Which of the following are common sources of nitrates and phosphates?

• A. Fertilizers, detergents, animal waste, sewage, and agricultural runoff
• B. Carbonates, nitrates, and heavy metals
• C. Industrial solvents and pesticides
• D. Natural mineral deposits only

Answer: (A)

Nitrates and phosphates in water mainly come from human activities that add nutrients to the environment, which can fuel excessive algae growth and harm aquatic life. Fertilizers introduce nitrogen and phosphorus to soils, and when rain or irrigation moves water through the land, these nutrients wash into streams and rivers. Detergents have historically contained phosphates that end up in wastewater and then in surface waters. Animal waste and sewage are rich sources of both elements, releasing nitrates and phosphates as they break down. Agricultural runoff carries these nutrients from fields into nearby water bodies, especially during storms.

The other options don’t represent the typical nutrient inputs that cause eutrophication. Carbonates and heavy metals are not primary sources of nitrates or phosphates, industrial solvents and pesticides are pollutants of different types, and natural mineral deposits don’t usually supply these nutrients in significant amounts.