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Air Trends

1998 Air Trends Report - Download Graphics


Note: EPA no longer updates this information, but it may be useful as a reference or resource.

Please see www.epa.gov/airtrends for the latest information on Air Quality Trends.


Figure 2-1 Average daily maximum 1-hour CO concentrations by month, 1998.
Figure 2-2 Trend in 2nd maximum non-overlapping 8-hour average CO concentrations, 1989-1998.
Figure 2-3 Trend in 2nd maximum non-overlapping 8-hour average CO concentrations by type of location, 1989-1998.
Figure 2-4 Trend in national total CO emissions, 1989-1998.
Figure 2-5 CO emissions by source category, 1998.
Figure 2-6 Long-term trend in 2nd maximum non-overlapping 8-hour average CO concentrations, 1979-1998.
Figure 2-7 Trend in CO 2nd maximum non-overlapping 8-hour concentrations by EPA Region, 1989-1998.
Figure 2-8 Highest 2nd maximum non-overlapping 8-hour average CO concentration county, 1998.
Figure 2-9 Trend in maximum quarterly average Pb concentrations (excluding source-oriented sites), 1989-1998.
Figure 2-10 Pb maximum quarterly mean concentration trends by location (excluding point-source-oriented sites), 1989-1998.
Figure 2-11 National total Pb emissions trend, 1989-1998.
Figure 2-12 Pb emissions by source category, 1998.
Figure 2-13 Long-term ambient Pb trend, 1979-1998.
Figure 2-14 Trend in Pb maximum quarterly mean concentration by EPA Region, 1989-1998.
Figure 2-15 Pb maximum quarterly concentration in the vicinity of Pb point sources, 1998.
Figure 2-16 Highest Pb maximum quarterly mean by county, 1998.
Figure 2-17 Trend in annual NO2 mean concentrations, 1989-1998.
Figure 2-18 Trend in annual mean NO2 concentrations by type of location, 1989-1998.
Figure 2-19 Trend in national total NOx emissions, 1989-1998
Figure 2-20 NOx emissions by source category, 1998.
Figure 2-21 Long-term trend in annual mean NO2 concentrations, 1979-1998.
Figure 2-22 Trend in NO2 maximum quarterly mean concentration by EPA Region, 1989-1998.
Figure 2-23 Highest NO2 annual mean concentration by county, 1998.
Figure 2-24 Trend in annual 2nd-highest daily maximum 1-hour, and 4th-highest daily 8-hour O3 concentrations, 1989-1998.
Figure 2-25 Trend in O3 2nd maximum 1-hour concentration by EPA Region, 1989-1998.
Figure 2-26 Trend in O3 4th maximum 8-hour concentration by EPA Region, 1989-1998.
Figure 2-27 Summer 1998 statewide ranks for temperature and precipitation.
Figure 2-28 Trend in annual 2nd-highest daily maximum 1-hour O3 concentrations by location, 1989-1998.
Figure 2-29 Trend in 4th-highest 8-hour O3 based on 34 CASTNet sites in the rural eastern United States, 1989-1998.
Figure 2-30 Trend in annual 4th-highest daily maximum 8-hour O3 concentrations in National Parks, 1989-1998.
Figure 2-31 Trend in annual 2nd-highest daily maximum 1-hour O3 concentrations, 1979-1998.
Figure 2-32 Comparison of actual and meteorologically adjusted 1-hr ozone trends, 1989-1998.
Figure 2-33 Areas with PAMS networks.
Figure 2-34 The median changes in summer morning concentrations of the most abundant VOC species measured at PAMS sites.
Figure 2-35 Trend in national total anthropogenic VOC emissions, 1989-1998.
Figure 2-36 Anthropogenic VOC emissions by source category.
Figure 2-37 Highest second daily maximum 1-hour O3 concentration by county, 1998.
Figure 2-38 Highest fourth daily maximum 8-hour O3 concentration by county, 1998.
Figure 2-39 Smoke/dust over North America for May 15, 1998.
Figure 2-40 Smoke/dust over North America for May 16, 1998.
Figure 2-41 Smoke/dust over North America for May 28, 1998.
Figure 2-42 Smoke/dust over North America for June 22, 1998.
Figure 2-43 Smoke/dust over North American for June 26, 1998.
Figure 2-44 Trend in annual mean PM10 concentrations, 1989-1998.
Figure 2-45 PM10 annual mean concentration trends by location, 1989-1998.
Figure 2-46 National PM10 emissions trend, 1989-1998 (traditionally inventoried sources only).
Figure 2-47 PM10 emissions from traditionally inventoried source categories, 1998.
Figure 2-48 Total PM10 emissions by source category, 1998.
Figure 2-49 Trend in PM10 annual mean concentration by EPA Region, 1989-1998.
Figure 2-50 Highest 2nd maximum 24-hour PM10 concentration by county, 1998.
Figure 2-51 Status of new PM2.5 Monitor Deployment, based on AIRS February, 2000.
Figure 2-52 Class I Areas in the Improve Network meeting the data completeness criteria in Appendix B.
Figure 2-53 Annual average 1998 PM2.5 concentrations (in :g/m3) at IMPROVE sites and contribution by individual constituents. Pie chart sizes are scaled by annual average PM2.5 concentrations.
Figure 2-54 PM2.5 Concentrations, 1989-1998 at eastern IMPROVE sites meeting trends criteria.
Figure 2-55 PM2.5 Concentrations, 1989-1998 at western IMPROVE sites meeting trends criteria.
Figure 2-56 PM2.5 Concentrations, 1989-1998, at the Washington, D.C. IMPROVE site.
Figure 2-57 Seasonal patterns in rural PM2.5, 1998.
Figure 2-58 Trend in annual mean SO2 concentrations, 1989-1998.
Figure 2-59 Annual mean SO2 concentration by trend location, 1989-1998.
Figure 2-60 Trend in 2nd max 24-hour average SO2 concentrations, 1989-1998.
Figure 2-61 National total SO2 emissions trend, 1989-1998.
Figure 2-62 SO2 emissions by source category, 1998.
Figure 2-63 Long-term ambient SO2 trend, 1979-1998.
Figure 2-64 Trend in SO2 annual arithmetic mean concentration by EPA Region, 1989-1998.
Figure 2-65 Plants affected by Phase I of the Acid Rain Program.
Figure 2-66 Highest 2nd maximum 24-hour SO2 concentration by county, 1998.
Figure 3-1 Air Quality Index logo.
Figure 3-2 Number of days with AQI values > 100, as a percentage of 1989 value.
Figure 4-1 Location of nonattainment areas for criteria pollutants, September 1999.
Figure 4-2 Classified ozone nonattainment areas where 1-hour standard still applies.
Figure 5-1a Relative variability in VOC and aldehyde annual average concentrations among urban sites, based on 1996 ambient measurements.
Figure 5-1b Relative variability in trace metal concentrations among urban sites, based on 1996 ambient measurements.
Figure 5-1c Relative variability in trace metal concentrations among rural sites, based on 1996 ambient measurements.
Figure 5-2 Locations for urban and rural air toxics monitors with long-term data.
Figure 5-3a National trend in annual/average benzene concentrations in metropolitan areas, 1993-1998.
Figure 5-3b National trend in annual/average 1,3-butadiene concentrations in metropolitan areas, 1993-1998.
Figure 5-3c National trend in annual/average total suspended lead concentrations in metropolitan areas, 1993-1998.
Figure 5-3d National trend in annual/average styrene concentrations in metropolitan areas, 1993-1998.
Figure 5-3e National trend in annual/average tetrachloroethylene concentrations in metropolitan areas, 1993-1998.
Figure 5-3f National trend in annual/average toluene concentrations in metropolitan areas, 1993-1998.
Figure 5-4a Trend in annual average benzene concentrations for metropolitan sites in California, 1989-1998.
Figure 5-4b Trend in annual average 1,3-butadiene concentrations for metropolitan sites in California, 1989-1998.
Figure 5-4c Trend in annual average lead concentrations for metropolitan sites in California, 1989-1998.
Figure 5-4d Trend in annual average styrene concentrations for metropolitan sites in California, 1989-1998.
Figure 5-4e Trend in annual average tetrachloroethylene concentrations for metropolitan sites in California, 1989-1998.
Figure 5-4f Trend in annual average toluene concentrations for metropolitan sites in California, 1989-1998.
Figure 5-5 Trends in Annual Average Fine Particle Chromium Concentrations in Rural Areas, 1993-1998.
Figure 6-1 Images of Glacier National Park and Dolly Sods Wilderness Area.
Figure 6-2 IMPROVE sites meeting data completeness requirements.
Figure 6-3 Shenandoah National Park on clear and hazy days and the effect of adding 10 g/m3 of fine particles to each.
Figure 6-4 Long-term trend for 75th percentile light coefficient from airport visual data (July-September).
Figure 6-5a Total light extinction trends for eastern Class I areas for clearest, middle, and haziest 20 percent of the days in the distribution, 1989-1998.
Figure 6-5b Total light extinction trends for western Class I areas for clearest, middle, and haziest 20 percent of the days in the distribution, 1989-1998.
Figure 6-6a Aerosol light extinction in eastern Class I areas for the clearest 20 percent of the days in the distribution, 1989-1998.
Figure 6-6d Aerosol light extinction in western Class I areas for the clearest 20 percent of the days in the distribution, 1989-1998.
Figure 6-7a Aerosol light extinction (in Mm-1) for the clearest 20 percent days and contribution by individual particulate matter constituents, based on 1995-1997 IMPROVE data.
Figure 6-7b Aerosol light extinction (in Mm-1) for the middle 20 percent days and contribution by individual particulate matter constituents, based on 1995-1997 IMPROVE data.
Figure 6-7c Aerosol light extinction (in Mm-1) for the haziest 20 percent days and contribution by individual particulate matter constituents, based on 1995-1997 IMPROVE data.
Figure 6-8a Current visibility impairment expressed in deciviews for the clearest 20 percent days based on 1995-1997 IMPROVE data.
Figure 6-8b Current visibility impairment expressed in deciviews for the middle 20 percent days based on 1995-1997 IMPROVE data.
Figure 6-8c Current visibility impairment expressed in deciviews for the haziest 20 percent days based on 1995-1997 IMPROVE data.
Figure 7-1 The NADP/NTN Network.
Figure 7-2 Percent differences in mean annual measured sulfate concentrations as compared to projected concentrations for 1995-1996 for the eastern United States (from NADP/NTN).
Figure 7-3a Trends in wet sulfate deposition (kg/ha); 1995-1997.
Figure 7-3b Trends in wet sulfate deposition (kg/ha); 1989-1991.
Figure 7-4 CASTNet Network and subset of 34 sites used for 1989-1998 trends analysis.
Figure 7-5d1
Figure 7-5d2
Figure 7-5d3
Comparison of ambient ammonium concentrations in the rural eastern United States from CASTNet data, 1990-1991 vs. 1997-1998.
Figure 7-6 Trend in ambient sulfates in the rural eastern United States, based on CASTNet monitoring data, 1989-1998.
Figure 7-7 Trend in ambient sulfur dioxide in the rural United States, based on CASTNet monitoring data, 1989-1998.
Figure 7-8 Trend in annual average ambient sulfur dioxide and sulfate concentrations, based on CASTNet monitoring data, and regional SO2 emissions from electric utilities in rural eastern United States, 1989-1998.
Figure 7-9a Trend in annual average ambient sulfur dioxide and sulfate concentrations, based on CASTNet monitoring data, and regional SO2 emissions from electric utilities in rural eastern United States by calendar quarter, 1989-1998; quarter 1.
Figure 7-9b Trend in annual average ambient sulfur dioxide and sulfate concentrations, based on CASTNet monitoring data, and regional SO2 emissions from electric utilities in rural eastern United States by calendar quarter, 1989-1998; quarter 2.
Figure 7-9c Trend in annual average ambient sulfur dioxide and sulfate concentrations, based on CASTNet monitoring data, and regional SO2 emissions from electric utilities in rural eastern United States by calendar quarter, 1989-1998; quarter 3.
Figure 7-9d Trend in annual average ambient sulfur dioxide and sulfate concentrations, based on CASTNet monitoring data, and regional SO2 emissions from electric utilities in rural eastern United States by calendar quarter, 1989-1998; quarter 4.
Figure B-1 Carbon monoxide monitoring program, 1998.
Figure B-2 Lead monitoring program, 1998.
Figure B-3 Nitrogen dioxide monitoring program, 1998.
Figure B-4 Ozone program, 1998.
Figure B-5 PM10 monitoring program, 1998.
Figure B-6 Sulfur dioxide monitoring program, 1998.
Figure B-7 Class I Areas in the Improve Network meeting data completeness criteria.

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