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PARTICULATE NITRATE MEASUREMENTSDURING CRPAQS
Judith C. ChowJohn G. WatsonDouglas H. LowenthalDesert Research Institute, Reno, NV
Susanne V. HeringAerosol Dynamics Inc., Berkeley, CA
presented at the
CRPAQS Data Analysis MeetingSacramento, CA
March 9, 2004
2
OBJECTIVES
• Present nitrate measurements fordifferent samplers, locations, andtime periods
• Evaluate the extent of nitratevolatilization
3
INTEGRATED SAMPLERS
Dual-channelsequential filter
samplerDesert Research
Institute, Reno, NV
RAAS-400PM2.5 speciation sampler
Andersen Instruments, Smyrna, GA
RAAS-100single-channel PM2.5 FRM sampler
Andersen Instruments, Smyrna, GA
Minivol samplerAirmetrics,Eugene, OR
4
Andersensingle-channel FRM
Louvered SA-246PM10 inlet
Frontquartz-fiber
Non-volatilizednitrate IC
16.7 L/min
PM2.5WINS
impactor
Variable-speedpump
Andersen RAAS louvered inlet
Teflon-coated modifiedAIHL a
PM2.5 cyclone inlet
FEP Teflon-coatedmodified AIHL
PM2.5 cyclone inlet
Manifold 2
Frontquartz-fiber
Non-volatilizedcarbon TORNitrate IC
Backupquartz-fiber
Adsorbedgaseous
carbon TOR
Frontquartz-fiber
Non-volatilizednitrate IC
Backupnylon
Volatilizednitrate IC
Manifold 1
24 L/min
Channel 27.3 L/min
to otherchannels
Channel 58.7 L/min 15.3 L/min
nitricacid
denuder
Critical orifice flow controller
24 L/min
fieldblank
no flow
to otherchannel
16.7 L/min
Desert Research Institutesequential filter sampler (SFS)
Bendix 240 cPM2.5 cyclone inlet
to otherchannel andbypass flow
93 L/min
113 L/min
Manifold
20 L/min
Differential pressure flow controller
fieldblank
no flow
Frontquartz-fiber
Non-volatilizednitrate IC
nitricacid
denuder
Backupsodium-chloride-
impregnated cellulose
Volatilizednitrate IC
Airmetrics Minivol sampler
Louvered SA-246PM10 inlet
5 L/min
PM2.5 impactor
PM10 impactor
Front
quartz-fiber Non-volatilized nitrate IC
Backup sodium-chloride-
impregnated cellulose
Volatilized nitrate IC
Diaphragm pump and flow set valve
INTEGRATED SAMPLERS (continued)
5
TYPES OF INLETSCut Point Slope Flow
Type (d50) (√d84/d16) Rate
EPA WINS 2.48 µm 1.18 16.7 L/minimpactor (FRM)
AIHL cyclone 2.5 µm 1.18 24 L/min(RAAS)
Bendix/Sensidyne 2.5 µm 1.7 113 L/min240 cyclone (SFS)
Impactor 2.5 µm 1.23 5 L/min(Minivol)
INDEX BAR (PM2.5B HASSPACERS UNDER THE BARAND LONGE R SCREWS)
6
TYPES OF DENUDERS
SamplingSystem Denuder Type
FRM None
RAAS Sodium-carbonate-coated glass denuder(flow rate = 8.7 L/min)
SFS Aluminum-oxide-coatedtubular denuder(flow rate = 20 L/min)
Minivol None
7
TYPES OF FILTER HOLDERSInlet surface Filter holder
FRM Anodized Delrin ringaluminum with stainless
steel grid
RAAS FEP Teflon Delrin ring,coated polycarbonate
holder
SFS Anodized Nucleporealuminum polycarbonate
holder
Minivol Anodized Nucleporealuminum polycarbonate
holder
8
SAMPLING SUBSTRATES FORION CHROMATOGRAPHY ANALYSIS
Analyte Filter type Sampling system
Non-volatilized Pallflex FRMNO3
– #2500 QAT-UP RAASquartz-fiber SFS
Minivol
Volatilized Schleicher & Schuell RAASNO3
– #66 nylon
Volatilized Whatman 31ET SFSNO3
– cellulose-fiber Minivolimpregnated with NaCl
9
NH4NO3 (p) <=> NH3 (g) + HNO3 (g)
low T, high RH <=> high T, low RH
THE AMMONIUM NITRATE EQUILIBRIUM
10
T (oC)
0 5 10 15 20 25 30 35
RH
(%)
20
40
60
80
100
BakersfieldFresno
24-HOUR AVERAGE TEMPERATURE (T) ANDRELATIVE HUMIDITY (RH) (Dec. 1999–Jan. 2001)
T and RH aresimilar at bothsites and varyinversely.
11
Date
12/1/99 4/1/00 8/1/00 12/1/00
Vola
tiliz
ed N
O3– /T
otal
Par
t. N
O3– (%
)
0
20
40
60
80
100
T (o C
)
5
10
15
20
25
30
35
Angiola BakersfieldFresnoBakersfield Temp.Fresno Temp.
Peaks duringwarmer months.Relatively lessvolatilization atAngiola.
MONTHLY AVERAGE NITRATE VOLATILIZATION
12
Peaks in winter and fall.
Volatilization is highestin spring and summerat the two urban sites.
Angiola
Winter Spring Summer FallN
itrat
e (u
g/m
3 )
0
5
10
15
20Non-VolatilizedVolatilized
Bakersfield
Winter Spring Summer Fall
Nitr
ate
(ug/
m3 )
0
5
10
15
20Non-VolatilizedVolatilized
Fresno
Winter Spring Summer Fall
Nitr
ate
(ug/
m3 )
0
5
10
15
20Non-VolatilizedVolatilized
PM2.5 PARTICULATENITRATE (PNO3
–)
13
Nitratevolatilizationincreasesthroughout theday withtemperature,even in winter.
WINTER INTENSIVE NITRATE VOLATILIZATIONBY SAMPLE PERIOD
CRPAQS Winter IntensiveNO3
– Volatilization by Period
Sampling Period (PST)
0-5 5-10 10-13 13-16 16-24
Vola
tiliz
ed N
O3– /T
otal
Par
t. N
O3– (%
)
0
5
10
15
20
T (o C
)
-2
0
2
4
6
8
10
12
14
16
-2
0
2
4
6
8
10
12
14
16
AngiolaBakersfieldBethel Isl.FresnoSierra NVBakersfield T oCFresno T oC
14
Sampling Date during 200010
-1410
-1610
-1710
-1810
-1910
-2010
-2210
-2310
-24 11-2
11-3
11-4
11-5
11-6
11-7
11-8
11-9
Vola
tiliz
ed N
O3– /T
otal
Par
t. N
O3– (%
)
0
20
40
60
80
100
Fres
no T
(o C)
8
10
12
14
16
18
20
22
AngiolaFresnoFresno Temp.
Degree ofvolatilizationdecreases withtemperatureat both sitesthrough theepisode.
FALL INTENSIVE DAILY NITRATE VOLATILIZATION
15
SFS (higherface velocity)volatilizesmore nitratethan the RAASsampler(lower facevelocity).
Date12
/1/99
1/1
/00
2/1/00
3/1
/00
4/1/00
5/1
/00
6/1/00
7/1
/00
8/1/00
9/1
/00
10/1/
00
11/1/
00
12/1/
00
1/1/01
2/1
/01
Vola
tiliz
ed N
O3– /T
otal
Par
t. N
O3– (%
)
0
20
40
60
80
100
SFS/
RAA
S
0
2
4
6
8
10
12
14
16SFSRAASSFS/RAAS
10.5 cm/s
24.2 cm/s
MONTHLY AVERAGE NITRATE VOLATILIZATION
16
VOLATILIZED NH4NO3NOT MEASURED BYGRAVIMETRIC MASS
Angiola Daily Nitrate Volatilization
Date12/1/99 2/1/00 4/1/00 6/1/00 8/1/00 10/1/00 12/1/00 2/1/01 Vo
latil
ized
NH
4NO
3/PM
2.5 (
%)
0
10
20
30
40
50
60
Bakersfield Daily Nitrate Volatilization
12/1/99 2/1/00 4/1/00 6/1/00 8/1/00 10/1/00 12/1/00 2/1/01 Vola
tiliz
ed N
H4N
O3/P
M2.
5 (%
)
0
10
20
30
40
50
Fresno Daily Nitrate Volatilization
Date12/1/99 2/1/00 4/1/00 6/1/00 8/1/00 10/1/00 12/1/00 2/1/01 Vo
latil
ized
NH
4NO
3/PM
2.5 (
%)
0
20
40
60
80
100
Range = 0-50%Average = 9.5%
Range = 0-46%Average = 15.4%
Range = 0-80%Average = 21%
Date
PM2.5 mass isunderestimated by up to80% on a daily basis dueto nitrate volatilization.
17
VOLATILIZED NH4NO3NOT MEASURED BYGRAVIMETRIC MASS
Nitrate volatilizationexceeded 20% only whenPM2.5 < 20-30 µg/m3.
Angiola
PM2.5 (µg/m3)
0 20 40 60 80 100 120 140 160Vola
tiliz
ed A
MN
IT/P
M2.
5 (%
)
0
20
40
60
80
100
N=51
Bakersfield
PM2.5 (µg/m3)
0 20 40 60 80 100 120 140 160Vola
tiliz
ed A
MN
IT/P
M2.
5 (%
)
0
20
40
60
80
100
N=62
Fresno
PM2.5 (µg/m3)
0 20 40 60 80 100 120 140 160Vola
tiliz
ed A
MN
IT/P
M2.
5 (%
)
0
20
40
60
80
100
N=64
18
In summer,SFS PNO3
– > FRM NO3–
4.8 > 2.4 µg/m3
(average)
In winter,SFS PNO3
– < FRM NO3–
13 < 16 µg/m3
(average)
Fresno
SFS PNO3– (µg/m3)
0 2 4 6 8 10
FRM
Non
-Vol
atiliz
ed N
O3– (u
g/m
3 )
0
2
4
6
8
10
y/x = 0.48±0.32N = 28
Fresno
SFS PNO3– (µg/m3)
0 10 20 30 40 50 60 70
FRM
Non
-Vol
atiliz
ed N
O3– (u
g/m
3 )
0
10
20
30
40
50
60
70
y/x = 1.12±0.25N = 16
Summer
Winter
19
PM2.5 mass and sulfatefor FRM aresystematically higherthan SFS.
This could explain in partwhy winter FRM non-volatilized NO3
– is higherthan SFS total particulateNO3
–.
Fresno sulfate
SFS SO4= (µg/m3)
0 2 4 6 8
FRM
SO
4= (µg/
m3 )
0
2
4
6
8
y/x = 1.11±0.13 N = 57
Fresno mass
SFS PM2.5 (µg/m3)0 20 40 60 80 100 120 140 160
FRM
PM
2.5 (
µg/m
3 )
0
20
40
60
80
100
120
140
160y/x = 1.06±0.25 N = 58
20
SFS particulate (denuded)nitrate is higher thanMinivol (undenuded)nitrate in summer, butsimilar in winter.
Bakersfield
Date
12/1/
991/1
/002/1
/003/1
/004/1
/005/1
/006/1
/007/1
/008/1
/009/1
/0010
/1/00
11/1/
0012
/1/00
1/1/01
2/1/01
Parti
cle
NO
3– (Non
-Vol
atiliz
ed +
Vol
atiliz
ed) (
ug/m
3 )
0.1
1
10
100
1000
SFS (denuded)Minivol (non-denuded)
Sierra NV
Date
12/2/
0012
/8/00
12/14
/0012
/20/00
12/26
/00
1/1/01
1/7/01
1/13/0
11/1
9/01
1/25/0
1
Parti
cle
NO
3– (Non
-Vol
atiliz
ed +
Vol
atiliz
ed) (
ug/m
3 )
0
5
10
15
20
25
SFS (denuded)Minivol (non-denuded)
21
Angiola Winter Intensive
PNO3– (ug/m3)
0 10 20 30 40 50 60R&P
840
0N N
O3– (u
g/m
3 )
0
10
20
30
40
50
60
Bakersfield Winter Intensive
PNO3– (ug/m3)
0 20 40 60 80 100 120R&P
840
0N N
O3– (u
g/m
3 )
0
20
40
60
80
100
120
Fresno Winter Intensive
PNO3– (ug/m3)
0 10 20 30 40 50 60 70R&P
840
0N N
O3– (u
g/m
3 )
0
10
20
30
40
50
60
SFS PNO3– and R&P NO3
–
agree up to 20-30 ug/m3,but R&P NO3
– is lower at
higher concentrations –most strongly at Angiola,least at Bakersfield.
This may be related tothe difference betweenambient and R&Psampling temperature.
22
Continuous andfilter HNO3 bydenuder differenceare only moderatelycorrelated.
CRPAQS Winter Intensive by Period at Fresno
Filter Denuder Difference HNO3 (µg/m3)
0 2 4 6 8 10 12
Con
tinuo
us H
NO
3 (µg
/m3 )
0
2
4
6
8
10
12
r = 0.61
23
Fresno Monthly HNO3 and Particulate Nitrate
Date
11/1/
00
1/1/01
3/1
/01
5/1/01
7/1
/01
9/1/01
11
/1/01
1/1
/02
3/1/02
5/1
/02
Tota
l Par
ticul
ate
NO
3 (µg
/m3 )
0
5
10
15
20
25
HN
O3 (
µg/m
3 )
0
1
2
3
4
5RAAS Total Part. NO3
Continuous HNO3
PNO3- peaks in
winter, while HNO3peaks in summerwhen it is dominant,as expectedthermodynamically.
24
CONCLUSIONS
• The degree of ammonium nitrate volatilization variesseasonally and diurnally with temperature.
• Ammonium nitrate volatilization also increases withsampling face velocity where the SFS (24.2 cm/s) >RAAS (10.5 cm/s).
• Volatilized ammonium nitrate is up to 80%, 50%, and46% of measured daily PM2.5 mass at Fresno, Angiola,and Bakersfield, respectively.
• Nitrate volatilization exceeds 20% only whenPM2.5 < 20–30 µg/m3.
25
CONCLUSIONS (continued)
• Total particulate nitrate measured by denuded SFS agreedwell with un-denuded Minivol sampler non-volatilized andvolatilized nitrate in winter but not in summer at Bakersfield.
• Continuous R&P nitrate agreed with SFS particle nitrate upto 20-30 µg/m3 but was lower at higher concentrations.
• Filter-based nitric acid measured by denuder difference wasmoderately correlated (r=0.61) with continuous nitric acid inFresno.
• Fresno gaseous nitric acid concentrations peaked at about 4µg/m3 in summer coinciding with the annual minimum inparticle nitrate.
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