Techniques for Determining PSD of PM: Laser Diffraction vs. Electrical Sensing Zone

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Techniques for Determining PSD of PM Laser
Diffraction vs. Electrical Sensing Zone
A 242nd ACS National Meeting Presentation Paper
ID18440
Z. Cao1, M. Buser2, D. Whitelock3, L. Wang-Li1,
Y. Zhang4, C.B. Parnell5 1NCSU, 2OSU, 3USDA-ARS,
4UIUC, 5TAMU
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Introduction

• PM NAAQS PM10 PM2.5
• Health effects, Source identification/estimation,
  Mitigation strategies PM characteristics
• Physical properties
• Mass, or number concentrations
• Particle size distribution (PSD)
• Morphology
• Density, etc.
• Chemical compositions
• Biological properties

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Introduction

• Various techniques for PSD measurement (analysis)
• Aerodynamic method (APS, Impactors, etc)
• Optical method (optical counters, light
  scattering analyzers, etc)
• Electrical sensing zone method (Coulter Counter)
• Electrical mobility and condensation method
  (DMACNC)
• Electron microscopy
• No single agreed upon method for different
  sources

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Aerodynamic Method for PSD Analysis
Aerodynamic Particle Sizer (APS)

• Aerosol entering the tube is assumed to be
  uniform
• Dilution system - reduce problems with particle
  coincidence in the sensor
• Light scattered - changes rapidly with dp
• small particle processor AED 0.5 15.9 mm
• large particle processor AED 5 30 mm
• Monodisperse latex spheres are used for
  calibration of full size range of the APS
• Not work for PSD on sampler filter
• Field real-time measurement

Ch5.8 pages 136-138 of Hinds
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Aerodynamic Method for PSD Analysis
Impactors

• On-site measurements in mass concentration and
  PSD
• Limited size ranges
• Particle bounce
• Particle losses

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Optical Method for PSD Analysis
Optical Particle Counters
http//en.wikipedia.org/wiki/Particle_counter

• Detect and counts one particle at a time
• Calibration?
• High level PM environment?

http//www.particlecounters.org/optical/
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Optical Method for PSD Analysis
LS13 320 Multi-wave Length Laser Diffraction
Particle Size Analyzer (0.04 2000 mm)
Polarization Intensity Differential Scattering
(PIDS)
Rayleigh Scattering Theory
(Source Beckman Coulter, Miami, FL)
Mie Scattering theory
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Optical Method for PSD Analysis
LA-300 Laser Scattering Particle Size Analyzer
Fraunhofer Diffraction and LA-300 (Source Horiba
Instrument Inc, Irvine, CA)
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Electrical Sensing Zone Method for PSD Analysis
Coulter Counter Multisizer

• Only suitable for insoluble particles
• Not an onsite measurement
• Ultrasonic bath all particles are fully
  dispersed in the liquid solution (PM on filter)
• Size calibrated with polystyrene spheres of known
  size
• Counting rate 3000 particles/s

Source Beckman Coulter, Miami, FL

• Current through the orifice
• Particle electrical resistance dp
• Change in current dp

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Electrical Mobility Method for PSD Analysis
Differential Mobility Analyzer (DMA)

• Used as a monodisper aerosol generator to produce
  sub-micrometer-sized aerosols for testing and
  calibration
• Measure PSD in the sub-micrometer size range
• Particles with greater mobility migrate to the
  center rod
• Exiting aerosol slightly charged and nearly
  monodisperse size controlled by the voltage on
  the central rod
• 0.005 1.0 mm

Condensation Nucleus Counter (CNC)
Ch15.9 of Hinds
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Electron Microscopy Method for PSD Analysis
Electron Scanning Microscopy (ESM)
Fly-ash
Corn Starch
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Objectives

• Differences in PSD measurements for PM with MMDs
  in micrometers (agricultural sources)
• Light scattering method
• Electrical sensing zone method
• PM sample types
• Filter-based PM samples with MMDgtgt10 mm
• Testing aerosols with MMD 10 mm

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Materials Methods

• PSD Analyzers
• LS13 320 multi-wave length laser diffraction
  particle size analyzer - NCSU
• LA-300 laser scattering particle size analyzer
  UIUC
• Coulter Counter Multisizer3 TAMU
• Coulter Counter Multisizer3 USDA
• LS230 laser diffraction particle size analyzer
  USDA

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Materials Methods
PM Field Sampling Low-volume TSP
Samplers High-rise Layer House
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Materials Methods

• Field PM samples filter-based
• 26 samples/season for two seasons distributed to
  the three locations
• Analyzed under the same operation procedure
• Testing materials not filter-based aerosols
• Limestone
• Starch
• No.3 Micro Aluminum
• No.5 Micro Aluminum

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Materials Methods
PM Sample Assignment/Distribution
Winter PM samples Spring PM samples Testing
aerosols
Winter PM samples
Spring PM samples Testing aerosols
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Materials Methods

• PM10 and PM2.5 mass fraction analyses
• Measured by the analyzer
• Calculated using the lognormal distribution
  equation
• Checked for agreements (Relative Difference, )
• Measured PM10 or PM2.5 measured by the
  analyzer
• Lognormal PM10 or PM2.5 calculated using the
  lognormal distribution equation

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Results Discussion
Measured MMDs (mm) for Winter Samples N26
LS13 320 LA-300 CCM3
17.130.81 22.711.43 13.941.00
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Results Discussion
Measured GSDs for Winter Samples N26
LS13 320 LA-300 CCM3
2.630.04 2.020.11 1.850.04
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Results Discussion
Measured MMDs (mm) for Spring Samples N26
LS13 320 LA-300 LS230 CCM3
18.441.44 22.622.68 18.471.38 13.990.74
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Results Discussion
Measured GSDs for Spring Samples N26
LS13 320 LA-300 LS230 CCM3
2.670.11 1.990.15 2.650.22 1.840.04
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Results Discussion

• Measured PSDs of Testing Aerosols

  LS13 320 LS13 320 LA-300 LA-300 LS230 LS230 CCM3 CCM3
 Testing aerosols MMD (µm) GSD MMD (µm) GSD MMD (µm) GSD MMD (µm) GSD
Limestone 7.50 3.07 12.29 1.83 8.11 3.15 8.56 1.72
Starch 13.31 1.59 16.78 1.50 14.38 1.55 14.32 1.33
3 Micro aluminum 5.28 1.98 7.62 1.56 5.37 1.93 5.03 1.42
5 Micro aluminum 7.09 1.69 8.38 1.49 7.21 1.71 6.31 1.39
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Results Discussion
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Results Discussion
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Results Discussion

• PM10 and PM2.5 Mass Fraction Analyses (NCSU)

LS13 320
  Measured mass fraction () Lognormal mass fraction () Relative difference ()
PM10 36.162.73 34.922.71 3.440.85
PM2.5 8.400.61 3.560.66 57.95.37
N52 (26 for Winter, 26 for Spring)
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Results Discussion
LS13 320
PM10
PM2.5
N52 26 for Winter 26 for Spring)
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Results Discussion

• PM10 and PM2.5 Mass Fraction Analyses (UIUC)

LA-300
  Measured mass fraction () Lognormal mass fraction () Relative difference ()
PM10 20.602.53 19.882.56 3.345.34
PM2.5 4.570.64 0.250.14 94.463.05
N52 (26 for Winter, 26 for Spring)
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Results Discussion
LA-300
PM10
PM2.5
N52 26 for Winter 26 for Spring
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Results Discussion

• PM10 Mass Fraction Analyses (TAMU)

CCM3
  Measured mass fraction () Lognormal mass fraction () Relative difference ()
PM10 41.753.74 40.764.19 2.462.06
N 26 for Winter
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Results Discussion
TAMU-CCM3 (N26)
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Results Discussion

• PM10 and PM2.5 Mass Fraction Analyses (USDA)

  Measured mass fraction () Lognormal mass fraction () Relative difference ()
PM10 33.713.29 33.392.99 0.794.45
PM2.5 8.180.96 3.281.06 60.4411.53
PM10 41.113.68 40.933.50 0.390.80
PM2.5 1.430.35 0.650.26 54.9613.04
LS230
CCM3
N 26 for Spring
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Results Discussion
LS230
PM10
PM2.5
N26 for Spring
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Results Discussion
CCM3
PM10
PM2.5
N26 for Spring
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Conclusions

• Different analyzers significant differences in
  MMDs and GSDs for filter-based samples
• LA-300 the largest MMDs CCM3 the smallest MMD
• LS13 320 the largest GSDs CCM3 the smallest
• The PSD results of testing aerosols - consistent
  with that of filter-based samples
• LA-300 large MMDs
• LS13 320 LS230 large GSD
• PSDs measured by LS13 320 LS230 agreed well

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Conclusions

• All RDs in PM10 mass fractions of the measured
  and the fitting values lt 5, which is acceptable
• All RDs in PM2.5 mass fractions of the measured
  and the fitting values gtgt 5, which is not
  acceptable.

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Acknowledgement

• The USDA NRI Grant No. 2008-35112-18757
• Help from Qianfeng Li Zifei Liu for field
  sampling
• Support from the egg production farm