Continuous Ambient Particulate Monitors A Review of Current Technologies by Michael Corvese, Product Manager Thermo Electron Corporation Air Quality Instruments

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

3 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) Aerosol Characteristics

4 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 SIZE, SHAPE, and REFRACTIVE INDEX Physical Characteristics Size: Shape: Refractive Index: µm aerosol research; µm common sampling (  m) Many irregular shapes; aerodynamic diameter emphasized Wide range; most consistent below 2.5  m

6 Physical Characteristics Human Hair (60  m diameter) PM 10 (10  m) PM 2.5 (2.5  m) Hair cross section (60  m)

7 Chemical Characteristics

8 Health Effects u Health effects are significant u Body of evidence is substantial

9 Health Effects Aggravated asthma Chronic bronchitis Increase in respiratory symptoms Decreased lung function Premature death Increased hospital admissions and emergency room visits during high PM conditions

10 Health Effects

11 Regulatory Background 1971—Promulgation of National Ambient Air Quality Standards (NAAQS) for SO 2, NO 2, O 3, CO, and total suspended particulates (TSP) 1978—Promulgation of particulate Pb standard 1987—Promulgation of PM 10 standard 1997—Promulgation of revised PM 10 standard and introduction of PM 2.5 standard (also a revision of the O 3 standard)

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

13 Common Gravimetric Ambient Aerosol Sampling Techniques (Gross - Tare) / Air Volume =  g/m 3 High volume methods: TSP, PM 10, PM 2.5, Air Toxics Sampler (PUF) Low volume methods: (PM 10, PM 2.5, PM Coarse ) Sampling and Analysis

14 Sampling and Analysis High Volume Methods: TSP and PM 10 Samplers

15 Sampling and Analysis Low Volume Methods PM 10 /PM 2.5 FRM & PM c /PM 2.5 Dichotomous Sampler

16 Common Gravimetric Ambient Aerosol Sampling Techniques (Gross - Tare) / Air Volume =  g/m 3 Advantages: Recognized reference method, low capital cost Disadvantages: Limited time resolution (typically 24-hr), long turnaround times, labor intensive, and gravimetric lab maintenance/cost Sampling and Analysis

17 Common Continuous Ambient Aerosol Sampling Techniques (  m /  t) / (  V /  t) =  g/m 3 Light Scattering, Absorption, and Extinction Tapered Element Oscillating Microbalance Beta (Electron) Attenuation Hybrid Methods Sampling and Analysis

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

19 Common Continuous Ambient Aerosol Sampling Techniques (  m /  t) / (  V /  t) =  g/m 3 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) Sampling and Analysis

20 Sampling and Analysis

21 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 Sampling and Analysis

22 Sampling and Analysis

23 Sampling and Analysis 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 Other Technologies Oscillation Frequency Measurement

24 Heating Considerations Actual and mean VOC loss (l and l m ) due to heated sample area at 50°C -100% -80% -60% -40% -20% 0% t in days VOC(NH 4 NO 3 ) loss l and l m l l m Fixed heating w/auto filter changes is an improvement over long term heating on spot. is an improvement over long term heating on fixed spot. Series FH 62 C14 Features and Benefits

25  Attenuation Principle 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 Monitor Principle 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 Direct  Attenuation Ambient inlet Sensing volume  Source & detector Disadvantage No known manufacturers Poor detection limit Requires very high concentrations Advantage Truly continuous Non-intrusive  Attenuation Technology Sampling and Analysis

28 Stepwise  Attenuation Ambient Inlet Sensing Volume  Source & detector Filter tape Disadvantage Semi-continuous Advantage Semi-continuous Sound technology Good hourly precision Sampling and Analysis  Attenuation Technology

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

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

31  Attenuation Principle of Operation

32 Refined Mass Measurement via Dual Detector  Attenuation

33  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 PM 2.5

34 Ambient Continuous Particulate Monitors Applications NAAQS Monitoring AQ Index Reporting Fenceline Monitoring Clean-up Sites In R&D … Unrivaled short-term detection limits/time resolution

35 Continuous Particulate Monitors Applications

36 Regulatory Developments 1997—promulgation of PM 2.5 and revision of PM —PM 2.5 standard challenged in court 1999—US Court of Appeals remanded PM 2.5 standard back to EPA for revision 2001—US Supreme Court decision - EPA has the right to promulgate a PM 2.5 standard - Compliance costs should not be considered - PM Coarse should replace PM Proposed revision of PM 2.5 expected 2006-Final PM 2.5 and proposed PM Coarse regulation expected

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