# Presentation: 939489

## Overview and Status of Lead NAAQS Review and Overview of Agency Technical Documents on Lead NAAQS Monitoring Issues

- Kevin Cavender and Joann Rice
- Presented at Clean Air Scientific Advisory Committee’s Ambient Air Monitoring and Methods Subcommittee
- Public Teleconference
- July 14, 2008

## 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

## 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

## Proposed Pb-PM10 FRM

## 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

## 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

## 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)

- 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-PM******10***

## 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?

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

## 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.

## 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)

## Plot of High Volume Sampler Efficiency vs. Wind Direction

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

## Plot of Sampler Efficiency vs. Wind Speed

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

## 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

## 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

## 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

## 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

## 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

## 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.

## 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

## 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

## 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?

## 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.