Carboxyl groups enhance organic carbon preservation with iron minerals in soils and sediments

New paper in the journal Communications Earth & Environment - “Carboxyl-richness controls organic carbon preservation during coprecipitation with iron (oxyhydr)oxides in the natural environment"

The preservation of organic carbon in soils and sediments in association with iron minerals is hypothesised to protect carbon from microbial degradation and prolong its lifetime over hundreds to thousands of years. In this way soils and sediments provide a stable sink that locks carbon away from the atmosphere, which  helps regulate Earth’s climate. Exactly what controls the formation of stable carbon-mineral associations, and how these associations survive over long timescales, however, is far from understood. New research by University of Leeds researcher Professor Caroline Peacock and her team of early career researchers shows that carboxyl functional groups, that are found abundantly in natural organic matter, stick very strongly to iron minerals, and that with increasing carboxyl-richness, increasingly strong and stable carbon-mineral associations are formed, that can withstand chemical breakdown.

This work is published in a new paper in the journal Communications Earth & Environment, entitled “Carboxyl-richness controls organic carbon preservation during coprecipitation with iron (oxyhydr)oxides in the natural environment”. PhD student Lisa Curti who is first author of the paper explains that: “Despite many years of research, the exact mechanisms that stick carbon and minerals together are poorly understood because of the different chemical and physical processes involved and the variety of different organic molecules and functionalities that can be found in nature. This work shows for the first time that carbon that is rich in carboxyl groups sticks more strongly to iron minerals in soils and sediments, and is subsequently stabilised against degradation.”

She adds: “Carboxyl-richness could provide an important control on organic carbon preservation in the natural environment.  This is really exciting because carbon preservation over very long timescales in sediments effects Earth’s long-term climate and oxygenation, but carbon preservation over shorter decadal to centennial timescales in soils plays an important role in Earth’s short-term climate, and finding new ways to increase the storage of carbon in soils might help offset current climate change.”

Professor Caroline Peacock concludes: “Lisa’s work shows how carbon chemistry plays a key role in how well it sticks to minerals and provides a new platform for us to understand the interplay between carbon chemistry and minerals in carbon preservation.”

Lisa is co-funded by University of Leeds and Diamond Light Source, the UK’s national synchrotron radiation source. Professor Caroline Peacock highlights that: “We could not have achieved this fantastic result without access to a world leading large scale science facility like Diamond.”

The study was funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 725613 MinOrg). Professor Peacock gratefully acknowledges a Royal Society Wolfson Research Merit Award, and access to Diamond Light Source Beamline I08 that contributed to the study described here.

The paper is available at: