| Objectives-Results: |
The U.S. National Park Service (NPS) initiated IMPROVE (Interagency Monitoring of Protected Visual Environments) (Joseph et al., 1987; Eldred et al., 1988), a regional visibility monitoring program, to evaluate visibility impairment in selected Class I areas. IMPROVE is an integrated, cooperative air quality study, jointly sponsored by NPS, U.S. EPA, U.S. Forest Service (USFS), U.S. Fish and Wildlife Service (FWS), and the Bureau of Land Management (BLM). Since 1988, two samples per week have been taken at many locations, most of which are located in non-urban Class I National Parks and Wilderness Areas that are protected from degradation of air quality and visibility. This sampling changed to every-third-day frequency to correspond with aerosol chemistry measurements that have been taken in urban areas as part of EPA’s PM2.5 Speciation Trends Network (STN) during 2000. With the promulgation of the new National Ambient Air Quality Standard (NAAQS) for PM2.5 and PM10 (U.S. EPA, 1997) and rules for regional haze (U.S. EPA, 1999), IMPROVE monitoring has developed the following additional objectives:
- Evaluate contributions from regional background and transport to excessive PM2.5 concentrations in urban areas.
- Establish a baseline (for 2001 to 2005) and monitor changes in contributions to regional haze through 2060.
The first of these new objectives requires that comparability be established between mass- and chemical measurements taken at IMPROVE sites and those measured at the STN sites. The second objective requires the application of chemical speciation methods that are consistent with previous, current, and future measurements. Organic and elemental carbon (OC and EC) fractions derived from the U.S. EPA STN method have been shown to be non-equivalent to IMPROVE carbon fractions in ambient samples. DRI has conducted more than 110,000 IMPROVE carbon analyses following the IMPROVE protocol. Eight carbon fractions (OC1, OC2, OC3, OC4, pyrolyzed OC [POC], EC1, EC2, EC3) are quantified, and the remaining filter samples are archived in a sealed container under refrigeration (~4 °C). Carbon fractions from different environments or under specific source impacts (e.g., forest fires, dust storms) can be evaluated further. DRI is planning to begin analysis of IMPROVE samples on the DRI Model 2001 thermal/optical carbon analyzer, and to report the optical pyrolysis fraction determined by both reflectance and transmittance. After receiving authorization from the IMPROVE steering committee, these archived samples can be used for additional analysis using different thermal-evolution protocols.
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