Overview of Characterization Methods for Submicron

Overview of Characterization Methods for Submicron Particulate Matter (PM)

John Kinsey, Richard ShoresU. S. Environmental Protection AgencyOffice of Research and Development

National Risk Management Research LaboratoryAir Pollution Prevention and Control Division

October 30, 2002

General Characteristics of Submicron Particles Inertial properties are low—diffusion and

phoretic effects predominate Isokinetic sampling is generally not critical Particles are of anthropogenic origin—little

submicron PM is generated by natural processes such as wind-blown dust

Combustion (internal and external) sources are most important—condensation and nucleation are primary particle forming mechanisms

(Continued)

Characteristics (continued) Particle size distribution tends to be both

lognormal and bimodal (nuclei and accumulation modes)

Characterization of submicron PM is far more difficult than for supermicron PM requiring sophisticated methods and equipment

Particle number concentration could be more important than mass concentration in health effects studies

On-Line Mass Measurement Techniques

Tapered-element oscillating microbalance (TEOM)

Quartz-crystal microbalance (QCM) Beta-attenuation mass monitors Mass transfer of volatiles—on/off

collected sample is important in PM mass measurements

On-Line Techniques for Number Concentration

Aerosol photometers Condensation nuclei counters (CNCs) In-situ single-particle optical counters

and ensemble analysis techniques Extractive instruments generally

limited to low particle concentrations—usually requires diluted sample stream

Techniques for Particle Size Distribution Measurement Electrical, quartz-crystal, and manual

low-pressure cascade impactors (~ 30 nm to 10 m aerodynamic diameter)

Laser velocimeters (> 0.5 m aerodynamic diameter)

Scanning mobility particle sizer (differential mobility analyzer + CNC; 2 to ~ 500 nm electrical mobility diameter)

(Continued)

Particle Size Distribution (continued) Serial- and parallel-flow diffusion

batteries (with and without CNCs) Single-particle optical counters Data reduction and interpretation for

most particle sizing instruments require considerable expertise especially when comparing data from different instruments

Manual Sample Collection/Analysis Techniques Filter sampling (e.g., prefired quartz

filters for elemental/organic carbon) Electrostatic and thermal precipitators Scanning electron microscopy (with and

without X-ray analysis for elemental composition)

Electron microscopy can provide physical verification of other measurement techniques within certain limitations

On-Line Chemical Characterization Methods Photoelectric ionization sensors for

polycyclic aromatic hydrocarbons Optical attenuation instruments for

“black” and “blue” carbon Automated thermal/CO2 analyzers for

elemental/organic carbon On-line analyzers can provide near real-

time results but must be validated against manual method for each source

Chemical Characterization of Collected Samples Elemental/organic carbon by NIOSH Method

5040 Elemental composition by X-ray diffraction or

X-ray fluorescence Water-soluble ions (e.g., SO3

-) by ion chromatography

Organic speciation by gas chromatography/mass spectroscopy

Sample analyses are generally expensive and time consuming

Calibration Issues Most analyzers for submicron PM are

essentially “black boxes” requiring substantial operator experience

Calibration standards for nanoparticles are limited at best

Dynamic instrument calibration is both expensive and difficult to implement

Conversions between various particle conventions (e.g., aerodynamic diameter to electrical mobility diameter) require numerous assumptions and associated potential errors

Sources Recently Tested by APPCD

Heavy-duty diesel engines Residential wood stoves and

fireplaces Biomass burning Wood- and wood-waste-fired

boilers

Contact Information

John Kinsey, Richard ShoresU. S. Environmental Protection Agency (MD E343-02)National Risk Management Research LaboratoryAir Pollution Prevention and Control Division Research Triangle Park, NC 27711(919) 541-4121, (919) [email protected], [email protected]

DD 60 on Engine Dynamometer

Secondary Tunnel and Instruments

Comparison of Paired Filter Samples

y = 0.9437xR2 = 0.9862

y = 0.9695xR2 = 0.9978

y = 0.9679xR2 = 0.9541

0.00

0.05

0.10

0.15

0.00 0.05 0.10 0.15

Filter No. 1 Concentration (mg/m3)

Filte

r No.

2 C

once

ntra

tion

(mg/

m3 )

FTP FiltersQuartz Filter ECQuartz Filter OCLinear (Quartz Filter OC)Linear (Quartz Filter EC)Linear (FTP Filters)

gValues for TEOM, DustTrak, and Filter

Samplers

y = 1.3437xR2 = 0.8424

y = 0.8984x + 0.0168R2 = 0.9345

0.00

0.05

0.10

0.15

0.20

0.00 0.05 0.10 0.15 0.20

FTP Filter Mass Concentration (mg/m3)

Inst

rum

ent M

ass

Conc

entra

tion

(mg/

m3 ) TEOM

DustTrak-No IdleDustTrak-Idle OnlyLinear (TEOM)Linear (DustTrak-No Idle)

Time for Steady-State and Cyclic Operation

-0.4

-0.2

0.0

0.2

0.4

0.6

0:00 1:00 2:00 3:00 4:00 5:00Run Time (h:mm)

Mas

s co

ncen

trat

ion

(mg/

m3 )

10-Sec Avg30-Sec Avg60-Sec Avg

-0.4

-0.2

0.0

0.2

0.4

0.6

0:00 1:00 2:00 3:00 4:00 5:00 6:00Run Time (h:mm)

Mas

s co

ncen

trat

ion

(mg/

m3 )

10-Sec Avg30-Sec Avg60-Sec Avg

FTP Cycles (Test 7)200 HP; Steady-State (Test 4)

Particle Number Concentration as Measured by Different On-Line Instruments

0.0E+00

5.0E+05

1.0E+06

1.5E+06

2.0E+06

2.5E+06

3.0E+06

1 2 3 4 5 6 7

Test Number

Num

ber c

once

ntra

tion

(par

ticle

s/cm

3 )

ELPI #CELPI #DSMPS 3934SMPS 3936CPC

Quartz Filters vs. Aethalometer Measurements

y = 0.3226x + 3.2856R2 = 0.7515

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Quartz Filter Value (μg/m3)

Aeth

alom

eter

Val

ue (μ

g/m

3 )

Elemental vs. Black C

Organic vs. Blue C--No Idle

Organic vs. Blue C--Idle Only

Linear (Elemental vs. Black C)

“Elemental/organic” carbon from manual NIOSH method“Black/blue” carbon from Aethalometer BC/UV channel

ELPI Mass Distribution Comparison: 200 HP"C" ELPI: June 19, 2001

0.0000.0100.0200.0300.0400.0500.0600.070

1 2 3 4 5 6 7 8 9 10 11 1213

Stage Number

Mas

s Co

llect

ed (m

g)

"D" ELPI: June 19, 2001

0.000

0.0100.020

0.030

0.040

0.0500.060

0.070

1 2 3 4 5 6 7 8 9 10 11 12 13

Stage Number

Mas

s C

olle

cted

(mg)

Stage 1 ~ 30 nmStage 13 ~ 10 m




"C" ELPI: June 20, 2001

0.000

0.010

0.020

0.030

0.040

1 2 3 4 5 6 7 8 9 10 11 12 13

Stage Number

Mas

s Co

llect

ed (m

g)

"D" ELPI: June 20, 2001

0.000

0.010

0.020

0.030

0.040

1 2 3 4 5 6 7 8 9 10 11 12 13

Stage Number

Mas

s C

olle

cted

(mg)



Example ELPI and SMPS Size Distributions

0.0E+00

2.0E+05

4.0E+05

6.0E+05

8.0E+05

10 100 1000Aerodynamic Diameter (nm)

dC/d

logD

p (p

artic

les/

cm3 )

ELPI #C

ELPI #D

SMPS 3934

SMPS 3936

200 HP; Steady-State (Test 4)

0.0E+00

2.0E+06

4.0E+06

6.0E+06

8.0E+06

10 100 1000Aerodynamic Diameter (nm)

dC/d

logD

p (p

artic

les/

cm3 )

ELPI #C

ELPI #D

SMPS 3934

SMPS 3936

Fast Idle (Test 6)

Example ELPI and APS Particle Size Distributions (0.7 to 5 μm Aerodynamic

Diameter)

Particle Size Distributions Measured by ELPI and APS for 70 to 500 nm Size Range (Test #3)

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

100 1000 10000

Aerodynamic Diameter (nm)

dC/d

logD

p (p

artic

les/

cm3 )

ELPI #C

ELPI #D

APS

200 HP; Steady-State (Test 3)

Particle Size Distributions Measured by ELPI and APS for 70 to 500 nm Size Range (Test #5)

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

100 1000 10000

Aerodynamic Diameter (nm)

dC/d

logD

p (p

artic

les/

cm3 )

ELPI #C

ELPI #D

APS

Fast Idle (Test 5)

Current Findings (1) Good precision was achieved during the analysis of

filter catches for split samples. Comparison of manual vs. automated methods

showed mixed results--some instruments (e.g., TEOM) correlated reasonably well, whereas others (e.g., DustTrak) were highly dependent on engine operating conditions.

Certain types of paired analyzers (e.g., SMPS) exhibited different response characteristics and/or produced substantially different results.

The 1105a TEOM provided a highly variable data output with many negative values—data are generally not useful for averaging times less than one minute.

Current Findings (2) Chemical analysis of the ELPI samples were not

conducted due to: • low sample weights;• inconsistencies in the gravimetric results between the two

instruments; and• Problems with lost samples due to poor collection substrate

preparation.

Both PAH analyzers were found to be malfunctioning after being returned to the manufacturer for post-test calibration.

Easy, inexpensive, and field-capable calibration methods/equipment are needed for all analyzer types to assure high quality data collection.

Second round of testing scheduled for November 2002 at WVU

Documents

Overview of Characterization Methods for Submicron