U. DusekU. Dusek11, R. Holzinger, R. Holzinger11, T. Röckmann, T. Röckmann11

Institute for Marine and Atmospheric research Utrecht (IMAU),Utrecht University, The NetherlandsInstitute for Marine and Atmospheric research Utrecht (IMAU),Utrecht University, The Netherlands

Combined measurements of organic aerosol isotopic and chemical composition –

A day/night test case

ORGANIC AEROSOL CHARACTERIZATION

Combination of 3 relatively new techniques:14C: fossil (no 14C) vs. non-fossil sources

13C: ? might give indication of aerosol processing and/or sources

Thermal desorption PTR-MS: detailed chemical composition

Apply to aerosol filter samples taken in Cabauw, NL during Pegasos

High volume filter samples:

•500 l/min•separate filters during day and night •each loaded for 2-3 days

High volume filter samples:

•500 l/min•separate filters during day and night •each loaded for 2-3 days

14C for source apportionment

Fossil fuel

fm = 0

Biomass burning Biogenic

fm = 1.1 - 1.2 fm ~ 1.04

14C: radioactive isotope, continuously replenished in the atmosphere

14C Measured on OC, EC, TC, WIOC

using extraction technique developed at IMAU

13C indicator of aerosol processing?

Photochemical aging:Oxidation by O3, OHLoss of OC

12C pref. reacted awayRemaining carbon:

Higher 13C

Gas phase formation of SV products:If gas phase precursors are partially reacted

12C pref. reacted to SVProducts

Lower 13C

13C and chemical measurement setup

Oven 1 Oven 2 Catalysts

50-450°C 500°C

Liquid N2

Remove H2O

CO2 is frozen and later released to be analyzed for isotopic composition

IRMS

Isotope measurement

PTR-MS

High resolution mass spectrometry of largely unfragmented compounds

2 cases

1) 24 - 27 MAY:

Aged cont. caseWarmSunnydryNight: stable stratification low inversion layer

2) 1-3 JUNE:

Recent pollution casecoolsunnyNight: stable stratification low inversion layer

Fossil and contemporary carbon in day and night

contemporary OCconcentration enhanced in the night

OC thermogram

Aged cont. case

Semi-volatile organics enhanced

Low volatile organics little change

13C thermogram

Aged cont. case Recent poll case

Consistent with partitioning:gas phase: 13C lowparticle phase: 13C high

condensation lowers particle 13C

Other effects must play a role:•Change in sources?•day-time photochemistry?•Recent SOA?

PTR-MS first results

Lighter molecules preferentially enhanced during night time

OC night / OC day

Summary

• Carbonaceous aerosol has higher fraction of contemporary carbon during night

• Mainly increase in contemporary OC, with small decrease in fossil OC and EC

Oven 1 Oven 2

50-450°C 500°C

• Semi-volatile carbon is enhanced during night time

IRMS

• Semi-volatile carbon depleted in 13C compared to low-volatile (less aged?)

• Day-night change only at oven T=150 °C

• Compounds with smaller mass more strongly enhanced during the night

Outook

IRMS

• Investigate isotopic effects of partitioning / photochemical aging in the lab

• Study source signatures

• Fall and winter studies

• Are O:C and H:C ratios higher during the night?

• Do any particular chemical compounds show a strong day/night difference (tracers?)

Outook

• B. Oyama, W. Ramon, P.A. de Wilde

• Grants:

• NWO grant number 820.01.001

• ALW- ‐Middelgroot program (Grant 834.08.002)

Thanks for your attention