 |
| Titel |
Isotope source apportionment of carbonaceous aerosol as a function of particle size and thermal refractiveness |
| VerfasserIn |
Agne Masalaite, Rupert Holzinger, Vidmantas Remeikis, Thomas Röckmann, Ulrike Dusek |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132612
|
| Publikation (Nr.) |
 EGU/EGU2016-13136.pdf |
|
|
|
|
|
| Zusammenfassung |
| The stable carbon isotopes can be used to get information about sources and processing
of carbonaceous aerosol. We will present results from source apportionment of
carbonaceous aerosol as a function of particle size thermal refractiveness. Separate source
apportionment for particles smaller than 200 nm and for different carbon volatility
classes are rarely reported and give new insights into aerosol sources in the urban
environment.
Stable carbon isotope ratios were measured for the organic carbon (OC) fraction and total
carbon (TC) of MOUDI impactor samples that were collected on a coastal site (Lithuania)
during the winter 2012 and in the city of Vilnius (Lithuania) during the winter of 2009. The
11 impactor stages spanned a size range from 0.056 to 18 μm, but only the 6 stages in the
submicron range were analysed.
The δ13C values of bulk total carbon (δ13CTC) were determined with an elemental
analyser (Flash EA 1112) coupled with an isotope ratio mass spectrometer (Thermo Finnigan
Delta Plus Advantage) (EA – IRMS). Meanwhile δ13COC was measured using
thermal–desorption isotope ratio mass spectrometry (IRMS) system. This allows a rough
separation of the more volatile OC fraction (desorbed in the oven of IRMS up to 250 0C)
from the more refractory fraction (desorbed up to 400 0C).
In this study we investigated the composition of organic aerosol desorbed from filter
samples at different temperatures using the thermal–desorption proton–transfer–reaction
mass spectrometry (TD–PTR–MS) technique.
During winter-time in Lithuania we expect photochemistry and biogenic emissions to be
of minor importance. The main sources of aerosol carbon should be fossil fuel and biomass
combustion. In both sites, the coastal and the urban site, δ13C measurements give a clear
indication that the source contributions differ for small and large particles. Small particles <
200 nm are depleted in 13C with respect to larger particles by 1 – 2 ‰Ṫhis shows that
OC in small particle arises mainly from fossil fuel sources, whereas OC in larger
particles from 200 nm to 1 μm has higher contribution from biomass burning/other
sources.
Moreover, there is a clear distinction in source contribution between the more
volatile OC fraction and the more refractory fraction. The more refractory fraction
is enriched in 13C by 1 to 2 ‰ for both small and large particles. These results
show that the fossil fuel combustion is associated to a larger degree with more
volatile carbon, whereas biomass burning is the main source of the more refractory
particles.
According to our source apportionment, the more volatile carbon fraction in the smallest
particles is almost completely from fossil fuels, whereas the more refractory carbon fraction
in the large size range is almost complete from biomass burning. The more refractory small
particles and the less refractory large particles are roughly an even mix of these two
sources.
The detailed chemical speciation of the carbonaceous aerosol will be presented as
well.
Acknowledgements
This study was funded by the Dutch Science Foundation (NWO grants Nr. 820.01.001,
and 834.08.002). |
|
|
|
|
|
|