Diffusive gradients in thin films for the measurement of labile metal species in water and soils: a review

Abstract

The determination of the concentration of an environmental pollutant is not sufficient to assess the related health risk because this pollutant may not be bioavailable. Therefore, methods to determine pollutant bioavailability are more relevant to assess toxicity than measuring the total concentration. For instance, the diffusive gradient in thin films (DGT) is an in situ dynamic technique used to measure the concentration of labile compounds in the environment. Here we review the latest developments achieved in speciation and bioavailability of metals and metalloids using this technique. We detail the technique, common binding agents and diffusive gels. We give laboratory procedures to prepare the gels, and we explain calculations using the DGT-induced fluxes in soils (DIFS) modeling. DIFS models can predict the resupply capacities from soils to porewater, and the uptake of trace elements by plants. Procedures for in situ field deployments, including issues of biofilm growth, are also discussed.