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Lecture 33: Air Pollution & The Lecture 33: Air Pollution & The Ozone Hole Ozone Hole

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Page 1: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Lecture 33: Air Pollution & The Ozone HoleLecture 33: Air Pollution & The Ozone Hole

Page 2: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Air Pollution and The Ozone HoleAir Pollution and The Ozone Hole

We will discuss:We will discuss:

1.1. Air pollution types, sources, and trendsAir pollution types, sources, and trends

2.2. Tropospheric and stratospheric ozoneTropospheric and stratospheric ozone

3.3. Pollution in the urban environmentPollution in the urban environment

Page 3: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Types & Sources of Air PollutionTypes & Sources of Air PollutionPrimary air Primary air pollutantspollutants enter enter the atmosphere the atmosphere directly, while directly, while secondary secondary pollutantspollutants form form by chemical by chemical reaction.reaction.

Pollutant Pollutant sources are both sources are both naturalnatural, such as , such as volcanoes and volcanoes and forest fires, and forest fires, and human causedhuman caused, , such as cars and such as cars and industry.industry.

Page 4: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Emission inventories

On-road and non-road mobile sources

Point source

s

Area source

s

Biogenic emissions

Page 5: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Principal Air PollutantsPrincipal Air Pollutants

Carbon monoxideCarbon monoxide, , sulfur oxidessulfur oxides, , nitrogen oxidesnitrogen oxides, , volatile organic volatile organic compoundscompounds, and , and particulate matterparticulate matter are the most are the most prevalent prevalent primaryprimary pollutants, and pollutants, and transportation transportation and power and power generationgeneration are the are the primary sources primary sources for these for these pollutants.pollutants.

SOX

NOX

VOC

Page 6: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Definitions: NOx oxides of nitrogen (NO + NO2)

NO colorless, odorless, nonflammable

NO2 orange, toxic, corrosive, sharp odor

Emitted by combustion processes

National emission inventory (18,690 tons N/day)

Page 7: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Definitions: Volatile Organic Compounds, VOCs

VOCs are a group of compounds, characterized by their ability to evaporate and their reactivity in the atmosphere

National emission inventory (133,200 tons C/day)

Emitted by combustion processes (especially vehicles), fuel and solvent evaporation

Page 8: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Particulate Matter PollutionParticulate Matter Pollution

Particulates (particles or droplets) are classified as having Particulates (particles or droplets) are classified as having diameters less than 10 diameters less than 10 μμm (PMm (PM1010) and ) and less than 2.5 less than 2.5 μμm m ((PMPM2.52.5). ). 1 inch = 25,000 microns (1 inch = 25,000 microns (μμm). One larger PMm). One larger PM2.52.5 particle width=30 times smaller than that of a human hair. particle width=30 times smaller than that of a human hair.

PMPM1010 pollutants settle out of the atmosphere relatively quickly pollutants settle out of the atmosphere relatively quickly

compared with the lingering PMcompared with the lingering PM2.52.5. .

Both can adversely affect human health and reduce visibility.Both can adversely affect human health and reduce visibility.

Page 9: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Visible & Invisible PollutantsVisible & Invisible Pollutants

Suspended hygroscopic particles may scatter light and create a Suspended hygroscopic particles may scatter light and create a white wet-haze, while carbon monoxide and sulfur dioxide are not white wet-haze, while carbon monoxide and sulfur dioxide are not visible.visible.

The reaction of nitrogen dioxide and hydrocarbons The reaction of nitrogen dioxide and hydrocarbons in the presence in the presence of sunlightof sunlight may generate unsightly photochemical smog. may generate unsightly photochemical smog.

Page 10: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Ozone in the TroposphereOzone in the Troposphere

Human health is compromised by exposure to ozone and Human health is compromised by exposure to ozone and photochemical smog, which is formed when on a daily cycle when photochemical smog, which is formed when on a daily cycle when sunlight dissociates sunlight dissociates NONO22. .

The product O reacts with atmospheric OThe product O reacts with atmospheric O22 to create O to create O33. .

Usually, the product NO would then react with and destroy the OUsually, the product NO would then react with and destroy the O33..

Excessive hydrocarbonsExcessive hydrocarbons, often from automobile exhaust, react with , often from automobile exhaust, react with the product NO and the product NO and OO33 concentrations concentrations increase to harmful levelsincrease to harmful levels..

OZONE = Volatile Organic

Compounds * Oxides of Nitrogen * Sunlight *

Stagnant Air

Page 11: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Ozone in the StratosphereOzone in the Stratosphere

UV radiation has enough energy to UV radiation has enough energy to adversely impact the health of adversely impact the health of plants and animals, including plants and animals, including humans.humans.

Naturally occurring ONaturally occurring O33 in the in the

stratosphere can block the most stratosphere can block the most harmful UV radiation from harmful UV radiation from entering the troposphere.entering the troposphere.

Page 12: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Stratospheric Ozone DestructionStratospheric Ozone DestructionNaturally destructive Naturally destructive agents of ozone include agents of ozone include NO and NONO and NO22, or oxides of , or oxides of

nitrogen, which largely nitrogen, which largely originate from originate from bacterial bacterial activityactivity at the earth's at the earth's surface.surface.

Human released Human released chlorofluorocarbons chlorofluorocarbons (CFCs) have upset the (CFCs) have upset the balance of Obalance of O33 production production

and destruction,and destruction, and have and have caused formation of caused formation of ozone holes and an ozone holes and an increase in human UV increase in human UV exposure.exposure.

Page 13: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

90% of ozone in atmosphere occurs in a ‘layer’ between 19 and 48 km altitude in stratosphere.

CFCs and Ozone Depletion

Stratospheric ozone protects life on Earth from harmful UV radiation

CFC’s destroy ozone:CFC’s + UV Cl

O3 + Cl ClO + O2

No loose O to make O3

Natural production and destruction O2 + O + UV O3

O3 + UV O2 + O

One Cl atom in a CFC molecule can destroy thousands of O3 molecules

Page 14: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Evidence of Ozone Depletion

Page 15: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

1995: Crutzen, Molina and Rowland share Nobel Prize.

Short history of discovery of ozone problem

1985: Ozone "hole" above Antarctica discovered

1976: M. Molina and F. Rowland theorized that chlorine in chlorofluorocarbons (CFCs: e.g., CH3Cl) also help destroy the ozone layer.

Cl + O3 ClO + O2

1970: P. Crutzen showed that nitrogen oxides are involved in reactions that destroy ozone. NO + O3 NO2 + O2

1987: Montreal Protocol signed to restrict CFCs emissions

Page 16: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric
Page 17: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric
Page 18: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Ozone depletion is a global problem!

Ozone depletion is not just confined to the stratospheric Arctic and Antarctic.

Over the United States in March, 1994, ozone levels fell between 8 and 16% below the values observed during March, 1979.

Page 19: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Decline of CFCs

1987: Montreal Protocol signed to restrict CFCs emissions1992: more than half the world’s nations called for a quicker-phase out1996: NOAA reported a 1% decline around the world from ground stations

1997: stratospheric chlorine concentrations peaked about 1997

Page 20: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Air Pollution Patterns & TrendsAir Pollution Patterns & Trends

Air quality in the U.S. may Air quality in the U.S. may have been at its worst in the have been at its worst in the 1970s, but programs 1970s, but programs implemented by the Clean Air implemented by the Clean Air Act have helped the U.S. move Act have helped the U.S. move toward primary ambient air toward primary ambient air quality standards.quality standards.

Regional Air Quality Indices Regional Air Quality Indices may identify certain non-may identify certain non-attainment areas, which are attainment areas, which are then targeted by the then targeted by the Environmental Protection Environmental Protection Agency for improvement.Agency for improvement.

Page 21: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Trends in Tropospheric OzoneTrends in Tropospheric Ozone

Yearly ozone trends are Yearly ozone trends are influenced by influenced by hot sunny hot sunny weatherweather and and light surface light surface windswinds, but many cities have , but many cities have demonstrated an overall demonstrated an overall decline in harmful ozone decline in harmful ozone levels during the 1980s.levels during the 1980s.

Page 22: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Air pollutants of concern in Texas

PM10 and PM2.5 - Fine particulate matter suspended in the atmosphere degrades visibility and has been associated with increased rates of mortality O3 - Ozone at ground level is an irritant, and is associated with increased incidence of respiratory disease and decreased respiratory function Hazardous air pollutants – A variety of health impacts associated with exposure to HAPs

Page 23: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

Air Quality in Texas cities

• Houston, Dallas/Fort Worth Beaumont/Port Arthur and El Paso violate the current ozone standard and Austin, San Antonio and Longview would violate the new ozone standard.

• El Paso violates the current particulate matter standard. Houston and possibly DFW would likely violate the new particulate matter standard.

Page 24: Lecture 33: Air Pollution & The Ozone Hole. Air Pollution and The Ozone Hole We will discuss: 1.Air pollution types, sources, and trends 2.Tropospheric

32-Hour back trajectories for days with peak 8-hour ozone levels over 75 ppb in Austin (1993-1999)