Organic Chemistry - Carbon Compounds

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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)

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Compounds

• Alkanes CnH2n2 (CH4, C2H6, etc)
• Alkenes CnH2n (C2H4, etc)
• Alkynes - CnH2n-2 (C2H2)
• Aromatic compounds (C6H6, benzene)
• Polycyclic aromatic hydrocarbons - PAH
  (naphthalene, C10H8)

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Models
Ethane
Methane
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Ethylene (Etene)
Pentane
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Ethanol
Benzene
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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)

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Fossil fuels
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Biomass Burning
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Other sources - testing
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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

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VOC, SVOC and PM

• Vapor pressure ranges
• VOC gt 102 Pa (10-1 Torr)
• SVOC 102 and 10-6 Pa (10-1 and 10-8 Torr)
• PM lt 10-6 Pa (10-8 Torr)

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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

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Criteria Pollutants National Ambient Air
Quality Standards (NAAQS)

• Particulate Matter (PM)
• Ozone
• NOx
• SO2
• CO
• Lead (Pb)

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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)

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

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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

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Operational Definitions of SVOC and PM -
Associated OC
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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.

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Gas Chromatography (GC)
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• 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