Nevada Regional Haze 5-Year Progress Report, November 2014 5-1

5

Chapter Five – Changes in Emissions: All 

Sources within the State

(40 CFR 51.308(g)(4))

Table of Contents

5.1 Status Summary................................................................................................................ 2

5.2 Baseline and Progress Periods for Tracking Emission Changes...................................... 2

5.3 Emissions from the 2002 Baseline Period........................................................................ 5

5.4 Emissions from the 2008 Progress Period ....................................................................... 7

5.5 Emission Differences between the Baseline and Progress Periods.................................. 9

5.5.1 Sulfur Dioxide........................................................................................................... 9

5.5.2 Oxides of Nitrogen.................................................................................................. 11

5.5.3 Ammonia................................................................................................................. 13

5.5.4 Volatile Organic Compounds ................................................................................. 15

5.5.5 Primary Organic Aerosol ........................................................................................ 17

5.5.6 Elemental Carbon.................................................................................................... 19

5.5.7 Fine Soil.................................................................................................................. 21

5.5.8 Coarse Mass............................................................................................................ 22
Nevada Regional Haze 5-Year Progress Report, November 2014 5-2

5.1 Status Summary

Table 5-1 shows that emissions of all visibility impairing pollutants decreased from the 2002 

baseline inventory to the 2008 comparison year inventory developed by the WRAP, except for 

fine soil and coarse mass. The increases in fine soil and coarse mass were likely due to updates 

in inventory development methodologies rather than actual increases. Sections 5.5.7 and 5.5.8. 

Notably, actual 2008 emissions are lower than the projected 2018 emissions for all pollutants

except fine soil and coarse mass. Point source SO2 emissions alone decreased by 78 percent 

between the baseline and 2008 inventories (Table 5-5), while NOx point source emissions 

decreased by over 50 percent (Table 5-7). This demonstrates a significant reduction in Nevada’s

anthropogenic emissions of SO2 and NOx and confirms the success of Nevada’s long-term 

strategy for reducing emissions that are controllable within the State.

Table 5-1. Comparison of 2002, 2008 and 2018 Emission Inventories for All Visibility 

Impairing Pollutants*

Pollutants 2002 Baseline

(tpy)

2008 Inventory

(tpy)

2018 Projection

(tpy)

2008 Actuals as 

a Percent of

2018 Projections

Sulfur Dioxide 67,743 17,058146,224 37%

Oxides of 

Nitrogen 162,397 119,513 135,496 88%

Ammonia 12,092 9,382 14,503 65%

Volatile Organic 

Compounds 897,102 351,142 897,707 39%

Primary Organic 

Aerosol 24,734 11,816 24,822 48%

Elemental 

Carbon 6,409 4,425 5,638 78%

Fine Soil 21,208 40,301 24,134 167%

Coarse Mass 161,142 321,257 188,287 171%

* The SO2 and NOx data include only gaseous emissions.

5.2 Baseline and Progress Periods for Tracking Emission Changes

40 CFR 51.308(g)(4) requires an analysis tracking the change over the past five years of the 

emissions of pollutants from all sources and activities within the state that contribute to visibility 

impairment. This chapter describes the change in emissions between the baseline period and the 

progress period. In doing so, it relies principally on the WRAP TSD prepared for the western

states to support the development of 5-year progress reports. Appendix A and WRAP 2013. The 

WRAP TSD includes extensive analyses and comparisons of emissions data from source

categories, displaying the differences between the baseline and progress period inventories for 

Nevada.

 

1 Nevada over-reported 2008 NEI SO2 emissions by 88 tons. This correction has been accounted for in Table 5-1.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-3

The baseline period is represented by the 2000-2004 emission inventory developed by the 

WRAP for use in the initial RH SIPs. The development of the baseline (referred to as “2002” by 

the WRAP) or “Plan02” inventories 

was a cooperative effort between the 

WRAP and the western states. The 

emissions reported by the states in 

the 2002 NEI served as the starting 

point for the Plan02 inventories. 

The data were enhanced via efforts 

by contractors, WRAP workgroups, 

and consultation with the WRAP 

states. Point, area, mobile, oil and 

gas, fire and dust source categories 

were better characterized through 

this effort. Section 5.3 further 

describes the development of the 

Plan02d inventory.

The inventory year chosen for 

comparison with the baseline year is 

2008 as provided in the WRAP TSD. WRAP 2013. The WRAP used the 2008 NEI as a starting 

point, then updated that inventory through its WestJump Air Quality Modeling Study (WestJump 

AQMS 2013), producing an updated and comprehensive inventory for year 2008. 

WestJump2008. Section 5.4 further describes the data sources used in developing the 2008 

inventory. Emissions data is presented showing the change from the 2008 NEI to the 2011 NEI, 

where available.

Emission inventories were complicated by the fact that a number of changes and enhancements 

have occurred between development of the baseline and current period inventories. Thus, some 

of the differences between inventories are more reflective of changes in methodology, rather than 

changes in actual emissions. Some examples of the changes include using a revised mobile 

model, different meteorological models, incorporation of state-specific data, re-categorization of 

sources into more appropriate source categories, regulatory changes, revised emission rates, and

improvements to activity data. The changes and enhancements are discussed more in Section 5.3

of this chapter and Table 3.2-1 of the WRAP TSD. WRAP 2013. These differences in 

methodologies will affect the ability to make comparisons of inventories used for 2002 and 2008 

estimates.

In Nevada’s 2009 RH SIP, emission summaries compared both gaseous and particulate 

emissions of sulfur oxides (SOx) and NOx. Emission summaries in the WRAP TSD compared 

just gaseous emissions of SO2 and NOx. The difference between gaseous and particulate 

emissions and gaseous only emissions for point and area source categories, the primary sources

51.308(g) Periodic progress reports must 

contain at a minimum . . .

(4) An analysis tracking the change over 

the past 5 years in emissions of pollutants 

contributing to visibility impairment from 

all sources and activities within the State. 

Emissions changes should be identified by 

type of source or activity. The analysis 

must be based on the most recent 

updated emissions inventory, with 

estimates projected forward as necessary 

and appropriate, to account for emissions 

changes during the applicable 5-year 

period.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-4

of SO2 and NOx emissions, is less than one percent. For this report, Nevada is conforming to the 

analysis performed by the WRAP for the TSD. Therefore, a comparison of the gaseous

emissions of SO2 and NOx is discussed in this chapter.

As evident in Section 5.3, the majority of anthropogenic point source emissions in the baseline 

period are SO2 and NOx. Thus, this chapter focuses on the emission reductions from point 

sources of SO2 and NOx. Table 5-2 lists the different source categories that comprise 

anthropogenic and natural sources of visibility-impairing pollutants generally.

Table 5-2. Anthropogenic and Natural Source Categories

Anthropogenic Source Categories Natural Source Categories

Point Sources Natural Fire Sources

Anthropogenic Fire Sources Biogenic Sources

Area Sources Wind Blown Dust

WRAP Oil and Gas Sources

On-Road Mobile Sources

Off-Road Mobile Sources

Road Dust

Fugitive Dust

Table 5-3 lists the major emitted pollutants inventoried, the related monitored aerosol species, 

some of the major sources for each pollutant, and some notes regarding implications of these 

pollutants. Appendix A, Table 6.8-7

Table 5-3. Pollutants, Aerosol Species and Major Sources

Emitted

Pollutant

Related 

Aerosol Major Sources Notes

Sulfur 

Dioxide 

(SO2)

Ammonium 

Sulfate

Point Sources;

On- and OffRoad Mobile 

Sources

SO2 emissions are generally associated with anthropogenic 

sources, such as coal-burning power plants, other industrial 

sources such as refineries and cement plants, and both on- and offroad diesel engines.

Oxides of 

Nitrogen

(NOx)

Ammonium

Nitrate

On- and OffRoad Mobile 

Sources;

Point Sources;

Area Sources

NOx emissions are generally associated with anthropogenic 

sources. Common sources include virtually all combustion 

activities, especially those involving cars, trucks, power plants, 

and other industrial processes.

Ammonia

(NH3)

Ammonium 

Sulfate

and 

Ammonium 

Nitrate

Area Sources;

On-Road 

Mobile Sources

Gaseous NH3 has implications in particle formation because it can 

form particulate ammonium. Ammonium is not directly measured 

by the IMPROVE program, but affects formation potential of 

ammonium sulfate and ammonium nitrate. All measured nitrate 

and sulfate is assumed to be associated with ammonium for 

IMPROVE reporting purposes.

Volatile 

Organic 

Compounds 

(VOCs) 

Particulate 

Organic 

Mass 

(POM)

Biogenic 

Emissions; 

Vehicle 

Emissions; Area 

Sources

VOCs are gaseous emissions of carbon compounds, which are

often converted to POM through chemical reactions in the 

atmosphere. 

Estimates for biogenic emissions of VOCs have undergone 

significant updates since 2002, so changes reported here are more 

reflective of methodology changes than actual changes in 
Nevada Regional Haze 5-Year Progress Report, November 2014 5-5

Emitted

Pollutant

Related 

Aerosol Major Sources Notes

emissions. See Section 3.2.1 of the WRAP TSD.

Primary 

Organic 

Aerosol 

(POA)

POM Wildfires;

Area Sources

POA represents organic aerosols that are emitted directly as 

particles, as opposed to gases. Wildfires in the west generally 

dominate POA emissions, and large wildfire events are generally 

sporadic and highly variable from year to year.

Elemental 

Carbon 

(EC)

EC Wildfires;

On- and OffRoad Mobile 

Sources

Large EC events are often associated with large POM events 

during wildfires. Other sources include both on- and off-road 

diesel engines.

Fine soil Soil Windblown 

Dust;

Fugitive Dust;

Road Dust;

Area Sources

Fine soil is reported here as the crustal or soil components of 

PM2.5. 

Coarse 

Mass 

(PMC)

Coarse 

Mass

Windblown 

Dust;

Fugitive Dust

Coarse mass is reported by the IMPROVE Network as the 

difference between PM10 and PM2.5 mass measurements. Coarse 

mass is not separated by species in the same way that PM2.5 is 

speciated, but these measurements are generally associated with 

crustal components. Similar to crustal PM2.5, natural windblown 

dust is often the largest contributor to PMC.

5.3 Emissions from the 2002 Baseline Period

The baseline period emissions are represented by the 2002 inventory developed by the WRAP 

for the initial RH SIPs. This effort built upon 2002 emissions submitted by states to USEPA for 

the 2002 NEI and incorporated work by contractors and WRAP workgroups in consultation with 

states. Base02 was the first inventory, which used actual 2002 data and represented actual 

conditions in calendar year 2002. Subsequent to the Base02 inventory, a series of Plan02 

inventories were developed (Plan02a, Plan02b, Plan02c and Plan02d) using 2000 through 2004 

data. The purpose of the inventory series was to represent baseline emission patterns based on

average, or typical, conditions rather than a single year. The Plan02d emission inventory was a 

result of minor changes to the Plan02c inventory. The Plan02d inventory provides the basis in 

this report for comparison with the 2018 projected emissions, as well as for gauging reasonable 

progress with respect to future year visibility. 

Data comparisons were made between the baseline and 2008 emission inventory periods for nine 

source categories. A summary of the emission inventory descriptions for the Plan02d source 

categories follows. A more detailed description can be found in the WRAP TSD. WRAP 2013, 

Table 3.2-1.

1. Point source inventory –This inventory was generated using hourly USEPA CAMD 

continuous emission monitoring (CEM) data for EGUs. Other point source emissions 

were developed in consultation with states.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-6

2. Area source inventory –This inventory was developed by the WRAP contractor, Eastern 

Research Group, in consultation with states.

3. Area oil and gas – The oil and gas inventories were developed for specific oil and gas 

basins using WRAP Phase II emissions methodologies. If Phase II emission 

methodologies were not available, then state-reported emissions were used. Nevada did 

not report oil and gas emissions. However, Nevada was included in the Phase II oil and 

gas inventory; therefore emissions for the baseline period for Nevada exist.

4. On-road mobile – This inventory was generated using USEPA’s MOBILE6 model as 

applied by ENVIRON using inputs from states.

5. Off-road mobile – This inventory was generated using NONROAD2004 model as 

applied by ENVIRON using inputs from states.

6. Fugitive dust and road dust – This inventory was generated using the WRAP 2002 

inventory by ENVIRON with initial inputs from states. Vegetative scavenging factors 

were applied pre-processing at the county level, as opposed to grid-level for 2008 data.

7. Windblown dust – This inventory was generated using the WRAP Windblown Dust 

Model and the 2002 Meteorological Mesoscale 5 (MM5) gridded meteorological data at 

36 km grid cell resolution. Vegetative scavenging factors were applied pre-processing at 

the county level, versus post-processing at the grid cell level for 2008.

8. Biogenic – This inventory was generated using BEIS3.12 model, BELD3 land use and 

2002 MM5 meteorological data, at 36 km grid cell resolution.

9. Fires (natural and anthropogenic) – This inventory was generated using the WRAP’s 

Phase III fire inventory, which represented a 5-year average of fire activity from 2000 to 

2004. 

Table 5-4 provides Nevada emissions data by pollutant from the Plan02d baseline inventory. 

Point sources contribute 32 percent of the total anthropogenic emissions. Of that 32 percent, SO2

and NOx emissions account for 92 percent of the anthropogenic point source emissions and 29 

percent of total anthropogenic emissions. Clearly, SO2 and NOx emissions from point sources

are the primary, controllable visibility impairing pollutants in the baseline inventory. 

Table 5-4. Emissions from Plan02d Baseline Inventory in Tons

Plan02d Point Source 

Anthropogenic Emissions

Total Anthropogenic 

Emissions

Total Natural 

Emissions

(fire + biogenic +

dust)

SO2 50,720 65,543 2,200

NOx 59,864 139,353 23,044

NH3 339 10,408 1,684

VOC 2,215 85,357 811,745
Nevada Regional Haze 5-Year Progress Report, November 2014 5-7

POA 256 2,233 22,501

EC 13 1,735 4,674

Fine Soil 2,158 9,364 11,845

Coarse Mass 4,093 62,020 99,122

Total 119,658 376,013 976,815

5.4 Emissions from the 2008 Progress Period

The progress period is represented by the WRAP’s WestJump2008 inventory. Data comparisons 

were made between the baseline and 2008 emission inventory periods for Nevada in nine 

different source categories. The WRAP continues to refine inventories and conduct studies to 

better estimate emissions from the different source categories. A summary of the sources of data 

used for each source category for the progress period follows; a more detailed description of the 

inventories used in developing the WestJump2008 inventory can be found in the WRAP TSD. 

WRAP 2103, Table 3.2-1. When different models or data sources were used in the 2008 

inventory as compared to the baseline inventory, those differences are noted below.

1. Point source – The WRAP WestJump2008 inventory was generated using hourly USEPA 

CAMD CEM data for EGUs. WestJump AQMS 2013. Other point sources emissions 

are from the 2008 NEI v2. Point source oil and gas inventories were inventoried 

separately for WestJump2008 and are included in this point source inventory.

2. Area source – The area source category is now referred to as the “non-point” emission 

sector category by USEPA. WRAP’s WestJump2008 inventory used state-reported area 

source inventories from the 2008 NEI v2. The WRAP included stationary area sources, 

agricultural and natural ammonia emission sources, oil and gas production operations, 

and biogenic emissions for the non-point sector in addition to the typical area source 

emission categories.

2 Beginning in 2008, some sources that were previously considered 

“off-road” were incorporated into the area source inventory, i.e., commercial marine 

vessels, vessels on in-land waterways and in-transit locomotive emissions. For the 

WestJump2008 inventory, area oil and gas emissions were reported separately.

3. Area oil and gas – The oil and gas inventories were developed for specific oil and gas 

basins using WRAP Phase III emission methodologies, based on Version 2.0 of the 2008 

NEI. Twelve additional categories were included for the 2008 progress period than were

used in the 2002 baseline inventory. New emission methodologies, especially for VOC 

emission rates, were used. If WRAP Phase III emissions methodologies were not 

available, area source oil and gas emissions as reported by the states to the 2008 NEI 

were used. Nevada did not report oil and gas emissions to the 2008 NEI. Furthermore, 

 

2TSS Stationary Area Source Emissions June 2011.doc (last viewed 5/21/2014), located on the TSS website, 

http://vista.cira.colostate.edu/docs/wrap/emissions.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-8

since Nevada was not included in the oil and gas basins for the WestJump study, there 

were no estimates for 2008 oil and gas emissions for Nevada.

4. On-road mobile – USEPA’s Motor Vehicle Emission Simulator (MOVES) 2010 model 

was applied to state inputs. Inputs were updated with new Vehicle Miles Traveled

(VMT) and controls on vehicles.

5. Off-road mobile – The 2008 off-road mobile inventory was obtained from the 2008 NEI

v2, using NONROAD model estimates from within the National Mobile Inventory 

Model. One important methodology change was the reclassification of some sources 

previously labeled off-road; these sources were included in the non-point (area) sources

in 2008.

6. Fugitive dust and road dust –These emissions were extracted from state-reported area 

source estimates from the 2008 NEI v2. Vegetative scavenging factors were applied 

post-processing at a higher resolution grid cell level than for the 2002 data.

7. Windblown dust – Emissions were generated using the WRAP Windblown Dust Model

and a different meteorological model, 2008 WRF, at 4 km and 12 km grid cell resolution 

versus 36 km resolution in the baseline period. There were significant updates to 

enhance the accuracy of the WRAP Windblown Dust Model; thus, it will affect 

comparisons between the baseline period and the 2008 inventory. Vegetative scavenging 

factors were applied post-processing at the grid cell level rather than pre-processing at the 

county level for 2002. The WestJump AQMS project included many technical updates 

and improvements including refinements to the grid, meteorology and land-cover data 

thus improving the data results for the dust modeling. The study on dust emission 

sources for the WestJump AQMS was presented as Technical Memorandum No. 6: Dust 

Source Emissions.3

8. Biogenic – A different model, Model of Emissions of Gases and Aerosols from Nature 

(MEGAN) 2.10, was used along with different meteorology data, 2008 WRF, at a finer 

grid cell resolution, 4 km and 12 km.

9. Fires (natural and anthropogenic) – The WRAP used DEASCO34fire summaries to

account for fires in 2008 rather than a 5-year average of fires as was used in the baseline 

inventory. The tables in this report compare fire inventories between the baseline period, 

a five-year average from 2000-2004, and 2008, one-year of data from the DEASCO3 

study, although this results in a somewhat misleading comparison. There was separate 

reporting of anthropogenic and natural fires.

 

3

http://wrapair2.org/pdf/Memo6_Dust_Mar11_2013review_draft.pdf (last viewed 5/21/2014)

4

“Deterministic and Empirical Assessment of Smoke’s Contribution to Ozone,” https://deasco3.wraptools.org/ (last 

viewed 5/20/2014)
Nevada Regional Haze 5-Year Progress Report, November 2014 5-9

5.5 Emission Differences between the Baseline and Progress Periods

This section analyzes the change in emissions between the baseline (Plan02d) and 2008 

(WestJump2008) inventories and includes comparison of some source category changes between 

the 2008 and 2011 NEIs. As noted earlier in this report, a number of changes and enhancements 

have occurred between development of the baseline and current period inventories. Where such 

changes in methodology affect the 2008 data, they are identified in the following discussion.

The data by source type are shown below for the following emission species: sulfur dioxide, 

oxides of nitrogen, ammonia, volatile organic compounds, primary organic aerosol, elemental 

carbon, fine soil and coarse mass.

5.5.1 Sulfur Dioxide

Table 5-5 shows SO2 emissions by source category for the baseline and 2008 inventories. Table 

5-6 presents 2008 and 2011 NEI data for the point and mobile source categories. The primary 

source of SO2 in Nevada is from point sources. Nevada’s point sources contribute 75 percent of 

total (anthropogenic and natural) statewide SO2 emissions in the Plan02d inventory and 65 

percent of total statewide SO2 emissions in the WestJump2008 inventory. Point source SO2

emissions alone decreased by 78 percent between the 2002 and 2008 inventories. The NEI point 

source inventory shows a further decrease of 44 percent in SO2 emissions from 2008 to 2011 

(Table 5-6).

5 Area source SO2 emissions decreased 63 percent from 2002 to 2008. Due to the 

complexity of the calculation of the area source emissions, there are no area (aka non-point) 

emissions obtained directly from the NEI. 

Table 5-5. Sulfur Dioxide Emissions by Category

Source Category

Sulfur Dioxide Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point 50,720 11,0676-39,653

Area 12,953 4,863 -8,090

On-Road Mobile 454 298 -156

Off-Road Mobile 1,403 322 -1,081

Area Oil and Gas 0 0 0

Fugitive and Road Dust 0 0 0

Anthropogenic Fire 12 2 -10

Total Anthropogenic 65,543 16,552 -48,991 (-75%)

Natural Sources

 

5 Note that the 2008 NEI emissions are slightly different from the WestJump2008 inventory, which leverages more 

recent inventory development work performed by the WRAP.

6 Nevada over- reported 2008 NEI SO2 point emissions by 88 tons, due to incorrect emission unit and transcription 

errors. This correction has been accounted for in Table 5-5 and Table 5-6.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-10

Natural Fire 2,200 506 -1,694

Biogenic 0 0 0

Wind Blown Dust 0 0 0

Total Natural 2,200 506 -1,694 (-77%)

All Sources

Total Emissions 67,743 17,058 -50,685 (-75%)

On-road mobile source SO2 emissions decreased 34 percent from the Plan02d to the 

WestJump2008 inventory, while the NEI data show a further 47 percent decrease from 2008 to 

2011. Off-road mobile source SO2 emissions decreased by 77 percent from the Plan02d 

inventory to WestJump2008 inventory and 87 percent from 2008 to 2011 based on the NEI.

In sum, Table 5-5 shows all source categories of SO2 decreased between the Plan02d and 

WestJump2008 inventories. Total anthropogenic and total anthropogenic plus natural emissions 

both saw a net decrease of 75 percent between the Plan02d and WestJump2008 emission 

inventories. The large reduction of SO2 emissions for point sources is primarily due to the 

closure of Mohave in southern Nevada. The reductions in SO2 emissions from mobile sources 

are likely due to the required use of low sulfur diesel fuel discussed in Chapter Three, Section 

3.3.

There is a significant decrease in SO2 emissions from point and mobile sources in the 2008 and

2011 NEI (Table 5-6). This is primarily due to reductions in coal-fired power plant emissions, as 

discussed in Chapter Three, as well as reductions from on-road and off-road mobile source 

emissions.

Table 5-6. SO2 NEI Emissions (2008 and 2011)

Source Category

SO2 Emissions (tons/year)

2008 NEI

2011 NEI

(% change from 

2008)

Point 10,40975,8638(-44%)

On-Road Mobile 511 270 (-47%)

Off-Road Mobile 316 41 (-87%)

Figure 5-1 presents a graphical display of the difference in SO2emissions by source category for 

the baseline period and the current progress period from the WRAP TSD. Appendix A. While 

there are significant reductions in SO2 emissions from both area and point sources, the reduction 

from point sources is especially noteworthy.

 

7

See supra n.7.

8 Nevada under-reported 2011 NEI SO2 point emissions by 427 tons, due to incorrect emission unit and transcription 

errors. This correction has been accounted for in Table 5-6. SO2 NEI Emissions (2008 and 2011)
Nevada Regional Haze 5-Year Progress Report, November 2014 5-11

Figure 5-1. 2002 and 2008 Sulfur Dioxide Emissions and Differences by Source Category

5.5.2 Oxides of Nitrogen

Table 5-7 shows NOx emissions by source category for the baseline and 2008 inventories; Table 

5-8 presents 2008 and 2011 NEI data for the point and mobile source categories. The primary 

anthropogenic source categories of NOx emissions in Nevada are point and on-road mobile, 

followed by off-road mobile, and area sources. Nevada’s point sources contribute 37 percent of 

total statewide NOx emissions in the Plan02d inventory, decreasing to 25 percent in the 

WestJump2008 inventory. Point source emissions alone decreased by over 50 percent between 

the 2002 and 2008 inventories. The NEI point source inventory shows a decrease of 57 percent 

in NOx emissions from 2008 to 2011.

NOx emissions from on-road mobile sources increased 22 percent from the Plan02d to the 

WestJump2008 inventory. The increase can be attributed in part to the use of a different model

to estimate on-road mobile emissions. MOBILE6 was used for the 2002 baseline inventory, 

whereas a new model, MOVES2010, was used for the 2008 progress period. The MOVES2010 

model results in higher overall NOx and PM2.5 emissions, but lower VOC emissions.9The 

increase may also be partly due to a growth in the vehicle population, coupled with the fact that

reductions from the federal vehicle emission standards have not yet been fully realized (see 

Chapter Two). Four Nevada counties, comprising nearly three-quarters of the State’s population,

contributed over 70 percent of the increase: Clark County, 28 percent; Elko County, 18 percent; 

Pershing County, 12 percent; and Humboldt County, 12 percent. http://nvdemography.org/data-

 

9

Introduction to MOVES for Non-Modelers, August 2012, 

http://www.dvrpc.org/NTAQS/pdf/MOVES_training.pdf
Nevada Regional Haze 5-Year Progress Report, November 2014 5-12

and-publications/, 2008 data. NEI data show a 36 percent increase in on-road mobile NOx

emissions from 2008 to 2011, possibly related to a 2 percent population growth in Clark County 

and 3 percent in Washoe County.

Off-road mobile source emissions contribute 20 percent of total statewide NOx emissions in the 

Plan02d inventory, decreasing to 14 percent in the WestJump2008 inventory. Off-road mobile

source emissions alone decreased by 48 percent. NEI data also show a decrease in off-road 

mobile emissions from 2008 to 2011 of 12 percent (Table 5-8).

Overall, in the progress period 2002 to 2008, total anthropogenic emissions of NOx in Nevada 

decreased by 23 percent (Table 5-7 and Figure 5-2). Total NOx emissions saw a net decrease of 

26 percent between the Plan02d and WestJump2008 emission inventories. Increases in on-road 

mobile and area source inventory totals were offset by larger decreases in point and off-road 

mobile totals. The increase in emissions for area sources from the 2002 to the 2008 inventory 

may be a result of a reclassification of some off-road mobile sources into the area source 

category. This reclassification may have also contributed to the decrease in the emissions for the 

off-road inventory totals.

Table 5-7. Oxides of Nitrogen Emissions by Category

Source Category

Oxides of nitrogen Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point 59,864 29,34410-30,520

Area 5,725 11,321 5,597

On-Road Mobile 41,089 50,068 8,979

Off-Road Mobile 32,565 17,081 -15,484

Area Oil and Gas 63 0 -63

Fugitive and Road Dust 0 0 0

Anthropogenic Fire 48 13 -35

Total Anthropogenic 139,353 107,827 -31,526 (-23%)

Natural Sources

Natural Fire 8,026 3,575 -4,451

Biogenic 15,018 7,364 -7,654

Wind Blown Dust 0 0 0

Total Natural 23,044 10,939 -12,105 (-53%)

All Sources

Total Emissions 162,397 118,76611-43,631 (-26%)

 

10 Nevada over-reported 2008 NEI NOx emissions by 746 tons, due to incorrect emission unit and transcription 

errors. This correction has been accounted for in Table 5-7 and Table 5-8.

11 See supra n. 10.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-13

Table 5-8. NOx NEI Emissions (2008 and 2011)

Source Category

NOx Emissions (tons/year)

2008 NEI

2011 NEI

(% change from 

2008)

Point 20,93412 10,54813 (-50%)

On-Road Mobile 40,643 55,389 (36%)

Off-Road Mobile 16,797 14,706 (-12%)

Figure 5-2 shows a graphical display of the difference in NOx emissions by source category for 

the baseline period and the current progress period from the WRAP TSD. Appendix A. The 

reduction in emissions from point and off-road mobile sources is noteworthy.

Figure 5-2. 2002 and 2008 Oxides of Nitrogen Emissions and Differences by Source 

Category

5.5.3 Ammonia

Table 5-9 shows NH3 emissions by source category, and Figure 5-3 shows the graphical display

from the WRAP TSD. Appendix A. The primary source of anthropogenic emissions of NH3 in 

Nevada is from area sources, while natural fire is the dominant natural source of NH3 emissions.

 

12 See supra n. 10.

13 Nevada under-reported 2011 NEI NOx point emissions by 1,494 tons, due to incorrect emission unit and 

transcription errors. This correction has been accounted for in Table 5-8.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-14

Nevada’s area sources contribute 66 percent of total statewide NH3 emissions in the Plan02d 

inventory and 61 percent of total NH3 emissions in the WestJump2008 inventory. Area sources 

of NH3 emissions alone decreased by 29 percent between the Plan02d and WestJump2008 

inventories.

On-road mobile sources showed a notable 58 percent decrease in NH3 emissions between the 

2002 and 2008 inventories. On-road mobile sources contribute 17 percent of total statewide NH3

emissions in the Plan02d inventory and nine percent in the WestJump2008 inventory. Natural 

fire contributes 14 and 27 percent in the 2002 and 2008 inventories, respectively.

In sum, all anthropogenic source categories of NH3 decreased between the Plan02d and 

WestJump2008 inventories. Total anthropogenic emissions of NH3 saw a net decrease of 34

percent between the Plan02d and WestJump2008 emission inventories. In spite of the fact that 

emissions from natural fires increased by almost 50 percent, total NH3 emissions still decreased 

by a net of 22 percent.

Ammonia is not a criteria pollutant and is not inventoried or reported to the NEI; thus, no NEI

emissions data for NH3 is provided.

Table 5-9. Ammonia Emissions by Category

Source Category

Ammonia Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point 339 302 -37

Area 8,009 5,717 -2,293

On-Road Mobile 2,030 849 -1,182

Off-Road Mobile 22 20 -2

Area Oil and Gas 0 0 0

Fugitive and Road 

Dust

0 0 0

Anthropogenic Fire 8 6 -2

Total Anthropogenic 10,408 6,893 -3,515 (-34%)

Natural Sources

Natural Fire 1,684 2,490 805

Biogenic 0 0 0

Wind Blown Dust 0 0 0

Total Natural 1,684 2,490 805 (48%)

All Sources

Total Emissions 12,092 9,382 -2,710 (-22%)
Nevada Regional Haze 5-Year Progress Report, November 2014 5-15

Figure 5-3. 2008 and 2008 Ammonia Emissions and Differences by Source Category

5.5.4 Volatile Organic Compounds

Table 5-10 shows VOC emissions by source category; Table 5-11 presents 2008 and 2011 NEI 

data for the point and mobile source categories. Figure 5-4 shows a graphical display from the 

WRAP TSD. Appendix A. The data show huge reductions in VOC emissions from natural 

sources with lesser reductions from anthropogenic sources. Biogenic emissions from natural 

sources dominate the Nevada VOC emissions inventory.

VOC emissions showed a 61 percent decrease overall, mostly due to a decrease in the biogenic 

emission inventory (67 percent). However, estimates for biogenic emissions of VOCs have 

undergone significant updates since 2002, hence changes reported here are more reflective of 

enhancements in the inventory methodology rather than actual changes in emissions. Table 5-3. 

Specifically, the Plan02d inventory used the BEIS3.12 model, while the WestJump2008 

inventory used the MEGAN2.10 model outputs. Also, different meteorological years were used, 

2002 MM5 for the Plan02d inventory and 2008 WRF for the WestJump2008 inventory. In 

addition, higher temporal and spatial variability of land cover and improved emission factors 

based on better sources of data (e.g., satellites and field studies) were used for the 

WestJump2008 inventory. 

There were also decreases in the on-road mobile, natural fire and anthropogenic fire source 

categories. The decrease in on-road mobile emissions of VOCs is partly due to the use of 

different models. MOBILE6 was used for the Plan02d inventory, while MOVES2010 was used 

for 2008. There were also new VMT data and new controls on vehicles (WRAP 2013, Table 

3.2-1), which may account for some of the decrease in emissions. Specifically, VOC emissions 

are reduced due to implementation of the Tier 2 Vehicle and Gasoline Sulfur Program discussed

Chapter Two.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-16

For natural fire emissions, a detailed and comprehensive inventory was conducted for year 2008

in the DEASCO3 study.14 VOC emissions decreased significantly in the WestJump2008 

inventory. However, only fire emissions from a single year (2008) are represented here for the 

progress period. Thus, not all fire events for the 2005-2009 period are represented in the 

WestJump2008 inventory. Due to the variability and sporadic nature of wildfire, a comparison 

between these inventories is complicated.

Table 5-10. Volatile Organic Compound Emissions by Category

Source Category

Volatile Organic Compound Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point 2,215 2,53015 338

Area 28,592 40,973 12,381

On-Road Mobile 36,257 21,302 -14,955

Off-Road Mobile 18,094 18,783 688

Area Oil and Gas 129 0 -129

Fugitive and Road 

Dust

0 0 0

Anthropogenic Fire 70 16 -54

Total Anthropogenic 85,357 84,026 -1,331 (-2%)

Natural Sources

Natural Fire 17,606 4,204 -13,403

Biogenic 794,139 262,912 -531,227

Wind Blown Dust 0 0 0

Total Natural 811,745 267,115 -544,630 (-67%)

All Sources

Total Emissions 897,102 351,142 -545,960 (-61%)

Table 5-11 shows a decrease in point source, on-road mobile and off-road mobile emissions of 

VOC from the 2008 NEI to the 2011 NEI of 17 percent, 20 percent and 18 percent, respectively.

 

14 See supra n. 4.

15 Nevada over-reported NEI 2008 VOC point emissions by 423 tons, due to incorrect emission unit and 

transcription errors. This correction has been accounted for in Table 5-10 and Table 5-11.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-17

Table 5-11. VOC NEI Emissions (2008 and 2011)

Source Category

VOC Emissions (tons/year)

2008 NEI 2011 NEI

(% change from 2008)

Point 1,17616 97117 (-17%)

On-Road 27,084 21,779 (-20%)

Off-Road 18,759 15,328 (-18%)

Figure 5-4. 2002 and 2008 Volatile Organic Compounds Emissions and Differences by 

Source Category 

5.5.5 Primary Organic Aerosol

Table 5-12 shows primary organic aerosol emissions by source category, and Figure 5-5 shows 

the graphical display from the WRAP TSD. Appendix A. Wildfires dominate the primary 

organic aerosol emissions for both the Plan02d and WestJump2008 inventories at 90 percent and 

58 percent, respectively, although anthropogenic sources (area and mobile) are also an important 

component of the inventory. Large wildfire events are generally sporadic and highly variable

from year to year. This variability is seen in the large reduction of primary organic aerosol 

natural fire emissions between the Plan02d and WestJump2008 inventory years. 

 

16 See supra n. 15.

17 Nevada under-reported NEI 2011VOC point emissions by 746 tons, due to incorrect emission unit and 

transcription errors. This correction has been accounted for in Table 5-11. 
Nevada Regional Haze 5-Year Progress Report, November 2014 5-18

Overall, total emissions of primary organic aerosols decreased by 52 percent from the Plan02d to 

the WestJump2008 inventory. Point source emissions of primary organic aerosols decreased by 

82 percent over that period. While source categories other than natural and anthropogenic fires 

and point sources saw increases in primary organic aerosol emissions, the total percentage of the 

other sources is eight percent and 42 percent of the total (anthropogenic plus natural) emissions 

for the Plan02d and WestJump2008 inventories, respectively. The increase in area emissions is 

explained in Section 5.4; beginning in 2008, some sources that were previously considered “offroad” were incorporated into the area source inventory. Clark and Washoe Counties, comprising 

87 percent of the State population (http://nvdemography.org/data-and-publications/, 2008 data), 

contribute over 75 percent to total area emissions and 63 percent to total on-road emissions in the 

WestJump2008 inventory.

Table 5-12. Primary Organic Aerosol Emissions by Category

Source Category

Primary Organic Aerosol Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point* 256 46 -210

Area 687 2,283 1,596

On-Road Mobile 314 1,053 739

Off-Road Mobile 572 689 117

Area Oil and Gas 0 0 0

Fugitive and Road 

Dust

332 891 559

Anthropogenic Fire 73 22 -51

Total Anthropogenic 2,233 4,985 2,752 (123%)

Natural Sources

Natural Fire 22,501 6,831 -15,670

Biogenic 0 0 0

Wind Blown Dust 0 0 0

Total Natural 22,501 6,831 -15,670 (-70%)

All Sources

Total Emissions 24,734 11,816 -12,918 (-52%)

*Point source data includes only oil and gas and regulated CEM sources. More comprehensive point source data 

were not available at the time this report was prepared but will be made available through the WRAP TSS 

(http://vista.cira.colostate.edu/tss/).
Nevada Regional Haze 5-Year Progress Report, November 2014 5-19

Figure 5-5. 2002 and 2008 Primary Organic Aerosol Emissions and Differences by Source 

Category 

5.5.6 Elemental Carbon

Table 5-13 shows elemental carbon emissions by source category, and Figure 5-6 shows the 

graphical display from the WRAP TSD. Appendix A. Wildfires dominated elemental carbon

emissions for the Plan02d inventory at 73 percent. Large wildfire events are generally sporadic 

and highly variable from year to year. Thus, variability is seen in the elemental carbon emissions 

from natural fire between the Plan02d and WestJump2008 inventory years. 

Total elemental carbon emissions showed a 31 percent decrease between 2002 and 2008. This 

was mostly due to a 76 percent decrease in emissions from natural fire. On-road mobile, area 

and point source emissions increased from 2002 to 2008. On-road mobile sources dominated the 

elemental carbon emissions for the WestJump2008 inventory at 43 percent, while wildfires 

contributed 26 percent. Area and point source emissions contribute less than one percent each to 

the 2008 inventory. 

Clark County and Washoe County, comprising 87 percent of the State population

(http://nvdemography.org/data-and-publications/, 2008 data), are the biggest contributors to the 

area and on-road mobile emissions for the 2008 inventory. In the area source category, Clark 

County’s contribution is 29 percent and Washoe County’s contribution is 17 percent. In the onroad source category, Clark County’s contribution is 43 percent and Washoe County’s 

contribution is 16 percent.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-20

Table 5-13. Elemental Carbon Emissions by Category

Source Category

Elemental Carbon Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point* 13 64 51

18

Area 96 368 272

On-Road Mobile 235 1,891 1,656

Off-Road Mobile 1,354 954 -400

Area Oil and Gas 0 0 0

Fugitive and Road 

Dust

24 14 -10

Anthropogenic Fire 13 6 -7

19

Total Anthropogenic 1,735 3,295 1,560 (90%)

20

Natural Sources

Natural Fire 4,674 1,130 -3,544

Biogenic 0 0 0

Wind Blown Dust 0 0 0

Total Natural 4,674 1,130 -3,544 (-76%)

All Sources

Total Emissions 6,409 4,425 -1,984 (-31%)

*Point source data includes only oil and gas and regulated CEM sources. More comprehensive point source data 

were not available at the time this report was prepared, but will be made available through the WRAP TSS 

(http://vista.cira.colostate.edu/tss/).

 

18 Note values in Table 5-13 are different than in the WRAP TSD, due to rounding. 

19 See supra n. 18.

20 See supra n. 18.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-21

Figure 5-6. 2002 and 2008 Elemental Carbon Emissions and Differences by Source 

Category 

5.5.7 Fine Soil

Table 5-14 shows fine soil emissions by source category, and Figure 5-7 shows the graphical 

display from the WRAP TSD. Appendix A. Fine soil emissions were identified as PM fine 

emissions in the 2009 RH SIP. Fine soil emissions inventories show increases in fugitive dust 

and natural windblown dust from the Plan02d to the WestJump2008 inventory. These increases

are likely due to updates in inventory development methodologies rather than actual increases. 

Appendix A, p. 6-2. 

Table 5-14. Fine Soil Emissions by Category

Source Category

Fine Soil Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point* 2,158 209 -1,948

Area 830 1,024 195

On-Road Mobile 23921 190 -49

Off-Road Mobile 0 49 49

Area Oil and Gas 0 0 0

Fugitive

and Road Dust

6,128 19,216 13,087

Anthropogenic Fire 9 10 1

 

21 Fine soil emissions showed zero emissions for the on-road source category in the 2009 RH SIP. This was strictly 

an oversight and has been corrected here.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-22

Source Category

Fine Soil Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Total Anthropogenic 9,364 20,698 11,334 (121%)

Natural Sources

Natural Fire 1,406 2,552 1,146

Biogenic 0 0 0

Wind Blown Dust 10,438 17,051 6,613

Total Natural 11,845 19,603 7,758 (65%)

All Sources

Total Emissions 21,208 40,301 19,092 (90%)

*Point source data includes only oil and gas and regulated CEM sources. More comprehensive point source data 

were not available at the time this report was prepared but will be made available through the WRAP TSS 

(http://vista.cira.colostate.edu/tss/).

Figure 5-7. 2002 and 2008 Fine Soil Emissions and Differences by Source Category 

5.5.8 Coarse Mass

Table 5-15 shows coarse mass emissions by source category, and Figure 5-8 shows the graphical 

display from the WRAP TSD. Appendix A. Coarse mass emissions were identified as PM 

coarse emissions in the 2009 RH SIP. Coarse mass emission inventories showed increases in 

fugitive and road dust and natural windblown dust from the Plan02d to the WestJump2008

inventory. Fugitive dust includes sources such as agricultural operations, construction and 

mining operations and windblown dust from vacant lands. These increases in part can be 

attributed to updates in inventory development methodologies rather than actual increases. 

Appendix A, p. 6-2. However, increases in the fugitive dust inventories may also be due to 

increases in population, while increases in road dust may be due to increases in estimated VMT.
Nevada Regional Haze 5-Year Progress Report, November 2014 5-23

The WestJump2008 inventory for coarse mass emissions is dominated by emissions in Clark and 

Elko Counties at 61 percent and 13 percent, respectively. In Clark County, particulate air 

pollution is largely associated with windblown dust, re-entrained road dust, or construction 

activities.22 The windblown dust category includes more of the natural influences such as wind 

erosion on natural lands. While point source and natural fire emissions decreased, most of the 

other sources of coarse mass showed emission increases.

Table 5-15. Coarse Mass Emissions by Category

Source Category

Coarse Mass Emissions (tons/year)

2002

(Plan02d)

2008

(WestJump2008)

Difference

(Percent Change)

Anthropogenic Sources

Point* 4,093 1,761 -2,331

Area 897 1,094 198

On-Road Mobile 245 2,014 1,769

Off-Road Mobile 0 82 82

Area Oil and Gas 0 0 0

Fugitive and Road 

Dust

56,779 161,532 104,753

Anthropogenic Fire 7 4 -3

Total Anthropogenic 62,020 166,488 104,468 (168%)

Natural Sources

Natural Fire 5,176 1,310 -3,866

Biogenic 0 0 0

Wind Blown Dust 93,946 153,459 59,513

Total Natural 99,122 154,769 55,647 (56%)

All Sources

Total Emissions 161,142 321,257 160,115 (99%)

*Point source data includes only oil and gas and regulated CEM sources. More comprehensive point source data 

were not available at the time this report was prepared but will be made available through the WRAP TSS 

(http://vista.cira.colostate.edu/tss/).

 

22

http://www.clarkcountynv.gov/Depts/AirQuality/Documents/Planning/SIP/PM10/PM10_SIP_PLAN_without_Appe

ndices.pdf (page 3-1; last viewed 8/29/ 2014)
Nevada Regional Haze 5-Year Progress Report, November 2014 5-24

Figure 5-8. 2002 and 2008 Coarse Mass Emissions and Differences by Source Category 

As can be seen from the tables and figures in this chapter, visibility-impairing emissions from 

point sources have significantly decreased with the exception of volatile organic compounds and 

elemental carbon. Point sources of both of these two pollutants contribute only a minor fraction 

of the anthropogenic emission sources.