Caroline is Associate Professor of Biogeochemistry at the University of Leeds’s School of Earth and Environment. She won the 2015 Houtermans Award, given to early career researchers who have made an exceptional contribution to geochemistry.
Hi Caroline, congratulations on winning the Houtermans Award. What a fantastic achievement! Did you always know you wanted to be a scientist?
Well I don’t think I was any more interested in science or nature than any other child, but I did always want to find out how things worked. I have always enjoyed the analytical approach; observing, recording and testing ideas. So I just found that science was my outlet for that rather than say languages or PE. At school I remember using a van der Graaf generator where one person would make contact with the machine while everybody else would hold hands forming a closed ring; all our hair stood up on end and I remember being fascinated by that and wanting to understand why it was happening.
You did your BSc in Environmental Geoscience at Bristol and then went on to do a PhD in Geochemistry there. What was your PhD project on, and why did you follow this?
For my PhD I was looking at the reactivity, or ‘cycling’, of trace metals in mainly the terrestrial environment – so freshwater environments, soils, soil pore waters – to study the processes that govern their mobility and fate. The processes that control the cycling of these metals are important because many of the trace metals are essential for life in low concentrations but become toxic at high concentrations; and these metals also form ore minerals, so there are economic as well as environmental implications.
After your PhD you did a short postdoc at Bristol on the mobility and fate of uranium, and then on to the University of Southampton to take up a lectureship in Geochemistry. What was your research focused on there?
Well towards the end of my PhD I became more interested in the marine environment and the reactivity and cycling of bioessential trace metals in marine sediments and seawater, and so after my postdoc, the National Oceanography Centre at Southampton was the obvious place to pursue this research.
What really interested me was the uptake and release of bioessential metals by iron and manganese minerals present in marine sediments, and how these minerals can control bioessential metal concentrations in seawater. I was focused on combining novel laboratory experiments with synchrotron spectroscopy and computational simulations to understand the reactions between these metals and minerals at the molecular level.
You were at Southampton for three years, and in 2012 you moved to University of Leeds. Did this change the direction of your research at all?
Southampton was a fantastic experience and allowed me to see how my small scale molecular work fitted into the cycling of bioessential metals on a global scale. When I went to Leeds I remained focused on the marine environment but began to really concentrate on the mechanistic and process side of trace metal cycling.
What I’m looking at now is the fate of carbon and bioessential metals in marine sediments, and whether the minerals in these sediments form a long term source or sink of these elements to seawater. This is important because the storage of carbon in the ocean, and the concentrations of the bioessential metals in seawater help regulate atmospheric CO2, which has implications for global climate.
How do you use Diamond to investigate these processes?
When you get down to the small scale, the mobility of elements associated with minerals depends on how the element chemically interacts with the minerals. There are a variety of different mechanisms by which elements can become stuck, and it’s basically the strength of the sticking that determines whether the element will be retained or released. The only way to elucidate this sorption mechanism is by looking at the immediate chemical bonding environment around the metal. The only way to do that is with synchrotron spectroscopy.
So I use the core EXAFS beamline (B18) for controlled labmade samples, and the Microfocus XAS beamline (I18) for natural samples, which can cater for their spatial heterogeneity. I’ve also started to use the Scanning X-ray Microscopy beamline (I08) too because I’m doing a lot of work now on how metals interact with minerals and organic carbon. In the real world, mineral surfaces are part-coated with organic matter, which fundamentally changes the reactivity of the mineral particles toward the metals. Therefore it’s important to be able to run experiments with mineral-organic composites as well as pure minerals. The more we know about carbon sorption the more we can understand and predict future levels of carbon in the earth’s atmosphere.
Thank you for talking to us Caroline, and best of luck with your future research!
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