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. OwensDepartment of ChemistryWinthrop University, Rock Hill, SC 29733

*Current address: Department of Chemistry, Duke University, Durham, NC 27708

2

ObjectivesShow 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

3

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, ’90-00CO: May-Sep, ’93-00NOy: May-Sep, ’95-00Hydrocarbons, ’95-99 

Arrowwood O3: May-Sep, ’90-00

Power Plant Emission Monitors

(CEM)

Riverbend, AllenMarshall, Buck

NOx: May-Sep, ’96-00 

4

Traffic Locations, Monitoring Sites, & Power Plants

5

Regional NOx Sources

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)

6

Traffic SitesRoadway Tachograph Loc. Data Available

Interstate 77 SC Welcome CenterBetween Exits 88 & 90

June-August 1990-1997(Hourly data)

South Blvd (Hwy521)

Between Poindexter &Marsh @ Pepsi Plant

May-Sept 1990-1998, (7-8AM, 5-6PM, Daily)

Wilkinson Blvd (Hwy 29&74)

Remount RdIntersection

May-Sept 1990-1998,(7-8AM, 5-6PM, Daily)

Graham St. Past Railroad Tracks @ 12th St.

May-Sept 1990-1998,(7-8AM, 5-6PM, Daily)

7

I-77 Traffic Volume vs. Time of Day

0

1000

2000

3000

4000

5000

Time of Day (Hour)

Hou

rly V

olum

e

Sun Mon Tues WedThu Fri Sat

8

510152025303540

1 3 5 7 9 11 13 15 17 19 21 23Time of Day

Avg

Hou

rly N

O y

Con

cent

ratio

n (p

pb)

Sunday Monday Tuesday WednesdayThursday Friday Saturday

May-Sep ‘95-‘98 Plaza Average Hourly NOy

9

May-Sep ‘93-‘98 Plaza Average Hourly CO

200300400500600700800900

1000

1 3 5 7 9 11 13 15 17 19 21 23Time of Day (Hour)

Avg

. Hou

rly C

O

Rea

ding

(ppb

)

Sunday Monday Tuesday WednesdayThursday Friday Saturday

10

1990-1998 May-Sep Diurnal Charlotte Ozone Averages

By Day of Week (weekend days-lines, weekdays-markersCounty Line

0

0. 01

0. 02

0. 03

0. 04

0. 05

0. 06

0. 07

0. 08

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Arrowwood

0

0. 01

0. 02

0. 03

0. 04

0. 05

0. 06

0. 07

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Plaza

0

0. 01

0. 02

0. 03

0. 04

0. 05

0. 06

0. 07

1 2 3 4 5 6 7 8 9 10 11 12 13 1415 16 17 18 19 2021 22 23

11

Day of Week NOx Emissions from Four Coal-fired Plants near Charlotte

-25-20-15-10-505

101520

Sun Mon Tue Wed Thu Fri Sat

Day of Week

% D

iffer

ence

from

7-D

ay A

vera

ge

Allen

Riverbend

Marshall

Buck

12

Coal-fired Power Plant Hourly NOx Emissions by Day of Week for a Recent

Season

25.00

30.00

35.00

40.00

45.00

50.00

55.00

0 5 10 15 20

Hour of Day

Dai

ly T

ons

NO

x Em

issi

ons

Sun

Mon

Tue

Wed

Thu

Fri

Sat

13

Day of Week Variation at Fontana Urban BTEX Sampling Site

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

Sun-Thu Thu-Sat Sat-Sun

BenzeneToluenem/p-XyleneI-77 Traffic Cts

Day of Week Variation at Kennedy Urban BTEX Sampling Site

-0.3

-0.2

-0.1

0

0.1

0.2

Sun-Thu Thu-Sat Sat-Sun

Frac

tion

of D

iff fr

om 7

-Day

Avg

Benzene

Toluene

m/p-Xylene

I-77 TrafficCts

Day of Week Variation in Average Noon to Noon BTEX Levels in Charlotte Aug-Sep ’96 and May-

Aug ’97Day of Week Variation at Dilworth Urban BTEX

Sampling Site

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

Sun-Thu Thu-Sat Sat-Sun

Benzene

Toluene

m/p-Xylene

I-77 TrafficCts

14

Traffic Growth for I-77 and South Blvd Locations

0500

10001500

20002500

300035004000

1990 1991 1992 1993 1994 1995 1996 1997 1998Year

Average Hour Traffic 8:00 Traffic 18:00 Traffic

0

1000

2000

3000

4000

5000

6000

1990 1991 1992 1993 1994 1995 1996 1997

Year

15

20

22

24

26

28

30

32

1995 1996 1997 1998 1999 2000

Year

NOy C

once

ntra

tion

(ppb

)

County Plaza

300

400

500

600

700

1993 1994 1995 1996 1997 1998 1999 2000

Year

CO

Con

cent

ratio

n (p

pb)

County Plaza

7-9 AM Yearly NOy and CO Trends at County Line and Plaza

(Gar ’00) Sites

16

May-Sep Mecklenburg County Ozone Trends

0.04500

0.05000

0.05500

0.06000

0.06500

0.07000

0.07500

1990 1992 1994 1996 1998 2000Year

County Line Arrowwood Plaza

17

NOx Emission Trends from the two Coal-fired Power Plants, Allen and Riverbend, near Charlotte

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

June July Aug Jun-Aug May-Sep

Avg

Ton

s N

Ox /

Day

1996

1997

1998

1999

2000

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Long-term Trends for Allen & RB NOx Emissions, Power, and Emissions per Unit of

Power

3000.00

4000.00

5000.00

6000.00

7000.00

8000.00

9000.00

1996 1997 1998 1999 2000

NO x

em

issi

ons

+ G

igaW

att-H

ours

2.00

2.50

3.00

3.50

4.00

4.50

5.00

5.50

Lbs

NO x

/ M

egaw

att-h

r

Tons NOx emissions GigaWatt-Hours Lbs NOx/Mwt-hr

19

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

Plaza Site

0

15

30

45

60

75

90

105

120

135

PAMS Tot. Paraffins Olefins Aromatics

MIR

* C

once

ntra

tion

(ppb

C)

1995 1996 1997* 1998 1999

20

’95-’99 AM NMOC/NOy Ratios for the Plaza Monitoring Site

0

5

10

15

20

1994 1995 1996 1997 1998 1999 2000

NM

OC

/NO

y

NOx Limited

VOC Limited

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7-8 AM Within Week Fluctuations for NOy, CO and Traffic Data

0.2

0.4

0.6

0.8

1

1.2

1.4

Sun Mon Tue-Fri SatRea

ding

/ 7

Day

Ave

rage

NOy CO Traffic

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May-Sep 1990-1998 Within Week Ozone Averages for the three Mecklenburg County

Monitors

0.95

0.97

0.99

1.01

1.03

1.05

Sun Mon Tue-Fri SatRea

ding

/ 7

Day

Ave

rage

County Line Arrowwood Plaza

23

Days Traffic CO NOy Ozone Power NOx

Su/Tu-Fr 0 0 0 0.3373 0

Mo/Tu-Fr 0.7488 0.9473 0.0381 0.3484 0.0023

Sa/Tu-Fr 0 0.0012 0 0.4683 0.0025

P-Values for Day of Week Comparisons of Traffic, Ambient Pollutants, and Power Plant NOx Emissions

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ConclusionsAM 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

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ConclusionsTotal 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%.

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ConclusionsHydrocarbon Trends 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

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RecommendationsFor 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

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AcknowledgementsNorth 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)