1. AIR POLLUTION IN THE US TODAY: Ozone and PM are the major pollutants
75 ppb (8-h average)
Milllions of people exposed to air pollutants
in excess of national ambient air quality standards (NAAQS), 2012
Any pollutant
PM2.5
Ozone
PM10
SO2
Lead
12 µg m-3 (annual average), 35 µg m-3 (24-h average)

2. TYPICAL AEROSOL SIZE DISTRIBUTION
by volume
PM10
PM2.5
This actually dN/d(log10(Diam)) .
PM2.5 ≡ concentration of particulate matter less than 2.5 µm diameter
PM10 ≡ concentration of particulate matter less than 10 µm diameter

3. Airflow interception obstacle diffusion impaction
Wiley Interdisciplinary Reviews

4. County life expectancies at birth for white males and females;1997–2001
CJL Murray et al, Eight Americas: Investigating Mortality Disparities across Races, Counties, and Race-Counties in the United States. PLoS Med Sep;3(9):e260

5. Life Expectancy vs annual PM2.5 1978-82
EPA NAAQS
Boston
Topeka
Steubenville, OH
Pope, Ezzati, Dockery. NEJM 2009; 360:376

6. Life Expectancy vs annual PM2.5 1997-2001
EPA NAAQS
Boston
Steubenville
Topeka
Pope, Ezzati, Dockery. NEJM 2009; 360:376

7. Life Expectancy vs annual PM2.5 1980-2000
Boston
Topeka
Steubenville
Pope, Ezzati, Dockery. NEJM 2009; 360:376

8. Annual PM2.5 distributions in US, 2005-2007 [EPA, 2009]

9. ANNUAL MEAN PM2.5 CONCENTRATIONS (2002) derived from MODIS satellite instrument data
Beijing US embassy current PM2.5 levels

10. WORLDWIDE MEASUREMENTS OF FINE AEROSOL COMPOSITION

11. FINE AEROSOL COMPOSITION IN NORTH AMERICA
Annual mean PM2.5 concentrations (NARSTO, 2004)
Current air quality standard is 15 μg m-3
note how high these are, and the composition – lots of sulfate in the midwest, organic and elemental carbon in some areas of the S and west (L.A.), dust in Mexico City,

12. U.S. SO2 EMISSIONS Main source is coal combustion GLOBAL UNITED STATES
coal! not much steel manufacturing these days…
GLOBAL
UNITED STATES
Sulfur emissions,
Tg a-1 78
8.3

13. SO2 columns over Midwest observed from space, 2005-2010
Ben De Foy,
Saint Louis U.

14. Global SO2 columns observed from space
bad data

15. Kasatochi eruption as seen in GOME-2 SO2
22/04/2017
Kasatochi eruption as seen in GOME-2 SO2
Lage eruption on August 8, 2008 injects SO2 to the upper troposphere
SO2 lifetime of 1-2 weeks
Kasatochi volcano

16. In surface air, however, sulfate observations imply an SO2 lifetime ~ 1 day
Sulfate deposition, kg ha-1 a Sulfate aerosol, µg m-3
Leibensperger et al. [2012]

17. OBSERVED TITRATION OF SO2 BY H2O2 IN CLOUD
First aircraft observations by Daum et al. [1984]

18. Ammonia and NOx emissions in the US (2006) Ammonia is mainly from agriculture
Zhang et al. [2012]

19. Formation of sulfate-nitrate-ammonium (SNA) aerosol
High RH (aqueous)
Low RH
H2SO4(aq),
HSO4-, SO42-
NH4+,SO42=, NO3- dry salts
oxidation
NH3(aq), NH4=
SO2
HNO3(aq), NO3-
NH3
oxidation
NOx
HNO3
EMISSIONS
Uptake of NH3 and HNO3 by sulfate aerosol follows thermodynamics
This uptake affects the mass and phase of the aerosol

20. Thermodynamic rules for SNA aerosol formation
H2SO4 condenses to aqueous solution; dissociation to HSO4-, SO42- governed by pH
NH3 condenses into acid aerosol until neutralization; no further uptake
HNO3 condenses only if excess NH3 is available
At low RH, equivalent equilibria apply to the solid salts

21. Three different regimes for SNA aerosol formation
[S(VI] = [H2SO4(aq)] + [HSO4-] + [SO42-]
[N(-III)] = [NH3(g)] + [NH3(aq)] + [NH4+]
[N(V)] = [HNO3(g)] + [HNO3(aq)] + [NO3-]
Equivalents per m3 of air
gas
aerosol
N(V)
N(V)
gas
aerosol
N(V)
gas
aerosol
S(VI)
S(VI)
S(VI)
N(-III)
N(-III)
N(-III)
[S(VI)] > [N(-III)]
[S(VI)]+[N(V)] > [N(-III)] > [S(VI)]
[S(VI)]+[N(V)] < [N(-III)]
Aerosol is acidic
N(-III) all in aerosol
No N(V) in aerosol
Aerosol is neutral
N(-III) all in aerosol
N(V) partly in aerosol
Aerosol is neutral
N(-III) partly in aerosol
N(V all in aerosol

22. SULFATE-NITRATE-AMMONIUM AEROSOLS IN U.S. (2001)
Highest concentrations in industrial Midwest
(coal-fired power plants)
Discuss effects of soil chemistry and nitrification on soil acidity and leaching of base cations.
Acidity

23. CARBONACEOUS AEROSOL SOURCES IN THE U.S.
ELEMENTAL CARBON
ORGANIC CARBON
2.7 Tg yr-1
0.66 Tg yr-1
Annual mean concentrations (2001)
organic
elemental

24. FORMATION OF ORGANIC AEROSOL FROM VEGETATIVE EMISSIONS
(C5H8)
Aldehydes
RC(O)H
Ketones
RC(O)R
Dicarbonyls
RC(O)-C(O)R
OH, O3
absorption
into aerosol
(C10H16)
oxidation
broadleaf vs pines
Carboxylic acids
RC(O)OH
polymerization

25. Van Krevelen diagram for chemical aging of organic material
Heald et al. [2010]

26. Van Krevelen diagram: application to organic aerosol
-1 slope suggests aging by adding of –COOH functionalities
Heald et al. [2010]

27. LONG-TERM TREND IN US SO2 EMISSIONS

28. Decline of sulfate aerosol in the US
Scrubbers on coal power plants, transition to natural gas
Observed sulfate concentrations (circles), GEOS-Chem (background)
1990
2010
µg m-3
µg m-3
Leibensperger
et al. [2012]

29. Long-term trends in BC and OC aerosol over the US
Annual mean
concentrations
Observed
Model
National trends
Leibensperger
et al. [2011]

30. EPA REGIONAL HAZE RULE: WILDERNESS AREAS MUST ACHIEVE NATURAL VISIBILITY CONDITIONS BY 2064
Visibility degradation by aerosols at Glacier National Park, Montana
7.6 µgm-3
12.0 µgm-3
21.7 µgm-3
65.3 µgm-3
U.S. annual air quality standard
Glacier
National
Park
2064? really? I can hardly wait….
Natural aerosol concentrations are typically less than 2 μg m-3

31. VISIBILITY IN U.S. WILDERNESS AREAS
Statistics for 20% worst visibility days
Deciviews
2001 observations
Natural
Background; includes
transboundary pollution
Visual
range (km)
Park et al. [2006]

32. WILDFIRES: A GROWING AEROSOL SOURCE
S. California fire plumes,
Oct
Total carbonaceous (TC) aerosol
averaged over U.S. IMPROVE sites
Interannual variability is driven
by wildfires