Department of the Environment The Basic Science of Air Pollution Transport Brian J. Hug Division Chief, Air Quality Planning and Policy Division.

Department of the Environment

The Basic Science of Air Pollution Transport

Brian J. Hug

Division Chief, Air Quality Planning and Policy Division

Maryland’s Air Quality

• Ozone levels in Maryland are very high

• Fine particulate levels are high

• Air pollution contributes significantly to Bay pollution

• Regional haze and air toxics are also significant air pollution problems in Maryland

Major Theme Across Entire Program

“TRANSPORT”

A Primer on Transport• Transport 101- Where does Maryland’s poor air quality come from

– Background on Maryland’s air quality

– The role of “transported” pollution

• Transport 201 – The three types of transport

– Short-range transport

– Westerly transport

– Low level night time jets

Nitrogen Deposition to the Chesapeake Bay

Air Deposition32%

Point Sources20%

Nonpoint Sources

48%

A Quick Primer on How Ground Level Ozone is Formed

Are Emissions Higher in Maryland?

Source: U.S. EPA - 1999 data

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NOxVOC

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Ozone Nonattainment Areas

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Baltimore Washington Philadelphia New YorkCity

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So Where Does It Come From? • Air pollution floating in from other states (called transport) is a

significant contributor to our air pollution problems

– Maryland – the meteorologically challenged state

– MDE/UMCP Aircraft that measure “incoming” pollution

– Models that predict state by state contributions

Classic Ozone Weather in the Mid-Atlantic

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Maryland sees its’ worst air pollution during the summer when a “Bermuda High” sets up over the Carolinas

Power Plant Emissions

H

• Very large power plant emissions concentrated along the Ohio River valley

• Air aloft circulates clockwise around the high

How Much Comes From Out of State?

• MDE works in partnership with the University of Maryland – College Park to measure and analyze pollution being transported into Maryland

• On our worst days we measure ozone at 110 parts per billion (ppb) floating into the state from the West– The 8-hour standard is 85

ppb

Who is Contributing to Maryland’s Ozone Problem?

• From EPA’s modeling to support the 22 state regional NOx reduction program called the “NOx SIP Call”

31%

69%

MD/DC/DE Other States

Are Local or Regional Reductions Better?

• In Maryland, our technical analyses show that on our worst days

– Local reductions are not very good at reducing local ozone.

– In other areas, like Atlanta, local reductions seem to be much more effective

• On days where our ozone is more “home grown” local reductions are more important

– Not our worst days, but we often see high ozone

Transport 201

• The different types of transport

• The elevated ozone reservoir

• Short range transport

• Westerly transport

• Low level night time jets

Is It Just Power Plants or are There Other Types of Transport?

• Maryland’s location places us at the “air pollution crossroads” when if comes to transport.

• Air pollution floats to us from the west and the south.

• Sometimes the air pollution we transport to the north actually “re-circulates” back to us.

• Power plants, cars and area sources are all involved in the transport process

Three Types of Transport That Affect Maryland

• Short range

– VA to MD to PA, etc.

• Long range (synoptic scale)

– 100s of miles

– Generally from W or NW

• Low Level Night-time Jets

– 100s of miles

– SW to NE along the Atlantic

• All types of transport collect in an “elevated reservoir” of ozone

The Elevated Ozone Reservoir

• Every bad ozone day, before any new ozone has been formed, a large reservoir of ozone sits above Maryland waiting to mix down.

• Ozone levels in the reservoir can routinely reach 80 to 100 ppb

Early Morning Ozone Western Maryland

Surface ozone is very low

Ozone 2000 feet above the surface is very high

What Creates the Reservoir?

• At night the earth cools and a “nocturnal inversion” is created several hundred meters above the surface

• Ozone, created earlier in the day is trapped above the inversion and moved to the north by night-time jets.

• Ozone below the inversion drops to very low levels.

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This hourly ozone graph for a summer day near Frederick, Maryland shows ozone concentrations reaching a minimum in the early morning hours.

Ground Level Ozone at Night

Regional Scale Ozone

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Long Park

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Little Buffalo

Methodist Hill

In this case from July, 1999, the high elevation monitor at Methodist Hill in southern PA is above the nocturnal inversion. By late morning, mixing has brought all monitors to the common regional level.

Where Does the Reservoir Come From?

• The elevated ozone reservoir above Maryland is a complex mix of pollution that originated in the west (primarily power plants) and the south (cars, area sources and stationary sources)

Short Range Transport

• Central VA to DC

• DC to Baltimore

• Baltimore to PA

• Ground level winds from the southwest to the northeast

• Emissions from cars, area sources and stationary sources float to the northeast and add to high ozone levels downwind

Westerly Transport

• On Maryland’s worst ozone days “westerly transport” plays a significant role in creating high ozone.

Classic Ozone Weather in the Mid-Atlantic

H

Maryland sees its’ worst air pollution during the summer when a “Bermuda High” sets up over the Carolinas

Power Plant Emissions

H

• Very large power plant emissions concentrated along the Ohio River valley

• Air aloft circulates clockwise around the high

Westerly Transport – What Does the Data Tell us About Its Origin?

CORRELATES WITHHIGH “AGED NOX”

* IT’S OLD *

CORRELATES WELLWITH SO2

* PROBABLY POWER PLANTS *

DOES NOT CORRELATE

WELL WITH CO* NOT CARS *

HIGH OZONEALOFT

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et

The Low Level Jet

• Night time transport that moves air from NC to MD, MD to NJ, etc.

• The Jet is funneled northward by the Appalachians on the west and the Atlantic on the east

• Wind speeds up to 40 miles per hour can move pollution hundreds of miles overnight.

Low Level Jet Recorded Above Fort Meade Maryland

LLJLLJ LLJ

WHAT DOES THIS GRAPH TELL US?

WIND SPEED AND DIRECTION

ABOVE FT MEADE MD

AUGUST 10

10 PM TO 8AM

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AUGUST 11

10 PM TO 8AM.

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AUGUST 12

10 PM TO 9AM am

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NOCTURNAL INVERSION UP TO ABOUT 1000 FEET

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AUGUST 10

WINDS FROM THE SOUTHWEST

AT ABOUT 25 to 30 MPH

1000 FEET ABOVE THE SURFACE

AUGUST 11

WINDS FROM THE SOUTHWEST

AT ABOUT 30 to 40 MPH

1000 FEET ABOVE THE SURFACE

AUGUST 12

WINDS FROM THE SOUTHWEST

AT ABOUT 30 to 40 MPH

1000 FEET ABOVE THE SURFACE

35 MPH FOR 6 HOURS IS ABOUT 200 MILES

Model Depiction of the Low Level JetHigh Wind Speeds In Red

9:00 PM 11:00 PM 01:00 AM

03:00 AM 05:00 AM 07:00 AM

How Much Ozone May be in the Low Level Jet?

• Still analyzing this issue

• Theory and recent work by Penn State around Philadelphia (using laser technology called LIDAR) indicates that the low level jet can routinely carry 80 to 90 ppb ozone.

Take Home Messages

• Maryland’s air quality is significantly affected by transport from upwind areas to the west and the south

• On the worst ozone days well over half of the measured ozone in Maryland originates in upwind states

• Sources that transport pollution to Maryland include power plants, cars and area sources.

Thanks…..

Brian HugDivision Chief, Planning and Policy Division410-537-4125bhug@mde.state.md.us