Harmonisation of micropollutant monitoring in large international river: Danube

Micropollutants (heavy metals, organic compounds) play an important role in the quality characterisation of surface waters. These pollutants are usually bioresistant, persistent compounds or may undergo biotransformation, photo-oxidation, sometimes resulting in more toxic breakdown products than their parents, or can accelerate dispersion of hydrophobic compounds and mobilisation of heavy metals from the solid phase. Because of multiple introduction of these pollutants along a large, international river, and due to the sedimentation and re-suspension of the particulate matter by the river hydrodynamics, the deposition of the polluting compounds into the bottom sediment may occur far downstream of the discharge. Appropriate micropollutant sampling and monitoring in both the water column and bottom sediment are discussed. It is concluded that the higher the fine fraction in the sample, the more representative the sediment-bound pollutant characterisation. In order to achieve water and sediment quality guidelines and objectives for micropollutants the guidelines and monitoring programmes must be harmonised, including the sampling, sample preparation, analytical and data interpretation methods among the riparian countries along the Danube river.