Chapter Two – Baseline and Natural Visibility Conditions and 

Uniform Rate of Progress 

2.1 INTRODUCTION 

2.2 BASELINE CONDITIONS FOR THE JARBIDGE WILDERNESS AREA 

2.3 NATURAL CONDITIONS FOR THE JARBIDGE WILDERNESS AREA 

2.4 UNIFORM RATE OF PROGRESS GLIDEPATH TO NATURAL 

CONDITIONS IN 2064 

2.5 HAZE IMPACTING PARTICLES – BASELINE PERIOD 

2.5.1 Aerosol Composition for the Jarbidge Wilderness Area 

 2.5.1.1 Summary of Aerosol Composition 

 2.5.1.2 20 Percent Worst Days 

 2.5.1.3 20 Percent Best Days 

 2.5.1.4 All IMPROVE Sample Days 

2.5.2 Comparison of Baseline Extinction for Best and Worst Days 

2.5.3 Aerosol Pollutant Trends 

2.6 REFERENCES 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-1 
2.1 INTRODUCTION

The goal of the Regional Haze Rule (RHR)(64 FR 35714) is the restoration of natural visibility 

conditions in the 156 mandatory Class I areas identified pursuant to the 1977 Clean Air Act 

Amendments. Federal visibility regulations detail how to establish goals to restore visibility to 

natural conditions by the year 2064 for the Class I areas. These regulations also require states to 

calculate baseline, current, and natural visibility conditions, which in turn are used to calculate 

the uniform rate of progress per year to achieve natural conditions by 2064. 

Natural visibility is determined by estimating the natural concentrations of visibility impairing 

pollutants and then calculating total light extinction. Baseline visibility is the starting point for 

the improvement of visibility conditions. The baseline for this regional haze state 

implementation plan (SIP) is the years 2000 through 2004. Current conditions are assessed 

every five years as part of the SIP review, where actual progress in reducing visibility 

impairment is compared to the reductions committed to in the SIP. 

The baseline and current visibility conditions for the Jarbidge Wilderness Area are based on 

measurements of particulate air pollution at the JARB1 Interagency Monitoring of Protected 

Visual Environments (IMPROVE) monitoring site, as discussed in Chapter One. The revised 

IMPROVE algorithm was used to calculate the Haze Index for the Jarbidge Wilderness Area. 

This chapter presents and interprets the IMPROVE monitoring data to identify the role of

individual components in visibility impairment at JARB1. The following chapters will present 

and interpret the emissions data and modeling results that, with this chapter, are the technical 

basis for determining Nevada’s reasonable progress. The following paragraphs present a 

synopsis of the analyses of the IMPROVE monitoring data. 

Analyses of the JARB1 monitor data have identified a baseline visibility condition of 12.07 

deciviews (dv) and natural visibility conditions of 7.87 dv for the 20 percent worst days. The 

comparison of the initial baseline conditions to natural visibility conditions indicates the amount 

of improvement necessary to attain natural visibility by 2064. The uniform rate of progress 

glidepath indicates a uniform rate of progress value of 11.09 dv for 2018 worst days leading to 

restoration of natural visibility conditions by 2064. 

Organic matter carbon and elemental carbon extinction account for more than 45 percent of the 

total average annual reconstructed extinction at the JARB1 monitor for the 20 percent worst days 

of the baseline. In addition, coarse and fine particle mass extinction account for an additional 30 

percent of the average annual extinction at JARB1. Approximately 20 percent of the annual 

extinction budget is due to the formation of ammonium sulfate and ammonium nitrate due to 

emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) from predominantly anthropogenic 

sources. These conclusions support the observations of Nevada Division of Environmental 

Protection (NDEP) staff, presented in Chapter One, regarding the significant contribution of

windblown dust and natural fire emissions to visibility impairment at the Jarbidge Wilderness 

Area. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-2 
2.2 BASELINE CONDITIONS FOR THE JARBIDGE WILDERNESS AREA

Baseline visibility is the annual average of the on-site IMPROVE monitoring data for the leastimpaired days (i.e. the 20 percent best days or “best days”) and most impaired days (i.e. the 20 

percent worst days or “worst days”) for the years 2000 through 2004, as specified in 40 CFR 

51.308(d)(2)(i). Baseline visibility is equivalent to current visibility conditions for this initial 

review period and is the reference point against which visibility improvement is tracked. 

Nevada has established baseline visibility conditions for the best and worst visibility days at the 

Jarbidge Wilderness Area using data from IMPROVE monitor JARB1. The average was 

calculated for the years 2000 through 2004 (the 2000 data is invalid for JARB1 as it fails to meet 

USEPA’s data completeness criteria) for the best and worst days. The baseline calculations were 

made in accordance with 40 CFR 51.308(d)(2) and USEPA’s Guidance for Tracking Progress 

Under the Regional Haze Rule (EPA-454/B-03-004, September 2003). 

The baseline conditions are the average of the annual haze index calculated from the IMPROVE 

monitor data over the five-year baseline period 2000 through 2004 for both the 20 percent worst 

(12.07 dv) and 20 percent best (2.56 dv) days. Figures 2-1 and 2-2 are photographs of reference 

vistas representative of baseline extinction conditions for the best and worst days, respectively, at 

the Jarbidge Wilderness Area. 

2.3 NATURAL CONDITIONS FOR THE JARBIDGE WILDERNESS AREA 

Natural visibility represents the visibility condition that would be observed in the absence of 

human-caused impairment. The natural condition for each Class I area represents the visibility 

goal expressed in deciviews for the 20 percent worst and the 20 percent best days that would 

exist if there were only naturally occurring impairment. The 20 percent worst days natural 

conditions correspond to the long-term natural visibility goal to be reached by 2064. 40 CFR 

51.308(d)(1) Each state must estimate natural visibility levels for Class I areas within its borders 

in consultation with federal land managers (FLMs) and other states. 40 CFR 51.308(d)(2) 

Natural background visibility is based on annual average concentrations of fine particle 

components. The natural conditions estimates were calculated consistent with USEPA’s 

Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule (EPA454/B-03-005, September 2003). The natural background visibility for Jarbidge is 7.87 dv for 

the 20 percent worst days and 1.14 dv for the 20 percent best days. 

Figures 2-3 and 2-4 are photographs of reference vistas representative of natural extinction 

conditions for the best and worst days at the Jarbidge Wilderness Area. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-3 
FIGURE 2-1 

REFERENCE VISTA OF THE JARBIDGE WILDERNESS AREA 

FOR BASELINE BEST DAYS

Reference Vista: Mary’s River Peak 

Photo taken at 3:00 pm

Haze Index (HI) = 3 deciview

Bext = 13 Mm-1

Visual Range = 300 km / 186 mi

FIGURE 2-2 

REFERENCE VISTA OF THE JARBIDGE WILDERNESS AREA 

FOR BASELINE WORST DAYS

Reference Vista: Mary’s River Peak 

Photo taken at 3:00 pm

Haze Index (HI) = 12 deciviews 

Bext = 33 Mm-1

Visual Range = 120 km / 75 mi

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-4 
FIGURE 2-3 

REFERENCE VISTA OF THE JARBIDGE WILDERNESS AREA 

FOR NATURAL CONDITIONS BEST DAYS

Reference Vista: Mary’s River Peak 

Photo taken at 9:00 am

Haze Index (HI) = 1 deciview

Bext = 11 Mm-1

Visual Range = 350 km / 218 mi

FIGURE 2-4 

REFERENCE VISTA OF THE JARBIDGE WILDERNESS AREA 

FOR NATURAL CONDITIONS WORST DAYS

Reference Vista: Mary’s River Peak 

Photo taken at 9:00 am

Haze Index (HI) = 8 deciviews 

Bext = 23 Mm-1

Visual Range = 170 km / 106 mi

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-5 
2.4 UNIFORM RATE OF PROGRESS GLIDEPATH TO NATURAL CONDITIONS 

IN 2064 

Each state must set goals that provide for reasonable progress towards achieving natural 

visibility conditions by 2064. The reasonable progress goals must: 1) provide for improvement 

in visibility for the most impaired days over the period of the implementation plan; and 2) ensure 

no degradation in visibility for the least impaired days over the same period. States are directed 

to graphically show a uniform rate of progress (URP) toward natural visibility conditions for 

each Class I area within the State. The revised IMPROVE II algorithm was used for the 

calculation of the URP glidepath for the Jarbidge Wilderness Area. 

A graph depicting the worst days glidepath for the Jarbidge Wilderness Area was developed in 

accordance with USEPA guidance for tracking progress (Guidance for Setting Reasonable 

Progress Goals Under the Regional Haze Rule, June 1, 2007), using data collected from the 

IMPROVE monitor JARB1. The glidepath is one of the indicators used to set reasonable 

progress goals and is simply a graph portraying a straight line drawn from the level of visibility 

impairment for the worst days baseline period to the natural background level with 2064 as the 

attainment date. 

The URP is determined by the following equation, which calculates the slope of the glidepath in 

deciviews per year: 

URP = (Baseline Condition – Natural Condition) / 60 years 

URP = (12.07 dv – 7.87 dv) / 60 years 

URP = 0.07 dv / year reduction 

The uniform progress needed by 2018, the end of the first planning period, to achieve worst days 

natural visibility conditions by 2064 is calculated by multiplying the URP by the number of 

years in the first planning period (i.e. 2004 to 2018), as follows: 

2018 URP = (URP) x (14 years) 

2018 URP = 0.07 dv / year x 14 years 

2018 URP = 0.98 dv reduction 

Table 2-1 provides the URP data for the worst days and identifies the baseline for the best days. 

The baseline visibility for the 20 percent worst days at the Jarbidge Wilderness Area is 

calculated to be 12.07 dv. For the baseline 20 percent best days, visibility is calculated to be 

2.56 dv. The URP glidepath is shown on Figure 2-5, which depicts the observed annual baseline 

visibility conditions by solid diamonds with the worst days baseline shown by the line through 

the solid diamonds. The glidepath for a URP toward reaching the goal of natural conditions is 

represented by the sloping line with the open triangles identifying the URP at five year intervals. 

Natural conditions for the worst days are shown by the horizontal line in the middle of the graph. 

The figure also shows the observed annual baseline conditions for the 20 percent best days by 

open diamonds with the baseline shown by the short line through the open diamonds. The 

reasonable progress goal must ensure no degradation in visibility for the best days over the 

planning period. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-6 
TABLE 2-1

UNIFORM RATE OF PROGRESS FOR THE 

JARBIDGE WILDERNESS AREA

Class I Area

20% Worst

Days

Baseline

Condition 

(dv)

20% Worst

Days 2018 

Uniform

Progress 

Goal 

(dv)

2018 

Reduction

Needed for 

20% Worst

Days 

(dv)

20% Worst

Days 2064

Natural

Conditions 

(dv)

2064

Reduction

Needed for

20% Worst

Days 

(dv)

20% Best

Days

Baseline

Condition 

(dv)

Jarbidge

Wilderness Area

12.07 11.09 0.98 7.87 4.20 2.56

FIGURE 2-5 

UNIFORM RATE OF PROGRESS GLIDEPATH FOR THE 

JARBIDGE WILDERNESS AREA

Uniform Rate of Progress Glidepath

Jarbidge Wilderness Area - 20 Percent Best and Worst Days

12.07 11.79 11.44 11.09 10.74 10.39 10.04 9.69 9.34 8.99 8.64 8.29 7.87

0

2

4

6

8

10

12

14

16

2000 2004 2008 2012 2016 2020 2024 2028 2032 2036 2040 2044 2048 2052 2056 2060 2064

Year

Baseline Obs 20% W 2000-2004 Baseline 20% W Glide Path

Baseline Obs 20% B 2000-2004 Baseline 20% B Natural Conditions

2018 - End of 1st Planning Period

Haze Index (Deciview)

2.5 HAZE IMPACTING PARTICLES – BASELINE PERIOD

Some of the fine particles that compose aerosols absorb light, while others reflect or scatter light, 

resulting in light extinction between the viewer and the light source. The IMPROVE monitor 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-7 
collects a 24-hour sample of these particles onto a filter, and they are analyzed at a laboratory to 

determine the standard components of the aerosol extinction. 

Monitored Components

The monitored concentrations of PM10 are divided into six major components, the first five of 

which are assumed to be PM2.5 and the sixth is PM2.5-10. The monitored species are listed below 

by identifier with the common name in parenthesis. 

• SO4 (sulfate) 

• NO3 (particulate nitrate)

• OC (organic carbon) 

• EC (elemental carbon) 

• OF (other fine particulate or soil) 

• CM (coarse matter) 

The concentrations of these species are used in conjunction with the IMPROVE equation to 

calculate the light extinction. 

Emission Species

The statewide emission inventory of pollutants that were used in the emission scenarios for this 

SIP include: 

• SO2 (Sulfur dioxide) 

• SOx (Sulfur oxides) 

• NOx (Nitrogen oxides) 

• POA (Primary organic aerosol) 

• EC (Elemental carbon) 

• PMF (Particulate matter fine)

• PMC (Particulate matter coarse) 

• NH3 (Ammonia) 

The baseline emissions and emission projections are discussed in detail in Chapter Three. 

Extinction Species

Visibility conditions are then estimated by relating the IMPROVE 24-hour average PM mass 

measurements (i.e. concentration data for the species listed above) to the PM components of light 

extinction as identified in the IMPROVE equation. The extinction components are listed below. 

The bold text indicates how the monitored extinction components will be identified in the 

remainder of the SIP. 

• Ammonium sulfate [(NH4)2SO4] or SO4

• Particulate ammonium nitrate [(NH4)NO3] or NO3

• Organic matter carbon [OMC] 

• Elemental carbon [EC] 

• Fine soil [SOIL] 

• Coarse matter [CM] 

• Sea Salt 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-8 
2.5.1 Aerosol Composition for the Jarbidge Wilderness Area

Analyses of the IMPROVE monitor data provides important insight to the relative importance of

the components of measured visibility impairing pollutants. The monitoring data for the 20 

percent worst, 20 percent best, and IMPROVE sample days were analyzed on an annual, 

monthly, and daily basis to evaluate the causes of visibility impairment during the baseline 

period. 

2.5.1.1 Summary of Aerosol Composition 

This section describes the aerosol composition observed at the JARB1 IMPROVE monitor 

during the baseline period. The following sections present the monitoring data for the 20 percent 

worst days, 20 percent best days, and all IMPROVE sample days. 

Organic matter carbon (OMC) is the most important contributor to fine particulate mass and 

light extinction on the most impaired days and for all IMPROVE sample days. OMC is also a 

significant contributor on the least impaired days of the baseline period at JARB1. Elevated 

levels of OMC and EC and their seasonal signature suggest impact from fire and biogenic 

sources, which are significant natural sources of primary organic aerosol (POA) and volatile 

organic compounds (VOCs), components of OMC. Anthropogenic emissions contributing to 

OMC include carbon from combustion of fossil fuels and wood burning, but are not likely 

significant sources of OC emissions at this rural site. However significant visibility impacts due 

to OC emissions from natural fire events are common at the Jarbidge Wilderness Area and 

explain the large daily, seasonal, and annual variations of the reconstructed OMC extinction 

described in the next sections. 

Coarse matter (CM) or particulate matter with particles having diameters between 2.5 and 10 

microns is the second most important contributor to reconstructed extinction for the worst days 

of the baseline period. CM has a relatively small contribution to visibility impairment on the 

best days, but is a significant contributor to visibility impairment for IMPROVE sample days. 

The light extinction efficiency of CM is very low compared to the extinction efficiency for 

sulfate, nitrate, and carbon, as described in Chapter One. The significant CM contributions to 

reconstructed extinction suggest the seasonal importance of local and regional transport of 

particulate matter due to naturally occurring windblown dust events. 

Ammonium sulfate (SO4) or sulfate is an important contributor to visibility impairment at JARB1 

for the worst days and IMPROVE sample days. SO4 is the most significant contributor on the 

best days. Sulfate particles are formed in the atmosphere from SO2 emissions. Sulfate particles 

occur as hydrogen sulfate, ammonium bisulfate and ammonium sulfate depending on the 

availability of ammonia in the atmosphere. Although SO4 contributions show some seasonal 

increases during the summer months, the lack of daily variability suggests the sulfate 

contributions are influenced by regional transport rather than local sources. 

Soil (SOIL) or particulate matter with particles having diameters less than 2.5 microns is a minor 

contributor to reconstructed extinction for the worst, best and IMPROVE sample days of the 

baseline period. Episodes of relatively high SOIL contribution coupled with relative high CM 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-9 
contributions may be indicative of local and regional seasonal transport of particulate matter due 

to windblown dust events. Occasionally, elevated SOIL can be attributed to long-range transport 

of international dust episodes originating outside the US. 

Elemental carbon (EC) is a minor contributor to visibility impairment at JARB1 for the worst, 

best and IMPROVE sample days of the baseline period. The light extinction efficiency of EC is 

high compared to the extinction efficiency for sulfate, nitrate and carbon, as described in Chapter 

One. Common sources of EC emissions are fire, including agricultural burning, prescribed fire, 

and natural fire, as well as incomplete combustion of fossil fuels. The seasonality and common 

trend shared with OMC extinction suggest fire emissions may also be the dominant source of EC 

extinction at JARB1. 

Ammonium nitrate (NO3) or nitrate is a minor contributor to reconstructed extinction for the 

worst, best and IMPROVE sample days of the baseline period at JARB1. However, NO3 is a 

significant contributor for some individual days. NO3 is formed in the atmosphere by the 

reaction of ammonia (NH3) and nitrogen oxides (NOx). NO3 formation is limited by the 

availability of ammonia and temperature. Ammonia preferentially reacts with SO2 and sulfate 

before reacting with NOx. Particle nitrate is formed at lower temperatures, so NO3 levels are 

lower in the summer months and higher in the winter months. Therefore the relative NO3

contribution to visibility impairment is seasonal as identified below. NOx emissions are the 

result of fossil fuel combustion by point, area, on-road, and off-road mobile sources. The 

relatively minor contribution of NO3 to reconstructed extinction at JARB1 suggests that 

formation is limited by both the availability of ammonia and the paucity of NOx sources in this 

rural setting. 

Sea Salt (SEA SALT) is a trace contributor to reconstructed extinction at JARB1. The new 

IMPROVE equation uses the chlorine ion from routine IMPROVE measurements to calculate 

sea salt levels, accounting for the occasional contribution of SEA SALT to extinction at JARB1. 

2.5.1.2 20 Percent Worst Days 

Figure 2-6 shows the annual reconstructed light extinction over the baseline period based on 

monitor data from JARB1 site for the 20 percent worst days. The variability of annual worst 

days reconstructed light extinction is nearly 8 Mm-1. 

The line graph shown as Figure 2-7 shows the individual components of the reconstructed light 

extinction over the baseline period based on JARB1 IMPROVE data for the 20 percent worst 

days. OMC is the most significant contributor to visibility impairment at JARB1 for the baseline 

period, followed by CM and SO4. SOIL, EC, and NO3 are less significant but sub-equal 

contributors to visibility impairment for the baseline period. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-10 
FIGURE 2-6 

ANNUAL RECONSTRUCTED EXTINCTION FOR WORST DAYS 

OF THE BASELINE PERIOD

The baseline period annual variation for OMC is nearly 7 Mm-1, indicating the large range of 

annual effects produced by fire emissions, one of the dominant sources of OMC. 2002 was a bad 

fire year in the western US, as reflected on Figure 2-7 by the OMC trend. The baseline period 

variation for CM is over 2 Mm-1, suggesting the range of effects produced by emissions from

localized wind events, especially during seasonal drought conditions. The remaining 

components show less variability during the baseline period. 

FIGURE 2-7 

ANNUAL RECONSTRUCTED EXTINCTION BY SPECIES FOR 

WORST DAYS OF BASELINE PERIOD

Figure 2-8 displays the monthly distribution of the reconstructed extinction for the 20 percent 

worst days of the baseline period for the Jarbidge Wilderness Area. The worst days are generally 

summer events, occurring during the period mid-March to the end of September of each year 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-11 
with a few exceptions. Fires, dust events, and photochemical processes are elevated during this 

time frame, which maximizes OMC and EC concentrations, CM and SOIL concentrations, and 

secondary particulate formation. 

FIGURE 2-8 

MONTHLY DISTRIBUTION OF WORST DAYS OF BASELINE PERIOD

Daily reconstructed light extinction for the 20 percent worst days of the baseline years at JARB1 

is presented in Figure 2-9 and shows OMC, and/or CM are generally the largest components of 

visibility impairment on the worst days at the Jarbidge Wilderness Area. SOIL, NO3, and SO4

are significant components for a handful of days. 

FIGURE 2-9 

DAILY RECONSTRUCTED LIGHT EXTINCTION FOR 

WORST DAYS OF BASELINE PERIOD

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-12 
2.5.1.3 20 Percent Best Days 

The bar graph shown in Figure 2-10 shows the reconstructed light extinction over the baseline 

period for the 20 percent best days based on data from JARB1. Note the baseline period annual 

variation is less than 0.5 Mm-1 for the best days, much less than the variability shown for the 

worst days. 

FIGURE 2-10 

ANNUAL RECONSTRUCTED EXTINCTION FOR 

BEST DAYS OF BASELINE PERIOD

The line graph in Figure 2-11 shows the individual components of the reconstructed light 

extinction over the baseline period for the 20 percent best days at JARB1. SO4 and OMC are the 

most significant contributors to visibility impairment for the best days of the baseline period, 

followed by sub-equal contributions from NO3, EC, and CM. SOIL is a minor contributor to 

visibility impairment for the best days. SO4 has approximately 0.5 Mm-1 variation, while OMC 

has approximately 0.2 Mm-1 variation for the best days of the baseline period. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-13 
FIGURE 2-11 

ANNUAL RECONSTRUCTED EXTINCTION BY SPECIES FOR 

BEST DAYS OF BASELINE PERIOD

Figure 2-12 displays the monthly distribution of the reconstruction extinction for the 20 percent 

best days of the baseline period for JARB1. The best days are generally winter events occurring 

from October to May of each year, when fires, dust events, and photochemical processes are at a 

minimum. 

FIGURE 2-12 

MONTHLY DISTRIBUTION OF BEST DAYS OF BASELINE PERIOD

Daily reconstructed light extinction for the 20 percent best days of the baseline period at JARB1 

is presented in Figure 2-13 and shows OMC and/or SO4 are generally the largest components of 

visibility impairment on the best days at the Jarbidge Wilderness Area. NO3, CM, and Sea Salt 

are significant components for a handful of days. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-14 
FIGURE 2-13 

DAILY RECONSTRUCTED LIGHT EXTINCTION FOR 

BEST DAYS OF BASELINE PERIOD

2.5.1.4 All IMPROVE Sample Days 

Figure 2-14 shows the annual reconstructed light extinction over the baseline period based on 

monitor data from JARB1 site for all IMPROVE sample days. The variability of the IMPROVE 

sample days reconstructed light extinction is approximately 2 Mm-1. 

FIGURE 2-14 

ANNUAL RECONSTRUCTED EXTINCTION FOR 

IMPROVE SAMPLE DAYS OF BASELINE PERIOD

The line graph shown in Figure 2-15 shows the individual components of the annual 

reconstructed light extinction over the baseline period based on JARB1 IMPROVE data for the 

IMPROVE sample days. OMC is the most significant contributor to visibility impairment at 

JARB1 for the IMPROVE sample days of the baseline period, followed by sub-equal CM and 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-15 
SO4. SOIL, EC, and NO3 are minor contributors to visibility impairment for the baseline period 

IMPROVE sample days. 

FIGURE 2-15 

ANNUAL RECONSTRUCTED EXTINCTION BY SPECIES FOR 

IMPROVE SAMPLE DAYS OF BASELINE PERIOD

The baseline period annual variation for OMC is nearly 1.5 Mm-1, indicating the range of annual 

effects produced by fire emissions. The baseline period variation for CM and SO4 is less than 1 

Mm-1. The remaining components show less variability during the baseline period for the 

IMPROVE sample days. 

Figure 2-16 displays the monthly reconstructed extinction for the IMPROVE sample days of the 

baseline period for the Jarbidge Wilderness Area, while Figure 2-17 presents the daily 

reconstructed light extinction for the IMPROVE sample days of the baseline period. These 

figures show pronounced seasonality of the reconstructed extinctions with the highest monthly 

extinctions occurring in the summer months and the lowest monthly extinctions occurring in the 

winter months. The visibility effects of CM, SOIL, EC, and OMC extinction overwhelm the 

contributions of SO4 and NO3 extinction, especially during the summer months. SO4 contributes 

more to visibility impairment during the spring and early summer months, contributing less 

during the remaining months of the year. The contribution of NO3 to visibility impairment is 

greatest during the winter months and is significant for some days. These effects are even more 

pronounced for the daily reconstructed extinctions presented in Figure 2-17. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-16 
FIGURE 2-16 

MONTHLY RECONSTRUCTED EXTINCTION FOR 

IMPROVE SAMPLE DAYS OF BASELINE PERIOD

FIGURE 2-17 

DAILY RECONSTRUCTED EXTINCTION FOR 

IMPROVE SAMPLE DAYS OF BASELINE PERIOD

2.5.2 Comparison of Baseline Extinction for Best and Worst Days

Figure 2-18 compares the average baseline extinction for the 20 percent worst days with the 20 

percent best days from the JARB1 monitor. All components of extinction are less on the best 

days, but significant reductions in CM and OMC extinction result in the majority of the visibility 

improvement on the best days, confirming the significant role of natural emissions in visibility 

impairment at the Jarbidge Wilderness Area. 

Table 2-2 presents the monitored contributions to reconstructed light extinction by species for 

the most and least impaired days of the baseline period based on data from the WRAP’s 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-17 
Technical Support System. For the most impaired days, OMC and CM, on average, contribute 

nearly two thirds of the extinction. Sources of OMC and CM emissions are predominantly 

natural and uncontrollable, as are SOIL and EC emission sources. SO4 and NO3 contribute more 

than 15 percent and less than 5 percent, respectively to reconstructed extinction for the most 

impaired days. For the least impaired days, SO4 and NO3 contribute more than 40 percent and 

nearly 10 percent, respectively to the reconstructed extinction. Sources of SO2 and NOx

emissions are largely anthropogenic and controllable. 

FIGURE 2-18 

COMPARISON OF BASELINE EXTINCTION FOR 

WORST AND BEST DAYS OF BASELINE PERIOD

Jarbidge Wilderness Area

Comparison of Baseline Period (2000-2004) Extinction on Best and Worst Days

0

5

10

15

20

25

20% Worst Days 20% Best Days

Extinction (M

m-1)

SeaSalt Extinction

CM Extinction

Soil Extinction

EC Extinction

OMC Extinction

NO3 Extinction

SO4 Extinction

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-18 
TABLE 2-2

MONITORED CONTRIBUTIONS TO ANNUAL RECONSTRUCTED 

EXTINCTION BY SPECIES FOR BASELINE PERIOD

Year

SO4 

Extinction

NO3 

Extinction

OMC 

Extinction

EC 

Extinction

SOIL

Extinction

CM

Extinction

SeaSalt

Extinction

2001 14.6% 3.5% 38.6% 8.4% 10.4% 24.2% 0.3%

2002 11.5% 5.6% 48.4% 6.5% 10.9% 17.1% 0.0%

2003 17.3% 3.1% 40.8% 6.3% 7.7% 24.8% 0.0%

2004 23.6% 5.7% 32.4% 5.0% 9.7% 23.0% 0.7%

Average 16.7% 4.5% 40.0% 6.5% 9.7% 22.3% 0.3%

2001 45.9% 12.3% 23.0% 8.5% 3.1% 7.2% 0.0%

2002 40.3% 8.3% 25.9% 9.4% 2.9% 11.9% 1.4%

2003 34.2% 9.2% 31.5% 11.0% 2.7% 9.6% 1.7%

2004 43.3% 9.3% 24.7% 8.9% 2.4% 8.2% 3.1%

Average 40.9% 9.8% 26.3% 9.4% 2.8% 9.2% 1.6%

20 Pecent Worst Days

20 Percent Best Days

2.5.3 Aerosol Pollutant Trends

Figure 2-19 presents the annual monitored light extinction in deciviews for the 20 percent worst 

and best days and a corresponding trend line. The long-term annual extinction trend for the 20 

percent worst days, shown by the diamonds, is essentially flat, although there are large annual 

variations. The trend for the 20 percent best days, shown by the triangles, has a downward trend 

indicating improvement in the long-term visibility conditions at the Jarbidge Wilderness Area for 

the best days. 

Figure 2-20 shows the annual extinction data on the 20 percent worst days for seven haze 

causing pollutants from JARB1 for the years 1992 through 2005 with a corresponding colorcoded, long-term trend line. The graphs utilize valid data from years prior to and including the 

baseline period. Data from the years 1996, 1997, and 2000 did not meet the USEPA data 

completeness requirements (75 percent for the year and 50 percent for each quarter) and 

therefore don’t have calculated annual concentrations. 

Examination of the data provides insight into the long-term trends of haze causing pollutants at 

the JARB1 IMPROVE monitor. SO4 and NO3, considered to be emitted by mostly 

anthropogenic sources, have slight downward trends, although NO3 is essentially flat. These 

data suggest slight improvement in the long-term control of SO2 and NOx emissions impairing 

visibility at the Jarbidge Wilderness Area for the worst days. 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-19 
OMC extinction, despite its large annual variation, has a well-defined, upward long-term trend, 

suggesting a larger role of fire emissions in regional haze with time. EC, also thought to be 

largely due to fire emissions, has a flat trend. 

FIGURE 2-19 

ANNUAL IMPROVE RECONSTRUCTED EXTINCTION TRENDS 

FOR WORST AND BEST DAYS

JARBIDGE WILDERNESS AREA

IMPROVE Extinction Trends for 20 Percent Worst and Best Days

[invalid data for 1996, 1997, and 2000]

0

2

4

6

8

10

12

14

16

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Year

Haze Index (Deciview)

Baseline Obs 20% W Baseline Obs 20% B

CM, also showing significant annual variations, has a long-term downward trend. SOIL shows 

an opposite, upward trend, although not as pronounced, perhaps due to increasing contributions 

to international transport resulting from climate change and increasing population pressure in the 

developing world. 

Continued improvements in regional sulfate and, to a lesser degree, nitrate levels are expected in 

the western states as further controls are realized on major sources as the result of BART and the 

implementation of other regional haze programs, as well as compliance with ozone and PM2.5

standards. We expect these regional downward trends in SO2 and NOx emissions will provide

continued visibility improvement. 

However, the trends in OMC and SOIL are not so encouraging. The wide variations in annual 

concentrations on the 20 percent worst days may be related to alternating drought and normal 

precipitation conditions with corresponding increases in carbon emissions due to wildfires and 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-20 
increases in dust (e.g., CM and SOIL) emissions resulting from increasingly prevalent dry and 

dusty conditions. 

FIGURE 2-20 

JARBIDGE WILDERNESS AREA 

SPECIATED EXTINCTION TRENDS FOR WORST DAYS

JARBIDGE WILDERNESS AREA

Speciated IMPROVE Extinction Trends for 20 Percent Worst Days

[invalid data for 1996, 1997, and 2000]

0

2

4

6

8

10

12

14

16

18

20

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Year

Extinction (

Mm-1)

SO4 Extinction

NO3 Extinction

OMC Extinction

EC Extinction

Soil Extinction

CM Extinction

SeaSalt Extinction

NDEP has analyzed the JARB1 monitor data; identified the baseline and natural visibility 

conditions; identified a 2018 URP value of 11.09 dv for the worst days; and determined OMC 

and CM extinction contribute the majority of visibility impairment on the worst days. These data 

suggest that visibility improvement due to emissions reductions of SO2 and NOx from

anthropogenic sources may be overwhelmed by seasonally variable OMC and CM, as well as EC 

and SOIL, extinction contributions due to emissions from natural sources. 

These data suggest control of sources of OMC, CM, and SO2 may be the most effective means of 

improving visibility impairment at the Jarbidge Wilderness Area. The following chapter 

discusses Nevada’s sources of visibility impairing pollutants.

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-21 
2.6 REFERENCES

U.S. EPA 2003. Guidance for Tracking Progress under the Regional Haze Rule. EPA-454/B-03-

004. September 2003. 

U.S. EPA 2003. Guidance for Estimating Natural Visibility Conditions under the Regional Haze 

Rule. EPA-454/B-03-005. September 2003. 

U.S. EPA 2007. Guidance for Setting Reasonable Progress Goals under the Regional Haze Rule. 

U.S. Environmental Protection Agency, Office of Air Quality and Standards, Research Triangle 

Park, North Carolina. June 1, 2007 rev. 

 

NEVADA REGIONAL HAZE STATE IMPLEMENTATION PLAN, October 2009 2-22