Overview and Status of Lead NAAQS Review and Overview of Agency

Technical Documents on Lead NAAQS Monitoring Issues

Kevin Cavender and Joann RicePresented at Clean Air Scientific Advisory Committee’s

Ambient Air Monitoring and Methods SubcommitteePublic Teleconference

July 14, 2008

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Outline

• Status of lead NAAQS review

• Proposed Federal Reference Method (FRM) for Pb-PM10

• Options for the development of a low-volume Pb-TSP sampler

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Status of Pb NAAQS Review

• Proposed rule signed May 1, 2008

• Comment period closes August 4, 2008

• Final rule due to be signed October 15, 2008

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Proposed Pb-PM10 FRM

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Background on current FRM for Pb-TSP

• Existing FRM based on high-volume TSP sampler with atomic absorption (AA) analysis.

• 21 existing FEM all based on high-volume TSP sampler with various analysis options

• CASAC and others have expressed concerns with TSP sampler– “Cut point” is affected by wind speed and

direction

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Draft Federal Reference Method (FRM) for Pb-PM10

• Sampling and analysis method considerations for the proposed FRM for Pb-PM10

• Sampling considerations– Recently promulgated low-volume (16.7 L/min) PM10c

sampler with 46.2-mm PTFE filters from PM10-2.5 FRM– Advantages:

• More demanding performance criteria of Appendix L (PM2.5 FRM) with sampling at local conditions

• Sequential sampling capability to meet increase sampling frequency if needed

• Affords network efficiencies and consistencies with other PM monitoring networks with low-volume samplers

• Consistent with QA requirements for PM2.5 and PM10-2.5

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• Analysis Method Considerations– X-Ray Fluorescence (XRF)– Advantages:

• No complicated sample preparation or extraction prior to analysis

• Non-destructive • Relatively cost effective • Relatively low method detection limits (MDLs)

– On the order of ~0.001 µg/m3 for low-volume collection

• Also used in other PM speciation monitoring programs (e.g., CSN and IMPROVE)

Draft Federal Reference Method (FRM) for Pb-PM10

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FRM Charge Questions

• What are your comments on the use of the low-volume PM10c FRM sampler as the Pb-PM10 FRM sampler ?

• What are your comments on the use of XRF as the Pb-PM10 FRM analysis method?

• What are your comments on the specific analysis details of the XRF method contained in the proposed Pb-PM10 FRM analysis method description?

• Do you think the XRF method precision, bias and MDL for the proposed Pb range will be adequate?

• Are there any method interferences that we have not considered?

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Options for the Development of a Low-volume Pb-TSP Sampler

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Overview of a Potential Low-Volume Pb-TSP Sampler

• A low-volume Pb-TSP sampler would consist of two parts – the inlet and the air sampler. – The air sampler could be based on the low-

volume air samplers used in the PM2.5 and PM10 networks.

– A particular inlet design (either existing or new) would need to be specified.

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Low-Volume Pb-TSP Inlet Considerations

• A number of vendors offer what they refer to as a “low-volume TSP inlet”– In many cases, these low-volume TSP inlets are a low-volume inlet with the

PM10 impactor removed. – An inlet of this design has many potential benefits –

• the PM10 FRM inlet is commercially available,• PM10 FRM inlet designs are uniform,• the PM10 FRM inlet design is already promulgated.

– None of the samplers which use this inlet have currently been approved as a TSP FRM or FEM.

• Although the overall effectiveness of the PM10 FRM’s inlet (including its internal PM10 fractionator) has been well-characterized, the aspiration characteristics of the inlet itself have not been well-characterized

– The omni-directional inlet design would eliminate variability in sampling efficiency due to wind direction.

– For larger particles (> PM10), the sampling efficiency would vary with particulate size due to windspeed-dependent aspiration characteristics and internal particle losses through the sampler.

– Limited information at low wind speeds is available in the literature (Lee Kenny et. al., JEM 2005)

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Plot of High Volume Sampler Efficiency vs. Wind Direction

0

20

40

60

80

100

120

0 10 20 30 40 50 60

Diameter (um)

Sam

pli

ng

eff

icie

ncy (

%)

High Vol 15 M/s 0 deg High Vol 15m/s 45 deg

Data from - Wedding, et. al., (1977)

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Plot of Sampler Efficiency vs. Wind Speed

0

20

40

60

80

100

120

0 10 20 30 40 50 60

Diameter (um)

Sam

pli

ng

eff

icie

ncy (

%)

Low Vol 0.5 m/s Low-Vol 1 m/s High Vol 0.5 M/s

High Vol 2m/s High Vol 7m/s

1. High volume data from - McFarland, et.al, (1979)2. Low volume (louvered inlet) data from – Kenny, et. al., (2005)

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Overview of a Potential Low-Volume Pb-TSP Sampler

• Advantages of a low-volume Pb-TSP sampler over a conventional high-volume Pb-TSP sampler include:– No variability in sampling efficiency due to wind direction– Improved flow control– Improved precision and bias– Sequential sampling capabilities– Reduced footprint requirement– Reduced noise– Network efficiencies with other low-volume PM samplers (i.e.,

PM2.5 and PM10 networks)– No metal interferences for other metals (e.g., copper) from

brushes on motors

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Potential Approaches for Development

• Two approaches could potentially be used to develop a low-volume Pb-TSP sampler– Develop a new Pb-TSP FRM– Test and approve a new Pb-TSP FEM

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FRM Approach

• One option for the development of a low-volume TSP sampler is to describe in detail and formally promulgate a new FRM for TSP sampling based on the modern low-volume sampler platform, and then designate. – Many of the FRM specifications from the PM10 FRM

could be referenced– Geometric specifications for a TSP inlet design would

need to be selected from designs currently available or newly developed

– Available commercial products that met the promulgated description could be designated as FRMs

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FRM Approach (continued)

• Ideally, the sampler capture efficiencies over a wide particulate size distribution would be understood prior to promulgation as an FRM. – Due to difficulties in generating and transporting the large

diameter particles required for wind tunnel evaluation of a TSP sampler, it may not be feasible to develop the data necessary to determine sampler capture efficiencies for ultra-coarse particulate matter.

– It would be especially difficult to develop the necessary data under the short timeline of the Pb NAAQS Review.

• Rather than waiting to develop the sampler capture efficiency data prior to promulgation of a low volume TSP FRM, the EPA could promulgate the new FRM without a full characterization of the sampler capture efficiency

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FRM Approach (continued)

• Advantages of this approach include:– Faster low-volume TSP sampler development and

approval– No need to “match” old high-volume TSP FRM

performance– No wind-tunnel or field test data needed

• Issues with this approach include:– Performance of new FRM could be worse than

current FRM– Difficulties in relating historic Pb-TSP data to new

data

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FEM Approach

• The second option for development of a low volume Pb-TSP sampler is to allow alternative inlet and sampler designs to be accepted as FEM Pb methods. – Currently, the Pb FEM requirements do not specify if different sampler

and inlet designs can be designated as FEM [53.33(d) seems to indicate that alternative samplers could be approved as FEM]

– The EPA has historically only approved Pb-TSP methods based on alternative analysis methods

– The EPA requested comments on the appropriateness of allowing alternative Pb-TSP sampler designs based on the Pb FEM requirements

• Under this approach, collocated field testing of the low volume Pb-TSP sampler versus the current Pb-TSP FRM would be conducted. If the two sampler’s readings matched within some acceptable level, the EPA would accept the low volume Pb-TSP sampler as part of a FEM Pb method.

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FEM Approach (continued)

• The current Pb FEM requirements (40 CFR 53.33) call for field testing – One or more site– 10 or more filter pairs per site (5 valid pairs)– Samplers orientated to minimize wind-direction

differences– Each filter is analyzed three times– Precision of replicate analyses required to be 15% or

less– Comparability for each filter pair (FEM vs. FRM) must

be 20% or less

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FEM Approach (continued)

• Advantages of this approach include:– Fast FEM development and approval– No need to perform wind tunnel testing to

characterize sampler capture efficiency– Some assurance of consistency with historic Pb-TSP

data • Issues with this approach include:

– Requires field testing by vendors or other sponsors (e.g., the EPA, monitoring agencies)

– Low-volume Pb-TSP samplers may not “match” high-volume Pb-TSP samplers well enough to pass FEM requirements, especially considering the variability of the high-volume FRM

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Low Volume Pb-TSP Charge Questions

• Would a low-volume Pb-TSP sampler be an improvement over the existing high-volume Pb-TSP sampler? What advantages and disadvantages do you see associated with a low-volume Pb-TSP sampler?

• What inlet designs would be best suited for a low volume Pb-TSP sampler? What designs are not appropriate for a low-volume Pb-TSP sampler?

• What is your preferred approach for the development of a low-volume Pb-TSP sampler, and why?

• If the EPA were to develop a low-volume Pb-TSP FRM, how important is it that the sampling capture efficiency be characterized for varying particle sizes?

• If the EPA were to develop a low-volume Pb-TSP FRM, should the new FRM replace the existing high-volume Pb-TSP FRM, or should the EPA maintain the existing FRM?

• Is it appropriate to accept alternative sampler and inlet designs as FEM?• Are the proposed FEM testing criteria for Pb methods adequate to ensure

equivalence of alternative sampler and inlet designs? If not, what additional testing requirements should be considered?

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References

• Kenny, G; Beaumont, G; Gudmundsson, A; Thorpe, A; Koch (2005) Aspiration and sampling efficiencies of the TSP and louvered particulate matter inlets. J. Environ. Monitoring 7:481-487.

• McFarland, A.R.; Ortiz, C.A.; and Rodes, C.E. Characteristics of aerosol samplers used in ambient air monitoring. Presented at 86th National Meeting of American Institue of Chemical Engineers (1979).

• Wedding, J.B.; McFarland, A.R.; and Cermak, J.E. (1977). Large particle collection characteristics of ambient aerosol samplers. Environ. Sci. Technol., 11(4):387-390.