molecular characterization of organic aerosols from the los angeles ground site during the calnex...

Molecular Characterization of Organic Aerosols from the Los Angeles Ground Site during the

CalNex 2010 Campaign Using High-Resolution Mass Spectrometry

T. Nguyen, N. Levac, D. Bones, A. Bateman, S. NizkorodovUniversity of California, Irvine

A. Laskin, J. Laskin, P. Roach, B. HeathPNNL

Specific Objective: Nitrogen Containing Organic Compounds

• Ubiquitous in atmospheric aerosol, yet poorly characterized on a molecular level

• May contributed to adverse health effects of particulate matter

• May absorb visible light and contribute to “brown carbon” aerosol

Conventional "Brown Carbon"• HULIS from biomass burning• Organic light-absorbing material from vehicular

emissionsAndreae, Gelencser, Atmos. Chem. Phys. 2006 Jacobson J. Geophys. Res. 1999

"Brown Carbon" from SOA Aging

Fresh SOA: scatters light; COOLS the surface

NH3 or amines

Aged SOA: absorbs light; WARMS the surface

• Known to contain hetero-N compounds• Both biogenic and anthropogenic SOA undergo this type of aging

Laboratory Studies (e.g. Bones et al, JGR 2010; Laskin J, et al Anal.Chem. 2010; Nakayama et al, JGR2010; De Haan et al, EST 2011)

Field Observations: Mexico city (Roach, et al Anal.Chem. 2010), Shanghai (Wang et al, EST 2010)

PILS (Particle-Into-Liquid Sampler)Particles collected straight in water30 min per sample

Types of Samples Collected

Substrates for SEM/EDX, X-ray spectro-microscopy, and Ice Nucleation studies

MOUDI Cascade Impactor

Particles collected on Teflon and Al foil substrates6-hours per set of size segregated samples0-6 am; 6 am - noon; noon -6 pm; 6 pm - midnight

PILS

High-Res.MS

Optical Microscopy of Heterogeneous Ice Nucleation

Bingbing Wang Dr. Daniel Knopf

Poster 38

Advantages of High Resolution MS

Analysis of OA Using Nano-DESI MS

Routine analysis of <10 ng OA Probe size <100 mm

Promising Days for the HR-MS AnalysisAMS data from P. Hayes, J. Jimenez et al. (U. Colorado)

June 5: unusually large “ amine OA" signal in the morning

Nano DESI HR-MS

0 200 400 600 800 1000 12000

1x104

2x104

3x104

4x104

5x104

6x104

inte

nsity

, arb

. uni

ts

m/z

June 5 IB-6

200 400 600 800 1000 12000.0

5.0x103

1.0x104

1.5x104

2.0x104

2.5x104

3.0x104

3.5x104

4.0x104

inte

nsity

, arb

. uni

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m/z

June 5 IIA-6

200 400 600 800 1000 12000

1x104

2x104

3x104

4x104

5x104

inte

nsity

, arb

. uni

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m/z

June 5 IIIB-6

200 400 600 800 1000 12000

1x104

2x104

3x104

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inte

nsity

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m/z

June 5 IVA-6

200 400 600 800 1000 12000.0

5.0x104

1.0x105

1.5x105

2.0x105

inte

nsity

, arb

. uni

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m/z

June 6 IIB-6

LVOOALVOOA

SVOOA

SVOOA

~40% peaks assigned

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

100 300 500 700 900

LVOOA and SVOOA are Chemically Related

C15H26O -(CH2)x H+

C16H30O3 -(CH2)x H+

C20H36O4 -(CH2)x H+

C38H64O6-(CH2)x H+

KMCH2, Da

KMD CH

2

(sample 6:00-12:00) LVOOA

SVOOA

0.0 0.1 0.2 0.3 0.4 0.5 0.60.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35fra

ctio

n

O/C

June 5 IB-6

0.0 0.1 0.2 0.3 0.4 0.5 0.60.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

fract

ion

O/C

June 5 IIa-6

0.0 0.1 0.2 0.3 0.4 0.5 0.60.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

fract

ion

O/C

June 5 IIIA-6

0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.1

0.2

0.3

fract

ion

O/C

June 5 IVA-6

O/C Histograms

0:00-6:00 6:00-12:00

12:00-18:00 18:00-24:00

CxHyNz fresh emissions..?

0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.1

0.2

0.3

0.4

0.5

0.6

fract

ion

N/C

June 5 IB-6

0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.1

0.2

0.3

0.4

0.5

0.6

fract

ion

N/C

June 5 IB-6

0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.1

0.2

0.3

0.4

0.5

0.6

fract

ion

N/C

June 5 IB-6

0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.1

0.2

0.3

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0.6

fract

ion

N/C

June 5 IB-6

N/C Histograms

0:00-6:00 6:00-12:00

12:00-18:00 18:00-24:00

CxHyNz

N-Organics in CARES samples (DOE 2010 field study)

Photos: S. Springston R. Zaveri

Sacramento, T0 site

Nanospray DESI – Line Scan Analysis

Nanospray DESI – Line Scan Analysis

200 300 400 500 600

1x103

2x103

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CxHyN1CxHyN2

5

7

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11

13

15

17

19

21

23

25

150 200 250 300 350 400 450 500 550

N1 speciesN2 speciesN>3 species

DBE

m/z

or

C16H11N1

Brown C Event

• CxHyNz – organics are ubiquitous in urban OAPossible Sources:

25% of identified peaks are:aliphatic CxHyN1, CxHyOzN1

- Amines

• CxHyN1 – are also observed at the Bakersfield site(R. Sellon, A. Goldstein, et al - Poster 31)

Intensive Road Construction Activity at the Time of CxHyNz

Episode (field notes of R. Zaveri) oFumes of Asphaltenes …?oEmissions from Vehicles with Catalytical Converters

…?

Outlook: PILS vs DESI: June 5, 12-6 pm

Very different subsets of compounds detected by two methods

Multiply Charged Ions in PILS Spectra (M-Ca2+, M-Mg2+, …)

Time Series of WSOC Detected by PILS

SUMMARY• Molecular-level HR-MS analysis provides critical

information for interpretation of the OA types, their chemistry

• Essential to assist with more detailed classification

• Outlook: Closure studies with the OA optical properties data indicative of “brown carbon”Closure studies with the gas phase, VOC data focused on chemistry of SOA formation and aging