Nitrogenated gas sensing in water using custom membranes
This project addresses the limitations of existing techniques for measuring greenhouse gas (GHG) concentrations in aquatic environments. Current methodologies offer restricted spatial and temporal coverage, hindering comprehensive understanding. Moreover, the project is designed to overcome the insufficient selectivity of polydimethylsiloxane (PDMS) membranes used in GHG detection, specifically for nitrous oxide (N2O) and ammonia (NH3). By using porous graphene membranes, the project aims to considerably improve selectivity, facilitating the precise detection and mapping of these crucial gases.
Simultaneously, the project confronts pressing scientific uncertainties in the marine nitrogen cycle. The relative contributions of different processes to N2O production in ocean environments remain contested, and the project's innovative methodology aims to provide the data required to resolve these questions. Similarly, the project tackles the disparity between models and observed data on the global oceanic source of ammonia, promising to bring clarity to this critical environmental issue.
The main objective of the project, as described, is to develop an in-situ instrument capable of monitoring the concentration and stable isotope composition of dissolved nitrous oxide (N2O) and ammonia (NH3) with high spatial resolution in real time in aquatic environments. This will be achieved by improving the membrane selectivity for these gases in the proposed probe, transitioning from polydimethylsiloxane (PDMS) membranes to a porous graphene membrane. The membrane will be designed to maximise the selectivity for NH3 and N2O compared to other dissolved gases. This way, the team hopes to resolve outstanding issues related to the nitrogen cycle in marine environments and provide better constraints on the evolution of the carbon cycle in response to anthropogenic warming.
What are the expected outputs of this project?
- To develop porous graphene membranes with high selectivity for nitrous oxide (N2O) and ammonia (NH3).
- To fabricate a novel instrument capable of real-time, in-situ monitoring of the concentration and stable isotope composition of dissolved NH3 and N2O in aquatic environments.
- To collect new data on the nitrogen cycle in marine environments, leading to new understandings of the transport pathways of NH3 and N2O through graphene nanopores.
- To produce dissemination material to communicate the results of the research and to do outreach with the public and high school students, including through direct engagement programs such as "study weeks" and presentations during annual visits to the EPFL campus.
- September 2023
Ground-truthing the state of the art with measurement of gas transport properties using commercial PDMS membranes before and after field tests
- September to December 2023
Characterization of gas transport properties and optimization of graphene nanopores to maximise gas selectivity for N2O and NH3
- December 2023 and January 2024
Dissolved gas analysis and calibration under different physical conditions and gas composition in a lab chamber, mimicking real marine conditions
- February and March 2024
Testing membranes on the LéXPLORE platform of EPFL on Lake Geneva
- April and May 2024
Deployment of a new laser spectrometer coupled with the best membrane in the context of the GreenFjord project in fjords of southwest Greenland, combined with other oceanographic analyses related to the N, C and O cycles in both the particular and dissolved phases. Importantly, the dissolved gas measurements will be compared with discrete stable isotope measurements of N and O in dissolved NO3, along selected vertical profiles
This project is financed by CLIMACT.