UNITED STATES ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIANGLE PARK, NC 27711

MEMORANDUM
SUBJECT: Consultation on Coarse Particle Speciation
FROM: Lewis Weinstock, Group Leader Ambient Air Monitoring Group Office of Air Quality Planning and Standards
TO: Kyndall Barry, Designated Federal Officer Ambient Air Monitoring & Methods Subcommittee Clean Air Scientific Advisory Committee EPA Science Advisory Board Staff Office
In October 2006, EPA issued the final rule to revise both the primary and secondary NAAQS for PM (71 FR 61144). The Agency decided to retain PM 10 as the indicator for thoracic coarse particles as promulgated in July 1997 (62 FR 38652). The final rule es tablishes ambient air monitoring requirements for a PM 10-2.5 indicator of thoracic coarse particles to support research on particle distribution, sources, and health effects. A new Federal Reference Method (FRM) was also promulgated in the rule for measuring the mass concentration of PM 10-2.5 in ambient air. As part of the revisions to the Ambient Air Monitoring Regulations, PM 10-2.5 speciation monitoring will be required at National Core (NCore) multi-pollutant monitoring stations by January 1, 2011. EPA OAR requested AAMMS c onsultative advice on the issues related to PM 10-2.5 speciation and monitoring.
Attached is the review document in which the sp eciation and monitoring issu es related to coarse particles are discussed. This document has b een prepared by staff from the Ambient Air monitoring Group in the Office of Air Quality Pla nning and Standards which will be the focus of the consultation by the CASAC AA MMS. We look forward to the upcoming discussions with AAMMS.
Charge to the CASAC AAMMS
Within each of the sections of the document, we ask the Subcommittee to address the following:

PM 10-2.5 Speciation Measurement

1. Table 1 provides a list of proposed PM 10-2.5 species and analysis methods. Are there additional PM 10-2.5 target species or methods that can be used to help identify the source of unidentified mass in order to obtain better mass closure?

2. Various sampling devices, including dichotomous samplers, MetOne SASS speciation monitors, PM 10 and PM 2.5 FRMs are potential sampling devices (with the appropriate filter types) forPM 10-2.5 speciation. Among these sampler types, which should be included or excluded from the pilot network design? Are there other sampling devi ces not listed here that should be considered?

3. What are the PM 10-2.5 speciation sampling artifacts that may be encountered using the samplers mentioned above and how should they be addr essed? Is speciation by the difference method problematic for PM 10-2.5 speciation and if so what specific issues make it problematic?

4. The current and most widely used PM 2.5 speciation sampler is the MetOne SASS and it has a flow rate of 6.7 Liters per minute (Lpm) which is significantly lower than either the FRM for PM 10-2.5 mass or the dichotomous sampler (16.7 Lpm) . If this sampler was configured for PM 10-2.5 by difference, would the 6.7 Lpm flow rate be pr oblematic, especially with the need to compare reconstructed mass to the mass collected by the PM 10-2.5 FRM?

5. Is the amount of particle mass collected on the dichotomous filters (especially the minor flow) sufficient for speciation chemical analysis?

PM 10-2.5 Species or Compone nts

1. Table 1 provides a list of proposed PM 10-2.5 species and analysis methods. Among these species, which are most important? Are there important PM 10-2.5 species or components missing from this list? Are there important analysis methods missing from this list?

2. In the consideration of potential ion measurements for PM 10-2.5 species, what ions should be on the target list? Are nitrate or ammonium ions important? If so, is an acid gas denuder and nylon filter required for the proper collection of these species in PM 10-2.5 ?

3. The 2004 CD included a list of important PM 10-2.5 components which included biological materials and fly ashes. If these species are important to characterize, what specific types of biological materials and fly ashes should be included? Is scanning electron microscopy (SEM) on Teflon filters sufficient to quantify and identify these species? Is the proposed total protein assay technique important to obtain a quantitative indicat or of the total biological material present?

4. Can the complication of particle size and absorpti on effects in XRF be resolved using absorption correction factors? If not, what othe r method(s) should be considered?

5. Are metal oxides a significant source of interference in thermal-optical analysis (TOA) of PM 10-2.5 for OC and EC given the large expected soil co mponent? If so, how should this interference be addressed?
Network Design

1. Are sites with high PM 10 and low PM 2.5 good candidate sites for PM 10-2.5 speciation? Given that there will be some urban and rural NCore monitoring sites with PM 10-2.5 speciation, what other factors should be considered in selecting the pilo t monitoring and long-term sites or locations?

2. If there is an opportunity to modify the NCore PM 10-2.5 speciation monitoring requirements during a future rulemaking, should changes to the netw ork design be considered? For example, changing the total number of required monito rs and/or the required locations?1 

### Key Issues Related to PM 10-2.5 

### Speciation Monitoring

As part of the recent revision to the Am bient Air Monitoring Regulations (U.S. EPA 2006a), PM 10-2.5 speciation monitoring is required at National Core (NCore) multi-pollutant monitoring stations by January 1, 2011. PM 10-2.5 speciation monitoring may also be useful in
other locations where characteri zation of thoracic coarse partic le speciation would be of high value. This paper describes the PM 10-2.5 speciation monitoring requi rements specified in the ambient air monitoring rule and pr ovides an overview of the mon itoring issues, discussion of the potential use of existing PM 10-2.5 speciation sampling and analysis techniques in a pilot study to inform the implementation and decision-making pr ocess, and related research questions to inform the planning and implementation process. This document also serves as a discussionpiece for obtaining feedback and comments on the development and implementation of a longterm PM 10-2.5 speciation monitoring program.



## Introduction

The EPA issued revisions to the Ambient Air Monitoring Regulations (40 CFR Parts 53 and 58) on October 17, 2006 (U.S. EPA 2006a). The final rule establishes ambient air monitoring requirements for an indicato r of thoracic coarse particles (PM 10-2.5 ) to support continued research on particle di stribution, sources, and health effects. At the same time, EPA also promulgated a new Federal Reference Meth od (FRM) for measuring the mass concentration
of PM 10-2.5 in ambient air. Although EPA is not adopting a National Ambient Air Quality Standard (NAAQS) for PM 10-2.5 at this time, the FRM for PM 10-2.5 is of value to aid in a variety of research studies and the development of sp eciation samplers capable of providing improved characterization and understanding of the comp osition of thoracic coar se particles. The final monitoring rule c ontains a requirement for PM 10-2.5 speciation at NCore multipollutant monitoring sites by January 1, 2011, with state monitoring implementation plans due July 1, 2009. As compared to the proposed rule, the final rule in creases the number of monitoring sites from ~20 to ~75 and shifts th e focus from urban monitoring to both urban and rural monitoring locations. Manually-operated PM 10-2.5 speciation samplers must operate on at least a 1-in-3 day schedule and be collocated with PM 2.5 speciation at NCore stations. Since2 EPA is requiring PM 10-2.5 speciation monitoring primarily fo r scientific purposes, it is appropriate to have monitoring at a variety of urban and rural loca tions to increase the diversity of areas that will have available chemical species data. NCore will have about 75 sites mostly in urban areas, with a subset of about 20 rural sites. For more information on NCore, see: http://www.epa.gov/ttn/amtic/ncore/index.html

. The primary objective for PM 10-2.5 speciation data in the m onitoring rule is to support further research in understanding the ch emical composition and sources of PM 10 , PM 10-2.5 , and
PM 2.5 . In addition, more specific uses for the data can be inferred and include:

• Collection of PM 10-2.5 composition data to inform he alth effect studies, both in terms of the relationship between specific PM 10-2.5 species and health, and between PM emitted from different source types and health.

• Advancement of PM 10-2.5 speciation monitoring methods in anticipation of wider
use under a PM 10-2.5 NAAQS if one is adopted later.

• Use of PM 10-2.5 speciation data to promote a dvancement of source attribution
methods.

• Determination of spatial and temporal variations in PM 10-2.5 concentrations in
urban and rural environments.



## PM 10-2.5 

## Speciation Measurement Issues

The Criteria Document (CD), prepared for th e previous PM NAAQS review, provides an overview of the current information on coarse pa rticle formation, sources, composition, and mass measurement issues (U.S. EPA 2004). No clear r ecommendations were given for an approach to collecting PM 10-2.5 speciation data. It was noted that “satisfactory techniques are available to separate fine particles from c oarse particles and to collect th e fine particles on a filter. However, no consensus exists as yet on the best technique for collecting a coarse particle sample for determination of mass and composition. Cand idates include multistage impaction, virtual impaction, and difference (subtracting PM 2.5 mass or composition from PM 10 mass or composition).” Since the writing of the CD, the EPA Office of Research and De velopment (ORD) has
conducted a multi-site field evaluati on of candidate methodologies for PM 10-2.5 mass (U.S. EPA 2006b). Five PM 10-2.5 measurement approaches were ini tially selected for study and included3 virtual impaction (dichotomous sampling), differe nce, and continuous methods. In addition to continuous monitoring devices, integr ated filter-based monitors were used to collect filters for subsequent speciation analysis. The ORD results from speciation analyses of the filters are pending and when available, can be used to inform this planning process. So far, ORD has found that when reconstructing PM 10-2.5 mass using the specia tion results (sum of species), there is a significant portion (10-50%) of the mass that is unaccounted for or unidentified in some locations. It is important to not e that this includes uncertainties associated with the factors used in reconstructing mass (e.g., the factor used in conversion from OC to OM ). Linear regression comparisons between constructed mass and meas ured mass did show high correlation. The
PM 2.5 , PM 10-2.5 and PM 10 mass comparisons of the dichotomous (dichot) sampler with FRMs in Phoenix, AZ showed the dic hot to be 10% higher for PM 2.5 , 7% lower for PM 10-2.5 and 4% lower
for PM 10 . It was hypothesized that the higher PM 2.5 dichot mass was due to coarse particle intrusion into the fine mode and significant measurement biases will occur only if the coarse
fraction of PM 10 appreciably exceeds the PM 2.5 size fraction, as was s een in Phoenix. Mass comparisons in other locations (Birmingham, AL and Lindon, UT) showed very good agreement ( ≤ 4%) between the dichots and FRMs for PM 2.5 , PM 10-2.5 and PM 10 . High correlations (R 2 > 0.973) were found in all cases, indi cating that the respons e between the dichot and FRM is very consistent from one sampling event to another.
Limited PM 10-2.5 speciation monitoring studies have been conducted in the U.S. and most
of these studies were con ducted using the difference method. The uncertainties and inconsistencies between the analytical tech niques used in these studies are unknown. PM 10-2.5 speciation has been studied at both urban locatio ns (Chow et al., 1996; Chow et al., 1993; Sardar et al., 2005, Edgerton et al., 2005) and rural IMPROVE monitoring lo cations (Eldred et al., 1997; Malm et al., 2007; Lee et al., 2007). Soil compon ents (e.g., Si, Al, Ti, Ca, Fe, K), and organic carbon (OC) were consistently found to be dominant components of PM 10-2.5 and the significance of nitrate and sulfate found was dependent on th e location studied. For coarse mass in rural locations, Malm et al. (2007) found the soil co mponents (61%) and particulate organic carbon mass (24%) to be the major components, with n itrate at 8%, elemental carbon (EC) at 1%, sea salt at only 2%, and sulfate as negligible. Pa rticulate organic carbon ma ss was defined as OM = OC*1.8. In southeastern urban locations, Edgerton et al., (2005) found simila r results to Malm et al. (2007), but also showed a significan t portion (26-38%) of the reconstructed PM 10-2.5 mass to4 be unidentified when accounting for OM as OC* 1.4 and on the order of 16-23% when using OM as OC*2.5. In the San Joaquin Valley, Chow et al., (1996) also found tota l carbon aerosol (TC); ions (e.g., nitrate, sulfate, sodium, chloride); and soil components to be abundant in the PM 10 fraction and in Southern Califor nia, Sardar et al., (2005) found the soil components, OC and
nitrate to be dominant. A list of coarse particle constituents was provided in the Criteria Document and includes suspended soil or dust; fly ash; nitrates/chlorides /sulfates; soil components (Si, Al, Ti, Ca, Fe); sea salt; tire/brake/road wear debr is; and biological materials. Not all of these components can be measured directly thr ough a filter-based speciation monitoring program (e.g., fly ash, tire/brake/road wear debris); however, some components or species may be represented by components that can be measured w ith existing techniques used for PM 2.5 speciation (e.g., sodium and chloride ion for sea salt).
The current PM 10-2.5 FRM difference method, dichotomous sampler, and current speciation filter-based samplers serve as logical choices for the basis of a PM 10-2.5 speciation sampler design. A combination of filter types and analytical methods are currently being used in
both the PM 2.5 Chemical Speciation Network (CSN) and IMPROVE monitoring programs to collect components of PM 2.5 . These existing techniques can also be applied to a PM 10-2.5 speciation monitoring program, but not without some complication.
The FRMs for PM 2.5 and PM 10 (low-volume sampling at 16.7 Lpm) provide relatively precise (within ± 10%) methods for determin ing the mass on a Teflon filter. However, uncertainties remain about the relationship between the mass and composition of material remaining on the filter as determined by the FR M and the mass and compos ition of material that existed in the atmosphere. Measurement errors of concern for PM 10 sampling include uncertainty in cut point tolerances, partic le bounce and re-entrainment, impaction surface overloading, and losses to sampler internal su rfaces (U.S.EPA 2004). Another measurement uncertainty for PM 2.5 sampling is the potential for inclusion of a small fraction of coarse particles
in the fine mass fraction under some circumstances.
Modification of the PM 2.5 speciation sampler inlets to PM 10 was suggested by CASAC (EPA-SAB-CASAC-CON-04-005) as an option for PM 10-2.5 speciation by difference. This may
be a viable alternative as long as both speciation samplers have identical flow rates, filter sizes, and filter handling procedures. One limitation of the most widely used PM 2.5 speciation sampler5 (MetOne SASS) is the difference in flow rate (6.7 Lpm) from the PM 2.5 and PM 10 FRMs (16.7 Lpm). Differences in flow rates result in differences in filter face velocity and pressure drop across the filters, which may adversely affect th e volatile species and s ubsequent comparison of
mass closure or reconstructed mass with the FRM total mass; however, volatility issues are most likely less important for PM 10-2.5 particles than for PM 2.5 .


### PM 10-2.5 

### FRM Difference Method

As is the case with all PM measurement methods, uncertainties exist with the PM 10-2.5 difference method. These include data loss if either
the PM 2.5 or the PM 10 sampler fails; uncertainties in flow rate and filter weights (both before use and after collection and equilibrat ion of particles); and
uncertainties due to the loss of semi-volatile components which may occur for each size cut. Allen et al. (1999) have suggested ways to improve coarse particle difference measurements by instituting careful control of sampling aspects (e.g., flow rate control), management of gravimetric analysis issu es, and proper implementation of field blanks. The viability of PM 10-2.5 speciation by a difference method requi res further evaluation. However, preliminary regression comparisons for specia tion by difference and the dichot method have shown high correlation for predominate species. While there is currently no consensus on whether the mixing of PM 2.5 and PM 10-2.5 aerosols causes a bias in either measurement, CASAC mentioned the need for sampling separation and colle ction of filters with only coarse particles to avoid mixing of PM 2.5 and coarse particles and the potential for subsequent chemical interaction. Allen et al. (1999) also mentions the importance of maintaining filter flow rates greater than 10 Lpm, preferably 16.7 Lpm, to avoid degraded pr ecision. As mentioned above, the most widely used speciation sampler has a flow rate of 6.7 Lpm. per channel. The impact of this low flow
rate should be evaluated if the low-fl ow speciation samplers are used for PM 10-2.5 by difference. Fi g ure 1 - taken from EPA 2006b6 

### Dichotomous Samplers (Dichots)

Measurement uncertainties have also been identified with Virtual Impactors in dichotomous samplers. These include fine and coarse particle intrusion; and potential errors in
the results from the di chotomous sampler caused by uncertainties in the coarse mass channel
enrichment factor which is used to estimate virtual impactor performance (Allen et al., 1999). Improvements have been made to
address some of these issues. Current commercial impactors reflect design changes earlie r identified to reduce the contamination of coarse particles by fine particles, while main taining low losses and sh arper size cuts. Fine particle intrusion of 10% into the coarse m ode is well known (Loo and Cork, 1988) and can be mathematically corrected for. ORD continues to evaluate and characterized virtual impactors. As mentioned previously, results from the multi-site evaluation of PM 2.5 , PM 10-2.5 and PM 10 mass comparisons of the dichotomous sampler with FRMs showed very good agreement (except in Phoenix) and very good corre lations (U.S. EPA 2006b).



### PM 10-2.5 

### Species or Components

Table 1 provides a list of candidate or potential PM 10-2.5 species that can be measured with the existing PM 2.5 speciation methods. The specific spec ies that need to be measured for
PM 10-2.5 must be identified in orde r to design a monitoring program. For example, ions (e.g., nitrate and sulfate) have been iden tified as only minor components of PM 10-2.5 in some locations.
It is not clear whether the res ources to measure ions are needed to support research needs for
PM 10-2.5 speciation. Elemental analysis methods (e .g., X-Ray Fluorescence) can provide sulfur, potassium, chloride, and sodium elements; therefore, it needs to be determined if these elements are sufficient surrogates for the information needed for PM 10-2.5 . If ions are not needed, then it would eliminate the need to collect an additional filter (nylon) and resources for an additional lab Fi g ure 2 - taken from EPA 2006b7 analysis. In addition, the need for elements by XR F versus extractable or water soluble elements by ICP/MS should be determined.

Table 1. List of Candidate PM 10-2.5 Species Species Filter Type Denuder Analysis Method

PM 10-2.5 Gravimetric Mass Teflon None Filter weighing Elements:

• Crustal or soil (Si, Al, Ti, Ca, Fe)

• Several other elements currently measured routinely for PM 2.5 , including: K, Cl, P, Mg, Cr, etc. Teflon None EDXRF (Energy Dispersive X-Ray Fluorescence) or alternative extraction method

Soluble Ions

• Nitrate, sulfate, sodium, potassium, chloride, ammonium Nylon MgO? Ion Chromatography

Carbon

• Organic and Elemental Carbon

• Carbonate Carbon Quartz None Thermal Optical Reflectance (TOR) and transmittance (TOT) by IMPROVE_A
Separate acidification and analysis

Biological Material (Bioaerosols) Teflon, Quartz None Scanning Electron Microscopy (SEM)
Total Protein Assay as indicator Fly ash Polycarbonate or Teflon None Scanning Electron Microscopy (SEM)

Potential issues with XRF measurement of particles have been identified. XRF is typically done under vacuum to improve perf ormance, enhance detection limits, and reduce
contamination of detector sources. Use of XR F under vacuum and the loss of volatile nitrate (as much as 30%) have been demonstrated (U.S. EPA 2001). In the PM 2.5 speciation program, the effects of vacuum are eliminated by analyzing the filter for mass prior to analysis of elements by XRF. A separate, denuded nylon filter is used for nitrate and other i onic species. Large or coarse particle size effects may also be problemat ic for XRF. Larger particles (greater than 38 micrometers) may absorb some of the emitted x-rays for light elements such as sodium, magnesium, aluminum, silicon, phosphorus, sulfur , chlorine, and potassium (Chow 1995). Absorption corrections procedures for particle size effects on XR F results can be applied (Van Dyck et al., 1985) and these factors will have to be optimized for PM 10-2.5 element analysis by
XRF. Another issue to consider is the sensitivity of XRF a nd the sampling method or sampler chosen. If the dichotomous sampler is used, then the adequacy of XRF detection limits will need
to be evaluated for the coarse mode. Alternative techniques like Inductively Coupled Plasma/M ass Spectrometry (ICP/MS). ICP/MS have some advantages (e.g., improved de tection limits for many species but lower for some), but also some disadvantages which in clude increased cost, labor intensive sample preparation, the need for strong acid extraction, incomplete extr action efficiencies, and sample filter destruction (XRF is a non-de structive analysis). If the pa rticle size effects are addressed with XRF and the method sensitivity is adequate for dichotomous sampling, then XRF may be a more appropriate choice for elemental analysis.
PM 10-2.5 organic and elemental carbon (OC and EC ) species can be measured using the same thermal-optical analysis (TOA) method that is used for PM 2.5 speciation. It is well known that both positive and negative OC sampling artifacts exist (Eatough et al., 1990; Turpin et al., 1994, Mader et al., 2001). Some of the positive artifact can be addressed by the use of backup quartz filter collection and subsequent subtraction. The artif act correction method to be applied
to the urban PM 2.5 CSN is currently being evaluated and developed. Once developed, it will
need to be evaluated for use in the PM 10-2.5 program. Organic vapor denuders are not currently being used for either the PM 2.5 CSN or IMPROVE programs. Although denuders may be appropriate, they are still not ready for “prime time” and ma y introduce negative OC artifacts due to the disruption of the gas-particle equilib rium during sampling. Han et al., (2007) mention
an interference with metal oxide s (e.g., iron oxides) and TOA an alysis; whereby certain metal
oxides can serve as a source of O 2 in the helium atmosphere. Since the soil component of PM 10-

2.5 is expected to be significant, any effects of metal oxides on the OC and EC results will need to be explored. Carbonate carbon may also be a significant constituent of PM 10-2.5 and a separate punch from the quartz filter will have to be analyzed to quantify it. Biological materials (bioaerosols) are collecte d with the filter-based particle sampling techniques used for PM 10-2.5 or PM 2.5 monitoring and included in the OC measurement, but are9 not quantified separately from ot her components. If bioaerosol species (e.g., pollens and molds) need to be qualitatively or qua ntitatively identified for the PM 10-2.5 speciation program, an appropriate measurement technique will need to be identified (or developed) and evaluated. Some biological materials can be identified using the scanning electron microscopy (SEM) technique (U.S. EPA 2002). Existing bioaerosol monitoring programs (e.g., BioWatch) collect particles using filters and qualita tively test for biological pathogens (e.g., anthrax). Total protein has been measured from filters with an assay technique and used as an indicator of total biological material (Menetrez et al, 2007). The specific bioaeros ol species of interest (or indicator/surrogate species) need to be specified in order to explore ap propriate collection and analysis techniques. Fly ash is also included in the list of PM 10-2.5 constituents of interest in the CD. Like bioaerosols, fly ash is collected with the filter-based particle sampling techniques used for PM 10-

2.5 or PM 2.5 , but not quantified separately from other co mponents. If fly ash is needed for the
PM 10-2.5 speciation program, an appropriate measuremen t technique will need to be identified or developed and evaluated. Some fly ashes can be identified using the SE M analytical technique (U.S. EPA 2002).


## Network Design Issues

The final monitoring rule contains a requirement for PM 10-2.5 speciation at NCore multi-pollutant monitoring sites by January 1, 2011. As mentioned previously, this was revised from the proposed rule. The NCore will have about 75 sites mostly in urban areas, with a subset of about 20 rural sites. Spatially, the candidate NCore locations (see map) may not be the best
choice for PM 10-2.5 speciation given that the highest PM 10-2.5 mass concentrations are in the Southwest and Southern CA (summer peak). The NCore site selection is based on representative monitoring to provide community -wide characterization of expos ure and sites leveraged with10 other measurement systems (e.g., PAMS, NATTS). Since PM 10-2.5 mass is more likely to be influenced by local sources or wind-blown dust in areas with little vegetation, NCore is not necessarily the optimal design for PM 10-2.5 speciation. The spatial adequacy and representativeness of the NC ore sites for long-term PM 10-2.5 speciation monitoring will need to
be evaluated.



## PM 10-2.5 

## Monitoring Plan and Method Research Needs

There are still many unanswered questions regarding PM 10-2.5 speciation monitoring; however, a few PM 10-2.5 by difference and dichotomous monitoring sites (3 to 5 locations) should be used for pilot monitoring to answer some of the questions outlined below and to fine tune the final monitoring approach. The CASAC (EPA -SAB-CASAC-CON-04-005) expressed concerns about speciation by difference due to the cumu lative effects of the imprecision in both PM 2.5 and
PM 10 measurements. White (1998) showed the uncer tainty in coarse mass by difference to be about 3 times the uncertainty in the fine measur ement. An evaluation of the practicality and validity of PM 10-2.5 speciation by difference method is n eeded. The CASAC comments also leaned toward virtual impaction and felt it ha d significant advantages (e.g., collects the PM 10-2.5 size fraction directly). For those PM 10-2.5 species that are in common with the PM 2.5 speciation program, the existing National Laboratory Contract for PM 2.5 speciation can be used to analyze the filters. In order to sample for the current suite of species in the PM 2.5 speciation program (including ions) by difference, identical PM 10 versions of the PM 2.5 speciation sampling devices can be collocated with existing PM 2.5 samplers. PM 10 sharp cut cyclones would need to be commercially available at a flow rate of 6.7 Lpm for the MetOne SASS speciation samplers and the vendor has been contacted about developi ng and characterizing such cyclones. A PM 10 cyclone is already available for the 22 Lpm sp eciation carbon sampling device. The existing SASS sampler could be retrofitted to have two PM 2.5 channels with Teflon and nylon filters and
two PM 10 channels with Teflon and nylon filters if needed. One additional PM 10 speciation carbon sampler would need to be collocated with the existing PM 2.5 sampler for OC/EC aerosol species. If PM 10-2.5 speciation was based on the dichotom ous sampler, it would require three samplers at each location to collect the Tefl on, nylon, and quartz filters for speciation if elements, ions, and carbon species are needed.11 John et al., (1988) found the anodized aluminum inlet of the dichotomous sampler to be efficient at removing nitric aci d. No difference in measured pa rticle nitrate was found between a dichotomous sampler with no denuder and a sa mpler with a conventional magnesium oxide (MgO) denuder. If ions are on the PM 10-2.5 target list, dichotomous samplers for PM 10-2.5 speciation would need to be fitted with acid ga s denuders for the proper collection of particlephase ions on the nylon filters if the uncoated in let is not sufficient for acid gas capture. Some of the questions relevant to PM 10-2.5 speciation monitoring are outlined below:
 What are the important PM 10-2.5 species to measure?  Are ions important PM 10-2.5 species? If so, what ions should be on the target species list? If nitrate or ammonium ions are needed, is an acid gas denuder needed for the proper collection of these species in PM 10-2.5 ? If dichotomous samplers are used, would a denuder be needed?  What are the PM 10-2.5 speciation sampling artifacts that may be encountered and how should they be addressed in the monitoring program? Is speci ation by the difference method problematic for
PM 10-2.5 speciation and if so what specific issues make it problematic?  The current and most widely used PM 2.5 speciation sampler is the MetOne SASS and it has a flow rate of 6.7 Lpm which is significantly lower than either the FRM for PM 10-2.5 mass or the dichotomous sampler (16.7 Lpm). If this sampler was configured to do PM 10-2.5 by difference, would the 6.7 Lpm flow rate be problematic, esp ecially with our knowle dge of concerns about low-flow cut-points and particle intrusion, and th e need to compare to wh at is collected by the
PM 10-2.5 FRM for mass?  Is the particle mass collected on the dichotomous filters (especially for the minor flow) sufficient for speciation chemical analysis? Is there enough ma terial to obtain adequate detection limits with the potential methods used?  What analysis methods should be used? What PM 2.5 speciation analysis methods are appropriate
to also use in the PM 10-2.5 speciation program?  Is XRF the most appropriate method for PM 10-2.5 speciation? Can the complication of particle size and absorption effects in XRF be adequately r esolved using absorption correction factors? Does XRF provide adequate sensitivity (detection lim its) to measure elements if a dichotomous sampler is used? If XRF sensitivity is not ad equate, should some other more sensitive and potentially more expensive and destructive analyti cal technique be considered? If an elemental method that has more sensitivity and applies aci d extraction is needed, is the recovery of extractable metals adequate vers us total metals by XRF?  Are metal oxides a significant source of interference in thermal-optical analysis (TOA) of PM 10-2.512 for OC and EC given the large expected soil component?  If biological particles and fly ash need to be characterized, what specifi c types of biological materials and fly ashes should be measured? What analysis methods should be used to identify and quantify these species? Is scanning electron micr oscopy (SEM) on Teflon filters adequate to quantify and identify th e biological material present? Is the use of other assay techniques necessary to adequately obtain a quantitative indicat or (e.g., total protein) of the total biological material present?  When reconstructing PM 10-2.5 mass using the sum of PM 10-2.5 species concentrations, a significant portion of unidentified mass has been identified. Are there other PM 10-2.5 target species or analysis methods that can be used to help identify the s ource of this mass in order to reduce the amount of
unidentified mass and obtain better mass closure?  What factors should be considered in the selection of pilot monitoring site locations or areas? One key issue in the proposed PM rule (January 2006) was the need to distinguish urban from rural coarse particles. What pilot site selection criteria would help in selecting urban and rural sites for collecting data to address this issue? What analys is methods or target species are particularly important to inform this issue?  Various sampling devices, including dichotomous samplers, MetOne SASS speciation monitors,
PM 10 and PM 2.5 FRMs are potential sampling devices (with the appropriate filter types) for PM 10-

2.5 speciation. Which of these sampler types s hould be included or excluded from the pilot network design? Additional information may be provided to in form some of the questions above when ORD publishes results on PM 10-2.5 speciation from the multi-city fi eld evaluation. In addition, any pilot monitoring program that is developed and implemented for PM 10-2.5 speciation may also provide information to resolve some of these issues. 

## Quality Assurance (QA)

The PM 10-2.5 speciation monitoring program is expect ed to follow similar requirements as specified for the PM 2.5 speciation monitoring program, whic h include collocation for precision estimates and sampler flow-rate audits. PM 10-2.5 species-specific goals for bias and precision have not been specified. A dditional QA procedures and pos sibly DQOs will need to be developed for PM 10-2.5 speciation.13 

## References

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