midwest research institute€¦ · agricultural soil 1.06 21.6 2 nmr new mexico las cruces landfill...
TRANSCRIPT
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Midwest Research InstituteSolutions through science
and technology
Proposed Revisions to Fine Fraction Ratios Used for AP-42 Fugitive Dust
Emission Factors
Chatten CowherdMidwest Research Institute
Duane OnoGreat Basin UAPCD
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Fugitive Dust Emissions
• Highly fluctuating plume impacts at emission measurement site
• PM concentrations vary from background to plume core values
• Emissions depend on energy inputs and properties of emitting surface material
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Road Dust Plume ConcentrationsDustTRAK 1.6(m) CS-X5
0
5
10
15
20
25
30
35
9:27
:22
9:28
:48
9:30
:14
9:31
:41
9:33
:07
9:34
:34
9:36
:00
9:37
:26
9:38
:53
9:40
:19
9:41
:46
9:43
:12
9:44
:38
9:46
:05
Time
Con
cent
ratio
n (m
g/m
3)
DustTRAK 1.6(m) CS-X5
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AP-42 Emission Factors• Predictive equations with particle size
multipliers
• Historically, particle size multipliers based on data from high-volume cyclone/cascade impactors
• Potential for particle size bias in overpredicting fine fractions
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Discrepancy in Fine Fraction Data
• Emission data from the high-volume cyclone/impactor system have provided the basis for a PM2.5/PM10 of ~0.20 for many fugitive dust sources in EPA’s AP-42
• Ambient air monitoring data suggest that PM2.5/PM10 may be less than 0.10
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MRI Cyclone/CascadeImpactor System
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Plume Characterization Options
• Field studies produce highly variable results because of wind variations
• Laboratory exposure chambers can produce nearly steady-state conditions
• Confounding factors can be reduced in controlled laboratory flow settings
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EPA Field Study in 1990s
• Purpose to resolve fine fraction emission biases for paved and unpaved roads
• Geographic distribution of test sites
• Cyclone/Impactor biases evident
• New AP-42 fine fractions were averages between cyclone/impactorand dichotomous sampler results
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C/I Biases from Prior Field Study
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
PM 10 Concentration (ug/m3)
PM 2
.5/ P
M 1
0 R
atio
CycloneDTDQ
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Revisions to AP-42 Fine Fractions
• PM2.5/PM10 ratio for unpaved roads (dominated by fugitive dust) was reduced from 0.26 to 0.15
• PM2.5/PM10 ratio for paved roads was reduced from 0.46 to 0.25
• Non-dust component of paved road emissions assigned a PM2.5/PM10 ratio of 0.76, accounting for vehicle exhaust and brake and tire wear
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Purpose of Controlled Lab Study
• Collect new controlled data from collocated reference PM monitors with MRI high-volume cyclone/impactorsystem
• Determine extent of any bias in the PM2.5/PM10 ratio as determined by the cyclone/impactor system
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Looking throughtunnel toward
Inlet flowstraighteners
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Viewing Window with Continuous PM Mass Monitor
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Ref. Method Sampling Equipment
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Phase I Testing
• Purpose: Determine potential bias in PM-2.5 concentration as measured by cyclone/impactor system
• RFM: Partisol Model 2000 for PM-2.5
• Test materials: ISO 12103-1 Arizona Test Dusts—fine and coarse grades; Owens Dry Lake surface soil
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Air Samplers: Phase IUnit Sampler Manufacturer/
modelFlow rate
Particle size cutpoint
2 Cyclone pre-separators
Sierra Model 230 CP
20 acfm 10.2 μmA
2 Multistage impactor
Sierra Model 230
20 acfm
2.1 μmA
2 Partisol R&P Model 2000
16.7 alpm
2.5 μmA
2 DustTRAK TSI Model 8520
5 alpm 2.5 μmA and 10 μmA
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MRI Cyclonefor Sampling of PM-10
in Fugitive Dust
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Exposure Chamber
withSampler
Inlets
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Phase II Testing
• Purpose: Determine PM-2.5/PM-10 ratios for a variety of western surface materials
• FRMs: Partisol Model 2000 for PM-2.5 and PM-10
• Test materials: Soils, aggregates, and unpaved road surface materials
• Aerosolization system: Constant flow energy
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Air Samplers: Phase II
Unit Sampler Manufacturer/model
Flow rate
Particle size cutpoint
2 Partisol R&P Model 2000
16.7 alpm
2.5 μmA
2 Partisol R&P Model 2000
16.7 alpm
10 μmA
2 DustTRAK TSI Model 8520
5 alpm 2.5 μmA and 10 μmA.
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Contributors of Test Samples
• Great Basin UAPCD—Owens Dry Lake
• CH2MHill—Salton Sea
• WY AQD—Thunder Basin mine
• NM AQB—South-Central New Mexico
• Alaska DEC—Matanuska Valley
• Arizona DEQ—Maricopa & Pima Counties
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Code State Location Type of materialMoisture
content (%)Dry silt
content (%)Dry Silt
rank
TF Arizona – Standard Test Dust—Fine
– – –
TC Arizona – Standard Test Dust—Coarse
0.60 87.6 1
AK Alaska MAT-SU KnikRiver Bed
Sediments 0.80 8.69 6
AZal Arizona Phoenix Area
Alluvial Channel 0.33 17.3 3
AZag Arizona Phoenix Area
Agricultural Soil 1.06 21.6 2
NMr New Mexico
Las Cruces Landfill
Road Dust 1.27 12.2 4
NMs New Mexico
Radium Springs
Grazing Soil 0.47 10.9 5
OW California Owens Dry Lake
Lakebed Soil 0.27 3.14 9
SS California Salton Sea Shoreline Soils 5.46* 3.63 8
WY Wyoming Thunder Basin Mine
Barrow Pit for Access Road
Surface Material
2.47* 6.83 7
Properties of Test Soils/Surface Materials
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Wind Erodibility Groups• WEG values developed by USDA/NRCS to
indicate the susceptibility of surface soil to blowing (Nine WEG values)
• Soil blowing correlated with:– Soil texture
– Organic matter content
– Effervescence due to carbonate reaction with HCl
– Rock and pararock fragment content
– Mineralogy
– Soil moisture and frozen soil
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PM-10 Emission Categories vs. Wind Erodibility Groups
• 1 – Silty Sand & Clay (WEG 4 and 5)
• 2 – Sandy Silt (WEG 2 and 3)
• 3 – Loam (WEG 4L)
• 4 – Sand (WEG 1)
• 5 – Silt (WEG 6 and 7)
Note: USDA provides national soil database (SSURGO)with WEG values for GIS analysis.
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Soil Texture Triangle
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Test Soils
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Results of Controlled Wind Tunnel Study
• PM2.5 concentrations measured by the high-volume cyclone/impactorwere factor-of-2 higher than measured by reference-method samplers.
• Geometric mean bias of 2.01
• Arithmetic mean bias of 2.15
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Comparability of Field and Laboratory Test Results
• PM2.5 bias of cyclone/impactorsystem
– Measured under controlled laboratory conditions
– Closely replicated by the bias observed in the prior EPA-funded field study
– Both studies used reference method samplers for comparison
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Reporting Process
• Test Plan--with opportunity to observe laboratory wind tunnel facility
• Draft Test Report--with independent peer reviewers
• Comment/Response Log--for each review comment
• Revised Test Report
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C/I Biases from Lab Study
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000
PM 10 Concentration (mg/m3)
PM 2
.5 /
PM 1
0 R
atio
AZ Ag Soil
Knik RiverSediments
Las Cruces LandfillRoad
Thunder Basin Mine
AZ Alluvial Channel
Radium Springs
Salton Sea
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Recommended AP-42 Fine Fractions
• Paved Roads [13.2.1]
• Unpaved Roads (Public & Industrial) [13.2.2]
• Construction & Demolition [13.2.3]
• Aggregate Handling & Storage Piles [13.2.4]
• Industrial Wind Erosion [13.2.5]
• Agricultural Tilling
• Open Area Wind Erosion
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Paved Roads
• Current PM2.5/PM10 Ratios– Dust component: 0.25
– Non-dust component: 0.76
• Proposed Change– Dust component: 0.15
• Justification– Factor of 2 bias in cyclone/impactor data
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Unpaved Roads
• Current PM2.5/PM10 ratio: 0.15
• Proposed PM2.5/PM10 ratio: 0.1
• Justification– Controlled wind tunnel test results
– Field test results
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Construction & Demolition
• AP-42 recommends referring to other sections (e.g., unpaved roads)
• Category emissions normally dominated by travel over unpaved surfaces
• Proposed PM2.5/PM10 ratio: 0.1(ref. earlier justification)
• Large cleared areas possible significant source of wind erosion (ref. section on open area wind erosion)
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Aggregate Handling and Storage Piles
• Open storage pile emissions usually dominated by traffic on unpaved surfaces around piles
• Proposed PM2.5/PM10 ratio: 0.1(ref. earlier justification)
• Proposed PM2.5/PM10 ratio for transfer operations: 0.15 (justification based on factor-of-two bias in cyclone/impactor system)
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Industrial Wind Erosion
• Examples include open tailings piles or raw material storage piles
• Proposed PM2.5/PM10 ratio: 0.15
• Justification based on– Controlled wind tunnel test results
– Prior tests with portable wind tunnel
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Agricultural Tilling
• Original AP-42 section “under review”
• WRAP Handbook recommends PM2.5/PM10 ratio of 0.2
• Ratio of 0.2 consistent with controlled wind tunnel results, considering lower plume concentrations generated by slow moving implements
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Open Area Wind Erosion• Examples are disturbed soils such as
agricultural fields
• Prior portable wind tunnel tests show ratios in the range of 0.3
• Proposed PM2.5/PM10 ratio: 0.15• Justification:
– Factor-of-two bias in C/I system
– Owens Lake plume data
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PM2.5/PM10 RatioFugitive dust source category
AP-42section
Current Proposed
Paved Roads 13.2.1 0.25 0.15
Unpaved Roads (Public & Industrial) 13.2.2 0.15 0.1
Construction & Demolition 13.2.3 0.208 0.1
Aggregate Handling & Storage Piles 13.2.4 0.314
(transfer)
0.1 (traffic)
0.15 (transfer)
Industrial Wind Erosion 13.2.5 0.40 0.15
Agricultural Tilling – 0.222 0.2 (no change)
Open Area Wind Erosion – - 0.15
Summary of Proposed Fine Fractions
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Conclusions
• Tested materials showed consistent particle size characteristics under constant energy input
• Tests results consistent with prior field study
• Sound basis for proposed revisions to PM2.5/PM10 ratios in AP-42