Phosphorus Inventory for the Conterminous United States (2002–2012)

• Published in: Journal of geophysical research. Biogeosciences 2021-04, Vol.126 (4), p.1-n/a
• Main Authors: Sabo, Robert D., Clark, Christopher M., Gibbs, David A., Metson, Geneviève S., Todd, M. Jason, LeDuc, Stephen D., Greiner, Diana, Fry, Meridith M., Polinsky, Robyn, Yang, Qichun, Tian, Hanqin, Compton, Jana E.
• Format: Article
• Language: English
• Subjects: Accumulation; Agricultural land; Agricultural wastes; Algae; Algal blooms; Atmospheric Deposition; Deposition; Detergents; Eutrophication; Fertilizer; Fertilizer application; Fertilizers; Fluxes; Human wastes; Hydrology; Hypoxia; Inventory; Loads (forces); Phosphorus; Point Sources; Pollution; Pollution control; Pollution sources; Population decline; Population growth; Public health; Regions; Surface water; Total Phosphorus; Urban areas; Water pollution; Water quality; Watersheds
• ISSN: 2169-8953; 2169-8961; 2169-8961
• DOI: 10.1029/2020JG005684

Published reports suggest efforts designed to prevent the occurrence of harmful algal blooms and hypoxia by reducing non‐point and point source phosphorus (P) pollution are not delivering water quality improvements in many areas. Part of the uncertainty in evaluating watershed responses to management practices is the lack of standardized estimates of phosphorus inputs and outputs. To assess P trends across the conterminous United States, we compiled an inventory using publicly available datasets of agricultural P fluxes, atmospheric P deposition, human P demand and waste, and point source discharges for 2002, 2007, and 2012 at the scale of the 8‐digit Hydrologic Unit Code subbasin (∼1,800 km2). Estimates of agricultural legacy P surplus accumulated from 1945 to 2001 were also developed. Fertilizer and manure inputs were found to exceed crop removal rates by up to 50% in many agricultural regions. This excess in inputs has led to the continued accumulation of legacy P in agricultural lands. Atmospheric P deposition increased throughout the Rockies, potentially contributing to reported increases in surface water P concentrations in undisturbed watersheds. In some urban areas, P fluxes associated with human waste and non‐farm fertilizer use has declined despite population growth, likely due, in part, to various sales bans on P‐containing detergents and fertilizers. Although regions and individual subbasins have different contemporary and legacy P sources, a standardized method of accounting for large and small fluxes and ready to use inventory numbers provide essential infromation to coordinate targeted interventions to reduce P concentrations in the nation's waters. Plain Language Summary Excessive phosphorus (P) concentrations in surface water endanger public health and welfare by contributing to harmful algal blooms and hypoxic zones. Many efforts to decrease P pollution to the nation's waters have not achieved desired outcomes. To help decision‐makers develop strategies to decrease P loads, we developed an inventory of inputs and outputs of P across the United States. This inventory reveals the source and magnitude of P in a local area and how it changes through time. We found that agricultural P inputs were the largest source of P nationwide and inefficiencies in use contribute to the continued accumulation of phosphorus across the landscape. This excess phosphorus may make it more difficult to achieve water quality goals. However, many agricultural regi