An analysis of seven coastal streams in Israel found that they contained more than 60 types of pollutants with the highest concentrations of pesticides found in the Kishon Stream near Haifa.
Every year, after the first winter flood, rainwater washes out the remnants of various pollutants, carrying them in relatively high concentrations to different streambeds. In the first study of its kind, a team from the Hebrew University and the Ruppin Academic Center collected water samples and sediments that had accumulated at the bottom of seven coastal streams after a flood and examined the composition and concentration of pollutants in them.
The results of the study, conducted last year, by Prof. Benny Chefetz and Itamar Mendelev of the Hebrew University and Tom Topaz of the Ruppin Academic Center will be presented next week at the annual conference of the Environment and Health Fund, a non-profit organization. They will also be published soon in the [Hebrew] journal Ecology and Environment.
The samples contained more than 60 types of pollutants. These were substances that are not usually monitored in routine checks of the water of these streams. There is currently no binding standard for these compounds that would limit their concentration in water sources. The highest concentrations of medical substances were found in the Hilazon Stream, which flows into the sea near Acre, while the highest concentrations of pesticides were found in the Kishon Stream, which empties into the Mediterranean near Haifa.
An analysis of the toxicity of the pesticides showed that the concentrations present after the first flood were sufficient to cause significant harm to animals living at the bottom of these streams. These creatures, including tiny worms and crabs, are an important part of the food chain in the stream.
The researchers believe the source of these pesticides are adjacent agricultural fields. They attributed the presence of medical compounds and beauty products in the water to the flow of sewage as well as pollutants which water treatment plants cannot filter out. The water was also found to contain pollutants that should have been removed at these plants.
The diversity of pollutants and the fact that they were present in all the streams shows that the phenomenon is widespread, occurs every rainy season and likely hampers the rehabilitation of these streams.
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Recently, the Ministry of Agriculture has adopted a policy to better manage the floodwaters, in the hope of preventing widespread pollution of these streams. According to Chefetz, this policy should include examination of the use of pesticides and finding substitutes that are less toxic. Furthermore, he recommends embracing methods of tilling the land that prevent erosion, which further exacerbates the flow of pollutants into these streams.