Within-Week Variability and Long-Term Trends in Traffic, Power Plant Emissions, and Ambient CO, NOy and Ozone for the Charlotte Metropolitan Area Jennifer L. Perry* and Patrick M. Owens Department of Chemistry Winthrop University, Rock Hill, SC 29733 *Current address: Department of Chemistry, Duke University, Durham, NC 27708

Objectives Show Charlotte regional growth by traffic volumes and power plant emissions Characterize trends in NOy, CO, Hydrocarbon, and Ozone monitoring data Understand how traffic and power plant emission fluctuations within each week affect pollutant levels

Type of Data Monitoring Site Selected Data Traffic Counts Interstate I-77 Jun-Aug, 1990-1997   South Blvd, Wilkinson Blvd, Graham St. May-Sep, 1990-1997 (8-9 AM, 6-7 PM, daily) Mecklenburg County Ambient Air Monitors Plaza, County Line O3 : May-Sep, ’90-00 CO: May-Sep, ’93-00 NOy: May-Sep, ’95-00 Hydrocarbons, ’95-99 Arrowwood O3: May-Sep, ’90-00 Power Plant Emission Monitors (CEM) Riverbend, Allen Marshall, Buck NOx: May-Sep, ’96-00

Traffic Locations, Monitoring Sites, & Power Plants

Regional NOx Sources 1996 Mecklenburg County Emissions 1997 Gaston County Power Plant Emissions 12,930 tons (Allen) 3,780 tons (Riverbend) 1996 Mecklenburg County Emissions 17,295 tons (mobile sources) 687 tons (stationary sources)

Traffic Sites

I-77 Traffic Volume vs. Time of Day 5000 4000 3000 Hourly Volume 2000 1000 Time of Day (Hour) Sun Mon Tues Wed Thu Fri Sat

May-Sep ‘95-‘98 Plaza Average Hourly NOy 40 y 35 30 25 Avg Hourly NO Concentration (ppb) 20 15 10 5 1 3 5 7 9 11 13 15 17 19 21 23 Time of Day Sunday Monday Tuesday Wednesday Thursday Friday Saturday

May-Sep ‘93-‘98 Plaza Average Hourly CO 1000 900 800 700 Avg. Hourly CO Reading (ppb) 600 500 400 300 200 1 3 5 7 9 11 13 15 17 19 21 23 Time of Day (Hour) Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1990-1998 May-Sep Diurnal Charlotte Ozone Averages By Day of Week (weekend days-lines, weekdays-markers

Day of Week NOx Emissions from Four Coal-fired Plants near Charlotte 20 15 10 5 Allen % Difference from 7-Day Average -5 Riverbend -10 Marshall -15 Buck -20 -25 Sun Mon Tue Wed Thu Fri Sat Day of Week

Coal-fired Power Plant Hourly NOx Emissions by Day of Week for a Recent Season 55.00 50.00 Emissions Sun 45.00 Mon x 40.00 Tue Wed 35.00 Daily Tons NO Thu Fri 30.00 Sat 25.00 5 10 15 20 Hour of Day

Day of Week Variation in Average Noon to Noon BTEX Levels in Charlotte Aug-Sep ’96 and May-Aug ’97 Day of Week Variation at Dilworth Urban BTEX Day of Week Variation at Fontana Urban BTEX Sampling Site 0.15 Sampling Site 0.1 0.15 0.05 0.1 Benzene 0.05 Benzene Toluene -0.05 Toluene m/p-Xylene -0.05 I-77 Traffic Cts -0.1 m/p-Xylene -0.1 -0.15 I-77 Traffic -0.15 Sun-Thu Thu-Sat Sat-Sun Cts Sun-Thu Thu-Sat Sat-Sun Day of Week Variation at Kennedy Urban BTEX Sampling Site 0.2 Benzene 0.1 Toluene Fraction of Diff from 7-Day Avg m/p-Xylene -0.1 I-77 Traffic Cts -0.2 -0.3 Sun-Thu Thu-Sat Sat-Sun

Traffic Growth for I-77 and South Blvd Locations 6000 5000 4000 3000 2000 1000 4000 1990 1991 1992 1993 1994 1995 1996 1997 3500 Year 3000 2500 2000 1500 1000 500 1990 1991 1992 1993 1994 1995 1996 1997 1998 Year Average Hour Traffic 8:00 Traffic 18:00 Traffic

7-9 AM Yearly NOy and CO Trends at County Line and Plaza (Gar ’00) Sites

May-Sep Mecklenburg County Ozone Trends 0.07500 0.07000 0.06500 0.06000 0.05500 0.05000 0.04500 1990 1992 1994 1996 1998 2000 Year County Line Arrowwood Plaza

NOx Emission Trends from the two Coal-fired Power Plants, Allen and Riverbend, near Charlotte 80.00 70.00 60.00 / Day 1996 50.00 x 1997 40.00 1998 Avg Tons NO 1999 30.00 2000 20.00 10.00 0.00 June July Aug Jun-Aug May-Sep

Long-term Trends for Allen & RB NOx Emissions, Power, and Emissions per Unit of Power 9000.00 5.50 5.00 8000.00 4.50 7000.00 / Megawatt-hr emissions + GigaWatt-Hours 4.00 6000.00 3.50 x 5000.00 3.00 Lbs NO 4000.00 2.50 x NO 3000.00 2.00 1996 1997 1998 1999 2000 Tons NOx emissions GigaWatt-Hours Lbs NOx/Mwt-hr

’95-’99 AM Hydrocarbon Reactivity-weighted Concentration Trends for the Plaza Site

’95-’99 AM NMOC/NOy Ratios for the Plaza Monitoring Site 20 NO Limited x 15 y NMOC/NO 10 VOC Limited 5 1994 1995 1996 1997 1998 1999 2000

7-8 AM Within Week Fluctuations for NOy, CO and Traffic Data 1.4 1.2 1 0.8 Reading / 7 Day Average 0.6 0.4 0.2 Sun Mon Tue-Fri Sat NOy CO Traffic

May-Sep 1990-1998 Within Week Ozone Averages for the three Mecklenburg County Monitors 1.05 1.03 1.01 Reading / 7 Day Average 0.99 0.97 0.95 Sun Mon Tue-Fri Sat County Line Arrowwood Plaza

P-Values for Day of Week Comparisons of Traffic, Ambient Pollutants, and Power Plant NOx Emissions Days Traffic CO NOy Ozone Power NOx Su/Tu-Fr 0.3373 Mo/Tu-Fr 0.7488 0.9473 0.0381 0.3484 0.0023 Sa/Tu-Fr 0.0012 0.4683 0.0025

Conclusions AM CO and NOy ambient concentrations correlate well with observed traffic patterns Weekend AM levels much lower than weekdays Monday AM CO comparable to other weekdays Monday AM NOy lower than other weekdays Within week power plant NOx emissions Tues-Fri 10% above 7-day average Mon & Sat 7.5% below 7-day average Sun 19% below 7-day average Monday AM NOx lowest in week; low Monday AM NOy ambient levels may be due to this

Conclusions Total Power Plant NOx emissions from Allen and Riverbend Power Plants are stable From 1996-2000, power generated during May-Sep by the two Gaston Co. plants increased 27%. From 1996-2000, NOx emissions per unit of power decreased 20%. From 1996-2000, total NOX emissions from Allen and Riverbend increased 4%.

Conclusions Hydrocarbon Trends Ozone within week variation: From 1997-1999, average AM Hydrocarbons levels at Plaza decreased The Charlotte metropolitan region appears to be a VOC-limited area 1995-1999 Plaza AM VOC/NOy ratios are primarily between four and eight. Ozone within week variation: Weekend ozone levels in Mecklenburg County are equivalent to weekday levels

Recommendations For the city of Charlotte, implement ozone control measures that reduce ambient VOC levels Replace the use of ozone action days with practices to be implemented throughout ozone season Evaluate the use of total NOx emissions budgets for all power plants in the Charlotte region

Acknowledgements North Carolina Division of Air Quality (Steve Few, Brian Timin) Winthrop University students (Gentry Ridgeway and Steve Hudson) City of Charlotte Department of Transportation (Charles Able) South Carolina Department of Transportation (Joe Boozer) Duke Energy (Buddy Davis and Kris Knudsen)