Rationale for Development of Mobile Monitoring Technologies for Paved Roads

Transcription

1 Rationale for Development of Mobile Monitoring Technologies for Paved Roads Workshop on Standardization of Open Source Test Methods November 17, 2010 Rodney Langston Clark County, Nevada 1

2 Open Sources The Forgotten Emissions Sources No open source emissions standards Therefore, no mandate for open source standardized test methods Open sources not critical for NAAQS attainment in many areas So are open sources really that important? 2

3 Why Open Sources Matter Las Vegas Valley 2006 Controlled PM 10 Emissions 6% Vacant Land 21% 29% 44% Road Dust Construction Other Sources 3

4 Clark County Road Dust Inventory PM 10 SIP paved roads emissions inventory developed in 1999 Used 24 sampling sites to determine AP 42 silt loadings Freeways & Expressways 108 miles Arterial Roads (major & minor) 408 miles Collector Roads 280 miles Local Roads 3,100 miles Total Road Network Miles 3,896 miles (2008) 4

5 Road Dust Inventory (cont.) Public works agencies very critical, argued 24 spot samples were not statically representative of the Clark County road network Public Works engineers: this is not science Dept. of Air Quality staff: best available information EPA approved method Criticism lead to consideration of better methods to estimate road dust emissions 5

6 Paved Road Dust Inventory (cont.) From : Clark County sampled silt loadings each quarter Inventory based on 240 silt samples Clark County s road dust inventory better than others, but still not good enough Ambient PM 10 concentrations declined significantly beginning mid-2003 Enhanced track-on controls and enforcement began in early

7 Traditional AP-42 Method Issues Spot samples not representative of road network Too few samples Can t randomly select sampling sites Selection of each spot sampling site requires site selection judgments and introduces bias 7

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10 AP-42 Method Issues (cont.) Can t sample highest ADT roads Can t sample freeways Major arterial roads (not permitted or only at night) Can t adequately address speed issues Reference profile measurement data characterization of speed not robust Would require complex modeling to implement Method expensive and dangerous 10

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12 Mobile Sampling System Basics Use ambient (front or roof) and source (rear) sampling inlets Use GPS system for location coordinate and data time stamp Use isokinetic speed independent sampling systems On-board computer used for data recording and computing deferential emissions flux values 12

13 Paved Road Studies Phase I Phase I feasibility study completed in 2004 Utilized TRAKER (DRI) and SCAMPER (UCR CE-CERT) mobile measurement systems Sampled valley-wide worst case and best case areas to evaluate equipment Study sampled valley wide urban area Insufficient pre-study sampling route mapping No reference sampling (AP-42 or profile) 13

14 Paved Road Studies Phase II Phase II study occurred in February of 2005 Sampling route modified to better reflect overall valley conditions Sampling route mapped by road class, road infrastructure, etc. Study occurred over a 4-day period Other agencies invited to observe 14

15 Paved Road Studies Phase II (cont.) Study contractors and equipment: DRI TRAKER system (Testing Re-entrained Aerosol Kinetic Emissions from Roads) UCR CE-CERT SCAMPER system (System of Continuous Aerosol Monitoring of Particulate Emissions from Roadways) UNLV (AP-42 reference sampling) Where TRAKER measured high, scamper measured high 15

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19 Paved Road Studies Phase III Phase III study occurred November of 2005 Study designed around SCAMPER system and AP-42 road silt samples Study focused on road infrastructure development and deposition sources for local, collector and arterial streets Three sampling routes: Developed community Transitional area Industrial area 19

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21 Paved Road Studies Phase III (cont.) Utilized video recording system on SCAMPER Data variability less than in previous studies SCAMPER measurements spatially consistent with AP-42 estimates, but only 1/3 of the values Report provided emissions factors for various silt deposition sources and road infrastructure by road classification 21

22 Paved Road Studies Phase III (cont.) Too little spacing between deposition sources Road dust never reached equilibrium between sources True extent of individual source impacts unclear Region 9 requested additional uncertainty analysis and documentation 22

23 Paved Road Studies Phase III (cont.) Using AP-42 as a reference test method to demonstrate low levels of uncertainty seemed futile Can t sample with mobile systems when lane blocked for silt sampling AP-42 is an arithmetic approximation, not a precise reference measurement method AP-42 a destructive method, silt removed from road 23

24 Paved Road Studies Phase IV Planned as an empirical study to validate vehicle mounted mobile sampling systems Phase IV study components All measurements made under controlled conditions Used both SCAMPER and TRAKER systems AP-42 sampling Source profile sampling Deposition of known quantities of road silt Controlled vehicle passes (sampling vehicles only) 24

25 Phase IV Study Objectives Determine and quantify the relationships among emissions measured using: Vehicle mounted mobile measurement systems PM 10 horizontal flux tower techniques AP-42 silt loading methods Evaluate the reduction of paved road dust emissions over time in the absence of replenishing sources 25

26 Study Site Roadway Selection Perpendicular prevailing wind direction No obstructions in close proximity No significantly elevated topography in close proximity Four-lane road divided by a median Light traffic so that can block two lanes on one side No elevated background PM 10 sources Uninterrupted distance at least ¾ mile (1.2 km) 26

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28 Study Site Layout Southeast to Northwest orientation Acceleration zone 543 feet Staging area 250 feet Constant speed zone 3188 feet AP42 south sampling zone feet Straightaway AP42 north sampling zone feet Deceleration zone 500 feet Total length 4481 feet 28

29 Staging Area Beginning of Course 29

30 Acceleration Zone 30

31 South AP42 Sampling Zone 31

32 Constant Speed Straightaway 32

33 North AP42 Sampling and Deceleration Zone November

34 Soil Selection Criteria 50 th percentile silt content from AP42 monitoring of collector roads 13% from 15 samples Accessible for excavation Sufficient material for excavation Selected Sunset Park site, sandy soil, in Wind Erodibility Group 2 14% average silt content from 6 of 50 buckets 34

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37 Source Profile Measurements 37

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39 The Study Early November

40 Silt Application and AP-42 Sampling 40

41 Silt Sampling by UNLV Grad Students 41

42 The Sampling Towers 42

43 Sampling Run with TRAKER I 43

44 Sampling Run with TRAKER II 44

45 SCAMPER System 45

46 Cleaning Sampling Area After Sampling Series 46

47 Weighing Silt 47

48 How Do We Proceed From Here? Imperative that we move beyond use of decade old silt samples Vehicle mounted mobile sampling systems are clearly the preferred method for measuring road dust Major research milestones met Need to standarize a test method and develop calibration libraries for different systems? 48

49 Discussion 49