Clean Air Status and Trends Network (CASTNET)
Revised Quarterly Data Summary for
Fourth Quarter 2021 (October through December)
Prepared for: U.S. Environmental Protection Agency (EPA), Clean Air Markets Division
EPA Contract No.: 68HERH21D0006, CASTNET Base Program (0003)
Prepared by: Wood Environment & Infrastructure Solutions, Inc. (Wood), Gainesville, Florida
Wood Project No.: 6064216003
Submitted: April 25, 2022
Introduction
This quarterly report summarizes the Clean Air Status and Trends Network (CASTNET) data
collected during fourth quarter 2021. Trends in pollutants measured at eastern and western
reference sites are shown. Results from the quality assurance/quality control (QA/QC) program are
presented for fourth quarter data and include completeness and precision of filter concentrations
and hourly 03 concentrations. This report also analyzes data for continuous, trace-level NOy from
eight sites and continuous S02 concentrations from three sites. Other QC statistics are given in the
CASTNET Fourth Quarter 2021 Quality Assurance Report with 2021 Annual Summary (Wood, 2022).
Figure 1. Fourth Highest Daily Maximum 8-hour Average 03 Concentrations (ppb) through Fourth
Quarter 2021
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Figure 1 shows fourth highest daily maximum 8-hour average (DM8A) 03 concentrations measured
through fourth quarter 2021. Ten western and two eastern sites exceeded the 0.070 parts per
million (ppm) National Ambient Air Quality Standard for 03. The western sites include a new 2021
site at Carlsbad Caverns National Park, NM (CAV436).
Trends
Trend analyses were performed based on filter pack pollutant concentrations measured in
micrograms per cubic meter (|jg/m3) of air at the 34 eastern and 16 western reference sites during
fourth quarter. Trends in quarterly mean filter pack and 03 concentrations are shown using box
plots in Figures 2 through 13.
Fourth Quarter Concentrations
Fourth quarter mean N03, total N03, S02, CI, and Na+ concentrations decreased at eastern sites
from fourth quarter 2020 to fourth quarter 2021, and HN03, S024, Ca2+, K+ and Mg2+ concentrations
increased. Fourth quarter mean concentrations of NH4 remained unchanged between fourth
quarter 2020 and 2021. Fourth quarter mean concentrations for all parameters decreased at western
sites in 2021.
Quarterly 03 concentrations were analyzed using box plots constructed by averaging all valid
hourly 03 concentrations within fourth quarter 2021 by site and then averaging those averages for
all eastern and western reference sites (Figure 13). The figure shows a small increase in quarterly
mean 03 concentrations at eastern sites. Quarterly mean concentrations were higher at the western
reference sites than at the eastern sites.
Figure 2. Trends in Fourth Quarter Mean HN03 Concentrations
Western Reference Sites
Eastern Reference Sites
2.0
1.5
¦s 1.0
0.5-
0.0-
t- 90th Percentile
-h 75th Percentile
¦ Mean
— Median
-7- 25th Percentile
-1- 10th Percentile
5-
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2-
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-h 75th Percentile
~ Mean
Median
25th Percentile
10th Percentile
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2027
Figure 3. Trends in Fourth Quarter Mean NO, Concentrations
Western Reference Sites
Eastern Reference Sites
1.0
0.8-
E
O)
0.6-
0.4
0.2-
o.o-
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
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90th Percentile
75th Percentile
Mean
Median
- 25th Percentile
10th Percentile
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t— t— t— t—t— t— t— (NCMCNJCMfMfMtNCNJCNICNICNJtNJCMCNjfNJCNJCMCNJCNJfNiCMCNI
Figure 4. Trends in Fourth Quarter Mean NH't Concentrations
Western Reference Sites
Eastern Reference Sites
0.5
0.4 -
E
D)
0.3
0.2
0.1
0.0
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
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Figure 5. Trends in Fourth Quarter Mean Total NO, Concentrations
Western Reference Sites
Eastern Reference Sites
2.5
2.0-
E
O)
1.5-
1.0
0.5-
o.o-
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
T
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90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2027
Figure 6. Trends in Fourth Quarter Mean S0:, Concentrations
Western Reference Sites
Eastern Reference Sites
1.5
E
O)
1.0
0.5-
o.o-
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
CDr^-COCTJO-^-CMCO^-LOCDI^-COaJOT-CMCO^rLOCDI^COOJO^-
050^C73Q30000000000t— t—t— t— t—t—t— t—t—t—C\ICM
0)0)0)0)0000000000000000000000
T-T-T-T-CNICMCMCSJCvJCMCNCMCNCMCMfMCMfSJCMfMCNfNJCNCNCNCN
25
20
15
10
5
7 90th Percentile
-*-i 75th Percentile
¦ Mean
Median
y 25th Percentile
10th Percentile
OT-c\icO'3-incDr^coo)OT-(NcO'^-LOo-<-r>jco-^-io«5i^coa)OT-
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T-T-T-T-T-T-T-T-T-T-CMCMCMCMCNCMCMCNCNCMCNOJCNJCMCMCNOJCMCMCMCMfN
Figure 7. Trends in Fourth Quarter Mean SO; Concentrations
Western Reference Sites
Eastern Reference Sites
1.0
0,8
0.6
0.4
O
° 0.2
0,0
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
T
A
T
T
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V
¦
i
-
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—
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050)00)0000000000000000000000
t- -r--*— t-CNCNICNJCNICNCNJCNCNJCNCNICNICNCNCMCNICNCNICNICMCNCMCN
o
o
Figures. Trends in Fourth Quarter Mean CI Concentrations
Western Reference Sites
90th Percentile
75th Percentile
Mean
— Median
25th Percentile
10th Percentile
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0.25
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0.10
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c
o
° 0.05
0.00
Eastern Reference Sites
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
a
a
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90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2027
Figure 9. Trends in Fourth Quarter Mean Ca2+ Concentrations
Western Reference Sites
Eastern Reference Sites
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
A
V
J
OT-CMCO^lOCDNCOOlOT-CMCO^inCDNCOOTOT-
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5 0.05
0.00
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2027
Figure 12. Trends in Fourth Quarter Mean Na+ Concentrations
Western Reference Sites
Eastern Reference Sites
90th Percentile
75th Percentile
Mean
Median
25th Percentile
10th Percentile
OT-ojco^incoscorooT-cMro^ifiCDScorooT-
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-T-v-T-T-T-T-T-^CMCM(N(NC\JCMCMCv4fM(NCNCN(NCNJ(NIC«J(SJCM(N(Nr\ir
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EPA Contract No. 68HERH2W0006
Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Table 2. Western Reference Sites: 3-Year Mean Nitrogen, Sulfur, and 03 Pollutant Concentrations
Total N03
nh;
SO,
so24
o3
(Mg/m3)
(Mg/m3)
(Mg/m3)
(Mg/m3)
(ppb)
1996-1998
0.8
0.2
0.7
0.6
38
2019-2021
0.5
0.1
0.2
0.3
38
Percent Change
-39
-41
-69
-46
0
Time Series of Laboratory Analysis Parameters for All Sites
Figures 14 through 24 give time series of laboratory-analyzed concentrations of field samples and
field blanks in milligrams per liter (mg/L) of 11 parameters from first quarter 2019 through fourth
quarter 2021. These figures provide indications of potential issues with concentration
measurements relative to detection and reporting limits.
Figure 14. Concentrations of N03 (as N) from Nylon Filters
Jb kQ> kQ> Sb .0) kQ> k°) kP) ,5b o0> o0> o0> nQ> nQ> nQ) nN nN -,N nN nN nN nN nN nN nN r>fVrirt'
####################
Note: Nominal reporting limit is 0.008 mg/L.
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2027
Figure 15. Concentrations of NO. (as N) from Teflon Filters
K k°> Kq> K°> & Kq> K°> .0, o, o> o> q> q> q Oo> Oo> 0q „n „\ n\ „\ n\ 0\ n\ „\ n\ „\ 0\ n q^ q^-* q^ n^> q^ q^ q1^ q*^ q1^ q^ q^ q^1 q1^ q^ q^ q*1" q^ q*^ q'V q'V
Note: Nominal reporting limit is 0.020 mg/L.
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Figure 17. Concentrations of S0:, from K CO: impregnated Cellulose Filters
• All Samples • Median ~ Field Blanks
or or v5 C \uor or or or or or or cr
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EPA Contract No. 68HERH21D0006
Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Figure 19. Concentrations of S024 from Teflon Filters
All Samples • Median • Field Blanks
t
»• •
• " , . , • a, • •
• . ~ ,•/ *•
, . *.i• .i . -
...* •.-!/•••. . . -J •,» " * * ;
¦r*: f*.
> ..4. U..
K Kq> Kq> 3 Kq> K°> .0, o, o> o> q> q> q> q> q Oo> Oo> Oo> 0q „n „\ n\ „\ n\ «\ n\ „\ n\ „\ 0\ n? •*? *>? n? "v* '>? 0^ <{p n*^ 0^ n1^ <1*^ n*^ n*^ n1^ n*^ tr0r
Note: Nominal reporting limit is 0.020 mg/L.
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Figure 21. Concentrations of Ca2+ from Teflon Filters
K k°> k°> k°) k°> A k°> & <£> r£> oN nN nN oN oN oN oN nN oN oN n*V o'V
Note: Nominal reporting limit is 0.006 mg/L.
Figure 22. Concentrations of K+ from Teflon Filters
n6 «?*? •? *? •? »P »? -? v5 •? (1° <1° 1° i° r{? <1° rj? <£> <1° <1? n° n>Is 1> iN nN<£• n> nN <£¦ i>nN
^ & >?* '\s' ft' ft*
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EPA Contract No. 68HERH21D0006
Revised CASTNET Quarterly Data Summary - Fourth Quarter 2027
Figure 23. Concentrations of Mg2+ from Teflon Filters
3>S> K* K* K^> r£>W& <£> oN oNnN oN nN oNnN oN oN nN oNoN o'Vn'V
Note: Nominal reporting limit is 0.003 mg/L.
Figure 24. Concentrations of Na+ from Teflon Filters
O
'§0.101
0.05-
o.oo-
N 0, 0) O) o> o, o> o, o, o> o> o> Q> c> Q Q Q Q> Q> Q> Q> Q> ,A A N \ \ \ \ \ \ \ N
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EPA Contract No. 68HERH2W0006
Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Time Series of Concentration Differences from Co-located Sites
Figures 25 and 26 show times series of concentration differences between the two sets of co-
located sites. The differences shown in Figure 25 were caused by flow issues at MCK231 during
mid- to late November. See also Table 3.
Figure 25. Time Series of Filter Concentration Differences between MCK131 and MCK231, KY
0.4
CN
CN
CN
CN
CN
CN
CN
CN
CN
CN
00
CN
G)
CO
CN
o5
CO
CO
O
CN
t—
t—
CN
" •
" •
t—
CN
CO
o
5)
T-
O
O
O
CN
csi
CN
CN
^r
T—
¦*—
CN
CN
CN
- Teflon S024
-•-Teflon Ca2+
-•-Nylon SO2
- Teflon N03
- Teflon Mg2+
—Nylon HNO3
Teflon NH4
-•-Teflon Na+
-•-Cellulose SO,
- Teflon CI
-•-Teflon K+
Figure 26. Time Series of Filter Concentration Differences between ROM406 and ROM206, CO
0.20
CN
CN
CN
CN
CN
CN
CN CN
CN
CN
00
LO
CN
5)
CO
5) co
0
CN
0
T—
CN
^ t—
CN
CO
5)
0
O
O
T—
T—
T-
—Teflon SO^
—Teflon N03
—Teflon NH^
- Teflon CI
—Teflon Ca2+
—Teflon Mg2+
—Teflon Na+
—Teflon K+
CN
CN
Nylon SO4
¦Nylon HNO3
-Cellulose SO,
CN
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Precision of Filter Pack Concentrations
Table 3 shows mean absolute relative percent differences (MARPD) for concentrations measured at
MCK131/231 and ROM406/206 during fourth quarter 2021. The MARPD values met the 20 percent
criterion.
Table 3. Precision (MARPD) for Co-located Filter Pack Data during Fourth Quarter 2021
Total
SO4
N03
NH+4
2+
Ca
» A 2+
Mg
Na+
K+
CI"
HNO3
S02
N03
MCK131/231,
KY
XQag/m3)
0.96
0.65
0.38
0.34
0.04
0.08
0.07
0.06
0.76
0.50
1.39
Y (M-g/m3)
0.96
0.64
0.38
0.36
0.04
0.08
0.08
0.07
0.79
0.53
1.42
MAD
0.05
0.07
0.02
0.04
0.00
0.01
0.01
0.01
0.05
0.06
0.09
MARPD
5.03
11.08
4.85
10.90
12.19
10.09
9.77
15.21
7.03
11.41
6.94
ROM406/206,
CO
XQag/m3)
0.24
0.10
0.11
0.07
0.01
0.02
0.02
0.02
0.24
0.14
0.33
Y (M-g/m3)
0.25
0.10
0.11
0.07
0.01
0.02
0.02
0.02
0.25
0.14
0.33
MAD
0.01
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.02
0.02
0.02
MARPD
3.94
12.89
4.81
7.57
11.58
8.54
16.43
10.17
7.53
13.96
7.30
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Completeness for Filter Pack Concentrations
Table 4 shows CASTNET sites with less than 90 percent completeness for weekly filter pack concentrations. Comments are included to
provide information on why these sites experienced low data completeness.
Table 4. Sites with less than 90 Percent Data Completeness for Filter Concentrations for Fourth Quarter 2021 (1 of 2)
Teflon
Teflon
Teflon
Teflon
Minor
Teflon
Nylon
Nylon
Cellulose
Site ID
so24
no3
nh;
Cations
Cf
hno3
so24
SO,
Comment
EGB181, ON
0
0
0
0
0
0
0
0
The dry deposition monitoring system was
turned off while the shelter is beinq refurbished.
THR422, ND
23
23
23
23
23
23
23
23
An EEMS audit on 10/19/21 identified a leak in
the flow system. It was repaired 11/16/21.
WNC429, SD
54
54
54
54
54
54
54
54
A flow system leak was identified 8/3/21 and was
repaired 11/9/21.
GRS420, TN
69
69
69
69
69
69
69
69
Flow issues affected two samples. December
samples were analyzed but are not yet finalized
in the database.
KIC003, KS
77
77
77
77
77
77
77
77
Intermittent power failures affected three filter
packs.
LAV410, CA
77
77
77
77
77
77
77
77
A power failure affected all December filter
packs.
SEK430, CA
77
77
77
77
77
77
77
77
Wildfire in the park resulted in its extended
closure. Power to the site was turned off. The
filter pack installed 9/7/21 remained on the
tower until 10/14/21.
ALC188, TX
85
85
85
85
85
85
85
85
Two December samples were analyzed but are
not yet finalized in the database.
BEL116, MD
85
85
85
85
85
85
85
85
The quarter included one 2-week sample.
Another was received late and was not
processed in time for this report.
BWR139, MD
85
85
85
85
85
85
85
85
The quarter included two 2-week samples.
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Table 4. Sites with less than 90 Percent Data Completeness for Filter Concentrations for Fourth Quarter 2021 (2 of 2)
Teflon
Teflon
Teflon
Teflon
Minor
Teflon
Nylon
Nylon
Cellulose
Site ID
so24
no3
nh;
Cations
Cf
hno3
so24
SO,
Comment
CNT169, WY
85
85
85
85
85
85
85
85
One filter pack was lost in shipping. Another was
received late and was not processed in time for
this report.
FOR605, WY
85
85
85
85
85
85
85
85
Flow issues affected two samples.
PAL190, TX
85
85
85
85
85
85
85
85
Flow issues affected two samples.
YOS404, CA
85
85
85
85
85
85
85
85
Two December samples were analyzed but are
not yet finalized in the database.
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Precision of Ozone Concentrations
Time series of co-located hourly 03 concentration differences for fourth quarter 2021 are provided
in Figures 27 and 28 for MCK131/231 and ROM406/206, respectively. The figures indicate no
consistent bias between the co-located analyzers at these site locations.
Figure 27. Time Series of the Differences in Co-located 03 Concentrations for MCK131/231, KY
6
-Q
o 9-
sz Q.
b O
C °
5 6
TO O
' I
S
O 05 "
§.i
O n
CN
O
CM
CM
CM
O
CM
CO
o
CM
O
CM
O
CM
CM
O
CO
CM
O
CM
O
CM
CM
O
CO
Figure 28. Time Series of the Differences in Co-located 03 Concentrations for ROM406/206, CO
6
a> -Q
o £-
c O-
cd ^
¦ ~o
CD
h— -r~
Q o
c o
¦B 6
ro O
-i—< i
s ^
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o|
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-6
CM
O
CM
CM
CM
O
CM
CO
o
CM
O
CM
O
CM
CM
O
CO
CM
O
CM
O
CM
CM
O
CO
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Table 5 gives MARPD data for 03 data measured at the two co-located sites.
Table 5. Quarterly Precision (MARPD) for Co-located 03 Concentrations
Site Pair
Quarter
Start Date
MARPD
Records
MCK131/231, KY
1
1/1/21
1.0
2046
2
4/1/21
0.6
2075
3
7/1/21
0.8
2082
4
10/1/21
1.0
2086
ROM406/206, CO
1
1/1/21
4.5
2015
2
4/1/21
1.9
2013
3
7/1/21
1.4
2078
4
10/1/21
1.7
2075
Completeness for 03 Concentrations
Calculation of an annual 03 value requires 75 percent completeness. However, calculation of the
3-year design value used for regulatory purposes requires 90 percent completeness. Table 6 shows
CASTNET sites with less than 90 percent completeness for DM8A 03 concentrations. Comments are
provided for these sites.
Table 6. Sites with less than 90 Percent Data Completeness for DM8A Concentrations during
Fourth Quarter 2021
Site ID
Percent
Completeness
Comments
CAD 150, AR
71.7
The analyzer solenoid malfunctioned, and the analyzer was replaced
11/30/21.
LAV410, CA
81.5
The ozone sample pump failed 11/11/21 and was replaced 11/17/21. In
addition, intermittent power failures occurred in December.
BBE401, TX
82.6
The ozone sample pump failed on 12/10/21 and was replaced 12/21/21.
ASH135, ME
87.0
The ozone sample pump failed on 11/3/21 and was replaced 11/12/21.
PND165, WY
88.0
The ozone sample pump failed on 11/21/21 and was replaced 11/30/21.
JOT403, CA
88.0
The ozone sample pump failed on 12/13/21 and was replaced 12/22/21.
SEK430, CA
89.1
Power to the monitoring site was shut off on 9/14/21 due to wildfires
near the site. Power to the site was restored on 10/8/21.
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Table 7 shows CASTNET sites with less than 90 percent completeness for hourly 03 concentrations.
Comments are provided for these sites. The annual average for each of these sites is included for
reference.
Table 7. Sites with less than 90 Percent Data Completeness for 03 Concentrations
Q1 2021-
Site ID
Q4 2021
Q4 2021
Comments
CAD 150, AR
72.3
92.5
The analyzer solenoid malfunctioned, and the analyzer was
replaced 11/30/21.
BBE401, TX
84.3
92.9
The ozone sample pump failed on 12/10/21 and was replaced
12/21/21.
LAV410, CA
85.5
94.9
The ozone sample pump failed 11/11/21 and was replaced
11/17/21. In addition, intermittent power failures occurred in
December.
JOT403, CA
88.4
95.9
The ozone sample pump failed on 12/13/21 and was replaced
12/22/21.
PND165, WY
89.1
95.0
The ozone sample pump failed on 11/21/21 and was replaced
11/30/21.
ASH135, ME
89.3
97.1
The ozone sample pump failed on 11/3/21 and was replaced
11/12/21.
Filter Pack Total Nitrate and Continuous Trace-level NOy Concentrations at Eight CASTNET Sites
Figures 29 through 36 show a comparison of weekly average continuous NOy measurements with
weekly filter pack total N03 concentrations collected at the eight sites with NOy measurements. The
NOy concentrations were consistently higher than the total N03 levels at all sites. The average
weekly NOy levels, the weekly total N03 concentrations, and their ratios for the eight sites with
available data are shown in Table 8. Ratios of NOy to total N03 varied from 3.44 at PNF126 to 8.22
at HWF187.
Table 8. Summary of Total N03 and NOy Measurements for Fourth Quarter 2021
Site ID
Elevation
Total NOs (ppb)
NOy (ppb)
Ratio
DUK008, NC
164*
0.49
2.80
5.88
BVL130, IL
213
0.78
4.04
5.14
MAC426, KY
243
0.54
2.29
4.31
HWF187, NY
497
0.17
1.22
8.22
GRS420, TN
793
0.40
1.63
4.19
PNF126, NC
1216
0.28
0.94
3.44
PND165, WY
2386
0.09
0.38
4.38
ROM206, CO
2742
0.10
0.55
5.48
Note: *Enhanced NOy monitor is located at the top of the 30-meter tower.
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 202 7
Figure 29. Comparison of DUK008 Weekly Mean NOy and Total N03 Concentrations
- Mean Continuous NOy
- Filter Pack Total Nitrate
1.5
1.0
0.5
-Q
Q.
Q.
C
o
(D
O
c
o
O
(D
03
(0
-i—¦
O
o.o
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 202 7
Figure 31. Comparison of MAC426 Weekly Mean NOy and Total N03 Concentrations
2.0
¦ Mean Continuous NOy
• Filter Pack Total Nitrate
_Q
1.5 &
1.0
c
(D
O
C
o
O
0.5 ro
,o
0.0
CO
o
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Figure 34. Comparison of PNF126 Weekly Mean NOy and Total N03 Concentrations
—m— Mean Continuous NOy
—~— Filter Pack Total Nitrate
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Figure 36. Comparison of ROM206 Weekly Mean NOy and Total N03 Concentrations
—¦— Mean Continuous NOy
—o— Filter Pack Total Nitrate
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Filter Pack and Continuous Trace-level Gas Sulfur Dioxide Concentrations
Figures 37 through 39 provide diagrams that compare weekly filter pack S02 concentrations with
continuous trace-level gas data measured at BVL130, MAC426, and GRS420. The continuously
measured trace-level concentrations were higher than filter pack concentrations at BVL130 and
were comparable at MAC426 and GRS420.
Figure
2.0
1.5
Q.
Q.
C
0
1 1.0
c
0
o
c
o
O
0.5
0.0
37. Comparison of BVL130 Weekly Mean S02 Concentrations
Figure 38. Comparison of MAC426 Weekly Mean S02 Concentrations
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
Figure 39. Comparison of GRS420 Weekly Mean S02 Concentrations
Completeness for Continuous Trace-level Gas Measurements
Table 9 shows the percent completeness for CASTNET trace-level gas measurements. Comments
are provided for sites with less than 90 percent completeness for hourly trace-level gas
concentrations during fourth quarter 2021. The average for first quarter 2021 through fourth
quarter 2021 for each of the sites is included for reference.
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Table 9. Percent Data Completeness for Continuous Trace-level Gas Measurements
Q1 2021 -
Site ID
Parameter*
Q4 2021
Q4 2021
Comments
BVL130, IL
CO
29
42
The CO analyzer malfunctioned and was
replaced in December 2021.
NO
95
94
NOY
95
94
NOYDIF
95
94
S02_GA
92
87
CHC432, NM
NO
97
97
NOX
97
97
NOXDIF
97
97
DUK008, NC
HN03
90
Monitoring restarted in August 2021, but QC
NH3
91
functions were not fully operational until
NO
91
December 2021. Since no valid data are
N02 TRUE
91
available until December 2021, the average for
NOX TRUE
91
Q1 2021 through Q4 2021 was not calculated.
NOY
91
NOY MINUS
91
NOYDIF
91
TNX
91
GRS420, TN
CO
90
91
NO
92
93
NOY
92
93
NOYDIF
92
94
S02_GA
92
95
HWF187, NY
NO
90
93
NOY
90
93
NOYDIF
90
93
MAC426, KY
CO
95
86
NO
97
96
NOY
97
96
NOYDIF
97
96
S02_GA
97
97
PND165, WY
NO
95
88
NOY
95
87
NOYDIF
95
87
PNF126, NC
NO
89
80
The bypass box was off from 10/7/21 to
NOY
89
81
10/12/21.
NOYDIF
89
79
ROM206, CO
NO
95
91
NOY
95
94
NOYDIF
95
91
Note: * See Table 10
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Revised CASTNET Quarterly Data Summary - Fourth Quarter 2021
The parameters listed in Table 9 are both calculated and measured. Table 10 provides information
on how the parameters listed in Table 9 are obtained.
Table 10. CASTNET Trace-level Gas Measurements
Parameter Name
How Obtained
Description of Process
CO
Measured
Gas filter correlation
HN03
Calculated
NOY minus NOY_MINUS
NH3
Calculated
TNX minus NOY
NO
Measured
Chemiluminescence reaction/no converter used
N02_TRUE
Calculated
NOX_TRUE minus NO
NOX_TRUE
Measured
Photolytic converter
NOY
Measured
Molybdenum converter at 315° Celsius
NOYDIF
Calculated
NOY minus NO
NOY_MINUS
Measured
Sodium carbonate denuder followed by molybdenum converter
at 315° Celsius
NOX
Measured
Molybdenum converter at 325° Celsius
NOXDIF
Calculated
NOX minus NO
S02_GA
Measured
Ultraviolet fluorescence
TNX
Measured
Platinum/stainless steel converter at 825° Celsius followed by
molybdenum converter at 315° Celsius
References
Wood Environment & Infrastructure Solutions, Inc. 2022. Clean Air Status and Trends Network
(CASTNET) Fourth Quarter 2021 Quality Assurance Report with 2021 Annual Summary.
https://java.epa.gov/castnet/documents.do
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