Monitoring freshwater sediments.

The objectives of the SENSPOL Expert Meeting on 'Monitoring Freshwater Sediments' held in Antwerp, Belgium, 12-13 September, 2001, were firstly to identify and define problems and secondly to develop a realistic strategy to solve these problems. Both of the stakeholder groups (governmental authorities and the dredging industry) present at the workshop participated in detailed discussions to elucidate the role of sensors in the field of sediments and sediment/water interfaces. The 19 invited experts were agreed that in situ monitoring systems are needed to monitor freshwater sediments. New recognised tools for sediment monitoring would help industry to meet the governmental sediment quality criteria and to handle the data concerning historic river contamination and geological background data. The need to monitor by effect-related studies together with chemical monitoring was stressed. The main focus for development of new sensor tools should be for on site determination of certain priority pollutants where there would be advantage over existing methods or where no suitable method exists, and to monitor biological effects (alarm systems and effect-related on site tests). Sensing technologies would also be useful to monitor bioavailability in sediments in situ to provide information for risk assessment. In addition, they could be of use to monitor bioremediation in situ. A useful role was forseen in dredging sediments, for in situ sediment screening and to guide treatment of dredged material. The new sensing tools presented, included determination of metal concentrations in sediments using the diffuse gradients in thin films (DGT) technique (Lancaster University, UK), an analytical protocol for determination of metal speciation in sediments (Universitat Autonoma de Barcelona, Spain), microbiotests for determination of sediment toxicity (University of Ghent, Belgium), a portable whole cell sensors device for heavy metal bioavailability (VITO, Belgium) and a microfabricated sensor array system for Pb concentration profile measurement in the microM range at the liquid-solid interface (University of Geneva, Switzerland).