Organic Chemistry - Carbon Compounds

1. Organic Chemistry - Carbon Compounds • Carbon - C, atomic number 6, molecular weight 12 • Electron configuration: 1s22s22p2 • Tetravalent – 4 single bonds (sp3); 2 double bonds (sp2) one triple (sp) plus one single bond • Other atoms: hydrogen, oxygen, nitrogen, sulfur, halogens (Cl, F, Br)

2. Compounds • Alkanes – CnH2n+2 (CH4, C2H6, etc) • Alkenes – CnH2n (C2H4, etc) • Alkynes - CnH2n-2 (C2H2) • Aromatic compounds (C6H6, benzene) • Polycyclic aromatic hydrocarbons - PAH (naphthalene, C10H8)

3. Models Ethane Methane

4. Ethylene (Etene) Pentane

5. Ethanol Benzene

6. Sources of Organics in Air • Anthropogenic: • Incomplete combustion of fossil fuels • Biomass burning • Industrial processes • Cooking • Natural sources • Biogenic emissions (from vegetation) • Volcanic • Evaporation of sea spray • Atmospheric reaction products (from VOC, SVOC), secondary organic aerosol (SOA)

7. Fossil fuels

8. Biomass Burning

9. Other sources - testing

10. Secondary Organic Aerosol (SOA) • SOA processes are studied in photoreactors • European photoreactor (EUPHORE) in Valencia, Spain, is one of the largest (200 m3) and the best-equipped outdoor simulation chamber in the world • We are studying atmospheric transformation of diesel emissions under the influence of sunlight, ozone, hydroxyl radicals that occur during transport in ambient air

11. VOC, SVOC and PM • Vapor pressure ranges: VOC: > 102 Pa (10-1 Torr) SVOC: 102 and 10-6 Pa; (10-1 and 10-8 Torr) PM: < 10-6 Pa (10-8 Torr)

12. Hazardous Air Pollutants (HAPs) • Full list – 188 compounds, most of them organics • The short list – 33 air toxics, most prevalent in urban area • No ambient standards – regulation of emissions from sources

14. Criteria Pollutants – National Ambient Air Quality Standards (NAAQS) • Particulate Matter (PM) • Ozone • NOx • SO2 • CO • Lead (Pb)

15. Why Particulate Matter? • Health effects: particulate matter (fine, PM2.5 and to lesser degree, coarse PM10-2.5) has been associated with adverse health effects at low-to-moderate concentrations • NAAQS exist for PM (since 1971): • current (since 1997): PM2.5 annual 15 µg/m3 and 24-hr 65 µg/m3; PM10 annual 50 µg/m3 and 24-hr 150 µg/m3 _ announced in September 2006: PM2.5 annual 15 µg/m3 and 24-hr 35 µg/m3; PM10 annual only • Climate change • Visibility problem (Haze Rule)

16. Average Ambient PM2.5 Composition in Urban Areas EPA STN network

17. Average PM10-2.5, PM2.5, and PM0.1 composition at EPA “supersite” in Los Angeles, CA, 10/2001 to 9/2002 US EPA OAQPS PM Staff Paper, June 2005

18. Organic Aerosol • Organic aerosols are solid or liquid particles suspended in the atmosphere containing organic carbon • Semi-volatile organic compounds (SVOC) - distributed between gas and particle phases –reversibly condensable • Particle associated organics – complex mixture, incorporated into/onto particles; includes condensed SVOC and non-volatile organic compounds

19. Measurement Methods • Collection of VOC and aerosol samples followed by off-site laboratory analyses • VOC collection: stainless steel SUMMA canisters • PM and SVOC: Filters followed by solid adsorbents

20. Filter-Adsorbent (FA) F A Filter-Filter-Adsorbent (FFA) F1 F A D E Denuder-Filter-Adsorbent (DFA) F A A Electrostatic precipitator (EA) Operational Definitions of SVOC and PM - Associated OC

21. Analysis - Chromatography • Chromatography is a separation method that relies on differences in partitioning behavior between a flowing mobile phase and a stationary phase to separate the components in a mixture.

22. Gas Chromatography (GC)

23. Examples of "hyphenated techniques" include gas and liquid chromatography with mass spectrometry (GC-MS and LC-MS), Fourier-transform infrared spectroscopy (GC-FTIR), and photo diode-array UV-VIS absorption spectroscopy (HPLC-UV-VIS). HPLC - liquid chromatography that utilizes high-pressure pumps to increase the efficiency of the separation