Aim of the open session is to create a multidisciplinary platform, where presentations which include studies on systematics in stable isotopes or studies which use stable isotopes as a tool, can be presented if no specialized session is organized elsewhere in the EGU General Assembly program.

The open session part includes blocks of special interest on:

- Isotope techniques for revisiting water cycling in catchments
Pollution, droughts and floods, ground-surface water connection are significant elements of the aquatic environment in catchments.
One aim of the session is to explore the use of isotope tracing technique to determine the sources, dynamics, and chemistry of water sustaining catchments with the goal of managing the quantity and quality of water in a catchment context. The second aim is to look at the sensitivity of hydrology and biogeochemical processes through isotope tracing, to specific external influences, especially those related to impact of human activities like agriculture (soil organic matter, erosion, water and nutrient use efficiency) and global change in catchments, including wetlands. We strongly encourage studies bringing classical isotope tools (O, H) or more recent developed ones into play.

- Stable Isotope Analysis by Optical Spectrometry.
In recent years optical stable isotope ratio analyzers have seen a tremendous increase in end-user acceptance and ever-wider application in both laboratory and field studies. Here we provide a podium for new developments in this field, whether it concern the optical technology or its interfacing to peripheral equipment, as well as specific demonstration or intercomparison studies.

- Major Stratigraphic Boundaries and Isotopic Signatures.

Stable and radiogenic isotope trends play an important role in the interpretation of the causes and consequences of biotic turnovers at major stratigraphic boundaries, such as the Precambrian-Cambrian (Pcb-Cb), Permian-Triassic (P/Tr), Triassic-Jurassic (Tr/J), Cretaceous-Paleogene (K/Pg) boundaries. Contributions are solicited of all isotopic studies - stable isotope (δ13C, δ8O, δ14N) as well as radiogenic isotope (Nd/Sm, Rb/Sr, 53Cr/52Cr etc.) studies - that are relevant for the understanding of those important events in earth history.