March New study uses Gamma rays to put Ireland at the forefront of peatland mapping research

Findings will aid in updating national greenhouse gas emission inventories

Researchers at University of Galway have created a new approach to finding peat soil, giving insight to where carbon is stored in the ground.

Through a combination of state-of-the-art analytical techniques and data from the Geological Survey Ireland nationwide Tellus aerial survey, the research team has provided a revised picture of where peat soils are present across 80 % of Ireland, based on environmental gamma radiation measurements. The findings also offer huge potential to influence policy around land use and interventions to mitigate against greenhouse gas emissions.

The study was led by Dr Eve Daly and Dr Dave O’Leary from the Hydrogeophysics and Remote Sensing research group at University of Galway in collaboration with Trinity College Dublin, Teagasc and Geological Survey Ireland.

Lead author, Dr Dave O’Leary, PhD researcher, School of Natural Sciences, University of Galway, said: “Gamma rays are invisible, high-energy photons, like light, that are released during natural radioactive decay of materials in rocks and soils. Peat soils have a unique ability to block this type of naturally occurring radiation, drastically reducing the number of gamma rays detected by the sensor mounted on the Tellus aircraft when flying over peat soils.” 

The research team focused on this trait of peat soils to train a machine learning algorithm to identify and provide confidence of similar soils occurring in the top 60 cm of the land where the Tellus survey has been flown to date.

While peat depth cannot be directly measured this new analysis gave insights into the extent of peat soil and, importantly, identified the areas where soil changes from peat to mineral, which are typically hidden under things like forests and grasslands. Using this new research approach, the area of soil considered “peaty” within the Tellus geophysical survey potentially increased from 24 % to 30 %.

The findings have been published in the leading soil science journal Geoderma.

 Soils are a mixture of broken bits of rock, water, and air. Peat soils are distinct from mineral soils as they are formed from decaying plant material, mixed with water and air, and contain a very high amount of carbon. When waterlogged, this carbon is stored in the soils and their value has been increasingly recognised in recent years. When water is removed, for example via drainage, peat soils then emit carbon dioxide as the decay process restarts.

Dr O’Leary added: “In general, people are relatively familiar or have heard of radon, but what they might not know is that this is a by-product of naturally occurring uranium in the rocks below our feet, which also emits gamma radiation. There are several sources of this natural radiation in the environment and our study uses the unique relationship between this radiation and peat soils to identify where peat is likely to be present.”

“The Tellus survey has provided consistent coverage and measurements across about 80 % of the country at present. As this is a direct measurement from the soil, it allows us to create maps with boundaries showing realistic change from peat to mineral soils, regardless of what is covering the ground, be it trees or grass.”

“Few countries have invested in such an incredible dataset, which puts Ireland at the forefront of peatland mapping research. Importantly, the data is free to use. We hope that our research will encourage and incentivise other countries to invest in such surveys to meet their peatland mapping needs.”

Dr Eve Daly, Geophysicist and lecturer in Earth & Ocean Sciences, School of Natural Sciences, University of Galway, said: “This study gives decision makers and regulators more accurate spatial data on the extent of peat soil in Ireland and will assist in highlighting specific areas that are suitable, or not, for interventions to mitigate greenhouse gas emissions.”

The study was funded by Geological Survey Ireland, a division of the Department of the Environment, Climate and Communications.

The full study can be read in Geoderma here:

https://www.sciencedirect.com/science/article/pii/S0016706124003586

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