REVIEW OF DIFFUSIVE GRADIENTS IN THIN FILMS (DGT): AN EMERGING TECHNOLOGY FOR MEASUREMENTS OF BIOAVAILABLE PHOSPHORUS AND METALS IN SEDIMENTS AND SOILS

This paper provides an overview of the principle and latest development of the diffusive gradients in thin films (DGT) technology and its applications in environmental studies with a focus on bioavailability assessment of phosphorus and metals. Compared with conventional methods, DGT has significant advantages: “in situ” measurement, time averaged concentrations and high spatial resolution. The “in situ” feature avoids the artificial influences including contamination of sample collection and treatment which may change the forms of chemicals, thus providing “true” information of the bioavailable or labile forms in the environment. Due to the strong temporal variations of the dissolved forms of chemicals in waters, the time-averaged concentrations provide reliable and robust results. As the labile chemicals are adsorbed on the binding gel, the micro-scale spatial distribution of their concentrations in the environment can be obtained at a resolution of sub-millimetres and at the two-dimensional level in combination with the analyses by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), computer-imaging densitometry techniques (CID) or a routine procedure consisting of 2D slicing, elution, and detection. The feature of high-resolution measurement with DGT provides novel information for the understanding of the micro-scale environmental processes and mechanisms. DGT provides promising potential for novel applications in agriculture, environmental monitoring and mining industry for the measurement of bioavailable forms of phosphorus and metals. However, further studies are needed to properly interpret the DGT measured results in relation to bioavailability under different environmental conditions and standard procedures are required to make the DGT results comparable.