Transboundary influences on US background ozone Huiqun Wang 1 ([email protected]) Philippe Le Sager 2 ([email protected]) Rokjin Park 3 ([email protected])

Transboundary influences on US background ozone

Huiqun Wang1 ([email protected])Philippe Le Sager2 ([email protected])

Rokjin Park3 ([email protected])Daniel Jacob2 ([email protected])

1. Smithsonian Astrophysical Observatory2. Harvard University3. Seoul National University

Work sponsored by U.S. Department of Energy, Office of Fossil Energy, through a contract with Argonne National Laboratory

2

According to EPA, counties violating the current 80 ppb ozone standard are largely limited to southern California, the Northeast

coastal corridor, and isolated other parts of the eastern US

3

EPA further shows that lowering the standard to 75 ppb or 70 ppb would significantly increase the number of counties in violation,

based on current air quality data

4

Application of GEOS-Chem global air quality modelto quantify transboundary pollution influence

GEOS-Chem is a global model of ozone-PM chemistry using here NASA/GEOS assimilated meteorological data for 2001; horizontal resolution is 1o lat x 1o long (about 70x50 sq. mi.)

(1) Standard simulation; compare w/ observations to assess confidence in the model

(2) Set U.S. or N. American anthropogenic emissions to zero quantify U.S. background and North American background

(3) Difference between U.S. background and North American background Canadian+Mexican pollution enhancement (CANMEX)

(4) Set global anthropogenic emissions to zero quantify natural background

3-D model structure

5

Data from Fiore et al. [JGR, 2003b] for the period Mar-Oct 2001

Background ozone is important for setting the standard

Background is not directly measurableand needs to be estimated from models

CASTNet sites observations

GEOS-Chem at CASTNet

NA backgroundfrom GEOS-Chem

Natural backgroundfrom GEOS-Chem

NA backgroundfrom MOZART-2

6

NA background – no anthropogenic emissions in North AmericaUS background – no anthropogenic emissions in the US

AnthropogenicNOx Emissions World

NorthAmerica

USA Canada Mexico

(Tg N/Year) 25.4 8.1 6.7 0.5 0.9

The national totals of CAN and MEX are small, but there arenon-negligible emission sources close to the border

7

NA background (without NA anthropogenic emissions)

US background (without US anthropogenic emissions)

JJA

200

1 m

ean

, b

ased

on

dai

ly-8

h-m

ax

8

Canadian and Mexican influences (ppb)(JJA mean, based on daily-8h-max)

Enhancement to NA background is foundIn the Northeast and Southwest US

Selected rural measurement sites under CANMEX influences, avoiding mountain-top sites and sites with complex topography, traffic influence, and missing data

9

Canadian enhancement in the Northeast (ppb)(JJA mean, based on daily-8h-max)

The largest mean Canadian enhancement is 8.8 ppb(among all US grid boxes)

• Rural sites under CAN influence

10The largest mean Mexican enhancement is 13.1 ppb(among all US grid boxes)

• Rural sites under MEX influence

Mexican enhancement in the Southwest (ppb)(JJA mean, based on daily-8h-max)

11

BuffaloWestfield

Williamson

Kane Exp Forest

Unionville

Lykens

CAN enhancement at selected sites in the Northeastclose to Canadian sources

Daily-8h-max time series for these six locations follow …

12

Measurement Std-run US-background NA-background CANMEX

The largest episodic CAN enhancement at Unionville, MI (34 ppb) increases US background to 47 ppb (red circle)

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb

13


Westfield, NY


14


Williamson, NY


15


Kane Exp Forest, PA


16


Lykens, OH


17


Buffalo, NY: At Buffalo, the CAN influence is frequently above 10 ppb, and US background is frequently above 30 ppb


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2010 CAIR: Source Apportionment: Buffalo Average Contribution by State/Sector to Exceedance-level Ozone

Canada-NR28%

Canada-NEGU14%

Canada-MV11%

Other-NR10%

Other-MV9%

Other-EGU7%

Other-NEGU5%

NY-NR3%

Other-ST3%

NY-MV3%

NY-ST1%

NY-EGU1%

NY-NEGU0%

Nearby-MV0%

Canada-EGU0%

Nearby-NR0%

Nearby-NEGU0%

Canada-ST6%

Percentage Contribution by State: Buffalo nonattainment area

0

10

20

30

40

50

60

70

CN NY WI MI KS IL IA MO

Percentage Contribution by Sector:Buffalo nonattainment area

0

10

20

30

40

50

Non-RoadMobile (NR)

On-RoadMobile(MV)

Non-EGUPoint

(NEGU)

StationaryArea (ST)

EGU Point(EGU)

AverageFires (AV)

For Buffalo, EPA has shown that Canadian sources contribute 59% to ozone precursors on peak ozone days

(Slide from EPA presentation)

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BuffaloWestfield

Williamson

Kane Exp Forest

Unionville

Lykens

Greenbelt

Stow

Wash. Crossing

High episodic CAN contributions are experienced as far south and east as Eastern MA, New Jersey, and the Washington DC area

Daily-8h-max time series for these more distant locations follow …

20


Stow, MA


21


Washington Crossing, NJ


22


Greenbelt, MD


23


Alpine, CA: The situation in the Southwest is different from the Northeast; there is a larger mean enhancement but fewer sharp

episodes. MEX influence is frequently above 10 ppb, and US background is frequently above 30 ppb

Inverted black triangles show days in which MEX enhancement is >10 ppb and observed ozone concentration is >80 ppb

24

Canadian influence is >10 ppb on some peak ozone days (>80 ppb) Canadian influence is always <10 ppb on peak ozone days (>80 ppb) Untagged color boxes have max surface ozone <= 80 ppb

Max CAN contribution on peak ozone days is 23 ppb among boxes shown as: ■

CAN influence is important for areas near the Great Lakes and the Northeast coast

25


26

Note that as the reference ozone value is decreased, increasingly larger areas of the Southeast and industrial Midwest are influenced


27


28


29


At CAN = >5 ppb and ozone = >70 ppb, much of the eastern US is influenced, even into North Carolina

30

70 75

2850

280

93

527

85416792936

Contribution of CAN pollution to exceedances of different levels of ozone concentration (I)

Includes all US grid boxes within [36N-48N, 88W-66W] (15,180 data points)

Y:

X:

138

Number of data points exceeding specified values of CAN enhancement and ozone concentration (cumulative)

En\Oz >70 ppb >75 ppb >80 ppb

>10 ppb 3.2% 3.0% 3.3%

>5 ppb 17.9% 16.7% 16.2%

30

31

Scatter plot based on timeseries at the gridboxes withOzone > 80ppb and Canadian influence > 5ppb

284371

138

540

225

916

359

1409

Sorted to include only the 56 grid boxes that had at least one case of X >80 ppb and Y >5 ppb, i.e., under some Canadian influence (5,152 data points)


>10 ppb 5.0% 4.7% 5.2%

>5 ppb 25.5% 24.6% 25.6%

Number of data points exceeding specified values of CAN enhancement and ozone concentration (cumulative)

Contribution of CAN pollution to exceedances of different levels of ozone concentration (II)

31

32

Mexican influence is >10 ppb on some peak ozone days (>80 ppb) Mexican influence is always <10 ppb on peak ozone days (>80 ppb) Untagged color boxes have max surface ozone <= 80 ppb

Max MEX contribution on peak ozone days is 18 ppb among boxes shown as: ■

MEX influence is important for southern California and parts of Arizona and Texas

33


34


35


36


37


At MEX = >5 ppb and ozone = >70 ppb, MEX influence extends into Nevada, New Mexico, and NW Texas

38

142853

49109271

41310022453

70 75

Contribution of MEX pollution to exceedances of different levels of ozone concentration (I)Y

:

X:

Includes all US grid boxes within [26N-42N, 120W-90W] (34,960 data points)

Number of data points exceeding specified values of MEX enhancement and ozone concentration (cumulative)


>10 ppb 2.2% 2.8% 3.4%

>5 ppb 11.0% 10.9% 11.9%

38

39

Scatterplot based on timeseries at gridboxes with Ozone > 80 ppb & Mexican enhancement > 5 ppb

14

49

125

27

90

223

43

155

379


>10 ppb 11.3% 12.1% 11.2%

>5 ppb 40.9% 40.4% 39.2%

Number of data points exceeding specified values of MEX enhancement and ozone concentration (cumulative)

Contribution of MEX pollution to exceedances of different levels of ozone concentration (II)

Sorted to include only the 15 grid boxes that had at least one case of X >80 ppb and Y >5 ppb, i.e., under some Mexican influence (1,380 data points)

39

40

CONCLUSIONS• Transboundary pollution from Canada and Mexico increases the mean background surface ozone

concentration in the US in JJA by 1-13 ppb.

• The largest Canadian enhancement is 8.8 ppb (JJA mean), with an episodic maximum of 34 ppb (at

Unionville, MI) in the daily-8h-max time series.

• The largest Mexican enhancement is higher, 13.1 ppb (JJA mean), but the maximum in the daily-8h-

max time series is smaller (21 ppb, not shown).

• For peak ozone cases, the US background can be >30 ppb and even 40 ppb due to transboundary

influences.

• Transboundary pollution can contribute significantly (up to 23 ppb in the Northeast and 18 ppb in

the Southwest) to peak ozone levels (in this case, defined as >80 ppb).

• Canadian contributions on peak days (>70, > 75, or > 80 ppb ozone) can exceed 10 ppb as far from

Canada as near Washington, DC; central New Jersey, and eastern Massachusetts; Mexican

contributions can be consistently higher in some cases, but focused on closer areas of S. California,

S. Nevada, and western to central Arizona.

• Cross-border contributions of these magnitudes impose significant penalties for some regions of the

country, i.e., in order to achieve a tightened ozone standard, parts of MI, NY, PA, and other

Northeastern and Midwestern locations would have to get substantial additional emission reductions,

depending on location, to offset the Canadian influence.

Documents

Transboundary influences on US background ozone Huiqun Wang 1 ([email protected]) Philippe Le Sager 2 ([email protected]) Rokjin Park 3 ([email protected])