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Ozone Budget

Ozone Budget. From: Jacob. Ozone in the Atmosphere. Lifetime: ~1 month Highly variable – dependent on season, latitude, altitude, etc. Background concentrations: less than 40 ppbv can reach over 200 ppb in urban areas. Ozone in the Atmosphere.

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Ozone Budget

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  1. Ozone Budget From: Jacob

  2. Ozone in the Atmosphere • Lifetime: • ~1 month • Highly variable – dependent on season, latitude, altitude, etc. • Background concentrations: • less than 40 ppbv • can reach over 200 ppb in urban areas

  3. Ozone in the Atmosphere From: Fishman et al., 2005, Atmos. Chem Phys. Discuss., 3, 1453

  4. HOx Sources and Sinks Source: oxidation of VOCs: Sinks:

  5. HOx Cycle

  6. HOx in the Atmosphere • Lifetime: • ~1 second • highly variable (same reasons as for O3) • Typical concentrations: • ~5 x 106 molecules/cm3 • higher over oceans and southern hemisphere • less anthropogenic CO and methane

  7. NOx Sources and Sinks Sinks: From: Jacob

  8. Nighttime NOx Chemistry There is no NO at night: sink -when the sun comes up

  9. Peroxyacetylnitrates (PANs) Organic radicals of the form: RO ROO R(O)OO can sequester NO2. The most common is PAN: CH3C(O)OONO2.

  10. NOx Cycle

  11. NOx in the Atmosphere • The lifetime of NOx varies, but is about 1 day near the surface and about 1 week in the upper troposphere. • Concentrations range from a few pptv to 10’s of pptv. • higher concentrations near the ground. • Urban areas may reach concentrations of 10s of ppbv.

  12. NOx in the Atmosphere From: Lamsal et al., 2008, J. Geophys. Res., 113, D16308, doi:10.1029/2007JD009235

  13. CO Budget From: Jacob

  14. CO in the Atmosphere • The lifetime of CO is about 2 months with respect to oxidation by OH • CO is not well mixed globally • remote concentrations: 50-150 ppbv • over populated continental regions: 100-300 ppbv • in urban centers: > 1ppmv

  15. CO in the Atmosphere From: Barret et al., 2005, Atmos. Chem Phys. Discuss., 5, 4599

  16. CO in the Atmosphere

  17. Methane Budget From: Jacob

  18. Methane in the Atmosphere • The overall lifetime of methane is 8.5 yrs. • Current concentrations are about 1.8ppmv. • up from 800 ppbv preindustrial • methane and CO2 concentrations track each other over geological time periods.

  19. Methane in the Atmosphere

  20. Methane in the Atmosphere

  21. Beyond CO and Methane • There are literally thousands of volatile organic compounds (VOCs) present in the atmosphere in trace amounts (pptv-ppbv). • Many have short lifetimes • Low concentrations • Big influence on chemistry

  22. Biogenic VOCs Terpene compounds are emitted by trees: Isoprene Monoterpene Sesquiterpene

  23. Biogenic VOCs • Globally, about 80% of VOCs emitted to the atmosphere are biogenic. • Anthropogenic VOCs dominate only in industrial or some urban areas.

  24. Photochemical Smog

  25. Photochemical Smog O3 RO2 RO k2 k3 k1 PHOx k4 O3 OH HO2 k6 k5 O3 H2O2 HNO3

  26. Photochemical Smog

  27. Case 1: Low NOx -O3 production varies linearly with NOx -independent of hydrocarbons NOx-limited regime

  28. Case 2: High NOx

  29. Case 2: High NOx -O3 production varies linearly with hydrocarbons -varies inversely with NOx Hydrocarbon-limited regime

  30. Ozone Pollution From: Jacob

  31. Ozone Pollution • In the background atmosphere:

  32. Ozone Pollution • In the urban atmosphere, there is a competition between NO2 and RH for the OH radical: • As a rule of thumb:

  33. Why too much O3 is a bad thing • Health effects: • Irritation of the lungs (short exposure to high concentrations). • Permanent lung damage (long-term exposure). • Effects are worst for the elderly and people with asthma. • Ecosystem effects: • Reduced photosynthesis (low crop yields). • Increased susceptibility to pests. • Leaf scarring.

  34. Ozone Air Quality Standards • Federal: • 1 hour maximum concentration = 120 ppbv • 8 hour average maximum concentration = 75 ppbv • State of California: • 1 hour maximum concentration = 90 ppbv

  35. Ozone Problem Areas From: EPA

  36. Air Quality Index From: EPA

  37. Air Quality Index

  38. Peak Ozone for California AQI From: www.airnow.gov

  39. LA Region Maximum Ozone From: California Air Resources Board

  40. LA Region Ozone Exceedance From: California Air Resources Board

  41. Sacramento Region Max Ozone From: California Air Resources Board

  42. Sacramento Region Annual Ozone From: California Air Resources Board

  43. Sacramento Ozone Exceedance From: California Air Resources Board

  44. Sacramento Region Ozone Ozone data from: California Air Resources Board

  45. AQI Ozone data from: www.airnow.gov

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