|Barry and the synchrotron|
"Yes”, he replied, “but what do you want it for?"
I almost sighed. I knew if I had to explain thoroughly why I wanted it, my answer would be long and complicated. "Well, I want to do an experiment where I take lumps of your soil to a lead-lined room in Oxfordshire and shine light onto it that is 10 billion times brighter than the sun."
He looked over at his colleague with a confused expression, as if to say, we've got a right one here. But he did let me take some of his soil.
So, why did I need these lumps of soil? I want to understand what might help or prevent bugs (bacteria) in the soil eating their source of food – carbon. When bugs eat the carbon it is released to the air as carbon dioxide, the main greenhouse gas. If we understand this process better, we might be able to store more carbon in the soil and slow down climate change.
| A slice through a soil aggregate showing the |
position of organic matter, minerals and pores.
A novel way to answer this was to do three things: first, measure how well the bugs fed on carbon in many soil aggregates in the laboratory; second, stain the carbon in these aggregates using a chemical, and finally put the stained aggregates of soil into a bright light source called a synchrotron. The synchrotron shows us in three dimensions the location of the stained carbon inside the aggregates. It also shows us the location of the pore spaces.
(When I was explaining this to the friendly farmer to make it sound exciting I said, "No one has done this before!" He still didn't look convinced.)
After the experiment I compared the amount of carbon the bugs had eaten with how it was spread out inside each aggregate. I found that the bugs had eaten more of the carbon when it was distributed more frequently, more pieces throughout the aggregate. I need to analyse more aggregates to have greater confidence in this finding, so I will have to visit some more friendly farmers and hope I can convince them to give me some lumps of their soil. I am expecting to see more confused expressions.
The research I describe above was a collaboration of several BGS scientists and other colleagues at the Diamond Light Source campus in Harwell. We wrote this paper and there is a movie on the BGS YouTube channel that shows me talking about the experiment at the synchrotron.