Oral Presentation Society for Freshwater Science 2025 Annual Meeting

The next generation of the US EPA's National Nutrient Inventory: a county and HUC12-level accounting of nitrogen and phosphorus across the CONUS (1987-2017) (118650)

Meredith Brehob 1 , Robert D Sabo 2 , Michael J Pennino 2 , Jana Compton 3 , Ryan A Hill 3 , Marc Weber 3 , Chris Clark 2 , Jiajia Lin 4 , Gerardo Ruiz-Mercado 5 , Lauren Knose 6 , Sarah M Stackpoole 7 , James N Carleton 2 , Anne Rea 6
  1. ORISE Fellow at US EPA Office of Research and Development, Washington, D.C.
  2. US EPA Office of Research and Development, Washington, D.C.
  3. US EPA Office of Research and Development, Corvallis, Oregon
  4. Oregon DEQ, Portland, Oregon
  5. US EPA Office of Research and Development, Cincinnati, Ohio
  6. US EPA Office of Research and Development, Research Triangle Park, North Carolina
  7. USGS Water Resources Mission Area, Denver, Colorado

Nutrient inventories assess nitrogen (N) and phosphorus (P) inputs and provide inference into the evolution of nutrient pollution sources. The information generated by inventories informs nutrient reduction strategies by quantifying the magnitude of agricultural, urban, and atmospheric pollution sources, and provides a standardized platform to weigh the effects of reducing sector-specific sources of nutrient pollution on water quality and other environmental endpoints. This work is a spatially and temporally detailed update to EPA’s National Nutrient Inventory (NNI), summarizing N and P at the county and Watershed Boundary Dataset (WBD) HUC12 scale annually from 1987 to 2017 across the conterminous United States (CONUS). In addition, this dataset leverages agricultural data back to the year 1950 to approximate legacy nutrient pollution hotspots. The NNI contains data on agricultural (crop and livestock), urban, atmospheric, and natural sources of N and P and derives management relevant metrics (e.g., agricultural surplus, nutrient use efficiency). Using the NNI, we identified trends in nutrient dynamics, such as the increase in agricultural yield relative to nutrient surplus across the CONUS, which suggests general improvement in agricultural nutrient management. Applications for these nutrient inventory data include predicting drinking water violations, harmful algal blooms, and drivers of nutrient delivery to sensitive freshwater and coastal ecosystems. The NNI data can also be used to track the effectiveness of nutrient reduction policies such as the P detergent ban, which our analysis shows has resulted in a 18% reduction in human P waste between 1987 and 2017. The NNI is invaluable for informing research and policy decisions regarding nutrient pollution across a variety of spatial and temporal scales. Our goal in sharing this dataset is to provide an easily accessible one-stop source for nutrient input data across the CONUS.

The views expressed in this abstract are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.