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 PM10 as the indicator for thoracic coarse 

particles as promulgated in July 1997 (62 FR 38652). The final rule establishes ambient air 

monitoring requirements for a PM10-2.5 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 PM10-2.5 in ambient air. 

As part of the revisions to the Ambient Air Monitoring Regulations, PM10-2.5 speciation 

monitoring will be required at National Core (NCore) multi-pollutant monitoring stations by 

January 1, 2011. EPA OAR requested AAMMS consultative advice on the issues related to 

PM10-2.5 speciation and monitoring. 

Attached is the review document in which the speciation and monitoring issues related to coarse 

particles are discussed. This document has been prepared by staff from the Ambient Air 

monitoring Group in the Office of Air Quality Planning and Standards which will be the focus of 

the consultation by the CASAC AAMMS. 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: 

PM10-2.5 Speciation Measurement

1. Table 1 provides a list of proposed PM10-2.5 species and analysis methods. Are there additional 

PM10-2.5 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, 

PM10 and PM2.5 FRMs are potential sampling devices (with the appropriate filter types) for 
PM10-2.5 speciation. Among these sampler types, which should be included or excluded from the 

pilot network design? Are there other sampling devices not listed here that should be considered? 

3. What are the PM10-2.5 speciation sampling artifacts that may be encountered using the samplers 

mentioned above and how should they be addressed? Is speciation by the difference method 

problematic for PM10-2.5 speciation and if so what specific issues make it problematic? 

4. The current and most widely used PM2.5 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 PM10-2.5

mass or the dichotomous sampler (16.7 Lpm). If this sampler was configured for PM10-2.5 by 

difference, would the 6.7 Lpm flow rate be problematic, especially with the need to compare 

reconstructed mass to the mass collected by the PM10-2.5 FRM? 

5. Is the amount of particle mass collected on the dichotomous filters (especially the minor flow) 

sufficient for speciation chemical analysis?

PM10-2.5 Species or Components 

1. Table 1 provides a list of proposed PM10-2.5 species and analysis methods. Among these species, 

which are most important? Are there important PM10-2.5 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 PM10-2.5 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 PM10-2.5? 

3. The 2004 CD included a list of important PM10-2.5 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 indicator of the total biological material present? 

4. Can the complication of particle size and absorption effects in XRF be resolved using absorption 

correction factors? If not, what other method(s) should be considered? 

5. Are metal oxides a significant source of interference in thermal-optical analysis (TOA) of PM10-2.5

for OC and EC given the large expected soil component? If so, how should this interference be 

addressed? 

Network Design

1. Are sites with high PM10 and low PM2.5 good candidate sites for PM10-2.5 speciation? Given that 

there will be some urban and rural NCore monitoring sites with PM10-2.5 speciation, what other 

factors should be considered in selecting the pilot monitoring and long-term sites or locations? 

2. If there is an opportunity to modify the NCore PM10-2.5 speciation monitoring requirements during 

a future rulemaking, should changes to the network design be considered? For example, changing 

the total number of required monitors and/or the required locations?
1

Key Issues Related to PM10-2.5 Speciation Monitoring 

As part of the recent revision to the Ambient Air Monitoring Regulations (U.S. EPA 

2006a), PM10-2.5 speciation monitoring is required at National Core (NCore) multi-pollutant 

monitoring stations by January 1, 2011. PM10-2.5 speciation monitoring may also be useful in 

other locations where characterization of thoracic coarse particle speciation would be of high 

value. This paper describes the PM10-2.5 speciation monitoring requirements specified in the 

ambient air monitoring rule and provides an overview of the monitoring issues, discussion of the 

potential use of existing PM10-2.5 speciation sampling and analysis techniques in a pilot study to 

inform the implementation and decision-making process, and related research questions to 

inform the planning and implementation process. This document also serves as a discussion 

piece for obtaining feedback and comments on the development and implementation of a longterm PM10-2.5 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 indicator of thoracic coarse particles (PM10-2.5) to support 

continued research on particle distribution, sources, and health effects. At the same time, EPA 

also promulgated a new Federal Reference Method (FRM) for measuring the mass concentration 

of PM10-2.5 in ambient air. Although EPA is not adopting a National Ambient Air Quality 

Standard (NAAQS) for PM10-2.5 at this time, the FRM for PM10-2.5 is of value to aid in a variety 

of research studies and the development of speciation samplers capable of providing improved 

characterization and understanding of the composition of thoracic coarse particles. 

The final monitoring rule contains a requirement for PM10-2.5 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 increases the number of 

monitoring sites from ~20 to ~75 and shifts the focus from urban monitoring to both urban and 

rural monitoring locations. Manually-operated PM10-2.5 speciation samplers must operate on at 

least a 1-in-3 day schedule and be collocated with PM2.5 speciation at NCore stations. Since 
2

EPA is requiring PM10-2.5 speciation monitoring primarily for scientific purposes, it is 

appropriate to have monitoring at a variety of urban and rural locations 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 PM10-2.5 speciation data in the monitoring rule is to support 

further research in understanding the chemical composition and sources of PM10, PM10-2.5, and 

PM2.5. In addition, more specific uses for the data can be inferred and include: 

• Collection of PM10-2.5 composition data to inform health effect studies, both in 

terms of the relationship between specific PM10-2.5 species and health, and 

between PM emitted from different source types and health. 

• Advancement of PM10-2.5 speciation monitoring methods in anticipation of wider 

use under a PM10-2.5 NAAQS if one is adopted later. 

• Use of PM10-2.5 speciation data to promote advancement of source attribution 

methods. 

• Determination of spatial and temporal variations in PM10-2.5 concentrations in 

urban and rural environments. 

PM10-2.5 Speciation Measurement Issues 

The Criteria Document (CD), prepared for the previous PM NAAQS review, provides an 

overview of the current information on coarse particle formation, sources, composition, and mass 

measurement issues (U.S. EPA 2004). No clear recommendations were given for an approach to 

collecting PM10-2.5 speciation data. It was noted that “satisfactory techniques are available to 

separate fine particles from coarse particles and to collect the 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. Candidates include multistage impaction, virtual 

impaction, and difference (subtracting PM2.5 mass or composition from PM10 mass or 

composition).” 

Since the writing of the CD, the EPA Office of Research and Development (ORD) has 

conducted a multi-site field evaluation of candidate methodologies for PM10-2.5 mass (U.S. EPA 

2006b). Five PM10-2.5 measurement approaches were initially selected for study and included 
3

virtual impaction (dichotomous sampling), difference, and continuous methods. In addition to 

continuous monitoring devices, integrated 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 PM10-2.5 mass using the speciation 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 note 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 measured mass did show high correlation. The 

PM2.5, PM10-2.5 and PM10 mass comparisons of the dichotomous (dichot) sampler with FRMs in 

Phoenix, AZ showed the dichot to be 10% higher for PM2.5, 7% lower for PM10-2.5 and 4% lower 

for PM10. It was hypothesized that the higher PM2.5 dichot mass was due to coarse particle 

intrusion into the fine mode and significant measurement biases will occur only if the coarse 

fraction of PM10 appreciably exceeds the PM2.5 size fraction, as was seen in Phoenix. Mass 

comparisons in other locations (Birmingham, AL and Lindon, UT) showed very good agreement 

(≤ 4%) between the dichots and FRMs for PM2.5, PM10-2.5 and PM10. High correlations (R2 > 

0.973) were found in all cases, indicating that the response between the dichot and FRM is very 

consistent from one sampling event to another. 

Limited PM10-2.5 speciation monitoring studies have been conducted in the U.S. and most 

of these studies were conducted using the difference method. The uncertainties and 

inconsistencies between the analytical techniques used in these studies are unknown. PM10-2.5

speciation has been studied at both urban locations (Chow et al., 1996; Chow et al., 1993; Sardar 

et al., 2005, Edgerton et al., 2005) and rural IMPROVE monitoring locations (Eldred et al., 1997; 

Malm et al., 2007; Lee et al., 2007). Soil components (e.g., Si, Al, Ti, Ca, Fe, K), and organic 

carbon (OC) were consistently found to be dominant components of PM10-2.5 and the significance 

of nitrate and sulfate found was dependent on the location studied. For coarse mass in rural 

locations, Malm et al. (2007) found the soil components (61%) and particulate organic carbon 

mass (24%) to be the major components, with nitrate at 8%, elemental carbon (EC) at 1%, sea 

salt at only 2%, and sulfate as negligible. Particulate organic carbon mass was defined as OM = 

OC*1.8. In southeastern urban locations, Edgerton et al., (2005) found similar results to Malm et 

al. (2007), but also showed a significant portion (26-38%) of the reconstructed PM10-2.5 mass to 
4

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 total carbon aerosol (TC); 

ions (e.g., nitrate, sulfate, sodium, chloride); and soil components to be abundant in the PM10

fraction and in Southern California, 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 debris; and biological materials. Not all of these components can 

be measured directly through 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 with existing techniques used for PM2.5 speciation (e.g., 

sodium and chloride ion for sea salt). 

The current PM10-2.5 FRM difference method, dichotomous sampler, and current 

speciation filter-based samplers serve as logical choices for the basis of a PM10-2.5 speciation 

sampler design. A combination of filter types and analytical methods are currently being used in 

both the PM2.5 Chemical Speciation Network (CSN) and IMPROVE monitoring programs to 

collect components of PM2.5. These existing techniques can also be applied to a PM10-2.5

speciation monitoring program, but not without some complication. 

The FRMs for PM2.5 and PM10 (low-volume sampling at 16.7 Lpm) provide relatively 

precise (within ± 10%) methods for determining 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 FRM and the mass and composition of material that 

existed in the atmosphere. Measurement errors of concern for PM10 sampling include 

uncertainty in cut point tolerances, particle bounce and re-entrainment, impaction surface 

overloading, and losses to sampler internal surfaces (U.S.EPA 2004). Another measurement 

uncertainty for PM2.5 sampling is the potential for inclusion of a small fraction of coarse particles 

in the fine mass fraction under some circumstances. 

Modification of the PM2.5 speciation sampler inlets to PM10 was suggested by CASAC 

(EPA-SAB-CASAC-CON-04-005) as an option for PM10-2.5 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 PM2.5 speciation sampler 
5

(MetOne SASS) is the difference in flow rate (6.7 Lpm) from the PM2.5 and PM10 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 the volatile species and subsequent comparison of 

mass closure or reconstructed mass with the FRM total mass; however, volatility issues are most 

likely less important for PM10-2.5 particles than for PM2.5. 

PM10-2.5 FRM Difference Method 

As is the case with all PM measurement 

methods, uncertainties exist with the PM10-2.5

difference method. These include data loss if either 

the PM2.5 or the PM10 sampler fails; uncertainties in 

flow rate and filter weights (both before use and after 

collection and equilibration 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 issues, and proper implementation of field blanks. 

The viability of PM10-2.5 speciation by a difference method requires further evaluation. However, 

preliminary regression comparisons for speciation by difference and the dichot method have 

shown high correlation for predominate species. While there is currently no consensus on 

whether the mixing of PM2.5 and PM10-2.5 aerosols causes a bias in either measurement, CASAC 

mentioned the need for sampling separation and collection of filters with only coarse particles to 

avoid mixing of PM2.5 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 precision. 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-flow speciation samplers are used for PM10-2.5 by difference. 

Figure 1 - taken from EPA 2006b
6

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 dichotomous 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 earlier identified to reduce the contamination of 

coarse particles by fine particles, while maintaining low losses and sharper size cuts. Fine 

particle intrusion of 10% into the coarse mode 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 PM2.5, PM10-2.5 and PM10 mass 

comparisons of the dichotomous sampler with FRMs showed very good agreement (except in 

Phoenix) and very good correlations (U.S. EPA 2006b). 

PM10-2.5 Species or Components 

Table 1 provides a list of candidate or potential PM10-2.5 species that can be measured 

with the existing PM2.5 speciation methods. The specific species that need to be measured for 

PM10-2.5 must be identified in order to design a monitoring program. For example, ions (e.g., 

nitrate and sulfate) have been identified as only minor components of PM10-2.5 in some locations. 

It is not clear whether the resources to measure ions are needed to support research needs for 

PM10-2.5 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 PM10-2.5. If ions are not needed, then it 

would eliminate the need to collect an additional filter (nylon) and resources for an additional lab 

Figure 2 - taken from EPA 2006b 
7

analysis. In addition, the need for elements by XRF versus extractable or water soluble elements 

by ICP/MS should be determined. 

Table 1. List of Candidate PM10-2.5 Species 

Species Filter Type Denuder Analysis Method 

PM10-2.5 Gravimetric Mass Teflon None Filter weighing 

Elements: 

• Crustal or soil (Si, Al, Ti, Ca, 

Fe) 

• Several other elements 

currently measured routinely 

for PM2.5, 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 performance, enhance detection limits, and reduce 

contamination of detector sources. Use of XRF under vacuum and the loss of volatile nitrate (as 

much as 30%) have been demonstrated (U.S. EPA 2001). In the PM2.5 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 ionic species. Large or 

coarse particle size effects may also be problematic for XRF. Larger particles (greater than 3 
8

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 XRF results can be applied (Van 

Dyck et al., 1985) and these factors will have to be optimized for PM10-2.5 element analysis by 

XRF. Another issue to consider is the sensitivity of XRF and 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/Mass Spectrometry (ICP/MS). 

ICP/MS have some advantages (e.g., improved detection limits for many species but lower for 

some), but also some disadvantages which include increased cost, labor intensive sample 

preparation, the need for strong acid extraction, incomplete extraction efficiencies, and sample 

filter destruction (XRF is a non-destructive analysis). If the particle 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. 

PM10-2.5 organic and elemental carbon (OC and EC) species can be measured using the 

same thermal-optical analysis (TOA) method that is used for PM2.5 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 artifact correction method to be applied 

to the urban PM2.5 CSN is currently being evaluated and developed. Once developed, it will 

need to be evaluated for use in the PM10-2.5 program. Organic vapor denuders are not currently 

being used for either the PM2.5 CSN or IMPROVE programs. Although denuders may be 

appropriate, they are still not ready for “prime time” and may introduce negative OC artifacts 

due to the disruption of the gas-particle equilibrium during sampling. Han et al., (2007) mention 

an interference with metal oxides (e.g., iron oxides) and TOA analysis; whereby certain metal 

oxides can serve as a source of O2 in the helium atmosphere. Since the soil component of PM10-

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 PM10-2.5 and a separate 

punch from the quartz filter will have to be analyzed to quantify it. 

Biological materials (bioaerosols) are collected with the filter-based particle sampling 

techniques used for PM10-2.5 or PM2.5 monitoring and included in the OC measurement, but are 
9

not quantified separately from other components. If bioaerosol species (e.g., pollens and molds) 

need to be qualitatively or quantitatively identified for the PM10-2.5 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 qualitatively 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 bioaerosol species of interest (or 

indicator/surrogate species) need to be specified in order to explore appropriate collection and 

analysis techniques. 

Fly ash is also included in the list of PM10-2.5 constituents of interest in the CD. Like 

bioaerosols, fly ash is collected with the filter-based particle sampling techniques used for PM10-

2.5 or PM2.5, but not quantified separately from other components. If fly ash is needed for the 

PM10-2.5 speciation program, an appropriate measurement technique will need to be identified or 

developed and evaluated. Some fly ashes can be identified using the SEM analytical technique 

(U.S. EPA 2002). 

Network Design Issues 

The final monitoring rule 

contains a requirement for PM10-2.5

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 PM10-2.5 speciation given that the highest PM10-2.5 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 exposure and sites leveraged with 
10

other measurement systems (e.g., PAMS, NATTS). Since PM10-2.5 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 PM10-2.5 speciation. The spatial adequacy and 

representativeness of the NCore sites for long-term PM10-2.5 speciation monitoring will need to 

be evaluated. 

PM10-2.5 Monitoring Plan and Method Research Needs 

There are still many unanswered questions regarding PM10-2.5 speciation monitoring; 

however, a few PM10-2.5 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 cumulative effects of the imprecision in both PM2.5 and 

PM10 measurements. White (1998) showed the uncertainty in coarse mass by difference to be 

about 3 times the uncertainty in the fine measurement. An evaluation of the practicality and 

validity of PM10-2.5 speciation by difference method is needed. The CASAC comments also 

leaned toward virtual impaction and felt it had significant advantages (e.g., collects the PM10-2.5

size fraction directly). For those PM10-2.5 species that are in common with the PM2.5 speciation 

program, the existing National Laboratory Contract for PM2.5 speciation can be used to analyze 

the filters. In order to sample for the current suite of species in the PM2.5 speciation program 

(including ions) by difference, identical PM10 versions of the PM2.5 speciation sampling devices 

can be collocated with existing PM2.5 samplers. PM10 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 developing and characterizing such cyclones. A PM10

cyclone is already available for the 22 Lpm speciation carbon sampling device. The existing 

SASS sampler could be retrofitted to have two PM2.5 channels with Teflon and nylon filters and 

two PM10 channels with Teflon and nylon filters if needed. One additional PM10 speciation 

carbon sampler would need to be collocated with the existing PM2.5 sampler for OC/EC aerosol 

species. If PM10-2.5 speciation was based on the dichotomous sampler, it would require three 

samplers at each location to collect the Teflon, 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 acid. No difference in measured particle nitrate was found between a 

dichotomous sampler with no denuder and a sampler with a conventional magnesium oxide 

(MgO) denuder. If ions are on the PM10-2.5 target list, dichotomous samplers for PM10-2.5

speciation would need to be fitted with acid gas denuders for the proper collection of particlephase ions on the nylon filters if the uncoated inlet is not sufficient for acid gas capture. 

Some of the questions relevant to PM10-2.5 speciation monitoring are outlined below: 

 What are the important PM10-2.5 species to measure? 

 Are ions important PM10-2.5 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 PM10-2.5? If dichotomous samplers are used, would a denuder be needed? 

 What are the PM10-2.5 speciation sampling artifacts that may be encountered and how should they 

be addressed in the monitoring program? Is speciation by the difference method problematic for 

PM10-2.5 speciation and if so what specific issues make it problematic? 

 The current and most widely used PM2.5 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 PM10-2.5 mass or the 

dichotomous sampler (16.7 Lpm). If this sampler was configured to do PM10-2.5 by difference, 

would the 6.7 Lpm flow rate be problematic, especially with our knowledge of concerns about 

low-flow cut-points and particle intrusion, and the need to compare to what is collected by the 

PM10-2.5 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 material to obtain adequate detection limits with 

the potential methods used? 

 What analysis methods should be used? What PM2.5 speciation analysis methods are appropriate 

to also use in the PM10-2.5 speciation program? 

 Is XRF the most appropriate method for PM10-2.5 speciation? Can the complication of particle size 

and absorption effects in XRF be adequately resolved using absorption correction factors? Does 

XRF provide adequate sensitivity (detection limits) to measure elements if a dichotomous 

sampler is used? If XRF sensitivity is not adequate, should some other more sensitive and 

potentially more expensive and destructive analytical technique be considered? If an elemental 

method that has more sensitivity and applies acid extraction is needed, is the recovery of 

extractable metals adequate versus total metals by XRF? 

 Are metal oxides a significant source of interference in thermal-optical analysis (TOA) of PM10-2.5
12

for OC and EC given the large expected soil component? 

 If biological particles and fly ash need to be characterized, what specific 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 microscopy (SEM) on Teflon filters adequate to 

quantify and identify the biological material present? Is the use of other assay techniques 

necessary to adequately obtain a quantitative indicator (e.g., total protein) of the total biological 

material present? 

 When reconstructing PM10-2.5 mass using the sum of PM10-2.5 species concentrations, a significant 

portion of unidentified mass has been identified. Are there other PM10-2.5 target species or analysis 

methods that can be used to help identify the source 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 analysis methods or target species are particularly 

important to inform this issue? 

 Various sampling devices, including dichotomous samplers, MetOne SASS speciation monitors, 

PM10 and PM2.5 FRMs are potential sampling devices (with the appropriate filter types) for PM10-

2.5 speciation. Which of these sampler types should be included or excluded from the pilot 

network design? 

Additional information may be provided to inform some of the questions above when ORD 

publishes results on PM10-2.5 speciation from the multi-city field evaluation. In addition, any 

pilot monitoring program that is developed and implemented for PM10-2.5 speciation may also 

provide information to resolve some of these issues. 

Quality Assurance (QA) 

The PM10-2.5 speciation monitoring program is expected to follow similar requirements as 

specified for the PM2.5 speciation monitoring program, which include collocation for precision 

estimates and sampler flow-rate audits. PM10-2.5 species-specific goals for bias and precision 

have not been specified. Additional QA procedures and possibly DQOs will need to be 

developed for PM10-2.5 speciation. 
13

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