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)

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)

Models

Methane

Ethane

Pentane

Ethylene (Etene)

Benzene

Ethanol

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)

Fossil fuels

Biomass Burning

Other sources - testing

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

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)

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

1. acetaldehyde 18. formaldehyde

2. acrolein 19. hexachlorobenzene

3. acrylonitrile 20. hydrazine

4. arsenic compounds 21. lead compounds

5. benzene 22. manganese compounds

6. beryllium compounds 23. mercury compounds

7. 1, 3-butadiene 24. methylene chloride

8. cadmium compounds 25. nickel compounds

9. carbon tetrachloride 26. perchloroethylene

10. chloroform 27. polychlorinated biphenyls (PCBs)

11. chromium compounds 28. polycyclic organic matter (POM)*

12. coke oven emissions 29. propylene dichloride

13. 1, 3-dichloropropene 30. quinoline

14. diesel particulate matter 31. 1, 1, 2, 2-tetrachloroethane

15. ethylene dibromide 32. trichloroethylene

16. ethylene dichloride 33. vinyl chloride

17. ethylene oxide

Criteria Pollutants – National Ambient Air Quality Standards (NAAQS)

• Particulate Matter (PM)

• Ozone

• NOx

• SO2

• CO

• Lead (Pb)

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)

Average Ambient PM2.5 Composition in Urban Areas

EPA STN network

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

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

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

Operational Definitions of SVOC and PM - Associated OC

Filter-Adsorbent (FA) AF

AFDDenuder-Filter-Adsorbent (DFA)

AEElectrostatic precipitator (EA)

Filter-Filter-Adsorbent (FFA)

F1F A

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.

Gas Chromatography (GC)

• 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