ROGRAM
PROGRESS
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• Program Basics • Affected Units • Emission Reductions
• Emission Controls & Monitoring • Program Compliance • Market Activity
• Air Quality • Acid Deposition • Ecosystem Response
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2016 Program Progress - Cross-State Air Pollution Rule and Acid Rain Program
https://www3.epa.gov/airmarkets/progress/reports/index.html
Executive Summary
This report summarizes annual progress through 2016 under the Acid Rain Program (ARP) and the Cross-
State Air Pollution Rule (CSAPR). This reporting year marks the second year of the CSAPR
implementation and twenty-first year of the ARP.
Substantial reductions in power sector emissions of sulfur dioxide (S02) and nitrogen oxides (NOx), along
with improvements in air quality and the environment, demonstrate the success of these programs.
Transparency and data availability are a cornerstone of this success. This report highlights data that EPA
systematically collects on emissions, compliance, and environmental effects.
Contents
Executive Summary 2
2016 ARP and CSAPR at a Glance 7
Chapter 1: Program Basics 8
Highlights 8
Acid Rain Program (ARP): 1995 - present 8
NOx Budget Trading Program (NBP): 2003 - 2008 8
Clean Air Interstate Rule (CAIR): 2009 - 2014 9
Cross-State Air Pollution Rule (CSAPR): 2015 - present 9
Cross-State Air Pollution Rule Update (CSAPR Update): 2017 - present 9
Analysis and Background Information 10
Acid Rain Program 10
NOx Budget Trading Program 10
Clean Air Interstate Rule 10
Cross-State Air Pollution Rule 11
Cross-State Air Pollution Rule Update 11
Next Steps to Address Interstate Air Pollution Transport 11
More Information 12
Figures 13
Chapter 2: Affected Units 15
Highlights 15
Acid Rain Program (ARP) 15
Cross-State Air Pollution Rule (CSAPR) 15
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Executive Summary
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Analysis and Background Information 15
More Information 15
Figures 16
Chapter 3: Emission Reductions 18
Sulfur Dioxide (SO2) 18
Highlights 18
Overall Results 18
S02 Emission Trends 18
S02 State-by-State Emissions 18
S02 Emission Rates 19
Analysis and Background Information 19
More Information 19
Figures 20
Annual Nitrogen Oxides 24
Highlights 24
Overall Results 24
Annual N0X Emissions Trends 24
Annual N0X State-by-State Emissions 24
Annual N0X Emission Rates 24
Analysis and Background Information 25
More Information 25
Figures 26
Ozone Season Nitrogen Oxides 30
Highlights 30
Overall Results 30
Ozone Season NOx Emissions Trends 30
Ozone Season NOx State-by-State Emissions 30
Ozone Season NOx Emission Rates 30
Analysis and Background Information 31
More Information 31
Figures 32
Chapter 4: Emission Controls and Monitoring 36
Executive Summary
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Highlights 36
ARP and CSAPR S02 Program Controls and Monitoring 36
CSAPR N0X Annual Program Controls and Monitoring 36
CSAPR N0X Ozone Season Program Controls and Monitoring 36
Analysis and Background Information 37
Continuous Emission Monitoring Systems (CEMS) 37
S02 Emission Controls 37
N0X Emission Controls 37
More Information 37
Figures 38
Chapter 5: Program Compliance 44
Highlights 44
ARP S02 Programs 44
CSAPR S02 Group 1 Program 44
CSAPR S02 Group 2 Program 44
CSAPR N0X Annual Program 44
CSAPR N0X Ozone Season Program 45
Analysis and Background Information 45
More Information 45
Figures 46
Chapter 6: Market Activity 51
Highlights 51
Transaction Types and Volumes 51
2016 Allowance Prices 51
Analysis and Background Information 52
Transaction Types and Volumes 52
Allowance Markets 52
More Information 52
Figures 53
Chapter 7: Air Quality 55
Sulfur Dioxide and Nitrogen Oxides Trends 55
Highlights 55
National S02 Air Quality 55
Regional Changes in Air Quality 55
Executive Summary
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Analysis and Background Information 55
Sulfur Dioxide 55
Nitrogen Oxides 56
More Information 56
References 56
Figures 57
Ozone 59
Highlights 59
Changes in 1-Hour Ozone during Ozone Season 59
Trends in Rural 8-Hour Ozone 59
Changes in 8-Hour Ozone Concentrations 59
Changes in Ozone Nonattainment Areas 59
Analysis and Background Information 60
Ozone Standards 60
Regional Trends in Ozone 60
Meteorologically-Adjusted Daily Maximum 8-Hour Ozone Concentrations 60
Changes in Ozone Nonattainment Areas 61
More Information 61
References 61
Figures 62
Particulate Matter 67
Highlights 67
PM Seasonal Trends 67
Changes in PM2.5 Nonattainment 67
Analysis and Background Information 67
Particulate Matter Standards 68
Changes in PM2.5 Nonattainment Areas 68
More Information 68
References 68
Figures 69
Chapter 8: Acid Deposition 71
Highlights 71
Wet Sulfate Deposition 71
Wet Inorganic Nitrogen Deposition 71
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Regional Trends in Total Deposition 71
Analysis and Background Information 71
Acid Deposition 71
Monitoring Networks 72
More Information 72
References 72
Figures 73
Chapter 9: Ecosystem Response 76
Ecosystem Health 76
Highlights 76
Regional Trends in Water Quality 76
Ozone Impacts on Forests 76
Analysis and Background Information 77
Acidified Surface Water Trends 77
Surface Water Monitoring Networks 78
Forest Health 78
More Information 78
References 78
Figures 79
Critical Loads Analysis 82
Highlights 82
Critical Loads and Exceedances 82
Analysis and Background Information 82
More Information 82
References 83
Figures 84
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Executive Summary
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2016 ARP and CSAPR at a Glance
• Annual S02 emissions:
CSAPR -1.2 million tons (87 percent below 2005)
ARP-1.5 million tons (91 percent below 1990)
• Annual NOx emissions
CSAPR - 0.8 million tons (69 percent below 2005)
ARP-1.2 million tons (81 percent below 1990)
• CSAPR ozone season NO* emissions: 420,000 tons (53 percent below 2005)
• Compliance: 100 percent compliance for power plants in the ARP and CSAPR programs.
• Ambient particulate sulfate concentrations: The eastern United States has shown substantial
improvement, decreasing 71 to 75 percent between 1989-1991 and 2014-2016.
• Ozone NAAQS attainment: Based on 2014-2016 data, all 92 areas in the East originally designated
as nonattainment for the 1997 ozone NAAQS are now meeting the standard.
• PM2.5 NAAQS attainment: Based on 2014-2016 data, 34 of the 39 areas in the East originally
designated as nonattainment for the 1997 PM2.s NAAQS are now meeting the standard (two areas
have incomplete data).
• Wet sulfate deposition: All areas of the eastern United States have shown significant improvement
with an overall 66 percent reduction in wet sulfate deposition from 1989-1991 to 2014-2016.
• Levels of acid neutralizing capacity (ANC): This indicator of recovery improved (i.e., increased)
significantly from 1990 levels at lake and stream monitoring sites in the Adirondack region, New
England and the Catskill mountains.
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Chapter 1: Program Basics
The Acid Rain Program (ARP) and the Cross-State Air Pollution Rule (CSAPR) are cap and trade programs
designed to reduce emissions of sulfur dioxide (S02) and nitrogen oxides (N0X) from covered power
plants. The Acid Rain Program was the first nationwide cap and trade program, with a goal of reducing
the emissions that cause acid rain under Title IV of the Clean Air Act. The undisputed success of the
program in achieving significant emission reductions in a cost effective manner led to the deployment of
the market-based cap and trade tool to additional environmental problems, namely interstate air
pollution transport, or pollution from upwind emission sources that impact air quality in downwind
areas. Interstate transport makes it difficult for downwind states to meet health-based air quality
standards for PM2.5 and ozone. EPA first deployed the N0X Budget Trading Program (NBP) to help
northeastern states address the interstate transport of N0X emissions adversely impacting ozone air
quality in northeastern states. Next, the NBP was effectively replaced by the ozone season N0X program
under the Clean Air Interstate Rule, which required further summertime N0X emission reductions from
the power sector, and also required annual reductions of N0X as well as S02 to address PM2.5 transport.
The CSAPR replaced CAIR beginning in 2015 to continue reducing annual S02 and NOx emissions, as well
as seasonal NOx emissions, to facilitate attainment of the ozone and fine particle NAAQS.
Highlights
Acid Rain Program (ARP): 1995 - present
• The ARP began in 1995 and covers fossil fuel-fired power plants across the contiguous United States.
The ARP is designed to reduce S02 and NOx emissions, the primary precursors of acid rain under
Title IV of the Clean Air Act.
• The ARP's market-based S02 cap and trade program sets an annual cap on the total amount of S02
that may be emitted by electricity generating units (EGUs). The final annual S02 emissions cap was
set at 8.95 million tons in 2010, a level of about one-half of the emissions from the power sector in
1980.
• NOx reductions under the ARP are achieved through a rate-based approach that applies to a subset
of coal-fired EGUs.
NOx Budget Trading Program (NBP): 2003 - 2008
• The NBP was a cap and trade program that operated from 2003 to 2008, requiring NOx emission
reductions from affected power plants and industrial units in 21 eastern jurisdictions (20 states plus
Washington D.C.) during the ozone season (May 1 - September 30, the warm summer months when
ozone formation is highest). The NBP was designed as a mechanism that states could use to address
regional interstate transport for the 1979 ozone air quality standard (known as a National Ambient
Air Quality Standard, or NAAQS).
• In 2009, the CAIR NOx ozone season program replaced the NBP to continue ozone season NOx
emission reductions from the power sector.
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Clean Air Interstate Rule (CAIR): 2009 - 2014
• CAIR implementation began in 2009 (for the annual and ozone season NOxprograms) and 2010 (for
the S02 program) and ended on December 31, 2014. CAIR required 28 eastern jurisdictions (27
states plus Washington, D.C.) to reduce power sector S02 and/or NOx emissions to address regional
interstate transport for the 1997 fine particle pollution (PM2.5) and ozone NAAQS.
• CAIR included three separate cap and trade programs to achieve the required reductions: the CAIR
S02 trading program, the CAIR NOx annual trading program, and the CAIR NOx ozone season trading
program.
• Two 2008 court decisions kept the requirements of CAIR in place temporarily but directed EPA to
issue a new rule to replace it.
Cross-State Air Pollution Rule (CSAPR): 2015 - present
• The CSAPR was developed in response to the 2008 court decisions on CAIR and replaced CAIR
starting on January 1, 2015.
• The CSAPR addresses regional interstate transport of fine particle and ozone pollution for the 1997
ozone and PM2.5 NAAQS and the 2006 PM2.5 NAAQS. In 2015, the CSAPR required a total of 28
eastern states to reduce S02 emissions, annual NOx emissions and/or ozone season NOx emissions.
Specifically, the CSAPR requires reductions in annual emissions of S02 and NOxfrom power plants in
23 eastern states and reductions of NOx emissions during the ozone season from 25 eastern states.
• The CSAPR includes four separate cap and trade programs to achieve these reductions: the CSAPR
S02 Group 1 and Group 2 trading programs, the CSAPR NOx annual trading program, and the CSAPR
NOx ozone season trading program.
• The total CSAPR budget for each of the four trading programs equals the sum of the individual state
budgets for those states affected by each program. In 2017, some original CSAPR budgets tighten,
particularly in the S02 Group 1 program. Also, the CSAPR Update replaces the original CSAPR Ozone
Season NOx program for most states. The total CSAPR budget for each program is set at the
following level in 2017:
o S02 Group 1 - 1,372,631 tons
o S02 Group 2 - 892,050 tons
o Annual NOx- 1,206,957 tons
o Ozone Season NOx - 316,464 tons
Cross-State Air Pollution Rule Update (CSAPR Update): 2017 - present
• The CSAPR Update was developed to address regional interstate transport for the 2008 ozone
NAAQS and to respond to the July 2015 court remand of certain CSAPR ozone season requirements.
• Starting in May 2017, the CSAPR Update began further reducing ozone season NOx emissions from
power plants in 22 states in the eastern U.S.
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• The CSAPR Update achieves these reductions through an ozone season N0X cap and trade program.
The total CSAPR Update budget equals the sum of the individual state budgets for those states
included in the program. The CSAPR Update budget is set at 316,464 tons in 2017.1
Analysis and Background Information
Acid Rain Program
Title IV of the 1990 Clean Air Act (CAA) Amendments established the ARP to address acid deposition
nationwide by reducing annual S02 and NOx emissions from fossil fuel-fired power plants. In contrast to
traditional command and control regulatory methods that establish specific emissions limitations, the
ARP S02 program introduced a novel allowance trading system that harnessed the economic incentives
of the market to reduce pollution. This market-based cap and trade program was implemented in two
phases. Phase I began in 1995 and affected the most polluting coal-burning units in 21 eastern and
midwestern states. Phase II began in 2000 and expanded the program to include other units fired by
coal, oil, and gas. Under Phase II, EPA also tightened the annual S02 emissions cap, with a permanent
annual cap set at 8.95 million allowances starting in 2010. The NOx program has a similar results-
oriented approach and ensures program integrity through measurement and reporting. However, it
does not cap NOx emissions, nor does it utilize an allowance trading system. Instead, the ARP NOx
program provisions apply boiler-specific NOx emission limits-or rates-in pounds per million British
thermal units (Ib/mmBtu) on certain coal-fired boilers. There is a degree of flexibility, however. Units
under common control can comply through the use of emission rate averaging plans, subject to
requirements ensuring that the total mass emissions from the units in an averaging plan do not exceed
the total mass emissions the units would have emitted at their individual emission rate limits.
NOx Budget Trading Program
The NBP was a market-based cap and trade program created to reduce NOx emissions from power
plants and other large combustion sources during the summer ozone season to address regional air
pollution transport that contributes to the formation of ozone in the eastern United States. The
program, which operated during the ozone season from 2003 to 2008, was a central component of the
NOx State Implementation Plan (SIP) Call, promulgated in 1998, to help states achieve the 1979 ozone
NAAQS. All 21 jurisdictions (20 states plus Washington, D.C.) covered by the NOx SIP Call opted to
participate in the NBP. In 2009, CAIR's NOx ozone season program began, effectively replacing the NBP
to continue achieving ozone season NOx emission reductions from the power sector.
Clean Air Interstate Rule
CAIR required 28 eastern jurisdictions (27 states plus Washington, D.C.) to make reductions in S02 and
NOx emissions that cross state lines and contribute to unhealthy levels of fine particulate matter and
ozone pollution in downwind areas. CAIR required 25 eastern jurisdictions (24 states plus Washington,
D.C.) to limit annual power sector emissions of S02 and NOx to address regional interstate transport of
air pollution that contributes to the formation of fine particulates. It also required 26 jurisdictions (25
states plus Washington, D.C.) to limit power sector ozone season NOx emissions to address regional
interstate transport of air pollution that contributes to the formation of ozone during the ozone season.
Georgia's Ozone Season NOx budget adds 24,041 tons of emissions to the total for states covered by
CSAPR Update.
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CAIR used three separate market-based cap and trade programs to achieve emission reductions and to
help states meet the 1997 ozone and fine particle NAAQS.
EPA issued CAIR on May 12, 2005 and the CAIR federal implementation plans (FIPs) on April 26, 2006. In
2008, the U.S. Court of Appeals for the DC Circuit remanded CAIR to the Agency, leaving existing CAIR
programs in place while directing EPA to replace them as rapidly as possible with a new rule consistent
with the Clean Air Act. The CAIR NOx ozone season and NOx annual programs began in 2009, while the
CAIR S02 program began in 2010.
The CSAPR replaced CAIR starting on January 1, 2015.
Cross-State Air Pollution Rule
EPA issued the CSAPR in July 2011, requiring 28 states in the eastern half of the United States to
significantly improve air quality by reducing power plant emissions that cross state lines and contribute
to fine particle and summertime ozone pollution in downwind states. The CSAPR requires 23 states to
reduce annual S02 and NOx emissions to help downwind areas attain the 2006 and/or 1997 annual PM2.5
NAAQS. The CSAPR also requires 25 states to reduce ozone season NOx emissions to help downwind
areas attain the 1997 ozone NAAQS. The CSAPR divides the states required to reduce S02 emissions into
two groups (Group 1 and Group 2). Both groups must reduce their S02 emissions in Phase I. All Group 1
states, as well as some Group 2 states, must make additional reductions in S02 emissions in Phase II in
order to eliminate their significant contribution to air quality problems in downwind areas.
The CSAPR was scheduled to replace CAIR starting on January 1, 2012. However, the timing of the
CSAPR's implementation was affected by D.C. Circuit actions that stayed and then vacated the CSAPR
before implementation. On April 29, 2014, the U.S. Supreme Court reversed the D.C. Circuit's vacatur,
and on October 23, 2014, the D.C. Circuit granted EPA's motion to lift the stay and shift the CSAPR
compliance deadlines by three years. Accordingly, CSAPR Phase I implementation began January 1, 2015
and Phase II began January 1, 2017.
Cross-State Air Pollution Rule Update
On September 7, 2016, EPA finalized an update to the CSAPR ozone season program by issuing the
CSAPR Update. This rule addresses the summertime ozone pollution in the eastern U.S. that crosses
state lines and will help downwind states and communities meet and maintain the 2008 ozone NAAQS.
In May 2017, the CSAPR Update began further reducing ozone season NOx emissions from power plants
in 22 states in the eastern U.S.
Next Steps to Address Interstate Air Pollution Transport
The CSAPR Update will result in meaningful, near-term reductions in ozone pollution that crosses state
lines. However, the CSAPR Update may only partially resolve covered states' interstate ozone transport
obligations for the 2008 ozone NAAQS. Under the Clean Air Act's "good neighbor" provisions (Section
110(a)(2)(D)(i)(l)), upwind states that contribute significantly to nonattainment or interfere with
maintenance of the NAAQS in downwind areas must implement emission reductions through a state
implementation plan (SIP), or in the absence of an approved SIP, a federal implementation plan (FIP).
The CSAPR Update, however, may not be sufficient to fulfill this requirement. States and EPA will need
to determine whether additional actions are needed to fully address regional ozone transport for this
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NAAQS. In October 2017, EPA issued a memo with supplemental information intended to help states
determine whether they have additional interstate transport obligations for the 2008 ozone NAAQS. For
states that have not addressed this through their SIPs, EPA has committed to making this determination
regarding remaining 2008 obligations by December, 2018.
Additionally, EPA promulgated a new, tighter ozone standard in 2015. Good neighbor SIPs for the 2015
ozone NAAQS are due in October 2018. EPA issued a Notice of Data Availability in December 2016,
soliciting comments on preliminary interstate ozone transport modeling for the 2015 ozone NAAQS. In
March 2018, EPA released a memo providing updated projected air quality modeling results for ozone,
including projected ozone concentrations in 2023 at potential nonattainment and maintenance sites for
the 2015 ozone NAAQS and projected upwind state contribution data. This memo also noted that the
"good neighbor" provision for the 2015 ozone NAAQS can be addressed in a timely fashion using the 4-
step transport framework that has evolved through previous state and federal regulatory actions,
including the CSAPR and CSAPR Update.
More Information
• Acid Rain Program (ARP) https://www.epa.gov/airmarkets/acid-rain-program
• Cross-State Air Pollution Rule (CSAPR) https://www.epa.gov/csapr
• Cross-State Air Pollution Update Rule (CSAPR Update) https://www.epa.gov/airmarkets/final-cross-
state-air-pollution-rule-update
• Clean Air Interstate Rule (CAIR)
https://archive.epa.gov/airmarkets/programs/cair/web/html/index.html
• NOx Budget Trading Program (NBP) / NOx SIP Call https://www.epa.gov/airmarkets/nox-budget-
trading-program
• National Ambient Air Quality Standards (NAAQS) https://www.epa.gov/criteria-air-pollutants
• Learn more about EPA's Clean Air Market Programs https://www.epa.gov/airmarkets/programs
• Learn more about emissions trading https://www.epa.gov/emissions-trading-resources
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Figures
History of ARP, NBP, CAIR, and CSAPR
2010 - Full implementation of the ARP
1995-ARP
PHASE 1 BEGINS
2000 - ARP
PHASE 2 BEGINS
ARP
1990 - Clean Air Act
Amendments
establish Title IV ARP
Acid Rain Program (ARP)
NOx Budget Trading Program (NBP)
Clean Air Interstate Rule (CAIR)
Cross-State Air Pollution Rule (CSAPR)
NBP
CAIR
2003- NBP begins
(additional states added
in 2004 and 2007)
2009 - CAIR NOx ozone season and
NOx annual programs begin,
replacing NBP in most states
2010 - CAIR S02 program begins
CSAPR
2015- CSAPR S02,
NOx annual, and
NOxozone programs
begin, replacing CAIR
2017 - CSAPR Update begins
Source: EPA, 2018
Figure 1. History of ARP, NBP, CAIR, and CSAPR
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Map of Cross-State Air Pollution Rule Implementation for 2016
~ CSAPR States controlled for both fine particles (S02 and annual NO*) and ozone (ozone season N0X) - 20 states
E3 CSAPR States controlled for fine particles only (S02 and annual N0X) - 3 states
~ CSAPR States controlled for ozone only (ozone season N0X) - 5 stefes
The ARP covers sources in the lower 48 states.
Source: EPA, 2Q18
Figure 2. Map of Cross-State Air Pollution Rule States
Chapter 1: Program Basics
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Chapter 2: Affected Units
The Acid Rain Program (ARP) and the Cross-State Air Pollution Rule's (CSAPR) sulfur dioxide (S02) and
nitrogen oxides (N0X) emission reduction programs generally apply to large electricity generating units
(EGUs) that burn fossil fuels to generate electricity for sale. This section covers units affected in 2016.
Highlights
Acid Rain Program (ARP)
• In 2016, the ARP S02 requirements applied to 3,446 fossil fuel-fired combustion units at 1,216
facilities across the country; 710 units at 314 facilities were subject to the ARP NOx program.
Cross-State Air Pollution Rule (CSAPR)
• In 2016, there were 2,708 affected EGUs at 846 facilities in the CSAPR S02 program. Of those, 2,160
(80 percent) were also covered by the ARP.
• In 2016, there were 2,708 affected EGUs at 846 facilities in the CSAPR NOx annual program and
3,106 affected EGUs at 929 facilities in the CSAPR NOx ozone season program. Of those, 2,160 (80
percent) and 2,474 (80 percent), respectively, were also covered by the ARP.
Analysis and Background Information
In general, the ARP and the CSAPR S02, NOx annual, and NOx ozone season trading programs apply to
large EGUs—boilers, turbines, and combined cycle units-that burn fossil fuel, serve generators with
nameplate capacity greater than 25 megawatts, and that produce electricity for sale. These EGUs
include a range of unit types, including units that operated year-round to provide baseload power to the
electric grid, as well as units that provided power only on peak demand days. The ARP NOx program
applies to ARP-affected units that are older, historically coal-fired boilers.
More Information
• Acid Rain Program (ARP) https://www.epa.gov/airmarkets/acid-rain-program
• Cross-State Air Pollution Rule (CSAPR) https://www.epa.gov/csapr
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Chapter 2: Affected Units
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Figures
Affected Units in CSAPR and ARP, 2016
3,106
2,708
710
ARP NO, Program ARP SOi Program
¦ Coal EGUs ¦ Gas EGUs ¦ Oil EGUs
CSAPR SO2 and NO, Annual Programs CSAPR NO, Ozone Season Program
Other Fuel EGUs ¦ Unclassified EGUs
¦ "Unclassified" units have not submitted a fuel type in their monitoring plan and did not report emissions.
• "Other" fuel refers to units that burn waste, wood, petroleum coke, tire-derived fuel, etc.
Source: ERA, 2018
Figure 1. Affected Units in CSAPR and ARP, 2016
Chapter 2: Affected Units
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% pRo^s°
Affected Units in CSAPR and ARP, 2016
Coal
655
749
612
598
Gas
53
2,537
1,790
2,145
Oil
0
123
261
314
Other
2
28
37
40
Unclassified
0
9
8
9
Total Units
710
3,446
2,708
3,106
NoSes
¦ ~Uncias5if«ed" units have not submited a fuel type in their monitoring p&i and 4a not report evasions
• "Other find refers to mm that bum wssie. wood. petroleum ©osce. we-5e
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Chapter 3: Emission Reductions
The Acid Rain Program (ARP) and Cross-State Air Pollution Rule (CSAPR) programs significantly reduced
sulfur dioxide (S02), annual nitrogen oxides (N0X), and ozone season N0X emissions from power plants.
Most of the emission reductions since 2005 occurred in response to the Clean Air Interstate Rule (CAIR),
which was replaced by CSAPR in 2015. This section covers changes in emissions at units affected by the
CSAPR and ARP in 2016.
Highlights
Overall Results
• Under the ARP, CAIR, and now CSAPR, power plants have significantly lowered S02 emissions while
electricity demand (measured as heat input) remained relatively stable, indicating that the emission
reductions were not driven by decreased electric generation.
• These emission reductions are a result of an overall increase in the environmental efficiency at
affected sources as power generators installed controls, switched to lower emitting fuels, or
otherwise reduced their S02 emissions while meeting relatively steady electricity demand.
S02 Emission Trends
• ARP: Units in the ARP emitted 1.5 million tons of S02 in 2016, well below the ARP's statutory annual
cap of 8.95 million tons. ARP sources reduced emissions by 14.3 million tons (91 percent) from 1990
levels and 15.8 million tons (91 percent) from 1980 levels.
• CSAPR and ARP: In 2016, the second year of operation of the CSAPR S02 program, sources in both
the CSAPR S02 annual program and the ARP together reduced S02 emissions by 14.2 million tons (91
percent) from 1990 levels (before implementation of the ARP), 9.7 million tons (87 percent) from
2000 levels (ARP Phase II), and 8.8 million tons (85 percent) from 2005 levels (before
implementation of CAIR and CSAPR). All ARP and CSAPR sources together emitted a total of 1.5
million tons of S02 in 2016.
• CSAPR: Annual S02 emissions from sources in the CSAPR S02 program alone fell from 8.8 million
tons in 2005 to 1.2 million tons in 2016, a 87 percent reduction. In 2016, S02 emissions were about
2.3 million tons below the regional CSAPR emission budgets (1.8 million in Group 1 and 0.5 million in
Group 2); the CSAPR S02 annual program's 2016 regional budget are 2,551,802 and 917,787 tons for
Group 1 and Group 2, respectively.
S02 State-by-State Emissions
• CSAPR and ARP: From 1990 to 2016, annual S02 emissions from sources in the ARP and the CSAPR
S02 program dropped in 45 states plus Washington, D.C. by a total of approximately 14.2 million
tons. In contrast, annual S02 emissions increased in three states (Idaho, Nebraska, and Vermont) by
a combined total of 550 tons from 1990 to 2016.
Sulfur Dioxide
Chapter 3: Emission Reductions - Sulfur Dioxide (SO2)
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• CSAPR: All 23 states (16 states in Group 1 and 7 states in Group 2) had emissions below their CSAPR
allowance budgets, collectively by about 2.3 million tons.
S02 Emission Rates
• The average S02 emission rate for units in the ARP or CSAPR S02 program fell to 0.13 Ib/mmBtu. This
indicates an 81 percent reduction from 2005 rates, with the majority of reductions coming from
coal-fired units.
• Although heat input has decreased slightly over the past 11 years, emissions have decreased
dramatically since 2005, indicating an improvement in emission rate at the sources. This is due in
large part to greater use of control technology on coal-fired units and increased generation at
natural gas-fired units that emit very little S02 emissions.
Analysis and Background Information
S02 is a highly reactive gas that is generated primarily from the burning of fossil fuels at power plants. In
addition to contributing to the formation of fine particle pollution (PM2.5), S02 emissions are linked with
a number of adverse effects to human health and ecosystems.
The states with the highest emitting sources in 1990 have generally seen the greatest S02 emission
reductions under the ARP, and this trend continued under CAIR and CSAPR. Most of these states are
located in the Ohio River Valley and are upwind of the areas the ARP and CSAPR were designed to
protect. Reductions under these programs have provided important environmental and health benefits
over a large region.
More Information
• Visit EPA's Power Plant Emission Trends site for the most up-to-date emissions and control data for
sources in CSAPR and the ARP https://www3.epa.gov/airmarkets/progress/datatrends/index.html
• Air Markets Program Data (AMPD) https://ampd.epa.gov/ampd/
• Acid Rain Program (ARP) https://www.epa.gov/airmarkets/acid-rain-program
• Cross-State Air Pollution Rule (CSAPR) https://www.epa.gov/csapr
• Learn more about sulfur dioxide (S02) https://www.epa.gov/so2-pollution
• Learn more about particulate matter (PM) https://www.epa.gov/pm-pollution
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Chapter 3: Emission Reductions - Sulfur Dioxide (SO2)
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Figures
SO: Emissions from CSAPR and ARP Sources, 1980-2016
2016 CSAPR SO: Phase 1 Budget (2015/2016)
¦ ARP HARP and CSAPR bJ CSAPR not ARP ARP not CSAPR
ffcses:
¦ SO; vates are shown as millions of tons
• Pof CSAPR units not in the ARP 9* 20t 5 annuaJ SOi iiwjws were a$c*ed retnjactvefy for each pre-CSAPR year foltowinfl the yea* m whch the unit fcejan operasnj
• There art a imali number of soukm m CSAPR 6w: w»« ARP Emsjonj from: th«»« »jfcti comprise abou? 1 percent of «oal emisiions and *re net eraiy vis-We on sh* full chart
Source: EPA, 2018
Figure 1. SO2 Emissions from CSAPR and ARP Sources, 1980-2016
Chapter 3: Emission Reductions - Sulfur Dioxide (SO2)
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State-by-State SO: Emissions from CSAPR and ARP Sources, 1990-2016
SO: Emissions (thousand tons)
CSAPR states controlled for fine particles
1990 SOj emissions (tons)
Notes:
* S0> vjluts »re sto*n h ton#
300
200
100
0
2000 2005 2016
¦ Alabama
Source: EPA, 2018
Figure 2. State-by-State SO2 Emissions
from CSAPR and ARP Sources, 1990-2016
Chapter 3: Emission Reductions - Sulfur Dioxide (SO2)
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% pRo^s°
Comparison of SO: Emissions and Heat Input for CSAPR and ARP Sources, 2000-2016
SO: Envssors
15
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
¦ COAL ¦ GAS ¦ OIL OTHER
Heat Ifipvt
30
ffl
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
¦ COAL ¦ GAS ¦ OIL OTHER
Notes
• The data shown here refect to-late for tJrose faeces required to CQrr&y with each program in each respective year This means that CSAPR-on fy SO* program facilities are not included fin the SC-. das poor to 2015
• Fu«f fype rep&ttits pwisfy fuftt typt; units mgh! eembus? mow than on* fu%)
• Units* och*?wis* rvocn SPA dsu cuiTtnt is c? Jtnusty 2017. and mjy diff*f past«future reports as aremit of res«6fliis»>«u By scufc« and data quality assarene* actvit«
Source: EPA 2018
Figure 3. Comparison of SO2 Emissions and Heat Input for CSAPR and ARP Sources,
2000-2016
Chapter 3: Emission Reductions - Sulfur Dioxide (SO2)
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% PRo^°
CSAPR and ARP SO: Emissions Trends, 2016
SO; Emissions (thousand tons)
SO2 Rate (Ib/mmBtu)
leat Input (bilDon mmBtu
Primary Fuel
2000
2005
2010
2016
2000
2005
2010
2016
2000
2005
2010
2016
Coal
10,708
9,835
5,051
1,466
1.04
0.95
0.53
0.22
20.67
20.77
19.04
13.30
Gas
108
91
19
9
0.06
0.03
0.01
0.00
3.88
5.49
7.06
10.07
Oil
384
292
28
3
0.73
0.70
0.19
0.03
1.05
0.84
0.30
0.16
Other
1
4
22
12
0.20
0.27
0.57
0.17
0.01
0.03
0.08
0.14
Total
11,201
10|222
5,120
1,490
0.88
0,75
0.39
0.11
25.61
27.13
26.48
23.67
Nows:
• The data sho*n here reflect totals for those facilities required to compfy with each program m each respective year. This means that CSAPR-onty S0= program facStes are not incJuded in the SO= emssons data pwi to 2015.
• Fuel type represents pnmay fuel type; units might combust mere than one fuel
• Touis may not reflect tit* sum of individual twt Sue to rounding
• The emission rate reflects the emissions (pounds} per unit of heat input (mmStu) for each fuel category The tonal SOi emsssaon rate m each oelunw Of the table a rat cumulative ana does not equal the arahmetie mean of the four fuel-
spedftc rates. The total for each year indicates the average rate across ail umts in the program because each facSty influences the arvnual emission irate in proportion to its heat input, and heat input is unevenly distributed across the fuel
categories .
• Units* other**** noted. EPA data art eminent as of January 20*®, and may differ from past or future resorts a* a result of resubmissions by sources and oryjomg data qualify assuranot aeuvifets
Source: EPA, 2018
Figure 4. CSAPR and ARP SO2 Emissions Trends, 2016
Chapter 3: Emission Reductions - Sulfur Dioxide (SO2)
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Annual Nitrogen Oxides
Highlights
Overall Results
• Annual N0X emissions have declined dramatically under the ARP, N0X Budget Trading Program
(NBP), CAIR, and CSAPR programs, with the majority of reductions coming from coal-fired units.
• These reductions have occurred while electricity demand (measured as heat input) remained
relatively stable, indicating that the emission reductions were not driven by decreased electric
• These emission reductions are a result of an overall increase in the environmental efficiency at
affected sources as power generators installed controls, ran their controls year-round, switched to
lower emitting fuels, or otherwise reduced their N0X emissions while meeting relatively steady
electricity demand.
• Other programs—such as regional and state N0X emission control programs—also contributed
significantly to the annual N0X emission reductions achieved by sources in 2016.
Annual NOx Emissions Trends
• ARP: Units in the ARP NOx program emitted 1.2 million tons of NOx emissions in 2016. Sources
reduced emissions by 6.9 million tons from the projected level in 2000 without the ARP, and over
three times the Title IV NOx emission reduction objective.
• CSAPR and ARP: In 2016, the second year of operation of the CSAPR NOx annual program, sources in
both the CSAPR NOx annual program and the ARP together emitted 1.2 million tons, a reduction of
5.2 million tons (81 percent reduction) from 1990 levels, 3.9 million tons (77 percent reduction)
from 2000, and 2.5 million tons (67 percent reduction) from 2005 levels.
• CSAPR: Emissions from CSAPR NOx annual program sources alone were about 802,000 tons in 2016.
This is about 1.8 million tons (69 percent) lower than in 2005 and 470,000 tons (37 percent) below
the CSAPR NOx annual program's 2016 regional budget of 1,269,837 tons.
Annual NOx State-by-State Emissions
• CSAPR and ARP: From 1990 to 2016, annual NOx emissions in the ARP and the CSAPR NOx program
dropped in 47 states plus Washington, D.C. by a total of approximately 5.2 million tons. In contrast,
annual emissions increased in one state (Idaho) by 200 tons from 1990 to 2016.
• CSAPR: Twenty-two states had emissions below their CSAPR 2016 allowance budgets, collectively by
about 470,000 tons. A single state (Missouri) exceeded its 2016 budget by about 7,800 tons.
Annual NOx Emission Rates
• In 2016, the CSAPR and ARP average annual NOx emission rate was 0.10 Ib/mmBtu, a 63 percent
reduction from 2005.
• Although heat input has decreased slightly over the past 11 years, emissions have decreased
dramatically since 2005, indicating an improvement in NOx emission rates. This is due in large part to
generation.
Chapter 3: Emission Reductions - Annual Nitrogen Oxides (NOx)
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greater use of control technology on coal-fired units and increased heat input at natural gas-fired
units that emit less N0X emissions than coal-fired units.
Analysis and Background Information
Nitrogen oxides are made up of a group of highly reactive gases that are emitted from power plants and
motor vehicles, as well as other sources. N0X emissions contribute to the formation of ground-level
ozone and fine particle pollution, which cause a variety of adverse health effects.
More Information
• Visit EPA's Power Plant Emission Trends site for the most up-to-date emissions and control data for
sources in CSAPR and the ARP https://www3.epa.gov/airmarkets/progress/datatrends/index.html
• Air Markets Program Data (AMPD) https://ampd.epa.gov/ampd/
• Acid Rain Program (ARP) https://www.epa.gov/airmarkets/acid-rain-program
• Cross-State Air Pollution Rule (CSAPR) https://www.epa.gov/csapr
• Learn more about nitrogen oxides (N0X) https://www.epa.gov/no2-pollution
• Learn more about particulate matter (PM) https://www.epa.gov/pm-pollution
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Chapter 3: Emission Reductions - Annual Nitrogen Oxides (N0X)
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% pRo^s°
Figures
Annual NO* Emissions from CSAPR and ARP Sources, 1990-2016
CSAPR annual NO* Phase 1 Budget (2015/2016)
¦ ARP ¦ ARP and CSAPR ¦ ARP, not CSAPR CSAPR, not ARP
Noses:
¦ NO, values are shown as millions o# tons.
¦ For CSAPR ones in the ARP. the 2015 annual NO. emissions were applied retroactivity for ea# pre-CSAPR year fellowinQ fre yea-' in vrtiich the unit be^an operating
* Th*c» are a jrruli numeer d sou'c« =n CSAPR out n« *i ARP Emanonj from these MufCd comprise atout 1 percent tA wsat eminent im v* not tasty vis^e on the full chart
Source: EPA, 2018
Figure 1. Annual NOx Emissions from CSAPR and ARP Sources, 1990-2016
Chapter 3: Emission Reductions - Annual Nitrogen Oxides (NOx)
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% pRo^s°
1990 2000 2005 2016
Source: EPA, 2018
Figure 2. State-by-State Annual NOx Emissions from CSAPR and ARP Sources, 1990-
2016
NOx Emissions (thousand tons)
III.
1990 2000 2005 2016
¦ Alabama
State-by-State Annual NO* Emissions from CSAPR and ARP Sources,
1990-2016
CSAPR states controlled for fine particles
© 1990 NO* emissions (tons)
Chapter 3: Emission Reductions - Annual Nitrogen Oxides (NOx)
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% pRo^s°
Comparison of Annual NO* Emissions and Heat Input for CSAPR and ARP Sources, 2000-2016
NO. Emissions
6
COAL
OTHER
Meat input
30
1,0
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
¦ COAL ¦ GAS ¦ OIL OTHER
Noees:
• The dsts shown here for the annual programs refect totals fix those baKs required So compty wfli e3c* program in each respecwre yes: Tfes means that CSAPR NO, annual program facS&es are no? included in the annual NOs emissions data
prior Co 2015.
• Fuei typ« prsna?y tu#-' typ«: tmiss might ccmbutt mort than e«i« fw*i
• um«M oi"**wse notw. EPA data are cuwk h of January 20'7, and may from past or taur* rtports u a r**u* of r«u&rr>«>on$ by ioure« and on^g data Quality Hurixt ac
Source: EPA; 2018
Figure 3. Comparison of Annual NOx Emissions and Heat Input for CSAPR and ARP
Sources, 2000-2016
Chapter 3: Emission Reductions - Annual Nitrogen Oxides (NOx)
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CSAPR and ARP Annual NOx Emissions Trends, 2016
NOx Emissions (thousand tons)
NO. Rate (Ib/mmBtu)
Heat Input (billion mmBtu)
Primary Fuel
2000
2005
2010
2016
2000
2005
2010
2016
2000
2005
2010
2016
Coal
4,587
3,356
1,896
1,029
0-44
0*32
0.20
0.16
20.67
20.77
19.04
13.30
Gas
355
167
143
155
0.18
0.06
0.04
0.03
3.88
5.50
7.06
10.08
Oil
162
104
19
9
0.31
0.25
0.13
0.10
1.05
0.84
030
0.16
Other
2
6
5
7
0.24
0.42
0.13
0.10
0.01
0.03
0.08
0.14
Total
5,104
3,633
2,063
1,373
0.40
0.27
0.16
0.10
25.61
27.14
26.48
23.68
Notes:
• The data shown here reflect totals for those faciities reqvrad to compty wrth each program m each respective year Ths means that CSAPR-onfy annuaJ NO, program 'assises are not rociuded m the NO, emissions data prior to 201S.
• Fuel type represents pnmwy fuel type: units might oomtust more than one fuel
• Touts may not reflect the sum of in^vitfuas rows flue to founding.
• The emission rale reflects the emissions {pounds) per una of heat input (mmStu) for each fuel category The total annual NO, emission rate m each column of the table & rot cumulative and does not equal the arithmetic mean of the four
fuel-specific rates. Tre total fw each year indraies the average rate across all units in the program because each facSty influences the annual emss'en rate in proportion to its heat input, and heat input is unevenly distributed across the
fuel categories
• Unfess othwriM noted. EPA dan ft euwtnt as of January 2058. and may differ from past or future reports as a result of rwu6m
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Ozone Season Nitrogen Oxides
Highlights
Overall Results
• Ozone season N0X emissions have declined dramatically under the ARP, NBP, CAIR, and CSAPR
• These reductions have occurred while electricity demand (measured as heat input) remained
relatively stable, indicating that the emission reductions were not driven by decreased electric
• These emission reductions are a result of an overall increase in the environmental efficiency at
affected sources as power generators installed controls, switched to lower emitting fuels, or
otherwise reduced their ozone season N0X emissions while meeting relatively steady electricity
demand.
• Other programs—such as regional and state N0X emission control programs—also contributed
significantly to the ozone season N0X emission reductions achieved by sources in 2016.
Ozone Season NOx Emissions Trends
• Units in the CSAPR N0X ozone season program emitted 420,000 tons in 2016,
o a reduction of 1.8 million tons (81 percent) from 1990,
o 1.4 million tons lower (77 percent reduction) than in 2000 (before implementation of
the NBP),
o 480,000 tons lower (53 percent reduction) than in 2005 (before implementation of
CAIR), and
o 30,000 tons lower (7 percent reduction) than in 2015.
• In 2016, CSAPR NOx ozone season program emissions were 33 percent below the regional emission
budget of 628,392 tons.
Ozone Season NOx State-by-State Emissions
• Between 2005 and 2016, ozone season NOx emissions from CSAPR sources fell in every state
participating in the CSAPR NOx ozone season program.
• Twenty-three states had emissions below their CSAPR 2016 allowance budgets, collectively by about
210,000 tons. Two states (Louisiana and Missouri) exceeded their 2016 budgets by about 3,900 tons
Ozone Season NOx Emission Rates
• In 2016, the average NOx ozone season emission rate fell to 0.09 Ib/mmBtu for CSAPR ozone season
program states and 0.10 Ib/mmBtu nationally. This represents a 50 percent reduction from 2005
emission rates, with the majority of reductions coming from coal-fired units.
programs.
generation.
combined.
Chapter 3: Emission Reductions - Ozone Season Nitrogen Oxides (NOx)
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• Although heat input has decreased slightly over the past 11 years, emissions have decreased
dramatically since 2005, indicating an improvement in N0X emission rate. This is due in large part to
greater use of control technology on coal-fired units and increased heat input at natural gas-fired
units, which emit less N0X emissions than coal-fired units.
Analysis and Background Information
Nitrogen oxides are made up of a group of highly reactive gases that are emitted from power plants and
motor vehicles, as well as other sources. NOx emissions contribute to the formation of ground-level
ozone and fine particle pollution, which cause a variety of adverse human health effects.
The CSAPR NOx ozone season program was established to reduce interstate transport during the ozone
season (May 1 - September 30), the warm summer months when ozone formation is highest, and to
help eastern U.S. counties attain the 1997 ozone standard.
In general, the states with the highest emitting sources of ozone season NOx emissions in 2000 have
seen the greatest reductions under the CSAPR NOx ozone season program. Most of these states are in
the Ohio River Valley and are upwind of the areas CSAPR was designed to protect. Reductions by
sources in these states have resulted in important environmental and human health benefits over a
large region.
More Information
• Visit EPA's Power Plant Emission Trends site for the most up-to-date emissions and control data for
sources in CSAPR and the ARP https://www3.epa.gov/airmarkets/progress/datatrends/index.html
• Air Markets Program Data (AMPD) https://ampd.epa.gov/ampd/
• Cross-State Air Pollution Rule (CSAPR) https://www.epa.gov/csapr
• Learn more about nitrogen oxides (NOx) https://www.epa.gov/no2-pollution
• Learn more about ozone https://www.epa.gov/ozone-pollution
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Chapter 3: Emission Reductions - Ozone Season Nitrogen Oxides (NOx)
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Ozone Season NOx Emissions from CSAPR Sources, 2005-2016
c/> 0,25
CSAPR Ozone Season NO, Budget
¦CSAPR
Noses:
¦ NO, wa!ues are shovm as millions of tons.
¦ f of CSAPR urncs not in the AFP. the 20*5 ozoie season NO, emssions were applied retroactwety ft* each pce-CSAPR yeat fallowing the year in which the unit began operating.
• There are a small number o* sources « CSAPR but not« ARP Em>is>ons from these scj*c« comprise about 1 percent of soul emissions and are not «siy vis^e on the full chart
Source: EPA 2018
Figure 1. Ozone Season NOx Emissions from CSAPR Sources, 2005-2016
Chapter 3: Emission Reductions - Ozone Season Nitrogen Oxides (NOx)
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* A \
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State-by-State Ozone Season NO, Emissions from CSAPR Sources,
2000-2016
NO* Emissions (thousand tons)
I-
CSAPR states controlled for ozone
2000 NO, emissions (tons)
• Tn# 2000 and 20©5 «on# »j:j« r*$M( it'i thM ftpontd u«d«r «h«r p-*ojrjmi for !k-a« tf»« ww fto! cov*f*3 by arietft*f program and e< no! rapon 2000 Of 2005 omunons, :h«ir **$o«« irniwj for 2015 w*f» saMKuwd
Source EPA. 2018
Figure 2. State-by-State Ozone Season NOx Emissions
from CSAPR Sources, 2000-2016
Chapter 3: Emission Reductions - Ozone Season Nitrogen Oxides (NOx)
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E
Comparison of Ozone Season NOx Emissions and Heat Input for CSAPR Sources, 2000-2016
NO. Emissions
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
¦ coal Bgas Boil other
Haas input
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
¦ COAL ¦ GAS ¦ OIL OTHER
Nores.
• Tne dasa shown here for «ie ozone season program reflect totafs for those facilities required to comply with each program in eac*i respective year This means that CSAPR NO, ozone season only program facilities 3re not included in the ozone
season NO. emissions data prior so 20'5
• Fuel type primary fuel type; units flight combu« mow than one fuel
• Unsm oBtonim noiel s?A data are current n of January 2017. and may dtfte from past or future reports u • result of resubmissions by sources ana oajwj data Quality assurer actvibes.
Source: EPA 2018
Figure 3. Comparison of Ozone Season NOx Emissions and Heat Input for CSAPR
Sources, 2000-2016
Chapter 3: Emission Reductions - Ozone Season Nitrogen Oxides (NOx)
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CSAPR Ozone Season NO* Emissions Trends, 2016
Ozone Emissions (thousand tons)
Dzone Rate (Ib/mmBtu]
eat Input (bitUon mmBtu
Primary Fuel
2000
2005
2010
2016
2000
2005
2010
2016
2000
2005
2010
2016
Coal
1,926
1,117
821
460
0.43
0.25
0.19
0.15
8.96
9.06
8.45
6.31
Gas
195
95
78
83
0.19
0.06
0.04
0.03
2.10
2.96
3.60
4.99
Oil
79
53
13
5
0.31
0.25
0.13
0.11
0.51
0.43
0.20
0.10
Other
1
2
2
4
0.21
0.39
0.11
0.10
0.01
0.01
0.04
0.08
Total
2,201
1,267
915
552
0.38
0.20
0.15
0.10
11.58
12.45
12.29
11.47
Hem:
• The data show here reflect tools for those facilities repaired to comply with each program m each respective yew. This means thai CSAPR NO, ozone season only program facilities are not induced in the ozone season NO. emissions
data prior to 2015.
• Fuei type represents primary fuel type; units might combust mors than one fuel.
• Totals m»y not reflect the Sum of individuall ro*s due to rowndmg
• The emission fate reflects the emissions (pounds) per uwt of heat input (mmBtU) for each fuel category The total NO, ozone season emission rate in each ootomn of the taWe is not cumutative and does noi equal the arithmetic mean of
the four fuel-specif>c rates. The total for each year indicates the average rate across aU units in the program because each facility influences the annual emission rate in proportion to its heat input, and heat input is unevenly distributed
across the fuel categories.
• Units# othwwM noted. EPA data art ewrrtflt as of January 2016. and may differ
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Chapter 4: Emission Controls and Monitoring
Allowance trading provisions in cap and trade programs allow sources to choose the most cost-effective
strategy to reduce emissions. Many sources opted to install control technologie to meet the Acid Rain
Program (ARP) and Cross-State Air Pollution Rule (CSAPR) emission reduction targets. A wide range of
controls is available to help reduce emissions. However sources choose to comply, they are held to very
high standards of accountability for emissions. Accurate and consistent emissions monitoring data is
critical to ensure program results. Most sources are required to use continuous emission monitoring
systems (CEMS).
Highlights
ARP and CSAPR S02 Program Controls and Monitoring
• Units with advanced flue gas desulfurization (FGD) controls (also known as scrubbers) accounted for
68 percent of coal-fired units and 84 percent of coal-fired generation, measured in megawatt hours,
or MWh, in 2016.
• In 2016, 30 percent of CSAPR units (including 100 percent of coal-fired units) monitored S02
emissions using CEMS. Ninety-nine percent of S02 emissions were measured by CEMS.
CSAPR NOx Annual Program Controls and Monitoring
• Seventy-two percent of fossil fuel-fired generation (as measured in megawatt hours, or MWh) was
produced by units with advanced pollution controls (either selective catalytic reduction [SCR] or
selective non-catalytic reduction [SNCR]).
• In 2016, the 325 coal-fired units with advanced add-on controls (either SCRs or SNCRs) generated 72
percent of coal-fired generation. At oil- and natural gas-fired units, SCR- and SNCR- controlled units
produced 72 percent of generation.
• In 2016, 72 percent of CSAPR units (including 100 percent of coal-fired units) monitored NOx
emissions using CEMS. Ninety-nine percent of NOx emissions were measured by CEMS.
CSAPR NOx Ozone Season Program Controls and Monitoring
• Seventy percent of all the fossil fuel-fired generation (as measured in megawatt hours, or MWh) was
produced by units with advanced pollution controls (either SCRs or SNCRs).
• In 2016, units with advanced add-on controls (either SCR or SNCR) accounted for 68 percent of coal-
fired generation. At oil- and natural gas-fired units, SCR- and SNCR- controlled units produced 69
percent of generation.
• In 2016, 73 percent of CSAPR units (including 100 percent of coal-fired units) monitored ozone
season NOx emissions using CEMS. Ninety-eight percent of ozone season NOx emissions were
measured by CEMS.
Chapter 4: Emission Controls and Monitoring
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Analysis and Background Information
Continuous Emission Monitoring Systems (CEMS)
Accurate and consistent emissions monitoring is the foundation of a successful cap and trade program.
EPA has developed detailed procedures codified in federal regulations (40 CFR Part 75) to ensure that
sources monitor and report emissions with a high degree of precision, reliability, accessibility, and
timeliness. Sources are required to use CEMS or other approved methods to record and report pollutant
emissions data. Sources conduct stringent quality assurance tests of their monitoring systems to ensure
the accuracy of emissions data and to provide assurance to market participants that a ton of emissions
measured at one facility is equivalent to a ton measured at a different facility. EPA conducts
comprehensive electronic and field data audits to validate the reported data.
While some units with low levels of S02 and N0X emissions are allowed to use other approved
monitoring methods, the vast majority of S02 and N0X emissions are measured by CEMS.
SO2 Emission Controls
Sources in the ARP and CSAPR S02 program have a number of S02 emission control options available.
These include switching to low sulfur coal, employing various types of FGDs, or utilizing fluidized bed
limestone units. FGDs - also known as scrubbers - on coal-fired generators are the principal means of
controlling S02 emissions and tend to be present on the highest generating coal-fired units.
NOx Emission Controls
Sources in the ARP and CSAPR N0X annual and ozone season programs have a variety of options by
which to reduce N0X emissions, including advanced post-combustion controls such as SCR or SNCR, and
combustion controls, such as low N0X burners.
More Information
• Visit EPA's Power Plant Emission Trends site for the most up-to-date emissions and control data for
sources in CSAPR and the ARP https://www3.epa.gov/airmarkets/progress/datatrends/index.html
• Air Markets Program Data (AMPD) https://ampd.epa.gov/ampd/
• Learn more about emissions monitoring https://www.epa.gov/airmarkets/emissions-monitoring
• Plain English guide to 40 CRF Part 75 https://www.epa.gov/airmarkets/plain-english-guide-part-75-
rule
• Continuous emission monitoring systems (CEMS) https://www.epa.gov/emc/emc-continuous-
emission-monitoring-systems
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Chapter 4: Emission Controls and Monitoring
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Figures
SO: Emissions Controls in the ARP and CSAPR SO: Program in 2016
Generation (million MWh) by SO: Emission Control Generation by Number of Units with and without SO:
Type Emission Controls
¦ FGD ¦ Other ¦ FGD ¦ Other
¦ Uncontrolled ¦ Unknown ¦ Uncontrolled ¦ Unknown
Notes:
• Due to rounding. percentages show may no! add up to 100%.
- "FGD" refers to Flue-gas desuifuriatwn: "Other* fueJ refers to urats that barn wasie. -#ood. petroSetim coke. t*e
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CSAPR SO: Program Monitoring Methodology in 2016
Monitoring Methodology by Number of Units in 2016 Monitoring Methodology by S0: Emissions in 2016
I Coal Units wCEMS
I Gas Units w/CEMS
! Oil Units w/CEMS
I Other Units w/CEMS
! Coal Units w/o CEMS
Gas Units w/o CEMS
I Oil Units w/0 CEMS
I Other Units w/o CEMS
I Coal Units w/CEMS
I Gas Units w/CEMS
I Oil Units w/CEMS
I Other Units w/CEMS
! Coal Units w/o CEMS
Gas Units w/o CEMS
I Oil Units w/o CEMS
I Other Units w/o CEMS
- Percent totais sway not add up to 100 percent due to rounding.
• fuel uftfti" mdua* uM» that commit*3 primary *003 wut*. or other nonfotsi full.
Source: EPA. 2018
Figure 2. CSAPR SO2 Program Monitoring Methodology in 2016
Chapter 4: Emission Controls and Monitoring
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NOx Emissions Controls in CSAPR NO* Annual Program in 2016
Generation (million MWh) by NO* Control Type
Generation by Number of Units with and without NO*
Controls
I Combustion Only
I SNCR
I Other
I SCR
Uncontrolled
I Combustion Only
I SNCR
I Other
I SCR
Uncontrolled
Notts:
• Owe to round*>g. percentages shown may no! add up to 1W%.
• "SCR" refers to selective catalytic reductoo. "SMCR" fuel refers to selective non-catalytic reduction; "Combustion OnJy* refers to low NO, burners, combustion modification.'fuel returning, or overftre air: and "Other" fuel refers to units
thai burn waste, «nod. petrOSRim coke, twe-denved fuel, etc.
• Emissions Z3U collected *nd reports OEMS.
• EPA data m this figure are current as of Apr* 2018, and may differ from past o» future reports as a result of resubmissions by sources and ongoing eata quality assurance activities
• There is a srrtai amount of generation from units with "Other* controls and from "UncontroSed* units. The data for these unrts is not easiy visible on the full chart To more ciearfy see the generation data for these units, especially for 0i
and Other f uel types, use the «iteractive features of the figure: oficfc on the boxes « the legend to him off the btoe. dark orange, and green categories of control types (labeled 'Combustion Only." "SCR," and "SNCR") and turn on the
yttow and tight orange categories of control types (labeled "UncontroSed" "Other")
Source: EPA, 2018
Figure 3. NOx Emissions Controls in CSAPR NOx Annual Program in 2016
Chapter 4: Emission Controls and Monitoring
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CSAPR NOx Annual Program Monitoring Methodology in 2016
Monitoring Methodology by Number of Units in 2016 Monitoring Methodology by NO* Emissions in 2016
I Coal Units w/CEMS
I Gas Units w/CEMS
! Oil Units w/CEMS
[ Other Units w/CEMS
I Coal Units w/o CEMS
Gas Units w/oCEMS
I Oil Units w/oCEMS
I Other Units w/o CEMS
I Coal Units w/CEMS
] Gas Units w/CEMS
] Oil Units w/CEMS
I Other Units w/CEMS
I Coal Units w/oCEMS
Gas Units w/oCEMS
I Oil Units w/oCEMS
I Other Units w/o CEMS
• Percent totals m*y net #S<3 u*> to 100 percent due to rowrfif>g.
• fuel units' include units tfui combusted pomaniy wood, waste, or otooafoss.il f«es
Source: ERft, 2018
Figure 4. CSAPR NOx Annual Program Monitoring Methodology in 2016
Chapter 4: Emission Controls and Monitoring
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NOx Emissions Controls in CSAPR NO* Ozone Season Program in 2016
Generation (million MWh) by NO* Emission Control
Type
Generation by Number of Units with and without NOx
Emission Controls
I Combustion Only
J SNCR
I Other
I SCR
Uncontrolled
I Combustion Only
I SNCR
] Other
I SCR
Uncontrolled
No!«:
• Doe lo roura&ng. percentages shewn may add up to 100%.
• "SCR" refers to selective catalytic reduction: "SNCR" fuel refers to selective non-catalytic reduction; "Combustion Only" refers to low NO* burners, combustion modification/fuel reburning. or overfire air. and 'Other' fuel refers to units
thai bom waste, wood, petroitom oofce. tire-denved fuel. etc.
• Emissions ajia coseeted wsd reported uung CEMS
• EM data m this figure are current as of April 201S. and may differ from past or future reports as a result of resuibmessiofts by sojfees 3nc ongoing data quality assurance activities.
«There is a small amount of generation from units with "Other" controls and from "Unoontioted" utwts. The data for these units s not easily visible on the full chart. To more dearly see the generation dala for these uti«ts. especially for Oil
and Other fuel types, use the interactive features of the figure- click on the boxes in the teger-d to turn off the blue, dart? orange, and green categories of controJ types (labeled "Combustion Only." "SCR." and "SNCR") and turn on the
y*i
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CSAPR NOx Ozone Season Program Monitoring Methodology in 2016
Monitoring Methodology by Number of Units in 2016 Monitoring Methodology by Ozone Emissions in 2016
I Coal Units w/CEMS
I Gas Units w/CEMS
I Oil Units w/CEMS
I Other Units w/CEMS
[ Coal Units w/o CEMS
Gas Units w/o CEMS
I Oil Units w/o CEMS
I Other Units w/o CEMS
Notes;
• Percent rotate may not up lo 100 peroefli due to rousrfng
• "0:h*? fuel uswu" «ctede vma »K»t oombuiTtd primarily wood. «»», w otfie* noniossi fuel
I Coal Units w/CEMS
Gas Units w/CEMS
: Oil Units w/CEMS
I Other Units w/CEMS
I Coal Units w/o CEMS
Gas Units w/o CEMS
I Oil Units w/o CEMS
I Other Units w/o CEMS
Source: EfW, 2018
Figure 6. CSAPR NOx Ozone Season Program Monitoring Methodology in 2016
Chapter 4: Emission Controls and Monitoring
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Chapter 5: Program Compliance
This analysis shows how the Acid Rain Program (ARP) and Cross-State Air Pollution Rule (CSAPR)
allowances are used for compliance under the trading programs in 2016.
Highlights
ARP SO2 Programs
• The reported 2016 S02 emissions by ARP sources totaled 1,469,779 tons.
• Almost 42 million S02 allowances were available for compliance (9 million vintage 2016 and nearly
33 million banked from prior years).
• EPA deducted just under 1.5 million allowances for ARP compliance. After reconciliation, over 40.2
million ARP S02 allowances were banked and carried forward to the 2017 ARP compliance year.
• All ARP S02 facilities were in compliance in 2016 (holding sufficient allowances to cover their S02
emissions).
CSAPR SO2 Group 1 Program
• The reported 2016 S02 emissions by CSAPR Group 1 sources totaled 785,248 tons.
• Over 3.7 million S02 Group 1 allowances were available for compliance.
• EPA deducted just over 785,000 million allowances for CSAPR S02 Group 1 compliance. After
reconciliation, over 2.9 million CSAPR S02 Group 1 allowances were banked and carried forward to
the 2017 compliance year.
• All CSAPR S02 Group 1 facilities were in compliance in 2016 (holding sufficient allowances to cover
their S02 emissions).
CSAPR SO2 Group 2 Program
• The reported 2016 S02 emissions by CSAPR Group 2 sources totaled 371,723 tons.
• Over 1.3 million S02 Group 2 allowances were available for compliance.
• EPA deducted just over 371,000 allowances for CSAPR S02 Group 2 compliance. After reconciliation,
over 961,000 CSAPR S02 Group 2 allowances were banked and carried forward to the 2017
compliance year.
• All CSAPR S02 Group 2 facilities were in compliance in 2016 (holding sufficient allowances to cover
their S02 emissions).
CSAPR NOx Annual Program
• The reported 2016 annual NOx emissions by CSAPR sources totaled 801,872 tons.
• Just over 1.6 million NOx Annual allowances were available for compliance.
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Chapter 5: Program Compliance
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• EPA deducted just over 801,000 allowances for CSAPR NOx Annual compliance. After reconciliation,
over 802,000 CSAPR NOx Annual allowances were banked and carried forward to the 2017
compliance year.
• All CSAPR NOx Annual facilities were in compliance with the CSAPR NOx Annual program (holding
sufficient allowances to cover their NOx emissions).
CSAPR NOx Ozone Season Program
• The reported 2016 ozone season NOx emissions by CSAPR sources totaled 422,361 tons.
• Just over 777,000 NOx ozone season allowances were available for compliance.
• EPA deducted just over 422,000 allowances for CSAPR NOx Ozone Season compliance. After
reconciliation, almost 354,000 CSAPR NOx Ozone Season allowances were banked. These banked
allowances were converted to CSAPR NOx ozone season group 1 and group 2 allowances under the
CSAPR Update Rule. Banked allowances held in Georgia facility accounts were converted at 1 for 1
to CSAPR NOx ozone season group 1 allowances. All other banked allowances were converted at a
ratio of 3.278 to 1 to vintage 2017 CSAPR NOx ozone season group 2 allowances. The conversion
resulted in 100,134 year 2017 CSAPR NOx ozone season group 2 allowances, and 18,513 CSAPR NOx
ozone season group 1 allowances.
• Two facilities were out of compliance with the CSAPR NOx Ozone Season program and had 17 total
tons of excess emissions.
Analysis and Background Information
The year 2016 was the second year of compliance for the CSAPR S02 (Group 1 and Group 2), annual NOx
and ozone season NOx programs. Each program has its own distinct set of allowances, which cannot be
used for compliance with the other programs (e.g., CSAPR S02 Group 1 allowances cannot be used to
comply with the CSAPR S02 Group 2 Program).
The compliance summary emissions number cited in "Highlights" may differ slightly from the sums of
emissions used for reconciliation purposes shown in the "Allowance Reconciliation Summary" figures
because of variation in rounding conventions, changes due to resubmissions by sources, and compliance
issues at certain units. Therefore, the allowance totals deducted for actual emissions in those figures
differ slightly from the number of emissions shown elsewhere in this report.
More Information
• Learn more about allowance markets https://www.epa.gov/airmarkets/allowance-markets
• Air Markets Business Center https://www.epa.gov/airmarkets/business-center
• Air Markets Program Data (AMPD) https://ampd.epa.gov/ampd/
• Learn more about emissions trading https://www.epa.gov/emissions-trading-resources
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Chapter 5: Program Compliance
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Figures
Acid Rain Program S02 Program Allowance Reconciliation Summary, 2016
Held by Affected Fadlity Accounts 26,526,882
Total Allowances Held (1995 - 2016 Vintage)
41.723,807
Held by Other Accounts (General 15,196,925
and Non-Affected Facility Accounts)
Allowances Deducted for Acid Rain Compliance*
Penalty Allowance Deductions
Held by Affected Facility Accounts
25,049,370
Banked Allowances
40,246,295
Held by Other Accounts (General
and Non-Affected Facility Accounts)
15,196,925
* Allowances deducted for ARP Compliance Includes 649 allowances deducted from opt ins for reduced utilization.
ARP SO, Program Compliance Results
Reported Emissions (tons) 1,469,779
Compliance issues, rounding, and report resubmission adjustments (tons) 7.084
Emissions not covered by allowances (tons) 0
Total allowances deducted for emissions 1,476,863
Notes:
• Compliance emissions data may vary from other report sections as a result of variation in rounding conventions, changes due to resubmissions by sources, or allowance compliance issues at certain units.
• Reconciliation and compliance data are current as of July 2017 and subsequent allowance deduction adjustments and penalties are not reflected.
Source: EPA, 2018
Figure 1. ARP SO2 Program Allowance Reconciliation Summary, 2016
Chapter 5: Program Compliance
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Cross-State Air Pollution Rule S0Z Group 1 Program Allowance Reconciliation Summary, 2016
Held by Affected Facility Accounts
3,286,939
Total Allowances Held (2015 - 2016 Vintage) 3,709,960
Held by Other Accounts (General,
State Holding and Non Affected
Facility Accounts)
423,021
Allowances Deducted for Cross-State Air Pollution Rule 785,247
SO, Group 1 Program
Penalty Allowance Deductions 0
Held by Affected Facility Accounts
2,501,692
Banked Allowances 2,924,713
Held by Other Accounts (General,
State Holding and Non Affected
Facility Accounts)
423,021
CSAPR S02 Group 1 Program Compliance Results
Reported Emissions (tons)
785,248
Compliance issues, rounding, and report resubmission adjustments (tons) -1
Emissions not covered by allowances (tons)
0
Total allowances deducted for emissions 785,247
Notes:
• CompSanoe emissions data may wary from other report sections as a result of variation m rounding conventions, changes due to resubmissions by sources, or allowance compliance issues at certain units.
• Reconciliation and compliance data are current as of July 2017 and subsequent allowance deduction adjustments and penalties are not reflected.
Source: EPA, 2018
Figure 2. CSAPR SO2 Group 1 Program Allowance Reconciliation Summary, 2016
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Cross-State Air Pollution Rule S02 Group 2 Program Allowance Reconciliation Summary, 2016
Held by Affected Facility Accounts
1,174,231
Total Allowances Held (2015 - 2016 Vintage) 1,332,789
Held by Other Accounts (General,
State Holding and Non-Affected
Facility Accounts)
158,558
Allowances Deducted for Cross State Air Pollution Rule 371,565
SO, Group 2 Program
Penalty Allowance Deductions 0
Held by Affected Facility Accounts
802,666
Banked Allowances 961,224
Held by Other Accounts (General,
State Holding and Non Affected
Facility Accounts)
158.558
CSAPR SO, Group 2 Program Compliance Results
Reported Emissions (tons)
371,723
Compliance issues, rounding, and report resubmission adjustments (tons)
-158
Emissions not covered by allowances (tons)
0
Total allowances deducted for emissions 371.565
Notes:
• Compliance emissions data may vary from other report sections as a result of variation in rounding conventions, changes due to resubmissions by sources, or allowance compliance issues at certain units.
¦ Reconciliation and compliance data are current as of July 2017 and subsequent allowance deduction adjustments and penaihes are not reflected
Source: EPA, 2018
Figure 3. CSAPR SO2 Group 2 Program Allowance Reconciliation Summary, 2016
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Cross-State Air Pollution Rule N0X Annual Program Allowance Reconciliation Summary, 2016
Total Allowances Held (2015 • 2016 Vintage) 1,603,562
Held by Affected Facility Accounts
1,404,344
Held by Other Accounts (General,
State Holding and Non Affected
Facility Accounts)
199,218
Allowances Deducted for Cross-State Air Pollution Rule 800,945
NO* Annual Program
Penalty Allowance Deductions 0
Banked Allowances 802,617
Held by Affected Facility Accounts
603,399
Held by Other Accounts (General,
State Holding and Non Affected
Facility Accounts)
199.218
CSAPR NOx Annual Program Compliance Results
Reported Emissions (tons)
801,872
Compliance issues, rounding, and report resubmission adjustments (tons)
-927
Emissions not covered by allowances (tons)
0
Total allowances deducted for emissions 800,945
Notes:
¦ Compliance emissions data may vary from o'.ber report sections as a result of variation in rounding conventions, changes due to resubmissions by sources, or allowance compliance issues a! certain units.
• Reconciliation and compliance data are current as of July 2017 and subsequent allowance deduction adjustments and penalties are not reflected.
Source: EPA, 2018
Figure 4. CSAPR NOx Annua! Program Allowance Reconciliation Summary, 2016
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Cross-State Air Pollution Rule N0X Ozone Season Program Allowance Reconciliation Summary, 2016
Held by Affected Facility Accounts
713,087
Total Allowances Held (2015 - 2016 Vintage) 776,979
Held by Other Accounts (General,
State Holding and Non Affected
Facility Accounts)
63,892
Allowances Deducted for Cross-State Air Pollution Rule 422,573
NO* Ozone Season Program
Penalty Allowance Deductions 34
Held by Affected Facility Accounts
290,480
Banked Allowances 354,372
Held by Other Accounts (General.
State Holding and Non Affected
Facility Accounts)
63,892
CSAPR NOx Ozone Season Program Compliance Results
Reported Emissions (tons)
422,361
Compliance issues, rounding, and report resubmission adjustments (tons)
195
Emissions not covered by allowances (tons)
17
Total allowances deducted for emissions 422,573
Motes:
• Compliance emissions data may vary from other report sections as a result of variation in rounding conventions, changes due to resubmissions by sources, or allowance compliance issues at certain units.
• Reconciliation and compliance data are current as of July 2017 and subsequent allowance deduction adjustments and penalties are not reflected.
Source: EPA, 2018
Figure 5. CSAPR NOx Ozone Season Program Allowance Reconciliation Summary, 2016
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Chapter 6: Market Activity
Cap and trade programs allow participants to independently determine their best compliance strategy.
Participants that reduce their emissions below the number of allowances they hold may trade
allowances, sell them, or bank them for use in future years.
Highlights
Transaction Types and Volumes
• In 2016, more than 1,000,000 allowances were traded across all four of the CSAPR trading programs.
Just under one-third of the transactions within the CSAPR programs were between distinct
organizations.
• In 2016, over 2 million ARP allowances were traded, the majority (82 percent) between related
organizations.
2016 Allowance Prices2
• ARP S02 allowance prices averaged less than $1 per ton in 2016.
• CSAPR S02 Group 1 allowance prices started 2016 at $2.75 per ton and ended 2016 at $5.25 per ton.
• CSAPR S02 Group 2 allowance prices started 2016 at $5 per ton and ended 2016 at $5.25 per ton.
• CSAPR NOx annual program allowances started 2016 at $80 per ton and ended 2016 at $6 per ton.
• CSAPR NOx ozone season program allowances started 2016 at $182.5 per ton and ended 2016 at
$142.5 per ton.2
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2 Allowance prices as reported by SNL Finance, 2017.
2 These prices reflect CSAPR ozone season NOx allowances. In October 2016, EPA published an update to the CSAPR ozone
season allowance trading programs. On October 23rd, 2017, CSAPR most ozone season NOx allowances were converted to
CSAPR Update ozone season NOx allowances.
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Analysis and Background Information
Transaction Types and Volumes
Allowance transfer activity includes two types of transfers: EPA transfers to accounts and private
transactions. EPA transfers to accounts include the initial allocation of allowances by states or EPA, as
well as transfers into accounts related to set-asides. This category does not include transfers due to
allowance retirements. Private transactions include all transfers initiated by authorized account
representatives for any compliance or general account purposes.
To better understand the trends in market performance and transfer history, EPA classifies private
transfers of allowance transactions into two categories:
• Transfers between separate and unrelated parties (distinct organizations), which may include
companies with contractual relationships (such as power purchase agreements), but excludes
parent-subsidiary types of relationships.
• Transfers within a company or between related entities (e.g., holding company transfers between a
facility compliance account and any account held by a company with an ownership interest in the
facility).
While all transactions are important to proper market operation, EPA follows trends in transactions
between distinct economic entities with particular interest. These transactions represent an actual
exchange of assets between unaffiliated participants, which reflect companies making the most of the
cost-minimizing flexibility of emission trading programs by finding the cheapest emission reductions not
only among their own generating assets, but across the entire marketplace of power generators.
Allowance Markets
The 2016 emissions were below emission budgets for the Acid Rain Program (ARP) and for all four Cross-
State Air Pollution Rule (CSAPR) programs. As a result, CSAPR allowance prices were well below the
marginal cost for reductions projected at the time of the final rule, and are subject, in part, to downward
pressure from the available banks of allowances.
More Information
• Learn more about allowance markets https://www.epa.gov/airmarkets/allowance-markets
• Air Markets Business Center https://www.epa.gov/airmarkets/business-center
• Air Markets Program Data (AMPD) https://ampd.epa.gov/ampd/
• Learn more about emissions trading https://www.epa.gov/emissions-trading-resources
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Figures
2016 Allowance Transfers under CSAPR and ARP
Transactions Conducted
Allowances Transferred
Share of Program's Allowances Transferred
Related (%)
Distinct (%)
ARP SO;
880
2,797,308
82%
18%
CSAPR SO; Group 1
433
387,886
66%
34%
CSAPR SO; Group 2
208
189,845
83%
17%
CSAPR NO, Annual
893
321,699
74%
26%
CSAPR NO* Ozone Season
1,093
177,488
65%
35%
Noses:
¦ The breakout between distinct and related organizations s not an exact value as seSatamships are often difficult lo cate^yrce in a sirrapie bifurcated manner. ERfts analyse is conservative and the "Distinct Organizations" percentage ts
fteJy higher
• ?e?e*nt*3es m»y not up «0 100% due :o roynsing,
Source: EflV 2018
Figure 1, 2016 Allowance Transfers under CSAPR and ARP
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pro^
Allowance Spot Price (Prompt Vintage), January - December 2016
1,200
CSAPR S02 Group 1 CSAPR S02 Group 2 CSAPR NOx Annual CSAPR NOx Seasonal Group 1 CSAPR NOx Seasonal Group 2
Notes:
- Prompt vintage is the vintage for the "current" compliance year.
¦ CSAPR NOx Seasonal Group 2 allowance prices reflect the CSAPR Update Rule, which was published in October 2016 and created two geographically distinct trading groups, the other being CSAPR NO*
Seasonal Group 1.
Source: SNL Financial, 2018
Figure 2. Allowance Spot Price (Prompt Vintage), January-December 2016
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Chapter 7: Air Quality
The Acid Rain Program (ARP) and Cross-State Air Pollution Rule (CSAPR) were designed to reduce sulfur
dioxide (S02) and nitrogen oxides (N0X) emissions from power plants. These pollutants contribute to the
formation of ground-level ozone and particulate matter, which cause a range of serious health effects
and degrade visibility in many American cities and scenic areas, including National Parks. The dramatic
emission reductions achieved under these programs have improved air quality and delivered significant
human health and ecological benefits across the United States.
To evaluate the impact of emission reductions on air quality, scientists and policymakers use data
collected from long-term national air quality monitoring networks. These networks provide information
on a variety of indicators useful for tracking and understanding trends in regional air quality over time
and in different areas.
Sulfur Dioxide and Nitrogen Oxides Trends
Highlights
National SO2 Air Quality
• Based on EPA's air trends data, the national average of S02 annual mean ambient concentrations
decreased from 12.0 parts per billion (ppb) to 1.1 ppb (91 percent) between 1980 and 2016.
• The two largest single-year reductions (over 20 percent) occurred in the first year of the ARP,
between 1994 and 1995, and more recently between 2008 and 2009, just prior to the start of the
CAIR S02 program.
Regional Changes in Air Quality
• Average ambient S02 concentrations declined in the eastern United States following
implementation of the ARP and other emission reduction programs. Regional average
concentrations declined 87 percent from the 1989-1991 to the 2014-2016 observation periods.
• Ambient particulate sulfate concentrations have decreased since the ARP was implemented, with
average concentrations decreasing by 71 to 75 percent in observed regions from 1989-1991 to
2014-2016.
• Average annual ambient total nitrate concentrations declined 51 percent from 1989-1991 to 2014-
2016 in the eastern United States, with the largest reductions in the Mid-Atlantic and Northeast.
Analysis and Background Information
Sulfur Dioxide
Sulfur oxides are a group of highly reactive gases that can travel long distances in the upper atmosphere
and predominantly exist as sulfur dioxide (S02). The primary source of S02 emissions is fossil fuel
combustion at power plants. Smaller sources of S02 emissions include industrial processes, such as
extracting metal from ore, as well as the burning of high sulfur-containing fuels by locomotives, large
ships, and non-road equipment. S02 emissions contribute to the formation of fine particle pollution
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(PM2.5) and are linked with a number of adverse effects on the respiratory system.1 In addition,
particulate sulfate degrades visibility and, because sulfate compounds are typically acidic, they can harm
ecosystems when deposited.
Nitrogen Oxides
Nitrogen oxides are a group of highly reactive gases including nitric oxide (NO) and nitrogen dioxide
(N02). In addition to contributing to the formation of ground-level ozone and PM2.5, N0X emissions are
linked with a number of adverse effects on the respiratory system.2,3 N0X also reacts in the atmosphere
to form nitric acid (HN03) and particulate ammonium nitrate (NH4NO3). HN03 and NH4NO3, reported as
total nitrate, can also lead to adverse health effects and, when deposited, cause damage to sensitive
ecosystems.
Although the ARP and CSAPR programs have significantly reduced N0X emissions (primarily from power
plants) and improved air quality, emissions from other sources (such as motor vehicles and agriculture)
contribute to total nitrate concentrations in many areas. Ambient nitrate levels can also be affected by
emissions transported via air currents over wide regions.
More Information
• Clean Air Status and Trends Network (CASTNET) https://www.epa.gov/castnet
• Air Quality System (AQS) https://www.epa.gov/aqs
• National Ambient Air Quality Standards (NAAQS) https://www.epa.gov/criteria-air-pollutants
• Learn more about sulfur dioxide (S02) https://www.epa.gov/so2-pollution
• Learn more about nitrogen oxides (N0X) https://www.epa.gov/no2-pollution
• Learn more about EPA's Clean Air Market Programs https://www.epa.gov/airmarkets/programs
References
1. Katsouyanni, K., Schwartz, J., Spix, C., Touloumi, G., Zmirou, D., Zanobetti, A., Wojtyniak, B.,
Vonk, J.M., Tobias, A., Ponka, A., Medina, S., Bacharova, L., & Anderson, H.R. (1996). Short term
effects of air pollution on health: a European approach using epidemiologic time series data: the
APHEA protocol. J. of Epidemiol Community Health, 50: S12-S18.
2 Peel, J.L., Tolbert, P.E., Klein, M., Metzger, K.B., Flanders, W.D., Todd, K., Mulholland, J.A., Ryan,
P.B., & Frumkin, H. (2005). Ambient air pollution and respiratory emergency department visits.
Epidemiology, 16: 164-174.
3. Hong, C., Goldberg, M.S., Burnett, R.T., Jerrett, M., Wheeler, A.J., & Villeneuve, P.J. (2013) Long-
term exposure to traffic-related air pollution and cardiovascular mortality. Epidemiology, 24:
35-43.
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Figures
~ 35
3
a
Ol
c 30
National SO; Air Quality Trend, 1980-2016
5 25
u
C
0
2 20
c
Q>
3
1 <5
c
ro
o>
s 10
Average Concentration
90% of sites have concentrations
below this line
10% of sites have concentrations
below this line
* 0a«a bas«4 or. tut*. and EW momtotiog wNcfe aft teeattd pnmanly m wtan art**
Source: ER*. 2018
Figure 1. National SO2 Air Quality Trend, 1980-2016
Chapter 7: Air Quality-Sulfer Dioxide and Nitrogen Oxides Trends
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% PRo^°
Regional Changes in Air Quality
Measurement
Region
Annual Average,
1989-1991
Annual Average,
2014-2016
Percent Change
Number of Sites
Statistical
Significance
Mid-Atlantic
6.3
1.6
-75
12
...
Ambient particulate
sulfate concentration
(ng/m3)
Midwest
5.8
1,7
-71
9
...
Northeast
3.4
0.9
-74
4
Southeast
5.5
1.5
-73
8
—
Mid-Atlantic
13.0
2.0
-85
12
...
Ambient sulfur dioxide
Midwest
11.0
JL5
-86
9
...
concentration (ng/m3)
Northeast
5.2
0.7
-87
4
Southeast
5.1
0.6
-88
8
—
Mid-Atlantic
3.3
1.5
-55
12
...
Ambient total nitrate
Midwest
4.6
2.4
-48
9
...
concentration (ng/m3)
Northeast
1.7
0.7
-59
4
Southeast
2.2
LI
-50
8
...
NO?##:
• Avenges are the aMbnetis rftean of an sites tn a region that were present and fret the completeness criteria m both a veragmg penoas Thus, average concentrates for 1389 so 1991 may differ from past reports.
- Statistics! significance was de?errritned at the S5 percent confidence Sevel (p <0.05) us Fig Student's t-test. Changes ttiat are not stafetcaBy significant fray be unduJy irfiuen.c&3 by measurements at on»y a fe» iooarons or Barge
vanafeffity ii measurements.
Source: ERA, 2018
Figure 2. Regional Changes in Air Quality
Chapter 7: Air Quality-Sulfer Dioxide and Nitrogen Oxides Trends
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Ozone
Highlights
Changes in 1-Hour Ozone during Ozone Season
• There was an overall regional reduction in ozone levels between 2000-2002 and 2014-2016, with a
25 percent reduction in the highest (99th percentile) ozone concentrations in CSAPR states.
• Results demonstrate how NOx emission reduction policies have affected 1-hour ozone
concentrations in the eastern United States - the region that the policies were designed to target.
Trends in Rural 8-Hour Ozone
• From 2014 to 2016, rural ozone concentrations averaged 66 ppb in CSAPR states, a decrease of 24
ppb (26 percent) from the 1990 to 2002 period.
• The Autoregressive Integrated Moving Average (ARIMA) model shows how the reductions in rural
ozone concentrations compare with the implementation of the NBP in 2003 (two-year 14 ppb
reduction from 2002) and the start of the CAIR NOx Ozone Season program in 2009 (two-year 7 ppb
reduction from 2007).
• Four of the five lowest observed ozone concentrations were between 2013 and 2016. Ozone season
NOx emissions fell steadily under CAIR and continued to drop after implementation of CSAPR in
2015. In addition, implementation of the mercury and air toxics standards (MATS), which began in
2015, achieves co-benefit reductions of NOx emissions.
Changes in 8-Hour Ozone Concentrations
• The average reduction in ozone concentrations (not adjusted for weather) in the CSAPR NOx Ozone
Season program region from 2000-2002 to 2014-2016 was about 10 ppb (18 percent).
• The average reduction in the meteorologically-adjusted ozone concentrations in the CSAPR NOx
Ozone Season program region from 2000-2002 to 2014-2016 was about 11 ppb (20 percent).
Changes in Ozone Nonattainment Areas
• Ninety-two of the 113 areas originally designated as nonattainment for the 1997 8-hour ozone
National Ambient Air Quality Standard (NAAQS) (0.08 ppm) are in the eastern United States and are
home to about 122 million people.1 These nonattainment areas were designated in 2004 using air
quality data from 2001 to 2003.2
o Based on data from 2014 to 2016, all 92 of the eastern ozone nonattainment areas now
show concentrations below the level of the 1997 standard.
• Twenty-two of the 46 areas originally designated as nonattainment for the 2008 8-hour ozone
NAAQS (0.075 ppm) are in the eastern United States and are home to about 80 million people.
These nonattainment areas were designated in 2012 using air quality data from 2008 to 2010 or
2009 to 2011.
o Based on data from 2014-2016, 77 percent (17 areas) of the eastern ozone
nonattainment areas now show concentrations below the level of the 2008 standard.
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While five areas continue to show concentrations above the 2008 standard, three of
those areas made progress toward meeting the standard in the 2014-2016 period. Given
that power sector emissions are an important component of the NOx emission inventory
and that the majority of programs that reduce power sector ozone season NOx
emissions reductions in the power sector that occurred after 2003 are attributable to
the NBP, CAIR, and CSAPR, it is reasonable to conclude that ozone season NOx emission
have significantly contributed to these improvements in ozone air quality.
Analysis and Background Information
Ozone pollution - also known as smog - forms when NOx and volatile organic compounds (VOCs) react
in the presence of sunlight. Major sources of NOx and VOC emissions include electric power plants,
motor vehicles, solvents, and industrial facilities. Meteorology plays a significant role in ozone formation
and hot, sunny days are most favorable for ozone production. For ozone, EPA and states typically
regulate NOx emissions during the summer when sunlight intensity and temperatures are highest.
Ozone Standards
In 1979, EPA established NAAQS for 1-hour ozone at 0.12 parts per million (ppm, or 124 parts per
billion). In 1997, a more stringent 8-hour ozone standard of 0.08 ppm (84 ppb) was finalized, revising the
1979 standard. CSAPR was designed to help downwind states in the eastern United States achieve the
1997 ozone NAAQS. Based on extensive scientific evidence about ozone's effects on public health and
welfare, EPA strengthened the 8-hour ozone standard to 0.075 ppm (75 ppb) in 2008, and further
strengthened the 8-hour NAAQS for ground-level ozone to 0.070 ppm (70 ppb) in 2015. EPA revoked the
1-hour ozone standard in 2005 and also recently revoked the 1997 8-hour ozone standard in 2015.
Regional Trends in Ozone
EPA investigated trends in daily maximum 8-hour ozone concentrations measured at rural Clean Air
Status and Trends Network (CASTNET) monitoring sites within the CSAPR NOx ozone season program
region and in adjacent states. Rural ozone measurements are useful in assessing the impacts on air
quality resulting from regional NOx emission reductions because they are typically less affected by local
sources of NOx emissions (e.g., industrial and mobile) than urban measurements. Reductions in rural
ozone concentrations are largely attributed to reductions in regional NOx emissions and transported
ozone.
The Autoregressive Integrated Moving Average (ARIMA) model is an advanced statistical analysis tool
used to visualize the trend in regional ozone concentrations following implementation of various
programs geared toward reducing ozone season NOx emissions. To show the shift in the highest daily
ozone levels, EPA modeled the average of the 99th percentile of the daily maximum 8-hour ozone
concentrations measured at CASTNET sites (as described above).
Meteorologically-Adjusted Daily Maximum 8-Hour Ozone Concentrations
Meteorologically-adjusted ozone trends provide additional insight on the influence of CSAPR NOx Ozone
Season program emission reductions on regional air quality. CASTNET retrieved daily maximum 8-hour
ozone concentration data from EPA and daily meteorology data from the National Weather Service for
79 urban areas and 37 rural CASTNET monitoring sites located in the CSAPR NOx Ozone Season program
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region. EPA uses these data in a statistical model to account for the influence of weather on seasonal
average ozone concentrations at each monitoring site.3,4
Changes in Ozone Nonattainment Areas
The majority of ozone season N0X emission reductions in the power sector after 2003 are attributable to
the NBP, CAIR, and CSAPR. As power sector emissions are an important component of the NOx emission
inventory, it is reasonable to conclude that the reduction in ozone season NOx emissions from these
programs have significantly contributed to improvements in ozone air quality and attainment of the
1997 ozone health-based air quality standard. In fact, all areas originally designated as nonattainment
for the 1997 ozone NAAQS are now meeting the standard.
Emission reductions under these power sector programs also have helped many areas in the eastern
United States reach attainment for the 2008 ozone NAAQS. However, several areas continue to be out
of compliance with the 2008 ozone NAAQS, and additional ozone season NOx emission reductions are
needed to attain that standard as well as the strengthened ozone standard that was finalized in 2015.
In order to help downwind states and communities meet and maintain the 2008 ozone standard, EPA
finalized the CSAPR Update in September 2016 to address the transport of ozone pollution that crosses
state lines in the eastern United States. Implementation began in May 2017 to further reduce ozone
season NOx emissions from power plants in 22 states in the eastern US.
More Information
• Clean Air Status and Trends Network (CASTNET) https://www.epa.gov/castnet
• Air Quality System (AQS) https://www.epa.gov/aqs
• National Ambient Air Quality Standards (NAAQS) https://www.epa.gov/criteria-air-pollutants
• Learn more about ozone https://www.epa.gov/ozone-pollution
• Learn more about nitrogen oxides (NOx) https://www.epa.gov/no2-pollution
• Learn more about Nonattainment Areas https://www.epa.gov/green-book
• Learn more about EPA's Clean Air Market Programs https://www.epa.gov/airmarkets/programs
References
1. U.S. Census. (2010).
2. 40 CFR Part 81. Designation of Areas for Air Quality Planning Purposes.
3. Cox, W.M. & Chu, S.H. (1996). Assessment of interannual ozone variation in urban areas from a
climatological perspective. Atmospheric Environment, 30 (16): 2615-2625.
4. Camalier, L., Cox, W.M., & Dolwick, P. 2007. The effects of meteorology on ozone in urban areas
and their use in assessing ozone trends. Atmospheric Environment, 41(33): 7127-7137.
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Figures
Percent Change in the Highest Values (99th percentile) of 1-hour Ozone Concentrations during the Ozone Season,
2000-2002 versus 2014-2016
• Data are from State and Local Air Monitoring Stations (SLAMS) AQS and CASTNET monitoring sites with two or more years of data within each three-year monitoring period.
¦ The 99th percentile represents the highest 1 % of hourly ozone measurements at a given monitor.
Source: EPA, 2018
Figure 1. Percent Change in the Highest Values (99th percentile) of 1-hour Ozone
Concentrations during the Ozone Season, 2000-2002 versus 2014-2016
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% pRo^s°
Shifts in 8-Hour Seasonal Rural Ozone Concentrations in the CSAPR NO* Ozone Season Region, 1990-2016
£t
CL
Q.
C
o
c
o
O
c
o
o
o
c
o
N
O
60
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
o Actual Predicted ~ 95% Confidence Limits
Notes:
- Ozone concentration data are an average of the 99* percentile of the 8-houf daily maximum ozone concentrations measured at rural CASTNET sites that meet completeness criteria and are located «n and
adjacent to the CSAPR NO, ozone season program region.
Source: EPA, 2018
Figure 2. Shifts in 8-hour Seasonal Rural Ozone Concentrations in CSAPR NOx Ozone
Season Region, 1990-2016
Chapter 7: Air Quality - Ozone
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% pRo^s°
Seasonal Average of 8-Hour Ozone Concentrations in CSAPR States, Unadjusted and Adjusted for Weather
80 | | |
s 60
0 ' i 1 _
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
¦ Unadjusted concentrations ¦ Adjusted concentrations
Notts:
• 8-Hour daily maximum ozone concentration data from ErAs AOS arid 43tfy meteorotogy data from the National Weather Service were relieved for 75 urban 3re3S and 37 rural CASTNET monitoring sites boated « the CSAPR NO, ozone
season program region.
• Fix 3 monitor to be included m this trends analysis, n had to provide complete and vai>d iau for 75 percent of the days m the May to September penod. for eacii of (he years from 20QQ to 2015. In urban areas with more than one
mentoring site, the highest otewved ossne conoenttatiofl «the area used for each day.
Source: EPA, 2018
Figure 3. Seasonal Average of 8-Hour Ozone Concentrations
in CSAPR States, Unadjusted and Adjusted for Weather
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Changes in 1997 Ozone NAAQS Nonattainment Areas in the CSAPR Region. 2001-2003 (Original Designations)
versus 2014-2016
~
I | Mwrts 1997 8-hr Ozone NAAQS <9t areas)
I i*»ropseie Da*.a for 2014-2016(1 area)
I I CSAPR Slates (Cowro««t for Ozone}
Source: EPA: 2018
Figure 4. Changes in 1997 Ozone NAAQS Nonattainment Areas in CSAPR Region,
2001-2003 (Original Designations) versus 2014-2016
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% pRo^s°
Changes in 2008 Ozone NAAQS Nonattainment Areas, 2008-2010 (Original Designations) versus 2014-2016
Meets 2008 8-hr Ozone NAAQS (23 areas)
Above 2008 8-hr Ozone NAAQS (22 areas)
Incomplete Dala for 2014-2016 (1 area)
Source: EPA, 2018
Figure 5. Changes in 2008 Ozone NAAQS Nonattainment Areas,
2008-2010 (Original Designations) versus 2014-2016
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Particulate Matter
Highlights
PM Seasonal Trends
• The Air Quality System (AQS) includes average PM2.5 concentration data for 249 sites located in the
CSAPR S02 and annual N0X program region. Trend lines in PM2.5 concentrations show decreasing
trends in both the warm months (April to September) and cool months (October to March)
unadjusted for the influence of weather.
• The seasonal average PM2.5 concentrations have decreased by about 48 and 45 percent in the warm
and cool season months, respectively, between 2000 and 2016.
Changes in PM2.5 Nonattainment
• Thirty-six of the 39 designated nonattainment areas for the 1997 annual average PM2.5 NAAQS are in
the eastern United States and are home to about 75 million people.1,2 The nonattainment areas
were designated in January 2005 using 2001 to 2003 data.
o Based on data gathered from 2014 to 2016, 34 of these eastern areas originally
designated nonattainment show concentrations below the level of the 1997 PM2.5
standard (15 ng/m3), indicating improvements in PM2.5 air quality. Two areas have
incomplete data.
• Given that power sector emissions are an important component of the S02 and annual NOx emission
inventory and that the majority of power sector S02 and annual NOx emission reductions occurring
after 2003 are attributable in part to the ARP, NBP, CAIR, and CSAPR, it is reasonable to conclude
that these emission reduction programs have significantly contributed to these improvements in
PM2.5 air quality.
Analysis and Background Information
Particulate matter—also known as soot, particle pollution, or PM—is a complex mixture of extremely
small particles and liquid droplets. Particle pollution is made up of a number of components, including
acid-forming nitrate and sulfate compounds, organic compounds, metals, and soil or dust particles. Fine
particles (defined as particulate matter with aerodynamic diameter < 2.5 (j,m, and abbreviated as PM2.5)
can be directly emitted or can form when gases emitted from power plants, industrial sources,
automobiles, and other sources react in the air.
Particle pollution—especially fine particles—contains microscopic solids or liquid droplets so small that
they can get deep into the lungs and cause serious health problems. Numerous scientific studies have
linked particle pollution exposure to a variety of problems, including the following: premature death;
increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing;
decreased lung function; aggravated asthma; development of chronic bronchitis; irregular heartbeat;
and nonfatal heart attacks.3,4,5
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Particulate Matter Standards
The CAA requires EPA to set NAAQS for particle pollution. In 1997, EPA set the first standards for fine
particles at 65 micrograms per cubic meter (ng/m3) measured as the three-year average of the 98th
percentile for 24-hour exposure, and at 15 ng/m3 for annual exposure measured as the three-year
annual mean. EPA revised the air quality standards for particle pollution in 2006, tightening the 24-hour
fine particle standard to 35 ng/m3 and retaining the annual fine particle standard at 15 ng/m3. In
December 2012, EPA strengthened the annual fine particle standard to 12 ng/m3.
CSAPR was promulgated to help downwind states in the eastern United States achieve the 1997 annual
average PM2.5 NAAQS and the 2006 24-hour PM2.5 NAAQS; therefore, analyses in this report focus on
those standards.
Changes in PM2.5 Nonattainment Areas
In the eastern US, recent data indicate that no areas are violating the 1997 or 2006 PM2.5 NAAQS. The
majority of S02 and annual NOx emission reductions in the power sector that occurred after 2003 are
attributable to the ARP, NBP, CAIR, and CSAPR. As power sector emissions are an important component
of the S02 and annual NOx emission inventory, it is reasonable to conclude that these emission
reduction programs have significantly contributed to these improvements in PM2.5 air quality.
More Information
• Clean Air Status and Trends Network (CASTNET) https://www.epa.gov/castnet
• Air Quality System (AQS) https://www.epa.gov/aqs
• National Ambient Air Quality Standards https://www.epa.gov/criteria-air-pollutants
• Learn more about particulate matter (PM) https://www.epa.gov/pm-pollution
• Learn more about sulfur dioxide (S02) https://www.epa.gov/so2-pollution
• Learn more about nitrogen oxides (N0X) https://www.epa.gov/no2-pollution
• Learn more about Nonattainment Areas https://www.epa.gov/green-book
• Learn more about EPA's Clean Air Market Programs https://www.epa.gov/airmarkets/programs
References
1. 40 CFR Part 81. Designation of Areas for Air Quality Planning Purposes.
2. U.S. Census. (2010).
3. Dockery, D.W., Speizer F.E., Stram, D.O., Ware, J.H., Spengler, J.D., & Ferris Jr., B.G. (1989).
Effects of inhalable particles on respiratory health of children. American Review of Respiratory
Disease 139: 587-594.
4. Schwartz, J. & Lucas, N. (2000). Fine particles are more strongly associated than coarse particles
with acute respiratory health effects in school children. I 11: 6-10.
5. Bell, M.L., Dominici, F., Ebisu, K., Zeger, S.L., & Samet, J.M. (2007). Spatial and temporal variation
in PM2.5 chemical composition in the United States for health effects studies. Environmental
Health Perspectives 115: 989-995.
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% pRo^s°
Figures
PM:.s Seasonal Trends, 2000-2016
0
2000 2001 2002 2Q03 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
— Cool season — Warm season
Notts:
• For a PMu mar&ormg site to be swfuded m the trenas analysts, it had to meet all si the fefcwing errtera 1) each sde-year quarterly mean ooficenifation vaiue had to encompass at feast 11 Of more samples. 2) all four quarterly mean
vatoes had to be vand for a given year (i.e . meet criterion #1). and 3) a> 16 years of srte-tevel seaso-iaf means had to be valid for the given srte fi e meet criteria #1 and *2)
¦ Annual "eeoT »jwi mean vatjes for mc*i s*e-yeaf wtr* computed as the average of the first and fourth auanefty mean values. Annual "warm" season mean values for each site-yeas- *ve computed as the average of the second and
ttafd quarterly mean values. Fo* a given ye*. »« of the seasonal mean values for the monitoring sites tocated m tfte CSAPR regon **<¦» then averted together to obta* a s«gie year (composite) seasonal mean vatut
Source: EPA, 2018
Figure 1. PM2.5 Seasonal Trends, 2000-2016
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Changes in PM,.5 NAAQS Nonattainment Areas in CSAPR Region, 2001-2003 (Original Designations)
versus 2014-2016
] Meets 1997 Annual PM 2 5 NAAQS (36 areas)
! | CSAPR States
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Chapter 8: Acid Deposition
Acid deposition, commonly known as "acid rain/' is a broad term referring to the mixture of wet and dry
deposition from the atmosphere containing higher than normal amounts of sulfur and nitrogen-
containing acidic pollutants. The precursors of acid deposition are primarily the result of emissions of
sulfur dioxide (S02) and nitrogen oxides (N0X) from fossil fuel combustion; however, natural sources,
such as volcanoes and decaying vegetation, also contribute a small amount.
Highlights
Wet Sulfate Deposition
• All areas of the eastern United States have shown significant improvement, with an overall 66
percent reduction in wet sulfate deposition from 1989-1991 to 2014-2016.
• Between 1989-1991 and 2014-2016, the Northeast and Mid-Atlantic experienced the largest
reductions in wet sulfate deposition, of 69 percent and 71 percent, respectively.
• A decrease in both S02 emissions from sources in the Ohio River Valley and the formation of sulfates
that are transported long distances have resulted in reduced sulfate deposition in the Northeast.
The sulfate reductions documented in the region, particularly across New England and portions of
New York, were also affected by lowered S02 emissions in eastern Canada.1
Wet Inorganic Nitrogen Deposition
• Wet deposition of inorganic nitrogen decreased an average of 35 percent in the Mid-Atlantic and
Northeast but decreased only 15 percent in the Midwest from 1989-1991 to 2014-2016. Smaller
reductions in wet deposition of inorganic nitrogen deposition in the Midwest are attributed to a 15
percent increase in wet deposition of reduced nitrogen (NH4+) over the same time period.
• Reductions in nitrogen deposition recorded since the early 1990s have been less pronounced than
those for sulfur. Emissions from other source categories (e.g., mobile sources, agriculture, and
manufacturing) contribute to air concentrations and deposition of nitrogen.
Regional Trends in Total Deposition
• The reduction in total sulfur deposition (wet plus dry) has been of similar magnitude to that of wet
deposition with an overall average reduction of 88 percent from 1989-1991 to 2014-2016.
• Decreases in dry and total inorganic nitrogen deposition have generally been greater than that of
wet deposition, with average reductions of 62 percent and 71 percent, respectively. In contrast, wet
deposition from inorganic nitrogen decreased by an average of 26 percent from 1989-1991 to
Analysis and Background Information
Acid Deposition
As S02 and NOx gases react in the atmosphere with water, oxygen, and other chemicals, they form acidic
compounds that are deposited to the earth's surface in the form of wet and dry acid deposition.
2014-2016.
Chapter 8: Acid Deposition
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Long-term monitoring network data show significant improvements in the primary indicators of acid
deposition. For example, wet sulfate deposition (sulfate that falls to the earth through rain, snow, and
other precipitation) has decreased in much of the Ohio River Valley and Northeastern United States due
to S02 emission reductions achieved through implementation of the Acid Rain Program (ARP), the Clean
Air Interstate Rule (CAIR) and the Cross-State Air Pollution Rule (CSAPR). Some of the most dramatic
reductions have occurred in the mid-Appalachian region, including Maryland, New York, West Virginia,
Virginia, and most of Pennsylvania. Along with wet sulfate deposition, precipitation acidity, expressed as
hydrogen ion (H+ or pH) concentration, has also decreased by similar percentages.
Reductions in nitrogen deposition compared to the early 1990s have been less pronounced than those
for sulfur. As noted earlier, emissions from source categories other than ARP and CSAPR sources
contribute to changes in air concentrations and deposition of nitrogen.
Monitoring Networks
The Clean Air Status and Trends Network (CASTNET) provides long-term monitoring of regional air
quality to determine trends in atmospheric concentrations and deposition of nitrogen, sulfur, and ozone
in order to evaluate the effectiveness of national and regional air pollution control programs. CASTNET
now operates more than 90 regional sites throughout the contiguous United States, Alaska, and Canada.
Sites are located in areas where urban influences are minimal.
The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) is a nationwide,
long-term network tracking the chemistry of precipitation. The NADP/NTN provides concentration and
wet deposition data on hydrogen ion (acidity as pH), sulfate, nitrate, ammonium, chloride, and base
cations. The NADP/NTN has grown to more than 250 sites spanning the United States, Canada, Puerto
Rico, and the Virgin Islands.
Together, these complementary networks provide long-term data needed to estimate spatial patterns
and temporal trends in total deposition.
More Information
• Learn more about acid rain https://www.epa.gov/acidrain
• Clean Air Status and Trends Network (CASTNET) https://epa.gov/castnet
• National Atmospheric Deposition Program (NADP) http://nadp.isws.illinois.edu/
References
1. Government of Canada, Environment Canada. (2017). Canada-United States Air Quality
Agreement Progress Report 2016. ISSN: 1910-5223: Cat. No.: En85-1E-PDF.
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Figures
Figure 1. Three-Year Wet Sulfate Deposition
1989-1991
Three-Year Wet Sulfate Deposition
2014-2016
Source: NADP/NTN & PRISM, 2018
Wet S042"
(kg/ha)
Chapters: Acid Deposition
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% pRo^s°
Three-Year Wet Inorganic Nitrogen Deposition
1989-1991
2014-2016
Inorg. N
(kg/ha)
¦
-0.0
-1.0
-2,0
•
-3.0
-4.0
-5.0
m
-6.0
-
-7.0
-8.0
_
-9.0
¦
->10.0
Source: NADP/NTN & PRISM, 2018
Figure 2. Three-Year Wet Inorganic Nitrogen Deposition
Chapters: Acid Deposition
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Regional Trends in Deposition
Measurement
Region
Annua I Average,
1989-1991
Annual Average,
2014-2016
Percent Change
Number of Sites
Statistical
Significance
Mid-Atlantic
2.5
0.9
-64
12
...
Dry inorganic nitrogen
Midwest
2.4
1.1
•54
9
...
deposition (kg-N/ha)
Northeast
1.3
0.4
-69
4
Southeast
1.7
0.7
-59
8
...
Mid-Atlantic
7.0
0.9
-87
12
...
Dry sulfur deposition (kg-
Midwest
6.6
1.1
-83
9
...
S/ha)
Northeast
2.6
0.4
-85
4
Southeast
3.1
0.5
-84
8
...
Mid-Atlantic
8.8
5.0
-43
12
...
Totalinorganic nitrogen
Midwest
8.6
6.1
-29
9
"¦
deposition (kg-N/ha)
Northeast
6.7
3.7
-45
4
Southeast
6.4
4.0
-38
8
...
Mid-Atlantic
16.0
3.0
-81
12
...
Totalsulfurdeposition (kg-
Midwest
15.0
4.0
-73
9
...
S/ha)
Northeast
9.8
2.0
-80
4
Southeast
10.3
2.6
-75
8
...
Mid-Atla ntic
6.2
3.9
-37
11
...
Wet nitrogen deposition from
Midwest
6.0
5.1
-15
22
...
inorganic nitrogen (kg-N/ha)
Northeast
5.7
3.9
-32
16
...
Southeast
4.3
3.4
-21
22
...
Mid-Atlantic
9.2
2.7
-71
11
...
Wet sulfur deposition from
Midwest
7.7
2.9
-62
22
...
sulfate (kg-5/ha)
Northeast
7.5
2.3
-69
16
...
Southeast
5.9
2.2
-63
22
...
• Averages are Itie arithmetic mean or all sites In a region that were present and met the completeness criteria In both averaging periods. Thus, average concentrations for 19B9 to 1991 may differ from past reports.
¦ Total deposition is estimated from raw measurement data, not rounded, and may not equal Ihe sum of dry and wet deposition.
• Statistical significance was determined at Ihe 95 percent confidence level (p <0.05) using Student's t-test. Changes that are not statistically significant may be unduly Influenced by measurements at only a few locations or large variability in
measurements.
Source: EPA. 2018
Figure 3. Regional Trends in Deposition
Chapters: Acid Deposition
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Chapter 9: Ecosystem Response
Acidic deposition resulting from sulfur dioxide (S02) and nitrogen oxides (N0X) emissions may negatively
affect the biological health of lakes, streams, forests, grasslands, and other ecosystems in the United
States. Trends in measured chemical indicators allow scientists to determine whether water bodies are
improving and heading towards recovery or if they are still acidifying. Assessment tools, such as critical
loads analysis, provide a quantitative estimate of whether acidic deposition levels of sulfur and nitrogen
resulting from S02 and N0X emission reductions may protect aquatic resources.
Ground-level ozone is an air pollutant that can impact ecological systems like forests, altering a plant's
health and leading to changes in individual tree growth (e.g., biomass loss) and to the biological
community. Analyzing the biomass loss of certain trees before and after implementation of N0X
emission reduction programs provides information about the effect of reduced N0X emissions and
ozone concentrations on forested areas.
Highlights
Regional Trends in Water Quality
• Between 1990 and 2016, significant decreasing trends in sulfate concentrations, demonstrating
improved lake and stream health, are found at all long-term monitoring (LTM) program lake and
stream monitoring sites in New England, the Adirondacks, and the Catskill mountains.
• On the other hand, between 1990 and 2016, streams in the central Appalachian region have
experienced mixed results due in part to their soils and geology. Only 39 percent of monitored
streams show lower sulfate concentrations (and statistically significant trends), while 12 percent
show increased sulfate concentrations.
• Nitrate concentrations and trends are highly variable and many sites do not show improving trends
between 1990 and 2016, despite reductions in NOx emissions and inorganic nitrogen deposition.
• In 2016, levels of acid neutralizing capacity (ANC), a key indicator of aquatic ecosystem recovery,
have increased significantly from 1990 in lake and stream sites in the Adirondack Mountains, New
England, and the Catskill mountains.
Ozone Impacts on Forests
• Between 2000-2002 and 2014-2016, the area in the eastern United States with significant forest
biomass loss (>2% biomass loss) decreased from 34 percent to 5.8 percent for seven tree species
combined - black cherry, yellow poplar, sugar maple, eastern white pine, Virginia pine, red maple,
and quaking aspen.
• For black cherry and yellow poplar individually (the tree species most sensitive to ground-level
ozone), the total land area in the eastern United States with significant biomass loss decreased from
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15 percent to 5.1 percent for black cherry, and from 3 percent to 0 percent for yellow poplar
between 2000-2002 and 2014-2016.
• For the period 2014-2016, total land area in the eastern United States with significant biomass loss
for the remaining five species combined (red maple, sugar maple, quaking aspen, Virginia pine, and
eastern white pine) is now zero. This is in contrast to 3.4% for the period of 2000-2002.
• While this change in biomass loss cannot be exclusively attributed to the implementation of the
NBP, CAIR, and CSAPR, it is likely that NOx ozone season emission reductions achieved under these
programs, and the corresponding decreases in ozone concentration, contributed to this
environmental improvement.
Analysis and Background Information
Acidified Surface Water Trends
Acidified precipitation can impact lakes and streams by mobilizing toxic forms of aluminum from soils
(particularly in clay rich soils) and/or by lowering the pH of the water, harming fish and other aquatic
wildlife. In a healthy well-buffered lake or stream, decreased acid deposition would be reflected by
decreasing trends in surface water acidity. Four chemical indicators of aquatic ecosystem response to
emission changes are presented here: trends in sulfate and nitrate anions, acid neutralizing capacity
(ANC), and sum of base cations. Improvement in surface water status is generally indicated by
decreasing concentration of sulfate and nitrate anions, decreasing base cations, and increasing ANC. The
following is a description of each indicator:
• Sulfate is the primary anion in most acid-sensitive waters and has the potential to acidify surface
waters (lower the pH) and leach base cations and toxic forms of aluminum from soils, leaving soils
depleted of buffering base cations and releasing harmful aluminum into the surface waters.
• Nitrate also has the potential to acidify surface waters. However, nitrogen is an important nutrient
for plant and algae growth, and most of the nitrogen inputs from deposition are quickly taken up by
plants and algae, leaving less in surface waters.
• Base cations neutralize both sulfate and nitrate anions, thereby preventing surface water
acidification. Base cation availability is a function of local geology, soil type, and the vegetation
community. Surface waters with fewer base cations are more susceptible to acidification.
• ANC is a key indicator of ecosystem impacts and recovery and is a measure of overall buffering
capacity of surface waters against acidification. Higher ANC values indicate the ability to neutralize
strong acids that enter aquatic systems from deposition and other sources. In acidified systems with
poor base cation availability, ANC can be negative, indicating chronic acidification.
In the central Appalachian region, some watersheds have depleted, base cation-poor soils which have
also accumulated and stored sulfate over the past decades of high sulfate deposition. As a result, the
substantial decrease in acidic deposition has not yet resulted in comparably lower sulfate
concentrations in many of the monitored Appalachian streams. A combination of low base cation
availability and stored sulfate in the soils means that stream sulfate concentrations in some areas are
not changing, or may be increasing, as the stored sulfate slowly bleeds out without adequate base
cation concentrations to neutralize sulfate anions.1
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Surface Water Monitoring Networks
In collaboration with other federal and state agencies and universities, EPA has administered two
monitoring programs that provide information on the impacts of acidic deposition on otherwise pristine
lakes and streams: the Long-term Monitoring (LTM) program and the Temporally Integrated Monitoring
of Ecosystems (TIME) program. These programs are designed to track changes in surface water
chemistry in four regions sensitive to acid rain in the eastern United States: New England, the
Adirondack Mountains, the Northern Appalachian Plateau, and the central Appalachians (the Valley,
Ridge, and Blue Ridge geologic provinces). After 20 years of collection, the TIME program ended in 2015,
having provided trend-based acidification probabilities for larger lake and stream populations. Like the
LTM program, TIME trends suggest that surface waters in these regions are recovering from
acidification, though the most sensitive surface waters remain impacted from air pollution. All data and
trends presented here reflect the results of LTM program monitoring activities.
Forest Health
Ground-level ozone is one of many air pollutants that can alter a plant's health and ability to reproduce
and can make the plant more susceptible to disease, insects, fungus, harsh weather, etc. These impacts
can lead to changes in the biological community, both in the diversity of species and in the health, vigor,
and growth of individual species. As an example, many studies have shown that ground-level ozone
reduces the health of many commercial and ecologically important forest tree species throughout the
United States.2,3 By looking at the distribution and abundance of seven sensitive tree species and the
level of ozone at particular locations, it is possible to estimate reduction in growth - or biomass loss -
for each species. The EPA evaluated biomass loss for seven common tree species in the eastern United
States that have a higher sensitivity to ozone (black cherry, yellow poplar, sugar maple, eastern white
pine, Virginia pine, red maple, and quaking aspen) to determine whether decreasing ozone
concentrations are reducing biomass loss in forest ecosystems.
More Information
• Learn more about surface water monitoring at EPA http://www.epa.gov/airmarkets/clearn-air-
martkets-monitoring-surface-water-chemistry
• Learn more about acid rain https://www.epa.gov/acidrain/
References
1. Burns, D.A., Lynch, J. A., Cosby, B.J., Fenn, M.E., & Baron, J.S. (2011). National Acid Precipitation
Assessment Program Report to Congress 2011: An Integrated Assessment. U.S. EPA, National
Science and Technology Council, Washington, D.C.: 114 p
2. Chappelka, A.H. & Samuelson, L.J. (1998). Ambient ozone effects on forest trees of the eastern
United States: A review. New Phytologist 139: 91-108.
3. Ollinger, S.V., Aber, J.D., & Reich, P.B. (1997). Simulating ozone effects on forest productivity:
interactions among leaf-canopy and stand-level processes. Ecological Applications 7(4), 1237-
1251.
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Figures
Long-term Monitoring Program Sites and Trends, 1990-2016
{hover aver a site for more information)
• LTM lakes • LTM streams
Notes:
¦ Trends are significant at the 95 percent comfdence ir-tervaS (p < 0.05).
• Base cat>ons are calculates] as tb* sum of calcium, magr*sjum. potassium. and sodium pons.
¦ Trtnds art d«»rmin*d by mutovariatt M*fin-K«ndatl mi*.
Source: EWk, 2018
Figure 1. Long-term Monitoring Program Sites and Trends, 1990-2016
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Regional Trends in Sulfate, Nitrate, ANC, and Base Cations at Long-term Monitoring Sites, 1990-2016
Region
Water Bodies
Covered
% of Sites with Improving
Sulfate Trend
% of Sites with Improving
Nitrate Trend
% of Sites with Improving
ANC Trei»d
% of Sites with Improving Base
Cations Trend
Adirondack Mountains
38 lakes in NY"
100%
76%
92%
89%
New England
26 lakes in ME
and VT
100%
26%
70%
64%
Catskills/ N. Appalachian
Plateau
9 streams in NY
and PA*"
8094>
40%
70%
90%
Central Appalachians
66 streams in VA
39%
80%
18%
26%
Notes:
• Trends are determined by rnultivarate Mann-KefwSal tests
• Trends are significant at the 95 percent confidence interval (p < 0.05)
• Sum of Base Caw«s calculated as (Ca*Mg*K*Na)
• Data for A^cxiae* from
—Data for PA streams * N Apjjaiaefeaa Plateau is onJy through 20T5
Source: EPA. 2018
Figure 2. Regional Trends in Sulfate, Nitrate, ANC, and Base Cations
at Long-term Monitoring Sites, 1990-2016
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Estimated Black Cherry, Yellow Poplar. Sugar Maple. Eastern White Pine. Virginia Pine; Red Maple, and Quaking Aspen
Biomass Loss Due to Ozone Exposure, 2000-2002 versus 2014-2016
Biomass (% Loss)
>1%
1 to 3%
3 3 to 6%
Notes:
• Biomass loss was calculated by incorporating each tree's C-R functions with the three-month, 12-hour W126 exposure metric.
• The W126 exposure metric is a cumulative exposure index that is biologically based and emphasizes hourly ozone concentrations taken from 2000-2016 data.
Source: EPA, 2018
Figure 3. Estimated Black Cherry, Yellow Poplar, Sugar Maple, Eastern White Pine,
Virginia Pine, Red Maple, and Quaking Aspen Biomass Loss Due to Ozone Exposure,
2000-2002 versus 2014-2016
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Critical Loads Analysis
Highlights
Critical Loads and Exceedances
• For the period from 2014 to 2016, 9 percent of all studied lakes and streams still received levels of
combined total sulfur and nitrogen deposition exceeding their calculated critical load. This is a 77
percent improvement over the period from 2000 to 2002 when 34 percent of all studied lakes and
streams exceeded their calculated critical load.
• Emission reductions achieved between 2000 and 2016 have contributed and will continue to
contribute to broad surface water improvements and increased aquatic ecosystem protection across
the five regions along the Appalachian Mountains.
• Based on this analysis, current sulfur and nitrogen deposition loadings in 2016 still exceed levels
required for recovery of some lakes and streams, indicating that some additional emission
reductions are necessary for some acid-sensitive aquatic ecosystems along the Appalachian
Mountains to recover and be protected from acid deposition.
Analysis and Background Information
A critical loads analysis is an assessment used to provide a quantitative estimate of whether acid
deposition levels resulting from S02 and NOx emissions are sufficient to protect aquatic biological
resources. If acidic deposition is less than the calculated critical load, harmful ecological effects (e.g.,
reduced reproductive success, stunted growth, loss of biological diversity) are not expected to occur,
and ecosystems damaged by past exposure are expected to eventually recover.1
Lake and stream waters having an ANC value greater than 50 neq/L are classified as having a moderately
healthy aquatic biological community; therefore, this ANC concentration is often used as a goal for
ecological protection of surface waters affected by acidic deposition. In this analysis, the critical load
represents the amount of sulfur and nitrogen that could be deposited annually to a lake or stream and
its watershed and still support a moderately healthy aquatic ecosystem (i.e., having an ANC greater than
50 neq/L). Surface water samples from 6,001 lakes and streams along acid-sensitive regions of the
Appalachian Mountains and some adjoining northern coastal plain regions were collected through a
number of water quality monitoring programs. Critical load exceedances were calculated using the
Steady-State Water Chemistry model.2,3
More Information
• Learn more about surface water monitoring at EPA https://www.epa.gov/airmarkets/monitoring-
surface-water-chemistry
• National Acid Precipitation Assessment Program (NAPAP) Report to Congress
https://ny.water.usgs.gov/projects/NAPAP/
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References
1. Dupont,J., Clair, T.A., Gagnon, C., Jeffries, D.S., Kahl, J.S., Nelson, S.J., & Peckenham, J.M. (2005).
Estimation of critical loads of acidity for lakes in the northeastern United States and eastern
Canada. Environmental Monitoring and Assessment, 109:275-291.
2. Sullivan, T.J., Cosby, B.J., Webb, J.R., Dennis, R.L., Bulger, A.J., & Deviney, Jr. F.A. (2007).
Streamwater acid-base chemistry and critical loads of atmospheric sulfur deposition in
Shenandoah National Park, Virginia. Environmental Monitoring and Assessment, 137: 85-99.
3. Nilsson, J. & Grennfelt, P. (Eds) (1988). Critical loads for sulphur and nitrogen. UNECE/Nordic
Council workshop report, Skokloster, Sweden. Nordic Council of Ministers: Copenhagen.
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Figures
Lake and Stream Exceedances of Estimated Critical Loads for Total Nitrogen and Sulfur Deposition.
2000-2002 versus 2014-2016
I t
- { |W /
• Srtet thai now do not oxccod th« crttleal load compared to 2000-2002
• Sflet thai f«cctd the critical toad
Stlo» thai never exceeded the critical load
Notes:
¦ Surface water samples from the represented lakes and streams complied from surface monitoring programs, such as National Surface Water Survey (NSWS). Environmental Monitoring and Assessment
Program (EMAP), Wadeable Stream Assessment (WSA), National Lake Assessment (NLA). Temporally Integrated Monitoring of Ecosystems (TIME). Long Term Monitoring (LTM), and other water quality
monitoring programs.
• Steady state exceedances calculated in units of meq/rn^/yr.
Source: EPA, 2018
Figure 1. Lake and Stream Exceedances of Estimated Critical Loads for Total
Nitrogen and Sulfur Deposition, 2000-2002 versus 2014-2016
Chapter 9: Ecosystem Response - Critical Load Analysis
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Critical Load Exceedances by Region, 2000-2002 versus 2014-2016
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Water Bodies in Exceedance of Critical Load
Region
Number of Water
Bodies Modeled
2000-2002
2014-2016
Percent
Reduction
Number of Sites
Percent of Sites
Number of Sites
Percent of Sites
New England
(CT, MA, ME, NH, Rl, VT)
2,195
580
26%
129
6%
78%
Adirondack
(NY)
312
163
52%
41
13%
75%
Northern Mid-Atlantic
(NY, NJ, PA)
1,146
301
26%
57
5%
81%
Southern Mid-Atlantic
(KY,MD,VA,WV)
1,740
968
56%
239
14%
75%
Southern Appalachian Mountains
(AL, GA, SC, TN)
882
298
34%
73
8%
76%
Total Units
6,275
2,310
37%
539
9%
77%
Notes:
• Surface water samples from the represented lakes and streams compiles from surface monitoring programs, such as National Surface Water Survey (NSWS), Environmental Monitoring and Assessment Program (EMAP), Wadeatte
Stream Assessment (WSA), Natonal Lake .Assessment {NLA}, Temporalty Integrated Monitoring of Ecosystems (TIME), Long Term Monitoring (LTM), and other water aua&ty monitoring programs.
• Steady state exceedances calculated in ismts of me^'m^/yr.
Source: ERA, 2018
Figure 2. Critical Load Exceedances by Region, 2000-2002 versus 2014-2016
Chapter 9: Ecosystem Response - Critical Load Analysis
Page 85 of 85
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