Water Quality and Pollution
The Seine River's water isn't the best, and there are quite a few reasons as to why.
The Seine River doesn't have the best water. Running through such a big city like Paris, you are guaranteed to have some pollution. The Seine's water is polluted with high levels of heavy metals, nutrients, sediment, and bacteria. This is mainly caused by the waste water and the surface runoffs from Paris. Heavy Metals include copper, cadmium, lead, and zinc. The toxic pollutants in the surface runoffs include mercury, nickel, chromium, toluene, DDT, and other pesticides and herbicides. These pollutants are at an even greater amount when there are high rainfalls. This is not mainly because of the high runoffs cause by the rainfalls, but also because the sewage systems in Paris experience a "sanitary sewage overflow". Under these conditions, if the untreated sewage is leaked, it will discharge in the Seine River. Therefore causing pollution.
Despite all this pollution, the Seine's water has fortunately improved.