12. Ozone pollution

Daniel J. Jacob, Atmospheric Chemistry, Harvard University, Spring 2017

The industrial revolution and air pollution

“Make great efforts to build China into a strong and prosperous industrialized

country under the leadership of the Party and chairman Mao!”

Pittsburgh in the 1940s

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LONDON FOGAerosols a.k.a.particulate matter (PM) from domestic+industrial coal combustion

“Killer fog” of December 1952 resulted in 10,000 excess deaths

Coal combustionTemperature

Altitude

inversion

sulfateorganic carbonblack carbon

particles< 1km

http://www-as.harvard.edu/chemistry/trop/news.htmlhttp://www-as.harvard.edu/chemistry/trop/news.html

Los Angeles smogRespiratory problems, vegetation damage due to high surface ozone

troposphere

stratosphere~ 10 km

temperature

inversionozone

altitude

Nitrogen oxides (NOx ≡ NO + NO2)Volatile organic compounds (VOCs)

UV radiationOzone (O3)

vehicles, industry, vegetation

produced by photolysisof oxygen (O2)

PM

~ 1 km

http://iconbazaar.com/bars/contributed/pg04.htmlhttp://iconbazaar.com/bars/contributed/pg04.htmlhttp://www-as.harvard.edu/chemistry/trop/news.htmlhttp://www-as.harvard.edu/chemistry/trop/news.htmlhttp://iconbazaar.com/cars/fiat_multipla.gifhttp://iconbazaar.com/cars/fiat_multipla.gif

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

http://epa.gov/airtrends

US population exposed to air pollutants in excess of national ambient air quality standards (NAAQS), 2015

PM2.5

PM10

SO2

Lead

Ozone

CO

NO2

108M

31M31M

0

1M

5M

11M

0

70 ppb (8-h average)

12 µg m-3 (annual), 35 µg m-3 (24-h)

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.)

Ozone air quality standards in the US and in the world

20082014 1997

China AQS(8-h avg.)

4th-highest annual maximum of daily 8-h average ozone,2010-2012

EPA [2014]

Ozone production mechanism:

2

2

O2

2 2O

2 3

VOC + OH HO products

HO +

1.

2.

3.

NO OH + NO

NO NO + Ohν

→ +

→

+ →

Production can be VOC- or NOx-limited:

O3

VOC

O3

NOx

Standard: 70 ppb

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

NOx-saturated

NOx-limited Ridge

1970-2003 TREND OF U.S. EMISSIONS

Focus until past decade was on VOC emission controls

Dominant VOC is biogenic isoprene

OMI satellite observations of formaldehyde (HCHO) columns, May-Aug 2005-2014

HCHOhν , OHoxidation~ 1 hour

isoprene

~ 1 hour

Other VOCs

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OMI NO2, summer 2005

Russell et al. [2012]

Post-2000 decline in US emissions of NOx (≡ NO + NO2) as seen by OMI satellite observations of NO2

OMI NO2, summer 2005OMI NO2, summer 2011

30% decrease in NOx emissions from 2005 to 2011

Russell et al. [2012]

Post-2000 decline in US emissions of NOx (≡ NO + NO2) as seen by OMI satellite observations of NO2

Trend in 95th percentile daytime ozone, 1990-2010

Spring

Summer

Cooper et al. [2012]

• Decrease in eastern US driven by NOx emission controls;• Increase or flat in Intermountain West

Ozone production efficiency (OPE) per unit NOx emitted

HO2 OH

NO2NOHNO3

VOC

hv

O3Emission Deposition

xx

ozone producedOPE = = chain length of NO cycleNO emitted

OPE ↑ as NOx ↓ and VOC ↑

Thus the response of ozone to decreasing NOx emissions is much less than linear

4

57

Intermountain West: high plateau, deep boundary layer mixing→ downwelling of ozone from the middle troposphere

EPA [2014]

Ozone over NE Pacific(INTEX-B, Apr-May 2006)

ppb

observedmodel

Downwelling of high background ozoneover the Intermountain West

4th highest annual8-h average ozone,2010-2012

Source attribution of ozone in Intermountain West

NA background ≡ simulation with no anthropogenic sources in N America

2006Most ozone is from non US sources, including ~10 ppb intercontinental pollution

Zhang et al. [2014]

Stratosphericintrusion

using the GEOS-Chem global 3-D chemical transport model

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

Ozone trends in remote air at northern mid-latitudes

D.D. Parrish, NOAA

Cause of increase is not clear. Asian emissions? Ships? Aircraft? Wildfires? Increasing transport from stratosphere?

A global view of air pollution enabled by satellites

http://disc.sci.gsfc.nasa.gov/giovanni

OMI NO22013

1015 molecules cm-2

Aura observations have provided unprecedented detail, coverage, precision

http://disc.sci.gsfc.nasa.gov/giovanni

A global view of air pollution enabled by satellites

Verstraeten et al. [2014]

OMI NO22013

1015 molecules cm-2 s-1

Aura observations have provided unprecedented detail, coverage, precision

OMI NO2 trend2005-2010

fractional change

Rising surface ozone pollution in China

D.D. Parrish, NOAA

INTERCONTINENTAL OZONE POLLUTION INFLUENCES

Surface O3enhancements from North American anthropogenic emissions

from European anthropogenic emissions

from Asian anthropogenic emissions

Lin Zhang, Harvard

GEOS-Chem model results for 2006

12. Ozone pollutionThe industrial revolution and air pollutionLONDON FOGLos Angeles smogAIR POLLUTION IN THE US TODAY:�Ozone and fine particulate matter (PM2.5) are the major pollutantsSlide Number 64th-highest annual maximum of daily 8-h average ozone,�2010-2012OZONE CONCENTRATIONS vs. NOx AND VOC EMISSIONS�Air pollution model calculation for a typical urban airshed1970-2003 TREND OF U.S. EMISSIONSDominant VOC is biogenic isoprene Slide Number 11Slide Number 12Trend in 95th percentile daytime ozone, 1990-2010Ozone production efficiency (OPE) per unit NOx emittedIntermountain West: high plateau, deep boundary layer mixing�→ downwelling of ozone from the middle troposphereSource attribution of ozone in Intermountain WestNorth American ozone background over the USOzone trends in remote air at northern mid-latitudesA global view of air pollution enabled by satellitesA global view of air pollution enabled by satellitesRising surface ozone pollution in ChinaINTERCONTINENTAL OZONE POLLUTION INFLUENCES