What are two common sources of nitrates in water systems?

What are two common sources of nitrates in water systems?

• A. Industrial solvents.
• B. Atmospheric deposition and soil organic matter.
• C. Agricultural runoff and sewage effluent.
• D. Groundwater depth.

Answer: (C)

Nitrates in water primarily come from nitrogen-containing inputs related to farming and waste. They’re highly water-soluble, so they readily move with water as it runs off fields or leaches through soil, and they can also come from human waste in wastewater and septic systems. Agricultural runoff and sewage effluent are the two common sources because fertilizers and manure/urine contain nitrate forms that readily enter streams, rivers, and groundwater. Fertilizers used on crops add large amounts of nitrate-N to the environment, and rain or irrigation can wash these nitrates into water bodies or through the soil into groundwater. Sewage effluent, from people’s waste and treated wastewater, releases nitrates into nearby water bodies, especially in urban and suburban areas. The other options aren’t the primary sources: industrial solvents involve different contaminants, atmospheric deposition and soil organic matter contribute only smaller amounts of nitrates, and groundwater depth isn’t a source of nitrates at all—it's a factor that affects movement and concentration rather than the input.

Nitrates in water primarily come from nitrogen-containing inputs related to farming and waste. They’re highly water-soluble, so they readily move with water as it runs off fields or leaches through soil, and they can also come from human waste in wastewater and septic systems.

Agricultural runoff and sewage effluent are the two common sources because fertilizers and manure/urine contain nitrate forms that readily enter streams, rivers, and groundwater. Fertilizers used on crops add large amounts of nitrate-N to the environment, and rain or irrigation can wash these nitrates into water bodies or through the soil into groundwater. Sewage effluent, from people’s waste and treated wastewater, releases nitrates into nearby water bodies, especially in urban and suburban areas.

The other options aren’t the primary sources: industrial solvents involve different contaminants, atmospheric deposition and soil organic matter contribute only smaller amounts of nitrates, and groundwater depth isn’t a source of nitrates at all—it's a factor that affects movement and concentration rather than the input.