EGU21-14936
https://doi.org/10.5194/egusphere-egu21-14936
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Seasonal changes of sources, processes, and volatility of organic aerosol at urban, coastal and forest sites in Eastern Europe

Ulrike Dusek1, Agne Masalaite2, Harro Meijer1, Peng Yao1, Rupert Holzinger3, and Vidmantas Remeikis2
Ulrike Dusek et al.
  • 1University of Groningen, Energy and Sustainability Research Institute Groningen (ESRIG), Centre for Isotope Research (CIO), Groningen, Netherlands (u.dusek@rug.nl)
  • 2State research institute Center for Physical Sciences and Technology, Vilnius, Lithuania
  • 3Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, Utrecht, The Netherlands

The stable carbon isotope 13C has the potential to give insights into sources and processing of organic aerosol. However, the use for source apportionment has been somewhat limited, because the 13C source signatures vary and show some overlap. 13C/12C ratios are usually reported as δ13C indicating a permil deviation from the international reference standard Vienna Pee Dee Belemnite (V-PDB).

We use a method to measure δ13C  in OC desorbed from filter samples at three different temperature steps: 200 °C, 350°C and 650°C (Zenker et al.,2020). The results give a rough indication of aerosol volatility, as more volatile compounds usually desorb at lower temperatures.

We demonstrate with an extensive source study that in Lithuania and likely other Eastern European regions, the main anthropogenic primary sources for organic carbon (OC) have distinct isotopic signatures. δ13C  values of vehicular emissions show the most negative values around - 29 ‰, emissions from combustion of the most common wood types are more enriched with values around -26 to -27 ‰, and coal burning is around -25‰. For source samples d13C values at the three desorption temperature steps usually do not differ more than 1 ‰.

For ambient aerosol samples, the differences in δ13C values at different desorption temperatures are usually larger. This indicates varying source contribution or different chemical processes leading to the different volatility fractions. Combined isotopic and chemical analysis showed that in winter was a clear distinction in source contribution between the less refractory OC and the more refractory OC. We were able to identify fossil fuel burning as predominant source of the less refractory OC in the small particle size range (D< 0.18 μm), and biomass burning as predominant source of the more refractory OC in the larger size range (0.32< D<1 μm).

At all three sites, OC had more negative δ13C values in summer than in winter which can be explained by the contribution of biomass/coal burning sources in winter. At the urban site δ13C of OC did not change much with increasing desorption temperature in winter, which is typical for primary sources. In the summer δ13C of OC was clearly more negative for lower desorption temperatures at all three sites. This is likely due to the influence of secondary organic aerosol formation in summer, which should have depleted (more negative) isotopic signature and contributes strongly to the more volatile fraction.

A higher fraction of more refractory OC in summer compared to winter-time suggests active photochemical processing of the primary organic aerosol as an important process at all three sites. During a pollution episode transporting aged pollution from Poland and southern Europe to the otherwise clean forest site, a potential isotopic signature for photochemical aging was identified.

How to cite: Dusek, U., Masalaite, A., Meijer, H., Yao, P., Holzinger, R., and Remeikis, V.: Seasonal changes of sources, processes, and volatility of organic aerosol at urban, coastal and forest sites in Eastern Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14936, https://doi.org/10.5194/egusphere-egu21-14936, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.