Technical Support for the 2008 Ozone Standard Designation 

Recommendation for the State of Mississippi 

Mississippi Department of Environmental Quality 

Air Division 

March 2009 
2

Executive Summary 

DeSoto, Harrison and Jackson Counties in Mississippi are the only counties in the state 

with monitors that are reading above the 2008 National Ambient Air Quality Standard 

(NAAQS). Therefore, Mississippi is recommending that only DeSoto, Harrison and 

Jackson Counties be designated as non-attainment for the 2008 ozone NAAQS. Figure 1 

below shows the location of all of the monitors in the state. 

Figure 1. Mississippi Ozone Monitoring Locations 
3

EPA recommends that the Metropolitan Statistical Area (MSA) or Combined 

Statistical Area (CSA) serve as the starting point for determining the geographic 

boundaries of an ozone non-attainment area. Additionally, there are nine factors to be 

evaluated in making the boundary determination. These factors are:

• Factor 1: Air quality data 

• Factor 2: Emission data (location of sources and contribution to ozone 

concentrations) 

• Factor 3: Population density and degree of urbanization (including commercial 

development) 

• Factor 4: Traffic and commuting patterns 

• Factor 5: Growth rates and patterns 

• Factor 6: Meteorology (weather/transport patterns) 

• Factor 7: Geography/topography (mountain ranges or other air basin boundaries) 

• Factor 8: Jurisdictional boundaries (e.g., counties, air districts, Reservations, 

metropolitan planning organizations) 

• Factor 9: Level of control of emission sources 

DeSoto, Marshall, Tate, and Tunica Counties are all in the Memphis, Tennessee 

MSA. The Gulfport-Biloxi-Pascagoula CSA consists of George, Hancock, Harrison, 

Jackson and Stone Counties. An analysis of the nine factors determined that only 

DeSoto, Harrison and Jackson Counties should be designated as non-attainment for 

the 2008 ozone NAAQS. The surrounding counties should be excluded from these 

non-attainment areas.
4

Mississippi Counties in the Memphis MSA 

DeSoto, Marshall, Tate and Tunica Counties are all part of the Memphis, Tennessee 

MSA. Mississippi is recommending that only DeSoto County be designated as nonattainment for the 2008 ozone NAAQS. Current monitoring data indicate that the 

Hernando monitor, located in Desoto County, is not attaining the standard of 0.075 ppm. 

Figure 2 below shows the location of the Hernando monitor in DeSoto County. 

Marshall, Tate, and Tunica Counties do not have monitors. They contribute little to the 

overall emissions in the area, and have significantly lower populations and traffic; 

therefore, based on an analysis of the nine factors, Marshall, Tate, and Tunica Counties 

should not be included in the non-attainment designation. 

Figure 2. Mississippi Counties and Monitoring Locations in the Memphis MSA 
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Nine Factor Analysis for Mississippi Counties in Memphis MSA 

Factor 1: Air Quality Analysis 

The following table is data collected from the Hernando monitor in DeSoto County, 

Mississippi. The surrounding counties of Marshall, Tate, and Tunica do not have 

monitors. 

4th Annual 

Maximum 

8-Hour Ozone 

County AIRS ID Site 

2006 2007 2008 

3-Year 

Average 

2006-2008 

DeSoto 28-033-0002 Hernando 87 84 74 81 

 Table 1. Hernando, MS Monitor Data 

Factor 2: Location of Emissions Sources and Contribution to Ozone Concentrations 

The Mississippi counties in the Memphis MSA have a small number of major emission 

sources as shown in Figure 3. DeSoto County has two facilities that are classified as 

major sources of Nitrogen Oxides (NOx) and three facilities classified as major sources 

of Volatile Organic Compounds (VOCs). Tate County has one major source of NOx and 

three major sources of VOCs. However, there are no major sources in Marshall or 

Tunica counties. 
6

 Figure 3. Mississippi Major Emission Sources in the Memphis MSA 

The largest contributor of ozone precursor emissions in the area is Shelby County, 

Tennessee. Chart 1 gives a comparison of NOx and VOC emissions from all source 

categories in the four Mississippi counties and Shelby County, Tennessee. The total 

emissions from Marshall, Tate and Tunica Counties are small in comparison to DeSoto 

County’s emissions and very small in comparison to Shelby County, Tennessee’s 

emissions. Based on the emission data, Marshall, Tate, and Tunica County would not 

have a significant contribution to the Hernando monitor. 

County Emissions - 2005

0

10,000

20,000

30,000

40,000

50,000

60,000

DeSoto Marshall Tate Tunica Shelby, TN

Tons per year

Nox (tons)

VOC (tons)

Chart 1. NOx and VOC emission comparison for Memphis MSA (2005 NEI) 
7

Factor 3: Population Density and Degree of Urbanization 

Marshall, Tate and Tunica Counties are below the national average for population density 

with little or no urbanized areas. They are much lower than DeSoto County’s population 

density and degree of urbanization. Chart 2 compares population densities and Chart 3 

compares degrees of urbanization for the Memphis MSA. 

Population Density

0

200

400

600

800

1,000

1,200

1,400

DeSoto Marshall Tate Tunica Shelby

Population per square mile

Density

U.S. Average

Chart 2. Population Density of Memphis MSA (2000 census data) 

Degree of Urbanization

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

1,000,000

DeSoto Marshall Tate Tunica Shelby

Rural Population

Urban Population

Chart 3. Degree of Urbanization for Memphis MSA (2000 census data)
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Factor 4: Traffic and Commuting Patterns

The overall amount of traffic is minor in Marshall, Tate, and Tunica Counties and their 

commuting patterns do not indicate an impact on the DeSoto County monitor. The 

amount of traffic is measured Vehicle Miles Traveled (VMT) and is developed by the 

Mississippi Department of Transportation. Chart 4 compares the traffic data for the 

Mississippi Counties in the Memphis MSA. Data from the 2000 census was used to 

determine the commuting patterns. Chart 5 summarizes this information and 

demonstrates that the residents in Marshall, Tate and Tunica counties commute primarily 

within their own county. Consequently, the traffic from these counties would have no 

substantial impact on the monitor in Hernanado. 

County Traffic

0

200,000,000

400,000,000

600,000,000

800,000,000

1,000,000,000

1,200,000,000

1,400,000,000

1,600,000,000

1,800,000,000

2,000,000,000

DeSoto Tate Tunica Marshall

VMT

Other

Principal Arterials

Freeway

Interstate

Chart 4. Traffic Data for the Mississippi Counties in the Memphis MSA (2005 

HPMS Data) 
9

Commuting Patterns

0 50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000

DeSoto

Marshall

Tate

Tunica

Shelby

Work County

Commuters

DeSoto 

Marshall

Tate

Tunica

Shelby

Chart 5. Commuting Patterns for Memphis MSA (2000 Census) 
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Factor 5: Growth Rates and Patterns 

Growth rates were determined for DeSoto, Marshall, Tate, and Tunica Counties using the 

2000 census figures and the 2007 census estimates. Table 2 shows that Marshall, Tate 

and Tunica counties have not experienced significant growth since the 2000 census data. 

County 2000 

Census 

Population 

2007 

Census 

Estimate 

Increase % annual 

Growth 

DeSoto 107,199 149,393 42,194 5.6% 

Marshall 34,993 36,695 1,702 0.7% 

Tate 25,370 26,910 1,540 0.9% 

Tunica 9,227 10,453 1,226 1.9% 

Table 2. Population Growth Rates for Mississippi Counties in the Memphis MSA 

Factor 6: Meteorology (Weather and Transport) 

Backward trajectories were created using the National Weather Service’s HYSPLIT 

program to examine the path air parcels followed for the 24 hours prior to midnight for 

each day that the maximum 8-hour ozone concentration exceeded 75 ppb for the period 

1999 - 2008 in DeSoto County. The results from this backward trajectory analysis show 

that 76% of the non-stagnant back trajectories that ended in Hernando originated from the 

north or northeast. This indicates emissions from Marshall, Tate, and Tunica counties 

contribute little to the Hernando monitor on the higher ozone days. 

Factor 7: Geography and Topography 

The Mississippi counties in the Memphis MSA are located in northwestern Mississippi. 

DeSoto and Tunica counties border the Mississippi River. DeSoto and Marshall Counties 

border Tennessee while Tate is directly south of DeSoto County. The topography of the 

area ranges from the flat lowland of the Mississippi Delta in the west to rolling hills in 

the central and eastern part of the MSA. 

Factor 8: Jurisdictional Boundaries 

DeSoto, Marshall, Tate, and Tunica Counties are within the Memphis MSA. DeSoto 

County is within the Memphis Metropolitan Air Quality Control Region. Tunica County 

is within the Mississippi Delta Air Quality Control Region. Marshall and Tate counties 

are within the Northeast Mississippi Air Quality Control Region. The Mississippi 

Department of Environmental Quality is responsible for monitoring air quality in these 

counties. 
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Factor 9: Level of Control of Emissions 

No additional emissions standards apply to this area beyond federal and state standards. 

Considering the low air emissions in Marshall, Tate, and Tunica Counties, there are no 

specific measures that could be applied that would yield significant reductions. 
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Gulfport-Biloxi-Pascagoula CSA 

Mississippi is recommending that only Jackson and Harrison Counties in the GulfportBiloxi-Pascagoula CSA be designated as non-attainment for the 2008 ozone NAAQS. 

Current monitoring data indicates that the Pascagoula monitor in Jackson County and the 

Gulfport monitor in Harrison County are not attaining the standard of 0.075 ppm. The 

surrounding counties of George and Stone do not have monitors. The Hancock County 

monitor has not been in operation since it 2005, but should be in operation for the 2009 

ozone season. Based on an analysis of the nine factors, George, Hancock and Stone 

Counties should not be included in the non-attainment designation. These counties 

contribute little to the overall emissions in the area and have significantly lower 

populations and traffic. Figure 4 below shows the monitoring locations in the GulfportBiloxi-Pascagoula CSA. 

Figure 4. Gulfport-Biloxi-Pascagoula CSA Monitoring Locations
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Nine Factor analysis for Gulfport-Biloxi-Pascagoula CSA 

Factor 1: Air Quality Analysis 

The following table is data collected from the Gulfport and Pascagoula monitors in 

Mississippi. The surrounding counties of George and Stone do not have monitors. The 

Hancock County monitor has not operated since 2005 due to damage caused by 

Hurricane Katrina. This monitor will resume operation for the 2009 ozone season. 

4th Annual 

Maximum 

8-Hour Ozone 

County AIRS ID Site 

2006 2007 2008 

3-Year Average

2006-2008 

Harrison 28-047-0008 Gulfport 84 81 78 81 

Jackson 28-059-0006 Pascagoula 82 78 76 78 

Table 3. Gulfport and Pascagoula, MS Monitoring Data 
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Factor 2: Location of Emissions Sources and Contribution to Ozone Concentrations 

Figure 4 shows the location of the major point sources of NOx or VOC in the GulfportBiloxi-Pascagoula CSA. Chart 6 gives the total emissions from all sources in each 

county. The total emissions in Hancock, George and Stone Counties are much less than 

the emissions in Jackson and Harrison Counties. Due to the location and size of the 

sources in Hancock, George and Stone Counties, they would not contribute significantly 

to the ambient ozone levels in Harrison or Jackson Counties. 

Figure 5. Major Emission Sources in the Gulfport-Biloxi-Pascagoula CSA 
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County Emissions

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

Hancock Harrison Jackson George Stone

tons per year

Nox (tons)

VOC (tons)

Chart 6. NOx and VOC emission comparison for Gulfport-Biloxi-Pascagoula CSA 

(2005 NEI)
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Factor 3: Population Density and Degree of Urbanization 

Hancock, George and Stone Counties are below the national average for population 

density with little or no urbanized areas. They are much lower than Harrison and Jackson 

Counties’ population density and degree of urbanization. Chart 7 compares population 

densities and Chart 8 compares degrees of urbanization for the Gulfport-BiloxiPascagoula CSA. 

Population Density

0

50

100

150

200

250

Hancock Harrison Jackson George Stone

population/square mile

Density

U.S. Average

Chart 7. Population Density of Gulfport-Biloxi-Pascagoula CSA (2000 Census) 

Degree of Urbanization

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

Hancock Harrison Jackson George Stone

Population

Rural Population

Urban Population

Chart 8. Degree of Urbanization for Gulfport-Biloxi-Pascagoula CSA (2000 

Census) 
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Factor 4: Traffic and Commuting Patterns 

The overall amount of traffic in Hancock, George and Stone Counties is significantly 

lower than the VMT in Harrison and Jackson Counties. The amount of traffic is measured 

in Vehicle Miles Traveled (VMT) and is developed by the Mississippi Department of 

Transportation. Chart 9 compares the traffic data for the Gulfport-Biloxi-Pascagoula 

CSA. Data from the 200 Census was used to determine the commuting patters. Chart 10 

summarizes this information and demonstrates that the residents in Hancock, George, and 

Stone Counties commute primarily within their own county. Consequently, the traffic 

from these counties would have no substantial impact on the monitors in Gulfport and 

Pascagoula. 

County Traffic

0

500,000,000

1,000,000,000

1,500,000,000

2,000,000,000

2,500,000,000

Harrison Jackson Hancock George Stone

VMT

Other

Principal Arterials

Freeway

Interstate

Chart 9. Traffic Data for Gulfport-Biloxi-Pascagoula CSA (2005 HPMS Data) 
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Commuting Patterns

0 20,000 40,000 60,000 80,000 100,000 120,000

Hancock

Harrison

Jackson

George

Stone

Work County

Commuters

Hancock

Harrison

Jackson

George

Stone

Chart 10. Commuting Patterns for Gulfport-Biloxi-Pascagoula CSA (2000 Census) 
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Factor 5: Growth Rates and Patterns 

Comparing the 2000 census and 2007 census estimates, there has been negative growth in 

Hancock, Harrison and Jackson Counties due to the devastation from Hurricane Katrina. 

There has been positive growth in George and Stone Counties; however, the growth is 

minimal and these counties have low populations. 

County Population 

(2000 

census) 

2007 

Census 

Estimate

Increase % Annual 

Growth 

Hancock 42,967 39,687 -3,280 -1.1% 

Harrison 189,601 176,105 -13,496 -1.0% 

Jackson 131,420 130,098 -1,322 -0.1% 

George 19,144 21,937 2,793 2.1% 

Stone 13,622 15,731 2,109 2.2% 

Table 4. Population Growth Rates for Gulfport-Biloxi-Pascagoula CSA 

Factor 6: Meteorology (Weather and Transport) 

Backward trajectories were created using the National Weather Service’s HYSPLIT 

program to examine the path air parcels followed for the 24 hours prior to midnight for 

each day that the maximum 8-hour ozone concentration exceeded 75 ppb for the period 

1999 - 2008 in Harrison and Jackson counties. The results from this backward trajectory 

analysis show that 40-45% of the back trajectories that ended in Gulfport or Pascagoula 

demonstrated a diurnal land/sea breeze circulation along the coast. Only 9-14% of the 

back trajectories originated from the north or northwest. This indicates emissions from 

George, Hancock and Stone Counties contribute little to the Gulfport and Pascagoula 

monitors on the higher ozone days. 

 

Factor 7: Geography and Topography 

The Gulfport-Biloxi-Pascagoula Combined Statistical Area is located in southeastern 

Mississippi. Hancock, Harrison, and Jackson Counties border the Gulf of Mexico. 

George and Jackson Counties border Alabama while Hancock County borders Louisiana. 

The topography ranges from rolling hills in the northern portion of this region to the 

beach in the southern portion. 

The diurnal land-sea breeze recirculation, caused by the proximity of the Gulf of Mexico 

and by weather conditions with light steering winds, results in higher ozone 

concentrations generally along the coastline. Historical inland monitoring data (5-10 

miles) in the coastal counties revealed little effect on ozone concentrations from this 

recirculation. 
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Factor 8: Factor Jurisdictional Boundaries 

George, Hancock, Harrison, Jackson, and Stone counties are within the Biloxi-GulfportPascagoula Combined Statistical Area. These counties are also located within the Mobile 

– Pensacola - Panama City - Southern Mississippi Air Quality Control Region. The 

Mississippi Department of Environmental Quality is responsible for monitoring air 

quality in these counties. 

Factor 9: Level of Control of Emissions 

No additional emissions standards apply to this area beyond federal and state standards. 

Considering the low air emissions in George, Hancock and Stone Counties, there are no 

specific measures that could be applied that would yield significant reductions.