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Simona Breu | Geoecology | Department of Environmental Sciences | University of Basel

Changes in fossil chironomid and cladoceran assemblages along water depth gradients

Thanks to the generous support from CH-QUAT, I had the opportunity to present my research on the use of fossil chironomid assemblages for reconstructing past water depths at the 22nd International Symposium on Chironomidae (ISC22) in Niš, Serbia.

Fossil remains of chironomids, whether in larvae or adult form, provide a unique perspective on the development of aquatic ecosystems over long periods. My study offers new insights into changes in fossil chironomid assemblages along the water depth gradient in Central European lakes. This dataset, detailing the composition of the chironomid assemblages along increasing water depth gradients, was used as a reference dataset to investigate water depth changes in a downcore study from Lake Lucerne (Switzerland). The results generally align with known geological records of water level fluctuations in Lake Lucerne. However, comparison with other proxies like for example pollen could be beneficial to support the current reconstruction.

Presenting my research findings at ISC22 allowed me to get a valuable exchanges of ideas and feedback from fellow researchers. Thank you, CH-QUAT, for making this possible.

Contact: Simona Breu (

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Francois Burgay | Oeschger Centre for Climate Change Research | University of Bern

Non-target screening analysis on ice and snow samples: a new opportunity to enhance our understanding on past and present atmospheric aerosol composition

Ice cores are unique environmental archives used to reconstruct past environmental and climate changes. So far, most studies have focused on the analysis of inorganic species, such as nitrate, sulfate, and trace elements. While their quantification has been extremely important for identifying past wildfires, volcanic eruptions, and the impact of human activities on the environment, these species only represent a small fraction of the submicron atmospheric aerosol mass. The large component is indeed composed of organic compounds. Despite constituting up to 70-90% of the submicron aerosol mass, organic compounds have been largely overlooked in ice-core studies, with few exceptions. This was primarily due to analytical limitations. Today, thanks to the development of high-resolution mass spectrometry and the implementation of non-target screening (NTS) workflows, it is possible to detect and identify an unprecedented number of compounds (several hundreds) from a single ice sample, unlocking the potential to improve our understanding of past environmental conditions.

With the support from CH-QUAT, I presented a poster at the European Geosciences Union General Assembly 2024 (EGU24), where I summarized the main findings obtained during my post-doc at the Laboratory of Environmental Chemistry of the Paul Scherrer Institute, under the supervision of Prof. Margit Schwikowski and Dr. Saša Bjelić. These include the development of a novel and highly sensitive NTS method for snow and ice-core analysis, and its application on two mid-latitude ice cores, namely Belukha (Siberia) and Colle Gnifetti (Europe), covering the period from 1750 to 2000 CE. A clear anthropogenic fingerprint has been identified during the industrial period with the occurrence of new, previously unknown chemical substances, mainly constituted by carbon, hydrogen, oxygen, nitrogen, and sulfur. Also, changes in the oxidation state of the organic compounds were observed, suggesting a possible increase in the oxidative capacity of the atmosphere. The conference represented a unique opportunity to connect with other ice-core and atmospheric scientists, and thanks to this event, exciting collaborations will start soon.

Contact: Francois Burgay (