Overview of Frag-table Method

Qi Chen

Nanjing AMS/ACSM Clinic

2018-04-20

Allan et al., J. Aerosol Science 35:909 (2004)Middlebrook, Drewnick, Matthew …

Necessary for quantifying individual aerosol components because:1) more than one ion at unit m/z resolution2) some ions may be formed from the fragmentation

Specific values within the current frag list come from a number of AMS studies from several groups

Not fixed values: users’ responsibility to adjust to specific experiments/conditions

Aiken et al., EST, 42:4478–4485 (2008)

Chen et al., EST, 45:4763-4770 (2011) - SupplementaryCanagaratna, MR, et al., ACP, 15:253-272 (2015)Chen et al., GRL, 42: 4182 (2015) - SupplementarySome other papers

Fragtable for high-loading OA: Amber M. Ortega, Jill Craven …

UMR

HR

CO2+: CO2 and decomposition of particulate OA

Important for low loading (remote) or plumes (high CO2)

…more discussion in Xu, Jianzhong (Xinghua)’s talk

CO+: COair and decomposition of particulate OA

(m/z 28)total = (N2+)air + (CO+)air + (CO+)particle

(CO+)org:(CO2+)org can be estimated from the PToF mode signal

Or, use Ar for lab

2.0

1.5

1.0

0.5

0.0

m/z

44

3.02.52.01.51.00.50.0

1.5

0.0

-0.20.00.2

0

86420

m/z

28

3.02.52.01.51.00.50.0

5

0

-0.20.00.2

0

1

A major ambiguity: H2O+ (OH+, O+) - decomposition of sulfate ororganic, aerosol water, or water vapor. Default frag list rules

used in this case: H2O+(org)=CO2+(org)

AMS_13th_UsersMtg_OxidizedOrganicStandards_Manjula

Determine (H2O+)org

(m/z 18.01)total = (18O+)air + (H2O+)humidity + (H2O+)particle

(m/z 18.01)total = (18O+)air + (H2O+)humidity + (H2O+)unevap + (H2O+)sulf + (H2O+)org

At stable RH: Filter

Or Filter + scan sampling RH

298.3 K296.4 K293.1 K

Chen et al., EST, 45:4763-4770 (2011) Supplementary

(H2O+)unevap + (H2O+)sulf + (H2O+)org

Dry (at 3% RH) ammonium sulfate particles: 0.5 (SO+ + SO2+)

dry completely

scan sampling RH: about 10% of the residual H2O+ -> particle-phase water at 40% RH,

as is consistent with the measurements of hygroscopic growth factor

0.6

0.7

0.8

0.9

1.0

1.1

(H2O

+) o

rg :

((H

2O

+) u

nev

ap+

(H2O

+) o

rg)

806040200

AMS Inlet RH [%]

isoprene photooxidation

-pinene ozonolysis

-caryophyllene ozonolysis

Chen et al., EST, 45:4763-4770 (2011)

SOM(CO+)org: (CO2

+)org

(H2O+)org:(CO2

+)org

[(H2O+)org:(CO2

+)org]frag

this study

isoprenephotooxidation

2.63 ± 0.39 3.91 ± 0.56 2.74 ± 0.39

β-caryophylleneozonolysis

1.22 ± 0.21 1.27 ± 0.22 0.89 ± 0.16

α-pineneozonolysis

1.08 ± 0.16 0.84 ± 0.14 0.59 ± 0.10

Aiken et al.2008

general organic material

1.00 0.225 0.225

Treat Org-H2O as H2O(g): x RIEOrg/RIEH2O

= x 0.7

Also increase organic concentrations by 5-20%

Chamber SOA: R-OOH etc.

Chen et al., EST, 45:4763-4770 (2011)

…more discussion in Huang, Dandan’s talk

AMS_13th_UsersMtg_OxidizedOrganicStandards_Manjula

“Improved Method” for Elemental Analysis for Ambient OA; But should be Specific for Lab OA!!!

Based on Good HR-MS!

Chen et al., GRL, 2015/Updated Ambient and Lab Elemental Ratios for HR- and Q-AMS

Chen et al., GRL, 42: 4182 (2015) - Supplementary

Based on Ng, et al., ACP, 2011

Canagaratna, et al., ACP, 2015

High organic loadings: the effects of anyinterferences by organic species: ON, OS, Others(e.g., BBOA plume)

BBOA – Flame ChamberOver subtraction! Fine for HR but not for ACSM.

AMS_12th_UsersMtg_Ortega_FragTableMods

Clinic_6th_HROgCheckPanel_Donna_EA

(Q-, ToF-) ACSM frag: different from AMS

• Air (ambient-filter): but noisy (shown?), downweighting in PMF!

• Sulfate: more discussion in Liao, Keren’s talk