QUESTIONS1. Using the EKMA diagram (the ozone isopleth discussed at the end of last class), find what

ozone levels would result if emissions of NOx were 10x1011 molecules/cm2/s and emissions of HC were 2x1011 atomsC/cm2/s. Given your understanding of how these values compare with the O3 NAAQS, suggest a US city that this might represent.

2. What would be the effect of reducing NOx emissions on local ozone levels in the city of question #1?

3. In the NOx-limited regime, we saw that the ozone production rate is independent of the hydrocarbon concentration. Nevertheless, when we write the net stoichiometric reaction resulting from the propagation reaction:

RH + 4O2 R’CHO + 2O3 + H2O

We see that ozone production depends on hydrocarbon being consumed. How is that consistent with ozone production being independent of hydrocarbon concentration?

4. What is the effect of PAN formation on ozone production over the U.S.?

CHAPTER 8: ATMOSPHERIC AEROSOLS

ORIGIN OF THE ATMOSPHERIC AEROSOL

Soil dustSea salt

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

Environmental importance: health (respiration), visibility, climate,cloud formation, heterogeneous reactions, long-range transport of nutrients…

N u c lea tio n B u rs t o n 10 /6 /01

10

2

4

6

8100

2

4

Dp

(nm

)

280.0279.8279.6279.4279.2279.0

Day

dN/dlog(Dp) (cm-3

)

80006000400020000[Lunden et al., 2006]

FINE PARTICLE GROWTH AT BLODGETT FOREST“Banana Plot”

ADVERSE HEALTH EFFECTS OF PM

Epidemiological studies show that PM:• affects cardiorespiratory system• can cause cancer• impairs lung development

The EPA estimates that over 35,000 premature deaths per year can be attributed to PM. More deadly than car accidents!

[NARSTO, 2003]

75 ppb (new standard, set in 2008)

15 g m-3 (annual), 35 (daily)

AIR POLLUTANTION IN THE U.S.

PM2.5 ≡ Particulate Matter (aerosols) less than 2.5 m diameter

50 g m-3 (annual), 150 (daily)

PARTICULATE MATTER (PM) CONCENTRATIONS AT U.S. SITES, 2008

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

Yellow and red sites are in violation of national air quality standard:150 g m-3 for daily PM10 15 g m-3 for annual PM2.5

Modest decline in PM2.5 over last decade (< 20%)

Our National Air, EPA Report, 2008

FINE AEROSOL COMPOSITION IN NORTH AMERICAAnnual mean PM2.5 concentrations (NARSTO, 2004)

TYPICAL AEROSOL SIZE DISTRIBUTION

fine coarseultrafine

accumulation PM2.5 PM10

pp

dNn(D )

dD

N=number concentration (particles/cm3)

p p

0

N n(D )dD

s pp

2p p

dSn (D )

dD

D n(D )

v pp

3p p

dVn (D )

dD

D n(D )6

WHY SIZE MATTERS

[NARSTO, 2003]

[Finlayson-Pitts & Pitts]

=550 nm

(1) Toxicity (3) Particle Lifetime

(4) Surface Reactions: smaller particles have greater relative surface area

(2) Light Scattering

[Seinfeld & Pandis]

AEROSOLS AND VISIBILITY:PM10 IN BEIJING 2008

8 ug/m3

12 July26 ug/m3

15 July32 ug/m3

20 July

104 ug/m3

5 August191 ug/m3

7 August278 ug/m3

10 August

http://news.bbc.co.uk/2/hi/in_pictures/7506925.stm

WHO Guideline: 50 ug/m3 averaged over 24 hrs

EPA REGIONAL HAZE RULE: WILDERNESS AREAS MUST ACHIEVE NATURAL VISIBILITY CONDITIONS BY 2064

GlacierNationalPark

7.6 µgm-3

12.0 µgm-3

21.7 µgm-3 65.3 µgm-3

(previous) U.S. air quality standard

Visibility degradation by aerosols at Glacier National Park, Montana

Natural aerosol concentrations are typically less than 2 g m-3

VISIBILITY IN U.S. WILDERNESS AREASStatistics for 20% worst visibility days

Deciviews

2001 observations Natural Background; includestransboundary pollution

300 150 80 40 20 Visual range (km)

deciviews: dv = 10ln(bext/10)

PROGRESS TOWARDS REGIONAL HAZE RULE

Shenandoah National Park

[EPA Report, Visibility, 2008]

ANNUAL MEAN PM2.5 CONCENTRATIONS (2002)derived from MODIS satellite instrument data

SURFACE

AEROSOL

0.47 m0.65 m2.13 m

DUST: MOST IMPORTANT(?) NATURALLY EMITTED AEROSOL

[Fairlie et al. 2007]

g m-2 y-1

Dust Emissions (2001)

Sources: arid / semi-arid regions

Emission in both fine and coarse mode, depends on surface properties and wind speed.

Resulting lifetime ~weeks

[Husar et al., 2002]

MEAN SEA SALT AEROSOL CONCENTRATIONS

[Alexander et al. 2005]

Lower marine boundary layer (0-100 m)

CARBONACEOUS AEROSOL SOURCES

ORGANIC CARBON (OC) ELEMENTAL CARBON (EC)

GLOBAL

UNITEDSTATES

130 Tg yr-1 22 Tg yr-1

2.7 Tg yr-1 0.66 Tg yr-1

= BSOA

BLACK CARBON EMISSIONS

DIESEL

DOMESTICCOAL BURNING

BIOMASSBURNING

WILDFIRES: A GROWING AEROSOL SOURCES. California fire plumes,Oct. 25 2004

Total carbonaceous (TC) aerosol averaged over U.S. IMPROVE sites

Interannual variability is driven by wildfires

SECONDARY ORGANIC AEROSOL PRODUCTION FROM BIOGENIC VOC EMISSIONS

Biogenic VOC

EmissionsOxidation Reactions

(OH, O3,NO3)

Nucleation (oxidation products) Growth

Condensation on pre-existing aerosol

Over 500 reactions to describe the formation of SOA precursors, ozone, and other photochemical pollutants [Griffin et al., 2002; Griffin et al., 2005; Chen and Griffin, 2005]

Isoprene (C5H8)

Monoterpenes(C10H1

6)

Sesquiterpenes (C15H24)

BIOGENIC HYDROCARBONS

Anthropogenic SOA-precursors = aromatics (emissions are 10x smaller)

"Trees cause more pollution than automobiles do.“

(when talking about ozone in 1981)

PRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP)

POLLEN

BACTERIA VIRUSES

FUNGUS

ALGAEPLANTDEBRIS

These particles have not traditionally been considered part of the OA budget, but this has been revised in recent years.

Not much is known about emissions, processing, climate effects.

Very large and likely short-lived