Diffusive gradients in thin films: devices, materials and applications

A large number of ex situ sampling techniques have been used traditionally to investigate the impact and fate of pollutants in soil, sediment and waters. However, the distribution and form of chemical species present are often altered prior analysis, due to the alterations during sampling and transfer to the laboratory. Alternatively, a robust in situ passive sampling technique, diffusive gradients in thin films (DGT), has been developed for the measurement of labile concentrations, species and distribution of various solutes in soil, sediment and waters. Here we review the recent developments in DGT device configurations and components, e.g., binding agents, diffusive phases and filter membranes. We highlight new configurations for effectively reducing the measurement errors and the disturbance of environmental media. We discuss DGT applications for the analysis of soil, sediment and water, such as evaluation of bioavailability and toxicity, measurement of nutrients and organic substances, and assessment of relationships between multiple solutes. We also present the coupling of DGT with other in situ measurement techniques such as dialysis samplers (Peeper), diffusive equilibrium in thin films (DET) and planar optodes (PO).