Appendix N 

Contingency Measures Documentation
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TABLE OF CONTENTS 

1 Introduction .................................................................................................................................. 1

2 Region for Contingency Measures ............................................................................................... 2

3 2002 Baseline SO2 Emissions ...................................................................................................... 3

4 Contingency Measures ................................................................................................................. 5

4.1 Hickory Area Contingency Measure Reductions .............................................................. 10

4.2 Triad Area Contingency Measure Reductions ................................................................... 10

5 Conclusions ................................................................................................................................ 11

LIST OF TABLES 

Table 3-1 2002 Baseline SO2 Emissions For Hickory Region of Influence ................................. 4

Table 3-2 2002 Baseline SO2 Emissions For Triad Region of Influence...................................... 4

Table 4-1 Comparison of Modeled 2009 Emissions to Expected 2009 Emissions ........................ 7

Table 4-2 Estimated Emission Reductions Expected from Clean Smokestacks Act ...................... 8

LIST OF FIGURES 

Figure 2-1. The shaded counties represent the region where SO2 contingency measures were 

considered for the Hickory nonattainment area. ..................................................................... 2

Figure 2-2. The shaded counties represent the region where SO2 contingency measures were 

considered for the Triad nonattainment area........................................................................... 3

Figure 4-1. Location of the Utilities Subject to the CSA. .............................................................. 9

Figure 4-2. Back Trajectory Analysis for Hickory PM2.5 Monitor. ............................................... 9

Figure 4-3. Back Trajectory Analysis for Lexington PM2.5 Monitor........................................... 10
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1 Introduction 

Section 172(c)(9) requires that the nonattainment State Implementation Plan (SIP) contain 

specific measures that would take effect upon a State’s failure to attain the fine particulate matter 

(PM2.5) standard in a given area. These contingency measures must be fully adopted rules or 

control measures that are ready to be implemented quickly upon failure to meet the standard by 

the attainment date. Additionally, the contingency measures must be beyond the modeled 

controls needed to demonstrate attainment of the standard. Finally, the SIP should contain 

trigger mechanisms for the contingency measures, specify a schedule for implementation, and 

indicate that the measures will be implemented without further action by the State or by the 

United States Environmental Protection Agency (USEPA). 

In the April 25, 2007, Clean Air Fine Particle Implementation Rule (72 FR 20586), the USEPA 

stated that the measures should provide for emission reductions equivalent to about one year of 

reductions needed for Reasonable Further Progress (RFP). However, since North Carolina is 

able to model attainment of the PM2.5 National Ambient Air Quality Standard (NAAQS) within 

five years of designation, RFP is not required. The USEPA’s guidance to the North Carolina 

Division of Air Quality (NCDAQ) was to have contingency measures that amounted to oneseventh of the emission reductions that occurred between the base year 2002 and the attainment 

year 2009, or approximately one year’s worth of emission reductions. 

The NCDAQ modeled the emission reductions that occurred as a result of the North Carolina 

Clean Smokestacks Act (CSA) legislation, which requires coal-fired power plants in North 

Carolina to reduce annual sulfur dioxide (SO2) emissions by 49% by 2009 and by 74% by 2013 

and to reduce the annual nitrogen oxides (NOx) emissions by 78% by 2009. These emission 

reductions went well beyond what was needed to attain the annual PM2.5 NAAQS of 15.0 

microgram per cubic meter (μg/m3), evident by the predicted future design values being over 

1.5 μg/m3

 below the PM2.5 NAAQS. Therefore, the NCDAQ thought it was unreasonable to 

require contingency measures of such a large quantity when the State had already reduced a 

significant amount of the precursor pollutants throughout the State. 

Another suggestion by the USEPA was to do sensitivity modeling to determine approximately 

the level of emission reductions needed to model 15.0 μg/m3

 and use one-seventh of this 

emission reduction level to determine the amount of contingency measures needed. The 

NCDAQ did not believe it was a wise use of State resources to perform further modeling when 

both nonattainment areas have already attained the annual PM2.5 NAAQS. 

Therefore, the NCDAQ has documented the expected 2009 utility emissions, based on the latest 

CSA compliance plans, which go beyond what was modeled in the attainment demonstration, as 

well as the estimated emission reductions expected in 2010. All of these emission reductions 

will take place without further action from the State. Since the purpose of the contingency 

measures is to provide for the implementation of measures in the event an area fails to attain the 

NAAQS, the NCDAQ believes it has met the spirit of this requirement. 
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2 Region for Contingency Measures 

Since the most significant man-made emissions contributor to PM2.5 formation in North Carolina 

is the precursor pollutant SO2, the NCDAQ has elected to have only SO2 contingency measures. 

Under the section for RFP in the Implementation Rule, geographic coverage of emission sources 

is discussed (72 FR 20636). Due to the regional nature of PM2.5, it makes senses that sources of 

SO2 outside of the nonattainment area may be impacting the PM2.5 concentrations in the 

nonattainment area. Therefore, the USEPA is allowing states to consider emission reductions 

from emission sources up to 200 kilometer (km) beyond the nonattainment area for contingency 

measures. The NCDAQ has elected to go beyond the nonattainment areas for its contingency 

measure plan. 

For the Hickory nonattainment area’s contingency measures, the NCDAQ has elected to include 

all counties that are within, or bisected by, a 75 km circle from the nonattainment area boundary. 

Figure 2-1 displays the region that contingency measures are being considered for the Hickory 

nonattainment area. The yellow and blue lines represents a 75 km and 200 km radius, 

respectively, from the nonattainment area boundary. The emissions from all counties that are 

shaded are considered in the analysis. For simplicity, these counties will be referred to as the 

region of influence for the Hickory nonattainment area. 

Figure 2-1. The shaded counties represent the region where SO2 contingency measures 

were considered for the Hickory nonattainment area. 
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Similarly, for the Greensboro/Winston-Salem/High Point nonattainment area (referred to as the 

Triad area), all counties within, or bisected by, a 75 km circle from the nonattainment area 

boundary are considered for contingency measures. Figure 2-2 displays the region that 

contingency measures are being considered for the Triad nonattainment area. Again, the yellow 

and blue lines represents a 75 km and 200 km radius, respectively, from the nonattainment area 

boundary. The emissions from all counties that are shaded are considered in the analysis. For 

simplicity, these counties will be referred to as the region of influence for the Triad 

nonattainment area. 

Figure 2-2. The shaded counties represent the region where SO2 contingency measures 

were considered for the Triad nonattainment area. 

3 2002 Baseline SO2 Emissions 

Table 3-1 displays the 2002 baseline SO2 emissions, by source sector, for the counties located 

within the region of influence for the Hickory nonattainment area. The total 2002 baseline SO2

emissions for the region of influence is 215,080 tons per year. Table 3-2 displays the 2002 

baseline SO2 emissions, by source sector, for the counties located within the region of influence 

for the Triad nonattainment area. The total 2002 baseline SO2 emissions for the region of 

influence is 401,290 tons per year. 
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Table 3-1 2002 Baseline SO2 Emissions For Hickory Region of Influence 

County Point Non-road 

Mobile Area Highway Mobile 

Alexander 4.0 17.4 23.5 28.2

Alleghany 0.3 8.8 13.0 10.7

Ashe 22.0 16.8 31.1 29.2

Avery 12.2 15.7 43.7 24.3

Buncombe 17,031.5 137.5 235.0 278.4

Burke 242.3 36.9 70.5 166.6

Cabarrus 2,081.4 126.9 57.0 233.2

Caldwell 37.8 34.3 56.9 101.5

Catawba 82,371.7 99.7 91.5 259.8

Cleveland 172.4 54.6 88.9 119.8

Davidson 408.0 101.7 97.5 229.9

Davie 16.0 24.3 24.7 75.4

Forsyth 3,784.3 157.6 244.0 455.3

Gaston 54,597.3 106.2 90.8 296.1

Henderson 1.7 58.2 62.2 105.4

Iredell 539.6 102.4 108.2 323.6

Lincoln 17.8 42.5 68.5 90.4

Mc Dowell 50.7 55.5 32.2 88.9

Mecklenburg 867.7 836.8 356.5 1,122.0

Mitchell 23.6 42.9 21.1 16.2

Polk 1.2 11.1 28.2 41.7

Rowan 10,600.6 86.6 116.1 229.0

Rutherford 29,902.4 45.0 47.3 71.8

Stanly 1,654.0 39.2 40.9 92.0

Surry 320.5 36.2 55.2 125.5

Union 169.1 187.0 62.5 170.7

Watauga 40.1 46.3 85.0 47.6

Wilkes 95.1 26.6 83.8 82.6

Yadkin 7.0 21.3 28.2 72.0

Yancey 5.3 26.6 29.5 18.9

Total 205,077.6 2,602.6 2,393.5 5,006.7 

Table 3-2 2002 Baseline SO2 Emissions For Triad Region of Influence 

County Point Non-road 

Mobile Area Highway Mobile 

Alamance 23.9 77.2 75.6 210.8 

Alexander 4.0 17.4 23.5 28.2 

Alleghany 0.3 8.8 13.0 10.7 

Anson 172.1 36.8 20.3 39.4 
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Table 3-2 2002 Baseline SO2 Emissions For Triad Region of Influence 

County Point Non-road 

Mobile Area Highway Mobile 

Cabarrus 2,081.4 126.9 57.0 233.2 

Caswell 0.0 17.4 18.9 27.1 

Catawba 82,371.7 99.7 91.5 259.8 

Chatham 11,871.7 55.2 42.3 99.9 

Davidson 408.0 101.7 97.5 229.9 

Davie 16.0 24.3 24.7 75.4 

Durham 593.3 215.6 117.3 337.8 

Forsyth 3,784.3 157.6 244.0 455.3 

Gaston 54,597.3 106.2 90.8 296.1 

Granville 1.5 49.6 33.6 117.6 

Guilford 282.2 376.3 231.8 675.2 

Harnett 0.0 72.4 62.1 107.0 

Iredell 539.6 102.4 108.2 323.6 

Lee 90.7 45.3 31.1 64.8 

Lincoln 17.8 42.5 68.5 90.4 

Mecklenburg 867.7 836.8 356.5 1,122.0 

Montgomery 54.2 18.8 31.8 46.8 

Moore 14.7 48.9 54.3 87.1 

Orange 148.6 96.0 122.9 247.7 

Person 126,780.3 23.2 40.8 33.8 

Randolph 3.0 66.4 88.1 218.2 

Richmond 64.8 47.4 37.9 65.5 

Rockingham 5,290.8 56.4 66.6 109.3 

Rowan 10,600.6 86.6 116.1 229.0 

Scotland 252.1 31.9 46.1 48.0 

Stanly 1,654.0 39.2 40.9 92.0 

Stokes 83,483.9 24.7 45.8 43.9 

Surry 320.5 36.2 55.2 125.5 

Union 169.1 187.0 62.5 170.7 

Wake 76.4 657.4 346.1 961.5 

Wilkes 95.1 26.6 83.8 82.6 

Yadkin 7.0 21.3 28.2 72.0 

Total 386,738.6 4,038.1 3,075.3 7,437.8 

4 Contingency Measures 

As stated above, the NCDAQ has elected to have only SO2 contingency measures. As can be 

seen in Tables 3-1 and 3-2, the vast majority of the SO2 emissions come from point sources 
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(approximately 96%). Therefore, the NCDAQ only looked at the point source sector for 

emissions reductions, and specifically the coal-fired power plants since they make up the 

majority of the point source SO2 emissions. 

In June 2002, the North Carolina General Assembly enacted the CSA, requiring coal-fired power 

plants to reduce annual SO2 emissions by 49% by 2009 and 74% by 2013. Additionally, this 

legislation required reductions in annual nitrogen oxide emissions. One of the first state laws of 

its kind in the nation, this legislation provides a model for other states in controlling multiple air 

pollutants from older coal-fired power plants. The reduction in emissions achieved through the 

CSA are not allowed to be traded in the National emissions trading program, but rather are held 

in trust by the citizens of North Carolina. 

Since the first phase-in year is 2009, which coincides with the attainment year for the PM2.5

nonattainment areas, some of the SO2 reductions expected from the CSA were modeled as part of 

the attainment demonstration. However, not all of the units expecting to have controls 

operational in 2009 were modeled at full compliance. Additionally, one facility’s controls will 

be fully implemented during the middle of 2010. Since these additional emission reductions 

were not modeled as part of the attainment demonstrations and will take place in 2010 without 

further action from the State or the USEPA, they can be considered as contingency measures. 

Additionally, when the attainment demonstration modeling project started, the latest compliance 

plan for CSA was the 2006 plan. The utility companies now have a better understanding of what 

the SO2 emissions will be in 2009 and are reflected in the 2009 CSA compliance plan. The 

difference between the emissions modeled and the current expectations for the 2009 emissions 

are further emission reductions that are expected to occur that were not modeled as part of the 

attainment demonstration. 

All the Duke Energy and Progress Energy units that are in the area of influence for both 

nonattainment areas were reviewed to determine the difference in the 2009 emissions modeled 

and the current expectation based on the latest CSA compliance plan. The units that were 

considered for the analysis of emission reductions to occur in 2010 include: 

• Duke Energy Allen Steam Station, units 1 through 5, located in Gaston County; 

• Duke Energy Cliffside, unit 5, located in Rutherford County; and 

• Progress Energy Mayo, unit 1, located in Person County. 

The table below shows the 2009 emissions modeled based on the 2006 CSA compliance plan, 

the expected 2009 emissions based on the latest CSA compliance plan and the difference 

between them. The 2006 CSA compliance plan is attached to this appendix and the 2009 CSA 

compliance plan can be found in Appendix M. 
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Table 4-1 Comparison of Modeled 2009 Emissions to Expected 2009 Emissions 

Unit Area of Influence 2009 Modeled 

Emissions 

Expected 2009 

Emissions Difference 

Duke Energy Facilities 

Allen Unit 1 

Both Areas 

2,659 1,336 -1,323 

Allen Unit 2 2,488 1,842 -646 

Allen Unit 3 9,864 5,694 -4,170 

Allen Unit 4 10,746 6,556 -4,190 

Allen Unit 5 4,215 4,333 118 

Belews Unit 1 Triad Area 5,927 5,476 -451 

Belews Unit 2 4,579 4,535 -44 

Buck Unit 3 Both Areas 1,542 1,017 -525 

Buck Unit 4 983 642 -341 

Buck Unit 5 Both Areas 4,412 4,472 60 

Buck Unit 6 4,410 4,784 374 

Dan River Unit 1 

Triad Area 

2,184 1,919 -265 

Dan River Unit 2 2,336 2,081 -255 

Dan River Unit 3 5,202 5,062 -140 

Cliffside Unit 1 

Hickory Area 

1,170 488 -682 

Cliffside Unit 2 1,198 469 -729 

Cliffside Unit 3 2,243 1,385 -858 

Cliffside Unit 4 2,213 1,414 -799 

Cliffside Unit 5 31,193 28,476 -2717 

Marshall Unit 1 

Both Areas 

1,952 1,742 -210 

Marshall Unit 2 1,940 1,742 -198 

Marshall Unit 3 3,539 3,439 -100 

Marshall Unit 4 3,333 3,354 21 

Riverbend Unit 4 

Both Areas 

3,635 3,344 -291 

Riverbend Unit 5 3,641 3,219 -422 

Riverbend Unit 6 5,799 5,320 -479 

Riverbend Unit 7 5,942 5,260 -682 

Progress Energy Facilities 

Asheville Unit 1 Hickory Area 864 1,003 139 

Asheville Unit 2 886 770 -116 

Cape Fear Unit 5 Triad Area 6,249 4,829 -1,420 

Cape Fear Unit 6 7,725 6,705 -1,020 

Mayo Unit 1 Triad Area 14,361 5,232 -9,129 

Roxboro Unit 1 

Triad Area 

1,741 1,341 -400 

Roxboro Unit 2 2,853 2,687 -166 

Roxboro Unit 3 2,928 2,716 -212 

Roxboro Unit 4 2,363 3,120 757 

Total Emissions 169,315 137,804 -31511 
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This difference of 31,511 tons per year of SO2 emissions represents emissions that were not 

modeled but are expected to occur in 2009 within the area of influences of the two nonattainment 

areas combined. The expected versus modeled SO2 emissions will be 25,749 tons per year lower 

within the Triad’s area of influence and 18,766 tons per year lower within the Hickory’s area of 

influence. 

To estimate the additional amount of SO2 emissions that will be reduced in 2010, the 2009 

annual SO2 emissions that were listed in the 2009 CSA compliance plan were subtracted from 

the 2013 annual emissions. For the unit that the control equipment is expected to come on-line 

in the middle of 2010, only a half-year compliance was considered, i.e., half of the controlled 

emissions plus half of the uncontrolled emissions. The 2013 annual emissions represent full 

implementation of the control measures and is a conservative surrogate for estimating 2010 SO2

emissions since 2013 energy demands will be higher than 2010 and therefore the expected 

emissions for 2013 will be slightly higher than 2010. Table 4-2 displays the expected 

compliance period, the expected 2009 emissions, the estimated 2010 emissions, area impacted 

and the estimated emission reductions for the units considered for the contingency measures. 

Table 4-2 Estimated Emission Reductions Expected from Clean Smokestacks Act 

Unit Compliance 

Period 

Area of 

Influence 

2009 SO2 

(tons/year) 

2010 SO2 

(tons/year) 

Reductions 

(tons/year) 

Allen –1 Early 2009 

Both areas 

1,336 660 - 676 

Allen – 2 Early 2009 1,842 644 -1,198 

Allen – 3 Late 2009 5,694 1,239 -4,455 

Allen – 4 Late 2009 6,556 1,321 -5,235 

Allen – 5 Mid 2009 4,333 1,134 -3,199 

Cliffside – 5 Mid 2010 Hickory 28,476 15,667 -12,809 

Mayo – 1 Late 2009 Triad 5,232 1,969 -3,263 

To demonstrate that the expected emission reductions have an impact on the nonattainment 

areas, the NCDAQ relied on the back trajectory analysis that was done for the PM2.5

nonattainment boundary recommendation package. For the details of how these trajectory 

analyses were created, please refer to the documentation used for the boundary recommendation 

package attached to this appendix. 

Figure 4-1 displays the location of the utilities subject to the CSA. Figures 4-2 and 4-3 displays 

the back trajectory analysis for the Hickory and Lexington PM2.5 monitors, respectively. The 

back trajectories were overlaid on a map with the utility locations displayed with red dots. It is 

clear from these figures that the air masses pass over or near large utility plants on days when 

high PM2.5 levels were observed at the monitors. 
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Figure 4-1. Location of the Utilities Subject to the CSA. 

Figure 4-2. Back Trajectory Analysis for Hickory PM2.5 Monitor. 
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Figure 4-3. Back Trajectory Analysis for Lexington PM2.5 Monitor. 

4.1 Hickory Area Contingency Measure Reductions 

In order to estimate the total emission reductions from point sources in 2010, the other point 

sources located within the region of influence had to be grown from 2009 to 2010. The NCDAQ 

estimated that the other point sources within the region of influence would grow approximately 

50 tons. 

The total reduction that is expected beyond the emissions that were modeled in the attainment 

demonstration is 18,766 tons in 2009 emissions and approximately 27,500 tons per year that are 

expected to occur between 2009 and 2010, for a total of over 46,000 tons per year of SO2

emissions reduced. This is approximately a twenty-two percent reduction from the 2002 baseline 

SO2 emissions for the Hickory region of influence, which is a significant reduction of emissions. 

This reduction in emissions beyond what was modeled should satisfy the contingency measure 

requirement for this nonattainment area. 

4.2 Triad Area Contingency Measure Reductions 

Again, in order to estimate the total emission reductions from point sources in 2010 for the Triad 

region of influence, the other point sources located within the region of influences had to be 

grown from 2009 to 2010. The NCDAQ estimated that the other point sources within the region 

of influence would grow approximately 85 tons. 
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The total reduction that is expected beyond the emissions that were modeled in the attainment 

demonstration is 25,749 tons in 2009 emissions and approximately 18,000 tons per year that are 

expected to occur between 2009 and 2010, for a total of over 43,000 tons per year of SO2

emissions reduced. This is approximately an eleven percent reduction from the 2002 baseline 

SO2 emissions for the Triad area of influence, which again is a significant reduction of 

emissions. This reduction in emissions beyond what was modeled should satisfy the contingency 

measure requirement for this nonattainment area. 

5 Conclusions 

The NCDAQ believes that existing control measures required by the North Carolina Clean 

Smokestacks Act results in a sufficient amount of SO2 emission reductions to adequately meet 

the contingency measure requirements of Section 172(c)(9). The Hickory area is expected to 

achieve over 46,000 tons per year of SO2 reduction and the Triad area is expected to achieve 

over 43,000 tons per year SO2 reductions. Considering the purpose of contingency measures is 

to require further emission reductions in case a nonattainment area does not attain the NAAQS 

by the prescribed attainment date and both nonattainment areas in have already attained the 

PM2.5 NAAQS, the NCDAQ firmly believes that North Carolina has more than fulfilled the 

contingency measure requirement. 
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Attachment 1 

2006 Clean Smokestacks Act Compliance Plan 
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Catawba and Davidson Counties HYSPLIT Back-Trajectory Analysis 

to Determine PM2.5 Source Regions 

Michael A. Abraczinskas, K. Wyat Appel, George M. Bridgers, Scott A. Jackson 

North Carolina Division of Air Quality 

Raleigh, NC 

March 8, 2004 

1. Introduction 

The purpose of this analysis is to access the source regions, in particular according to 

state boundaries, which contribute significantly to elevated daily Fine Particulate Matter 

(PM2.5) levels in North Carolina. The North Carolina Division of Air Quality (NC DAQ) 

has identified a specific need to know the regions, specifically according to state 

boundaries, which contribute significantly to primary and secondary PM2.5 in North 

Carolina. The Environmental Protection Agency (EPA) has established standards for 

PM2.5 at 15 μg/m3

 for the annual standard and 65 μg/m3 for the 24-hour standard. 

2. Methodology 

An analysis of the National Oceanic and Atmospheric Administration Air Resource 

Laboratory (NOAA ARL) HYbrid Single-Particle Lagrangian Integrated Trajectory 

(HYSPLIT; Draxler and Rolph, 2003) model back trajectories was performed in order to 

access the sources that contribute to elevated PM2.5 levels in North Carolina. An analysis 

of observed 24-hour average PM2.5 values throughout from North Carolina’s PM2.5 

monitor network determined that the two monitors with the highest annual PM2.5 values 

in North Carolina are located in Catawba and Davidson Counties. The monitors located 

in these counties are Federal Reference Method (FRM) monitors and sample PM2.5 every 

three days. Because these monitors had the two highest annual-average PM2.5 values, the 

monitors located in these two counties were chosen as the endpoints for the HYSPLIT 

back trajectories. The specific location of Catawba County monitor is 35.73°N, 

81.36°W, while the Davidson County monitor is located at 35.81°N, 80.26°W. 

 

PM2.5 data from January 1, 1999 through June 30, 2002 was analyzed to identify days 

when the 24-hour average PM2.5 value was greater than or equal to 27.9 μg/m3

. This 

concentration was chosen since it represents the midpoint of the yellow AQI range 

(15.5μg/m3 – 40.4μg/m3

) for PM2.5, and conversations with EPA representatives have 

indicated that values above this point could pose a significant health risk. From the three 

and half years of available PM2.5 data from those two monitors, there were a total of 41 

days from the Catawba County monitor and 32 days from the Davidson County monitor 

where the 24-hour average PM2.5 value was greater than or equal to 27.9 μg/m3

. The 

dates and observed 24-hour average PM2.5 of these days are shown in Table 1. 

For the days indicated above, HYSPLIT back trajectories were run. Thirty-six hour back 

trajectories ending at 17UTC, noon Eastern Daylight Time, were run separately for each 

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monitor using the model vertical velocity option. The trajectories were run at three 

separate heights, specifically 10, 300 and 1000 meters above ground level (AGL). The 

10 and 300-meter trajectory levels are heights of lower level circulations, while the 1000-

meter trajectory level represents the top of the mixed layer and is generally a transport 

level. The choice of these levels is based on the experience of NC DAQ meteorologists, 

who use the HYSPLIT model trajectories as a routine part of their ozone and PM2.5

forecast process. 17UTC (Noon EDT) was chosen as the ending time of the trajectories 

because it represents a time when significant mixing of the boundary and residual layers 

has occurred, but significant contributions from local-secondary production has not 

occurred. 

 

3. Results 

Table 1 shows the results of the analysis of the back trajectories. Columns 4 and 5 in 

Table 1 identify the primary and secondary source regions. The primary source region 

identifies the most significant region(s) contributing to the PM2.5 in that county on that 

day, as determined by the meteorologists. The secondary source region identifies a 

region(s) that, while is not a primary contributor, does appear to contribute to a 

significant portion of the PM2.5 on that day. Note that while there is always a primary 

source identified for a given day, there may not be secondary source identified. 

Figures 1-4 show composites of the back trajectories originating from the Catawba 

County site at 10, 300, and 1000 meters AGL for those days when PM2.5 concentrations 

were high. Note that the trajectories are relatively short, indicating regional stagnation 

and recirculation. Figures 5-8 show similar composites for the Davidson County site. 

Analysis of the HYSPLIT back trajectories showed that on the majority of the days the 

primary source region of the back trajectory was North Carolina. Table 2 shows the 

distribution of both primary and secondary source regions for the trajectories for both 

Catawba and Davidson counties. Of the 41 days for which back trajectories were run for 

the Catawba County monitor, 31 (76%) of them were considered to have North Carolina 

as the primary source region (Figure 9). Tennessee and Virginia were considered to be 

primary sources on 9 (22%) and 6 (15%) days, respectively. Significant secondary 

sources were South Carolina, Tennessee, and Georgia, which contributed on 9 (22%), 8 

(20%), and 7 (17%) days respectively (Figure 10). Figure 11 shows the percent of the 

days in which each region was identified as either a primary or secondary source, or both. 

There were 27 (66%) days when North Carolina was identified to be the only primary 

source region, while there were 4 (10 %) days when North Carolina and another state(s) 

was identified to be the source region, and 10 (24%) days when North Carolina was not 

identified as part of the source region. This result is significant, since it indicates that 

nearly 35 percent of the days when PM2.5 was greater than or equal to 27.9 μg/m3

, backtrajectory analysis indicates transport from neighboring states, in particular Tennessee, 

Virginia, Georgia and South Carolina. 

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For the Davidson county monitor, 26 (81%) of the 31 days for which the trajectories were 

run indicated North Carolina as the primary source (Table 2, Figure 12). Note that there 

was one day for which a trajectory could not be run due to missing data. Other 

significant primary sources were Virginia, with 7 (23%) days, and South Carolina and 

Tennessee, each with 4 (13%) days. Significant secondary sources were South Carolina, 

Tennessee, and Virginia, each with 5 (16%) days, and Ohio with 4 (13%) days (Figure 

13). Of the 31 days for which the back trajectories were run, 17 (55%) of them indicated 

North Carolina as the only primary source region, while on 14 (45%) days trajectories 

indicated another state as the primary source region. As with the Catawba County 

analysis, there were a significant percentage of days when trajectory analysis indicates 

transport from neighboring states on days when PM2.5 was greater than or equal to 27.9 

μg/m3

. The percent of days in which each region contributed as a primary or secondary 

source (or both), is shown in Figure 14. 

Another interesting analysis is examining the 24-hour average PM2.5 value and the 

associated primary source region. The trajectories run for each monitor were divided into 

an upper third, a middle third, and a lower third based on the observed PM2.5 

concentration. For the Catawba County monitor the upper third consists of a PM2.5 range 

between 32.8 and 54.7 μg/m3

, the middle third from 30.0 and 32.7 μg/m3, and the lower 

third from 28.1 to 29.6 μg/m3

. Note that there are 14 days included in the upper and 

middle thirds, and only 13 days included in the bottom third (Tables 3-5). 

For the upper third of the days for the Catawba County monitor site, North Carolina was 

the primary source on 10 days, followed by Tennessee and Virginia with 2 days each. 

South Carolina, Tennessee, Virginia and Georgia are common secondary source regions. 

For total days (primary and secondary combined), North Carolina was identified on 10 

days, followed by Tennessee on 5 days and South Carolina, Virginia, and Georgia each 

on 3 days. The results for the middle and lower third of the days are similar to those for 

the upper third. The same analysis for the Davidson County monitor site yields similar 

results. Note also that 11 days are included in the upper and middle thirds, while only 10 

days are included in the bottom third. 

Another analysis that was performed using the back trajectories was to quantify the 

residence time that the trajectories spent in each state, other than North Carolina. This 

was accomplished by analyzing each trajectory individually and recording the amount of 

time the trajectory spent in each individual state. Since trajectories were run at multiple 

heights, to avoid double counting, only the maximum time that all trajectory heights 

spent in any one state are reported. Obviously, since the end points of the trajectories are 

within North Carolina, some time for each trajectory must be spent in North Carolina. 

The results of the analysis for Davidson and Catawba counties are shown in Tables 6 and 

7 respectively. Note that this analysis contains seven events in 2002 for Catawba County 

and four events in 2002 for Davidson County that are not included in the previous 

analysis of the trajectories. 

For Catawba County, the maximum number of hours the trajectories spent in another 

state for all events was 258 in Tennessee (recall that an event is a day where the PM2.5 

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concentration exceeded 27.9 μg/m3

 at the monitor in that county). This represents 15.6 

percent of the total trajectory time (36 hours/event * 46 events = 1656), with an average 

of 18.4 hours per event. The average represents the average hours the trajectory spent in 

each state for only those events where the trajectory spent at least some amount of time in 

the state (zero hour events are not included in the average). Other results include 207 

hours (12.5% of total) for South Carolina, with an average of 18.8 hours per event, and 

201 hours (12.1% of total) for Kentucky, with an average of 14.4 hours per event. 

For Davidson County, the maximum number of hours the trajectories spent in another 

state for all events was 278 in South Carolina. This was 22.7 percent of the total 

trajectory time (36 hours/event * 34 days), with an average of 19.9 hours spent in South 

Carolina for each event. Virginia had a total of 275 hours (22.5% of total) with an 

average of 14.5 hours per event. Tennessee had a total of 166 hours (13.6 % of total) 

with an average of 15.1 hours per event. 

 

4. Discussion 

 

Analysis of HYSPLIT back trajectories from two PM2.5 monitor locations in North 

Carolina on days when 24-hour average PM2.5 levels were 27.9 μg/m3

 or greater indicates 

that while North Carolina is the primary source region for the majority of those days, 

states neighboring and near North Carolina (including Kentucky, West Virginia, and 

Ohio) were shown through the trajectory analysis to be potential sources of transported 

pollution. Back trajectories run from points in Catawba and Davidson Counties in North 

Carolina show a significant percentage of days for which neighboring states could be 

considered primary sources for transported pollution. Significant secondary states include 

South Carolina, Tennessee, and Virginia. Other states with slightly fewer days when 

back trajectories indicated potential transport include Georgia, Kentucky, and the Ohio 

Valley. 

REFERENCES 

Draxler, R.R. and Rolph, G.D., 2003. HYSPLIT (HYbrid Single-Particle Lagrangian 

Integrated Trajectory) Model access via NOAA ARL READY Website 

(http://www.arl.noaa.gov/ready/hysplit4.html). NOAA Air Resources Laboratory, Silver 

Spring, MD. 

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County Date PM 2.5 Primary Secondary Notes

Davidson 1/1/2000 46.8 NC (Millenium Celebration) Low: NC (calm conditions) and CLT; Mid and Upper: Upstate SC and GA

Davidson 8/13/1999 44.8 NC / SC Low: NC and Eastern SC; Mid: SC and NC; Upper: NC and Upstate SC

Davidson 6/21/2001 41.6 NC Central SC Low and Mid: NC and Central SC; Upper: NC, Northeast TN and SW Virginia (minor)

Davidson 7/23/1999 40.5 E. KY, SW. VA Ohio Valley Low and Mid: SW Virginia and E. KY; Upper: long transport from Ohio ValleyDavidson 1/5/2002 39.2 NC / TN Low: NC and NE TN; Mid: NC and Eastern TN; Upper: TNDavidson 7/17/1999 38.9 NC Central SC Low: NC (CLT); Mid: NC and SC; Upper: NC and SW Virginia

Davidson 12/11/2000 38.7 Missing DataDavidson 10/21/2000 37.7 SW. VA / E. TN NC Low: NC and Upstate SC; Mid: Eastern TN: Upper: SW VA and Eastern TNDavidson 7/18/2001 37.7 NC / SC SE. TN / N. GA Low: SC and some NC; Mid: NC and Northern GA; Upper: NC, Eastern TN, N. GA

Davidson 7/5/1999 36.6 NC Eastern TN (significant) Low: All in NC; Mid: Origin in NE TN; Upper: Crosses KY, WV, VA

Davidson 6/2/2000 34.9 NC Eastern TN Missing Data

Davidson 6/29/2000 34.1 NC / N. GA / N. SC Aloft from Ohio Valley Low: NC, SC, and GA; Mid: NC and GA (ATL); Upper: Ohio ValleyDavidson 8/7/1999 33.8 NC SW. VA Low: NC; Mid: NC and SW VA; Upper: NC (CLT)

Davidson 7/2/2000 32.7 NC (CLT) North Central SC Low: Completely in NC; Mid: NC and Upstate SC; Upper: NC and Upstate SC

Davidson 8/28/1999 32.1 NC SW. VA (less sig) Low: NC; Mid: NC and SW VA; Upper NC and SW VADavidson 11/11/1999 31.8 TN Low, Mid, and Upper: Long transport from TennesseeDavidson 8/16/2000 31.2 NC / VA Ohio Valley Missing DataDavidson 8/19/1999 31.1 NC / VA Ohio Valley Low: NC, VA, and WV; Mid: Eastern VA; Upper: NC, SW VA, and Ohio Valley

Davidson 10/27/2000 31.1 VA Low, Mid, and Upper: VirginiaDavidson 1/21/1999 31.0 NC (CLT, I-85) Upstate SC Low: All in NC; Mid and Upper: long transport from the west

Davidson 11/8/2000 30.7 NC Low: Short over NC; Mid and Upper: Long transport from the south (SC, GA, FL)

Davidson 7/20/1999 30.6 NE. TN, SW. VA, NC Low: NC and Upstate SC; Mid: E. TN and NC Upper: VA, KY, and TNDavidson 8/16/1999 30.1 NC Low, Mid, and Upper: All completely in NC (short trajectories)

Davidson 6/11/1999 29.8 NC (PP, I-40) Tidewater of VA (minimal) Low, Mid, and Upper all over NC and originate in the AtlanticDavidson 2/9/2000 29.4 NC I-95 Virginia Low: NC and VA; Mid: NC and VA; Upper: NC (over the mountains)Davidson 5/30/1999 29.1 NC (CLT) NC Low, Mid, and Upper all in NC and very northern SCDavidson 8/8/2001 29.0 Ohio Valley WV / VA / NC Low: NC and SW VA; Mid: VA and WV; Upper: VA, WV and Ohio Valley

Davidson 10/30/1999 28.5 NC Missing Data

Davidson 8/17/2001 28.5 NC / SC GA (ATL) Low: NC (CLT) and SC; Mid: Mostly SC, some NC; Upper: NC and GA (ATL)

Davidson 7/8/1999 28.4 NC Upstate SC, Eastern TN (3rd) Low: NC; Mid: Upstate SC; Upper: NE Tennessee

Davidson 10/18/2000 28.0 NC Eastern TN Low: Completely in NC; Mid: Completely in NC; Upper: long transport from TN

Davidson 8/14/2001 27.9 NC / VA WV Low: NC and SW VA; Mid: NC, Central VA, and WV; Upper: VA, WV, and Ohio Valley

Table 1. Days when observed PM2.5 values in Catawba and Davidson Counties was above 27.8 ug/m3. Indicated in the table is the county, date, PM2.5 observed value, the primary and secondary sources as determined

by the NC DAQ meteorologists, and any notes made by the meteorologists concerning that days trajectories. Purple shading indicates observed values greater than 39.9 ug/m3, red shading between 35.0 ug/m3 and 39.9

ug/m3, orange shading between 30.0 ug/m3 to 34.9 ug/m3, yellow shading between 27.9 ug/m3 and 29.9 ug/m3. Blue shading indicates known fire events in North Carolina. On days with missing EDAS data, surface

maps were used to determine the source region(s).

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County Date PM 2.5 Primary Secondary Notes

Catawba 11/2/2000 54.7 NC (Fire Event) Ohio Valley Low and Mid: Completely in NC; Upper: Long transport from the Ohio Valley

Catawba 11/8/2000 50.1 NC (Fire Event) SC / E. GA / FL (minor) Low, Mid, and Upper: Short trajectories in NC, then long transport from the south

Catawba 1/21/1999 41.0 NC Upstate, North Central GA Low: all in NC; Mid: NC, Upstate SC, and N. GA; Upper: long transport from the southwest

Catawba 6/21/2001 40.0 NC SC (minor) Low: NC and Upstate SC; Mid: Completely NC; Upper: All NC except for couple hours in TN

Catawba 10/21/2000 38.0 NC N. SC and E. TN Low: NC and Upstate SC; Mid: Eastern TN and N. GA; Upper: Central TN and Northern MS

Catawba 10/27/2000 36.7 SW. VA / WV Southern Ohio Valley Low: SW VA and Eastern KY; Mid and Upper: SW VA, Western WV, Southern Ohio Valley

Catawba 7/23/1999 36.1 NE. TN / OV / SW. VA Low and Mid: Northern TN; Upper: long transport from the northwest

Catawba 8/7/2000 34.2 NC Eastern TN, GA (ATL) Low and Mid: NC and Northern GA; Upper: Eastern TN and Northern GACatawba 3/31/1999 30.0 NC Northern SC Low: NC; Mid: NC, minor SC and VA; Upper; Upstate SCCatawba 2/9/2000 33.5 NC Eastern TN, Northern GA Low: NC and very minor VA; Mid: NC and very minor SC; Upper: NC, E. TN, and N. GA

Catawba 6/5/1999 33.2 NC Low, Mid, and Upper: NC (CLT and Triad)

Catawba 8/7/1999 33.1 NC SW. VA Low and Mid: Mostly NC, few hours in SW VA; Upper: Mostly in NC, few hours in NE TN

Catawba 1/1/2000 33.0 Millenium Low, Mid, and Upper: NC and transport from the west

Catawba 2/21/2001 32.8 Eastern TN Northern GA Low: Eastern TN and Northern GA; Mid: NE TN, SW VA (minor), and TN; Upper: TN and KY

Catawba 7/8/2000 32.7 NC Low and Mid: Completely in NC; Upper: NC and Upstate SC (minor, mostly NC)

Catawba 7/17/1999 32.3 NC Upstate SC Low and Mid: NC and Upstate SC; Upper: All in NC

Catawba 8/2/2001 32.0 NC Low, Mid, and Upper: Trajectories completely in NC

Catawba 6/8/1999 31.7 NE. TN / SW. VA / KY Low: NE TN and SW VA; Mid and Upper: NE TN, SW VA, KY;

Catawba 8/16/1999 31.1 NC Low and Mid: Completely in NC; Upper: NC and Upstate SC (CLT area)

Catawba 8/13/1999 31.0 NC SC Low: Completely in NC; Mid: NC and Upstate SC (CLT); Upper: NC

Catawba 6/2/2000 31.0 Eastern TN N. GA and NC missing dataCatawba 7/20/1999 30.9 NC / E. TN Low: Completely in NC; Mid and Upper: Eastern TNCatawba 5/3/2000 30.8 NC VA and SC Low: majority NC and VA; Mid: NC (half), VA (half); Upper: mostly NC, minor SC

Catawba 7/23/2000 30.6 NC Low, Mid, and Upper: Completely in NC

Catawba 9/7/2001 30.4 NC NE. TN Low and Mid: Completely in NC; Upper: NC and NE Tennessee

Catawba 8/26/2001 30.2 NC Eastern TN and SC (minor) Low: Completely in NC; Mid: Mostly in NC, few hours in Upstate SC; Upper: Eastern TN

Catawba 1/30/1999 30.0 NC Low, Mid, and Upper: NC and VA (few hours);Catawba 2/17/1999 30.0 NC / N. GA / Upstate SC missing data

Catawba 8/19/1999 29.6 Ohio Valley / SW. VA Low: NC, SW VA, and WV; Mid: NC, VA, and WV; Upper: NC, NE TN, SW VA, and E. KY

Catawba 7/2/2000 29.4 NC SC Low: NC (CLT); Mid: NC and Upstate SC; Upper: NC and Central SC

Catawba 7/18/2001 29.3 NC SE. TN and N. GA Low: NC and Northern GA; Mid and Upper: Southeast TN and Northest MS

Catawba 7/5/2000 29.1 Eastern and Central TN Low, Mid, and Upper: Transport from Central and Eastern TennesseeCatawba 11/18/2001 29.0 NC VA / Ohio Valley (upper) Low and Mid: NC and VA; Upper: SW VA, KY, and Southern Ohio Valley

Catawba 8/10/1999 28.4 NC E. TN Low and Mid: All in NC; Upper: transport from KY and TN

Catawba 6/4/2002 28.4 SC NC Low: Upstate SC and NC; Mid: SC and NC; Upper: SC and NC

Catawba 7/5/1999 28.2 NE. TN SW. VA / KY Low: NE TN; Mid: NE TN and SW VA; Upper: SW VA and KYCatawba 6/11/2000 28.2 NC / NE. TN / SC Low and Mid: Majority Upstate SC, some NC; Upper: NC and some NE TN and Upstate SC

Catawba 8/16/2000 28.2 NE. TN / SW. VA KY missing data

Catawba 10/18/2000 28.2 NC NE and Central TN Low: Completely in NC; Mid and Upper: Eastern and Central TNCatawba 8/4/1999 28.1 NC / VA Low, Mid, and Upper: NC and SW VACatawba 9/31/01 28.1 NC SW. VA and E. KY Low and Mid: Completely in NC; Upper: SW VA and SE KY

Table 1 Continued

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Table 2. Number of days that the HYSPLIT back trajectories indicated a region as a primary or secondary 

source for locations in Catawba and Davidson Counties in North Carolina. 

Catawba County Davidson County 

State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) 

North 

Carolina 31 2 33 North Carolina 26 2 28 

South 

Carolina 3 9 12 South Carolina 4 5 9 

Tennessee 9 8 17 Tennessee 4 5 9 

Virginia 6 5 11 Virginia 7 5 12 

Georgia 1 7 8 Georgia 1 2 3 

Kentucky 1 3 4 Kentucky 1 0 1 

Ohio Valley 2 3 5 Ohio Valley 1 4 5 

NC Only 27 NC Only 17 

NC + Other 4 NC + Other 9 

No NC 10 No NC 5 

Table 3. Number of days in the highest one-third of 24-hour average PM2.5 values for all days for which 

HYSPLIT trajectories were run. Specific PM2.5 values were 32.8 – 54.7 μg/m3

 for Catawba County and 

34.9 – 46.8 μg/m3

 for Davidson County. 

Catawba County – Upper Third Davidson County – Upper Third 

State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) 

North 

Carolina 10 0 10 North Carolina 8 1 9 

South 

Carolina 0 3 3 South Carolina 2 2 4 

Tennessee 2 3 5 Tennessee 2 3 5 

Virginia 2 1 3 Virginia 2 0 2 

Georgia 0 3 3 Georgia 0 1 1 

Kentucky 0 0 0 Kentucky 1 0 1 

Ohio Valley 1 1 2 Ohio Valley 0 1 1 

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Table 4. Number of days in the middle one-third of 24-hour average PM2.5 values for all days for which 

HYSPLIT trajectories were run. Specific PM2.5 values were 30.0 – 32.8 μg/m3

 for Catawba County and 

30.6 – 34.1 μg/m3

 for Davidson County. 

Catawba County – Middle Third Davidson County – Middle Third 

State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) 

North 

Carolina 10 0 10 North Carolina 9 0 9 

South 

Carolina 1 4 5 South Carolina 1 2 3 

Tennessee 3 2 5 Tennessee 2 0 2 

Virginia 2 1 3 Virginia 4 2 6 

Georgia 1 0 1 Georgia 1 0 1 

Kentucky 1 0 1 Kentucky 0 0 0 

Ohio Valley 1 0 1 Ohio Valley 0 3 3 

Table 5. Number of days in the lowest one-third of 24-hour average PM2.5 values for all days for which 

HYSPLIT trajectories were run. Specific PM2.5 values were 28.1 – 29.6 μg/m3

 for Catawba County and 

27.9 – 30.1 μg/m3

 for Davidson County. 

Catawba County – Lower Third Davidson County – Lower Third 

State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) State/Area Primary 

(days) 

Secondary 

(days) 

Total 

(days) 

North 

Carolina 8 1 9 North Carolina 9 2 11 

South 

Carolina 2 1 3 South Carolina 1 1 2 

Tennessee 4 3 7 Tennessee 0 1 1 

Virginia 3 3 6 Virginia 1 3 4 

Georgia 0 1 1 Georgia 0 1 1 

Kentucky 0 2 2 Kentucky 0 0 0 

Ohio Valley 1 1 2 Ohio Valley 1 0 1 

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Table 6. Total number of hours back trajectories spent in states other than North Carolina for all events for 

the Davidson County PM2.5 monitor. Hours are based on the maximum of all trajectory heights, and 

therefore do not double count. Percent of total hours based on maximum hours of all events (1224 hours). 

Average hours based on average of each event, excluding zero hour events.

Davidson County 

Date PM2.5 SC (hrs) GA (hrs) TN (hrs) VA (hrs) KT (hrs) WV (hrs) OH (hrs) MAX

1/21/1999 31.0 12 8 36 

5/30/1999 29.1 20 36 

6/11/1999 29.8 36 

7/5/1999 36.6 6 16 12 36 

7/8/1999 28.4 23 10 20 36 

7/17/1999 38.9 22 22 36 

7/20/1999 30.6 22 12 11 36 

7/23/1999 40.5 18 13 7 4 36 

8/7/1999 33.8 7 36 

8/13/1999 44.8 23 36 

8/16/1999 30.1 36 

8/19/1999 31.1 28 13 8 36 

8/28/1999 32.1 25 36 

11/11/1999 31.8 15 9 36 

1/17/2000 N/A 36 

2/9/2000 29.4 13 36 

6/2/2000 34.9 36 

6/29/2000 34.1 10 16 6 18 6 36 

7/2/2000 32.7 21 36 

10/18/2000 28.0 25 36 

10/21/2000 37.7 16 9 10 6 6 36 

10/27/2000 31.1 34 36 

11/8/2000 30.7 14 9 36 

12/11/2000 38.7 12 36 

6/21/2001 41.6 28 10 3 3 36 

7/18/2001 37.7 29 11 14 36 

8/8/2001 29.0 20 14 18 36 

8/14/2001 27.9 20 11 36 

8/17/2001 28.5 17 16 36 

1/5/2002 39.2 20 4 36 

7/1/2002 31.1 23 18 36 

7/16/2002 33.1 6 12 12 36 

8/12/2002 36.9 20 12 19 36 

12/7/2002 43.7 6 5 9 36 

Total Hours 278 94 166 275 81 73 30 1224

% of Total 22.7 7.7 13.6 22.5 6.6 6.0 2.5 

Avg. Hours 19.9 11.8 15.1 14.5 10.1 12.2 7.5 

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Table 7. As in Table 6, except for Catawba County. 

Catawba County

Date PM2.5 SC (hrs) GA (hrs) TN (hrs) VA (hrs) KT (hrs) WV (hrs) OH (hrs) MAX

1/21/1999 31.0 12 10 36 

1/30/1999 30.0 10 3 36 

3/31/1999 30.0 9 6 36 

5/30/1999 29.1 36 

6/8/1999 31.7 7 25 36 

7/5/1999 28.2 25 15 21 36 

7/17/1999 32.3 20 36 

7/20/1999 30.9 28 36 

7/23/1999 36.1 30 12 36 

8/4/1999 28.1 17 2 36 

8/7/1999 33.1 36 

8/10/1999 28.4 10 26 36 

8/13/1999 31.0 31 36 

8/16/1999 31.1 36 

8/19/1999 29.0 6 12 16 36 

1/1/2000 33.0 36 

2/9/2000 33.5 6 15 12 4 36 

5/3/2000 30.8 4 21 7 36 

6/2/2000 31.0 36 

6/11/2000 28.2 25 36 

7/2/2000 29.4 24 36 

7/5/2000 29.1 34 36 

7/8/2000 32.7 36 

7/23/2000 30.6 36 

8/7/2000 34.2 26 6 36 

8/16/2000 28.2 36 

10/18/2000 28.2 31 6 36 

10/21/2000 38.0 19 13 3 6 36 

10/27/2000 36.7 13 13 10 12 36 

11/2/2000 54.7 36 

11/8/2000 50.1 36 

2/21/2001 32.8 6 9 13 36 

6/21/2001 40.0 20 36 

7/18/2001 29.3 16 10 36 

8/2/2001 32.0 36 

8/26/2001 30.2 34 36 

9/7/2001 30.4 10 36 

9/13/2001 28.1 6 26 36 

11/18/2001 29.0 12 15 5 36 

6/4/2002 28.4 31 36 

7/1/2002 33.5 25 9 16 36 

7/7/2002 28.3 8 36 

7/16/2002 33.5 11 15 15 36 

8/3/2002 30.0 36 

8/12/2002 40.7 20 8 36 

12/7/2002 29.2 6 10 36 

12/31/2002 28.9 12 19 36 

Total Hours 207 92 258 168 201 61 32 1656

% of Total 12.5 5.6 15.6 10.1 12.1 3.7 1.9 

Avg. Hours 18.8 15.3 18.4 10.5 14.4 10.2 10.7 

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FIG 1. 36-hour back trajectories at 10 meters (red), 300 meters (blue) and 1000 meters (green) from the Catawba County site for 

days when the PM2.5 concentration was high.

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FIG 2. 36-hour back trajectories at 10 meters from the Catawba County site for days when the PM2.5 concentration was high.

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FIG 3. 36-hour back trajectories at 300 meters from the Catawba County site for days when the PM2.5 concentration was high.

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FIG 4. 36-hour back trajectories at 1000 meters from the Catawba County site for days when the PM2.5 concentration was high.

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FIG 5. As in Figure 1, except for Davidson County.

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FIG 6. As in Figure 2, except for Davidson County.

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FIG 7. As in Figure 3, except for Davidson County.

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FIG 8. As in Figure 4, except for Davidson County.

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Catawba County - Primary PM2.5 Sources

58%

6%

17%

11%

2%

2%

4%

North CarolinaSouth CarolinaTennesseeVirginiaGeorgiaKentuckyOhio Valley

FIG 9. Percent of the days for which HYSPLIT back trajectories were run for the Catawba County PM2.5 monitor for which each 

region was determined to be a primary source. Dark Blue: North Carolina; Burgundy: South Carolina; Yellow: Tennessee; Light Blue: Virginia; Orange: Georgia; Pink: Kentucky; Green: Ohio Valley.

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FIG 10. Percent of the days for which HYSPLIT back trajectories were run for the Catawba County PM2.5 monitor for which 

each region was determined to be a secondary source. Dark Blue: North Carolina; Burgundy: South Carolina; Yellow: Tennessee; Light Blue: Virginia; Orange: Georgia; Pink: Kentucky; Green: Ohio Valley.

Catawba County - Secondary PM2.5 Sources

5%

24%

22% 14%

19%

8%

8%

North CarolinaSouth CarolinaTennesseeVirginiaGeorgiaKentuckyOhio Valley

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FIG 11. Percent of the days for which HYSPLIT back trajectories were run for the Catawba County PM2.5 monitor for which 

each region was determined to be a primary source, secondary source, or both. Dark Blue: North Carolina; Burgundy: South Carolina; Yellow: Tennessee; Light Blue: Virginia; Orange: Georgia; Pink: Kentucky; Green: Ohio Valley.

Catawba County - Total Sources (Primary and Secondary PM2.5)

37%

13%

19%

12%

9%

4%

6%

North CarolinaSouth CarolinaTennesseeVirginiaGeorgiaKentuckyOhio Valley

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Davidson County - Primary PM2.5 Sources

60%

9%

9%

16%

2%

2%

2%

North CarolinaSouth CarolinaTennesseeVirginiaGeorgiaKentuckyOhio Valley

FIG 12. Percent of the days for which HYSPLIT back trajectories were run for the Davidson County PM2.5 monitor for which 

each region was determined to be a primary source. Dark Blue: North Carolina; Burgundy: South Carolina; Yellow: Tennessee; Light Blue: Virginia; Orange: Georgia; Pink: Kentucky; Green: Ohio Valley.

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FIG 13. Percent of the days for which HYSPLIT back trajectories were run for the Davidson County PM2.5 monitor for which 

each region was determined to be a secondary source. Dark Blue: North Carolina; Burgundy: South Carolina; Yellow: Tennessee; Light Blue: Virginia; Orange: Georgia; Pink: Kentucky; Green: Ohio Valley.

Davidson County - Secondary PM2.5 Sources

9%

21%

22%

22%

9%

0%

17%

North CarolinaSouth CarolinaTennesseeVirginiaGeorgiaKentuckyOhio Valley

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FIG 14. Percent of the days for which HYSPLIT back trajectories were run for the Davidson County PM2.5 monitor for which 

each region was determined to be a primary source, secondary source, or both. Dark Blue: North Carolina; Burgundy: South Carolina; Yellow: Tennessee; Light Blue: Virginia; Orange: Georgia; Pink: Kentucky; Green: Ohio Valley.

Davidson County - Total Sources (Primary and Secondary PM2.5)

43%

13%

13%

19%

4%

1% 7%

North CarolinaSouth CarolinaTennesseeVirginiaGeorgiaKentuckyOhio Valley

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August 21, 2009