Project description

Metals such as cadmium, nickel and lead are considered to pose aquatic hazard and are classified as Priority Substances under the Water Framework Directive (WFD). However, they are particularly problematic to assess because their toxicity to aquatic life depends on their chemical form (metal speciation), as well as environmental parameters such as pH, calcium concentration and alkalinity, and the presence of dissolved organic ligands, all of which impact the concentration of metal that is bioavailable to aquatic life. Currently, however, metal bioavailability is not considered in regulatory monitoring, and chemical status of water bodies is established by comparing dissolved metal concentrations (i.e. 0.45-μm filtered) with established Environmental Quality Standards (EQS).

Diffusive Gradient in Thin Films (DGT), and passive samplers (PS) in general, are already widely used in investigative monitoring and there is an increasing interest in their use for the environmental assessment of water bodies, within European policies requirements, as they can determine the labile metal concentrations in coastal and transitional waterbodies, i.e. they can more closely approximate metal bioavailability. However, DGTs are not currently utilised for regulatory purposes for metal EQSs. A significant barrier hindering the regulatory acceptance of PS for compliance checking is the lack of appropriate EQS, i.e. EQS based on labile metal concentration and not on dissolved metal concentrations.

The MONITOOL Project has been developed to address this challenge, and specifically aims to define suitable EQS based on labile metal concentrations, and therefore enable the use of DGTs to monitor priority metals in a regulatory context. Priority metals will be analysed in coastal and transitional waters using both spot sampling and DGT deployments and statistical analysis applied to study relationships between metal concentrations in DGT and in spot water samples, allowing suitable EQS for DGTs to be developed. This will permit DGTs to be utilised within a regulatory framework in Europe.