An adaptable automatic trace metal monitoring system for on line measuring in natural waters.

An adaptable automatic trace metal monitoring system (ATMS) was assembled and embedded in a mobile monitoring station belonging to the French Water Agency Artois-Picardie (AEAP) and deployed in the field to measure the concentration of trace metals (electroactive and acid leachable fractions) in natural waters by anodic stripping voltammetry with a hanging mercury drop electrode. Cathodic stripping voltammetry procedures were included to estimate the concentration of dissolved oxygen and reduced sulphur species. The concept of the measuring system enables easy adaptation of methods and procedures to analytes of concern and gives the opportunity to undertake in real-time a routine analysis of the dynamic behaviour of trace metals in river, pond and seawater. The system was tested in two aquatic bodies: in a pond where eutrophication processes occur recurrently and in the Deûle River, where sediments are highly contaminated by several metals such as Pb and Zn and frequently resuspended because of the river traffic. Preliminary field studies demonstrated that trace metal concentrations can evolve quickly as a function of time, depending on the turbidity and luminescence, i.e. day-night cycles. The obtained results were compared with an Environmental Quality Standard (EQS), the Criteria Maximum Concentration (CMC) and the Criterion Continuous Concentration (CCC). The whole system is also prepared for the task of "early warning".