Air Pollution (1)

CVEN 301 Introduction to Environmental EngineeringFall 2012

Dr. Qi Ying

Department of Civil Engineering

Introduction

Smoke from coal burning became a serious problem in London as early as the 13th century

“ … As I was walking in your Majesty’s Palace at Whitehall … a presumptuous smoke … did so invade the court .. [that] men could hardly discern on another from the cloud of sea-coal … [an] impure and thick mist, accompanied with a fuliginous and filthy vapor…”

John Evelyn, 1661

“… whosoever found guilty of burning coal shall suffer the loss of his head.”

King Edward II, circa 1300 AD

Criteria Pollutants

(CO)

(P)

(NOx)

(SOx)

(O3)

Nonattainment Areas

Definition: A locality where air pollution levels persistently exceed NAAQS, or that contributes to ambient air quality in a nearby area that fails to meet standards

Maintenance areas are those geographic areas that had a history of nonattainment, but are now consistently meeting the NAAQS.

PARTICULATE MATTER (PM)

National Ambient Air Quality Standard = 15 µg/m3

Air Toxics (Hazardous Air Pollutants - HAPs)

Definition: Pollutants that are known or suspected to cause cancer or other serious health effects.

Example HAPs: Benzene, toluene, asbestos, metals such as mercury and chromium.

Exposure pathways: Breathing contaminated air. Eating contaminated food products. Drinking water contaminated by toxic air pollutants. Ingesting contaminated soil. Touching (making skin contact with) contaminated

soil, dust, or water.

Effects of Air Pollution

Material Deterioration

Vegetation damage

Adverse health effects on humans

Respiratory (asthma, lung cancer, etc)

Cardiovascular

Global climate change

London Smog

Smog = smoke + fog

Adverse effects due to soot particles + acid fog droplets

http://www.metoffice.gov.uk/education/secondary/students/smog.html

Adverse Effects of PM – Health Effect

Dockery D.W. (1993), NEW ENGLAND JOURNAL OF MEDICINE, AN ASSOCIATION

BETWEEN AIR-POLLUTION AND MORTALITY IN 6 UNITED-STATES CITIES

P: Portage, Wisconsin; T: Topeka, Kansas; W: Watertown, Massachusetts; L: St. Louis; H: Harriman, Tennessee;S: Steubenville, Ohio.

Adverse Effects of PM - Visibility

Same PM loading as Houston today(visual range = 10 miles)

Clear Day

(Simulated with WinHaze)

Smog over Burbank, CA

Air Pollution in Various Scales

Indoor Air Pollution (Home and work environment)

Local (near emission source)

Regional

“Smog” and “Photochemical Smog”

Global

Stratospheric Ozone Depletion

Global warming /climate change

GLOBAL ISSUES

Formation of Ozone Layer

An orbit of retrieved GOME ozone profiles on October 22, 1997 overpass Indonesia in the tropics. The red line shows the NCEP tropopause.

O2+UV photon O + OO + O2 + M O3 + M

Both reactions are fast

Formation:

Destruction:O3+UV photon O2 +OO+O3 2O2

Second reaction is slow.O3 life time ~ 1-10 years.

Vertical Structure of the Atmosphere

Each layer is characterized by a uniform change in temperature with increasing altitude. In some layers there is an increase in temperature with altitude, whilst in others it decreases with increasing altitude. The top or boundary of each layer is denoted by a 'pause' where the temperature profile abruptly changes

Ozone depletion

In 1976, Rowland and Molina at UC Irvine proposed that long-lived organic halocarbon compounds used by the chemical industry may cause the destruction of ozone layer

The Chair of the Board of DuPont was quoted as saying that ozone depletion theory is "a science fiction tale...a load of rubbish...utter nonsense"

Ozone Depletion Mechanism

CFCs (Chlorofluorocarbon) have shown to be the major cause of ozone depletion.

They are non-reactive in the troposphere due to lack of UV

They gradually fill the troposphere and diffuse into the stratosphere

3 2

3 22

Cl O ClO O

ClO O Cl O

3 3 23ClO O O

UVCFCs Cl

Net:

Step1: Photolysis (splitting by sunlight) of CFC’s in the stratosphere

Step2: Catalytic destruction of ozone

However …

Largest ozone hole –September 2006

From September 21-30, 2006 the average area of the ozone hold was the largest ever observed. 11.4 million square miles

(Area of USA: 3.5 million square miles)

http://www.nasa.gov/vision/earth/lookingatearth/ozone_record.html

CFC and Montreal Protocol

CFCs are very stable (life time ~100 years) and have been used extensively before 1990 Refrigerants Propellants Solvents

The Montreal Protocol led to the phase out of CFCs by 2000

Recovery of ozone layer won’t happen until ~2050 due to the long life time of CFCs

Recent Surface Temperature Variations

Surface temperatures have shown significant fluctuation over the last 1000 years.

Temperatures rose abruptly over the last century

The cause of these changes is still debated although it can be captured reproducibly in the most sophisticated models.

The Greenhouse Effect

A Runaway Green House Effect

Venus

Surface temperature: 735KAir Composition: 96% CO2

Trend in Green House Gases

Global warming is only the beginning…

Sea level increase

Extreme Weather

The Kyoto Protocol

UN treaty entered into enforce February 2005

Developed countries to reduce their green house emission by an average of 5% below their 1990 level.

EU: 8%

US: 7%

Japan: 6%

United States signed the protocol but didn’t ratify it.

Participation in the Kyoto Protocol

Participation in the Kyoto Protocol: dark green indicates countries that have signed and ratified the treaty, yellow indicates those that have signed and hope to ratify it, and red indicates those that have signed but not ratified it.

REGIONAL AIR POLLUTION

Ozone and photochemical smog

“Air pollution in the Los Angeles area is characterized by a decrease of visibility, crop damage, eye irritation, objectionable odor and rubber deterioration. These effects are attributed to the release of large quantities of hydrocarbon and nitrogen oxides to the atmosphere. The photochemical action of the nitrogen oxides oxidizes the hydrocarbon and thereby forms ozone.”

A.J. Haagen Smit, 1952

Formation of Ground Level Ozone

Ozone formation NO2 + UV NO + O

O + O2 O3

Recycling of NO to NO2 due to radicals generated by VOC oxidation VOC + OH + O2 RO2

. + H2O

RO2. + NO NO2 + RO.

Formation of OH radical O3 + UV O2 + O

O + H2O 2OH

Effects of photochemical smog

Ozone

Severe eye, nose and throat irritants

Lung damage

Plant damage, including leaf discoloration and cell collapse

A factor causing forest losses

NO2

Visibility reduction (brownish color)

Sources of VOC

http://www.tceq.state.tx.us/cgi-bin/compliance/monops/ozone_animation.pl

Calculate Pollutant Emissions

Emission Factor

Representative value that relates the quantity of a pollutant released to the atmosphere with an activity associated with the release of the pollutant.

E = A x EF x (1-ER/100)

E: emission rate

A: activity rate

ER: overall emission reduction efficiency

AP-42

EPA document AP-42 is a compilation of emissions factors

Lists uncontrolled emission factors

Also lists possible controls and their efficiency

Websitehttp://www.epa.gov/ttn/chief/ap42/index.html

Example emission calculation

A reciprocating engine burning 2000 m3 gas per day, calculate carbon monoxide emission per hour using Table 5.1-1, assuming a control efficiency of 80%.

Solution:From the table, EF=7.02 kg/1000 m3 gas burned.

E=2000m3/day x 7.02kg/1000m3 x (1-0.8) / 24 = 0.117 kg/hour