arep gaw section 7 chemical aspects of air pollution overview of basic pollutants ozone particulate...

AREPGAW

Section 7Chemical Aspects

of Air PollutionOverview of Basic Pollutants

OzoneParticulate MatterCarbon Monoxide

Sulfur DioxideNitrogen Oxides

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Section 7 – Chemical Aspects of Air Pollution

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Photochemical Smog

Air pollution formed by sunlight catalyzing chemical reactions of emitted compounds

Los Angeles, California• Early pollution due to London-type smog.

1905-1912, L.A. City Council adopts regulation controlling smoke

• Early 1900’s, automobile use increases.1939-1943 visibility decreases significantly.

• Plume of pollution engulfs downtown (26 July 1943).1943: L.A. County Board of Supervisors bans emission of dense

smoke and creates office called Director of Air Pollution Control

• 1945. L.A. Health Officer suggests pollution due to locomotives, diesel trucks, backyard incinerators, lumber mills, dumps, cars.

• 1946. L.A. Times hires air pollution expert to find methods to ameliorate pollution.

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Los Angeles, California (December 3, 1909)

Library of Congress Prints and Photographs Division, Washington, D. C.

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Discovery of Ozone in Smog

• 1948: Arie Haagen-Smit (1900-1977), biochemistry professor at Caltech, begins to study plants damaged by smog.

• 1950: Finds that plants sealed in a chamber and exposed to ozone exhibit similar damage as did plants in smog

• Also finds that ozone caused eye irritation, damage to materials, respiratory problems.

• Other researchers find that rubber cracks within minutes when exposed to high ozone.

• 1952: Haagen-Smit finds that ozone forms when oxides of nitrogen and reactive organic gases are exposed to sunlight. Postulates that ozone and precursors are main constituents of L.A. smog.

• Oil companies and business leaders argue that ozone in L.A. originates from stratosphere.

• Measurements of low ozone over Catalina Island disprove this.

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Basic Pollutants (1 of 3)

Categories of pollutants● Primary – emitted directly from a source● Secondary – formed in the atmosphere from a reaction of

primary pollutants● Precursors – primary pollutants (gases) that participate in

the formation of secondary pollutants

Pollutants originate from● Combustion of fossil fuels and organic matter● Evaporation of petroleum products or compounds used in

commercial products, services, and manufacturing● Natural production of smoke from fires, dust from strong

winds, and emissions from the biosphere and geosphere

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PrimarySO2Sulfur Dioxide

Primary & SecondaryPMParticulate Matter

Primary & SecondaryHCHydrocarbon Compounds

(also called VOCs – volatile organic compounds )

SecondaryNO2Nitrogen Dioxide

SecondaryO3Ozone

PrimaryCOCarbon Monoxide

TypeAbbreviationPollutant


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Basic Pollutants – Toxics (1 of 2)

● Air toxics (hazardous air pollutants) are known or suspected to cause cancer or other serious health effects.

● EPA’s 188 hazardous air pollutants include– Benzene (motor fuel, oil refineries, chemical processes)– Perchlorethylene (dry cleaning, degreasing)– Chloroform (solvent in adhesive and pesticides, by-product of

chlorination processes)– BTEX, Dioxins, PAHs, Metals (Hg, Cr)

National air toxics emissions sources in 1996U.S. Environmental Protection Agency, 1998

Area/Other25%

Mobile (nonroad)

20%

Mobile (onroad)

31%

Point24%

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Basic Pollutants – Toxics (2 of 2)

• Differences between toxics and criteria pollutants– Health criteria are different

• No AQI-like standards for toxics• Cancer/non-cancer benchmarks (long-term exposures)• Short-term exposure limits for some

– A challenge to monitor• Usually not available in real-time• Example: Dioxin requires 28 days of sampling

to acquire measurable amounts in ambient air– Often localized near source

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Basic Pollutants – Sources (1 of 4)

• Combustion• Evaporation• Natural Production

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Combustion• Complete combustion

Fuel water and carbon dioxide (CO2)

• Incomplete combustion

Fuel water, CO2, and other pollutants

Pollutants are both gases and particles

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Evaporation• Thousands of chemical compounds• Liquids evaporating or gases being released• Some harmful by themselves, some react to produce other

pollutants• Many items you can smell are evaporative pollutants

– Gasoline – benzene (sweet odor, toxic, carcinogenic)

– Bleach – chlorine (toxic, greenhouse gas)

– Trees – pinenes, limonene (ozone- and particulate matter forming)

– Paint – volatile organic compounds (ozone- and particulate matter forming)

– Baking bread, fermenting wine and beer – VOCs and ethanol (ozone-forming)

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Natural Production• Fires (combustion) produce

gases and particles• Winds “pick up” dust, dirt,

sand and create particles of various sizes

• Biosphere emits gases from trees, plants, soil, ocean, animals, microbes

• Volcanoes and oil seeps produce particles and gases

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Ozone

• Colorless gas • Composed of three oxygen atoms

– Oxygen molecule (O2)—needed to sustain life– Ozone (O3) —the extra oxygen atom makes ozone

very reactive

• Secondary pollutant that forms from precursor gases – Nitric oxide – combustion product– Volatile organic compounds (VOCs) – evaporative

and combustion products

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Solar radiation and chemistry

• The reaction that produces ozone in the atmosphere:

O + O2 + M O3 + M

• Difference between stratospheric and tropospheric ozone generation is in the source of atomic O

• For solar radiation with a wavelength of less than 242 nm:

O2 + hv O + O

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Solar radiation and chemistry

• Photochemical production of O3 in troposphere tied to NOx (NO + NO2)

• For wavelengths less than 424 nm:

NO2 + hv NO + O

• But NO will react with O3

NO + O3 NO2

• Cycling has no net effect on ozone

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Tropospheric Ozone Photolysis

Troposphere ozone photolysis takes place in a narrow UV window

(300-320 nm), NO2 broadly below 428

30o equinoxmiddaySolar spectrum

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Nitrogen Oxides

● Nitrogen oxides, or NOx, is the generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts.

● Nitrogen dioxide is most visually prominent (it is the yellow-brown color in smog)

● The primary man-made sources of NOx are motor vehicles; electric utilities; and other industrial, commercial, and residential sources that burn fuels

● Affects the respiratory system● Involved in other pollutant chemistry

– One of the main ingredients in the formation of ground-level ozone – Reacts to form nitrate particles, acid aerosols, and NO2, which also

cause respiratory problems– Contributes to the formation of acid rain (deposition)

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Must make NO2

• To make significant amounts of ozone must have a way to make NO2 without consuming ozone

• Presence of peroxy radicals, from the oxidation of hydrocarbons, disturbs O3-NO-NO2 cycle

NO + HO2· NO2 + OH·

NO + RO2· NO2 + RO·

– leads to net production of ozone

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The Hydroxyl Radical

• produced from ozone photolysis– for radiation with wavelengths less than 320

nm:O3 + hv O(1D) + O2

followed byO(1D) + M O(3P) + M (+O2O3) (~90%)

O(1D) + H2O 2 OH· (~10%)

• OH initiates the atmospheric oxidation of a wide range of compounds in the atmosphere– referred to as ‘detergent of the atmosphere’– typical concentrations near the surface ~106 - 107cm-3

– very reactive, effectively recycled

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THE OH RADICAL: MAIN TROPOSPHERIC OXIDANT

• Primary source:• O3 + hn O2 + O(1D) (1)• O(1D) + M O + M

(2)• O(1D) + H2O 2OH

(3)

• Sink: oxidation of reduced species –leads to HO2(RO2) production

• CO + OH CO2 + H

• CH4 + OH CH3 + H2O

• HCFC + OH

• Global Mean [OH] = 1.0x106 molecules cm-3

Major OH sinks

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Oxidation of CO - production of ozone

CO + OH· CO2 + H·

H· + O2 + M HO2· + M

NO + HO2· NO2 + OH·

NO2 + hv NO + O

O + O2 + M O3

CO + 2 O2 + hv CO2 + O3

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Carbon Monoxide

• Odorless, colorless gas• Caused by incomplete combustion of fuel • Most of it comes from motor vehicles• Reduces the transport of oxygen through the

bloodstream• Affects mental functions and visual acuity,

even at low levels

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What breaks the cycle?

• Cycle terminated byOH· + NO2 HNO3

HO2· + HO2· H2O2

• Both HNO3 and H2O2 will photolyze or react with OH to, in effect, reverse these pathways– but reactions are slow (lifetime of several days)– both are very soluble - though H2O2 less-so

• washout by precipitation• dry deposition

– in PBL they are effectively a loss– situation is more complicated in the upper

troposphere• no dry deposition, limited wet removal

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Ozone ChemistrySummary of ozone chemistry

• NO2 + Sunlight NO + O Production

• O+ O2 O3 Production

• NO + O3 NO2 + O2 Destruction

• VOC + OH RO2 + H2O Production of NO2 without the• RO2 + NO NO2 + RO Destruction of O3

Emissions Chemistry

Meteorology

Key processes• Ample sunlight (ultraviolet)• High concentrations of precursors (VOC, NO, NO2)

– Weak horizontal dispersion– Weak vertical mixing

• Warm air

RO=Reactive Organic compound such as VOC

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Day and Night Chemistry

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Ozone Precursor Emissions (1 of 2)

● Man-made sources– Oxides of nitrogen (NOx) through

combustion – VOCs through combustion and

numerous other sources● Natural sources (biogenic)

– VOCs from trees/vegetation– NOx from soils (Midwest fertilizer)

● Concentration depends on– Source location, density, and

strength– Meteorology

Emissions Chemistry

Meteorology

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NOx EMISSIONS (Tg N yr-1) TO TROPOSPHERE

Fossil Fuel 23.1

Aircraft 0.5

Biofuel 2.2

BiomassBurning 5.2

Soils 5.1

Lightning 5.8

Stratosphere 0.2

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An example of gridded NOx emissions

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Mapping of Tropospheric NO2

From the GOME satellite instrument (July 1996)

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GOME Can Provide Info on Daily Info

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Lightning Flashes Seen from Space

2000 data

DJF

JJA

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Global Budget of CO

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Satellite Observations of Biomass Fires (1997)

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Daily Los Angeles Emission (1987)

Gas Emission (tons/day) Percent of totalCarbon monoxide 9796 69.3

Nitric oxide 754Nitrogen dioxide 129Nitrous acid 6.5

Total NOx+HONO 889.5 6.3Sulfur dioxide 109Sulfur trioxide 4.5

Total SOx 113.5 0.8Alkanes 1399Alkenes 313Aldehydes 108Ketones 29Alcohols 33Aromatics 500Hemiterpenes 47

Total ROGs 2429 27.2Methane 904 6.4

Total emission 14,132 100

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Percent Emission by Source-LA

Table 4.2

Source Category CO(g) NOx(g) SOx(g) ROG Stationary 2 24 38 50Mobile 98 76 62 50Total 100 100 100 100

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Most Important Gases in Smog in Terms of Ozone Reactivity and Abundance

Table 4.4

1. m- and p-Xylene2. Ethene3. Acetaldehyde4. Toluene5. Formaldehyde6. i-Pentane7. Propene8. o-Xylene9. Butane10. Methylcyclopentane

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Lifetimes of ROGs Against Chemical Loss in Urban Air

Table 4.3

ROG Species Phot. OH HO2 O NO3 O3 n-Butane --- 22 h 1000 y 18 y 29 d 650 ytrans-2-butene --- 52 m 4 y 6.3 d 4 m 17 mAcetylene --- 3 d --- 2.5 y --- 200 dFormaldehyde 7 h 6 h 1.8 h 2.5 y 2 d 3200 yAcetone 23 d 9.6 d --- --- --- ---Ethanol --- 19 h --- --- --- ---Toluene --- 9 h --- 6 y 33 d 200 dIsoprene --- 34 m --- 4 d 5 m 4.6 h

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Summary

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Ozone Meteorology – Key Processes

• Dispersion (horizontal mixing) • Vertical mixing• Sunlight• Transport• Weather pattern• Geography• Diurnal• Season

Emissions Chemistry

Meteorology

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Ozone Precursor Emissions (2 of 2)

● Key processes– Source location, density, and strength

– Dispersion (horizontal mixing) - wind speed– Vertical mixing - inversion

Concentration S/WS

Wind speed (WS)

S

Courtesy of New Jersey Department of Environmental Protection

Concentration S/VM

Vertical mixing (VM)S

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Daily Variation

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Source/Receptor Regions in Los Angeles

0

0.1

0.2

0.3

0 6 12 18 24

Vol

ume

mix

ing

rati

o (p

pmv)

Hour of day

O3

NO2NO

Central Los AngelesAugust 28, 1987

Vol

ume

mix

ing

rati

o (p

pmv)

Figure 4.10

0

0.1

0.2

0.3

0 6 12 18 7224

Vol

ume

mix

ing

rati

o (p

pmv)

Hour of day

O3

NO2

NO

San BernardinoAugust 28, 1987

Vol

ume

mix

ing

rati

o (p

pmv)Urban center Sub-urban

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0 0.5 1 1.5 20

0.05

0.1

0.15

0.2

0.25

ROG (ppmC)

NO x

(g)

(ppm

v)

0.4

0.32

0.24

0.16

0.08

= O 3

(g),

ppm

v

Ozone Isopleth Plot

Figure 4.9Contours are ozone (ppmv)

NO

x (pp

mv)

0.240.

08 0.32

0.16

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THIS OZONE BACKGROUND IS A SIZABLE INCREMENT THIS OZONE BACKGROUND IS A SIZABLE INCREMENT TOWARDS VIOLATION OF U.S. AIR QUALITY STANDARDSTOWARDS VIOLATION OF U.S. AIR QUALITY STANDARDS

(even more so in Europe!)(even more so in Europe!)

0 20 40 60 80 100 120 ppbv

Europe(seasonal)

U.S.(8-h avg.)

U.S.(1-h avg.)

preindustrial presentbackground

Europe(8-h avg.)

Slide courtesy of D. Jacob

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SURFACE OZONE ENHANCEMENTS CAUSED BYSURFACE OZONE ENHANCEMENTS CAUSED BY

ANTHROPOGENIC EMISSIONS FROM DIFFERENT CONTINENTSANTHROPOGENIC EMISSIONS FROM DIFFERENT CONTINENTSGEOS-CHEMmodel, July 1997

North America

Europe

Asia

Li et al. [2002]

EU/USA

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Particulate Matter (1 of 3)

Ultra-fine fly-ash or

carbon soot

* 24-hour average24-hour average

● Complex mixture of solid and liquid particles ● Composed of many different compounds● Both a primary and secondary pollutant● Sizes vary tremendously● Forms in many ways

● Clean-air levels are < 5 µg/m3 *● Background concentrations can be higher

due to dust and smoke● Concentrations range from 0 to 500+ µg/m3 *

● Health concerns– Can aggravate heart diseases

– Associated with cardiac arrhythmias and heart attacks

– Can aggravate lung diseases such as asthma and bronchitis

– Can increase susceptibility to respiratory infection

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Particles come in different shapes and sizes

Particle sizes• Ultra-fine particles (<0.1 μm)• Fine particles (0.1 to 2.5 μm)• Coarse particles (2.5 to 10 μm)

PM10

Carbon chain agglomeratesCrustal material

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A clear (left) and dirty (right) PM filter

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Particulate Matter Composition (1 of 3)

● Primary PM (directly emitted)– Suspended dust– Sea salt– Organic carbon– Elemental carbon– Metals from combustion– Small amounts of sulfate

and nitrate

● Secondary PM (precursor gases that form PM in the atmosphere)– Sulfur dioxide (SO2): forms sulfates

– Nitrogen oxides (NOx): forms nitrates

– Ammonia (NH3): forms ammonium compounds

– Volatile organic compounds (VOCs): form organic carbon compounds

PM is composed of a mixture of primary and secondary compounds.

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• NaCl – salt is found in PM near sea coasts and after de-icing materials are applied

• Organic Carbon (OC) – consists of hundreds of separate compounds containing mainly carbon, hydrogen, and oxygen

• Elemental Carbon (EC) – composed of carbon without much hydrocarbon or oxygen. EC is black, often called soot.

• Liquid Water – soluble nitrates, sulfates, ammonium, sodium, other inorganic ions, and some organic material absorb water vapor from the atmosphere


Chow and Watson (1997)

• Geological Material – suspended dust consists mainly of oxides of Al, Si, Ca, Ti, Fe, and other metal oxides

• Ammonium – ammonium bisulfate, sulfate, and nitrate are most common

• Sulfate – results from conversion of SO2 gas to sulfate-containing particles

• Nitrate – results from a reversible gas/particle equilibrium between ammonia (NH3), nitric acid (HNO3), and particulate ammonium nitrate

Most PM mass in urban and nonurban areas is composed of a combination of the following chemical components

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PM Emissions Sources (1 of 4)

Point – generally a major facility emitting pollutants from identifiable sources (pipe or smoke stack). Facilities are typically permitted.

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Area – any low-level source of air pollution released over a diffuse area (not a point) such as consumer products, architectural coatings, waste treatment facilities, animal feeding operations, construction, open burning, residential wood burning, swimming pools, and charbroilers

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PM Emissions Sources (3 of 4)Mobile• On-road is any moving source of air pollution such as cars, trucks,

motorcycles, and buses

• Non-road sources include pollutants emitted by combustion engines on farm and construction equipment, locomotives, commercial marine vessels, recreational watercraft, airplanes, snow mobiles, agricultural equipment, and lawn and garden equipment

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Natural – biogenic and geogenic emissions from wildfires, wind blown dust, plants, trees, grasses, volcanoes, geysers, seeps, soil, and lightning

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Toronto (1997-99)Egbert (1994-99)

Abbotsford (1994-95)

Quaker City OH (1999)

Arendstville PA (1999)

Atlanta (1999)Yorkville (1999)Mexico City - Pedregal (1997)

Los Angeles (1995-96)

Fresno (1988-89)

Kern Wildlife Refuge (1988-89)

Sulfate

Nitrate

Ammonium

Black carbon

Organic carbon

Soil

Other

12.3 ug m-38.9 ug m-3

7.8 ug m-3

12.4 ug m-3

10.4 ug m-3

19.2 ug m-314.7 ug m-3

55.4 ug m-3

30.3 ug m-3

23.3 ug m-3

39.2 ug m-3

Washington DC (1996-99)

14.5 ug m-3

Colorado Plateau (1996-99)3.0 ug m-3

Mexico City - Netzahualcoyotl (1997)

24.6 ug m-3

Esther (1995-99)

St. Andrews (1994-97)5.3 ug m-3

4.6 ug m-3

COMPOSITION OF PM2.5 IS HIGHLY VARIABLE (NARSTO PM ASSESSMENT)

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ORIGIN OF THE ATMOSPHERIC AEROSOL

Soil dustSea salt

Aerosol: dispersed condensed matter suspended in a gasSize range: 0.001 m (molecular cluster) to 100 m (small raindrop)

Environmental importance: health (respiration), visibility, radiative balance,cloud formation, heterogeneous reactions, delivery of nutrients…

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Particulate Matter Chemistry (1 of 4)

Coagulation: Particles collide and stick together.

Condensation: Gases condense onto a small solid particle to form a liquid droplet.

Chemical Reaction: Gases react to form particles.

Cloud/Fog Processes: Gases dissolve in a water droplet and chemically react. A particle exists when the water evaporates.

Sulfate

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NOx

Ammonia

VOCs


PM contains many compoundsPrimary Particles(directly emitted)

Secondary Particles(from precursor gases)

Other(sea salt)

Other(sea salt)

Crustal(soil,dust)

Crustal(soil,dust)

OrganicCarbon

OrganicCarbon

Carbon(Soot)

Carbon(Soot)

SO2

AmmoniumSulfate

AmmoniumSulfate

AmmoniumNitrate

AmmoniumNitrate

MetalsMetals

Composition of PM tells us about the sources and formation processes

Gas

ParticleParticle

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Sulfur Dioxide

• Sulfur dioxide (SO2) belongs to the family of sulfur oxide (SOx) gases.

• Gases are formed when fuel containing sulfur (mainly coal and oil) is burned and during metal smelting and other industrial processes.

• Affects the respiratory system• Reacts in the atmosphere to form acids, sulfates, and

sulfites• Contributes to acid rain

Low crown density of spruce trees

German sandstone statue, 1908, 1969

Impact of low soil pH on agriculture in Victoria

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Sulfate Chemistry● Virtually all ambient sulfate (99%)

is secondary, formed within the atmosphere from SO2 during the summer.

● About half of SO2 oxidation to sulfate occurs in the gas phase through photochemical oxidation in the daytime. NOx and hydrocarbon emissions tend to enhance the photochemical oxidation rate.

● At least half of SO2 oxidation takes place in cloud droplets as air molecules react in clouds.

● Within clouds, soluble pollutant gases, such as SO2, are scavenged by water droplets and rapidly oxidize to sulfate.

● Only a small fraction of cloud droplets deposit out as rain; most droplets evaporate and leave a sulfate residue or “convective debris”.

● Typical conversion rate 1-10% per hour

Husar (1999)

Heterogeneous Oxidation


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Mechanisms of Converting S(IV) to S(VI)

Why is converting to S(VI) important?It allows sulfuric acid to enter or form within cloud drops and aerosol particles, increasing their acidity

Mechanisms1. Gas-phase oxidation of SO2(g) to H2SO4(g) followed by condensation of H2SO4(g)

2. Dissolution of SO2(g) into liquid water to form H2SO3(aq) followed by aqueous chemical conversion of H2SO3(aq) and its dissociation products to H2SO4(aq) and its dissociation products.

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Nitrate Chemistry● NO2 can be converted to nitric acid (HNO3) by reaction with

hydroxyl radicals (OH) during the day.– The reaction of OH with NO2 is about 10 times faster than the OH

reaction with SO2.

– The peak daytime conversion rate of NO2 to HNO3 in the gas phase is about 10% to 50% per hour.

● During the nighttime, NO2 is converted into HNO3 by a series of reactions involving ozone and the nitrate radical.

● HNO3 reacts with ammonia to form particulate ammonium nitrate (NH4NO3).

● Thus, PM nitrate can be formed at night and during the day; daytime photochemistry also forms ozone.

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Winds Clouds, fog Winds Temperature

Temperature Temperature Precipitation Relative humiditySolar radiation Relative humidity WindsVertical mixing Solar radiation

condensation andcoagulation

photochemical productioncloud/fog processes

gases condense onto particles

cloud/fog processes Measurement Issues

• Inlet cut points• Vaporization of

nitrate, H2O, VOCs• Adsorption of VOCs• Absorption of H2O

transport

sedimentation(dry deposition)

wet deposition

Mechanical• Sea salt• Dust

Combustion• Motor vehicles• Industrial• Fires

Other gaseous• Biogenic• Anthropogenic

Particles• NaCl• Crustal

Particles• Soot• Metals• OC

Gases• NOx

• SO2

• VOCs• NH3

Gases• VOCs• NH3

• NOx

SourcesSample

CollectionPM Transport/LossPM

FormationEmissionsChemical Processes

Meteorological Processes


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Phenomena Emissions PM Formation PM Transport/Loss

Aloft Pressure Pattern

No direct impact. No direct impact. Ridges tend to produce conditions conducive for accumulation of PM2.5.

Troughs tend to produce conditions conducive for dispersion and removal of PM and ozone.In mountain-valley regions, strong wintertime inversions and high PM2.5 levels may not be

altered by weak troughs. High PM2.5 concentrations often occur during the approach of a trough from the west.

Winds and Transport

No direct impact. In general, stronger winds disperse pollutants, resulting in a less ideal mixture of pollutants for chemical reactions that produce PM2.5.

Strong surface winds tend to disperse PM2.5 regardless of season.

Strong winds can create dust which can increase PM2.5 concentrations.

Temperature Inversions

No direct impact. Inversions reduce vertical mixing and therefore increase chemical concentrations of precursors. Higher concentrations of precursors can produce faster, more efficient chemical reactions that produce PM2.5.

A strong inversion acts to limit vertical mixing allowing for the accumulation of PM2.5.

Rain Reduces soil and fire emissions Rain can remove precursors of PM2.5. Rain can remove PM2.5.

Moisture No direct impact. Moisture acts to increase the production of secondary PM2.5

including sulfates and nitrates.

No direct impact.

Temperature Warm temperatures are associated with increased evaporative, biogenic, and power plant emissions, which act to increase PM2.5. Cold temperatures can also

indirectly influence PM2.5

concentrations (i.e., home heating on winter nights).

Photochemical reaction rates increase with temperature.

Although warm surface temperatures are generally associated with poor air quality conditions, very warm temperatures can increase vertical mixing and dispersion of pollutants.Warm temperatures may volatize Nitrates from a solid to a gas.Very cold surface temperatures during the winter may produce strong surface-based inversions that confine pollutants to a shallow layer.

Clouds/Fog No direct impact. Water droplets can enhance the formation of secondary PM2.5. Clouds

can limit photochemistry, which limits photochemical production.

Convective clouds are an indication of strong vertical mixing, which disperses pollutants.

Season Forest fires, wood burning, agriculture burning, field tilling, windblown dust, road dust, and construction vary by season.

The sun angle changes with season, which changes the amount of solar radiation available for photochemistry.

No direct impact.

Particulate Matter MeteorologyHow weather affects PM emissions, formation, and transport

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ANNUAL MEAN PARTICULATE MATTER (PM) CONCENTRATIONS AT

U.S. SITES, 1995-2000NARSTO PM Assessment, 2003

PM10 (particles > 10 m) PM2.5 (particles > 2.5 m)

Red circles indicate violations of national air quality standard:50 g m-3 for PM10 15 g m-3 for PM2.5

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AEROSOL OPTICAL DEPTH (GLOBAL MODEL)

Annual mean

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AEROSOL OBSERVATIONS FROM SPACE

Biomass fire haze in central America yesterday (4/30/03)

Fire locationsin red

Modis.gsfc.nasa.gov

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BLACK CARBON EMISSIONS

Chin et al. [2000]

DIESEL

DOMESTICCOAL BURNING

BIOMASSBURNING

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RADIATIVE FORCING OF CLIMATE, 1750-PRESENT

“Kyoto also failed to address two major pollutants that have an impact on warming: black soot and tropospheric ozone. Both are proven health hazards. Reducing both would not only address climate change, but also dramatically improve people's health.” (George W. Bush, June 11 2001 Rose Garden speech)

IPCC [2001]

AREPGAW Particles Impact Human Health and

MORE

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EPA REGIONAL HAZE RULE: FEDERAL CLASS I AREAS TO RETURN TO “NATURAL” VISIBILITY LEVELS BY 2064

•

Acadia National Park

clean day moderately polluted day

http://www.hazecam.net/

…will require essentially total elimination of anthropogenic aerosols!

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ASIAN DUST INFLUENCE IN UNITED STATESDust observations from U.S. IMPROVE network

April 16, 2001Asian dust in western U.S.

April 22, 2001Asian dust in southeastern U.S.

GlenCanyon, AZ

Clear day April 16, 2001: Asian dust!

0 2 4 6 8g m-3

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Aerosols Link Air Quality, Health and Climate:

Dirtier Air and a Dimmer Sun

Anderson et al., Science 2003 Smith et al., 2003 He et al., 2002

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