The Basic Science of Air Pollution Transport

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The Basic Science of Air Pollution Transport

• Brian J. Hug
• Division Chief, Air Quality Planning and Policy
  Division

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Marylands 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

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Major Theme Across Entire ProgramTRANSPORT
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A Primer on Transport

• Transport 101- Where does Marylands poor air
  quality come from
• Background on Marylands air quality
• The role of transported pollution
• Transport 201 The three types of transport
• Short-range transport
• Westerly transport
• Low level night time jets

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Nitrogen Deposition to the Chesapeake Bay
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A Quick Primer on How Ground Level Ozone is
Formed
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Are Emissions Higher in Maryland?
States
Source U.S. EPA - 1999 data
tons per year
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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

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Classic Ozone Weather in the Mid-Atlantic
Maryland sees its worst air pollution during the
summer when a Bermuda High sets up over the
Carolinas
H
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Power Plant Emissions

• Very large power plant emissions concentrated
  along the Ohio River valley
• Air aloft circulates clockwise around the high

H
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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

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Who is Contributing to Marylands Ozone Problem?

• From EPAs modeling to support the 22 state
  regional NOx reduction program called the NOx
  SIP Call

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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

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Transport 201

• The different types of transport
• The elevated ozone reservoir
• Short range transport
• Westerly transport
• Low level night time jets

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

• Marylands 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

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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

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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
Ozone 2000 feet above the surface is very high
Surface ozone is very low
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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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Ground Level Ozone at Night
This hourly ozone graph for a summer day near
Frederick, Maryland shows ozone concentrations
reaching a minimum in the early morning hours.
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Regional Scale Ozone
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.
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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)

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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

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Westerly Transport

• On Marylands worst ozone days westerly
  transport plays a significant role in creating
  high ozone.

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Classic Ozone Weather in the Mid-Atlantic
Maryland sees its worst air pollution during the
summer when a Bermuda High sets up over the
Carolinas
H
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Power Plant Emissions

• Very large power plant emissions concentrated
  along the Ohio River valley
• Air aloft circulates clockwise around the high

H
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Westerly Transport What Does the Data Tell us
About Its Origin?
DOES NOT CORRELATE WELL WITH CO NOT CARS
HIGH OZONE ALOFT
CORRELATES WELL WITH SO2 PROBABLY POWER PLANTS

CORRELATES WITH HIGH AGED NOX ITS OLD
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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
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Low Level Jet Recorded Above Fort Meade Maryland
WHAT DOES THIS GRAPH TELL US? WIND SPEED AND
DIRECTION ABOVE FT MEADE MD
35 MPH FOR 6 HOURS IS ABOUT 200 MILES
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
AUGUST 10 10 PM TO 8AM . . .
AUGUST 12 10 PM TO 9AM am . . .
AUGUST 11 10 PM TO 8AM. . . .
LLJ
LLJ
LLJ
NOCTURNAL INVERSION UP TO ABOUT 1000 FEET .
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Model Depiction of the Low Level Jet High Wind
Speeds In Red
900 PM
1100 PM
0100 AM
0300 AM
0500 AM
0700 AM
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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.

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Take Home Messages

• Marylands 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.

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Thanks..Brian HugDivision Chief, Planning
and Policy Division410-537-4125bhug_at_mde.state.md
.us