LECTURE 01
Cast of Characters
AOSC 434
Air Pollution
Russell R. Dickerson
www.atmos.umd.edu/~russ/syllabus434.html
London killer smog
Donora, PA October 29, 1948; 2:00pm LST
1950’s local – 2000’s global.
Washington Post Jan. 25, 2014
“China’s air pollution prompts
creative, sometimes wacky,
solutions”
Pollution and Smog
Seinfeld & Pandis Ch. 2
Finlayson-Pitts & Pitts Ch. 1
Wark & Warner Ch. 1
Jacob Chapters 12 & 13.
Definitions
• Los Angeles Smog (photochemical smog) is the mixture of ozone,
hydrocarbons, partially oxidized hydrocarbons, oxides of nitrogen and
other trace gases that results from the action of sunlight on automobile
exhaust and other pollutants. It is characterized by high temperatures
stagnant winds (high barometric pressure), and sunny conditions.
• London Smog (particulate, or sulfurous smog) is a mixture of sulfur
dioxide and sulfate and sulfite aerosol resulting primarily from the
combustion of high sulfur coal followed by conversion of SO2 to H2SO4. It
is characterized by low temperatures, high humidity and stagnant winds.
Air Pollutants
Photochemical and London Smog
Species Involved
Including Criteria Pollutants
Limit here refers to the National Ambient Air
Quality Standard (NAAQS) established by the
US-EPA.
1. Ozone, O3 (Photochemical Oxidant)
criteria pollutant
Secondary
• Effects:
1. Respiration - premature aging of lungs (Bascom et al., 1996);
mortality (e.g., Jerrett et al., 2009). 4%/10ppb
2. Phytotoxin, i.e. Vegetation damage (Heck et al., JAPCA., 1982;
Schmalwieser et al. 2003; MacKinzie and El-Ashry, 1988)
3. Materials damage - rubber
4. Greenhouse effect (9.6 m)
• Limit: (National Ambient Air Quality Standard)
80 ppb for 1 hr.
1971
120 ppb for 1 hr. 1979
84 ppb for 8 hr
1997
75 ppb for 8 hr
2010
70 ppb for 8 hr 2015
• Ozone is an indicator of smog.
• Ozone regulates many other oxidants
Ozone damaged plants.
What does history tell us?
• Denora, Pitt, and London were sulfurous smogs.
• Early work in Los Angeles focused on SO2 from
refineries – smog got worse.
• VOC’s targeted next – smog got worse.
• Denora, London, etc. were worse in winter – LA was
worse in summer.
• Burning eyes in LA.
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What does history tell us?
P. L. McGill, Stanford Research Institute*, “The Los Angeles Smog
Problem” Industrial and Engineering Chemistry, 2476-86, 1949.
“Unquestionably the most disagreeable aspect of smog is eye
irritation.” They blamed elemental sulfur.
Mechanism of the Smog: “Weather conditions control the time of
occurrence of eye-irritating smog in Los Angeles.” Meteorology and
topography. Identified temperature inversions and stagnant winds as
contributors.
No mention of combustion, ozone, photochemistry, or automobiles
other than as a source of H2CO that did not cause eye irritation.
*supported by The Western Oil and Gas Association.
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Haagen-Smit (1952) “Photochemical action of
nitrogen oxides oxidized the hydrocarbons and thereby
forms ozone….”
Almost right.
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Ozone is a national problem
2. Nitrogen Dioxide, NO2
criteria pollutant
Primary
Effects:
1. Lungs (acute chemical pneumonia)
EPA Criteria Pollutant
2. Phytotoxin
3. Catalyst for ozone formation.
4. Atmospheric acidity (about 1/3 of problem and growing)
Limit: 100 g m-3 (53 ppb) annual mean
200 g m-3 (100 ppb) hourly mean (2010)
3. Carbon Monoxide, CO
criteria pollutant
Primary
Effects:
1. Respiration (acute); EPA Criteria Pollutant
2. Cardiovascular system (chronic)
3. Contributor to photochemical smog
4. Changes global HOx cycle (oxidizing capacity of atmosphere).
Limits:
9.0 ppm for 8 hr
35 ppm for 1 hr
50 ppm for 8 hr is the "level of significant harm"
3. Carbon Monoxide, CO (cont…)
•
•
•
•
Affinity for hemoglobin 200 times that of O2.
Displaces O2 at [CO] = 0.2x106/ 200 = 103 ppm.
Concentrations above 750 ppm are fatal.
Concentrations > 100 ppm cause dizziness, headache, loss of visual &
mental acuity.
• Cigarette smoke contains ca. 400 ppm CO (also HCN, H2CO, Ni(CO)4,
NO2).
4. Peroxyacetyl Nitrate, "PAN"
(CH3 C(O)-O-O- NO2)
not a criteria pollutant
Secondary
Effects:
1. Eye irritation
2. Respiratory tract (carcinogen?)
3. Phytotoxin
Limits: None (too hard to measure)
• Compound "X" in LA smog
• NOx reservoir.
An interesting history
Smogtown, by Jacobs and Kelly,
Overlook Press, 2008.
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5. Polynuclear Aromatic Hydrocarbons, "PAH"
(Also Polycyclic Aromatic Hydrocarbons)
See Also Finlayson-Pitts Chapt. 9&10.
Primary
Effects:
1. Carcinogenic (one of the few known
carcinogens in air)
Limits: None
• Low/moderate vapor pressure; divided
between particulate & gas-phases.
• Example: Benzo(a)pyrene (BaP)
• Nitrated PAH even stronger carcinogens .
6. Ethylene, H2C=CH2
Primary
Effects:
1. Ozone formation
2. Plant hormone (e.g. oranges)
Limits: None
• Other biogenic hydrocarbons, isoprene, pinenes.
• Some plants when stressed release more ethylene
7. Formaldehyde, H2CO
Primary and secondary
Effects:
1. Ozone formation
2. Eye irritant
3. Mutagen, suspected carcinogen
Limits: None
• Indoor air pollutant too, (ureaformaldehyde insulation)
• Produced by HC oxidation
• Represents class of partially oxidized HC
8. Lead, Pb
criteria pollutant
Primary
Effects:
1. Toxic, leads to loss of mental
acuity.
Limits: 0.15 µg/m3 rolling three
month average.
Now primarily a problem of the
developing world.
9. Other Pollutants (toxics)
Halogenated Hydrocarbons
Example: Dioxin
Effects: 1. Teratogen
2. LD50 in guinea pigs is 0.5 to 1.0 g/kg
Limits: None
• Produced as byproduct in 2,4-D and 2,4,5-T synthesis and by incomplete
combustion of chlorine containing refuse such as plastics.
• "Freons" will be considered as part of stratospheric air pollution.
LONDON-TYPE SMOG
10. Sulfur Dioxide, SO2
Primary
Effects
1. Produces H2SO4 found on particles and in precipitation
- Acid Deposition
2. Cloud Condensation Nuclei (climate)
3. Materials degradation
4. Respiratory tract (esp. bisulfites, HSO3-)
5. Phytotoxin
10. Sulfur Dioxide, SO2 (cont…)
Limits:
Primary 1-hr Standard: 75 ppb (June 2010)
Secondary standard 500 ppb for 3 hr
SO2  (HSO3-)aq  H2SO4 (+ NH3)  NH4HSO4 (+ NH3)  (NH4)2SO4
• EPA Criteria Pollutant
• No catalytic photochemistry
• More on chemistry and physics later
11. Fine Particulate Matter (PM2.5)
Aerodynamic Diameter < 2.5 μm
Limits:
35 μg m-3 for 24 hr
12 μg m-3 annual mean
(150 μg m-3 for 24 hr for PM10)
• Primary and secondary pollutants.
• Major health effects:
• More on chemistry and physics later
Wet deposition of sulfate
12. Carbon Dioxide, CO2
Primary
Non toxic below percent levels.
Dominant greenhouse gas.
Health Effects
3 Steps for Estimating
• Epi Study determines C-R function
• Estimate incidences and change in exposure
• Calculate deaths and assign a value
Local, Regional, Global Pollution
Before 1950s:
Local
1970s-1990s:
Regional
Smoke, Fly ash
Acid Rain, Haze
Post- 2000s:
Global
Global Change
Lecture Summary
There are a variety of pollutants.
They have health and environmental or welfare effects.
You will be expected to know the name and basic facts of
each pollutant or pollutant family.
This course will provide you with the tools to understand
the impact, sources, chemistry, transport, trends, and
sinks for all of these pollutants – and some that have not
been discovered yet.
TROPOSPHERIC Ozone Photochemistry
CLEAN AIR
(1) O3 + h  O2 + O(1D)
(2) O(1D) + H2O  2OH
(3) OH + O3  HO2 + O2
(4) HO2 + O3  2O2 + OH
----------------------------------------(3+4) 2O3  3O2
NET
DIRTY AIR
(3') OH + CO  H + CO2
(4') H + O2 + M  HO2 + M
(5') HO2 + NO  NO2 + OH
(6') NO2 + h  NO + O
(7') O + O2 + M  O3 + M
------------------------------------------------(3'-7') CO + 2 O2  CO2 + O3
NET
Similar Reaction Sequence For Methane
CH4 + OH  CH3 + H2O
CH3 + O2 + M  CH3O2 + M
CH3O2 + NO  NO2 + CH3O
CH3O + O2  H2CO + HO2
HO2 + NO  NO2 + OH
NO2 + h  NO + O
O + O 2 + M  O3 + M
---------------------------------------------------------------------CH4 + 4 O2 + h 2 O3 + H2CO + H2O
NET
What Is The Fate Of Formaldehyde?
2H2CO + h  H2 + CO
 HCO + H
H + O2 + M  HO2 + M
HCO + O2  HO2 + CO
-------------------------------------------2H2CO + 2O2  2CO + 2HO2 + H2
This means two ozone molecules are produced per
formaldehyde. The grand total for methane is four O3
produced! Methane is a good model for all alkanes, but by
itself reacts too slowly to form much ozone locally, it is,
however, important on a global scale. The net production
of ozone requires converting of NO to NO2 without
consuming O2.
International Journal of Chronic Obstructive
Pulmonary Disease, 2014