raised.

20. Sources of pollutants in the USA

21. Sulfur Dioxide emissions

23. Annual mean haze, United States IMPROVE network Flight area

24. Detection Techniques In situ via UV pulsed fluorescence. –Modified commercial instrument –Detection limit ~70 ppt (  ) –Response time ~3 min Satellite via UV (315 to 327 nm ) spectroscopy (modified DOAS)

25. Scale height ~1.1 km