4.1.2	PM Monitoring Networks and Measurement Techniques

4.1.2.1 TSP and PM-10: NAMS/SLAMS

Since the switch from a Total Suspended Particulates (TSP) to a PM10 standard, most national-level particulate matter monitoring is for PM10, although 530 monitors still measure TSP. PM10 monitoring locations are shown in Figure 1. Of these, 279 are designated as part of the National Air Monitoring System (NAMS) which is a subset of the 1198 State and Local Air Monitoring System (SLAMS). An additional 412 monitors classified as special purpose (or other monitoring) are reported to EPA's Aerometric Information Retrieval System (AIRS).

4.1.2.2	TSP/PM10 Sampling frequency and Instrumentation

Particulate matter currently are measured in ambient air quality monitoring networks with a variety of sampling devices, each of which corresponds to different indicators of total ambient particulate matter. These indicators can be broadly classified into Total Suspended Particulates (TSP), PM-10 and fine particles. TSP is measured with a high volume sampler (hi-vol) and generally includes particles up to 25-45 u in diameter. PM-10 represents particles which are nominally less than 10u* (* particles whose aerodynamic diameter is less than 10u) and fine particles (or PM-fine) generally represents particles whose diameter is less than 2.5u. Most of the monitoring devices are situated in urban areas and are generally population-oriented with an emphasis on determining the maximum concentrations.

At present, TSP data from XX locations are reported to EPA. The measurements represent an integrated 24-hour average concentration. For many of these sites, the primary purpose of data collection is the measurement of atmospheric lead (Pb) or other metals. In other cases, hi-vols are used as a upper bound surrogate for PM-10, i.e. in areas with low PM concentrations. In general, TSP samplers operate once every six days producing at most 61 measurements per year.

PM-10 is measured by a variety of instruments and is produced on a frequency of ranging from every sixth day to everyday. Ten samplers have been designated as reference or equivalent methods by the USEPA. These include 6 manual methods which produce an integrated 24-hour measurment and 4 automated methods which produce hourly data.*

(*reference: List of Designated Reference and Equivalent Methods, September 1995?)

Instrumentation

- every 6th day

-filter devices

-cutoffs

-component analyses discussed in 4.1.2.4

- visibility type instuments...relation to PM

[to be completed]

4.1.2.3 Fine-particulate Monitoring Networks

Very limited monitoring of fine particles has been conducted on a national scale. Our current understanding of the U.S. national fine-particle pattern arises from nonurban, regional background monitoring networks, the Interagency Monitoring of Protected Visual Environments (IMPROVE) (Sisler et al., 1993) and the Northeast States for Coordinated Air Use Management (NESCAUM) (Poirot et al., 1990, 1991). The IMPROVE network, discussed below in Section 4.1.3, represents the most comprehensive coverage of PM-fine for the contiguous U.S., although IMPROVE sites are located in rural areas and therfore miss important urban areas. In addition to measuring "visibility", IMPROVE measures various components responsible for visibility degradation, including fine particles (2.5 ) and associated chemical component analyses.	The limited amount of fine particle data reported to EPA has been produced with "dichotomous" samplers (dicot) which produce a measurement of both PM-2.5 and the coarse fraction between PM-10 and PM-2.5. A total of 20 sites have submitted these data to EPA in 1995. Other sources of PM2.5 (fine) and PM(10-2.5) (coarse) data include the California Air Resources Board (CARB) (CARB, 1995), the Harvard Six-Cities Data Base (Spengler et al., 1986b; Neas, 1996), and the Harvard Philadelphia Data Base (Koutrakis, 1995). The Inhalable Particulate Network (IPN) (IPN, 1985; Rodes and Evans, 1982) provides TSP, PM15 and PM2.5 data with only a small amount of PM10 data.

Data suitable for characterizing the daily variability in PM2.5 and PM10 are available from only one site in southwestern Philadelphia. The National Weather Service provides daily observations of visual range, which when suitably treated, can provide an indication of fine mode particle concentration. The Harvard Six Cities study obtained data for PM2.5 every other day for several years. The California Air Resources Board operates about twenty sites that collect PM2.5 and PM(10-2.5) data with a sampling frequency of every sixth day. Every sixth day data for a few sites may be found in AIRS. Because of the small number of data sets for PM2.5 and either PM(10-2.5) or PM10 levels detailed intercomparisons of the behavior of these aerosol size fractions in different regions of the United States cannot yet be made.

4.1.2.4	Fine particle monitoring methods

to be completed Sources: Chow paper; CD chapter 3

-	continuous methods

-	filter/impact/etc.

-	impact of inlets

-	chemica/physical analyses

FRM proposal