Supplementary Information for:
Determination of particulate lead
MILAGRO/MCMA-2006 observations
using
Aerosol
Mass
Spectrometry:
D. Salcedo1, T.B. Onasch2, A.C. Aiken3*, L.R. Williams2, B. de Foy4, M.J. Cubison3, D.R.
Worsnop2, L.T. Molina5,6, and J.L. Jimenez3
1
Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos,
Cuernavaca, México
2
Center for Aerosol and Cloud Chemistry, Aerodyne Research, Billerica, MA, USA
3
Cooperative Institute for Research in the Environmental Sciences (CIRES) and
Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
4
Department of Earth and Atmospheric Sciences, Saint Louis University, Saint Louis,
MO, USA
5
Molina Center for Energy and the Environment, La Jolla, CA, USA
6
Earth Atmospheric and Planetary Sciences Department, Massachusetts Institute of
Technology, Cambridge, MA, USA
* Now at ETH-Zurich, Switzerland
Fig. S1. Topographical map of the Mexico City Metropolitan Area and surrounding region
indicating the approximate location of measurements sites. The division and limits of the Federal
District are shown in black.
2
Fig. S2. 2.5 minute averaged open V and W mass spectra at m/z 206, 207, 208 at a time period
with high Pb signal at T0 (as marked in Fig. 6). Black lines and circles correspond to the HRAMS raw signal. Grey lines are modified Gaussian functions that represent the signal of
individuals ions whose exact mass is indicated by the vertical black lines. The height of the
vertical lines corresponds to the peak height of the modified Gaussian functions. Red lines are the
sum of the individual ion peaks and represent the fitted total signal at the given nominal m/z.
signal
individual ion fits
total signal fit
206
0.3
High Pb event
Pb
5
V mode
Open (Hz)
Open (Hz)
10
0
206.0
207
206.1
206.2
Pb
5
207.0
207.1
207.2
High Pb event
W mode
205.9
206.0
207
206.1
206.2
207.1
207.2
208.1
208.2
Pb
0.2
0.1
206.8
0.3
208
Open (Hz)
Open (Hz)
Pb
0.0
206.9
Pb
5
0
207.8
206
0.1
205.8
0.3
0
206.8
10
0.2
0.0
205.9
Open (Hz)
Open (Hz)
205.8
10
signal
individual ion fits
total signal fit
206.9
207.0
208
Pb
0.2
0.1
0.0
207.9
208.0
208.1
208.2
207.8
m/z
207.9
208.0
m/z
3
Fig. S3. 2.5 minute averaged open V and W mass spectra at m/z 103, 103.5, and 104 at a time
period with high Pb signal at T0 (as marked in Fig. 6). Black lines and circles correspond to the
HR-AMS raw signal. Grey lines are modified Gaussian functions that represent the signal of
individuals ions whose exact mass is indicated by the vertical black lines. The height of the
vertical lines corresponds to the peak height of the modified Gaussian functions. Red lines are the
sum of the individual ion peaks and represent the fitted total signal at the given nominal m/z.
10
signal
individual ion fits
total signal fit
206
High Pb event
V mode
++
Pb
5
0.6
Open (Hz)
Open (Hz)
15
0
Pb
103.0
10
207
Pb
Open (Hz)
0.6
++
5
0
103.1
207
Pb
0.4
++
0.2
0.0
103.4
103.5
208
103.6
103.4
0.6
++
Pb
Open (Hz)
Open (Hz)
W mode
++
0.2
103.1
15
Open (Hz)
206
High Pb event
0.0
103.0
15
0.4
signal
individual ion fits
total signal fit
10
5
0
103.5
208
103.6
++
Pb
0.4
0.2
0.0
104.0
104.1
104.0
m/z
104.1
m/z
4
Fig. S4. Scatter plots showing correlations between the singly and doubly charged lead ions at
T0. V and W from open and closed spectra signals are shown. Lines correspond to linear fits to
the data.
—— W mode linear fit
—— V mode linear fit
-3
20
15
10
5
0
-3
25
20
15
10
5
10
15
20
25
+
30
0
208
10
20
30
40
50
+
60
-3
Pb closed signal (Nit-eq. ng m )
10
5
20
m=0.64; R=0.96
m=0.44; R=0.64
15
10
5
++
207
0
206
Pb
0
0
0
-3
++
Pb
0
15
Pb open signal (Nit-eq. ng m )
-3
closed signal (Nit-eq. ng m )
m=0.49; R=0.96
m=0.39; R=0.80
30
5
207
Pb open signal (Nit-eq. ng m )
35
m=0.47; R=0.78
m=0.39; R=0.74
20
5
10
+
15
20
10
25
30
-3
Pb closed signal (Nit-eq. ng m )
20
30
+
-3
Pb open signal (Nit-eq. ng m )
25
-3
+
0
closed signal (Nit-eq. ng m )
60
Pb
++
Pb
40
207
20
207
Pb
208
0
++
-3
closed signal (Nit-eq. ng m )
open signal (Nit-eq. ng m )
10
25
++
20
m=0.64; R=0.97
m=0.70; R=0.53
25
206
30
208
Pb
30
m=0.51; R=0.83
m=0.34; R=0.61
20
15
10
5
0
206
m=0.47; R=0.94
m=0.42; R=0.90
0
208
single vs doubly charged Pb ions
-3
open signal (Nit-eq. ng m )
40
++
-3
open signal (Nit-eq. ng m )
W mode signal
V mode signal
0
206
10
+
20
30
-3
Pb closed signal (Nit-eq. ng m )
Fig. S5. Time series of 2.5 averaged V open and closed signals for
208
Pb+ ions for a time period
of alternating ambient (closed symbols) and concentrator sampling (open symbols) at T0.
25
208
Pb signal (Hz)
20
+
Pb signal
2.5 min averaged V-mode signal
open
closed
15
10
5
0
02:00 a.m.
21/03/06
03:00 a.m.
04:00 a.m.
05:00 a.m.
5
06:00 a.m.
07:00 a.m.
Fig. S6. Laboratory measurement of the ionization efficiency of Pb relative to NO3 (RIEPb) using
size selected Pb(NO3)2 particles: (red line and circles) laboratory measured Pb+ in open, (black
line and circles) laboratory measured Pb+ in closed. The same model used for the field data is
applied to the laboratory data in order to determine the actual Pb+ input: (yellow line and circles)
modeled incoming Pb+, (dashed black line and circles) modeled Pb+ in closed. Panel (a) shows
data for a vaporizer temperature of 630oC. The model gives a smaller fraction in the slowly
vaporizing component, consistent with the lower Pb+ signal in closed relative to open. Panel (b)
shows data for a vaporizer temperature of 548oC, yielding a higher closed Pb+ signal and a larger
slowly vaporizing fraction in the model. Pb(NO3)2 decomposes at 270oC. The faster vaporizing
component may be flash vaporized Pb(NO3)2, while the slowly vaporizing component may be a
decomposition product with a higher melting temperature, e.g., PbO (melting point 888oC).
300
(b)
125 nm Pb(NO3)2
125 nm Pb(NO3)2
Vaporizer 548 C
Vaporizer 630 C
250
-1
-1
k_slow= 0.04 s
fraction_slow=0.8
Incoming Pb model
Pb open lab
Pb closed lab
Pb closed model
k_slow= 0.01 s
fraction_slow=0.42
Incoming Pb model
Pb open lab
Pb closed lab
Pb closed model
200
800
600
+
Pb Signal (Hz)
150
+
Pb Signal (Hz)
(a)
400
100
200
50
0
0
5
10
15
20
25
Time (min)
30
35
40
5
10
6
15
20
25
Time (min)
30
35
40
Fig. S7. 2.5 minute averaged open and closed V and W mass spectra at m/z 238, 239 and 240
corresponding to PbS ions. Black lines and circles correspond to the HR-AMS raw signal. Grey
lines are modified Gaussian functions that represent the signal of individuals ions whose exact
mass is indicated by the vertical black lines. The height of the vertical lines corresponds to the
peak height of the modified Gaussian functions. Red lines are the sum of the individual ion peaks
Open (Hz)
signal
individual ion fits
total signal fit
V mode
4
206
PbS
+
2
Closed (Hz)
and represent the fitted total signal at the given nominal m/z.
0
207
PbS
238.2
+
1.0
238.0
207
239.0
238.8
0
239.0
1.0
PbS
240.0
240.2
240.4
239.8
240.0
206
PbS
signal
individual ion fits
total signal fit
W mode
Closed (Hz)
Open (Hz)
signal
individual ion fits
total signal fit
+
0.05
206
W mode
+
PbS
0.00
238.0
207
PbS
238.2
238.4
237.8
Closed (Hz)
237.8
0.2
Open (Hz)
240.4
m/z
0.0
+
0.05
0.0
238.0
207
238.2
238.4
239.2
239.4
240.2
240.4
+
PbS
0.00
239.0
208
239.2
239.4
238.8
239.0
208
+
PbS
Closed (Hz)
Open (Hz)
240.2
0.5
m/z
PbS
+
0.05
0.1
0.0
239.8
239.4
+
0.0
239.8
238.8
0.2
239.2
+
PbS
208
+
PbS
2
0.1
238.4
0.5
239.4
Closed (Hz)
208
239.2
4
0.1
238.2
0.0
238.8
0.2
V mode
+
PbS
237.8
0
Open (Hz)
206
0.5
238.4
Closed (Hz)
Open (Hz)
238.0
2
6
1.0
0.0
237.8
6
4
signal
individual ion fits
total signal fit
0.00
240.0
240.2
240.4
239.8
m/z
240.0
m/z
7
Fig. S8. 2.5 minute averaged open and closed V and W mass spectra at m/z 241, 242 and 243
corresponding to PbCl ions. Black lines and circles correspond to the HR-AMS raw signal. Grey
lines are modified Gaussian functions that represent the signal of individuals ions whose exact
mass is indicated by the vertical black lines. The height of the vertical lines corresponds to the
peak height of the modified Gaussian functions. Red lines are the sum of the individual ion peaks
and represent the fitted total signal at the given nominal m/z.
signal
individual ion fits
total signal fit
206
0.2
35
Pb Cl
W mode
+
0.1
0.0
241.0
207
0.2
35
Pb Cl
241.2
206
35
V mode
+
Pb Cl
4
2
240.8
8
Open (Hz)
Open (Hz)
6
0
240.8
0.3
+
0.1
0.0
241.0
6
207
4
35
241.2
241.4
242.2
242.4
243.2
243.4
+
Pb Cl
2
0
242.0
35
+
Pb Cl and
206
37
Pb Cl
242.2
241.8
8 208
+
Open (Hz)
241.8
0.3 208
Open (Hz)
signal
individual ion fits
total signal fit
8
Open (Hz)
Open (Hz)
0.3
0.2
0.1
0.0
242.8
6
242.0
35
+
Pb Cl and
206
37
+
Pb Cl
4
2
0
243.0
243.2
242.8
m/z
243.0
m/z
8
Fig. S9. Scatter plots of PbS+ and PbCl+ isotopic ions when the HR-AMS was sampling through
the concentrator. V and W from open and closed spectra signals are shown. Black lines
2.0
1.5
1.0
0.5
30
40
-3
PbCl open signal (Nit-eq. ng m )
2.0
1.5
1.0
0.5
1
2
3
4
+
5
-3
PbCl closed signal (Nit-eq. ng m )
208
PbS open signal (Nit-eq. ng m )
0
1
2
3
+
4
5
-3
-3
0
208
5
10
15
20
25
+
0
0
-3
PbS open signal (Nit-eq. ng m )
8
6
4
2
0
0
208
PbCl closed signal (Nit-eq. ng m )
2
+
0
+
0.0
4
207
20
6
208
-3
10
+
+
0.0
2
8
5
10
15
20
25
+
-3
PbS open signal (Nit-eq. ng m )
8
6
4
2
+
PbCl open signal (Nit-eq. ng m )
0
208
4
PbS closed signal (Nit-eq. ng m )
+
40
6
206
206
0
207
30
-3
0
208
2
-3
20
+
-3
10
+
PbCl closed signal (Nit-eq. ng m )
206
0
208
4
207
+
2
6
10
5
10
15
+
0
207
4
8
8
+
6
10
10
206
8
12
-3
10
14
PbS closed signal (Nit-eq. ng m )
12
concentrator
PbS ions
-3
-3
PbS open signal (Nit-eq. ng m )
PbCl open signal (Nit-eq. ng m )
14
0
PbCl closed signal (Nit-eq. ng m )
W mode
V mode
—— natural isotopic ratio
concentrator
PbCl ions
-3
PbCl open signal (Nit-eq. ng m )
correspond to the expected isotopic ratio.
20
-3
PbS closed signal (Nit-eq. ng m )
0
208
5
+
10
15
20
-3
PbS closed signal (Nit-eq. ng m )
Fig. S10. The lower panel shows the time series of the open Pb+ signal when sampling through
the concentrator (black lines and circles), and the reconstructed signal as a linear combination of
PbS+ and PbCl+ signals (shaded stacked areas). The upper panel shows the relative residual of the
-3
signal (Nit-eq. ng m )
relative residual
fit ((fit – field data)/field data).
2
0
-2
300
SPb+
SPbS+ * 7.2 (stacked on SPbCl+)
SPbCl+ * 6.2
250
200
150
100
50
0
21/03/06
22/03/06
23/03/06
24/03/06
25/03/06
9
26/03/06
27/03/06
28/03/06
29/03/06
30/03/06
Fig. S11. Wind rose using Radar Wind Profiler for 0 to 500 m of the boundary layer for 208PbS+
and
208
PbCl+ open signals at T0. Shown in blue is the data for low signal levels
(< 3 Nitr.-eq. ng m-3) and in red, data for high signal levels (> 3 ng Nitr.-eq. ng m-3).
208
PbS+
208
PbCl+
PbCl+
PbS+
10