4 th AMS Users Meeting Brainstorming on (1) Experiments to Nail our Absolute Quantification (2) Best Operating Procedures

Transcription

1 th AMS Users Meeting Brainstorming on (1) Experiments to Nail our Absolute Quantification () Best Operating Procedures Jose-Luis Jimenez Caltech Pasadena, CA Oct. -7, Reminder of the Quantification Issues. Quad. Transmission & multiplier response vs. m/z 1. IE NO3 (Number of molecules in calibration particles). RIE species (specially organics) 3. Fragmentation patterns of species (organics). Transmission vs. D va 5. Collection efficiency due to shape Shape factor vs. beam width

2 Issue #: Quad and Multiplier vs. m/z From Jimenez et al. (3), Paper # on web page T m/z : transmission of the quadrupole vs. m/z Should be quite flat according to Balzers Hard to measure G m/z : gain & detection efficiency of multiplier Easy (if laborious) to measure gain Harder to measure detection efficiency (compare to Faraday cup) Issue #1, Part 1: IE NO3 Maybe another molecule? DMA vs APM experiment APM classifies vs. particle mass With Peter McMurry With Ehara AIST in Japan With Japanese company Kanomax Inc. Nobu will investigate DMA vs Ion Chromatography Next time you are next to a PILS Tim Bates & Trish Quinn, Eiko & David, Caltech, Ann, Leaitch Coordinate with Roya (S and beam width)

3 Is H O evaporating into the lens from the calibration particles? Some evidence for this Hyper drying experiment With second DMA (TDMA) Ann & Brendan: don t think this can be important Already did drying Atomization in methanol did not change IE_NO3 Rick: can produce by evaporation & condensation Brendan: walk beam around heater to check IE_NO3 (IPP) as a function of position on the vaporizer Issue #1, Part : IE NO3 Understand differences between χ and χ v Search literature Experiments with PSL doublets Kousaka, aerosol journal Osaka prefecture university

4 Issue #1, Part 3: IE NO3 Follow up on Brendan & Ann s experiments Account for all m/z s If we are really losing particle mass, can we design a different critical orifice that minimizes this effect? Measure beam width as a function of mode Issue #: RIE species We have to do more experiments Important to: Count particles See if there could be shape effects AMS / CPC counting % +/-% for NHNO3 Care with q >= from DMA S ( Jayne shape factor or effective density )? Beam width with the wire Condense oleic acid after DMA Look at single particle signal Experiments with APM & IC or other techniques With TDMA, calculating the mass from G f Use lens simulation results to look at this Jose & Feng Dry vs. wet calibrations Check IPP Ann & Brendan Rami will redo some of this (oleic acid, fulvic acid, i )

5 Issue #3: Fragmentation Patterns for Species Do more experiments Ann for inorganics (Frank) Vs. vaporizer temperature: 6C (NaNO3 pulse width) Especially for organics Rami, Kathy & Shao-Meng (Organic nitrates) Mixed organic/inorganic Brendan CE & fragmentation Look for matrix effect when mixing low and high volatility species Issue #: Transmission vs. D va for spheres Lab experiments with monodisperse particles Large end May not depend on D va if they are lost at critical orifice Particles may bounce after C.O. liquid vs. solid Aerodyne & Brendan-Ann & Peter Liu Small end Aerodyne & Peter Liu Comparison of tails with APS (> 8 nm for D a_aps ) or OPCs or MOUDI or anything else you can get your hands on Jose & Peter, Ann for Ron Brown, UMIST + Peter Impactor with controlled flow to vary the cut MOUDI

6 Issue #5: Characterizing CE due to shape Use the beam width probe systematically Measure beam width and S for various species Roya Measure spheres at various sizes, compare to ambient -Jose More ambient data & analysis Brendan may look at NaCl & other salts PSL doublets Microscopy: (NH ) SO before and after vacuum UMIST, collaborate with Peter Busek (Scot Martin) Electrometer either at the oven or at the wire Look at Paul Ziemann s work Compare to other instruments PILS, others Tokyo, Richard Leaitch MSC Comprehensive constrained model Peter & Jose Explore the theoretical aspects Rick? RH control dry vs humid UMIST

7 Issue #5: Mitigating CE due to shape Shortening the chamber cm cm later on Existing instruments T and RH control RH-Control Both will perturb the aerosol, but T+RH will always be worse Ambient data Pandis: 35% SOA evaporation for C Filters: can loose 3% of mass to evaporation Concentrator data (coming up) Careful not to add NH3 along with the HO Cycle dry and humid on square wave Denuders? Important not to introduce a problem as we fix another one! Uncontrolled Inlet Temperature 35 3 Temperature Cenica AMS inlet Temperature (C) 5 15 /6/3 /11/3 /16/3 /1/3 /6/3 5/1/3 8 Relative Humididty Cenica AMS inlet relative humidity /6/3 /11/3 /16/3 /1/3 /6/3 5/1/3

8 RH-Control System (Don Collins) From Don Collins a couple of weeks ago: We briefly described the technique in a paper we recently submitted to Atmospheric Environment. I have attached a schematic that I sent to Peter McMurry and crew a couple of years ago. I think the only thing that has changed since then is that we use Teknocraft valves instead of Alicat. The approach is embarrassingly simple, but it works pretty well. Nitrate Partitioning

9 5 3 Sept, Average size dist Sulfate Sept, Average size dist Ammonium Sept, Average size dist Nitrate Sept, Average size dist Organics Solid lines: concentrator off dashed line: concentrator on Sept 18, Average size dist Sulfate Sept 18, Average size dist Ammonium Sept 18, Average size dist Nitrate Sept 18, Average size dist Organics Solid lines: concentrator off dashed line: concentrator on

10 15 5 Sept 19, Average size dist Sulfate Sept 19, Average size dist Ammonium Sept 19, Average size dist Nitrate Sept 19, Average size dist Organics Solid lines: concentrator off dashed line: concentrator on