Continuous Ambient Particulate Monitors A Review of Current Technologies

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Continuous Ambient Particulate MonitorsA Review
of Current Technologies

• by
• Michael Corvese, Product Manager
• Thermo Electron Corporation
• Air Quality Instruments

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Aerosol Monitoring

• Aerosol Characteristics
• Health effects
• Regulatory Background
• Sampling Analysis
• Regulatory Developments

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Aerosol Characteristics
DEFINITION Aerosol small solid or liquid
particles suspended in gas

• Dust from nature, wind, human activity
  (pollen, road dust fly ash)
• Fog from heating/cooling
  (clouds and fog)
• Mist from atomization and nebulizer
  (sulfuric acid mist)
• Spray from ultrasonics
  (insecticide spray)
• Smoke from combustion or flame
  (cigarette, soot, diesel)
• Smog from photochemicals (Urban Smog)

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Aerosol Characteristics
Physical characteristics Size distribution
Shape Refractive Index Concentration (mass
or number) Chemical characteristics Composition
(chemical or elemental) Acidity/alkalinity
Temporal characteristics Chemical and physical
characteristics changing with time Spatial
characteristics Characteristics changing with
location
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Physical Characteristics
SIZE, SHAPE, and REFRACTIVE INDEX

• 0.002-100µm aerosol research
• 0.1-100µm common sampling (0.1-10 mm)

• Size
• Shape
• Refractive Index

• Many irregular shapes
• aerodynamic diameter emphasized

• Wide range
• most consistent below 2.5mm

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Physical Characteristics
Hair cross section (60 mm)
Human Hair (60 mm diameter)
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Chemical Characteristics
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Health Effects

• Health effects are significant
• Body of evidence is substantial

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Health Effects
Increased hospital admissions and emergency room
visits during high PM conditions

• Aggravated asthma
• Chronic bronchitis
• Increase in respiratory symptoms
• Decreased lung function
• Premature death

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Health Effects
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Regulatory Background

• 1971Promulgation of National Ambient Air
  Quality Standards (NAAQS) for SO2, NO2, O3, CO,
  and total suspended particulates (TSP)
• 1978Promulgation of particulate Pb standard
• 1987Promulgation of PM10 standard
• 1997Promulgation of revised PM10 standard and
• introduction of PM2.5 standard (also a revision
  of
• the O3 standard)

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Regulatory Background
U.S. National Ambient Air Quality Standards
(NAAQS)
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Sampling and Analysis
Common Gravimetric Ambient Aerosol Sampling
Techniques (Gross - Tare) / Air Volume mg/m3

• High volume methods TSP, PM10, PM2.5, Air
  Toxics Sampler (PUF)
• Low volume methods (PM10, PM2.5, PMCoarse)

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Sampling and Analysis

• High Volume Methods TSP and PM10 Samplers

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Sampling and Analysis

• Low Volume Methods
• PM10/PM2.5 FRM PMc/PM2.5 Dichotomous Sampler

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Sampling and Analysis
Common Gravimetric Ambient Aerosol Sampling
Techniques (Gross - Tare) / Air Volume mg/m3

• Advantages Recognized reference method, low
  capital cost
• Disadvantages Limited time resolution (typically
  24-hr), long turnaround times, labor intensive,
  and gravimetric lab maintenance/cost

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Sampling and Analysis
Common Continuous Ambient Aerosol Sampling
Techniques (Dm / Dt) / (DV / Dt) mg/m3

• Light Scattering, Absorption, and Extinction
• Tapered Element Oscillating Microbalance
• Beta (Electron) Attenuation
• Hybrid Methods

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Sampling and Analysis
Impaction Separation
Cyclone Separation
Cut Point
100
Eficiency
50
0
PM100
PM10
PM1.0
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Sampling and Analysis
Common Continuous Ambient Aerosol Sampling
Techniques (Dm / Dt) / (DV / Dt) mg/m3

• Advantages Low operational cost, better time
  resolution, increased statistical database,
  instantaneous turnaround (index reporting,
  increased knowledge of air shed characteristics)
• Disadvantages 2-3x capital cost, limited
  reference capabilities (pending USEPA CASAC
  Guidelines)

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Sampling and Analysis
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Sampling and Analysis
Continuous Methods

• Light Scattering Excellent time resolution
  limited by refractive index and aerosol
  distribution (particle size)
• Oscillation Frequency Measurement Good time
  resolution, seasonal regional performance
  issues
• Beta (Electron) Attenuation Proven technology,
  minimal performance issues, versatile

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Sampling and Analysis
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Sampling and Analysis
Other Technologies Oscillation Frequency
Measurement

• Disadvantages
• Temperature dependency
• Affected by vibration
• Manual filter changes necessary
• Seasonal and regional dependencies
• Complex systems require some skill
• Volatile losses

• Advantages
• Continuous method
• Highly time resolved
• High resolution

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Series FH 62 C14Features and Benefits

• Heating Considerations

Fixed heating w/auto filter changes is an
improvement over long term heating on fixed spot.
Actual and mean VOC
loss (l and l
) due to

m
heated sample area at 50C
0
m
-20
) loss l and l
-40
3
NO
-60
4
l
m
VOC(NH
-80
l
-100
0
5
10
15
20
25
30
t in days

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b AttenuationPrinciple of Operation

• Constant flow of aerosol is metered and sampled
  onto a filter stain area.
• The detection of Beta Attenuation is proportional
  to increased mass.
• Every 1-24 hrs a new filter area is zeroed and
  introduced.

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SHARP MonitorPrinciple of Operation

• Combination nephelometer beta attenuation
• High sensitivity light scattering photometer is
  continuously calibrated by an integral time
  averaged beta attenuation mass sensor
• Measured mass concentration remains independent
  of changes in the particle population being
  sampled

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Sampling and Analysis
b Attenuation Technology
Direct b Attenuation

• Advantage
• Truly continuous
• Non-intrusive

• Ambient inlet
• Sensing volume
• b Source detector

• Disadvantage
• No known manufacturers
• Poor detection limit
• Requires very high concentrations

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Sampling and Analysis
b Attenuation Technology
Stepwise b Attenuation

• Advantage
• Semi-continuous
• Sound technology
• Good hourly precision

• Ambient Inlet
• Sensing Volume
• ß Source detector
• Filter tape

• Disadvantage
• Semi-continuous

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Sampling and Analysis
b Attenuation Technology
Continuous ß-Attenuation

• Advantage
• Continuous
• Sound technology
• Significant loading for post-collection analysis

• Ambient inlet
• Sensing volume
• b Source detector
• Filter tape

• Disadvantage
• Potential extended sample loss

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Sampling and Analysis
Hybrid Technology
Continuous SHARP Monitor

• Advantage
• Truly continuous
• Low detection limits
• High time resolution
• Intelligent moisture control

• Ambient inlet
• Sensing volume
• b Source, detector, nephelometer
• Filter tape

• Disadvantage
• None

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b Attenuation Principle of Operation
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b Attenuation

• Refined Mass Measurement via Dual Detector

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b Attenuation

• Refined Mass Measurement via Dual Detector

• A dual (a.k.a. proportional) detector allows
  the daughter nuclides of Radon gas to be measured
  and accounted for as a mass refining step.

• This allows the C14 BETA to be consistently
  stable at lower ambient concentrations.
• Important for PM2.5

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Continuous Particulate MonitorsApplications

• NAAQS Monitoring
• AQ Index Reporting
• Fenceline Monitoring
• Clean-up Sites

Ambient
In RD

• Unrivaled short-term detection limits/time
  resolution

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Continuous Particulate MonitorsApplications
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Regulatory Developments

• 1997promulgation of PM2.5 and revision of PM10
• 1998PM2.5 standard challenged in court
• 1999US Court of Appeals remanded PM2.5
• standard back to EPA for revision
• 2001US Supreme Court decision
• - EPA has the right to promulgate a PM2.5
  standard
• - Compliance costs should not be considered
• - PM Coarse should replace PM10
• 2005- Proposed revision of PM2.5 expected
• 2006-Final PM2.5 and proposed PM Coarse
  regulation expected

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Continuous Particulate Monitors
The End Thank you for your time and attention