Introduction to the PM Data Analysis Workbook

1
Introduction to the PM Data Analysis Workbook

• Guide to the Workbook
• PM2.5 Background
• Overview of the PM Monitoring Program
• Critical Issues for Data Uses and Interpretation
• Workbook Contents
• Motivating Examples

• The objective of the workbook is to guide
  federal, state, and local agencies and other
  interested people in using particulate matter
  data to meet their objectives.

2
Introduction
Nature and sources of particulate matter (PM).
Particulate matter is the general term used for a
mixture of solid particles and liquid droplets
found in the air. These particles, which come in
a wide range of sizes, originate from many
different stationary and mobile sources as well
as from natural sources. They may be emitted
directly by a source or formed in the atmosphere
by the transformation of gaseous emissions. Their
chemical and physical compositions vary depending
on location, time of year, and meteorology. Healt
h and other effects of PM. Scientific studies
show a link between PM (alone, or combined with
other pollutants in the air) and a series of
significant health effects. These health effects
include premature death, increased hospital
admissions and emergency room visits, increased
respiratory symptoms and disease, and decreased
lung function, and alterations in lung tissue and
structure and in respiratory tract defense
mechanisms. Sensitive groups that appear to be at
greater risk to such effects include the elderly,
individuals with cardiopulmonary disease such as
asthma, and children. In addition to health
problems, particulate matter is the major cause
of reduced visibility in many parts of the United
States. Airborne particles also can cause soiling
and damage to materials. New PM standards. The
primary (health-based) standards were revised to
add two new PM2.5 standards, set at 15µg/m3
(annual) and 65 µg/m3 (24-hr), and to change the
form of the 24-hour PM10 standard. The selected
levels are based on the judgement that public
health will be protected with an adequate margin
of safety. The secondary (welfare-based)
standards were revised by making them identical
to the primary standards. In conjunction with the
Regional Haze Program, the secondary standards
will protect against major PM welfare effects,
such as visibility impairment, soiling, and
materials damage. PM2.5 composition. PM2.5
consists of those particles that are less than
2.5 micrometers in diameter. They are also
referred to as "fine" particles, while those
between 2.5 and 10 µ m are known as "coarse"
particles. Fine particles result from fuel
combustion from motor vehicles, power generation,
and industrial facilities, and from residential
fireplaces and wood stoves. Fine particles can
also be formed in the atmosphere by the
transformation of gaseous emissions such as SO2,
NOx, and VOCs. Coarse particles are generally
emitted from sources such as vehicles traveling
on unpaved roads, materials handling, crushing
and grinding operations, and windblown dust.
Goals of PM2.5 monitoring. The goal of the PM2.5
monitoring program is to provide ambient data
that support the nation's air quality programs,
including both mass measurements and chemically
resolved, or speciated, data. Data from this
program will be used for PM2.5 NAAQS comparisons,
development and tracking of implementation plans,
assessments for regional haze, and assistance for
studies of health effects, and other ambient PM
research activities.
Key reference U.S. EPA, 1999
3
PM Data Analysis Workbook Design Goals

• Relevant. The workbook should contain material
  that the State PM Data Analysts need and omit
  material that they dont need.
• Technically sound. The workbook should be
  prepared and agreed upon by experienced PM
  analysts.
• Educational. The workbook content should be
  presented in a manner that State PM Data Analysts
  can learn relevant new PM analyses.
• Practical. Beyond theory, the workbook should
  contain practical advice and access to examples,
  tools and methods.
• Gateway. The core workbook should be a gateway to
  additional on-line resources.
• Evolving. The on-line and hard copy workbooks
  should improve in time through feedback from the
  user and producer communities.

4
Why PM Data Analysis by the States?

• There is an ever-growing data vs. analysis
  imbalance in favor of data collection.
• The new PM2.5 regulations will further increase
  the need to better understand the nature, causes,
  effects, and reduction strategies for PM.
• States collecting data have unique 'local'
  perspectives on data quality, meteorology, and
  sources, and in articulating policy-relevant data
  analysis questions. States also face
• large, complex new PM2.5 data quantities,
• large uncertainties about causes and effects,
• immature nature and inherent complexity of
  analysis techniques,
• importance of both local and transport sources
  for PM2.5, and
• connections between PM2.5, visibility, ozone,
  climate change, and toxics.
• Collaborative data analysis is needed, to develop
  and support linkages between
• data analysis 'experts', 'novices' and
  'beginners'
• data analysts and modelers, health researchers,
  and policymakers
• multiple states, regions, nations, environmental
  groups industrial stakeholders

5
Workbook Content

• Introduction
• Ensuring High Quality Data
• Quantifying PM NAAQS Attainment Status
• Characterizing Ambient PM Concentrations and
  Processes
• Quantifying Trends in PM and its Precursors
• Quantifying the Contribution of Important Sources
  to PM Concentrations
• Evaluating PM and Precursor Emission Inventories
• Identifying and Quantifying the Potential for
  Control Strategies in Helping Attain the Standard
• Using PM Data to Assess Visibility
• Glossary
• References

6
Using the Workbook

• Decision matrix to be used to identify
  example activities that will help the analyst
  meet policy-relevant objectives. To use the
  matrix, find your policy-relevant objective at
  the top left. Follow this line across to see
  which example activities will be useful to meet
  the objective. For each of these activities,
  look down the column to see which data and data
  analysis tools are useful for the activity.

7
PM2.5 Emission Sources
Most of the PM mass in urban and nonurban areas
can be explained by a combination of the
following chemical components

• Geological material suspended dust consists
  mainly of oxides of Al, Si, Ca, Ti, Fe, and other
  metal oxides.
• Sulfate results from conversion of SO2 gas to
  sulfate-containing particles.
• Nitrate results from a reversible gas/particle
  equilibrium between NH3, HNO3, and particulate
  ammonium nitrate.
• Ammonium ammonium bisulfate, sulfate, and
  nitrate are most common from the irreversible
  reaction between H2SO4 and NH3.

• NaCl Salt is found in PM near sea coasts, open
  playas, and after de-icing materials are applied.
• Organic carbon (OC) consists of hundreds of
  separate compounds that contain gtC20.
• Elemental carbon (EC) is black, often called
  soot.
• Liquid Water soluble nitrates, sulfates,
  ammonium, sodium, other inorganic ions, and some
  organic material absorb water vapor from the
  atmosphere.

Key reference Chow and Watson, 1997
8
Common Emission Source Profiles
9
Properties of Particulate Matter

• Physical, Chemical and Optical Properties
• Size Range of Particulate Matter (PM)
• Mass Distribution of PM vs. Size PM10, PM2.5
• Fine and Coarse Particles
• Fine Particles - PM2.5
• Coarse Particle Fraction - PM10-PM2.5
• Chemical Composition of PM vs. Size
• Optical Properties of PM

Key reference Capita, 1999
10
Physical, Chemical and Optical Properties

• PM is characterized by its physical, chemical,
  and optical properties
• Physical properties include particle size and
  shape. Particle size refers to particle diameter
  or equivalent diameter for odd-shaped
  particles. Particles may be liquid droplets,
  regular or irregular shaped crystals, or
  aggregates of odd shape.
• Particle chemical composition may vary including
  dilute water solutions of acids or salts, organic
  liquids, earth's crust materials (dust), soot
  (unburned carbon), and toxic metals.
• Optical properties determine the visual
  appearance of dust, smoke and haze and include
  light extinction, scattering and absorption . The
  optical properties are determined by the physical
  and chemical properties of the ambient PM.
• Each PM source type produces particles with a
  specific physical, chemical and optical
  signature. Hence, PM may be viewed as several
  pollutants since each PM type has its own
  properties, and sources and may require different
  controls.

11
Size Range of Particulate Matter

• The size of PM particles ranges from about tens
  of nanometers (nm) (which corresponds to
  molecular aggregates) to tens of microns (1 ?m ?
  the size of human hair).
• The smallest particles are generally more
  numerous and the number distribution of particles
  generally peaks below 0.1 ?m. The size range
  below 0.1 ?m is also referred to as the ultrafine
  range.
• The largest particles (0.1-10 ?m) are small in
  number but contain most of the PM volume (mass).
  The volume (mass) distribution can have two or
  three peaks (modes). The bi-modal mass
  distribution has two peaks.
• The peak of the PM surface area distribution is
  always between the number and the volume peaks.

12
Mass Distribution of PM vs. Size PM10, PM2.5
Fine
Coarse

• The mass distribution tends to be bi-modal with
  the saddle in the 1-3 ?m size rage
• PM10 refers to the fraction of the PM mass less
  than 10 ?m in diameter
• PM2.5 or fine mass refers to the fraction of the
  PM mass less than 2.5 ?m in size.
• The difference between PM10 and PM2.5 constitutes
  the coarse fraction
• The fine and coarse particles have different
  sources, properties and effects. Many of the
  known environmental impacts (health, visibility,
  acid deposition) are attributed to PM2.5.
• There is a natural division of atmospheric
  particulates into Fine and Coarse fraction based
  on particle size.

13
Fine and Coarse Particles
Key reference Seinfeld and Pandis, 1998
14
Fine Particles - PM2.5

• Fine particles (? 2.5 ?m) result primarily from
  combustion of fossil fuels in industrial boilers,
  automobiles, and residential heating systems.
• A significant fraction of the PM2.5 mass over the
  US is produced in the atmosphere through
  gas-particle conversion of precursor gases such
  as sulfur oxides, nitrogen oxides, organics, and
  ammonia. The resulting secondary PM products are
  sulfates, nitrates, organics, and ammonium.
• Some PM2.5 is emitted as primary emissions from
  industrial activities and motor vehicles
  including soot (unburned carbon), trace metals,
  and oily residues.
• Fine particles are mostly droplets except for
  soot which is in the form of chain aggregates.
• Over the industrialized regions of the US,
  anthropogenic emissions from fossil fuel
  combustion contribute most of the PM2.5. In
  remote areas, biomass burning, windblown dust,
  and sea salt also contribute.
• Fine particles can remain suspended for long
  periods (days to weeks) and contribute to ambient
  PM levels hundreds of km away from where they are
  formed.

15
Coarse Particles - PM10-PM2.5

• Coarse particles (2.5 - 10 ?m) are generated by
  mechanical processes that break down crustal
  material into dust that can be suspended by the
  wind, agricultural practices, and vehicular
  traffic on unpaved roads.
• Coarse particles are primary in that they are
  emitted as windblown dust and sea spray in
  coastal areas. Anthropogenic coarse particle
  sources include flyash from coal combustion and
  road dust from automobiles.
• The chemical composition of the coarse particle
  fraction is similar to that of the earth's crust
  or the sea but sometimes coarse particles also
  carry trace metals and nitrates.
• Coarse particles are removed from the atmosphere
  by gravitational settling, impaction to surfaces,
  and scavenging by precipitation. Their
  atmospheric residence time is generally less than
  a day, and their typical transport distance is
  below a few hundred km. Some dust storms tend to
  lift the dust to several km altitude, which
  increases the transport distance to many thousand
  km.

Key reference Albritton and Greenbaum, 1998
16
Relationship of PM2.5 and PM10

• The historical PM2.5 network is sparse and thus
  it is difficult to assess PM2.5 concentrations
  over the US.
• In many areas of the country, PM10 and PM2.5 are
  related since most of the PM10 is contributed by
  PM2.5. Evaluating the relationship between the
  two measurements provides information on PM2.5
  concentrations in areas not monitored for PM2.5.
• PM2.5 compromises a larger fraction and has a
  more similar seasonal pattern in the N.E. than in
  Southern California.

17
Chemical Composition of PM vs. Size

• The chemical species that make up the PM occur at
  different sizes.
• For example in Los Angeles, ammonium and sulfate
  occur in the fine mode, lt2.5 ?m in diameter.
  Carbonaceous soot, organic compounds and trace
  metals tend to be in the fine particle mode.
• The sea salt components, sodium and chloride
  occur in the coarse fraction, gt 2.5 ?m.
  Wind-blown and fugitive dust are also found
  mainly in the coarse mode.
• Nitrates may occur in fine and coarse modes.

18
Optical Properties of PM

• Particles effectively scatter and absorb solar
  radiation.
• The scattering efficiency per PM mass is highest
  at about 0.5 ?m. This is why, say, 10 ?g of fine
  particles (0.2ltDlt1 ?m) scatter over ten times
  more than 10 ?g of coarse particles (Dgt2.5 ?m)

19
PM Formation in the Atmosphere

• Sulfate Formation in the Atmosphere
• Sulfate Formation in Clouds
• Season SO2-Sulfate Transformation rate
• Residence Time of Sulfur and Organics
• Internal and External Mixtures of Particles
• Need to add nitrate discussion, ammonium
  discussion

Key reference Capita, 1999
20
Sulfate Formation in the Atmosphere

• Sulfates constitute about half of the PM2.5 in
  the Eastern US. Virtually all the ambient sulfate
  (99) is secondary, formed within the atmosphere
  from SO2.
• About half of the SO2 oxidation to sulfate occurs
  in the gas phase through photochemical oxidation
  in the daytime. NOx and hydrocarbon emissions
  tend to enhance the photochemical oxidation rate.

• The condensation of H2SO4 molecules results in
  the accumulation and growth of particles in the
  0.1-1.0 ?m size range - hence the name
  accumulation-mode particles.

21
Sulfate Formation in Clouds

• At least half of the SO2 oxidation is taking
  place in cloud droplets as air molecules pass
  through convective clouds at least once every
  summer day.
• Within clouds, the soluble pollutant gases such
  as SO2, get scavenged by the water droplets and
  rapidly oxidize to sulfate.

• Only a small fraction of the cloud droplets rain
  out, most droplets evaporate at night and leave a
  sulfate residue or convective debris. Most
  elevated layers above the mixing layer are
  pancake-like cloud residues.
• Such cloud processing is responsible for
  internally mixing PM particles from many
  different sources. It is also believed that such
  wet processes are significant in the formation
  of the organic fraction of PM2.5.

Key reference Capita
22
Season SO2-Sulfate Transformation rate
The SO2 to sulfate transformation rates peak in
the summer due to enhanced summertime
photochemical oxidation and SO2 oxidation in
clouds.
23
Residence Time of Sulfur and Organics.

• SO2 is depleted mostly by dry deposition
  (2-3/hr), and also by conversion to sulfate (up
  to 1/hr). This gives SO2 an atmospheric
  residence time of only 1 to 1.5 days.
• It takes about a day to form the sulfate PM. Once
  formed, sulfate is removed mostly by wet
  deposition at a rate of 1-2 /hr yielding a
  residence time of 3 to 5 days.
• Overall, sulfur as SO2 and sulfate is removed at
  a rate of 2-3/hr, which corresponds to a
  residence time of 2-4 days.
• These processes have at least a factor of two
  seasonal and geographic variation.
• It is believed that the organics in PM2.5 have a
  similar conversion rate, removal rate and
  atmospheric residence time.

24
PM, ozone, and other pollutants
Key reference
25
Atmospheric Transport of PM

• Transport mechanisms
• Influence of transport on source regions
• Plume transport
• Long-range transport

Key reference Capita, 1999
26
Transport Mechanisms

• Pollutants are transported by the atmospheric
  flow field which consists of the mean flow and
  the fluctuating turbulent flow

The three transport processes that shape regional
dispersion are wind shear, veer, and eddy motion.
Homogeneous hazy airmasses are created through
shear and veer at night followed by vigorous
vertical mixing during the day.
The three major airmass source regions that
influence North America are the northern Pacific,
the Arctic, and the tropical Atlantic. During the
summer, the eastern US is influenced by the
tropical airmass from Gulf of Mexico.
27
Influence of Transport on Source Regions
Horizontal Dilution
Vertical Dilution
In urban areas, during the night and early
morning, the emissions are trapped by poor
ventilation. In the afternoon, vertical mixing
and horizontal transport tend to dilute the
concentrations.
Low wind speeds over a source region allows for
pollutants to accumulate. High wind speeds
ventilate a source region preventing local
emissions from accumulating.
28
Plume Transport
Much of the man-made PM2.5 in the East is from
SO2 emitted by power plants.

• Plume transport varies diurnally from a
  ribbon-like layer near the surface at night to a
  well-mixed plume during the daytime.
• Even during the daytime mixing, individual power
  plant plumes remain coherent and have been
  tracked for 300 km from the source.
• Most of the plume mixing is due to nighttime
  lateral dispersion followed by daytime vertical
  mixing.

29
Long Range Transport

• In many remote areas of the US, high
  concentrations of PM2.5 have been observed. Such
  events have been attributed to long range
  transport.
• Long range transport events occur when there is
  an airmass stagnation over a source region, such
  as the Ohio River Valley and the PM2.5
  accumulates. Following the accumulation, the hazy
  airmass is transported to the receptor areas.
• Satellite and surface observations of fine
  particles in hazy airmasses provide a clear
  manifestation of long range pollutant transport
  over Eastern N. America.

30
Objectives of the PM Monitoring Program

• The primary objective of the PM monitoring
  program is to provide ambient data that support
  the Nations air quality program objectives
• Assess annual and seasonal spatial
  characterization of PM
• Perform air quality trends analysis and track
  progress of control programs
• Develop emission control strategies

Key reference Homolya et al., 1998
31
Overview of National PM2.5 Network
Key reference Homolya et al., 1998
32
Implementation update

• maps?
• implementation schedule?

Key reference
33
Sampling Schedule
Key reference
34
Critical Issues for Data Uses and Interpretation

• Sampling losses on the order of 30 percent of the
  annual federal standard for PM2.5 may be expected
  due to volatilization of ammonium nitrate in
  those areas of the country where nitrate is a
  significant contributor to the fine particle mass
  and where ambient temperatures tend to be warm
  (Hering and Cass, 1999).
• Add bullet on organic carbon losses.
• Discuss how these issues relate to data
  interoperation and can affect uses of the data.
• More

Key reference
35
Site Types
The larger check marks reflect the primary use of
the data.
Key reference Homolya et al., 1998
36
Data Collected
Key reference Homolya et al., 1998
37
Sampling Artifacts, Interferences, and Limitations
Key reference Homolya et al., 1998
38
Motivating Examples

• To be added as we complete the other sections -
  these will be examples that illustrate key PM
  data analysis and validation issues.

39
References

• Albritton D.L. and Greenbaum D.S. (1998)
  Atmospheric observations Helping build the
  scientific basis for decisions related to
  airborne particulate matter.
• Chow J.C. (1995) Measurement methods to determine
  compliance with ambient air quality standards for
  suspended particles. J. Air Waste Manage., 45,
  pp. 320-382.
• Chow J.C. and Watson J.G. (1997) Guideline on
  speciated particulate monitoring. Report
  prepared by Desert Research Institute and
  available at http//www.epa.gov/ttn/amtic/files/am
  bient/pm25/spec/drispec.pdf
• Hering S. and Cass G. (1999) the magnitude of
  bias in the measurement of PM2.5 arising from
  volatilization of particulate nitrate from Teflon
  filters. J. Air Waste Manage. Assoc., 49, pp.
  725-733.
• Homolya J.B., Rice J., Scheffe R.D. (1998) PM2.5
  speciation - objectives, requirements, and
  approach. Presentation. September.
• Seinfeld J.H. and Pandis S.N. (1998) Atmospheric
  chemistry and physics from air pollution to
  climate change. John Wiley and Sons, Inc., New
  York, New York.
• U.S. EPA (1999) Particulate matter (PM2.5)
  speciation guidance document.
• U.S. EPA (1999) General Information regarding
  PM2.5 data analysis posted on the EPA Internet
  web site http//www.epa.gov/oar/oaqps/pm25/general
  .html