Particulate Matter:
What Floats in the Air?
Alex Cuclis
Houston Advanced Research Center
(HARC)
What Floats in the Air?
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Particulate Matter
Total Suspended Particulates
Aerosols
Haze
What Floats in the Air?
Particulate matter consists of tiny particles
in the atmosphere that can be solid or
liquid (except for water or ice) and is
produced by a wide variety of natural and
manmade sources.
Size Matters
• Total Suspended Particulates (TSP) range
from 0 – 50 microns
• Human hair is about 70 microns in
diameter.
• > 50 micron particulates tend to settle out
of the air.
Size Matters
• PM10 – “PM50” – too large for respiratory
system
• PM2.5 – PM10 - can enter lungs through
mouth.
• PM2.5 and less – can enter lungs through
nose.
Primary and Secondary PM
• “Primary” particles, such as dust from roads or
elemental carbon (soot) from wood combustion,
are emitted directly into the atmosphere.
• “Secondary” particles are formed in the
atmosphere from primary gaseous emissions.
Examples include sulfates, formed from SO2
emissions from power plants and industrial
facilities, and nitrates, formed from NOx
emissions from power plants, automobiles, and
other types of combustion sources.
Sources of PM2.5
• Primary mobile source emissions account for
approximately 25-33% of fine PM mass.
• Primary emissions from cooking account for
approximately 10-15% of fine PM mass.
• Primary point source emissions of fine
particulate matter have not yet been estimated.
• Secondary emissions of organic carbon and
elemental carbon make up approximately 2530% of fine PM mass.
- Dave Allen
Sources of PM10
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Fly ash from power plants,
Carbon black from automotive industries
Various manufacturing processes,
Ash from wood stoves and fireplaces
Agriculture and forestry practices
Fugitive dust sources (paved and unpaved
roads)
- Dave Allen
Sources of PM10
• In the U.S., PM10 emissions from fuel combustion,
industrial processes, and transportation each
contribute about one-third of the traditionally
inventoried particulate source categories. These
source categories, however, only account for 6% of
total PM10 emissions nationwide. The vast majority
of PM10 emissions are from natural sources,
agriculture, forestry, wildfires, managed burning, and
fugitive dust.
Chemistry Matters
The chemical composition of particles depends on
location, time of year, and weather.
The different constituents of PM are the result of very
different types of emissions, and therefore, as
emission reduction plans are developed to reduce
health impacts of fine particulate matter, it will be
important to understand whether particular chemical
or physical properties of the PM are causing health
impacts.
Travel Time Matters
• How long?
PM10 particles can stay in the air for
minutes or hours, while PM2.5 particles can
stay in the air for days or weeks.
• What distance?
PM10 particles can travel as little as a
hundred yards or as much as 30 miles.
PM2.5 particles can go many hundreds of
miles.
Travel Time Matters
Examples…
• The fires of Mexico
• The Dust of Africa – at times makes up
50% of the breathable particles in Miami
Travel Time Matters
• Gravity is the driving force for settling, but
does not control the rate of settling.
• Many individual particles cannot be seen
by the naked eye, but as a group they can
be seen by satellites.
Deposition Matters
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When it rains
Humidity
Wind Speed
Size
Composition/Chemistry
Smoke from Mexico
April 16,
2003
Dust from Saharan Africa
July 16,
2003