Geochronology of anthropogenic contaminants in a dated sediment core of the Rhine River (Germany): emission sources and risk assessment

A subaquatic sediment core was taken from the Rhine River to determine substance specific concentration profiles in correlation to time and depth. Based on these data emission histories were related for selected contaminants. Significant emission sources and emission pathways were compiled. In correlation to investigations of national and international monitoring programmes a significant reduction of environmental emissions up to a tenth of previous values were found since 1998. Some selected compounds, discharged by municipal and industrial activities, for example disinfectants (methyltriclosan), flame retardants (tris(chloropropyl)phosphate), chlorinated benzenes, anilines and naphthalenes, can be classified as significant synthetic substances in the scope of the Water Framework Directive. Because of their chemical characters, their persistence, bioaccumulation and ecotoxicity, as well as their occurrence within the sediment core, these compounds create a significant potential risk for water quality, but a reduction of these synthetic compounds to zero cannot be expected for the next future. In summary, this study provides a comprehensive reconstruction of the pollution history of anthropogenic contaminants, their fate and behaviour in the fluvial system. In addition, an estimation of the time period required for environmental measurements and monitoring programmes to improve, achieve and save a good status of the river systems are given.