Which term refers to nutrient runoff containing NO3 and PO4 from agriculture?

• A. Raw Sewage
• B. Saltwater Intrusion
• C. Sewage Runoff
• D. Nutrient Runoff

Answer: (D)

Nutrient runoff is the movement of dissolved nutrients, especially nitrate (NO3−) and phosphate (PO4^3−), from agricultural land into nearby water bodies via rain and irrigation-driven runoff or drainage. These nutrients come from fertilizers, manure, and crop residues and fuel algal blooms that can lead to eutrophication and low oxygen levels in streams, lakes, and oceans. The term specifically describes the transport of these nutrients from land to water, which is why it fits this scenario best. The other terms refer to different sources or processes—raw sewage and sewage runoff involve human waste, while saltwater intrusion is the inland movement of saline water into freshwater aquifers.