LECTURE 01 Cast of Characters

AOSC 434

Air PollutionRussell 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 PollutantsPhotochemical 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. 1971120 ppb for 1 hr. 1979 84 ppb for 8 hr 1997

75 ppb for 8 hr 2010 65 ppb on the books.

• 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. 16

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.

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 pollutantSecondary

 

Effects:

1. Eye irritation

2. Respiratory tract (carcinogen?)

3. Phytotoxin

  Limits: None (too hard to measure)

• Compound "X" in LA smog

• NOx reservoir.

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An interesting history

Smogtown, by Jacobs and Kelly, Overlook Press, 2008.

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, Pbcriteria 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 Deposition2. 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 Effects3 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

Smoke, Fly ash

Post- 2000s:

GlobalGlobal Change

1970s-1990s:

RegionalAcid Rain, Haze

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 + O2 + 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