About the Project
Project Rationale
The implementation of new approaches for reducing atmospheric CO2 levels is urgently required if we are to achieve the Paris Agreement goal of limiting the post-industrialization increase in global temperature to 1.5°C. Enhanced Rock Weathering (ERW) is a geoengineering strategy that helps facilitate CO2 removal by accelerating the rate of silicate rock weathering via the application of basalt to agricultural environments [1]. Although ERW has been tested in laboratories and on small field scales, its effectiveness at sequestering significant quantities of CO2 over human timescales has yet to be determined [2].
This project will provide important new constraints on the effectiveness of ERW as a mechanism for mitigating climate change by quantifying the rate of weathering, and hence atmospheric CO2 drawdown, in a series of large-scale field trials being conducted in the UK, USA and Malaysia. The project will use a combination of chemical and isotopic techniques to characterise the extent and stability of CO2 removal via the generation of alkalinity and pedogenic carbonate formation, and how these vary with prevailing climate conditions, crop type and basalt mineralogy. The outcomes of this project are ultimately expected to contribute to the development of an IPCC Tier 1 ERW Greenhouse Gas Removal methodology.
Methodology
The student will determine the chemical composition (including alkalinity, pH and elemental concentrations) of water, soil and plant samples collected from the active field trials to establish the rate of basalt weathering under contrasting climatic and agricultural environments. Together with radiogenic Sr isotopic analyses (87Sr/86Sr), these data will enable the extent of silicate vs. carbonate weathering to be quantified, and the rate of atmospheric CO2 drawdown determined. Stable isotope systems (d88/86Sr, d7/6Li and d26/24Mg) will be used to help quantify the formation of secondary minerals including pedogenic carbonate and clays during the weathering process, and will be complemented by laboratory-based experiments that enable the rate of precipitation and extent of isotopic fractionation to be characterised under contrasting conditions [e.g. 3].
The project will directly contribute to research being conducted by the Leverhulme Centre for Climate Change Mitigation (www.lc3m.org); a multi-institution centre dedicated to evaluating the viability of Enhanced Rock Weathering from field, laboratory, modeling, and societal impact perspectives. LC3M is currently conducting large-scale ERW field trials in Norfolk UK, Illinois USA, and Sabah Malaysia, which will provide the majority of samples to be worked on in this project. Fieldwork opportunities at all of these locations will be available through this project.
Training
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre. Specific training will include:
i. The collection of water, soil and plant samples, and associated in-situ chemical measurements (e.g. pH and alkalinity).
ii. The determination of trace element concentrations and isotopic ratios by inductively coupled plasma mass spectrometry (ICP-MS), thermal ionization mass spectrometry (TIMS) and multi-collector (MC) ICP-MS.
iii. Laboratory-based experimental approaches for quantifying the rate of precipitation of pedogenic carbonate and other secondary minerals, and their effect on the chemical and isotopic composition of the surrounding fluid.
iv. Use of geochemical models such as PHREEQC and CO2SYS to constrain changes in aqueous geochemistry, mineral saturation states and CO2 drawdown.
In addition to the exchanges associated with INSPIRE, the student will also have opportunities to work closely with national and international collaborators on the LC3M project.
References
[1] Beerling D.J., Kantzas E., Lomas, M.R., Wade, P., Eufrasio, R.M., Renforth, P., Sarkar, B., Andrews, M.G., James, R.H., Pearce, C.R., Mercure, J.F., Pollitt, H., Holden, P.B., Edwards, N.R., Khanna, M., Koh, L., Quegan, S., Pidgeon, N.F., Janssens, I.A., Hansen, J., and Banwart, S.A. 2020. Potential for large-scale CO2 removal via enhanced rock weathering with croplands. Nature v583, p242-248.
[2] Andrews, M.G. and Taylor, L.L. 2019. Combating climate change through enhanced weathering of agricultural soils. Elements v15, p253-258.
[3] Wimpenny, J., Gislason, S.R., James, R.H., Gannoun, A., Pogge von Strandmann, P.A.E., Burton., K.W. 2010. The behaviour of Li and Mg isotopes during primary phase dissolution and secondary mineral formation in basalt. Geochimica et Cosmochimica Acta v74, p5259-5279.