Benchmarking source specific isotopic ratios of levoglucosan to better constrain the contribution of domestic heating to the air pollution

Due to the potential to fingerprint emissions, carbon stable isotopes are considered a powerful tool to get insight into sources of air pollutants and to study their atmospheric life cycle. Including the independent isotopic knowledge into chemical models, not only concentration but also isotope ratios can be predicted. This provides the possibility to differentiate the impact of source strength from that of chemical reactions in the atmosphere. In a recent study comparing Lagrangian-particle-dispersion-simulations with ambient observations, Betancourt et al. [1] (ACPD2020) found that the observed isotopic age of levoglucosan, a biomass burning tracer, agrees well with the isotopic age derived from back-plumes analyses. This showed that the wintertime aerosol burden from domestic heating observed in residential areas of North-Rheine-Westphalia, Germany, is of local or regional origin. Error analyses though indicated that the largest source of uncertainty was the limited information on emission isotope ratios.

In this work, the stable isotope ratios of levoglucosan in aerosol particles emitted from the combustion of 18 different biomass fuels typically used for domestic heating in Western and Eastern Europe (soft and hard woods, brown coals and corn cobs, respectively) were measured by Thermal Desorption- Two-Dimensional Gas Chromatographie- Isotope Ratio Mass Spectrometry (TD-2DGC-IRMS). Additionally to the compound specific measurements, isotopic ratios of total carbon in the fuel parent material, in the precursor cellulose, as well as in sampled aerosol particles were determined.

Levoglucosan δ¹³C was found to vary between -23.6 and -21.7‰ for the C3 plant samples, showing good agreement with Sang et al [2] (EST2012). The brown coal and the C4 plant samples were isotopically heavier, showing isotopic ratios in the range of -21,1 to -18.6‰ and -12.9‰, respectively. In this presentation, the observed levoglucosan δ¹³C will be discussed with respect to the carbon isotopic composition of the parent materials. The potential of using compound specific δ¹³C measurements of levoglucosan for improved source apportionment will be addressed.

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