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 58 of 136
9 LEVEL OF POLLUTION IN WATER AND SEDIMENT
In the [ENVIRONMENTAL ATLAS BERLIN] it is said that there is a continual accumulation
of pollutants in water bottom soils, such as heavy metals and chlorinated hydrocarbons.
In the material cycle of waters sediments form a natural buffer and filter system. The
waters are subject to strong variations of current, substance input, substance transport
and sedimentation. In addition to the water sample analyses practised for years, sediment
analyses is increasingly important in evaluating qualities of the total ecosystem of
a water body. In comparison to water analyses and independent of current inputs,
sediment tests reflect the long term quality situation. For this reason, sediment tests are
a better basis for fundamental comparisons with other flowing waters. The suspended
and precipitate substances stored on the water bottom form a reservoir for many pollutants
and trace substances of low solubility and low degree of degradability. According
to their chemical persistence and the physical-chemical and biochemical characteristics
the substances are conserved in sediments over longer periods of time. Even after
sedimentation, portions of fixed substances can be remobilised and re-enter the material
cycle of water. Analyses of sediment samples from different depths give a chronological
record of inputs in waters and can also allow conclusions to be drawn regarding
sources of contamination. Also mineral suspension and precipitation substances are
able to store heavy metal ions on their outer surface and they can also be bound in
water organisms. The heavy metals can be taken up by higher organisms through the
food chain, or they sink to the bottom as sediment, depending on the flow velocity of
water. Various pesticides and PCB have the characteristic of being stored adsorptively
on suspended matter or in plant organisms. After attaining into the sediment this substances
and by ingestion of the organisms they reach the food chain. Eels have a high
fat content and eat bottom organisms and bury themselves in sediment. That way, the
intake of pesticides and PCB not only takes place through nutrients. They also ingest
them through the skin and accumulate them in the body fat [ENVIRONMENTAL ATLAS
BERLIN].
9.1 TRANSPORT AND ACTION OF TRANSPORT IN WATER
[FENT 1998] refers that several processes are responsible for the destiny of chemicals
in water bodies, like disposition, dilution in the water, volatility in the atmosphere, sedimentation,
abiotic chemical conversation (hydrolysis, photolysis, oxidative and reductive
processes), biotic conversations(microbial reduction, metabolism) and bioaccumulation.
He continues that chemicals having a high vapour pressure and a low water solubility
are given to the atmosphere very fast. If substances have a low water solubility and a
low vapour pressure they prefer to adhere at particles and sediment. Figure 9-1 shows
the apply of contaminants to their volatility in a simplified version.