Hard X-ray synchrotron biogeochemistry: piecing together the increasingly detailed puzzle

Abstract

Synchrotron techniques have increasingly been used to explore complex biogeochemical processes over the last two decades. In this reasonably short period of time the advances in optics, detector systems and ultimately beamline performance and capabilities have been staggering. Although a very large number of synchrotron methods are available and are employed in biogeochemistry, this perspective article will mainly explore recent developments and trajectories for ‘hard’ X-ray techniques. State-of-the-art beamlines, such as the nano-imaging and nanoanalysis (NINA) end-stations at the European Synchrotron Radiation Facility, will increasingly provide users with unprecedented analytical capabilities. For instance, the NINA end-stations will provide nanoscale resolution (10–20 nm for imaging and 50–100 nm for X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD)) together with high photon fluxes, a wide energy range and sophisticated sample environments. It is pertinent to note that the scientific case for the development of this project specifically mentions environmental and earth science as one of the three main drivers. To take full advantage of this increase in lateral resolution two further areas also need to simultaneously develop: sample preparation or preservation and detector technologies. The need for fast detection is dictated by both the necessity to representatively explore the heterogeneity of environmental samples and to minimise the risk of beam damage. In the last few years, the advent of a new generation of fast fluorescence detectors has gone a long way towards meeting this need (e.g. Lombi et al.). Similarly, an increasing number of beamlines are developing cryo-compatible platforms to reduce radiation damage and allow hydrated samples to be investigated in a frozen state. With several upgrade programs at synchrotrons throughout the world and new facilities coming online (http://www. lightsources.org, accessed 15 November 2013), biogeochemists will be able to delve more and more deeply into the complexity of small scale processes that drive element cycling. However, we would argue that this will also translate into a substantial increase in responsibility for users. First of all, sample preparation and preservation, which is always a key step in any successful spectroscopic investigation, will become even more critical. Some approaches, such as 2-D and 3-D tomography approaches (e.g. de Jonge and Vogt, [5] De Samber et al.) will benefit from the development of cryo-stages. However, in many