Year-long CToF-AMS measurements at an urban background...
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Nicky Young 1 , James Allan 1,2 , Dave Green 3 , Anja Tremper 3 , Paul Williams 1,2 , & Hugh Coe 1,2 1 School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK 2 National Centre for Atmospheric Science, University of Manchester, Oxford Road, Manchester, M13 9PL, UK 3 King's College London, Environmental Research Group, Franklin-Wilkins Building, 150 Stamford Street, London, SE1 9NH, UK Year-long CToF-AMS measurements at an urban background site in London, UK
Transcript of Year-long CToF-AMS measurements at an urban background...
Nicky Young1, James Allan1,2, Dave Green3, Anja Tremper3, Paul Williams1,2, &
Hugh Coe1,2
1School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road,
Manchester, M13 9PL, UK 2National Centre for Atmospheric Science, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
3King's College London, Environmental Research Group, Franklin-Wilkins Building, 150 Stamford Street, London, SE1 9NH, UK
Year-long CToF-AMS measurements at an urban background site in
London, UK
Long-term AMS overview
• Ran as part of ClearfLo project at the urban background supersite in North Kensington in London
• 11 January 2012 – 23 January 2013 • 97% up time
• Operation
– Ran at low filament current – Detuned mass spectrometer to minimise potassium
background – Calibrated once per month – fairly stable throughout – Checked instrument remotely, IE cals performed every
other day
Time series
70
60
50
40
30
20
10
0
Ma
ss c
on
ce
ntr
atio
n (
µg
m-3
)
01/03/2012 01/05/2012 01/07/2012 01/09/2012 01/11/2012 01/01/2013
Date and Time
Organics Nitrate Sulphate Ammonium Chloride
Flagged data (flowrate=2, NaN)
PMF
• Run on whole data set
• Problems with PMF prep panel due to very large data set (toolkit can only handle ~100,000 runs, we have ~106,000). Resolved.
• Outputs highlighted problems with the data set – Step changes in summer period
– Flow issues
• Bug in squirrel errors for PMF
PMF run on full AMS data set
12
8
4
0
Ma
ss
01/03/2012 01/05/2012 01/07/2012 01/09/2012 01/11/2012 01/01/2013
dat
12
8
4
0
8
6
4
2
0
10
8
6
4
2
0
25
20
15
10
5
0
HOA
SFOA
LV-OOA
COA
SV-OOA
• 5 factors identified: HOA, SFOA, COA, LV-OOA, SV-OOA
Changes to instrument tuning
46
45
44
43
42
41
40
39
01/03/2012 01/05/2012 01/07/2012 01/09/2012 01/11/2012 01/01/2013
Date and Time
Filament EmissionHeater Bias (V)
12
8
4
0
Mass
01/03/2012 01/05/2012 01/07/2012 01/09/2012 01/11/2012 01/01/2013
dat
12
8
4
0
8
6
4
2
0
10
8
6
4
2
0
25
20
15
10
5
0
HOA
SFOA
LV-OOA
COA
SV-OOA
Comparison of MS for different PMF runs
Full year without summer period Before summer After summer
Factor SV-
OOA
COA LV-
OOA
SFOA HOA SV-
OOA
COA LV-
OOA
SFOA HOA SV-
OOA
COA LV-
OOA
SFOA HOA
Full
year
PMF
SV-OOA 0.91 0.51 0.98 0.41 0.31 0.98 0.57 0.68 0.84 0.34 0.87 0.39 0.99 0.86 0.35
COA 0.30 0.98 0.23 0.41 0.73 0.23 0.97 0.31 0.50 0.75 0.40 0.99 0.24 0.30 0.78
LV-OOA 0.81 0.29 0.97 0.12 0.19 0.95 0.34 0.73 0.61 0.21 0.73 0.15 0.96 0.72 0.23
SFOA 0.27 0.41 0.26 0.97 0.36 0.35 0.45 0.19 0.80 0.38 0.44 0.41 0.29 0.73 0.35
HOA 0.17 0.74 0.19 0.37 0.99 0.24 0.75 0.28 0.42 0.99 0.30 0.75 0.20 0.31 0.98
Before summer After summer
Factor SV-OOA COA LV-OOA SFOA HOA SV-OOA COA LV-OOA SFOA HOA
Full year
without
summer
period
SV-OOA 0.83 0.49 0.96 0.36 0.34 0.68 0.56 0.82 0.81 0.35
COA 0.26 0.99 0.30 0.46 0.78 0.31 0.98 0.27 0.53 0.81
LV-OOA 1.00 0.40 0.89 0.31 0.22 0.69 0.45 0.99 0.77 0.24
SFOA 0.81 0.45 0.67 0.76 0.29 0.53 0.50 0.87 0.93 0.34
HOA 0.25 0.82 0.24 0.36 0.99 0.35 0.83 0.29 0.45 0.99
After summer
Factor SV-OOA COA LV-OOA SFOA HOA
Before summer
SV-OOA 0.69 0.45 0.99 0.75 0.24
COA 0.40 0.99 0.40 0.60 0.80
LV-OOA 0.68 0.47 0.86 0.74 0.22
SFOA 0.17 0.49 0.38 0.79 0.39
HOA 0.30 0.79 0.26 0.43 0.99
Mass spectral profile correlations for different PMF runs
Time series correlations
Full year without summer period Before summer After summer
Factor SV-
OOA
COA LV-
OOA
SFOA HOA SV-
OOA
COA LV-
OOA
SFOA HOA SV-
OOA
COA LV-
OOA
SFOA HOA
Full
year
PMF
SV-
OOA
0.86 0.96 0.75
COA 0.97 0.97 0.99
LV-
OOA
0.95 0.77 0.93
SFOA 0.58 0.51 0.63
HOA 0.99 1.00 0.74
Before summer After summer
Factor SV-OOA COA LV-OOA SFOA HOA SV-OOA COA LV-OOA SFOA HOA
Full
year
without
summe
r period
SV-OOA 0.46 0.99 0.82
COA 1.00 0.99
LV-OOA 0.98 0.51 0.95
SFOA 0.99 0.98
HOA 1.00 1.00
Flow rate – mass concentration issues
60
40
20
0
Mass c
oncentr
ation (
µg m
-3)
05/05/2012 09/05/2012 13/05/2012 17/05/2012 21/05/2012 25/05/2012
Date and Time
0.000.000.000.00
NO
x (u
g/m
3)
1.30
1.25
1.20
1.15
1.10
1.05 Organics Nitrate Sulphate Ammonium Chloride flowrate
Step changes on 22/05 and 24/05 -> flow adjusted itself
Bad step changes in flow and mass
25
20
15
10
5
0
Mass c
oncentr
ation (
µg m
-3)
12:0001/06/2012
00:0002/06/2012
12:00 00:0003/06/2012
12:00
Date and Time
0.000.000.000.00
NO
x (u
g/m
3)
1.3
1.2
1.1
1.0
Organics Nitrate Sulphate Ammonium Chloride flowrate
60
40
20
0
Mass c
oncentr
ation (
µg m
-3)
13/08/2012 17/08/2012 21/08/2012 25/08/2012 29/08/2012 02/09/2012 06/09/2012 10/09/2012
Date and Time
0.000.000.000.00
NO
x (u
g/m
3)
1.3
1.2
1.1
1.0 Organics Nitrate Sulphate Ammonium Chloride flowrate
Pinhole clean – no obvious effect
Final flagged data
200
150
100
50
0
Mass c
oncentr
ation (
µg m
-3)
01/03/2012 01/05/2012 01/07/2012 01/09/2012 01/11/2012 01/01/2013
Date and Time
0.000.000.000.00
NO
x (u
g/m
3)
1.3
1.2
1.1
1.0 Organics Nitrate Sulphate Ammonium Chloride flowrate
4
3
2
1
0
0 = good data1 = flow <= 1.22 = flow <= 1.2 & bad3 = flow <= 1.2 & suspect4 = flow > 1.2 & suspect
Factor number
Slope Pearson’s r R2
1 0.99328 0.999623 0.999247 2 0.97607 0.999183 0.998367 3 1.0095 0.999202 0.998405 4 1.0439 0.998953 0.997907 5 0.99204 0.999677 0.999355
140
120
100
80
60
40
20
0
Ne
w s
quirre
l fa
cto
r
140120100806040200
Old squirrel factor
Coefficient values ± one standard deviationa =0.010502 ± 0.000115b =0.99204 ± 8.15e-005
V_Pr= 0.999677;V_r2= 0.999355;
Less than 5% difference for all 5 factors
Squirrel errors bug – PMF vs 1.53 (fixed) vs 1.52C (contains bug)
HR-ToF-AMS
• Ran during the winter and summer IOPs at North Kensington
• Several different modes – V and W as well as laser on/off and thermal denuder in winter IOP
• PMF run on V mode ambient data from both IOPs
• Winter IOP – 5 factors identified: HOA, COA, SFOA 1, SFOA 2, OOA
• Summer IOP – 5 factors identified: HOA, COA, aged COA?, LV-OOA, SV-OOA
Aged COA factor? Summer IOP
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
Pe
rce
nt
of
tota
l sig
na
l
10080604020
m/z
Cx CH CHO1 CHOgt1 CHN CHO1N CHOgt1N CS HO Air
Factor 3
80x10-3
60
40
20
0
Per
cent
of t
otal
sig
nal
10080604020
m/z
Cx CH CHO1 CHOgt1 CHN CHO1N CHOgt1N CS HO Air
Factor 4
2.5
2.0
1.5
1.0
0.5
Mass
2015105
Hour of day
Median_factor1_5sol Median_factor4_5sol Median_factor5_5sol Median_split_factor
OOA COA HOA Combined SFOA
Explore COA/HOA rotation 1.0
0.8
0.6
0.4
0.2
0.0
Ma
ss c
once
ntr
atio
n (
µg
m-3
)
242322212019181716151413121110987654321
Hour of Day
HOA COA SFOA LVOOA SVOOA
3.0
2.5
2.0
1.5
1.0
0.5Ma
ss c
once
ntr
atio
n (
µg
m-3
)2015105
Hour of Day
LV-OOA SV-OOA Aged COA? COA HOA
CToF-AMS – full year
HR-ToF-AMS – winter IOP
HR-ToF-AMS – summer IOP
HR vs CToF
20
15
10
5
0
16/01/2012 21/01/2012 26/01/2012 31/01/2012 05/02/2012
dat
COA COA HR
30
25
20
15
10
5
0
16/01/2012 21/01/2012 26/01/2012 31/01/2012 05/02/2012
dat
HOA HR HOA
16
14
12
10
8
6
4
2
0
16/01/2012 21/01/2012 26/01/2012 31/01/2012 05/02/2012
dat
SFOA HR SFOA SVOOA
6
5
4
3
2
1
0
16/01/2012 21/01/2012 26/01/2012 31/01/2012 05/02/2012
dat
OOA HR LVOOA
Conclusions
• Unique dataset – full calendar year of CToF-AMS data from North Kensington – Good performance throughout year – User and software issues identified -> now resolved (I think)
• Changes in tuning, flow rate, bugs in code
• Comparisons with HR-ToF-AMS data from two IOPs in 2012 (and other instruments deployed) – Increased accuracy of CToF PMF factors (including rotational
ambiguity) • BUT possible mix of SFOA/SV-OOA -> needs addressing
– Interesting factors identified from these data sets alone (2 x SFOA in winter, aged COA in summer?)
• Will allow comparisons with ACSM data (March 2013 – present) -> Dave Green’s presentation after the coffee break
Acknowledgements
• NERC Clean Air For London (CLEARFLO) project [Grant ref: NE/H00324X/1]
• Department of the Environment, Food and Rural Affairs (DEFRA)
