Even though the detection frequency for most compounds decreased significantly over the ten years , still the pollution caused by pesticides and industrial chemicals was found to be so high that flora and fauna will almost certainly suffer toxic impacts. "These results cast doubt on the assumption that rivers aren't significantly impaired because the chemicals in them are diluted," said Peter von der Ohe from the Helmholtz Centre for Environmental Research. The scientists agree that if this pollution in the major rivers remains unchanged, it will be difficult to meet the ecological objectives of the EU's Water Framework Directive.
To assess the concentrations of chemicals in river water, the scientists compared data from official monitoring with laboratory results from standard tests involving water fleas, fish and algae. "In some cases we found worrying concentrations of substances at levels which under laboratory conditions would kill 50 per cent of water fleas and could lead to the significant decline of the algae population," explained Prof Schfer. Dr von der Ohe pointed out that the monitoring data were collected using point water grab sampling, although pesticides occur episodically, meaning that pollution levels are likely to be even higher at times. He added that official river monitoring is currently only carried out at a few times a year and in order to cut costs the number of measured chemicals has been reduced focusing on the 33 priority substances - hardly any of which were found to play a role in water pollution in the rivers investigated. Instead, the greatest risks were caused by other substances, according to the researchers. They advocate that future water monitoring should pay more attention to these substances and identify their exact sources. In addition to point sampling, integrated and event-driven sampling methods should be used.
|Contact: Andreas Staak|
Helmholtz Association of German Research Centres