Citation:

Metson, G., J. Lin, J. Harrison, AND J. Compton. Influences of climate and land use on contemporary anthropogenic watershed phosphorus input and riverine export across the United States. Sustainable Phosphorus Summit, Kunming, CHINA, August 08 - 14, 2016.

Impact/Purpose:

Human activities have altered the cycling of nitrogen and phosphorus through applications of fertilizers, manures, sewage and septic releases. Phosphorus is of particular interest because it is an important driver of freshwater food webs and too much phosphorus has resulted in a growing number of harmful algal blooms across the US in recent years. A group of scientists from the National Research Council, US EPA and Washington State University are assembling a current inventory of phosphorus inputs to the conterminous US landscape. These data will become part of EPA's EnviroAtlas, so that others can access and use it. The study compares inputs of phosphorus to runoff into rivers in 94 US watersheds, and focuses on determining the controls on phosphorus losses from watersheds in to inform management. This abstract contributes to a deliverable for FY SHC 4.61.

Description:

Human beings have greatly accelerated nitrogen and phosphorus flows from land to aquatic ecosystems, often resulting in eutrophication, harmful algal blooms, and hypoxia in lakes and coastal waters. Although differences in nitrogen export from watersheds have been clearly linked to a combination of human nitrogen sources and climate in the U.S., relatively less is known about how natural and anthropogenic landscape characteristics mediate losses of phosphorus from watersheds. We quantified major phosphorus inputs (fertilizer, manure, and human waste) and outputs (riverine export, crop harvest and sewage treatment) for 94 watersheds in 2012 across the continental U.S. and examined how climate, hydrology, soil characteristics, and land use influenced phosphorus exports from watersheds to rivers as total phosphorus and dissolved inorganic phosphorus concentrations and yields. We identified regional differences in major input sources as well as the importance of landscape mediating factors, highlighting the importance of both the biophysical and anthropogenic contexts on the relationship between major phosphorus sources and water quality. This study represents the most up-to-date spatially explicit inventory of anthropogenic P inputs and outputs for the conterminous United States. Linking this inventory with losses of phosphorus to waterways is an important step in understanding what policies and practices may be most effective in mitigating water quality problems.

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