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Continuous Instream Monitoring of Nutrients and Sediment in Agricultural Watersheds
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The US EPA's National Nutrient Inventory: Critical Shifts in US Nutrient Pollution Sources from 1987 to 2017
Meredith M Brehob1, Michael J Pennino2, Jana E Compton3
1Office of Research and Development, ORISE Fellow c/o U.S. Environmental Protection Agency, Washington, District of Columbia 20460, United States.
Environmental Science & Technology
|December 15, 2025
Summary
Innovative management strategies have reduced nitrogen (N) and phosphorus (P) pollution from agriculture, urban, and atmospheric sources. These efforts, despite increased agricultural production, show a positive trend for environmental quality and human health.
Area of Science:
- Environmental Science
- Agricultural Science
- Water Quality Management
Background:
- Excess nitrogen (N) and phosphorus (P) cause significant environmental damage.
- Inconsistent nutrient source reporting hinders effective local decision-making.
- Accurate, spatially-resolved data is crucial for managing nutrient pollution.
Purpose of the Study:
- To provide county and HUC12 scale annual estimates of nutrient fluxes in the contiguous U.S.
- To track changes in nutrient sources from 1987-2017 (agriculture from 1950).
- To evaluate the effectiveness of management strategies in reducing nutrient pollution.
Main Methods:
- Utilized the U.S. Environmental Protection Agency's National Nutrient Inventory.
- Estimated nutrient fluxes from agricultural, urban, atmospheric, and natural sources.
- Analyzed temporal trends from 1950/1987 to 2017.
Main Results:
- Total N emissions and atmospheric N deposition decreased by 22% and 15%, respectively.
- Municipal wastewater N and P loads remained stable despite population growth.
- Agricultural efficiency increased by ~25% for N and P, with stable on-field surplus.
Conclusions:
- Technological and management innovations have successfully reduced major nutrient pollution sources.
- Continued efforts can lead to improved air, land, and water quality.
- These trends indicate a positive shift towards better environmental and human health outcomes.
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