Natural Background

Visibility

Feb. 6, 2004Presentation to

VISTAS State Air Directors

Mt. Cammerer,Great Smoky Mtn. National Park

Natural Conditions – the IMPROVE Equation

IMPROVE equation is used in regional haze rules for calculating reconstructed extinction from IMPROVE chemical composition data:

Bext = 3 * f(RH)*([Ammonium] Sulfate + [Ammonium] Nitrate) +

4 * 1.4 x OC +1 * SOIL Mass +0.6 * Coarse Mass +10 * EC + Rayleigh Scattering

The EPA RHR calls for expressing visibility conditions in terms of

deciviews (dv) that is defined as:

dv = 10 ln (bext/10)

Natural Conditions: EPA Default Approach

East (mg/m3)

Ammonium Sulfate 0.23

Ammonium Nitrate 0.10

Organic Carbon Mass 1.40

Elemental Carbon 0.02

Soil 0.50

Coarse Mass 3.00

The default annual natural levels of PM components in EPA’s guidance (based on values that were developed for the NAPAP by Trijonis,1990) are used in the equation to calculate annual average Natural Conditions

20% worst natural conditions (dv) determined from the annual average

20% Worst (dv) = Annual Average (dv) + 1.28x 3 dv (sites in East)

Natural Background Visibility: Policy Considerations

VISTAS assumptions must be comparable to EPA and other RPOs Retain defaults for this first SIP? Identify alternative ranges for each Class I area in

southeastern US? How/when address non-US transported

anthropogenic emissions? Does change in assumptions for 2064 affect

reasonable progress goals for 2018?

VISTAS Class 1 Area Visibility TargetsWorst 20% days

0

5

10

15

20

25

30

35

19

88

-19

92

19

90

-19

94

19

92

-19

96

19

94

-19

98

19

96

-20

00

19

98

-20

02

20

10

20

20

20

30

20

40

20

50

20

60

20

64

De

civi

ew

s

5 y

ea

r A

vera

ge

0

10

20

30

40

50

60

70

80

90

Sta

nd

ard

Vis

ua

l Ra

ng

eM

iles

Everglades

Mammoth Cave

Median SVR

20

18

Default vs Alternative Calculations: Does it make a difference in 2018?

Natural Background (EPA default)

Natural Background (with changes)

2000 2018 YEAR 2064

29.9

dV

20% Haziest Days

Extin

ctio

n (M

m-1

) Coarse

Soil

Organics

EC

NH3NO3

(NH4)2SO4

Rayleigh

Dol

ly S

ods,

WV

Shen

ando

ah, V

A

Jam

es R

vier

Fac

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A

Mam

mot

h C

ave,

KY

Sips

ey, A

L

Gre

at S

mok

y M

tns,

TN

Linv

ille

Gor

ge, N

C

Swan

Qua

rter

, NC

Cap

e R

omai

n, S

C

Oke

feno

kee,

GA

Cha

ssah

owitz

ka, F

L

Ever

glad

es, F

L

Shin

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Roc

k, N

C

Light Extinction on 20% Haziest Days - IMPROVE 1998 - 2001

50

100

150

200

250

0

Natural Background Visibility: Potential Changes to Default Calculations for VISTAS Class I Areas

Potential change Confidence Controversy Magnitude1

Change applied to daily and annual calculations Mm-1

20% haziest days represented by 92nd percentile, not 90th H L (+.42 dv)

20% haziest days represented differently than normal distribution L M ?

Multiplier for Total Organic Carbon mass is >1.4 M

L (1.6-1.8) M-H (2.0-2.1)

H (+2.8)

Decrease extinction efficiency for S, N, or OC to offset increased OC mass M M ? decrease

1Magnitude estimated as high (H), medium (M), or low (L) impact to light extinction in mm-1 on 20% haziest days

Potential change Confidence Controversy Magnitude1

Change applied to daily and annual calculations Mm-1

Seasalt as NaCl M L M (>+1)

Transported non-US anthropogenic Sulfur, Nitrogen M M M (~+1)

1Magnitude estimated as high (H), medium (M), or low (L) impact to light extinction in mm-1

on 20% haziest days

Natural Background Visibility: Potential Changes to Default Calculations for VISTAS Class I Areas

Potential change Confidence Controversy Magnitude

Episodic events – How apply to 20% haziest days or annual? How accounted in annual default assumptions?

Organic Carbon (OC) gaseous emissions from vegetation: Apr – Oct L-M L-M M-H (+1-5)

OC and Elemental Carbon (EC) from “natural” fires events in US L-M L-M L (+<1)

Transported non-US anthropogenic Carbon (OC+EC) (including fire) M-L L-M L (?)

OC from ocean L M L (+<1)

Natural Background Visibility: Potential Changes to Default Calculations for VISTAS Class I Areas

1Magnitude estimated as high (H), medium (M), or low (L) impact to light extinction in mm-1 on 20% haziest days

Potential change Confidence Controversy Magnitude

Episodic events – How apply to 20% haziest days or annual? How accounted in annual default assumptions?

Asian Dust M L L (<0.5)

African Dust M L L (<0.5)

Seasalt reaction increases NO3 L-M L-M L (?)

Others?

1Magnitude estimated as high (H), medium (M), or low (L) impact to light extinction in mm-1

on 20% haziest days

Natural Background Visibility: Potential Changes to Default Calculations for VISTAS Class I Areas

EPRI Recommendations for Refining Natural Background Calculation

The table on following slide shows impact of using alternative assumptions taking into account: Background concentrations of ammonium

sulfate, ammonium nitrate, OCM and EC as estimated by Dr. Daniel Jacob’s group

STI approach to calculate natural visibility for the 20% worst days

A factor of 2.0 to convert OC to OCM A varying scattering efficiency for ammonium sulfate

and ammonium nitrate using equation developed by STI

Impact of using EPRI-recommended approach on concentration reductions* needed by 2018

 Class I site

All Species Reduction

(EPA Default)

All Species Reduction (EPRI

Approach)

Sulfate and Nitrate

Reduction (EPA Default)

Sulfate and Nitrate

Reduction (EPRI Approach)

Acadia 35% 30% 44% 37%

Big Bend 34% 26% 62% 49%

Boundary Waters 32% 26% 46% 33%

Grand Canyon 28% 23% 70% >100%#

Great Smoky 41% 35% 49% 40%

Mount Rainier 35% 23% 60% 50%

*Assuming uniform reductions in anthropogenically caused portion of the baseline concentrations# Sulfate and nitrate concentrations reductions alone will not be sufficient to achieve the first progress goal

15-35 percent lower concentrations reductions needed by 2018 using EPRI’s recommended approach than if use EPA’s default approach

VISTAS Recommendations: Feb 6, 2004

Follow up with VISTAS Data Workgroup Evaluate changes in assumptions where agreement among

states and stakeholders 92% used to represent 20% haziest days OC multiplied by 1.8 to calculate OC mass Others?

Define level of effort to refine estimates seasalt, biogenic, fire, dust, transported non-US

Follow up with VISTAS Planning Workgroup Evaluate benefits of control strategies against reasonable

progress goals Don’t change the reasonable progress goal for inter-continental

transport, but estimate contribution if goal not met in 2018 Coordinate with EPA and other RPOS

Jan 2004Revised 2002 VISTAS Em Inv

Feb 2004MM5 Met runs6 mo 2002

Apr 2004Draft “2018” National Inv

Sep 2004Revised 2002National Inv

Mar-Sep 2004Annual 2002 CMAQ modelperformance

Dec 04 ?“2018” Base Run

Apr 2004:DDM in CMAQ

May-Oct 2004“2018” Emissions Sensitivity Runs

Sep 2004“Typical” 2002Modeling Inv

Oct-Dec 2004:Control Strategy Inventories

Jan 2005Phase II “2018”Sensitivity Runs

Jan-Jun 2005 “2018” Control Strategy Runs

Apr 2004CART:selectepisodes

July-Dec 2005:ObservationsConclusionsRecommendations

Jan 2005Interim Future Year Model Runs

Dec 2004Interim Future Year Inventories

Emissions, Meteorological, Air Quality Modeling Deliverables

State Regulatory Activities

Jan-Jun 2004Define BART sources

Jun 2004Identify BART controls

Draft 1/16/04

EPA- approvedModeling Protocol

June 2005Economic Analyses

Feb 2004Em Modeling QA + Fill Gaps

Jan 2004Met modelingprotocol

Feb 2004AQ modelingprotocol

Jan 2004AQ Phase I wrapup

Jan-Mar 2004Define inv growth and control assumptions

Dec 2004Revised 2002Base Run (model performance)

Oct 2004:Revised “2018”Em Inv

Sept 2004MM5 Met Final Report Dec 2004

“Typical” 2002 Run (compare to “2018” runs)

Aug 2004Natural Background and Reasonable Progress Goals