Clean Air Status and
  Trends Network
    (CASTNET)

       2003
   Program and
Technical Summary

      May 2005
                               A

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         CASTNET 2003 Program and Technical Summary

                           Table of Contents
About CASTNET	2
CASTNET Operations	3
Cooperative Long-Term Environmental Monitoring at CASTNET Sites	3
CASTNET Monitoring Sites	4
Atmospheric Species Measured by CASTNET	5
Total Deposition	6
Ozone Monitoring	7
CASTNET Monitoring in Sensitive Ecosystems
   Coastal Environments	8
   Great Smoky Mountains National Park and the Southern Appalachians	9
   Documentation for the network including past annual reports and the CASTNET Quality
          Assurance Project Plan can be found at the CASTNET on-line library:
                      www.epa.gov/castnet/library.html
             The CASTNET database is available to the public via EPA's
                          CASTNET data web page:
                       www.epa.gov/castnet/data.html
             Prepared by MACTEC Engineering and Consulting, Inc. for:
                     U.S. Environmental Protection Agency
                          Office of Air and Radiation
                          Clean Air Markets Division
                              Washington, DC

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                       EPA's Clean Air Status and Trends Network
       Pisgah National Forest, NC (PNF126)

Air  pollution  has far-reaching effects.  It  negatively
impacts human health, agricultural  crops, natural
ecosystems,  national  monuments,   buildings,  and
other  man-made  products. Emissions  of sulfur,
nitrogen,   and   other  substances   react  in  the
atmosphere with particles,  water droplets,  oxygen,
and oxidants to form  acidic  compounds.  These
compounds are often transported long distances and
then deposited to the environment by  precipitation,
clouds,  and  other  meteorological  events.  Dry
deposition, a component of total deposition, involves
complex  atmospheric  processes such as  settling,
  impaction, and absorption whereby,  in the absence
  of precipitation, airborne particles and gases reach
  the earth's surface. Dry deposition makes up 10 to
  70 percent of total deposition depending on location
  and climate.
  In  1990,  Congress  passed  the Clean  Air  Act
  Amendments  (CAAA),  which  mandated  ambient
  monitoring to provide information and to track trends
  in pollutant  concentrations and the  dry  deposition
  component  of total atmospheric deposition. The
  information  and  trends  data  collected  through
  ambient  monitoring are  used  to  determine  the
  effectiveness of sulfur dioxide  (SO^ and  nitrogen
  oxides (NOX) emission  reductions promulgated  by
  the CAAA. To meet this monitoring  need, the U.S.
  Environmental  Protection Agency (EPA) established
  the  Clean  Air  Status  and   Trends   Network
  (CASTNET)  in  1991, incorporating  sites from the
  National  Dry Deposition  Network (NDDN),  which
  began  operation in 1987. Since  1991, many sites
  have been added, and there are now more than 85
  sites across the United States.  The National Park
  Service (NPS) joined with EPA in 1994 as a principal
  sponsor and currently sponsors 30 CASTNET sites.
                                CASTNET Principal Sponsors
                         United States Environmental Protection Agency
                                      National Park Service
                                      CASTNET Partners

  In addition to EPA and NPS, other partners support the operation of CASTNET sites. These partners include:

  Alabama-Coushatta Tribe                         Long Term Ecological Research Program (LTER)
  Canadian Air and Precipitation Monitoring
  Network (CAPMON)
Interagency Monitoring of Protected
Visual Environments (IMPROVE)
  Cherokee Nation                                  St. Johns River Water Management District

  Kansas State University                            State University of New York

  National Atmospheric Deposition Program (NADP)     U.S. Department of Agriculture Forest Service

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                                       CASTNET Operations
The original  network  design was  based  on  the
assumption that dry deposition,  or flux, could be
estimated  as   the  linear  product  of  measured
pollutant  concentration  and  modeled  deposition
velocity.

Weekly   integrated   averages    of  atmospheric
concentrations  are  obtained  through  laboratory
analysis  of the  3-stage filter packs installed weekly
at  each   CASTNET   site.  The   influence   of
meteorological conditions, vegetation, and chemistry
is simulated by the deposition  velocity, which is
calculated  using the Multi-Layer Model. To  support
the estimation  of deposition velocity, all  CASTNET
sites include equipment to measure a
                       comprehensive suite of meteorological parameters.
                       All  field   equipment  is  subject  to  semiannual
                       inspections   and   multipoint   calibrations   using
                       standards  traceable  to  the  National Institute  of
                       Standards and Technology  (NIST). Results of field
                       calibrations are used to assess sensor accuracy and
                       validate field data.

                       CASTNET  operations  include   a comprehensive
                       quality  assurance (QA) program that  was designed
                       to ensure  that all reported data  are  of known and
                       documented quality.  QA is emphasized in  order  for
                       CASTNET data to meet CASTNET objectives and
                       be  reproducible   and   comparable   with   other
                       monitoring networks and laboratories.
        Cooperative Long-Term Environmental Monitoring at CASTNET Sites

Many CASTNET site locations serve multiple monitoring efforts, some  of which  belong to long-term networks
designed to monitor environmental factors not covered by the CASTNET design. The following table summarizes
10 such networks whose activities include a wide range of measurements. The number of sites listed for each
network represents the number of sites located within 10 kilometers of a CASTNET site.
             Network
 Year
Began
Sites Collocated
 with CASTNET
  Sponsoring Agency
Types of Measurements
  Atmospheric Integrated Research        1992
  Monitoring Network (AIRMoN)

  Canadian Air and Precipitation           1978
  Monitoring (CAPMoN)

  Climate Reference Network (CRN)       2004
  Interagency Monitoring of Protected       1985
  Visual Environments (IMPROVE)

  Long-Term Ecological Research         1980
  Network (LTER)

  Mercury Deposition Network (MDN)       1995
  National Dioxin Air Monitoring Network    1997
  (NDAMN)
  National Trends Network (NTN)          1978
  Surface Radiation Budget Network       1993
  (SURFRAD)

  UV-B Monitoring and Research          1992
  Program
                5 active
                17 planned

                35
                12
                58
                 National Atmospheric Deposition Program (NADP)
                 Wet deposition - event-based sampling
                 http://nadp.sws.uiuc.edu
                 Environment Canada
                 Dry and wet components of total deposition
                 http://www.msc.ec.gc.ca/capmon
                 National Oceanic and Atmospheric Administration (NOAA)
                 Homogenous measurements of temperature/ precipitation
                 http://www.ncdc.noaa.gov/oa/climate/uscrn
                 Multi-agency collaboration
                 Visibility in Class I areas
                 http://vista.cira.colostate.edu/improve
                 National Science Foundation
                 Ecological processes
                 http://www.lternet.edu
                 National Atmospheric Deposition Program (NADP)
                 Wet deposition/ methyl mercury
                 http://nadp.sws.uiuc.edu
                 Environmental Protection Agency (EPA)
                 Dioxinsand PCBs
                 National Atmospheric Deposition Program (NADP)
                 Wet deposition component of total deposition
                 http://nadp.sws.uiuc.edu
                 National Oceanic and Atmospheric Administration (NOAA)
                 U.S. radiation budget
                 http://www.srrb.noaa.gov/surfrad
                 U.S. Department of Agriculture
                 Ultraviolet-B radiation
                 http://nadp.nrel.colostate.edu

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State
AL
AK

AZ


AR
CA






CO



CT
FL


GA
HI
IL


IN

KS
KY



ME


MD

Ml


MN
MS
MT
NV
NH
NJ
NY


NC



ND
OH



OK
ON
PA




SD
TN


TX
UT
VT
VI
VA


WA


WV

Wl
WY


Site ID
SND152
DEN417
POF425
CHA467
GRC474
PET427
CAD150
CON186
DEV412
JOT403
LAV410
PIN414
SEK402
YOS404
GTH161
MEV405
ROM206
ROM406
ABT147
EVE419
IRL141
SUM156
GAS153
HVT424
ALH157
BVL130
STK138
SAL133
VIN140
KNZ184
CDZ171
CKT136
MAC426
MCK131
ACA416
ASH135
HOW132
BEL116
BWR139
ANA115
HOX148
UVL124
VOY413
CVL151
GLR468
GRB411
WST109
WSP144
CAT 175
CTH110
HWF187
BFT142
CND125
COW137
PNF126
THR422
DCP114
LYK123
OXF122
QAK172
CHE185
EGB181
ARE128
KEF112
LRL117
MKG113
PSU106
WNC429
ESP127
GRS420
SPD111
BBE401
CAN407
LYE145
VII423
PED108
SHN418
VPI120
MOR409
NCS415
OLY421
CDR119
PAR107
PRK134
CNT169
PND165
YEL408
Station
Sand Mountain
Denali National Park
Poker Flats Research Range
Chiricahua National Monument
Grand Canyon National Park
Petrified Forest National Park
Caddo Valley
Converse Station
Death Valley National Monument
Joshua Tree National Monument
Lassen Volcanic National Park
Pinnacles National Monument
Sequoia National Park
Yosemite National Park
Gothic
Mesa Verde National Park
Rocky Mountain National Park
Rocky Mountain National Park
Abington
Everglades National Park
Indian River Lagoon
Sumatra
Georgia Station
Hawaii Volcanoes National Park
Alhambra
Bondville
Stockton
Salamonie Reservoir
Vincennes
Konza Prairie
Cadiz
Crockett
Mammoth Cave National Park
Mackville
Acadia National Park
Ashland
Howland
Beltsville
Blackwater National Wildlife Refuge
Ann Arbor
Hoxeyville
Unionville
Voyageurs National Park
Coffeeville
Glacier National Park
Great Basin National Park
Woodstock
Washington's Crossing
Claryville
Connecticut Hill
Huntington Wildlife Forest
Beaufort
Candor
Coweeta
Pisgah National Forest
Theodore Roosevelt National Park
Deer Creek State Park
Lykens
Oxford
Quaker City
Cherokee Nation
Egbert, Ontario, Canada
Arendtsville
Kane Experimental Forest
Laurel Hill State Park
M.K Goddard State Park
Pennsylvania State University
Wind Cave National Park
Edgar Evins State Park
Great Smoky Mountains National Park
Speedwell
Big Bend National Park
Canyonlands National Park
Lye Brook
Virgin Islands National Park
Prince Edward
Shenandoah National Park
Virginia Poly Tech
Mount Rainier National Park
North Cascades National Park
Olympic National Park
Cedar Creek State Park
Parsons
Perkinstown
Centennial
Pinedale
Yellowstone National Park
        CASTNET Monitoring Sites

As of December 2003, 87 CASTNET monitoring  sites
were operational (Figure 1).  Most CASTNET sites are
located in rural, regionally representative locations away
from pollution emission sources and heavily populated
areas. The map shows reasonable geographic coverage
in most regions of the United States. Less coverage is
provided in the central United States from South Dakota
to Texas. The addition of new sites in the central United
States  will  enhance  the  ability  of  the network  to
determine  patterns   and   trends  in   air  pollutant
concentrations and deposition rates and will help assess
the effectiveness of emission control regulations.
CASTNET's  primary  goal   is  to  monitor  trends  in
regional-scale air quality and dry deposition.  For the
time  period  1990 through 2003,  34  CASTNET  sites
were selected as  reference sites  (shown  in red on
Figure 1) based on the  completeness of their 14-year
data record and on criteria similar to those used by the
U.S.  Environmental Protection Agency in its National Air
Quality and  Emission Trends  Report (2000).  As the
network ages  and  the period  of interest changes,
additional sites will meet these requirements and will be
added as reference sites.
Figure 1. CASTNET Sites as of December 2003
  Sites
Not Displayed:

Alaska - 2 sites
Hawaii -1 site
U.S. Virgin Islands - 1 site

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                      Atmospheric Species Measured by CASTNET
Figure 2. Mean Annual SO2
Concentrations (ug/m3)
                        (1991-1993)
                           D18
                           D 14
                           D 10
                           D 6
                           D 2
                        (2001-2003)
The table  below  details the atmospheric species routinely
measured  at CASTNET sites. Following laboratory analysis
of a filter pack, atmospheric concentrations for each of the
analytes, except ozone, are calculated by dividing the mass
on each filter by the total flow volume through the filter pack
during  the sampling  period.  Ozone concentrations are
measured  hourly by a separate instrument.
The maps to the left (Figure 2) display annual mean SO2
concentrations  in ug/m3 for 1991  through  1993 (top) and
2001 through 2003 (bottom). The dramatic reduction of SO2
between the  two periods  indicates  the  success  of the
Phase I  and II SO2  emission reductions mandated  by the
Clean Air Act Amendments of 1990.  Only CASTNET sites
with  valid  measurements  during both 3-year  periods are
included on the maps.   For CASTNET sites along the Ohio
River Valley, SO2 concentrations decreased by an average
of approximately 60 percent.
Particulate sulfate concentrations also decreased between
the two time  periods while  atmospheric concentrations  of
nitrogen species and ozone showed no significant change.
For maps of concentrations of other analytes, please see the
CASTNET 2003 Annual Report.
Species
Chemical
Symbol
State
Description
Sulfur Compounds
Sulfur dioxide
Sulfate
S02
so24
gas
particle
Emitted through the combustion of coal and oil that contain sulfur; reacts to form various
acidic compounds including sulfuric acid (H2SO4), a significant contributor to acid rain.
Typically exists in the atmosphere as ammonium sulfate (NH4)2SO4, major component of fine
particle matter (PM2.5).
Nitrogen Compounds
Nitric acid
Nitrate
Ammonium
HNO3
NO;
NH*4
gas
particle
particle
Created by emissions of nitrogen oxides (NOX) produced during combustion; a significant
contributor to acid rain.
Created by emissions of nitrogen oxides (NOX) produced during combustion; typically exists
as ammonium nitrate (NH4)NO3, a major component of PM25.
Formed when ammonia (NH3) reacts with sulfate and nitrate particles in the atmosphere.
Other Ions and Cations
Potassium
Sodium
Magnesium
Calcium
Chloride
K+
Na+
Mg2+
Ca2+
cr
particle
particle
particle
particle
particle
These particles occur naturally in the atmosphere through weathering and soil erosion and
from urban and industrial sources. Cation particles counteract the acidity of the sulfur and
nitrogen anion particles through their ability to neutralize the anions.
Surface Level Ozone
Ozone
03
gas
Formed through complex chemical reactions among precursor emissions of volatile organic
compounds (VOC) and nitrogen oxides (NOX) in the presence of sunlight.

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                                          Total Deposition
Total deposition at CASTNET sites is  estimated by
combining dry deposition  fluxes modeled using the
Multi-Layer Model (see  page 3) with wet deposition
estimated from  National  Atmospheric  Deposition
Program/National  Trends  Network   (NADP/NTN)
sites.  Dry  deposition   accounts  for  about  10  to
70 percent, depending  on location and  climate,  of
total deposition for both sulfur and nitrogen. Median
values  are  approximately  40  percent for sulfur
deposition and 30 percent for nitrogen deposition.
Figure 3  illustrates  the  magnitude of total sulfur
deposition during  2003, shown by the diameter  of
the circles and  the  relative  contributions  from dry
and  wet deposition.  Relatively high rates  of sulfur
deposition were observed in the states along and
downwind of the Ohio River Valley. Lower rates  of
sulfur   deposition   were  observed   along  the
peripheries of the  network, i.e., in the  northernmost
states, the Great Plains, Florida, and throughout the
western states.
Figure 4 depicts  the  magnitude  of  total  nitrogen
deposition rates during 2003. In the states along the
Ohio  River  Valley,  contributions  to  total  nitrogen
deposition from  dry  and wet deposition were more
evenly distributed  than  the  respective contributions
to total sulfur deposition for the same area. Lower
nitrogen fluxes  were observed in the  northernmost
states, Florida, and throughout the West.
Figure 5 shows that total sulfur deposition  at the
reference sites  (Figure  1) has  declined significantly
over the last 14 years.  The  sharp decline in 1995
closely parallels  the  decline in  sulfur  dioxide
emissions that resulted  from the electric generating
utilities' compliance  with  Phase I of the Acid  Rain
Program. The trend  line for total nitrogen deposition
shows no significant change over the time period.
However, there  has  been an increase in rates  over
the last two years. Increases in sulfur and nitrogen
are associated,  in part, with increased precipitation
in the Eastern United States particularly in 2003.
Figure 3. Total Sulfur Deposition for 2003 (kg/ha/yr)
  D Dry Deposition
  D Wet Deposition
Figure 4. Total Nitrogen Deposition for 2003 (kg/ha/yr)
  D Dry Deposition
  D Wet Deposition
Figure 5. Timeline of Total Deposition (kg/ha/yr)
   16
 
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                          Ozone Monitoring
Although not a regulatory network, CASTNET ozone
(O3) monitoring provides  information on geographic
patterns   in    regional   ozone  and   on   how
concentrations in rural areas compare to the national
standard for  the  pollutant.   The  8-hour  ozone
standard  is   0.080  ppm  and   is  assessed  by
calculating  an 8-hour  "design  value,"  which  is
determined by taking the fourth highest daily value
measured at a site for each year of a 3-year period
and finding  the average.  In practice, sites  with
design values  greater than or equal to 85 ppb are
considered to  be  in  violation  of  the  standard.
CASTNET ozone  data are not explicitly used in the
determination  of attainment,  and,  therefore,  design
values  are  not  calculated   for  CASTNET sites.
However,  fourth  highest daily  maximum   8-hour
concentrations  are  calculated  according  to EPA
protocol  for  specific years  for  the   purpose  of
examining non-urban ozone levels.

Figure  6. Fourth Highest Daily Maximum  8-Hour
Ozone Concentrations (ppb) for 2003

                 Eastern Sites
                    (2003)
                                         Figure  6 shows the fourth  highest daily maximum
                                         8-hour  concentrations for CASTNET  sites in the
                                         eastern United States for 2003.  To  demonstrate
                                         where  nonattainment regions exist and relate the
                                         depicted  CASTNET concentrations to  these areas,
                                         EPA attainment  designations  for counties in the
                                         eastern United States are also shown  on the  map.
                                         The  maps are  based  on  designations released
                                         in 2004.

                                         CASTNET sites with fourth  highest daily maximum
                                         8-hour  concentrations for 2003 that are greater than
                                         or equal  to 85 ppb are  shown in  blue.  Sites with
                                         concentrations lower than  85 ppb  are shown in
                                         black.  Of the 42  sites considered,  five  eastern sites
                                         observed a  fourth highest  daily maximum 8-hour
                                         value greater than or equal to 85 ppb.  For 2003, the
                                         mean of the fourth highest daily  maximum 8-hour
                                         concentrations for the 42 sites is 77 ppb.
                                         Figure 7. Timeline of Fourth Highest Daily Maximum
                                         8-hour Ozone Concentrations (ppb)
                                            100
                                          .1 90 H
                                          'ro

                                          I
                                          ° 80 H
                                            70
                                                OT-CNco-a-iocor^oo
                                                O5O5O5O5O5O5O5O5O5O5OOOO
                                                O5O5O5O5O5O5O5O5O5O5OOOO
                                                                             CNCNCNCN
] Nonattainment Areas (full county)
] Nonattainment Areas (partial county)
1 Unclassified Areas
                                                       Figure  7 depicts trends  in  fourth  highest  daily
                                                       maximum 8-hour O3 concentrations aggregated over
                                                       all  eastern  reference sites  (Figure 1)  for  1990-
                                                       2003. The diagram shows that the 2003 value was
                                                       the lowest in CASTNET history. No overall trend is
                                                       evident in the time series. The lower value in 2003
                                                       was produced in part by cool, cloudy, wet weather
                                                       during the ozone season.

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                      CASTNET Monitoring in Sensitive Ecosystems:
                                       Coastal Environments
CASTNET includes  five  sites along  the eastern
coast of the United  States  that provide valuable
information   about  the  coastal   and   estuarine
environment  (Figure  8). Two of these sites are in
national parks: Acadia National Park, ME (ACA416)
and  Everglades National  Park, FL  (EVE419). The
other three sites are located  in estuaries that are
part  of EPA's National Estuary Program:  Maryland
Coastal Bays,  MD  (BWR139); Albemarle-Pamlico
Sounds, NC (BFT142); and Indian River Lagoon,  FL
(IRL141).  The  National   Estuary   Program  was
established  by Congress  in  1987  to  improve the
quality of important estuaries.

Figure 8. Costal CASTNET Sites
                          Acadia
                          (ACA416)
                     Maryland Coastal Bays
                     (BWR139)
                     Albemarle-Pamlico Sounds
                     (BFT142)
                 Indian River Lagoon
                 (IRL141)

                  Everglades
                  (EVE419)
analyses suggest that  approximately  13 percent of
total external  nitrogen loading into  the  Sebastian
Inlet region of the Indian River Lagoon results from
atmospheric deposition processes. Estimates of the
dry deposition of nitrogen are  being used in similar
estuarine  research  efforts  as  interest  increases
regarding  the  role of atmospheric deposition in the
nutrient enrichment and  eutrophication of sensitive
water bodies.
Figure 9 shows 3-year annual averages (2001-2003)
of the wet and dry components of total  nitrogen
deposition  for the  five   coastal CASTNET  sites
(Figure 7). Also  included  for comparison is  the total
nitrogen deposition profile for the same time period
for the 34 CASTNET reference sites (Figure 1).

Figure 9. Components of Annual Mean Total
Nitrogen Deposition (kg/ha/yr) 2001-2003
   10 -,
    9 -
    8 -
    7 -
  i e-
  !5
  & 4
    3
    2 -
    1 -
D NH4+Wet Deposition (as N)
D NO3" Wet Deposition (as N)
D NH4+ Dry Deposition (as N)
D NO3" Dry Deposition (as N)
D HNO3 Dry Deposition (as N)
        Acadia   Maryland   Albemarle-   Indian    Everglades  Mean of
        National    Coastal    Pamlico    River    National   CASTNET
        Park     Bays     Sounds    Lagoon    Park    Reference
      (ACA416, ME) (BWR139, MD) (BFT142, NC)  (IRL141, FL) (EVE419, FL)   Sites
The  site at IRL141, FL  is sponsored by Florida's
St. Johns  River Water Management District to help
quantify the contribution  of atmospheric deposition
to the total nutrient load to the estuary. Using the dry
deposition  estimates from the CASTNET site with
wet  deposition  data  from  an  adjacent National
Atmospheric Deposition Program / National Trends
Network (NADP/NTN) style collector, preliminary
Nitrogen deposition levels are highest at the coastal
sites  in  North Carolina  and  Maryland  with  total
deposition for BWR139, MD greater than the mean
of the reference sites.  Sites in  Maine and Florida
have  lower deposition rates. The Florida sites show
dry deposition of nitrogen  as contributing the lowest
percentage of the total deposition with an average of
17 percent. The splits for the other  sites are similar
to the split for the reference sites.

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                     CASTNET Monitoring in Sensitive Ecosystems:
          Great Smoky Mountains National Park and the Southern Appalachians
High elevation ecosystems  are  often sensitive to
deposition because they lack the ability to neutralize
and/or   assimilate  atmospheric  inputs.   Several
CASTNET sites  span the  Southern  Appalachian
Mountains (Figure 10) including, from north to south,
Shenandoah National Park,  VA (SHN418); Virginia
Polytechnic Institute, VA  (VPI120); Pisgah National
Forest,  NC  (PNF126);  Great  Smoky Mountains
National   Park,  TN   (GRS420);  and   Coweeta
Hydrologic Laboratory, NC (COW137).
Figure 10. Southern Appalachian CASTNET Sites
                        Shenandoah
                        (SHN418)7 O
   iGreat Smoky Mountains
              (GRS420)
                            ' Virgin ia Tech v
                             (VPI120)
                                       ,
                        Pisgah National Forest1
                        (PNF126)
        Coweeta Hydrologic Lab
        (COW137)
These sites experience relatively high rates of total
atmospheric deposition. Figures 11 and  12  show
annual  mean  contributions  to total  sulfur and
nitrogen deposition rates, respectively, for the 3-year
period 2001  -  2003. Annual total sulfur deposition
was more than 9 kg/ha/yr  at all of the Appalachian
sites except COW137, NC, which experienced a rate
of  6 kg/ha/yr.  Annual  total  nitrogen  deposition
ranged from 5 kg/ha/yr at COW137,  NC to more
than 8 kg/ha/yr at GRS420, TN.

Figure 11. Components of Annual Mean Total
Sulfur Deposition (kg/ha/yr) 2001-2003
14 -,
12 -
10 -
0 p
+3 O ~
'(/I
O
Q. r*
0) D
Q
4 -
-
n

n
n
n
S04
SO4
S02



• Wet Dep
" Dry Dep
Dry Depo

ositior
osition
sition


(asS)
(asS)
asS)














Shenandoah Virginia Pisgah Great Smoky Coweeta
National Polytechnic National Mountains Hydrologic
Park Institute Forest National Park Laboratory
(SHN418, VA) (VPI120, VA) (PNF126, NC) (GRS420, TN) (COW137, NC)
                                                     Figure 12. Components of Annual Mean Total
                                                     Nitrogen Deposition (kg/ha/yr) 2001-2003
12 -


10 -

8 -
c
•e
8 6 -
Q.
Q
4 -
2


n NH4+ Wet Deposition (as N)
D NO3" Wet Deposition
D NH4+ Dry Deposition
D NO3" Dry Deposition
as N)
asN)
asN)
D HNO3 Dry Deposition (as N)














^^^^~






























^^~


























Shenandoah Virginia Pisgah Great Smoky Coweeta
National Polytechnic National Mountains Hydrologic
Park Institute Forest National Park Laboratory
(SHN418, VA) (VPI120, VA) (PNF126, NC) (GRS420, TN) (COW137, NC)
         Clingmans Dome, TN (CLD303)
In  addition  to  wet  and  dry  deposition,  higher
elevation sites in the Appalachians may experience
significant  cloud   water  deposition.  Clingmans
Dome, TN (CLD303), at an elevation of 2014 meters

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 in Great Smoky Mountains National Park, is the only
 CASTNET site at which cloud  water deposition is
 measured. The site is  sponsored  by the National
 Park Service and  the Tennessee Valley Authority in
 cooperation with EPA's Region IV. Figure 13 shows
 the large amount  of sulfur and  nitrogen  deposition
 that   is    contributed   by  clouds  bringing  total
 deposition  estimates up to 17  kg/ha  and 12 kg/ha,
 respectively, for June through September 2003.
 Because the CASTNET  cloud  monitor at CLD303,
 TN only operates during the summer season,  the
 park also measures throughfall, which incorporates
 wet, dry, and cloud water deposition on a  year-round
 basis.  Throughfall measurements conducted at the
 CLD303, TN site  during 2003 were  approximately
 24 kg/ha/yr for sulfur and 17 kg/ha/yr for nitrogen.
Figure 13. Total Deposition (kg/ha) at CLD303, TN
for June - September 2003
                              • Cloud Deposition
                              DWet Deposition
                              D Dry Deposition
              Sulfur
                             Nitrogen
Atmospheric deposition at Great Smoky Mountains
National Park is one of many stressors affecting the
park's  ecosystems.  Research  shows  that   both
chronic and episodic acidification  adversely affect
streams, soils, and sensitive plants including spruce
fir forests. Due to high rates of atmospheric nitrogen
deposition,   high    elevation   ecosystems   are
experiencing   advanced   stages   of   nitrogen
saturation.  This condition  limits the  availability of
nutrients (mainly calcium) to plants and causes the
release  of toxic aluminum that can harm vegetation
and stream biota.

 Figure  14. Timeline  of Total Deposition (kg/ha/yr)
 with Precipitation (cm) at GRS420, TN
12 -,

10 -
8 -
0
1 6-
Q.
* 4
2 -
0 -
CH Total Sulfur Deposition
EH Total Nitrogen Deposition
-•- Precipitation


















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U.S. Environmental Protection Agency
         Office of Air and Radiation
          Clean Air Markets Division
               Washington, D.C.

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