Quantification of Aerosol Species

with AMS and ACSM:

Presented by: Manjula Canagaratna

2021 Virtual AMS/ACSM User Meeting

Jan 19-22, 2021

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Nitra

te E

quiv

ale

nt

Ma

ss C

once

ntr

atio

n (

µg

m-3

)

16014012010080604020

m/z (Daltons)

Ammonium 4.8 ug/m3Nitrate 5.8Sulphate 9.4Organics 13.4Chloride 0.15

Mexico City 2/2002

Overview

Ion

In

ten

sity (

Hz)

1) How do we convert AMS ion signal to species mass

concentrations in AMS and ACSM?

2) Interferences/ Biases observed with thermal vaporizer

Aerosol Mass Concentrations

Avogadro’s Number (NA), Flow (Q), Molecular weight (MW)

Ionization Efficiency (IENO3 ) – primary calibrant

Collection Efficiency (CES)

Relative Ionization Efficiency (RIES)

(Calibrations and empirical parameterizations)

See Usr mtg talks: Leah Williams, Ben Nault

Apportion ion

intensities to

species

(Frag Table)

Collection Efficiency

Lens TransmissionOverlap between particle

beam and vaporizer

Particle

Bounce on

oven

Huffman et al.

Efficiency with which particles are transmitted to and collected at vaporizer

Collection Efficiency: EL

Standard Lens: Liu et al. (2007)

EL: Size dependent Transmission through lens

AMS, ACSM, SP-AMS: All use same Lens, same CEL effects

PM2.5 Lens: Xu et al. (2017)

See usr mtg Talk: Ben Nault, Day2 AM

• The lens cutoffs should to be taken into

account when comparing AMS with other

instruments

How de we account for this in AMS concentration

calcs?

• Since the curve for each lens is slightly different

from these curves, we do not directly apply these

curves to correct the AMS measurements.

Collection Efficiency: Es

Most particles (even aspherical soot particles) are collected with

greater that 95% efficiency.

Huffman et al. AS&T. 2005

Es: Overlap

between particle

beam and

Vaporizer

Use Es =1 for most situations

Standard Vaporizer: Eb is dominant contribution to CE.

Bounce depends on particle phaseReferences: Matthew et al.,AS&T, 2018.

Quinn et al., JGR, 2006. Allan et al., JGR, 2004,Drewnick et al, AS&T, 2004. Docherty, AS&T, 2013, Middlebrook et al.,

AS&T, 2011

Collection Efficiency: Eb

Eb < 1 (solids), Eb =1 (Liquids)

1) Nitrate content

2) Acidity

3) Relative humidity in sampling line

Ambient

CE≈ 0.5 (internally mixed SO4)

Empirical parameterization for ambient

particles (Middlebrook et al.)

• Included in analysis programs

Lab Eb values are highly variable.

Calibrate CE OR use SMPS for

concentrations

Capture Vaporizer to increase Eb

AMS and ACSM: SV

CE dominated by Eb = f(composition,phase, size)– Ambient- Empirical parameterization

– Lab – Measure explicitly

AMS and ACSM: CV

Eb = 1

Fragmentation patterns of CV different from SV

Need to account for these changes in frag patterns

when quantifying species

Eb: Correction

factor for particle

bounce off

vaporizer

CV: Capture

SV: Bounce

Xu et al., AS&T, 2017

SV: Flash Vap

Hu et al., AS&T,2017

Ambient Aerosol

during SOAS

field campaign

Collection Efficiency: SP-AMS

Onasch et al., AS&T, 2015

SP2 Module: 1064 nm laser

Lens TransmissionOverlap between particle beam

and laser beam (ES <1)

Particle

Bounce

AMS Mass Quantification

Converting AMS ion signal to species mass

Collection Efficiency (CE)

Relative Ionization Efficiency (RIES)

- Measure of (ions/unit mass)s / (ions/unit mass)NO3

NOTE: if you use RIES=1, then mass concentration is

expressed as NITRATE EQUIVALENT MASS

RIE (Relative Ionization Efficiency)Inorganic Species

Early lab calibrations on inorganics by Frank Drewnick, Ann Middlebrook

RIENO3 accounts for fact that NO3 mass loading is calculated from additional ions besides m/z 30 and 46 used in NO3 IE calibration

Other inorganic RIEs are variable and should be calibrated

RIENH4 - 3-5

RIE SO4 - 1.2 (0.5-2)

RIE Cl - 1.3 (1.6-2.5)

RIE (organic species, OA)

Ambient OA is made up of thousands of individual

organic species. What do we use as a calibrant?

Ambient Measurements:

- RIEOA = 1.4 is based on

laboratory work

(Jimenez et al., AS&T, 2016)

Dependence of RIEOA on OSc

Lab RIEOA = 1.7 for Osc > -1.5 (within 20% of 1.4 used for ambient)

Should we use different RIE for ambient POA and SOA components?

Xu et al. AS&T,(2018)

See Usr mtg talks: Day 1, PM

Offsetting of RIE by CE differences?

RIE (POA) > RIE (SOA)

CE (POA) < CE (SOA)

RIEOA of POA and SOA

Jimenez et al. AS&T, 2017

Large biases not observed for

ambient OA mass calculated with

constant RIE =1.4 (even for high

POA content)

More ambient measurements needed to

derive variable RIE parameterizations

Organic Nitrates (ON) and Sulfates (OS)

1) Investigate fragment ion

ratios

ON: 30 (NO+)/m/z 46 (NO2+)

typically ranges from 5-10

IN: typically 2-3(Fry et al., ACP, 2009, Bruns et al., ES&T, 2010. Farmer et al., PNAS, 2010, Boyd et al., ACP, 2015,Kiendler-Scharr, GRL, 2016, Ng et al., ACP, 2017)

OS: SOX+ ratios

(Phinney et al., Deep Sea Res, 2006. Ge et al., Environ. Chem., 2012., Gilardoni, PNAS, 2016.

Song., ACP, 2019. Chen et al., ES&T, 2019)

2) Lab Calibrations

3) Combined PMF (organic

and inorganic)

See Usr mtg talks: Day 3, AM

Kiendler-Scharr, GRL, 2016.

Chen et al., ES&T, 2019

C-S or C-N containing fragments are minor

Quantification of semi-refractory species

• Slow vaporization- Monitor open &closed signal

- Ions have different vaporization

timescales.

- Pick fragment ions with

faster response for quantification

(e.g. NaCl+, HCl+)

• Pb, NaCl, metal halides (e.g., chlorides,

bromides or iodides of Al, Ba, Cd, Cu, Fe, Hg,

K, Na, Pb, Sr, Zn)

• Reactions on

vaporizer

Salcedo et al., AS&T, 2010. Ovadnevaite et

al., JGR, 2012. Drewnick et al., AMT, 2015.

Drewnick et al., AMT, 2015.

Ambient Cl : Tobler et al., AMT, 2020.

See Usr mtg talks: Day 3, AM

“Pieber” Effect

Pieber et al. ES&T, 2016.

Multiple ACSM instruments at ACMCC(Freney et al., AS&T, 2019)-Application of lab calibrations of Pieber effect for pure

NH4NO3 can overcorrect ambient data-Pieber effect is a function of NO3_MF

-In ambient, NO3_MF < 50% most of the time So, Pieber effect small, but should be aware of it

(test mixtures of (NH4)2NO3 and

(NH4)2SO4)

The End

Thank you for your attention!

Happy to take questions now or at end of

session.

Questions : mrcana@aerodyne.com