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) http://epa.gov/airtrends

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

Airflow interception obstacle diffusion impaction Wiley Interdisciplinary Reviews

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. 2006 Sep;3(9):e260

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

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

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

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

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

WORLDWIDE MEASUREMENTS OF FINE AEROSOL COMPOSITION

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,

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

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

Global SO2 columns observed from space bad data Andreas.Richter@iup.physik.uni-bremen.de

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 http://www.avo.alaska.edu/

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

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

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

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

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

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

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

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

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

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

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

LONG-TERM TREND IN US SO2 EMISSIONS

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]

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

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

VISIBILITY IN U.S. WILDERNESS AREAS Statistics for 20% worst visibility days Deciviews 2001 observations Natural Background; includes transboundary pollution 300 150 80 40 20 Visual range (km) Park et al. [2006]

WILDFIRES: A GROWING AEROSOL SOURCE S. California fire plumes, Oct. 25 2004 Total carbonaceous (TC) aerosol averaged over U.S. IMPROVE sites Interannual variability is driven by wildfires