1. Nature
1.1. Artificial
1.1.1. Pesticides
1.1.2. Fertilizer
1.1.3. Toxic Chemicals
1.1.4. Radioactive Waste
1.1.5. Organic waste water
1.1.6. Dioxin
1.1.7. Hazardous waste
1.2. Natural
1.2.1. Volatile Organic Compound (VOCs)
1.2.2. Aquatic toxicology
1.2.3. Decomposing organisms
1.2.4. Heavy metals
2. Sources
2.1. Natural
2.1.1. Disaster
2.1.1.1. Storm
2.1.1.2. Forest Fires
2.1.1.3. Drought
2.1.1.4. Tsunami
2.1.1.5. Acid Rain
2.1.1.6. Earthquake
2.1.1.7. Flood
2.1.2. Others
2.1.2.1. Alga
2.1.2.2. Soil Erosion
2.1.2.3. Animal Waste Water
2.1.2.4. Burning Of Fossil Fuels
2.1.2.5. Nutrient Pollution
2.1.2.6. Atmospheric Deposition
2.1.2.7. Underground storage leakages
2.2. Artificial
2.2.1. Business/Production Activities
2.2.1.1. oil spills
2.2.1.2. Mining
2.2.1.3. Industrial Nuclear Power
2.2.1.4. Biological Weapon
2.2.1.5. Agriculture industry
2.2.1.6. Metallurgical industry
2.2.1.7. Oil refineries
2.2.1.8. Agricultural runoff
2.2.2. Human Activities
2.2.2.1. Urbanization
2.2.2.2. Burying trash indiscriminately
2.2.2.3. Cultural pollution
2.2.2.4. Waste dump
2.2.2.5. Car Wash
2.2.2.6. Hospital waste water
2.2.2.7. Overfishing
2.2.2.8. Throwing garbage into water
2.2.2.9. Domestic waste water
2.2.3. Others
2.2.3.1. Polluted runoff
2.2.3.2. Sewage Leaks
2.2.3.3. Deforestation
2.2.3.4. Population Growth