US EPA

3121718 

Technical Report 

Spatial and seasonal patterns and temporal variability of haze and its constituents in the United States. Report IV 

Debell, L; Gebhart, K; Malm, W; Pitchford, M; Schichtel, B; White, W 

2006 

Interagency Monitoring of Protected Visual Environments 

Fort Collins, CO 

290 

English 

http://vista.cira.colostate.edu/Improve/wp-content/uploads/2016/04/IMPROVE_Report_IV.pdf
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This report is the fourth in a series of periodic reports that describe the data collected by the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network. The IMPROVE program is a cooperative measurement effort between the U.S. Environmental Protection Agency (EPA), federal land management agencies, and state air agencies designed to

1. establish current visibility and aerosol conditions in mandatory Class I areas (CIAs);
2. identify chemical species and emission sources responsible for existing man-made visibility impairment;
3. document long-term trends for assessing progress towards the national visibility goal;
4. and, with the enactment of the Regional Haze Rule, provide regional haze monitoring representing all visibility-protected federal CIAs where practical.

When the IMPROVE monitoring program was initiated, it was resource and funding limited so that it was not practical to place monitoring stations at all 156 mandatory Class I areas where visibility is an important attribute. Therefore, the first IMPROVE report reflected data that were collected at only 36 sites for the time period March 1988 through February 1991. Over subsequent years the IMPROVE network evolved and a second IMPROVE report was published that covered data gathered between March 1992 and February 1995 at 43 sites. The network is now composed of 110 IMPROVE sites representative of 155 of the 156 visibility-protected federal Class I areas (national parks and wilderness areas). There are an additional ~50 IMPROVE protocol sites operated identically to the 110 IMPROVE sites but which are individually sponsored by federal, state, and tribal organizations (see Figure S.1).


This report provides a broad examination of the IMPROVE data as well as results from special field studies and data analyses conducted since the 2000 IMPROVE report. The IMPROVE data analysis includes the examination of the spatial and seasonal aerosol concentrations and composition for 159 sites from 2000 through 2004 and long-term trends for 38–49 sites, depending upon the parameter examined, using data from 1988 and 2004. A unique aspect of this report compared to previous IMPROVE reports is the inclusion of 84 sites from the EPA’s Speciated Trend Network (STN) in the spatial and seasonal pattern analyses. The STN network collects speciated aerosol data similar to the IMPROVE network, but the sites are located primarily in urban/suburban settings. Incorporation of data from these sites into the assessment permits the extension of the spatial and season aerosol patterns from the surrounding remote areas into urban areas, providing insights into the fraction of the particulate matter (PM) that is contributed by regional and local sources.

IMPROVE quality assurance (QA) procedures are continually reviewed and enhanced. During the recent network expansion (2000 to 2002), collocated monitors were installed at a number of IMPROVE sites to provide data needed to assess measurement precision. This report summarizes the current QA procedures and the results of precision estimates from collocated monitors.