Side-by-side ambient comparison of Capture vs Standard...
Transcript of Side-by-side ambient comparison of Capture vs Standard...
Side-by-side ambient comparison of Capture vs
Standard Vaporizer
Weiwei Hu, Pedro Campuzano-Jost, Doug Day, Jose L. Jimenez, Phil Croteau, and John T. Jayne
University of Colorado-Boulder & Aerodyne Research
7-Sep-2013: AMS Users Meeting, Prague(Analysis still preliminary)
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Motivation: Field Comparison of OA for 3 AMSs + 1 ACSM (all standard vaporizer)
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So just compare the AMS w SMPS!
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Experimental Setup
HR-AMS 2STD
VAPORIZER,ePToF
HR-AMS 1Capture
VAPORIZER
CU Roof
10 lpm
1.2 lpm
0.6 lpm
0.6 lpm
5 min V5 min W
5 min V/PToF5 min V/ePToF
Both AMS were AN, AS and size calibrated before the comparison
Capture Vaporizer was being run at 4 W, PToF sample time ~ 1 min/5 min cycle
Dry (< 15% RH)
CE = 0.5 for Std vaporizer (per Middlebrook et al., AS&T 2012)
John Jaynes’s presentation forePToF results
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Time Series of Main Species
Using measured IE, NH4 RIE and SO4 RIE on each vaporizer
Fresh Plumes Period, CE=1 was applied to Org in standard Vaporizer
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CaptureStandard
Species scatter plots
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Cap
ture
Standard
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Tge
Monodisperse NH4NO3 in PToF
Capture vaporizer has delayed signals (e.g 30 s for 400 nm), and broader peaks
Capture
Standard
Monodisperse (NH4)2SO4 in PToF
The size distribution of pure (NH4)2SO4 in the capture vaporizer was broadened due to the longer vaporization time. 8
Capture
Standard
Ambient size distribution: Std vs captureShifting the standard vapPToF by 500 us makes the high volatity species (AN) collapse on top of each other. So while delayed and slightly smeared, PToFseems useful!
Warning: Slightly unfair comparison 1% chopper (capture vap) vs ePToF (standard vap)9
CaptureStandard
Sulfate Fragmentation
• Only SO2+ & SO+
• SO2+/SO+ ratio slightly larger 10
CaptureStandard
Nitrate Fragmentation
While detecting RONO2 with the capture vaporizer is not impossible, at ambient concentrations it might be quite challenging… 11
CaptureStandard
HR average spectra (Normalized to 1)
More small fragments (e.g m/z 28, 40, 44) in capture vaporizer, and less higher m/z 12
Capture
Standard
Capture - Standard
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HR Spectra of Fresh “Cooking” Plumes
Capture
Standard
Capture - Standard
f44 comparison and Sally’s Triangle
• f44 is probably still an O/C proxy but some new complications, may need replacement for f43
• m/z 40 and 55 can be enhanced, so possibly we can use those instead 14
f 44
Cap
ture
f44 Standard
Standard
Capture
Nominally higher O/C and lower H/C w/ capture vap.
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Still shows the same evolution Need to re-calibrate the elemental analysis
Capture
Standard
CO+/CO2+ & H2O+/CO2
+
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Cap
ture
Stan
dard
V
Cap
ture
Stan
dard
W
Frag
Tab
le
Stan
dard
V
Stan
dard
W
Frag
Tab
le
Biomass Burning Tracer f60
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Capture
Standard
Non-BB background
Non-BB background
PMF Comparison
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CaptureStandard
Spectra of OA PMF factors
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CaptureStandard
Time series of PMF OA factors
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CaptureStandard
Conclusions• Capture vaporizer works, CE ~1 !
• Need to recalibrate RIEs, O/C…• Slower evaporation, PToF ok for ambient• MS shifted to smaller fragments
• Still see same trends in VK diagram, Sally’s triangle
• Much higher signal at CO2+, H2O+
• Seem to lose f60, organic nitrates• Other tracers may still be usable
• Additional testing for SOAS, to be analyzed21