NUTRIENT, HEAVY-METAL AND ORGANIC POLLUTANT COMPOSITION OF SUSPENDED AND BED SEDIMENTS IN THE RHONE RIVER

The environmental quality of the Rhone River (Switzerland-France) has been assessed with a geochemical survey of the pollutants bound to sus pended sediments. Ten samples were collected between Lake Geneva and t he Mediterranean Sea in November 1989 by continuous flow centrifugatio n and analysed for grain size distribution, carbonate, organic C, N, f orms of particulate P, trace metals, and organic compounds (chlorobenz enes, organochlorine pesticides, PCBs, and PAHs). Four bed sediment sa mples win also studied for comparative purposes. The suspended solids provide lower variance by parameter than the bed sediments and are cle arly most suitable for synoptic monitoring. The Upper Rhone River carr ies a glacial derived sediment with a low nutrient content, the stretc h from Geneva to Lyon provides a sediment dominated by carbonate, and in the Lower Rhone the organic matter and phosphorus are relatively in creased, mainly due to wastewater effluents and to an industrial P sou rce. High concentrations of metals and organic micropollutants downstr eam of Lyon indicate a multiple contamination in the Lower Rhone, wher eas mon specific inputs are located downstream of Geneva and Arles. Th e comparison with data from other polluted major systems, the Rhine, t he Niagara and the Detroit rivers, shows on overall similarity confirm ing that the Rhone quality is degraded downstream of Lyon. The levels of particular concern are for Hg, DDT metabolites which reveal a recen t release in the basin, PCBs with a likely high chlorine content, and PAHs. The statistical evaluation of the compositional variables indica tes a limited number of well defined associations, suggesting that the contamination of the suspended sediments results from the combination of numerous and intermittent point and diffuse sources in the Rhone R iver basin.