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.