Preliminary Whistler HR-ToF-AMS Data

Shao-Meng Li, John Liggio, Kathy Hayden, Qi Zhang

Others:

D. Worsnop, R. Leaitch, A.Macdonald, D. Halpin, J.Deary, M. Cubisan.

ToF-AMS Instrument Details

• Provides detailed particle mass spectra with high time resolution ( 5 min @ whistler)

• Quantifies particle sulfate, nitrate, ammonium, and total organic mass (< ~1 um diameter)

• Quantification based on relative Ionization efficiency (IE)• size segregated mass distribution for every m/z• Higher mass range than Q-AMS (~800 amu)• Two modes of operation:

– V-mode: High sensitivity (20X more than Q-AMS), better than unit mass resolution

– W-mode: Lower sensitivity (~same as Q-AMS), high mass resolution (~5000 vs 20 for the Q-AMS)

– Alternated between modes (5 min each)

Status of HR-ToF data

• April 19 @18:20 – May 16 @18:35, ~66% data recovery, data gaps due to many different instrument problems

• Particle concentrator was used intermittently • Concentrator on/off time periods in the data have been defined

– Δ[SO42-] used as indicator and to determine enhancement factor

• Ionization efficiency (IE) nominally determined, nominal factors have been applied to data

• Particle time-of-flight calibration function analyzed, but size distributions need work – (need to develop a routine to minimize effect of noisy m/z’s)

Whistler HR-ToF AMS April-May 2006

Courtesy: Peter Liu

Asian Dust

Vmode concentrator on

Not corrected for concentrator enhancement

factor

Case 2: Possible Valley Influence (biogenic component?)

High organics, May 15 evening to May 16 evening

Case 1: Possible Transport Layer

High sulphate, May 15 morning to afternoon

Transport Layer

Case 1:Case 2:

*

Oxygenated organics (CO2

+)

C4H9+, C3H5O+

Biogenic signature

1

2

Cessna 207 Aircraft ProfilesFlight 30, May 15, late evening (~6pm)

0

1000

2000

3000

4000

5000

6000

-5 0 5 10 15 20 25

PCASP divided by 100

AMS Sulphate

AMS Organics

Temp

PCASP <0.6um massest.

0

1000

2000

3000

4000

5000

6000

-5 0 5 10 15 20 25

PCASP divided by 100

AMS Sulphate

AMS Organics

Temp

PCASP <0.6um massest.SO4+Org

UP

DOWN

•boundary layer ~2000 m

•SO42- increased between 2600-

2900 m, above boundary layer (UP)

•layered elevated organics: 2200-2900m and 3000-4000 m

•at tail end of high SO42- observed at

Whistler site (Case 1)

•transport layer

Comparison of High Sulphate vs High Organic Periods

44

44

Mass Resolution of V versus W mode

High Resolving Power of ToF-AMS

100

80

60

40

20

0

Inte

nsi

ty

100806040200

m/z

(CH

4SO

3)+

(CH

3SO

2)+

(SO

2)+

(SO

)+

(CH3)+

(CH

3O)+

(HS

O3)

+

MSA (NIST) MSA (AMS)

(HS

O2)

+

Path ForwardPath Forward• Quantify biogenic sulphur – ie: MSA in particles with AMS

CH3 S

O

O

OH

• Use ToF-AMS data to infer particle sources- Principal component analysis (PCA)

• Quantify the biogenic component of aerosols at whistler

Path Forward…Path Forward…