1. Fertilizer loss. Fertilizer is the main source of nutrition in many eutrophic areas. For example, in the Mississippi River basin, 67% of nitrogen flows into the water body and then into the Gulf of Mexico. More than 50% of nitrogen in the Baltic Sea and Taihu Lake also comes from fertilizer loss.
2. Domestic sewage, including human domestic wastewater and phosphorus-containing detergents.
3. Livestock and poultry breeding. Livestock manure contains a lot of nutrient wastes such as nitrogen and phosphorus, which can lead to eutrophication of water bodies.
4. Industrial pollution, including fertilizer plants and wastewater discharge.
5. Burning fossil fuels, about 30% of nitrogen in the Baltic Sea and about 13% of nitrogen in the Mississippi River come from this.
6, cyanobacteria make water anoxic, make animals die, decomposers consume oxygen, resulting in a vicious circle.
Danger:
1, a large-scale outbreak of cyanobacteria, known as green tide, leads to the deterioration of water quality, and in severe cases, the oxygen in the water is exhausted, leading to the death of fish. More seriously, some kinds of cyanobacteria (such as Microcystis) also produce microcystins, which are not only directly toxic to fish, humans and animals, but also an important cause of liver cancer.
2. When a large number of cyanobacteria appear, the nearby water body is generally blue or green, and the water surface is covered by thick blue-green lake indigo, which is blown to the shore by the wind to accumulate. Not only does it give off an unpleasant smell, but also cyanobacteria cells containing toxins are scattered in the water body, and when they are complexed with some suspended substances or preyed on by cultured objects, they are precipitated with their excreta and enriched at the bottom of fish ponds, which will have a huge negative impact on the production of pollution-free aquatic products.
3. Chlamydomonas in cyanobacteria can quickly produce lethal factors, destroy the gill tissue of cultured objects, interfere with the normal progress of their metabolism, paralyze the nerves and make them die. A large number of cyanobacteria toxins can directly lead to poisoning and death of cultured objects; Or even if the number is small, it can harm the breeding object through the accumulation effect of the food chain until it harms the human body.
Extended data
The growth period of cyanobacteria is short, and the whole life cycle can be divided into three stages: growth period, peak period and decline period. During the growth period of cyanobacteria, the total amount of algae in water increased rapidly through the proliferation of photosynthetic cells. During the peak period, the density of cyanobacteria reached the maximum, and airbags and rubber sheaths appeared, floating under suitable meteorological and hydrological conditions, and the water surface was bright green.
In the descending period, cyanobacteria began to rot and degrade, and turned yellow-green after 5 days of decline, pale yellow after 22 days of decline, and white after 50 days of decline. There are two bottlenecks in the comprehensive promotion of treatment technology, on the one hand, the cost, on the other hand, the natural characteristics and service functions of large shallow lakes.
The winding coastline and numerous lakes and bays in East Taihu Lake provide good conditions for the development of submerged vegetation and the implementation of ecological control technology. The coastline of west taihu lake is straight, the dikes are mostly cement revetment, and the lake is wide. The erosion of the lake bottom by strong winds and waves and the erosion of the lake shore basement by wave-generated currents are serious, which greatly increases the difficulty of ecological reconstruction of lakeside wetlands and lakes.
Taihu Lake is located in the economically developed and densely populated Yangtze River Delta region. In addition to controlling endogenous release, the key to improving lake water quality lies in river basin pollution control to further reduce the pollution load into the lake from the source. At the same time, to solve the problem of cyanobacteria outbreak from the root, we should establish the concept of algae control first, strictly control pollutants entering the lake, and set up ecological buffer zones at the estuary of the lake; At the same time, dredging is carried out regularly to reduce endogenous pollution.
Baidu encyclopedia-cyanobacteria
People's Daily Online-Is the flooding of pale yellow cyanobacteria in Taihu Lake in Wuxi related to water pollution in summer?