STARS PhD Researcher Dan Evans (Lancaster University) was last month awarded a £19,000 grant from the NERC Cosmogenic Isotope Analysis Facility (CIAF). Based in East Kilbride, Scotland, the facility provides cosmogenic radionuclide analytical facilities to scientists interested in yielding fundamental information about rates of landform evolution.
Dan spent just under a year formulating the application with his primary supervisor Professor John Quinton at Lancaster University and was expertly assisted by Dr Andy Tye (British Geological Survey), Dr Jess Davies (Lancaster University) and Professor Simon Mudd (University of Edinburgh). The application’s success is a milestone in his PhD, allowing him to get one step closer to calculating the first rates of soil formation for UK arable land systems.
“It’s a bit like your bank account,” Dan commented. “You can’t work out your overall balance from the withdrawals alone; you need to know how much is entering the system too. It’s the same for our soils. We need to know the rates at which our soils are forming.”
Not only will these rates of soil formation significantly contribute to our knowledge of pedogenesis in the UK, but Dan suggests that it allows work on soil erosion to be more holistically assessed.
“If Soil A is eroding at a faster rate than Soil B, we often immediately conclude that Soil A must be thinning considerably quicker. But this erosion data only tells half of the story. It could be that the soil at point A is being formed quickly too, so the overall net erosion is lower than that at point B. Therefore, it makes us consider the validity of the many soil erosion maps that report gross erosion, without acknowledging the influence of soil formation.”
Quantifying soil formation is a long and complex process which Dan began in August last year, by hiring a drilling rig team from the British Geological Survey to help him excavate many metres of sandstone bedrock from underneath an arable farm in Nottinghamshire. Accessing the rock directly below the soil was especially important given that it is at this interface where mineral particles slowly weather away to become incorporated into the soil above. After excavating over fifteen cores, Dan subsequently spent a month at the British Geological Survey’s core store, subsampling this weathered bedrock in preparation for Cosmogenic Radionuclide analysis at East Kilbride.
“When cosmic rays bombard the Earth’s surface, Beryllium-10 atoms are produced within the first few metres of the soil and their concentration decreases exponentially with depth,” Dan explained. “Over the last twenty years, mathematical models have established the relationship between this Beryllium-10 concentration and the rates of soil formation. In essence, my work at CIAF will be to prepare my samples for a technique called Accelerated Mass Spectrometry which will quantify the Beryllium-10 concentration in each of my samples. With these concentrations, I shall then be able to calculate the rates of soil formation across my study site.”
Not only will Dan quantify the first rates of soil formation for arable settings in the UK but this marks the first time Cosmogenic Radionuclide analysis has been used to study soil formation for arable landscapes across the world. Despite this significant contribution to the discipline, Dan suggests there is a more integral reason for doing the work.
“Deriving and understanding the rates of soil formation is often a small component in a much larger scaled investigation into long-term landscape evolution and unsurprisingly this work is often conducted by geologists and sedimentologists. When the Soil Scientist thinks about soil formation, I’d argue their focus is often placed on the processes within the profile, such as the development of horizons. In other words, the focus isn’t on calculating how much soil is being formed every year. This is odd given the fact that in the study of erosion, we’ve been quantifying volumes of eroded soil for over a century.”
Dan hypothesises that the soil profiles that drape the slopes at his Nottinghamshire arable site are thinning and if this is the case, he is interested to find out how long it would theoretically take for these soils to erode down to bedrock. Dan plans to use his soil formation rates, along with some corresponding erosion rates, to build a soil lifespan model which will provide the first estimates into the long-term sustainability of the soil at the arable site.
You can follow more of Dan’s work on Twitter @DanEvansol or via his blog: http://www.soilwithdan.blogspot.co.uk. Alternatively, you can email him: firstname.lastname@example.org