Stable Isotopes in Aerosols

About

Our ongoing research focuses on innovative applications of stable carbon isotopes in atmospheric studies, aiming at constraining sources and processing of pollutants. Based on the fact that C13 provides additional information, it is possible to distinguish the contribution of source strength from the chemical degradation of an organic compound in the atmosphere, which would not be possible with C12 concentration measurements alone. For that, we use two setups to measure compound specific isotope ratios in gas- and particle phase samples, both combining two-dimensional gas-chromatography (2DGC) with isotope ratio mass spectrometry (IRMS).

Research Topics

  • isotopic experiments to determine the kinetic isotope effect (KIE) of atmospheric relevant reactions for aging studies;
  • laboratory studies to scrutinize the mechanisms of secondary organic aerosol (SOA) formation and evolution;
  • compound specific isotopic measurements of chemical tracers in source- and ambient field samples for pollution 'forensic' studies;

Contact

Dr. Iulia Gensch

ICE-3

Building 05.2 / Room 2033

+49 2461/61-6930

E-Mail

Aging studies and air pollution 'forensics' by stable isotopes

Stable Isotopes in Aerosols

The application of stable isotopes in aging studies and air pollution 'forensics' rests upon two basic principles:

  • the isotope ratio of atmospheric organic compounds – expressed as delta value, δ13C - depends on that of the emissions. Both delta values of emissions and at the exposure site are measured independently in the lab. Remarkably, isotopic ratios are source specific. These isotopic 'fingerprints/signatures' can be used to trace back the origin of emitted pollutants;
  • the change of isotope ratios during atmospheric transport depends on the isotope fractionation resulting from reactions or physical loss processes alone. The kinetic isotope effect (KIE), representing the rate constant ratio of the reaction involving the 12C reactant and that involving the 13C, can be measured in laboratory.

The 'isotopic hydrocarbon clock' equation allows for determining the isotopic photo-chemical age of any single compound from its isotopic composition, when knowing the source signature δ13C0 and the reaction KIE.

Isotope modelling studies

Stable Isotopes in Aerosols

The use of the two independent isotopic pieces of information – δ¹³C at the source and at the exposure site, as well as the KIE of chemical degradation – in a wind-driven model results in a set of parallel equations. Based on that, the impact of source strength can be separated from that of chemical loss in the atmosphere.

The comparison of isotopic and trajectory-based photo-chemical age is a highly innovative method for testing models.

Carbon Budget and chemical mechanisms by means of isotopes

Stable Isotopes in Aerosols

Due to the additional information they provide, isotopes serve as an innovative tool for gaining insight into complex atmospheric reaction mechanisms. By analyzing the δ¹³C balance of secondary organic compounds formed in both the first and subsequent generations of the investigated photochemical processes, they enable a deeper understanding of these reactions.

At ICE-3, we use various measurement techniques and instruments for our research. A significant number of these devices were developed in-house to meet specific requirements arising from extremely low concentrations or difficult measurement conditions in the field and on aircraft.

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IRMS - Isotope Mass Spectrometry

Compound specific measurements are carried out by using TD-GC-IRMS (Thermal Desorption - Gas Chromatography - Isotope Ratio Mass Spectrometry). The main goal is to identify and quantify the sources and the atmospheric chemical processing of volatile organic compounds (VOC) as well as of organic aerosols.

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Last Modified: 20.05.2025
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