The distribution of the lanthanum anomaly in the Dutch branches of the Rhine River
Résumé
The elements lanthanum to lutetium, usually referred as the REE, are increasingly used in numerous high technology products and processes. Such products are Gadolinium chelates, used as contrasting agents in medical imaging, and produce positive anthropogenic Gd-anomalies in rare earth shale normalized (Reenasc) patterns in rivers, surface and ground waters and shallow seas. Because of the increased use of the REE, the monitoring program of the Rhine-Meuse branches and surface water influenced by them in the Netherlands was extended from 2008 with the REE. In this monitoring program both the total and dissolved (< 0.45 μm) fraction are analyzed. At the monitoring station Lobith, where the River Rhine enters the Netherlands, the REEnasc-patterns show beside the well-known Gd-anomaly a distinct La-anomaly. This positive La-anomaly in the Rhine River is recently also reported by Kulaksiz and Bau (2011, sampling was done in 2009) and first occur in the Rhine River north of the city of Worms, 400km upstream of the Dutch-German border. Kulaksiz and Bau could show that this anomaly is of anthropogenic origin and can be traced back to the effluent from a production plant for fluid catalytic cracking catalysts at Rhine river-km 447.4. The amount of anthropogenic lanthanum in the total fraction in Lobith station is an order of magnitude larger than in the dissolved fraction indicating that the suspended matter in the Rhine River is the major carrier of the anthropogenic lanthanum. All REEnasc- patterns of the branches of the Rhine River show in addition to the Gd-anomaly a positive La-anomaly, while in the Meuse River only a Gd-anomaly is observed. In the influenced surface waters of the Rhine and Meuse Rivers always a Gd-anomaly occurs but in those influenced by the Rhine tributaries also the La-anomaly occurs. In the poster the load of lanthanum over the years 2008, 2009 and 2010 in the dissolved and total fraction at Lobith and the distribution of the La anomaly over the branches of the Rhine River in the Netherlands (4 monitoring stations) and influenced surface water (5 monitoring stations) will be shown. The Meuse monitoring stations will be given for comparison.