With the development and utilization of environmental resources, the development of industry and the high concentration of urban population, a large number of industrial wastewater and domestic sewage containing pollutants are discharged into water without proper treatment, which increases the concentration of oxygen-consuming substances such as ammonia nitrogen, phosphorus and organic pollutants in water and increases the load of nutrients in water. In order to improve the yield of crops, the application amount of chemical fertilizer is increasing year by year. After rain erosion and infiltration, more nutrients are lost into the water, which also increases the load of nutrients in the water. In aquaculture, in order to obtain higher fishery yield, bait is used in some areas, and bait has become the main channel for water bodies to receive nutrients such as nitrogen and phosphorus. Therefore, it is not others but ourselves who release the devil.
Well, the above is for reference only, and the following is true.
1. Loss of chemical fertilizer, which 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, and more than 50% of nitrogen in the Baltic Sea and Taihu Lake also comes from the loss of chemical fertilizers.
2. Domestic sewage, including human domestic wastewater and phosphorus-containing detergents.
3. Livestock and poultry breeding, livestock and poultry 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.