AIR POLLUTION IN THE US :Ozone and fine particulate matter (PM2.5) are the two main pollutants

75 ppb (8-h average)15 g m-3 (1-y av.)

http://epa.gov/airtrends/2010/

OzonePM2.5

0 20 40 60 80 100 120 ppb

Europe AQS(seasonal)

U.S. AQS(8-h avg.)

U.S. AQS(1-h avg.)

Preindustrialozone

background

Present-day ozone background at

northern mid-latitudes

Europe AQS (8-h avg.)

Canadian AQS (8-h avg.)

Mexican AQS(1-h avg.)

Ozone air quality standards in the US and in the world

20082014? 1997

4th-highest annual maximum for daily 8-h average ozone,2008-2010

OZONE CONCENTRATIONS vs. NOx AND VOC EMISSIONSAir pollution model calculation for a typical urban airshed

NOx-saturated

NOx-limited Ridge

LARGE SUPPLY OF BIOGENIC VOCs – unrecognized until the 1990s

Isoprene (biogenic VOC)Anthropogenic VOCs

Jacob et al., 1993

Switches polluted areas in U.S. from NOx-saturated to NOx-limited regime!recognized in Revised Clean Air Act of 1999

MAPPING OF VOC EMISSIONS FROM SPACEusing satellite measurements of formaldehyde

confirms dominance of biogenic over anthropogenic VOCs

Millet et al. [2008]

1970-2003 TREND OF U.S. EMISSIONS

Focus until past decade was on VOC emission controls

OZONE TRENDS IN U.S. http://www.epa.gov/airtrends/

Boston trend

National trend

• The national trend is heavily weighted by California sites;• other parts of the country have seen marginal improvement

DECREASE OF POWER PLANT NODECREASE OF POWER PLANT NOx x EMISSIONS EMISSIONS

OVER THE PAST DECADEOVER THE PAST DECADE

Decreasing US NOx emissions from power plants

Decrease of North American NOx emisssions, 2005-2009

as seen with annual mean NO2 columns from the OMI satellite instrument

Shailesh Kharol (Dalhousie)

20092005

Decreases in both the eastern US and eastern Canada

EVEN IN NOEVEN IN NOxx-LIMITED REGIME,-LIMITED REGIME,

THE THE TOTALTOTAL O O33 PRODUCED IS ONLY A WEAK FUNCTION OF NO PRODUCED IS ONLY A WEAK FUNCTION OF NOxx

NO NO2 HNO3hv

HO2,RO2,O3 OH, O3

P(O3) L(NOx)

3 5 2 4

8 2 8 2

( ) 2 [ ][ ] 2 [ ]

( ) [ ][ ] [ ] OPE =

x

P O k HO NO k VOC

L NO k NO OH k NO

Emission Deposition

Assuming NOx steady state, efficient HOx cycling, and loss of NO2 by reaction with OH:

OPE as NOx strong nonlinearity; in models, decreasing NOx emissionsby 50% reduces ozone only by ~15%

Define ozone production efficiency (OPE) as the total number of O3 molecules produced per unit NOx emitted.

MEAN AFTERNOON SUMMER OZONE (2006)

ppb

CASTNet sites (regional background)

High ozone concentrations at sites in intermountain west

8-h daily maximum ozone in the intermountain West (2006)

56.3 ppb 53.2 ppb12.3 ppb

58.1 ppb 56.4 ppb

15.0 ppb

GEOS-Chem model US pollutioncontribution

Zhang et al., 2011

North American ozone background over the US

4th highest annual North American background ozone (GEOS-Chem model)

Zhang et al. [2011]

defined as the surface ozone concentrations that would be present in the absence of North American anthropogenic emissions

Decrease of North American NODecrease of North American NOx x emisssions, 2005-2009 emisssions, 2005-2009

as seen with annual mean NO2 columns from the OMI satellite instrument

Shailesh Kharol (Dalhousie)

20092005

Decreases in both the eastern US and eastern Canada

Daytime surface ozone distributions, 2006-2010

Spring SummerCooper et al. [2012]

Daytime surface ozone trends, 1990-2010

Spring SummerCooper et al. [2012]

Using OMI observationsto monitor growth in emissions from Canadian oil sands

Oil sand recoveryIn Alberta

OMI NO2 columns, 2004-2010

NO2 increase of 10.4 ±3.5% per year

McLinden et al. [GRL 2012]

AQAST PI: DIckerson

Ozone trends in remote air at northern mid-latitudes

D.D. Parrish, NOAA

Rising surface ozone pollution in China

D.D. Parrish, NOAA

INTERCONTINENTAL OZONE POLLUTION INFLUENCESINTERCONTINENTAL OZONE POLLUTION INFLUENCES

Surface O3 enhancements from North American anthropogenic emissions

from European anthropogenic emissions

from Asian anthropogenic emissions

Lin Zhang, Harvard

GEOS-Chem model results for 2006