Concept of eutrophication
A river, lake or reservoir eutrophication suffer when their waters are richer in nutrients. It might seem at first glance it’s good that the waters are well packed with nutrients, because that could live easier living. But the situation is not so simple. The problem is that if there is excess nutrients plants grow in abundance and other agencies. Later, when they die, rot and fill the water smells and give it a foul, drastically reducing its quality.
The putrefaction process consumes large amounts of dissolved oxygen and water are no longer suitable for most living things. The end result is an ecosystem all but destroyed.
Eutrophic and oligotrophic water
When a lake or reservoir is poor in nutrients (oligotrophic) has the clear waters, light penetrates the algal growth is small and keeps a few animals. Plants and animals found are the characteristics of well-oxygenated waters such as trout.
Nutrient loads to go the lake becomes eutrophic. They grow algae in large quantities so that the water is cloudy. Algae and other organisms when they die they are decomposed by the activity of bacteria with spent oxygen. They can not live fish need oxygen-rich waters, so in a lake of this kind will find catfish, perch and other water bodies poorly ventilated. In some cases occur accompanied by anaerobic putrefaction odors are murky waters and low quality from the standpoint of human consumption or use for sporting activities. The bottom of the lake is filled with sediment and the depth is decreasing.
Nutrients water eutrophication
Nutrients that influence this process are the phosphates and nitrates. In some ecosystems the limiting factor is phosphate, as in most freshwater lakes, but in many seas the limiting factor is nitrogen for most plant species.
In the past 20 or 30 years the concentrations of nitrogen and phosphorus in many seas and lakes have almost doubled. Most of them come down the rivers. In the case of nitrogen, a high proportion (about 30%) comes through air pollution. Nitrogen is more mobile than phosphorus and can be washed through the ground or jump into the air by evaporation of ammonia or by denitrification. Phosphorus is more readily absorbed by soil particles and is carried away by erosion eroded or dissolved by surface runoff.
Under natural conditions aquatic system enters a less than 1 kg of phosphate per hectare per year. With human waste this amount rises sharply. For many years, soaps and detergents were the main causes of this problem. In the decades of 60 and 70 to 65% by weight of the detergent was a compound of phosphorus, sodium tripolyphosphate, which was used to “hold” (chelates) to Ca, Mg, Fe and Mn. This was achieved by these ions do not impede the work of surfactant molecules that are doing the washing. These detergents were about 16% by weight of phosphorus. The result was that the domestic and laundries discharges contained a large proportion of phosphate ion. In 1973 Canada first and then other countries have banned the use of detergents that have more than 2.2% phosphorus, forcing to use other binders with less content of this element. Some laws have come to ban detergents containing more than 0.5% phosphorus.
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