Continuous Ambient Particulate Monitors A Review of Current Technologies

1. Continuous Ambient Particulate MonitorsA Review of Current Technologies by Michael Corvese, Product Manager Thermo Electron Corporation Air Quality Instruments

2. Aerosol Monitoring • Aerosol Characteristics • Health effects • Regulatory Background • Sampling & Analysis • Regulatory Developments

3. 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)

4. 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

5. 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

6. Physical Characteristics PM10 (10 mm) PM2.5 (2.5 mm) Hair cross section (60 mm) Human Hair (60 mm diameter)

7. Chemical Characteristics

8. Health Effects • Health effects are significant • Body of evidence is substantial

9. 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

10. Health Effects

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

12. Regulatory Background U.S. National Ambient Air Quality Standards (NAAQS)

13. Sampling and Analysis • High volume methods: TSP, PM10, PM2.5, Air Toxics Sampler (PUF) • Low volume methods: (PM10, PM2.5, PMCoarse) Common Gravimetric Ambient Aerosol Sampling Techniques (Gross - Tare) / Air Volume = mg/m3

14. Sampling and Analysis High Volume Methods: TSP and PM10 Samplers

15. Sampling and Analysis Low Volume Methods PM10/PM2.5 FRM & PMc/PM2.5 Dichotomous Sampler

16. 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

17. 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

18. Sampling and Analysis Impaction Separation Cyclone Separation Cut Point 100% Eficiency 50% 0% PM100 PM1.0 PM10

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

20. Sampling and Analysis

21. 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

22. Sampling and Analysis

23. Advantages Continuous method Highly time resolved High resolution Disadvantages Temperature dependency Affected by vibration Manual filter changes necessary Seasonal and regional dependencies Complex systems require some skill Volatile losses Sampling and Analysis Other Technologies Oscillation Frequency Measurement

24. Series FH 62 C14Features and Benefits Mean NH NO -Loss l due to heated suction tube 4 3 m 10% 0% -10% m l -20% -30% t t = * exp(E / k T) 0 B t t l = /t * (1 - exp(-t/ )) - 1 -40% m -50% 10 20 30 40 50 60 70 80 J in °C Fixed heating w/auto filter changes is an improvement over long term heating on fixed spot. Heating Considerations Actual and mean VOC loss (l and l ) due to m heated sample area at 50°C 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

25. 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.

26. 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

27. Sampling and Analysis b Attenuation Technology • Ambient inlet • Sensing volume • b Source & detector Direct b Attenuation • Advantage • Truly continuous • Non-intrusive • Disadvantage • No known manufacturers • Poor detection limit • Requires very high concentrations

28. Sampling and Analysis b Attenuation Technology • Ambient Inlet • Sensing Volume • β Source & detector • Filter tape Stepwise b Attenuation • Advantage • Semi-continuous • Sound technology • Good hourly precision • Disadvantage • Semi-continuous

29. Sampling and Analysis b Attenuation Technology • Ambient inlet • Sensing volume • b Source & detector • Filter tape Continuous β-Attenuation • Advantage • Continuous • Sound technology • Significant loading for post-collection analysis • Disadvantage • Potential extended sample loss

30. Sampling and Analysis Hybrid Technology • Ambient inlet • Sensing volume • b Source, detector, nephelometer • Filter tape Continuous SHARP Monitor • Advantage • Truly continuous • Low detection limits • High time resolution • Intelligent moisture control • Disadvantage • None

31. b Attenuation Principle of Operation

32. b Attenuation Refined Mass Measurement via Dual Detector

33. 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

34. Continuous Particulate MonitorsApplications • NAAQS Monitoring • AQ Index Reporting • Fenceline Monitoring • Clean-up Sites Ambient In R&D … • Unrivaled short-term detection limits/timeresolution

35. Continuous Particulate MonitorsApplications

36. Regulatory Developments • 1997—promulgation of PM2.5 and revision of PM10 • 1998—PM2.5 standard challenged in court • 1999—US Court of Appeals remanded PM2.5 standard back to EPA for revision • 2001—US 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

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