Heavy metals in the River Danube: Water, suspended matter, periphyton

Summary

Both the dissolved and suspended concentration values of heavy metals can be used for distinguishing point and non-point pollution sources and for establishing trends in pollution if the dataset is analysed with consideration for the hydrological characteristics of the river: Distribution of water discharge ranges (LWD, HWD), relationship of suspended matter and water discharge, etc.

Ag, Cd, Cr, Cu, Ni, Pb and Zn can be considered as constant or intermittent point-like pollutants derived from a few pollution sources situated upstream from the reach of the Danube examined.

In the case of Ag, Cd, Co, Mn and Zn, mainly in the range of HWD, the effect of watershed (e.g. leaching from inundated soils) can be detected, too.

The investigation of suspended heavy metals provides the similar or the same results as that from sediment analysis. Since sediment has a mosaic distribution in the main arm suspended matter analysis preferable for this reach of the river.

A major conclusion of this study is that the majority of elements studied (Ca, Cu, Cr, Fe, Mn, Ni, Pb, Zn) are better enriching in suspended matter than in periphyton. Hence, in the case of these metals for analysis of suspended phase would appear to be the most reliable method for monitoring the level of heavy metals in the river. In the case of Ag, ed and eo however a biomonitor organism, Cladophora glomerata proves to be more suitable for this purpose.