Analytical Methods For Diesel Particulate Matter(DPM)

Transcription

1 Analytical Methods For Diesel Particulate Matter(DPM) Igor Levin OHAO - Fall Symposium October 24 th 2013 Toronto, Ontario

2 Acknowledgements Occupational Hygiene Association of Ontario. CANMET, Sudbury Laboratory. Sunset Laboratory Inc. National Research Council of Canada. Concord Analytical coworkers.

3 Analytical Services since 1997 Respirable Quartz on Ag membrane filters by XRD (Equivalent to NIOSH 7500). Metals by ICP (NIOSH 7300). Diesel Particulate Matter (NIOSH 5040). Accredited by Canadian Association for Laboratory Accreditation (CALA) to ISO for specific tests including NIOSH 5040.

4 Diesel Particulate Matter (DPM) is a complex aggregate of solid and liquid material. Its origin is carbonaceous particles generated in the engine cylinder during combustion. The primary carbon particles form larger agglomerates and combine with several other, both organic and inorganic, components of diesel exhaust. Generally, DPM is divided into three basic fractions.

5 DPM Solids Dry carbon particles, commonly known as soot. SOF Heavy hydrocarbons adsorbed and condensed on the carbon particles, called Soluble Organic Fraction. SO 4 Sulfate fraction, hydrated sulfuric acid. The actual composition of DPM will depend on the particular engine and its load and speed conditions. Wet particulates can contain up to 60% of the hydrocarbon fraction (SOF), while dry particulates are comprised mostly of dry carbon.

6

7 Available DPM Analytical Methods Respirable Combustible Dust (RCD) Gravimetric Thermal-Optical Carbon Analysis (NIOSH 5040)

8 Respirable Combustible Dust (RCD) Analysis Sampling: Filter media: 25mm, 0.8 micron Silver Membrane filter. Flow Rate: 1.7 L/min Cyclone

9 Respirable Combustible Dust (RCD) Analysis Sampled filter is weighed and dust weight is determined. Filter is transferred to a metal tray. Tray is placed in muffle furnace at 400 ₀ C for minimum 90 minutes. The ashing temperature and the catalytic action of the silver membrane filter combine to make the carbon-based dust react with Oxygen. The mass loss on ashing is considered to be the mass of RCD. Limit of Detection: 0.05 mg

10 Respirable Combustible Dust (RCD) Analysis Advantages Disadvantages Simple Economical Resp. Quartz and RCD can be done on the same filter. Non Selective Inadequate for compliance monitoring at lower limits of exposure. Carbon based mineral dust interference. Sulfide minerals dusts interference. Problems with DPM overloaded filters.

11 Thermal-Optical Carbon Analysis (NIOSH 5040) Principle of Analysis: Two-phase heating of sample with measurement of combustion gases. Low Limit of Detection: OC = mg EC = mg Equipment: Lab OC-EC Aerosol Analyzer by Sunset Laboratory Inc.

12 Description Tissuquartz Filters Filter Media Pure Quartz, no binder Typical Thickness 432 μm Typical Filter Weight 508 mg/cm 2 Typical Water Flow Rate 0.35 bar (35kPa, 5 psi) 220 ml/min/cm 2 Typical Air Flow Rate 0.7 bar ( 70 kpa, 10 psi) 73 ml/min/cm 2 Maximum Operating Temperature - Air 1093 ₀ C (2000 ₀ F) Typical Aerosol Retention ** % PH in Boiled water Extract ** Following ASTM D A 0.3μm (DOP) at 32 L/min/100cm 2 filter media. Filter media for DPM sampling

13 Support pad choices (as per NIOSH 5040) Pre-fired quartz fiber filter, 37 mm, in a standard three piece holder. Cellulose: High OC blanks Stainless steel screen: Expensive, Potential OC contamination during cleaning. Pre-fired 37mm quartz fiber filter: Low OC blanks, mg.

14 Diesel Particulate Matter Cassette with Precision-jeweled Impactor. Screens out respirable particles > 1.0 µm. Particles less than 1.0 µm are collected on the filter. Filter diameter: 37mm Sampled area diameter : 32 mm Sampled area: 8.04 cm 2

15 Collection of submicron particulates only eliminates mineral dusts interference Source:

16 Single punch : 1.5 cm 2 Filter diameter: 37 mm Sampled area diameter : 33mm Sampled area: 8.55 cm 2 2 nd Punch

17 Filters are arranged in order of an increasing concentration of Elemental Carbon (EC) < 0.002mg mg

18 Schematic of thermal-optical instrument (V= valve) for determination of OC and EC in diesel particulate exhaust and other carbonaceous aerosols.

19 Instrument Calibration 10 μl of 1% or 0.5% of Sucrose (sugar) solution is deposited on a pre-fired 1.5 cm 2 quartz fiber punch and dried for 10 minutes under a heating lamp.

20

21

22

23 NIOSH 5040 Protocol Mode Temperature ( ₀ C) Time (s) He He He He He / O He / O He / O He / O He / O He / O Total Time = 615

24 Thermogram of Sucrose Standard μg OC He 2% O 2 / He

25 Calculated Results For Sucrose Standard μg OC

26 OC/ EC Split Point for Sucrose Standard μg OC OC/EC Split Point He 2 % O 2 / He

27 Thermogram Of The Sample Containing Organic, Elemental & Carbonate Carbon He 2% O 2 / He

28 Calculated Results for a sample Containing Organic, Elemental & Carbonate Carbon

29 Standard Operating Procedure Wipe all the tools and Aluminum foil pad with Acetone. Turn on the instrument computer. Initiate Instrument software. Set Gas flows Light FID detector and wait 10 minutes. Load Five blank 1.5cm 2 punches into the oven. Run Clean program.

30 Clean program

31 Standard Operating Procedure Place four pre-fired punches on the standards tray Aluminum pad. Pipette two 10 μl aliquots of each 1% and 0.5% of Sucrose solutions (42.10 μg and μg of OC respectively). Dry punches under a heating lamp for 10 minutes.

32 Standard Operating Procedure Analyze blank punch using NIOSH 5040 protocol. Analyze μg Spike Analyze samples

33 Quality Control Daily QC checks Analyze cleaned blank punch. Run alternatively 10μL of 0.5% and 1% Sucrose QC spikes every 8-10 samples. Replicate Samples One replicate sample is analyzed for every 10 samples Linearity Check Every six months Spikes of 10μL of 2%, 1%, 0.5% and 0.25% Sucrose are tested. Dextrose QC spike New Sucrose reagent is tested with Dextrose solution to verify the integrity of the reagent. Annually Round Robin 47 mm filter is analyzed by CASL, CANMET & Sunset Laboratory.

34 Uncertainty Parameter associated with the result of a measurement, that characterises the dispersion of the values that could reasonably be attributed to the measurant (OC/EC /TC). The uncertainties given by the instrument software provided by the manufacturer are: 0.2 μg /cm 2 ± 5% for OC/EC and 0.3 μg /cm 2 ± 5% for TC. About 400 pairs of data that had been taken over an extensive period of time were analyzed by the method, kindly supplied by Dr. Paski to CANMET laboratory. The data were divided into ranges, as shown in the table on the following slide.

35 Uncertainty summary for 400 pairs of Analyzed filters Range (μg/ cm 2 ) Range (mg) Organic Carbon (OC) U-rel. % Elemental Carbon (EC) U-rel. % U- rel. at 95% confidence levels. Total Carbon (TC) U-rel. % 0.6 to to to to to to >50 > Filter diameter: 37 mm Sampled area diameter : 33mm Sampled area: 8.55 cm 2

36 Issues Unknown filter media Wet filters Loose dust material Low instrument load DPM Overloaded filters Laser Radiation is almost fully absorbed by the EC. Split point can not be determined accurately if the concentration of EC is greater than μg/cm 2 (equivalent to mg of EC on a 37 mm filter).

37 NRC System for the absolute calibration of black carbon mass concentration measurement instruments The SAE E-31 Aircraft Exhaust Emissions Measurement Committee has specified an instrument calibration methodology and schedule whereby NIOSH 5040 EC measurements are used to calibrate BC mass concentration instruments. NIOSH 5040 analysis performed by Concord Analytical Services.

38 CALIBRATION STABILITY/REPEATIBILITY One LII 300 instrument was calibrated by Missouri University of Science and Technology against NIOSH 5040 EC during a previous measurement campaign. The calibration results are shown below. Excellent agreement with calibrations performed by a different team and using a different NIOSH 5040 analysis provider No observable drift in the calibration over the one year period between the first and last calibration.

39 A-PRIDE 4 Pre-Test Correction Factor: A-PRIDE 4 Post-Test Correction Factor: 0.798

40 8540 Keele Street, Unit 38 Concord, Ontario L4K 2N2 Canada Tel: Fax: