Benjamin A. Nault, Pedro Campuzano-Jost, Doug A. Day, Hongyu Guo, Jason C. Schroder, Jose L. Jimenez, and the Science Teams from KORUS-AQ and ATom

Transcription

1 AMS Quantification Calibrations and Comparisons from Recent Campaigns Benjamin A. Nault, Pedro Campuzano-Jost, Doug A. Day, Hongyu Guo, Jason C. Schroder, Jose L. Jimenez, and the Science Teams from KORUS-AQ and ATom 1

2 When AMS is fully and carefully calibrated and characterized, the measurements are completely quantitative MC-IC Sulfate Slope: 1.11, r2 =.72 AMS Sulfate (IC Resolution, Response Adjusted) /22/216 Sulfate (µg sm 3 ) 2 1 AMS Sulfate (µg sm 3 ) 2 1 1:1 Line 8/18/216 8/14/216 8/1/216 8/6/216 8/2/216 8/1/216 8/3/216 8/4/216 8/7/216 8/9/216 8/13/216 8/15/216 Time 8/17/216 8/2/216 8/22/216 8/23/ SAGA MC-IC Sulfate (µg sm 3 ) 3 4 2

3 When AMS is fully and carefully calibrated and characterized, the measurements are completely quantitative UHSAS PM1 Volume Slope:.95, r2 =.92 AMS Volume (including SS and BC) 14 8 PM 1 Volume (µm 3 cm 3 ) /3/216 8/2/216 8/4/216 8/7/216 8/9/216 8/13/216 8/15/216 Time 8/16/216 8/17/216 8/2/216 8/22/216 8/23/216 AMS Volume (incl. BC and SS) (µm 3 cm 3 ) :1 Line UHSAS PM 1 Volume (µm 3 cm 3 ) 6 8 8/22/216 8/2/216 8/18/216 8/16/216 8/14/216 8/12/216 8/1/216 8/8/216 8/6/216 8/4/216 8/2/216 7/31/216 3

4 Calibrations (not including exotic species) General Calibrations Transmission Curve First Order Intercomparisons Filter Evaporation 4

5 Current CU-AMS Aircraft Configuration General Calibrations Transmission Curve First Order Intercomparisons Filter Evaporation 5

6 General Calibrations General Calibrations Transmission Curve First Order Intercomparisons Filter Evaporation 6

7 Calibrations of the Ammonium Salts for RIEs and Ion Ratios See John Jayne s, Manjula Canagaratna s, and Phil Croteau s Talks Calibrate NO 3 IE as often as possible (for aircraft). Look for changes in AB to help determine if you should calibrate for ground (4/28 for MCP) For ground, calibrate as often as you feel comfortable (maybe 2 4 days) Calibrate everything before and after a filament change Calibrate SO 4 RIE Average observed during one campaign 1.56 Typical value in Batch Table is 1.2 The NO 2 :NO ratio, NH 4 RIE, and CO 2+ /NO 3 Artifact NO 2 :NO ratio needed for particle organic nitrate values NO 2 :NO ratio can be used for instrument performance evaluation Ideally, calibrate Chl before and after campaign Typically not much non-refractory Chl Chl can linger on vaporizer, causing artifacts General Calibrations Nault, Campuzano-Jost, Jimenez et al., ACPD, (SI Fig. 3) Transmission Curve First Order Intercomparisons Filter Evaporation 7

8 IE, RIE, and Comparisons NOT Always Stable General Calibrations Transmission Curve First Order Intercomparisons Filter Evaporation 8

9 Impact of Mixtures vs Pure Ammonium Salts on the RIEs No variation of RIE from pure particles to mixtures of variable composition This implies that RIE should be constant for ambient particles as composition varies NO 3 /(NO 3 + SO 4 ) General Calibrations Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig. 7 Transmission Curve First Order Intercomparisons Filter Evaporation 9

10 Impact of Mixtures vs Pure Ammonium Salts on the RIEs Field Data Lab Calibrations General Calibrations Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig 6 Transmission Curve First Order Intercomparisons Filter Evaporation 1

11 Calibrating (e)ptof PSLs provide calibration of (e)ptof, and a check of the sizing of the DMA calibration system as well Check the DMA sizing of NH 4 NO 3 (and its lack of evaporation) by comparing with PSL cals Calibrate at beginning of intensive measurements Calibration only works for a given pressure inside the lens E.g. if flying in aircraft may experience some changes in lens pressure calibrate (e)ptof at those pressures as well! Vacuum General Calibrations Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig 5 Transmission Curve First Order Intercomparisons Filter Evaporation 11

12 Calibrating vaporizer temperature for nonrefractory compounds and to minimize refractory compounds Leah Williams General Calibrations Transmission Curve First Order Intercomparisons Filter Evaporation 12

13 Select power setting prior to sharp NaNO 3 PToF peak INSTRUMENT DEPENDENT! Depends on boards and vaporizer Only needs to be calibrated at beginning of intensive measurements, UNLESS: Any boards are changed Vaporizer was changed Wires were changed Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig 8 General Calibrations Transmission Curve First Order Intercomparisons Filter Evaporation 13

14 Check MCP voltage not too low & calibrating single ion - Instrument Specific General Calibrations Air Amm MSA Transmission Curve First Order Intercomparisons Filter Evaporation Ratio of air ions shows that for big ions, the stable setting is ~1.8 mv ns, or ~21 V Air ions show that for small ones, the stable setting is ~1.3 mv ns, or ~2 V For aerosol, same trend INSTRUMENT & MCP SPECIFIC, CHANGES IN TIME! NEED TO CALIBRATE

15 Conclusion on Calibrations Calibrate NO 3 IE and NH 4+ RIE frequently (for aircraft) and as often as you feel confident (for aircraft, laboratory, ground) Provides insight into instrumental performance Prevents headaches later if the instrument values drastically change Provides insight into NO 2+ /NO + ratio But problems can be introduced when trying to calibrate (need a lot of practice) Calibrate SO 4 2- RIE frequently as well Our group has consistently observed the calibrated RIE is not the same as the default value in Squirrel/PIKA Only calibrate halogens beginning and end of campaign RIEs not impacted by mixtures Calibrate (e)ptof sizing at beginning of measurements Calibrate vaporizer temperature once a campaign/intensive laboratory study (more often if parts or electronics are replaced) Check MCP voltage is appropriate before and during the campaign General Calibrations Transmission Curve First Order Intercomparisons Filter Evaporation 15

16 Transmission Curve 16

17 Differences in two different literature transmission curves Transmission (%) Aerodynamic Diameter (nm) Liu et al. (27) Hu et al. (217b) Ideally, calibrate at least once prior to intensive measurements If in a moving environment (e.g., airplane, mobile lab), may need to calibrate more often during intensive measurements (it can change, although unusual) BE CAREFUL! Mass based transmission curves can be challenging due to doubly-charged particles at low concentrations. (ET cal can be found at this talk). Need to know the curve to do quantitative comparisons with other measurements or with models MAYBE instrument specific 17

18 CU AMS, beginning of one campaign Campaign 1a 12 1 Transmission (%) Aerodynamic Diameter (nm) 18

19 CU AMS, end of campaign Campaign 1a Campaign 1b 12 1 Transmission (%) Aerodynamic Diameter (nm) 19

20 CU AMS, campaign 2 years later Campaign 1a Campaign 1b 12 1 Campaign 2 Transmission (%) Aerodynamic Diameter (nm) 2

21 CU AMS, campaign 1 year later Campaign 1a 12 Campaign 1b 1 Campaign 2 Campaign 3 Transmission (%) Aerodynamic Diameter (nm) 21

22 Using Beam Width Probes to Probe Transmission Use BWP to spot check center of air and particle beam every day (flight calibrate every day) Changes in location of center of particle beam full transmission curve calibration realignment full transmission curve For aircraft measurements, have not seen center of beam move after each flight (and some VERY rough landings) 22

23 Comparison of two AMSs during 1 campaign AMS Lens Transmission curve > 2 nm from Hu et al. (217b) CU-AMS Ammonium Nitrate Mass Transmission Calibration CU-AMS Ammonium Nitrate Event Trigger Transmission Calibration K-AMS Ammonium Nitrate Mass Transmission Calibration Fit to K-AMS Transmission Calibration Average CU-AMS BL PToF Transmission (%) Normalized PToF Distribution Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig Aerodynamic Diameter (nm) 23.

24 Average size distribution of species peaked above size cut-off for one AMS Ambient size distributions Transmission (%) AMS Lens Transmission curve > 2 nm from Hu et al. (217b) CU-AMS Ammonium Nitrate Mass Transmission Calibration CU-AMS Ammonium Nitrate Event Trigger Transmission Calibration K-AMS Ammonium Nitrate Mass Transmission Calibration Fit to K-AMS Transmission Calibration Average CU-AMS BL PToF OA pno 3 SO 4 NH Normalized PToF Distribution Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig 26 Nault, Campuzano-Jost, Jimenez et al., ACPD, Aerodynamic Diameter (nm) 24.

25 Very different fits and R 2 between periods with high and low aerosol sizes Periods when ambient PM 1 below size cut-off Period when ambient PM 1 above size cut-off Capture Vaporizer AMS (µg sm 3 ) Standard Vaporizer AMS (µg sm 3 ) Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig

26 The fit is more exponential due to transmission curve Periods when PM 1 below size cut-off Period when PM 1 above size cut-off Capture Vaporizer AMS (µg sm 3 ) Standard Vaporizer AMS (µg sm 3 ) Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig

27 Conclusions on transmission curve calibration This should be done prior to start campaign/laboratory study Spot checks throughout study maybe necessary, as alignment/performance may change Calibrated transmission curve is NECESSARY to compare against volume and other aerosol measurements Calibrated transmission curve is NECESSARY to know what is being measured and in order to be able to provide insight on the chemistry 27

28 First order comparisons 28

29 Total nr-pm 1 measured by capture and standard vaporizer agreed across different collection efficiencies Nault, Campuzano-Jost, Jimenez et al., ACPD, SI Fig 28 Standard Vaporizer / Capture Vaporizer Calculated Dry SV CE

30 Comparison of calculated PM 1 volume (AMS species +... ) versus any optical particle counter (OPC) Settings for Laser Aerosol Spectrometer Air flow AMS OPC I believe you re right in concluding that the differences at high concentrations are caused by saturation or particle coincidence in the LAS. We ve been talking to another collaborator about deploying a sample dilution system during FIREX-AQ so that we can avoid these types of problems when flying through fresh biomass burning plumes. (PI of LAS OPC team) Nault, Campuzano-Jost, Jimenez et al., ACPD, /acp supplement.pdf 3

31 Comparison of total PM 1 versus optical volume measurement Nault, Campuzano-Jost, Jimenez et al., ACPD, /acp supplement.pdf, SI Fig 3 31

32 Investigating whether Organic RIE caused the discrepancy (a) Ratio, All Data 1 Line (AMS+BC)/LAS Volume Ratio (b) OA/Total AMS Mass (c) Nault, Campuzano-Jost, Jimenez et al., ACPD, /acp supplement.pdf, SI Fig LAS Number Concentration (particles cm 3 ) 2 4 AMS Total Mass (µg sm 3 ) 6 32

33 Instead, it appears that optical saturation of the LAS is causing the discrepancy Nault, Campuzano-Jost, Jimenez et al., ACPD, /acp supplement.pdf, SI Fig

34 Improved slopes when saturation is taken into account Submicron Volume (µm 3 cm 3 ) (a) 9: AM 22-May : PM 3: PM Local Time AMS + BC Volume (µm 3 cm 3 ) (b) 2 4 LAS Volume (µm 3 cm 3 ) 6 8 Legend LAS Volume AMS + BC Volume 1:1 Line All Data; y = 1.56(±.1)*x 1.88(±.13); R 2 =.86 Data by # Conc (16 part./cm 3 ); y = 1.25(±.1)*x.2(±.6); R 2 =.85 Filtered by #: Slope = 1.25, R 2 =.85 Filtered Data by Mass Conc. (4 μg sm 3 ); y = 1.21(±.1)*x.32(±.8); R 2 =.87 Filtered Data by by # Conc Mass (16 part./cm (4): 3 + <.35 μg smslope 3 Ca 2+ ); = 1.21, R 2 =.87 y = 1.19(±.1)*x+.12(±.3); R 2 =.91 Filtered by Mass (2): Slope = 1., R 2 =.79 Filtered Data by Mass Conc. (2 μg sm 3 ); y = 1.(±.1)*x+.19(±.3); R 2 = AMS Total Mass (µg sm 3 ) 4 5 Nault, Campuzano-Jost, Jimenez et al., ACPD, /acp supplement.pdf, SI Fig

35 Conclusions for first order intercomparisons Be aware of size cut-offs prior to comparisons E.g., optical particle counters have a lower size cut that s often larger than the small size cut for the AMS OPCs measure particles above the AMS size range Be aware of other instrumental limitations OPCs can easily saturate under moderately polluted conditions. OPC operators are not always aware of this, and it is easy to blame the AMS Nault, Campuzano-Jost, Jimenez et al., ACPD,

36 Filters 36

37 Aircraft OFR Operation Air flow PAM Residence Time: 2.5 minutes P A M AM S Sample Residence Time to AMS:.4 sec Filters collected and handled for ~3-15 minutes

38 Losses of organic aerosol mass during hot periods due to evaporation Sit in the field at ambient T for few days after sampling, shipped without refrigeration Kim, Campuzano-Jost, Jimenez et al., ACP, 215 Measured in situ every 1 hr 38

39 Comparison of AMS and filter NO 3 measured on airplane changed with date 3 Slope = 1.21, R 2 =.69 1:1 Line 25 6/1/216 AMS NO 3 (μg sm 3 ) /31/216 5/21/216 5/11/216 Date Filter NO 3 (μg sm 3 ) Heim, Dibb, Nault, Campuzano-Jost, Jimenez et al., JGR, in review 39

40 However, total nitrate (PM 1 NO 3 + HNO 3 ) agreed throughout campaign Heim, Dibb, Nault, Campuzano-Jost, Jimenez et al., JGR, in review 4

41 Ammonium nitrate shows large losses in non-chemistry OFR as there was a large temperature difference OFR Mass Concentration, Lights Off (µg sm 3 ) (a) SO 4 Slope =.9, R 2 =.96 NO 3 Slope =.18, R 2 =.71 NH 4 Slope =.51, R 2 =.9 1:1 Line Normalized Distribution (b) Ambient Mass Concentration (µg sm 3 ) Cabin Temperature Ambient Temperature (K) Heim, Dibb, Nault, Campuzano-Jost, Jimenez et al., JGR, in review 41

42 Differences between OFR and Ambient are same as differences between Filter and Ambient Ambient OFR NO 3 (μg sm 3 ) (a) -5 Data y = *x, R 2 = AMS Filter NO 3 (μg sm 3 ) 2 25 Ambient OFR NH 4 (μg sm 3 ) (b) Data y = *x, R 2 = AMS Filter NH 4 (μg sm 3 ) Heim, Dibb, Nault, Campuzano-Jost, Jimenez et al., JGR, in review 42 15

43 Conclusions for comparisons with filter measurements Though not shown here, be aware what size cut-off is for filters vs AMS BE CAREFUL: Be aware sampling time and handling of filters. May cause evaporation of aerosol species. Also, handling of filters may lead to other forms of biases (positive or negative) E.g. if particles are very acidic, filters will pick up NH 3 (g) from human breath etc., and show particles that are more neutralized than what the AMS sees 43