1.1 PM2.5, PM10 and PM10-2.5 Mass Networks

13

14 The 1997 promulgation of a fine particulate NAAQS (EPA, 1997) led to deployment of

15 over 1500 PM2.5 sites (about 1000 currently) used to determine whether an area complies with

16 the standard. These sites use a Federal Reference Method (FRM) or Federal Equivalent Method

17 (FEM), daily sampling over 24-hours, or every third or sixth day. Nearly 300 additional

18 measurements not meeting FRM or FEM specifications are provided by the chemical speciation

19 sites (Figure A-1). Approximately 600 stations provide indirect measurements of continuous

20 (hourly resolution) PM2.5 mass using a variety of techniques.

21

22 1.2 Interagency Monitoring of Protected Visual Environments (IMPROVE) Program

23

24 The IMPROVE network, with over 100 sites, has provided nearly a two-decade record of

25 major components of PM2.5 (sulfate, nitrate, organic and elemental carbon fractions, and trace

26 metals) in pristine areas of the United States (Figure A-1). IMPROVE is led by the National

27 Park Service; various federal and state agencies support its operations. The primary focus of the

28 network is to track visibility and trends in visibility.

29

30 1.3 PM2.5Chemical Speciation Monitoring

31

32 In addition to the IMPROVE network, over 300 EPA speciation sites were added from

33 2000 - 2002 in urban areas of the United States to assist PM2.5 assessment efforts. No FRM

34 exists for particulate speciation, which is not directly required to determine attainment, and there

35 are slight differences between monitors and methods used in the Speciation Trends Network

36 (STN). However, the network’s coverage (Figure A-1) across urban and rural areas has proved

37 essential for a wide range of research and analysis. The speciation networks typically collect a

38 24-hour sample every three, and sometimes six, days.

 

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