u. dusek 1 , r. holzinger 1 , t. röckmann 1
DESCRIPTION
Combined measurements of organic aerosol isotopic and chemical composition – A day/night test case. U. Dusek 1 , R. Holzinger 1 , T. Röckmann 1 Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, The Netherlands. ORGANIC AEROSOL CHARACTERIZATION. - PowerPoint PPT PresentationTRANSCRIPT
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