Investigation of f variability in AMS and ACSM instruments

27 Pages·2015·1.98 MB·English

by  John Jayne

Investigation of f
44
variability in AMS and
ACSM instruments
Update from Aerodyne Research
Experiments by Phil Croteau, Andy Lambe, Wen Xu, Tim
Onasch, Lindsay Wolff, Manjula Canagaratna
John Jayne
Mass 44
A Marker Ion for OOA
CO , CO and water is formed by thermal
2
decomposition of organic acids
Δ
H C O  H O + CO + CO
2 2 4 2 2
Oxalic acid, smallest di-acid
f44 = m/z44 / Org
Background
ACTRIS-ACSM intercomparison study
10 European countries
15 mass spectrometers
13 QACSM, TOF ACSM,
AMS partner
HTOF AMS
ACSM-ACTRIS stations
Led by Jean Sciare, Vincent
Crenn (LSCE) and Olivier
Favez (INERIS)
Three weeks during the fall period (Nov. – Dec. 2013)
Results of ACTRIS-ACSM intercomparison study
are summarized in two AMT papers
Crenn et al
ACTRIS ACSM Intercomparison: Part I - Intercomparison of concentration and
fragment results from 13 individual co-located Aerosol Chemical Speciation
Monitor (ACSM)
Frohlich et al,
ACTRIS ACSM intercomparison – Part 2: Intercomparison of ME-2 organic
source apportionment results from 15 individual, co-located aerosol mass
spectrometers
ACSM – Org versus ACSM median-ORG values
for the 13 QACSM Instruments
Crenn et al (2015)
Deviation of Selected Organic Ion Fragments
from the Median Values
f44 follows an opposite pattern compare to the other organic fragments
(a) 50 40
OM
40
f f f f
29 41 43 44
30 C
f f f f
55 57 60 73 20 o
n
20
c
) e
% n
10 t
( r
M a
t
D 0 0 oi
R n
z -10 R
m
D
f
M
-20

-20 (
%
-30
)
-40
-50 -40
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13
ACSM ID
Figure 7. Relative deviation to the median (RDM) of ACSM concentrations and major
fragments (f ) for (a) OM (f , f , f , f , f , f and f ), (b) NH (f and f ), (c) NO (f
mz 29 43 44 55 57 60 73 4 16 17 3 30
and f ), and (d) SO (f , f , f , f and f ) obtained from orthogonal distance regression
46 4 48 64 80 81 98
fits with zero intercept.
Crenn et al (2015)
1c. f44 Timescales for PAM α-pinene
SOA (ACSM)
High OH, Org=100 ug/m3
“Slow” CO rise and fall. Other org masses are “fast”
2
Anantomy of the m/z 44 Signal
Slow rise and fall times on seconds timescale
msDiff = Open - Closed
100 Open
480
4

z60
Closed
/
m
mz30_open
40 mz30_closed
20
30 sec window
11:18:30 AM 11:19:00 AM 11:19:30 AM 11:20:00 AM 11:20:30 AM 11:21:00 AM 11:21:30 AM
8/14/14
dat
Data recording mode can influence how m/z44 is
sampled
Slow rise and fall times of org44 signals on second
timescales can introduce variability in f44
AMS averaging window
(5 sec typ.)
Open Closed
100
480
4

z60
/
m msDiff
mz30_open
40 mz30_closed
20
30 sec window
11:18:30 AM 11:19:00 AM 11:19:30 AM 11:20:00 AM 11:20:30 AM 11:21:00 AM 11:21:30 AM
8/14/14
dat
AMS MS open/closed : 5s (several thousand spectra)
pTOF : 2 ms, 50 ms (Single Particle)
Slow rise and fall times of org44 signals on second
timescales can introduce variability in f44
QACSM measures m/z 44
about 9s after switch
Open Closed
100
80
4
4
60
z
msDiff
/
mz30_open
m
40 mz30_closed
20
30 sec window
11:18:30 AM 11:19:00 AM 11:19:30 AM 11:20:00 AM 11:20:30 AM 11:21:00 AM 11:21:30 AM
8/14/14
dat
QACSM 30s scan, one mass spectra 10-150 amu