Techniques for Determining PSD of PM: Laser Diffraction vs. Electrical Sensing Zone A 242 nd ACS National Meeting Presentation: Paper ID18440 Z. Cao 1, M. Buser 2, D. Whitelock 3, L. Wang-Li* 1, Y. Zhang 4, C.B. Parnell 5 1 NCSU, 2 OSU, 3 USDA-ARS, 4 UIUC, 5 TAMU

Introduction: PM – NAAQS: PM 10 & PM 2.5PM – NAAQS: PM 10 & PM 2.5 Health effects, Source identification/estimation, Mitigation strategies – PM characteristics: 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

Introduction: Various techniques for PSD measurement (analysis)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 (DMA+CNC)  Electron microscopy No single agreed upon method – for different sourcesNo single agreed upon method – for different sources

Aerodynamic Particle Sizer (APS) Aerosol entering the tube is assumed to be uniformAerosol entering the tube is assumed to be uniform Dilution system - reduce problems with particle coincidence in the sensorDilution system - reduce problems with particle coincidence in the sensor Light scattered - changes rapidly with d p :Light scattered - changes rapidly with d p :  small particle processor : AED 0.5 – 15.9  m  large particle processor: AED 5 – 30  m Monodisperse latex spheres are used for calibration of full size range of the APSMonodisperse latex spheres are used for calibration of full size range of the APS Not work for PSD on sampler filterNot work for PSD on sampler filter Field real-time measurementField real-time measurement Ch5.8: pages of Hinds Aerodynamic Method for PSD Analysis:

Impactors On-site measurements in mass concentration and PSDOn-site measurements in mass concentration and PSD Limited size rangesLimited size ranges Particle bounceParticle bounce Particle lossesParticle losses

Optical Particle Counters Optical Method for PSD Analysis: Detect and counts one particle at a time Detect and counts one particle at a time Calibration? Calibration? High level PM environment? High level PM environment?

LS Multi-wave Length Laser Diffraction Particle Size Analyzer (0.04 – 2000  m) Rayleigh Scattering Theory Mie Scattering theory Polarization Intensity Differential Scattering (PIDS) Optical Method for PSD Analysis: (Source: Beckman Coulter, Miami, FL)

Fraunhofer Diffraction and LA-300 (Source: Horiba Instrument Inc, Irvine, CA) Optical Method for PSD Analysis: LA-300 Laser Scattering Particle Size Analyzer

Electrical Sensing Zone Method for PSD Analysis: Source: Beckman Coulter, Miami, FL Only suitable for insoluble particles Only suitable for insoluble particles Not an onsite measurement Not an onsite measurement Ultrasonic bath – all particles are fully dispersed in the liquid solution (PM on filter)Ultrasonic bath – all particles are fully dispersed in the liquid solution (PM on filter) Size calibrated with polystyrene spheres of known sizeSize calibrated with polystyrene spheres of known size Counting rate – 3000 particles/s Counting rate – 3000 particles/s Coulter Counter Multisizer Current through the orifice Current through the orifice Particle electrical resistance ~ d p Particle electrical resistance ~ d p Change in current ~ d p Change in current ~ d p

Differential Mobility Analyzer (DMA) Used as a monodisper aerosol generator to produce sub-micrometer-sized aerosols for testing and calibrationUsed as a monodisper aerosol generator to produce sub-micrometer-sized aerosols for testing and calibration Measure PSD in the sub-micrometer size rangeMeasure PSD in the sub-micrometer size range Particles with greater mobility migrate to the center rodParticles with greater mobility migrate to the center rod Exiting aerosol – slightly charged and nearly monodisperse –size controlled by the voltage on the central rodExiting aerosol – slightly charged and nearly monodisperse –size controlled by the voltage on the central rod – 1.0  m0.005 – 1.0  m Ch15.9 of Hinds Electrical Mobility Method for PSD Analysis: Condensation Nucleus Counter (CNC)

Fly-ash Corn Starch Electron Microscopy Method for PSD Analysis: Electron Scanning Microscopy (ESM)

Differences in PSD measurements for PM with MMDs in micrometers (agricultural sources)Differences in PSD measurements for PM with MMDs in micrometers (agricultural sources)  Light scattering method  Electrical sensing zone method PM sample typesPM sample types Filter-based PM samples with MMD>>10  mFilter-based PM samples with MMD>>10  m Testing aerosols with MMD ~ 10  mTesting aerosols with MMD ~ 10  mObjectives:

PSD Analyzers  LS 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 Materials & Methods

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

Field PM samples: filter-basedField 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 aerosolsTesting materials: not filter-based aerosols  Limestone  Starch  No.3 Micro Aluminum  No.5 Micro Aluminum Materials & Methods

NCSU LS UIUC LA-300 TAMU CCM3 PM Samples USDA CCM3LS230 Materials & Methods PM Sample Assignment/Distribution Winter PM samples Spring PM samples Testing aerosols Winter PM samples Spring PM samples Testing aerosols

PM 10 and PM 2.5 mass fraction analysesPM 10 and PM 2.5 mass fraction analyses  Measured by the analyzer  Calculated using the lognormal distribution equation  Checked for agreements (Relative Difference, %) Measured = PM 10 or PM 2.5 measured by the analyzer Lognormal = PM 10 or PM 2.5 calculated using the lognormal distribution equation Materials & Methods

Results & Discussion Measured MMDs (  m) for Winter Samples: N=26 LS LA-300CCM317.13± ± ±1.00

Results & Discussion Measured GSDs for Winter Samples: N=26 LS LA-300CCM32.63± ± ±0.04

Results & Discussion Measured MMDs (  m) for Spring Samples: N=26 LS LA-300LS230CCM318.44± ± ± ±0.74

Results & Discussion Measured GSDs for Spring Samples: N=26 LS LA-300LS230CCM32.67± ± ± ±0.04

Measured PSDs of Testing Aerosols LS LA-300LS230CCM3 Testing aerosols Testing aerosols MMD (µm) GSD GSD GSD GSD Limestone Starch #3 Micro aluminum #5 Micro aluminum Results & Discussion

PM 10 and PM 2.5 Mass Fraction Analyses (NCSU) Measured mass fraction (%) Lognormal mass fraction (%) Relative difference (%) PM ± ± ±0.85 PM ± ± ±5.37 Results & Discussion LS N=52 (26 for Winter, 26 for Spring)

Results & Discussion N=52 26 for Winter 26 for Spring) LS PM 10 PM 2.5

PM 10 and PM 2.5 Mass Fraction Analyses (UIUC) Measured mass fraction (%) Lognormal mass fraction (%) Relative difference (%) PM ± ± ±5.34 PM ± ± ±3.05 Results & Discussion LA-300 N=52 (26 for Winter, 26 for Spring)

Results & Discussion N=52 26 for Winter 26 for Spring LA-300 PM 10 PM 2.5

PM 10 Mass Fraction Analyses (TAMU) Measured mass fraction (%) Lognormal mass fraction (%) Relative difference (%) PM ± ± ±2.06 Results & Discussion N= 26 for Winter CCM3

Results & Discussion TAMU-CCM3(N=26)

PM 10 and PM 2.5 Mass Fraction Analyses (USDA) Measured mass fraction (%) Lognormal mass fraction (%) Relative difference (%) PM ± ± ±4.45 PM ± ± ±11.53 PM ± ± ±0.80 PM ± ± ±13.04 Results & Discussion LS230 CCM3 N= 26 for Spring

Results & Discussion N=26 for Spring LS230 PM 10 PM 2.5

Results & Discussion N=26 for Spring CCM3 PM 10 PM 2.5

Conclusions Different analyzers: significant differences in MMDs and GSDs for filter-based samples 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 The PSD results of testing aerosols - consistent with that of filter-based samples  LA-300: large MMDs  LS & LS230: large GSD PSDs measured by LS & LS230 agreed well PSDs measured by LS & LS230 agreed well

Conclusions All RDs in PM 10 mass fractions of the measured and the fitting values < 5%, which is acceptable All RDs in PM 10 mass fractions of the measured and the fitting values < 5%, which is acceptable All RDs in PM 2.5 mass fractions of the measured and the fitting values >> 5%, which is not acceptable. All RDs in PM 2.5 mass fractions of the measured and the fitting values >> 5%, which is not acceptable.

Acknowledgement The USDA NRI Grant No The USDA NRI Grant No Help from Qianfeng Li & Zifei Liu for field sampling Help from Qianfeng Li & Zifei Liu for field sampling Support from the egg production farm Support from the egg production farm