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OVERVIEW OF METHODS

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OVERVIEW OF METHODS. ESTIMATING ROADWAY EMISSIONS Rodney Langston February 24, 2004. EPA Approved Method for Estimating Entrained/Re-entrained Road Dust. AP- 42 Emission Equation – Revision Published Nov. 2003 Applicable to Paved and Unpaved Roads

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OVERVIEW OF METHODS
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  1. OVERVIEW OF METHODS ESTIMATING ROADWAY EMISSIONS Rodney Langston February 24, 2004

  2. EPA Approved Method for Estimating Entrained/Re-entrained Road Dust • AP- 42 Emission Equation – Revision Published Nov. 2003 • Applicable to Paved and Unpaved Roads • Developed from Regression Analysis Utilizing 65 Samples

  3. AP-42 Emission Equation E = k(sL/2)0.65 (W/3)1.5 - C where: E = PM Emission Factor Having Units Matching Units of k k = A constant dependent on particle Size and Emission Units sL = Road surface silt loading of material smaller than 75µm in g/m2 W = Mean Fleet Vehicle Weight in Tons C = Emission Factor for 1980’s Vehicle Fleet Exhaust, Break Wear, and Tire Wear

  4. AP-42 Equation Issues • No Mechanistic Basis – A Purely Statistical Model • Formulation Wholly Dependent on the Data Set Derived From

  5. AP-42 Equation Issues (Continued) • Speed Not Accounted For • AP- 42 Equation Assumes 10-55 mph • Speed Is A Huge Factor in Emission Rate • Silt Loading Measurements Required • Must Be Collected Manually • Requires Lane Closures • Process Costly – Limited Sampling Feasible

  6. AP-42 Equation Issues (Continued) • AP- 42 Equation Assumes A Stable Reservoir of Silt Loading • This Is A Physical Impossibility • Many Sources Contribute to Deposition Independent of Vehicle Entrainment • Emissions Estimates Increase In Direct Proportion to VMT • Makes Demonstrating Transportation Conformity or PM Attainment Very Problematic

  7. Alternative Approach to AP-42 • Vehicle Mounted Assessment Systems – Mounts Samplers on Vehicle • Systems Have Been Developed by Desert Research Institute and University of California, Riverside

  8. Desert Research Institute “TRACKER”

  9. Top View Top View Background Monitor Front Front Influence Monitor Background Monitor Side View Side View Front Front Influence Monitor Testing Re-entrained Aerosol Kinetic Emissions from Roads (TRAKER)

  10. Sampling Plenum: Can Support Up To Five Sampling Instruments

  11. TRACKER Instrumentation • Particle Sensors • TSI DustTrack • Grimm Particle Size Analyzer • GPS • Ashtech/Magellan Promark X • Isokinetic System – Speed Independent

  12. Data Acquisition and Processing • Lab View program displays and logs data from 6 DustTraks, 3 Grimms, and 1 GPS • Uniform time stamp applied to all data for consistent synchronization • Data tables are loaded into MS Access for processing

  13. Street Survey Data Logging

  14. University of California, Riverside CE-CERT On-Board Particle Sensor System

  15. CE-CERT Mobile Sensor System

  16. Features of the CE-CERT System • Samples Emissions Behind Tow Vehicle • Adjustable Hitch – 1.4 m to 4.9 m • Isokinetic Sampler Probes May Be Adjusted to Different Positions on Trailer

  17. Vehicle Configuration

  18. Schematic Diagram Isokinetic Sampling Probe

  19. Emission Measurements Comparison • DRI System Tested Extensively on Unpaved Roads in Idaho • More Calibration Work Needed for Paved Roads • Prototype System – Measured Higher Emissions Than Predicted by AP-42 Equation and Manual Silt Measurements on Paved Roads in Las Vegas

  20. Emission Measurements Comparison (continued) • CE-CERT System Tested on Paved Roads • Calibrated Emissions Measurements in General Agreement With, But on the Low Side, of Previously Reported Emissions Measurements • Measured Emissions Lower than AP-42 Methodology and California Silt Loadings

  21. Advantages of Vehicle Mounted Assessment Systems • Reduces Cost – Allows Expanded Sampling of Road Network • Allows More Representative Sample Set – Eliminates Sampling Bias • Does Not Require Lane Closures for Manual Silt Collection

  22. Vehicle Mounted Assessment Systems (continued) • Effective Tool for Evaluating Control Measure Effectiveness • Street Sweeping • Track Out Control • Road Improvements

  23. Clark County DAQM & RTC Evaluation-Vehicle Mounted Systems • Planning A Competitive “Drive Off” Evaluation of Available Systems • Consultants will Operate Systems Over Fixed Course & Controlled Conditions • RTC Consultant will Evaluate Data & Seek U.S. EPA Approval of Selected System as an Alternative to AP- 42

  24. DISCUSSION