12. Ozone pollution. Daniel J. Jacob, Atmospheric Chemistry, Harvard University, Spring 2017

Transcription

1 12. Ozone pollution Daniel J. Jacob, Atmospheric Chemistry, Harvard University, Spring 2017

2 The industrial revolution and air pollution Pittsburgh in the 1940s Make great efforts to build China into a strong and prosperous industrialized country under the leadership of the Party and chairman Mao!

3 LONDON FOG Aerosols a.k.a.particulate matter (PM) from domestic+industrial coal combustion Killer fog of December 1952 resulted in 10,000 excess deaths Altitude < 1km inversion particles sulfate organic carbon black carbon Temperature Coal combustion

4 Los Angeles smog Respiratory problems, vegetation damage due to high surface ozone altitude produced by photolysis of oxygen (O 2 ) ~ 10 km stratosphere troposphere ~ 1 km ozone temperature inversion Nitrogen oxides (NO x NO + NO 2 ) Volatile organic compounds (VOCs) UV radiation Ozone (O3 ) PM vehicles, industry, vegetation

5 AIR POLLUTION IN THE US TODAY: Ozone and fine particulate matter (PM 2.5 ) are the major pollutants US population exposed to air pollutants in excess of national ambient air quality standards (NAAQS), 2015 Ozone 108M 70 ppb (8-h average) PM M 12 µg m -3 (annual), 35 µg m -3 (24-h) PM 10 SO 2 Lead CO NO 2 11M 5M 1M 0 0

6 Ozone air quality standards in the US and in the world Europe AQS (8-h avg.) Europe AQS (seasonal) Canadian AQS (8-h avg.) U.S. AQS (8-h avg.) U.S. AQS (1-h avg.) ppb Preindustrial ozone background Present-day ozone background at northern mid-latitudes China AQS (8-h avg.)

7 4 th -highest annual maximum of daily 8-h average ozone, EPA [2014] Standard: 70 ppb Ozone production mechanism: Production can be VOC- or NO x -limited: O2 VOC + OH HO + products HO + NO NO OH + NO 2 2 O2 + hν NO + O O 3 O 3 VOC NO x

8 OZONE CONCENTRATIONS vs. NO x AND VOC EMISSIONS Air pollution model calculation for a typical urban airshed NO x -limited Ridge NO x - saturated

9 TREND OF U.S. EMISSIONS Focus until past decade was on VOC emission controls

10 Dominant VOC is biogenic isoprene isoprene oxidation hν, OH HCHO ~ 1 hour ~ 1 hour Other VOCs OMI satellite observations of formaldehyde (HCHO) columns, May-Aug

11 Post-2000 decline in US emissions of NO x ( NO + NO 2 ) as seen by OMI satellite observations of NO 2 OMI NO 2, summer 2005 Russell et al. [2012]

12 Post-2000 decline in US emissions of NO x ( NO + NO 2 ) as seen by OMI satellite observations of NO 2 OMI NO 2, summer % decrease in NO x emissions from 2005 to 2011 Russell et al. [2012]

13 Trend in 95 th percentile daytime ozone, Spring Summer Decrease in eastern US driven by NO x emission controls; Increase or flat in Intermountain West Cooper et al. [2012]

14 Ozone production efficiency (OPE) per unit NO x emitted OPE = ozone produced NO emitted x = chain length of NO cycle x VOC HO OH 7 HNO 3 NO hv NO 2 Emission O 3 Deposition OPE as NO x and VOC Thus the response of ozone to decreasing NO x emissions is much less than linear

15 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) observed model 4 th highest annual 8-h average ozone, Downwelling of high background ozone over the Intermountain West ppb

16 Source attribution of ozone in Intermountain West using the GEOS-Chem global 3-D chemical transport model NA background simulation with no anthropogenic sources in N America Stratospheric intrusion 2006 Most ozone is from non US sources, including ~10 ppb intercontinental pollution Zhang et al. [2014]

17 North American ozone background over the US defined as the surface ozone concentrations that would be present in the absence of North American anthropogenic emissions 4 th highest annual North American background ozone (GEOS-Chem model) Zhang et al. [2011]

18 Ozone trends in remote air at northern mid-latitudes Cause of increase is not clear. Asian emissions? Ships? Aircraft? Wildfires? Increasing transport from stratosphere? D.D. Parrish, NOAA

19 A global view of air pollution enabled by satellites Aura observations have provided unprecedented detail, coverage, precision OMI NO molecules cm -2

20 A global view of air pollution enabled by satellites Aura observations have provided unprecedented detail, coverage, precision OMI NO 2 OMI 2013NO 2 trend molecules cm -2 s -1 fractional change Verstraeten et al. [2014]

21 Rising surface ozone pollution in China D.D. Parrish, NOAA

22 INTERCONTINENTAL OZONE POLLUTION INFLUENCES GEOS-Chem model results for 2006 Surface O 3 enhancements from North American anthropogenic emissions from European anthropogenic emissions from Asian anthropogenic emissions Lin Zhang, Harvard