Rhine River Constance

The Rhine River above Lake Constance (alpine and prealpine catchment area) averages the following composition ... 

The Rhine River (above Lake Constance) averages a Mg2+ composition of 9 mg L-1 (see Stumm, 1996). If the annual runoff in that area is approximately 1 m3 per m2 of geographical area, estimate the erosion rate of Mg2+ (as MgC03), in g m 2 y 1. 

Results of studies on recent mud deposits of the heavily polluted lower Rhine River 31, 33) near the German/Dutch border (13) are compared with the data from a sediment study on Lake Constance (33), where the contamination by heavy metals is still relatively low (34). 

Some properties of the sediment samples from Lake Constance and the Rhine River, possibly relevant for the study of the accumulative eflFects on heavy metals, are summarized in Figure 1. The concentrations of the metals in both samples (13,33) indicate an increase from coarser to fine grained fractions, as exemplified by zinc. Elevated concentrations of metals in the sand-sized material probably originate from heavy minerals or from corrosion products. An even greater grain size effect occurs for phosphorus approximately 0.35% (dry weight) has been... 

Figure 1, Percentages and concentrations of zinc, various sedimentary phases, and specific surface area in different grain size intervals of sediments from the Rhine River and Lake Constance...

Of the other forms of nonresidual associations, some metal-organic compounds, for example, fulvic and humic acids, have been shown to be particularly effective in the transfer of (toxic) metals from inorganic matter into organisms 51). According to Table II, where data of humate extractions with O.IN NaOH are compared, these effects should be more relevant for iron, copper, zinc, and lead in the sample from the Rhine River than in the sediment material from Lake Constance. The other nonresidual metal associations (easily reducible, carbonates, moderately reducible forms) partly indicate higher percentages in Lake Constance sediments (Mn and Pb), whereas others (chromium, copper, and zinc) are enriched in the Rhine sample. 

Many of the measurements in the Rhine catchment area were done by AWBR (Association of Waterworks Lake Constance-Rhine), ARW (Association of Waterworks in the Rhine River Basin), and RIWA (Association of River Water Supply Companies). The concentrations reported from the different locations on the Rhine River are discussed below from the upper Rhine to the lower Rhine including tributaries. For clarity purposes Figure 1 shows the catchment area of the Rhine river with important confluents. 

---