APES

Get out lab – keep at table

SMOG

Ch. 18

Smog

• Localized air pollution in urban areas, mixture of pollutants that form with interaction with sunlight

TYPES:1. Brown2. Gray

Air Pollution & Primary Pollutants

Primary Pollutants Undergo Reactions to form Secondary Pollutants

C + O2 CO2

2C + O2 2CO + Soot

S + O2 SO2

N2 + O2 2NO

Photochemical (Brown) Smog

• Brown haze• Light initiates complex chemical

reactions

Photochemical Smog in Santiago, Chile

Photochemical Smog Reaction

• VOCs + NOx + Heat + Sunlight yields

– Ground level O3 and other photochemical oxidants

– Aldehydes– Other secondary pollutants

Fig. 18-11, p. 475

PANS and other pollutantsVolatile organic compounds (VOCs)

Ozone (O3)

Oxygen (O2)

Nitric oxide (NO) + Oxygen atom (O)

Water vapor (H2O)

Hydrocarbons UV radiationPeroxyacyl nitrates (PANs) Nitrogen dioxide (NO2)

Oxygen (O2)

Nitric oxide (NO)

Oxygen (O2) Burning fossil fuels

Nitrogen (N) in fossil fuel

SimplifiedModel

HOW? (Nitric Acid AKA Acid Rain)

NO2 +UV NO + O

2NO + O2 2NO2

3NO2 + H2O 2HNO3 + NO

N2 & O2 in air react @ high temps nitrogen monoxide

Stinky, yellowish brown gas, haze above cities (Nitrogen dioxide)

Forms nitric acid & Nitrogen monoxide

Nitric Acid = Acid Precipitation

HOW? Tropospheric Ozone (BAD!)

NO2 +UV NO + O

O + O2 O3

Produces free oxygen

Tropospheric ozone

HOW? Peroxyacyl Nitrates (PANS)

O2 + hydrocarbons + NO PANS (peroxyacyl nitrates)

• Burning Eyes • Damage

Vegetation

Photochemical Smog Reaction

Fig. 17-6 p. 424

Photochemical Oxidants

• NO2, O3, PANS

• Able to react with & oxidize compounds in atm. or our lungs

• Respiratory health issues• Damaging to vegetation

Industrial (Gray) Smog

• Smoke pollution• Sulfur oxides• Particulates from burning

coal/oil,• Problems in China/India/Russia

due to lack of pollution controls on smokestacks

Industrial Smog Reaction

• When burned, most carbon in coal and oil converted to CO & CO2

• Soot = unburned coal (suspended particulates)

• Sulfur dioxide & sulfuric acid created

Fig. 18-9, p. 474

Ammonium sulfate [(NH 4 )2SO4]

Ammonia (NH3)

Sulfuric acid (H2SO4)

Water vapor (H2O) Carbon monoxide (CO) and carbon

dioxide (CO2)Sulfur trioxide (SO3)

Oxygen (O2)

Sulfur dioxide (SO2)

Burning coal and oil

Oxygen (O2)

Sulfur (S) in coal and oil Carbon (C) in coal and oil

How? (Carbon)

C + O2 CO2 + Soot (gray color)

2C + O2 2CO + Soot

#1 human made GHG

Incomplete combustion

How? (Sulfur)

S + O2 SO2 (suffocating gas)

2SO2 + O2 2SO3

SO3 + H2O H2SO4 (sulfuric acid, acid rain)

2NH3 + H2SO4 (NH4)2SO4

(Ammonium Sulfate – GRAY COLOR)

Smog also creates greenhouse gases

• Methane (CH4)

• Nitrous Oxide (N2O

Smog

• Hotter days = O3 & other components

What’s location got to do with it?

• Cities with sunny, warm & dry climates

• Greater number of motor vehicles EX: LA; Salt Lake City, Utah; Syndey, Australia; Sao Paulo, Brazil; Bangkok, Thailand; Mexico City, Mexico and Santiago, Chile

What’s Location Got to Do With It?

• Temperature differences help to disperse air pollutants preventing harmful buildup of air toxins

• Ground air is warmed, rises, then cools = CONVECTION

Temperature Inversions• Ground air colder than

upper air – trap harmful pollutants near ground

• Cooler air is denser than warmer air above it

• Pollutants concentrate in stagnant cool layer

• NO mixing due to density

Types of Temperature Inversions

• Subsidence - Warmer mass enters high altitude region and floats atop a colder air mass. Prevents vertical mixing.

Types of Temperature Inversions

• Subsidence

Types of Temperature Inversions

• Radiation – Occurs at night as ground air cools faster than air above. Sun rises and warms surface – dispersing pollutants that were trapped during night

Inversion layer

Mountainrange

Sea breeze

Descending warm air mass

Decreasing temperature

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Types of Temperature Inversions*

Where does this occur?

• Valleys surrounded by mountains

Where does this occur?

• Near coastlines with sunny climage, and surrounded by mountains

EX: Los Angeles, CA

Where does this occur?

• Leeward side of mountains