CHEN/EVEN 4386 Lecture 1

Introduction to Air Pollution

- The Atmosphere

- Definitions and Types of Pollutants

- Important Air Pollutants and Their Effects

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Important air environmental

problems

Urban Ambient Air

Air toxics

Acid rain

Ozone depletion

Global climate change

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What is the Atmosphere?

Gaesous envelope surrounding the Earth

Mixture of gases, also contains suspended solid and liquid particles (aerosols)

Aerosol = dispersed condensed phase suspended in a gas

Aerosols are the visible components of the atmosphere

Pollution haze over East Coast Dust off West Africa

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Vertical Structure of the Atmosphere

Tropopause

Stratopause

Mesopause

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Troposphere

The lowest layer of the atmosphere

extends from the Earths surface up to the tropopause, which is at 10 to 15 km

contains about 90% of the total mass of

the atmosphere

divided into the boundary layer (from the

surface to above 0.5 -3 km) and the free

troposphere, which is rest of the

troposphere 5

Stratosphere

Extends from the tropopause to the stratopause

(~45-50 km)

Contains natural ozone layer which absorbs

ultraviolet sunlight

Mesosphere

Extends from the stratopause to the mesopause

(~80-90 km)

Thermosphere

The region above the mesopause

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The Natural Atmospheric Environment

Gas % by volume ppm ppm by year

2000

Nitrogen (N2) 78.1

Oxygen (O2) 20.9

Argon (Ar) 0.9

Neon (Ne) 18.2

Helium (He) 5.2

Krypton (Kr) 1.14

Xenon (Xe) 0.09

Carbon Dioxide

(CO2)

280.0 360.0

Methane (CH4) 0.75 1.75

Nitrous Oxide (N2O) 0.27 0.31

Trace Gases

Greenhouse

Gases

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What is Air Pollution?

Air pollution: Presence of

one or more contaminants

in the indoor or outdoor

atmosphere in such

quantities and durations as

to be or may be injurious

to human, plant or animal

life, or property.

Air pollutant: A harmful

contaminant in the

atmosphere

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The Problem Air Pollution

American Lung Association (2009): > 60%

of the populations (~186.1 millions) in the

U.S. live in counties where they are exposed

to unhealthful levels of air pollution in the

form of either ozone or short-term or year-

round levels of particles.

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Air Pollutant Phases

Air pollutants are found in three phases

Gas: e.g., ozone, carbon monoxide (CO), sulfur

dioxides, etc.

Liquid: e.g., some organics, aqueous phase ions

like sulfate and nitrate

Solid: e.g., non-aqueous phase ions, crustal

material, elemental carbon

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Important Air Pollutants

Sulfur dioxide (SO2)

Nitrogen dioxide (NO2)

Carbon monoxide (CO)

Lead

Ozone (O3)

- precursors: NOx, VOCs, etc.

Particulate matter (PM) PM2.5

(particulate matter with an aerodynamic

diameter less than 2.5 micrometers)

- precursors: SO2, NOx, NH3, VOCs, etc.

Primary

Pollutants

Secondary

Pollutants

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NADP

The National Atmospheric Deposition Program monitors precipitation

chemistry providing data on the amounts, trends, and geographic

distributions of acids, nutrients, and base cations in precipitation

The program is a cooperative effort between many different group,

including federal, state, tribal and local governmental agencies,

educational institutions, private companies, and non-governmental

agencies.

The Mercury Deposition Network (MDN) joined the NADP in 1996,

and currently has over 100 sites in the United States and Canada. All

MDN samples are analyzed for total mercury, and some for the more

toxic methyl mercury.

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http://nadp.sws.uiuc.edu/

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Units of Air Pollutants Mass Concentration

g/m3: g = 10-6 gram

- Mainly used for particulate matter, sometime for gaseous species

Mixing ratio

ppm: parts per million

- # moles of compound /106 moles of all molecules present

- used for gaseous species, e.g., O3, CO, SO2, etc.

ppb: parts per billion

- # moles of compound /109 moles of all molecules present

- Used for gaseous species, e.g., O3, CO, SO2, etc

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National Ambient Air Quality

Standards (NAAQS) Primary Standards Secondary Standards

Pollutant Level Averaging Time Level Averaging Time

Carbon Monoxide (CO) 9 ppm 8-hour

None 35 ppm 1-hour

Lead (Pb) 0.15 g/m3 Rolling 3-Month Average Same as Primary

1.5 g/m3 Quarterly Average Same as Primary

Nitrogen Nioxide (NO2) 53 ppb Annual Same as Primary

100 ppb 1-hour None

PM10 150 g/m3 24-hour Same as Primary

PM2.5 15 g/m3 Annual Same as Primary

35 g/m3 24-hour Same as Primary

Ozone 0.075 ppm 8-hour Same as Primary

0.12 ppm 1-hour Same as Primary

Sulfur Dioxide (SO2) 0.03 ppm Annual 0.5 ppm 3-hour

0.14 ppm 24-hour

75 ppb 1-hour None 18

CO: Major Causes for Concern

Carbon monoxide can cause harmful health effects by reducing oxygen delivery to the body's

organs (like the heart and brain) and tissues.

Cardiovascular Effects. Central Nervous System Effects. Smog. CO contributes to the formation of smog ground-level ozone, which can trigger serious

respiratory problems

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Control of Motor Vehicle

Emissions

Year Control Action

1970 Clean Air Act sets first auto emissions standards.

1974 EPA sets fuel economy standards.

1975 First catalytic converters are used for CO and hydrocarbons.

First use of unleaded gas in catalyst-equipped cars.

1983 Vehicle inspection and maintenance programs established in 64 cities.

1990 Clean Air Act Amendments set new tailpipe standards.

1992 Oxyfuel introduced in cities with high CO levels.

1994 Phase-in of new vehicle standards and technologies begins

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CO Air Quality Trend

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Lead: Health Effects, Trends and

Emission Sources Reproductive problems (in both men and women) High blood pressure and hypertension Nerve disorders Memory and concentration problems Muscle and joint pain

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