QUESTIONS 1.Using the EKMA diagram (the ozone isopleth discussed at the end of last class), find what ozone levels would result if emissions of NO x were 10x10 11 molecules/cm 2 /s and emissions of HC were 2x10 11 atomsC/cm 2 /s. Given your understanding of how these values compare with the O 3 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 + 4O 2  R’CHO + 2O 3 + H 2 O 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 dust Sea salt Aerosol: dispersed condensed phases suspended in a gas Size range:  m (molecular cluster) to 100  m (small raindrop) Environmental importance: health (respiration), visibility, climate, cloud formation, heterogeneous reactions, long-range transport of nutrients…

[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. PM 2.5 ≡ 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 AMERICA Annual mean PM 2.5 concentrations (NARSTO, 2004)

TYPICAL AEROSOL SIZE DISTRIBUTION finecoarse ultrafine accumulation PM 2.5 PM 10 N=number concentration (particles/cm 3 )

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]

SIZE, COMPOSITION AND IMPACTS…

INHALABILITY AND SIZE! Total suspended particles (TSP) PM 10 – thoracic particles PM 2.5 – respirable particles

AEROSOLS AND VISIBILITY: PM10 IN BEIJING ug/m 3 12 July 26 ug/m 3 15 July 32 ug/m 3 20 July 104 ug/m 3 5 August 191 ug/m 3 7 August 278 ug/m 3 10 August WHO Guideline: 50 ug/m 3 averaged over 24 hrs

EPA REGIONAL HAZE RULE: WILDERNESS AREAS MUST ACHIEVE NATURAL VISIBILITY CONDITIONS BY 2064 Glacier National Park 7.6 µgm µgm µgm 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 AREAS Statistics for 20% worst visibility days Deciviews 2001 observationsNatural Background; includes transboundary pollution Visual range (km) deciviews: dv = 10ln(b ext /10)

PROGRESS TOWARDS REGIONAL HAZE RULE Shenandoah National Park [EPA Report, Visibility, 2008]

ANNUAL MEAN PM 2.5 CONCENTRATIONS (2002) derived from MODIS satellite instrument data SURFACE AEROSOL 0.47  m 0.65  m 2.13  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 UNITED STATES 130 Tg yr Tg yr Tg yr Tg yr -1 = BSOA

BLACK CARBON EMISSIONS DIESEL DOMESTIC COAL BURNING BIOMASS BURNING

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

SECONDARY ORGANIC AEROSOL PRODUCTION FROM BIOGENIC VOC EMISSIONS Biogenic VOC Emissions Oxidation Reactions (OH, O 3,NO 3 ) 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 (C 5 H 8 ) Monoterpenes(C 10 H 16 ) Sesquiterpenes (C 15 H 24 ) 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 ALGAE PLANT DEBRIS 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