D10: Impact of Contaminants - Hydromod

Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas
EUROLAKES
D10: Impact of Contaminants
FP5_Contract No.: EVK1-CT1999-00004
Version: 4.0
Date: 25/07/01
File: D10-vers.4.0.doc
Page 66 of 136
The existing threshold values are fixed on the basis of the substances toxicity to humans
and not on their ecotoxicity. The threshold values refer on the open water but a
plurality of foreign matter was measured partly in higher concentrations in the sediment.
About the impacts of these substances is known very less the more so as between different
substances interactions could happen. Aggravating is the fact, that the detection
limit for some substances and groups of substances is already relative high. Chronic
toxic impacts and interference of natural biological processes like reproduction and
search for food can not be excluded even at very low concentrations [UBR 1994].
In the UBR-study it is mentioned, that the direct discharges into the open water of Lake
Constance are caused by navigation because the exhaust gases of the outboard motors
are discharged directly into the lake. That way a significant amount of the emission
products come into the water like polycyclic aromatic hydrocarbons (PAH) and
emulsified oils. A direct connection between the amount of hydrocarbons into the water
and the intensity of the shipping traffic on Lake Constance could be proved. The mixture
and the quantity depend very much on the motor type and fuel. At local places high
concentrations are reached. Calculations in 1980 reveal that the emissions caused by
navigation lie approximately at 1120 t highly volatile hydrocarbons for the whole lake.
Approximately 67 % of this emissions are caused by sport sips and 50 % by two-stroke
engines. Ecotoxicological surveys have shown that the exhaust gases of two-stroke engines
have high toxicological impacts to standardised biological test procedures. For
the four-stroke engines the results have shown lower values.
The input of polycyclic aromatic hydrocarbons result particularly from the road dust
contaminated with asphalt particles. The input of these pollutants can be prevented by
a purification of the surface and street effluents in special plants at the main streets
near the lake [UBR 1994]. An other safety hazard is the transport of hazardous goods
on the roads and rail roads near the lake. The annual transport of hazardous goods in
the inflow area of Lake Constance is substantial, at approximate 3.4 million tonnes. The
ratio of road to rail transport is 54:46. The most significant traffic streams are the transport
of mineral oil from the Singen region to Konstanz, and further on to the area of
Switzerland around Lake Constance, and from around Ulm and Freiburg to the area of
southern Germany around the lake, and further on to Austria [KREUTLER et. al. 2000].
The high concentrations of heavy hydrocarbons are found also in younger sedimentation
layers consist of minimum 90 % of fossil hydrocarbons. The sources of these hydrocarbons
can not be named but the emission at several sources can be estimated.
Motorboats are account for approximately 42 t/a, inputs of road effluents mount up to
approximately 32.5 t/a, inputs from the burning of coal as well as from exhaust fumes
and oil heating. An other aspect are accidents. Between 1988 and 1990 18 000 l oil
were leaked in the administrative district of Konstanz. In the period 1986 to 1990 64
300 l water-endangering substances were leaked in the administrative district of Bodenseekreis
[UBR 1994].
The UBR-study points out, that volatile hydrocarbons belong to the substances, to be
descended from industrial manufacturing processes and are found in the sediment of
Lake Constance in higher concentrations. They are used as solvents in great quantities.
To these substances also belong phthalates (plasticizer in plastics) which were emitted
by use. Different heavy metals were partly remobilized from the sediment if the oxygen