ROC-CO2 developed new geochemical techniques to study rock weathering, testing and applying them to field areas around the world. These included shale catchments: the Draix-Bleone Observatory in France; North Island, New Zealand; Arctic tributaries of the Mackenzie River; Shale Hills Critical Zone Research Observatory in the Eastern USA; and a mountains to floodplain transect of the RIo Madre de Dios in Peru. At these locations we collaborated with local organisations (including scientific researchers and local government).
Returning these samples to the laboratories resulted in a large number of analyses. For the river samples, this focused on trace metal analysis of river water, sediment and soil by Inductively Coupled Plasma Mass Spectrometry. We were also the first to make measurements of rhenium isotopes in river water samples by multi-collector ICP-MS. For the CO2 gas samples, we measured their radiocarbon content and stable isotope ratios. The isotope measurements allow us to measure directly carbon emissions from weathering of organic matter in rocks.
The major results can be linked to the outputs and dissemination of the results. These include:
- Measurements of un-weathered rock-organic carbon exported by mountain rivers (e.g. Hilton, 2017, Clark et al., 2017).
- Identifying the important role of microbes in the oxidation or rock organic carbon in mountain soils (Hemingway et al., 2018) and ongoing work by PDRA Georgiadis (presented at AGU 2021).
- Estimation of CO2 emissions during rock weathering catchments around the world using the trace element rhenium (e.g. Horan, et al., 2019, Hilton et al., 2021).
- Development of a new method to direct measure CO2 emissions during weathering of sedimentary rocks (Soulet, Hilton et al., 2018, Biogeosciences).
- Development and refinement of methods to measure the isotopes of rhenium in river waters, soils and sediments (Dellinger et al., 2020, JAAS) which allow the first measurements of Re isotopes on river waters as a weathering proxy (Dellinger et al., 2021, EPSL).
- Demonstrating a previously unknown feedback in the geological carbon cycle, showing CO2 emissions from rock weathering increase with temperature (Soulet et al., 2021, Nature Geoscience).
- Ongoing research on themes of microbial communities and global upscaling of measurements. These have been presented by team members (Hilton, Ogric, Soulet, Grant, Roylands, Zondervan, Georgiadis) at international scientific conferences, including several invited talks (EGU, AGU, Goldschmidt).
