Author(s): M. Zessner; H. Kroiss
Linked Author(s):
Keywords: Black Sea protection; Danube; Emission estimation; Nitrogen; Phosphorus; Regional nutrient balance; Water quality monitoring
Abstract: Eutrophication of the Black Sea is one of the main water quality problems related to the Danube catchment area. A tremendous increase since the fiftieth of phosphorus and nitrogen loads that are transported by the big rivers entering the Black Sea is seen as one of the main reasons for this problem. In order to take effective measures for the load reduction of these nutrients it is necessary to know their sources, pathways and sinks in the region. Regional materials accounting including all the internal nutrient cycles of the anthroposphere (e. g. agricultural nutrient turnover, food consumption) is a useful tool for the control of emissions. A lack of knowledge seems to exist in regard to the transition of nutrients from the antroposphere to the hydrosphere and the transport and transformation of these nutrients within the hydrosphere. A comparison of estimated emissions of a catchment area with loads calculated from instream measurements of the river shows discrepancies in many cases. Mostly emission estimations are higher than instream loads. Uncertainties of emission estimations are obvious. This paper tries to show problems with the calculation of instream loads from a restricted number of measurements and tries to underline the attention that should be paid to the understanding and quantification of retention and losses of nutrients in the hydrosphere. To do so, this contribution gives an interpretation of water quality monitoring in the Danube at Vienna from about 400 days and the comparison of emissions from 12 (sub-) catchment areas of Austrian Danube tributaries and measured loads in these rivers. The main outcome is that for measurement of loads in a river the transport characteristic of a material has to be taken into account for the sampling strategy as well as for the calculation method used and that a high average area specific surface water runoff assists transport of nutrients in the hydrosphere. Respectively the importance of retention and losses increases with decreasing area specific runoff.
Year: 1999