Lake Constance samples from

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... 

Metal Concentrations and Average Percentages of Metals Samples from Lake Constance (L.C.)... 

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. 

In the O.IN NaOH extractable fraction (which is assumed to reflect the humic acid phases) of the Rhine sediment, PCF values are particularly high for iron, copper, and lead, exhibiting a slight increase in the fine-grained particles compared with the silt-sized material. For the sample from Lake Constance, the concentration factors in the humate phase have been found to be 11 and 40 for copper, 9 and 12 for iron, and 5 and 9 for chromium, in the pelitic and silty sediment fractions, respectively. Similar concentration factors of trace metals in the NaOH-extractable matter have been observed by Chen et al. (14) for chromium, lead, copper, and zinc, whereas iron and manganese showed no significant association with this fraction. 

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